Change search
Refine search result
23358233592336023361233622336323364 1168001 - 1168050 of 1209152
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1168001.
    You, Junxin
    et al.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences. Lishui University, China.
    Zheng, Guangjin
    University of Gävle, Faculty of Health and Occupational Studies, Department of Health and Caring Sciences. Lishui University, China.
    Nursing interventions in improving the postoperative recovery of patients with orthopedic hip andknee surgery: A descriptive literature review2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 1168002. You, L.
    et al.
    Yuan, D.
    Load Optimization With User Association in Cooperative and Load-Coupled LTE Networks2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 5, p. 3218-3231Article in journal (Refereed)
  • 1168003. You, L.
    et al.
    Yuan, D.
    Lei, L.
    Sun, S.
    Chatzinotas, S.
    Ottersten, Björn
    Institute for Infocomm Research, Agency for Science, Technology, and Research, Singapore, 138632, Singapore.
    Resource Optimization With Load Coupling in Multi-Cell NOMA2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 7, p. 4735-4749Article in journal (Refereed)
    Abstract [en]

    This paper investigates the problem of the interference among multiple simultaneous transmissions in the downlink channel of a multiantenna wireless system. A symbol-level precoding scheme is considered, in order to exploit the multiuser interference and transform it into useful power at the receiver side, through a joint utilization of the data information and the channel state information. In this context, this paper presents novel strategies that exploit the potential of symbol-level precoding to control the per-antenna instantaneous transmit power. In particular, the power peaks among the transmitting antennas and the instantaneous power imbalances across the different transmitted streams are minimized. These objectives are particularly relevant with respect to the nonlinear amplitude and phase distortions induced by the per-antenna amplifiers, which are important sources of performance degradation in practical systems. More specifically, this paper proposes two different symbol-level precoding approaches. The first approach performs a weighted per-antenna power minimization, under quality-of-service constraints and under a lower bound constraint on the per-antenna transmit power. The second strategy performs a minimization of the spatial peak-to-average power ratio, evaluated among the transmitting antennas. Numerical results are presented in a comparative fashion to show the effectiveness of the proposed techniques, which outperform the state-of-the-art symbol-level precoding schemes in terms of spatial peak-to-average power ratio, spatial dynamic range, and symbol error rate over nonlinear channels.

  • 1168004.
    You, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computing Science. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Network Optimization of Evolving Mobile Systems with Presence of Interference Coupling2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The rapid development from 4G to 5G of mobile communications poses significant challenges in providing high rate and capacity, making it more crucial for efficient utilization of time-frequency resource via optimally configuring the network. Mathematical optimization serves as a powerful tool for addressing this type of problems. However, gauging its potential in large-scale cellular networks is non-trivial due to the inherent coupling relation of interference among cells. To address this issue, the dissertation adopts a so-called load-coupling system that mathe-matically formulates the mutual influence caused by radio resource allocation among cells. The model defines the time-frequency resource consumption in each cell as the cell load. The load of one cell governs the interference that the cell generates to the others, since the cell trans-mits more frequently with higher load. The model enables joint optimization of resource al-location in multiple cells with respect to the dynamics of resource occupancy of cells. Under the load coupling model, the dissertation applies mathematical optimization to resolve resource management problems with respect to a number of evolving technologies, such as coordinated multipoint (CoMP) transmission, wireless relays, cloud radio access networks (C-RAN), and non-orthogonal multiple access (NOMA). Six research papers are included in the dissertation. Paper I addresses the question of how network planning and coordination may increase the ef-ficiency of spectrum usage, by jointly optimizing user association and resource allocation with CoMP. Paper II investigates the potential of relay cooperation for energy saving. As an extension of Paper I, Paper III studies the capacity maximization for a target group of users, while keep-ing the quality-of-service (QoS) of other users being strictly met. Paper IV provides a general framework and a series of theoretical analysis for algorithmically enabling resource optimization in multi-cell NOMA with load coupling, where users are allowed to group together for sharing time-frequency resource by successive interference cancellation (SIC). Under this framework, Paper V explores the potential of NOMA networks. For a restricted setup of NOMA, the paper achieves globally optimal resource usage efficiency, in terms of power allocation, user pair se-lection, and time-frequency resource allocation. Finally, Paper VI, serving as a complementary note, overcomes a key obstacle in analyzing convergence of applying load coupling in NOMA networks.

  • 1168005.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Ding, Lianghui
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Wu, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Pan, Zhiwen
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, China.
    Hu, Honglin
    Shanghai Research Center for Wireless Communcations, Shanghai, China.
    Song, Mei
    PCN CAD Center, Beijing University of Posts and Telecommunications, Beijing, China.
    Song, Junde
    PCN CAD Center, Beijing University of Posts and Telecommunications, Beijing, China.
    Cross-layer optimization of wireless multihop networks with one-hop two-way network coding2011In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 55, no 8, p. 1747-1769Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate optimal cross-layer design of congestion control, routing, one-hop two-way inter-commodity (OTIC) network coding and scheduling in wireless multihop networks utilizing the broadcast advantage of wireless medium. We first present an achievable rate region with OTIC network coding by introducing virtual flow rates in a node. Then we formulate the network utility maximization problem subject to constraints on this achievable rate region, and analyze the complexities of both node- and path-based formulation with no network coding, OTIC network coding, and overhearing network coding. After that, we solve it using dual decomposition and subgradient method. Based on the solution, we present a new queue model, which is able to facilitate the coding operation between two-way commodities, and then propose a backpressure-based cross-layer optimization algorithm with low coding complexity and overhead. Afterwards, we analyze the stability and asymptotical optimality of the proposed cross-layer algorithm by Lyapunov drift technique, and evaluate its performance through extensive simulation. By comparing with the pure routing scheme under both primary and two-hop interference models in an illustrative topology, it is shown that with the proposed joint optimization algorithms, the OTIC network coding can interact adaptively and optimally with other components in different layers and achieve high throughput gain. Simulation of the proposed algorithm in a mesh network with base station and a random ad hoc network justifies that OTIC network coding can obtain considerable throughput gain with low complexity in various kinds of networks.

  • 1168006.
    You, Lei
    et al.
    Qingdao University, Peoples R China.
    Lei, Lei
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD USA.
    A Performance Study of Energy Minimization for Interleaved and Localized FDMA2014In: 2014 IEEE 19TH INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD), IEEE , 2014, p. 16-20Conference paper (Refereed)
    Abstract [en]

    Optimal channel allocation is a key performance engineering aspect in single-carrier frequency-division multiple access (SC-FDMA). It is of significance to consider minimum sum power (Min-Power), subject to meeting specified users demand, since mobile users typically employ battery-powered handsets. In this paper, we prove that Min-Power is polynomial-time solvable for interleaved SC-FDMA (IFDMA). Then we propose a channel allocation algorithm for IFDMA, which is guaranteed to achieve global optimum in polynomial time. We numerically compare the proposed algorithm with optimal localized SC-FDMA (LFDMA) for Min-Power. The results show that LFDMA outperforms IFDMA in the maximal supported user demand. When the user demand can be satisfied in both LFDMA and IFDMA, LFDMA performs slightly better than IFDMA. However MinPower is polynomial-time solvable for IFDMA whereas it is not for LFDMA.

