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21.
Dumitru Oancea Valentin Munteanu Domnina Razus 《Journal of Thermal Analysis and Calorimetry》2010,102(3):993-1000
The transient response of the input power necessary to maintain isothermal conditions after a step temperature perturbation applied to a platinum wire immersed in a gaseous fuel/air mixture allows for the measurement of the reaction heat flow rate, directly related to the rate of the catalytic combustion. The S-shaped variation of this rate in time is employed to evaluate the induction period of the catalytic ignition. The effect of mixture composition, total pressure, and catalyst temperature on the induction period for the catalytic ignition of lean to stoichiometric n-pentane/air mixtures on isothermally heated platinum wire is reported and discussed. The mixture composition was varied between 1.40 and 2.56% n-pentane in air, the total pressure between 20 and 101 kPa, and the wire temperature between 470 and 600 K. The reaction rates, turnover frequencies, overall and partial reaction orders, and activation energies were determined from the analysis of the obtained results and compared to other reported data. 相似文献
22.
Dumitru‐Claudiu Sergentu Dr. David Teze Dr. Andréa Sabatié‐Gogova Dr. Cyrille Alliot Ning Guo Dr. Fadel Bassal Dr. Isidro Da Silva Prof. Dr. David Deniaud Dr. Rémi Maurice Dr. Julie Champion Dr. Nicolas Galland Dr. Gilles Montavon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2964-2971
It is generally assumed that astatide (At?) is the predominant astatine species in basic aqueous media. This assumption is questioned in non‐complexing and non‐reductive aqueous solutions by means of high‐pressure anion‐exchange chromatography. Contrary to what is usually believed, astatide is found to be a minor species at pH=11. A different species, which also bears a single negative charge, becomes predominant when the pH is increased beyond 7. Using competition experiments, an equilibrium constant value of 10?6.9 has been determined for the formation of this species from AtO(OH) with the exchange of one proton. The identification of this species, AtO(OH)2?, is achieved through relativistic quantum mechanical calculations, which rule out the significant formation of the AtO2? species, while leading to a hydrolysis constant of AtO(OH) in excellent agreement with experiment when the AtO(OH)2? species is considered. Beyond the completion of the Pourbaix diagram of astatine, this new information is of interest for the development of 211At radiolabeling protocols. 相似文献
23.
Carpino LA Abdel-Maksoud AA Ionescu D Mansour EM Zewail MA 《The Journal of organic chemistry》2007,72(5):1729-1736
Of the three theoretically possible, Bsmoc-related, naphthothiophene sulfone-based amino-protecting groups, the two most readily available derivatives, the alpha- and beta-Nsmoc analogues, have been examined as substitutes for the Bsmoc residue in cases where the latter lead to oily protected amino acids or amino acid fluorides. All of the naphtho systems gave easily handled solid amino acid derivatives. The intermediate sulfone alcohol 11 used as the key reagent for introduction of the alpha-Nsmoc protecting group was readily made from alpha-tetralone (Scheme 1). The corresponding beta-analogue 17 was made similarly on a small scale, but due to the high cost of beta-tetralone, an alternate route involving reaction of rhodanine with alpha-naphthaldehyde was used for large-scale work (Scheme 2). All proteinogenic amino acids were converted to their alpha- and beta-Nsmoc derivatives. Deblocking studies showed that the reactivity toward deblocking by piperidine followed the order alpha-Nsmoc > Bsmoc > beta-Nsmoc. 1H NMR experiments showed that deblocking of the two new systems was mechanistically similar to that previously established for the Bsmoc derivative in that the reaction is initiated by Michael addition to the beta-carbon atom of the alpha,beta-unsaturated sulfone system. Application of alpha- and beta-Nsmoc amino acids to the solid-phase synthesis of two model peptides was examined. An advantage of the alpha-Nsmoc system over the long-known Bsmoc system proved to be the milder conditions needed for the deblocking step relative to the Bsmoc case, which is itself more readily deblocked than the classic Fmoc analogue. 相似文献
24.
Ranjbarzadeh Ramin Akhgar Alireza Taherialekouhi Roozbeh DOrazio Annunziata Mohammad Sajadi S. Ghaemi Ferial Baleanu Dumitru 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7509-7521
Journal of Thermal Analysis and Calorimetry - In this research, the effect of using GO/ water nanofluid as a coolant fluid in an isothermal heat transfer system was studied. At first, to evaluate... 相似文献
25.
