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Articles by H. Xu
Total Records ( 10 ) for H. Xu
  D. Li , H.N. Chen and H. Xu
  A nanostructured surface layer was formed on a carbon steel by means of surface mechanical attrition treatment (SMAT). The microstructure of the surface layer of the SMATed sample was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness and residual stress distribution along the depth from the SMATed surface layer were measured at the same time. Fatigue behaviors of the carbon steel subjected to the SMAT process were investigated. A nanostructured layer with average grains size of ~12.7nm was formed, of which microhardness is more than twice as high as that in matrix and residual compressive stress can reach about −400MPa with maximum depth of ~600μm. The fatigue strength of as-received sample is 267MPa and that of SMATed sample is 302MPa based on fatigue life 5×106cycles. The SMAT process has improved the fatigue strength by as much as 13.1% for the carbon steel. It is shown that the SMAT is an effective method to render the material with the features, such as a nanostructured and work-hardened surface layer as well as compressive residual stresses, which can pronouncedly improve the fatigue strength of the carbon steel.
  R. Zang , J. Bai , H. Xu , L. Zhang , J. Yang , L. Yang , J. Lu and J. Wu
  Real-time quantitative PCR (qPCR) is the most accurate method of quantifying gene expression, provided that suitable endogenous controls are used to normalize the data. To date, no reference genes have been validated for development in Lanzhou fat-tailed sheep (Ovis aries). We have determined the expression profiles of 7 housekeeping genes as candidate reference genes (Actb, Ywhaz, Sdha, Gapdh, Tubb2, Pgk1 and 18S rRNA) in 7 developmental stages (1, 3, 5, 7, 9, 11 and 13 months of age) and 6 tissues (omental fat, liver, tail fat, thigh muscle, subcutaneous fat (backfat above 12th and 13th rib) and perirenal fat) in Lanzhou fat-tailed sheep. The software packages geNorm, NormFinder and BestKeeper were used to evaluate the stability of potential reference genes; each produced comparable results. Initial results showed several of the candidate genes exhibited stable expression throughout development while Actb was identified as the least stable gene. Further analysis with geNorm, NormFinder and BestKeeper identified Gapdh, Tubb2, Sdha and Ywhaz as acceptably stable in gene expression. Comparison of diacylglycerol O-acyltransferase 1 (Dgat1) expression data normalized with geometric averages obtained from combinations of either Gapdh, Sdha, Ywhaz or Tubb2, Sdha, Ywhaz showed no significant differences, indicating that these two combinations are similar. The data provided in this paper may also be useful in guiding researchers performing gene expression in other species of sheep.
  H. Xu , R. De Jong , S. Gameda and B. Qian
  Spatially representative climate data are required input in various agricultural and environmental modelling studies. An agricultural ecodistrict climate database for Canada was developed from climate station data using a spatial interpolation procedure. This database includes daily maximum and minimum air temperatures, precipitation and incoming global solar radiation, which are necessary inputs for many agricultural modelling studies. The spatial interpolation procedure combines inverse distance squared weighting with the nearest neighbour approach. Cross-validation was performed to evaluate the accuracy of the interpolation procedure. In addition to some common error measurements, such as mean biased error and root mean square error, empirical probability distributions and accurate rates of precipitation occurrence were also examined. Results show that the magnitude of errors for this database was similar to those in other studies that used similar or different interpolation procedures. The average root mean square error (RMSE) was 1.7°C, 2.2°C and 3.8 mm for daily maximum and minimum temperature, and precipitation, respectively. The RMSE for solar radiation varied from 16 to 19% of the climate normal during April through September and from 21 to 28% of the climate normal during the remainder of the year.
