762 research outputs found
Conductance of Pd-H nanojunctions
Results of an experimental study of palladium nanojunctions in hydrogen
environment are presented. Two new hydrogen-related atomic configurations are
found, which have a conductances of ~0.5 and ~1 quantum unit (2e^2/h). Phonon
spectrum measurements demonstrate that these configurations are situated
between electrodes containing dissolved hydrogen. The crucial differences
compared to the previously studied Pt-H_2 junctions, and the possible
microscopic realizations of the new configurations in palladium-hydrogen
atomic-sized contacts are discussed.Comment: 4 pages, 4 figure
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
Quantum interference structures in the conductance plateaus of gold nanojunctions
The conductance of breaking metallic nanojunctions shows plateaus alternated
with sudden jumps, corresponding to the stretching of stable atomic
configurations and atomic rearrangements, respectively. We investigate the
structure of the conductance plateaus both by measuring the voltage dependence
of the plateaus' slope on individual junctions and by a detailed statistical
analysis on a large amount of contacts. Though the atomic discreteness of the
junction plays a fundamental role in the evolution of the conductance, we find
that the fine structure of the conductance plateaus is determined by quantum
interference phenomenon to a great extent.Comment: 4 pages, 4 figure
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
Effectiveness of a home-based cognitive behavioral program to manage concerns about falls in community-dwelling, frail older people: results of a randomized controlled trial
Background: Concerns about falls are common among older people. These concerns, also referred to as fear of falling, can have serious physical and psychosocial consequences, such as functional decline, increased risk of falls, activity restriction, and lower social participation. Although cognitive behavioral group programs to reduce concerns about falls are available, no home-based approaches for older people with health problems, who may not be able to attend such group programs are available yet. The aim of this study was to assess the effectiveness of a home-based cognitive behavioral program on concerns about falls, in frail, older people living in the community. Methods: In a randomized controlled trial in the Netherlands, 389 people aged 70 years and older, in fair or poor perceived health, who reported at least some concerns about falls and related activity avoidance were allocated to a control (n = 195) or intervention group (n = 194). The intervention was a home-based, cognitive behavioral program consisting of seven sessions including three home visits and four telephone contacts. The program aims to instill adaptive and realistic views about fall risks via cognitive restructuring and to increase activity and safe behavior using goal setting and action planning and was facilitated by community nurses. Control group participants received usual care. Outcomes at 5 and 12 months follow-up were concerns about falls, activity avoidance due to concerns about falls, disability and falls. Results: At 12 months, the intervention group showed significant lower levels of concerns about falls compared to the control group. Furthermore, significant reductions in activity avoidance, disability and indoor falls were identified in the intervention group compared with the control group. Effect sizes were small to medium. No significant difference in total number of falls was noted between the groups. Conclusions: The home-based, cognitive behavioral program significantly reduces concerns about falls, related activity avoidance, disability and indoor falls in community-living, frail older people. The program may prolong independent living and provides an alternative for those people who are not able or willing to attend group programs
Chronic medical conditions and mental health in older people: disability and psychosocial resources mediate specific mental health effects
Transition from tunneling to direct contact in tungsten nanojunctions
We apply the mechanically controllable break junctions technique to
investigate the transition from tunneling to direct contact in tungsten. This
transition is quite different from that of other metals and is determined by
the local electronic properties of the tungsten surface and the relief of the
electrodes at the point of their closest proximity. The conductance traces show
a rich variety of patterns from the avalanche-like jump to a mesoscopic contact
to the completely smooth transition between direct contact and tunneling. Due
to the occasional absence of an adhesive jump the conductance of the contact
can be continuously monitored at ultra-small electrode separations. The
conductance histograms of tungsten are either featureless or show two distinct
peaks related to the sequential opening of spatially separated groups of
conductance channels. The role of surface states of tungsten and their
contribution to the junction conductance at sub-Angstrom electrode separations
are discussed.Comment: 6 pages, 6 figure
âZicht op Evenwichtâ: een effectieve interventie om bezorgdheid om te vallen en gerelateerd vermijdingsgedrag bij ouderen te verminderen
Valangst en gerelateerd vermijdingsgedrag komen veel voor bij ouderen en kunnen leiden tot een verminderde kwaliteit van
leven, verminderd fysiek en psychosociaal functioneren en vervroegde opname in een verpleeghuis. In een gerandomiseerd
onderzoek onder 540 zelfstandig wonende ouderen met valangst en gerelateerd vermijdingsgedrag zijn de uitvoerbaarheid
en effecten van een cognitief gedragsmatige groepscursus geĂŤvalueerd. De procesgegevens van de interventiegroep (n= 280)
en de cursusleiders (n= 6) wees uit dat de cursus goed uitvoerbaar is, positief beoordeeld wordt en dat deelnemers baat
hebben bij de cursus (61% rapporteert deze baat tot een jaar na de cursus). Wel meldde 26% van de interventiegroep zich
voor de start van de cursus af voor deelname, maar deelnemers die met de cursus begonnen maakten deze doorgaans af
(84%). De effectevaluatie liet positieve uitkomsten zien voor de interventiegroep vergeleken met de controle groep (n= 260);
na de cursus werd minder bezorgdheid om te vallen en gerelateerd vermijdingsgedrag gerapporteerd en meer dagelijkse
activiteit. Ook op de lange termijn waren positieve effecten zichtbaar, onder andere voor bezorgdheid om te vallen en
herhaalde valincidenten. Op basis van deze succesvolle resultaten is de implementatie van de cognitief gedragsmatige
groepscursus âZicht op Evenwichtâ in de Nederlandse gezondheidszorg gestart
The decline and rise of neighbourhoods: the importance of neighbourhood governance
There is a substantial literature on the explanation of neighbourhood change. Most of this literature concentrates on identifying factors and developments behind processes of decline. This paper reviews the literature, focusing on the identification of patterns of neighbourhood change, and argues that the concept of neighbourhood governance is a missing link in attempts to explain these patterns. Including neighbourhood governance in the explanations of neighbourhood change and decline will produce better explanatory models and, finally, a better view about what is actually steering neighbourhood change
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