Effects of elevation on litter-size variation among lizard populations in the Sceloporus grammicus complex (Phrynosomatidae) in Mexico

We examined the effect of elevation on litter-size variation in viviparous lizards of the Sceloporus grammicus complex in 10 states of Mexico. Female snout–vent length (SVL) decreased with increasing elevation, and absolute litter size based on embryos also tended to de crease with increasing elevation. However, after controlling for variation in female body size, we found that litter sizes tended to be relatively larger at higher elevation. Elevation therefore appears to influence litter size in these lizards; however, relatively little of the variation is explained by elevation; thus, other factors are likely making substantial contributions to the observed litter-size variation. The S. grammicus complex appears to be a good model system for examining the underlying causes of geographic and elevational variation in lizard life histories. Examinamos el efecto del altitud en la variación del tamaño de camada de las lagartijas vivíparas del complejo Sceloporus grammicus en 10 estados de México. La LHC de las hembras disminuyó con la altitud, y el tamaño absoluto de camada, calculado con base en el número de embriones, también tendió a disminuir. No obstante, después de controlar la variación en el tamaño corporal de las hembras, encontramos que los tamaños de camada tendieron a ser relativamente más grandes en altitudes mayores. La altitud, por tanto, parece influir en el tamaño de camada de estas lagartijas; sin embargo, la altitud explica relativamente poco de la variación, por lo que, es probable que otros factores contribuyan substancialmente a la variación observada en el tamaño de camada. El complejo S. grammicus parece ser un buen sistema para estudiar las causas fundamentales de la variación geográfica y altitudinal en la historia de vida de las lagartijas.     

Attributes associated with probability of infestation by the pi?on ips, Ips confusus (Coleoptera: Scolytidae), in pi?on pine, Pinus edulis

We examined attributes of pi?on pine ( Pinus edulis ) associated with the probability of infestation by pi?on ips ( Ips confuses ) in an outbreak in the Coconino National Forest, Arizona. We used data collected from 87 plots, 59 infested and 28 uninfested, and a logistic regression approach to estimate the probability of infestation based on plot and tree-level attributes. Pi?on pine stand density index was a good predictor of the likelihood of infestation by pi?on ips at the plot level, and a cross-validation analysis confirmed that the model correctly classified 82% of the cases. Diameter at root collar and pi?on dwarf mistletoe infestation level were good predictors of individual tree infestation, and a cross-validation analysis indicated that the model correctly classified 72% of the cases. Results suggest that the occurrence of pi?on ips infestations may be related to stress factors associated with increased stocking and pi?on dwarf mistletoe infestations.     

Sperm viability in the reproductive tract of females in a population of Sceloporus mucronatus exhibiting asynchronous reproduction

Asynchronous reproduction is a common phenomenon in high-elevation populations of lizards from Central México. Sperm storage in the reproductive tract of females is the mechanism for making oocyte fertilization possible. Our study addresses questions related to functional oviductal sperm storage of females mating on different dates throughout the reproductive season. A population of Sceloporus mucronatus with copulation in the summer and ovulation in the fall was chosen for this experiment. Eleven females that copulated in the field during June and 13 females that copulated in captivity during August were maintained in the laboratory until parturition. The number of pregnant females and the litter sizes produced in each experimental group were indicative of the viability of the stored sperm. Sperm stored in the reproductive tract of females were able to fertilize eggs after 4 months. No significant differences were found in the number of pregnant females between the 2 experimental groups nor in the litter sizes that they produced. We found that the amount of time sperm were held in the female reproductive tract (ca. 3 months) had no effect on the capacity of sperm to fertilize eggs. Histological examination of 8 oviducts collected before the mating season eliminated the possibility of sperm storage from one year to the next. In this system, sperm retention could have evolved as a response mechanism to deal with the asynchrony between sexes in the reproductive cycles. However, we cannot rule out alternative hypotheses.     

中小企业技术创新的现状与对策

分析了中国中小企业技术创新的特点和现状,指出中小企业技术创新能力不高、缺乏技术创新的人才队伍、产学研合作机制不健全、融资渠道少等问题,提出重视中小企业技术创新人才的培养、优化金融环境、建立健全产学研合作机制、通过培育中介组织推动企业自主创新、选择适合企业实际情况的技术创新战略等措施.     

具有抗艾滋病毒活性的多肽T22([T5,12yr,L7yr]-PolyphemusinⅡ)骨架构象模拟

用势能平滑搜索方法，在平滑修饰的势能面上对具有抗艾滋病毒HIV－1活性的肽T22（[Tyr^5,12,Tyr^7]-PolyphemusinⅡ）骨架结构进行了全程搜索，得到了该分子骨加结构在修饰势能面上的分子构象全集。用多构象优化方法，选择较适用于肽OPLS力场，采用GB／SA水溶剂模型，优化上述构象集，得到T22骨架结构在水溶液中优势构象集。结果表明势能平滑搜索与多构象优化相结合的构象分析方法是解决含有环结构的柔性分子构象分析中多重最小问题的有效方法。     

交错群A_p的数量刻画(英文)

证明了若p≥ 5且p与p - 2 均为素数 ,则交错群Ap 可用元的阶刻画     

H_∞ Control of a 5th- order Model of Synchronous Generators

1　IntroductionThe control of synchronous generators is one of the most important and widely studiedproblem in the area of power systems control.Such a problem is a non-trivial one,mainlybecause of the highly nonlinear behaviour of synchronous machines.As a matter of fact,their dynamic dramatically changes when passing from a working condition to another.Asa consequence,standard PID-based controllers can not guarantee high performances overthe entire working range.Among the various control a…     

A System for Generating Operational Sketches Based on the Multi- level Graphic Library

1　IntroductionLittle previous work has been reported on the generation of operational sketches.However,there are two major strategies for generating operational sketches. The first iscalled geometric model method in which geometric information of a work-piece is organizedinto a model called solid model or feature solid model with the 3 D modeler. Theoperational sketches are generated by projecting into a projective plane which is chosenwith care.Feasible as it appears,this drawing obtained d…     

利用有限域上伪辛几何构作两类Cartension认证码

本文利用有限域上的伪辛几何构作两类Cartension认证码,并且计算了它们的参数及成动的模仿攻击概率和成动的替挽攻击概率。     

A Java-Based Approach for Developing Web Application System

1.INTRoDUCTIONCreatingInternet,IntranetandExtranetapplicationsarecurrentlycenterofprogrammingfocus.Theyallbelongtoweb-basedbusinessapplications[1lthatrequiredatabaseconnec-tion,userauthentication,sessionmanagementanddynamicHTMLgeneration.Web-basedapplicationsshouldhavefollowingfeatures:1)Platform-independelltontheclientside,usuallyabrowser;2)Platform-independentontheserverside,suchasincludingbothUnixandWindowsenvironments;3)Beabletoconnecttoavarietyofdatabase,suchasincludingoracle,Inf…