Structural and surface property changes of macadamia nut-shell char upon activation and high temperature treatment

Structural and surface property changes of macadamia nut-shell (MNS) char upon activation and high temperature treatment (HTT) were studied by high-resolution nitrogen adsorption, diffuse reflectance infra-red Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption. It is found that activation of MNS char can be divided into the low extent activation which may involve the reactions of internal oxygen-containing groups and leads to the formation of comparatively uniform micropores, and the high extent activation which induces reactions between carbon and activating gas and produces a large amount of micropores. The surface functional groups (SFGs) basically increase with the increase of activation extent, but high extent activation preferentially increases the amount of -C-O and -C=O. HTT in air for a short tithe at a high temperature (1173 K) greatly increases the micropore volume and the amounts of SFGs. By appropriately choosing the activation and HTT conditions, it is possible to control both the textural structure and the type and amounts of SFG. (C) 2002 Published by Elsevier Science Ltd.

Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.

Inhibition of rat platelet aggregation by the diazeniumdiolate nitric oxide donor MAHMA NONOate

1 Inhibition of rat platelet aggregation by the nitric oxide (NO) donor MAHMA NONOate (Z-1-{N-methyl-N-[6-(N-methylammoniohexyl)amino]}diazen-l-ium-1,2-diolate) was investigated. The aims were to compare its anti-aggregatory effect with vasorelaxation, to determine the effects of the soluble guanylate cyclase inhibitor, ODQ (1H-[1,2,4]oxadiazolo[4,3-ajquinoxalin-1-one), and to investigate the possible role of activation of sarco-encloplasmic reticulum calcium-ATPase (SERCA), independent of soluble guanylate cyclase, using thapsigargin. 2 MAHMA NONOate concentration-dependently inhibited sub-maximal aggregation responses to collagen (2 - 10 mug ml(-1)) and adenosine diphosphate (ADP; 2 mum) in platelet rich plasma. It was (i) more effective at inhibiting aggregation induced by collagen than by ADP, and (ii) less potent at inhibiting platelet aggregation than relaxing rat pulmonary artery. 3 ODQ (10 mum) caused only a small shift (approximately half a log unit) in the concentration-response curve to MAHMA NONOate irrespective of the aggregating agent. 4 The NO-independent activator of soluble guanylate cyclase, YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzy] indazole; 1 - 100 mum), did not inhibit aggregation. The cGMP analogue, 8-pCPT-cGMP (8-(4-chlorophenylthio)guanosine 3'5' cyclic monophosphate; 0.1 - 1 mm), caused minimal inhibition. 5 On collagen-aggregated platelets responses to MAHMA NONOate (ODQ 10 PM present) were abolished by thapsigargin (200 nm). On ADP-aggregated platelets thapsigargin caused partial inhibition. 6 Results with S-nitrosoglutathione (GSNO) resembled those with MAHMA NONOate. Glyceryl trinitrate and sodium nitroprusside were poor inhibitors of aggregation. 7 Thus inhibition of rat platelet aggregation by MAHMA NONOate (like GSNO) is largely ODQ-resistant and, by implication, independent of soluble guanylate cyclase. A likely mechanism of inhibition is activation of SERCA.

Oxide ionic conductivity and microstructures of Sm- or La-doped CeO2-based systems

The concept of crystallographic index termed the effective index is suggested and applied to the design of ceria (CeO2)-based electrolytes to maximize oxide ionic conductivity. The suggested index considers the fluorite structure, and combines the expected oxygen vacancy level with the ionic radius mismatch between host and dopant cations. Using this approach, oxide ionic conductivity of Sm- or La-doped CeO2-based system has been optimized and tested under operating conditions of a solid oxide fuel cell. In the observation of microstructure in atomic scale, both Sm-doped CeO2 and La-doped CeO2 electrolytes had large micro-domains over 10 nm in the lattice. On the other hand, Sm or La and alkaline earth co-doped CeO2-based electrolytes with high effective index had small micro-domains around 1-3 nm in the microstructure. The large micro-domain would prevent oxide ion from passing through the lattice. Therefore, it is concluded that the improvement of ionic conductivity is reflected in changes of microstructure in atomic scale. (C) 2002 Elsevier Science B.V. All rights reserved.

