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Search Results: 1 - 10 of 370266 matches for " C. de Jager "
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Terrestrial ground temperature variations in relation to solar magnetic variability, including the present Schwabe cycle  [PDF]
C. de Jager, H. Nieuwenhuijzen
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.510136
Abstract: We study the influence of solar activity on climate by investigating the relation between the long-term components of the total magnetic fluxes of both the equatorial and polar fields of the sun and the average terrestrial ground temperature. This is done for the period 1610 (beginning of systematic sunspot observations) till present with an extrapolation to 2015. It is found that from 1610 till about the first half of the 20th century the variation of the long-term average terrestrial ground temperatures is chiefly due to the variation of solar activity, with seemingly random, non-solar residuals. Around 2007, after the Grand Maximum of the 20th century, solar activity, after having gone through a remarkable transition period (~2005 to ~2010), entered into another Grand Episode. That Episode started with the present solar cycle, in shape comparable to the equally weak Schwabe cycle #14. The transition period, in combination with the present low Schwabe cycle causes that the solar contribution to the total terrestrial temperature variation is small during the on-going decade. It results in a slowing down of the rise of temperature after ~2005.
Investigation of the Psychological factors determining the Magnitude of Auditory Sensation
L. C. De Jager
South African Journal of Industrial Psychology , 1975, DOI: 10.4102/sajip.v0i0.269
Abstract: This research deals with some psychological factors that may influence the determination of the magnitude of auditory sensation or pure loudness. Several factors and their influences are discussed. 17 Male and 3 female subjects between 18 and 26 years of age were tested under several different experimental conditions using the method of constant stimuli. Results are discussed in terms of both future research and implications for industry. Opsomming Twintig toetslinge, 17 mans en 3 dames, tussen die ouderdomme 18 en 26 jaar is onder verskillende eksperimentele situasies getoets om die invloed van 'n aantal sielkundige faktore op die bepaling van luidheid te bepaal. Die metode van konstante stimuli is gebruik om die luidheidspeil onder die verskillende eksperimentele situasies te verkry. Die resultate van die ondersoek word bespreek in terme van toekomstige navorsing op hierdie gebied asook die implikasies wat dit vir die bedryf inhou.
Die ontwikkeling van 'n instrument vir die meting van die konstruk sielkundige diepte-orientasie
L. C. De Jager
South African Journal of Industrial Psychology , 1981, DOI: 10.4102/sajip.v0i0.327
Abstract: The development of an instrument (the RD-Depth Questionnaire, Form B) for measuring the construct psychological depth orientation is discussed. Results show that the questionnaire has satisfactory internal consistency and that the items of the questionnaire in general measure the same characteristic. Further research is needed to refine and improve the questionnaire until it meets all the psychometric requirements of a good measuring instrument. Opsomming Die ontwikkeling van 'n instrument (die RD-Diepte Vraelys, Vorm B) vir die meting van die konstruk sielkundige diepteori ntasie word bespreek. Resultate dui daarop dat die vraelys bevredigende interne bestendigheid toon en dat die items van die vraelys oor die algemeen dieselfde eienskap meet. Verdere navorsing word egter nog vereis om die vraelys te verfyn en te verbeter sodat dit aan al die psigometriese vereistes van 'n goeie meetinstrument sal voldoen.
Die meting van sielkundige diepte-orientasie: 'n Verdere verfyning en omlyning
L. C. De Jager
South African Journal of Industrial Psychology , 1987, DOI: 10.4102/sajip.v13i2.462
Abstract: The measurement of psychological depth orientation: a further refinement. As a result of the psychometric weaknesses of the RD-Depth Questionnaire (de Jager, 1979) for measuring psychological depth orientation an effort was made to develop a new instrument. In the present study a new instrument with outstanding psychometric properties (the DJ-Behaviour Questionnaire) was successfully developed and evaluated. As a further step in construct validation the instrument was also successfully correlated with other variables. Reccomendations for future research are made. Opsomming As gevolg van die psigometriese tekortkominge van die RD- iepte Vraelys (de Jager, 1979) vir die meting van sielkundige diepte-orientasie, is 'n poging aangewend om 'n nuwe instrument te ontwikkel. In hierdie ondersoek is daar dan ook daarin geslaag om 'n instrument met besonder bevredigende psigometriese eienskappe (die DJ-Ge- dragsvraelys) te ontwikkel. As 'n verdere stap in konstrukvalidering is die instrument ook suksesvol met ander veranderlikes gekorreleer. Aanbevelings vir toekomstige navorsing word gemaak.