  Z. C. Luo , F. Simonet , S. Q. Wei , H. Xu , E. Rey and W. D. Fraser
  Aim  We tested the hypothesis that diabetes in pregnancy may differentially affect neonatal outcomes in twin vs. singleton pregnancies. Methods  In a retrospective cohort analysis of twins (n = 422 068) and singletons (n = 14 298 367) born in the USA from 1998 to 2001, we evaluated the adjusted odds ratios of adverse neonatal outcomes comparing diabetic vs. non-diabetic pregnancies, controlling for maternal characteristics. Primary outcomes include macrosomia (birthweight for gestational age > 90th percentile), congenital anomalies, low 5-min Apgar score (< 4) and neonatal death. Results  Diabetes in pregnancy was associated with a similarly increased risk of congenital anomalies (adjusted odds ratios 1.52 vs. 1.59) and smaller increased risks of preterm birth (adjusted odds ratios 1.27 vs. 1.49) and macrosomia (adjusted odds ratios 1.38 vs. 2.03) in twins vs. singletons, but reduced risks of low 5-min Apgar score (adjusted odds ratio 0.74) and neonatal death (adjusted odds ratio 0.76) in twins but not singletons. Conclusions  Diabetes in pregnancy may differentially affect neonatal outcomes in twins and singletons, indicating a need for further studies to differentiate the effects by clinical subtypes of diabetes in pregnancy, and to consider/evaluate differential clinical management protocols of diabetes in multiple vs. singleton pregnancies.
  M. Y. Kan , D. Z. Zhou , D. Zhang , Z. Zhang , Z. Chen , Y. F. Yang , X. Z. Guo , H. Xu , L. He and Y. Liu
  Aims  To investigate the two variants (rs1387153 and rs10830963) near/in the melatonin receptor 1B gene (MTNR1B) and to determine their association with Type 2 diabetes, as well as with the regulation of fasting plasma glucose (FPG) in Han Chinese subjects.

Methods  The two variants were genotyped in 1912 unrelated Type 2 diabetic patients and 2041 healthy individuals. Association with Type 2 diabetes was calculated by logistic regression with adjustments for sex, age and body mass index. The possible connection between the risk alleles and FPG was analysed by multiple linear regression.

Results  The two polymorphisms were associated with FPG levels in the healthy individuals (P = 0.003 and P = 0.002, respectively), and the G allele of rs10830963 was also associated with an increased risk of Type 2 diabetes in our patient sample (odds ratio, 1.12; 95% confidence interval, 1.02-1.23; P = 0.024). Moreover, the linkage disequilibrium degree of two single nucleotide polymorphisms was high (r2 = 0.66), which is similar to that of Europeans.

Conclusions  The common variant in MTNR1B confers the risk of Type 2 diabetes and modulates FPG in both the Han Chinese and European populations.

  W.L. Peng and H. Xu
  Critical chain method requires the non-critical activities to be executed as late as possible. However, in some project cases, such as software development projects, the critical chain method might result in the higher risk of project delay. In this study, we present a revised critical chain method for the projects where all the activities should be scheduled as early as possible. The revised critical chain method, defined as the Active Critical Chain Method (ACCM), is generated based on the active baseline schedule, where all activities are scheduled as early as possible. The generation procedure of ACCM schedule is illustrated, including searching critical chain and setting buffers. Referring to the conceptual models of the Resource Constrained Project Scheduling Problems (RCPSPs), we propose the scheduling problem of ACCM and formulate it. Since, the scheduling problem of ACCM is a NP hard problem, we resort to heuristics and the Genetic Algorithm (GA) is investigated to solve it. Finally, a full computation experiment is performed to determine the parameter configuration and effectiveness of the algorithm is verified by some modified benchmark instances.
