Methodology for instantaneous average exhaust gas mass flow rate measurement

This paper presents a new methodology for measurement of the instantaneous average exhaust mass flow rate in reciprocating internal combustion engines to be used to determinate real driving emissions on light duty vehicles, as part of a Portable Emission Measurement System (PEMS). Firstly a flow meter, named MIVECO flow meter, was designed based on a Pitot tube adapted to exhaust gases which are characterized by moisture and particle content, rapid changes in flow rate and chemical composition, pulsating and reverse flow at very low engine speed. Then, an off-line methodology was developed to calculate the instantaneous average flow, considering the ?square root error? phenomenon. The paper includes the theoretical fundamentals, the developed flow meter specifications, the calibration tests, the description of the proposed off-line methodology and the results of the validation test carried out in a chassis dynamometer, where the validity of the mass flow meter and the methodology developed are demonstrated.

Social status regulates growth rate: Consequences for life-history strategies

The life-history strategies of organisms are sculpted over evolutionary time by the relative prospects of present and future reproductive success. As a consequence, animals of many species show flexible behavioral responses to environmental and social change. Here we show that disruption of the habitat of a colony of African cichlid fish, Haplochromis burtoni (Günther) caused males to switch social status more frequently than animals kept in a stable environment. H. burtoni males can be either reproductively active, guarding a territory, or reproductively inactive (nonterritorial). Although on average 25–50% of the males are territorial in both the stable and unstable environments, during the 20-week study, nearly two-thirds of the animals became territorial for at least 1 week. Moreover, many fish changed social status several times. Surprisingly, the induced changes in social status caused changes in somatic growth. Nonterritorial males and animals ascending in social rank showed an increased growth rate whereas territorial males and animals descending in social rank slowed their growth rate or even shrank. Similar behavioral and physiological changes are caused by social change in animals kept in stable environmental conditions, although at a lower rate. This suggests that differential growth, in interaction with environmental conditions, is a central mechanism underlying the changes in social status. Such reversible phenotypic plasticity in a crucial life-history trait may have evolved to enable animals to shift resources from reproduction to growth or vice versa, depending on present and future reproductive prospects.

RANK is the intrinsic hematopoietic cell surface receptor that controls osteoclastogenesis and regulation of bone mass and calcium metabolism

We have generated RANK (receptor activator of NF-κB) nullizygous mice to determine the molecular genetic interactions between osteoprotegerin, osteoprotegerin ligand, and RANK during bone resorption and remodeling processes. RANK−/− mice lack osteoclasts and have a profound defect in bone resorption and remodeling and in the development of the cartilaginous growth plates of endochondral bone. The osteopetrosis observed in these mice can be reversed by transplantation of bone marrow from rag1−/− (recombinase activating gene 1) mice, indicating that RANK−/− mice have an intrinsic defect in osteoclast function. Calciotropic hormones and proresorptive cytokines that are known to induce bone resorption in mice and human were administered to RANK−/− mice without inducing hypercalcemia, although tumor necrosis factor α treatment leads to the rare appearance of osteoclast-like cells near the site of injection. Osteoclastogenesis can be initiated in RANK−/− mice by transfer of the RANK cDNA back into hematopoietic precursors, suggesting a means to critically evaluate RANK structural features required for bone resorption. Together these data indicate that RANK is the intrinsic cell surface determinant that mediates osteoprotegerin ligand effects on bone resorption and remodeling as well as the physiological and pathological effects of calciotropic hormones and proresorptive cytokines.

Circadian gating of cell division in cyanobacteria growing with average doubling times of less than 24 hours.

To ascertain whether the circadian oscillator in the prokaryotic cyanobacterium Synechococcus PCC 7942 regulates the timing of cell division in rapidly growing cultures, we measured the rate of cell division, DNA content, cell size, and gene expression (monitored by luminescence of the PpsbAI::luxAB reporter) in cultures that were continuously diluted to maintain an approximately equal cell density. We found that populations dividing at rates as rapid as once per 10 h manifest circadian gating of cell division, since phases in which cell division slows or stops recur with a circadian periodicity. The data clearly show that Synechococcus cells growing with doubling times that are considerably faster than once per 24 h nonetheless express robust circadian rhythms of cell division and gene expression. Apparently Synechococcus cells are able to simultaneously sustain two timing circuits that express significantly different periods.

