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La Tradition de Padma gling pa dans la Vallée des nuages au Spiti / The tradition of Padma gling pa in the clouds valley in SpitiNamgyal, Henry 30 March 2016 (has links)
Dans l’école des Tenants des anciennes traductions, les rNying ma pa-s, on trouve, en plus de la lignée de transmission orale dite longue (ring brgyud bka’ ma), une lignée de transmission courte des trésors (nye brgud gter ma). Par « trésors », on entend des textes qui auraient été cachés par Padmasambhava et ses disciples et qui, au moment où les circonstances l’exigent, sont redécouverts par des religieux prédestinés : les gter ston-s. Ceux-ci sont des milliers mais seuls certains d’entre eux, les cinq rois gter ston-s, font autorité pour authentifier un trésor et son découvreur. Le quatrième d’entre eux, Padma gling pa (1450-1521), naquit au Bhoutan où il œuvra et établit des centres religieux. Il étendit également sa sphère d’influence au Sud du Tibet où il fonda l’un de ses monastères principaux : Lha lung. Après sa mort, sa tradition spirituelle continua de se développer grâce à trois lignées d’incarnations. Bien loin de là, dans l’Ouest de l’Himalaya, la tradition rituelle de ce gter ston est encore aujourd’hui pratiquée dans la Vallée des nuages au Spiti. Jusqu’à présent, l’introduction de cette tradition, si éloignée de son lieu d’origine, reste mystérieuse. La présente étude vise, après avoir évoqué le cadre historique de la Vallée, à reconstituer dans un deuxième temps, grâce à des manuscrits que l’on croyait un temps perdus ainsi qu’à la tradition orale, l’histoire de cette tradition religieuse depuis son introduction jusqu’à nos jours. Dans un troisième temps, ce travail expose les pratiques et le calendrier rituel de la Vallée. Enfin, la dernière partie est consacrée au Rituel des vivants (gSon chog), rituel incontournable des habitants de la Vallée. / In the school of the Followers of the old translations, the rNying ma pa-s, there is not only the Long lineage of the oral transmission (ring brgyud bka’ ma) but also the Short lineage of the treasures (nye brgyud gter ma). “Tresaures” are texts that were hidden by Padmasambhava and his disciples and discovered by predestined religious figures : the gter ston-s, when the circumstances so require. Those gter ston-s are thousands but only few of them, the five gter ston-s kings are recognized authority who can authentify a treasure and its discoverer. The fourth of them Padma gling pa (1450-1521), was born in Bhutan where he built several important religious complexes. During his life time, he extended his influence to the South of Tibet where he founded one of his main monasteries : Lha lung. After his death, his tradition continued to develop thanks to three incarnation lineages. On the western part of the Himalaya, in the Clouds Valley, in Spiti, the ritual tradition of this gter ston is nowadays still practiced. Until recently, the introduction of this ritual tradition far from its place of origin, remained quite a mystery. After an evocation of the historic context, the present study attempt, secondly, thanks to old manuscripts that were supposed to be lost and thanks to the oral tradition, to redraw the history of this religious tradition from its origin until now. Thirdly, this work exposes the practices and the religous agenda of the Valley. Finally, its last part focus on the Ritual of the living beings (gSon chog) which is a key ritual in the life of the inhabitants of the Valley.
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Development and Application of a Flow-through Sampler for Semi-volatile Organic Compounds in AirXiao, Hang 18 March 2010 (has links)
The investigation of the atmospheric fate and transport of semi-volatile organic compounds (SOCs) often requires the sampling of large volumes of air (>100 m3) in a relatively short period of time. Conventionally high-volume pumps are not suitable for remote areas without access to reliable network power. We have developed a flow through sampler for such situations. It consists of a horizontally-oriented flow-tube, that can collect gaseous and particle-bound SOCs from large volumes of air by turning into the wind and having the wind blow through a porous sampling medium such as polyurethane foam. Through both indoor and outdoor experiments, we quantified its air sampling rate (through battery operated anemometers inside and outside of the flow tube), its sampling efficiency (by theoretical plate number analysis of the break-though curves for PCBs, PAHs, OCPs and PBDEs), and its accuracy (by comparison of concentrations, time trends, temperature dependences and isomer ratios with those obtained by conventional high-volume sampling) under conditions of constant and variable meteorological conditions (wind speed, temperature). The flow-through sampler was deployed to monitor SOC concentrations at a remote Chinese research station located close to Nam Co Lake, Tibet. During the campaign, fifteen 1 month-long samples were taken, corresponding to sample volumes between 5,000 and 20,000 m3. Despite those large sample volumes, only HCB and HCHs experienced break-through, but application of frontal chromatograph theory allows the estimation of breakthrough-corrected air concentrations even for those relatively volatile SOCs. The pesticide levels at Nam Co are generally very low. Most pesticides had higher levels during summer, resulting in a strong temperature dependence. This is correlated with air mass origin across the Himalayas in the Gangetic plains of India and Bangladesh. The flow through sampler constitutes a feasible method for reliably and quantitatively collecting SOCs from large air volumes.
