The integral mean diffusivity for particle-gas mass transfer calculations under thermal plasma conditions

Plasma Chemistry and Plasma Processing - A new integral mean diffusivity is proposed for the calculation of the mass transfer rate around a small particle immersed in a thermal plasma gas....     

Syntheses of New Unsymmetrical 2,5‐Disubstituted‐1,3,4‐oxadiazoles and 1,2,4‐Triazolo[3,4‐b]‐1,3,4‐thiadiazoles Bearing Thieno[2,3‐c]pyrazolo Moiety

New series of (thieno[2,3‐c]pyrazolo‐5‐yl)‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazoles 10a , 10b , 10c and (thieno[2,3‐c]pyrazol‐5‐yl)‐1,3,4‐oxadiazol‐3(2H)‐yl)ethanones 6a , 6b , 6c has been synthesized from thieno[2,3‐c]pyrazole‐5‐carbohydrazide 3 by multistep reaction sequence. (5‐Aryl‐1,3,4‐oxadiazol‐2‐yl)‐1H‐thieno[2,3‐c]pyrazoles 4a , 4b , 4c were also synthesized from thieno[2,3‐c]pyrazole‐5‐carbohydrazide 3 by cyclization with various aromatic carboxylic acids. The hydrazide 3 was obtained by reaction of thieno[2,3‐c]pyrazole‐5‐carboxylate 2 with hydrazine hydrate in good yield, and compound 2 was obtained by the reaction of 5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde 1 and 2‐ethyl thioglycolate in presence of sodium alcoholate in good yield.     

New Synthesis and Reactions of Ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate

Synthesis of ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate 5 has been achieved via abnormal Beckmann rearrangement of o‐chloroaldehyde 1 . Reaction of o‐aminocarbonitrile 5 with concentrated H₂SO₄ furnished expected o‐aminocarboxamide pyrazole 6 . Key intermediates o‐aminocarbonitrile 5 and o‐aminocarboxamide 6 were successfully utilized for the synthesis of pyrazolopyrimidine derivatives. The replacement of Cl in o‐chlorocarbonitrile 3 with secondary amine furnished new synthon 13 , which was further used for the synthesis of polysubstituted heterocycles. The obtained new products were well characterized by IR, ¹H and ¹³C NMR, and mass spectra.     

A rapid and highly sensitive UPLC-QTOF MS method for quantitative evaluation of Nardostachys jatamansi using Nardin as the marker

Nardostachys jatamansi DC. is a highly reputed Medhya and Nootropic (Learning and Memory) Ayurvedic medicinal plant. Its use as herbal medicine singly and as an ingredient of multi‐herbal formulations is fast increasing. In order to authenticate and evaluate it quantitatively, its standardization is highly warranted with respect to a reliable marker. In this connection a rapid and highly sensitive UPLC‐QTOF MS method has been developed. The analysis was carried out on an Acquity BEH C₁₈ column with gradient elution of methanol–water and 3 mm ammonium acetate using QTOF mass detector in negative ionization mode. The method was validated over a concentration range of 9.76–156.25 ng/mL nardin. The calibration curve is linear with the correlation coefficient (r) and coefficient of determination (R²) were 0.9997 and 0.9995 respectively. The LOD and LOQ were 3.050 and 9.277 ng/mL respectively. The recovery of nardin in the range 96.36–111.13% achieved from spiked samples was consistent and reproducible. The inter‐day and intra‐day assay precision of the analytes over the entire concentration range was less than 5%. The developed method required only 4 min for chromatography to authenticate and quantify the marker, viz. nardin in N. jatamansi samples, in addition to the sample preparation time. Copyright © 2010 John Wiley & Sons, Ltd.     

Discovery of Elusive K4O6, a Compound Stabilized by Configurational Entropy of Polarons

Synthesis of elusive K₄O₆ has disclosed implications of crucial relevance for new solid materials discovery. K₄O₆ forms in equilibrium from K₂O₂ and KO₂, in an all‐solid state, endothermic reaction at elevated temperature, undergoing back reaction upon cooling to ambient conditions. This tells that the compound is stabilized by entropy alone. Analyzing possible entropic contributions reveals that the configurational entropy of “localized” electrons, i.e., of polaronic quasi‐particles, provides the essential contribution to the stabilization. We corroborate this assumption by measuring the relevant heats of transformation and tracking the origin of entropy of formation computationally. These findings challenge current experimental and computational approaches towards exploring chemical systems for new materials by searching the potential energy landscape: one would fail in detecting candidates that are crucially stabilized by the configurational entropy of localized polarons.     

Enantiomeric deoxycholic acid: total synthesis, characterization, and preliminary toxicity toward colon cancer cell lines

Deoxycholic acid (DCA) is an endogenous secondary bile acid implicated in numerous pathological conditions including colon cancer formation and progression and cholestatic liver disease. DCA involvement in these disease processes results partly from its ability to modulate signaling cascades within the cell, presumably through both direct receptor activation and general detergent mediated membrane changes. To further explore DCA induced changes in cell signaling, we completed a total synthesis of enantiomeric deoxycholic acid (ent-DCA) from achiral 2-methyl-1,3-cyclopentanedione. Using a modified method of the synthesis of ent-testosterone that proceeds through the (R)-(-)-Hajos-Parrish ketone, we have completed the successful synthesis of ent-DCA in 25 steps with a yield of 0.3% with all stereochemical assignments of the product confirmed by X-ray crystallography. Our studies toward this synthesis also uncovered the methodology for the development of a novel A,B-cis steroidal skeleton system containing a C3-C9 single bond as well as conditions to selectively ketalize the typically less reactive 12-carbonyl in poly-keto A,B-cis androgens. The critical micelle concentration (cmc) of ent-DCA, determined by a dye solubilization method, was identical to the cmc of natural DCA. Toxicity studies toward HT-29 and HCT-116 human colon cancer cell lines demonstrated that ent-DCA had similar effects on proliferation, yet showed a markedly decreased ability to induce apoptosis as compared to natural DCA.     

Knudsen effect on plasma-particle mass transfer. I. Formulation and application to self-diffusion

The Knudsen effect on mass transfer between a plasma gas and a small particle is investigated. A predictive model is developed by incorporating the Z-potential approach into the jump theory. The predictions of the model are explored through a case study. The results indicate that the Knudsen effect is significant and depends strongly on the particle size and the surface conditions. The plasma and the particle surface temperatures are also found to be determining factors. Under certain conditions, it is observed that the Knudsen effect can enhance the plasma-particle mass transfer, contrary to the predictions of the previous near-isothermal models.