  • 1168007.
    You, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Lei, Lei
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20740 USA.
    Load Balancing via Joint Transmission in Heterogeneous LTE: Modeling and Computation2015In: 2015 IEEE 26TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR, AND MOBILE RADIO COMMUNICATIONS (PIMRC), IEEE , 2015, p. 1173-1177Conference paper (Refereed)
    Abstract [en]

    As one of the Coordinated Multipoint (CoMP) techniques, Joint Transmission (JT) can improve the overall system performance. In this paper, from the load balancing perspective, we study how the maximum load can be reduced by optimizing JT pattern that characterizes the association between cells and User Equipments (UEs). To give a model of the interference caused by cells with different time-frequency resource usage, we extend a load coupling model, by taking into account JT. In this model, the mutual interference depends on the load of cells coupled in a non-linear system with each other. Under this model, we study a two-cell case and proved that the optimality is achieved in linear time in the number of UEs. After showing the complexity of load balancing in the general network scenario, an iterative algorithm for minimizing the maximum load, named JT-MinMax, is proposed. We evaluate JT-MinMax in a heterogeneous Network (HetNet), though it is not limited to this type of scenarios. Numerical results demonstrate the significant performance improvement of JT-MinMax on min-max cell load, compared to the conventional non-JT solution where each UE is served by the cell with best received transmit signal.

  • 1168008.
    You, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Lei, Lei
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20740 USA.
    Optimizing Power and User Association for Energy Saving in Load-Coupled Cooperative LTE2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    We consider an energy minimization problem for cooperative LTE networks. To reduce energy consumption, we investigate how to jointly optimize the transmit power and the association between cells and user equipments (UEs), by taking into consideration joint transmission (JT), one of the coordinated multipoint (CoMP) techniques. We formulate the optimization problem mathematically. For solving the problem, a dynamic power allocation algorithm that adjusts the transmit power of all cells, and an algorithm for optimizing the cell-UE association, are proposed. The two algorithms are iteratively used in an algorithmic framework to enhance the energy performance. Numerically, the proposed algorithms can lead to lower energy consumption than the optimal energy setting in the non-JT case. In comparison to fixed power allocation in JT, the proposed dynamic power allocation algorithm is able to significantly reduce the energy consumption.

  • 1168009.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Lei, Lei
    Luxembourg Univ, Interdisciplinary Ctr Secur Reliabil & Trust, Luxembourg, Luxembourg..
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Sun, Sumei
    Inst Infocomm Res, A STAR, Singapore, Singapore..
    Chatzinotas, Symeon
    Luxembourg Univ, Interdisciplinary Ctr Secur Reliabil & Trust, Luxembourg, Luxembourg..
    Ottersten, Bjoern
    Luxembourg Univ, Interdisciplinary Ctr Secur Reliabil & Trust, Luxembourg, Luxembourg..
    A Framework for Optimizing Multi-cell NOMA: Delivering Demand with Less Resource2017In: GLOBECOM 2017 - 2017 IEEE Global Communications Conference, IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Non-orthogonal multiple access (NOMA) allows multiple users to simultaneously access the same time-frequency resource by using superposition coding and successive interference cancellation (SIC). Thus far, most papers on NOMA have focused on performance gain for one or sometimes two base stations. In this paper, we study multi-cell NOMA and provide a general framework for user clustering and power allocation, taking into account inter-cell interference, for optimizing resource allocation of NOMA in multi-cell networks of arbitrary topology. We provide a series of theoretical analysis, to algorithmically enable optimization approaches. The resulting algorithmic notion is very general. Namely, we prove that for any performance metric that monotonically increases in the cells' resource consumption, we have convergence guarantee for global optimum. We apply the framework with its algorithmic concept to a multi-cell scenario to demonstrate the gain of NOMA in achieving significantly higher efficiency.

  • 1168010.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Liao, Qi
    Nokia Bell Labs, D-70435 Stuttgart, Germany.
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Yuan, Di
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Resource Optimization With Flexible Numerology and Frame Structure for Heterogeneous Services2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 12, p. 2579-2582Article in journal (Refereed)
    Abstract [en]

    We explore the potential of optimizing resource allocation with flexible numerology in frequency domain and variable frame structure in time domain, with services of with different types of requirements. We prove the NP-hardness of the problem and propose a scalable optimization algorithm based on linear programming and Lagrangian duality. Numerical results show significant advantages of adopting flexibility in both time and frequency domains for capacity enhancement and meeting the requirements of mission critical services.

  • 1168011.
    You, Lei
    et al.
    Uppsala Univ, Sweden.
    Liao, Qi
    Nokia Bell Labs, Germany.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Resource Optimization With Flexible Numerology and Frame Structure for Heterogeneous Services2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 12, p. 2579-2582Article in journal (Refereed)
    Abstract [en]

    We explore the potential of optimizing resource allocation with flexible numerology in frequency domain and variable frame structure in time domain, with services of with different types of requirements. We prove the NP-hardness of the problem and propose a scalable optimization algorithm based on linear programming and Lagrangian duality. Numerical results show significant advantages of adopting flexibility in both time and frequency domains for capacity enhancement and meeting the requirements of mission critical services.

  • 1168012.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Wu, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Pan, Zhiwen
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, Jiangsu, PR China.
    Hu, Honglin
    Shanghai Research Center for Wireless Communications, Shanghai, PR China.
    Song, Junde
    PCN&CAD Center, Beijing University of Posts and Telecommunications, Beijing, PR China.
    Song, Mei
    PCN&CAD Center, Beijing University of Posts and Telecommunications, Beijing, PR China.
    Cross-layer optimization of wireless multi-hop networks with network coding2009In: 2009 International Conference on Wireless Communications and Signal Processing (WCSP), Nanjing, Kina, 2009Conference paper (Refereed)
  • 1168013.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Wu, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Song, Mei
    PCN CAD Center, Beijing University of Posts and Telecommunications, Beijing, China.
    Song, Junde
    PCN CAD Center, Beijing University of Posts and Telecommunications, Beijing, China.
    Zhang, Yong
    Cross-layer optimisation for uplink transmission in OFDMA cellular networks with fixed relays2011In: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 22, no 6, p. 296-314Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider a cross-layer design aimed to enhance performance for uplink transmission in an orthogonal frequency division multiple-access (OFDMA)-based cellular network with fixed relay stations. Because mobile stations (MSs) spend most of the power on the uplink transmission, power efficiency resource allocation becomes very important to MSs. We develop a cross-layer optimisation framework for two types of uplink flows (inelastic and elastic flows) that have different quality-of-service requirements. For inelastic flows with fixed-rate requirement, we formulate the cross-layer optimisation problem as the minimisation of the sum transmission power of MSs under the constraints of flow conservation law, subcarrier assignment, relaying path selection and power allocation. For elastic flows with flexible-service-rate requirement, we consider the cross-layer trade-off between uplink service rate and power consumption of MSs and pose the optimisation problem as the maximisation of a linear combination of utility (of service rates) and power consumption (of MSs). Different trade-offs can be achieved by varying the weighting parameters. Dual decomposition and subgradient methods are used to solve the problems optimally with reduced computational complexity. The simulation results show that, through the proposed cross-layer resource optimisation framework and algorithms, significant benefits of deployment of multiple fixed relays in an OFDMA cellular network can be fully obtained such as reduction in power consumption, increase in service rate and energy savings in the uplink transmission of MSs.

