Particle yields in heavy ion collisions and the influence of strong magnetic fields

It is expected that the magnetic field in the surface of magnetars do not exceed $10^{15}$ G. However, in heavy ion collisions, this value is expected to be much higher. We investigate the effects of a magnetic fields varying from $10^{18}$, to $10^{20}$ G in strange matter (composed of $u$, $d$ and $s$ quarks). We model matter as a free gas of baryons and mesons under the influence of an external magnetic field. We study the effects of such strong fields through a $\chi^2$ fit to some data sets of the STAR experiment. For this purpose we solve the Dirac, Rarita-Schwinger, Klein-Gordon and Proca equations subject to magnetic fields in order to obtain the energy expressions and the degeneracy for spin 1/2, spin 3/2, spin 0 and spin 1 particles, respectively. Our results show that a field of the order of $10^{19}$ G produces an improved fitting to the experimental data as compared to the calculations without magnetic field.Comment: 20 pages, 16 figures, 4 table

Managing performance in quality management: A two level study of employee-perceptions and workplace-performance

Purpose: This paper addresses potential effects of the control element in Quality Management. First, behavioural theories on how elements of performance management can affect organisational performance are examined. Secondly, theoretical models on how perceptions of work conditions may impact wellbeing and performance are considered. Direct and indirect pathways from performance management to productivity/quality are inferred. Methodology: Matched employee-workplace data from an economy-wide survey in Britain and two-level structural equation models are used to test the hypothesised associations. Findings: The use of practices in workplaces is inconsistent with a unified performance management approach. Distinct outcomes are expected from separate components in performance management and some may be contingent on workplace size. For example, within Quality-planning, strategy dissemination is positively associated with workplace-productivity; targets are negatively associated with perceptions of job demands and positively correlated with job satisfaction, which in turn can increase workplace-productivity. With respect to Information & Analysis: keeping and analysing records, or monitoring employee-performance via appraisals that assess training needs, are positively associated with workplace-productivity and quality. Originality: This paper illustrates how control in Quality Management can be effective. Although the merits of performance management are subject to ongoing debate, arguments in the literature have tended to focus on performance appraisal. Analyses of economy-wide data linking performance management practices, within Quality Management, to employee perceptions of work conditions, wellbeing and aggregate performance are rare

Measuring Liquidity in Gas Markets: The Case of the UK National Balancing Point. ESRI Research Bulletin 2019/06

Liquidity is the ability to match buyers and sellers at the lowest transaction costs. Therefore, in a liquid market, executing a transaction over a short-time horizon does not imply higher costs than spreading the same transaction over a longer horizon. Policymakers and practitioners traditionally use the churn ratio to measure liquidity in gas markets. The churn ratio is the ratio of traded volume to actual physical delivery. However, this measure does not consider the impact of trading activity on prices. This research focuses on applying different measures of liquidity, which are used in financial markets, to measure and assess the impact of trading activity on prices. The UK National Balancing Point (NBP) is used as a case study, since it is the most mature hub for gas trading in Europe. Therefore, conclusions from this study can be extended to other gas markets. The research shows that a positive correlation exists between trading activity and prices in the market. However, the strength of this correlation changes over time, depending upon market conditions. Specifically, in the presence of oversupply the impact of trading activity on prices is lower, thus implying that trading a high amount of gas is less expensive, and liquidity is high. Consequently, risk management costs are also less expensive

Job Satisfaction and Quality Management: An Empirical Analysis

Purpose – Quality management requires increasing employee involvement that could empower employees, leading to employee and customer satisfaction. Although the literature describes a picture of increasing job demands and work intensification, the evidence of an association between employee job satisfaction and quality management remains mixed and narrow. The purpose of this paper is to investigate this link in the wider economy, and address the roles of human resource management practices that target direct employee participation (job enrichment and high involvement management) in this relationship. Design/methodology/approach – The Workplace Employment Relations Survey of 2004 (WERS2004) provides information on British workplaces including the use of specific quality and human resource management practices, employees' job satisfaction and other outcomes. Latent variable analysis identifies employers' approaches to quality management, job enrichment and high involvement management. Workplace‐level regression analyses illustrate the link between job satisfaction and various desired organizational outcomes. Hierarchical two‐level regression models are used to assess the link between quality management at workplaces and employee job satisfaction. Findings – Although job satisfaction is positively associated with desired workplace outcomes (organizational commitment, productivity and quality), no significant link between quality management and employee job satisfaction is found. By contrast, a positive association between job enrichment and job satisfaction is confirmed, which may be weakened in the presence of quality management. Practical implications – Given the potential impact of job satisfaction on organizational outcomes, job enrichment features should not be neglected when designing jobs so that an effective quality management strategy can be in place. Some weak positive association between high involvement and quality managements with perceived job demands is also observed, and this should be further investigated in more detailed studies of employee well‐being. Originality/value – This is a large empirical study on an economy‐wide sample of workplaces and their employees

Magnetization profile for impurities in graphene nanoribbons

The magnetic properties of graphene-related materials and in particular the spin-polarised edge states predicted for pristine graphene nanoribbons (GNRs) with certain edge geometries have received much attention recently due to a range of possible technological applications. However, the magnetic properties of pristine GNRs are not predicted to be particularly robust in the presence of edge disorder. In this work, we examine the magnetic properties of GNRs doped with transition-metal atoms using a combination of mean-field Hubbard and Density Functional Theory techniques. The effect of impurity location on the magnetic moment of such dopants in GNRs is investigated for the two principal GNR edge geometries - armchair and zigzag. Moment profiles are calculated across the width of the ribbon for both substitutional and adsorbed impurities and regular features are observed for zigzag-edged GNRs in particular. Unlike the case of edge-state induced magnetisation, the moments of magnetic impurities embedded in GNRs are found to be particularly stable in the presence of edge disorder. Our results suggest that the magnetic properties of transition-metal doped GNRs are far more robust than those with moments arising intrinsically due to edge geometry.Comment: submitte

Germany’s Nuclear Power Plant Closures and the Integration of Electricity Markets in Europe

This paper examines the potential implications of national policies that lead to a sudden increase of wind power in the electricity mix for interconnected European electricity markets. More specifically, it examines market integration before and after the closures of eight nuclear power plants that occurred within a period of a few months in Germany during 2011. The short- and- long run interrelationships of daily electricity spot prices, from November 2009 to October 2012, in: APX-ENDEX, BELPEX, EPEX-DE, EPEX-FR, NORDPOOL, OMEL and SWISSIX; and wind power in the German system are analysed. Two MGARCH (Multivariate Generalized Autoregressive Conditional Heteroscedasticity) models with dynamic correlations are used to assess spot market behaviour in the short run, and a fractional cointegration analysis is conducted to investigate changes in the long-run behaviour of electricity spot prices. Results show: positive time-varying correlations between spot prices in markets with substantial shared interconnector capacity; a negative association between wind power penetration in Germany and electricity spot prices in the German and neighbouring markets; and, for most markets, a decreasing speed in mean reversion