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  • 1157951.
    Zhang, Hanmin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Sakamoto, K.
    Graduate School of Advanced Integration Science, Chiba University, Chiba 266-8522, Japan.
    Uhrberg, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Surface electronic structures of Au-induced reconstructions on the Ag/Ge(1 1 1) v3 × v3 surface2003In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 532-535, p. 934-939Article in journal (Refereed)
    Abstract [en]

    A small amount of Au atoms deposited at room temperature transforms the Ag/Ge(1 1 1)v3 × v3 surface into a v 39 × v39 surface. The presence of the Au atoms leads to downward shifts and modifications of the surface state bands compared to the initial v3 × v3 surface. Further deposition of Au on the v39 × v39 surface changes it into a 6 × 6 periodicity. At the same time the surface electronic structure changes from a metallic to a semiconducting phase with a gap of around 0.2 eV with respect to the Fermi-level. Finally, the 6 × 6 phase transforms into a new 2v3 × 2v3 phase when more Au is added, and the surface switches back to a metallic state. © 2003 Elsevier Science B.V. All rights reserved.

  • 1157952.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Sakamoto, Kazuyuki
    Hansson, G.V.
    Uhrberg, R.I.G.
    High temperature annealing and surface photovoltage shifts on Si(111)7x72008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 3Article in journal (Refereed)
  • 1157953.
    Zhang, Hanmin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Sakamoto, Kazuyuki
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Uhrberg, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Comprehensive study of the metal/semiconductor character of adatom-induced Ag/Si(111) reconstructions2001In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 64, no 24Article in journal (Refereed)
    Abstract [en]

    A √21×√21 reconstruction can be formed by either Ag or Au adsorption on the Ag/Si(111) √3×√3 surface. The electronic structures determined by angle-resolved photoemission from these two √21×√21 surfaces show clear similarities. The presence of the extra Ag or Au adatoms results in a metallic surface with two surface state bands near the Fermi level. Only one of these bands crosses the Fermi level instead of two as reported in the literature. A tiny amount of Ag deposited onto the √21×√21-Ag surface below 100 K transforms it into a 6×6 periodicity. The additional Ag leads to an interesting transition from the metallic √21×√21 surface to a semiconducting 6×6 surface with a gap of about 0.2 eV with respect to the Fermi level.

  • 1157954.
    Zhang, Hanmin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Sakamoto, Kazuyuki
    Department of Physics, Graduate School of Science, Tohoku University, Japan.
    Uhrberg, Roger I.G.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Surface electronic structure of K- and Cs-induced √21×√21 phases on Ag∕Si(111)√3×√32004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 24, p. 245301-Article in journal (Refereed)
    Abstract [en]

    A √21×√21 reconstruction has been formed by adding either K or Cs atoms on the Ag∕Si(111)√3×√3 surface at 120 K. The electronic structures of these surfaces have been studied by angle-resolved valence band and core-level spectroscopy. In similarity with Ag or Au adatoms, the presence of K or Cs adatoms on Ag∕Si(111)√3×√3 results in a metallic √21×√21 surface. The formation of two surface bands near the Fermi level can be explained by band folding of a partially occupied surface band originating from the underlying Ag∕Si(111)√3×√3 surface. A detailed analysis of the Si 2p core-level spectra of the above surfaces is presented and compared to the Ag∕Si(111)√3×√3 surface. In the case of Ag∕Si(111)√3×√3, we find that the metallic tail of the Si 2p spectra is related to extra Ag. Both the valence band and the Si 2p spectra of the Ag∕Si(111)√3×√3 surface show that the surface is semiconducting after annealing at ∼600°C.

  • 1157955.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uhrberg, R. I. G.
    Ag/Si(111)sqrt(3)×sqrt(3): Surface band splitting and the IET-model2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 19-15Article in journal (Refereed)
  • 1157956.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uhrberg,, R. I. G.
    Atomic structures of Ag/Ge(111)sqrt39xsqrt39 and 6x6 surfaces studied by STM: observations of bias dependent reconstruction transformations2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Appl. Surf. Sci., 212-213, 353 (2003), Vol. 212-213, p. 353-359Article in journal (Refereed)
  • 1157957.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uhrberg, R. I. G.
    Reinvestigation of the surface state band splitting on Ag/Si(111)sqrt3xsqrt32005Conference paper (Refereed)
  • 1157958.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uhrberg,, R. I. G.
    Surface reconstruction manipulation by STM2004Conference paper (Refereed)
  • 1157959.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uhrberg, R.I.G.
    Direct Manipulation of Surface Reconstructions by STM2002Conference paper (Refereed)
  • 1157960.
    Zhang, Hanmin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uhrberg, R.I.G.
    Scanning Tunneling Microscopy Study of Ag/Ge(111): Observation of Surface Reconstruction Transformations2003In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 546, no 1-2, p. L789-L796Article in journal (Refereed)
  • 1157961.
    Zhang, Hanmin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Uhrberg, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Ag∕Si(111)√3×√3: Surface band splitting and the inequivalent triangle model2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 19, p. 195329-Article in journal (Refereed)
    Abstract [en]

    The atomic and electronic structures of the Ag∕Si(111)√3×√3 surface are currently under debate. By employing angle-resolved valence-band spectroscopy, the surface band dispersions around the K̅ point of the Ag∕Si(111)√3×√3 surface have been investigated in detail. Contrary to a recent study, we conclude that the S2 and S3 surface state bands do not show any detectable split at 100 K. Thus, photoemission spectra at both room temperature and 100 K show only a single peak at the K̅ point without any direct evidence of a split. Calculated band structures for the inequivalent triangle (IET) model show a gap at the K̅ point in contrast to the honeycomb-chain-trimer (HCT) model. We find, however, that there is no real contradiction between our photoemission data and the IET model provided the energy gap of the latter model is small as indicated by a recent calculation [ Phys. Rev. B 70 245431 (2004)].

  • 1157962.
    Zhang, Hanmin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Uhrberg, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Atomic structures of Ag/Ge(1 1 1) v39 × v39 and 6 × 6 surfaces studied by STM: Observations of bias dependent reconstruction transformations2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 212-213, no SPEC., p. 353-359Article in journal (Refereed)
    Abstract [en]

    The 6 × 6 and v39 × v39 phases on Ag/Ge(1 1 1) have been studied by scanning tunneling microscopy (STM). Four types of 6 × 6 configurations are found which all consist of a v3 × v3 layer with six extra Ag adatoms per 6 × 6 unit cell. These reconstructions show either mirrored or complementary relations. We observe interesting transitions between the different 6 × 6 reconstructions. The v39 × v39 surface appears to have five extra Ag atoms per unit cell. By using various tip biases, we show that the v39 × v39 domain orientation can be changed. Surface structure models of the v39 × v39 and 6 × 6 phases are proposed based on the HCT structure of the underlying v3 × v3 surface. © 2003 Elsevier Science B.V. All rights reserved.

