Theory of spontaneous vesicle formation in surfactant mixtures

The curvature elastic energy of bilayer vesicles formed by a mixture of two surfactants, which individually form either micelles or lamellar bilayer phases is described theoretically. In the limit of large bending elastic modulus K being much greater than the temperature T, the free energy is minimized by vesicles with different concentrations of the two surfactants in each monolayer of the bilayer. Vesicles are more stable than lameliar structures only when interactions or complexing of the two surfactants is taken into account.     

Calving patterns in seasonal dairy herds

Two field studies examined the calving patterns of cows in seasonal dairy herds in the Waikato (Field Study 1) and South Taranaki regions (Field Study 2). The first study examined patterns for cows commencing their second or subsequent lactation in herds which had used an inseminating service during the previous season. The second study included first lactation heifers only in 15 herds where animals had been naturally mated, and in 15 herds in which they had been synchronised and then artificially inseminated at the synchronised oestrus. The parameters describing calving patterns were based on the date for each herd's planned start of calving (PSC), which was 282 days from the date on which breeding commenced in the preceding season. The average interval from PSC to mean calving date for the 35 herds in Field Study 1 was 22 days, with individual herds ranging from 15 to 30 days. In herds with heifers which had been naturally mated (Field Study 2), it was 17.6 days compared to 11.0 days for previously synchronised animals. Calculating the intervals from PSC to median calving date and separately for the last two quartiles more effectively described a herd's calving pattern. The duration for the last quartile of the calving pattern was influenced by the extent and timing of induced calving. In Field Study 1, 88.6% of the 35 herd owners induced premature parturition in at least one cow. In these herds, 11.3% of cows were treated and calved prematurely. Only 61.7% of heifers which had previously been naturally mated calved by 3 weeks after PSC. Their calving dates were not evenly distributed over this 3-week period, with 9.8% in the first week and 25.6% in the third week. The calving pattern for heifers which had been previously synchronised showed several distinct peaks. Calvings to the synchronised mating were completed 15 days after PSC, by which time 64.7% of animals had calved. By 3 weeks after PSC, 72.9% of these heifers had calved. The results showed that there was considerable variation in calving patterns in seasonal dairy herds. This variation would have been due to differences in conception pattern, and the way induced calving had been applied. The calving pattern in heifers which had been naturally mated was less concentrated than had been expected. Synchronisation can significantly concentrate the calving pattern of these first lactation animals. The parameters used to describe calving patterns may be less applicable in herds in which a high proportion of animals is induced to calve prematurely, or where a whole herd is synchronised. Nonetheless, they do serve as an illustrative example of the variation in calving patterns among herds.     

Strontium Uptake in Shell Aragonite from the Freshwater Gastropod Limnaea stagnalis

Shell aragonite from 96 specimens of the freshwater gastropod Limnaea stagnalis grown in laboratory tanks at different temperatures in water with variable strontium/calcium ratios have been analyzed for its strontium content in order to evaluate the mechanisms of strontium uptake in molluskan aragonite. Within the limits defined by natural freshwater environments, the strontium/calcium ratio in the aragonite was found to be linearly related to the strontium/calcium ratio in the water. A distribution coefficient k(A)(Sr) = 0.237 +/- 0.029, unaffected by variations in temperature and growth rate, has been found. This finding substantiates the existence of a strontium-discriminating effect in aragonite precipitated by mollusks as compared to the case for nonbiogenic aragonite which contains about five times as much strontium when precipitated under the same conditions.     

淀粉摄入量对断奶马生长和骨骼发育的影响

用44匹断奶马设计两个试验来评估淀粉摄人量对断奶马生长和骨骼发育的影响．存试验1中．试验断奶马被喂给谷物为基础，高淀粉浓度(31．1％)日粮或副产品为基础，不加淀粉加沿海绊根草(Cynodon dactylon)为试验组。利用玉米油补充日粮能量浓度。能量浓度：干草是64：36．两种日粮的摄入量是一致的．摄入高浓度淀粉的断奶马的体增重(0．81kg／d)与另一组(0．67kg／d)相比显著增加(P=0．01)。高摄入浓度淀粉的断奶马的体长增加(15．5cm)与另一组(13．2cm)相比也显著提高(P=0．045)．其它的身体指标测定和骨骼矿物质沉积物情况不受日粮影响。在试验期末．     

氟虫腈(锐劲特)对水稻害虫防治效果及增产效应

为了阐明新一代杀虫剂氟虫腈(锐劲特)对二化螟、三化螟、稻纵卷叶螟的防治效果及应用前景,进行了水稻盆栽试验、田间防效试验,并对施用锐劲特后水稻叶绿素含量、功能叶叶面积和产量进行了测定。结果表明,锐劲特施药后13天接虫的三化螟幼虫死亡率仍高达94.44％。在田间防效试验中,每公顷施用锐劲特80％WG有效成分24g防治二化螟,防止枯心效果达97.62％,防止白穗效果达94.44％,害虫死亡率达96.15％;每公顷施用锐劲特5％SC有效成分22.5g防治晚稻三化螟,保苗效果可达95.91％,害虫死亡率达99.04％;每公顷施用锐劲特5％SC有效成分30g防治稻纵卷叶螟,保叶效果达97.88％。叶绿素含量比对照增加32.4％;每公顷施用锐劲特80％WG有效成分36g时,功能叶叶面积增加16％～27.5％,并且杂交稻博优湛19比常规稻早糯3321和早熟早籼815对锐劲特更敏感。每公顷施用锐劲特5％SC有效成分22.5～37.5g时,水稻株高增加4.0～6.1cm,每稻丛穗数增加2.6％～31.18％,结实率提高19.43％～33.97％,水稻产量增加21.58％～28.19％。