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921.
Numerical Algorithms - Quasi-Newton methods for solving nonlinear systems of equations are generally defined in order to satisfy a “direct secant equation” or an “inverse secant... 相似文献
922.
DeborahF. dosSantos Mario Argentini Regin Weinreich Hans‐Jürgen Hansen 《Helvetica chimica acta》2000,83(11):2926-2938
We synthesized 2′‐carbaboranyl‐2,5′‐bi‐1H‐benzimidazoles containing 10 B‐atoms and labeled with Se or the positron‐emitting radionuclide 73Se (t1/2=7.1 h), with a view to their application to cancer treatment by boron‐neutron‐capture therapy (BNCT) and to compound‐distribution measurements in vivo by positron‐emission tomography (PET). Thus, 2,2′‐{{2′‐{4‐[1,2‐dicarba‐closo‐dodecaboran(12)‐2‐ylmethoxy]phenyl}‐[2,5′‐bi‐1H‐benzimidazol]‐5‐yl}imino}bis[ethanol] ( 26c ) was obtained by the reaction of 2,2′‐[(3,4‐diaminophenyl)imino]bis[ethanol] ( 19 ) with ethyl 2‐{4‐[1,2‐dicarba‐closo‐dodecaboran(12)‐2‐ylmethoxy]phenyl}‐1H‐benzimidazole‐5‐carboximidate hydrochloride ( 25 ), as well as the analogues 26a and 26b (Scheme 6). Tosylation of compound 26c gave 4 regioisomers 27a – d , which, after selenation, produced 2′‐{4‐[1,2‐dicarba‐closo‐dodecaboran(12)‐2‐ylmethoxy]phenyl}‐5‐(tetrahydro‐2H‐1,4‐selenazin‐4‐yl)‐2,5′‐bi‐1H‐benzimidazole ( 29 ) in 42% yield (Scheme 7). 相似文献
923.
924.
Juan Sebastin Gmez-Jeria Mario Ojeda-Vergara 《International journal of quantum chemistry》1997,61(6):997-1002
The binding of apomorphines (AM) to D1 and D2 dopamine receptors is analyzed through a formal quantum structure–activity relationship method. The calculations were carried out at the CNDO/2 level of the molecular orbital theory with a continuum representation of environmental effects. The results show that the D1 receptor affinity variation is related to the variation of the electron-donating capacity of a C atom of the hydroxylic region of apomorphines in a low-polarity medium. The N-chain probably interacts with a hydrophobic region of the receptor. It is also concluded that the poor results for the D2 binding affinity are explained by errors in the experimental measurements. Finally, it is proposed that future structure–activity relationship studies must be carried out for media of different polarities. © 1997 John Wiley & Sons, Inc. 相似文献
925.
The reaction of the ligand HL · (HCl)2 (HL = 2,6-di(aminomethyl)-4-tert-butyl-thiophenol) with MCl2 in methanol in the presence of sodium methanolate and air affords the dinuclear complexes [L3M2][ClO4]3 (M = Fe: 2 , Co: 3 ) in 85% and 68% yield, respectively. Both complexes were characterized by infrared spectroscopy, magnetic susceptibility measurements, and 1H NMR spectroscopy. By temperature-variable 57Fe Mössbauer spectroscopy diamagnetic 2 is shown to exhibit a gradual spin transition between the species [L3(low-spin-Fe)2]3+ ((ls,ls)- 2 ) and [L3(high-spin-Fe)2]3+ ((hs,hs)- 2 ). At room temperature the relative concentrations of both species are nearly equal. Well resolved quadrupole doublets at all temperatures for both (ls,ls)- 2 (γ in the range 0.22(1)–0.28(1) mm s–1) and (hs,hs)- 2 (γ in the range 0.48(1)–0.53(2) mm s–1) are indicative of a spin conversion time longer than the half-life of the I = 3/2 state of 57Fe. Cyclic voltammetry and square wave voltammetry of 2 in CH3CN solution reveal four quasi-reversible one-electron transfer processes. The first two processes were assigned to metal-centered reductions of (hs,hs)- 2 and (ls,ls)- 2 , respectively, to yield the mixed-valent species [L3FeIIFeIII]3+. 相似文献
926.
