Search results for "Butane"
showing 10 items of 184 documents
PERFORMANCE EVALUATION OF CASCADE REFRIGERATION SYSTEMS USING DIFFERENT REFRIGERANTS
2012
Due to the negative effects of synthetic refrigerants on the environment, natural refrigerants have obtained again interest as alternative refrigerants for different applications because of their zero ODP and negligible GWP. This paper presents a thermodynamic analysis of different two-stage cascade refrigeration systems using as refrigerant carbon dioxide (R744) in low-temperature circuit, and, respectively, ammonia (R717), propane (R290), butane (R600), R404A, R410A and R134a in high-temperature circuit. The operating parameters considered in this study include condensing and evaporating temperatures in high-temperature circuit, temperature difference in the cascade heat exchanger, and e…
Cracking behavior of zeolites with connected 12- and 10-member ring channels: The influence of pore structure on product distribution
1997
n-Heptane has been cracked on a CIT-1 zeolite which has connected 12- and 10-member ring (MR) channels, and its behavior was compared with that of MCM-22 with nonconnected 12- and 10-MR channels, and SSZ-24 and BETA with unidirectional and tridirectional 12-MR channels, respectively. The kinetic rate constant is highest for CIT-1, and the decay constant is lowest. From the selectivity point of view, its behavior can be better represented by a system with large cavities (the intersections between the 12- and 10-MR) connected by windows. This gives a behavior typical of that of large pore zeolites. CIT-1 produces a remarkably high selectivity toi-C4, and specially to isobutane. This zeolite s…
Squaramide-based reagent for selective chromogenic sensing of Cu(II) through a zwitterion radical.
2010
A minimalist squaramide-based chemodosimeter for Cu(2+) is described. Upon selective chelation to 2, Cu(2+) induces the formation of a highly colored zwitterionic radical, which is kinetically stable for hours. The presence of a radical is confirmed by EPR and ESI-MS. It is then possible to use reagent 2 for visual and selective sensing of Cu(2+) at neutral pH.
Numerical evidence for a thermal driving force during adsorption of butane in silicalite.
2009
International audience; The transport properties of nano-porous materials determine their applicability, e.g. as separators or catalysts (J. Ka¨rger, D. Ruthven. Diffusion in zeolites, Wiley, New York (1991); L.V.C. Rees, D. Shen. Adsorption of gases in zeolite molecular sieves. In Introduction to Zeolite Science and Practice, Studies in surface science and catalysis, H.V.C. van Bekkum, E.M. Flanigen, P.A. Jacobs, J.C. Jansen (Eds.), vol. 137, pp. 579–631, Elsevier, Amsterdam (2001)). Adsorption in zeolites is explained as a two-step process; adsorption to the external crystal surface and subsequent intra-crystalline diffusion (R. M. Barrer. Porous crystal membranes. J. Chem. Soc. Faraday T…
Fanconi anemia (FA) and crosslinker sensitivity: Re-appraising the origins of FA definition
2015
The commonly accepted definition of Fanconi anemia (FA) relying on DNA repair deficiency is submitted to a critical review starting from the early reports pointing to mitomycin C bioactivation and to the toxicity mechanisms of diepoxybutane and a group of nitrogen mustards causing DNA crosslinks in FA cells. A critical analysis of the literature prompts revisiting the FA phenotype and crosslinker sensitivity in terms of an oxidative stress (OS) background, redox-related anomalies of FA (FANC) proteins, and mitochondrial dysfunction. This re-appraisal of FA basic defect might lead to innovative approaches both in elucidating FA phenotypes and in clinical management.
