The absorption due to pairs of H2 molecules is an important opacity source in the atmospheres of various types of planets and cool stars, such as late stars, low-mass stars, brown dwarfs, certain white dwarfs, etc., and therefore of special astronomical interest [13]. The emission spectra of cool white dwarf stars differ signicantly from the expected blackbody spectra of the cores, due to collision-induced absorption by collisional complexes of hydrogen and helium in the stellar atmospheres. In order to model the radiative processes in these atmospheres, which have temperatures of several thousand kelvin, one needs accurate knowledge of the induced dipole and potential energy surfaces of collisional complexes such as H2-H2. These come from quantum-chemical calculations with the H2 bonds stretched or compressed far from equilibrium length. Since no measurements of the collision-induced absorption for these high temperatures exist, one has to undertake ab initio calculations which take into account the high vibrational excitations of the hydrogen molecules. However, before one attempts to proceed to higher temperatures where no laboratory measurements exist it is good to know that the formalism is correct and reproduces the results at temperatures where measurements exist. Therefore, in order to make sure that the calculations are reliable one compares the results of the calculations with existing laboratory measurements where possible before proceeding to higher temperatures. Molecular hydrogen has always played a special role in the collision-induced spectroscopies. The rotational transition frequencies of H2 are widely separated so that translational, rotational and vibrational induced spectral bands can be studied separately. Moreover, the H2 molecule has a small anisotropy of the intermolecular interactions which may often be ignored in first order approximations. In general hydrogen gas is a mixture of para- and ortho-hydrogen. Para-hydrogen at sufficiently low temperature is not rotationally excited and is therefore an isotropic system. However, the anisotropy can be turned on and of by raising and lowering the temperature, because the ratio of para- to ortho-hydrogen depends on the temperature. What is even more, roughly 90% of all the known matter in the universe is hydrogen, in the ionized, atomic or molecular states, which makes hydrogen one of the most important species in astrophysics. The hydrogen molecule is non-polar, and some of the most important spectra in the near and far infrared and microwave region are collision-induced, due to H2-H2 complexes. At the temperature of 297.5K measurements of the collision-induced absorption spectra of H2-H2 gas are reported in the frequency range from 1900 to 2260cm^{-1} [9]. The gas densities for these measurements ranged from 51 to 610 amagat. These measurements were compared with ab initio calculations of the absorption. For these calculations the isotropic potential approximation was used. In contrast to previous ab initio calculations [9] agreement between calculations and measured spectra is now observed over the full frequency range considered. A major difference to the earlier calculations is that in this work new dipole and potential energy surfaces were used. Furthermore, measurements exist of the fundamental band and first and second overtone of H2 in dense hydrogen gas. They have been compared with ab initio calculations based on the new method. Over the full range of frequencies considered the agreement between calculations and measurements is remarkable. This work demonstrates that the new method is capable of reproducing the measured spectra where those exist with high accuracy, and predicts reliable opacities where no laboratory measurements exist. / text

M.Mus. Faculty of Humanities, University of the Witwatersrand, 2008 / This report forms part of the output of a research team investigating the phenomenon of overtone singing as practiced by the women of the Ngqoko Women’s Ensemble in the village of Ngqoko outside the town of Lady Frere in the Eastern Cape, South Africa. This essay examines various systems of musical notation in terms of their possible application in the transcription process of overtone singing as found amongst these women. A selection of their music is transcribed using the formulated notational systems and the effectiveness of these systems is compared. A recommendation as to which system of notation is most effective for documenting this type of music is made. Utilising the soundworld of the Ngqoko recordings, an original piece of music is composed as part of this submission.

No description available.

