Livestock grazing, plateau pikas and the conservation of avian biodiversity on the Tibetan plateau

On the Qinghai-Tibet plateau increased livestock numbers have resulted in degradation of the grasslands with potential impacts on native biodiversity. Concurrently, perceived increases in populations of native small mammals such as plateau pikas (Ochotona curzoniae) have led to poisoning programs, with uncertain impacts on species such as ground-nesting birds. We explored the relationships between the local seasonal abundance of small birds and (1) the density of pika burrows; (2) livestock grazing practices; and (3) local poisoning of pikas. Around Naqu prefecture, central Tibet, we used a nested experimental design to collect data from areas rested from grazing over summer, nearby areas with year-round grazing and areas subjected to pika poisoning. Additional data were collected from a site where grazing had not occurred for at least 4 years prior to the study. Poisoning pikas in spring had no detectable effect on the local abundance of birds the following autumn. However, two ground-nesting species, white-rumped and rufous-necked snowfinches, showed positive associations with the density of pika burrows, indicating that long-term 'pika poisoning could reduce the density of these species by reducing the density of pika burrows. Rufous-necked snowfinches and non ground-nesting species including horned larks and common hoopoes showed positive responses to reduced grazing pressure from livestock, particularly in the long-rested site, indicating current grazing levels could be having a negative impact on these species. Conservation of small passerine biodiversity in this system will require changed management practices for livestock and pikas that consider the complex three-way interaction between livestock grazing, pikas and small birds. (C) 2008 Elsevier Ltd. All rights reserved.

Analysis of diets of upland buzzards using stable carbon and nitrogen isotopes

We measured the stable carbon and nitrogen isotope ratios for muscles of the upland buzzards (Buteo hemilasius) and their potential food sources, plateau pikas (Ochotona curzoniae), Qinghai voles (Lasiopodomys fuscus), plateau zokors (Myospalax fontanierii), and several passerine bird species at the alpine meadow in Maduo county, Guoluo prefecture of Qinghai province, People's Republic of China, to provide diet information of upland buzzards, highlighting different diet composition of upland buzzards exposed to different locations. The results demonstrated that stable carbon isotope ratios of upland buzzards, passerine birds, plateau pikas, plateau zokors, and Qinghai voles were -24.42 +/- 0.25parts per thousand, -22.89 +/- 1.48parts per thousand, -25.30 +/- 1.47parts per thousand, -25.78 +/- 0.22parts per thousand, and -25.41 +/- 0.01parts per thousand, respectively, and stable nitrogen isotope ratios were 7.89 +/- 0.38parts per thousand, 8.37 +/- 2.05parts per thousand, 5.83 +/- 1.10parts per thousand, 5.23 +/- 0.34parts per thousand, and 8.86 +/- 0.06parts per thousand, respectively. Fractionation of stable carbon and nitrogen isotope ratios between upland buzzards and their food were 1.03parts per thousand and 2.11parts per thousand, respectively. Based on mass balance principle of stable isotopes and the Euclidean distance mixing model, upland buzzards depended mainly on plateau pikas as food (74.56%). Plateau zokors, Qinghai voles, and passerine birds only contributed a small proportion (25.44%) to diets of upland buzzards. The results were closely accordant with analyses of stomach contents and food pellets, which firmly supported the feasibility of using stable carbon and nitrogen isotope ratios to investigate diet information of upland buzzards. Another study based on stable carbon isotopes showed that upland buzzards living in the Haibei prefecture (another prefecture located in the southeast Qinghai province) mainly preyed on passerine birds (64.96% or more) as food supply. We were alarmed by the preliminary results that widespread poisoning activities of small mammals could reshape the food composition of upland buzzards, influencing the stability and sustainability of the alpine meadow. Bio-control on rodent pests should be carried out rather than the chemical measures.

Burrowing rodents as ecosystem engineers: the ecology and management of plateau zokors Myospalax fontanierii in alpine meadow ecosystems on the Tibetan Plateau

1. Plateau zokors, Myospalax fontanierii, are the only subterranean herbivores on the Tibetan plateau of China. Although the population biology of plateau zokors has been studied for many years, the interactions between zokors and plants, especially for the maintenance and structure of ecological communities, have been poorly recognized. In the past, plateau zokors have been traditionally viewed as pests, competitors with cattle, and agents of soil erosion, thus eradication programmes have been carried out by local governments and farmers. Zokors are also widely and heavily exploited for their use in traditional Chinese medicine.2. Like other fossorial animals, such as pocket gophers Geomys spp. and prairie dogs Cynomys spp. in similar ecosystems, zokors may act to increase local environmental heterogeneity at the landscape level, aid in the formation, aeration and mixing of soil, and enhance infiltration of water into the soil thus curtailing erosion. The changes that zokors cause in the physical environment, vegetation and soil clearly affect the herbivore food web. Equally, plateau zokors also provide a significant food source for many avian and mammalian predators on the plateau. Zokor control leading to depletion of prey and secondary poisoning may therefore present problems for populations of numerous other animals.3. We highlight the important role plateau zokors play in the Tibetan plateau ecosystem. Plateau zokors should be managed in concert with other comprehensive rangeland treatments to ensure the ecological equilibrium and preservation of native biodiversity, as well as the long-term sustainable use of pastureland by domestic livestock.

