Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Sci Rep ; 5: 8273, 2015 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-25653128

RESUMO

Predicted increases in seawater temperatures accelerate coral reef decline due to mortality by heat-driven coral bleaching. Alteration of the natural nutrient environment of reef corals reduces tolerance of corals to heat and light stress and thus will exacerbate impacts of global warming on reefs. Still, many reefs demonstrate remarkable regeneration from past stress events. This paper investigates the effects of sea surface temperature (SST) and water column productivity on recovery of coral reefs. In 71 Indo-Pacific sites, coral cover changes over the past 1-3 decades correlated negative-exponentially with mean SST, chlorophyll a, and SST rise. At six monitoring sites (Persian/Arabian Gulf, Red Sea, northern and southern Galápagos, Easter Island, Panama), over half of all corals were <31 years, implying that measured environmental variables indeed shaped populations and community. An Indo-Pacific-wide model suggests reefs in the northwest and central Indian Ocean, as well as the central west Pacific, are at highest risk of degradation, and those at high latitudes the least. The model pinpoints regions where coral reefs presently have the best chances for survival. However, reefs best buffered against temperature and nutrient effects are those that current studies suggest to be most at peril from future ocean acidification.


Assuntos
Recifes de Corais , Água do Mar , Temperatura , Animais , Antozoários/classificação , Antozoários/genética , Clorofila/genética , Clorofila A , Ecossistema , Oceano Índico , Repetições de Microssatélites , Oceanografia , Oceano Pacífico , Regeneração
2.
Regul Toxicol Pharmacol ; 67(2): 252-65, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23959062

RESUMO

Statistical principles described in ISO 5725-1 (1994) are a robust basis for evaluating cigarette smoke data from collaborative studies under the ISO 3308 machine smoking and for specifying the criteria for the removal of outlier data and determination of mean yields and their variability. However, the standard only provides recommendations on outlier removal that should be taken into account by experts who undertake data interpretation. The potential for over-interpretation of data from small numbers of laboratories is highlighted and recommendations made to deal with this possibility. Key variables to the statistical analysis, the number of cigarettes per replicate and replicates performed in each laboratory, the number of participating laboratories and the use of linear and rotary smoking machines in smoke collection, are identified and their relevance to obtaining robust data are considered. The statistical methods routinely used for data analysis from the ISO regime, are re-assessed for their suitability to analyse data obtained under the Canadian intense (CI) regime, where yield differences between linear and rotary smoking machines are found. This machine effect can lead to more outliers being detected and difficulties in outlier detection which may affect the provision of robust estimates of mean yields, repeatability and reproducibility.


Assuntos
Monóxido de Carbono/análise , Nicotina/análise , Fumaça/análise , Alcatrões/análise , Interpretação Estatística de Dados , Projetos de Pesquisa , Nicotiana
3.
Regul Toxicol Pharmacol ; 66(1): 72-82, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23523712

RESUMO

Two US blend style cigarette products, one ventilated, were smoked under 16 smoking regimes. 'Tar', nicotine, carbon monoxide (TNCO) and water smoke yields determined with these regimes, are shown to form part of continuous functions linked with puffing intensity (the product of puff volume and puff frequency) and total puff volume (the product of puff volume and puff number). This allows the prediction of yields for any regime and leads to the conclusion that the characterisation of cigarette products with these analytes is achievable from using a single smoking regime. The rate of increase of TNCO yields decreases as the puffing intensity increases, due to the more rapid burning of the tobacco available for smoking, although (particulate phase) water yield, relative to TNCO, increases considerably with intensity. Total puff volume is linearly related to TNCO machine yields from a range of regimes, to duplicated human yields and to the nicotine and solanesol retained in spent filters. The concentration of these smoke components is essentially independent of the regime used to generate them. This is not the case with water for which the yield in smoke increases exponentially with the total puff volume and its concentration increases rapidly with intensity.


