Size-dependent predation by Dugesia lugubris (Turbellaria) on Physa acuta (Gastropoda): experiments and model

1. We investigated experimentally predation by the flatworm Dugesia lugubris on the snail Physa acuta in relation to predator body length and to prey morphology [shell length (SL) and aperture width (AW)]. 2. SL and AW correlate strongly in the field, but display significant and independent variance among populations. In the laboratory, predation by Dugesia resulted in large and significant selection differentials on both SL and AW. Analysis of partial effects suggests that selection on AW was indirect, and mediated through its strong correlation with SL. 3. The probability P(ij) for a snail of size category i (SL) to be preyed upon by a flatworm of size category j was fitted with a Poisson-probability distribution, the mean of which increased linearly with predator size (i). Despite the low number of parameters, the fit was excellent (r2 = 0.96). We offer brief biological interpretations of this relationship with reference to optimal foraging theory. 4. The largest size class of Dugesia (>2 cm) did not prey on snails larger than 7 mm shell length. This size threshold might offer Physa a refuge against flatworm predation and thereby allow coexistence in the field. 5. Our results are further discussed with respect to previous field and laboratory observations on P acuta life-history patterns, in particular its phenotypic variance in adult body size.

Pre-Treatment for Reduction of Asphalt Absorption in Porous Aggregate, April 2005

The objective of this research was to evaluate the performance of the product Ultracote® (a polymer based additive produced by Ultrapave, a division of Goodyear) as an aggregate pre-treatment for the reduction of asphalt binder absorption in hot mix asphalt (HMA). The product was tested with a paving project in Louisa county, Iowa with aggregate that had historically shown very high asphalt binder absorption. Results of the testing did not provide any evidence of reduction in binder absorption.

Thymic lineage commitment rather than selection causes genetic variations in size of CD4 and CD8 compartments.

During their development, immature CD4+ CD8+ thymocytes become committed to either the CD4 or CD8 lineage. Subsequent complete maturation of CD4+ and CD8+ cells requires a molecular match of the expressed coreceptor and the MHC specificity of the TCR. The final size of the mature CD4+ and CD8+ thymic compartments is therefore determined by a combination of lineage commitment and TCR-mediated selection. In humans and mice, the relative size of CD4+ and CD8+ peripheral T cell compartments shows marked genetic variability. We show here that genetic variations in thymic lineage commitment, rather than TCR-mediated selection processes, are responsible for the distinct CD4/CD8 ratios observed in common inbred mouse strains. Genetic variations in the regulation of lineage commitment open new ways to analyze this process and to identify the molecules involved.

Measurement with Some Theory: a New Approach to Evaluate Business Cycle Models

We propose a method to evaluate cyclical models which does not require knowledge of the DGP and the exact empirical specification of the aggregate decision rules. We derive robust restrictions in a class of models; use some to identify structural shocks and others to evaluate the model or contrast sub-models. The approach has good size and excellent power properties, even in small samples. We show how to examine the validity of a class of models, sort out the relevance of certain frictions, evaluate the importance of an added feature, and indirectly estimate structural parameters.

Population density and offspring size in the cladoceran Simocephalus vetulus (Müller)

r/K theory classically predicts that offspring size should increase under density-dependent selection. However, this is questionable, being based on implicit rather than explicit assumption (the logistic model does not include offsring size as a parameter). From recent models of optimal offspring size (Sibly & Calow, 1983; Taylor & Williams, 1984) it can be shown that density should select for larger offspring if density-dependence in the per capita rate of increase is mainly due to a reduction of the juvenile growth rate or survivorship. In contrast, density should select for smaller offspring if such density-dependence is mainly due to a reduction of adult fecundity or survivorship. Therfore, the outcome of selection cannot be predicted without precise knowledge of the density-dependence of age-specific reproduction and mortality rates. To test the above models, genetically identical individuals of Simocephalus vetulus (Müller) were reared in a density gradient; density-dependence in the per capita rate of increase was shown to be mainly due to a reduction of the juvenile growth rate, thereby selecting for larger offspring; offspring size at birth appeared to be phenotypically plastic and to increase with density. Models were therefore qualitatively supported. However, a discrepancy occurred in quantitative predictions; offspring were produced larger than predicted. Field and laboratory studies are suggested to address this.

