基于神经网络的网络验证码识别的研究

本文首先介绍了神经网络的基本思想，提出了一种基于神经网络的网络验证码的识别方法，并利用开源的神经网络包JOONE用JAVA技术实现了验证码识别软件.最后通过训练样本对其进行了实验分析,取得了较高的识别率.     

Novel Bacterial Production of Two Different Bioactive Forms of Human Stem-Cell Factor

Human stem-cell factor (hSCF) stimulates the survival, proliferation, and differentiation of hematopoietic cells by binding to the c-Kit receptor. Various applications of hSCF require the efficient and reliable production of hSCF. hSCF exists in three forms: as two membrane-spanning proteins hSCF248 and hSCF229 and truncated soluble N-terminal protein hSCF164. hSCF164 is known to be insoluble when expressed in Escherichia coli cytoplasm, requiring a complex refolding procedure. The activity of hSCF248 has never been studied. Here, we investigated novel production methods for recombinant hSCF164 and hSCF248 without the refolding process. To increase the solubility of hSCF164, maltose-binding protein (MBP) and protein disulfide isomerase b’a’ domain (PDIb’a’) tags were attached to the N-terminus of hSCF164. These fusion proteins were overexpressed in soluble form in the Origami 2(DE3) E. coli strain. These solubilization effects were enhanced at a low temperature. His-hSCF248, the poly-His tagged form of hSCF248, was expressed in a highly soluble form without a solubilization tag protein, which was unexpected because His-hSCF248 contains a transmembrane domain. hSCF164 was purified using affinity and ion-exchange chromatography, and His-hSCF248 was purified by ion-exchange and gel filtration chromatography. The purified proteins stimulated the proliferation of TF-1 cells. Interestingly, the EC₅₀ value of His-hSCF248 was 1 pg/mL, 100-fold lower than 9 ng/mL hSCF164. Additionally, His-hSCF248 decreased the doubling time, increased the proportion of S and G2/M stages in the cell cycle, and increased the c-Myc expression at a 1000-fold lower concentration than hSCF164. In conclusion, His-hSCF248 was expressed in a soluble form in E. coli and had stronger activity than hSCF164. The molecular chaperone, MBP, enabled the soluble overexpression of hSCF164.     

西九文化区

正OMA发展西九文化区,必须面对一项挑战:将一个盛载政府极大抱负,以及持分者多元利益的超大型多用途项目,转化成一个既有趣又严肃、既有规划又允许即兴、既中国化又国际化的文化区。这个文化区规模庞大,但不失亲密融洽的感觉;富地标性,但十分谦和;容易理解,却能带来惊喜。为避免造成过分冲击,OMA采纳了一种每个香港市民都熟悉的建筑类型作为方案的发展     

Biodegradation kinetics of trans‐4‐methyl‐1‐cyclohexane carboxylic acid in continuously stirred tank and immobilized cell bioreactors

BACKGROUND: Naphthenic acids are carboxylic acid compounds of oil sands wastewaters that contribute to aquatic toxicity. Biodegradation kinetics of an individual naphthenic acid compound in two types of continuous‐flow bioreactors were investigated as a means of improving remediation strategies for these compounds. RESULTS: This study evaluates the kinetics of biodegradation of trans‐4‐methy‐1‐cyclohexane carboxylic acid (trans‐4MCHCA) using two bioreactor systems and a microbial culture developed in previous work. Using a feed concentration of 500 mg L^?1 the biodegradation rate of trans‐4MCHCA in the immobilized cell bioreactor was almost two orders of magnitude higher than that in a continuously stirred tank bioreactor. The maximum reaction rates of 230 mg (L d)^?1 at a residence time of 1.6 d (40 h) and 22 000 mg (L d)^?1 at a residence time of 2.6 h were observed in the continuously stirred tank and immobilized cell bioreactors, respectively. In a second immobilized cell system operating with a feed concentration of 250 mg L^?1, a comparable maximum reaction rate (21 800 mg (L d)^?1) was achieved at a residence time of 1.0 h. CONCLUSION: The use of immobilized cell bioreactors can enhance the biodegradation rate of naphthenic acid compounds by two orders of magnitude. Further, biodegradation greatly reduces the toxicity of the effluent wastewater. Copyright © 2009 Society of Chemical Industry     