  • 1168014.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Wu, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Song, Mei
    Song, Junde
    Zhang, Yong
    Dynamic Control and Resource Allocation in Wireless-Infrastructured Distributed Cellular Networks with OFDMA2009In: 2009 INTERNATIONAL CONFERENCE ON PARALLEL PROCESSING WORKSHOPS (ICPPW 2009) / [ed] Barolli L, Feng WC, 2009, p. 337-343Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider joint optimization of end-to-end data transmission and resource allocation for Wireless-Infrastructured Distributed Cellular Networks (WIDCNs), where each base station (BS) in a cell is connected with its neighboring BSs via wireless links, and a mobile station (MS) can access one or multiple adjacent BSs simultaneously through time-varying OFDMA channels. The communications between a source MS and a destination MS are carried out with the help of BSs in the multi-hop, distributed manner. To achieve the joint optimization for such WIDCNs, a Stochastic Network Utility Maximization (SNUM) problem is formulated under the constraints of OFDMA sub-channel allocation on time-varying access links (both uplink and downlink), as well as routing and scheduling on forwarding links among BSs. By decomposing the corresponding dual problem, transforming it into a stochastic convex optimization problem and solving it by quasi-gradient method, we obtain distributed dynamic control algorithms for end-to-end data transmission. The algorithm can adapt to the OFMDA channel variation and converges asymptotically to the optimal solution. We also develop a distributed algorithm for OFDMA sub-channel allocation and link coordination between BSs. The simulation results show that the data rates of the flows can converge to optimal solution approximately, queues of the network is stable under the proposed distributed dynamic algorithm, and the multi-receiver scheme outperforms the single-receiver scheme due to diversity.

  • 1168015.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Wu, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Song, Mei
    PCN&CAD Center, Beijing University of Posts and Telecommunications, Beijing, PR China.
    Song, Junde
    PCN&CAD Center, Beijing University of Posts and Telecommunications, Beijing, PR China.
    Zhang, Yong
    PCN&CAD Center, Beijing University of Posts and Telecommunications, Beijing, PR China.
    Dynamic control and resource allocation in wireless-infrastructured distributed cellular networks with OFDMA2009In: 2nd International Workshop on Next Generation of Wireless and Mobile Networks (NGWMN), Vienna, Österrike, 2009Conference paper (Refereed)
  • 1168016.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    A Note on Decoding Order in Optimizing Multi-cell NOMAManuscript (preprint) (Other academic)
  • 1168017.
    You, Lei
    et al.
    Uppsala University, Sweden.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Uppsala University, Sweden.
    Joint CoMP-Cell Selection and Resource Allocation in Fronthaul-Constrained C-RAN2017In: 2017 15TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Cloud-based Radio Access Network (C-RAN) is a promising architecture for future cellular networks, in which Baseband Units (BBUs) are placed at a centralized location, with capacity-constrained fronthaul connected to multiple distributed Remote Radio Heads (RRHs) that are far away from the BBUs. The centralization of signal processing enables the flexibility for coordinated multi-point transmission (CoMP) to meet high traffic demand of users. We investigate how to jointly optimize CoMP-cell selection and base station resource allocation so as to enhance the quality of service (QoS), subject to the fronthaul capacity constraint in orthogonal frequency-division multiple access (OFDMA) based C-RAN. The problem is proved to be NP-hard in this paper. To deal with the computational complexity, we derive a partial optimality condition as the foundation for designing a cell-selection algorithm. Besides, we provide a solution method of the optimum of the time-frequency resource allocation problem without loss of fairness on the QoS enhancement of all users. The simulations show good performance of the proposed algorithms for jointly optimizing the cell selection and resource allocation in a C-RAN, with respect to QoS.

  • 1168018.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Joint CoMP-Cell Selection and Resource Allocation in Fronthaul-Constrained C-RAN2017In: Proc. 15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, IEEE, 2017Conference paper (Refereed)
  • 1168019.
    You, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Load Optimization With User Association in Cooperative and Load-Coupled LTE Networks2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 5, p. 3218-3231Article in journal (Refereed)
    Abstract [en]

    We extend the problem of optimizing user association for load balancing in cellular networks along 2-dimensions. First, we consider joint transmission, which is one of the coordinated multipoint techniques with which a user may be simultaneously served by multiple base stations. Second, we account for, mathematically, the coupling relation between the base stations load levels that are dependent on each other due to inter-cell interference. We formulate two optimization problems, sum load minimization (MinSumL) and maximum load minimization (MinMaxL). We prove that both MinSumL and MinMaxL are NP-hard. We propose a mixed integer linear programming based scheme by means of linearization. This approach also leads to a bounding scheme for performance benchmarking. Then, we derive a set of partial optimality conditions. Fulfillment of the conditions will guarantee performance improvement for both MinSumL and MinMaxL. A solution algorithm is then derived based on the conditions. Simulation results are provided to demonstrate the effectiveness of the approaches.

  • 1168020.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    User-centric Performance Optimization with Remote Radio Head Cooperation in C-RAN2017Manuscript (preprint) (Other academic)
  • 1168021.
    You, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Lei, Lei
    Sun, Sumei
    Chatzinotas, Symeon
    Ottersten, Björn
    Resource optimization with load coupling in multi-cell NOMA2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 7, p. 4735-4749Article in journal (Refereed)
  • 1168022.
    You, Lei
    et al.
    Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Varbrand, Peter
    Linkoping Univ, Dept Sci & Technol, S-60174 Linkoping, Sweden..
    Energy-Aware Wireless Relay Selection in Load-Coupled OFDMA Cellular Networks2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 1, p. 144-147Article in journal (Refereed)
    Abstract [en]

    We investigate transmission energy minimization via optimizing wireless relay selection in orthogonal-frequency-division multiple access networks. We take into account the impact of the load of cells on transmission energy. We prove the NP-hardness of the energy-aware wireless relay selection problem. To tackle computational complexity, a partial optimality condition is derived for providing insights in respect of designing an effective and efficient algorithm. Numerical results show the resulting algorithm achieves high energy performance.

  • 1168023.
    You, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Uppsala University, Sweden.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Värbrand, Peter
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Energy-Aware Wireless Relay Selection in Load-Coupled OFDMA Cellular Networks2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 1, p. 144-147Article in journal (Refereed)
    Abstract [en]

    We investigate transmission energy minimization via optimizing wireless relay selection in orthogonal-frequency-division multiple access networks. We take into account the impact of the load of cells on transmission energy. We prove the NP-hardness of the energy-aware wireless relay selection problem. To tackle computational complexity, a partial optimality condition is derived for providing insights in respect of designing an effective and efficient algorithm. Numerical results show the resulting algorithm achieves high energy performance.