  • 1157963.
    Zhang, Hanmin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Uhrberg, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Scanning tunneling microscopy study of Ag/Ge(1 1 1): Observation of surface reconstruction transformations2003In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 546, no 2-3, p. L789-L796Article in journal (Refereed)
    Abstract [en]

    The 6×6 and v39×v39 phases of Ag/Ge(1 1 1) have been studied by scanning tunneling microscopy (STM). Surface atomic structures of the 6×6 and the v39×v39 phase are proposed in terms of additional Ag adatoms on top of a v3×v3 layer described by the honeycomb-chain-trimer (HCT) model. By varying the STM tip bias, the reconstruction can be changed reversibly between the v39×v39 and the 6×6 phase. Besides the switching between two different phases, it is also possible to flip the domain orientation of the v39×v39 phase. The mechanisms of the reconstruction transformation have been discussed in terms of the role of the STM tip. © 2003 Elsevier B.V. All rights reserved.

  • 1157964.
    Zhang, Hanqian
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Congenital Recessive Ichthyosis: Studies of Gene Expressions Related to Keratinocyte Differentiation and Skin Barrier Repair2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Autosomal recessive congenital ichthyosis (ARCI) is a rare monogenetic disorder characterized by a defective skin barrier, hyperkeratosis, and dry, scaly skin. It affects keratinocyte differentiation and is caused by mutations in any of at least 12 genes believed to control the formation of ω-O-acylceramide and the corneocyte lipid envelope (CLE): ABCA12, ALOXE3, ALOX12B, CERS3, CYP4F22, ELOVL4, LIPN, NIPAL4, PNPLA1, SDR9C7, SLC27A4, and TGM1.

    Studies of keratinocyte differentiation and gene expression in ARCI may help us better understand the pathobiology of skin barrier formation. One way to verify that ARCI-related gene products are operating in a chain of events essential for lipid barrier formation is to use immunofluorescence and in situ proximity ligation assays to demonstrate the proteins’ colocalizations in the epidermis. In paper I, a new method for the objective quantitative image analysis of protein expression and colocalization in different epidermal layers of skin sections was developed using free, open-source software, CellProfiler. Using this method and microarray analyses of skin biopsies from ARCI patients with TGM1 mutations (n = 5) compared with those of healthy controls (n = 4), many ARCI-related genes were found to be upregulated in patient epidermis (paper II). Because many other genes involved in keratinocyte differentiation and immune/inflammatory response, including PPARD, were also induced in the patients’ microarrays, the effects of a ligand-dependent transcription factor, PPARδ, encoded by PPARD, were studied on ARCI-related gene expression in cultured keratinocytes, usually showing the pronounced upregulation by PPARδ agonists (paper III). Furthermore, using previous array data obtained from cultured differentiated keratinocytes and from skin biopsies of patients with TGM1 mutations, nine novel candidate markers of differentiation were identified, and the upregulation was verified by qPCR of mRNA from cultured keratinocytes and skin biopsies. These transcripts were also induced by PPARδ agonists in cultured proliferating keratinocytes (paper IV).

    To conclude, the upregulation of other ARCI-related genes in patients with TGM1 mutations might reflect a feedback mechanism in ω-O-acylceramide biosynthesis, which, however, is unable to restore the patients’ skin barrier. In theory, substitution therapy with ω-O-acylceramide and recombinant TGm-1 may be required. Because PPARδ activation appears involved in upregulating ARCI-related genes and nine novel differentiation marker genes, all potentially important for barrier repair, this approach could become a treatment option for several types of ichthyosis and wound healing.

  • 1157965.
    Zhang, Hanqian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Ericsson, Maja
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Virtanen, Marie
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Weström, Simone
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Wählby, Carolina
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Vahlquist, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Törmä, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Quantitative image analysis of protein expression and colocalisation in skin sections2018In: Experimental dermatology, ISSN 0906-6705, E-ISSN 1600-0625, Vol. 27, no 2, p. 196-199Article in journal (Refereed)
    Abstract [en]

    Immunofluorescence (IF) and in situ proximity ligation assay (isPLA) are techniques that are used for in situ protein expression and colocalisation analysis, respectively. However, an efficient quantitative method to analyse both IF and isPLA staining on skin sections is lacking. Therefore, we developed a new method for semi-automatic quantitative layer-by-layer measurement of protein expression and colocalisation in skin sections using the free open-source software CellProfiler. As a proof of principle, IF and isPLA of ichthyosis-related proteins TGm-1 and SDR9C7 were examined. The results indicate that this new method can be used for protein expression and colocalisation analysis in skin sections.

  • 1157966.
    Zhang, Hanqian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Ericsson, Maja
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Weström, Simone
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Vahlquist, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Virtanen, Marie
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Törmä, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Patients with congenital ichthyosis and TGM1 mutations overexpress other ARCI genes in the skin: Part of a barrier repair response?2018In: Experimental dermatology, ISSN 0906-6705, E-ISSN 1600-0625Article in journal (Refereed)
    Abstract [en]

    Autosomal recessive congenital ichthyosis (ARCI) is a group of monogenic skin disorders caused by mutations in any of at least 12 different genes, many of which are involved in the epidermal synthesis of ω-O-acylceramides (acylCer). AcylCer are essential precursors of the corneocyte lipid envelope crosslinked by transglutaminase-1 (TGm-1), or a yet unidentified enzyme, for normal skin barrier formation. We hypothesized that inactivating TGM1 mutations will lead to a compensatory overexpression of the transcripts involved in skin barrier repair, including many other ARCI-causing genes. Using microarray we examined the global mRNA expression profile in skin biopsies from five ARCI-patients with TGM1 mutations and four healthy controls. There were a total of 599 significantly differentially expressed genes (adjusted P<0.05), out of which 272 showed more than 1.5 log2fold-change (FC) up- or down-regulation. Functional classification of the latter group of transcripts showed enrichment of mRNA encoding proteins mainly associated with biological pathways involved in keratinocyte differentiation and immune response. Moreover, the expression of seven out of twelve ARCI-causing genes were significantly increased (FC=0.98-2.05). Also, many of the genes involved in keratinocyte differentiation (cornified envelope formation) and immune response (anti-microbial peptides and proinflammatory cytokines) were upregulated. The results from the microarray analysis were also verified for selected genes at the mRNA level by qPCR and at the protein level by semi-quantitative immunofluorescence. The upregulation of these genes might reflect a compensatory induction of acylCer biosynthesis as a part of a global barrier repair response in the patient´s epidermis.

