31 research outputs found
Ice sheets as a missing source of silica to the polar oceans
Ice sheets play a more important role in the global silicon cycle than previously appreciated. Input of dissolved and amorphous particulate silica into natural waters stimulates the growth of diatoms. Here we measure dissolved and amorphous silica in Greenland Ice Sheet meltwaters and icebergs, demonstrating the potential for high ice sheet export. Our dissolved and amorphous silica flux is 0.20 (0.06-0.79) Tmol year(-1), ∼50% of the input from Arctic rivers. Amorphous silica comprises >95% of this flux and is highly soluble in sea water, as indicated by a significant increase in dissolved silica across a fjord salinity gradient. Retreating palaeo ice sheets were therefore likely responsible for high dissolved and amorphous silica fluxes into the ocean during the last deglaciation, reaching values of ∼5.5 Tmol year(-1), similar to the estimated export from palaeo rivers. These elevated silica fluxes may explain high diatom productivity observed during the last glacial-interglacial period
Long-term changes (1979–89) in the intertidal macrozoobenthos of the Oosterschelde estuary: are patterns in total density, biomass and diversity induced by the construction of the storm-surge barrier?
Long-term changes (1979-89) in the intertidal macrozoobenthos of the Oosterschelde estuary: are patterns in total density, biomass and diversity induced by the construction of the storm-surge barrier?
CONSUMPTION OF BENTHIC INVERTEBRATES BY WATERBIRDS IN THE OOSTERSCHELDE ESTUARY, SW NETHERLANDS.
Changes in the waterbird populations of the Oosterschelde (SW Netherlands) as a result of large-scale coastal engineering works
CHANGES IN THE WATERBIRD POPULATIONS OF THE OOSTERSCHELDE (SW NETHERLANDS) AS A RESULT OF LARGE-SCALE COASTAL ENGINEERING WORKS.
A
Uso de drogas psicotrópicas por estudantes: prevalência e fatores sociais associados Use of psychotropics drugs among students: prevalence and associated social factors
OBJETIVO: Determinar a prevalência do uso pesado de drogas por estudantes de primeiro e segundo graus em uma amostra de escolas públicas e particulares, e identificar fatores demográficos, psicológicos e socioculturais associados. MÉTODOS: Trata-se de um estudo transversal com uma técnica de amostragem do tipo intencional comparando-se escolas públicas de áreas periféricas e centrais e escolas particulares. Foi utilizado um questionário anônimo de autopreenchimento. A amostra foi constituÃda por 2.287 estudantes de primeiro e segundo graus da cidade de Campinas, SP, no ano de 1998. Considerou-se uso pesado, o uso de drogas em 20 dias ou mais nos 30 dias que antecederam a pesquisa. Para análise estatÃstica, utilizou-se a análise de regressão logÃstica politômica - modelo logito, visando identificar fatores que influenciem este modo de usar drogas. RESULTADOS: O uso pesado de drogas lÃcitas e ilÃcitas foi de: álcool (11,9%), tabaco (11,7%), maconha (4,4%), solventes (1,8%), cocaÃna (1,4%), medicamentos (1,1%), ecstasy (0,7%). O uso pesado foi maior entre os estudantes da escola pública central, do perÃodo noturno, que trabalhavam, pertencentes aos nÃveis socioeconômicos A e B, e cuja educação religiosa na infância foi pouco intensa. CONCLUSÕES: Maior disponibilidade de dinheiro e padrões especÃficos de socialização foram identificados como fatores associados ao uso pesado de drogas em estudantes.<br>OBJECTIVE: To determine the prevalence of the heavy use of drugs among elementary and high school students in a sample of public and private schools, and to identify associated demographic, psychological, cultural and social factors. METHODS: This report describes a cross-sectional study using an intention-type sampling technique that compared public schools in central and peripheral areas and private schools. An anonymous self-administered questionnaire was applied. The sample consisted of 2,287 elementary and high school students in the city of Campinas in 1998. Heavy use of drugs was defined as the use of drugs on 20 or more days during the 30 days preceding the survey (WHO, 1981). For the statistical analysis, polytomic logistic regression analysis (logit model) was utilized to identify factors that influenced this manner of using drugs. RESULTS: Heavy use of legal and illegal drugs was found as follows: alcohol (11.9%), tobacco (11.7%), marijuana (4.4%), solvents (1.8%), cocaine (1.4%), medications (1.1%) and ecstasy (0.7%). The heavy use of drugs was greatest among students at the city-center public school who had daytime jobs and studied in the evenings. These students were in the A and B socioeconomic classes and had had little religious education during childhood. CONCLUSIONS: Greater availability of cash and specific socialization patterns were identified as factors associated with the heavy use of drugs among students