2,210 research outputs found

    Determination of biogeochemical properties of marine particles using above water measurements of the degree of polarization at the Brewster angle

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    Retrieval of biogeochemical parameters from remotely sensed data in optically complex waters such as those found in coastal zones is a challenging task due to the effects of various water constituents (biogenic, nonalgal and inorganic particles, dissolved matter) on the radiation exiting the ocean. Since scattering by molecules, aerosols, hydrosols and reflection at the sea surface introduce and modify the polarization state of light, the polarized upward radiation contains embedded information about the intrinsic nature of aerosols and suspended matter in the ocean. In this study, shipborne above water angularly resolved visible/near infrared multiband measurements of the degree of polarization are analysed against their corresponding in-situ biogeochemically characterized water samples for the first time. Water samples and radiometric data were collected in the English Channel along an inshore-offshore transect. Angular variations in the degree of polarization P are found to be consistent with theory. Maximum values of P are observed near the Brewster viewing angle in the specular direction. Variations in the degree of polarization at the Brewster angle (PB) with water content revealed that the suspended particulate matter, which is mainly composed of inorganic particles during the experiment, contributes to depolarise the skylight reflection, thus reducing PB. An empirical polarization-based approach is proposed to determine biogeochemical properties of the particles. The concentration of inorganic particles can be estimated using PB to within ±13% based on the dataset used. Larger sets of polarized measurements are recommended to corroborate the tendency observed in this study

    Six concerns about the data in aid debates: applying an epidemiological perspective to the analysis of aid effectiveness in health and development.

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    Is aid helping, hindering, or having no effect on development and health? The answer to this question is highly contested, with proponents on all sides adhering strongly to their competing interpretations. We ask how it is possible for those who are often using the same data to hold such divergent views. Here, we employ an epidemiological perspective and find that, in many cases, the arguments are characterised by methodological weaknesses. There may be selective citation of results and failure to account for bias and confounding, such as where an extraneous factor influencing the outcome is correlated with increased aid or, in confounding by indication, where increased aid is a consequence of a country being in an especially adverse situation. Studies may also lack external validity, whereby lack of data (a widespread problem) or similar considerations mean that analyses are undertaken on an unrepresentative subset of countries. Multiple outcome measures can also be problematic, where the main outcome of interest is not specified in advance. Many studies fail to account for differential time lags between changes in aid and the outcomes being studied. Some studies may also be underpowered to detect an association where one exists. Although, ideally, this debate should be informed by large scale randomised controlled trials, this will often be unfeasible. Given this limitation, it is essential that those engaged in it are cognisant of the many methodological issues that face any observational study

    Hand in the Cookie Jar: An Experimental Investigation of Equity-based Compensation and Managerial Fraud

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    The use of equity-based compensation is an increasingly popular means by which to align the incentives of top management with that of the shareholders. However, recent theoretical and empirical research suggests that the use of equity-based compensation has the unintended consequence of creating the incentive to commit managerial fraud of the type being reported in the press. This paper reports experimental evidence showing that the amount of fraud committed by subjects is positively correlated with the level of equity, as is the level of effort. As well, the amount of fraud that is committed is negatively correlated with the probability of detection and subjects’ risk aversion. The experimental design permits the identification of causal relations in the directions just noted. Key Words:

    Nutritional determinants of worldwide diabetes: an econometric study of food markets and diabetes prevalence in 173 countries.

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    OBJECTIVE: Ageing and urbanization leading to sedentary lifestyles have been the major explanations proposed for a dramatic rise in diabetes worldwide and have been the variables used to predict future diabetes rates. However, a transition to Western diets has been suggested as an alternative driver. We sought to determine what socio-economic and dietary factors are the most significant population-level contributors to diabetes prevalence rates internationally. DESIGN: Multivariate regression models were used to study how market sizes of major food products (sugars, cereals, vegetable oils, meats, total joules) corresponded to diabetes prevalence, incorporating lagged and cumulative effects. The underlying social determinants of food market sizes and diabetes prevalence rates were also studied, including ageing, income, urbanization, overweight prevalence and imports of foodstuffs. SETTING: Data were obtained from 173 countries. SUBJECTS: Population-based survey recipients were the basis for diabetes prevalence and food market data. RESULTS: We found that increased income tends to increase overall food market size among low- and middle-income countries, but the level of food importation significantly shifts the content of markets such that a greater proportion of available joules is composed of sugar and related sweeteners. Sugar exposure statistically explained why urbanization and income have been correlated with diabetes rates. CONCLUSIONS: Current diabetes projection methods may estimate future diabetes rates poorly if they fail to incorporate the impact of nutritional factors. Imported sugars deserve further investigation as a potential population-level driver of global diabetes

    Lyman alpha radiation in external galaxies

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    The Ly alpha line of atomic hydrogen is often a luminous component of the radiation emitted by distant galaxies. Except for those galaxies which have a substantial central source of non-stellar ionizing radiation, most of the Ly alpha radiation emitted by galaxies is generated within regions of the interstellar medium which are photoionized by starlight. Conversely, much of the energy radiated by photoionized regions is carried by the Ly alpha line. Only hot, massive stars are capable of ionizing hydrogen in the interstellar medium which surrounds them, and because such stars are necessarily short-lived, Ly alpha emission traces regions of active star formation. Researchers argue that the strength of the Ly alpha emission observed from external galaxies may be used to estimate quantitatively the dust content of the emitting region, while the Ly alpha line profile is sensitive to the presence of shock waves. Interstellar dust particles and shock waves are intimately associated with the process of star formation in two senses. First, both dust particles and shock waves owe their existence to stellar activity; second, they may both serve as agents which facilitate the formation of stars, shocks by triggering gravitational instabilities in the interstellar gas that they compress, and dust by shielding star-forming molecular clouds from the ionizing and dissociative effects of external UV radiation. By using Ly alpha observations as a probe of the dust content in diffuse gas at high redshift, we might hope to learn about the earliest epochs of star formation


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    When market transactions generate negative externalities, the injured party may initiate court action to prevent harm or to obtain compensation. The political response, in some cases, has been to broaden the set of agents who can intervene through the court, often by admitting entirely new categories of potential intervenors. We employ an experimental market setting to investigate the effect of an increase in the number of potential intervenors (introduced as admitting an additional class of persons having the necessary standing in law). The results suggest that there will be a substantial increase in the number of actual interventions. The increase means that social resources expended on interventions will increase and there may be a consequent reduction in trading activity in the affected markets.Public Economics,


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    An original composition in three movements for large orchestra. Following the score is a detailed analysis of the work, consisting of an introduction, three sections of analysis devoted to each of the three movements of the composition, and a short conclusion summarizing the analysis