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Search Results: 1 - 10 of 403958 matches for " M. Meyer "
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Standard Model thermodynamics across the electroweak crossover
M. Laine,M. Meyer
Physics , 2015, DOI: 10.1088/1475-7516/2015/07/035
Abstract: Even though the Standard Model with a Higgs mass mH = 125 GeV possesses no bulk phase transition, its thermodynamics still experiences a "soft point" at temperatures around T = 160 GeV, with a deviation from ideal gas thermodynamics. Such a deviation may have an effect on precision computations of weakly interacting dark matter relic abundances if their mass is in the few TeV range, or on leptogenesis scenarios operating in this temperature range. By making use of results from lattice simulations based on a dimensionally reduced effective field theory, we estimate the relevant thermodynamic functions across the crossover. The results are tabulated in a numerical form permitting for their insertion as a background equation of state into cosmological particle production/decoupling codes. We find that Higgs dynamics induces a non-trivial "structure" visible e.g. in the heat capacity, but that in general the largest radiative corrections originate from QCD effects, reducing the energy density by a couple of percent from the free value even at T > 160 GeV.
Hutchinson’s sign as a marker of ocular involvement in HIVpositive patients with herpes zoster ophthalmicus
M van Dyk, D Meyer Meyer
South African Medical Journal , 2010,
Abstract: Background. A positive Hutchinsonfs sign indicates an increased risk of ocular involvement in herpes zoster ophthalmicus (HZO). We examined the sensitivity of Hutchinsonfs sign as an indicator of ocular involvement in a consecutive series of patients presenting with HZO. Methods. We conducted a descriptive observational prospective study of patients .18 years old presenting with HZO and consenting to pre- and post-test counselling and HIV and CD4 testing. A full ophthalmological examination focused on the extent of ocular involvement, and the presence of Hutchinsonfs sign was confirmed by two clinicians. Results. Thirty-three patients were enrolled; 29 were HIV positive, of whom 18 (62%) had not been diagnosed with HIV prior to enrolment. Of the 29 HIV-positive patients, 21 (72%) were Hutchinsonfs sign positive (HSP), all of whom had intra-ocular involvement (95% confidence interval 88 - 100%) Of the 8 HIV-positive, Hutchinsonfs sign-negative (HSN) patients, 4 did and 4 did not display intra-ocular involvement. Neither the mean CD4 count nor the average age in the HSP group differed significantly from the HSN group. Conclusion. We confirmed that a Hutchinsonfs sign- and HIVpositive patient with HZO has a very high positive predictive value for intra-ocular involvement. Neither age nor CD4 count had predictive value for ocular involvement. Young adults presenting with HZO should be suspected of having HIV, and HIV-positive patients with HZO but HSN may still have ocular involvement. All patients with HZO should be seen by an ophthalmologist.
Telematic education: a reality in post-basic nursing education
Salomé M Meyer
Health SA Gesondheid , 2001, DOI: 10.4102/hsag.v6i4.85
Abstract: No institution is immune to the impact of technological change. Opsomming Geen instansie is immuun teen tegnologiese veranderinge nie. *Please note: This is a reduced version of the abstract. Please refer to PDF for full text.
C.M. Meyer
Scientia Militaria : South African Journal of Military Studies , 2012, DOI: 10.5787/18-2-405
Abstract: "He who is master of the sea is master of world trade. And he who is master of world trade is master of the riches of the earth and of the earth itself" Sir Walter Raleigh, quoted by the former Commander-in-Chief of the Soviet Navy, Admiral S.G. Gorshkov. Introduction Sir Walter Raleigh, the famous English adventurer, died three hundred and seventy years ago, but his words are just as valid today, as any television news programme on convoy operations in the Persian Gulf will show. Warships from the USA, UK, France, Belgium, Italy and the Netherlands have all been involved in patrols or minesweeping operations in the area to minimize threats to their oil supplies coming from the Gulf, the main export route of nine Middle Eastern countries possessing more than half of the world's proven oil reserves.
C.M. Meyer
Scientia Militaria : South African Journal of Military Studies , 2012, DOI: 10.5787/9-1-749
Abstract: To understand the significance of air weapons and their effectiveness, you have to look at the situation at the close of the October Warand extrapolate ... TheSAMS were totally destroyed and the air force could do whatever it wanted against the ground.
Soviet aims in Southern Africa: Economic considerations
C.M. Meyer
Scientia Militaria : South African Journal of Military Studies , 2012, DOI: 10.5787/14-2-522
Abstract: While much has been said about the increasing involvement of the USSR in Southern Africa, little has been said about how and why the USSR wishes to achieve its aims in the sub-continent. Little has really changed since 1917, when Lenin himself declared bluntly that the scientific concept of dictatorship means neither more nor less than unlimited power, resting directly on force, not limited by anything, nor restricted by any laws, nor any absolute rules. Nothing else but that.
