937 resultados para Polish Impact Factor


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Aim Habitat loss and climate change are two major drivers of biological diversity. Here we quantify how deforestation has already changed, and how future climate scenarios may change, environmental conditions within the highly disturbed Atlantic forests of Brazil. We also examine how environmental conditions have been altered within the range of selected bird species. Location Atlantic forests of south-eastern Brazil. Methods The historical distribution of 21 bird species was estimated using Maxent. After superimposing the present-day forest cover, we examined the environmental niches hypothesized to be occupied by these birds pre- and post-deforestation using environmental niche factor analysis (ENFA). ENFA was also used to compare conditions in the entire Atlantic forest ecosystem pre- and post-deforestation. The relative influence of land use and climate change on environmental conditions was examined using analysis of similarity and principal components analysis. Results Deforestation in the region has resulted in a decrease in suitable habitat of between 78% and 93% for the Atlantic forest birds included here. Further, Atlantic forest birds today experience generally wetter and less seasonal forest environments than they did historically. Models of future environmental conditions within forest remnants suggest generally warmer conditions and lower annual variation in rainfall due to greater precipitation in the driest quarter of the year. We found that deforestation resulted in a greater divergence of environmental conditions within Atlantic forests than that predicted by climate change. Main conclusions The changes in environmental conditions that have occurred with large-scale deforestation suggest that selective regimes may have shifted and, as a consequence, spatial patterns of intra-specific variation in morphology, behaviour and genes have probably been altered. Although the observed shifts in available environmental conditions resulting from deforestation are greater than those predicted by climate change, the latter will result in novel environments that exceed temperatures in any present-day climates and may lead to biotic attrition unless organisms can adapt to these warmer conditions. Conserving intra-specific diversity over the long term will require considering both how changes in the recent past have influenced contemporary populations and the impact of future environmental change.

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Our aim was to evaluate the effects of granulocyte colony-stimulating factor (G-CSF) on early cardiac arrhythmias after myocardial infarction (MI) and the impact on survival. Male Wistar rats received repeated doses of 50 mu g/kg G-CSF (MI-GCSF group) or vehicle (MI group) at 7, 3, and 1 days before surgery. MI was induced by permanent occlusion of left corollary artery. The electrocardiogram was obtained before occlusion and then for 30 minutes after surgery. Events and duration of ventricular arrhythmias were analyzed. The levels of connexin43 (Cx43) were measured by Western blot immediately before MI production. Survival was significantly increased in MI-GCSF pretreated group (74% versus 52.0% MI. P < 0.05). G-CSF pretreatment also significantly reduced the ventricular premature beats when compared with the untreated-MI group (201 +/- 47 versus 679 +/- 117, P < 0.05). The number and the duration of ventricular tachycardia were smaller in the MI-G-CSF group, as well as the number of ventricular fibrillation episodes (10% versus 69% in NIL P < 0.05). Cx43 levels were significantly increased by G-CSF treatment (1.27 +/- 0.13 versus 0.86 +/- 0.11; P < 0.05). The MI size 24 hours after occlusion was reduced by G-CSF pretreatment (36 +/- 3% versus 44 +/- 2% of left ventricle in MI group; P < 0.05). The increase of Cx43 expression in the heart may explain the reduced incidence in ventricular arrhythmias in the early phases after coronary artery occlusion in rats, thus increasing survival after MI.

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In the paper, we discuss dynamics of two kinds of mechanical systems. Initially, we consider vibro-impact systems which have many implementations in applied mechanics, ranging from drilling machinery and metal cutting processes to gear boxes. Moreover, from the point of view of dynamical systems, vibro-impact systems exhibit a rich variety of phenomena, particularly chaotic motion. In this paper, we review recent works on the dynamics of vibro-impact systems, focusing on chaotic motion and its control. The considered systems are a gear-rattling model and a smart damper to suppress chaotic motion. Furthermore, we investigate systems with non-ideal energy source, represented by a limited power supply. As an example of a non-ideal system, we analyse chaotic dynamics of the damped Duffing oscillator coupled to a rotor. Then, we show how to use a tuned liquid damper to control the attractors of this non-ideal oscillator.

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We develop and calibrate a model where differences in factor endowments lead countries to trade intermediate goods, and gains from trade reflect in total factor productivity. We perform several output and growth decompositions, to assess the impact that barriers to trade, as well as changes in terms of trade, have on measured TFP. We find that for very poor economies gains from trade are large, in some cases representing a doubling of GDP. Also, that an improvement in the terms of trade - by allowing the use of a better mix of intermediate inputs in the production process - translates into productivity growth.