Skin-friction measurements in high-enthalpy hypersonic boundary layers

Skin-friction measurements are reported for high-enthalpy and high-Mach-number laminar, transitional and turbulent boundary layers. The measurements were performed in a free-piston shock tunnel with air-flow Mach number, stagnation enthalpy and Reynolds numbers in the ranges of 4.4-6.7, 3-13 MJ kg(-1) and 0.16 x 10(6)-21 x 10(6), respectively. Wall temperatures were near 300 K and this resulted in ratios of wall enthalpy to flow-stagnation enthalpy in the range of 0.1-0.02. The experiments were performed using rectangular ducts. The measurements were accomplished using a new skin-friction gauge that was developed for impulse facility testing. The gauge was an acceleration compensated piezoelectric transducer and had a lowest natural frequency near 40 kHz. Turbulent skin-friction levels were measured to within a typical uncertainty of +/-7%. The systematic uncertainty in measured skin-friction coefficient was high for the tested laminar conditions; however, to within experimental uncertainty, the skin-friction and heat-transfer measurements were in agreement with the laminar theory of van Driest (1952). For predicting turbulent skin-friction coefficient, it was established that, for the range of Mach numbers and Reynolds numbers of the experiments, with cold walls and boundary layers approaching the turbulent equilibrium state, the Spalding & Chi (1964) method was the most suitable of the theories tested. It was also established that if the heat transfer rate to the wall is to be predicted, then the Spalding & Chi (1964) method should be used in conjunction with a Reynolds analogy factor near unity. If more accurate results are required, then an experimentally observed relationship between the Reynolds analogy factor and the skin-friction coefficient may be applied.

High frequency of BRAF mutations in nevi

To evaluate the timing of mutations in BRAF (v-raf murine sarcoma viral oncogene homolog B1) during melanocytic neoplasia, we carried out mutation analysis on microdissected melanoma and nevi samples. We observed mutations resulting in the V599E amino-acid substitution in 41 of 60 (68%) melanoma metastases, 4 of 5 (80%) primary melanomas and, unexpectedly, in 63 of 77 (82%) nevi. These data suggest that mutational activation of the RAS/RAF/MAPK pathway in nevi is a critical step in the initiation of melanocytic neoplasia but alone is insufficient for melanoma tumorigenesis.

ADH genotype does not modify the effects of alcohol on high-density lipoprotein

Background: Alcohol consumption has beneficial effects on mortality which are mainly due to reduction in cardiovascular disease. These are believed to be due, at least in part, to the increase in plasma high-density lipoprotein (HDL) which is associated with alcohol consumption. It has been proposed that ADH3 genotype modifies the relationships between alcohol intake and cardiovascular disease by altering the HDL response to alcohol. The aim of this paper was to test for effects of ADH2 and ADH3 genotypes on the response of HDL components to habitual alcohol consumption. Methods: Adult male and female subjects were genotyped for ADH2 and ADH3; and plasma HDL cholesterol, apolipoprotein A-I, and apolipoprotein A-II were measured. Nine hundred one subjects had both ADH2 and ADH3 genotypes and HDL cholesterol results, while 753 had both genotypes and all three lipid results. The effect of alcohol intake on the three measured HDL components, and a factor score derived from them, was estimated for each of the ADH2 and ADH3 genotype groups. Results: All the measured components of HDL increased with increasing alcohol consumption over the range of intakes studied, 0-4 drinks per day. There were no significant interactions between alcohol consumption and ADH2 or ADH3 genotypes. Conclusions: The concept that alcohol dehydrogenase genotype and alcohol metabolic rate modify the effects of alcohol on plasma HDL concentration is not supported by our results.

Nitrification of high strength ammonia wastewtaer treatment - process selection is the major factor.

Biological nitrogen removal via the nitrite pathway in wastewater treatment is very important in Saving the cost of aeration and as an electron donor for denitrification. Wastewater nitrification and nitrite accumulation were carried out in a biofilm airlift reactor with autotrophic nitrifying biofilm. The biofilm reactor showed almost complete nitrification and most of the oxidized ammonium was present as nitrite at the ammonium load of 1.5 to 3.5 kg N/m3.d. Nitrite accumulation was stably achieved by the selective inhibition of nitrite oxidizers with free ammonia and dissolved oxygen limitation. Stable 100% conversion to nitrite could also be achieved even under the absence of free ammonia inhibition on nitrite oxidizers. Batch ammonium oxidation and nitrite oxidation with nitrite accumulating nitrifying biofilm showed that nitrite Oxidation was completely inhibited when free ammonia is higher than 0.2 mg N/L. However, nitrite oxidation activity was recovered as soon as the free ammonia concentration was below the threshold level when dissolved oxygen concentration was not the limiting factor. Fluorescence in situ hybridization analysis of cryosectioned nitrite accumulating nitrifying biofilm showed that the β-subclass of Proteobacteria, where ammonia oxidizers belong, was distributed outside the biofilm whereas the α-subclass of Proteobacteria, where nitrite oxidizers belong, was found mainly in the inner part of the biofilm. It is likely that dissolved oxygen deficiency or limitation in the inner part of the nitrifying biofilm, where nitrite oxidizers exist, is responsible for the complete shut down of the nitrite oxidizers activity under the absence of free ammonia inhibition.