C.M. Meyer
Scientia Militaria : South African Journal of Military Studies , 2012, DOI: 10.5787/8-4-760
Abstract: Many sources maintain that the role played by air power in the 1973 Yom Kippur War was important. Other interpretations state that control of air space over the battlefield areas, (either by aircraft or anti-aircraft defences), was vital.
Sensitivity of the Cherenkov Telescope Array to the detection of axion-like particles at high gamma-ray opacities
M. Meyer,J. Conrad
Physics , 2014, DOI: 10.1088/1475-7516/2014/12/016
Abstract: Extensions of the Standard Model of particles commonly predict the existence of axion(-like) particles (ALPs) that could be detected through their coupling to photons in external magnetic fields. This coupling could lead to modifications of $\gamma$-ray spectra from extragalactic sources. Above a certain energy, the $\gamma$-ray flux should be exponentially damped due to the interaction with photons of background radiations fields. ALPs, on the other hand, propagate unimpeded over cosmological distances and a reconversion into $\gamma$-rays could lead to an additional component in the spectra. Here, we present the sensitivity of the proposed Cherenkov Telescope Array (CTA) to detect this spectral hardening. Using the full instrumental response functions of CTA, a combined likelihood analysis of four $\gamma$-ray sources shows that a significant detection of the ALP signal is possible for couplings $g_{a\gamma} \gtrsim 2\times10^{-11}\,\mathrm{GeV}^{-1}$ and ALP masses $m_a \lesssim 100\,\mathrm{neV}$. We discuss the dependency of these values on different model assumptions and magnetic-field scenarios and identify the best observation strategy to search for an ALP induced boost of the $\gamma$-ray flux.
School resources and student achievment: worldwide findings and methodological issues
Paulo A. Meyer. M. Nascimento
Educate~ , 2008,
Abstract: The issues raised in the Education Production Function literature since the US 1966 Coleman Report have fuelled high controversy on the role of school resources in relation to student performance. In several literature reviews and some self estimates, Erik Hanushek (1986, 1997, 2006) systematically affirms that these two factors are not associated one to another – neither in the US nor abroad. In recent cross-country analyses, Ludger Woessmann (2003; 2005a; 2005b) links international differences in attainment to institutional differences across educational systems – not to resourcing levels. In the opposite direction, Stephen Heyneman and William Loxley (1982, 1983) tried to demonstrate in the 1980’s that, at least for low income countries, school factors seemed to outweigh family characteristics on the determination of students’ outcomes – although other authors show evidence that such a phenomenon may have existed only during a limited period of the 20th Century. In the 1990s, meta-analyses raised the argument that school resources were sufficiently significant to be regarded as pedagogically important. The turn of the Century witnessed a new movement: the recognition that endogenous determination of resource allocation is a substantial methodological issue. Therefore, efforts have been made to incorporate the decision-making processes that involve families, schools and policy-makers in economic models. This implies changes in research designs that may affect the direction of future policy advices patronised by international development and educational organisations.
Deriving the true mass of an unresolved Brown Dwarf companion to an M-Dwarf with AO aided astrometry*
Meyer E.,Kürster M.
EPJ Web of Conferences , 2011, DOI: 10.1051/epjconf/20111604005
Abstract: From radial velocity (RV) detections alone one does not get all orbital parameters needed to derive the true mass of a non-transiting, unresolved substellar companion to a star. Additional astrometric measurements are needed to calculate the inclination and the longitude of the ascending node. Until today only few true substellar companion masses have been determined by this method with the HST fine guidance sensor [1, 2]. We aim to derive the true mass of a brown dwarf candidate companion to an early M 2.5V dwarf with groundbased high-resolution astrometry aided by adaptive optics. We found this unique brown dwarf desert object, whose distance to the host star is only 0.42 AU, in our UVES precision RV survey of M dwarfs, inferring a minimum companion mass of 27 Jupiter masses [3]. Combining the data with HIPPARCOS astrometry, we found a probability of only 2.9% that the companion is stellar. We therefore observed the host star together with a reference star within a monitoring program with VLT/NACO to derive the true mass of the companion and establish its nature (brown dwarf vs. star). Simultaneous observations of a reference field in a globular cluster are performed to determine the stability of the adaptive optics (AO) plus detector system and check its suitability for such high-precision astrometric measurements over several epochs which are needed to find and analyse extrasolar planet systems.
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