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Search Results: 1 - 10 of 73287 matches for " XU Tianhua "
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Existence and Stability Periodic Solution for Prey-Predator System with Functional Response
XU Tian-hua
Journal of Chongqing Normal University , 2010,
Abstract: The existence and stability of periodic solution in Prey-Predator system with diffusion, time-delay and Holing type Ⅱ are invertigated by using the method of upper and lower solutions and comparison principle. It is shown that the globally asymptotically stale trivial solution (0,0) when *, the globally asymptotically stale semi-trival periodic solutions *, of the system by construction of a pair of upper and lower solution of parabolic periodic system *. It was obtained that the system have a pair of T-periodic quasi-solutions and the sector between the quasi-solutions is an attractor of the system with respect to very nonnegative initial function.(* Indicates a formula, please see the full text)
Stability and Periodic Solution to Competitive Lotka-Volterra System with diffusion and Infinite Distributed Delay
XU Tian-hua
Journal of Chongqing Normal University , 2009,
Abstract: A competitive Lotka-volterra systemwith diffusion and infinite distributed delays is investigated. It is shown that the globally asymptotically stable trivial solution, when r1(ai)>=0,(i=1,2),the globally asymptotically stable semi-trivial periodic solution(r1(t,x),),and 0,r2(t,x)) when p1(a1)<0,p1(a2)>=0,p1(a2)<0 of the models byconstruction of a pair of upper and lower solution (u1,u2),(0,0)of parabolic periodic system (aui(t,x)/at-Aiui(t,x)=ui(t,x)[ai(t,x)-bi(t,x)ui(t,x)],and in the use of eigenvalue theory and comparison principle. A T-periodic series are established by using the monotone iteration technique. It was obtained that the systems have a pair of periodic positive solutions with respect to every nonnegative initial function.
Existence of Wave Front Solution of the PreyPredator System with Diffusion and Delays
XU Tianhua
Journal of Chongqing Normal University , 2012,
Abstract: Wave front solutions of reactiondiffusion equations can be a good performance of the phenomenon and the nature of the shock speed disturbances with limited spread. It is important area of research of nonlinear partial differential equations. A PreyPredator system with diffusion and delays was investigated. It is shown that the existence of wave front solutions of this system when the delays τ1 and τ4 are small by constructing a pair of upper and lower solution and using the existence theory of traveling wave solution.
Identification and characterization of a POU transcription factor in the cotton bollworm, Helicoverpa armigera
Tian-Yi Zhang, Wei-Hua Xu
BMC Molecular Biology , 2009, DOI: 10.1186/1471-2199-10-25
Abstract: Har-POU, a new member of the POU gene family, was cloned from the suboesophageal ganglion of Helicoverpa armigera (Har), and its potential functions in the development of the central nervous system (CNS) were analyzed. Southern blot analysis suggests that a single copy of this gene is present in the H. armigera haploid genome. Har-POU mRNA is distributed widely in various tissues and expressed highly in the CNS, salivary gland, and trachea. In vitro-translated Har-POU specifically bound canonical octamer motifs on the promoter of diapause hormone and pheromone biosynthesis activating neuropeptide (DH-PBAN) gene in H. armigera. Expression of the Har-POU gene is markedly higher in the CNS of nondiapause-destined pupae than in diapause-destined pupae. Expression of the Har-POU gene in diapausing pupae was upregulated quickly by injection of ecdysone.Har-POU may respond to ecdysone and bind to the promoter of DH-PBAN gene to regulate pupal development in H. armigera.The development of many insects is regulated by environmental signals such as photoperiod, temperature, humidity, and nutrients. The central nervous system (CNS) of insects accepts these environmental stimuli and transduces them into endogenous chemical messengers (neuropeptides or hormones) in the neuroendocrine organs [1]. The neuropeptides and hormones induce insect developmental arrest at a certain stage: embryonic, larval, pupal, or adult. The programmed arrest of development is called diapause. In Bombyx mori (Bom), embryonic diapause is caused by a neuropeptide diapause hormone (DH), which is secreted from the suboesophageal ganglion (SG) and acts on the developing ovaries of the pharate adult to induce the laying of diapause eggs in the next generation [2]. Interestingly, neuropeptide pheromone biosynthesis activating peptide (PBAN), which can stimulate the pheromone gland of female adults to secrete sex pheromone to attract male adults for mating in Lepidoptera, is also encoded by DH cDNA [3]. Thus,
Ethyl 2-(3,3-dibutylthioureido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate
Hong-Mei Wang,Jing Xu,Xiao-Hua Zeng,Jia-Hua Tian
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809047230
Abstract: In the title compound, C20H32N2O2S2, the cyclohexene ring is disordered over two half-boat conformations with occupancy factors of 0.71:0.29. One n-butyl chain is also disordered over two positions with occupancy factors of 0.83:0.17. The molecular conformation is stabilized by an intramolecular N—H...O hydrogen bond.
3-Isopropyl-2-(4-methoxyphenoxy)-1-benzofuro[3,2-d]pyrimidin-4(3H)-one
Xiao-Bao Chen,Jing Xu,Ai-Hua Zheng,Jia-Hua Tian
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809042925
Abstract: In the title compound, C20H18N2O4, all non-H atoms of the three fused rings of the benzofuro[3,2-d]pyrimidine system are almost coplanar (r.m.s. deviation 0.021 ). The dihedral angle between the fused ring system and the benzene ring is 1.47 (12)°. Intramolecular and intermolecular C—H...O hydrogen bonds together with weak C—H...π interactions stabilize the structure.
