359 research outputs found

    Solving linear multiplicative programs via branch-and-bound: a computational experience

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    In this paper, linear multiplicative programs are approached with a branch-and-bound scheme and a detailed computational study is provided. Several underestimation functions are analyzed and various partitioning criteria are presented. A particular class of linear multiplicative programs, useful to solve some applicative bilevel problems, is considered from a theoretical point of view to emphasize an efficient solution method. Detailed results of the computational study are provided to point out the performances provided by using various underestimation functions and partitioning criteria, thus improving some of the results of the current literature

    Comparative high-resolution chemostratigraphy of the Bonarelli Level from the reference Bottaccione section (Umbria-Marche Apennines) and from an equivalent section in NW Sicily: Consistent and contrasting responses to the OAE2.

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    The Bonarelli Level (BL) from the upper Cenomanian portion of the reference Bottaccione section (central Italy) is characterized by the presence of black shales containing high TOC concentrations (up to 17%) and amounts of CaCO3 near to zero. In the absence of carbonate and, consequently, of relative carbon- and oxygen- isotopic data, the elemental geochemistry revealed to be a very useful tool to obtain information about the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean during the OAE2. Based on several geochemical proxies (Rb, V, Ni, Cr, Si, Ba), the BL is interpreted as a high-productivity event driven by increasingly warm and humid climatic conditions promoting an accelerated hydrological cycle. The enrichment factors of peculiar trace metals (Zn, Cd, Pb, Sb, Mo, U) provide further insight about the H2S activity at the seafloor during the organic-rich sediment deposition and permitted us to evaluate the use of Ba as palaeoproductivity tracer in conditions of high rate of sulphate reduction. By comparing geochemical records from the reference Bottaccione section (central Italy) with those previously obtained for the coeval Calabianca section (northwestern Sicily), different degrees of oceanic anoxia were delineated and ascribed to different abundance and type (degradable or refractory) of organic matter, which are limiting factors in the bacterial sulphate reduction reactions and in subsequent euxinic conditions at seafloor in the Tethys realm. Based on a ciclostratigraphic approach, consistent fluctuations at 100 kyr scale in the chemostratigraphic signals from the two sections are inferred to be expression of a strong orbital-climatic forcing driving changes in the oceanic environment during the BL deposition

    Use of dipicolinate-based complexes for producing ion-imprinted polystyrene resins for the extraction of yttrium-90 and heavy lanthanide cations

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    Highly selective separation of yttrium (and lanthanides) is of interest for the design of radiopharmaceuticals, and an efficient method based on the ion-imprinting concept is proposed here. The synthesis and structural, thermodynamic and photophysical characterization of complexes of trivalent yttrium and lanthanides with two new vinyl derivatives of dipicolinic acid, HL1 and L2, are described. The feasibility of using ion-imprinted resins for yttrium and lanthanide separation is demonstrated. The resins were obtained by copolymerization with styrene and divinylbenzene and subsequent acid treatment to remove the metal ion. High-resolution Eu luminescence experiments revealed that the geometry of the complexation sites is well preserved in the imprinted polymers. The ion-imprinted polymer based on HL1 proved to be particularly well adapted for yttrium extraction, having a sizeable capacity (8.9 +- 0.2 g/mg resin) and a fast rate of extraction (t1/2 = 1.7 min). In addition, lighter and heavier lanthanide ions are separated. Finally, the resin displays high selectivity for yttrium and lanthanide cations against alkali and alkaline earth metals. For instance, in a typical experiment, 10 mg of yttrium was extracted from 5 g of milk ash sample by 2 g of the resin. The good separation properties displayed by the resin based on HL1 open interesting perspectives for the production of highly pure 90Y and radiolanthanides for medical applications, and for trace analysis of these radiochemicals in food and in the environment

    Behavior of a forest of NiFe nanowires in KOH and NaCl solution for water electrolysis

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    The present work investigates the behavior of nanostructured electrodes consisting of an array of nanowires of NiFe alloy in KOH + 0.5 M NaCl solution. The aim is to explore the possibility of using these electrodes for hydrogen production by seawater electrolysis. Seawater splitting requires a highly selective electrode on the anode side, where the evolution of molecular chlorine or the formation of other active chlorine compounds can compete with the oxygen evolution reaction. Nanostructured electrodes, obtained by template electrosynthesis, were tested at room temperature in KOH + 0.5 M NaCl solution, and the results were compared with those obtained in pure KOH. The results showed that the presence of NaCl does not affect the electrocatalytic behavior of the nanostructured NiFe alloy. Furthermore, the chemical–physical characterizations carried out after the long-term galvanostatic tests, have shown that the nanostructured electrodes are also stable in terms of morphology and composition. In addition, the solution used to perform the long-term galvanostatic tests was analyzed to investigate the possible formation of chlorine compounds. The absence of these compounds, together with the measured potential value measured for the oxygen evolution reaction, which was always lower than the thermodynamic redox potential for the hypochlorite formation reaction, leads us to conclude that these electrodes are potentially suitable for seawater electrolysis

    Cabergoline as an adjuvant to standard heart failure treatment in peripartum cardiomyopathy: a case report and review of the literature

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    Introduction: Peripartum cardiomyopathy (PPCM) is a rare and idiopathic form of dilated cardiomyopathy presenting late in pregnancy or early postpartum. Since the 16-kDa fragment of prolactin has been identified as a key factor in the pathophysiology of PPCM, prolactin inhibitors have been used as an adjuvant to standard heart failure treatment. Although bromocriptine is the current first choice, promising results have been reported with cabergoline, albeit scant. Case Presentation: We presented the case of a 41-year-old woman who received a diagnosis of PPCM one week after delivery and was successfully treated with cabergoline, finally experiencing a complete recovery. Conclusion: The case adds to the scant evidence supporting the use of cabergoline in PPCM patients. We argue that the favorable pharmacokinetic and metabolic profiles of this drug should prompt its consideration as a valid alternative prolactin inhibitor in these critical patients

    The Videofluorographic Swallowing Study in Rheumatologic Diseases: A Comprehensive Review

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    Autoimmune connective tissue diseases are a heterogeneous group of pathologies that affect about 10% of world population with chronic evolution in 20%-80%. Inflammation in autoimmune diseases may lead to serious damage to other organs including the gastrointestinal tract. Gastrointestinal tract involvement in these patients may also due to both a direct action of antibodies against organs and pharmacological therapies. Dysphagia is one of the most important symptom, and it is caused by failure of the swallowing function and may lead to aspiration pneumonia, malnutrition, dehydration, weight loss, and airway obstruction. The videofluorographic swallowing study is a key diagnostic tool in the detection of swallowing disorders, allowing to make an early diagnosis and to reduce the risk of gastrointestinal and pulmonary complications. This technique helps to identify both functional and structural anomalies of the anatomic chain involved in swallowing function. The aim of this review is to systematically analyze the basis of the pathological involvement of the swallowing function for each rheumatological disease and to show the main features of the videofluorographic study that may be encountered in these patients
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