2,044 research outputs found
Direct methods for incommensurate intergrowth compounds. II. Determination of the modulation using only main reflections
Time-resolved observation of ballistic acceleration of electrons in GaAs quantum wells
The authors have studied high-field parallel transport of photoinjected carriers in GaAs quantum wells using femtosecond optical spectroscopy. They have directly observed the transient nonequilibrium distribution functions that occur during the field-induced acceleration of the electrons. At a high field (16 kV cm-1), a nonthermal high-energy tail in the distribution function is apparent during the first 150 fs, which is due to electrons ballistically accelerated from the band edge. At later times, the authors observe the relaxation of the applied electric field due both to radiation from the accelerating carriers and from the build-up of space charge as the electron and hole gases separate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48929/2/ss920b31.pd
Labour Market and Social Policy in Italy: Challenges and Changes. Bertelsmann Policy Brief #2016/02
vEight years after the outbreak of the financial crisis, Italy has still to cope with and
overcome a plethora of economic and social challenges. On top of this, it faces an
unfavourable demographic structure and severe disparities between its northern and
southern regions. Some promising reforms have recently been enacted, specifically
targeting poverty and social exclusion. However, much more remains to be done on
the way towards greater economic stability and widely shared prosperity
Aharonov-Anandan Effect Induced by Spin-Orbit Interaction and Charge-Density-Waves in Mesoscopic Rings
We study the spin-dependent geometric phase effect in mesoscopic rings of
charge-density-wave(CDW) materials. When electron spin is explicitly taken into
account, we show that the spin-dependent Aharonov-Casher phase can have a
pronounced frustration effects on such CDW materials with appropriate electron
filling. We show that this frustration has observable consequences for
transport experiment. We identify a phase transition from a Peierls insulator
to metal, which is induced by spin-dependent phase interference effects.
Mesoscopic CDW materials and spin-dependent geometric phase effects, and their
interplay, are becoming attractive opportunities for exploitation with the
rapid development of modern fabrication technology.Comment: 5 pages, 6 figures, to appear in Phys.Rev.B(Aug.15, 1998
Enhancing staff attitudes, knowledge and skills in supporting the self-determination of adults with intellectual disability in residential settings in Hong Kong: A pretest-posttest comparison group design
Background: The ecological perspective recognizes the critical role that is played by rehabilitation personnel in helping people with intellectual disability (ID) to exercise self-determination, particularly in residential settings. In Hong Kong, the authors developed the first staff training programme of its kind to strengthen the competence of personnel in this area. The purpose of this study was to examine the effectiveness of staff training in enhancing residential staff's attitudes, knowledge and facilitation skills in assisting residents with ID to exercise self-determination. Methods: A pretest-posttest comparison group design was adopted. Thirty-two participants in an experimental group attended a six-session staff training programme. A 34-item self-constructed scale was designed and used for measuring the effectiveness of the staff training. Results: The results showed that the experimental group achieved statistically significant positive changes in all domains, whereas no significant changes were found in the comparison group. Conclusions: The findings provided initial evidence of the effectiveness of staff training that uses an interactional attitude-knowledge-skills model for Chinese rehabilitation personnel. The factors that contributed to its effectiveness were discussed and recommendations for future research were made. © Journal Compilation © 2007 Blackwell Publishing Ltd.postprin
A model-based approach for multiple QoS in scheduling: from models to implementation
Meeting multiple Quality of Service (QoS) requirements is an important factor in the success of complex software systems. This paper presents an automated, model-based scheduler synthesis approach for scheduling application software tasks to meet multiple QoS requirements. As a first step, it shows how designers can meet deadlock-freedom and timeliness requirements, in a manner that (i) does not over-provision resources, (ii) does not require architectural changes to the system, and that (iii) leaves enough degrees of freedom to pursue further properties. A major benefit of our synthesis methodology is that it increases traceability, by linking each scheduling constraint with a specific pair of QoS property and underlying platform execution model, so as to facilitate the validation of the scheduling constraints and the understanding of the overall system behaviour, required to meet further QoS properties.
The paper shows how the methodology is applied in practice and also presents a prototype implementation infrastructure for executing an application on top of common operating systems, without requiring modifications of the latter
Stripes, Vibrations and Superconductivity
We propose a model of a spatially modulated collective charge state of
superconducting cuprates. The regions of higher carrier density (stripes) are
described in terms of Luttinger liquids and the regions of lower density as a
two-dimensional interacting bosonic gas of d_{x^2-y^2} hole pairs. The
interactions among the elementary excitations are repulsive and the transition
to the superconducting state is driven by decay processes. Vibrations of the
CCS and the lattice, although not participating directly in the binding
mechanism, are fundamental for superconductivity. The superfluid density and
the lattice have a strong tendency to modulation implying a still unobserved
dimerized stripe phase in cuprates. The phase diagram of the model has a
crossover from 1D to 2D behavior and a pseudogap region where the amplitude of
the order parameters are finite but phase coherence is not established. We
discuss the nature of the spin fluctuations and the unusual isotope effect
within the model.Comment: 51 pages, 20 figures. Post-March Meeting version: New references are
added, some of the typos are corrected, and a few new discussions are
include
- …