Photometric properties of lunar terrains derived from Hapke's equation

Hapke's bidirectional reflectance equations provide the most rigorous available description of photometric behavior in terms of physically meaningful parameters. The primary objective of this study was to derive Hapke parameters for the lunar surface from both disk-integrated and disk-resolved photometric data. Hapke's equation was fit to the disk-integrated phase curves and disk-resolved data for dark, average, and bright terrain classes using an iterative, nonlinear least squares algorithm described by Helfenstein. Parameters were initially determined from the disk-integrated data, and the result was applied as a first guess to the iterative solution of parameters for individual terrain classes. Plots are presented of the disk-resolved data normalized to corresponding brightnesses predicted from the disk-integrated solution under the same illumination and viewing geometries. Systematic trends in disk-resolved parameters can be identified. Values for single scattering albedo (w) of the dominantly anorthositic average and bright terrains are significantly larger than the value for the basaltic dark terrains (mare). Values for surge brightness parameters, particle phase function, and average topographic slope angle are also discussed

Anomalous scattering of light on Triton

Researchers report here the discovery of an isolated region of anomalously forward scattering materials on the surface of Triton. The researchers' best-fit Hapke parameters indicate that regolith particles in the anomalous scattering region are not only less backward scattering, but also slightly lower in single scattering albedo than average materials on Triton's surface. While it might be possible to account for such differences in terms of differences in particle size and transparency, it is also possible that the anomalous region is compositionally distinct from other terrains. It is noteworthy that, for the anomalous region, there exists a distinctively strong spatial correlation between the photometric ratios at different phase angles, and that, relative to other terrains, the anomalous region reddens at a different rate with increasing phase angle

Pharmacokinetics of statins

Statins are lipid lowering agents that promote their effects on plasma lipids through the inhibition of HMG-CoA reductase, a crucial enzyme in the cascade of cholesterol synthesis, leading to reduction of tissue cholesterol pool and consequently, to an upregulation of the LDL receptor expression. There are considerable differences among statins regarding some pharmacokinetic properties, such as the coefficient of hydrophilicity, via liver metabolism (especially regarding P450 cytochrome and isoenzymes), plasma half-life and efficacy of serum lipid changes. They may also differ regarding interactions with other drugs that share the same pathway of metabolism. Recently, many pleiotropic effects have been reported with these drugs, such as anti-inflammatory properties, improvement in endothelial function and benefits on hemostasis.As estatinas são agentes hipolipemiantes que exercem os seus efeitos através da inibição da HMG-CoA redutase, enzima fundamental na síntese do colesterol, levando a uma redução do colesterol tecidual e um conseqüente aumento na expressão dos receptores de LDL. Existem consideráveis diferenças entre as estatinas, no que tange às propriedades farmacocinéticas, bem como ao coeficiente de hidrofilicidade, via hepática de metabolização (especialmente, do citocromo P450 e isoenzimas), meia-vida plasmática e eficácia na redução lipídica. As estatinas também podem diferir na capacidade de interação com outras drogas que utilizam a mesma via de metabolização. Recentemente, muitos efeitos pleiotrópicos têm sido relatados com estas drogas, bem como propriedades antiinflamatórias, melhora na função endotelial e benefícios na hemostasia.UNIFESP-EPM Setor de Lípides, Aterosclerose e Biologia VascularUNIFESP, EPM, Setor de Lípides, Aterosclerose e Biologia VascularSciEL

The Use of Measures of Influence in Epidemiology

Helfenstein U (Biostatistical Centre for the Medical Department, University of Zurich, Plattenstrasse 54, CH-8032, Zurich, Switzerland) and Minder C. International Journal of Epidemiology 1990, 19: 197-204. In epidemiological studies the units of observation often consist of political entities such as countries, each of which has its own specific inner structure. When a multiple regression is performed it is therefore of particular interest to ana-lyse not only the overall behaviour of the dataset, but in addition, to investigate how each individual country contributes to, and deviates from, this overall behaviour. By means of the example ‘relation between infant mortality and structural data of countries' several ways are discussed of how each individual country can influence the regression model. Firstly the potential influonco which each country might exhibit due to the explanatory variables alone is analysed. Then the actual influence of each country is analysed by taking the explanatory variables and the target variable into account simultaneously. This is done by means of statistical measures not generally familiar to epidemiologists, which have been developed in recent years (leverage values, Cook's distances). These measures also point to deviations of countries from the model, and suggest directions in which to search for explanation. Finally the influence of the ‘size' of the countries is investigate

The Use of Transfer Function Models, Intervention Analysis and Related Time Series Methods in Epidemiology

In epidemiology, data often arise in the form of time series e.g. notifications of diseases, entries to a hospital, mortality rates etc. are frequently collected at weekly or monthly intervals, Usual statistical methods assume that the observed data are realizations of independent random variables. However, if data which arise in a time sequence have to be analysed, it is possible that consecutive observations are dependent. In environmental epidemiology, where series such as daily concentrations of pollutants were collected and analysed, it became clear that stochastic dependence of consecutive measurements may be important. A high concentration of a pollutants today e.g. has a certain inertia i.e. a tendency to be high tomorrow as well. Since the early 1970s, time series methods, in particular ARIMA models (autoregressive integrated moving average models) which have the ability to cope with stochastic dependence of consecutive data, have become well established in such fields as industry and economics. Recently, time series methods are of increasing interest in epidemiology. Since these methods are not generally familiar to epidemiologists this article presents their basic concepts in a condensed form. This may encourage readers to consider the methods described and enable them to avoid pitfalls inherent in time series data. In particular, the following topics are discussed: Assessment of relations between time series (transfer function models). Assessment of changes of time series (intervention analysis), forecasting and some related time series method

