Unemployment rate as predictor of rate of psychiatric admission.

OBJECTIVE--To examine the relation between rates of psychiatric admissions and both the rate of unemployment and the underprivileged area score within small areas. DESIGN--Calculation of correlation coefficients and explanatory power by using data on psychiatric admissions from April 1990 to March 1992. Crude and age standardised rates were used based on all admissions and also on the number of people admitted regardless of the number of times each person was admitted. SETTING--Sectors with an average population of 45,000 consisting of aggregations of neighbouring wards in Bristol and District Health Authority and electoral wards with an average population of 9400 in the city of Bristol. RESULTS--Unemployment rates explained 93% of the variation in the crude person based admission rates standardised for age for those aged under 65 in the sectors. Person based rates correlated more strongly with unemployment than did rates based on all separate admissions. Inclusion of people aged 65 and over weakened the relation. Within electoral wards unemployment rates explained only about 50-60% of the variation but were still more powerful than the underprivileged area score. There was a significant negative correlation between average length of stay and readmission rates--that is, sectors with short lengths of stay were more likely to have patients readmitted (r = -0.64, 95% confidence interval -0.25 to -0.85). CONCLUSIONS--Unemployment rates are an extremely powerful indicator of the rates of serious mental illness that will need treatment in hospital in those aged under 65. This should be considered in the process of resource allocation, particularly to fundholders in general practice, or people with serious mental illness living in areas of high unemployment could be considerably disadvantaged.     

Allometric estimation of metabolic rate from heart rate in penguins

Studies of the relationship between heart rate (f(H)) and rate of oxygen consumption (V(.) (O(2))), which are then used to predict field metabolic rate, frequently fail to incorporate body mass as a predictive variable. This is a potentially important omission in the study of animals whose body mass fluctuates substantially during their annual cycle. In an attempt further to improve estimates of field metabolic rate from f(H), we re-evaluated data on M(b), f(H) and V(.) (O(2)) from previous studies of macaroni penguins (Eudyptes chrysolophus) and king penguins (Aptenodytes patagonicus) and derived a new relationship to integrate these three quantities. This relationship is at least as accurate and precise as previously determined relationships. We applied this same principle to published data on 11 of the 20 recognised penguin taxa to derive a relationship to predict V(.) (O(2)) from f(H) and M(b) in penguins of any species. This result has interesting implications in terms of reducing the logistical burden in studies of field metabolic rate.     

Estimating the rate of evolution of the rate of molecular evolution

A simple model for the evolution of the rate of molecular evolution is presented. With a Bayesian approach, this model can serve as the basis for estimating dates of important evolutionary events even in the absence of the assumption of constant rates among evolutionary lineages. The method can be used in conjunction with any of the widely used models for nucleotide substitution or amino acid replacement. It is illustrated by analyzing a data set of rbcL protein sequences.      

Phylogenetic estimates of diversification rate are affected by molecular rate variation

Molecular phylogenies are increasingly being used to investigate the patterns and mechanisms of macroevolution. In particular, node heights in a phylogeny can be used to detect changes in rates of diversification over time. Such analyses rest on the assumption that node heights in a phylogeny represent the timing of diversification events, which in turn rests on the assumption that evolutionary time can be accurately predicted from DNA sequence divergence. But there are many influences on the rate of molecular evolution, which might also influence node heights in molecular phylogenies, and thus affect estimates of diversification rate. In particular, a growing number of studies have revealed an association between the net diversification rate estimated from phylogenies and the rate of molecular evolution. Such an association might, by influencing the relative position of node heights, systematically bias estimates of diversification time. We simulated the evolution of DNA sequences under several scenarios where rates of diversification and molecular evolution vary through time, including models where diversification and molecular evolutionary rates are linked. We show that commonly used methods, including metric‐based, likelihood and Bayesian approaches, can have a low power to identify changes in diversification rate when molecular substitution rates vary. Furthermore, the association between the rates of speciation and molecular evolution rate can cause the signature of a slowdown or speedup in speciation rates to be lost or misidentified. These results suggest that the multiple sources of variation in molecular evolutionary rates need to be considered when inferring macroevolutionary processes from phylogenies.     

