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Culling the Masses by Professors David Scott FitzGerald and David Cook-Martín is an impressive work that makes important scholarly contributions. It analyses the trend in the USA, Canada, Cuba, Mexico, Brazil and Argentina away from explicit racial discrimination in immigration laws. One layer of the book's argument examines how ‘vertical’ (domestic) and ‘horizontal’ (external) forces led these countries to abandon explicit racism. In another layer, the book argues that this anti-racist turn was not a product of democracy. Instead, racist immigration laws were often the product of democratic influences and institutions. The nuanced examination of external influences on national immigration laws in Culling the Masses is an invaluable contribution. However, its inconsistent definition of ‘immigration law’ across countries leaves incomplete both its assessment of racism in the present-day immigration laws, and in turn, its assessment of the relationship between democracy and racism.     

不同饵料对匙吻鲟仔鱼生长发育和消化酶活性的影响

本文研究了不同强化饵料对匙吻鲟(Polyodon spathala)仔鱼生长和发育的影响,实验采用蛋黄或鱼油强化卤虫无节幼体或桡足幼体为饵料的共6个实验组,即未强化卤虫组、蛋黄强化卤虫组、鱼油强化卤虫组和未强化桡足幼体组、蛋黄强化桡足幼体组、鱼油强化桡足幼体组,对匙吻鲟仔鱼开口驯化14 d,动态监测和统计不同饵料组匙吻鲟仔鱼的生长和存活情况,并对消化酶活性进行相关性分析。体重、体长、日增重和存活率4个指标,均为桡足幼体组显著高于卤虫组(P0.05),尤其在存活率方面,鱼油强化卤虫组不足50%,而未强化桡足幼体组最高可达86.59%;不同饵料组生长模式方程都获得较好的拟合,从体重和体长生长曲线看,桡足幼体组从饲喂8天起体长和体重进入快速生长期,而卤虫组生长一直相对缓慢;胃蛋白酶活性在未强化桡足幼体组显著高于其他组(P0.05),不同饵料组对仔鱼的淀粉酶活性无显著性影响。结果表明,在匙吻鲟仔鱼开口期以桡足幼体开口饵料驯化效果较好,特别是未强化桡足幼体组仔鱼的存活率高,鱼油强化桡足幼体组仔鱼生长速度较快,而以卤虫饲喂效果相对较差。     

川东地区白背飞虱迁入种群虫源地分布与降落机制

【目的】本研究旨在确定四川达州白背飞虱Sogatella furcifera(Horváth)迁入虫源地及其降落机制,以期为川东地区白背飞虱预警和有效防控提供依据。【方法】运用大气质点轨迹分析平台HYSPLIT4.8对1991-2013年达州灯下白背飞虱主要迁入高峰日进行轨迹模拟,并运用气象图形处理软件Grads对主要迁入高峰日进行气象背景分析。【结果】达州白背飞虱主要在6-7月迁入,7月份是迁入高峰期。6月虫源主要来自广西西北、中部地区;7月虫源主要来自贵州中西部、北部,广西西北部和云南东北部也可提供部分虫源。【结论】四川达州白背飞虱迁入虫源主要来自贵州大部,部分来自云南东北部和广西西北部。由于气候条件和地形胁迫引起的降水、垂直气流和风向切变是白背飞虱大规模集中降落的主要原因。     

The effects of climate change and land‐use change on demographic rates and population viability

Understanding the processes that lead to species extinctions is vital for lessening pressures on biodiversity. While species diversity, presence and abundance are most commonly used to measure the effects of human pressures, demographic responses give a more proximal indication of how pressures affect population viability and contribute to extinction risk. We reviewed how demographic rates are affected by the major anthropogenic pressures, changed landscape condition caused by human land use, and climate change. We synthesized the results of 147 empirical studies to compare the relative effect size of climate and landscape condition on birth, death, immigration and emigration rates in plant and animal populations. While changed landscape condition is recognized as the major driver of species declines and losses worldwide, we found that, on average, climate variables had equally strong effects on demographic rates in plant and animal populations. This is significant given that the pressures of climate change will continue to intensify in coming decades. The effects of climate change on some populations may be underestimated because changes in climate conditions during critical windows of species life cycles may have disproportionate effects on demographic rates. The combined pressures of land‐use change and climate change may result in species declines and extinctions occurring faster than otherwise predicted, particularly if their effects are multiplicative.     

SEXUAL REPRODUCTION IN STEPHANODISCUS NIAGARAE (BACILLARIOPHYTA)1

We observed sexual reproduction in a clonal culture of Stephanodiscus niagarae Ehrenb. and used light and scanning electron microscopy to absent flagellated male cells, auxospore growth, initial valve structure and production, and subsequent daughter cell division. Free auxospores were spherical and nonsiliceous throughout growth, producing hemispherical initial valves devoid of spines and with nonfasciculate striae. Pregametangial cells averaged 43% of the diameter of the daughter cell population and were 1/9 the biovolume of initial, cells. This paper is the first confirmed report of sexual reproduction in S. niagarae, although it appears that specimens of Actinocyclus niagarae H. L. Smith, described from Lake Erie in 1878, are actually initial valves of S. niagarae.     

