Stability of delayed memristive neural networks with time-varying impulses

This paper addresses the stability problem on the memristive neural networks with time-varying impulses. Based on the memristor theory and neural network theory, the model of the memristor-based neural network is established. Different from the most publications on memristive networks with fixed-time impulse effects, we consider the case of time-varying impulses. Both the destabilizing and stabilizing impulses exist in the model simultaneously. Through controlling the time intervals of the stabilizing and destabilizing impulses, we ensure the effect of the impulses is stabilizing. Several sufficient conditions for the globally exponentially stability of memristive neural networks with time-varying impulses are proposed. The simulation results demonstrate the effectiveness of the theoretical results.     

基于翻转课堂的《生物资源学导论》混合式教学模式的构建与实践

不断发展与创新信息化教学模式是高校人才培养的必然选择,也是落实国家创新发展战略的重要路径。随着信息技术的飞速发展,使得混合式教学改革理念应运而生。同时,大量实用的信息技术工具也为混合式教学的顺利开展提供了强有力的后勤保障。在本研究中,我们通过对混合式教学相关理论的深入分析以及对微信功能的充分挖掘,设计了基于翻转课堂的混合式教学模式,并在《生物资源学导论》课程中开展了基于该模式的教学实践。结果证明,该教学模式能有效提高学生的学习积极性、自主学习能力和学习绩效。此外,我们还对该混合式教学模式的优势和实践过程中出现的问题进行了讨论和总结,为今后进一步深化教学改革与创新提供参考。     

Roles of Greatwall kinase in the regulation of cdc25 phosphatase

We previously reported that immunodepletion of Greatwall kinase prevents Xenopus egg extracts from entering or maintaining M phase due to the accumulation of inhibitory phosphorylations on Thr14 and Tyr15 of Cdc2. M phase-promoting factor (MPF) in turn activates Greatwall, implying that Greatwall participates in an MPF autoregulatory loop. We show here that activated Greatwall both accelerates the mitotic G2/M transition in cycling egg extracts and induces meiotic maturation in G2-arrested Xenopus oocytes in the absence of progesterone. Activated Greatwall can induce phosphorylations of Cdc25 in the absence of the activity of Cdc2, Plx1 (Xenopus Polo-like kinase) or mitogen-activated protein kinase, or in the presence of an activator of protein kinase A that normally blocks mitotic entry. The effects of active Greatwall mimic in many respects those associated with addition of the phosphatase inhibitor okadaic acid (OA); moreover, OA allows cycling extracts to enter M phase in the absence of Greatwall. Taken together, these findings support a model in which Greatwall negatively regulates a crucial phosphatase that inhibits Cdc25 activation and M phase induction.     

Chemical modification of chitosan under high-intensity ultrasound and properties of chitosan derivatives

Chitosan (CTS), a biocompatible, biodegradable, nontoxic polymer, shows poor affinity for organic solvents. A novel chitosan derivative carrying the p-acetamidobenzoylate group was synthesized by the acylation reaction of chitosan with p-acetamidobenzoylate chloride in an acetic acid system under high-intensity ultrasound. The maximum substitution degree of the derivative was 0.42. The structure of the p-acetamidobenzoylate chitosan was characterized by FT-IR spectrometry, UV spectrometry and elemental analysis. The UV results showed that the derivative had good ultraviolet absorption at 273 nm. The solubility of the derivative was higher than that of chitosan. Taking advantage of the known capacity of solubility and ultraviolet absorption, the new derivative opens new possibilities for use as a sunscreen.     

The effects of vegetation on restoration of physical stability of a severely degraded soil in China

Vegetative restoration may increase stability of degraded soil through enrichment of soil organic carbon (SOC). It is not clear whether hydrophobic fractions of dissolved organic carbon (DOC) function, although soil water repellency is generally linked to soil stability. The objectives of this study were to determine the effects of vegetative restoration and hydrophobic DOC fractions on soil hydrological and mechanical stability. Five investigated plots included eroded bare soil as a control, restored eroded soils planted either with Camphor tree (Cinnamomum camphora) or Lespedeza shrub (Lespedeza bicolor) since 1987, and two undisturbed soils with the same vegetation types. Water stability (WS), tensile strength (TS), and soil water repellency (SWR) of soil aggregates were measured at three water potentials, i.e., ?6, ?60 hPa and oven drying at 40 °C and at three depths (0–5, 5–10 and 10–20 cm). Reforestation of Lespedeza and Camphor trees for over 15 years increased SOC, hydrophobic DOC (H-DOC) and hydrophobic acid DOC (HA-DOC), WS and TS of the restored soils compared with the eroded bare soil, with more profound effects under Lespedeza shrubs than under Camphor trees, especially for TS. No significant differences were found between the restored and undisturbed soil under the same vegetation type. SOC was significantly correlated to total porosity, hydrological and mechanical stability and soil water repellency, suggesting the significant effect of SOC on soil restoration. SWR was more closely correlated to SOC and to H-DOC concentration than to total DOC and HA-DOC in the top soil. The humification and aromaticity indices of DOC indicated that greater SWR in the soils under Lespedeza than under Camphor trees can be attributed to greater amount of litter fall and more active microbial decomposition. Although WS and TS varied with soil water potentials, TS was strongly correlated to SWR, but no link was found with WS. This study suggests that the combined influences of soil organic compounds binding and coating soil particles, retarding water wettability and modifying soil porosity are probably extremely important mechanisms of mechanical stabilization in soil. Such intricate feedback during vegetation restoration needs further study.     

