129 research outputs found
Determinantes regionais da sobrevivência e da mortalidade das empresas : o caso português
O objectivo do presente trabalho consiste fundamentalmente, em identificar
e analisar os principais determinantes da sobrevivência e da mortalidade das empresas
em Portugal, no ano 2006, com recurso às técnicas próprias de árvores de classificação
binária. No que diz respeito à mortalidade empresarial, o modelo utilizado, árvore
de classificação binária demonstrou que quanto maior for o número de nascimentos
reais de empresas num determinado sector maior será a mortalidade destas. Para os
determinantes da sobrevivência, os nossos resultados evidenciam que o número médio
do pessoal ao serviço nos nascimentos das empresas afecta as suas sobrevivências, ou
seja, as empresas que iniciam as suas actividades com maior número de pessoal ao
serviço têm maior probabilidade de sobreviver.Fundação para a Ciência e a Tecnologia (FCT
Marine organism sulfated polysaccharides exhibiting significant antimalarial activity and inhibition of red blood cell invasion by Plasmodium
The antimalarial activity of heparin, against which there are no
resistances known, has not been therapeutically exploited due to
its potent anticoagulating activity. Here, we have explored the
antiplasmodial capacity of heparin-like sulfated polysaccharides
from the sea cucumbers Ludwigothurea grisea and Isostichopus
badionotus, from the red alga Botryocladia occidentalis, and
from the marine sponge Desmapsamma anchorata. In vitro
experiments demonstrated for most compounds significant
inhibition of Plasmodium falciparum growth at low-anticoagulant
concentrations. This activity was found to operate through
inhibition of erythrocyte invasion by Plasmodium, likely
mediated by a coating of the parasite similar to that observed
for heparin. In vivo four-day suppressive tests showed that
several of the sulfated polysaccharides improved the survival of
Plasmodium yoelii-infected mice. In one animal treated with I.
badionotus fucan parasitemia was reduced from 10.4% to
undetectable levels, and Western blot analysis revealed the
presence of antibodies against P. yoelii antigens in its plasma.
The retarded invasion mediated by sulfated polysaccharides, and
the ensuing prolonged exposure of Plasmodium to the immune
system, can be explored for the design of new therapeutic
approaches against malaria where heparin-related polysaccharides
of low anticoagulating activity could play a dual role as drugs
and as potentiators of immune responses
Modification and Optimization of Activated Carbons for Phenolic Compounds Removal
Phenols are generally considered to be one of the important organic pollutants discharged into the environment causing unpleasant taste and odour of drinking water. Development of inexpensive adsorbents from industrial wastes for the treatment of wastewaters is an important area in environmental sciences. For the phenolic compounds removal, it appears that the pH of the solution, the real surface area of the solid, and functional groups play a major role. The objective of this study was to screen various adsorbents for potential application for the removal of phenolic compounds for drinking water concentration range. The adsorbents used in this study were AC prepared from recycled PET and AC prepared from cork submitted to a reduction post treatment
Direct Nitrogen Enrichment of Activated Carbon Produced from Synthetic or Natural Precursor
The specific application of activated carbons (AC) as adsorbents for gases and vapours depends on the properties of pollutants to be removed, but the performance of the AC depends on various properties. If their porosity is the main parameter in gas adsorption, the chemical nature of their surface plays a significant role in liquid phase interactions and in their usefulness as catalyst support materials. Of particularly interest are the AC containing heteroatoms, such as oxygen, hydrogen, phosphorus, sulphur and nitrogen. Generally, the AC containing various nitrogen groups,present more basic character and increased adsorption of acidic agents is expected. These AC
found widespread applications as adsorbents for hydrogen sulphide, sulphur dioxide, sulphur and carbon dioxide and as catalysts for selective oxidation of hydrogen sulphide
Microporosity evaluation of active carbon from polish lignite by the use of ethanol
Microporous activated carbons prepared by KOH chemical activation or steam activation from lignite were characterised by adsorption of N2 at 77 K and CO2 at 298 K. Subsequently, the adsorption of ethanol was carried out and complemented by adsorption of benzene and cyclohexane. The isotherm analysis included application of the αs method using ethanol reference data obtained here by also studying non-porous carbon blacks. The work confirmed that ethanol is an experimentally convenient adsorptive to use and leads to results in overall agreement with those obtained using other probe molecules. Of particular interest was the observation that ethanol can gain access to the whole microporosity even in the case of samples containing constricted micropore entrances
Activated Carbon Post Treatment - Influence on Phenolic Compounds Removal
● AC preparation from different precursors and their modification / optimisation with sodium hydroxide and urea to improve the adsorption
capacities for phenolic compounds from the liquid phase.
● Comparative study of the influence of textural and chemical parameters of AC on the liquid phase adsorption
Modification and Optimization of Activated Carbons for Phenolic Compounds removals
Phenols are generally considered to be one of the important organic pollutants discharged into the environment causing unpleasant taste and odour of drinking water. Development of inexpensive adsorbents from industrial wastes for the treatment of wastewaters is an important area in environmental sciences. For the phenolic compounds removal, it appears that the pH of the solution, the real surface area of the solid, and functional groups play a major role. The objective of this study was to screen various adsorbents for potential application for the removal of phenolic compounds for drinking water concentration range. The adsorbents used in this study were AC prepared from recycled PET and AC prepared from cork submitted to a reduction post treatment
Modification and Optimization of Activated Carbons for Phenolic
Phenolic compounds are generally considered to be one of the important organic
pollutants discharged into the environment causing unpleasant taste and odour of drinking water [1,2]. So,
removal of phenolics compounds from industrial effluents is required before sewage disposal. The
development of inexpensive adsorbents from industrial wastes for the treatment of wastewaters is an
important area in environmental sciences. For the phenolic compounds removal, it appears that the pH of
the solution, the real surface area of the solid and functional groups play a major role. Adsorption onto
activated carbons (AC) is often considered, amongst the methods currently employed to remove inorganic
and organic pollutants, from aqueous or gaseous phases, as the most efficient and one of the most
economical. A detailed characterization of physical and chemical surface properties of an AC has become
one of the most important issues in adsorption technology because it ascertain its suitability for one or
more of the application fields
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