Skill-biased technological change and the business cycle

Over the past two decades, technological progress in the United States hasbeen biased towards skilled labor. What does this imply for business cycles?We construct a quarterly skill premium from the CPS and use it to identifyskill-biased technology shocks in a VAR with long-run restrictions. Hours fallin response to skill-biased technology shocks, indicating that at least part of thetechnology-induced fall in total hours is due to a compositional shift in labordemand. Skill-biased technology shocks have no effect on the relative price ofinvestment, suggesting that capital and skill are not complementary in aggregateproduction.

An evaluation of the life-cycle effects of minimum pensions on retirement behavior

In this paper we explore the effects of the minimum pension program on welfare andretirement in Spain. This is done with a stylized life-cycle model which provides a convenient analytical characterization of optimal behavior. We use data from the Spanish Social Security to estimate the behavioral parameters of the model and then simulate the changes induced by the minimum pension in aggregate retirement patterns. The impact is substantial: there is threefold increase in retirement at 60 (the age of first entitlement) with respect to the economy without minimum pensions, and total early retirement (before or at 60) is almost 50% larger.

Le cycle de la conjoncture chez Schumpeter : éternel retour du même ?

Cet article s'inscrit dans la lignée de précédents travaux visant à rapprocher l'entrepreneur schumpétérien et le surhumain nietzschéen. Les deux partagent une créativité pouvant s'interpréter comme l'extériorisation d'un surcroît de force qui, dans l'optique nietzschéenne, s'assimile à la source extra-morale de l'accrois- sement de la vie. Reste à savoir si le cadre dans lequel ils évoluent est le même. Au-delà d'une approche historique du cycle de la conjoncture, notre hypothèse est que l'approche philosophique d'un cycle du devenir s'avère être féconde pour une interprétation enrichie du cycle de la conjoncture, complétant et prolongeant ainsi notre interprétation du surhumain et de l'entrepreneur. Abstract: This article is in line with previous works aiming to analyse together Schumpeter's entrepreneur and Nietzsche's superhuman. Both share a creativity that can be interpreted as the externalization of an extra force. The latter, through Nietzsche's perspective, is very close to the extra-moral source of the increase of life. But what we have not analysed yet, is the context in which each of

Life cycle of Phoebemima ensifera Tippmann (Coleoptera, Cerambycidae)

An account of host plant selection, larval development and behaviour, and behaviour of adult Phoebemima ensifera. Illustrations of the host plant, plant parts, larva, pupa, and adult are provided.

Use of a combined ex vivo/in vivo population approach for screening of human genes involved in the human immunodeficiency virus type 1 life cycle for variants influencing disease progression.

Humans differ substantially with respect to susceptibility to human immunodeficiency virus type 1 (HIV-1). We evaluated variants of nine host genes participating in the viral life cycle for their role in modulating HIV-1 infection. Alleles were assessed ex vivo for their impact on viral replication in purified CD4 T cells from healthy blood donors (n = 128). Thereafter, candidate alleles were assessed in vivo in a cohort of HIV-1-infected individuals (n = 851) not receiving potent antiretroviral therapy. As a benchmark test, we tested 12 previously reported host genetic variants influencing HIV-1 infection as well as single nucleotide polymorphisms in the nine candidate genes. This led to the proposition of three alleles of PML, TSG101, and PPIA as potentially associated with differences in progression of HIV-1 disease. In a model considering the combined effects of new and previously reported gene variants, we estimated that their effect might be responsible for lengthening or shortening by up to 2.8 years the period from 500 CD4 T cells/mul to <200 CD4 T cells/mul.

Endogenous labor market participation and the business cycle

Existing models of equilibrium unemployment with endogenous labor market participation are complex, generate procyclical unemployment rates and cannot match unemployment variability relative to GDP. We embed endogenous participation in a simple, tractable job market matching model, show analytically how variations in the participation rate are driven by the cross-sectional density of home productivity near the participation threshold, andhow this density translates into an extensive-margin labor supply elasticity. A calibration of the model to macro data not only matches employment and participation variabilities but also generates strongly countercyclical unemployment rates. With some wage rigidity the model also matches unemployment variations well. Furthermore, the labor supply elasticity implied by our calibration is consistent with microeconometric evidence for the US.

