Showing papers by "Southwest University published in 2008"

Threshold Dynamics for Compartmental Epidemic Models in Periodic Environments

Abstract: The basic reproduction ratio and its computation formulae are established for a large class of compartmental epidemic models in periodic environments. It is proved that a disease cannot invade the disease-free state if the ratio is less than unity and can invade if it is greater than unity. It is also shown that the basic reproduction number of the time-averaged autonomous system is applicable in the case where both the matrix of new infection rate and the matrix of transition and dissipation within infectious compartments are diagonal, but it may underestimate and overestimate infection risks in other cases. The global dynamics of a periodic epidemic model with patch structure is analyzed in order to study the impact of periodic contacts or periodic migrations on the disease transmission.

Vacancy-induced magnetism in ZnO thin films and nanowires

Abstract: Extensive calculations based on density functional theory have been carried out to understand the origin of magnetism in undoped ZnO thin films as found in recent experiments. The observed magnetism is confirmed to be due to Zn, instead of O, vacancy. The main source of the magnetic moment, however, arises from the unpaired 2p electrons at O sites surrounding the Zn vacancy with each nearest-neighbor O atom carrying a magnetic moment ranging from 0.490 to 0.740 B. Moreover, the study of vacancy-vacancy interactions indicates that in the ground state, the magnetic moments induced by Zn vacancies prefer to ferromagnetically couple with the antiferromagnetic state lying 44 meV higher in energy. Since this is larger than the thermal energy at room temperature, the ferromagnetic state can be stable against thermal fluctuations. Calculations and discussions are also extended to ZnO nanowires that have larger surface to volume ratio. Here, the Zn vacancies are found to lead to the ferromagnetic state too. The present theoretical study not only demonstrates that ZnO samples can be magnetic even without transition-metal doping but also suggests that introducing Zn vacancy is a natural and an effective way to fabricate magnetic ZnO nanostructures. In addition, vacancy mediated magnetic ZnO nanostructures may have certain advantages over transition-metal doped systems in biomedical applications.

Ultrasensitive electrochemical immunosensor for clinical immunoassay using thionine-doped magnetic gold nanospheres as labels and horseradish peroxidase as enhancer.

Abstract: A new signal amplification strategy based on thionine (TH)-doped magnetic gold nanospheres as labels and horseradish peroxidase (HRP) as enhancer holds promise to improve the sensitivity and detection limit of the immunoassay for carcinoembryonic antigen (CEA), as a model protein. This immunoassay system was fabricated on a carbon fiber microelectrode (CFME) covered with a well-ordered anti-CEA/protein A/nanogold architecture. The reverse micelle method was initially used for the preparation of TH-doped magnetic gold nanospheres (nanospheres), and the synthesized nanospheres were then labeled on HRP-bound anti-CEA as a secondary antibody (bionanospheres). Sandwich-type protocol was successfully introduced to develop a new high-efficiency electrochemical immunoassay with the labeled bionanospheres toward the reduction of H2O2. Under optimized conditions, the linear range of the proposed immunoassay without HRP as enhancer was 1.2−125 ng/mL CEA, whereas the assay sensitivity by using HRP as enhancer could b...

Sexual Dimorphic Expression of Genes in Gonads During Early Differentiation of a Teleost Fish, the Nile Tilapia Oreochromis niloticus

Abstract: The Nile tilapia, a gonochoristic teleost fish with an XX/XY sex-determining system, provides an excellent model for studying gonadal sex differentiation because genetic all-females and all-males are available. In this study, we used quantitative real-time RT-PCR to determine the precise timing of the gonadal expression of 17 genes thought to be associated with gonadal sex differentiation in vertebrates. Gonads were isolated from allfemale and all-male tilapia before (5–15 days after hatching [dah]) and after (25–70 dah) morphological sex differentiation. The transcript of aromatase (cyp19a1a), an enzyme responsible for producing estradiol-17beta, was expressed only in XX gonads at 5 dah, with a marked elevation in expression thereafter. In contrast, mRNA expression of steroid 11beta-hydroxylase (cyp11b2), an enzyme responsible for the synthesis of 11ketotestosterone (11-KT, a potent androgen in fish), was found in XY gonads from 35 dah only. These results, combined with the presence of transcripts for other steroidogenic enzymes and estrogen receptors in XX gonads at 5–7 dah, are consistent with our earlier suggestion that estradiol-17beta plays a critical role in ovarian differentiation in tilapia, whereas a role for 11-KT in testicular differentiation is questionable. A close relationship between the expression of foxl2, but not nr5a1 (Ad4BP/SF-1), and that of cyp19a1a in XX gonads suggests an important role for Foxl2 in the transcriptional regulation of cyp19a1a. Dmrt1 exhibited a male-specific expression in XY gonads from 6 dah onward, suggesting an important role for Dmrt1 in testicular differentiation. Sox9 and amh (anti-Mullerian hormone) showed a testis-specific expression, being evident only in the later stages of testicular differentiation. It is concluded that the sex-specific expression of foxl2 and cyp19a1a in XX gonads and dmrt1 in XY gonads during early gonadal differentiation (5–6 dah) is critical for undifferentiated gonads to differentiate into either the ovary or testis in the Nile tilapia. aromatase, DMRT1, fish, Foxl2, sex differentiation

