Optical properties of Mn4+ ions in GaN:Mn codoped with Mg acceptors

The optical properties of Mn-Mg codoped epitaxial GaN were studied. Addition of Mg acceptors quenches the weak manganese-related photoluminescence (PL) band at 1.3 eV in GaN:Mn and a series of sharp PL peaks are observed at 1 eV in codoped epilayers. The change in PL spectra indicates that Mg addition stabilizes the Mn4+ charge state by decreasing the Fermi level. The 1 eV PL peaks are tentatively attributed to intra center transitions involving Mn4+ ions. Spin allowed 3d-shell 4T2-4T1 transitions and their phonon replicas are involved. The relative intensities of the sharp peaks are strongly dependent on the excitation wavelength, indicating the optically active Mn4+ centers involved in the separate peaks are different. The temperature dependence of the PL spectrum suggests the presence of at least three distinct Mn4+ complex centers.Comment: 14 pages, 3 figures, 1 table, accepted by Appl. Phys. Let

A Lindley-type equation arising from a carousel problem

In this paper we consider a system with two carousels operated by one picker. The items to be picked are randomly located on the carousels and the pick times follow a phase-type distribution. The picker alternates between the two carousels, picking one item at a time. Important performance characteristics are the waiting time of the picker and the throughput of the two carousels. The waiting time of the picker satisfies an equation very similar to Lindley's equation for the waiting time in the PH/U/1 queue. Although the latter equation has no simple solution, we show that the one for the waiting time of the picker can be solved explicitly. Furthermore, it is well known that the mean waiting time in the PH/U/1 queue depends on to the complete interarrival time distribution, but numerical results show that, for the carousel system, the mean waiting time and throughput are rather insensitive to the pick-time distribution.Comment: 10 pages, 1 figure, 19 reference

Cross-Border Insolvency Law in Europe: Present Status and Future Prospects

In May 2007 the European countries celebrated the first lustrum of the EU Insolvency Regulation (1346/2000). This article describes where Europe stands with its model which is based on well known theories of private international law for dealing with cross-border insolvencies. The EU Insolvency Regulation provides for a national court to exercise international jurisdiction to open insolvency proceedings. The basis for international jurisdiction is the debtor\'s “centre of main interests” or COMI. The two most important cases decided by the European Court of Justice (17 January 2006 Staubitz Schreiber and 2 May 2006 Eurofood) are discussed. The article further analyses the regulation\'s legal concept and its procedural context and explains that \'financial institutions\' are not covered by the Insolvency Regulation, but by separate directives (2001/17; 2001/24). After having taken stock several suggestions are submitted for improvement of the system of cross-border insolvency in Europe. * Prof Bob Wessels. Independent legal counsel and advisor.PER/PELJ Vol. 1 2008: pp. 1-3

The Deterrents To CPE Effectiveness In The Accounting Profession: A Factor Analytic Study

This paper examines the effectiveness of CPE programs for accountants and whether there are deterrents that prevent some CPAs from getting the most out of their CPE hours.  Previous studies (Cross, 1981; Dao, 1975; Darkenwald & Merriam 1982; Darkenwald & Valentine, 1985, Chanidinia & Griffith, 1975; Johnstone & Rivera, 1965; Scanlan & Darkenwald, 1984) identified several deterrents or barriers which inhibit voluntary participation in continuing professional education.  However, little research has been conducted exploring the relative importance of deterrents to participation in settings in which participation is mandatory.  A survey of 1,957 North Carolina CPAs showed that deterrents identified in earlier participation studies are negatively and significantly related to the effectiveness of mandatory continuing professional education for the accounting profession

An Examination Of The Support For Changes In CPE Regulations For Accountants

This paper investigates the relationship between perceptions of effectiveness of mandatory continuing professional education (CPE) programs and what support, if any, there is for changes in those regulations.  A survey of North Carolina Certified Public Accountants was conducted to determine which of three components of CPE effectiveness was most important and the degree of support for nine possible changes which would either increase the rigor of the regulations or relax the standards