  • 1157967.
    Zhang, Hanqian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Vahlquist, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Virtanen, Marie
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Törmä, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Ichthyosis patients with TGM1 mutations show aberrant transcriptomic expression2017In: Journal of Investigative Dermatology, ISSN 0022-202X, E-ISSN 1523-1747, Vol. 137, no 10, p. S214-S214Article in journal (Other academic)
  • 1157968.
    Zhang, Hanqian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Virtanen, Marie
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology. en..
    Weström, Simone
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Bygum, A.
    Odense Univ Hosp, Dept Dermatol & Allergy, Odense, Denmark..
    Wählby, Carolina
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Vahlquist, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Törmä, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Dermatology and Venereology.
    Quantitative analysis of immunofluorescence and in situ PLA staining using CellProfiler reveals impaired epidermal lipid processing pathway in ARCI patients with CYP4F22 mutations2016In: Journal of Investigative Dermatology, ISSN 0022-202X, E-ISSN 1523-1747, Vol. 136, no 9, p. S180-S180Article in journal (Other academic)
  • 1157969.
    Zhang, Hanqian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Weström, Simone
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Vahlquist, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Törmä, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    PPARδ agonists upregulate transcripts in the ω-O-acylceramide pathway essential for the formation of corneocyte lipid envelopes in epidermis and pathogenic in ichthyosisManuscript (preprint) (Other academic)
    Abstract [en]

    At least twelve proteins are involved in the biosynthesis and transport of ω-O-acylceramide (acylCer), a lipid which is covalently attached to the cornified cell envelope of epidermal keratinocytes essential for a proper permeability barrier. Deleterious mutations in any of the involved genes may cause autosomal recessive congenital ichthyosis (ARCI). The regulation of mRNA transcripts involved in the acylCer pathway is sparsely studied although it is known that retinoids reduce the expression of most of these transcripts and that peroxisome proliferator-activated receptor-d (PPARd) agonists induce the expression of at least three genes (ABCA12, CERS3 and ELOVL4). In this study, we examined the effect of several PPAR agonists on the mRNA expression of twelve ARCI-related genes in cultured human epidermal keratinocytes. In short, PPARd agonists, but not PPARa- and PPARg-agonists, markedly induced the genes after 24 hours exposure, and the induction was more pronounced in pre-confluent proliferating cells as compared to post-confluent differentiated cells, although the latter cells showed a much higher baseline expression. For eight of the genes the induction by PPARd-agonist GW501516 could be abolished by pre-treatment with PPARd-antagonist GSK0660. Reassuringly, GW501516 induced the same genes also in human epidermal equivalents. These results suggest that ligand activation of PPARd should be tested for its ability to restore a defect skin barrier caused by an insufficient production of acylCer.

  • 1157970.
    Zhang, Hanqian
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Weström, Simone
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Vahlquist, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Virtanen, Marie
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Törmä, Hans
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Identification of novel gene products involved in epidermal keratinocyte differentiation and pathologic skin barrier repairManuscript (preprint) (Other academic)
    Abstract [en]

    A functional skin barrier relies on a correct structural organization of the outermost epidermal layer, stratum corneum, as the final stage of keratinocyte terminal differentiation. However, the factors involved in keratinocyte differentiation, especially those which are important for the skin barrier function and barrier repair, are still largely unknown. In this study we re-analysed two sets of microarrays obtained from cultured differentiated keratinocytes or skin biopsies of autosomal recessive congenital ichthyosis (ARCI) patients with hyperkeratosis and defect skin barrier due to TGM1 mutations. When comparing these arrays to those of proliferating keratinocytes and healthy control epidermis respectively, we identified 24 augmented genes not previously associated with keratinocyte differentiation and skin barrier repair. Increased expression of 9 of these genes, i.e. AKR1B10, BLNK, ENDOU, GCNT4, GLTP, RHCG, SLC15A1, TMEM86A, VSNL1, was verified by qPCR of differentiated keratinocytes and patients skin extracts. In a separate experiment, the regulation of the genes by two well-known transcription factors, retinoic acid receptors (RARs) and peroxisome proliferator activating receptors (PPARs), was studied in cell cultures by adding the pan-RAR agonist all-trans retinoic acid (atRA) or PPARd agonist GW501516. In line with the anti-keratinizing effects of retinoids, atRA reduced the mRNA expressions of some of these genes both in monolayer and organotypic keratinocyte cultures. Confirming the importance of PPARd for keratinocyte differentiation, PPARd-agonist GW501516 induced all 9 novel genes associated with differentiation and skin barrier repair. The results increase the understanding about genes involved in human epidermal keratinocyte differentiation, with potential repercussions on the development of new ways to restore the barrier function in conditions with a defect skin barrier.

  • 1157971.
    Zhang, Hanqing
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Construction of an Optical Tweezers Instrumentation and Validation of Brownian motion2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We constructed a standalone optical trapping system that was steerable in three dimensions and allowed for sufficient imaging of one цm particles with a CCD camera. The motion of the trapped particles was monitored by both a position sensitive detector as well with the CCD camera. The trap stiffness was evaluated by the power spectrum method and the equipartition theorem. For calibration of the stiffness of the trap, we found that the power spectrum method with data assessed by the PSD was most straightforward and accurate. The equipartition method was compromised by noise, low resolution and the bandwidth of the detector. With a HeNe laser run at 10 mW output power the trap strength of our system reached ~2 pN/um. The results also showed a decrease in the trap stiffness and particle's position variance when the size of trapped particles increased.

  • 1157972.
    Zhang, Hanqing
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Digital holography and image processing methods for applications in biophysics2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding dynamic mechanisms, morphology and behavior of bacteria are important to develop new therapeutics to cure diseases. For example, bacterial adhesion mechanisms are prerequisites for initiation of infections and for several bacterial strains this adhesion process is mediated by adhesive surface organelles, also known as fimbriae. Escherichia coli (E. coli) is a bacterium expressing fimbriae of which pathogenic strains can cause severe diseases in fluidic environments such as the urinary tract and intestine. To better understand how E. coli cells attach and remain attached to surfaces when exposed to a fluid flow using their fimbriae, experiments using microfluidic channels are important; and to assess quantitative information of the adhesion process and cellular information of morphology, location and orientation, the imaging capability of the experimental technique is vital.

    In-line digital holographic microscopy (DHM) is a powerful imaging technique that can be realized around a conventional light microscope. It is a non-invasive technique without the need of staining or sectioning of the sample to be observed in vitro. DHM provides holograms containing three-dimensional (3D) intensity and phase information of cells under study with high temporal and spatial resolution. By applying image processing algorithms to the holograms, quantitative measurements can provide information of position, shape, orientation, optical thickness of the cell, as well as dynamic cell properties such as speed, growing rate, etc.

    In this thesis, we aim to improve the DHM technique and develop image processing methods to track and assess cellular properties in microfluidic channels to shed light on bacterial adhesion and cell morphology. To achieve this, we implemented a DHM technique and developed image processing algorithms to provide for a robust and quantitative analysis of holograms. We improved the cell detection accuracy and efficiency in DHM holograms by developing an algorithm for detection of cell diffraction patterns. To improve the 3D detection accuracy using in-line digital holography, we developed a novel iterative algorithm that use multiple-wavelengths. We verified our algorithms using synthetic, colloidal and cell data and applied the algorithms for detecting, tracking and analysis. We demonstrated the performance when tracking bacteria with sub-micrometer accuracy and kHz temporal resolution, as well as how DHM can be used to profile a microfluidic flow using a large number of colloidal particles. We also demonstrated how the results of cell shape analysis based on image segmentation can be used to estimate the hydrodynamic force on tethered capsule-shaped cells in micro-fluidic flows near a surface.