Cette thèse est une étude ethnomusicologique à dimension historique portant sur la transmission globale du höömij en Mongolie. Pour expliquer l’évolution de cette technique vocale, sont explorés les légendes, les conceptions autochtones, l’histoire des années 1950 au début des années 2010 et la mise en patrimoine pour l’avenir.La première partie montre comment le chant diphonique prend forme dans sa culture. Perçu comme un art du timbre par ses détenteurs, il entretient des relations avec la nature, ainsi qu’un ensemble de techniques vocales et instrumentales issues des contextes rituel et pastoral. Ces fondements du höömij sont ensuite examinés à la lumière de l’histoire de la Mongolie. Entre les périodes soviétique etcontemporaine, la deuxième partie brosse les changements survenus dans la pratique, entre la scène et l’enregistrement. À côté de l’usage rural, se développe une nouvelle forme professionnelle. Tous ces apports ont façonné le chant diphonique mongol dans son état actuel. La troisième partie étudie la transmission à travers l’enseignement et la patrimonialisation. Les maîtres évoluent entre deux pôles : un village de l’Altaï perçu comme le lieu des origines, et une université d’Ulaanbaatar, qui académise la pratique et diffuse son modèle au niveau national. Tout cela participe au processus de patrimonialisation du höömij, desa constitution en emblème musical sous la période soviétique à son inscription sur la liste du Patrimoine Culturel Immatériel de l’Unesco. Le höömij mongol apparaît dans toute sa contemporanéité / This thesis is an ethnomusicological study on the global transmission of höömij in Mongolia with a historic dimension. In order to explain the evolution of this vocal technique, this dissertation links the legends, the native conceptions, the history from the 1950’s to the begining of the 2010’s and the patrimonialization for the future.The first part shows how höömij takes place in its culture. Perceived as an art of timbre by its bearers, it maintains relations with nature and a set of vocal and instrumental techniques that derive from ritual and pastoral contexts. These foundations of höömij are then investigated in light of Mongolia’s history. Examinging both Soviet and contemporarytimes, the second part looks into the changes that occured in relation to the stage and recordings. Alongside höömij’s rural function, a newer professional form developed, which has primarily shaped contemporary performance.The third part studies transmission as teaching and patrimonialization. Masters evolve between two poles : a village in the Altai perceived as the very place of origins, and a university in Ulaanbaatar, which academicizes the practice and spread its model to the whole nation. All of this contributes to höömij’s patrimonialization process, from the building of a musical emblem under Soviet times, to its registration on Unesco’s Intangible Cultural Heritage list. Mongolian höömij appears in its whole contemporaneity

Part 1.Thesis: Chapter 1: The people of the Lumko district (the villages of Ngqoko and Sikhwankqeni) are AbaThembu, mostly of the Gcina clan cluster. Their history has caused them to be linked with (now vanished) San peoples in special ways, which have undoubtedly influenced their music. Chapter 2: The music of these people is centred around their religious and social life. This affects the way they classify their songs; and song classifications (and the way songs are used) affect their performance, in particular, the dance styles associated with the song classes. Chapter 3: A variety of musical instruments is used in the Lumko district, the most important being the musical bows. Once again, the use of these bows gives an insight into the musical influences that have affected the people historically. The ways the bows work are described, as well as ways to play them. Chapter 4: Overtone singing, not previously documented anywhere in traditional African music, is practised in certain ways by these AmaGcina. These, and other vocal techniques, are described. Chapter 5: From the terminology and the methods of conceptualisation about music in the Lumko district, it is possible to gain an insight into a truly Xhosa technical understanding of Xhosa music. Once again a historical insight is gained, because so many of the important terms are KhoiSan words. Chapter 6: A Western technological (i. e. musicological) understanding of the music is also necessary in a study of this nature. This chapter applies musicological concepts to an examination of the relationship between speech and song, of the usages in melody and scale, harmony theory, rhythm, polyphony, song form, instrumental roles and methods of performance. Chapter 7: This is the conclusion of the thesis. It sums up what has been studied: musical techniques, principles, the importance of Ntsikana 's song as a basis for musical comparisons, and the import of the historical aspects of the study - a possible glimpse of the music of the San. PART 2. MUSIC TRANSCRIPTIONS AND DESCRIPTIONS. The transcriptions of 62 songs provide the material for this study. The songs were chosen to represent all the major song classes used in the Lumko district, and to represent all the important music techniques as well. The songs are in fifteen categories. Each song is accompanied by its technical details, and sufficient commentary to make the song transcription intelligible and meaningful. Certain key songs are chosen as type-songs or other special examples, and are used as the bases for discussion on song style characteristics, principles of performance, bow adaptation, and so on. A general Introduction to Part 2 describes and accounts for the method of transcription, and also attempts to make it possible for the score reader not only to analyse, but also to perform the songs. In a further attempt to bring the transcriptions to life, a video recording of certain key songs and techniques, and audio tapes with examples taken from all the songs, accompany this study

