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Articles by Xiang Li
Total Records ( 12 ) for Xiang Li
  Aditi Singh , Helen H. Lou , Ralph W. Pike , Adedeji Agboola , Xiang Li , Jack R. Hopper and Carl L. Yaws
  As an emerging discipline, nanotechnology has the potential to improve environmental sustainability through its application in pollution prevention, treatment, remediation, etc. One challenging issue in the growth of nanotechnology is how to produce purified carbon nanotubes (CNT) in commercial quantities at affordable price and with low environmental impacts. A detailed assessment of such a manufacturing process from both economic and environmental aspects at the design phase will benefit both the industry and the society. In this work, an LCA type of environmental impact assessment is conducted for the conceptual design of two catalytic, chemical vapor deposition processes (CNT-PFR and CNT-FBR) used for continuous large–scale production of CNT. The core of both processes is a high-temperature catalytic reactor. Mineral acids are used in the purification steps, from which liquid and solid wastes are generated and must be treated before discharge. Based on the simulation results, the environmental impacts of each process are calculated. The results provide vital information that can be used during the design phase of these processes for better decision-making.
  Xihui Zhang , Yingping Huang , John Crabtree and Xiang Li
  A Wireless Local Loop (WLL) uses radio signals to connect customer premise equipment to a local exchange on the public switched telephone network. Compared to wireline local loops, WLLs are easier to deploy and less costly to maintain. As such, WLLs have the potential to help telephony providers overcome the “last mile” problem in delivering telephony services. One of the most important considerations in deploying WLLs is to determine the best channel allocation algorithm. Numerous channel allocation algorithms exist, including no repacking, always repacking and repacking on demand. This study provides an overview of channel allocation algorithms for WLLs, using a decision-tree approach. It also reviews related studies and recommends several future research directions. The algorithm overview and research review can help Information Systems (IS) and Computer Science (CS) researchers as well as practitioners gain a solid understanding of these channel allocation algorithms. The recommended research directions can serve to guide interested IS and CS researchers in future research.
  Xiang Li and Jing Zhang
  Multi-core processors are becoming ubiquitous with the continuous development of hardware technology. But many applications are sequential applications and they receive no benefits running on multi-core processors. Addressing this problem, using parallel techniques improve the sequential program running on the multi-core processors. In this paper, we introduced three parallel types of thread level parallelism. Typical DOALL, DOACROSS, DSWP and PS-DSWP techniques are described. These techniques can explore the parallel from sequential application, but much dependence is not easily predictable or manifests them infrequently by the non-speculative transformation. So many speculative techniques, such as thread level speculation (TLS), Speculation DSWP (SpecDSWP), Speculative PS-DSWP (SpecPS-DSWP) and Interprocedural SpecPS-DSWP (iSpecPS-DSWP), are proposed to break problematic dependences to enhance parallelism. We introduced these speculative parallel techniques and described their execution. SpecDSWP, SpecPS-DSWP and iSpecPS-DSWP are compared from supporting speculation types, memory version and implement steps. At last, some extended TM systems which support TLS techniques are analyzed from thread spawning mechanism, context passing mechanism and sequential ordering.
  Genghuang Yang , Xiang Li , Mingkun Ma and Mingzhe Cao
  Electroencephalogram (EEG) and electromyography (EMG) are used to control manipulator in human-machine interface. Steady-state Visual Evoked Potentials (SSVEP) in EEG and common EMG coding are the control of information for detail tasks. Experiments under the simulated space environment are done to test the reliability of manipulator controlling in key operation on a panel.
  Wei Wei , Xiang Li , Bin Zhou , Hongfang Zhou , Peiyi Shen , Lei Wang and Jing Zhang
  Wireless Radio Frequency (RF) technology, which can take the place of cable, has been widely used in many current fields as one of information technologies with widest horizon of development. The problems caused by the environment restrictions and the unfavorable conditions for cable wiring have been solved because of the emergence of the wireless. Its three important characteristics and advantages are low costing, low power consumption and peer-to-peer communication. During the design procedure, the system is divided into three major modules according to the functional structure, namely central control module, wireless transceiver module and computer dealing software, The central control module uses Sygnal company's low power enhanced 51 MCU C8051F310 as CPU, mainly to complete the data acquisition and processing. The wireless transceiver module is made up of TI CC1101 wireless transceiver chip, which mainly realizes wireless data transmission and The computer dealing software real-timely displays and deals with the data through visual, friendly programming interface, based on C#.NET. Final achievement of the system design is two compact communication devices, one of them connects with PC through RS-232 interface, System is operated through the graphical user interface based on windows, which is very convenient to operate. Debugging result indicated that data acquisition, processing and transmission could be achieved in wireless or wired way under the control of PC and it visually displays the results to the user, satisfies request of the wireless power monitoring data communication system, reaches the technical index.
