973 resultados para RISING ELUTION FRACTIONATION


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Journal impact factors have become an important criterion to judge the quality of scientific publications over the years, influencing the evaluation of institutions and individual researchers worldwide. However, they are also subject to a number of criticisms. Here we point out that the calculation of a journal’s impact factor is mainly based on the date of publication of its articles in print form, despite the fact that most journals now make their articles available online before that date. We analyze 61 neuroscience journals and show that delays between online and print publication of articles increased steadily over the last decade. Importantly, such a practice varies widely among journals, as some of them have no delays, while for others this period is longer than a year. Using a modified impact factor based on online rather than print publication dates, we demonstrate that online-to-print delays can artificially raise a journal’s impact factor, and that this inflation is greater for longer publication lags. We also show that correcting the effect of publication delay on impact factors changes journal rankings based on this metric. We thus suggest that indexing of articles in citation databases and calculation of citation metrics should be based on the date of an article’s online appearance, rather than on that of its publication in print.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Abiotic factors are fundamental drivers of the dynamics of wild marine fish populations. Identifying and quantifying their influence on species targeted by the fishing industry is difficult and very important for managing fisheries in a changing climate. Using multiple regression, we investigated the influence of both temperature and rainfall on the variability of recruitment of a tropical species, the brown tiger prawn (Penaeus esculentus), in Moreton Bay which is located near the southern limit of its distribution on the east coast of Australia. A step-wise selection between environmental variables identified that variations in recruitment from 1990 to 2014 were best explained by a combination of temperature and spawning stock biomass. Temperature explains 35% of recruitment variability and spawning stock biomass 33%. This analysis suggests that increasing temperatures have increased recruitment of brown tiger prawn in Moreton Bay.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Nickel isotope ratios were measured in ores, fly ash, slags and FeNi samples from two metallurgical plants located in the Goiás State, Brazil (Barro Alto, Niquelândia). This allowed investigating the mass-dependent fractionation of Ni isotopes during the Ni-laterite ore smelting and refining. Feeding material exhibits a large range of δ60Ni values (from 0.02 ± 0.10 ‰ to 0.20 ± 0.05 ‰, n=7), explained by the diversity of Ni-bearing phases, and the average of δ60Nifeeding materials was found equal to 0.08 ± 0.08‰ (2SD, n=7). Both δ60Ni values of fly ash (δ60Ni = 0.07 ± 0.07‰, n=10) and final FeNi produced (0.05 ± 0.02 ‰, n=2) were not significantly different from the feeding materials ones. These values are consistent with the very high production yield of the factories. However, smelting slags present the heaviest δ60Ni values of all the smelter samples, with δ60Ni ranging from 0.11 ± 0.05 ‰ to 0.27 ± 0.05 ‰ (n=8). Soils were also collected near and far from the Niquelândia metallurgical plant, to evaluate the potential of Ni isotopes for tracing the natural vs anthropogenic Ni in soils. The Ni isotopic composition of the non-impacted topsoils developed on ultramafic rocks ranges from -0.26 ± 0.09 ‰ to -0.04 ± 0.05 ‰ (n=20). On the contrary, the Ni isotopic composition of the non-ultramafic topsoils, collected close to the plant, exhibit a large variation of δ60Ni, ranging from -0.19 ± 0.13 ‰ up to 0.10 ± 0.05 ‰ (n=4). This slight but significant enrichment in heavy isotopes highlight the potential impact of smelting activity in the surrounding area, as well as the potential of Ni isotopes for discerning anthropogenic samples (heavier δ60Ni values) from natural ones (lighter δ60Ni values). However, given the global range of published δ60Ni values (from -1.03 to 2.5 ‰) and more particularly those associated to natural weathering of ultramafic rocks (from -0.61 to 0.32‰), the use of Ni isotopes for tracing environmental contamination from smelters will remain challenging.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The liver is one of the most important organs of human body, being involved in several vital functions and regulation of physiological processes. Given its pivotal role in the excretion of waste metabolites and drugs detoxification, the liver is often subjected to oxidative stress that leads to lipid peroxidation and severe cellular damage. The conventional treatments of liver diseases such as cirrhosis, fatty liver and chronic hepatitis are frequently inadequate due to side effects caused by hepatotoxic chemical drugs. To overcome this problematic paradox, medicinal plants, owing to their natural richness in phenolic compounds, have been intensively exploited concerning their extracts and fraction composition in order to find bioactive compounds that could be isolated and applied in the treatment of liver ailments. The present review