Mario Bergeron 《Fortschritte der Physik》1992,40(2):119-159
Definition and formulas for harmonic oscillator coherent states and spin coherent states are reviewed in detail. The path integral formalism and its relation with the partition function of a system are also reviewed. The harmonic oscillator coherent state path integral is evaluated exactly at the discrete level and then used to find its continuum limit using various regularizations. The computation of the path integral for a particle of spin s put in a constant magnetic field is carried out using harmonic oscillator coherent states and spin coherent states, with a careful analysis of infinitesimal terms (in 1/N where N is the number of time slices) appearing in the Lagrangian. A mapping of the spin system into a CP1 model is shown explicitly. The theory of a spinless particle in the field of a magnetic monopole and its relation with the spin system are explained. The equivalence of these two models is established up to infinitesimal order by the introduction of an external field correction. This gives a new representation of a coherent state path integral in terms of a more familiar Feynman path integral. 相似文献
927.
Ndahita De Dios-Avila Juan Manuel Tirado-Gallegos Claudio Rios-Velasco Gregorio Luna-Esquivel Nstor Isiordia-Aquino Paul Baruk Zamudio-Flores Mario Orlando Estrada-Virgen Octavio Jhonathan Cambero-Campos 《Molecules (Basel, Switzerland)》2022,27(3)
The objective of this study was to obtain and characterize flours and starches from the avocado seeds of Hass and landrace cultivars. The morphological, physical-chemical, structural, thermal and rheological characteristics were evaluated. The flour yield of the Hass and landrace cultivars was 41.56 to 46.86% (w/w), while for starch, it was 35.47 to 39.57% (w/w) (cv. Hass and landrace, respectively). Scanning electron microscopy (SEM) revealed the presence of oval starch granules and other particles in flour, in contrast to flours, starches showed lower ash, proteins and lipids content. However, the amylose content was higher in starches (42.25–48.2%). Flours showed a higher gelatinization temperature (Tp = 73.17–73.62 °C), and their starches presented greater gelatinization enthalpy (∆Hgel = 11.82–13.43 J/g). All samples showed a B-type diffraction pattern, and the crystallinity was higher in the flours. The rheological analysis (flow curves and viscoelastic tests) evidenced a pseudoplastic (n = 0.28–0.36) behavior in all samples analyzed, but the consistency index (k) was higher in starches. In general, the flours and starches from avocado seeds presented interesting proximal, thermal and functional properties for possible application in food systems, and these findings could contribute to the revaluation of this by-product. 相似文献
928.
929.
Barbara Immirzi Mario Malinconico Ezio Martuscelli Maria G. Volpe 《Macromolecular Symposia》1994,78(1):243-258
Reactive polymer blending of poly(β-hydroxybutyrate) (PHB) and its valerate copolymers (PHBV) are reported, following two different methodologies, namely polymerization of rubber inclusions in the preformed matrix or reactive melt blending of preformed polymers. As second phase, poly(butyl acrylate) (PBA) and polycaprolactone (PCL) are used. The results of spectroscopic, thermal, mechanical and morphological analysis indicate the existence of chemical interactions between the blend components. Such interactions are also responsible of a drastic change in the morphology. 相似文献
930.
Mario Minale Giuseppe Apuzzo Francesco Greco Giuseppe Marrucci 《Macromolecular theory and simulations》1993,2(6):863-873
The dynamic transition of nematics in (slow) shear from flow-aligning to tumbling behaviour is here predicted by using the rigid rod-like molecular model together with an extension of the Maier-Saupe mean-field potential. Such an extension, already available in the literature with reference to equilibrium data, includes interactions of rank higher than the basic quadrupolar one considered by Maier and Saupe. The theoretical predictions are then compared with the few existing sets of dynamic data. Although an acceptable qualitative agreement is found, the theory generally overpredicts the value of the relevant ratio α3/α2 of Leslie coefficients. 相似文献