QUANTITATION OF PROTEIN DAMAGE IN METAL ION-CATALYZED OXIDATION SYSTEMS

The loss of enzymatic activity of lactate dehydrogenase was studied in several ascorbate, iron and hydrogen peroxide metal catalyzed oxidation solutions in which the initial concentration of each reactant was varied independently. Nonmonotonic concentration dependencies of enzymatic inactivation were observed for all three reactants. with minimum activity levels occurring in the 0·1 to 8 mM range. A first effort has been made to predict these concentration dependencies with a mathematical simulation model. The model consisted of the most commonly reported reactions and assumed that protein damage occurred through reaction with the hydroxyl radical. The simulation predicted nonmonotonic concentration dependencies of enzyme inactivation on each of the reactants. The predicted concentrations of the minima differed from the experimentally observed points by a factor of 2 to 4. Mathematically the minima occurred because each reactant was reported to react with hydroxyl radicals and form less reactive compounds. The plausibility that competition caused or contributed to the extrema was further explored with experimental competition studies between peroxide and the radical scavenger dimethylsulfoxide. A point of maximum hydroxyl radical formation was observed with increasing peroxide concentration. This maxima corresponded to the point of maximum lactate dehydrogenase damage observed with increasing peroxide concentration.     

Loss of the thalamic nuclei for "head direction" impairs performance on spatial memory tasks in rats.

This study sought to characterize the effects of removing the nuclei of primary importance in relaying the thalamic head direction signal to the hippocampal formation (the anterior dorsal [AD] and lateral dorsal [LD] nuclei) on the performance of a variety of spatial and nonspatial tasks. The results indicate that combined excitotoxic lesions of the AD and LD nuclei produce marked deficits on a variety of spatial tasks. These tasks included T-maze alternation and the ability to locate a hidden platform set at a fixed distance and fixed direction from a beacon in a Morris water maze. Although object recognition appeared unaffected, marked impairments were found in the ability to detect when an object was placed in a novel position (object-in-place memory). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Refinements in the assessment of dementia-related behaviors: Factor structure of the memory and behavior problem checklist.

This study explored the factor structure of the Memory and Behavior Problem Checklist (MBPC) of S. H. Zarit et al (1980), a 29-item inventory that samples negative behavior changes associated with dementia (e.g., incontinence and destroying property). Family caregivers for 185 progressive-dementia patients provided information on their affected relatives. A principal-components factor analysis with an oblique (nonorthogonal) rotation produced an 8-factor solution that accounted for 62.9% of the variance. A second-order factor analysis of the first 5 factors produced a 3-factor solution that accounted for 74.7% of the variance. The 3 factors were (a) self-care and self-maintenance functions, (b) memory problems and psychiatric symptoms associated with dementia, and (c) communication problems and agitation. Correlations between MBPC frequency scores and measures of adaptive ability and level of dementia were high and positive. Potential clinical and research applications of the scale in other related populations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mathematics instruction in Korean primary schools: Structures, processes, and a linguistic analysis of questioning.

This article reports results of a collaborative study of mathematics instruction in 1st and 5th grades in 5 schools in Pusan, Korea. The purpose of this collaborative effort was to describe classroom structures and processes in mathematics lessons, using the instruments and methodology developed by Stigler and Stevenson for their studies in Japan, Taiwan, and the United States (H. W. Stevenson et al., 1987; J. W. Stigler, S. -Y. Lee, G. W. Lucker, & H. W. Stevenson, 1982). Classes in Korea were teacher centered and organized in the whole-class structure. Lessons were made up of sequences of highly organized, systematic patterns of instruction dominated by teacher questions that included higher level procedural and conceptual questions. Instructional sequences were followed by short periods of practice and evaluation. Systematic conceptual development of mathematical procedures characterized the lesson content. These observations have implications for educators on both sides of the Pacific interested in why Asian students perform so well on international tests of mathematical achievement compared with students in the United States. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive deficits in docosahexaenoic acid-deficient rats.

This study investigated the influence of brain docosahexaenoic acid (DHA) deficiency on simple and complex olfactory-based learning and memory in 2nd generation (F2) adult male rats. Rats raised and maintained on either an n-3-adequate or an n-3-deficient diet were tested for acquisition of an olfactory learning set and an olfactory memory task, and for motivation to obtain a water reward. Despite a 76% decrease in brain DHA, n-3-deficient rats were able to acquire most simple 2-odor discrimination tasks but were deficient in the acquisition of a 20-problem olfactory learning set. This deficit could not be attributed to changes in sensory capacity but, instead, appeared to represent a deficit in higher order learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)