aimed to collect the main results of recent studies carried out in this field and systematize the information for a better understanding of the hepatoprotective capacity of medicinal plants in in vitro and in vivo systems. Generally, the assessed plant extracts revealed good hepatoprotective properties, justifying the fractionation and further isolation of phenolic compounds from different parts of the plant. Twenty-five phenolic compounds, including flavonoids, lignan compounds, phenolic acids and other phenolic compounds, have been isolated and identified, and proved to be effective in the prevention and/or treatment of chemically induced liver damage. In this perspective, the use of medicinal plant extracts, fractions and phenolic compounds seems to be a promising strategy to avoid side effects caused by hepatotoxic chemicals.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Bogotá : Universidad de La Salle. Facultad de Ciencias Agropecuarias. Programa de Zootecnia

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In its open and private-based dimension, the Internet is the epitome of the Liberal International Order in its global spatial dimension. Therefore, normative questions arise from the emergence of powerful non-liberal actors such as China in Internet governance. In particular, China has supported a UN-based multilateral Internet governance model based on state sovereignty aimed at replacing the existing ICANN-based multistakeholder model. While persistent, this debate has become less dualistic through time. However, fear of Internet fragmentation has increased as the US-China technological competition grew harsher. This thesis inquires “(To what extent) are Chinese stakeholders reshaping the rules of Global Internet Governance?”. This is further unpacked in three smaller questions: (i) (To what extent) are Chinese stakeholders contributing to increased state influence in multistakeholder fora?; (ii) (how) is China contributing to Internet fragmentation?; and (iii) what are the main drivers of Chinese stakeholders’ stances? To answer these questions, Chinese stakeholders’ actions are observed in the making and management of critical Internet resources at the IETF and ICANN respectively, and in mobile connectivity standard-making at 3GPP. Through the lens of norm entrepreneurship in regime complexes, this thesis interprets changes and persistence in the Internet governance normative order and Chinese attitudes towards it. Three research methods are employed: network analysis, semi-structured expert interviews, and thematic document analysis. While China has enhanced state intervention in several technological fields, fostering debates on digital sovereignty, this research finds that the Chinese government does not exert full control on its domestic private actors and concludes that Chinese stakeholders have increasingly adapted to multistakeholder Internet governance as they grew influential within it. To enhance control over Internet-based activities, the Chinese government resorted to regulatory and technical control domestically rather than establishing a splinternet. This is due to Chinese stakeholders’ interest in retaining the network benefits of global interconnectivity.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In questo elaborato viene proposta la traduzione di un capitolo di "The Plant", libro inedito di Stephen King. Vengono illustrati il procedimento, l'approccio alla traduzione e le sfide maggiori riscontrate nel testo originale con relativi esempi. All'inizio è presente anche un capitolo introduttivo sull'autore, con biografia, storia e trama del libro preso in questione, nonché una breve parentesi sui suoi traduttori italiani più famosi.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An HPLC-PAD method using a gold working electrode and a triple-potential waveform was developed for the simultaneous determination of streptomycin and dihydrostreptomycin in veterinary drugs. Glucose was used as the internal standard, and the triple-potential waveform was optimized using a factorial and a central composite design. The optimum potentials were as follows: amperometric detection, E1=-0.15V; cleaning potential, E2=+0.85V; and reactivation of the electrode surface, E3=-0.65V. For the separation of the aminoglycosides and the internal standard of glucose, a CarboPac™ PA1 anion exchange column was used together with a mobile phase consisting of a 0.070 mol L(-1) sodium hydroxide solution in the isocratic elution mode with a flow rate of 0.8 mL min(-1). The method was validated and applied to the determination of streptomycin and dihydrostreptomycin in veterinary formulations (injection, suspension and ointment) without any previous sample pretreatment, except for the ointments, for which a liquid-liquid extraction was required before HPLC-PAD analysis. The method showed adequate selectivity, with an accuracy of 98-107% and a precision of less than 3.9%.