  • 1157973.
    Zhang, Hanqing
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stangner, Tim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Object plane detection and phase retrieval from single-shot holograms using multi-wavelength in-line holographyManuscript (preprint) (Other academic)
    Abstract [en]

    Phase retrieval and the twin-image problem in digital in-line holographic microscopy can be resolvedby iterative reconstruction routines. However, recovering the phase properties of an object in a hologramneeds an object plane to be chosen correctly for reconstruction. In this work, we present a novelmulti-wavelength Gerchberg-Saxton algorithm to determine the object plane using single-shot hologramsrecorded with multiple wavelengths in an in-line holographic microscope. For micro-sized objects, weverify the object positioning capabilities of the method for various shapes and derive the phase informationusing synthetic and experimental data. Experimentally, we built a compact digital in-line holographicmicroscopy setup around a standard optical microscope with a regular RGB-CCD camera andacquire holograms of micro-spheres, E. coli and red blood cells, that are illuminated using three lasersoperating at 491nm, 532nm and 633nm, respectively. We demonstrate that our method provides accurateobject plane detection and phase retrieval under noisy conditions, e.g., using low-contrast hologramswithout background normalization. This method allows for automatic positioning and phase retrievalsuitable for holographic particle velocimetry, and object tracking in biophysical or colloidal research.

  • 1157974.
    Zhang, Hanqing
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stangner, Tim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Object plane detection and phase retrieval from single-shot holograms using multi-wavelength in-line holography2018In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 57, no 33, p. 9855-9862Article in journal (Refereed)
    Abstract [en]

    Phase retrieval and the twin-image problem in digital in-line holographic microscopy can be resolved by iterative reconstruction routines. However, recovering the phase properties of an object in a hologram requires an object plane to be chosen correctly for reconstruction. In this work, we present a novel multi-wavelength iterative algorithm to determine the object plane using single-shot holograms recorded at multiple wavelengths in an in-line holographic microscope. Using micro-sized objects, we verify the object positioning capabilities of the method for various shapes and derive the phase information using synthetic and experimental data. Experimentally, we built a compact digital in-line holographic microscopy setup around a standard optical microscope with a regular RGB-CCD camera and acquired holograms of micro-spheres, E. coli, and red blood cells, which are illuminated using three lasers operating at 491 nm, 532 nm, and 633 nm, respectively. We demonstrate that our method provides accurate object plane detection and phase retrieval under noisy conditions, e.g., using low-contrast holograms with an inhomogeneous background. This method allows for automatic positioning and phase retrieval suitable for holographic particle velocimetry, and object tracking in biophysical or colloidal research. 

  • 1157975.
    Zhang, Hanqing
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stangner, Tim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rodrigues, Alvaro
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    UmUTracker: a versatile MATLAB program for automated particle tracking of 2D light microscopy or 3D digital holography data2017In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 219, p. 390-399Article in journal (Refereed)
    Abstract [en]

    We present a versatile and fast MATLAB program (UmUTracker) that automatically detects and tracks particles by analyzing video sequences acquired by either light microscopy or digital in-line holographic microscopy. Our program detects the 2D lateral positions of particles with an algorithm based on the isosceles triangle transform, and reconstructs their 3D axial positions by a fast implementation of the Rayleigh-Sommerfeld model using a radial intensity profile. To validate the accuracy and performance of our program, we first track the 2D position of polystyrene particles using bright field and digital holographic microscopy. Second, we determine the 3D particle position by analyzing synthetic and experimentally acquired holograms. Finally, to highlight the full program features, we profile the microfluidic flow in a 100 gm high flow chamber. This result agrees with computational fluid dynamic simulations. On a regular desktop computer UmUTracker can detect, analyze, and track multiple particles at 5 frames per second for a template size of 201 x 201 in a 1024 x 1024 image. To enhance usability and to make it easy to implement new functions we used object-oriented programming. UmUTracker is suitable for studies related to: particle dynamics, cell localization, colloids and microfluidic flow measurement.

    Program summary

    Program title: UmUTracker Program Files doi: http://dx.doi.org/10.17632/fkprs4s6xp.1

    Licensing provisions: Creative Commons by 4.0 (CC by 4.0)

    Programming language: MATLAB Nature of problem: 3D multi-particle tracking is a common technique in physics, chemistry and biology. However, in terms of accuracy, reliable particle tracking is a challenging task since results depend on sample illumination, particle overlap, motion blur and noise from recording sensors. Additionally, the computational performance is also an issue if, for example, a computationally expensive process is executed, such as axial particle position reconstruction from digital holographic microscopy data. Versatile robust tracking programs handling these concerns and providing a powerful post-processing option are significantly limited.

    Solution method: UmUTracker is a multi-functional tool to extract particle positions from long video sequences acquired with either light microscopy or digital holographic microscopy. The program provides an easy-to-use graphical user interface (GUI) for both tracking and post-processing that does not require any programming skills to analyze data from particle tracking experiments. UmUTracker first conduct automatic 2D particle detection even under noisy conditions using a novel circle detector based on the isosceles triangle sampling technique with a multi-scale strategy. To reduce the computational load for 3D tracking, it uses an efficient implementation of the Rayleigh-Sommerfeld light propagation model. To analyze and visualize the data, an efficient data analysis step, which can for example show 4D flow visualization using 3D trajectories, is included. Additionally, UmUTracker is easy to modify with user customized modules due to the object-oriented programming style.

    Additional comments: Program obtainable from https://sourceforge.net/projects/umutracker/

  • 1157976.
    Zhang, Hanqing
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Söderholm, Niklas
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Sandblad, Linda
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    DSeg: a dynamic image segmentation program to extract backbone patterns for filamentous bacteria and hyphae structures2019In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 25, no 3, p. 711-719Article in journal (Refereed)
    Abstract [en]

    Analysis of numerous filamentous structures in an image is often limited by the ability of algorithms to accurately segment complex structures or structures within a dense population. It is even more problematic if these structures continuously grow when recording a time-series of images. To overcome these issues we present DSeg; an image analysis program designed to process time-series image data, as well as single images, to segment filamentous structures. The program includes a robust binary level-set algorithm modified to use size constraints, edge intensity, and past information. We verify our algorithms using synthetic data, differential interference contrast images of filamentous prokaryotes, and transmission electron microscopy images of bacterial adhesion fimbriae. DSeg includes automatic segmentation, tools for analysis, and drift correction, and outputs statistical data such as persistence length, growth rate, and growth direction. The program is available at Sourceforge.

  • 1157977.
    Zhang, Hanzhao
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Master Programme of Medical Research.
    Impact of SETD2 mutation in the regulation of Autophagy in Clear Cell Renal Cell Carcinoma Cells2018Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Background: Autophagy is an important cellular pathway in cell growth and maintenance, during which unnecessary organelles and materials in cells can be degraded. Regulation of autophagy is related to tumorigenesis. SETD2 is a histone methyltransferase and mutation of SETD2 has been identified in different human cancers, especially in clear cell renal cell carcinoma. Previous results of the laboratory showed evidence of SETD2 involvement in autophagy regulation. Therefore, the focus of this report is on autophagy regulation of SETD2 in clear cell renal cell carcinoma.

    Aim: To investigate the impact of SETD2 mutation in autophagy pathway in clear cell renal cell carcinoma cells

    Methods: Cells were cultured in standard procedure in optimal medium. Immunoblotting was used to examine protein expression level. RT-qPCR was used to determine mRNA expression level of certain gene. Localization of protein expression was detected by immunofluorescence.

    Results: SETD2 deficient cell lines showed less accumulation of p62 and LC3B when blocking the fusion of autophagosome and lysosome. In SETD2 deficient cell lines, an extra band and higher signal of free ATG12 were found when blotted with ATG12-ATG5. Expression of alternative splicing marker was also lower when SETD2 was mutated.