Structure of the HERG K+ channel S5P extracellular linker - Role of an amphipathic alpha-helix in C-type inactivation

The HERG K+ channel has very unusual kinetic behavior that includes slow activation but rapid inactivation. These features are critical for normal cardiac repolarization as well as in preventing lethal ventricular arrhythmias. Mutagenesis studies have shown that the extracellular peptide linker joining the fifth transmembrane domain to the pore helix is critical for rapid inactivation of the HERG K+ channel. This peptide linker is also considerably longer in HERG K+ channels, 40 amino acids, than in most other voltage-gated K+ channels. In this study we show that a synthetic 42-residue peptide corresponding to this linker region of the HERG K+ channel does not have defined structural elements in aqueous solution; however, it displays two well defined helical regions when in the presence of SDS micelles. The helices correspond to Trp(585)-Ile(593) and Gly(604)-Tyr(611) of the channel. The Trp(585)-Ile(593) helix has distinct hydrophilic and hydrophobic surfaces. The Gly(604)-Tyr(611) helix corresponds to an N-terminal extension of the pore helix. Electrophysiological studies of HERG currents following application of exogenous S5P peptides show that the amphipathic helix in the S5P linker interacts with the pore region of the channel in a voltage-dependent manner.

Compositional changes of Australia-grown Western Schley pecans [Carya illinoinensis (Wangenh.) K. Koch] during maturation

Changes in composition during the maturation of Western Schley pecans [Carya illinoinensis (Wangenh.) K. Koch] grown in Australia were investigated. Pecans of different maturity levels were collected at monthly intervals between March and June in. 1999 and 2000 and analyzed for the concentrations of moisture, total lipid, sucrose, raffinose, protein, and the minerals aluminum, boron, calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, sulfur, and zinc. Moisture, total lipid, and calcium contents changed significantly (p < 0.05) with harvest time and maturity, whereas the other components did not. Western Schley pecans grown in Australia should be harvested after the shuck has opened and it is either green or brown in color to maximize total lipid content and quality. This occurred after May 11 in 1999 and after May 17 in 2000.

Water sorption into poly[(2-hydroxyethyl methacrylate)-co-(1-vinyl-2-pyrrolidone]at 310 K

Poly(2-hydroxyethyl methacrylate) and copolymers of 2-hydroxyethyl methacrylate (HEMA) and 1-vinyl-2-pyrrolidone (VP) in the form of cylindrical samples (approximate to8mm x 20mm) have been prepared and the sorption of water into these cylinders has been studied by the mass-uptake methods and by magnetic-resonance imaging. The equilibrium water contents for the cylinders were found to vary systematically with the copolymer composition. Diffusion of water into the cylinders was found to follow Fickian behaviour for cylinders with high HEMA contents, with the diffusion coefficients obtained from mass-uptake studies dependent on the copolymer composition, varying from 1.7 x 10(-11) m(2) s(-1) for poly(HEMA) to 2.0 x 10(-11) m(2) s(-1) for poly(HEMA-co-VP) with a composition of 1:1. However, NMR-imaging studies showed that, while the profiles of the water diffusion fronts for cylinders with high HEMA contents were Fickian, that for the 1:1 copolymer was not and indicated that the mechanism was Case III. The polymers which were rich in VP were characterized by a water-sorption process which follows Case-III behaviour. (C) 2003 Society of Chemical Industry.

G-values for scission and crosslinking on γ-radiolysis of Ultem at 303 K

The radiation chemical yields G(S) and G(X) for H-linking and Y-linking models for Ultem have been calculated from molecular weight analysis by gel permeation chromatography. These G-values have been compared with the G-values obtained from analysis of soluble fractions above the gel dose, Which have been reported in previous works. An analysis of the molecular weight data in terms of H-linking and Y-linking mechanisms yielded values of G(S-H) = 1.0 x 10(-3) and G(H) = 6.0 x 10(-3) and G(S-Y) = 1.3 x 10(-2) and G(Y) = 1.8 x 10(-2). The corresponding values obtained from the solubility data were G(SH) = 0.53 x 10(-2), G(H) = 1.39 x 10(-2), G(S-Y) = 4.2 x 10(-2) and G(Y) - 4.6 x 10(-2). The origin of the disagreement between the molecular weight and solubility values is not clear, but it could arise as a result of observed microgel formation below the reported gel dose of 0.13 MGy. Whether the crosslink mechanism proceeds by an H-linking or Y-linking process is also unclear and will require direct observation of the crosslinking structures.

High energy radiation grafting of fluoropolymers

Fluoropolymers are known as chemically inert materials with good high temperature resistance, so they are often the materials of choice for harsh chemical environments. These properties arise because the carbon-fluorine bond is the strongest of all bonds between other elements and carbon, and, because of their large size, fluorine atoms can protect the carbon backbone of polymers such as poly(tetrafluoroethylene), PTFE, from chemical attack. However, while the carbon-fluorine bond is much stronger than the carbon hydrogen bond, the G values for radical formation on high energy radiolysis of fluoropolymers are roughly comparable to those of their protonated counterparts. Thus, efficient high energy radiation grafting of fluoropolymers is practical, and this process can be used to modify either the surface or bulk properties of a fluoropolymer. Indeed, radiation grafted fluoropolymers are currently being used as separation membranes for fuel cells, hydrophilic filtration membranes and matrix substrate materials for use in combinatorial chemistry. Herein we present a review of recent studies of the high energy radiation grafting of fluoropolymers and of the analytical methods available to characterize the grafts. (C) 2003 Elsevier Ltd. All rights reserved.