The effect of rapid rotation on a vertical bridgman furnace at large Rayleigh number

In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate.     

Liquid secondary ion mass spectrometry of porphyrin dimers: reduction reactions and structural characterisation

New synthesised porphyrin dimers, with an amide or ester linkage between the two porphyrin units, were studied using liquid secondary ion mass spectrometry (LSIMS). The formation of reduced species was observed for all the compounds and it was found that the extent of reduction is dependent on the matrix used and on the structure of the porphyrin dimer. The main fragmentation pathways lead to monomer fragments resulting from cleavage of the amide or ester linkage between the two porphyrin units. The consistency of the fragmentations for all the dimers studied leads to the proposal of a common designation for the fragment ions. LSIMS, in addition to molecular weight determination, can provide important structural information for this type of compound.     

Constant neutral loss scanning for the characterization of glycerol phosphatidylcholine phospholipids

The product-ion spectra of the sodiated molecules of glycerol phosphatidylcholine phospholipids (GPC) were obtained, using fast-atom bombardment (FAB) as the ionization method, in a tandem mass spectrometer. The product-ion spectra of these sodiated molecules of GPCs were found to differ significantly from those of the protonated GPC molecules. This difference is due to the absence of the ion of m/z 184 (protonated-phosphocholine moiety) and to the presence of an ion resulting from the loss of trimethylamine (m=59 Da) from the polar head group, which is the dominant fragmentation. This characteristic neutral loss provides a means of identification of this class of phospholipids and of differentiation from other phospholipid classes in complex mixtures by performing a constant-neutral-loss scan of 59.     

Influence of trace elements supplementation on the production of recombinant frutalin by Pichia pastoris KM71H in fed-batch process

Frutalin, a galactose-specific lectin used to detect specific tumour markers, is a protein with low expression level in breadfruit. In the present study, fed-batch fermentation in a stirred tank bioreactor was used as a strategy to enhance protein production by a recombinant Pichia pastoris KM71H. By using this process, the production of recombinant frutalin was 4-fold higher than the value obtained in shaker flasks batch assays. Supplementation of the fermentation medium with trace elements (Pichia trace minerals, PTM) was also evaluated in order to stimulate production of the recombinant protein. The addition of PTM to the minimum medium afforded a recombinant protein production of 13.4 mg L^?1, which was 2.5-fold higher than that achieved from the culture medium without PTM supplementation. These results are significant as the development of strategies to improve the production of recombinant frutalin may broaden its application in cancer diagnosis.     

Zn[aminoacid]2 hybrid materials applied as heterogeneous catalysts in the synthesis of β-enaminones

Hybrid materials have seized attention from scientific community mainly as heterogenic catalysts in organic reactions on a large scale succeeding in some organic compounds with high yields. One of the most important classes of hybrid materials used for this purpose involves the complexation of Zn and aminoacids. Herein, we introduced Zn[Pro]₂ and Zn[Gly]₂ in the synthesis of several β-enaminones via solvent free protocol and using an ultrasound device.     

Optimization and validation of organochlorine compounds in adipose tissue by SPE‐gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C₁₈‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP₁₈ SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C₁₈‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of Phenothiazine Hybrids with Potential Medicinal Interest: A Review

The molecular hybridization approach has been used to develop compounds with improved efficacy by combining two or more pharmacophores of bioactive scaffolds. In this context, hybridization of various relevant pharmacophores with phenothiazine derivatives has resulted in pertinent compounds with diverse biological activities, interacting with specific or multiple targets. In fact, the development of new drugs or drug candidates based on phenothiazine system has been a promising approach due to the diverse activities associated with this tricyclic system, traditionally present in compounds with antipsychotic, antihistaminic and antimuscarinic effects. Actually, the pharmacological actions of phenothiazine hybrids include promising antibacterial, antifungal, anticancer, anti-inflammatory, antimalarial, analgesic and multi-drug resistance reversal properties. The present review summarizes the progress in the development of phenothiazine hybrids and their biological activity.     

Thermal relaxation times and heat conduction in β-cristobalite and α-quartz silica structures

Several studies have shown the key role of the rigid unit modes, i.e. rotational motions between neighbouring SiO₄ tetrahedra, in glass and in β-cristobalite due to the disorder generated by the large atomic amplitudes. They do not however reach a conclusion concerning heat conduction. To determine the nature of the heat carriers in the amorphous phase, we carry out an ultrashort timescale analysis of heat transfer in β-cristobalite; the behaviour is comparable to that of amorphous silica, as shown by our density of states and heat flux autocorrelation function calculations. We prove that rigid unit modes can be identified as the heat carriers by showing that the thermal relaxation time is in very good agreement with the rigid unit mode relaxation time predicted in the literature. Finally, we provide thermal conductivity data for β-cristobalite which are not available in the literature.