[Average salaries of the presidents and professors, 1803]

One leaf containing a handwritten list of figures comparing the salaries and grants received by Harvard Presidents and Professors for various time ranges from 1775 to 1803. The paper includes the inscription "Merrill 1st."

Satisfação profissional dos enfermeiros especialistas em enfermagem de reabilitação

Introdução: Portugal enfrenta, actualmente, um período de mudanças profundas nos seus pilares sociais, económicos e organizacionais, sendo o sector da saúde um dois envoltos neste processo de mudança, o qual provoca, inevitavelmente, stress, emoções e ajustamentos de vária ordem. A avaliação da satisfação dos profissionais é assim um fator chave na mensuração dos efeitos destas alterações, daí que o objetivo deste estudo seja conhecer a satisfação profissional dos enfermeiros especialistas de Reabilitação, e seus determinantes de contexto pessoal, profissional e organizacional. Método: Realizou-se um estudo transversal, descritivo-correlacional, de natureza quantitativa, no qual participaram 141 Enfermeiros, Especialistas em Enfermagem de Reabilitação, em funções em instituições públicas e privadas na zona centro do País, na sua maioria do sexo feminino (58.87%) e com uma média de idades de 40.43 anos (Dp=7.49 anos). Para a mensuração das variáveis recorreu-se a uma ficha sociodemográfica e profissional, Escala de Avaliação da Satisfação no Trabalho (EASTEnf) e Escala de Empenhamento Atitudinal, ambas validadas para a população portuguesa. Resultados: Constatou-se que a maioria dos especialistas em Enfermagem de Reabilitação apresentam um nível regular de satisfação (70,92%). Os resultados obtidos evidenciam a existência de um efeito significativo das variáveis género, estado civil, experiência profissional, perfil de cuidados prestados, tipo de horário, vínculo laboral e local de trabalho, sobre o nível de satisfação dos enfermeiros. Na generalidade, são os enfermeiros do género feminino, casados, com menor experiência profissional, que prestam de cuidados especializados, que exercem funções em regime de horário fixo, que integram os quadros da instituição onde desempenham funções e que exercem a sua profissão no sector privado, aqueles que evidenciam, em algumas das dimensões da escala de avaliação da satisfação com o trabalho, níveis de satisfação profissional mais elevados. Por outro lado, constatou-se que são os enfermeiros que consideram as alterações decorrentes nos últimos dois anos benéficas para o cliente (Mean Rank= 90,04, p=0,001) a manifestar uma satisfação mais elevada; como também foi identificada uma relação estaticamente significativa (moderada e positiva) entre o empenhamento atitudinal e a satisfação dos enfermeiros (p=0,000). Conclusões: As evidências encontradas neste estudo convidam-nos a refletir sobre estratégias que possibilitem, em comunhão de esforços com o enfermeiro e organização, a obtenção de um melhor conhecimento dos determinantes da satisfação que potenciem uma intervenção com vista à sua promoção/melhoria. Palavras-Chave: Satisfação; trabalho, empenhamento atitudinal, enfermeiros, especialistas, reabilitação.

Revisiting the synthetic control estimator

The synthetic control (SC) method has been recently proposed as an alternative to estimate treatment effects in comparative case studies. The SC relies on the assumption that there is a weighted average of the control units that reconstruct the potential outcome of the treated unit in the absence of treatment. If these weights were known, then one could estimate the counterfactual for the treated unit using this weighted average. With these weights, the SC would provide an unbiased estimator for the treatment effect even if selection into treatment is correlated with the unobserved heterogeneity. In this paper, we revisit the SC method in a linear factor model where the SC weights are considered nuisance parameters that are estimated to construct the SC estimator. We show that, when the number of control units is fixed, the estimated SC weights will generally not converge to the weights that reconstruct the factor loadings of the treated unit, even when the number of pre-intervention periods goes to infinity. As a consequence, the SC estimator will be asymptotically biased if treatment assignment is correlated with the unobserved heterogeneity. The asymptotic bias only vanishes when the variance of the idiosyncratic error goes to zero. We suggest a slight modification in the SC method that guarantees that the SC estimator is asymptotically unbiased and has a lower asymptotic variance than the difference-in-differences (DID) estimator when the DID identification assumption is satisfied. If the DID assumption is not satisfied, then both estimators would be asymptotically biased, and it would not be possible to rank them in terms of their asymptotic bias.