Search results for "Dispersion"
showing 10 items of 1101 documents
Hadronic τ Decays as New Physics Probes in the LHC Era
2019
We analyze the sensitivity of hadronic tau decays to non-standard interactions within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the $\tau \to \pi\pi\nu_\tau$ channel representing an unexpected powerful New Physics probe. We find that the ratios of non-standard couplings to the Fermi constant are bound at the sub-percent level. These bounds are complementary to the ones from electroweak precision observable…
Dielectric response of disordered BaBi2Nb2O9perovskite ceramics
2007
Studies of dielectric properties of BaBi2Nb2O9 ceramics are reported. Considerable dispersion of ?* at low- and infra-low frequencies has been revealed in the region of the diffused phase transition. Dispersion of ?* is divided into ''low-temperature'' dispersion related to relaxation of polar formations and their boundaries and ''high-temperature'' dispersion (at T ? Tm) the main contribution to which comes from Maxwell-Wagner relaxation.
Uniaxial Pressure Effects on the Dielectric Properties of the PLZT-x/65/35 (x = 9.75 and 10) Ceramics
2012
The influence of uniaxial pressure (0-1000 bars) applied parallel to the ac electric field on the dielectric properties of PLZT-x/65/35 ceramics (x = 9.75 and 10) was investigated. The results show that the applied stress has a significant influence on the dielectric properties of PLZT ceramics. Applying uniaxial pressure leads to the reduction of the electric permittivity (ϵ) peak and the frequency dispersion. Moreover, the peak of ϵ becomes diffuse and shifts to a higher temperature with increasing pressure. The results show that applying uniaxial pressure induces similar effects as the increase in Ti−ion concentration in the PZT system. We interpreted our results based on the domain swit…
Conditions for achieving invisibility of hyperbolic multilayered nanotubes
2016
Invisibility of nanotubes has recently been demonstrated in highly anisotropic metamaterials in the transition regime from hyperbolic to elliptic dispersion [Sci. Rep. 5 (2015) 16027]. In such study, the characterization of a realistic multilayered metamaterial was carried out by means of an effective medium approach providing average components of the permittivity tensor and wave fields. Here, the edge effects of the metal-dielectric stratified nanotube for different combinations were thoroughly analyzed. We show how the boundary layers, which in principle remain fully irrelevant in the estimation of the effective permittivity of the nanotube, however play a critical role in the scattering…
The Nature of Dielectric Nonlinearity in the Region of Diffused Phase Transition in Layered Ferroelectric BaBi2Nb2O9
2008
By studying the dielectric properties of BaBi 2 Nb 2 O 9 ceramics, a representative of layered ferroelectrics, significant dispersion of ϵ* has been revealed at low- and infra-low frequences in the region of phase transition. Dispersion of ϵ* observed in “low-temperature” region (T T m where the basic contribution to ϵ* is provided by processes of the Maxwell-Wagner relaxation.
Interactions of benzodiazepines with human serum albumin. Circular dichroism studies.
1973
The circular dichroism spectra of 12 benzodiazepine derivatives studied in presence of human serum albumin are presented. Nearly all substances give biphasic extrinsic Cotton effects. At the CD maxima the molar ellipticities and the anisotropy factors are calculated. The influence of the chemical structure of the benzodiazepines on the induced Cotton effect is discussed. There is a linear correlation between the anisotropy factors and the logarithms of the partition coefficients of the substances. It is suggested that the phenyl ring of the benzodiazepine molecule is one of the essential groups for the binding of these substances to human serum albumin.
Entrapment of Phenytoin into Microspheres of Oleaginous Materials: Process Development and in Vitro Evaluation of Drug Release
1997
AbstractA novel multiparticulate preparation of the antiepileptic agent phenytoin (1) was developed and evaluated in vitro. The preparation consists of gastroresistant microparticulate drug delivery system formulated with oleaginous material (lipospheres) to minimize unwanted effects of l on gastric apparatus. The drug was dispersed in a spherical micromatrix consisting of a mixture of stearyl alcohol and glycerol esters of various fatty acids. The best mixture to obtain discrete, reproducible, free-flowing lipospheres consisted of glyceryl monostearate dilaurate and stearyl alcohol (ratio 3: 17). The lipospheres were obtained by a technique involving melting and dispersion of drug-containi…
Carnauba wax microspheres loaded with valproic acid: Preparation and evaluation of drug release
1995
AbstractTo minimize unwanted toxic effects of valproic acid (1) by the kinetic control of drug release, gastroresistant carnauba wax microspheres loaded with the antiepileptic agent were prepared. The preparation was based on a technique involving melting and dispersion of drug-containing wax in an aqueous medium. The resulting emulsion after cooling under rapid stirring produced solid, discrete, reproducible free flowing microspheres which converted the liquid drug droplets into solid material. About 94% of the isolated microspheres were of particle size range 200-425 μm. The microspheres were analyzed to determine the drug content in various particle size range and to characterize the in …
High-Pressure Raman Study of Fe(IO3)3: Soft-Mode Behavior Driven by Coordination Changes of Iodine Atoms
2020
[EN] We report high-pressure Raman spectroscopy studies of Fe(IO3)(3) up to nearly 21 GPa that have been interpreted with the help of density functional theory calculations, which include the calculation of phonon dispersion curves and elastic constants at different pressures. Zero-pressure Raman-active mode frequencies and their pressure dependences have been determined. Modes have been assigned and correlated to atomic movements with the help of calculations. Interestingly, in the high-frequency region, there are several modes that soften under compression. These modes have been identified as internal vibrations of the IO3 coordination polyhedron. Their unusual behavior is a consequence o…
Broadband Dielectric Spectroscopy of Ferroelectric Phase Transitions in PbSc1/2Nb1/2O3Ordered Ceramics
2008
Broadband dielectric spectroscopy of PbSc 1/2 Nb 1/2 O 3 (PSN) ordered ceramics are reported within the range of 20 Hz ≤ ν ≤ 2 THz in 80 K ≤ T ≤ 300 K temperatures. Spectrally very broad dielectric dispersion consisting of two parts − at lower frequencies, ferroelectric domains cause a dispersion and at higher frequencies, higher temperatures the relaxation soft mode is responsible for the dispersion. The relaxation soft mode exhibit pronounced hardening on cooling, whilst the ferroelectric phase transition is connected with an abrupt freezing and rise of polar nanoregions into ferroelectric domains.