Groove in Cuban Dance Music: An Analysis of Son and Salsa

The rhythmic feel or 'groove' of Cuban dance music is typically characterised by a dynamic rhythmic energy, drive and sense of forward motion that, for those attuned, has the ability to produce heightened emotional responses and evoke engagement and participation through physical movement and dance. No single work on groove in Cuban dance music considers together the cognitive, cultural, socio-musical and emotional dimensions of the music-making practices and aesthetics that characterise groove production. This study integrates these perspectives into a single theoretical framework with the aim of gaining fresh insights into the nature of groove in two prominent styles of Cuban and Cuban-related dance music: son and salsa. Methodologically, this study blends ethnography and the analysis of timing data extracted from real-world performances to explore the shared cultural knowledge, socio-musical processes, aesthetics and emotional dimensions of groove. Ethnography facilitates the detailed investigation of how performers talk about the music-making practices that characterise aspects of musical culture while the use of timing data, recorded in situ, facilitates the investigation of the real-time nuanced micro-timing relationships that shape effective groove production. The findings of this study paint a picture of groove that is rich, complex and multidimensional, one that is built upon the expressive performances, socio-musical interactions and collectivist attitudes of rhythm section musicians as well as powerful cultural models and intersubjectively shared knowledge. When rhythm section musicians engage in expressive and interactive dialogues and work effectively as a synchronous collective, the resultant groove embodies the dynamic rhythmic, communicative and emotional energies of the individuals that comprise the group. In performance situations, when the groove of the rhythm section spontaneously finds union with the kinaesthetic and emotional energies of dancers and audiences, the cumulative energy possesses the power to inspire, excite, energise, invite participation and unite people in joyous celebration

A W:B4C multilayer phase retarder for broadband polarization analysis of soft x-ray radiation \ud

A W:B4C multilayer phase retarder has been designed and characterized which shows a nearly constant phase retardance between 640 and 850 eV photon energies when operated near the Bragg condition. This freestanding transmission multilayer was used successfully to determine, for the first time, the full polarization vector at soft x-ray energies above 600 eV, which was not possible before due to the lack of suitable optical elements. Thus, quantitative polarimetry is now possible at the 2p edges of the magnetic substances Fe, Co, and Ni for the benefit of magnetic circular dichroism spectroscopy employing circularly polarized synchrotron radiatio

The impact of competition on elephant musth strategies: a game–theoretic model

Mature male African Savannah elephants are known to periodically enter a temporary state of heightened aggression called “musth,” often linked with increased androgens, particularly testosterone. Sexually mature males are capable of entering musth at any time of year, and will often travel long distances to find estrous females. When two musth bulls or two non-musth bulls encounter one another, the agonistic interaction is usually won by the larger male. However, When a smaller musth bull encounters a larger non-musth bull, the smaller musth male can win. The relative mating success of musth males is due partly to this fighting advantage, and partly to estrous females’ general preference for musth males. Though musth behavior has long been observed and documented, the evolutionary advantages of musth remain poorly understood. Here we develop a game–theoretic model of male musth behavior which assumes musth duration as a parameter, and distributions of small, medium and large musth males are predicted in both time and space. The predicted results are similar to the musth timing behavior observed in the Amboseli National Park elephant population, and further results are generated with relevance to Samburu National Park. We discuss small male musth behavior, the effects of estrous female spatial heterogeneity on musth timing, conservation applications, and the assumptions underpinning the model

Concentrating solar power in South Africa - a comparison between parabolic trough and power tower technologies with molten salt as heat transfer fluid

