A short-range weather prediction system for South Africa based on a multi-model approach

The accurate prediction of rainfall events, in terms of their timing, location and rainfall depth, is important to a wide range of social and economic applications. At many operational weather prediction centres, as is also the case at the South African Weather Service, forecasters use deterministic model outputs as guidance to produce subjective probabilistic rainfall forecasts. The aim of this research was to determine the skill of a new objective multi-model, multi-institute probabilistic ensemble forecast system for South Africa. Such forecasts are obtained by combining the rainfall forecasts of 2 operational high-resolution regional atmospheric models in South Africa. The first model is the Unified Model (UM), which is operational at the South African Weather Service. The UM contributes 3 ensemble members, each with a different physics scheme, data assimilation techniques and horizontal resolution. The second model is the Conformal-Cubic Atmospheric Model (CCAM) which is operational at the Council for Scientific and Industrial Research, which in turn contributed 2 members to the ensemble system based on different horizontal resolutions. A single-model ensemble forecast, with each of the ensemble members having equal weights, was constructed for the UM and CCAM models, respectively. These UM and CCAM single-model ensemble predictions are then combined into a multi-model ensemble prediction, using simple un-weighted averaging. The probabilistic forecasts produced by the single-model system as well as the multi-model system have been tested against observed rainfall data over 3 austral summer 6-month periods from 2006/07 to 2008/09, using the Brier skill score, relative operating characteristics, and the reliability diagram. The forecast system was found to be more skilful than the persistence forecast. Moreover, the system outscores the forecast skill of the individual models

Dr. G. D. Scholtz se Geskiedenis van die nederduitse hervormde of gereformeerde kerk

No Abstract

Die persoonlikheidseienskappe en bestuurspotensiaal van bestuursgemotiveerde persone

The original publication is available at http://www.sajip.co.zaThe personality traits and managerial potential of managerial motivated persons: In the ligth of criticisms of the psychometric suitability of existing measures of managerial motivation a new scale, the Managerial Motivation Questionnaire (MMQ), was developed. This was done on the basis of a comprehensive study of the literature on managerial motivation and the role-motivation theory of Miner. The MMQ demonstrated adequate internal consistency. The aim of this study is to clarify the construct validity of the MMQ. Significant and positive correlations were found between managerial motivation, overall managerial potential, and nine managerial dimensions. The construct validity of the MMQ was further supported by correlations between sixteen personality traits and managerial motivation.In die lig van kritiek teen die psigometriese geskiktheid van bestaande meetinstrumente van bestuursmotivering is 'n nuwe skaal, die Bestuursmotiveringsvraelys (BMV)/ ontwikkel. Dit is gedoen op grond van die konseptuele omiyning van bestuursmotivering en die rolmotiveringsteorie van Miner. Die BMV vertoon toereikende interne konsekwentheid. Die doel van hierdie studie is om die konstrukgeldigheid van die BMV verder op te klaar. Beduidend positiewe korrelasies is tussen bestuursmotivering/ globale bestuurspotensiaal en nege bestuursdimensies gevind. Hierbenewens het die korrelasies tussen sestien persoonlikheidseienskappe en bestuursmotivering verdere ondersteunende bewyse gelewer van die konstrukgeldigheid van die BMV.SA Journal of Industrial PsychologyPublishers' Versio

Die ware kerk en 'n valse kerk Mens mag jou van die kerk nie afske! Nie

No Abstract

Application of Monte Carlo-based statistical significance determinations to the Beta Cephei stars V400 Car, V401 Car, V403 Car and V405 Car

We have used Lomb-Scargle periodogram analysis and Monte Carlo significance tests to detect periodicities above the 3-sigma level in the Beta Cephei stars V400 Car, V401 Car, V403 Car and V405 Car. These methods produce six previously unreported periodicities in the expected frequency range of excited pulsations: one in V400 Car, three in V401 Car, one in V403 Car and one in V405 Car. One of these six frequencies is significant above the 4-sigma level. We provide statistical significances for all of the periodicities found in these four stars.Comment: 11 pages, 17 figure

End-to-End QoS Support for a Medical Grid Service Infrastructure

Quality of Service support is an important prerequisite for the adoption of Grid technologies for medical applications. The GEMSS Grid infrastructure addressed this issue by offering end-to-end QoS in the form of explicit timeliness guarantees for compute-intensive medical simulation services. Within GEMSS, parallel applications installed on clusters or other HPC hardware may be exposed as QoS-aware Grid services for which clients may dynamically negotiate QoS constraints with respect to response time and price using Service Level Agreements. The GEMSS infrastructure and middleware is based on standard Web services technology and relies on a reservation based approach to QoS coupled with application specific performance models. In this paper we present an overview of the GEMSS infrastructure, describe the available QoS and security mechanisms, and demonstrate the effectiveness of our methods with a Grid-enabled medical imaging service

Short-coherence length superconductivity in the Attractive Hubbard Model in three dimensions

We study the normal state and the superconducting transition in the Attractive Hubbard Model in three dimensions, using self-consistent diagrammatics. Our results for the self-consistent $T$-matrix approximation are consistent with 3D-XY power-law critical scaling and finite-size scaling. This is in contrast to the exponential 2D-XY scaling the method was able to capture in our previous 2D calculation. We find the 3D transition temperature at quarter-filling and $U=-4t$ to be $T_c=0.207t$. The 3D critical regime is much narrower than in 2D and the ratio of the mean-field transition to $T_c$ is about 5 times smaller than in 2D. We also find that, for the parameters we consider, the pseudogap regime in 3D (as in 2D) coincides with the critical scaling regime.Comment: 4 pages, 5 figure

D S Pieter Vandrimmelen

No Abstract

Fragmentation of chloroplast coupling factor in dependence of bound nucleotides Preparation of a reconstitutionally active form of subunit δ

AbstractPrevious studies on the ability of CF1, fragments to reconstitute photophosphorylation in CF1,-depleted thylakoids have shown that the degree of reconstitution was correlated with the presence of subunit δ in the fragment. This was taken as evidence that subunit δ was necessary for plugging the active proton channel CF0 [(1986) Eur. J. Biochem. 160, 635–643]. We questioned whether or not δ alone had this ability. In order to obtain δ we investigated the role of bound nucleotides in the stability of CF1. Starting from ammonium sulfate-precipitated CF1, we found that a low content of bound ADP (1 mol ADP/mol CF1) seemed to stabilize the β—δ interaction, while loosening the interaction between α,β and γ. By elution from an anion-exchange column in the presence of the nonionic surfactant Mega 9 we obtained β3δ and CF1(—δ) (both containing one ADP) or, after washing with alcohol/glycerol mixtures, β (nucleotide-free) and CF1/CF1(—ϵ). On the other hand, with a further 2 ADP and 2 ATP bound to CF1, (after incubation with excess ATP) the α-β-γ interaction was stabilized in such a way that subunit δ alone could be isolated from the complex. Subunit δ, when isolated by this procedure and added back to CF1-depleted thylakoids, reconstituted a high rate of photophosphorylation