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Articles by J. Xu
Total Records ( 14 ) for J. Xu
  A.M.J.B. Adikari , W.A.D. Nayananjalie , J. Xu and E.J. Smith
  This study was carried out with the aim of comparing the phenotypic variations of growth and reproductive performances among seven heritage varieties of turkeys with hybrid turkeys. Differences among turkey varieties for Body Weight (BW), Average Daily Gain (ADG) and Feed Conversion Ratio (FCR) were significant (p≤0.05) with Narragansett being the heaviest and Royal Palm showed the lowest BW and ADG. The mean ADG gradually increased up to 159 days of age and then decreased thereafter in heritage turkeys. Consistently better FCR for males and females reported in Blue Slate and White Holland, respectively. Narragansett was characterized by the highest semen volume and sperm count, while Bourbon Red had the lowest. White Holland had the highest sperm concentration and viability, while Bourbon Red had the lowest. Age at first egg (AFE) was also different among turkey varieties. Heritage turkeys are generally characterized by late sexual maturity. Among heritage varieties, Midget White reported the least AFE and highest egg productions than others. As expected, hybrid turkeys were superior to heritage birds in performance for most of the traits evaluated in the study. In conclusion, the differences observed in growth and reproductive performances within heritage turkeys could be useful for future breeding programs to improve the existing production and reproductive performances of turkeys.
  J. Xu
 

Using official police records, interviews with motorcycle taxi drivers and the participant observation of their working activities in Tianzhi city, China, this paper examines how and why a dimension of social stratification—household registration (hukou)—is related to the risk of robbery victimization and attempts to evaluate the effectiveness of applying lifestyle/routine activity theory to contemporary urban China. It discloses that migrant motorcycle taxi drivers are highly overrepresented in robbery victimization. Their night-time working practices enhance their chances of being robbed by both increasing exposure to likely offenders and reducing the presence of capable guardians. The study further explores how a structural factor—motorcycle ban policy—shapes different routine activities between migrant and resident motorcycle taxi drivers and, by extension, differential risks of robbery victimization. The paper concludes by pointing out the importance of locating lifestyle/routine activities in a larger Chinese macro-social structural context. The outcome is one of the very first ethnographic analyses of crime conducted in situ in China.

  S. L Zheng , V. L Stevens , F Wiklund , S. D Isaacs , J Sun , S Smith , K Pruett , K. E Wiley , S. T Kim , Y Zhu , Z Zhang , F. C Hsu , A. R Turner , J. E Johansson , W Liu , J. W Kim , B. L Chang , D Duggan , J Carpten , C Rodriguez , W Isaacs , H Gronberg and J. Xu
 

Single nucleotide polymorphisms (SNP) at 11q13 were recently implicated in prostate cancer risk by two genome-wide association studies and were consistently replicated in multiple study populations. To explore prostate cancer association in the regions flanking these SNPs, we genotyped 31 tagging SNPs in a ~110 kb region at 11q13 in a Swedish case-control study (Cancer of the Prostate in Sweden), including 2,899 cases and 1,722 controls. We found evidence of prostate cancer association for the previously implicated SNPs including rs10896449, which we termed locus 1. In addition, multiple SNPs on the centromeric side of the region, including rs12418451, were also significantly associated with prostate cancer risk (termed locus 2). The two groups of SNPs were separated by a recombination hotspot. We then evaluated these two representative SNPs in an additional ~4,000 cases and ~3,000 controls from three study populations and confirmed both loci at 11q13. In the combined allelic test of all four populations, P = 4.0 x 10–11 for rs10896449 at locus 1 and P = 1.2 x 10–6 for rs12418451 at locus 2, and both remained significant after adjusting for the other locus and study population. The prostate cancer association at these two 11q13 loci was unlikely confounded by prostate-specific antigen (PSA) detection bias because neither SNP was associated with PSA levels in controls. Unlike locus 1, in which no known gene is located, several putative mRNAs are in close proximity to locus 2. Additional confirmation studies at locus 2 and functional studies for both loci are needed to advance our knowledge on the etiology of prostate cancer. (Cancer Epidemiol Biomarkers Prev 2009;18(6):1815–20)

  S Hu , Z Zheng , X Yuan , W Wang , Y Song , H Sun and J. Xu
 

Background— Despite its widespread use and short-term efficacy, substantial uncertainty remains about the long-term outcomes and cost-effectiveness of off-pump coronary artery bypass (OPCAB).