    Conclusion: SETD2 might be related to a lower autophagic flux and might be involved in autophagosome formation by affecting formation of ATG12-ATG5-ATG16L complex. SETD2 deficiency might also decrease alternative splicing. Further investigations are required to give solid statement.

  • 1157978. Zhang, Hanzhi
    et al.
    Lu, Huayu
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Feng, Han
    Fu, Yu
    Geng, Junyan
    Wang, Hanlin
    Expansion of dust provenance and aridification of Asia since ~7.2 Ma revealed by detrital zircon U-Pb dating2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 24, p. 13,437-13,448Article in journal (Refereed)
    Abstract [en]

    The relative importance of global cooling and Tibetan Plateau uplift in driving the aridification of Asia during the late Cenozoic is debated, largely due to the lack of appropriate proxy indicators. Here we address this problem by investigating changes in the source of Chinese loess and Red Clay, which is directly controlled by changes in the extent and distribution of the arid zone of Asia and the intensity of the East Asian winter monsoon, using zircon U‐Pb dating of 27 levels in a near‐continuous eolian sedimentary sequence in southern Chinese Loess Plateau. The results show that source regions expanded stepwise at ~7.2, ~2.6, 1.2–0.9 Ma, and at the Last Glacial Maximum. These changes were synchronous with global cooling and ice cover expansion in the Northern Hemisphere, suggesting that the drivers of aridification of the Asian interior were intimately related to global cooling in the late Cenozoic.

    Plain Language Summary

    The arid and semiarid regions of Central Asia are one of the most important dust sources on Earth. Dust emitted from these regions is deposited in the Chinese Loess Plateau, the North Pacific Ocean, and even in Greenland, with broad environmental impacts. Although there is evidence that the drying of the Asian interior occurred gradually over several tens of million years, the driving factor remains unclear. Here we investigate the evolution of the sediment sources of the Chinese Loess Plateau and find that the changes in the source regions of wind‐blown sediment were synchronous with global cooling since ~7.2 Ma. This indicates that the long‐term aridification of the Asian interior was most likely driven by global cooling.

  • 1157979.
    Zhang, Hanzhi
    et al.
    School of Geography and Ocean Science, Nanjing University, Nanjing, China.
    Lu, Huayu
    School of Geography and Ocean Science, Nanjing University, Nanjing, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, China.
    Xu, Xisheng
    State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China.
    Liu, Xiaoming
    State Key Laboratory of Continent Dynamics, Department of Geology, Northwest University, Xi'an, China.
    Yang, Tao
    State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bird, Anna
    Department of Geography, Environment, and Earth Sciences, University of Hull, Hull, UK.
    Xu, Zhiwei
    School of Geography and Ocean Science, Nanjing University, Nanjing, China.
    Zhang, Tian
    School of Geography and Ocean Science, Nanjing University, Nanjing, China.
    Lei, Fang
    School of Geography and Ocean Science, Nanjing University, Nanjing, China.
    Feng, Han
    School of Geography and Ocean Science, Nanjing University, Nanjing, China.
    Quantitative estimation of the contribution of dustsources to Chinese loess using detrital zircon U-Pbage patterns2016In: Journal of Geophysical Research - Earth Surface, ISSN 2169-9003, E-ISSN 2169-9011, Vol. 121, no 11, p. 2085-2099Article in journal (Refereed)
    Abstract [en]

    The origin and provenance of the loess deposits of the Chinese Loess Plateau (CLP) are stilldebated. In order to pinpoint the dust sources, surface samples from the piedmont of the NortheasternTibetan Plateau, the Gobi Altai Mountains, and modern eolian dunes from the Tengger desert and Mu Ussand field were analyzed by using the detrital zircon dating technique. In order to quantitatively discriminatethe content of different potential sources, zircon grains of different ages were grouped according to theirtectonic origin. Zircon grains aged from 1300 to 550 Ma were assigned to the Northeastern Tibetan Plateau,and grains aged from 550 to 0 Ma to the Northeastern Tibetan Plateau or the Gobi Altai Mountains, or to acombination of the two. Zircon ages of around 2.8 Ga to 1.3 Ga may be a mixture of sources from theNortheastern Tibetan Plateau, Gobi Altai Mountains, or North China Craton. Sediments from the Tenggerdesert and Mu Us sand field consist of a mixture of the three sources and exhibit a high degree of spatialvariability in terms of their source. In the northern part of the two deserts, 43–83% of the sediments arederived from the Gobi Altai Mountains, while in the south, material from the Northeastern Tibetan Plateaucomprises 51–98% of the sediments. Loess deposits from the CLP also comprise a mixture of the threedifferent sources, with material from the Northeastern Tibetan Plateau making the dominant contribution(65–100%), with material from the North China Craton and the Gobi Altai Mountains comprising 0–35% and0–40% of the loess deposits, respectively. The contributions from the three sources to the loess deposits onCLP vary spatially. Application of the novel statistical method of provenance group analysis demonstratesthat the loess deposits comprise a mixture of material from a broad region of northern China and that theNortheastern Tibetan Plateau material makes the dominant contribution.

  • 1157980.
    Zhang, Hanzhu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Synthesis of metallic/high entropy ceramic composite and a study of the phase transformation mechanism2018Licentiate thesis, comprehensive summary (Other academic)
  • 1157981.
    Zhang, Hanzhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Processing and Characterization of Refractory Quaternary and Quinary High-Entropy Carbide Composite2019In: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 21, no 5, article id 474Article in journal (Refereed)
    Abstract [en]

    Quaternary high-entropy ceramic (HEC) composite was synthesized from HfC, Mo2C, TaC, and TiC in pulsed current processing. A high-entropy solid solution that contained all principal elements along with a minor amount of a Ta-rich phase was observed in the microstructure. The high entropy phase and Ta-rich phase displayed a face-centered cubic (FCC) crystal structure with similar lattice parameters, suggesting that TaC acted as a solvent carbide during phase evolution. The addition of B4C to the quaternary carbide system induced the formation of two high-entropy solid solutions with different elemental compositions. With the increase in the number of principal elements, on the addition of B4C, the crystal structure of the HEC phase transformed from FCC to a hexagonal structure. The study on the effect of starting particle sizes on the phase composition and properties of the HEC composites showed that reducing the size of solute carbide components HfC, Mo2C, and TiC could effectively promote the interdiffusion process, resulting in a higher fraction of a hexagonal structured HEC phase in the material. On the other hand, tuning the particle size of solvent carbide, TaC, showed a negligible effect on the composition of the final product. However, reducing the TaC size from −325 mesh down to <1 µm resulted in an improvement of the nanohardness of the HEC composite from 21 GPa to 23 GPa. These findings suggested the possibility of forming a high-entropy ceramic phase despite the vast difference in the precursor crystal structures, provided a clearer understanding of the phase transformation process which could be applied for the designing of HEC materials.