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Silver nanoparticles have attracted considerable attention due to their beneficial properties. But toxicity issues associated with them are also rising. The reports in the past suggested health hazards of silver nanoparticles at the cellular, molecular, or whole organismal level in eukaryotes. Whereas, there is also need to examine the exposure effects of silver nanoparticle to the microbes, which are beneficial to humans as well as environment. The available literature suggests the harmful effects of physically and chemically synthesised silver nanoparticles. The toxicity of biogenically synthesized nanoparticles has been less studied than physically and chemically synthesised nanoparticles. Hence, there is a greater need to study the toxic effects of biologically synthesised silver nanoparticles in general and mycosynthesized nanoparticles in particular. In the present study, attempts have been made to assess the risk associated with the exposure of mycosynthesized silver nanoparticles on a beneficial soil microbe Pseudomonas putida. KT2440. The study demonstrates mycosynthesis of silver nanoparticles and their characterisation by UV-vis spectrophotometry, FTIR, X-ray diffraction, nanosight LM20 - a particle size distribution analyzer and TEM. Silver nanoparticles obtained herein were found to exert the hazardous effect at the concentration of 0.4μg/ml, which warrants further detailed investigations concerning toxicity.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The objective of this research was to determine the levels of enrichment of vitamins B1, B2, B6 and B3 in different types and brands of enriched cookies. The chromatographic separation was performed in a C18 column with gradient elution and UV detection at 254 and 287 nm. The results show that only 5 of the 24 brands evaluated are in accordance with the Brazilian legislation with respect to the vitamin content declared on the labels. However, consumption of approximately 100-150 g of most of the brands supplies the recommended dietary intake for children and adults of the vitamins evaluated.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Activity guided fractionation of Sinningia allagophylla (Mart.) Wiehler ethanolic extract yielded a new benzochromene 8-methoxylapachenol, besides seven known compounds: lapachenol, sitosteryl oleate, sitosteryl linoleate, stigmasteryl oleate, stigmasteryl linoleate, dunniol and tectoquinone. Extract, fractions, and compounds lapachenol, 8-methoxylapachenol, and dunniol were tested in vitro against human cancer cell lines U251 (glioma, CNS), MCF-7 (breast), NCI-ADR/RES (drug-resistant ovarian), 786-0 (kidney), NCI-H460 (lung, no small cells), PC-3 (prostate), OVCAR-3 (ovarian), HT-29 (colon), K562 (leukemia) and against VERO, a normal cell line. The most active compound was dunniol, which inhibited the growth of U251, MCF-7, NCI-ADR/RES, OVCAR-3 and K562 cell lines.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Culture supernatant of Staphylococcus aureus 722 in 3% triptone plus 1% yeast extract was used for EEA purification, proceeding comparison between dye ligand Red A affinity chromatography and classic chromatography. The capture of SEA with Amberlite CG-50 allowed rapid enterotoxin concentration from the culture supernatant. However, the ratio of 15 mg of the resin to a total of 150 mg of the toxin satured the resin, giving only 10 to 30% of SEA recuperation from the supernatant. The elution of concentrated material throught the Red A column resulted in a recovery of 60,87% of the toxin, and required 76 hours, indicating advantage on classic chromatography. Ion exchange column plus gel filtration recovered only 6,5 % of the SEA, and required 114 hours to conclude the procedure. The eletrophoresis of purified SEA indicated high grade of toxin obtained from Red A column, with 90 % of purity, compared to 60 % of classic column.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The inhibitory activity of crude extracts of Meliaceae and Rutaceae plants on glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) enzyme from Trypanosoma cruzi was evaluated at 100 μg/mL. Forty-six extracts were tested and fifteen of them showed significant inhibitory activity (IA % > 50). The majority of the assayed extracts of Meliaceae plants (Cedrela fissilis, Cipadessa fruticosa and Trichilia ramalhoi) showed high ability to inhibit the enzymatic activity. The fractionation of the hexane extract from branches of C. fruticosa led to the isolation of three flavonoids: flavone, 7-methoxyflavone and 3',4',5',5,7-pentamethoxyflavone. The two last compounds showed high ability to inhibit the gGAPDH activity. Therefore, the assayed Meliaceae species could be considered as a promising source of lead compounds against Chagas' disease.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A method using ultrasonication extraction for the determination of 17 polycyclic aromatic hydrocarbons (PAHs), selected by the USEPA and NIOSH as "consent decree" priority pollutants, in soil by High Performance Liquid Chromatography (HPLC) was studied. Separation and detection were completed in 20 min with a C18 columm, acetonitrile-water gradient elution and ultraviolet absorption and fluorescence detections. The detection limits, for a 10 µL of solution injection, were less than 9,917 ng/g in UV detection and less than 1,866 ng/g in fluorescence detection. Several organic solvents were tested for extraction of the 17 PAHs from soils. Acetone was the best solvent among the three solvents tested, and the order of the extraction efficiencies was: acetone>methanol>acetonitrile. Ultrasonication using acetone as solvent extraction was used to evaluate the biodegradation of those compounds in contaminated soil during a vermicomposting process.