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

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

‘Zicht op Evenwicht’: 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 geëvalueerd. 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 “Zicht op Evenwicht” 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