  • 1157982.
    Zhang, Hanzhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Aluminium matrix tungsten aluminide and tungsten reinforced composites by solid-state diffusion mechanism2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 12391Article in journal (Refereed)
    Abstract [en]

    In-situ processing of tungsten aluminide and tungsten reinforced aluminium matrix composites from elemental tungsten (W) and aluminium (Al) was investigated by thermal analysis and pulsed current processing (PCP). The formation mechanism of tungsten aluminides in 80 at.% Al-20 at.% W system was controlled by atomic diffusion. The particle size of W and Al in the starting powder mixture regulated the phase formation and microstructure. PCP of micron sized elemental Al and W resulted in formation of particulate reinforcements, W, Al4W and Al12W, dispersed in Al matrix. W particles were surrounded by a ~3 μm thick dual-layer structure of Al12W and Al4W. The hardness of Al matrix, containing Al12W reinforcements, was increased by 50% compared to pure Al, from 0.3 GPa to 0.45 GPa and W reinforcements showed a hardness of 4.35 GPa. On PCP of 80 at.% Al-20 at.% W mixture with particle size of W and Al ~70 nm, resulted in formation of Al4W as major phase along with small fractions of Al5W and unreacted W phase. This suggested strongly that the particle size of the starting elemental Al and W could be the controlling parameter in processing and tailoring of phase evolution, microstructure of particulate reinforced Al matrix composite.

  • 1157983.
    Zhang, Hanzhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Feng, Peizhong
    China University of Mining and Technology.
    Han, Gang
    University of Science and Technology Beijing.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A high entropy B4(HfMo2TaTi)C and SiC ceramic composite2019Conference paper (Refereed)
    Abstract [en]

    Refractory carbides HfC, Mo2C, TiC, TaC, B4C, and SiC were mixed with a molar ratio of 2:1:2:2:1:2 to fabricate multicomponent ceramic composite by pulsed current processing (PCP). From the starting materials that consist of face-centered cubic (FCC), hexagonal and rhombohedral crystal structures, the investigated carbide system is reported to form a single phase B4(HfMo2TaTi)C high-entropy ceramic (HEC) with SiC. The HEC phase contains uniform distribution of constitutional elements Hf, Mo, Ta, Ti, B and C, according to Energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) results.

    The fabricated HEC phase displays a hexagonal crystal structure, with a high average lattice distortion of 8.26% (Figure 1). The HCP structure was observed by X-ray diffraction and selected area diffraction in transmission electron microscopy (TEM). Density-functional theory (DFT) optimization suggested that the hexagonal crystal structure has alternating layers of metal atoms and carbon/boron atoms, i.e. metal atoms of Hf, Mo, Ta and Ti were distributed on the (0001) plane in the hexagonal lattice, while the carbon/boron atoms formed hexagonal 2D grids on the (0002) plane in the hexagonal unit cell. Despite of the vast differences in the crystal structures and lattice parameters among the utilized carbides, the formation of the unique hexagonal lattice structure of B4HfMo2TaTi)C can be a result of independent diffusion of the metal and nonmetal atoms. The sintered HEC ceramic composite exhibits excellent oxidation resistance at mediate temperature, 900 ºC for 50h, and elevated temperature, 2000 ºC for 20 s. Nanoindentation test shows that the HEC phase has a high hardness of 35 GPa. The remarkable improvement compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa) was contributed by the severe lattice distortion in the hexagonal structure.

  • 1157984.
    Zhang, Hanzhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Luleå university of technology.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Feng, Peizhong
    China University of Mining and Technology.
    Han, Gang
    University of Science and Technology Beijing.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 16, p. 5161-5167Article in journal (Refereed)
    Abstract [en]

    A multicomponent composite of refractory carbides, B4C, HfC, Mo2C, TaC, TiC and SiC, of rhombohedral, face-centered cubic (FCC) and hexagonal crystal structures is reported to form a single phase B4(HfMo2TaTi)C ceramic with SiC. The independent diffusion of the metal and nonmetal atoms led to a unique hexagonal lattice structure of the B4(HfMo2TaTi)C ceramic with alternating layers of metal atoms and C/B atoms. In addition, the classical differences in the crystal structures and lattice parameters among the utilized carbides were overcome. Electron microscopy, X-ray diffraction and calculations using density functional theory (DFT) confirmed the formation of a single phase B4(HfMo2TaTi)C ceramic with a hexagonal close-packed (HCP) crystal structure. The DFT based crystal structure prediction suggests that the metal atoms of Hf, Mo, Ta and Ti are distributed on the (0001) plane in the HCP lattice, while the carbon/boron atoms form hexagonal 2D grids on the (0002) plane in the HCP unit cell. The nanoindentation of the high-entropy phase showed hardness values of 35 GPa compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa). The higher hardness was contributed by the solid solution strengthening effect in the multicomponent hexagonal structure. The addition of SiC as the secondary phase in the sintered material tailored the microstructure of the composite and offered oxidation resistance to the high-entropy ceramic composite at high temperatures.

  • 1157985.
    Zhang, Hanzhu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Luleå university of technology.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Feng, Peizhong
    China University of Mining and Technology.
    Han, Gang
    University of Science and Technology Beijing.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Correction: A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 19, p. 6647-6647Article in journal (Refereed)
    Abstract [en]

    The authors regret that there is an error in writing the crystal structure in the article. The authors would like to address as follows:

    The presented XRD and TEM results revealed a hexagonal crystal structure. The following analyses including the identification of the lattice parameters and the DFT calculation were based on a hexagonal lattice. Therefore, the HCP (hexagonal close-packed) structure mentioned in the article should be regarded as a hexagonal structure. The HCP term used in the introduction, where the article from Joshua Gild et al. was cited, should also be regarded as hexagonal AlB2 structure.

    The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

  • 1157986.
    Zhang, Hao
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    A Peer to Peer Security Protocol for the Internet of Things: Secure Communication for the SensibleThings Platform2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the rapid development of the Internet connected technologies and applications, people are keen on embracing the convenience and practi-­‐‑ calities they brings. As all kinds of technologies improve, the Internet of Things matures and is able to provide more advanced services to people, which connects a variety of devices, systems and applications beyond traditional machine-­‐‑to-­‐‑machine. However, it covers a variety of devices, protocols and applications, which makes it much more complex than a normal network. Nevertheless, equipped with appropriate security solutions, the Internet of Things is promising to bring us more conven-­‐‑ iences and be widely applied in our daily life. And like the main appli-­‐‑ cation areas, wireless sensor networks with a frequent but short com-­‐‑ munication character, it requires an efficient and flexible protocol to protect the information. To protect the traffic of the Internet of Things is the focal point of this research work. Although many protocols for the Internet have been put forward, it is still not enough to meet the increas-­‐‑ ingly complex requirements from applications. Many of them are not efficient enough to adapt the device diversity and timely communica-­‐‑ tion environment. This research work is trying to address this problem, by proposing a peer-­‐‑to-­‐‑peer security protocol to satisfy this varied environment. Secure communication is implemented on an open sourced platform for the Internet of Things. The philosophy of the platform it implemented on is also inherited to this protocol and the implementation. It avoids unnecessary handshakes between entities, which makes it more efficient in a wireless sensor network. Modulariza-­‐‑ tion and unit test are adapted in implementation to enhance the robust of the system. Its dynamic security level adjustment feature satisfies the realistic demand on one platform this protocol is implemented on. Finally, with a comparison test and an analysis using the BAN logic, the result shows that the proposed protocol is efficient to meet the specific goals and applicable for the platform. 