Body Size, Activity, Employment and Wages in Europe: A First Approach

In this article we present the first empirical analysis on the associations between body size, activity, employment and wages for several European countries. The main advantage of the present work with respect to the previous literature is offered by the comparability of the data and its large geographical coverage. According to our results, for Spanish women, being obese is associated with both a 9% lower wage and probability of being employed, while for Swedish and Danish, obesity is associated with a 12% lower probability of being employed, and a 10% lower wage respectively. In Belgium, obesity is associated with a 19% lower probability of being employed for men. These robust estimates are strongly informative and may be used as a simple statistical rule of thumb to decide the countries in which lab and field experiments should be run.

Recognition judgments and the performance of the recognition heuristic depend on the size of the reference class

In a series of three experiments, participants made inferences about which one of a pair of two objects scored higher on a criterion. The first experiment was designed to contrast the prediction of Probabilistic Mental Model theory (Gigerenzer, Hoffrage, & Kleinbölting, 1991) concerning sampling procedure with the hard-easy effect. The experiment failed to support the theory's prediction that a particular pair of randomly sampled item sets would differ in percentage correct; but the observation that German participants performed practically as well on comparisons between U.S. cities (many of which they did not even recognize) than on comparisons between German cities (about which they knew much more) ultimately led to the formulation of the recognition heuristic. Experiment 2 was a second, this time successful, attempt to unconfound item difficulty and sampling procedure. In Experiment 3, participants' knowledge and recognition of each city was elicited, and how often this could be used to make an inference was manipulated. Choices were consistent with the recognition heuristic in about 80% of the cases when it discriminated and people had no additional knowledge about the recognized city (and in about 90% when they had such knowledge). The frequency with which the heuristic could be used affected the percentage correct, mean confidence, and overconfidence as predicted. The size of the reference class, which was also manipulated, modified these effects in meaningful and theoretically important ways.

Management of basic health units in municipalities of different size: profile and management instruments

Objective To identify the characteristics of managers and their use of management instruments in primary care and to analyze differences in these features among municipalities of different sizes. Method The present cross-sectional descriptive study was conducted at 108 basic health units from 21 municipalities in northern Paraná, Brazil. The data were collected using a semi-structured questionnaire during the second half of 2010. Results Most managers had graduate degrees and were female and nurses. The managers from the small municipalities were younger, their payment was lower, and they had less work experience. The use of management instruments was expressive for both the organization and work management; however, the instruments were used less in the small municipalities. Conclusion The managers were committed to their role; it is recommended that policies and guidance should be formulated at the federal and state levels to support small municipalities.

Nursing workload in specialized Semi-intensive Therapy unit: workforce size criteria

Abstract OBJECTIVE To assess the nursing workload (NW) in Semi-intensive Therapy Unit, specialized in the care of children with Craniofacial anomalies and associated syndromes; to compare the amount of workforce required according to the Nursing Activities Score (NAS) and the COFEN Resolution 293/04. METHOD Cross-sectional study, whose sample was composed of 72 patients. Nursing workload was assessed through retrospective application of the NAS. RESULTS the NAS mean was 49.5%. Nursing workload for the last day of hospitalization was lower in patients being discharged to home (p<0.001) and higher on the first compared to last day of hospitalization (p< 0.001). The number of professionals required according to NAS was superior to the COFEN Resolution 293/04, being 17 and 14, respectively. CONCLUSION the nursing workload corresponded to approximately 50% of the working time of nursing professional and was influenced by day and outcome of hospitalization. The amount of professionals was greater than that determined by the existing legislation.

Hemoglobin enhances the biological activity of synthetic and natural bacterial (endotoxic) virulence factors: a general principle.

Although hemoglobin (Hb) is mainly present in the cytoplasm of erythrocytes (red blood cells), lower concentrations of pure, cell-free Hb are released permanently into the circulation due to an inherent intravascular hemolytic disruption of erythrocytes. Previously it was shown that the interaction of Hb with bacterial endotoxins (lipopolysaccharides, LPS) results in a significant increase of the biological activity of LPS. There is clear evidence that the enhancement of the biological activity of LPS by Hb is connected with a disaggregation of LPS. From these findings one questions whether the property to enhance the biological activity of endotoxin, in most cases proven by the ability to increase the cytokine (tumor-necrosis-factor-alpha, interleukins) production in human mononuclear cells, is restricted to bacterial endotoxin or is a more general principle in nature. To elucidate this question, we investigated the interaction of various synthetic and natural virulence (pathogenicity) factors with hemoglobin of human or sheep origin. In addition to enterobacterial R-type LPS a synthetic bacterial lipopeptide and synthetic phospholipid-like structures mimicking the lipid A portion of LPS were analysed. Furthermore, we also tested endotoxically inactive LPS and lipid A compounds such as those from Chlamydia trachomatis. We found that the observations made for endotoxically active form of LPS can be generalized for the other synthetic and natural virulence factors: In every case, the cytokine-production induced by them is increased by the addition of Hb. This biological property of Hb is connected with its physical property to convert the aggregate structures of the virulence factors into one with cubic symmetry, accompanied with a considerable reduction of the size and number of the original aggregates.

