Absence of exponential sensitivity to small perturbations in nonintegrable systems of spins 1/2

We show that macroscopic nonintegrable lattices of spins 1/2, which are often considered to be chaotic, do not exhibit the basic property of classical chaotic systems, namely, exponential sensitivity to small perturbations. We compare chaotic lattices of classical spins and nonintegrable lattices of spins 1/2 in terms of their magnetization responses to imperfect reversal of spin dynamics known as Loschmidt echo. In the classical case, magnetization exhibits exponential sensitivity to small perturbations of Loschmidt echoes, which is characterized by twice the value of the largest Lyapunov exponent of the system. In the case of spins 1/2, magnetization is only power-law sensitive to small perturbations. Our findings imply that it is impossible to define Lyapunov exponents for lattices of spins 1/2 even in the macroscopic limit. At the same time, the above absence of exponential sensitivity to small perturbations is an encouraging news for the efforts to create quantum simulators. The power-law sensitivity of spin 1/2 lattices to small perturbations is predicted to be measurable in nuclear magnetic resonance experiments.Comment: 12 pages, 8 figures, minor changes, new reference

Job Tasks, Computer Use, and the Decreasing Part-Time Pay Penalty for Women in the UK

Using data from the UK Skills Surveys, we show that the part-time pay penalty for female workers within low- and medium-skilled occupations decreased significantly over the period 1997-2006. The convergence in computer use between part-time and full-time workers within these occupations explains a large share of the decrease in the part-time pay penalty. However, the lower part-time pay penalty is also related to lower wage returns to reading and writing which are performed more intensively by full-time workers. Conversely, the increasing returns to influencing has increased the part-time pay penalty despite the convergence in the influencing task input between part-time and full-time workers. The relative changes in the input and prices of computer use and job tasks together explain more than 50 percent of the decrease in the part-time pay penalty

Terrorism and Integration of Muslim Immigrants

We study the effect that a series of fundamentalist-Islamic terrorist attacks in Europe had on the attitudes of Muslim immigrants in the Netherlands towards integration. Shortly after the attacks, Muslim immigrants' perceived integration, as measured by various indicators, decreased significantly relative to that of non-Muslims immigrants whereas there is no evidence for the existence of a negative trend in the integration of Muslims prior to the terrorist attacks. We further show that terrorism has a particularly negative impact on the integration of the highly educated, employed, and less religious Muslims - those who arguably have a strong potential for integration

Gradual Retirement, Financial Incentives, and Labour Supply of Older Workers: Evidence from a Stated Preference Analysis

Using data from a stated preferences experiment in the Netherlands, we find that replacing full-time pension schemes with schemes that offer gradual retirement opportunities induce workers to retire one year later on average. Total life-time labour supply, however, decreases with 3.4 months because the positive effect of delayed retirement on labour supply is cancelled out by the reduction in working hours before full retirement. The impact of gradual retirement schemes is, however, heterogeneous across groups of workers. Workers with non-routine job tasks retire at a later age when they can gradually retire. Financial incentives, either in terms of changing pension income or the price of leisure, also affect the expected retirement age, but the impact of these financial incentives does not differ with the possibility of gradual retirement. Finally, we find that gradual retirement is not a preferred option among workers as the large majority still prefers full retirement. This especially holds for workers with a lower wage and those with higher life expectancy

Proposal for generalised Supersymmetry Les Houches Accord for see-saw models and PDG numbering scheme

The SUSY Les Houches Accord (SLHA) 2 extended the first SLHA to include various generalisations of the Minimal Supersymmetric Standard Model (MSSM) as well as its simplest next-to-minimal version. Here, we propose further extensions to it, to include the most general and well-established see-saw descriptions (types I/II/III, inverse, and linear) in both an effective and a simple gauged extension of the MSSM framework. In addition, we generalise the PDG numbering scheme to reflect the properties of the particles.Comment: 44 pages. Changed titl