  • 1157987.
    Zhang, Hao
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    IP Multimedia Subsystem (IMS) Test Environment Simulator2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The IP Multimedia Subsystem (IMS) is the key element in the 3G mobile network architecture. IMS makes it possible to provide subscribers with ubiquitous cellular access to all the Internet provided services. This thesis report fully describes the project which aims on investigation and implementation of a test environment simulating key functional entities within the IMS core network. The achieved test environment simulator is intended to be used to facilitate development and test of IMS based systems without requiring access to a live IMS network.

    This report starts with an overview of IMS concepts and system requirements. Then it will give thorough description on system design and implementation. Several major communication protocols in IMS core network, such as SIP, RTP and Diameter, are implemented. The main IMS network elements, CSCF and HSS, are simulated. In addition, a handset simulator that is capable of depositing and retrieving voice mail is also implemented. Tests are conducted between completed IMS Test Environment Simulator and external IMS Voice Mail System by performing signaling and media communication in between. Finally, the report discusses potential future work based on the accomplished system prototype and summarizes achievements as well as challenges of the project.

  • 1157988.
    Zhang, Hao
    et al.
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Jia, Tan
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Discuss employee wellbeing in project based organizations from a human resource management perspective2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In our paper, we introduced employee wellbeing through physical, psychological and social dimensions. We discuss employee wellbeing in the context of project-based organization (PBO). Meanwhile we summarize features of project-based organizations and this kind of work settings brings some negative effects to employee wellbeing. We figure out some human resource management (HRM) policies and practices for improving employee wellbeing in PBO based on our case study results and theoretical research. These HRM policies and practices can be concluded that performance evaluation and appraisal in PBO should be dynamic and autonomic; employees in PBO should be more involved in work process; trainings and development should include basic skills, broad knowledge and deep technical excellence.

  • 1157989.
    Zhang, Hao
    et al.
    Chinese Univ Hong Kong, Peoples Republic of China.
    Yoshizawa, Susumu
    Univ Tokyo, Japan.
    Sun, Ying
    Chinese Univ Hong Kong, Peoples Republic of China.
    Huang, Yongjie
    Chinese Univ Hong Kong, Peoples Republic of China.
    Chu, Xiao
    Chinese Univ Hong Kong, Peoples Republic of China.
    Gonzalez, Jose M.
    Univ La Laguna, Spain.
    Pinhassi, Jarone
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Luo, Haiwei
    Chinese Univ Hong Kong, Peoples Republic of China.
    Repeated evolutionary transitions of flavobacteria from marine to non-marine habitats2019In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 21, no 2, p. 648-666Article in journal (Refereed)
    Abstract [en]

    The taxonomy of marine and non-marine organisms rarely overlap, but the mechanisms underlying this distinction are often unknown. Here, we predicted three major ocean-to-land transitions in the evolutionary history of Flavobacteriaceae, a family known for polysaccharide and peptide degradation. These unidirectional transitions were associated with repeated losses of marine signature genes and repeated gains of non-marine adaptive genes. This included various Na+-dependent transporters, osmolyte transporters and glycoside hydrolases (GH) for sulfated polysaccharide utilization in marine descendants, and in non-marine descendants genes for utilizing the land plant material pectin and genes facilitating terrestrial host interactions. The K+ scavenging ATPase was repeatedly gained whereas the corresponding low-affinity transporter repeatedly lost upon transitions, reflecting K+ ions are less available to non-marine bacteria. Strikingly, the central metabolism Na+-translocating NADH: quinone dehydrogenase gene was repeatedly gained in marine descendants, whereas the H+-translocating counterpart was repeatedly gained in non-marine lineages. Furthermore, GH genes were depleted in isolates colonizing animal hosts but abundant in bacteria inhabiting other non-marine niches; thus relative abundances of GH versus peptidase genes among Flavobacteriaceae lineages were inconsistent with the marine versus non-marine dichotomy. We suggest that phylogenomic analyses can cast novel light on mechanisms explaining the distribution and ecology of key microbiome components.

  • 1157990. Zhang, Hao
    et al.
    Yoshizawa, Susumu
    Sun, Ying
    Huang, Yongjie
    Chu, Xiao
    Gonzalez, Jose M.
    Pinhassi, Jarone
    Luo, Haiwei
    Repeated evolutionary transitions of flavobacteria from marine to non-marine habitats2019In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 21, no 2, p. 648-666Article in journal (Refereed)
    Abstract [en]

    The taxonomy of marine and non-marine organisms rarely overlap, but the mechanisms underlying this distinction are often unknown. Here, we predicted three major ocean-to-land transitions in the evolutionary history of Flavobacteriaceae, a family known for polysaccharide and peptide degradation. These unidirectional transitions were associated with repeated losses of marine signature genes and repeated gains of non-marine adaptive genes. This included various Na+-dependent transporters, osmolyte transporters and glycoside hydrolases (GH) for sulfated polysaccharide utilization in marine descendants, and in non-marine descendants genes for utilizing the land plant material pectin and genes facilitating terrestrial host interactions. The K+ scavenging ATPase was repeatedly gained whereas the corresponding low-affinity transporter repeatedly lost upon transitions, reflecting K+ ions are less available to non-marine bacteria. Strikingly, the central metabolism Na+-translocating NADH: quinone dehydrogenase gene was repeatedly gained in marine descendants, whereas the H+-translocating counterpart was repeatedly gained in non-marine lineages. Furthermore, GH genes were depleted in isolates colonizing animal hosts but abundant in bacteria inhabiting other non-marine niches; thus relative abundances of GH versus peptidase genes among Flavobacteriaceae lineages were inconsistent with the marine versus non-marine dichotomy. We suggest that phylogenomic analyses can cast novel light on mechanisms explaining the distribution and ecology of key microbiome components.

  • 1157991.
    Zhang, He
    Örebro University, Swedish Business School at Örebro University.
    Exports, FDI and productivity in Swedish manufacturing2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 1157992.
    Zhang, He
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Non-Standard Neutrino Interactions and Non-Unitarity Effects from TeV Seesaw Models2010In: NEUTRINO FACTORIES, SUPERBEAMS, AND BETA BEAMS / [ed] Goodman MC; Kaplan DM; Sullivan Z, 2010, Vol. 1222, p. 145-149Conference paper (Refereed)
    Abstract [en]

    The motivations and phenomena of seesaw models at the TeV scale are briefly reviewed. We show that nonstandard neutrino interactions and non-unitary effects are two typical features of low-scale scalar and fermionic seesaw models, respectively. For scalar seesaw models, in principle, significant non-standard interaction effects can be accommodated in the type-II seesaw model. As for the low-scale fermionic seesaw models, the inverse seesaw model turns out to be the most natural one, and could be well tested at the future long-baseline neutrino oscillation experiments and the LHC.

  • 1157993.
    Zhang, He
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Non-standard neutrino interactions in the type-II seesaw model2010In: TOPICS IN ASTROPARTICLE AND UNDERGROUND PHYSICS (TAUP2009), 2010, Vol. 203Conference paper (Other academic)
    Abstract [en]

    Within the framework of the type-II seesaw model, we investigate in detail the non-standard neutrino interactions (NSIs). Non-trivial correlations between NSI parameters and neutrino masses and mixing parameters are established. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Significant zero distance effects in the near detector of a future neutrino factory, as well as characteristic decays of the doubly charged Higgs at the Large Hadron Collider are discussed.