Growing at the production frontier. European aggregate growth, 1870-1914

The view of a 1870-1913 expanding European economy providing increasing welfare to everybody has been challenged by many, then and now. We focus on the amazing growth that was experienced, its diffusion and its sources, in the context of the permanent competition among European nation states. During 1870-193 the globalized European economy reached a silver age . GDP growth was quite rapid (2.15% per annum) and diffused all over Europe. Even discounting the high rates of population growth (1.06%), per capita growth was left at a respectable 1.08%. Income per capita was rising in every country, and the rates of improvement were quite similar. This was a major achievement after two generations of highly localized growth, both geographically and socially. Growth was based on the increased use of labour and capital, but a good part of growth (73 per cent for the weighted average of the best documented European countries) came out of total factor productivity efficiency gains resulting from not well specified ultimate sources of growth. This proportion suggests that the European economy was growing at full capacity at its production frontier. It would have been very difficult to improve its performance. Within Europe, convergence was limited, and it only was in motion after 1900. What happened was more the end of the era of big divergence rather than an era of convergence.

On the distribution of income and worker assignment under intra-firm spillovers, with an application to ideas and networks

We study the earnings structure and the equilibrium assignment of workers when workers exert intra-firm spillovers on each other.We allow for arbitrary spillovers provided output depends on some aggregate index of workers' skill. Despite the possibility of increasing returns to skills, equilibrium typically exists. We show that equilibrium will typically be segregated; that the skill space can be partitioned into a set of segments and any firm hires from only one segment. Next, we apply the model to analyze the effect of information technology on segmentation and the distribution of income. There are two types of human capital, productivity and creativity, i.e. the ability to produce ideas that may be duplicated over a network. Under plausible assumptions, inequality rises and then falls when network size increases, and the poorest workers cannot lose. We also analyze the impact of an improvement in worker quality and of an increased international mobility of ideas.

Sex allocation and sex-dependent selection for body size in Trypoxylon rogenhoferi Kohl (Hymenoptera, Sphecidae)

Two populations of the wasp Trypoxylon rogenhoferi Kohl, 1884 from São Carlos and Luís Antônio, State of São Paulo, Brazil, were observed and sampled from May 1999 to February 2001 using trap-nests. This mass-provisioning wasp was used to test some aspects of optimal sex allocation theory. Both populations fit all the predictions of the models of Green and Brockmann and Grafen. Maternal provisions determined the size of each offspring, and females allocated well-stocked brood cells to daughters, the sex that benefits most being large. This strategy resulted in a difference in size between the sexes. In São Carlos, female weight at emergence was 1.18 times that of males, in Luís Antônio this value was 1.13. The brood cell volume was correlated with both wing length and weight at emergence in both sexes, and the chance that a given brood cell contained a male offspring decreased with increased brood cell volume. In T. rogenhoferi female body size was related to fitness. Larger females were able to collect more mass of spiders per day, the spiders they captured were heavier, and they provisioned more brood cells per day. They also produced larger daughters. For males, no relationship between body size and fitness was found, but the data were scarce. Since the patterns of provisioning were variable among different females in both study sites, it is possible that the females not follow a unique strategy for sex allocation. The sex ratio and/or investment ratio in the São Carlos population was female-biased and in Luís Antônio, male-biased. In spite of the influence of trap-nests diameters on male production in Luís Antônio, there is some evidence that in São Carlos population the local availability of prey and/or lower rate of parasitism may be major forces in determining the observed sex ratio, but further studies are necessary to verify such hypothesis.

Notes for a new guide to Keynes (I): Wages, aggregate demand, and employment

I revisit the General Theory's discussion of the role of wages inemployment determination through the lens of the New Keynesianmodel. The analysis points to the key role played by the monetarypolicy rule in shaping the link between wages and employment, andin determining the welfare impact of enhanced wage flexibility. I showthat the latter is not always welfare improving.