Knowledge gaps related to mass transfer processes involved in passive air sampling of semivolatile organic compounds and factors potentially influencing passive sampling rates (PSRs) were addressed with controlled laboratory experiments, mass transfer modeling, and a field sampling campaign. The observed non-uniform SVOC distributions within porous passive sampling media (PSMs) contradict an assumption in an earlier passive air sampling theory and proved the existence of a kinetic resistance on the PSM side. This resistance can affect PSRs as revealed by a new PAS model which is based on fundamental laws of mass transfer in air and porous media. By considering mass transfer processes within the PSM, the model is able to explain the large variations of field calibrated PSRs with temperature and between SVOC species and the two-stage uptake process, which cannot be addressed by the earlier PAS theory. Because the PSM side kinetic resistance invalidates the assumption that depuration compounds added to the PSM prior to deployment are subject to the same kinetic resistance as the sampled SVOCs, PSRs derived from the loss rates of depuration compounds can differ from the actual PSRs of the sampled SVOCs. Using such PSRs could thus introduce additional uncertainty to PAS-derived air concentrations. Experiments using XAD-resin and silica-gel filled mesh cylinder as PSMs for the uptake of SVOCs and water vapor respectively revealed that sorbent in the inner portion of the PSM does not take part in chemical uptake; PSRs are thus proportional to the interfacial transfer area but not the amount of the sorbent. Accordingly, thinner PSM can be used to reduce the amount of sorbent while keeping or even increasing the PSRs. Optimized designs of PASs could be tested time efficiently using the gravimetrical approach based on water vapor uptake by silica gel.

Knowledge gaps related to mass transfer processes involved in passive air sampling of semivolatile organic compounds and factors potentially influencing passive sampling rates (PSRs) were addressed with controlled laboratory experiments, mass transfer modeling, and a field sampling campaign. The observed non-uniform SVOC distributions within porous passive sampling media (PSMs) contradict an assumption in an earlier passive air sampling theory and proved the existence of a kinetic resistance on the PSM side. This resistance can affect PSRs as revealed by a new PAS model which is based on fundamental laws of mass transfer in air and porous media. By considering mass transfer processes within the PSM, the model is able to explain the large variations of field calibrated PSRs with temperature and between SVOC species and the two-stage uptake process, which cannot be addressed by the earlier PAS theory. Because the PSM side kinetic resistance invalidates the assumption that depuration compounds added to the PSM prior to deployment are subject to the same kinetic resistance as the sampled SVOCs, PSRs derived from the loss rates of depuration compounds can differ from the actual PSRs of the sampled SVOCs. Using such PSRs could thus introduce additional uncertainty to PAS-derived air concentrations. Experiments using XAD-resin and silica-gel filled mesh cylinder as PSMs for the uptake of SVOCs and water vapor respectively revealed that sorbent in the inner portion of the PSM does not take part in chemical uptake; PSRs are thus proportional to the interfacial transfer area but not the amount of the sorbent. Accordingly, thinner PSM can be used to reduce the amount of sorbent while keeping or even increasing the PSRs. Optimized designs of PASs could be tested time efficiently using the gravimetrical approach based on water vapor uptake by silica gel.

No description available.

Soil properties and their spatial variability was measured to provide a strong database to assess the modification in soil properties associated with future changes in land use. Surface (0--10 cm) soil samples were collected from a 9 ha, 46-year-old pasture being converted to a native tree plantation and a neighboring control pasture near Sardinilla, Panama. A small-scale nested grid of surface soil samples was replicated in the future plantation and a primary forest in the region to evaluate the spatial variability of soil properties. Seven 1 m profiles were sampled in the future plantation and litter samples were collected at the forest and the future plantation. / Assuming the three sites were identical before the conversion to pasture, the difference in surface soil organic carbon (SOC) was 0.75 kg m-2 or equivalent to a loss of 0.017 kg m-2 yr -1 since the original land-use change. The control pasture is higher in bulk density but lower in percent SOC than the future plantation, which is critical to future comparisons. / The pasture soils showed signs of soil compaction and of the homogenization of soil properties. For the 7 profiles in the future plantation, total SOC mass ranged from 13.45 to 23.80 kg m-2, and stable isotopes revealed that 82% of the SOC in the top 10 cm is derived from the pasture vegetation, down to 23% at 1 m depth. / Spatially, the full scale of spatial variability was not determined from the nested grids alone. In addition, the 15 x 15 m grid in the future plantation generally over-estimated the semivariance at the scales below 3 m. The nested grids assessed the minimum measurable semivariance below 5 m. / The precision of surface estimations from point observations can be improved by adding a 5 x 5 m grid to any large-scale sampling scheme.