Sielkundige diepte-orientasie: 'n Koseptuele omskrywing en verfyning
L. C. De Jager
South African Journal of Industrial Psychology , 1980, DOI: 10.4102/sajip.v0i0.323
Abstract: An effort is made to define and describe on a conceptual basis the psychological depth dimension of the 4-dimensional classification theory of human behaviour (Raubenheimer, 1978) as a construct of human behaviour. Cognitive and non-cognitive behavioural correlates of different cognitive styles are also related on a logical basis to the construct psychological depth orientation. Opsomming Die sielkundige diepte-dimensie as konstruk van menslike gedrag in die 4-dimensionele klassifikasieteorie van menslike gedrag (Raubenheimer, 1978) word konseptueel omskryf en afgebaken. Kognitiewe en nie kognitiewe gedragskorrelate van verskillende kognitiewe style word ook op 'n logiese wyse aan die konstruk sielkundige diepte-ori ntasie gekoppel.
'n Multidimensionele skaleringstudie van personeelkonsultantgroepe in Suid Afrika
C. C. Theron,L. C. De Jager
South African Journal of Industrial Psychology , 1988, DOI: 10.4102/sajip.v14i2.472
Abstract: A multidimentional scaling study of personnel consultancy groups in South Africa. Ten 12x12 symetric dissimilarity matrices of inter personnel consultant comparisons were submitted to weigthed multidimensional scaling. Vector and ideal point models were used to relate preference and con- sultant attributes to the group stimulus space. Results indicate that the hypothetical ideal consultant differs significantly from existing consultancies and that there exists a partial incongruence between the attributes used spontaneously when comparing a number of consultancies and the critical consultant attributes identified in the literature. Recommendations for further research are made. Opsomming Tien 12x12 simmetriese dissimilariteitsmatrikse van interpersoneelkonsultante-beoordelings is onderwerp aan matriksgeweegde multidimensionele skating. Vektor n "ideal point" modelle is gebruik om voorkeur en konsultantattribute met die groepstimulusruimte in verband te bring. Resultate dui daarop dat die hipotetiese ideate konsultant betekenisvol verskil van bestaande konsultantaanbiedinge en dat daar 'n element van inkongruensie bestaan tussen die attribute wat spontaan na vore tree by onderlinge vergelyking van konsultantgroepe en die kritieke attribute soos deur die literatuur geidentifiseer. Aanbevelings vir verdere studie word gemaak.
Estimates for Very High Energy Gamma Rays from Globular Cluster Pulsars
C. Venter,O. C. de Jager
Physics , 2009, DOI: 10.1063/1.3076659
Abstract: Low-Mass X-ray Binaries (LMXRBs), believed to be the progenitors of recycled millisecond pulsars (MSPs), occur abundantly in globular clusters (GCs). GCs are therefore expected to host large numbers of MSPs. This is also confirmed observationally. The MSPs continuously inject relativistic electrons into the ambient region beyond their light cylinders, and these relativistic particles produce unpulsed radiation via the synchrotron and inverse Compton (IC) processes. It is thus possible, in the context of General Relativistic (GR) frame-dragging MSP models, to predict unpulsed very high energy radiation expected from nearby GCs. We use a period-derivative cleaned sample of MSPs in 47 Tucanae, where the effects of the cluster potential on the individual period derivatives have been removed. Using a Monte Carlo process to include effects of pulsar geometry, we obtain average injection spectra (with relatively small errors) of particles leaving the MSPs. These spectra are next used to predict cumulative synchrotron and IC spectra expected from 47 Tucanae, which is a lower limit, as no reacceleration is assumed. We find that the IC radiation from 47 Tucanae may be visible for H.E.S.S., depending on the nebular field B as well as the number of MSPs N in the GC. Telescopes such as Chandra and Hubble may find it difficult to test the SR component prediction of diffuse radiation if there are many unresolved sources in the field of view. These results may be rescaled for other GCs where less information is available, assuming universal GC MSP characteristics.
