Initial Group Size Research Articles

Modelling persistence over generations in biological and cultural evolution based on differential paces of change

Paces of change are faster in cultural evolution than in biological evolution due to different levels of stability in information storage. This study develops mathematical models to investigate the consequences of differential mutation rates on the ability of groups of information units to survive over many generations. We examined the ability of groups composed of connected units to live on despite the occurrence of deleterious mutations that occur at probabilities ranging from 10−1 to 10−6. It appears that the degree of connection between units should be high enough for groups to persist across generations, but this alone did not ensure their survival; when groups of units were limited in size and subjected to high mutation rates, they did not survive for very long. By contrast, a significant proportion of groups were able to survive numerous generations if mutation rates were low and/or group size was large. The results revealed that the mean number of surviving generations was minimized for certain sizes of groups. When allowing information units to duplicate at each generation, simulation showed that a great number of groups avoided extinction even when mutating at the rate of cultural change if the initial group size was large and the duplication rate was high enough to counteract the consequences of environmental perturbations. The modelling described in this study sets out the conditions under which groups of units can survive along generations. It should serve as a basis for further investigations about the links between processes of biological and cultural changes.

Effects of Ground Floor Type on Selected Health-Parameters and Weight of Rabbits Reared in Group Pens.

Simple SummaryCage housing of growing rabbits is associated with welfare concerns. An alternative system that has already been introduced involves pens with non-wire floors. An important aspect of group pens, for which the best solution has not yet been clearly demonstrated, is the choice of floor material. We investigated effects of two ground floor types—slatted plastic floor versus concrete floor with straw litter—on health-related parameters and weight of rabbits reared in large group pens on a commercial rabbit farm, i.e., with preventive coccidiostatic, and if required, additional therapeutic medical treatment. Pens were identical in dimensions, equipment (including platforms), and initial group size (60 animals/pen). Four pens were studied per ground floor type in three consecutive rearing periods, i.e., 12 pens/ground floor type. A higher percentage of rabbits per pen had clean fur if reared on straw. No significant differences were found in parasitic burden, mortality, pathological alterations, or causes of loss. Thus, often-expressed concerns that parasitic load and mortality would be higher in groups kept on straw were not confirmed when rabbits were housed under otherwise equal conditions. Average slaughter weight was higher in rabbits reared on a slatted plastic floor, confirming previous findings of a negative impact of straw litter on weight gain.Cage housing of growing rabbits is associated with welfare concerns. An alternative system that has already been introduced involves pens with non-wire floors. An important aspect of group pens, for which the best solution has not yet been clearly demonstrated, is the choice of floor material. The study investigated effects of two ground floor types—slatted plastic floor versus concrete floor with straw litter—on health-related parameters and weight of rabbits reared in large group pens on a commercial rabbit farm, i.e., with preventive coccidiostatic, and if required, additional therapeutic medical treatment. Pens were identical in dimensions, equipment (including platforms), and initial group size (60 animals/pen). Four pens were studied per ground floor type in three consecutive rearing periods (in total, 12 pens per floor type). A higher percentage of rabbits per pen had clean fur if reared on straw (p < 0.05). No significant differences were found in the load of coccidial oocysts in collective faecal samples, mortality, pathological alterations, or causes of loss (p > 0.05). Thus, often-expressed concerns that parasitic load and mortality would be higher in groups kept on straw were not confirmed when rabbits were housed under otherwise equal conditions. Average slaughter weight was higher in rabbits reared on a slatted plastic floor (p < 0.05), confirming previous findings of a negative impact of straw litter on weight gain.

Results of the First Steps study: a randomised controlled trial and economic evaluation of the Group Family Nurse Partnership (gFNP) programme compared with usual care in improving outcomes for high-risk mothers and their children and preventing abuse

