Kinetics of adsorption on activated carbon: application of heterogeneous vacancy solution theory

The kinetics of single component adsorption on activated carbon is investigated here using a heterogeneous vacancy solution theory (VST) of adsorption. The adsorption isotherm is developed to account for the adsorbate non-ideality due to the size difference between the adsorbate molecule and the vacant site, while incorporating adsorbent heterogeneity through a pore-width-related potential energy. The transport process in the bidisperse carbon considers coupled mass transfer in both macropore and micropore phases simultaneously. Adsorbate diffusion in the micropore network is modeled through effective medium theory, thus considering pore network connectivity in the adsorbent, with the activation energy for adsorbate diffusion related to the adsorption energy, represented by the Steele 10-4-3 potential for carbons. Experimental data of five hydrocarbons, CO2 and SO2 on Ajax carbon at multiple temperatures, as well as three hydrocarbons on Norit carbon at three temperatures are first fitted by the heterogeneous VST model to obtain the isotherm parameters, followed by application of the kinetic model to uptake data on carbon particles of different sizes and geometry at various temperatures. For the hydrocarbons studied, the model can successfully correlate the experimental data for both adsorption equilibrium and kinetics. However, there is some deviation in the fit of the desorption kinetics for polar compounds such as CO2 and SO2, due to the inadequacy of the L-J potential model in this case. The significance of viscous transport in the micropores is also considered here and found to be negligible, consistent with recent molecular simulation studies. (C) 2002 Elsevier Science Ltd. All rights reserved.

Vacancy solution theory for binary adsorption equilibria in heterogeneous carbon

A heterogeneous modified vacancy solution model of adsorption developed is evaluated. The new model considers the adsorption process through a mass-action law and is thermodynamically consistent, while maintaining the simplicity in calculation of multicomponent adsorption equilibria, as in the original vacancy solution theory. It incorporates the adsorbent heterogeneity through a pore-width-related potential energy, represented by Steele's 10-4-3 potential expression. The experimental data of various hydrocarbons, CO2 and SO2 on four different activated carbons - Ajax, Norit, Nuxit, and BPL - at multiple temperatures over a wide range of pressures were studied by the heterogeneous modified VST model to obtain the isotherm parameters and micropore-size distribution of carbons. The model successfully correlates the single-component adsorption equilibrium data for all compounds studied on various carbons. The fitting results for the vacancy occupancy parameter are consistent with the pressure change on different carbons, and the effect of pore heterogeneity is important in adsorption at elevated pressure. It predicts binary adsorption equilibria better than the IAST scheme, reflecting the significance of molecular size nonideality.

Cellular responses to Schistosoma japonicum cathepsin D aspartic protease

Lymphocyte proliferation and cytokine production were measured in groups of mice vaccinated (but not subsequently challenge infected) with recombinant forms of Schistosoma japonicum cathepsin D aspartic protease, rSjASP1 (expressed in bacteria; enzymatically inactive) and rSjASP2 (expressed in insect cells; enzymatically active). Both forms of the schistosome enzyme induced significant proliferation of splenocytes recovered from vaccinated mice, and expression of interferon (IFN)-gamma, interleukin (IL)-4 and IL-10 mRNA in these cells was detected using reverse transcriptase-polymerase chain reaction. Secretion of IFN-gamma, IL-4 and IL-10 by splenocytes from vaccinated mice was confirmed and quantified using enzyme-linked immunosorbent assay. IFN-gamma was the most abundant cytokine produced, followed by IL-4 and IL-10 in rank order. These findings indicated that vaccination of mice with the schistosome protease induces a mixed Th1/Th2 cytokine response, which may explain the modest level of protection after challenge infection in cathepsin d-vaccinated mice, reported previously.

