First principles investigation of finite-temperature behavior in small sodium clusters

A systematic and detailed investigation of the finite-temperature behavior of small sodium clusters, Na_n, in the size range of n= 8 to 50 are carried out. The simulations are performed using density-functional molecular-dynamics with ultrasoft pseudopotentials. A number of thermodynamic indicators such as specific heat, caloric curve, root-mean-square bond length fluctuation, deviation energy, etc. are calculated for each of the clusters. Size dependence of these indicators reveals several interesting features. The smallest clusters with n= 8 and 10, do not show any signature of melting transition. With the increase in size, broad peak in the specific heat is developed, which alternately for larger clusters evolves into a sharper one, indicating a solidlike to liquidlike transition. The melting temperatures show irregular pattern similar to experimentally observed one for larger clusters [ M. Schmidt et al., Nature (London) 393, 238 (1998) ]. The present calculations also reveal a remarkable size-sensitive effect in the size range of n= 40 to 55. While Na_40 and Na_55 show well developed peaks in the specific heat curve, Na_50 cluster exhibits a rather broad peak, indicating a poorly-defined melting transition. Such a feature has been experimentally observed for gallium and aluminum clusters [ G. A. Breaux et al., J. Am. Chem. Soc. 126, 8628 (2004); G. A.Breaux et al., Phys. Rev. Lett. 94, 173401 (2005) ].Comment: 8 pages, 11 figure

Measuring Technology Achievement of Nations and the Capacity to Participate in the Network Age

human development, democracy

What Do They Do Different? A Comparison of Practices at Award Winning Technology Centers That Work and Non-Award Winning Centers

Objective: The purpose of this study was to determine characteristics of award winning Career and Technical Centers that may contribute to best practices in the integration of core academic concepts into the Career and Technical Education curriculum. These responses were compared to non-award winning schools in order to determine what award winning schools may have done differently that could have contributed to their success. Background: It is widely accepted that educators should place an increased emphasis on workforce readiness in secondary education to prepare students for a global economy that is becoming increasingly complex and knowledge-based. New participants must enter our nation’s workforce, properly equipped with the applied skills and knowledge to remain competitive throughout the twenty-first century. Methods: A researcher-developed questionnaire was used to collect data for this study. The questionnaire was based on related literature concerning integrating academic concepts into the CTE curriculum. Results: The data indicated that participants at award-winning schools perceived their school’s integration practices to be much more successful than these at non-award-winning schools in presage, process, and context variables. Conclusion: This study proved to be consistent with much of the previously published body of literature concerning the integration of academics in to the context of CTE and the value of properly supported and educated teachers and administrators. Application: The results do imply that previous researchers and practitioners were correct in their assumptions that an integrated CTE curriculum leads to higher student achieveme

Exchange parameters from approximate self-interaction correction scheme

The approximate atomic self-interaction corrections (ASIC) method to density functional theory is put to the test by calculating the exchange interaction for a number of prototypical materials, critical to local exchange and correlation functionals. ASIC total energy calculations are mapped onto an Heisenberg pair-wise interaction and the exchange constants J are compared to those obtained with other methods. In general the ASIC scheme drastically improves the bandstructure, which for almost all the cases investigated resemble closely available photo-emission data. In contrast the results for the exchange parameters are less satisfactory. Although ASIC performs reasonably well for systems where the magnetism originates from half-filled bands, it suffers from similar problems than those of LDA for other situations. In particular the exchange constants are still overestimated. This reflects a subtle interplay between exchange and correlation energy, not captured by the ASIC.Comment: 10 page

Origin of negative differential resistance in a strongly coupled single molecule-metal junction device

A new mechanism is proposed to explain the origin of negative differential resistance (NDR) in a strongly coupled single molecule-metal junction. A first-principles quantum transport calculation in a Fe-terpyridine linker molecule sandwiched between a pair of gold electrodes is presented. Upon increasing applied bias, it is found that a new phase in the broken symmetry wavefunction of the molecule emerges from the mixing of occupied and unoccupied molecular orbital. As a consequence, a non-linear change in the coupling between molecule and lead is evolved resulting to NDR. This model can be used to explain NDR in other class of metal-molecule junction device.Comment: Submitted for review on Feb 4, 200

Design and Implementation of a Measurement-Based Policy-Driven Resource Management Framework For Converged Networks

This paper presents the design and implementation of a measurement-based QoS and resource management framework, CNQF (Converged Networks QoS Management Framework). CNQF is designed to provide unified, scalable QoS control and resource management through the use of a policy-based network management paradigm. It achieves this via distributed functional entities that are deployed to co-ordinate the resources of the transport network through centralized policy-driven decisions supported by measurement-based control architecture. We present the CNQF architecture, implementation of the prototype and validation of various inbuilt QoS control mechanisms using real traffic flows on a Linux-based experimental test bed.Comment: in Ictact Journal On Communication Technology: Special Issue On Next Generation Wireless Networks And Applications, June 2011, Volume 2, Issue 2, Issn: 2229-6948(Online

Conceptualising 'the relationship' in intensive key worker support as a therapeutic medium

Across various welfare and justice systems, intensive key worker support is a model of working considered effective for individuals and families identified as having multiple and complex needs. The high profile 'troubled families' programme in England is the most recent prominent example of such a model. The key worker role is to assess an individual’s needs, carry out support planning, provide and/or co-ordinate the delivery of supportive interventions and complete care plan reviews. This requires the key worker to work on a one-to-one basis with individuals which, in turn, demands the ability to form effective relationships. In this paper and using evidence from a number of studies, I look at how the key worker-client relationship is developed and maintained. I examine the skills, processes and communication strategies that allow key workers to engage clients, build relationships and drive change. I also explore the notion that the key worker-service user relationship is itself a ‘therapeutic’ medium and is therefore a productive practice in its own right. The paper suggests that while key workers might not be trained therapists or counsellors, they might be equipped to address some emotional challenges that individuals with complex needs face and build therapeutic relationships with them