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We develop and calibrate a model where diferences in factor en-dowments lead countries to trade di¤erent goods, so that the existence of international trade changes the sectorial composition of output from one country to another. Gains from trade re ect in total factor productivity. We perform a development decomposition, to assess the impact of trade and barriers to trade on measured TFP. In our sample, the median size of that e¤ect is about 6.5% of output, with a median of 17% and a maximum of 89%. Also, the model predicts that changes in the terms of trade cause a change of productivity, and that efect has an average elasticity of 0.71.

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One looming question has persisted in the minds of economists the world over in the aftermath of the 2007-2008 American Housing and Debt Crisis: How did it begin and who is responsible for making this happen? Another two-part question is: What measures were implemented to help end the crisis and what changes are being implemented to ensure that it will never happen again? Many speculate that the major contributing factor was the repeal of the Glass-Steagall Act in 1999 that prompted a virtual feeding frenzy among the banking community when new calls from Capitol Hill encouraged home ownership in America as well as the secondary mortgage market which skyrocketed thereafter. The Glass-Steagall Act will be among many of the topics explored in this paper along with the events leading up to the 2007-2008 housing/debt crisis as well as the aftermath.

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Purpose of reviewPhysical exercise can be both beneficial and harmful for the gastrointestinal tract in a dose-effect relationship between its intensity and health. Mild-to-moderate intensity exercises play a protective role against colon cancer, diverticular disease, cholelithiasis and constipation, whereas acute strenuous exercise may provoke heartburn, nausea, vomiting, abdominal pain, diarrhea and even gastrointestinal bleeding. This review focuses on mechanisms involved in those symptoms and their associations with type of exercises in humans.Recent findingsOne quarter to one half of elite athletes are hampered by the gastrointestinal symptoms that may deter them from participation in training and competitive events. Vigorous exercise-induced gastrointestinal symptoms are often attributed to altered motility, mechanical factor or altered neuroimmunoendocrine secretions. Training, lifestyle modifications, meal composition, adequate hydration and avoidance of excessive use of some medications are the recommendations.SummaryStrenuous exercise and dehydrated states would be the causes of gastrointestinal symptoms referred by 70% of the athletes. Gut ischemia would be the main cause of nausea, vomiting, abdominal pain and (bloody) diarrhea. The frequency is almost twice as high during running than during other endurance sports as cycling or swimming and 1.5-3.0 times higher in the elite athletes than the recreational exercisers.

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Malnutrition may be a consequence of energy deficit or micronutrient deficiency. It is considered the most relevant risk factor for illness and death, particularly in developing countries. In this review we described the magnitude of this problem, as well as its direct effect on the immune system and how it results in higher susceptibility to infections. A special emphasis was given to experimental models used to investigate the relationship between undernutrition and immunity. Malnutrition is obviously a challenge that must be addressed to health authorities and the scientific community.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Includes bibliography