  A. Jasek , X. Li , H. Xu , R.M. Raab , J.N. Broomhead and J.T. Lee
  Background and Objectives: An experiment (phase 1) was conducted to evaluate the retained activity of a maize-derived, recombinant carbohydrase enzyme (AC1) when exposed to heat during the pelleting process and homogeneity when mixed into mash diet. A second experiment (phase 2) was conducted to evaluate the effects of increasing AC1 concentrations on male broiler growth performance and ileal nutrient digestibility. Materials and Methods: A total of 728 broilers were randomly assigned to seven dietary treatments with each treatment consisting of 13 replicates with eight Cobb 500 male broilers. The experimental design included a positive control (PC), a reduced energy negative control (NC, comprising the PC less 132 kcal kg1) diet and five additional treatments with increasing dose of AC1 (5, 50, 100, 250 and 500 U glucanase kg1) added to the NC diet. Birds were fed a starter ration for the duration of the study (16 d). Average body weight (BW), mortality adjusted feed conversion ratio (FCR) and feed consumption (FC) were determined on 16 d of age. At the conclusion of the experiment, all birds from each replicate pen were necropsied and ileal contents pooled within replicate to determine ileal digestibility of energy (IDE) and nitrogen (IDN). Results: In Phase 1, the recovery of ß-glucanase activity in the pellets (in relation to mash feed) were 111, 83 and 82% when pelleted at 80, 85 and 90°C, respectively. The coefficient of variation of glucanase recovered when AC1 was mixed into feed and was less than 10%. In Phase 2, the inclusion of AC1 at 100 and 250 U glucanase kg1 increased (p<0.01) BW compared to both the PC and NC fed broilers. This elevation in BW was related to an increase (p<0.01) in FC. As expected, reducing energy in the NC diet decreased (p<0.01) IDE value of the feed as compared to the PC diet. The addition of AC1 to supply ≥100 U glucanase kg1 increased (p<0.01) IDE compared to the NC diet and restored IDE equivalent (p>0.05) to the PC diet. Regression analysis confirmed linear and quadratic increases in IDE and IDN with the addition of AC1. Conclusion: These data demonstrate the thermal stability of maize-derived, recombinant AC1 and that increasing levels positively influences nutrient digestibility leading to significant improvements in broiler performance.
  H. Xu , D. Hartono and K. -L. Yang
  We report a method for detecting Escherichia coli using a nematic liquid crystal (LC), 4-cyano-4′-pentylbiphenyl (5CB). Among three E. coli strains tested, TOP10 strain grown on agar plates induces a homeotropic orientation of LCs whereas DH5α and JM109 strains do not. This results in a clear distinction in the optical appearance of LCs as either uniformly dark or bright under polarised light. The LC-based method provides a simple, rapid and low-cost method of identifying E. coli strains.
  C. Zhu , H. Xu , J. Zhang , K. Wang and P. Zhu
  Suppressor of cytokine signaling (SOCS) molecules belong to intracellular proteins that inhibit Janus kinase as well as signal transduction and activators of transcription pathways. In this study, we investigated whether SOCS-1–silenced dendritic cells (DCs) prolonged allograft survival in rat intestinal transplantation. Donor bone marrow–derived DCs were genetically transfected with SOCS-1 siRNA using liposomes. The level of SOCS-1 expression was quantitated by Western blots. DC function was assessed by MTT in mixed leukocyte reactions. We injected donor-derived SOCS-1 silenced DCs 7 days before heterotopic intestinal transplantation between SD donors and Wistar recipients. We compared untransfected DCs and silenced DCs to suppress allogeneic mixed leukocyte reactions. Recipients pretreated with SOCS-1–silenced DCs showed moderate survival prolongation with a mean allograft survival of 18.3 ± 5.3 days (P < .05), compared with 6.4 ± 2.0 days in the control group and 7.2 ± 2.1 days in a control siRNA transfection DC group. The difference between untreated DCs group and the control group was not significant. In summary, SOCS-1 silenced DCs induced allogeneic T-cell hyporesponsiveness in vitro, promoting allograft survival in rat intestinal transplantation.
  T. Chen , H. Xu , H.Q. Wang , Y. Zhao , C.F. Zhu , Y.H. Zhang , M.J. Ji , Y.B. Hua and W.X. Wu
  Severe graft rejection remains an important obstacle in intestinal transplantation. In this study, dendritic cells (DCs) isolated from rat bone marrow were cultured for 5 days, and triptolide applied for 3 more days. The recipient rats were pretreated with donor triptolide-modified or not modified DC. Small bowel transplantation was performed to observed survival times. We demonstrated that triptolide markedly inhibited both the expression of CD80 and MHCII expression on DCs. Triptolide-modified DCs stimulated lower proliferative responses among allogeneic T cells, prolonging the survival of intestinal allografts in rats. These results suggested that pretreatment with triptolide-modified DC prolonged the survival of rat small bowel allografts after transplantation.
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