  • 1168024.
    You, Liwen
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Computational prediction models for proteolytic cleavage and epitope identification2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The biological functions of proteins depend on their physical interactions with other molecules, such as proteins and peptides. Therefore, modeling the protein-ligand interactions is important for understanding protein functions in different biological processes. We have focused on the cleavage specificities of HIV-1 protease, HCV NS3 protease and caspases on short oligopeptides or in native proteins; the binding affinity of MHC molecules with short oligopeptides and identification of T cell epitopes. we expect that our findings on HIV-1 protease, HCV NS3 protease and caspases generalize to other proteases. In this thesis, we have performed analysis on these interactions from different perspectives - we have extended and collected new substrate data sets; used and compared different prediction methods (e.g. linear support vector machines, neural networks, OSRE method, rough set theory and Gaussian processes) to understand the underlying interaction problems; suggested new methods (i.e. a hierarchical method and Gaussian processes with test reject method) to improve predictions; and extracted cleavage rules for protease cleavage specificities. From our studies, we have extended oligopeptide substrate data sets and collected native protein substrates for HIV-1 protease, and a new oligopeptide substrate data set for HCV protease. We have shown that all current HIV-1 protease oligopeptide substratde data sets and our HCV data set are linearly separable; for HIV-1 protease, size and hydrophobicity are two important physicochemical properties in the recognition of short oligopeptide substrates to the protease; and linear support vector mahine is the state-of-the-art for this protease cleavage prediction problem. Our hierarchical method combining protein secondary structure information and experimental short oligopeptide cleavage information an improve the prediction of HIV-1 protease cleavage sites in native proteins. Our rule extraction method provides simple an accurate cleavage rules with high fidelity for HIV-1 and HCV proteases. For MHC molecules, we showed that high binding affinities are not necessarily correlated to immunogenicity on HLA-restricted peptides. Our test reject method combined with Gaussian processes can simplify experimental design by reducing false positives for detecting potential epitopes in large pathogen genomes.

  • 1168025.
    You, Liwen
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Detection of cleavage sites for HIV-1 protease in native proteins2006In: Proceedings of LSS Computational Systems Bioinformatics Conference: Computational Systems Bioinformatics Conference (vol. 5), Imperial College Press, 2006, p. 249-256Conference paper (Refereed)
    Abstract [en]

    Predicting novel cleavage sites for HIV-1 protease in non-viral proteins is a difficult task because of the scarcity of previous cleavage data on proteins in a native state. We introduce a three-level hierarchical classifier which combines information from experimentally verified short oligopeptides, secondary structure and solvent accessibility information from prediction servers to predict potential cleavage sites in non-viral proteins. The best classifier using secondary structure information on the second level classification of the hierarchical classifier is the one using logistic regression. By using this level of classification, the false positive ratio was reduced by more than half compared to the first level classifier using only the oligopeptide cleavage information. The method can be applied on other protease specificity problems too, to combine information from oligopeptides and structure from native proteins.

  • 1168026. You, Liwen
    et al.
    Garwicz, Daniel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Klinisk kemi och farmakologi.
    Rögnvaldsson, Thorsteinn
    Comprehensive bioinformatic analysis of the specificity of human immunodeficiency virus type 1 protease.2005In: J Virol, ISSN 0022-538X, Vol. 79, no 19, p. 12477-86Article in journal (Refereed)
    Abstract [en]

    Rapidly developing viral resistance to licensed human immunodeficiency virus type 1 (HIV-1) protease inhibitors is an increasing problem in the treatment of HIV-infected individuals and AIDS patients. A rational design of more effective protease inhibitors and discovery of potential biological substrates for the HIV-1 protease require accurate models for protease cleavage specificity. In this study, several popular bioinformatic machine learning methods, including support vector machines and artificial neural networks, were used to analyze the specificity of the HIV-1 protease. A new, extensive data set (746 peptides that have been experimentally tested for cleavage by the HIV-1 protease) was compiled, and the data were used to construct different classifiers that predicted whether the protease would cleave a given peptide substrate or not. The best predictor was a nonlinear predictor using two physicochemical parameters (hydrophobicity, or alternatively polarity, and size) for the amino acids, indicating that these properties are the key features recognized by the HIV-1 protease. The present in silico study provides new and important insights into the workings of the HIV-1 protease at the molecular level, supporting the recent hypothesis that the protease primarily recognizes a conformation rather than a specific amino acid sequence. Furthermore, we demonstrate that the presence of 1 to 2 lysine residues near the cleavage site of octameric peptide substrates seems to prevent cleavage efficiently, suggesting that this positively charged amino acid plays an important role in hindering the activity of the HIV-1 protease.

  • 1168027.
    You, Liwen
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Garwicz, Daniel
    Division of Hematology and Transfusion Medicine, Department of Laboratory Medicine, Lund University, Lund, Sweden.
    Rögnvaldsson, Thorsteinn
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Comprehensive Bioinformatic Analysis of the Specificity of Human Immunodeficiency Virus Type 1 Protease2005In: Journal of Virology, ISSN 0022-538X, E-ISSN 1098-5514, Vol. 79, no 19, p. 12477-12486Article in journal (Refereed)
    Abstract [en]

    Rapidly developing viral resistance to licensed human immunodeficiency virus type 1 (HIV-1) protease inhibitors is an increasing problem in the treatment of HIV-infected individuals and AIDS patients. A rational design of more effective protease inhibitors and discovery of potential biological substrates for the HIV-1 protease require accurate models for protease cleavage specificity. In this study, several popular bioinformatic machine learning methods, including support vector machines and artificial neural networks, were used to analyze the specificity of the HIV-1 protease. A new, extensive data set (746 peptides that have been experimentally tested for cleavage by the HIV-1 protease) was compiled, and the data were used to construct different classifiers that predicted whether the protease would cleave a given peptide substrate or not. The best predictor was a nonlinear predictor using two physicochemical parameters (hydrophobicity, or alternatively polarity, and size) for the amino acids, indicating that these properties are the key features recognized by the HIV-1 protease. The present in silico study provides new and important insights into the workings of the HIV-1 protease at the molecular level, supporting the recent hypothesis that the protease primarily recognizes a conformation rather than a specific amino acid sequence. Furthermore, we demonstrate that the presence of 1 to 2 lysine residues near the cleavage site of octameric peptide substrates seems to prevent cleavage efficiently, suggesting that this positively charged amino acid plays an important role in hindering the activity of the HIV-1 protease.

  • 1168028.
    You, Liwen
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Rögnvaldsson, Thorsteinn
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Almost Linear Biobasis Function Neural Networks2007In: The 2007 International Joint Conference on Neural Networks: IJCNN 2007 conference proceedings : August 12-17, 2007, Resaissance Orlando Resort, Orlando, Florida, USA, Piscataway, N.J.: IEEE Press, 2007, p. 1774-1778Conference paper (Other academic)
    Abstract [en]

    An analysis of biobasis function neural networks is presented, which shows that the similarity metric used is a linear function and that bio-basis function neural networks therefore often end up being just linear classifiers in high dimensional spaces. This is a consequence of four things: the linearity of the distance measure, the normalization of the distance measure, the recommended default values of the parameters, and that biological data sets are sparse.