Mihai Cosmin Corobea Oana Muhulet Florin Miculescu Iulian Vaile Antoniac Zina Vuluga Dorel Florea Dumitru Mircea Vuluga Maria Butnaru Daniela Ivanov Stefan Ioan Voicu Vijay Kumar Thakur 《先进技术聚合物》2016,27(12):1586-1595
In this study, a new class of heterogeneous membranes based on cellulose acetate (CA) polymer and a complex filler clay‐silica nanowires (SiO2NWs) was investigated for potential biomedical applications. SiO2NWs were synthesized using natural clay through a facile sol–gel method and were dispersed in the polymer solution by sonication in the 1.25, 2.5, and 5% weight ratio to the CA acetate polymer. Membranes were subsequently prepared via phase inversion by precipitation of the CA polymer in water. The pristine CA membrane and SiO2NWs based nanocomposites membranes were characterized using different characterization techniques. The presence of the SiO2NWs in the CA membrane was found to significantly enhance the protein retention, water wettability and thermal as well as mechanical properties in comparison to the pristine CA membrane. Water flows studies at different temperatures and the retention of bovine serum albumin have been studied and the nanocomposite membranes were found to exhibit superior performances compared with the pristine CA membranes. SiO2NWs‐CA membranes showed a much higher stability to the water temperature change during separation than CA membranes. Morphological changes clearly revealed that the composite membrane were much more compact than the pristine CA membranes. The rabbit dermal fibroblasts cell viability in cultures after 72 hr of incubation was found to be greater than 80%. These newly synthesized composite membranes exhibit a high potential to be used for various medical applications because of their non‐cytotoxic characteristics. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
26.
Raluca Dumitru Florica Manea Lavinia Lupa Cornelia Păcurariu Adelina Ianculescu Anamaria Baciu Sorina Negrea 《Journal of Thermal Analysis and Calorimetry》2017,128(3):1305-1312
Nanosized cobalt aluminate (CoAl2O4) was prepared by thermolysis of heteronuclear coordination compound, namely [Al2Co(C2O4)4(OH2)6]. The synthesized precursor was characterized by chemical analysis, vibrational spectra and thermal analysis. The cobalt aluminate obtained after a heating treatment of the precursor at 700 °C was characterized by IR, XRD, TEM coupled with SAED measurements. Two types of carbon-based electrodes, glassy carbon and boron-doped diamond electrodes were decorated with the obtained cobalt aluminate in order to enhance the electroanalytical performance for the tetracycline (TC) detection in the aqueous solutions. Cyclic voltammetry technique was used to determine the effect of the nanosized CoAl2O4 on the electrochemical oxidation of TC and as consequence, for TC detection at both carbon-based electrodes. The obtained cobalt aluminate exhibited the electrocatalytic activity toward TC detection in direct relation with the type of the carbon substrate, which allowed enhancing the electroanalytical parameters of TC detection in the aqueous solution. 相似文献
27.
Dumitru Popa 《Archiv der Mathematik》2014,103(3):291-300
We use the Maurey–Rosenthal factorization theorem to give a characterization of almost summing and multiple almost summing multilinear operators on a cartesian product of l p spaces. As applications we give the necessary and sufficient conditions for the multiplication operator on l p spaces be almost summing and multiple almost summing. 相似文献
28.
We provide existence results of multiple solutions for quasilinear elliptic equations depending on a parameter under the Neumann and Dirichlet boundary condition. Our main result shows the existence of two opposite constant sign solutions and a sign changing solution in the case where we do not impose the subcritical growth condition to the nonlinear term not including derivatives of the solution. The studied equations contain the \(p\) -Laplacian problems as a special case. Our approach is based on variational methods combining super- and sub-solution and the existence of critical points via descending flow. 相似文献
29.
We prove that, if F, G: 𝒞 → 𝒟 are two right exact functors between two Grothendieck categories such that they commute with coproducts and U is a generator of 𝒞, then there is a bijection between Nat(F, G) and the centralizer of Hom𝒟(F(U), G(U)) considered as an Hom𝒞(U, U)-Hom𝒞(U, U)-bimodule. We also prove a dual of this result and give applications to Frobenius functors between Grothendieck categories. 相似文献
30.
Dumitru Popa 《Rendiconti del Circolo Matematico di Palermo》2012,61(3):307-319
We introduce the notion of multilinear nuclear operator with respect to a partition and extend Grothendieck??s characterizations of nuclear linear operators into $l_{1},$ resp. $L_{1}( \mu ),$ in this new setting. We give the necessary and sufficient conditions for a natural operator to be nuclear with respect to a partition. 相似文献