NO reduction and CO oxidation over Cu/Ce/Mg/Al mixed oxide catalyst in FCC operation

Simultaneous NO reduction and CO oxidation in the presence of O-2,H2O and SO2 over Cu/Mg/AUO (Cu-cat), Ce/Mg/Al/O (Ce-cat) and Cu/Ce/Mg/Al/O (CuCe-cat) were studied. At low temperatures (<340 degreesC), the presence of O-2 or H2O enhanced the activity of CuCe-cat for NO and CO conversions, but significantly suppressed the activity of Cu-cat and Ce-cat, At high temperature (720 degreesC), the presence of O-2 or H2O had no adverse effect on the NO and CO conversions over these catalysts. The addition of SO2 to NO + CO + O-2 + H2O system had no effect on the, reaction of CO + O-2 over Cu-cat, but deactivated this catalyst for NO + CO and CO + H2O reactions; over Ce-cat, all of these reactions of NO + CO, CO + O-2 and CO + H2O were suppressed significantly; over CuCe-cat, NO + CO and CO + O-2 reactions were not affected while the reaction of CO + H2O was slightly inhibited. (C) 2002 Elsevier Science B.V. All rights reserved.

Composite anode for CO tolerance proton exchange membrane fuel cells

Fuel of proton exchange membrane fuel cells (PEMFC) mostly comes from reformate containing CO. which will poison the fuel cell electrocatalyst. The effect of CO on the performance of PEMFC is studied in this paper. Several electrode structures are investigated for CO containing fuel. The experimental results show that thin-film catalyst electrode has higher specific catalyst activity and traditional electrode structure can stand for CO poisoning to some extent. A composite electrode structure is proposed for improving CO tolerance of PEMFCs. With the same catalyst loading. the new composite electrode has improved cell performance than traditional electrode with PtRu/C electrocatalyst for both pure hydrogen and CO/H-2. The EDX test of composite anode is also performed in this paper, the effective catalyst distribution is found in the composite anode. (C) 2002 Elsevier Science B.V. All rights reserved.

An efficient approach to modify the catalyst activity for the hydrogenation of nitrobenzene

The addition of a suitable amount of PPh3 to PdCl2 or PdCl2(PhCN)(2) in situ can considerably increase the catalytic activity in the hydrogenation of nitrobenzene, while the catalytic activities of PdCl2 (reduced)+PPh3, PdCl2(PPh3)(2) and Pd(PPh3)(4) are very poor. The poisoning of catalyst by mercury indicates that the catalytically active species are composed of Pd(0) colloidal particles. Transmission electron micrographs show that the size of nanometric Pd(0) particles of PdCl2 with PPh3 added in situ is smaller than that of PhCl2(PPh3) or PdCl2 (reduced)+PPh3. A synergic effect of bimetallic catalysts such as PdCl2+nPPh(3)+NiCl2 (n= 0.5, 1) and PdCl2(PhCN)(2)+PPh3+FeCl3 gives rise to a further increase in the catalytic activity.

As neurotoxinas de clostridium sp.