Knowledge, Attitudes and Beliefs about Dementia in an Urban Xhosa-Speaking Community in South Africa  [PDF]
V. Khonje, C. Milligan, Y. Yako, M. Mabelane, K. E. Borochowitz, C. A. de Jager
Advances in Alzheimer's Disease (AAD) , 2015, DOI: 10.4236/aad.2015.42004
Abstract: Background: Dementia, a debilitating condition, requires particular attention in Southern Africa where there is a dearth of prevalence data. Population ageing and other risk factors are driving an increasing incidence of dementia. However, limited knowledge and understanding may impact the attitudes and practices towards persons with dementia. Aim: To investigate the relationship between the knowledge of dementia, its effect on the attitudes and practices toward people with dementia in an urban community setting. To determine the perceived availability of services for those with dementia, the awareness of elder abuse and care-giver burden. Methods: A descriptive, cross-sectional study was performed in Khayelitsha. An interviewer administered questionnaire was used with assistance from isiXhosa speaking translators. A sample of 100 individuals was surveyed door-to-door from both the informal and formal housing settlements, using cluster random sampling methods. Results: There was deficient knowledge about dementia, with an average accuracy of 53.44% on the knowledge test. Only 10% reported knowing what dementia was. Participants had generally tolerant views about people with dementia. No significant relationship was found between knowledge and attitudes about dementia. There was a significant difference between people who would share their house with a family member with dementia or send them to nursing homes (p = 0.03). 64% of participants knew what elder abuse was. 19% knew of an elder who had been abused; amongst the most common forms reported were being locked alone in their house and being deprived of food. Conclusions: This study showed that knowledge about dementia was limited with no relationship to attitudes of high tolerance towards people with dementia. Elder abuse was well recognized, but poorly reported. Appropriate health promotion strategies and education should be conducted and further research should be done into dementia in South Africa.
Ventricular perforation as a complication of percutaneous valve replacement
C de Jager, IL Norval, JR Tynan
South African Journal of Radiology , 2012,
Abstract: Aortic stenosis (AS) is the most commonly encountered valvular disease in developed countries. Once symptomatic, this disease carries a dismal prognosis. Patients unfit for surgical valve replacement may require transcatheter aortic valve implantations (TAVI). We present a complication of this novel approach where a prosthetic valve is delivered through the femoral artery by means of a Retroflex delivery system developed by Edwards Lifesciences.
Die betroubaarheid en faktorstruktuur van die aangepaste meervoudige keuse-formaat van die miner sentence completion scale (MSCS)
A. S. Engelbrecht,L. C. de Jager
South African Journal of Industrial Psychology , 1991, DOI: 10.4102/sajip.v17i2.525
Abstract: The reliability and factor structure of the adapted multiple choice version of the Miner Sentence Completion Scale (MSCS). In this study the multiple choice MSCS was adapted as a result of several criticisms thereof. The internal consistency and factor structure of the adapted MSCS were determined to ascertain the reliability and construct validity of the questionnaire. Results show that the internal consistency is unsatisfactory and that the factor structure is so complex that interpretation becomes virtually impossible. In light of the results of this study and other research findings of the psychometric properties of the MSCS, it is recommended that a new measuring instrument for managerial motivation be developed that will enable a valid testing of the managerial rolemotivation theory. Opsomming Na aanleiding van verskeie punte van kritiek teen die MSCS is die meervoudige keuse-MSCS in hierdie studie aangepas. Ten einde 'n aanduiding van die betroubaarheid en konstrukgeldigheid van die aangepaste MSCS te verkry, is die interne konsekwentheid en faktorstruktuur daarvan bepaal. Die resultate dui daarop dat die interne konsekwentheid onbevredigend en die faktorstruktuur te kompleks vir interpretasie is. In die lig van die bevindinge van hierdie studie, en ander navorsingsbevindinge oor die psigometriese eienskappe van die MSCS, word aanbeveel dat 'n nuwe meetinstrument van bestuursmotivering ontwikkel word wat 'n geldige toetsing van die bestuursrol-motiveringsteorie moontlik sal maak.
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