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Blue Buddha : Tibetan medicine in contemporary Russia (St Petersburg and Moscow)Manevskaia, Ilona January 2012 (has links)
This thesis focuses on the socio-cultural and anthropological aspects of Tibetan medicine in contemporary Russia and investigates how Tibetan medicine is practised, consumed and represented in two major Russian cities, Moscow and St Petersburg. It is the first case-study of such kind in the context of Russian culture, as the anthropological aspects of Tibetan medicine in contemporary Russia have not yet been the subject of a systematic research. Up till now, scholarly publications on Tibetan medicine in Russia have dealt either with the translation and textual analysis of ancient Tibetan medical treatises or with the history of the first appearance of Tibetan medicine in Buriatia, the traditionally Buddhist region of Russia, and St Petersburg / Petrograd, paying little attention to contemporary developments and, most importantly, ignoring how Tibetan practitioners and their patients are making sense of Tibetan medicine. Based on twenty four interviews with practitioners and consumers of Tibetan medicine in the two Russian capitals, my research fills in this lacuna by looking at personal experiences, perceptions and accounts of my interviewees and exploring how they adapt Tibetan medicine to their skills, beliefs and ideas. My approach to sources is informed by Iurii Lotman's theory of intercultural communication. Although this theory was developed by Lotman for the analyses of the processes of cultural reception of literary texts, it is also relevant, with some modifications, for the analysis of the process of reception of non-textual cultural forms. The analysis of data collected from interviews with doctors and patients and the textual analysis of media, cinematic and literary sources has revealed two dominant trends and representational techniques. The first trend amounts to representing Tibetan medicine as unique and exotic, while the second trend amounts to the conceiving of Tibetan medicine as Russia's indigenous tradition, a part of Russian history, which had been subverted and suppressed in the Soviet period, yet rediscovered post-1991. Thus, we see here a co-existence of the inter-cultural dialogue between Russian culture and an exotic 'other' and the intra-cultural dialogue with a recently rediscovered part of 'self'. Both trends, which, at first glance, might appear to stand in contradiction to each other, sometimes coexist within a single explanatory narrative. The thesis also focuses on inter-cultural interactions between doctors and patients. It is argued that these interactions take place in the context of a noteworthy sociological and cultural phenomenon that the thesis calls 'mutual counter-adaptation'. Mutual counter-adaptation is the key mechanism used, consciously or spontaneously, by Tibetan doctors and their patients in order to facilitate the process of understanding between the parties involved in an inter-cultural dialogue around Tibetan medicine. The thesis finally reveals how this mutual counter-adaption takes place within a wider Russian cultural and media environment which exploits a set of specific symbols and images in order to make Tibetan medicine comprehensible and attractive to the wider Russian public.
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Vad innebär den tibetanska konsttraditionen Thanka och på vilka sätt varierar den? / What involves the tibetan art tradition Thanka and in which ways does it vary?Wallenius, Sandra January 2006 (has links)
<p>Thanka är en tibetansk konsttradition som består av religiösa bilder föreställande en rad gudar och heliga personer ur den buddhistiska tron. Motiven är starkt symbolistiska och strängt traditionsbetingade. Detta arbete beskriver denna företeelse i tre delar där den första är hämtad ur litteratur, jag redogör här för uppkomsten, motiven, tekniken, de religiösa aspekterna och dagens plats. Den andra parten består av intervjuer och den tredje delen sammanfattar processen i den tavlan jag själv målat. Slutsatsen blir att denna konst är mycket komplex och tidskrävande, samt att den i sin lugna precision kontrasterar till den västerländska stressen. Kunskapen om thanka går att applicera i flera av skolans ämnen, så som Historia, Religion och Bild, på grund av sin av tradition befästa plats i det tibetanska samhället.</p> / <p>Thanka is a Tibetan art tradition which consists of religious pictures that portrays several gods, goddesses and holy individuals from the Buddhist faith. The motives are strongly symbolist and strictly traditional. This work describes this occurrence in three parts were the first is taken from literature; I give here an account of the origin, the motives, the technique, the religious aspects and its place today. The second part includes interviews and the third part summarizes the working process in my self-made painting. The conclusion is that this art is very complex and time-demanding, and that its calm precision is contrasting to the Western stress. The knowledge about Thanka is possible to apply in several school subjects such as History, Religion and Art, because of its traditional emplacement in the Tibetan society.</p>
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Reconstructing climate variability on the Tibetan Plateau : comparing aquatic and terrestrial signalsWischnewski, Juliane January 2011 (has links)
Spatial and temporal temperature and moisture patterns across the Tibetan Plateau are very complex. The onset and magnitude of the Holocene climate optimum in the Asian monsoon realm, in particular, is a subject of considerable debate as this time period is often used as an analogue for recent global warming. In the light of contradictory inferences regarding past climate and environmental change on the Tibetan Plateau, I have attempted to explain mismatches in the timing and magnitude of change.
