27,216 research outputs found
Torsion-Adding and Asymptotic Winding Number for Periodic Window Sequences
In parameter space of nonlinear dynamical systems, windows of periodic states
are aligned following routes of period-adding configuring periodic window
sequences. In state space of driven nonlinear oscillators, we determine the
torsion associated with the periodic states and identify regions of uniform
torsion in the window sequences. Moreover, we find that the measured of torsion
differs by a constant between successive windows in periodic window sequences.
We call this phenomenon as torsion-adding. Finally, combining the torsion and
the period adding rules, we deduce a general rule to obtain the asymptotic
winding number in the accumulation limit of such periodic window sequences
Irreversibility and the arrow of time in a quenched quantum system
Irreversibility is one of the most intriguing concepts in physics. While
microscopic physical laws are perfectly reversible, macroscopic average
behavior has a preferred direction of time. According to the second law of
thermodynamics, this arrow of time is associated with a positive mean entropy
production. Using a nuclear magnetic resonance setup, we measure the
nonequilibrium entropy produced in an isolated spin-1/2 system following fast
quenches of an external magnetic field and experimentally demonstrate that it
is equal to the entropic distance, expressed by the Kullback-Leibler
divergence, between a microscopic process and its time-reverse. Our result
addresses the concept of irreversibility from a microscopic quantum standpoint.Comment: 8 pages, 7 figures, RevTeX4-1; Accepted for publication Phys. Rev.
Let
Timescale for equilibration of N/Z gradients in dinuclear systems
Equilibration of N/Z in binary breakup of an excited and transiently deformed
projectile-like fragment (PLF*), produced in peripheral collisions of 64Zn +
27Al, 64Zn, 209Bi at E/A = 45 MeV, is examined. The composition of emitted
light fragments (3<=Z<=6) changes with the decay angle of the PLF*. The most
neutron-rich fragments observed are associated with a small rotation angle. A
clear target dependence is observed with the largest initial N/Z correlated
with the heavy, neutron-rich target. Using the rotation angle as a clock, we
deduce that N/Z equilibration persists for times as long as 3-4 zs (1zs = 1 x
10^-21 s = 300 fm/c). The rate of N/Z equilibration is found to depend on the
initial neutron gradient within the PLF*.Comment: 6 pages, 4 figure
The measurement and assessment of quality in agricultural research institutionS.
We present the measure of quality introduced by the review team of Embrapa to evaluate its research projects. The quality measurement scheme comprises four different dimensions (External Validity, Internal Validity, Institutional Adequacy, and Formal Adequacy). The quality measurements are used as dependent variables in a multivariate effort to identify important factors necessary to improve overall as well as specific quality aspects
Effect of nucleon exchange on projectile multifragmentation in the reactions of 28Si + 112Sn and 124Sn at 30 and 50 MeV/nucleon
Multifragmentation of quasiprojectiles was studied in reactions of 28Si beam
with 112Sn and 124Sn targets at projectile energies 30 and 50 MeV/nucleon. The
quasiprojectile observables were reconstructed using isotopically identified
charged particles with Z_f <= 5 detected at forward angles. The nucleon
exchange between projectile and target was investigated using isospin and
excitation energy of reconstructed quasiprojectile. For events with total
reconstructed charge equal to the charge of the beam (Z_tot = 14) the influence
of beam energy and target isospin on neutron transfer was studied in detail.
Simulations employing subsequently model of deep inelastic transfer,
statistical model of multifragmentation and software replica of FAUST detector
array were carried out. A concept of deep inelastic transfer provides good
description of production of highly excited quasiprojectiles. The isospin and
excitation energy of quasiprojectile were described with good overall
agreement. The fragment multiplicity, charge and isospin were reproduced
satisfactorily. The range of contributing impact parameters was determined
using backtracing procedure.Comment: 11 pages, 8 Postscript figures, LaTeX, to appear in Phys. Rev. C (
Dec 2000
- …