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排序方式: 共有226条查询结果,搜索用时 625 毫秒
81.
Marina Brustolon Teresa Cassol Lauretta Micheletti Ulderico Segre 《Molecular physics》2013,111(5):1005-1014
A new method for the investigation of methyl group rotation dynamics in free radicals in solids is described, based on the temperature dependence of the methyl protons ENDOR enhancement. The method is shown to work for hindering barriers of any height, and for both radicals trapped in single crystals and in powdered samples. As specific examples, the Arrhenius parameters for the methyl rotation in free radicals produced by γ-irradiation of 1-alanine and 4-methyl-2, 6 di-t-butyl-phenol are determined. 相似文献
82.
83.
Summary It is shown that the density functional definition of the Fukui function leads, when applied to the LCAO-MO formulation, to
the familiar density contour maps of the frontier orbitals. 相似文献
84.
B. Segre 《Annali di Matematica Pura ed Applicata》1964,64(1):1-76
Dedicato al Prof. L. J. Mordell in occasione del suo 75o compleanno 相似文献
85.
Stoupin S Rivera H Li Z Segre CU Korzeniewski C Casadonte DJ Inoue H Smotkin ES 《Physical chemistry chemical physics : PCCP》2008,10(42):6430-6437
Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray absorption spectroscopy in operating liquid feed direct methanol fuel cells. The total metal loadings were 4 mg cm(-2) unsupported catalysts at the anode and cathode of the membrane electrode assembly. Ex situ XRD lattice parameter analysis indicates partial segregation of the Ru from the PtRu fcc alloy in both catalysts. A comparison of the in situ DMFC EXAFS to that of the as-received catalyst shows that catalyst restructuring during DMFC operation increases the total metal coordination numbers. A combined analysis of XRD determined grain sizes and lattice parameters, ex situ and in situ EXAFS analysis, and XRF of the as-received catalysts enables determination of the catalyst shell composition. The multi-spectrum analysis shows that the core size increases during DMFC operation by reduction of Pt oxides and incorporation of Pt into the core. This increases the mole fraction of Ru in the catalyst shell structure. 相似文献
86.
Swarnagowri Nayak Santosh L. Gaonkar Ebraheem Abdu Musad Abdullah Mohammed AL Dawsar 《Journal of Saudi Chemical Society》2021,25(8):101284
Chemotherapy is an important therapeutic approach for the treatment of cancer. Currently, many anticancer drugs are available in the market that plays an important role in cancer treatment, but concerns such as, drug resistance and side effects create an urgent need for the development of new anti-tumor drugs with high potency and less side effects. Heterocycles are of great interest due to their fascinating anticancer activity. Among them, 1,3,4-oxadiazoles showed attracting anti-tumor activity and its derivatives are under clinical trials for the treatment of cancer. Hybridization of 1,3,4-oxadiazole moiety with other heterocyclic pharmacophoresis a promising approach to overcome various disadvantages of current anticancer drugs such as drug resistance, toxicity, and other side effects. Thus, 1,3,4-oxadiazole-heterocycle hybrids occupy a significant position in the discovery of anti-tumor drugs. Among the reported oxadiazole-based hybrids reviewed here, compounds 45i, 59j, and 62x showed the highest anticancer activity with IC50 values in the nanomolar range. This review summarizes the recent developments in the anticancer potential, structure–activity relationships, and mechanisms of actions of 1,3,4-oxadiazole-heterocycle hybrids. 相似文献
87.
Bailey AE Poon WC Christianson RJ Schofield AB Gasser U Prasad V Manley S Segre PN Cipelletti L Meyer WV Doherty MP Sankaran S Jankovsky AL Shiley WL Bowen JP Eggers JC Kurta C Lorik T Pusey PN Weitz DA 《Physical review letters》2007,99(20):205701
We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly. 相似文献
88.
C. Karanfil G. Bunker M. Newville C. U. Segre D. Chapman 《Journal of synchrotron radiation》2012,19(3):375-380
Third‐generation synchrotron radiation sources pose difficult challenges for energy‐dispersive detectors for XAFS because of their count rate limitations. One solution to this problem is the bent crystal Laue analyzer (BCLA), which removes most of the undesired scatter and fluorescence before it reaches the detector, effectively eliminating detector saturation due to background. In this paper experimental measurements of BCLA performance in conjunction with a 13‐element germanium detector, and a quantitative analysis of the signal‐to‐noise improvement of BCLAs are presented. The performance of BCLAs are compared with filters and slits. 相似文献
89.
Vittorio Crescenzi Andrea Francescangeli Anna Laura Segre Donatella Capitani Luisa Mannina Davide Renier Davide Bellini 《Macromolecular bioscience》2002,2(6):272-279
Hydrogels have been prepared using two partially deacetylated hyaluronan (deHA) samples having a molar ratio of free amino groups to total initial N-acetamido groups equal to 23 and 33%, respectively. Taking advantage of such primary amino functionalities, polymeric networks could be easily obtained in aqueous media by means of two different crosslinking procedures, namely: a) Ugi multicomponent reactions and, more simply, b) glutaraldehyde reticulation. In this paper, we wish to report on the synthesis of deHA based hydrogels and, in particular, on their structural elucidation as obtained by NMR studies.
90.
Elisabetta Princi Silvia Vicini Enrico Pedemonte Noemi Proietti Donatella Capitani Anna Laura Segre Loredana D'Orazio Gennaro Gentile Carmen Polcaro Ezio Martuscelli 《Macromolecular Symposia》2004,218(1):343-352
Conversion of dihydroxyl groups to dialdehyde by periodate oxidation is a useful method widely used in derivatization of cellulose to activate the polymer to further reactions as grafting polymerization. To investigate the cellulose behavior at different level of oxidation and to better understand the influence of the crystallinity on the effects induced by oxidative reactions on different cellulose materials, linen and cotton textiles have been oxidized with periodate solutions in different conditions. Oxidized cellulose samples have been characterized by several techniques: solid-state 13C NMR, Wide Angle X-Ray diffraction, and SEM. Moreover the mechanical properties of the untreated and oxidized yarns have been evaluated by means of tensile tests, the oxidation degree has been measured by means of the hydroxylamine hydrochloride method. 相似文献