Therefore, I analysed the temporal variation of fossil pollen and diatom spectra and the geochemical record from palaeo-ecological records covering different time scales (late Quaternary and the last 200 years) from two core regions in the NE and SE Tibetan Plateau. For interpretation purposes I combined my data with other available palaeo-ecological data to set up corresponding aquatic and terrestrial proxy data sets of two lake pairs and two sets of sites. I focused on the direct comparison of proxies representing lacustrine response to climate signals (e.g., diatoms, ostracods, geochemical record) and proxies representing changes in the terrestrial environment (i.e., terrestrial pollen), in order to asses whether the lake and its catchments respond at similar times and magnitudes to environmental changes. Therefore, I introduced the established numerical technique procrustes rotation as a new approach in palaeoecology to quantitatively compare raw data of any two sedimentary records of interest in order to assess their degree of concordance.
Focusing on the late Quaternary, sediment cores from two lakes (Kuhai Lake 35.3°N; 99.2°E; 4150 m asl; and Koucha Lake 34.0°N; 97.2°E; 4540 m asl) on the semi-arid northeastern Tibetan Plateau were analysed to identify post-glacial vegetation and environmental changes, and to investigate the responses of lake ecosystems to such changes. Based on the pollen record, five major vegetation and climate changes could be identified: (1) A shift from alpine desert to alpine steppe indicates a change from cold, dry conditions to warmer and more moist conditions at 14.8 cal. ka BP, (2) alpine steppe with tundra elements points to conditions of higher effective moisture and a stepwise warming climate at 13.6 cal. ka BP, (3) the appearance of high-alpine meadow vegetation indicates a further change towards increased moisture, but with colder temperatures, at 7.0 cal. ka BP, (4) the reoccurrence of alpine steppe with desert elements suggests a return to a significantly colder and drier phase at 6.3 cal. ka BP, and (5) the establishment of alpine steppe-meadow vegetation indicates a change back to relatively moist conditions at 2.2 cal. ka BP. To place the reconstructed climate inferences from the NE Tibetan Plateau into the context of Holocene moisture evolution across the Tibetan Plateau, I applied a five-scale moisture index and average link clustering to all available continuous pollen and non-pollen palaeoclimate records from the Tibetan Plateau, in an attempt to detect coherent regional and temporal patterns of moisture evolution on the Plateau. However, no common temporal or spatial pattern of moisture evolution during the Holocene could be detected, which can be assigned to the complex responses of different proxies to environmental changes in an already very heterogeneous mountain landscape, where minor differences in elevation can result in marked variations in microenvironments.
Focusing on the past 200 years, I analysed the sedimentary records (LC6 Lake 29.5°N, 94.3°E, 4132 m asl; and Wuxu Lake 29.9°N, 101.1°E, 3705 m asl) from the southeastern Tibetan Plateau. I found that despite presumed significant temperature increases over that period, pollen and diatom records from the SE Tibetan Plateau reveal only very subtle changes throughout their profiles. The compositional species turnover investigated over the last 200 years appears relatively low in comparison to the species reorganisations during the Holocene. The results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem. Forest clearances and reforestation have not caused forest decline in our study area, but a conversion of natural forests to semi-natural secondary forests.