Assuntos
Nicotiana/química , Fumaça/análise , Fumar/metabolismo , Produtos do Tabaco/análise , Monóxido de Carbono/química , Humanos , Nicotina/química , Alcatrões/química , Água/química
4.
Aquat Conserv ; 22(2): 232-261, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25505830

RESUMO

The Chagos Archipelago was designated a no-take marine protected area (MPA) in 2010; it covers 550 000 km2, with more than 60 000 km2 shallow limestone platform and reefs. This has doubled the global cover of such MPAs.It contains 25-50% of the Indian Ocean reef area remaining in excellent condition, as well as the world's largest contiguous undamaged reef area. It has suffered from warming episodes, but after the most severe mortality event of 1998, coral cover was restored after 10 years.Coral reef fishes are orders of magnitude more abundant than in other Indian Ocean locations, regardless of whether the latter are fished or protected.Coral diseases are extremely low, and no invasive marine species are known.Genetically, Chagos marine species are part of the Western Indian Ocean, and Chagos serves as a 'stepping-stone' in the ocean.The no-take MPA extends to the 200 nm boundary, and. includes 86 unfished seamounts and 243 deep knolls as well as encompassing important pelagic species.On the larger islands, native plants, coconut crabs, bird and turtle colonies were largely destroyed in plantation times, but several smaller islands are in relatively undamaged state.There are now 10 'important bird areas', coconut crab density is high and numbers of green and hawksbill turtles are recovering.Diego Garcia atoll contains a military facility; this atoll contains one Ramsar site and several 'strict nature reserves'. Pollutant monitoring shows it to be the least polluted inhabited atoll in the world. Today, strict environmental regulations are enforced.Shoreline erosion is significant in many places. Its economic cost in the inhabited part of Diego Garcia is very high, but all islands are vulnerable.Chagos is ideally situated for several monitoring programmes, and use is increasingly being made of the archipelago for this purpose.

5.
Food Chem Toxicol ; 49(12): 3238-48, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21983484

RESUMO

A series of experiments are described, undertaken on both volatile and non-volatile ingredients either during cigarette smoking or under pyrolysis conditions that try to simulate cigarette smoking. In particular, the fate of a series of deuterium and (13)C labelled volatiles was studied which demonstrated that, in a similar way to unlabelled volatiles, a large proportion of each was transferred intact into mainstream smoke. The unaccounted material, which was not transferred intact, in the studies of both volatile and non-volatile ingredients was primarily transformed into products of complete combustion such as carbon monoxide or carbon dioxide with only very minor amounts transformed into products of incomplete combustion. In addition, the studies on both unlabelled and deuterium labelled compounds demonstrated that the utility of pyrolysis studies lies mainly in distinguishing between those compounds that transfer intact into mainstream smoke from those that might be liable to degrade. Pyrolysis does not provide a robust prediction of the compounds that are formed from ingredients during cigarette smoking studies.


Assuntos
Nicotiana/química , Fumaça/análise , Fumar , Dióxido de Carbono/análise , Monóxido de Carbono/análise , Cromatografia Gasosa , Cromatografia Líquida de Alta Pressão , Deutério/química , Compostos Orgânicos Voláteis/análise
6.
Mar Pollut Bull ; 62(2): 246-50, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21094502

RESUMO

The corals of the Persian/Arabian Gulf are better adapted to temperature fluctuations than elsewhere in the Indo-Pacific. The Gulf is an extreme marine environment displaying the highest known summer water temperatures for any reef area. The small and shallow sea can be considered a good analogue to future conditions for the rest of the world's oceans under global warming. The fact that corals can persist in such a demanding environment indicates that they have been able to acclimatize and selectively adapt to elevated temperature. The implication being that colonies elsewhere may be able to follow suit. This in turn provides hope that corals may, given sufficient time, similarly adapt to survive even in an impoverished form, under conditions of acidification-driven lowering of CaCO3 saturation state, a further consequence of raised atmospheric CO2. This paper demonstrates, however, that the uniquely adapted corals of the Gulf may, within the next three centuries, be threatened by a chronic habitat shortage brought about by the dissolution of the lithified seabed on which they rely for colonisation. This will occur due to modifications in the chemical composition of the Gulf waters due to climate change.