Les complexes de van der Waals sont des entités constituées de différentes molécules liées par des interactions faibles (~kJ/mol). Ces agrégats présentent une réactivité particulière et jouent un rôle essentiel dans les phénomènes de solvatation et nucléation. Des moyens expérimentaux et théoriques pour étudier les complexes de van der Waals et en particulier ceux contenant de l’acétylène ont donc été développés dans ce travail. Nous avons utilisé et amélioré un montage expérimental appelé FANTASIO+ (Fourier trANsform, Tunable diode and quadrupole mAss spectrometers interfaced to a Supersonic expansIOn). Ce montage, composé d’un jet supersonique et d’un spectromètre à temps de déclin permet la production et la détection de ce genre de complexes. Le jet supersonique consiste en une détente adiabatique d’un gaz et assure par refroidissement à quelques Kelvins la production de complexes. La spectrométrie à temps de déclin mesure l’absorption d’un laser infra-rouge par ces molécules cibles assurant ainsi leur détection. <p>Une diode laser nous a permis d’exciter deux fois l’étirement CH de l’acétylène. Nous avons pu détecter et analyser le spectre de vibration-rotation des complexes suivants :C2H2-Ne, C2H2-Ar, C2H2-Kr, C2H2-CO2, C2H2-N2O, et C2H2-C2H2. La molécule C2H2-CO2 et des isotopologues de C2H2-C2H2 ont également été étudiés à plus basse énergie durant un séjour à Calgary au Canada. Nos études ont démontré que ces complexes restaient liés à une énergie pouvant aller jusqu’à 130 fois l’énergie d’interaction entre les deux monomères. L’obtention de données à haute résolution spectrale permet également d’obtenir des données de références pour la validation de modèles théoriques et la planétologie. En particulier, la première détection de C2H2-Kr permettra peut-être une future observation de cet agrégat dans des atmosphères planétaires comme par exemple Titan. <p>Pour avoir une approche globale de ces systèmes nous nous sommes tournés vers les outils de la chimie quantique pour caractériser l’interaction entre les entités du complexe. Des tests méthodologiques approfondis nous ont permis d’évaluer avec exactitude les surfaces d’énergie potentielle intermoléculaire des complexes contenant une molécule d’acétylène et un atome de krypton ou de xénon. <p><p>van der Waals complexes are molecular systems in which the units or molecules are held together by weak interactions (~kJ/mol). These complexes present a peculiar reactivity and play a critical role in solvation and nucleation. Theoretical and experimental means were developed in this work to study such systems and in particular, complexes containing acetylene. In the context of this work the FANTASIO+ (Fourier trANsform, Tunable diode and quadrupole mAss spectrometers interfaced to a Supersonic expansIOn) experimental set-up was used and improved. This set-up, composed of a supersonic expansion and a cavity ring-down spectrometer, provides a way to produce and detect these complexes. The supersonic expansion is an adiabatic expansion which produces the complexes by cooling of the gas to few Kelvin. The CRDS set-up detect those complexes by infra-red laser absorption.<p>Using laser diode to doubly excite the CH stretch of acetylene, one then succeeded to observe and analyze the ro-vibrational spectra of the following complexes: C2H2-Ne, C2H2-Ar, C2H2-Kr, C2H2-CO2, C2H2-N2O, et C2H2-C2H2. The C2H2-CO2 and isotopologues of C2H2-C2H2 were also studied at lower energy during a three months stay in Calgary, Canada. Our studies demonstrated that complexes stayed bound even at an energy 130 times higher than the energy holding the entities together. The high resolution data obtained during this work is also useful to validate theoretical models and planetology. The first detection of the C2H2-Kr complex, in particular, could allow its future detection in other atmospheres, i.e. on Titan.<p>To have a global approach to these systems, the quantum chemistry tools were used to characterize the interaction between the partners of the complexes. Numerous methodological tests allowed us to accurately evaluate the intermolecular potential energy surfaces of the complexes containing an acetylene molecule and a krypton or a xenon atom. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