  • 1168029.
    You, Liwen
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Zhang, Ping
    School of Land, Crop, and Food Sciences, University of Queensland, Brisbane, QLD, Australia.
    Bodén, Mikael
    School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, QLD, Australia.
    Brusic, Vladimir
    School of Land, Crop, and Food Sciences, University of Queensland, Brisbane, QLD, Australia.
    Understanding Prediction Systems for HLA-Binding Peptides and T-Cell Epitope Identification2007In: Pattern Recognition in Bioinformatics: Proceedings / [ed] Rajapakse, J C, Schmidt, B, Volkert, G, Berlin: Springer Berlin/Heidelberg, 2007, p. 337-348Conference paper (Refereed)
    Abstract [en]

    Peptide binding to HLA molecules is a critical step in induction and regulation of T-cell mediated immune responses. Because of combinatorial complexity of immune responses, systematic studies require combination of computational methods and experimentation. Most of available computational predictions are based on discriminating binders from non-binders based on use of suitable prediction thresholds. We compared four state-of-the-art binding affinity prediction models and found that nonlinear models show better performance than linear models. A comprehensive analysis of HLA binders (A*0101, A*0201, A*0301, A*1101, A*2402, B*0702, B*0801 and B*1501) showed that non-linear predictors predict peptide binding affinity with high accuracy. The analysis of known T-cell epitopes of survivin and known HIV T-cell epitopes showed lack of correlation between binding affinity and immunogenicity of HLA-presented peptides. T-cell epitopes, therefore, can not be directly determined from binding affinities by simple selection of the highest affinity binders.

  • 1168030. You, Qiangwei
    et al.
    Liu, Yongsheng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Polytechnical University, Xi’an, Shanxi, PR China.
    Wan, Jiajia
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Li, Hongxia
    Yuan, Bo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Sinosteel Luoyang Institute of Refractories Research Co., Ltd, PR China.
    Cheng, Laifei
    Wang, Gang
    Microstructure and properties of porous SiC ceramics by LPCVI technique regulation2017In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 43, no 15, p. 11855-11863Article in journal (Refereed)
    Abstract [en]

    A new gradient pore structure in porous SiC ceramics was fabricated by low pressure chemical vapor infiltration (LPCVI). Effects of deposition duration on the mechanical properties and permeability of porous SiC ceramics were investigated. Results demonstrated that pore diameter and shapes decreased from the surface to the interior along with LPCVI duration. Porous SiC ceramics with deposition duration of 160 h exhibited flexural strength of 48.05 MPa and fracture toughness of 1.30 MPa m(1/2), where 221% and 189% improvements were obtained compared to porous SiC ceramics without LPCVI, due to CVI-SiC layer strengthening effect. Additionally, at the same gas velocity, pressure drop increase rate was faster due to apparent porosity and pore size change.

  • 1168031.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kunz, Daniel
    Stöter, Matthias
    Kalo, Hussein
    Putz, Bernd
    Breu, Josef
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pressure-induced water insertion in synthetic clays2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 14, p. 3891-3895Article in journal (Refereed)
  • 1168032.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Szabo, Tamas
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Effect of synthesis method on solvation and exfoliation of graphite oxide2013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 52, p. 171-180Article in journal (Refereed)
    Abstract [en]

    Graphite oxides (GOs) synthesized by Brodie’s and Hummers’ methods are significantly different with respect to hydration, solvation and exfoliation properties. Hummers GO is more easily intercalated by liquid water and alcohols, exhibiting osmotic type of swelling. In contrast, Brodie GO shows crystalline swelling in alcohol solvents with step-like insertion of methanol or ethanol monolayers. However, the stronger hydration and easier dispersion in water observed for Hummers GO do not correlate with better dispersion of graphene powder obtained by thermal exfoliation. Higher surface area graphene powder was obtained by exfoliation of Brodie GO, while the temperature of its exfoliation is about 75 C higher than that for the studied sample of Hummers GO. It is suggested that higher exfoliation temperature and better crystallinity of GO are important factors for preparation of graphene powder using thermal exfoliation.

  • 1168033.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Phase transitions in graphite oxide solvates at temperatures near ambient2012In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 3, no 7, p. 812-817Article in journal (Refereed)
    Abstract [en]

    It is demonstrated that solvent-saturated graphite oxide can be considered to be solid solvate, and two phases with distinctly different solvent composition are found near room temperature. Phase transitions between these two solvated phases were observed using synchrotron powder X-ray diffraction and DSC for methanol, ethanol, acetone, and dimethylformamide (DMF) solvents. Solvate A, formed at room temperature, undergoes a reversible phase transition into expanded Solvate L at temperatures slightly below ambient due to insertion of one monolayer of solvent molecules between the GO planes. The phase transition is reversible upon heating, whereas the low-temperature expanded phase L can be quenched to room temperature for ethanol and DMF solvates.

  • 1168034. You, Shujie
    et al.
    Mases, Mattias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Green, Alexander A.
    Department of Materials Science and Engineering, Northwestern University, Evanston, IL.
    Hersam, Mark C.
    Department of Materials Science and Engineering, Northwestern University, Evanston, IL.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Probing structural stability of double-walled carbon nanotubes at high non-hydrostatic pressure by Raman spectroscopy2011In: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 31, no 1, p. 186-190Article in journal (Refereed)
    Abstract [en]

    Theoretical calculations predict that the collapse pressure for double-walled carbon nanotubes (DWCNTs) is proportional to 1/R3, where R is the effective or average radius of a DWCNT. In order to address the problem of CNT stability at high pressure and stress, we performed a resonance Raman study of DWCNTs dispersed in sodium cholate using 532 and 633 nm laser excitation. Raman spectra of the recovered samples show minor versus irreversible changes with increasing ID/IG ratio after exposure to high non-hydrostatic pressure of 23 and 35 GPa, respectively. The system exhibits nearly 70% pressure hysteresis in radial breathing vibrational mode signals recovery on pressure release which is twice that predicted by theory.

  • 1168035.
    You, Shujie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Patelli, Alessandro
    Department of Physics and Astronomy, University of Padova, Padova, Italy.
    Ghamgosar, Pedram
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cesca, Tiziana
    Department of Physics and Astronomy, University of Padova, Padova, Italy.
    Enrichi, Francesco
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Venezia Mestre, Italy.
    Mattei, Giovanni
    Department of Physics and Astronomy, University of Padova, Padova, Italy.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tuning ZnO nanorods photoluminescence through atmospheric plasma treatments2019In: APL Materials, ISSN 2166-532X, Vol. 7, no 8, article id 08111Article in journal (Refereed)
    Abstract [en]

    Room temperature atmospheric plasma treatments are widely used to activate and control chemical functionalities at surfaces. Here, we investigated the effect of atmospheric pressure plasma jet (APPJ) treatments in reducing atmosphere (Ar/1‰ H2 mixture) on the photoluminescence (PL) properties of single crystal ZnO nanorods (NRs) grown through hydrothermal synthesis on fluorine-doped tin oxide glass substrates. The results were compared with a standard annealing process in air at 300 °C. Steady-state photoluminescence showed strong suppression of the defect emission in ZnO NRs for both plasma and thermal treatments. On the other side, the APPJ process induced an increase in PL quantum efficiency (QE), while the annealing does not show any improvement. The QE in the plasma treated samples was mainly determined by the near band-edge emission, which increased 5–6 fold compared to the as-prepared samples. This behavior suggests that the quenching of the defect emission is related to the substitution of hydrogen probably in zinc vacancies (VZn), while the enhancement of UV emission is due to doping originated by interstitial hydrogen (Hi), which diffuses out during annealing. Our results demonstrate that atmospheric pressure plasma can induce a similar hydrogen doping as ordinarily used vacuum processes and highlight that the APPJ treatments are not limited to the surfaces but can lead to subsurface modifications. APPJ processes at room temperature and under ambient air conditions are stable, convenient, and efficient methods, compared to thermal treatments to improve the optical and surface properties of ZnO NRs, and remarkably increase the efficiency of UV emission.