Assessing Domestic Heat Storage Requirements for Energy Flexibility Over Varying Timescales

This paper explores the feasibility of storing heat in an encapsulated store to support thermal load shifting over three timescales: diurnal, weekly and seasonal. A building simulation tool was used to calculate the space heating and hot water demands for four common UK housing types and a range of operating conditions. A custom sizing methodology calculated the capacities of storage required to fully meet the heat demands over the three timescales. Corresponding storage volumes were calculated for a range of heat storage materials deemed suitable for storing heat within a dwelling, either in a tank or as an integral part of the building fabric: hot water, concrete, high-temperature magnetite blocks, and a phase change material. The results indicate that with low temperature heat storage, domestic load shifting is feasible over a few days. Beyond this timescale, the very large storage volumes required make integration in dwellings problematic. Supporting load shifting over 1–2 weeks is feasible with high temperature storage. Retention of heat over periods longer than this is challenging, even with significant levels of insulation. Seasonal storage of heat in an encapsulated store appeared impractical in all cases modelled due to the volume of material required

Needs assessment to strengthen capacity in water and sanitation research in Africa:experiences of the African SNOWS consortium

Despite its contribution to global disease burden, diarrhoeal disease is still a relatively neglected area for research funding, especially in low-income country settings. The SNOWS consortium (Scientists Networked for Outcomes from Water and Sanitation) is funded by the Wellcome Trust under an initiative to build the necessary research skills in Africa. This paper focuses on the research training needs of the consortium as identified during the first three years of the project

Staphylococcus aureus Nasal Carriage among Surgical personnel in National Ribat University Teaching Hospital-Khartoum-Sudan

Introduction: Staphylococcus aureus (S. aureus) is one of the most common causes of both community and hospital acquired bacterial infection. There is strong correlation between S aureus nasal carriage and disease progress. Nasal carriage is high among health care workers. Inappropriate usage of antibiotic may lead to emergence of resistant strains which has serious consequences. Objective: The objective of this study is to reveal the frequency of S aureus nasal carriage and its drug resistance among surgical personnel in National Ribat Teaching Hospital Khartoum Sudan. Methods: This is a hospital-based case study. Nasal smears were taken from medical workers in the surgical department and operational theater at National Ribat Teaching Hospital in Khartoum State, Sudan. Samples were processed, cultured, then susceptibility tests were performed using Bauer-Kirby disc diffusion methods following recommendations of National Committee for Laboratory Standards (NCCLS). Results were analyzed and discussed. Results: Sixty three samples were taken. Thirty were males. Growth was achieved in only eight (12.6%). Majority showed resistance to penicillin. However, alls strain were sensitive to amoxicillin/calvunalic acid, vancomycin and oxacillin. Conclusion: this study gives an early alarm on the problems related to S. aureus colonization rate and its drug resistance. Nevertheless, the small number of our study group is a bit fall. Keywords: drug resistance, hospital acquired bacterial infection Sudan Journal of Medical Science Vol. 3 (4) 2008: pp. 281-28

Risk assessment due to terrorist actions on public transportation networks : a case study in Portugal

The work presented in this paper was performed in collaboration with one of the largest Public Transportation Operator in Portugal and addresses the problem of risk assessment due to terrorist actions involving explosions at different levels. First, a region of the Operator is selected. The elements in the Operator's network with the highest associated risk are highlighted for each threat using the COUNTERACT guidelines. Subsequently, from the group of elements with the highest associated risk, an element is selected for structural safety evaluation under blast loading. Through numerical analysis, different explosion scenarios are studied and the behavior of the structure is presented.This work was performed under Project CH-SECURE, with reference PTDC/ECM/120118/2010, funded by the Portuguese Foundation of Science and Technology - FCT. The authors acknowledge the support. The first author also acknowledges the support from his PhD FCT grant with the reference SFRH/BD/45436/2008