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51.
N. Bilić C. A. Dominguez B. Guberina 《Zeitschrift fur Physik C Particles and Fields》1988,39(3):351-358
We calculate theB parameter for \(K^0 - \bar K^0 \) mixing in the framework of QCD sum rules for a three-point function involving pseudoscalar currents, and contrast our results with other calculations. We findB=0.5±0.1±0.2, where the first error reflects uncertainties in the various QCD parameters and the second one is an estimate of uncalculated three-loop radiative and higher order quark mass corrections. 相似文献
52.
53.
Krupa D Baszkiewicz J Kozubowski JA Mizera J Barcz A Sobczak JW Biliński A Rajchel B 《Analytical and bioanalytical chemistry》2005,381(3):617-625
The paper compares the effects of various surface modifications, ion implantation, alkaline treatment and anodic oxidation, upon the corrosion resistance and bioactivity of titanium. The chemical composition of the surface layers thus produced was determined by XPS, SIMS and EDS coupled with SEM. The structure of the layers was examined by TEM, and their phase composition by XRD. The corrosion resistance was determined by electrochemical methods after the samples were exposed to the test conditions for 13 h. The bioactivity of titanium was evaluated in a simulated body fluid at a temperature of 37°C after various exposure time. 相似文献
54.
We study the chiral phase transition in the linear sigma model with 2 quark flavors and N
c
colors. One-loop calculations predict a first-order phase transition at both μ = 0 and μ ≠ 0. We also discuss the phase diagram and make a comparison with a thermal parametrization of existing heavy-ion experimental
data. 相似文献
55.
Luka Bilić Dr. Danijela Barić Dr. Gregory M. Sandala Dr. David Mathew Smith Dr. Borislav Kovačević 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(29):7930-7941
Diol dehydratase, dependent on coenzyme B12 (B12-dDDH), displays a peculiar feature of being inactivated by its native substrate glycerol (GOL). Surprisingly, the isofunctional enzyme, B12-independent glycerol dehydratase (B12-iGDH), does not undergo suicide inactivation by GOL. Herein we present a series of QM/MM and MD calculations aimed at understanding the mechanisms of substrate-induced suicide inactivation in B12-dDDH and that of resistance of B12-iGDH to inactivation. We show that the first step in the enzymatic transformation of GOL, hydrogen abstraction, can occur from both ends of the substrate (either C1 or C3 of GOL). Whereas C1 abstraction in both enzymes leads to product formation, C3 abstraction in B12-dDDH results in the formation of a low energy radical intermediate, which is effectively trapped within a deep well on the potential energy surface. The long lifetime of this radical intermediate likely enables its side reactions, leading to inactivation. In B12-iGDH, by comparison, C3 abstraction is an endothermic step; consequently, the resultant radical intermediate is not of low energy, and the reverse process of reforming the reactant is possible. 相似文献
56.
57.
Bilińska B Pilawa B Zawada Z Wylegała E Wilczok T Dontsov AE Sakina NL Ostrovsky MA Ilyasova VB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(10):2257-2264
Electron spin resonance (ESR) examinations of human retinal pigment epithelium melanosomes isolated from eyes of young and old donors were carried out. The examined ESR signal was a single line, which is characteristic for free radicals of eumelanin o-semiquinones. The content of free radicals related to melanosomes dry weight for samples from older donors (ages over 45 years) were higher than for sample from younger donors (between 14 and 22 years). Simultaneously, the content of free radicals calculated for one melanosome is constant and does not depend on age. The homogeneous broadening of the recorded ESR lines shows that there are no isolated spin packets in all investigated melanin samples. Slow spin-lattice (T1 approximately 10(-5) s) and fast spin-spin (T2 approximately 10(-8) s) relaxation processes occur in these samples. Saturation of the ESR lines at low microwave power was measured. High concentration of free radicals in melanosome samples was responsible for the fast spin-spin relaxation process. 相似文献
58.
On the structure of human hair melanins from an infrared spectroscopy analysis of their interactions with Cu2+ ions. 总被引:1,自引:0,他引:1
B Bilińska 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(12):2525-2533
Melanins were isolated from dark and red human hair and complexed with copper ions at various pH values in a complexing medium. IR spectra of melanins and their Cu2+-complexes for pellets with KBr were obtained. The IR spectra indicate that Cu2+ ions bound to melanins are fixed by different carboxyl and hydroxyl (phenolic and/or alcoholic) groups in the macromolecule. From these results it is concluded that, generally, melanin carboxyl groups are responsible for interactions of metal ions with the melanin molecule. Complexes of melanins isolated from dark and red human hair show structural differences when analysed by IR spectroscopy. Conclusions from these investigations assist in the differentiation of structures of analysed hair melanins. IR spectral analysis of melanin samples and their complexes suggest that melanin samples obtained from red hair may contain eumelanin. 相似文献
59.
60.
M. Klobukowski S. Huzinaga L. Seijo Z. Barandiarán 《Theoretical chemistry accounts》1987,71(2-3):237-245
All-electron SCF calculations in contracted large Gaussian basis sets were performed for the molecules in the isoelectronic series XeF6, IF
6
–
, and TeF
6
2–
. Molecular equilibrium geometry of these molecules was studied first in O
h symmetry. Then, the gradient minimization technique was used to determine molecular structure of the studied systems near the local minima corresponding to C
3v
and C
2v
geometries involved in the internal motion.In the O
h symmetry, TeF
6
2–
and IF
6
–
are bound by 172 and 104 kcal/mol, respectively. The total energy of XeF6 is larger than the sum of total energies of the constituent atoms by 192 kcal/mol. Lowering the symmetry to C
3v
and C
2v
results in an energy gain of about 20 kcal/mol for all studied systems. 相似文献