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51.
We prove that a compact subset of the complex plane satisfies a local Markov inequality if and only if it satisfies a Kolmogorov type inequality. This result generalizes a theorem established by Bos and Milman in the real case. We also show that every set satisfying the local Markov inequality is a sum of Cantor type sets which are regular in the sense of the potential theory. 相似文献
52.
We study purely nonlocal Hamiltonian structures for systems of hydrodynamic type. In the case of a semi-Hamiltonian system, we show that such structures are related to quadratic expansions of the diagonal metrics naturally associated with the system. 相似文献
53.
Raimondo L Laicini M Spearman P Tavazzi S Borghesi A 《The Journal of chemical physics》2006,125(2):24702
The polarized optical absorption spectra of different quaterthiophene single crystals in the energy region of the exciton bands originating from the first molecular transition are reported as measured in the temperatures ranging from 7 to 140 K. The intrinsic higher mobility of the b-polarized 0-0 a(u) exciton both with respect to its replicas and to the a-polarized structures is demonstrated in high quality crystals at the lowest temperatures. The influence of structural disorder on mobility is discussed considering, for the different samples, the measured lineshape and linewidth of the absorption peaks, and the relative lineshift and intensity ratio between the 0-0 a(u) line and its first replica at the lowest temperature. The influence of dynamic disorder is discussed considering the lineshape and linewidth of the measured peaks as a function of temperature for both polarizations in the framework of the exciton-phonon coupling theory. 相似文献
54.
Guglielmo D’Amico Jacques Janssen Raimondo Manca 《Methodology and Computing in Applied Probability》2010,12(2):215-225
In this paper we show how it is possible to construct an efficient Migration models in the study of credit risk problems presented
in Jarrow et al. (Rev Financ Stud 10:481–523, 1997) with Markov environment. Recently it was introduced the semi-Markov process in the migration models (D’Amico et al. Decis
Econ Finan 28:79–93, 2005a). The introduction of semi-Markov processes permits to overtake some of the Markov constraints given by the dependence of
transition probabilities on the duration into a rating category. In this paper, it is shown how it is possible to take into
account simultaneously backward and forward processes at beginning and at the end of the time in which the credit risk model
is observed. With such a generalization, it is possible to consider what happens inside the time after the first transition
and before the last transition where the problem is studied. This paper generalizes other papers presented before. The model
is presented in a discrete time environment. 相似文献
55.
Francesco Alfani Maria Cantarella Nicoletta Spreti Raimondo Germani Gianfranco Savelli 《Applied biochemistry and biotechnology》2000,88(1-3):1-15
α-Chymotrypsin (α-CT) activity was tested with N-glutaryl-l-phenylalanine p-nitroanilide in buffered media with added cationic surfactants. The effect of the commercial cetyltrimethylammonium
bromide (CTABr) was compared with that of three other surfactants with ethyl (CTEABr), propyl (CTPABr), and butyl (CTBABr)
head groups. These were synthesized and purified in this laboratory. Surfactant head groups provided distinct environments
that largely modulated the catalytic performance. Larger alkyl head group hydrophobicity led to a marked enhancement of α-CT
activity. CTBABr-rich media induced the highest superactivity.
Kinetic measurements were performed in Tris-HCl buffer at a surfactant concentration either below or above CMC, and α-CT superactivity
occurred in both media. Positive interactions between the enzyme and surfactants happened independently of thesupramolecular
organization of the medium. The reaction followed the Michaelis-Menten kinetics. The substrate to micelle aggregates binding
constant was used to calculate the substrate concentration available for catalysis. The k
cat to k
m ratio was in CTBABr-rich media always higher than in pure buffer and depended on the surfactant concentration. α-CT superactivity
depended on the pH value of buffer solution. Enzyme inactivation followed a single-step mechanism in pure buffer and a series
mechanism in the presence of a surfactant. The rate of activity decay obeyed a first-order kinetics. 相似文献
56.
57.
Ascenzi P Bocedi A Bolognesi M Spallarossa A Coletta M De Cristofaro R Menegatti E 《Current protein & peptide science》2003,4(3):231-251
The pancreatic Kunitz inhibitor, also known as aprotinin, bovine basic pancreatic trypsin inhibitor (BPTI), and trypsin-kallikrein inhibitor, is one of the most extensively studied globular proteins. It has proved to be a particularly attractive and powerful tool for studying protein conformation as well as molecular bases of protein/protein interaction(s) and (macro)molecular recognition. BPTI has a relatively broad specificity, inhibiting trypsin- as well as chymotrypsin- and elastase-like serine (pro)enzymes endowed with very different primary specificity. BPTI reacts rapidly with serine proteases to form stable complexes, but the enzyme: inhibitor complex formation may involve several intermediates corresponding to discrete reaction steps. Moreover, BPTI inhibits the nitric oxide synthase type-I and -II action and impairs K+ transport by Ca2+-activated K+ channels. Clinically, the use of BPTI in selected surgical interventions, such as cardiopulmonary surgery and orthotopic liver transplantation, is advised, as it significantly reduces hemorrhagic complications and thus blood-transfusion requirements. Here, the structural, inhibition, and bio-medical aspects of BPTI are reported. 相似文献
58.
Silvia G. Manca Irma L. Botto Enrique J. Baran 《Monatshefte für Chemie / Chemical Monthly》1980,111(4):949-955
The infrared spectra of orthoarsenates with apatite structure, of the formulaM
5(AsO4)3
X (M=Ca, Sr, Ba, Pb andX=F, Cl,Br) are measured and interpreted on the basis of a site-symmetry analysis. The influence of the different cations on the internal vibrations of the AsO3
4-ions is discussed. 相似文献
59.
We studied decarboxylation of 6-nitrobenzisoxazole-3-carboxylate, 1, as a kinetic probe to investigate microinterface properties of aqueous micelles formed by cationic surfactants of increasing head group bulk, i.e., cetyltrialkylammonium bromide, with alkyl=Me (CTABr), Et (CTEABr), n-Pr (CTPABr), n-Bu (CTBABr) and p-octyloxybenzyltrialkylammonium bromide surfactants with alkyl=Me (pOOTABr), n-Pr (pOOTPABr), and n-Bu (pOOTBABr), and the longer p-dodecyloxybenzyltrimethylammonium bromide (pDoTABr) at concentrations higher than 0.05 M. The pseudophase kinetic treatment fails to fit the data that show anomalies with abrupt increases in k(obs) for CTPABr and CTBABr (but not for CTEABr) and with smooth and continuos increase of k(obs) for all p-alkyloxybenzyltrilakylammonium bromides. Abrupt and successive modifications of the micellar interface properties, undergoing only when the polar head or the alkyl chain have some covalent structure, account for the observed kinetic behavior. 相似文献
60.
P. A. Biondi Francesca Manca A. Negri Anna Berrini Tatjana Simonic C. Secchi 《Chromatographia》1988,25(7):659-662
Summary The activity of bacterial collagenase Clostridiopeptidase A was estimated using a labelled synthetic peptide, 4-phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg,
as substrate. The N-protected dipeptide obtained after enzymatic hydrolysis of Leu-Gly peptide bond was quantified by reversed-phase,
high-performance liquid chromatography using 4-phenylazobenzyloxycarbonyl-L-Pro-L-Phe as internal standard. The time dependence
of the appearance of the hydrolysis product and the dependence of rates of hydrolysis on collagenase concentration were linear.
Kinetic parameters for collagenase were determined to test the suitability of the described procedure. 相似文献