Search results for "CONSTANT"
showing 10 items of 1718 documents
Mutation of the important Tyr-33 residue of chicken avidin: functional and structural consequences
2002
The strong interaction between avidin and biotin is so tight (dissociation constant 10-15M) that conditions usually sufficient for protein denaturing fail to dislodge biotin from the avidin—biotin complex. This kind of irreversible binding hinders the use of avidin in applications such as affinity purification or protein immobilization. To address this concern, we have constructed a series of mutants of the strategically positioned Tyr-33 in order to study the role of this residue in biotin binding, and to create avidin variants with more reversible ligand-binding properties. Unexpectedly, an avidin mutant in which Tyr-33 was replaced with phenylalanine (Avm-Y33F) displayed similar biotin-b…
Relationship between ligand conformations and complexation properties in ditopic biphenyl thioureas
2007
Four new homoditopic biphenyl thiourea derivatives have been prepared to be used in carboxylate sensing. Experiments carried out with these ligands have demonstrated that the conformation of the free ligand has a strong influence on both complex stoichiometry and geometry. High equilibrium constants were obtained in DMSO.
LA CHIESA NELLO STATO
2010
The essay outlines the relationship between State and Church from Constantine to Theodosius I, through the various emperors who succeeded to the throne. Particular attention is paid to the granting of legal personality to the Church, the figure of the bishop and the episcopalis audientia.
The deformation tensor ∊ of the spin transition in the mixed crystal [Fe0.46Zn0.54(ptz)6](BF4)2
2004
The conversion of the spin state of complexes exhibiting thermal spin crossover from the1A1low-spin (LS) state to the5T2high-spin (HS) state is accompanied by a deformation of the lattice due to the larger bond lengths in the HS state as compared with the LS state. In a previous work [Kuszet al.(2000).J. Appl. Cryst.33, 201–205], it has been shown that the deformation of the lattice, corrected for its temperature dependence, can be described by an almost temperature-independent tensor ∊ multiplied by the fraction of molecules in the HS state, γHS. Here the dependence of ∊ in a mixed single crystal of [Fe0.46Zn0.54(ptz)6](BF4)2(ptz = propyltetrazole) with a transition temperature near 110 K …
Adiabatic-antiadiabatic crossover in a spin-Peierls chain
2004
We consider an XXZ spin-1/2 chain coupled to optical phonons with non-zero frequency $\omega_0$. In the adiabatic limit (small $\omega_0$), the chain is expected to spontaneously dimerize and open a spin gap, while the phonons become static. In the antiadiabatic limit (large $\omega_0$), phonons are expected to give rise to frustration, so that dimerization and formation of spin-gap are obtained only when the spin-phonon interaction is large enough. We study this crossover using bosonization technique. The effective action is solved both by the Self Consistent Harmonic Approximation (SCHA)and by Renormalization Group (RG) approach starting from a bosonized description. The SCHA allows to an…
Special Splines of Exponential Type for the Solutions of Mass Transfer Problems in Multilayer Domains
2016
We consider averaging methods for solving the 3-D boundary-value problem of second order in multilayer domain. The special hyperbolic and exponential type splines, with middle integral values of piece-wise smooth function interpolation are considered. With the help of these splines the problems of mathematical physics in 3-D with piece-wise coefficients are reduced with respect to one coordinate to 2-D problems. This procedure also allows to reduce the 2-D problems to 1-D problems and the solution of the approximated problemsa can be obtained analytically. In the case of constant piece-wise coefficients we obtain the exact discrete approximation of a steady-state 1-D boundary-value problem.…
Time-dependent asymmetric traveling salesman problem with time windows: Properties and an exact algorithm
2019
Abstract In this paper, we deal with the Time-Dependent Asymmetric Traveling Salesman Problem with Time Windows. First, we prove that under special conditions the problem can be solved as an Asymmetric Traveling Salesman Problem with Time Windows, with suitable-defined time windows and (constant) travel times. Second, we show that, if the special conditions do not hold, the time-independent optimal solution provides both a lower bound and (eventually) an upper bound with a worst-case guarantee for the Time-Dependent Asymmetric Traveling Salesman Problem with Time Windows. Finally, a branch-and-bound algorithm is presented and tested on a set of 4800 instances. The results have been compared…
Dissipative lattice model with exact traveling discrete kink-soliton solutions: Discrete breather generation and reaction diffusion regime
1999
International audience; We introduce a nonlinear Klein-Gordon lattice model with specific double-well on-site potential, additional constant external force and dissipation terms, which admits exact discrete kink or traveling wave fronts solutions. In the nondissipative or conservative regime, our numerical simulations show that narrow kinks can propagate freely, and reveal that static or moving discrete breathers, with a finite but long lifetime, can emerge from kink-antikink collisions. In the general dissipative regime, the lifetime of these breathers depends on the importance of the dissipative effects. In the overdamped or diffusive regime, the general equation of motion reduces to a di…
Subharmonic and homoclinic bifurcations in the driven and damped sine-Gordon system
1999
Abstract Chaotic responses induced by an applied biharmonic driven signal on the sine-Gordon (sG) system influenced by a constant dc-driven and the damping fields are investigated using a collective coordinate approach for the motion of the breather in the system. For this biharmonic signal, one term has a large amplitude at low frequency. Thus, the classical Melnikov method does not apply to such a system; however, we use the modified version of the Melnikov method to homoclinic bifurcations of the perturbed sG system. Additionally resonant breathers are studied using the modified subharmonic Melnikov theory. This dynamic behavior is illustrated by some numerical computations.
A Simple Apparatus for the Determination of the Optical Constants and the Thickness of Absorbing Thin Films
2001
We report on a simple and inexpensive apparatus useful for measuring the optical constants n, k and the thickness of weakly absorbing thin films. The measurement is based on an accurate determination of the reflectance and transmittance of a specimen illuminated by a laser beam. The laser beam is incident on a transparent substrate coated with the film to be evaluated, with an angle of incidence equal to the Brewster angle for the substrate, and its polarization can be switched between the p and s states. If the thickness is known to be within a presumptive range, measurements of the p and s reflectance and transmittance allow a calculation of the optical constants n, k and the thickness of…