Movement through slits: cellular migration via the Slit family

First isolated in the fly and now characterised in vertebrates, the Slit proteins have emerged as pivotal components controlling the guidance of axonal growth cones and the directional migration of neuronal precursors. As well as extensive expression during development of the central nervous system (CNS), the Slit proteins exhibit a striking array of expression sites in non-neuronal tissues, including the urogenital system, limb primordia and developing eye. Zebrafish Slit has been shown to mediate mesodermal migration during gastrulation, while Drosophila slit guides the migration of mesodermal cells during myogenesis. This suggests that the actions of these secreted molecules are not simply confined to the sphere of CNS development, but rather act in a more general fashion during development and throughout the lifetime of an organism. This review focuses on the non-neuronal activities of Slit proteins, highlighting a common role for the Slit family in cellular migration.

Localization of taurine transporters, taurine, and H-3 taurine accumulation in the rat retina, pituitary, and brain

The nervous system contains an abundance of taurine, a neuroactive sulfonic acid. Antibodies were generated against two cloned high-affinity taurine transporters, referred to in this study as TAUT-1 and TAUT-2. The distribution of such was compared with the distribution of taurine in the rat brain, pituitary, and retina. The cellular pattern of [H-3] taurine uptake in brain slices, pituitary slices, and retinas was examined by autoradiography. TAUT-2 was predominantly associated with glial cells, including the Bergmann glial cells of the cerebellum and astrocytes in brain areas such as hippocampus. Low-level labeling for TAUT-2 was also observed in some neurones such as CA1 pyramidal cells. TAUT-1 distribution was more limited; in the posterior pituitary TAUT-1 was associated with the pituicytes but was absent from glial cells in the intermediate and anterior lobes. Conversely, in the brain TAUT-1 was associated with cerebellar Purkinje cells and, in the retina, with photoreceptors and bipolar cells. Our data suggest that intracellular taurine levels in glial cells and neurons may be regulated in part by specific high-affinity taurine transporters. The heterogeneous distribution of taurine and its transporters in the brain does not reconcile well with the possibility that taurine acts solely as a ubiquitous osmolyte in nervous tissues. (C) 2002 Wiley-Liss, Inc.

The role of space as both a conflict trigger and a conflict control mechanism in culturally heterogeneous workgroups

The diversity literature is replete with examples of poor outcomes in Culturally Heterogeneous Workgroups (CHWs) caused by relational difficulties. Although it is widely recognised that culture shapes people's interpretation of behavior and their style of interaction with others in the workplace, what is ill understood is what the specific conflict triggers of these conflicts are. In this paper, we argue that differences in cultural norms and views of physical and psychological space are major triggers of conflict in CHWs. Findings from a field study support the proposition that different viewpoints regarding the use of space, the inability to retreat from exposure to others, decreased interpersonal space, and privacy invasion moderate the relationship between cultural diversity in the workgroup and the type, frequency, and duration of conflict events in CHWs. The paper represents a first step in elucidating the role of space in cross-cultural interactions in the workplace and how space may be a potentially important conflict control mechanism for managers of culturally diverse workgroups.

Localization of the Epstein-Barr virus protein LMP 1 to exosomes

The Epstein-Barr virus latent membrane protein (LMP 1) functions as a constitutively active signalling molecule and associates in lipid rafts clustered with other signalling molecules. Using immunofluorescent confocal microscopy, LMP 1 was shown to have an heterogeneous distribution among individual cells which was not related to the cell cycle stage. LMP 1 was shown to localize to intracellular compartments in cells other than the plasma membrane, Co-labelling of cells with both an LIMP 1 antibody and an antibody to the Golgi protein GS15 revealed that the intracellular LMP 1 partly co-localized with the Golgi apparatus. Further confirmation of intracellular LMP 1 localization was obtained by immunoelectron microscopy with rabbit polyclonal LIMP 1 antibodies and cryosectioning. As well as being present in intracellular foci, LMP 1 co-localized in part with MHC-II and was present on exosomes derived from a lymphoblastoid cell line. Preparations of LMP 1 containing exosomes were shown to inhibit the proliferation of peripheral blood mononuclear cells, suggesting that LIMP 1 could be involved in immune regulation. This may be of particular relevance in EBV-associated tumours such as nasopharyngeal carcinoma and Hodgkin's disease, as LMP 1-containing exosomes may be taken up by infiltrating T-lymphocytes, where LMP 1 could exert an anti-proliferative effect, allowing the tumour cells to evade the immune system.