Thesis (MEng)--Stellenbosch University, 2017.ENGLISH ABSTRACT: The most common type of concentrating solar power (CSP) plant in operation today is the parabolic trough plant. In recent years molten salt power tower plants have demonstrated the benefit of using molten salt as heat transfer fluid and a storage medium. New research has shown that molten salt can be used in parabolic trough technology in a similar manner. This thesis documents an investigation into both technologies in order to compare them on a qualitative and quantitative basis. South Africa has become a hotspot for the development of CSP thanks to the abundant solar resource and the implementation of the Renewable Energy Independent Power Producer Procurement Program (REIPPPP) in the country. South Africa therefore provides a realistic backdrop for the comparison of the two CSP technologies. Parabolic trough and a power tower simulation models are constructed for the comparison of the two technologies. Meteorological data for six selected sites in South Africa are used to simulate the performance of both of the technologies, while operating under a flat feed in tariff and a two-tiered feed in tariff. Results of plant simulations show that molten salt can be used effectively as heat transfer fluid in parabolic trough technology. Parabolic troughs are shown to have higher annual optical efficiency compared to power towers. The main drawback of the parabolic trough technology is the thermal losses experienced in the field during overnight recirculation of the hot molten salt. Parabolic trough solar fields show a large seasonal variation in efficiency while power tower plants are shown to benefit from relatively consistent solar field efficiency throughout the year. The seasonal variation in solar field efficiency results in substantially higher thermal energy being available in the summer than in the winter, thereby resulting in storages being filled and the subsequent dumping of solar energy in parabolic trough plants. A simple cost model is built to compare the financial performance of the two technologies and allow for the optimization of the plants according to levelized cost of electricity (LCOE). At a site near Springbok in the Northern Cape Province optimization of both plant types resulted in an estimated LCOE of 0.127 USD/kWhe and 0.129 USD/kWhe for parabolic trough and power tower plants respectively. This study demonstrates that both parabolic trough and power tower plants require careful consideration when selecting the most appropriate CSP technology for a given location. Depending on the available solar resource and the tariff structure under implementation, this thesis finds that both parabolic trough and power tower plants can offer competitive CSP solutions with their own set of strengths and weaknesses.Die mees algemene vorm van ‘n gekonsentreerde sonkrag (GSK) aanleg in hedendaagse bedryf is die paraboliese trog aanleg. In die afgeloope jare het gesmelte sout krag toring tegnologie voordeel getoon in die gebruik van gesmelte sout as hitte-oordrag vloeistof en as 'n stoor medium. Onlangse navorsing het getoon dat die gesmelte sout in paraboliese trog tegnologie op 'n soortgelyke wyse gebruik kan word. Hierdie tesis dokumenteer 'n ondersoek van altwee tegnologieë ten einde hulle te vergelyk op 'n kwalitatiewe en kwantitatiewe basis. Suid-Afrika het gewild geword vir GSK ontwikkeling te danke aan die oorvloed van son hulpbron en die implementering van die Hernubare Energie Onafhanklike Krag Aankoop Program in die land. Suid-Afrika bied dus 'n realistiese agtergrond vir die vergelyking tussen die twee GSK tegnologieë. Paraboliese trog en 'n krag toring modelle is gebou vir die vergelyking van die twee tegnologieë. Meteorologiese data vir ses gekiesde liggings in Suid-Afrika word gebruik om die optrede van beide tegnologieë te simuleer, terwyl dit bedryf word onder 'n vaste koers invoer tarief en 'n twee-vlak invoer tarief. Resultate van aanleg simulasies toon dat gesmelte sout effektief as hitte-oordrag vloeistof in paraboliese trog tegnologie gebruik kan word. Paraboliese trôe vertoon ‘n hoër jaarlikse optiese doeltreffendheid in vergelyking met krag torings. Die mees kenmerkende nadeel van die paraboliese trog tegnologie is die termiese verliese in die veld tydens oornag hersirkulasie van die warm gesmelte sout. Paraboliese trog sonvelde wys ‘n groot seisoenale verskil in doeltreffendheid terwyl die krag toring aanlegte wys ‘n konstante sonveld doeltreffendheid deur die jaar. Die seisoenale verskil in die sonveld doeltreffendheid beteeken dat meer termiese energie beskikbaar in die sommer in verlgelyking met die winter maande, daarvoor word die stoortenke vol en die daaropvolgende storting van sonenergie in paraboliese trog aanlegte. 'n Eenvoudige kostemodel is gebou om die finansiële prestasie van die twee tegnologieë te vergelyk en voorsiening te maak vir die optimering van die aanlegte volgens gelyke koste van elektrisiteit (GKVE). Op 'n ligging naby Springbok in die Noord-Kaap het optimering van beide aanlegsoorte gelei tot 'n geskatte GKVE van 0.127 USD/kWhe en 0.129 USD/kWhe vir paraboliese trog en krag toring aanlegte onderskeidelik Hierdie studie toon dat beide tegnologieë deeglike oorweging vereis vir die keuse van die mees geskikte GSK tegnologie vir 'n gegewe ligging. Afhangende van die beskikbare sonkrag hulpbron en die tariefstruktuur onder implementering, bevind hierdie tesis dat beide paraboliese trog en krag toring aanlegte mededingende GSK oplossings met hul eie stel sterk- en swakpunte kan bied