  Xihui Zhang , Tao Hu , Hua Dai and Xiang Li
  The practice of software development has evolved steadily over the decades. Numerous methods and models (e.g., life cycle models and agile methods) have been proposed to enhance its efficiency and effectiveness. This study provides a testing centric view of software development practices. Specifically, it reviews software development methodologies (i.e., methods and models), identifies the latest trends in the industry and discusses their implications. The review of methodologies, the identification of these trends and the discussion of their implications will be useful to software development educators, students, practitioners and researchers.
  Hongbing Han , Xiang Li , Kun Yu and Zhengxing Lian
  During the early stage of incubation of chicken eggs, different CO2 concentrations play an important role in the embryonic and postnatal growth. However, the mechanism involved in this process is still not well clarified. In this study, chicken eggs were incubated under different CO2 concentration levels (0.03-0.05, 2, 5 and 10%) during the 1st 4 days of incubation and measured of several embryo growth parameters. It was then found that higher CO2 concentration significantly played down the albumen pH value after 2 days of incubation and the embryo weight and length, diameter of area vasculosa of yolk sac and number of somite all decreased with the increasing of CO2 level. Compared with the mortality (3.23%) and abnormality (0%) in the control group, the corresponding percentages in three treatment groups were much higher with the lowest at 17 and 29%, respectively. Taking the two sides together, it might be well concluded that high CO2 concentration during the 1st 4 days of egg incubation inhibited chicken embryonic development through the lowering of albumen pH value.
  Khairy M.A. Zoheir , Nermin El-Halawany , Xiang Li , Moaeen-ud- Din and Li-Guo Yang
  The aim of the present study is to develop a new culture system, capable of producing healthy preantral follicles, which can reach full maturity especially in a long-term culture. To achieve this task we used CR1aa medium in combination with endocrine hormone (FSH), growth factor (EGF) and/or Insulin-Transferrin-Selenium (ITS). More over, we compared its efficacy with TCM-199 medium plus the same supplements. Culturing of the preantral follicles with diameters of 60, 80 and 100 μm were commenced at follicle recovery (day 1) and continued for 26 days. Follicle diameters and morphological deformity or degeneration were monitored on the day of collection and during the culture (days 5, 10, 15, 20 and 26). Compared with TCM-199 medium, culture system using CR1aa medium showed a significant increase in the size and viability of the follicles of all size classes regardless of the used supplements. The follicular survival rate at 26th day of the culture in CR1aa culture system reached 28%. Regardless of culture treatments, the greatest follicular growth rate was between days 5, 10 and 15 of culture. The survived follicles maintained their morphology throughout the culture, with presence of a thecal layer and basement membrane surrounding the granulosa cells. In conclusion, CR1aa medium plus FSH, EGF and/or ITS can be a promising culture system for long-term culture of bovine preantral follicles.
  Ming-Chieh Shun , Yair Botbol , Xiang Li , Francesca Di Nunzio , Janet E. Daigle , Nan Yan , Judy Lieberman , Marc Lavigne and Alan Engelman
  Lens epithelium-derived growth factor (LEDGF)/p75 functions as a bimodal tether during lentiviral DNA integration: its C-terminal integrase-binding domain interacts with the viral preintegration complex, whereas the N-terminal PWWP domain can bind to cellular chromatin. The molecular basis for the integrase-LEDGF/p75 interaction is understood, while the mechanism of chromatin binding is unknown. The PWWP domain is homologous to other protein interaction modules that together comprise the Tudor clan. Based on primary amino acid sequence and three-dimensional structural similarities, 24 residues of the LEDGF/p75 PWWP domain were mutagenized to garner essential details of its function during human immunodeficiency virus type 1 (HIV-1) infection. Mutating either Trp-21 or Ala-51, which line the inner wall of a hydrophobic cavity that is common to Tudor clan members, disrupts chromatin binding and virus infectivity. Consistent with a role for chromatin-associated LEDGF/p75 in stimulating integrase activity during infection, recombinant W21A protein is preferentially defective for enhancing integration into chromatinized target DNA in vitro. The A51P mutation corresponds to the S270P change in DNA methyltransferase 3B that causes human immunodeficiency, centromeric instability, and facial anomaly syndrome, revealing a critical role for this amino acid position in the chromatin binding functions of varied PWWP domains. Our results furthermore highlight the requirement for a conserved Glu in the hydrophobic core that mediates interactions between other Tudor clan members and their substrates. This initial systematic mutagenesis of a PWWP domain identifies amino acid residues critical for chromatin binding function and the consequences of their changes on HIV-1 integration and infection.