Capacity Enhancement Using MIMO Antenna Arrays in Realistic Macro-Cellular Urban Environment

In MIMO systems the antenna array configuration in the BS and MS has a large influence on the available channel capacity. In this paper, we first introduce a new Frequency Selective (FS) MIMO framework for macro-cells in a realistic urban environment. The MIMO channel is built over a previously developed directional channel model, which considers the terrain and clutter information in the cluster, line-of-sight and link loss calculations. Next, MIMO configuration characteristics are investigated in order to maximize capacity, mainly the number of antennas, inter-antenna spacing and SNR impact. Channel and capacity simulation results are presented for the city of Lisbon, Portugal, using different antenna configurations. Two power allocations schemes are considered, uniform distribution and FS spatial water-filling. The results suggest optimized MIMO configurations, considering the antenna array size limitations, specially at the MS side.

New heterogeneous catalysts for trans-esterification of triglycerides

This paper describes preliminary work done towards the development of new metallic heterogeneous catalysts to be used in the transesterification reaction of triglycerides, which is of considerable interest in the production of biodiesel. Biodiesel, is a mixture of mono-alkyl esters of fatty acids, and is currently manufactured by transesterification of triglycerides with methanol using NaOH or KOH as liquid base catalyst. Catalysts as such are corrosive to the equipment, and as these catalysts are in liquid phase must be neutralized after the completion of the reaction, typically using HCl, thus producing salt streams. Moreover, due to the presence of free fatty acids it reacts to form soaps as unwanted by-products, hence requiring more expensive separation processes. Therefore, there is a great need on the development of industrial processes for biodiesel production using solid acid catalysts. The key benefit of using solid acid catalysts is that no polluting by-products are formed and the catalysts do not have to be removed since they do not mix with the biodiesel product.

Advances on the development of novel heterogeneous catalysts for transesterification of triglycerides in biodiesel

This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work resulted in the selection of CaO and CaO modified with Li catalysts, which showed very good catalytic performances with high activity and stability. In fact FAME yields higher than 92% were observed in two consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.

DRhoGEF2 regulates cellular tension and cell pulsations in the Amnioserosa during Drosophila dorsal closure

Coordination of apical constriction in epithelial sheets is a fundamental process during embryogenesis. Here, we show that DRhoGEF2 is a key regulator of apical pulsation and constriction of amnioserosal cells during Drosophila dorsal closure. Amnioserosal cells mutant for DRhoGEF2 exhibit a consistent decrease in amnioserosa pulsations whereas overexpression of DRhoGEF2 in this tissue leads to an increase in the contraction time of pulsations. We probed the physical properties of the amnioserosa to show that the average tension in DRhoGEF2 mutant cells is lower than wild-type and that overexpression of DRhoGEF2 results in a tissue that is more solid-like than wild-type. We also observe that in the DRhoGEF2 overexpressing cells there is a dramatic increase of apical actomyosin coalescence that can contribute to the generation of more contractile forces, leading to amnioserosal cells with smaller apical surface than wild-type. Conversely, in DRhoGEF2 mutants, the apical actomyosin coalescence is impaired. These results identify DRhoGEF2 as an upstream regulator of the actomyosin contractile machinery that drives amnioserosa cells pulsations and apical constriction.