Influence of day of postpartum breeding on pregnancy rate, pregnancy loss rate, and foaling rate in Thoroughbred mares

Records (years 2005-2007) were analyzed from a Thoroughbred stud farm in central Kentucky. Data from all breeding cycles of foaling mares were tabulated (3184 cycles of 2003 foaling mares bred between 7 and 163 days postpartum). A multiple logistic regression model employing Bayesian statistics was used to adjust for factors that significantly affected outcome; odds ratios (ORs) for pregnancy rate, pregnancy loss rate, and foaling rate were determined to examine the influence of day of postpartum breeding on these parameters. Mares bred before Day 22 (Day 0 = day of foaling) postpartum had a decreased OR for becoming pregnant (P < 0.05); the median OR for becoming pregnant (1.00) was not reached until Day 46 postpartum. Mares bred before Day 13 postpartum had an increased OR for pregnancy loss (P < 0.05). The median OR for pregnancy loss did not decline below 1.00 until Day 78 postpartum. Mares bred before Day 20 postpartum had a decreased OR for producing a foal (P < 0.05). The median OR for producing a foal (1.00) was not reached until Day 75 postpartum. We concluded that fertility (in terms of a higher OR for becoming pregnant and a lower OR for pregnancy loss, resulting in a higher OR for producing a foal) continued to improve in Thoroughbred mares for approximately 2.5 mo postpartum. These findings are of importance to management strategies directed at early postpartum breeding, and explain some of the reported drift in subsequent foaling dates of Thoroughbred mares, despite management practices that employ early postpartum breeding.     

两性具有不同出生率和死亡率的种群动态

以往的种群动力学模型均隐含假设性比为1：1,而实际上并非总如此,不同性别的出生和死亡是不完全相同的。文中就考虑了两性具有不同出生率和死亡率的种群动态问题。可以知道种群动态只是受雌性控制,与雄性无关。     

pH对5种臂尾轮虫后代存活率和混交雌体率及种群内禀增长率的影响

水生生态系统中,pH是重要的非生物因子之一.pH可以通过影响水生生物的存活和繁殖,进而影响其在水体中的分布和多度,最终决定水生群落的物种组成和丰富度[1].     

Synexin enhances the aggregation rate but not the fusion rate of liposomes

The effect of synexin on the calcium-induced fusion of large unilamellar liposomes was studied by using two assays for the mixing of aqueous contents. The results were analyzed in terms of the mass action kinetic model, which describes the overall fusion reaction as a two-step sequence consisting of a second-order process of liposome aggregation followed by a first-order fusion reaction. By using several different lipid compositions and varying the electrolyte composition, it was possible to select the rate-limiting step of the overall fusion process. When aggregation was the rate-limiting step, as in the case of Ca2+-induced fusion of phosphatidylserine (PS), phosphatidate (PA)/phosphatidylethanolamine (PE) (1:3), and PS/PE (1:3) liposomes, synexin increased the overall fusion kinetics by increasing the aggregation rate constant (up to 100-fold). When aggregation was rapid compared to destabilization of apposed membranes, i.e., fusion was rate limiting, synexin either had no effect or reduced the overall fusion kinetics. In one such case involving liposomes composed of PA/PS/PE/phosphatidylcholine (PC) (10:15:65:10), synexin reduced the fusion rate constant by 50%. The effect of calcium-induced synexin polymerization was investigated by preincubation of synexin with calcium prior to addition of liposomes. Prepolymerization by Ca2+ always decreased the activity of synexin such that it was less than the activity of an equal amount of untreated monomers. However, it was found that the activity of synexin monomers polymerized to an average hexameric size was greater than that of one-sixth as many untreated monomers, with respect to the liposome aggregation rate constant. Neither polymers nor monomers increased the fusion rate constant.