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Articles by X. Chen
Total Records ( 9 ) for X. Chen
  Y.F. Li , Y.P. Li , G.H. Huang and X. Chen
  In this study, an inexact fuzzy-stochastic energy model (IFS-EM) is developed for planning energy and environmental systems (EES) management under multiple uncertainties. In the IFS-EM, methods of interval parameter fuzzy linear programming (IFLP) and multistage stochastic programming with recourse (MSP) are introduced into a mixed-integer linear programming (MILP) framework, such that the developed model can tackle uncertainties described in terms of interval values, fuzzy sets and probability distributions. Moreover, it can reflect dynamic decisions for facility-capacity expansion and energy supply over a multistage context. The developed model is applied to a case of planning regional-scale energy and environmental systems to demonstrate its applicability, where three cases are considered based on different energy and environmental management policies. The results indicate that reasonable solutions have been generated. They are helpful for supporting: (a) adjustment or justification of allocation patterns of regional energy resources and services, (b) formulation of local policies regarding energy consumption, economic development and environmental protection, and (c) in-depth analysis of tradeoffs among system cost, satisfaction degree and environmental requirement under multiple uncertainties.
  D Zou , J. H Park , T. H Kim and X. Chen

The requirements for access control have been increased significantly in smart home systems. Many factors such as user ID, user location, service usage conditions and so on, regarded as authorization attributes, are important in making authorization decision in smart home systems. We investigate into the dynamic characteristics of the authorization in smart home systems and propose a new access-control model, SH-CRBAC, which aims to combine the advantages of attribute-based authorization mechanism and role-based access-control mechanism, and imposes attribute and status constraints on the RBAC model and enhances the generality and flexibility of authorization significantly in smart home systems. The status consistency of SH-CRBAC is analysed, and we also analyse the characteristics of SH-CRBAC through comparison with other popular existing authorization models in smart home systems.

  H. Yang , Y. Wei , X. Gao , X. Xu , L. Fan , J. He , Y. Hu , X. Liu , X. Chen , Z. Yang and C. Zhang
  Aims  To determine the incidence of gestational diabetes mellitus (GDM) in China and to further identify population specific risk factors for GDM.

Methods  Following a universal GDM screening recommendation, 16 286 pregnant women who underwent a 50-g glucose challenge test from 18 cities in China were followed up through pregnancy. GDM was confirmed by oral glucose tolerance test according to American Diabetes Association criteria.

Results  The incidence of GDM was 4.3%. Previously reported risk factors for GDM, including advanced maternal age, pre-pregnancy obesity and family history of diabetes, were strongly associated with an elevated GDM risk. Moreover, after the adjustment for the above-mentioned risk factors, a history of recurrent vulvovaginal candidiasis, residency in south China and a history of spontaneous abortion were significantly associated with an increased GDM risk; adjusted odds ratio (OR) [95% confidence interval (95% CI)] were 1.97 (1.39, 2.80), 1.84 (1.59-2.13), and 1.46 (1.12, 1.91), respectively.

Conclusions  In this large study of GDM in Chinese women, advanced maternal age, pre-pregnancy overweight or obesity and family history of diabetes were confirmed to be risk factors. In addition, a history of recurrent vulvovaginal candidiasis or spontaneous abortion and residency in south China appeared to be novel risk factors in this population.

  Z. Pei , X. Chen , C. Sun , H. Du , H. Wei , W. Song , Y. Yang , M. Zhang , W. Lu , R. Cheng and F. Luo


To examine single nucleotide polymorphisms in the protein tyrosine phosphatase N22 gene (PTPN22) and to study their association with Type 1 diabetes in a Chinese cohort.


Three hundred and sixty-four young patients with Type 1 diabetes and 719 healthy children were included in this case-controlled study. The genotypes of rs1217385, rs2488457 (-1123C>G), rs1217414, rs1217419, rs3765598 and rs2476601 (1858C>T) in the PTPN22 gene were determined using the SNaPshot method. Alleles, genotypes and haplotype frequencies were compared between patients with Type 1 diabetes and healthy control subjects. The association between single nucleotide polymorphisms and clinical traits/autoantibody status was also analysed.