Copper Bis(oxazoline) Encapsulated in Zeolites and Its Application as Heterogeneous Catalysts for the Cyclopropanation of Styrene

A copper C(2)-symmetric bis(oxazoline), CuBox, was introduced in two forms of commercial Y zeolite: a sodium form (NaY) and an ultrastable form (NaUSY). CuBox was introduced by first partially exchanging the sodium cations of both zeolites for copper and then by refluxing the obtained materials with a solution of bis(oxazoline) (Box). Two different loadings were prepared for each form of zeolite. The materials were characterized by copper ICP-AES, elemental analysis, XPS, FTIR, TG, and nitrogen adsorption isotherms at -196 degrees C. Evidence for Box ligand location in the supercages of NaY and NaUSY zeolites and its coordination to the exchanged copper(II) was obtained by the several techniques used. The materials were all active in the cyclopropanation of styrene with ethyldiazoacetate at room temperature and diastereoselective toward trans cydopropanes. Although the materials containing Box showed low enantioselectivities, their catalytic activities were higher than the parent copper exchanged zeolites, and did not decrease with reuse, at least during three consecutive cycles.

Study on the use of MgAl hydrotalcites as solid heterogeneous catalysts for biodiesel production

This paper, reports experimental work on the use of new heterogeneous solid basic catalysts for biodiesel production: double oxides of Mg and Al, produced by calcination, at high temperature, of MgAl lamellar structures, the hydrotalcites (HT). The most suitable catalyst system studied are hydrotalcite Mg:Al 2:1 calcinated at 507 degrees C and 700 degrees C, leading to higher values of FAME also in the second reaction stage. One of the prepared catalysts resulted in 97.1% Fatty acids methyl esters (FAME) in the 1st reaction step, 92.2% FAME in the 2nd reaction step and 34% FAME in the 3rd reaction step. The biodiesel obtained in the transesterification reaction showed composition and quality parameters within the limits specified by the European Standard EN 14214. 2.5% wt catalyst/oil and a molar ratio methanol:oil of 9:1 or 12:1 at 60 -65 degrees C and 4 h of reaction time are the best operating conditions achieved in this study. This study showed the potential of Mg/Al hydrotalcites as heterogeneous catalysts for biodiesel production. (C) 2011 Elsevier Ltd. All rights reserved.

Cellular hypomethylation is associated with impaired nitric oxide production by cultured human endothelial cells

Hyperhomocysteinemia (HHcy) is a risk factor for vascular disease, but the underlying mechanisms remain incompletely defined. Reduced bioavailability of nitric oxide (NO) is a principal manifestation of underlying endothelial dysfunction, which is an initial event in vascular disease. Inhibition of cellular methylation reactions by S-adenosylhomocysteine (AdoHcy), which accumulates during HHcy, has been suggested to contribute to vascular dysfunction. However, thus far, the effect of intracellular AdoHcy accumulation on NO bioavailability has not yet been fully substantiated by experimental evidence. The present study was carried out to evaluate whether disturbances in cellular methylation status affect NO production by cultured human endothelial cells. Here, we show that a hypomethylating environment, induced by the accumulation of AdoHcy, impairs NO production. Consistent with this finding, we observed decreased eNOS expression and activity, but, by contrast, enhanced NOS3 transcription. Taken together, our data support the existence of regulatory post-transcriptional mechanisms modulated by cellular methylation potential leading to impaired NO production by cultured human endothelial cells. As such, our conclusions may have implications for the HHcy-mediated reductions in NO bioavailability and endothelial dysfunction.

Cellular uptake of BCG-loaded chitosan microparticles and in vivo evaluation of immune response following intranasal immunisation

Attenuated Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the only currently available vaccine against tuberculosis. It is highly effective in pre-exposure immunisation against TB in children when administered by subcutaneous route to newborns. However, it does not provide permanent protection in adults. In this work, polymeric chitosan-alginate microparticles have been evaluated as potential nasal delivery systems and mucosal adjuvants for live attenuated BCG. Chitosan (CS) has been employed as adjuvant and mucosal permeation-enhancer, and, together with alginate (ALG), as additive to enhance BCG-loaded microparticles (MPs) cellular uptake in a human monocyte cell line, by particle surface modification. The most suitable particles were used for vaccine formulation and evaluation of immune response following intranasal immunisation of BALB/c mice.