In Situ Amplified Electrochemical Immunoassay for Carcinoembryonic Antigen Using Horseradish Peroxidase-Encapsulated Nanogold Hollow Microspheres as Labels

Abstract: Methods based on sandwich-type electrochemical enzyme immunoassay protocol have been extensively developed for the detection of biomolecules, but most often exhibit low detection signals and low detection sensitivity, and are unsuitable for routine use. In this study, we initially synthesized specially horseradish peroxidase-encapsulated nanogold hollow microspheres (HRP-GHS), and then the prepared HRP-GHS was conjugated to the secondary carcinoembryonic antibody (HRP-GHS-anti-CEA). Carcinoembryonic antigen (CEA), as a model protein, was monitored by using the electrochemical sandwich-type enzyme immunoassay format. Under optimized conditions, the linear range of the immunoassay by using single HRP-labeled anti-CEA (HRP-anti-CEA) as secondary antibodies is 2.5−120 ng/mL with a detection limit of 1.5 ng/mL CEA, while the assay sensitivity by using HRP-GHS-anti-CEA as secondary antibodies is further increased from 0.01 to 200 ng/mL with a lower detection limit of 1.5 pg/mL CEA. The intra- and interassay rep...

Gender differences in behavioral inhibitory control: ERP evidence from a two-choice oddball task

Abstract: Theinhibitionofinappropriatebehaviorsisimportantforadaptivelivinginchangingenvironments.Thepresentstudyinvestigated gender-related behavioral inhibitory control by recording event-related potentials for standard and de-viant stimuli while subjects performed a standard/deviant distinction taskby accurately pressingdifferent keys within1000 ms. The results showed faster reaction times (RTs) for deviant stimuli in women than in men, although RTs forstandard stimuli were similar across genders. There were significant gender and stimulus interaction effects on meanamplitudes during each of the 170–230-ms, 250–330-ms, and 350–600-ms intervals, and women exhibited shorterlatenciesandlargeramplitudesthanmenatdeviant-relatedP2,N2,andP3components.Asanaccurate,fastresponsetotheraredeviantstimuliinvolvesbehavioralinhibitorycontrolontheprepotentresponsewhereastheresponsetothestandard stimuli does not, it is clear that there is a general gender difference in behavioral control for human adults.This may relate to differential inhibitory demands by each gender during evolution.Descriptors: ERP, Gender differences, Response conflict, Behavioral controlBehavioral control, which enables humans to withhold inappro-priate behaviors in some contexts, allows people appropriate re-sponses to meet complicated demands and to live adaptively inthe changing environments (Goldstein et al., 2007; Li, Huang,Constable, & Sinha, 2006a; Norman & Shallice, 1986). As animportant executive function, this ability is essential to the suc-cess of both men and women in modern (and, presumably, an-cestral) society and may have played a critical role in theevolution of human intelligence, particularly social intelligence(BjorklundSLi,Huang,Constable,SRosenblitt, Soler, Johnson, & Quadagno, 2001). Moreover, itwas indicated that behavioral inhibitory control of women wasless impaired by alcohol consumption relative to that of men(FillmoreW Fillmore W Kochanska, Murry, H Kochanska et al., 2000). Nonetheless,whether gender differences in behavioral control during earlyyears can predict the existence of the same difference in adults isstill unknown. It is still unclear whether there is a general differ-ence between men and women in behavioral control. Therefore,the present study investigates behavioral control and its associ-ationwithgender,whichmay provideaninsightintoourknowl-edge about behavioral inhibitory control and its relatedindividual differences.As is known, the go/no go task is frequently used to inves-tigate behavioral inhibitory control and its related neural corre-lates (Donkers and van Boxtel, 2004; Goldstein et al., 2007). Inthe go/no go task, subjects are typically asked to generate aresponseasfastaspossiblewhenthegostimulusispresentedand

Mobile carbohydrates in Himalayan treeline trees I. Evidence for carbon gain limitation but not for growth limitation.