MA, Faculty of Humanities, University of the Witwatersrand, 2012 / This research-report presents a theoretical exploration of musical encoding which has its basis in general semiotic theory. By examining what this reveals about the problematic and mysterious issue of music’s meaning, I argue that the most visceral and direct form of it is found in the manner in which the composer shapes a certain kind of temporal experience (erlebnis) which is engendered by the music itself. This reveals that sensations of goal-directed movement, closure, tension and release are shaped in a phenomenological way against a background of continuity that is established by metrical cyclicity and phrasal periodisation. As a result, the interpretation of certain kinds of accumulative structural effects generated by the gestural (rhythmic and melodic/harmonic) inflections of the temporal and intonational planes become meaningful in a rhetorical, affective (affekten) and topical sense. A study of Ngqoko (Xhosa) overtone-music, as a case study into African indigenous music (as opposed to the examples cited of Western art music), shows that an intensification of the relationships between pitch and rhythm that exist in speech-tone results in the formation of melody and a culturally embedded vocabulary of intonations. I argue that this resultant edifice exists in the music of most cultures and that this ultimately serves as the basis of musical encoding. Therefore musical meaning develops in ways that are completely intrinsic to music.

No description available.

Magnetism is a familiar phenomenon, and is applied in a variety of devices, from simple ones, like compasses, to the more sophisticated magnetic hard disk drives. It is also known that the magnetization of a material can change, for example by heating or by exposure to an external magnetic field. The dynamics of transitions between different magnetizations, however, is largely unknown, particularly in complex materials. To further the understanding of such dynamics, this thesis presents an observational study of the dynamics of laser induced demagnetization of permalloy (Ni0.8Fe0.2). Dynamics were studied with element-specificity, i.e. Fe and Ni were studied simultaneously, but separately, rather than studying the overall material. The study was conducted at the HELIOS laboratory at Uppsala University, which features equipment for the study of magnetization dynamics. Important concepts like high-order harmonic generation (HHG) and the transverse magneto-optic Kerr effect (T-MOKE) are discussed. HHG is the laser induced generation of high energy photons, and T-MOKE relates the intensity of reflected light to the magnetization of the reflecting material. The study revealed a very short demagnetization time, and maximum demagnetization of both elements was achieved within 1 picosecond. An onset delay in the demagnetizations of Fe and Ni of about 25 femtoseconds was also observed. Both phenomena have been previously reported. The results further imply that the magnetizations diverge over a 10 picosecond time interval after the onset of demagnetization, which has not been previously reported. The apparent divergence may be due to an unknown transient setup-related issue. The short demagnetization times, as well as the onset delay could potentially contribute to the development of a more complete theory of magnetization dynamics. / Magnetism är ett bekant fenomen, som utnyttjas i allt från enkla tillämpningar, som kompasser,till mer sofistikerade sådana, som hårddiskar. Det är också känt att magnetiseringen i ett material kan ändras, t.ex. genom upphettning eller genom att det utsätts för ett yttremagnetiskt fält. Dynamiken vid övergångar mellan olika magnetiseringstillstånd är dock ett relativt okänt ämne, i synnerhet när det kommer till komplexa material. För främjandet av en större förståelse inom ämnet, presenteras här en observationell studie av dynamiken för laserinducerad avmagnetisering av permalloy (Ni0.8Fe0.2). Dynamiken undersöktes med grundämnesspecificitet, d.v.s. Fe och Ni undersöktes samtidigt, men var för sig, snarare än att materialet undersöktes som helhet. Undersökningen gjordes vid HELIOS-laboratoriet vid Uppsala Universitet, som tillhandahåller utrustning för undersökning av magnetiseringsdynamik. Viktiga koncept diskuteras, såsom övertonsgenerering och den transversella magnetooptiska Kerr-effekten (T-MOKE). Övertonsgenerering innebär laserinducerad generering av högenergifotoner, och T-MOKE relaterar reflekterad intensitet till magnetiseringen i det reflekterande materialet. Undersökningen påvisade en mycket kort avmagnetiseringstid, och maximal avmagnetisering nåddes inom en pikosekund. En relativ tidsförskjutning mellan avmagnetiseringsförloppen för Fe och Ni om ungefär 25 femtosekunder observerades också. Båda fenomen har rapporterats tidigare. Resultatet visar även en divergens mellan magnetiseringsförloppen under ett tidsspann på 10 pikosekunder efter avmagnetiseringens början, vilket inte har rapporterats förr. Den skenbara divergensen kan bero på ett okänt, tillfälligt problem i uppställningen. Den korta avmagnetiseringstiden och den relativa tidsförskjutningen skulle kunna bidra till utvecklingen av en mer komplett teori för magnetiseringsdynamik.