Shell-Controlled Photoluminescence in CdSe/CNT Nanohybrids
Si Hua-Yan,Liu Cai-Hong,Xu Hua,Wang Tian-Ming
Nanoscale Research Letters , 2009,
Abstract: A new type of nanohybrids containing carbon nanotubes (CNTs) and CdSe quantum dots (QDs) was prepared using an electrostatic self-assembly method. The CdSe QDs were capped by various mercaptocarboxylic acids, including thioglycolic acid (TGA), dihydrolipoic acid (DHLA) and mercaptoundecanoic acid (MUA), which provide shell thicknesses of ~5.2, 10.6 and 15.2 , respectively. The surface-modified CdSe QDs are then self-assembled onto aridine orange-modified CNTs via electrostatic interaction to give CdSe/CNT nanohybrids. The photoluminescence (PL) efficiencies of the obtained nanohybrids increase significantly with the increase of the shell thickness, which is attributed to a distance-dependent photo-induced charge-transfer mechanism. This work demonstrates a simple mean for fine tuning the PL properties of the CdSe/CNT nanohybrids and gains new insights to the photo-induced charge transfer in such nanostructures.
Regulation of MntH by a Dual Mn(II)- and Fe(II)-Dependent Transcriptional Repressor (DR2539) in Deinococcus radiodurans
Hongxing Sun, Mingfeng Li, Guangzhi Xu, Huan Chen, Jiandong Jiao, Bing Tian, Liangyan Wang, Yuejin Hua
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035057
Abstract: The high intracellular Mn/Fe ratio observed within the bacteria Deinococcus radiodurans may contribute to its remarkable resistance to environmental stresses. We isolated DR2539, a novel regulator of intracellular Mn/Fe homeostasis in D. radiodurans. Electrophoretic gel mobility shift assays (EMSAs) revealed that DR2539 binds specifically to the promoter of the manganese acquisition transporter (MntH) gene, and that DR0865, the only Fur homologue in D. radiodurans, cannot bind to the promoter of mntH, but it can bind to the promoter of another manganese acquisition transporter, MntABC. β-galactosidase expression analysis indicated that DR2539 acts as a manganese- and iron-dependent transcriptional repressor. Further sequence alignment analysis revealed that DR2539 has evolved some special characteristics. Site-directed mutagenesis suggested that His98 plays an important role in the activities of DR2539, and further protein-DNA binding activity assays showed that the activity of H98Y mutants decreased dramatically relative to wild type DR2539. Our study suggests that D. radiodurans has evolved a very efficient manganese regulation mechanism that involves its high intracellular Mn/Fe ratio and permits resistance to extreme conditions.
Identification and evaluation of the role of the manganese efflux protein in Deinococcus radiodurans
Hongxing Sun, Guangzhi Xu, Hongdan Zhan, Huan Chen, Zongtao Sun, Bing Tian, Yuejin Hua
BMC Microbiology , 2010, DOI: 10.1186/1471-2180-10-319
Abstract: In this study, we identified the manganese efflux protein (MntE) in D. radiodurans. The null mutant of mntE was more sensitive than the wild-type strain to manganese ions, and the growth of the mntE mutant was delayed in manganese-supplemented media. Furthermore, there was a substantial increase in the in vivo concentration of manganese ions. Consistent with these characteristics, the mntE mutant was more resistant to H2O2, ultraviolet rays, and γ-radiation. The intracellular protein oxidation (carbonylation) level of the mutant strain was remarkably lower than that of the wild-type strain.Our results indicated that dr1236 is indeed a mntE homologue and is indispensable for maintaining manganese homeostasis in D. radiodurans. The data also provide additional evidence for the involvement of intracellular manganese ions in the radiation resistance of D. radiodurans.Deinococcus radiodurans is an extreme bacterium known for its resistance to ionizing radiation (IR), ultraviolet (UV) radiation, oxidative stress, and desiccation [1,2]. It has been reported that D. radiodurans can recover from exposure to γ-radiation at 15 kGy, a dose lethal to most life forms. IR can directly damage biomacromolecules and can also produce reactive oxygen species (ROS) that can indirectly attack both proteins and DNA [3,4]. Therefore, cellular defense against ROS-induced protein and DNA damage is proposed to be important to the radiation resistance of D. radiodurans [5].Manganese plays an important role in the antioxidant systems of bacteria and can relieve the phenotypic deficit of sod-null Escherichia coli [6]. Interestingly, Daly and coworkers found that the Mn/Fe ratio of most IR-resistant bacteria is higher than that of IR-sensitive bacteria. The group also found that D. radiodurans grown in manganese-deficient medium was relatively more sensitive to IR than the bacteria grown in manganese-containing medium, suggesting that the accumulation of intracellular manganese ions can protect p
Cooperation of PprI and DrRRA in response to extreme ionizing radiation in Deinococcus radiodurans
LiangYan Wang,LongFei Yin,GuangZhi Xu,MingFeng Li,Hui Zhang,Bing Tian,YueJin Hua
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-011-4790-7
Abstract: Deinococcus radiodurans possesses extreme resistance to ionizing radiation, and has been engineered for the remediation of toxic components in radioactive environments. We have previously shown that PprI (also named IrrE) and DrRRA are essential for the DNA protection and repair pathways that respond to ionizing radiation stress in this species. Here, we investigated the combined roles of PprI and DrRRA in resistance to gamma radiation (800 Gy). The double mutant, ΔdrRRA ΔpprI, was more sensitive to gamma rays than either ΔdrRRA or ΔpprI single mutants, and exhibited an elevated level of intracellular protein carbonylation, an extended delay in genome reconstitution and reduced transcriptional levels of certain DNA protection and repair proteins, such as kat, sod, recA and pprA. Interestingly, the induction of DrRRA by ionizing radiation was partially inhibited by the deletion of pprI. Taken together, these results suggest that DrRRA and PprI might have collaborative roles in the response of D. radiodurans to extreme ionizing radiation.
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