Changes of enzyme activity in lipid signaling pathways related to substrate reordering

The static fluid mosaic model of biological membranes has been progressively complemented by a dynamic membrane model that includes phospholipid reordering in domains that are proposed to extend from nanometers to microns. Kinetic models for lipolytic enzymes have only been developed for homogeneous lipid phases. In this work, we develop a generalization of the well-known surface dilution kinetic theory to cases where, in a same lipid phase, both domain and nondomain phases coexist. Our model also allows understanding the changes in enzymatic activity due to a decrease of free substrate concentration when domains are induced by peptides. This lipid reordering and domain dynamics can affect the activity of lipolytic enzymes, and can provide a simple explanation for how basic peptides, with a strong direct interaction with acidic phospholipids (such as beta-amyloid peptide), may cause a complex modulation of the activities of many important enzymes in lipid signaling pathways.     

Kinetics and mechanism of a reaction catalyzed by PST-01 protease from Pseudomonas aeruginosa PST-01

The initial rates of carboxybenzoyl-alanyl-l-leucyl-amide (Z-L-Ala-L-Leu-NH(2)) synthesis from carboxybenzoyl-L-alanine (Z-L-Ala) and L-leucineamide (L-Leu-NH(2)) and Z-L-Ala-L-Leu-NH(2) hydrolysis in a homogeneous dimethyl sulfoxide-aqueous buffer solution [1:1 (v/v)] system catalyzed by PST-01 protease from Pseudomonas aeruginosa were measured under a wide range of Z-L-Ala, L-Leu-NH(2) and Z-L-Ala-L-Leu-NH(2) concentrations. The initial rates of the synthetic reaction, in which Z-L-Ala-L-Leu-NH(2) was produced from Z-L-Ala and L-Leu-NH(2), were inhibited by the substrates. Furthermore, the initial rates of the synthetic reaction were not inhibited by the product Z-L-Ala-L-Leu-NH(2), and those of the hydrolytic reaction were inhibited by Z-L-Ala and L-Leu-NH(2). All the initial rate data of the synthetic and hydrolytic reactions were well correlated with the rate equation derived based on the proposed reaction scheme.     

Impact and efficiency of GH10 and GH11 thermostable endoxylanases on wheat bran and alkali-extractable arabinoxylans

The results of a comparative study of two thermostable (1-->4)-beta-xylan endoxylanases using a multi-technical approach indicate that a GH11 xylanase is more useful than a GH10 xylanase for the upgrading of wheat bran into soluble oligosaccharides. Both enzymes liberated complex mixtures of xylooligosaccharides. 13C NMR analysis provided evidence that xylanases cause the co-solubilisation of beta-glucan, which is a result of cell-wall disassembly. The simultaneous use of both xylanases did not result in a synergistic action on wheat bran arabinoxylans, but instead led to the production of a product mixture whose profile resembled that produced by the action of the GH10 xylanase alone. Upon treatment with either xylanase, the diferulic acid levels in residual bran were unaltered, whereas content in ferulic and p-coumaric acids were unequally decreased. With regard to the major differences between the enzymes, the products resulting from the action of the GH10 xylanase were smaller in size than those produced by the GH11 xylanase, indicating a higher proportion of cleavage sites for the GH10 xylanase. The comparison of the kinetic parameters of each xylanase using various alkali-extractable arabinoxylans indicated that the GH10 xylanase was most active on soluble arabinoxylans. In contrast, probably because GH11 xylanase can better penetrate the cell-wall network, this enzyme was more efficient than the GH10 xylanase in the hydrolysis of wheat bran. Indeed the former enzyme displayed a nearly 2-fold higher affinity and a 6.8-fold higher turnover rate in the presence of this important by-product of the milling industry.     

Genetic identification of immigrants to the Scandinavian wolf population

Continued gene flow is fundamental to the survival of small, isolated populations. However, geography and human intervention can often act contrary to this requirement. The Scandinavian wolf population is threatened with a loss of genetic variation yet limited in the accessibility to new immigrants by the geographical distance of this peninsular population from its nearest neighbouring population and by human reluctance to allow wolves in the northern reindeer-breeding areas. In this study, we describe the identification of immigrants into this population using autosomal microsatellites, and maternally inherited mtDNA. Samples of 14 wolves collected in the “dispersal corridor” in northern Sweden in 2002–2005 were compared with 185 resident Scandinavian wolves and 79 wolves from the neighbouring Finnish population. We identified four immigrant wolves, suggesting some westward migration, although only one of these is likely to still survive. The integration of such immigrants into the breeding population is necessary to assure the long-term survival of this isolated and inbred population and highlights the importance of genetics techniques to the management of threatened populations.