314 research outputs found
Keijsers, Shklyarevskii and van Kempen Reply
Answer to the Comment on ``Point-Contact Study of Fast and Slow Two-Level
Fluctuators in Metallic Glasses'' by Jan von Delft et al.Comment: 3 pages, no figures, accepted Phys. Rev. Letter
Экономическое обоснование сущности расходов предприятия
This study examined the development of adolescents' conflict frequency and conflict resolution with their best friends, and tested whether adolescents with different personality types differed in these developmental changes from early to middle adolescence. Dutch adolescents (N = 922, 468 boys; Mage = 12.4 years at first wave) annually filled in questionnaires for five consecutive years. Growth modelling revealed that, whereas adolescents' conflict frequency and hostile conflict resolution did not change, positive problem solving, withdrawal, and compliance during conflict with best friends increased from age 12 to 16 years. Adolescents with different personality types differed in the mean levels of conflict frequency and conflict resolution strategies. That is, resilients had less conflict with friends than undercontrollers and overcontrollers. During conflict, resilients used the least hostile conflict resolution and compliance, and employed the most positive problem solving. Undercontrollers adopted the least positive problem solving, and overcontrollers complied and withdrew the most. Using a person-centred approach, three developmental conflict resolution types were identified based on different constellations of the four conflict resolution strategies over time. Adolescents with different personality types had different distributions on the conflict resolution types
Transport properties and point contact spectra of Ni_xNb_{1-x} metallic glasses
Bulk resistivity and point contact spectra of Ni_xNb_{1-x} metallic glasses
have been investigated as functions of temperature (0.3-300K) and magnetic
field (0-12T). Metallic glasses in this family undergo a superconducting phase
transition determined by the Nb concentration. When superconductivity was
suppressed by a strong magnetic field, both the bulk sample R(T) and the point
contact differential resistance curves of Ni_xNb_{1-x} showed logarithmic
behavior at low energies, which is explained by a strong electron - "two level
system" coupling. We studied the temperature, magnetic field and contact
resistance dependence of Ni_{44}Nb_{56} point-contact spectra in the
superconducting state and found telegraph-like fluctuations superimposed on
superconducting characteristics. These R(V) characteristics are extremely
sensitive detectors for slow relaxing "two level system" motion.Comment: 4 pages, 5 figure
Moving in and out of poverty: The within-individual association between socioeconomic status and juvenile delinquency
A family's SES can be changeable over time. This study was the first to investigate if such within-individual changes in family SES are associated with parallel fluctuations in boys' delinquent behavior from childhood to adolescence. Participants were a community sample of boys and their caregivers (N = 503) who were assessed annually for ten consecutive years spanning ages 7-18. Fixed effects models revealed that changes in familial SES were related to changes in delinquency: Youths were more likely to offend during years in which their parents' SES was lower than during years in which their parents' SES was higher. Contrary to expectations, we found no evidence that this association was accounted for by families moving to different neighborhoods or by changes in parenting. Since withinindividual models provide a stricter test of causality than between-individual models, these findings support claims that impacting familial SES may have a direct effect on youths' delinquency. Copyright
Nonlinear Response of a Kondo system: Direct and Alternating Tunneling Currents
Non - equilibrium tunneling current of an Anderson impurity system subject to
both constant and alternating electric fields is studied. A time - dependent
Schrieffer - Wolff transformation maps the time - dependent Anderson
Hamiltonian onto a Kondo one. Perturbation expansion in powers of the Kondo
coupling strength is carried out up to third order, yielding a remarkably
simple analytical expression for the tunneling current. It is found that the
zero - bias anomaly is suppressed by an ac - field. Both dc and the first
harmonic are equally enhanced by the Kondo effect, while the higher harmonics
are relatively small. These results are shown to be valid also below the Kondo
temperature.Comment: 7 pages, RevTeX, 3 PS figures attached, the article has been
significantly developed: time - dependent Schrieffer - Wolff transformation
is presented in the full form, the results are applied to the change in the
direct current induced by an alternating field (2 figures are new
Spin-Orbit-Induced Magnetic Anisotropy for Impurities in Metallic Samples II. Finite Size Dependence in the Kondo Resistivity
The electrical resistivity including the Kondo resistivity increase at low
temperature is calculated for thin films of dilute magnetic alloys. Assuming
that in the non-magnetic host the spin-orbit interaction is strong like in Au
and Cu, the magnetic impurities have a surface anisotropy calculated in part I.
That anisotropy hinders the motion of the spin. Including that anisotropy the
effective electron-impurity coupling is calculated by using the second order
renormalization group equations. The amplitude of the Kondo resistivity
contribution is reduced as the position of the impurity approaches the surface
but the increase occurs approximately at the bulk Kondo temperature. Different
proximity effects observed by Giordano are also explained qualitatively where
the films of magnetic alloys are covered by pure second films with different
mean free path. The theory explains the experimental results in those cases
where a considerable amount of impurities is at the surface inside the
ballistic region.Comment: 39 pages, RevTeX (using epsfig), 15 eps figures included, submitted
to PR
- …