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Articles by Yi Chen
Total Records ( 6 ) for Yi Chen
  Theodore M. Hammett , Zunyou Wu , Tran Tien Duc , David Stephens , Sheena Sullivan , Wei Liu , Yi Chen , Doan Ngu and Don C. Des Jarlais

Aims  This paper reviews the evolution of government policies in China and Vietnam regarding harm reduction interventions for human immunodeficiency virus (HIV) prevention, such as needle/syringe provision and opioid substitution treatment.

Methods  The work is based upon the authors` experiences in and observations of these policy developments, as well as relevant government policy documents and legislation.

Results  Both countries are experiencing HIV epidemics driven by injection drug use and have maintained generally severe policies towards injection drug users (IDUs). In recent years, however, they have also officially endorsed harm reduction. We sought to understand how and why this apparently surprising policy evolution took place. Factors associated with growing support for harm reduction were similar but not identical in China and Vietnam. These included the emergence of effective `champions` for such policies, an ethos of pragmatism and receptivity to evidence, growing collaboration across public health, police and other sectors, the influence of contingent events such as the severe acute respiratory syndrome (SARS) epidemic and pressure from donors and international organizations to adopt best practice in HIV prevention.

Conclusions  Ongoing challenges and lessons learned include the persistence of tensions between drug control and harm reduction that may have negative effects on programs until a fully harmonized policy environment is established. Excessive reliance on law enforcement and forced detoxification will not solve the problems of substance abuse or of HIV among drug users. Ongoing evaluation of harm reduction programs, as well as increased levels of multi-sectoral training, collaboration and support are also needed.