Abstract: To test whether the altitudinal distribution of trees is determined by a carbon shortage or an insufficient sugar fraction (sugar:starch ratio) in treeline trees, we studied the status of nonstructural carbohydrates (NSC) and their components (total soluble sugars and starch) in Abies fabri (Mast.) Craib and Picea balfouriana var. hirtella Rehd. et Wils. trees along three elevational gradients, ranging from lower elevations to the alpine treeline, oil the eastern edge of the Tibetan Plateau. For comparison, we investigated a low-altitude species (Tsuga, yunnanensis (Franch.) Pritz.) which served as a warm-climate reference because it is distributed in closed montane forests below 3100 m a.s.l. in the Study area. The carbon status of T.yunnanensis responded to altitude differently from that of the treeline species. At the species level, total NSC was not consistently more abundant in treeline trees than in trees of the same species growing at lower elevations. Thus there was no consistent evidence for carbon limitation of growth in treeline trees. For the three treeline species Studied (P. balfouriana and A. fabri in Kang-Ding Valley and A. fabri in the Mo-Xi Valley), winter NSC concentrations in treeline trees were significantly lower than in lower-elevation trees of the same species, suggesting that, in winter, carbon is limited in treeline trees. However, in no case was there total overwinter depletion of NSC or its components in treeline trees. Treeline and low-altitude species had similar sugar:starch ratios of about three at their upper-elevational limits in April. We conclude that survival and growth of trees at the elevational or latitudinal climate limit depend not only oil NSC concentration in perennial tissues, but also oil the maintenance of an over-wintering sugar:starch ratio greater than three.

Annotation and analysis of a large cuticular protein family with the R&R Consensus in Anopheles gambiae

Abstract: The most abundant family of insect cuticular proteins, the CPR family, is recognized by the R&R Consensus, a domain of about 64 amino acids that binds to chitin and is present throughout arthropods. Several species have now been shown to have more than 100 CPR genes, inviting speculation as to the functional importance of this large number and diversity. We have identified 156 genes in Anopheles gambiae that code for putative cuticular proteins in this CPR family, over 1% of the total number of predicted genes in this species. Annotation was verified using several criteria including identification of TATA boxes, INRs, and DPEs plus support from proteomic and gene expression analyses. Two previously recognized CPR classes, RR-1 and RR-2, form separate, well-supported clades with the exception of a small set of genes with long branches whose relationships are poorly resolved. Several of these outliers have clear orthologs in other species. Although both clades are under purifying selection, the RR-1 variant of the R&R Consensus is evolving at twice the rate of the RR-2 variant and is structurally more labile. In contrast, the regions flanking the R&R Consensus have diversified in amino-acid composition to a much greater extent in RR-2 genes compared with RR-1 genes. Many genes are found in compact tandem arrays that may include similar or dissimilar genes but always include just one of the two classes. Tandem arrays of RR-2 genes frequently contain subsets of genes coding for highly similar proteins (sequence clusters). Properties of the proteins indicated that each cluster may serve a distinct function in the cuticle. The complete annotation of this large gene family provides insight on the mechanisms of gene family evolution and clues about the need for so many CPR genes. These data also should assist annotation of other Anopheles genes.

One-step label-free optical genosensing system for sequence-specific DNA related to the human immunodeficiency virus based on the measurements of light scattering signals of gold nanorods.

Abstract: A one-step label-free optical genosensing method has been developed in this contribution by taking short DNA target with its sequence related to the human immunodeficiency virus type 1 (HIV-1) as an example. By employing anisotropic nonspherical and positively charged gold nanorods (Au-NRs) as the recognition platform, which show high stability against aggregation under high ionic strength conditions without any additional stable reagent, we found that the addition of target DNA to the mixture of nonmodified Au-NRs suspension and label-free probe DNA in high ionic strength buffer leads to a color change from red to light purple in less than 5 min, displaying strong plasmon resonance light scattering (PRLS) signals. Mechanism investigations showed that the strong PRLS signals should be ascribed to the aggregation of Au-NRs induced by the formed double-stranded oligonucleotides (dsDNA) from the hybridization of target DNA with probe DNA. With the PRLS signals, we monitored the hybridization process of a 21-...