<p>Background and objectives: Apoptosis is a process in which a cell programmes its own death. It is a highly organized physiological mechanism in which injured or damaged cells are destroyed. Apart from physiological stimuli however, exogenous factors can induce apoptosis. Many anti-cancer drugs work by activating apoptosis in cancer cells. Natural substances have been found to have the ability to induce apoptosis in various tumour cells and these substances have been used as templates for the construction of&nbsp / novel lead compounds in anticancer treatment. On the other hand, alkylating agents such as cisplatin, cis- [PtCl2 (NH3) 2] have been widely used as antineoplastic agents for a&nbsp / wide variety of cancers including testicular, ovarian, neck and head cancers, amongst others. However, the use of cisplatin as an anticancer agent is limited due to toxicity and resistance problems. The aim of this present study was to screen the leaves of Rhus laevigata, a South African indigenous plant, for the presence of pro-apoptotic and&nbsp / anti-proliferative natural compounds and also to screen newly synthesised palladium based complexes (15 and 57) and a platinum based complex (58) for their antineoplastic&nbsp / activities tested against a panel of cell lines. Results. The results showed that crude methanol extracts from Rhus laevigata as well as the newly synthesised palladium based complexes (15 and 57) and a platinum based complex (58) induced apoptosis in the cell lines tested, as demonstrated by the externalization of phosphatidylserine, mitochondrial membrane permeabilization,caspase-3 activation, and DNA fragmentation. Caski (cervical cancer) and H157 (non small cell lung carcinoma) cell lines treated with the methanol extract from Rhus laevigata however, were more resistant to apoptosis induction. Among the metallocomplexes, complexes 15 and 57, palladium based complexes, were the most active. Conclusion: The methanol extract from the leaves of Rhus laevigata contain pro-apoptotic and antiproliferative natural compound(s), which need to be characterised and elucidated as they could provide the much-needed lead compounds in the fight against cancer. On the other hand the newly synthesized palladium complexes also need further evaluation to&nbsp / see if they can be used as anticancer agents that can overcome the problems associated with cisplatin.</p>

No description available.

No description available.

Dissolved organic matter (DOM) is operationally defined as soluble/colloidal material passing through a 0.45~m filter paper. The importance of DOM in soils relies on its role in soil formation and weathering processes, plant and microbial assimilation and soil and water acidification. However, the scientific community studying DOM still disagrees on whether fresh or humified material is the major source of DOM within the forest floor.[...] / La matière organique dissoute (DOM) est composée de particules dissoutes et colloïdales passant au travers un filtre de 0.45 Ilm. L'importance de DOM dans les sols est liée à son rôle dans la pédogenèse, les processus d'altération des minéraux, l'assimilation par les plantes et microbes, ainsi que l'acidification des plans d'eau et des sols.[...]

Peppers are a rich source of diverse bioactive compounds with potential health-promoting properties. The levels of bioactive compounds and antioxidant activity can be affected by analytical methods, pre-harvest factors, and the quality of peppers. In order to understand the nutrient composition and antioxidant activity in peppers, determination of factors influencing the contents of bioactive compounds is important. The overall objectives were to determine the efficient conditions of sample preparation and the impact of pre-harvest factors affecting bioactive compounds and antioxidant activity. Optimal extraction procedures were developed, and HPLC methods were validated for bioactive compounds in peppers. The highest flavonoids were extracted in ethanol, while myricetin was extracted using N-N-dimethylformamide. Optimized conditions for flavonoids were obtained during 3 h of extraction time and hydrolysis in M HCl for 60 min at 95 degrees C. Capsaicinoids and ascorbic acid were simultaneously separated and extracted using a solvent mixture consisting of 3% metaphosphoric acid: ethanol (2:8) after 30 min of sonication. To determine the relationship between bioactive compounds and antioxidant activities in pepper extracts from different solvent properties, bioactive compounds were analyzed, and the antioxidant activities were assayed by 2,2,-Diphenyl-1-picryl hydrazyl (DPPH), reducing power, and degradation of deoxyribose. Hexane extracts had the highest levels of capsaicinoids and carotenoids, while methanol extracts had the highest levels of flavonoids. Strong DPPH scavenging activity and reducing power were found in lipophilic extracts, while hydrophilic extracts were appropriate for inhibition of deoxyribose degradation. Variation in content of ascorbic acid, capsaicinoids, and flavonoids was evaluated at immature and mature stages of pepper cultivars in different locations over two years. Mature peppers contained the highest levels of capsaicinoids and ascorbic acid. Flavonoids were variable at different maturity stages. Interactions between pre-harvest factors and bioactive compounds were highly significant. This study demonstrated the efficient sample preparation methods and simultaneous separation of bioactive compounds, which reduces analysis time and leads to reduced cost. The antioxidant properties were strongly associated with the concentration of bioactive compounds based on selective pepper extracts. The pepper quality can be improved by using appropriate pre-harvest conditions that increase the levels of bioactive compounds in peppers.

We review several nonparametric regression techniques and discuss their various strengths and weaknesses with an emphasis on derivative estimation and confidence band creation. We develop a generalized C(p) criterion for tuning parameter selection when interest lies in estimating one or more derivatives and the estimator is both linear in the observed responses and self-consistent. We propose a method for constructing simultaneous confidence bands for the mean response and one or more derivatives, where simultaneous now refers both to values of the covariate and to all derivatives under consideration. In addition we generalize the simultaneous confidence bands to account for heteroscedastic noise. Finally, we consider the characterization of nanoparticles and propose a method for identifying a proper subset of the covariate space that is most useful for characterization purposes.