Tempo and mode of evolutionary radiation in iguanian lizards

Identification of general properties of evolutionary radiations has been hindered by the lack of a general statistical and phylogenetic approach applicable across diverse taxa. We present a comparative analytical framework for examining phylogenetic patterns of diversification and morphological disparity with data from four iguanian-lizard taxa that exhibit substantially different patterns of evolution. Taxa whose diversification occurred disproportionately early in their evolutionary history partition more of their morphological disparity among, rather than within, subclades. This inverse relationship between timing of diversification and morphological disparity within subclades may be a general feature that transcends the historically contingent properties of different evolutionary radiations.     

Contingency and determinism in replicated adaptive radiations of island lizards

The vagaries of history lead to the prediction that repeated instances of evolutionary diversification will lead to disparate outcomes even if starting conditions are similar. We tested this proposition by examining the evolutionary radiation of Anolis lizards on the four islands of the Greater Antilles. Morphometric analyses indicate that the same set of habitat specialists, termed ecomorphs, occurs on all four islands. Although these similar assemblages could result from a single evolutionary origin of each ecomorph, followed by dispersal or vicariance, phylogenetic analysis indicates that the ecomorphs originated independently on each island. Thus, adaptive radiation in similar environments can overcome historical contingencies to produce strikingly similar evolutionary outcomes.     

Water transport in the cloaca of lizards: active or passive?

The withdrawal of water from the lizard cloaca can be a passive process resulting from the colloidal osmotic pressure of the plasma proteins. The forces necessary to withdraw water from lizard urine, the forces prevailing within the cloaca in vivo, and the counterbalancing of these forces by a protein solution placed in the cloaca all are in accord with this hypothesis.     

Behavioral thermoregulation in lizards: importance of associated costs

The Puerto Rican lizard Anolis cristatellus behaviorally regulates body temperature in an open habitat but passively tolerates lower and more variable temperatures in an adjacent forest where basking sites are few and distant. Thermoregulation may be adaptive only when costs resulting from associated losses of time and energy are low.     

Gene dosage at the lactate dehydrogenase b locus in triploid and diploid teiid lizards

Triploid parthenogenetic lizards which are heterozygous at the lactate dehydrogenase b locus show approximately two doses of the b allele and approximately one dose of the b' allele. This finding agrees with the triploid karyotype composed of two haploid complements of chromosomes indistinguishable from those of species carrying the b allele and one complement indistinguishable from that of the species which carries the b' allele. Densitometry of electrophoretic patterns of lactate dehydrogenase from heart muscle and from kidney indicates approximately equal expression of each of the b alleles in the triploid lizards. Heterozygouis diploid lizards from the same parthenogenetic species, in agreement with their karyotype, show equal doses of b and b' alleles.     

基于形态特征探讨宁夏蜥蜴的系统关系

通过对采自宁夏境内的百余头蜥蜴类动物标本进行整理和分类鉴定,表明宁夏分布的蜥蜴亚目动物共4科6属11种,分别为草原沙蜥(Phrynocephalus frontalis)、荒漠沙蜥(Phrynocephalus przewalskii)、变色沙蜥(Phrynocephalus versicolor)、无蹼壁虎(Gekko swinhonis)、隐耳漠虎(Alsophylax pipiens)、黄纹石龙子(Eumeces capito)、秦岭滑蜥(Scincella tsinlingensis)、虫纹麻蜥(Eremias vermiculata)、丽斑麻蜥(Eremias argus)、荒漠麻蜥(Eremias przewalskii)、密点麻蜥(Eremias multiocellata).选取15条分类性状,用DPS软件包对11种蜥蜴进行聚类分析,对其系统关系进行了初步探讨.结果表明:在麻蜥属的4种中,虫纹麻蜥和密点麻蜥的关系最近;沙蜥属的3种中,草原沙蜥和荒漠沙蜥的关系明显近于和变色沙蜥的关系.在科间关系上,蜥蜴科与石龙子科关系较其他科近,鬣蜥科与其他科关系较远,聚类结果与传统的分类结果基本一致.     

Contribution of gular pumping to lung ventilation in monitor lizards

A controversial hypothesis has proposed that lizards are subject to a speed-dependent axial constraint that prevents effective lung ventilation during moderate- and high-speed locomotion. This hypothesis has been challenged by results demonstrating that monitor lizards (genus Varanus) experience no axial constraint. Evidence presented here shows that, during locomotion, varanids use a positive pressure gular pump to assist lung ventilation. Disabling the gular pump reveals that the axial constraint is present in varanids but it is masked by gular pumping under normal conditions. These findings support the prediction that the axial constraint may be found in other tetrapods that breathe by costal aspiration and locomote with a lateral undulatory gait.     

Aerodynamic analysis and CFD simulation of several cellulose evaporative cooling pads used in Mediterranean greenhouses

The present work makes an aerodynamic analysis and computational fluid dynamics (CFD) simulation of the four commercial models of corrugated cellulose evaporative cooling pads that are most widely used in Mediterranean greenhouses. The geometric characteristics of the pads have been determined as well as the volume of water they retain at different flows of water, thus obtaining the mean thickness of the sheet of water which runs down them and their porosity. By means of low velocity wind tunnel experiments, the pressure drop produced by the pads has been recorded at different wind speeds and water flows. In this way it has been possible to obtain the relationship of the permeability and the inertial factor with pad porosity using a cubic type equation. Finally, a CFD simulation with a 3D model has been carried out for both dry pads (Q_w = 0 l s⁻¹ m⁻²) and wet ones (Q_w = 0.256 l s⁻¹ m⁻²), finding good correlation between the simulated and experimental pressure drop, with maximum differences of 9.08% for dry pads and 15.53% for wet ones at an airspeed of 3 m s⁻¹.     