A Model for Transgenerational Imprinting Variation in Complex Traits

Despite the fact that genetic imprinting, i.e., differential expression of the same allele due to its different parental origins, plays a pivotal role in controlling complex traits or diseases, the origin, action and transmission mode of imprinted genes have still remained largely unexplored. We present a new strategy for studying these properties of genetic imprinting with a two-stage reciprocal F mating design, initiated with two contrasting inbred lines. This strategy maps quantitative trait loci that are imprinted (i.e., iQTLs) based on their segregation and transmission across different generations. By incorporating the allelic configuration of an iQTL genotype into a mixture model framework, this strategy provides a path to trace the parental origin of alleles from previous generations. The imprinting effects of iQTLs and their interactions with other traditionally defined genetic effects, expressed in different generations, are estimated and tested by implementing the EM algorithm. The strategy was used to map iQTLs responsible for survival time with four reciprocal F populations and test whether and how the detected iQTLs inherit their imprinting effects into the next generation. The new strategy will provide a tool for quantifying the role of imprinting effects in the creation and maintenance of phenotypic diversity and elucidating a comprehensive picture of the genetic architecture of complex traits and diseases.     

Structural basis of ALMT1-mediated aluminum resistance in Arabidopsis

The plant aluminum (Al)-activated malate transporter ALMT1 mediates the efflux of malate to chelate the Al in acidic soils and underlies the plant Al resistance...     

The NLRP3 inflammasome is differentially activated by pneumolysin variants and contributes to host defense in pneumococcal pneumonia

Streptococcus pneumoniae is a leading cause of pneumonia, meningitis, and sepsis. Pneumococci can be divided into >90 serotypes that show differences in the pathogenicity and invasiveness. We tested the hypotheses that the innate immune inflammasome pathway is involved in fighting pneumococcal pneumonia and that some invasive pneumococcal types are not recognized by this pathway. We show that human and murine mononuclear cells responded to S. pneumoniae expressing hemolytic pneumolysin by producing IL-1β. This IL-1β production depended on the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome. Some serotype 1, serotype 8, and serotype 7F bacteria, which have previously been associated with increased invasiveness and with production of toxins with reduced hemolytic activity, or bacterial mutants lacking pneumolysin did not stimulate notable IL-1β production. We further found that NLRP3 was beneficial for mice during pneumonia caused by pneumococci expressing hemolytic pneumolysin and was involved in cytokine production and maintenance of the pulmonary microvascular barrier. Overall, the inflammasome pathway is protective in pneumonia caused by pneumococci expressing hemolytic toxin but is not activated by clinically important pneumococcal sequence types causing invasive disease. The study indicates that a virulence factor polymorphism may substantially affect the recognition of bacteria by the innate immune system.     

Serum LDL- and HDL-cholesterol determined by ultracentrifugation and HPLC

Simple and precise methods for LDL-cholesterol (LDL-C) and HDL-cholesterol (HDL-C) measurements are essential for assessment of cardiovascular disease (CVD) risks and for lipid and lipoprotein studies. We report here an ultracentrifugation (UC) and HPLC method that requires substantially less specimen volume and provides the necessary reliability and throughput required by large-volume, high-quality research and clinical studies. 2-Mercaptoethanol (ME) was used to dissociate serum lipoprotein [a] (Lp[a]) into apolipoprotein [a] and Lp[a] remnant (Lp[a-]) and eliminated the contamination of Lp[a] in HDL separated by UC. Serum aliquots were centrifuged at a density of 1.006 kg/l for the separation of HDL plus LDL, and in the presence of ME at a density of 1.063 kg/l for the separation of HDL. Cholesterol concentrations of the bottom fractions were analyzed by HPLC. LDL-C and HDL-C determined using this method were equivalent to those with β-quantification and the designated comparison method of the Centers for Disease Control. The total coefficient of variations for LDL-C and HDL-C were 0.65-1.12% and 0.96-2.07%, respectively. This method requires a small amount of specimen and is easy to operate. This method may be used in research or in clinical laboratories where precise and specific lipoprotein cholesterol analysis is needed.     

On generalized Simes critical constants

We consider the problem treated by Simes of testing the overall null hypothesis formed by the intersection of a set of elementary null hypotheses based on ordered p‐values of the associated test statistics. The Simes test uses critical constants that do not need tabulation. Cai and Sarkar gave a method to compute generalized Simes critical constants which improve upon the power of the Simes test when more than a few hypotheses are false. The Simes constants can be viewed as the first order (requiring solution of a linear equation) and the Cai‐Sarkar constants as the second order (requiring solution of a quadratic equation) constants. We extend the method to third order (requiring solution of a cubic equation) constants, and also offer an extension to an arbitrary kth order. We show by simulation that the third order constants are more powerful than the second order constants for testing the overall null hypothesis in most cases. However, there are some drawbacks associated with these higher order constants especially for , which limits their practical usefulness.