1,566 research outputs found
Nonlinear Model of non-Debye Relaxation
We present a simple nonlinear relaxation equation which contains the Debye
equation as a particular case. The suggested relaxation equation results in
power-law decay of fluctuations. This equation contains a parameter defining
the frequency dependence of the dielectric permittivity similarly to the
well-known one-parameter phenomenological equations of Cole-Cole, Davidson-Cole
and Kohlrausch-Williams-Watts. Unlike these models, the obtained dielectric
permittivity (i) obeys to the Kramers-Kronig relation; (ii) has proper
behaviour at large frequency; (iii) its imaginary part, conductivity, shows a
power-law frequency dependence \sigma ~ \omega^n where n<1 corresponds to
empirical Jonscher's universal relaxation law while n>1 is also observed in
several experiments. The nonlinear equation proposed may be useful in various
fields of relaxation theory
Deflection of field-free aligned molecules
We consider deflection of polarizable molecules by inhomogeneous optical
fields, and analyze the role of molecular orientation and rotation in the
scattering process. It is shown that molecular rotation induces spectacular
rainbow-like features in the distribution of the scattering angle. Moreover, by
pre-shaping molecular angular distribution with the help of short and strong
femtosecond laser pulses, one may efficiently control the scattering process,
manipulate the average deflection angle and its distribution, and reduce
substantially the angular dispersion of the deflected molecules. This opens new
ways for many applications involving molecular focusing, guiding and trapping
by optical and static fields.Comment: 4 pages, 4 figure
Radiative orbital electron capture by the atomic nucleus
The rate for the photon emission accompanying orbital 1S electron capture by
the atomic nucleus is recalculated. While a photon can be emitted by the
electron or by the nucleus, the use of the length gauge significantly
suppresses the nuclear contribution. Our calculations resolve the long standing
discrepancy of theoretical predictions with experimental data for
forbidden transitions. We illustrate the results by comparison with the data
established experimentally for the first forbidden unique decays of Ca
and Tl.Comment: 18 pages, 2 figures, submitted to Phys. Rev.
Radiative electron capture in the first forbidden unique decay of 81Kr
The photon spectrum accompanying the orbital K-electron capture in the first
forbidden unique decay of 81Kr was measured. The total radiation intensity for
the photon energies larger than 50 keV was found to be 1.47(6) x 10^{-4} per
K-capture. Both the shape of the spectrum and its intensity relative to the
ordinary, non-radiative capture rate, are compared to theoretical predictions.
The best agreement is found for the recently developed model which employs the
length gauge for the electromagnetic field.Comment: 7 pages, 6 figure
Optimal molecular alignment and orientation through rotational ladder climbing
We study the control by electromagnetic fields of molecular alignment and
orientation, in a linear, rigid rotor model. With the help of a monotonically
convergent algorithm, we find that the optimal field is in the microwave part
of the spectrum and acts by resonantly exciting the rotation of the molecule
progressively from the ground state, i.e., by rotational ladder climbing. This
mechanism is present not only when maximizing orientation or alignment, but
also when using prescribed target states that simultaneously optimize the
efficiency of orientation/alignment and its duration. The extension of the
optimization method to consider a finite rotational temperature is also
presented.Comment: 14 pages, 12 figure
Wage Divergence and Asymmetries in Unemployment in a Model with Biased Technical Change
In this article we assume two levels of skills and two classes of goods, one produced with a technology requiring high skills, the other produced with a technology that can be operated by both low and high skilled workers. Our model generates two distinct labour market regimes. In one regime we show technical change can be the cause of wage divergence between skilled and unskilled workers. This result is consistent with recent evidence on wage differentials. Adding the Phillips-effect shows this wage divergence can be "traded off" against unemployment of low skilled workers, and hence explains evidence on skill asymmetries in unemployment. Under the alternative regime these effects do not exist but high skilled workers may replace low skilled workers driving them out of their jobs.economics of technology ;
Controlling Molecular Scattering by Laser-Induced Field-Free Alignment
We consider deflection of polarizable molecules by inhomogeneous optical
fields, and analyze the role of molecular orientation and rotation in the
scattering process. It is shown that molecular rotation induces spectacular
rainbow-like features in the distribution of the scattering angle. Moreover, by
preshaping molecular angular distribution with the help of short and strong
femtosecond laser pulses, one may efficiently control the scattering process,
manipulate the average deflection angle and its distribution, and reduce
substantially the angular dispersion of the deflected molecules. We provide
quantum and classical treatment of the deflection process. The effects of
strong deflecting field on the scattering of rotating molecules are considered
by the means of the adiabatic invariants formalism. This new control scheme
opens new ways for many applications involving molecular focusing, guiding and
trapping by optical and static fields
Structure and Dynamics of the VAULT COMPLEX
Vaults are the largest ribonucleoprotein particles found in eukaryotic cells. The maincomponent of these 13 MDa structures is the Mr 100,000 major vault protein (MVP).In mammalian cells, about 96 copies of this protein are necessary to form one vaultparticle. Two additional proteins are associated with the complex, the so-called minorvault proteins of Mr 193,000 (VPARP) and Mr 240,000 (TEP1), as well as severaluntranslated RNA molecules of 86-141 bases. The components are arranged into ahollow barrel-like structure with each half representing eight arches, which are reminiscent to the arched vaulted ceilings of cathedrals. Therefore, when vaults werefirst observed as contaminants in a preparation of clathrin coated vesicles form rat liver,the large complexes were named ‘vaults’. The typical morphology and the individualvault constituents appear conserved throughout evolution, implying an important rolefor vaults in cellular metabolism. A number of functions have been suggested for theseunique particles, but the general idea is that vaults function in intracellular transportprocesses. Nevertheless, the precise cellular function of the vault complex has not yetbeen elucidated. In this study we attempted to gain insight in vault biogenesis,dynamics and their interaction with other cellular components in order to unravel thephysiological significance of vault
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