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Articles by Ke Zhang
Total Records ( 6 ) for Ke Zhang
  Ke Zhang , Shijun Zhang and Yilu Liu
  This study has proposed a data preprocessing scheme to overcome the negative effects of non-linearity and signal-to-noise ratio level of multiple input signals on the application of Prony algorithm. Technology including short time fourier transform and filtering are utilized to mitigate the negative effects. One case with simulated data and one case with practical measured data are investigated. The results show that the proposed scheme can mitigate the negative effects of input signal on Prony algorithm and should be able to benefit electromechanical mode identification.
  Yuanzhi Wang , Ke Zhang , Yali Zhang , Hui Wang , Fei Guo , Lin Zhang , Hui Zhang , Lijuan CaoBuyun , Cui , Chengyao Li , Li Yuan , Wanjiang Zhang , Ze Xu and Chuangfu Chen
  An outbreak of brucellosis occurred in students on field practice at sheep farm in 2005 at Shihezi, Xinjiang Province, the North-West of China. Five of 7 (71.4%) students were seropositive, showing titers ≥1:160 IU mL-1 in STAT and diagnosed as acute brucellosis with physical examination. To characterize Brucella isolates from the outbreak, the research including face to face investigation, Brucella isolation, multiple locus VNTR-16 analysis (MLVA-16) and genome sequencing were carried out. The investigation showed 42.5% (1,293/3,042) of ewes are sero-positive with RBPT and almost half of ewes aborted. Although, no bacteria were isolated from student blood samples, five individual colonies were isolated from aborted sheep fetuses and were identified as B. melitensis biovar 3 by conventional microbiological tests. MLVA-16 typing indicated that the isolates were clustered in the East Mediterranean with genotype 42. They were similar to wild strains from Guangdong in 2008 and Inner Mongolia in 1994 and 1995. They were most close to strain bru0261 from Pakistan student studying in Germany. Genome sequence and phylogenomic tree showed that pathogen in this study was close to Chinese wild and vaccine strains such as B. melitensis M28, M5-90. Researchers first report pathogens isolated in 1980 and 2005 are genotype 42 containing novel MLVA-16 patterns (1-5-3-13-2-2-3-2-4-20-8-8-4-3-7-7) compared to that both in China and other countries.
  Ke Zhang , Na Liu , Robert J. Twieg , Brian C. Auman and Philip J. Bos
  A novel double-layer alignment film (DLAF) was developed to obtain greater control of the alignment characteristics of the liquid crystal director. The DLAF consists of a thin fluorinated polymer layer on the top of a rubbed non-fluorinated, non-branched polyimide layer (PI 2555). Two types of fluorinated polymer with different chemical structures and wetting behaviour on PI 2555 were chosen, to provide either continuous or discontinuous top layers. The continuous top layer DLAF (DLAF-1) exhibits an abrupt pretilt transition from planar to homeotropic as the top layer thickness increases. The discontinuous top layer DLAF (DLAF-2) exhibits a gradual transition where the pretilt correlates with the coverage of fluorinated top layer. These two types of transitions fit with de Gennes′ local Frederick′s transition and Kwok′s inhomogeneous alignment theories, respectively. The abrupt pretilt transition system may be promising for chemical/biosensor applications, whereas the gradual transition system is suitable for pretilt control in LCD devices.
  Ke Zhang , Na Liu , Robert J. Twieg and Philip J. Bos
  Liquid crystal-based detectors of bio/chemical molecules based on a surface alignment transition of the liquid crystal director have been demonstrated. This type of detector could be made more sensitive if the alignment transition was more abrupt and tunable to be at a 'trigger' point for the desired level of concentration of the target molecule. In this study, we investigate the use of 'double layer alignment films' to cause a more abrupt change in the bulk surface alignment of a liquid crystal-based sensor of lecithin. We show that the detection level of the percentage of lecithin dissolved in the liquid crystal host can be controlled from greater than 4% for a conventional single layer alignment film, to less than 0.1% using the double layer alignment film method. This result verifies an earlier theory, which predicted that a double layer alignment film should provide an abrupt surface alignment transition. The utility of this controllable surface alignment transition as a sensor lies in the anisotropy of liquid crystal materials and the amplification of a detectable signal arising from this anisotropy that results from the alignment of the bulk liquid crystal material in contact with it. For example, the surface alignment change would be expected to cause a large change in capacitance (x2) of a micro-capacitor on an integrated circuit. This work provides a direction for enhancement of liquid crystal-based sensors of other biomolecules, drugs and chemicals.
  Phuong Pham , Marcus B. Smolka , Peter Calabrese , Alice Landolph , Ke Zhang , Huilin Zhou and Myron F. Goodman
  Activation-induced cytidine deaminase (AID) initiates somatic hypermutation and class switch recombination in B cells by deaminating C → U on transcribed DNA. Here we analyze the role of phosphorylation and phosphorylation-null mutants on the biochemical behavior of AID, including enzyme specific activity, processivity, deamination spectra, deamination motif specificity, and transcription-dependent deamination in the presence and absence of RPA. We show that a small fraction of recombinant human AID expressed in Sf9 insect cells is phosphorylated at previously identified residues Ser38 and Thr27 and also at Ser41 and Ser43. S43P AID has been identified in a patient with hyper-IgM immunodeficiency syndrome. Ser-substituted phosphorylation-null mutants (S38A, S41A, S43A, and S43P) exhibit wild type (WT) activity on single-stranded DNA. Deamination of transcribed double-stranded DNA is similar for WT and mutant AID and occurs with or without RPA. Although WT and AID mutants catalyze processive deamination favoring canonical WRC hot spot motifs (where W represents A/T and R is A/G), their deamination spectra differ significantly. The differences between the WT and AID mutants appear to be caused by the replacement of Ser as opposed to an absence of phosphorylation. The spectral differences reflect a marked change in deamination efficiencies in two motifs, GGC and AGC, which are preferred by mutant AID but disfavored by WT AID. Both motifs occur with exceptionally high frequency in human switch regions, suggesting a possible relationship between AID deamination specificity and a loss of antibody diversification.
  Phuong Pham , Ke Zhang and Myron F. Goodman
  Somatic hypermutation in the variable regions of immunoglobulin genes is required to produce high affinity antibody molecules. Somatic hypermutation results by processing G·U mismatches generated when activation-induced cytidine deaminase (AID) deaminates C to U. Mutations at C/G sites are targeted mainly at deamination sites, whereas mutations at A/T sites entail error-prone DNA gap repair. We used B-cell lysates to analyze salient features of somatic hypermutation with in vitro mutational assays. Tonsil and hypermutating Ramos B-cells convert C→U in accord with AID motif specificities, whereas HeLa cells do not. Using tonsil cell lysates to repair a G·U mismatch, A/T and G/C targeted mutations occur about equally, whereas Ramos cell lysates make fewer mutations at A/T sites (~24%) compared with G/C sites (~76%). In contrast, mutations in HeLa cell lysates occur almost exclusively at G/C sites (>95%). By recapitulating two basic features of B-cell-specific somatic hypermutation, G/C mutations targeted to AID hot spot motifs and elevated A/T mutations dependent on error-prone processing of G·U mispairs, these cell free assays provide a practical method to reconstitute error-prone mismatch repair using purified B-cell proteins.
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