Re-examining the water affordability: A comparison of alternative measures

Water affordability is determined by the percentage of income households that must allocate to municipal water services, while factoring in essential or basic needs water use. With the rise in water prices reported in most areas of the country along with somewhat stagnant income growth—a combination that suggests ceteris paribus—more of a household's disposable income is being spent on water services. This paper adds to the discussion in three ways. First, given the lack of a consistent definition for “affordability” and the subjective connotation associated with such a term, we develop and compare five different water expenditure ratios, including two different measures of water for essential needs, as well as measures for indoor, efficient, and actual water use. Second, because of the granularity of our data, we illustrate how such “affordability” measures can vary significantly within a water district and thus highlight how using district- or county-level income measures can mask the degree to which affordability is an issue for households living in low-income block groups. Our results indicate that the choice of income measure and type of water service use can influence affordability measures substantially.     

5种结构障碍物对火焰传播影响的试验研究

为了研究障碍物结构对预混甲烷管道内火焰传播速度和峰值超压的影响,自行设计一套火焰加速系统。在火焰加速管道上安装光电传感器和压力传感器分别测定火焰传播速度和超压,试验中选取5种结构障碍物,即平板、长方体、三棱柱、四棱柱和圆柱,其阻塞比分别为20%,40%和60%3种。研究结果表明:初始阶段障碍物阻碍火焰传播,当火焰越过障碍物后,障碍物能显著加速火焰传播。随着阻塞比增加,相同结构障碍物的火焰传播速度总体上不断增加,而峰值超压先变大后减小。相同阻塞比下,平板、三棱柱对火焰传播速度和超压影响相对较大;长方体居中;圆柱、四棱柱对增加火焰传播速度和超压作用相对较小。较小阻塞比障碍物管道内超压与无障碍物管道中的超压相比显著增加,但此后,管道中超压随阻塞比变化不明显。     

短程反硝化的启动及多参数优化下NO2--N积累特性

采用本实验室长期培养的厌氧（S-A）、好氧（S-O）和交替厌氧/好氧（S-A/O）活性污泥为种泥,分别启动短程反硝化SBR反应器R1、R2和R3,控制进水C/N比为3,缺氧搅拌时间为1h时,在第15d、7d和4d亚硝酸盐积累率（NAR）分别达到75.34%、84.51%和86.23%.选取C/N比、初始pH值、缺氧搅拌时间和初始NO₃^--N浓度对NAR进行四因素三水平响应面实验,方差分析结果表明,以上因素对NAR均有显著影响（P<0.05）,模型R²为0.983.通过模型预测得最佳运行条件：C/N比为3.16,初始pH值为8.51,缺氧搅拌时间为1.27h,初始NO₃^--N浓度为60mg/L的条件下,NAR高达91.32%.     

Changes in the sex structure of pine populations related to temperature anomalies

The results of ten-year observations on fluctuations in the sex of individual trees and the sex structure of tree stands in two insular pine forests in the south of Central Siberia are presented. It is noted that the ratio of sex types of pine trees has markedly changed since 1998–1999. Significant correlations between the sex structure of stands and anomalies of the annual average air temperature have been recorded since the early 1990s. The male generative sphere of pine has changed to the greatest extent. Periodicity and delay in the change of shoot sexualization in response to changes in temperature are discussed.     

Understanding the opposition

Current debates about sex selection start from a paradox: on the one hand, the ‘liberal’ argument in favour of sex selection is often thought to be sound; but on the other hand there is widespread public opposition to sex selection. So it is worth spending some time examining the arguments against sex selection. Four different types of argument are identified: (i) religious arguments; (ii) consequentialist arguments, mainly concerning disturbance to the sex ratio; (iii) arguments to the effect that sex selection involves a failure to respect the autonomy of a child; (iv) arguments to the effect that the motivation for sex selection brings with it an instrumental attitude to children not compatible with a child's need for unconditional acceptance and love. In the end the conclusion is reached that none of these arguments provide decisive arguments against the liberal thesis that sex selection ought to be permitted, especially where 'family balancing' is envisaged. In the light of this conclusion the issue of fetal sexing followed by selective feticide as a method of sex selection is discussed. It is argued that sex selection is not in general a good reason for abortion, but that this practice may become unstoppable. Copyright © 2006 John Wiley & Sons, Ltd.     

Ecomorphological Characteristics of the Marsh Frog Rana ridibunda from the Galich'ya Gora Nature Reserve

Russian Journal of Ecology -     

Offspring sex ratio in relation to female size in southern elephant seals,Mirounga leonina

Southern elephant seals Mirounga leonina display extreme sexual dimorphism. In addition females show great variation in size and stored resources at parturition. Therefore they present an excellent opportunity for examination of responses of sex ratio to resource availability. We studied the relationships between the size of southern elephant seal females at parturition and the size and sex of their pups at South Georgia over four breeding seasons. We found a large individual variation in maternal post-partum mass (range 296–977 kg, n=151). Larger mothers gave birth to larger pups, irrespective of the sex of their pup. Male pups were on average 14% larger than females at birth and consequently more costly to bring to parturition. Our results suggest that female southern elephant seals must weigh more than 300 kg if they are to breed at all, and more than 380 kg if they are to give birth to a male pup. Above this threshold the proportion of males among offspring rapidly increases with maternal mass, and stabilizes at a level not significantly different from parity. These results show that smaller females of southern elephant seals vary offspring sex ratio in a way that is consistent with theories on adaptive offspring sex ratio. A smaller mother with a male foetus may benefit from terminating her pregnancy and allocating the resources she saves to her own growth. She could then give birth to and raise a larger pup in the subsequent season.     

复合垂直流人工湿地微生物特征对典型污水的响应差异

污水性质是影响人工湿地微生物特征的重要因子,而微生物对人工湿地污染物净化功能的发挥至关重要. 运用两组IVCW(复合垂直流人工湿地)分别处理模拟生活污水和污水处理厂尾水,比较研究两组系统下行流、上行流池的基质酶活性及硝化反硝化强度,并通过脂肪酸甲酯图谱分析系统中的微生物群落结构,以解析人工湿地微生物特征对两种污水的响应差异. 结果表明:处理生活污水的IVCW下行流池中脱氢酶、过氧化氢酶、脲酶及硝酸盐还原酶活性均显著高于其他单元,四者平均值分别为其他单元的2.8~4.6、7.9~10.3、19.3~41.7和4.5~10.8倍. 处理生活污水IVCW基质的硝化强度是尾水处理系统对应单元的1.4~5.3倍(下行流)和1.3~3.9倍(上行流),而两组IVCW对应单元基质的反硝化强度之间无显著差异. IVCW下行流池中特征脂肪酸比值及微生物群落结构受污水类型的影响较小,均以厌氧细菌和革兰氏阳性菌为优势菌;上行流池微生物群落结构则受到污水类型的一定影响,真菌的相对丰度较高. 两种污水对IVCW基质酶活性和硝化强度的影响高于对反硝化强度和微生物群落结构的影响.