Methods and Results— A retrospective review of prospectively collected data was conducted of 6665 consecutive patients undergoing isolated coronary artery bypass graft (CABG) at our institution during 1999 to 2006. All patients were followed up until September 30, 2008. Short- and long-term outcomes were compared between OPCAB and conventional CABG. The 2 main long-term outcome measures were repeat revascularization and the composite outcome of major vascular events. Cost comparison at 2 years in a propensity-matched sample during follow-up was also a study interest. The overall mean baseline age was 60.3±8.6 years, and 17.0% were women. Compared with conventional CABG, patients who underwent OPCAB had lower rates of atrial fibrillation (P=0.003) and requirements for blood transfusion (P=0.03) and ventilation time >24 hours (P<0.001). After an average of 4.5 years of follow-up, the rates of repeat revascularization (adjusted hazard ratio, 1.40; 95% confidence interval, 1.03 to 1.89) and major vascular events (adjusted hazard ratio, 1.23; 95% confidence interval, 1.09 to 1.39) were significantly higher in the OPCAB than the conventional CABG group. At 2 years, OPCAB was associated with increased additional direct costs per patient compared with conventional CABG and had a similar survival rate.

Conclusions— Compared with conventional CABG, OPCAB is associated with small short-term gain but increased long-term risks of repeat revascularization and major vascular events, especially among high-risk patients. Moreover, OPCAB consumes more resources and is less cost-effective in the long run.

  B. I. Freedman , D. W. Bowden , S. S. Rich , J. Xu , L. E. Wagenknecht , J. Ziegler , P. J. Hicks and C. D. Langefeld
  Aims/hypothesis  Glomerular filtration rate (GFR), end-stage renal disease and albuminuria are highly heritable. We performed a genome-wide linkage scan in 416 Diabetes Heart Study (DHS) families to detect loci that contributed to renal function and albuminuria.

Materials and methods  A total of 1067 individuals (900 with Type 2 diabetes mellitus) from 348 European American and 68 African American DHS families had measures of urine albumin : creatinine ratio (ACR), serum creatinine concentration and Modification of Diet in Renal Disease estimated GFR (eGFR). Variance components quantitative trait linkage analysis (using SOLAR) was computed.

Results  Participants had mean ± sd age 61.4 ± 9.4 years; diabetes duration 10.5 ± 7.4 years; eGFR 1.15 ± 0.32 ml/sec; and urine ACR 15.8 ± 67.2 mmol/l (median 1.4). In all families, significant evidence for linkage of GFR was observed on chromosome 2p16 (log of the odds; LOD = 4.31 at 72.0 cM, ATA47C04P/D2S1352) and 1p36 (LOD = 3.81 at 45.0 cM, D1S3669/D1S3720), with suggestive evidence on 7q21 (LOD = 2.42 at 99.0 cM, D7S820/D7S821) and 13q13 (LOD = 2.28 at 28.0 cM, D13S1493/D13S894). The evidence for linkage to ACR was far weaker, on 13q21-q22 (LOD = 1.84 at 50 cM, D13S1807/D13S800), 3p24-p23 (LOD = 1.81 at 58 cM, D3S3038/D3S2432) and 10p11 (LOD = 1.78 at 71.0 cM, D10S1208/D10S1221).

Conclusions/interpretations  The eGFR linkage peaks on 2p16, 7q21 and 13q13 closely overlap with nephropathy peaks identified in family studies enriched for severe kidney disease. These diabetes-enriched families provide an opportunity to map genes regulating renal function, potentially leading to the identification of genes producing nephropathy susceptibility in subjects with Type 2 diabetes.

  A. J. Bleyer , D. Hire , G. B. Russell , J. Xu , J. Divers , Z. Shihabi , D. W. Bowden and B. I. Freedman
  Aims  To determine if the relationship between serum glucose concentration and glycated haemoglobin is different between African-Americans and whites.