Credit constraints, firms' precautionary investment and the business cycle

This paper studies the macroeconomic implications of firms' investment composition choices in the presence of credit constraints. Following a negative andpersistent aggregate productivity shock, firms shift into short-term investments because they produce more pledgeable output and because they help alleviate futureborrowing constraints. This produces a short-run dampening of the effects of theshock, at the expense of lower long-term investment and future output, relativeto an economy with no credit market imperfections. The effects are exacerbatedby a steepening of the term structure of interest rates that further encourages ashift towards short-term investments in the short-run. Small temporary shocks tothe severity of financing frictions generate large and long-lasting effects on outputthrough their impact on the composition of investment. A positive financial shockproduces much stronger effects than an identical negative shock, while the responsesto positive and negative shocks to aggregate productivity are roughly symmetric.Finally, the paper introduces a novel explanation for the countercyclicality of financing constraints of firms.

Biological cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets of three rubber tree clones

Life cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets from three rubber tree clones. The biological cycle of Tenuipalpus heveae Baker, 1945 (Tenuipalpidae), a potential rubber tree pest mite, was studied by the observation of individuals reared on leaflets of the clones GT 1, PB 235 and RRIM 600, in controlled environmental conditions. Three daily observations were done of 60 eggs on leaflets from each clone in order to verify the development of immature stages and the female oviposition. The fertility life table was constructed based in the collected data. Mites reared on PB 235 had faster rate of development, requiring less time in days, to double its population in number (TD), and had the highest values for egg production, female longevity, net reproductive rate (Ro), intrinsic rate of natural increase (r m) and finite rate of increase (λ). Lower reproductive values and the longest time necessary to reach adult stage were recorded for the mites on GT 1. In all studied clones, the deutonymphal phase had the highest viability, while the larval phase had the lowest, highlighted by the survivorship curve that indicated high mortality during this life stage. The clone PB 235 allowed the most suitable conditions for the development of T. heveae, followed by RRIM 600, while GT 1 was the less suitable substratum to rear this mite species.

Colony cycle of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae)

Colony cycle of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae). This study describes some aspects of the colony cycle of the Neotropical social wasp Mischocyttarus consimilis, from data obtained under field conditions. Our results showed that the colony cycle in M. consimilis is annual and asynchronous in relation to the months of the year. The colonies remained active for approximately eight months. Most of the abandonments were associated with natural causes, and were most frequent in the pre-emergence stage. The nests were constructed preferentially in man-made structures, especially in sites protected from direct sunlight and rain. Colony foundation was either by haplometrosis or pleometrosis, being the first form predominant.

Trends in hours, balanced growth and the role of technology in the business cycle

The present paper revisits a property embedded in most dynamic macroeconomic models: the stationarity of hours worked. First, I argue that, contrary to what is often believed, there are many reasons why hours could be nonstationary in those models, while preserving the property of balanced growth. Second, I show that the postwar evidence for most industrialized economies is clearly at odds with the assumption of stationary hours per capita. Third, I examine the implications of that evidence for the role of technology as a source of economic fluctuations in the G7 countries.

Current concepts in the pathogenesis of urea cycle disorders.

