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961.
Mohsan Nawaz Faiza Jan Iftikhar Musa Kaleem Baloch Wajid Rehman Iftikhar Ahmad 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(13):2169-2172
Single-phase giant magnetoresistance (GMR) compounds were prepared by doping the parent compound, NdMnO3, with Sr at Nd sites. The resistivity of the doped samples showed two prominent regions (Δρ/ΔT < 0, insulating and Δρ/ΔT > 0, metallic). The doped samples exhibited an enhancement in double exchange (DE) interactions causing an increase in T
c (transition temperature). Magnetic field decreased the resistance of all the samples because of the suppression of spin fluctuations
and an increase in disorder in the system. The polaron and variable range hopping (VRH) models were good for studying the
transport mechanism of electrons and understand their behavior at T > T
c. 相似文献
962.
I. S. Al’tman I. E. Agranovskii M. Choi V. A. Zagainov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(12):2097-2102
An attempt is made to critically analyze the modern state of the theory of homogeneous nucleation as concerns its ability to describe experiments with high accuracy. An analysis of the experimental data led us to conclude that the dependence of the nucleation rate on supersaturation and temperature T was not described by the theory, which underestimates the critical cluster size compared with the Gibbs-Thomson equation. The possibility of applying density functional theory (one of the latest achievements in the theory of homogeneous nucleation) was questioned. Within this theory, the Gibbs-Thomson equation remains valid even outside the classic capillary approximation. It is suggested that, to bring theory in consistency with experiment, certain fundamental propositions of the theory of nucleation should be revised. The inclusion of an additional contribution to the Gibbs energy of a cluster caused by the size dependence of the specific heat capacity of the cluster decreases the critical cluster size compared with the value calculated by the Gibbs-Thomson equation. The calculated dependence of nucleation rate on supersaturation was in agreement with the experimental results. 相似文献
963.
A series of pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines were prepared via oxidative cyclization of aldehyde N-(1,3-diphenylpyrazolo[3,4-d]pyrimidin-4-yl)hydrazones. Dimroth rearrangement of such a series yielded pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines. 相似文献
964.
This paper introduces four different modes of multiple-injection CZE (MICZE). The validity of these MICZE models was evaluated by the experimental data. Prior to the application of MICZE, the electrophoretic conditions are developed in the single-injection mode by adjusting different experimental parameters such as pH, type and concentration of buffer additives and temperature. Based on the migration time difference (Deltatmig) between the analyte and the internal standard or injection marker, one or more MICZE modes can be employed. The injection marker is added to the sample to compensate for injection-volume fluctuations. The inter-plug distance is regulated by applying an electrical field over the capillary for a short period of time between each injection. After the final injection, the separation is completed by electrophoresis for a time period corresponding to that in the single-injection mode. 相似文献
965.
Mehrnejad F Naderi-Manesh H Ranjbar B Maroufi B Asoodeh A Doustdar F 《Applied biochemistry and biotechnology》2008,149(2):109-118
Brevinin-2R, a member of a new family of antimicrobial peptides isolated from the skin of Rana ridibunda, displays antimicrobial activity against bacteria and fungi. In this study, we have used an assembly PCR method for the fast
and extremely accurate synthesis of the brevinin-2R gene. A total of six primers were assembled in a single step PCR, and the assembly was then amplified by PCR to produce the
final gene. The synthetic gene was cloned into the pET32a (+) vector to allow the expression of brevinin-2R as a Trx fusion
protein in Escherichia coli. The results indicated that the expression level of the fusion protein could reach up to 25% of the total cell proteins.
The expression products could be easily purified by Ni-NTA chromatography and released from the fusion protein by factor Xa
protease. The peptide displayed antimicrobial activity similar to that of the purified brevinin that was reported earlier.
This method allows the fast synthesis of a gene that optimized the overexpression in the E. coli system and production of sufficiently large amounts of peptide for functional and structural characterizations. 相似文献
966.
The interaction of a new derivative of thiazole orange (TO-3) with calf thymus DNA (ctDNA) has been investigated by fluorescence
and absorption spectroscopy. When TO-3 binds to ctDNA, absorption bands exhibit significant hypochromicity at low base pair/dye
ratio (BP/D ratio), and high BP/D show hyperchromicity with red shift. The spectral changes are attributed to the different
species formed between TO-3 and ctDNA in the titration course of the dye molecule with DNA. Multivariate curve resolutions–alternating
least squares (MCR–ALS) is applied to the absorption measurements recorded to recover the concentration profiles and the pure
spectra of the DNA/TO-3 complexes involved in the process. The binding constant and size of the binding site have been determined
spectrophotometrically using the McGhee von Hippel equation. MCR–ALS has been used to reveal the precise concentration profiles
of all detectable species formed between ctDNA and TO-3 and their pure spectral profiles. 相似文献
967.
Sayed M. Riyadh Hamad M. Al‐Matar Mohamed H. Elnagdi 《Journal of heterocyclic chemistry》2008,45(4):975-979
968.
Alías S Andreu R Blesa MJ Cerdán MA Franco S Garín J López C Orduna J Sanz J Alicante R Villacampa B Allain M 《The Journal of organic chemistry》2008,73(15):5890-5898
A short, high-yielding route to omega-dithiafulvenylpolyenals (1) via the corresponding iminium salts (2) and starting from trimethyl-1,3-dithiolium tetrafluoroborate is reported. The Knoevenagel reactions of either 1 or 2 with isoxazolone-containing acceptors afford merocyanines 7 and 9, in a process that is often accompanied by a vinylene-shortening side reaction. Experimental and theoretical studies reveal that compounds 7 and 9, featuring two proaromatic end groups, are strongly polarized and show good second-order nonlinear optical responses. 相似文献
969.
Hanan Al‐Awadi Maher R. Ibrahim Nouria A. Al‐Awadi Yehia A. Ibrahim 《Journal of heterocyclic chemistry》2008,45(3):723-727
970.
The thioenols derived from cyanomonothiocarbonylmalonamides and a cyanodithiocarbonylmalonamide were found to be very reactive species. They react under a variety of conditions such as crystallization, reaction with several carbonyl compounds, and reactions with another thioenol molecule to give a variety of products, mostly heterocycles, including substituted 2,3-dihydroisothiazole-3-ones and 3-thione, 2-substituted methylenethiazoles, 3,4-dihydro-1,3-thiazine-4-ones and 4-thiones, divinyl sulfides, a 1,2-dithiolane radical, and a 3,7-diaza[3.3.0]bicyclooctane derivative. Mechanisms suggested for these reactions include radical mechanisms, nucleophilic substitutions, and condensations. 相似文献