  • 1157994.
    Zhang, He
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Zhou, Shun
    The minimal seesaw model at the TeV scale2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 685, no 4-5, p. 297-301Article in journal (Refereed)
    Abstract [en]

    We point out that the minimal seesaw model can provide a natural framework to accommodate tiny neutrino masses, while its experimental testability and notable predictiveness are still maintained. This possibility is based on the Observation that two heavy right-handed Majorana neutrinos in the minimal seesaw model may naturally emerge as a pseudo-Dirac fermion In a specific scenario, we show that the tri-bimaximal neutrino mixing can be produced, and only the inverted neutrino mass hierarchy is allowed The low-energy phenomena, including non-unitarity effects in neutrino oscillations, neutrinoless double-beta decays and rare lepton-flavor-violating decays of charged leptons l(alpha) -> l(beta)gamma, have been explored. The collider signatures of the heavy singlet neutrino are also briefly discussed (C) 2010 Elsevier B.V All rights reserved

  • 1157995. Zhang, Hejin
    et al.
    Zhao, Zhiyun
    Meng, Ziyang
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lin, Zongli
    Experimental verification of a multi-robot distributed control algorithm with containment and group dispersion behaviors: The case of dynamic leaders2014In: IEEE/CAA Journal of Automatica Sinica, ISSN 2329-9266, Vol. 1, no 1, p. 54-60, article id 7004620Article in journal (Refereed)
    Abstract [en]

    This paper studies the containment and group dispersion control for a multi-robot system in the presence of dynamic leaders. Each robot is represented by a doubleintegrator dynamic model and a distributed control algorithm is developed to drive the multi-robot system to follow a group of dynamic leaders with containment and group dispersion behaviors. The effectiveness of the algorithm is then verified on a multi-robot control platform.

  • 1157996.
    ZHANG, HENG
    Kristianstad University College. Kristianstad University College, Department of Teacher Education.
    A Journey of Racial Neutrality: the symbolic meaning of the Mississippi in The Adventures of Huckleberry Finn2009Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
  • 1157997.
    ZHANG, HENG
    Kristianstad University, Department of Teacher Education.
    Assessing test Reliability: Comparing Two Versions of Reading Comprehension Testin the TOEFL test2010Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This paper analyzes the two test forms used by TOEFL: IBT and PBT. The analysiswill focus on the reading comprehension section, its design features, content, andscoring results. The aim is to assess the reliability of the two test forms as well as toidentify factors influencing candidate performance in the reading comprehension test.Three factors are identified: test setting, test difficulty and scoring methods and results.The latter two will be focused on because test difficulty consistency directly decides thetest result consistency. And as the goal of the candidate is to achieve as high a score aspossible, and success is measured in terms of numbers, score reliability is a primaryconcern for both candidate and examining body alike.

  • 1157998.
    Zhang, Heng
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Efficient database management based on complex association rules2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The large amount of data accumulated by applications is stored in a database. Because of the large amount, name conflicts or missing values sometimes occur. This prevents certain types of analysis. In this work, we solve the name conflict problem by comparing the similarity of the data, and changing the test data into the form of a given template dataset. Studies on data use many methods to discover knowledge from a given dataset. One popular method is association rules mining, which can find associations between items. This study unifies the incomplete data based on association rules. However, most rules based on traditional association rules mining are item-to-item rules, which is a less than perfect solution to the problem. The data recovery system is based on complex association rules able to find two more types of association rules, prefix pattern-to-item, and suffix pattern-to-item rules. Using complex association rules, several missing values are filled in. In order to find the frequent prefixes and frequent suffixes, this system used FP-tree to reduce the time, cost and redundancy. The segment phrases method can also be used for this system, which is a method based on the viscosity of two words to split a sentence into several phrases. Additionally, methods like data compression and hash map were used to speed up the search.

  • 1157999.
    Zhang, Heng
    et al.
    School of Information Engineering, East China Jiaotong University.
    Liu, Yanli
    School of Information Engineering, East China Jiaotong University.
    Xiong, Nealnaixue
    Department of Business and Computer Science, Southwestern Oklahoma State University.
    Imran, Muhammad Al
    College of Computer and Information Sciences, Almuzahmiyah, King Saud University.
    Vasilakos, Athanasios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    An improved similarity based adaptive step size glowworm algorithm2015In: Journal of Internet Technology, ISSN 1607-9264, E-ISSN 2079-4029, Vol. 16, no 5, p. 905-914Article in journal (Refereed)
    Abstract [en]

    This paper presents the similarity based adaptive step size glowworm swarm optimization algorithm (SBASS-GSO), an improved version of glowworm swarm optimization algorithm (GSO). The standard GSO algorithm lacks unified metric standard to different problems in the selection of neighbor set, which makes the algorithm converge slowly because of improper selection. Because the step size s is fixed, the oscillation phenomenon may occur in local search space, which leads to inferior search accuracy In SBASS-GSO algorithm, we change neighborhood definition base on the similarity not on the distance. The neighborhood is selected by computing average similarity, which provides priori knowledge for the adaptive size s. The dynamic size s is useful for removing oscillation phenomenon and improving the convergence speed. Experimental results demonstrate the efficacy of the proposed glowworm algorithm in capturing multiple optima of a series of complex test functions, such as Zakharov and Sphere functions. We also provide some comparisons of SBASS-GSO with GSO and verify the superiority in the precision and convergence speed.

  • 1158000.
    Zhang, Heng
    et al.
    Huaihai Inst Technol, Lianyungang, Peoples R China..
    Qi, Yifei
    Zhejiang Univ, State Key Lab Ind Control Technol, Hangzhou, Zhejiang, Peoples R China..
    Wu, Junfeng
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Fu, Lingkun
    Zhejiang Univ, State Key Lab Ind Control Technol, Hangzhou, Zhejiang, Peoples R China..
    He, Lidong
    Zhejiang Univ, State Key Lab Ind Control Technol, Hangzhou, Zhejiang, Peoples R China..
    DoS Attack Energy Management Against Remote State Estimation2018In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 5, no 1, p. 383-394Article in journal (Refereed)
    Abstract [en]

    This paper considers a remote state estimation problem, where a sensor measures the state of a linear discrete-time process and has computational capability to implement a local Kalman filter based on its own measurements. The sensor sends its local estimates to a remote estimator over a communication channel that is exposed to a Denial-of-Service (DoS) attacker. The DoS attacker, subject to limited energy budget, intentionally jams the communication channel by emitting interference noises with the purpose of deteriorating estimation performance. In order to maximize attack effect, following the existing answer to "when to attack the communication channel", in this paper we manage to solve the problem of "how much power the attacker should use to jam the channel in each time". For the static attack energy allocation problem, when the system matrix is normal, we derive a sufficient condition for when the maximum number of jamming operations should be used. The associated jamming power is explicitly provided. For a general system case, we propose an attack power allocation algorithm and show the computational complexity of the proposed algorithm is not worse than O(T), where T is the length of the time horizon considered. When the attack can receive the real-time ACK information, we formulate a dynamic attack energy allocation problem, and transform it to a Markov Decision Process to find the optimal solution.

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