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Background: Throughout dairy cows evolution, milk production was always the key point to select the superior animal. Currently, several evidences has shown that high milk production have intensively contributed to the decline of dairy cattle fertility. Beyond milk production, dairy cows have their reproductive performance impaired by another factors, heat stress and repeat-breeding. Methods like fixed time artificial insemination and embryo transfer were developed to minimize the effects of these factors, and improve dairy herds profitability. This review aims to show some key-point experiments conducted to improve the efficiency of the self-appointed protocols for artificial insemination and embryo transfer in Brazil, overcoming several reproductive problems. Our goal is to develop cheap and easy self-appointed programs that facilitate animal handling and maximize their reproductive outcomes all over the year. Review: Failure in estrus detection is the mainly limiting factor for the use of artificial insemination in high-production dairy herd. An excellent alternative to overcome the need of estrus detection is fixed time artificial insemination. Many protocols with and without the use of estradiol have been developed to that end. Among the protocols for fixed time artificial insemination without estradiol, DoubleOvsynch has been extensively used recently in American dairy herds. In Brazil, similar pregnancy rate was obtained compared to progesterone-estradiol based protocols for fixed time artificial insemination. Particularities of progesterone-estradiol based protocols as (1) new progesterone device or devices previously used for eight days; (2) different doses of eCG; and (3) the use of estradiol cypionate for fixed time artificial insemination have been studied in Brazil. The use of self-appointed artificial insemination also enabled the reduction of the interval calving-conception compared to cows inseminated following the standing estrus. Regarding the low fertility of repeat breeders and the effect of heat stress at early pregnancy, other methods like embryo transfer became important tools to enhance reproductive efficiency of Brazilian dairy herds. Protocols were also developed to allow fixed time embryo transfer, eliminating the need of estrus detection and improving the reproductive efficiency of lactating recipients. As well as described for fixed time artificial insemination treatments, there is a large variety of hormone combination for fixed time embryo transfer (with and without estradiol). An experiment conducted in Brazil demonstrated that protocols for fixed time embryo transfer without estradiol can be as good as with estradiol to synchronize high-producing Holstein recipients, essentially during summer. Particularities related to embryos cryopreservation, synchronization of the estrus cycle of donors and recipients and the site of embryo release into the uterine horn were also investigated. Greater conception rates were achieved when fresh embryos were transferred compared to frozen-thawed ones. Also, the tight synchronization between donor and recipient (same day of estrus) resulted more pregnancies than when recipients were one day later or in advantage in relation to donors. Moreover, the site of embryo release into the uterine horn (ipsilateral to the corpus luteum) had no effect on pregnancy rates after in vivo produced embryo transfer. Conclusion: Both fixed time artificial insemination and fixed time embryo transfer are important tools to improve reproductive efficiency of high-producing dairy cows. These biotechnologies help bypassing some of the greatest challenges of dairy cattle reproduction: the difficulties of estrus detection, and the low fertility associated to heat stress and repeat breeding.

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Includes bibliography

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The external detector method (EDM) is a widely used technique in fission track thermochronology (FTT) in which two different minerals are concomitantly employed: spontaneous tracks are observed in apatite and induced ones in the muscovite external detector. They show intrinsic differences in detection and etching properties that should be taken into account. In this work, new geometry factor values, g, in apatite, were obtained by directly measuring the ρed/ρis ratios and independently determined [GQR]ed/is values through the measurement of projected lengths. Five mounts, two of which were large area prismatic sections and three samples composed of random-orientation pieces have been used to determine the g-values. A side effect of applying EDM is that the value of the initial confined induced fission track, L0, is not measured in routine analyses. The L 0-value is an important parameter to quantify with good confidence the degree of annealing of the spontaneous fission tracks in unknown-age samples, and is essential for accurate thermal history modeling. The impact of using arbitrary L0-values on the inference of sample thermal history is investigated and discussed. The measurement of the L0-value for each sample to be dated using an extra irradiated apatite mount is proposed. This extra mount can be also used for determining the g value as an extension of the ρed/ρis ratio method. Eight apatite samples from crystalline basement, with grains at random orientation, were used to determine the g-values. The results found are statistically in agreement with the values found for apatite samples (from Durango, Mexico) measured in prismatic section and also measured at random orientation. There was no observable variation in efficiency regarding crystal orientation, showing that it is relatively safe using non-prismatic grains, especially in samples with paucity of grains, as it is the case of most basin samples. Implications for the ζ-calibration and for the calibration of the direct (spectrometer-based) fission-track dating are also discussed.

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Historically, the ichthyofauna of large Brazilian rivers has been subject to anthropogenic interference, such as impoundments. Currently, cage fish farming systems are a new source of impact on aquatic ecosystems. The objective of this study was to characterise the impact of freshwater fish farms on the feeding of five species of Neotropical freshwater fish. Specimens of Astyanax altiparanae, Galeocharax knerii, Iheringicthys labrosus, Pimelodus maculatus and Plagioscion squamosissimus were sampled in areas around two systems of cage fish farming (CF), and two control areas (CT) that were not influenced by this activity. Results show that there were significant changes in the diet of trophic generalist species (A. altiparanae, P. maculatus and I. labrosus) accompanied by a related increase in the condition factor values of these species in cage areas. Trophic specialist species, such as the carnivorous fish species G. knerii and P. squamosissimus, presented small differences between the CF and CT areas with regard to diet and showed no differences in other analyses performed. In conclusion, cage fish farms can affect the natural diet of trophic generalist fish species, directly affecting the nutritional status (condition factor), where food wastes was found to be one of the principal items consumed by this trophic guild. Results indicate that these species are responsible for recycling a great quantity of organic matter transferred by this type of activity, which, along with local fishery activities, contribute to mitigation of associated processes of eutrophication. © 2013 Elsevier B.V.

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Includes bibliography