1,596 research outputs found

    An index for estimating the potential impact on the environment of the pollutant content in aquatic populations

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    The so-called "Concentration factor" (C.F.) should express a direct positive relationship between the concentration of a pollutant (e.g. metals, radioisotopes) in an organism and the concentration of the same pollutant in the water. While this index is very useful in some cases, it cannot give any information on the influence of the biota on its environment, an important topic in research on biogeochemical cycles. A new index (the Influence index) has consequently been developed to quantify the potential influence of the pollutant content in the population biomass on the habitat in which the population lives. The value of this index is calculated as the ratio between the pollutant content in the population biomass per sediment surface unit (e.g. m2) and the concentration of the same pollutant in the water, and is expressed as water volume with the same pollutant concentration as in the water of the population habitat. The value increases with the increase of the pollutant content in the population biomass and the decrease of the pollutant concentration in the water. As an example, some applications of the index to heavy metal contaminations of a freshwater mussel (Unio pictorum mancus) population are described

    Richard A. Vollenweider (Z?rich 1922 ? Burlington 2007)

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    This brief article is a short obituary of Professor R.A. Vollenweider

    Seasonal variations in population dynamics and biomass of two Unio pictorum mancus (Mollusca, Unionidae) populations from two lakes of different trophic state

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    Samples of Unio pictorum mancus collected monthly from spring 2003 to summer 2004 in the meso-oligotrophic Lake Maggiore and the eutrophic Lake Candia were compared to evaluate the influence of lake trophic conditions on mussel populations. Shell form, maximum age (8 years) and percentage of organic matter in the shell and soft tissues were similar in both lakes. However, comparisons between same size classes revealed that mussels from Lake Maggiore were generally older, their shells heavier and their soft tissues lighter than those from Lake Candia. Recruitment occurred in both populations in June-July. The frequency distributions of adult mussels (>30 mm) and their soft tissues and shell biomasses in all size classes (range = 2 mm) were normal, but the curves of the mussels from Lake Candia were flat in comparison to those of mussels from Lake Maggiore. The median body size of Lake Maggiore mussels was 58 mm, while that of the Lake Candia population was 72 mm. During the study period the population density of each lake was fairly constant, whereas the population structure, and consequently the biomass, showed seasonal variations. The greatest differences were found between population density and shell and tissue biomass of the two populations, which were respectively 46.86 ind. m-2; 408 g d.w. m-2 and 38.67 g d.w. m-2 in Lake Maggiore, and 6.93 ind. m-2; 92.29 g d.w. m-2 and 14.04 g d.w. m-2 in Lake Candia. These values testify to the phenotypical plasticity of Unio pictorum mancus in relation to environmental characteristics, without excluding a possible genetic influence as a result of geographical isolation and the respective selection mechanisms. The influence exerted by the lake trophic level and by the physical environment on some population characteristics is discussed

    Seasonal variations in metal content of two Unio pictorum mancus (Mollusca, Unionidae) populations from two lakes of different trophic state

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    To assess the impact of lake trophy on trace element accumulation by Unio pictorum mancus, a population from the mesooligotrophic Lake Maggiore was compared with a population from the eutrophic Lake Candia. The element content in soft tissue and shell biomass, the seasonal variations of element concentrations in soft tissues and shell, and the relationship between element concentrations in the water and those in the tissues were estimated in pursuit of this objective. Thirteen mussel samplings were performed in Lake Maggiore between May 2003 and September 2004 and in Lake Candia between June 2003 and August 2004. Filtered water samples were collected seasonally. Water, shell and soft tissue samples were analysed by ICP-OES and ICP-MS for the measurement of following elements: Zn, Cu, Fe, Mn, Ni, As, Pb, Co, Cr, Mo, V, Cd, Be and Ca. The element concentrations in the mussel tissues and shell from Lake Maggiore were higher than those from Lake Candia. Due to the higher population density and higher element concentrations in the mussels of Lake Maggiore, the element content in the biomass per m2 in this lake far exceeded that in Lake Candia

    Relationship between element concentrations and body size in the Lake Maggiore population of Unio pictorum mancus (Mollusca, Bivalvia)

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    The study focused on using a fresh-water mussel (Unio pictorum mancus) as a bioindicator of various pollutants, and particularly metals. The elements considered were: Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, V and Zn. This research was carried out at a site where various other studies have been conducted on important characteristics of the same population of Unio. This site is a small bay called "Sabbie d\u27Oro" located on the south-east coast of Lake Maggiore. Our study involved quantifying the capacity of this mollusc to concentrate large amounts of metal in its body without evident consequences by using detoxification mechanisms. We analysed not only element concentrations, but also their variability (expressed as CV%) in the soft tissues and in the shell, for two main reasons: i) the sampling design should include a preliminary analysis to determine how many specimens is necessary collect to ensure a specified level of precision; ii) the sample variability value may be combined with the value of analytical precision (BCR) to obtain an estimate of the "experimental" precision. In soft tissue, Ca accumulation tended to increase with size, and Al accumulation decreased with size. In shell, Ca and Ni were stored more than in soft tissue, but not proportionally to size. V, Cr and Mo tended to accumulate in the shell progressively over the years, whereas Co and Al are "diluted" during growth, or are absorbed mainly during the juvenile stage. Partition between shell and soft tissue resulted roughly the same in the juvenile and adult stages for the following elements: Fe, Al, Co, As, Pb. The relationships among the various elements were schematized in a hierarchical tree plot

    Diagnosis and Treatment of Chronic Neuropathic and Mixed Pain in Children and Adolescents: Results of a Survey Study amongst Practitioners

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    Validated diagnostic tools to diagnose chronic neuropathic and mixed pain in children are missing. Therapeutic options are often derived from therapeutics for adults. To investigate the international practice amongst practitioners for the diagnosis and treatment of chronic, neuropathic pain in children and adolescents, we performed a survey study among members of learned societies or groups whose members are known to treat pediatric pain. The survey included questions concerning practitioners and practice characteristics, assessment and diagnosis, treatment and medication. We analyzed 117 returned questionnaires, of which 41 (35%) were fully completed and 76 (65%) were partially completed. Most respondents based the diagnosis of neuropathic pain on physical examination (68 (58.1%)), patient history (67 (57.3%)), and underlying disease (59 (50.4%)) combined. Gabapentin, amitriptyline, and pregabalin were the first-choice treatments for moderate neuropathic pain. Tramadol, ibuprofen, amitriptyline, and paracetamol were the first-choice treatments for moderate mixed pain. Consensus on the diagnostic process of neuropathic pain in children and adolescents is lacking. Drug treatment varies widely for moderate, severe neuropathic, and mixed pain. Hence, diagnostic tools and therapy need to be harmonized and validated for use in children

    The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

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    The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged).Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editin

    The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

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    The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.The French contribution to X-IFU is funded by CNES, CNRS and CEA. This work has been also supported by ASI (Italian Space Agency) through the Contract 2019-27-HH.0, and by the ESA (European Space Agency) Core Technology Program (CTP) Contract No. 4000114932/15/NL/BW and the AREMBES - ESA CTP No.4000116655/16/NL/BW. This publication is part of grant RTI2018-096686-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This publication is part of grant RTI2018-096686-B-C21 and PID2020-115325GB-C31 funded by MCIN/AEI/10.13039/501100011033

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

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    Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis
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