BackgroundFamily Nurse Partnership (FNP) is a home-based nurse home-visiting programme to support vulnerable parents. Group Family Nurse Partnership (gFNP) has similar aims and materials and was demonstrated to be feasible in implementation evaluations.ObjectivesTo determine whether or not gFNP, compared with usual care, could reduce risk factors for maltreatment in a vulnerable group and be cost-effective.DesignA multisite randomised controlled parallel-group trial and prospective economic evaluation, with eligible women allocated (minimised by site and maternal age group) to gFNP or usual care.SettingCommunity locations in the UK.ParticipantsExpectant mothers aged &lt; 20 years with one or more previous live births, or expectant mothers aged 20–24 years with no previous live births and with low educational qualifications (defined as General Certificate of Education at grade C or higher in neither mathematics nor English language or, if they had both, no more than four General Certificates of Education at grade C or higher).InterventionForty-four sessions of gFNP (14 during pregnancy and 30 in the first 12 months after birth) were offered to groups of between 8 and 12 women with similar expected delivery dates (the difference between the earliest and latest expected delivery date ranged from 8 to 10 weeks depending on the group) by two family nurses (FNs), one of whom had notified her intention to practise as a midwife.Main outcome measuresParenting was assessed by a self-report measure of parenting opinions, the Adult Adolescent Parenting Inventory Version 2 (AAPI-2), and an objective measure of maternal sensitivity, the CARE-Index. Cost-effectiveness was primarily expressed in terms of incremental cost per quality-adjusted life-year (QALY) gained.Data sourcesInterviews with participants at baseline and when infants were aged 2, 6 and 12 months. Cost information from nurse weekly logs and other service delivery data.ResultsIn total, 166 women were enrolled (99 to the intervention group and 67 to the control group). Adjusting for site and maternal age group, the intention-to-treat analysis found no effect of gFNP on either of the primary outcomes. AAPI-2 total was 7.5/10 [standard error (SE) 0.1] in both arms [difference also adjusted for baseline 0.08, 95% confidence interval (CI) –0.15 to 0.28;p = 0.50]. CARE-Index maternal sensitivity mean: intervention 4.0 (SE 0.3); control 4.7 (SE 0.4) (difference –0.76, 95% CI –1.67 to 0.13;p = 0.21). The sensitivity analyses supported the primary analyses. The probability that the gFNP intervention was cost-effective based on the QALY measure did not exceed 3%. However, in terms ofchangein AAPI-2 score (baseline to 12 months), the probability that gFNP was cost-effective reached 25.1%. A separate discrete choice experiment highlighted the value placed by both pregnant women and members of the general population on non-health outcomes that were not included in the QALY metric.LimitationsSlow recruitment resulted in smaller than ideal group sizes. In some cases, few or no sessions took place owing to low initial group size, and small groups may have contributed to attrition from the intervention. Exposure to gFNP sessions was below maximum for most group members, with only 58 of the 97 intervention participants receiving any sessions; FNs were experienced with FNP but were mainly new to delivering gFNP.ConclusionsThe trial does not support the delivery of gFNP as a means of reducing the risk of child abuse or neglect in this population.Future workA randomised controlled trial with modified eligibility to enable first-time mothers aged &lt; 20 years to be included, and a modified recruitment strategy to enable faster identification of potential participants from antenatal medical records.Trial registrationCurrent Controlled Trials ISRCTN78814904.FundingThis project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full inPublic Health Research; Vol. 5, No. 9. See the NIHR Journals Library website for further project information.

The Kinetics Model Study of Al-Fe &lt;i&gt;In Situ&lt;/i&gt; Composites and Applications

Through the reaction model of Fe powder in liquid Al melt, constructed the dynamic model of Al-Fe reaction and analyzed it’s forming kinetics of in-situ Al composites manufactured by reaction synthesis. The results showed that the time of Fe and Al complete response to forming strengthening phase has a square relation with the Fe powder original size in Al melt. According the kinetics model to improve the powder add method, and decrease the initial group size of Fe powder in the melt, can significantly accelerate the reaction. Then optimize stirring equipments and parameters to improve the microstructure and mechanical properties of composites.

Estimating abundance of killer whales in the nearshore waters of the Gulf of Alaska and Aleutian Islands using line-transect sampling

Killer whale (Orcinus orca Linnaeus, 1758) abundance in the North PaciWc is known only for a few populations for which extensive longitudinal data are available, with little quantitative data from more remote regions. Line-transect ship surveys were con- ducted in July and August of 2001-2003 in coastal waters of the western Gulf of Alaska and the Aleutian Islands. Conventional and Multiple Covariate Distance Sampling methods were used to estimate the abun- dance of diVerent killer whale ecotypes, which were distinguished based upon morphological and genetic data. Abundance was calculated separately for two data sets that diVered in the method by which killer whale group size data were obtained. Initial group size (IGS) data corresponded to estimates of group size at the time of Wrst sighting, and post-encounter group size (PEGS) corresponded to estimates made after closely approach- ing sighted groups. 'Resident'-type (Wsh-eating) killer whales were more abundant than the 'transient'-type (mammal-eating). Abundance estimates of resident killer whales (991 (95% CI = 379-2,585) (IGS) and 1,587 (95% CI = 608-4,140) (PEGS)), were at least four times greater than those of the transient killer whales (200 (95% CI = 81-488) (IGS) and 251 (95% CI = 97-644) whales (PEGS)). The IGS estimate of abundance is preferred for resident killer whales because the estimate based on PEGS data may show an upward bias. The PEGS estimate of abundance is likely more accurate for transients. Residents were most abundant near Kodiak Island in the northern Gulf of Alaska, around Umnak and Unalaska Islands in the eastern Aleutians, and in Seguam Pass in the central Aleutians. This ecotype was not observed between 156 and 164°W, south of the Alaska Peninsula. In contrast, transient killer whale sightings were found at higher densities south of the Alaska Peninsula between the Shumagin Islands and the eastern Aleutians. Only two sightings of 'oVshore'-type killer whales were recorded during the surveys, one northeast of Unalaska Island and the other south of Kodiak Island. These are the Wrst estimates of abundance of killer whale ecotypes in the Aleutian Islands and Alaska Peninsula area and provide a baseline for quantifying the role of these top predators in their ecosystem.