The single nucleotide polymorphism, rs1217419, located in the second intron of the PTPN22 gene was associated with Type 1 diabetes (odds ratio 1.5, 95% CI 1.14-1.97, P = 0.003). An additional single nucleotide polymorphism, rs1217385, was also associated with Type 1 diabetes; however, the association was secondary to that of rs1217419. The previously reported single nucleotide polymorphism that is associated with Type 1 diabetes (-1123G>C) had only marginal association with Type 1 diabetes in our study. A marginal association was also identified between -1123G>C and glutamic acid decarboxylase autoantibody positivity in patients with Type 1 diabetes. There was no association between the single nucleotide polymorphism 1858C>T and Type 1 diabetes in our studied cohort.


Our study confirmed that PTPN22 is a gene that contributes to Type 1 diabetes susceptibility. The primary association occurs with single nucleotide polymorphism rs1217419 and there is clear heterogeneity of the association between PTPTN22 polymorphisms and Type 1 diabetes in a Chinese population compared with other populations.

  S. Liao , J. Mei , W. Song , Y. Liu , Y.-D. Tan , S. Chi , P. Li , X. Chen and S. Deng


The International Association of Diabetes and Pregnancy Study Groups (IADPSG) proposed that a one-time value of fasting plasma glucose of 5.1 mmol/l or over at any time of the pregnancy is sufficient to diagnose gestational diabetes. We evaluated the repercussions of the application of this threshold in pregnant Han Chinese women.


This is a retrospective study of 5360 (72.3% of total) consecutively recruited pregnant Han Chinese women in one centre from 2008 to 2011. These women underwent a two-step gestational diabetes diagnostic protocol according to the previous American Diabetes Association criteria. The IADPSG fasting plasma glucose criterion was used to reclassify these 5360 women. The prevalence, clinical characteristics and obstetric outcomes were compared among the women classified as having gestational diabetes by the previous American Diabetes Association criteria (approximately 90% were treated), those reclassified as having gestational diabetes by the single IADPSG fasting plasma glucose criterion (untreated), but not as having gestational diabetes by the previous American Diabetes Association criteria, and those with normal glucose tolerance.


There were 626 cases of gestational diabetes defined by the previous American Diabetes Association criteria (11.7%) and these cases were associated with increased risks of maternal and neonatal outcomes when compared with the women with normal glucose tolerance. With the IADPSG fasting plasma glucose criterion, another 1314 (24.5%) women were reclassified as having gestational diabetes. Gestational diabetes classified by the IADPSG fasting plasma glucose criterion was associated with gestational hypertension (P = 0.0094) and neonatal admission to nursery (= 0.035) prior to adjustment for maternal age and BMI, but was no longer a predictor for adverse pregnancy outcomes after adjustment.


The simple IADPSG fasting plasma glucose criterion increased the Chinese population with gestational diabetes by 200%. The increased population with gestational diabetes was not significantly associated with excess obstetric and neonatal morbidity.

  B Zheng , Z Wang , S Li , B Yu , J. Y Liu and X. Chen

Intergenic transcription by RNA Polymerase II (Pol II) is widespread in plant and animal genomes, but the functions of intergenic transcription or the resulting noncoding transcripts are poorly understood. Here, we show that Arabidopsis Pol II is indispensable for endogenous siRNA-mediated transcriptional gene silencing (TGS) at intergenic low-copy-number loci, despite the presence of two other polymerases—Pol IV and Pol V—that specialize in TGS through siRNAs. We show that Pol II produces noncoding scaffold transcripts that originate outside of heterochromatic, siRNA-generating loci. Through these transcripts and physical interactions with the siRNA effector protein ARGONAUTE4 (AGO4), Pol II recruits AGO4/siRNAs to homologous loci to result in TGS. Meanwhile, Pol II transcription also recruits Pol IV and Pol V to different locations at heterochromatic loci to promote siRNA biogenesis and siRNA-mediated TGS, respectively. This study establishes that intergenic transcription by Pol II is required for siRNA-mediated TGS, and reveals an intricate collaboration and division of labor among the three polymerases in gene silencing.