Squaric Acid Mediated Synthesis and Biological Activity of a Library of Linear and Hyperbranched Poly(Glycerol)-Protein Conjugates
2012
Polymer-protein conjugates generated from side chain functional synthetic polymers are attractive because they can be easily further modified with, for example, labeling groups or targeting ligands. The residue specific modification of proteins with side chain functional synthetic polymers using the traditional coupling strategies may be compromised due to the nonorthogonality of the side-chain and chain-end functional groups of the synthetic polymer, which may lead to side reactions. This study explores the feasibility of the squaric acid diethyl ester mediated coupling as an amine selective, hydroxyl tolerant, and hydrolysis insensitive route for the preparation of side-chain functional, …
Intra- and extra-cellular DNA damage by harmine and 9-methyl-harmine
2014
It is known that b-carbolines are able to produce photosensitized damage in cell-free DNA, but there is little information on their effects on cellular DNA. Therefore, we have analyzed the DNA damage produced by harmine and 9-methyl-harmine under UVA irradiation in V79 cells, together with the associated generation of micronuclei and photocytotoxicity. The results indicate that the most frequent photoproducts generated in the cellular DNA are modified purines such as 8-oxo-7,8-dihydroguanine. Only relatively few single-strand breaks were observed. CPDs were absent, although they were generated in cell-free DNA irradiated under the same conditions. The overall extent of DNA damage in the cel…
Strukturuntersuchungen von polyamiden aus cyclischen dicarbonsäuren und piperazin durch direkten abbau im massenspektrometer
1977
Polyamide aus 1,2-Cyclobutan-, 1,2-Cyclopentan- und 1,2-Cyclohexandicarbonsaure und Piperazin wurden direkt in der Ionenquelle eines Massenspektrometers pyrolysiert. Die hohe Empfindlichkeit der massenspektrometrischen Methode erlaubt, bei Abbauraten von ca. 1%/min zu pyrolysieren und dadurch selektive thermische Abbaumechanismen neben den Fragmentierungsreaktionen nachzuweisen. Durch thermischen Abbau werden dabei Oligomere mit Piperazinendgruppen sowie gesattigte und ungesattigte Cyclobutan-, -pentan- und -hexanendgruppen gebildet. Polyamides of 1,2-cyclobutane-, 1,2-cyclopentane- and 1,2-cyclohexane-dicarboxylic acid and piperazine were pyrolyzed directly in the ion source of a mass spec…
Oxygen atom transfer reaction involving oxomolybdenum complexes with sterically bulky thiocarboxylate ligands and biochemical interesting substrates …
1999
Abstract Oxidation–reduction reactions of substrates in systems containing the complex [Mo VI O 2 (O 2 CC(S)CH 3 Ph) 2 ] 2− in methanol have been investigated as models of oxo-transfer reactions. At neutral pH, the [Mo VI O 2 (O 2 CC(S)CH 3 Ph) 2 ] 2− reacts with Me 2 PhP or n -butanethiol to yield a [Mo IV O(O 2 CC(S)CH 3 Ph) 2 ] 2− species and Me 2 PhPO or disulfide, respectively. The Mo IV O complex reduces a variety of substrates XO = Me 2 SO and pyridine N-oxide conducing formation of X = Me 2 S and pyridine. The occurrence of these reactions produces a catalytic system Me 2 PhP + XO → Me 2 PhPO + X and 2BuSH + XO → [BuS] 2 + X + H 2 O. In this work we have also included the study of …
Selective oxidative activation of isobutane on a novel vanadium-substituted bimodal mesoporous oxide V-UVM-7
2006
Abstract New vanado-silicates with a bimodal mesoporous system (V-UVM-7) and high vanadium contents (Si/V ≥ 7) have been prepared by a modification of the so-called atrane method. Its morphology consists of aggregation of nano-particles with V-MCM-41 structure, creating a second broader porous system in their interparticle space. Its structure allows to incorporate a high V contents into tetrahedral sites of the framework while keeping vanadium dispersion. V-UVM-7 catalysts are very active and selective for the direct transformation of isobutane to isobutene and methacrolein. Total conversion and methacrolein-to-isobutene ratio in the products increased with increasing vanadium contents. Th…