  • 1168036.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Enormous lattice expansion of hummers graphite oxide in alcohols at low temperatures2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 2, p. 1395-1399Article in journal (Refereed)
    Abstract [en]

    A structural study of swelling of Hummers graphite oxide (H-GO) in excess of liquid alcohols was performed as a function of temperature using synchrotron X-ray diffraction and revealed a strong “negative thermal expansion” effect. The increase of the distance between graphene oxide layers is explained by insertion of additional solvent upon cooling of the H-GO/solvent system. The interlayer distance of H-GO is found to increase gradually upon temperature decrease, reaching 19.4 and 20.6 Å at 140 K for methanol and ethanol, respectively. The gradual expansion of the H-GO lattice upon cooling corresponds to insertion of at least two additional solvent monolayers and can be described as osmotic swelling. This phenomenon is distinctly different from the solvation of Brodie graphite oxide (B-GO), which was found earlier to exhibit crystalline swelling: single-step insertion of an additional solvent monolayer at low temperatures. The enormous structural expansion of H-GO at low temperatures is suggested to be useful for solution-based intercalation of graphite oxide with relatively large molecules and the synthesis of various composite materials.

  • 1168037.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Belyaeva, L. A.
    Avramenko, Natalya V.
    Korobov, Mikhail V.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Selective Intercalation of Graphite Oxide by Methanol in Water/Methanol Mixtures2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 4, p. 1963-1968Article in journal (Refereed)
    Abstract [en]

    Graphite oxide is selectively intercalated by methanol when exposed to liquid water/methanol mixtures with methanol fraction in the range 20-100%. Insertion of water into the GO structure occurs only when the content of water in the mixture with methanol is increased up to 90%. This conclusion is confirmed by both ambient temperature XRD data and specific temperature variations of the GO structure due to insertion/deinsertion of an additional methanol monolayer observed upon cooling/heating. The composition of GO-methanol solvate phases was determined for both low temperature and ambient temperature phases. Understanding of graphite oxide structural properties in binary water/methanol mixtures is important for the unusual permeation properties of graphene oxide membranes for water and alcohols. It is suggested that graphite oxide prepared by Brodie's method can be used for purification of water using selective extraction of methanol from water/alcohol mixtures.

  • 1168038.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Solvation of graphite oxide in water-methanol binary polar solvents2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2568-2571Article in journal (Refereed)
    Abstract [en]

    The phase transition between two solvated phases was studied by DSC for graphite oxide (GO) powders immersed in water–methanol mixtures of various compositions. GO forms solid solvates with two different compositions when immersed in methanol. Reversible phase transition between two solvate states due to insertion/desertion of methanol monolayer occurs upon temperature variations. The temperature point and the enthalpy (DH) of the phase transition are maximal for pure methanol and decrease linearly with increase of water fraction up to 30%.

     

  • 1168039. You, TS
    et al.
    Lidin, Sven
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Gourdon, O
    To What Extent Does the Zintl-Klemm Formalism Work? : The Eu(Zn1-xGex)(2) Series2009In: Inroganic Chemistry, Vol. 48, no 14, p. 6380-6390Article in journal (Refereed)
    Abstract [en]

    The series of ternary polar intermetallics Eu(Zn1−xGex)2 (0 ≤ x ≤ 1) has been investigated and characterized by powder and single-crystal X-ray diffraction as well as physical property measurements. For 0.50(2) ≤ x < 0.75(2), this series shows a homogeneity width of hexagonal AlB2-type phases (space group P6/mmm, Pearson symbol hP3) with Zn and Ge atoms statistically distributed in the planar polyanionic 63 nets. As the Ge content increases in this range, a decreases from 4.3631(6) Å to 4.2358(6) Å, while c increases from 4.3014(9) Å to 4.5759(9) Å, resulting in an increasing c/a ratio. Furthermore, the Zn−Ge bond distance in the hexagonal net drops from 2.5190(3) Å to 2.4455(3) Å, while the anisotropy of the displacement ellipsoids significantly increases along the c direction. For x < 0.50 and x > 0.75, respectively, orthorhombic KHg2-type and trigonal EuGe2-type phases occur as a second phase in mixtures with an AlB2-type phase. Diffraction of the x = 0.75(2) sample shows incommensurate modulation along the c direction; a structural model in super space group P31(00γ)00s reveals puckered 63 nets. Temperature-dependent magnetic susceptibility measurements for two AlB2-type compounds show Curie−Weiss behavior above 40.0(2) K and 45.5(2) K with magnetic moments of 7.98(1) μB for Eu(Zn0.48Ge0.52(2))2 and 7.96(1) μB for Eu(Zn0.30Ge0.70(2))2, respectively, indicating a (4f)7 electronic configuration for Eu atoms (Eu2+). The Zintl−Klemm formalism accounts for the lower limit of Ge content in the AlB2-type phases but does not identify the observed upper limit. In a companion paper, the intrinsic relationships among chemical structures, compositions, and electronic structures are analyzed by electronic structure calculations.

  • 1168040.
    You, Wenjing
    et al.
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Tengdin, Phoebe
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Chen, Cong
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Shi, Xun
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Zusin, Dmitriy
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Zhang, Yingchao
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Gentry, Christian
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Blonsky, Adam
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Keller, Mark
    NIST, 325 Broadway, Boulder, CO 80305 USA.
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kapteyn, Henry
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Tao, Zhensheng
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;Fudan Univ, Dept Phys, State Key Lab Surface Phys, Shanghai 200438, Peoples R China;NIST, Boulder, CO 80309 USA.
    Murnane, Margaret
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA;Univ Colorado, JILA, Boulder, CO 80309 USA;NIST, Boulder, CO 80309 USA.
    Revealing the Nature of the Ultrafast Magnetic Phase Transition in Ni by Correlating Extreme Ultraviolet Magneto-Optic and Photoemission Spectroscopies2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 7, article id 077204Article in journal (Refereed)
    Abstract [en]

    By correlating time-and angle-resolved photoemission and time-resolved transverse magneto-optical Kerr effect measurements, both at extreme ultraviolet wavelengths, we uncover the universal nature of the ultrafast photoinduced magnetic phase transition in Ni. This allows us to explain the ultrafast magnetic response of Ni at all laser fluences-from a small reduction of the magnetization at low laser fluences, to complete quenching at high laser fluences. Both probe methods exhibit the same demagnetization and recovery timescales. The spin system absorbs the energy required to proceed through a magnetic phase transition within 20 fs after the peak of the pump pulse. However, the spectroscopic signatures of demagnetization of the material appear only after approximate to 200 fs and the subsequent recovery of magnetization on timescales ranging from 500 fs to >70 ps. We also provide evidence of two competing channels with two distinct timescales in the recovery process that suggest the presence of coexisting phases in the material.