Methods  Retrospective cross-sectional study comparing the association between glycated haemoglobin and serum glucose levels, based upon ethnicity. Two databases were evaluated: (i) 4215 African-American and 6359 white outpatients who had simultaneous glycated haemoglobin, random serum glucose and creatinine concentration measurements between 2000 and 2007 at the North Carolina Baptist Hospital and (ii) 1021 white and 312 African-American Diabetes Heart Study (DHS) participants.

Results  In North Carolina Baptist Hospital clinic attendees, a given glycated haemoglobin was associated with higher serum glucose concentrations in African-Americans compared with whites. In a multivariate model with glycated haemoglobin as the outcome variable, racial differences remained significant after adjustment for serum glucose, age, gender and kidney function. For individuals with a serum glucose between 5.6 and 8.3 mmol/l, the glucose : glycated haemoglobin ratio was 1.03 ± 0.16 mmol/l/% in white individuals and 0.99 ± 0.17 mmol/l/% in African-Americans (P < 0.0001). For a glycated haemoglobin value of 7.0%, there was a 0.98-mmol/l difference in predicted serum glucose concentration in 50-year-old African-American men, relative to white. Results were replicated in the DHS, where in a best-fit linear model, after adjustment for glucose, African-American race was a significant predictor of glycated haemoglobin (P < 0.0001).

Conclusions  African-Americans have higher glycated haemoglobin values at given serum glucose concentrations relative to whites. This finding may contribute to the observed difference in glycated haemoglobin values reported between these race groups.