The common feature of urea cycle diseases (UCD) is a defect in ammonium elimination in liver, leading to hyperammonemia. This excess of circulating ammonium eventually reaches the central nervous system, where the main toxic effects of ammonium occur. These are reversible or irreversible, depending on the age of onset as well as the duration and the level of ammonium exposure. The brain is much more susceptible to the deleterious effects of ammonium during development than in adulthood, and surviving UCD patients may develop cortical and basal ganglia hypodensities, cortical atrophy, white matter atrophy or hypomyelination and ventricular dilatation. While for a long time, the mechanisms leading to these irreversible effects of ammonium exposure on the brain remained poorly understood, these last few years have brought new data showing in particular that ammonium exposure alters several amino acid pathways and neurotransmitter systems, cerebral energy, nitric oxide synthesis, axonal and dendritic growth, signal transduction pathways, as well as K(+) and water channels. All these effects of ammonium on CNS may eventually lead to energy deficit, oxidative stress and cell death. Recent work also proposed neuroprotective strategies, such as the use of NMDA receptor antagonists, nitric oxide inhibitors, creatine and acetyl-l-carnitine, to counteract the toxic effects of ammonium. Better understanding the pathophysiology of ammonium toxicity to the brain under UCD will allow the development of new strategies for neuroprotection.

Troubles du cycle à l'adolescence: une banalité [Menstrual disorders in adolescents: commonplace or worrisome?].

The first menstrual cycles following menarche are often caracterized by irregular and/or heavy bleeding. The adolescent patient may be worried by these episodes of bleeding. In 50-80% of cases these are anovulatory bleeding due to the immaturity of the gonadotrophic axis. Nevertheless pathologies such as von Willebrand disease, genital infection, polycystic ovary syndrom, eating disorders, a tumor or a pregnancy may be diagnosed by bleeding abnormalities. The challenge for the physician is to distinguish between bleeding abnormalities secondary to anovulation and pathologies where investigations and specific follow-up is mandatory. Adolescents who experience abnormal bleeding must be counceled according to their perceptions and expectations.

Effects of (p)ppGpp on the progression of the cell cycle of Caulobacter crescentus.

Bacteria must control the progression of their cell cycle in response to nutrient availability. This regulation can be mediated by guanosine tetra- or pentaphosphate [(p)ppGpp], which are synthesized by enzymes of the RelA/SpoT homologue (Rsh) family, particularly under starvation conditions. Here, we study the effects of (p)ppGpp on the cell cycle of Caulobacter crescentus, an oligotrophic bacterium with a dimorphic life cycle. C. crescentus divides asymmetrically, producing a motile swarmer cell that cannot replicate its chromosome and a sessile stalked cell that is replication competent. The swarmer cell rapidly differentiates into a stalked cell in appropriate conditions. An artificial increase in the levels of (p)ppGpp in nonstarved C. crescentus cells was achieved by expressing a truncated relA gene from Escherichia coli, encoding a constitutively active (p)ppGpp synthetase. By combining single-cell microscopy, flow cytometry approaches, and swarming assays, we show that an increase in the intracellular concentration of (p)ppGpp is sufficient to slow down the swarmer-to-stalked cell differentiation process and to delay the initiation of chromosome replication. We also present evidence that the intracellular levels of two master regulators of the cell cycle of C. crescentus, DnaA and CtrA, are modulated in response to (p)ppGpp accumulation, even in the absence of actual starvation. CtrA proteolysis and DnaA synthesis seem indirectly inhibited by (p)ppGpp accumulation. By extending the life span of the motile nonreproductive swarmer cell and thus promoting dispersal and foraging functions over multiplication under starvation conditions, (p)ppGpp may play a central role in the ecological adaptation of C. crescentus to nutritional stresses.

Rolf Bernander (1956-2014): pioneer of the archaeal cell cycle.

On 19 January 2014 Rolf ('Roffe') Bernander passed away unexpectedly. Rolf was a dedicated scientist; his research aimed at unravelling the cell biology of the archaeal domain of life, especially cell cycle-related questions, but he also made important contributions in other areas of microbiology. Rolf had a professor position in the Molecular Evolution programme at Uppsala University, Sweden for about 8 years, and in January 2013 he became chair professor at the Department of Molecular Biosciences, The Wenner-Gren Institute at Stockholm University in Sweden. Rolf was an exceptional colleague and will be deeply missed by his family and friends, and the colleagues and co-workers that he leaves behind in the scientific community. He will be remembered for his endless enthusiasm for science, his analytical mind, and his quirky sense of humour.