Efficient group sequential designs when there are several effect sizes under consideration

We consider the construction of efficient group sequential designs where the goal is a low expected sample size not only at the null hypothesis and the alternative (taken to be the minimal clinically meaningful effect size), but also at more optimistic anticipated effect sizes. Pre-specified Type I error rate and power requirements can be achieved both by standard group sequential tests and by more recently proposed adaptive procedures. We investigate four nested classes of designs: (A) group sequential tests with equal group sizes and stopping boundaries determined by a monomial error spending function (the 'rho-family'); (B) as A but the initial group size is allowed to be different from the others; (C) group sequential tests with arbitrary group sizes and arbitrary boundaries, fixed in advance; (D) adaptive tests-as C but at each analysis, future group sizes and critical values are updated depending on the current value of the test statistic. By examining the performance of optimal procedures within each class, we conclude that class B provides simple and efficient designs with efficiency close to that of the more complex designs of classes C and D. We provide tables and figures illustrating the performances of optimal designs within each class and defining the optimal procedures of classes A and B.

Life History of Natural Populations of the Imported Willow Leaf Beetle, Plagiodera versicolora (Coleoptera: Chrysomelidae)

Two populations of the imported willow leaf beetle, Plagiodera versicolora (Laicharting), in northern Illinois were studied during four spring seasons between 1979 and 1983. The life cycle includes an egg stage of 5–6 days, a larval stage of 14 days, a pupal stage of 4–5 days, and an adult stage lasting 3–4 weeks. Mean clutch size in the field ranged from 15 to 19 eggs for the four seasons; mean size of eclosing larval groups ranged from 8 to 13. Larvae remain aggregated during the first three stadia, and there is a positive effect of initial group size on larval survivorship

Soldier production and maintenance of soldier proportions in laboratory experimental groups ofCoptotermes formosanus Shiraki

Experimental groups of 100 percent pseudergates ofCoptotermes formosanus Shiraki were set up in the laboratory and allowed to differentiate for either 4, 8 or 12 weeks. The average percentage of pseudergates differentiating into presoldiers and soldiers at these time intervals was 3.8, 14.2, and 21.9 percent, respectively. Differentiation to the soldier caste was affected both by initial group size and colony origin. Groups initially composed of 100 pseudergates produced a significantly smaller proportion of soldiers than did groups of 300, 500, or 1000. Recently collected field colonies produced soldiers at significantly higher rates than one which had been maintained in the laboratory for 8 years. The number of soldiers produced was highly correlated with the total number of all individuals at 4, 8, and 12 weeks, which indicates a precise physiological mechanism for regulating soldier proportions.

Efficient Simulation of Mortality Experience for a Closed Cohort of Lives

A synthesis of various methods of simulating binomial random variables is found to be a computationally efficient approach for developing the probability distribution for the remaining size of an initial cohort. method can be used to simulate x paths for an initial group size. These paths were found to be highly variable and thus cause confidence levels associated with conventional actuarial valuation to be erratic. simulation of mortality experience is straight-forward in theory, but involves some niceties of computational design that make practical applications difficult. A risk class for life insurance purposes may be viewed as a closed cohort of individuals for whom the prior distributions for the Bernoulli parameter that represents the probability of death, q5 have a common mean. If there are kX members in a class aged x, each has a random probability of death, x is=1,2, *2 x ', For each of these QX members, the underwriter holds a prior distribution for x i. These prior distributions may take any form and need not be identical for all members of the class. It is sufficient that the means of the prior distributions are identical. Under these circumstances, it can be shown that the probability that t , the random variable representing the size of the surviving cohort at age x+n, equals some size k and is a function of multinomial probabilities:' Pr(1n =k) = Uf(d x+' * ' n-i, xx nPx(l) all permutations where F n=k William C. Scheel is a Lecturer in the Department of Actuarial Science, Risk and Insurance at the University of Wisconsin, Madison. He is a frequent contributor to Journal of Risk and Insurance and has participated in government hearings on insurance issues. He holds the M.A. degree and the C.P.C.U. designation. 1 See William C. Scheel, The Effects of Risk Reduction Inherent in Universal Life Insurance, A paper presented at the 1977 American Risk and Insurance Association's Risk Theory Seminar, University of Texas-Austin, 83 pp. ( 571 ) This content downloaded from 207.46.13.111 on Tue, 09 Aug 2016 05:51:20 UTC All use subject to http://about.jstor.org/terms 572 Journal of Risk and Insurance where qx = the mean of the prior distribution for the Bernoulli parameter, qx