On the measurement of the crack tip stress field as a means of determining Delta K(sub eff) under conditions of fatigue crack closure

The optical method of caustics has been successfully extended to enable stress intensity factors as low as 1MPa square root of m to be determined accurately for central fatigue cracks in 2024-T3 aluminium alloy test panels. The feasibility of using this technique to study crack closure, and to determine the effective stress intensity factor range, Delta K(sub eff), has been investigated. Comparisons have been made between the measured values of stress intensity factor, K(sub caus), and corresponding theoretical values, K(sub theo), for a range of fatigue cracks grown under different loading conditions. The values of K(sub caus) and K(sub theo) were in good agreement at maximum stress, where the cracks are fully open, while K(sub caus) exceeded K(sub theo) at minimum stress, due to crack closure. However, the levels of crack closure and values of Delta K(sub eff) obtained could not account for the variations of crack growth rate with loading conditions. It is concluded that the values of Delta K(sub eff), based on caustic measurements in a 1/square root of r stress field well outside the plastic zone, do not fully reflect local conditions which control crack tip behavior

Gradient flows in three dimensions

The α-function is a proposed quantity defined for quantum field theories which has a monotonic behaviour along renormalisation group flows, being related to the β-functions via a gradient flow equation involving a positive definite metric. We demonstrate the existence of a candidate α-function for renormalisable Chern-Simons theories in three dimensions, involving scalar and fermion fields, in both non-supersymmetric and supersymmetric cases

Models of the ICM with Heating and Cooling: Explaining the Global and Structural X-ray Properties of Clusters

(Abridged) Theoretical models that include only gravitationally-driven processes fail to match the observed mean X-ray properties of clusters. As a result, there has recently been increased interest in models in which either radiative cooling or entropy injection play a central role in mediating the properties of the intracluster medium. Both sets of models give reasonable fits to the mean properties of clusters, but cooling only models result in fractions of cold baryons in excess of observationally established limits and the simplest entropy injection models do not treat the "cooling core" structure present in many clusters and cannot account for entropy profiles revealed by recent X-ray observations. We consider models that marry radiative cooling with entropy injection, and confront model predictions for the global and structural properties of massive clusters with the latest X-ray data. The models successfully and simultaneously reproduce the observed L-T and L-M relations, yield detailed entropy, surface brightness, and temperature profiles in excellent agreement with observations, and predict a cooled gas fraction that is consistent with observational constraints. The model also provides a possible explanation for the significant intrinsic scatter present in the L-T and L-M relations and provides a natural way of distinguishing between clusters classically identified as "cooling flow" clusters and dynamically relaxed "non-cooling flow" clusters. The former correspond to systems that had only mild levels (< 300 keV cm^2) of entropy injection, while the latter are identified as systems that had much higher entropy injection. This is borne out by the entropy profiles derived from Chandra and XMM-Newton.Comment: 20 pages, 15 figures, accepted for publication in the Astrophysical Journa