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Farmacêuticas

Selénio e a importância para o organismo humano

O selénio (Se) é um micronutriente essencial para o crescimento, desenvolvimento e normal metabolismo dos animais, incluindo o ser humano. É parte integrante de um conjunto de proteínas, as selenoproteínas, com ação antioxidante (protegendo as membranas celulares contra danos dos radicais livres), envolvidas no metabolismo das hormonas da tiróide, na regulação do crescimento e viabilidade celular, nas funções do sistema imune e na reprodução. É introduzido na dieta alimentar (principalmente nas formas de selenometionina e selenocisteína) através das plantas, e de produtos que delas derivam, que assimilam os compostos de selénio presentes no solo. Uma vez que a quantidade de selénio existente nos solos é muito variável, o teor nos alimentos vai depender da sua origem geográfica e, por consequência, a ingestão de selénio varia entre regiões e países. Baixos níveis de selénio estão associados a um declínio na função imune e problemas cognitivos. A deficiência de Se pode também ocasionar problemas musculares e cardiomiopatia. Concentrações reduzidas foram observadas em indíviduos com crises epiléticas e também em casos de pré-eclampsia. A deficiência de selénio pode também desenvolver-se durante a nutrição parenteral. Atualmente, a Dose Diária Recomendada (DDR) é de 55 μg/dia para homens e mulheres adultos e saudáveis. No entanto, existem evidências clínicas de que a ingestão em doses superiores (200-300 μg/dia) pode ter um papel benéfico na prevenção de alguns tipos de cancro e doenças cardiovasculares, na melhoria da resposta imunológica, como neuroprotetor e na fertilidade. O Se desempenha um papel importante na fertilidade masculina, sendo necessário na biossíntese da testosterona e na formação e normal desenvolvimento dos espermatozóides. Em mulheres grávidas o Se, ajuda a prevenir complicações antes e durante o parto e promove o normal desenvolvimento do feto. Como antioxidante o selénio vai combater os danos provocados pelos radicais livres, impedindo que estes exerçam o seu papel prejudicial no organismo. Sendo o sistema imunológico muito suscetível aos danos provocados pelo stress oxidativo, o Se vai exercer efeitos benéficos combatendo os danos por ele causados. Relativamente à capacidade viral, não é possível saber com exatidão qual a quantidade de Se necessária ou concentração ideal no plasma para evitar a ocorrência e desenvolvimento de infeções virais. No entanto, sabe-se que tem um efeito benéfico em pacientes HIV positivos e em indivíduos infetados com o vírus da hepatite (B ou C) contra a progressão para o neoplasia de fígado. Em teoria, a nível cardiovascular, este elemento pode exercer um efeito protetor, embora alguns estudos epidemiológicos não tenham mostrado uma associação clara entre o risco cardiovascular e os níveis selénio. A nível cerebral o Se vai atuar como neuroprotetor, prevenindo o aparecimento de patologias como demência e doença de Alzheimer. Apesar destes indicadores, a maioria dos países europeus, incluindo Portugal, regista uma deficiente ingestão de selénio por parte da população. A suplementação poderá constituir uma opção para garantir os níveis nutricionais recomendados e/ou ser utilizada com o objetivo de prevenir algumas doenças e o envelhecimento. No entanto o selénio pode também ser tóxico se ingerido em excesso, estando a dose máxima admissível fixada em 400 μg/dia. A intoxicação por selénio é chamada selenose e os sintomas comuns incluem: hálito a alho, distúrbios gastrointestinais, perda de cabelo, descamação das unhas, danos neurológicos e fadiga. Assim, atualmente acredita-se que enquanto indivíduos com baixo nível de Se podem obter benefícios da suplementação, esta pode ser prejudicial aqueles com valores normais ou elevados.

Occupational lead neurotoxicity: A behavioural and electrophysiological evaluation. study design and year one results.

To evaluate the effects of chronic lead exposure on the nervous system in adults, a set of neurobehavioural and electrophysiological tests was administered to 99 lead exposed foundry employees and 61 unexposed workers. Current and past blood lead concentrations were used to estimate the degree of lead absorption; all previous blood lead concentrations had been less than or equal to 90 micrograms/100 ml. Characteristic signs (such as wrist extensor weakness) or symptoms (such as colic) of lead poisoning were not seen. Sensory conduction in the sural nerve was not affected. By contrast, various neurobehavioural functions deteriorated with increasing lead burden. Workers with blood lead concentrations between 40 and 60 micrograms/100 ml showed impaired performance on tests of verbal concept formation, visual/motor performance, memory, and mood. Thus impairment in central nervous system function in lead exposed adults occurred in the absence of peripheral nervous system derangement and increased in severity with increasing lead dose.

Survey of the potential environmental and health impacts in the immediate aftermath of the coal ash spill in Kingston, Tennessee.

An investigation of the potential environmental and health impacts in the immediate aftermath of one of the largest coal ash spills in U.S. history at the Tennessee Valley Authority (TVA) Kingston coal-burning power plant has revealed three major findings. First the surface release of coal ash with high levels of toxic elements (As = 75 mg/kg; Hg = 150 microg/kg) and radioactivity (226Ra + 228Ra = 8 pCi/g) to the environment has the potential to generate resuspended ambient fine particles (< 10 microm) containing these toxics into the atmosphere that may pose a health risk to local communities. Second, leaching of contaminants from the coal ash caused contamination of surface waters in areas of restricted water exchange, but only trace levels were found in the downstream Emory and Clinch Rivers due to river dilution. Third, the accumulation of Hg- and As-rich coal ash in river sediments has the potential to have an impact on the ecological system in the downstream rivers by fish poisoning and methylmercury formation in anaerobic river sediments.