Search results for "Metas"
showing 10 items of 1693 documents
Hyperfine structure measurements in the
1997
Clouds of stable and unstable Eu+ isotopes have been confined in a Paul trap, each containing about 105 particles. In a microwave-optical double resonance experiment several hyperfine separations in the 4f7 6s 7S3 exited level have been measured with the experimental uncertainties ranging between 10-8 and 3×10-6. These experiments have confirmed that also in the case of an excited level with a large number of hyperfine or Zeeman sublevels the microwave-optical double resonance technique in a Paul trap can be useful for precise hyperfine structure investigation. The hyperfine coupling constants A and B have been determined for the isotopes 153Eu+, 151Eu+, 150Eu+ and 148Eu+. The results compl…
Rotational Doppler Frequency Shift from Time‐Evolving High‐Order Pancharatnam–Berry Phase: A Metasurface Approach
2021
The Doppler frequency shift of sound or electromagnetic waves has been widely investigated in many different contexts and, nowadays, represents a formidable tool in medicine, engineering, astrophysics, and optics. Such effect is commonly described in the framework of the universal energy-momentum conservation law. In particular, the rotational Doppler effect has been recently demonstrated using light carrying orbital angular momentum. When a wave undergoes a cyclic adiabatic transformation of its Hamiltonian, it is known to acquire the so-called Pancharatnam–Berry (PB) phase. In this work, an experimental evidence of the direct connection between the high-order PB phase time evolution on th…
NOISE EFFECTS IN POLYMER DYNAMICS
2008
The study of the noise induced effects on the dynamics of a chain molecule crossing a potential barrier, in the presence of a metastable state, is presented. A two-dimensional stochastic version of the Rouse model for a flexible polymer has been adopted to mimic the molecular dynamics and to take into account the interactions between adjacent monomers. We obtain a nonmonotonic behavior of the mean first passage time and its standard deviation, of the polymer centre of inertia, with the noise intensity. These findings reveal a noise induced effect on the mean crossing time. The role of the polymer length is also investigated.
Shifts of the 3D - 4P transitions in different isotopes of positive calcium ions
1997
A sample of stable isotopes containing the masses 40, 42, 43 and 44 was stored under buffer-gas conditions in a Paul ion trap. After population of the metastable 3D levels by spontaneous decay of the laser-excited 4P state we observed laser-induced fluorescence when we scanned a laser across the different 3D - 4P fine-structure lines at 850, 854 and 866 nm. From the Doppler-limited lines of these transitions we deduced the isotope shifts, which are of the order of several GHz due to the large specific mass shift of the metastable 3D levels.
Experimental lifetime of the metastable 5D 3/2 state in Ba+
1992
A discrepancy exists between theoretical and experimental lifetimes of the metastable 5D3/2 state in Ba+. In order to redertermine that lifetime, we probe the population of the metastable 5D3/2 state of a Ba+ ion cloud stored in a Paul ion trap in the presence of He buffer gas as the function of time delay after pulsed laser excitation of this state. The measured decay rates at different buffer gas pressures are extrapolated to zero pressure and we obtain a radiative decay time of 48.0±5.9 s. This is not in agreement with theoretical predictions of about 80 s, but reduces the discrepancy from a previously reportet experimental value of 17.5 s. If the possibility of finestructure mixing to a…
Precise lifetime determination of the metastable 3d 2 D 5/2 level in Ca + by "electron shelving"
1996
Ca+ ions confined as a cloud in a Paul trap were excited and cooled by radiation from two lasers, tuned to the 4s2S1/2 − 4p2P1/2 and 4p2P1/2 − 3d2D3/2 transitions. The strong fluorescence of these lines disappears when we excite the ions simultaneously by a third laser on the 3d2D3/2 − 4p2P3/2 line because of population trapping in the metastable 3d2D5/2 state, into which the 4p2P3/2 level decays. From the time dependence of the fluorescence after blocking the third laser we determined the lifetime of the 3d2D5/2 level. Our result of τ = 1064(17) ms improves earlier results and agrees with the value recently computed by Liaw using the Brueckner approximation.
The bistable potential: An archetype for classical and quantum systems
2012
In this work we analyze the transient dynamics of three different classical and quantum systems. First, we consider a classical Brownian particle moving in an asymmetric bistable potential, subject to a multiplicative and additive noise source. We investigate the role of these two noise sources on the life time of the metastable state. A nonmonotonic behavior of the lifetime as a function of both additive and multiplicative noise intensities is found, revealing the phenomenon of noise enhanced stability. Afterward, by using a LotkaVolterra model, the dynamics of two competing species in the presence of Lévy noise sources is analyzed. Quasiperiodic oscillations and stochastic resonance pheno…
Physiologically-Based Pharmacokinetic/Pharmacodynamic Model of MBQ-167 to Predict Tumor Growth Inhibition in Mice
2020
MBQ-167 is a dual inhibitor of the Rho GTPases Rac and Cdc42 that has shown promising results as an anti-cancer therapeutic at the preclinical stage. This drug has been tested in vitro and in vivo in metastatic breast cancer mouse models. The aim of this study is to develop a physiologically based pharmacokinetic/pharmacodynamic (PBPK-PD) model of MBQ-167 to predict tumor growth inhibition following intraperitoneal (IP) administration in mice bearing Triple Negative and HER2+ mammary tumors. PBPK and Simeoni tumor growth inhibition (TGI) models were developed using the Simcyp V19 Animal Simulator. Our developed PBPK framework adequately describes the time course of MBQ-167 in each of the mo…
Activin A and bone metastasis
2010
Activin A, is a multifunctional cytokine of the transforming growth factor-b superfamily of growth factors. This molecule has been shown to be implicated in the regulation of a broad range of important biological functions including bone remodelling. Therefore, a deregulation in the activin signalling pathway may result in disturbances of normal bone metabolism and, eventually, in the onset of severe pathological conditions associated with an altered bone resorption. These observations support the concept that Act A might also be implicated in the pathogenesis of bone metastasis. This review provides insight into the most recent advances in understanding the role of this growth factor in th…
Nanoencapsulation in Lipid-Core Nanocapsules Controls Mometasone Furoate Skin Permeability Rate and Its Penetration to the Deeper Skin Layers
2013
<b><i>Aims:</i></b> The influence of nanoencapsulation of mometasone furoate (MF) in poly(ε-caprolactone) lipid-core nanocapsules (LNC) on its in vitro human skin permeation and penetration was evaluated. <b><i>Methods:</i></b> Semisolid formulations were prepared by increasing the viscosity of LNC using a carbomer (Carbopol® Ultrez at 0.5% w/v). Two complementary techniques (the static Franz diffusion cell model and the Saarbrücken penetration model) were used to evaluate skin permeation/penetration. <b><i>Results:</i></b> The drug release rate was decreased by nanoencapsulation. The skin permeability of MF was control…