Search results for "Time decay"
showing 8 items of 8 documents
Low-temperature phosphorescence of 1,4-benzodiazepines
1991
Abstract A highly sensitive method for the low-temperature phosphorescence determination of a series of 1,4-benzodiazepines has been developed. Oxazepam has been used as a test molecule to study the effects of instrumental parameters, such as time decay, gate time, excitation and emission slits, and ordinate, on the phosphorescence spectra. The corresponding analytical parameters have been established for different concentration levels. Under the best sensitivity conditions a limit of detection of 16 parts per trillion (ppt) for oxazepam, 3.8 ppt for medazepam, 2 ppt for prazepam, 5 × 10 −3 ppt for diazepam, and 0.09 ppt for lorazepam could be obtained. The proposed method is thus the most …
Magnetic properties of Cd–Mg–Tb quasicrystal
2004
Abstract The magnetic properties of an icosahedral Cd–Mg–Tb quasicrystal were studied by dc magnetization and thermoremanent magnetization time decay measurements. An unusual temperature dependence of the susceptibility below freezing temperature can be attributed to the inhomogeneous sample structure. In addition to the quasicrystalline portion which exhibits a spin-glass transition at 12.5 K a part of the sample behaves like a paramagnet. During aging of the sample in air the spin-glass part transforms into the paramagnetic one. The linear M ∝ H dependence of the thermoremanent magnetization time decay on magnetic field is quite different as compared to canonical spin glasses.
Photoluminescence time decay of surface oxygen deficient centers in un‐doped and Ge‐doped silica
2005
We report a study of the emission decay from the singlet excited state of two fold coordinated Si and Ge centers stabilized on the surface of silica and Ge-doped silica. The PL lifetimes are of the order of nanoseconds and increase on decreasing the temperature. The results suggest that, for the surface centers, the phonon assisted intersystem-crossing process linking the excited states affects the decay rates, is effective down to low temperatures and is distributed because of the inhomogeneity of the defects. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Anomalous time decay of transient nutations in S = 1/2 spin systems
1994
La decroissance temporelle des signaux de nutation transitoire a ete etudiee experimentalement a la frequence micro-onde sur des systemes de spin 1/2 (centres E' dans la silice and [AlO 4 ] o dans le quartz). Ces signaux decroissent exponentiellement mais avec une vitesse plus grande que la valeur habituellement donnee par les equations de Bloch. On trouve une dependence lineaire de cette vitesse avec la frequence de Rabi. Aucun interpretation pour le moment n'explique veritablement ce comportement anormal
Long time behavior for a dissipative shallow water model
2013
We consider the two-dimensional shallow water model derived by Levermore and Sammartino (Nonlinearity 14,2001), describing the motion of an incompressible fluid, confined in a shallow basin, with varying bottom topography. We construct the approximate inertial manifolds for the associated dynamical system and estimate its order. Finally, considering the whole domain R^2 and under suitable conditions on the time dependent forcing term, we prove the L^2 asymptotic decay of the weak solutions.
Simultaneous investigation of the T=1(Jπ=0+) and T=0(Jπ=9+) β decays in Br70
2017
The $\beta$ decay of the odd-odd nucleus $^{70}$Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The $T=0$ ($J^{\pi}=9^+$) and $T=1$ ($J^{\pi}=0^+$) isomers have both been produced in in-flight fragmentation of $^{78}$Kr with ratios of 41.6(8)\% and 58.4(8)\%, respectively. A half-life of $t_{1/2}=2157^{+53}_{-49}$ ms has been measured for the $J^{\pi}=9^+$ isomer from $\gamma$-ray time decay analysis. Based on this result, we provide a new value of the half-life for the $J^{\pi}=0^+$ ground state of $^{70}$Br, $t_{1/2}=78.42\pm0.51$ ms, which is slightly more precise, and in excellent agreement, with the bes…
Field-cooling experiments on the quadrupolar-glass state of (KBr)0.47(KCN)0.53
1990
The shear strain of a mixed cyanide crystal has been measured under field-cooling conditions. The time decay after field removal follows a Kohlrausch-Williams-Watts law. The results are analogous to spin glasses, except that residual permanent strains can be frozen-in.
Working Memory in Children: A Time-Constrained Functioning Similar to Adults
2009
International audience; Within the Time-Based Resource-Sharing (TBRS) model, we tested a new conception of the relationships between processing and storage in which the core mechanisms of WM are time constrained. However, our previous studies were restricted to adults. The present study aimed at demonstrating that these mechanisms are present and functional before adulthood. For this purpose, we investigated the effect on maintenance of the duration of the attentional capture induced by processing. In two experiments using computer-paced WM span tasks, 10- year-old children were asked to maintain letters while performing spatial location judgments. The duration of this processing was manipu…