Simultaneous measurement of Pb, Cd and Zn using differential pulse anodic stripping voltammetry at a bismuth/poly(p-aminobenzene sulfonic acid) film electrode

Abstract: A novel sensor was developed for simultaneous detection of Pb, Cd and Zn, based on the differential pulse anodic stripping response at a bismuth/poly(p-aminobenzene sulfonic acid) (Bi/poly(p-ABSA)) film electrode. This electrode was generated in situ by depositing simultaneously bismuth and the metals by reduction at −1.40 V on the poly(p-ABSA) modified electrode. Compared with the bismuth film electrode, the Bi/poly(p-ABSA) film electrode can yield a larger stripping signal for Pb, Cd and Zn. Under the optimum conditions, a linear response was observed for Cd and Zn in the range from 1.00 to 110.00 μg L−1 and for Pb in the range from 1.00 to 130.00 μg L−1. The detection limits of Pb(II), Cd(II) and Zn(II) were 0.80, 0.63 and 0.62 μg L−1, respectively. Finally this sensor had been applied to the simultaneous determination of Pb(II), Cd(II) and Zn(II) in river water samples and the results were quite corresponding to the value obtained by atomic absorption spectrometry.

Prevalence and sociodemographic correlates of eating disorder endorsements among adolescents and young adults from China.

Abstract: This research assessed the prevalence and sociodemographic correlates of eating disorder symptoms among young people from China. A sample of 1320 females and 783 males between 12 and 22 years of age was recruited from academic settings in various regions of China and completed a back-translated Chinese version of the Eating Disorder Diagnostic Scale, as well as measures of body dissatisfaction and demographics. As expected, reported eating disorder symptoms and body dissatisfaction were significantly higher for females than males. Eating disorder symptoms and body dissatisfaction were also more pronounced for participants from higher income households. Finally, age differences in symptoms and body dissatisfaction were inconsistent. In sum, findings extend past prevalence research and highlight specific sociodemographic correlates of eating pathology and body dissatisfaction among Chinese adolescents and young adults.

Evolution and dynamics of the Cenozoic tectonics of the South Balkan extensional system

Abstract: The South Balkan extensional system consists of normal faults and associated sedimentary basins within southern Bulgaria, Macedonia, eastern Albania, northern Greece, and northwestern Turkey. Extensional tectonism began during the final convergence across the Vardar, Intra-Pontide, and Izmir-Ankara suture zones, where oceanic regions closed between continental Europe and continental fragments that make up the Pelagonian, Sakar, and western Anatolian tectonic units. Earliest extension of latest Cretaceous-middle Eocene age appears to have occurred within a regional convergent tectonic setting and may be related to an increase in gravitation potential energy within a thickening continental lithosphere. Following diachron-ous closure across the suture zone, from the middle Eocene to late Oligocene, the transition from a regionally convergent to a regionally extensional tectonic setting occurred and was associated with abundant magmatism and formation of sedimentary basins. Extension was associated with lithospheric thinning probably related to changes in geometry of the subducted slab, dynamics of the mantle wedge, and beginning of slab rollback along the Hellenic subduction zone. A short period of local and diachronous (?) shortening (during latest Oligocene-early Miocene time) occurred in the Thrace basin of northwestern Turkey and in some basins in western Bulgaria and eastern Macedonia. Regional extension began in middle Miocene time and was related to the regional extensional tectonic setting that has dominated the Aegean extensional region to the present. Trench rollback was the dominant dynamic process, but during late Miocene time it was modi-fled by the formation of the western part of the North Anatolian fault zone that partially decoupled the South Balkan extensional system from the Aegean extensional region. During late Cenozoic time, east-west-striking normal faults and associated sedimentary basins in the eastern part of the South Balkan extensional system propagated westward in tandem with westward migration of north-south-striking normal faults and sedimentary basins from western Bulgaria into eastern Albania. This migration was caused by evolution of the Hellenic subduction zone as it increased its curvature during trench rollback and clockwise and counterclockwise rotation of crustal fragments in the west and east, respectively. After formation of the western part of the North Anatolian fault zone, extension within the eastern part of the South Balkan extensional system was related to southward movement of its lithosphere at a slower rate than the extension within the Aegean extensional region. Active extension and basin formation show two provinces of extension that are nearly at right angles to one another and their overlap in the central South Balkan extensional system: east-west extension in central Albania to eastern Macedonia and north-south extension from northwestern Greece and eastern Macedonia to eastern Bulgaria and northwestern Turkey.