  Shunji Jia , Zhen Ren , Xiang Li , Ying Zheng and Anming Meng
  The transforming growth factor-β ligands Nodal, activin, and Vg1 play important roles in mesendoderm induction and patterning during vertebrate embryogenesis. These ligands are believed to transduce the signal through the receptor-activated transcription factors Smad2 and Smad3. However, the roles of smad2/3 genes in development of zebrafish embryos are largely unknown because the presence of multiple smad2/3 genes and their maternal expression have hampered the investigation of their developmental roles. We generated potent and specific dominant-negative forms of zebrafish Smad2, Smad3a, and Smad3b by mutating multiple amino acids. Overexpression of these mutants abolished mesendoderm induction by ectopic Nodal signaling in zebrafish embryos. Expression of dominant-negative smad2/3 abrogated Smad2/3 activities in wild-type embryos and caused various mesendodermal defects similar to those in Nodal-deficient embryos. Smad2/3-deficient cells transplanted into the blastodermal margin of wild-type hosts preferentially differentiated into ectodermal tissues rather than mesendodermal tissues, supporting the idea that response of cells to mesendoderm inducers requires Smad2/3 activities. Interference with Smad2/3 activities in Zoep, Moep, and MZoep mutant embryos resulted in more severe mesendodermal defects. Thus, our data reveal that Nodal signaling and mesendoderm induction depend on Smad2/3 and suggest that transforming growth factor-β signals other than Nodal also contribute to Smad2/3 signaling and embryonic patterning.
  Bin Guan , Pooja Pungaliya , Xiang Li , Carlos Uquillas , Laura N. Mutton , Eric H. Rubin and Charles J. Bieberich
  The NKX3.1 gene located at 8p21.2 encodes a homeodomain-containing transcription factor that acts as a haploinsufficient tumor suppressor in prostate cancer. Diminished protein expression of NKX3.1 has been observed in prostate cancer precursors and carcinomas. TOPORS is a ubiquitously expressed E3 ubiquitin ligase that can ubiquitinate tumor suppressor p53. Here we report interaction between NKX3.1 and TOPORS. NKX3.1 can be ubiquitinated by TOPORS in vitro and in vivo, and overexpression of TOPORS leads to NKX3.1 proteasomal degradation in prostate cancer cells. Conversely, small interfering RNA-mediated knockdown of TOPORS leads to an increased steady-state level and prolonged half-life of NKX3.1. These data establish TOPORS as a negative regulator of NKX3.1 and implicate TOPORS in prostate cancer progression.
  Xia Gao , Jun Wen , Long Zhang , Xiang Li , Yuanheng Ning , Anming Meng and Ye-Guang Chen
  Wnt signaling, via the activation of the canonical β-catenin and lymphoid enhancer factor (LEF)/T-cell factor pathway, plays an important role in embryogenesis and cancer development by regulating the expression of genes involved in cell proliferation, differentiation, and survival. Dapper (Dpr), as a Dishevelled interactor, has been suggested to modulate Wnt signaling by promoting Dishevelled degradation. Here, we provide evidence that Dpr1 shuttles between the cytoplasm and the nucleus. Although overexpressed Dpr1 was mainly found in the cytoplasm, endogenous Dpr1 was localized over the cell, and Wnt1 induced its nuclear export. Treatment with leptomycin B induced nuclear accumulation of both endogenous and overexpressed Dpr1. We further identified the nuclear localization signal and the nuclear export signal within Dpr1. Using reporter assay and in vivo zebrafish embryo assay, we demonstrated that the forced nuclearly localized Dpr1 possessed the ability to antagonize Wnt signaling. Dpr1 interacted with β-catenin and LEF1 and disrupted their complex formation. Furthermore, Dpr1 could associate with histone deacetylase 1 (HDAC1) and enhance the LEF1-HDAC1 interaction. Together, our findings suggest that Dpr1 negatively modulates the basal activity of Wnt/β-catenin signaling in the nucleus by keeping LEF1 in the repressive state. Thus, Dpr1 controls Wnt/β-catenin signaling in both the cytoplasm and the nucleus.
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