  • 1168041.
    You, Xin
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Wang, Yongchun
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Implementation of a Function Generator2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Function generator has been widely used in each electronics fields recent years. In this thesis, the authors will introduce some basic structure and working principles of a function generator, moreover a function generator which can create three kinds of wave: sine wave, square wave and triangle wave has been implemented. There are many ways to build the function generator; a method of combine the operational amplifier and discrete components is introduced in this thesis. First use the RC Wien bridge oscillator to achieve sinusoidal wave; and convert it into square wave by using the shaping circuit. Lastly, use the integrating circuit to obtain triangle wave. The basic simulation software Multisim has been used to simulate the circuit.

  • 1168042.
    You, Yang
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Li, Zuxing
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Optimal Privacy-Enhancing and Cost-Efficient Energy Management Strategies for Smart Grid Consumers2018In: 2018 IEEE Statistical Signal Processing Workshop, SSP 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 144-148Conference paper (Refereed)
    Abstract [en]

    The design of optimal energy management strategies that trade-off consumers' privacy and expected energy cost by using an energy storage is studied. The Kullback-Leibler divergence rate is used to assess the privacy risk of the unauthorized testing on consumers' behavior. We further show how this design problem can be formulated as a belief state Markov decision process problem so that standard tools of the Markov decision process framework can be utilized, and the optimal solution can be obtained by using Bellman dynamic programming. Finally, we illustrate the privacy-enhancement and cost-saving by numerical examples. 

  • 1168043.
    You, Yang
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Qin, Chong
    Gong, Yi
    Resource Allocation for a Full-Duplex Base Station Aided OFDMA System2017In: PROCEEDINGS OF THE 2ND INTERNATIONAL CONFERENCE ON EDUCATIONAL MANAGEMENT AND ADMINISTRATION (COEMA 2017) / [ed] Kusumaningrum, D E, ATLANTIS PRESS , 2017Conference paper (Refereed)
    Abstract [en]

    Exploiting full-duplex (FD) technology on base stations (BSs) is a promising solution to enhancing the system performance. Motivated by this, we revisit a full-duplex base station (FD-BS) aided OFDMA system, which consists of one BS, several uplink/downlink users and multiple subcarriers. A joint 3-dimensional (3D) mapping scheme among subcarriers, down-link users (DUEs), uplink users (UUEs) is considered as well as an associated power allocation optimization. In detail, we first decompose the complex 3D mapping problem into three 2-dimensional sub ones and solve them by using the iterative Hungarian method, respectively. Then based on the Lagrange dual method, we sequentially solve the power allocation and 3-dimensional mapping problem by fixing a dual point. Finally, the optimal solution can be obtained by utilizing the sub-gradient method. Unlike existing work that only solves either 3D mapping or power allocation problem but with a high computation complexity, we tackle both of them and have successfully reduced computation complexity from exponential to polynomial order. Numerical simulations are conducted to verify the proposed scheme.

  • 1168044.
    You, Yantian
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Cloud Auto-Scaling Control Engine Based on Machine Learning2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the development of modern data centers and networks, many service providers have moved most of their computing functions to the cloud.  Considering the limitation of network bandwidth and hardware or virtual resources, how to manage different virtual resources in a cloud environment so as to achieve better resource allocation is a big problem.  Although some cloud infrastructures provide simple default auto-scaling and orchestration mechanisms, such as OpenStack Heat service, they usually only depend on a single parameter, such as CPU utilization and cannot respond to the network changes in a timely manner.<p> This thesis investigates different auto-scaling mechanisms and designs an on-line control engine that cooperates with different OpenStack service APIs based on various network resource data.  Two auto-scaling engines, Heat orchestration based engine and machine learning based online control engine, have been developed and compared for different client requests patterns.  Two machine learning methods, neural network, and linear regression have been considered to generate a control signal based on real-time network data.  This thesis also shows the network’s non-linear behaviors for heavy traffic and proposes a scaling policy based on deep network analysis.<p> The results show that for offline training, the neural network and linear regression provide 81.5% and 84.8% accuracy respectively.  However, for online testing with different client request patterns, the neural network results are different than we expected, while linear regression provided us with much better results.  The model comparison showed that these two auto-scaling mechanisms have similar behavior for a SMOOTH-load Pattern.  However, for the SPIKEY-load Pattern, the linear regression based online control engine responded faster to network changes while heat orchestration service shows some delay.  Compared with the proposed scaling policy with fewer web servers in use and acceptable response latency, both of the two auto-scaling models waste network resources.

  • 1168045.
    You, Yantian
    KTH, School of Information and Communication Technology (ICT).
    Sparsity Analysis of Deep Learning Models and Corresponding Accelerator Design on FPGA2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Machine learning has achieved great success in recent years, especially the deep learning algorithms based on Artificial Neural Network. However, high performance and large memories are needed for these models , which makes them not suitable for IoT device, as IoT devices have limited performance and should be low cost and less energy-consuming. Therefore, it is necessary to optimize the deep learning models to accommodate the resource-constrained IoT devices.

    This thesis is to seek for a possible solution of optimizing the ANN models to fit into the IoT devices and provide a hardware implementation of the ANN accelerator on FPGA. The contribution of this thesis mainly lies in two aspects: 1). analyze the sparsity in the two mainstream deep learning models – DBN and CNN. The DBN model consists of two hidden layers with Restricted Boltzmann Machines while the CNN model consists of 2 convolutional layers and 2 sub-sampling layer. Experiments have been done on the MNIST data set with the sparsity of 75%. The ratio of the multiplications resulting in near-zero values has been tested. 2). FPGA implementation of an ANN accelerator. This thesis designed a hardware accelerator for the inference process in ANN models on FPGA (Stratix IV: EP4SGX530KH40C2). The main part of hardware design is the processing array consists of 256 Multiply-Accumulators array, which can conduct multiply-accumulate operations of 256 synaptic connections simultaneously. 16-bit fixed point computation is used to reduce the hardware complexity, thus saving power and area.

    Based on the evaluation results, it is found that the ratio of the multiplications under the threshold of 2-5 is 75% for CNN with ReLU activation function, and is 83% for DBN with sigmoid activation function, respectively. Therefore, there still exists large space for complex ANN models to be optimized if the sparsity of data is fully utilized. Meanwhile, the implemented hardware accelerator is verified to provide correct results through 16-bit fixed point computation, which can be used as a hardware testing platform for evaluating the ANN models.

  • 1168046. You, Yintao
    et al.
    Yang, Kunlong
    Yuan, Sijian
    Dong, Shiqi
    Zhang, Huotian
    Huang, Qinglan
    Gillin, William P.
    Zhan, Yiqiang
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    An organic multilevel non-volatile memory device based on multiple independent switching modes2014In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 15, no 9, p. 1983-1989Article in journal (Refereed)
    Abstract [en]

    The demand for higher data density memory structures is greater today than ever before. Multilevel resistive organic memory devices (OMD) provide an ideal solution, in being easily fabricated, cost-effective and at the same time promising high storage capacity. However, conventional methods for multilevel OMDs impose demanding requirements on material properties and attain only limited performance. We hereby provide an alternative design concept that combines multiple switching modes in one device to realize multilevel function. The device possesses a simple structure by using a ferroelectric phase-separated blend as the active layer. Two switching modes, the ferroelectric switching and the metallic filament switching, are realized simultaneously in this device, and enable a ternary storage function. The cross-section scanning electron microscope (SEM) images provide a strong evidence of the formation and annihilation of the metallic filament.