Nitrogen and carbon source-sink relationships in trees at the Himalayan treelines compared with lower elevations

Abstract: No single hypothesis or theory has been widely accepted for explaining the functional mechanism of global alpine/arctic treeline formation. The present study tested whether the alpine treeline is determined by (1) the needle nitrogen content associated with photosynthesis (carbon gain); (2) a sufficient source-sink ratio of carbon; or (3) a sufficient C-N ratio. Nitrogen does not limit the growth and development of trees studied at the Himalayan treelines. Levels of non-structural carbohydrates (NSC) in trees were species-specific and site-dependent; therefore, the treeline cases studied did not show consistent evidence of source/carbon limitation or sink/growth limitation in treeline trees. However, results of the combined three treelines showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of a tree influence its tissue NSC concentrations and the carbon balance; therefore, we suggest that the persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration, a sufficiently high sugar:starch ratio, and a balanced carbon source-sink relationship.

The complete mitochondrial genome of the Chinese oak silkmoth, Antheraea pernyi (Lepidoptera: Saturniidae)

Abstract: We determined the complete nucleotide sequence of the mitogenome from Chinese oak silkmoth, Antheraea pernyi (Lepidoptera: Saturniidae). The 15,566 bp circular genome contains a typical gene organization and order for lepidopteran mitogenomes. The mitogenome contains the lowest A+T content (80.16%) among the known lepidopteran mitogenome sequences. An unusual feature is the occurrence of more Ts than As, with a slightly negative AT skewness (−0.021), in the composition of the major genome strand. All proteincoding genes are initiated by ATN codons, except for cytochrome oxidase subunit I, which is proposed by the TTAG sequence as observed in other lepidopterans. All transfer RNAs (tRNAs) have a typical clover-leaf structure of mitochondrial tRNA, except for tRNA Ser (AGN), the DHU arm of which could not form a stable stem-loop structure. Two aligned sequence blocks with a length of more than 50 bp and 90% of the sequence identity were identified in the A+T-rich region of the Saturniidae and Bombycoidae species.

Constrained Control of Positive Discrete-Time Systems With Delays

Abstract: This brief addresses the control problem of linear time-invariant discrete-time systems with delays. The control is under positivity constraint, which means that the resulting closed-loop systems are not only stable, but also positive. The contribution lies in three aspects. First, a necessary and sufficient condition is established for the existence of such controllers for discrete-time delayed systems. Second, a sufficient condition is provided under the additional constraint of bounded control, which means that the control inputs and the states of the closed-loop systems are bounded. Third, sufficient conditions are proposed for discrete-time delayed systems with uncertainties, whether or not bounded control is considered. All the results are formulated as linear programming problems, hence easy to be verified. And the controllers are explicitly constructed if existent.

The UDP-glucosyltransferase multigene family in Bombyx mori

Abstract: Glucosidation plays a major role in the inactivation and excretion of a great variety of both endogenous and exogenous compounds. A class of UDP-glycosyltransferases (UGTs) is involved in this process. Insect UGTs play important roles in several processes, including detoxication of substrates such as plant allelochemicals, cuticle formation, pigmentation, and olfaction. Identification and characterization of Bombyx mori UGT genes could provide valuable basic information for this important family and explain the detoxication mechanism and other processes in insects. Taking advantage of the newly assembled genome sequence, we performed a genome-wide analysis of the candidate UGT family in the silkworm, B. mori. Based on UGT signature and their similarity to UGT homologs from other organisms, we identified 42 putative silkworm UGT genes. Most of them are clustered on the silkworm chromosomes, with two major clusters on chromosomes 7 and 28, respectively. The phylogenetic analysis of these identified 42 UGT protein sequences revealed five major groups. A comparison of the silkworm UGTs with homologs from other sequenced insect genomes indicated that some UGTs are silkworm-specific genes. The expression patterns of these candidate genes were investigated with known expressed sequence tags (ESTs), microarray data, and RT-PCR method. In total, 36 genes were expressed in tissues examined and showed different patterns of expression profile, indicating that these UGT genes might have different functions. B. mori possesses a largest insect UGT gene family characterized to date, including 42 genes. Phylogenetic analysis, genomic organization and expression profiles provide an overview for the silkworm UGTs and facilitate their functional studies in future.