Assuntos
Aclimatação , Antozoários/fisiologia , Dióxido de Carbono/química , Sedimentos Geológicos/química , Poluentes Químicos da Água/química , Animais , Antozoários/crescimento & desenvolvimento , Carbonato de Cálcio/química , Dióxido de Carbono/análise , Aquecimento Global , Concentração de Íons de Hidrogênio , Oceanos e Mares , Estações do Ano , Água do Mar/química , Temperatura , Poluentes Químicos da Água/análise
7.
Mar Pollut Bull ; 58(1): 24-38, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19100585

RESUMO

With large-scale impacts on coral reefs due to global climatic change projected to increase dramatically, and suitability of many areas for reef growth projected to decrease, the question arises whether particular settings might serve as refugia that can maintain higher coral populations than surrounding areas. We examine this hypothesis on a small, local scale in Honduras, western Caribbean. Dense coral thickets containing high numbers of the endangered coral Acropora cervicornis occur on offshore banks while being rare on the fringing reef on nearby Roatán. Geomorphological setting and community dynamics were evaluated and monitored from 1996 to 2005. A model of population dynamics was developed to test assumptions derived from monitoring. Coral cover on the fringing reef declined in 1998 from >30% to <20%, but the banks maintained areas of very dense coral cover (32% cover by A. cervicornis on the banks but <1% on the fringing reef). Bathymetry from satellite images showed the banks to be well-separated from the fringing reef, making asexual connectivity between banks and fringing reef impossible but protecting the banks from direct land-runoff during storms. Exposure to SE tradewinds also causes good flushing. Only four A. cervicornis recruits were recorded on the fringing reef over 6 years. Runoff associated with hurricanes caused greater mortality than did bleaching in 1998 and 2005 on the fringing reef, but not on the banks. Since 1870, our analysis suggests that corals on the banks may have been favored during 17 runoff events associated with tropical depressions and storms and potentially also during five bleaching events, but this is more uncertain. Our model suggests that under this disturbance regime, the banks will indeed maintain higher coral populations than the fringing reef and supports the assumption that offshore banks could serve as refugia with the capacity to subsidize depleted mainland populations.


Assuntos
Antozoários/fisiologia , Conservação dos Recursos Naturais , Monitoramento Ambiental , Modelos Biológicos , Animais , Biodiversidade , Sedimentos Geológicos , Oceanos e Mares , Densidade Demográfica , Dinâmica Populacional
8.
J Drug Target ; 9(5): 361-78, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11770706

RESUMO

The micellar-like particle systems produced from poly-D,L-lactide-poly(ethylene glycol) (PLA-PEG) copolymers have been assessed using a range of physicochemical characterisation methods, followed by in vivo studies of their biodistribution after intravenous administration to the rat. The size of the PEG chain was kept constant at 5 or 2 kDa, while the PLA size increased within a series from 2 to 25 kDa. The results obtained reveal, that in an aqueous medium the copolymers assembled into micellar-like structures, with the PLA segments forming the core and the PEG segments the surrounding corona. The size of the PLA segments dominated the process of assembly of the molecules and the characteristics of the resultant micellar-like particles. The PLA-PEG micellar particles were found to be less dynamic than those obtained from conventional surfactants. Particles formed from the lower molecular weight PLA polymers allowed a level of chain mobility while the cores of the micellar particles formed from higher molecular weight PLA appeared to be solid-like in nature. The size of the micellar particles was dependent on the copolymer molecular weight and the z-average diameter increased from 25 to 76 nm as the molecular weight of the PLA moiety increased. This provides an ability to control the particle size by adjusting the molecular weight of the PLA moiety. Following intravenous administration to the rat model, micellar-like particles smaller than approximately 70 nm accumulated in the liver, despite the fact that the PEG corona provided an effective steric stabilization effect. Micellar-like particles with a diameter of more than approximately 70 nm exhibited prolonged systemic circulation and reduced liver uptake, although the steric stabilisation of these particles was shown to be less effective. These findings agree with recent observations from other research groups; that indicate a possibility that very small particulates can pass through the sinusoidal fenestrations in the liver and gain access to the parenchymal cells of the liver.


Assuntos
Lactatos/química , Lactatos/farmacocinética , Micelas , Polietilenoglicóis/química , Polietilenoglicóis/farmacocinética , Animais , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacocinética , Coloides , Portadores de Fármacos/química , Portadores de Fármacos/farmacologia , Lactatos/sangue , Fígado/metabolismo , Tamanho da Partícula , Ratos , Ratos Wistar , Distribuição Tecidual
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...