  J. Xu and J. Zhang
  This study investigates the features of synchronous collaboration tools, the meanings of the features and identifies common and key characteristics of synchronous collaboration tools. We organize features by the six stages of meeting process: starting meeting, communication, presentation, interaction, administration and ending meeting. We test nine collaboration tools that are today`s market leaders. Data collected in this study come from our experiments and online documents. This study will help professionals gain knowledge of what current online meeting market has to offer and aid them make right decisions in selecting tools based on their meeting needs.
  J. Xu , J. Zhang , T. Harvey and J. Young
  This study surveys current asynchronous collaboration tools and their features. Asynchronous collaboration tools, that allow users to collaborate at different times, have evolved from email, discussion board, weblogs and Wiki to advanced tools that integrate multiple functions to make collaboration more powerful and convenient. A great number of such tools have been developed that provide a variety of different features. This study investigates the available features of these tools, the meanings of these features and identifies common and key features. We organize features by four major functional categories: communication, information sharing, electronic calendar and project management. We tested ten asynchronous collaboration tools that present different ways of collaboration and different sets of features. Data collected in this study come from our experiments and online documents. This study will help users gain knowledge of what current asynchronous collaboration tools have to offer and help them select right tools based on their needs.
  A.M.J.B. Adikari , J. Xu , S. Casterlow , H. Li , E.R. Gilbert , A.P. McElroy , D.A. Emmerson , R.A. Dalloul , E.A. Wong and E.J. Smith
  Objective: The aim of this study was to screen the chLEAP-2 gene for DNA sequence variation and to evaluate the relationships among its haplotypes (based on haplogroups), expression levels, weight gain and lesion score in two chicken lines challenged with Eimeria maxima. Methodology: A total DNA sequence of 4.6 kb including the chLEAP-2 gene was screened by re-sequencing of individual amplicons. Sixteen SNPs, including seven each in the promoter and introns and two in exons, were identified. Results: One of the exonic single-nucleotide polymorphism (SNPs) was non-synonymous, involving a cysteine to tyrosine codon change. About 25% of the SNPs were in Hardy Weinberg equilibrium. Linkage disequilibrium (D’) among the SNPs ranged from 0.02-1.00. The haplotypes observed from the 16 SNPs were assembled into 5 haplogroups. The estimated frequencies of the haplogroups ranged from 0.17-0.23 in the combined chicken lines. Although not significant (p>0.05), the chLEAP-2 gene expression varied among haplogroups. Differences among haplogroups for lesion score and weight gain were consistent, but not statistically significant (p>0.05). However, Hap4 appeared to be the haplogroup least susceptible to coccidiosis. At a minimum, the data do not support an association between chLEAP-2 DNA sequence variation and symptoms of coccidiosis such as weight gain depression and lesion score. Conclusion: Therefore, earlier reports of differences between resistant and susceptible lines in chLEAP-2 expression may be due to trans-acting factors. The genomic results reported here provide resources for testing the trans-expression control theory and will be useful for future genotype:phenotype evaluation studies between chLEAP-2 and other traits in the chicken.
  A.M.J.B. Adikari , J. Xu and E.J. Smith
  Background and Objective: Biological clock controls behavioral, physiological and biochemical circadian rhythms of animals. Circadian clock genes including period3 are involved in the circadian clock mechanism. The present study was conducted to test the hypothesis that differences in DNA sequence variations of the turkey period3 (turPer3) gene may be associated with performance traits including growth and reproduction. Methodology: The turPer3 gene was screened for DNA sequence variations and evaluated the relationships among haplogroups with performance traits. The DNA sequences of turPer3 (16.6 kb) gene were screened using 290 turkey birds by re-sequencing the individual amplicons. Results: Seven SNPs, including one each in exon 18 and intron 5, two SNPs in exon 19 and three SNPs in intron 6, were detected. The SNPs detected in the exon 19 were non-synonymous, which changed the amino acids from methionine to threonine and serine to phenylalanine at 953rd and 955th positions, respectively. Linkage disequilibrium (D’) among SNPs ranged from 0.03-1.00. Pairwise FST ranged from 0.01-0.43. Haplogroup frequencies of the turPer3 ranged from 0.02-1.00, were significantly associated with body weight (BW) at 231 days of age, average daily gain (ADG) for the period of 160-231 d of age, FCR for the periods of 69-159 d and 160-231 d, egg production and semen quality traits (p≤0.05). Conclusion: The DNA sequence variations of turPer3 gene are significantly associated with BW, ADG, FCR, egg production, egg weight and semen quality traits. turPer3 gene may seem to have some regulatory role in the molecular mechanism of the circadian clock. Genomic reagents reported in the present study would be valuable for future genotype: phenotype evaluation studies in the turkey using a candidate gene approach.
  A.M.J.B. Adikari , J. Xu and E.J. Smith
  Background and Objective: A study was conducted to test the hypothesis that differences in DNA sequence variations of turkey Clock gene may be associated with growth and reproductive traits. The turClock gene for DNA sequence variations was screened and evaluated the relationships among its haplotypes (based on haplogroups) with growth and reproductive traits of the turkey. Methodology: A total of 290 birds including hybrid turkeys and seven different varieties of heritage turkeys were used. DNA sequences of turClock gene (24.6 kb) were screened by re-sequencing of individual amplicons. Haplogroups were determined based on the output from Visual Haplotypes and data were analyzed to find out the associations between genotype and phenotypic traits. Results: Twelve SNPs, including five, four and three in introns 6, 9 and 16 respectively, were identified in the turClock gene. Reported SNPs were not in the Hardy-Weinberg Equilibrium (HWE) (p≤0.05). Linkage disequilibrium (D‘) among SNPs ranged from 0.05-1.00. Pairwise fixation index (FST) ranged from 0.03-0.90. Five haplogroups were developed from 12 SNPs. Haplogroups frequencies ranged from 0.03-0.93, were significantly associated with body weight (BW) at 309 days of age, feed conversion ratio (FCR) for the periods of 34-68 and 69-159 days, egg production and average egg weight (p≤0.05). Conclusion: The haplogroups of the turClock gene are associated with growth and reproductive traits. DNA sequence variations of Clock genes at the nucleotide and haplotype levels are associated with differences in performance traits. The genomic information described in the present study would be valuable for future association studies between Clock gene and other economically important traits in the turkey using a candidate gene approach.
  J. Xu , K. Yin , H. Liu , J.H.W. Lee , D.M. Anderson , A.Y.T. Ho and P.J. Harrison
  Eutrophication impacts may vary spatially and temporally due to different physical processes. Using a 22-year time series data set (1986–2007), a comparison was made of eutrophication impacts between the two harbours with very different hydrodynamic conditions. Victoria Harbour (Victoria) receives sewage effluent and therefore nutrients are abundant. In the highly-flushed Victoria, the highest monthly average Chl a (13 μg L1) occurred during the period of strongest stratification in summer as a result of rainfall, runoff and the input of the nutrient-rich Pearl River estuarine waters, but the high flushing rate restricted nutrient utilization and further accumulation of algal biomass. In other seasons, vertical mixing induced light limitation and horizontal dilution led to low Chl a (< 2 μg L1) and no spring bloom. Few hypoxic events (DO < 2 mg L1) occurred due to re-aeration and limited accumulation at depth due to flushing and vertical mixing. Therefore, Victoria is resilient to nutrient enrichment. In contrast, in the weakly-flushed Tolo Harbour (Tolo), year long stratification, long residence times and weak tidal currents favored algal growth, resulting in a spring diatom bloom and high Chl a (10–30 μg L1) all year and frequent hypoxic events in summer. Hence, Tolo is susceptible to nutrient enrichment and responded to nutrient reduction after sewage diversion in 1997. Sewage diversion from Tolo resulted in a 32–38% decrease in algal biomass in Tolo, but not in Victoria. There has been a significant increase (11–22%) in bottom DO in both harbours. Our findings demonstrate that an understanding of the role of physical processes is critical in order to predict the effectiveness of sewage management strategies in reducing eutrophication impacts.
  X Chen , Z Liu and J. Xu
 

Nuclear receptor coactivator 1 [NCOA1/steroid receptor coactivator (SRC)-1] and NCOA3 (SRC-3/AIB1/ACTR) constitute two thirds of the SRC (steroid receptor coactivator) family. Although in vitro experiments have suggested overlapping functions between NCOA1 and NCOA3, their in vivo functional relationship is poorly understood. In this study, NCOA1 and NCOA3 double knockout mice were generated to determine the compensatory roles of NCOA1 and NCOA3 in development. NCOA1–/– mice survived normally, whereas most NCOA3–/– embryos were viable at embryonic d 13.5 (E13.5). In contrast, the majority of double-knockout (DKO) embryos died by E13.5. NCOA1 and NCOA3 are expressed in the labyrinth, and labyrinths of NCOA1+/–;NCOA3–/– and DKO placentas were small compared with wild-type and single-knockout labyrinths. DKO labyrinths exhibited low densities of maternal blood sinuses and fetal capillaries and displayed fetomaternal blood transfusion. At the interface between maternal and fetal circulations, layer I sinusoidal trophoblast giant cells showed a reduced density of microvilli. Layer III syncytiotrophoblasts appeared to accumulate large lipid droplets and have reduced density and deepened invaginations of the intrasyncytial bays. The endothelial layer in DKO labyrinth showed abnormal morphologies and had large lipid droplets. Furthermore, disruption of NCOA1 and NCOA3 increased labyrinth trophoblast proliferation and their progenitor gene expression but decreased their differentiation gene expression. NCOA1 and NCOA3 deficiencies also affected the expression of several genes for placental morphogenesis including TGFβ-, peroxisome proliferator-activated receptor-β-, and peroxisome proliferator-activated receptor--regulated genes and for glucose transportation including GLUT1 and Cx26. These findings demonstrate that NCOA1 and NCOA3 cooperatively regulate placental morphogenesis and embryo survival.

  J. M Griffin and J. Xu
 

Compared to mutual funds, hedge funds prefer smaller, opaque value securities, and have higher turnover and more active share bets. Decomposing returns into three components, we find that hedge funds are better than mutual funds at stock picking by only 1.32% per year on a value-weighted basis, and this result is insignificant on an equal-weighted basis or with price-to-sales benchmarks. Hedge funds exhibit no ability to time sectors or pick better stock styles. Surprisingly, we find only weak evidence of differential ability between hedge funds. Overall, our study raises serious questions about the perceived superior skill of hedge fund managers.

 
 
 
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