  Lianjun Liu , Bin Liu , Lihui Dong , Jie Zhu , Haiqin Wan , Keqin Sun , Bin Zhao , Haiyang Zhu , Lin Dong and Yi Chen
  In situ FT-IR was employed to investigate CO or/and NO interaction with CuO supported on Ce0.67Zr0.33O2 (hereafter denoted as CZ) catalysts. The physicochemical properties of CuO–CZ were also studied by combination of XRD, TPR and NO + CO activity tests. The results indicated that the dispersed CuO species were the main active components for this reaction. The catalysts showed different activities and selectivities at low and high temperatures, which should be resulted from the reduction of dispersed copper oxide species. This reaction went through different mechanisms at low and high temperatures due to the change of active species. FT-IR results suggested: (1) CO was activated by oxygen originating from CZ support, which led to surface carbonates formation, and partial dispersed CuO was reduced to Cu+ species above 150 °C; (2) NO interacted with the dispersed CuO and formed several types of nitrite/nitrate species, whereas crystalline CuO made little contribution to the formation of new NO adsorbates; (3) NO was preferentially adsorbed on CuO–CZ catalysts compared with CO in the reactants mixture. These adsorbed nitrite/nitrate species exhibited different thermal stability and reacted with CO at 250 °C. As a result, a possible mechanism was tentatively proposed to approach NO reduction by CO over CuO–CZ catalyst.
  Weirong Yao , Shitao Wang , Yi Chen and Heya Wang
  Essential oil was extracted from Flos Sophorae Immaturus (FSI) by simultaneous distilling-extraction (SDE) and vapor-distillation extraction (VDE), gave a yield of 2 and 1.2 mg/g, based on GC/MS analysis, 44 and 29 components were identified in SDE and VDE extracts, respectively. Essential oil extracted by SDE was active against common foodborne pathogens, however, it did not show any activity against fungus. The minimal lethal concentration (MLC) was 0.39 μL/mL using the spread-plate method. The antibacterial activity might be due to phenols, such as eugenol in the essential oil. For essential oil-treated Staphylococcus aureus, pretreatment with potassium sorbate, sodium benzoate, or the essential oil markedly lowered bacterial count (p < 0.05), suggesting that FSI essential oil might be used in food preservation to reduce the concentration of chemical preservatives.
  Yi Chen and Stephen J. Knabel
  A fragment end ligation-mediated PCR strategy was used to analyze the AscI pulsed-field gel electrophoresis patterns of Listeria monocytogenes epidemic clone II (ECII), which led to the identification of single-nucleotide polymorphisms (SNPs) in prophage regions that differentiated the two ECII outbreak clones. SNPs in prophages that differentiated the outbreak clones of ECIII and -IV were also identified.
  Yi CHEN , Xu TANG , Sheng-Mao YANG , Chun- Yan WU and Jia-Yu WANG
  Non-availability is one of the most important factors limiting crop yield enhancement. The recovery of applications of 15N-labeled fertilizer and crop residues in a rice-wheat cropping system was determined for up to 6 consecutive growing seasons. The crop residues from the previous season were either incorporated or removed as two different treatments. Our results showed that 16.55%–17.79% (17.17% on average) of the fertilizer N was recovered in the crop during the first growing season, suggesting that more than 80% of crop N was not directly from the N fertilizer. When 15N-labeled residues were applied, 12.01% was recovered in the crop in the first growing season. The average recoveries of fertilizer N and crop residue N in the soil after the first growing season were 33.46% and 85.64%, respectively. N from soil organic matter contributed approximately 83% of the N in the crop when 15N fertilizer was applied or 88% when crop residues were applied. There was a larger difference in the total 15N recovery in plant and soil between N applications in the forms of fertilizer and crop residues. Incorporation of crop residues following the 15N fertilizer application did not significantly promote 15N recovery in the crop or soil. On average, only additional 1.94% of N for the fertilizer-applied field or 5.97% of N for the crop residue-applied field was recovered by the crops during the 2nd and 3rd growing seasons. The total recoveries of 15N in crop and soil were approximately 64.38% for the fertilizer-applied field after 6 growing seasons and 79.11% for the crop residue-applied field after 5 growing seasons. Although fertilizer N appeared to be more readily available to crops than crop residue N, crop residue N replenished soil N pool, especially N from soil organic matter, much more than fertilizer N. Therefore, crop residue N was a better source for sustaining soil organic matter. Our results suggested that the long-term effect of fertilizer or crop residues on N recovery were different in the crop and soil. However, there was little difference between the practices of crop residue incorporation and residue removal following the N fertilizer application.
  Huang-Ying Le , Yong Zhang , Han Liu , Li-Heng Ma , Yi Jin , Qiu-Hua Huang , Yi Chen , Min Deng , Zhu Chen , Sai-Juan Chen and Ting Xi Liu
  The EEN (extra eleven nineteen) gene is one of the fusion partners of mixed-lineage leukemia, located on chromosome 19p13. Here we cloned two een genes (designated as eena and eenb) in zebrafish, which are assigned to linkage groups 8 and 2, respectively. Whole-mount in situ hybridization assay showed that eena and eenb have overlapping but distinct expression patterns during embryogenesis. Ubiquitous or targeted overexpression of eena, but not eenb, into wild-type or transgenic embryos (green fluorescent protein-labeled myeloid progenitors) induced a significant proliferation and ectopic distribution of myeloid progenitors in the yolk sac. Using a morpholino antisense gene knockdown approach, we showed that the number of myeloid progenitors and their downstream mature myelomonocytic cells was significantly decreased in the eena- deficient embryos. Mechanistically, overexpression of eena selectively stimulated ERK phosphorylation and increased the level of transcription factor c-Fos in vitro and in vivo, whereas eena lacking the Src homology 3 domain completely abolished these effects. Furthermore, a MAPK/ERK kinase (MEK) inhibitor, PD98059, blocked the eena-induced cell proliferation and activation of ERK signaling. The results suggest that eena plays an important role in the development of the myeloid cell through activation of the ERK pathway and may provide a valuable reference for future studies of the role of EEN in leukemogenesis.
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