  J Cheng , S Huang , H Yu , Y Li , K Lau and X. Chen

Trans-sialidases catalyze the transfer of a sialic acid from one sialoside to an acceptor to form a new sialoside. 2,3-Trans-sialidase activity was initially discovered in the parasitic protozoan Trypanosoma cruzi, and more recently was found in a multifunctional Pasteurella multocida sialyltransferase PmST1. 2,8-Trans-sialidase activity was also described for a multifunctional Campylobacter jejuni sialyltransferase CstII. We report here the discovery of the 2,6-trans-sialidase activity of a previously reported recombinant truncated bacterial 2,6-sialyltransferase from Photobacterium damsela (15Pd2,6ST). This is the first time that the 2,6-trans-sialidase activity has ever been identified. Kinetic studies indicate that 15Pd2,6ST-catalyzed trans-sialidase reaction follows a ping-pong bi-bi reaction mechanism. Cytidine 5'-monophosphate, the product of sialyltransferase reactions, is not required by the trans-sialidase activity of the enzyme but enhances the trans-sialidase activity modestly as a non-essential activator. Using chemically synthesized Neu5AcpNP and LacβMU, 2,6-linked sialoside Neu5Ac2,6LacβMU has been obtained in one-step in high yield using the trans-sialidase activity of 15Pd2,6ST. In addition to the 2,6-trans-sialidase activity, 15Pd2,6ST also has 2,6-sialidase activity. The multifunctionality is thus a common feature of many bacterial sialyltransferases.

  L Zhang , K Lau , J Cheng , H Yu , Y Li , G Sugiarto , S Huang , L Ding , V Thon , P. G Wang and X. Chen

Lewis x (Lex) and sialyl Lewis x (SLex)-containing glycans play important roles in numerous physiological and pathological processes. The key enzyme for the final step formation of these Lewis antigens is 1-3-fucosyltransferase. Here we report molecular cloning and functional expression of a novel Helicobacter hepaticus 1-3-fucosyltransferase (HhFT1) which shows activity towards both non-sialylated and sialylated Type II oligosaccharide acceptor substrates. It is a promising catalyst for enzymatic and chemoenzymatic synthesis of Lex, sialyl Lex and their derivatives. Unlike all other 1-3/4-fucosyltransferases characterized so far which belong to Carbohydrate Active Enzyme (CAZy, glycosyltransferase family GT10, the HhFT1 shares protein sequence homology with 1-2-fucosyltransferases and belongs to CAZy glycosyltransferase family GT11. The HhFT1 is thus the first 1-3-fucosyltransferase identified in the GT11 family.

  B.G. Sood , X. Chen , E.J. Dawe , M. Malian and K.R. Maddipati
  Inhaled prostaglandin E1 (IPGE1) is a potential selective pulmonary vasodilator in neonatal pulmonary hypertension. The objective of this study was to evaluate the bioavailability and metabolism of IPGE1. Anesthetized ventilated piglets received either high dose IPGE1 (1200 ng/kg/min) [Study group] or nebulized saline [Control group] using a jet nebulizer. PGE1 and its metabolite, 15-keto-PGE1, were quantified in blood, urine and lung tissue using high performance liquid chromatography-mass spectrometry. Fourteen piglets underwent the experimental protocol (age 1-9 days). Of these, nine received IPGE1 and five received nebulized saline. Among control pigs, two died of complications at 3-4 h, one at 12-13 h and the remaining two were euthanized at 24 h after start of aerosol. In the study group, three animals died after 14-15 h of aerosol treatment of iatrogenic complications and six animals received aerosol for 24 h. Plasma and urine PGE1 levels increased significantly over time in study (p<0.05) but not control animals. Plasma and urinary 15-keto-PGE1 levels and lung tissue prostaglandin profile were comparable in study and control animals. In conclusion, this is the first report of the tissue distribution, metabolism and excretion of prolonged high dose IPGE1. The increase in PGE1 levels in plasma and urine over time without accumulation in lung tissue or systemic side effects suggests effective aerosol delivery, extensive pulmonary metabolism and efficient excretory mechanisms.
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