  • 1168047.
    You, You
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Chen, Daxin
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Modal Analysis on a MIMO System: For an asphalt roller CC12002015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Impact hammer is the current modal testing way in Dynapac testing department. Due to highly damped characteristic of big construction machines, there are a few weaknesses for modal testing when using hammer, such as short response time, limited frequency resolution, poor quality of frequency response functions. Therefore, a more advanced excitation equipment is needed to improve the measurement quality.

    The object for this study is to compare two different measuring methods. The thesis will show a comparison between the hammer testing and the shaker MIMO testing compared with analytical model in a highly damped system. It will also give a reference for further highly damped modal analysis and budgetary assessment to decide the budget expenditure.

    Result from shaker testing shows a little better correlation than hammer testing compared with FEM model. While the correlation between FEM model and measurement is bad due to many reasons, such as many local modes that can not excited, lack of excitation points, unexpected noise and error from the measurement. While considering the compared results obtained from this machine for now, a simpler structure experiment is suggested to be carried on in the future. Shorter length of stinger can be used to enable higher amplitude of force to excite the property on this machine.

  • 1168048. You, Yuan
    et al.
    Sawikowska, Aneta
    Lee, Joanne E.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Benstein, Ruben M.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Neumann, Manuela
    Krajewski, Pawel
    Schmid, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Max Planck Institute for Developmental Biology, Department of Molecular Biology, Tübingen, Germany; Beijing Advanced Innovation Centre for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, People’s Republic of China.
    Phloem Companion Cell-Specific Transcriptomic and Epigenomic Analyses Identify MRF1, a Regulator of Flowering2019In: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 31, no 2, p. 325-345Article in journal (Refereed)
    Abstract [en]

    The phloem plays essential roles in the source-to-sink relationship and in long-distance communication, and thereby coordinates growth and development throughout the plant. Here we employed isolation of nuclei tagged in specific cell types coupled with low-input, high-throughput sequencing approaches to analyze the changes of the chromatin modifications H3K4me3 and H3K27me3 and their correlation with gene expression in the phloem companion cells (PCCs) of Arabidopsis (Arabidopsis thaliana) shoots in response to changes in photoperiod. We observed a positive correlation between changes in expression and H3K4me3 levels of genes that are involved in essential PCC functions, including regulation of metabolism, circadian rhythm, development, and epigenetic modifications. By contrast, changes in H3K27me3 signal appeared to contribute little to gene expression changes. These genomic data illustrate the complex gene-regulatory networks that integrate plant developmental and physiological processes in the PCCs. Emphasizing the importance of cell-specific analyses, we identified a previously uncharacterized MORN-motif repeat protein, MORN-MOTIF REPEAT PROTEIN REGULATING FLOWERING1 (MRF1), that was strongly up-regulated in the PCCs in response to inductive photoperiod. The mrf1 mutation delayed flowering, whereas MRF1 overexpression had the opposite effect, indicating that MRF1 acts as a floral promoter.

  • 1168049. You, Yuan
    et al.
    Sawikowska, Aneta
    Neumann, Manuela
    Pose, David
    Capovilla, Giovanna
    Langenecker, Tobias
    Neher, Richard A.
    Krajewski, Pawel
    Schmid, Markus
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Molecular Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
    Temporal dynamics of gene expression and histone marks at the Arabidopsis shoot meristem during flowering2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 15120Article in journal (Refereed)
    Abstract [en]

    Plants can produce organs throughout their entire life from pluripotent stem cells located at their growing tip, the shoot apical meristem (SAM). At the time of flowering, the SAM of Arabidopsis thaliana switches fate and starts producing flowers instead of leaves. Correct timing of flowering in part determines reproductive success, and is therefore under environmental and endogenous control. How epigenetic regulation contributes to the floral transition has eluded analysis so far, mostly because of the poor accessibility of the SAM. Here we report the temporal dynamics of the chromatin modifications H3K4me3 and H3K27me3 and their correlation with transcriptional changes at the SAM in response to photoperiod-induced flowering. Emphasizing the importance of tissue-specific epigenomic analyses we detect enrichments of chromatin states in the SAM that were not apparent in whole seedlings. Furthermore, our results suggest that regulation of translation might be involved in adjusting meristem function during the induction of flowering.

  • 1168050. You, Z-B
    et al.
    Herrera-Marschitz, M
    Pettersson, E
    Nylander, Ingrid
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Goiny, M
    Shou, H.-Z
    Kehr, J
    Godukhin, O
    Hokfelt, T
    Terenius, L
    Ungerstedt, U
    Modulation of neurotransmitter release by cholecystokinin in neostriatum and substantia nigra of the rat: regional and receptor specificity1996In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 74, no 3, p. 793-804Article in journal (Refereed)
    Abstract [en]

    The effect of cholecystokinin peptides on the release of dynorphin B, aspartate, glutamate, dopamine and GABA in the neostriatum and substantia nigra of the rat was investigated using in vivo microdialysis. Sulphated cholecystokinin-8S in the dialysis perfusate (1-100 microM) induced a concentration-dependent increase in extracellular dynorphin B and aspartate levels, both in the neostriatum and substantia nigra. Striatal dopamine levels were only increased by 100 microM of cholecystokinin-8S, while in the substantia nigra they were increased by 10-100 microM of cholecystokinin-8S. Extracellular GABA and glutamate levels were increased following 100 microM of cholecystokinin-8S only. Striatal cholecystokinin-8S administration also produced a significant increase in nigral dynorphin B levels. Local cholecystokinin-4 (100 microM) produced a moderate, but significant, increase of extracellular dynorphin B and aspartate levels in the neostriatum and substantia nigra. No effect was observed on the other neurotransmitters investigated. A 6-hydroxydopamine lesion of the nigrostriatal dopamine pathway did not affect the increases in dynorphin B and aspartate levels produced by local administration of cholecystokinin-8S. Basal extracellular GABA levels were increased significantly in both the neostriatum and substantia nigra ipsilateral to the lesion. Nigral glutamate and aspartate levels were also increased in the lesioned substantia nigra, but in the lesioned neostriatum aspartate levels were decreased. The cholecystokinin-B antagonist L-365,260 (20 mg/kg, s.c.), but not the cholecystokinin-A antagonist L-364,718 (devazepide; 20 mg/kg, s.c.), significantly inhibited the effect of cholecystokinin-8S on striatal dynorphin B and aspartate levels. In the substantia nigra, however, the effect of cholecystokinin-8S on dynorphin B and aspartate levels was inhibited to a similar extent by both L-365,260 and L-364,718. Pretreatment with L-364,718, but not with L-365.260, prevented the increase in nigral dopamine levels produced by nigral cholecystokinin-8S administration. Taken together, these results suggest that cholecystokinin-8S modulates dynorphin B and aspartate release in the neostriatum and substantia nigra of the rat via different receptor mechanisms. In the neostriatum, the effect of cholecystokinin-8S on dynorphin B and aspartate release is mediated via the cholecystokinin-B receptor subtype, while in the substantia nigra, cholecystokinin-8S modulates dynorphin B and aspartate release via both cholecystokinin-A and cholecystokinin-B receptor subtypes. Cholecystokinin-8S modulates dopamine release mainly in the substantia nigra, via the cholecystokinin-A receptor subtype.

23358233592336023361233622336323364 1168001 - 1168050 of 1209152
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf