Application of a simplified method based on regular regime approach to determine the effective moisture diffusivity of mixture of low molecular weight sugars and maltodextrin during desorption

The binary diffusivities of water in low molecular weight sugars; fructose, sucrose and a high molecular weight carbohydrate; maltodextrin (DE 11) and the effective diffusivities of water in mixtures of these sugars (sucrose, glucose, fructose) and maltodextrin (DE 11) were determined using a simplified procedure based on the Regular Regime Approach. The effective diffusivity of these mixtures exhibited both the concentration and molecular weight dependence. Surface stickiness was observed in all samples during desorption, with fructose exhibiting the highest and maltodextrin the lowest. (C) 2002 Elsevier Science Ltd. All rights reserved.

Molecular orbital theory calculations of the H2O-carbon reaction

Carbon gasification with steam to produce H-2 and CO is an important reaction widely used in industry for hydrogen generation. Although the literature is vast, the. mechanism for the formation of H-2 is still unclear. In particular, little has, been done to investigate the potential of molecular orbital theory to distinguish different mechanism possibilities. In this work, we used molecular orbital theory to demonstrate a favorable energetic pathway where H2O is first physically adsorbed on the virgin graphite surface with negligible change in molecular structure. Chemisorption occurs via O approaching the carbon edge site with one H atom stretching away from the O in the transition state. This is followed by a local minimum. state in which the stretching H is further disconnected from the O atoms and the remaining OH group is still on the carbon edge site. The disconnected H then pivot around the OH group to bond with the H of the OH group and forms H-2. The O atom remaining on the carbon edge site is subsequently desorbed as CO. The reverse occurs when H-2 reacts with the surface oxygen to produce H2O.

Use of liquid phase adsorption for characterizing pore network connectivity in activated carbon

A simple percolation theory-based method for determination of the pore network connectivity using liquid phase adsorption isotherm data combined with a density functional theory (DFT)-based pore size distribution is presented in this article. The liquid phase adsorption experiments have been performed using eight different esters as adsorbates and microporous-mesoporous activated carbons Filtrasorb-400, Norit ROW 0.8 and Norit ROX 0.8 as adsorbents. The density functional theory (DFT)-based pore size distributions of the carbons were obtained using DFT analysis of argon adsorption data. The mean micropore network coordination numbers, Z, of the carbons were determined based on DR characteristic plots and fitted saturation capacities using percolation theory. Based on this method, the critical molecular sizes of the model compounds used in this study were also obtained. The incorporation of percolation concepts in the prediction of multicomponent adsorption equilibria is also investigated, and found to improve the performance of the ideal adsorbed solution theory (IAST) model for the large molecules utilized in this study. (C) 2002 Elsevier Science B.V. All rights reserved.

Molecular confirmation of an adenovirus in brushtail possums (Trichosurus vulpecula)

Partial genome characterisation of a non-cultivable marsupial adenovirus is described. Adenovirus-like particles were found by electron microscopy (EM) in the intestinal contents of brushtail possums (Trichosurus vulpecula) in New Zealand. Using degenerate PCR primers complementary to the most conserved genome regions of adenoviruses, the complete nucleotide sequence of the penton base gene, and partial nucleotide sequences of the DNA polymerase, hexon, and pVII genes were obtained. Phylogenetic analysis of the penton base gene strongly suggested that the brushtail possum adenovirus (candidate PoAdV-1) belongs to the recently proposed genus Atadenovirus. Sequence analysis of the PCR products amplified from the intestinal contents of brushtail possums originating from different geographical regions of New Zealand identified a single genotype. This is the first report of molecular confirmation of an adenovirus in a marsupial.

Testing the applicability of molecular genetic markers to population analyses of scleratinian corals

The abundance of coral reefs worldwide is in decline, and despite the ecological importance of reefs, only a limited number of DNA markers have been identified for scleractinian coral genetic studies. This paper addresses the search for new coral molecular markers and investigates the applicability of the cytochrome c oxidase subunit I (COI), the internal transcribed spacer region 1 (ITS1), and the pocilloporin gene to the question of intraspecific variation in the scleractinian coral Pocillopora verrucosa along the southeast African coastline. The COI fragment was 710 bp long and was identical for P. verrucosa (n = 10) and P. damicornis (n = 3). Only two different ITS1 sequences were found (differing by 13 bp insertion), but more importantly, 24% of the sequences were heterogenous indicating that different multiple copies of the sequence exist. Pocilloporin is an intronless gene that was absolutely conserved throughout all P. verrucosa populations (n = 50). Thus, the three DNA regions studied appear unsuitable for the population genetic analyses of P. verrucosa.

Characterization of micro-mesoporous carbonaceous materials. Calculations of adsorption isotherm of hydrocarbons

In this paper we apply a method recently developed by Do and co-workers(1) for the prediction of adsorption isotherms of pure vapors on carbonaceous materials. The information required for the prediction is the pore size distribution and the BET constant, C, of a corresponding nonporous surface (graphite). The dispersive adsorption force is assumed to be the dominant force in adsorption mechanism. This applies to nonpolar and weakly polar hydrocarbons. We test this predictive model against the adsorption data of benzene, toluene, n-pentane, n-hexane, and ethanol on a commercial activated carbon. It is found that the predictions are excellent for all adsorbates tested with the exception of ethanol where the predicted values are about 10% less than the experimental data, and this is probably attributed to the electrostatic interaction between ethanol molecules and the functional groups on the carbon surfaces.

Effects of adsorbate-adsorbate interaction in the description of adsorption isotherm of hydrocarbons in micro-mesoporous carbonaceous materials

In this paper, we present a model accounting for the adsorbate-adsorbate interaction in the adsorbed phase in the description of adsorption of pure vapors on carbonaceous materials. The details of the adsorbate-adsorbate interaction of a particular species are obtained from the analysis of its adsorption data on non-porous carbon black. The predictability of the model is tested against the adsorption isotherm data for benzene, toluene, n-pentane, n-hexane, carbon tetrachloride, methanol and ethanol on microporous activated carbon. It was found that the model prediction for non-polar adsorbates are satisfactory while it under-predicts for polar adsorbates, which is attributed to their additional interaction with functional groups. (C) 2002 Elsevier Science B.V. All rights reserved.

Adsorption of aromatic compounds by activated carbon: Effects of functional groups and molecular size

The adsorption of three aromatic compounds on to an untreated carbon was investigated. The solution pH was lowered in all experiments so that all the solutes were in their molecular forms. It was shown that the difference in the maximum adsorption of the solutes was mainly a result of the difference in the sizes of the molecules and their functional groups. Further-more, it was illustrated that the packing arrangement was most likely edge-to-face (sorbate-sorbent) with various tilt angles. On the other hand, the affinity and heterogeneity of the adsorption systems were apparently related to the pK(a) values of the solutes.

Short report: Molecular evaluation of the efficacy of chloroquine treatment of uncomplicated Plasmodium falciparum malaria in East Timor

The efficacy of chloroquine treatment of uncomplicated Plasmodium falciparum malaria in East Timor was investigated via molecular tools. Genotyping of the polymorphic markers msp1 and msp2 was performed to investigate the number and type of parasite alleles in pre- and posttreatment blood samples collected from 48 patients. Patients were infected with a minimum of 8 msp1 and 14 msp2 allelic types of parasite, and 43% of the patients had more than one allelic type before treatment. The genotyping also revealed that 66.7% of the patients were infected with at least one identical allelic type of parasite before and after treatment and therefore were likely to have experienced recrudescence. All parasites in pre- and posttreatment blood samples carried the K76T mutation in pfcrt, regardless of the clinical response to chloroquine. The sequence polymorphism patterns in pfcrt in the majority of parasites examined were identical to those observed in Bougainville, Papua New Guinea.

gamma-alumina nanofibers prepared from aluminum hydrate with poly(ethylene oxide) surfactant

Introducing poly(ethylene oxide) surfactant to aluminum hydrate colloids can effectively direct the crystal growth of boehmite and the crystal morphology of final gamma-alumina crystallites. Fibrous crystallites of gamma-alumina about 3-4 nm thick and 30-60 nm long are obtained. They stack randomly, resulting in a structure with a low contact area between the fibers but with a very large porosity. Such a structure exhibits strong resistance to sintering when heated to high temperatures. A sample retains a BET surface area of 68 m(2)/g, after being heated to 1473 K. The surfactant molecules form micelles that interact with the colloid particles of aluminum hydroxide through hydrogen bonding. This interaction is not sufficient to change the intrinsic crystal structure of boehmite, but induces profound changes in the morphology of boehmite crystallites and their growth. The surfactant-induced fiber formation (SIFF) process has distinct features from templated synthesis but shows similarities in some respects to biomineralization processes in which inorganic crystals with complex morphological shapes can be formed in biological systems. SIFF offers an effective approach to create new nanostructures of inorganic oxide from aqueous media.

Short report: Molecular genetic characterization of an unusually severe case of hydatid disease in Alaska caused by the cervid strain of Echinococcus granulosusi

Distinct Echinococcus granulosus life cycle patterns have been described in North America: domestic and sylvatic. Gene sequences of the sylvatic E. granulosus indicate that it represents a separate variant. Case-based data have suggested that the course of sylvatic disease is less severe than that of domestic disease. which led to the recommendation to treat cystic echinococcosis patients in the Arctic by careful medical management rather than by aggressive surgery. We recently reported the first two documented E. granalosus human cases in Alaska with accompanying severe sequelae. Here we describe the results of molecular genetic analysis of the cyst material of one of the subjects that supported identification of the parasite as the sylvatic (cervid) strain and not the domestic (common sheep strain), which was initially thought to be implicated in these unusually severe Alaskan cases.

Resistance to antiparasitic drugs: The role of molecular diagnosis

Chemotherapy is central to the control of many parasite infections of both medical and veterinary importance. However, control has been compromised by the emergence of drug resistance in several important parasite species. Such parasites cover a broad phylogenetic range and include protozoa, helminths and arthropods. In order to achieve effective parasite control in the future, the recognition and diagnosis of resistance will be crucial. This demand for early, accurate diagnosis of resistance to specific drugs in different parasite species can potentially be met by modern molecular techniques. This paper summarises the resistance status of a range of important parasites and reviews the available molecular techniques for resistance diagnosis. Opportunities for applying successes in some species to other species where resistance is less well understood are explored. The practical application of molecular techniques and the impact of the technology on improving parasite control are discussed. (C) 2002 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

Caveolae — from ultrastructure to molecular mechanisms

Almost 50 years after the first sighting of small pits that covered the surface of mammalian cells, investigators are now getting to grips with the detailed workings of these enigmatic structures that we now know as caveolae.

Elucidating the molecular mechanisms that underlie the target control of motoneuron death

Approximately half of the motoneurons generated during normal embryonic development undergo programmed cell death. Most of this death occurs during the time when synaptic connections are being formed between motoneurons and their target, skeletal muscle. Subsequent muscle activity stemming from this connection helps determine the final number of surviving motoneurons. These observations have given rise to the idea that motoneuron survival is dependent upon access to muscle derived trophic factors, presumably through intact neuromuscular synapses. However, it is not yet understood how the muscle regulates the supply of such trophic factors, or if there are additional mechanisms operating to control the fate of the innervating motoneuron. Recent observations have highlighted target independent mechanisms that also operate to support the survival of motoneurons, such as early trophic-independent periods of motoneuron death, trophic factors derived from Schwann cells and selection of motoneurons during pathfinding. Here we review recent investigations into motoneuron cell death when the molecular signalling between motoneurons and muscle has been genetically disrupted. From these studies, we suggest that in addition to trophic factors from muscle and/or Schwann cells, specific adhesive interactions between motoneurons and muscle are needed to regulate motoneuron survival. Such interactions, along with intact synaptic basal lamina, may help to regulate the supply and presentation of trophic factors to motoneurons.