两收敛且等值的无穷限广义积分变量代换的存在唯一性

本文讨论两个收敛且等值的无穷限广义积分变量代换的存在性与唯一性，文中提出并证明了在一定的条件下，这个代换是存在的，也是唯一的。     

两收敛且等值的无穷限广义积分变量代换的存在唯一性

本文讨论两个收敛且等值的无穷限广义积分变量代换的存在性与唯一性,文中提出并证明了在一定的条件下,这个代换是存在的,也是唯一的。     

数字化农业与数字化作战的比较分析

1引言近年来，数字化农业的概念开始在我国流行[1]，但是对数字化农业这个概念起源于军事作战领域的研究则相当少见，因此不少人对数字化农业存在模糊的认识，错误的以为数字化农业是推动我国农业进步的一项关键技术，对此我们必须保持清醒的认识，这篇文章通过对数字化作战起源的讨论，分析了数字化作战与数字化农业之间的关系，数字化作战的思想在农业中应用的可行性，以及数字化农业发展的前景，最后指出，中国的农业必须走自己的发展道路，以机械化带动信息化，以信息化推动机械化，更好地适应在互连网时代农业发展的需要。2数字化作战…     

图书馆数字化网络化服务中的缺陷

图书馆的数字化网络化建设有着各种优越性，但数字化网络化服务并不是没有弊端，也产生了一些问题，本文从数字资源、网络条件、检索技术以及用户的信息素质等几方面，分析数字化网络化服务存在的缺陷，并探讨如何解决存在的不足。     

Proximate constraints on the evolution of egg size, number, and total clutch mass in lizards

Proximate constraints on egg size, number, and total clutch mass in side-blotched lizards were examined by experimentally reducing average clutch size from 4.6 eggs to one, two, and three eggs. Eggs from experimentally altered clutches were larger than those from controls, reflecting the trade-off between egg size and number. Moreover, the increased frequency of females with oviducally bound eggs or eggs that burst at oviposition suggests that egg size in clutches with very few eggs are at a functional upper size limit. These proximate constraints may also limit evolution of egg size in another group of lizards (Anolis) that only produces one-egged clutches.     

两收敛且等值的无界函数广义积分变量代换的存在性与唯一性

本文讨论两个收敛且等值的无界函数广义积分变量代换的存在性与唯一性,文中提出并证明了在一定的条件下,这个代换是存在的,也是唯一的     

黏性鱼卵的黏性机制及人工孵化技术研究进展

鱼卵按黏性程度可分为黏性卵、弱黏性卵和非黏性卵3类,许多重要的经济鱼类产黏性卵,黏性鱼卵遇水后,卵膜表面黏性物质即被激活,继而产生黏性,对人工授精和孵化技术提出了更高的要求.研究黏性鱼卵的黏性特征和黏性机制,对产黏性卵的经济鱼类人工繁育具有重要意义,本文综述了黏性卵的黏性特征和黏性机制研究进展,对比了各种脱黏方法在不同...     

黏性鱼卵的黏性机制及人工孵化技术研究进展

鱼卵按黏性程度可分为黏性卵、弱黏性卵和非黏性卵3类,许多重要的经济鱼类产黏性卵,黏性鱼卵遇水后,卵膜表面黏性物质即被激活,继而产生黏性,对人工授精和孵化技术提出了更高的要求。研究黏性鱼卵的黏性特征和黏性机制,对产黏性卵的经济鱼类人工繁育具有重要意义,本文综述了黏性卵的黏性特征和黏性机制研究进展,对比了各种脱黏方法在不同鱼类孵化过程中的效果,并对今后产黏性卵鱼类人工授精和孵化技术的研究方向进行了展望,以期为产黏性卵鱼类的人工繁育提供参考。     

黏性鱼卵的黏性机制及人工孵化技术研究进展

鱼卵按黏性程度可分为黏性卵、弱黏性卵和非黏性卵3类,许多重要的经济鱼类产黏性卵,黏性鱼卵遇水后,卵膜表面黏性物质即被激活,继而产生黏性,对人工授精和孵化技术提出了更高的要求。研究黏性鱼卵的黏性特征和黏性机制,对产黏性卵的经济鱼类人工繁育具有重要意义,本文综述了黏性卵的黏性特征和黏性机制研究进展,对比了各种脱黏方法在不同鱼类孵化过程中的效果,并对今后产黏性卵鱼类人工授精和孵化技术的研究方向进行了展望,以期为产黏性卵鱼类的人工繁育提供参考。     

两收敛且等值的无界函数广义积分变量代换的存在性与唯一性

本文讨论两个收敛且等值的无界函数广义积分变量代换的存在与唯一性，文中提出并证明了在一定的条件下，这个代换是存在的，也是唯一的。