Anserine syndrome

Knee pain is a common complaint in clinical practice, and pes anserinus tendino-bursitis syndrome (PATB) has been frequently diagnosed based only on clinical features that may cause equivocal interpretations. Patients complain of characteristic spontaneous medial knee pain with tenderness in the inferomedial aspect of the joint. Studies with different imaging modalities have been undertaken during the last years to identify whether these patients suffer from bursitis, tendinitis, or both. Nevertheless, little is known regarding the structural defect responsible for this disturbance. Due to these problems and some controversies, we suggest the term anserine syndrome for this condition. Diabetes Mellitus is a known predisposing factor for this syndrome. Overweight and osteoarthritis seem to represent additional risk factors; however, their role in the pathophysiology of the disease is not yet understood. Treatment includes non-steroidal anti-inflammatory drugs, physiotherapy, and injections of corticosteroid, with highly variable responses, from 10 days to 36 months to achieve recovery. The lack of knowledge about its epidemiological, etiological, and pathophysiological aspects requires future studies for this common and intriguing disorder.Dor no joelho é uma condição comum na clínica diária e a patologia anserina, também conhecida como pata de ganso, tem sido considerada uma das principais causas. O diagnóstico tem sido realizado de maneira eminentemente clínica, o que tem gerado equívocos. Os pacientes queixam-se tipicamente de dor na parte medial do joelho, com sensibilidade na porção ínferomedial. Estudos de imagem têm sido realizados para esclarecer se tais pacientes possuem bursite, tendinite ou ambos os distúrbios na região conhecida como pata de ganso. Entretanto, o defeito estrutural responsável pelos sintomas permanece desconhecido, motivo pelo qual preferimos intitular como Síndrome Anserina. O diabetes mellitus é um fator predisponente bem reconhecido. O sobrepeso e a osteoartrite de joelho parecem ser fatores adicionais de risco, contudo, seus papéis na gênese da moléstia ainda não são bem entendidos. O tratamento atual inclui anti-inflamatório, fisioterapia e infiltração de corticoide, com evolução muito variável, que oscila entre 10 dias e 36 meses. A falta de conhecimento sobre a etiofisiopatologia e dados epidemiológicos exige futuros estudos para esse frequente e intrigante distúrbio.Universidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM)INSSUNIFESP, EPMSciEL

Sperm morphology, swimming velocity, and longevity in the house sparrow Passer domesticus

Sperm competition exerts strong selection on males to produce spermatozoa with an optimal morphology that maximizes their fertilization success. Long sperm were first suggested to be favored because they should swim faster. However, studies that investigated the relationship between sperm length and sperm competitive ability or sperm swimming velocity yielded contradictory results. More recently, ratios of the different sections of a spermatozoon (the head, midpiece, and flagellum) were suggested to be more crucial in determining swimming velocity. Additionally, sperm ability to remain and survive in the female storage organs may also influence fertilization success, so that optimal sperm morphology may rather maximize sperm longevity than velocity. In this study, we investigated how sperm morphology is related to sperm velocity and sperm longevity in the house sparrow Passer domesticus. Sperm velocity was found to be correlated with head/flagellum ratio. Sperm with small heads relative to their flagellum showed higher swimming velocity. Additionally, shorter sperm were found to live longer. Finally, we found sperm morphological traits to vary substantially within males and the head/flagellum ratio to be unrelated to total sperm length. We discuss the hypothesis that the substantial within-male variation in sperm morphology reflects a male strategy to produce a diversity of sperm from long, fast-swimming to short, long-living sperm to maximize their fertilization success in a context of sperm competitio

Main-Belt Comet 238P/Read Revisited

We present a series of observations of the return of activity in main-belt comet 238P/Read. Using data obtained in July and August 2010 when 238P appeared to be largely inactive, we find best-fit IAU phase function parameters of H=19.05+/-0.05 mag, corresponding to a nucleus radius of r_n ~ 0.4 km (assuming an albedo of p_R=0.05), and G=-0.03+/-0.05. Observations from September 2010 onward show a clear rise in activity, causing both a notable change in visible morphology and increasing photometric excesses beyond what would be expected based on bare nucleus observations. By the end of the observing period reported on here, the dust mass in the coma shows indications of reaching a level comparable to that observed in 2005, but further observations are highly encouraged once 238P again becomes observable from Earth in mid-2011 to confirm whether this level of activity is achieved, or if a notable decrease in activity strength compared to 2005 can be detected. Comet 238P is now the second main-belt comet (after 133P/Elst-Pizarro) observed to exhibit recurrent activity, providing strong corroboration for the conclusion that it is a true comet whose active episodes are driven by sublimation of volatile ice.Comment: 13 pages, 3 figures, accepted for publication in ApJ Letter