Numerical study of solidification of a nano-enhanced phase change material (NEPCM) in a thermal storage system

The effects of nanoparticle dispersion on solidification of a Cu-n-hexadecane nanofluid inside a vertical enclosure are investigated numerically for different temperatures of the left vertical wall. An enthalpy porosity technique is used to trace the solid-liquid interface. The resulting nanoparticle-enhanced phase change materials (NEPCMs) exhibit enhanced thermal conductivity in comparison to the base material. The effect of the wall temperature and nanoparticle volume fraction are studied in terms of the solid fraction and the shape of the solid-liquid phase front. It has been found that a lower wall temperature and a higher nanoparticle volume fraction result in a larger solid fraction. The increase in the heat release rate of the NEPCM shows its great potential for diverse thermal energy storage applications.     

Curcumin and Nano-Curcumin Mitigate Copper Neurotoxicity by Modulating Oxidative Stress,Inflammation, and Akt/GSK-3β Signaling

Copper (Cu) is essential for multiple biochemical processes, and copper sulphate (CuSO₄) is a pesticide used for repelling pests. Accidental or intentional intoxication can induce multiorgan toxicity and could be fatal. Curcumin (CUR) is a potent antioxidant, but its poor systemic bioavailability is the main drawback in its therapeutic uses. This study investigated the protective effect of CUR and N-CUR on CuSO₄-induced cerebral oxidative stress, inflammation, and apoptosis in rats, pointing to the possible involvement of Akt/GSK-3β. Rats received 100 mg/kg CuSO₄ and were concurrently treated with CUR or N-CUR for 7 days. Cu-administered rats exhibited a remarkable increase in cerebral malondialdehyde (MDA), NF-κB p65, TNF-α, and IL-6 associated with decreased GSH, SOD, and catalase. Cu provoked DNA fragmentation, upregulated BAX, caspase-3, and p53, and decreased BCL-2 in the brain of rats. N-CUR and CUR ameliorated MDA, NF-κB p65, and pro-inflammatory cytokines, downregulated pro-apoptotic genes, upregulated BCL-2, and enhanced antioxidants and DNA integrity. In addition, both N-CUR and CUR increased AKT Ser473 and GSK-3β Ser9 phosphorylation in the brain of Cu-administered rats. In conclusion, N-CUR and CUR prevent Cu neurotoxicity by attenuating oxidative injury, inflammatory response, and apoptosis and upregulating AKT/GSK-3β signaling. The neuroprotective effect of N-CUR was more potent than CUR.     

Use of hydrolyzed chlorosilanes for the preparation of high resolution glass capillary columns

Summary A new procedure for the preparation of high resolution open tubular glass capillary columns is described. This procedure involves the preparation of polysiloxane polymers obtained by alkaline hydrolysis of alkyl chlorosilane. The mixture of polysiloxane polymers is then coated on the wall of previously HCl treated glass capillary columns using a dynamic method. A base-catalysed reaction using gaseous ammonia, applied to the coated polymers leads to a stable chemically bonded stationary phase, with non-polar characteristics. This type of column is easier to prepare than conventional ones and exhibits excellent chromatographic properties, both with regard to their resolution, stability and reproducibility. The flexibility of this method permits the use of other types of commercially available chlorosilanes (i.e. methylphenyl chlorosilane) to prepare polar polysiloxane polymers suitable for analysis of complex biochemical mixtures, such as steroid metabolites.     

Complexation diastereoselective d''alcools benzyliques par le chrome hexacarbonyle. Difference de reactivite des diastereoisomeres en milieu acide.

Reaction of ortho alkyl or alkoxy phenyl carbinol with Cr(CO)₆ affords arene chromium tricarbonyl complexes with 38 to 86% of diastereoisomeric excess. The behavior of the two diastereoisomers shows a striking difference. Equimolar mixture of (RR,SS) and (RS,SR) diastereoisomers treated with concentrated sulfuric acid and methanol gives (RS,SR) ether while (RR,SS) alcool remains unchanged.     

Ultrasound assisted pseudo-digestion for determination of iron and manganese in citric acid fermentation mediums by electrothermal atomic absorption spectroscopy

A sensitive, simple and rapid method for ultra-trace determination of iron and manganese based on ultrasound assisted pseudodigestion in citric acid fermentation medium samples (beet and cane molasses and raw sugar based mediums) is described. Parameters influencing pseudo-digestion, such as sonication time, sample mass and solvent system were fully optimized. Final solutions obtained upon sonication were analyzed by electrothermal atomic absorption spectrometry (ETAAS). The best conditions for metal pseudo-digestion were as follows: a 25, 30 and 20 min sonication time for beet molasses, cane molasses and raw sugar based medium samples, respectively, 0.7 g sample mass of raw sugar based samples, 0.5 g sample mass of molasses based samples and an extraction mixture of concentrated HNO₃-H₂O₂, in 25 mL of solvent. Analytical results obtained for the two metals by ultrasound assisted pseudo-digestion and conventional wet digestion methods showed a good agreement. This method reduces the time required for all treatments (heating to dryness, cooling and separation) in comparison with conventional wet digestion method. The accuracy of the method was tested by comparing the obtained results with that of conventional wet digestion method.      

The α,5-dicarboxy-2-nitrobenzyl caging group, a tool for biophysical applications with improved hydrophilicity: synthesis, photochemical properties and biological characterization

Earlier we reported on the synthesis of α,4-dicarboxy-2-nitrobenyzl caged compounds (Schaper, K. et al. [2002] Eur. J. Org. Chem., 1037–1046). These compounds have the advantage of an increased hydrophilicity compared with the well-established α-carboxy-2-nitrobenzyl caged compounds; however, the release of the active compound becomes slower due to the introduction of the additional carboxy group. Based upon theoretical calculations we predicted that the release would become faster when the additional carboxy group is moved to the 5-position. Here we describe the synthesis and the photochemical and biological characterization of an α,5-dicarboxy-2-nitrobenyzl caged compound. The high hydrophilicity of the new caging group is maintained due to the fact that the additional carboxy moiety is preserved, while the release of the active species from the new derivative is even faster than for the reference, an α-CNB caged compound.