The results from the numerical proxy comparison of the two sets of two pairs of Tibetan lakes indicate that the use of different proxies and the work with palaeo-ecological records from different lake types can cause deviant stories of inferred change. Irrespective of the timescale (Holocene or last 200 years) or region (SE or NE Tibetan Plateau) analysed, the agreement in terms of the direction, timing, and magnitude of change between the corresponding terrestrial data sets is generally better than the match between the corresponding lacustrine data sets, suggesting that lacustrine proxies may partly be influenced by in-lake or local catchment processes whereas the terrestrial proxy reflects a more regional climatic signal. The current disaccord on coherent temporal and spatial climate patterns on the Tibetan Plateau can partly be ascribed to the complexity of proxy response and lake systems on the Tibetan Plateau. Therefore, a multi-proxy, multi-site approach is important in order to gain a reliable climate interpretation for the complex mountain landscape of the Tibetan Plateau. / Die räumlichen und zeitlichen Temperatur- und Feuchtigkeitsmuster auf dem Tibet-Plateau sind sehr komplex. Im Einzugsbereich der asiatischen Monsune sind insbesondere der Beginn und das Ausmaß des Klimaoptimums während des Holozäns von wissenschaftlichem Interesse, da diese Periode oft als Analogie für die derzeitige globale Klimaerwärmung herangezogen wird. In Hinblick auf sich teilweise widersprechende Paläoklima- und Umweltrekonstruktionen für das Tibet-Plateau, ist es mein Ziel, die bestehenden Unstimmigkeiten bezüglich des Zeitpunktes und des Ausmaßes des Umweltwandels zu erklären.
Dafür wurden von mir zeitliche Variationen fossiler Pollen- und Diatomeenspektren und geochemische Untersuchungen an Seesedimenten unterschiedlicher Zeitskalen (Spätquartär und die letzten 200 Jahre) aus zwei Kernregionen auf dem NO und SO Tibet-Plateau analysiert. Zur Unterstützung der Interpretation wurden die hier erhobenen Daten mit bereits vorhandenen paläoökologischen Aufzeichnungen der Lokalitäten kombiniert, um Datensätze der entsprechenden aquatischen und terrestrischen Proxy-Daten (Stellvertreterdaten) zweier Seenpaare aus den beiden Regionen gegenüberstellen zu können. Hierbei konzentrierte ich mich auf den direkten Vergleich von Proxies, die die Seenentwicklung reflektieren (z.B. Diatomeen, Ostracoden, geochemische Eigenschaften), mit Proxies, die Veränderungen der terrestrischen Umgebung des Sees beschreiben (terrestrische Pollen). Durch diesen Vergleich lässt sich beurteilen, ob Veränderungen im See selbst mit Umweltveränderungen in dem jeweiligen Einzugsgebiet zeitlich übereinstimmen. Dafür habe ich die bereits etablierte numerische Methode Procrustes-Rotation als neuen Ansatz in der Paläoökologie eingeführt. Damit ist ein quantitativer Vergleich von Rohdaten zweier beliebiger sedimentärer Datensätze möglich, um den Grad der Übereinstimmung zu prüfen.
Um die in dieser Arbeit rekonstruierten Umwelt- und Klimaereignisse des nordöstlichen Tibet-Plateaus in einen größeren Zusammenhang hinsichtlich holozäner Klimaentwicklung des gesamten Plateaus setzen zu können, und um schlüssige zeitliche und räumliche Klimatrends auf dem Plateau erkennen zu können, habe ich auf alle vorhandenen Paläoklimadatensätze einen Fünf-Skalen Feuchtigkeitsindex und eine Clusteranalyse angewandt. Es konnten jedoch keine einheitlichen zeitlichen und räumlichen Trends der holozänen Klimaentwicklung nachgewiesen werden, was meiner Analyse entsprechend, auf die komplexen Reaktionen verschiedener Proxies auf Umweltveränderungen in einer ohnehin sehr heterogen Berglandschaft, zurückgeführt werden kann.
Die Ergebnisse des numerischen Proxy-Vergleichs beider Seenpaare zeigen, dass die Verwendung von verschiedenen Proxies und die Arbeit mit paläo-ökologischen Datensätzen unterschiedlicher See-Typen zu abweichenden Klimaableitungen führen können. Unabhängig vom untersuchten Zeitraum (Holozän oder die letzten 200 Jahren) oder der Region (SO oder NO Tibet-Plateau), ist die Übereinstimmung zweier Datensätze hinsichtlich der Richtung, des Zeitpunktes und des Ausmaßes der abgeleiteten Paläo-Umweltverhältnisse in der Regel zwischen den entsprechenden terrestrischen Datensätzen besser als zwischen den entsprechenden lakustrinen Datensätzen. Die derzeitige Uneinigkeit über stimmige zeitliche und räumliche Klimatrends auf dem Tibet-Plateau kann daher teilweise der Komplexität der verschieden Proxies und ihrer individuellen Empfindlichkeiten gegenüber Umweltveränderungen sowie der unterschiedlichen Reaktionsweise verschiedenartiger See-Systeme auf dem Plateau zugeschrieben werden. Meine Ergebnisse zeigen, dass ein „Multi-Proxy-Multi-Site-Ansatz“ für zuverlässige Paläoklimaableitungen für das Tibet-Plateau von zentraler Bedeutung ist.
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Vad innebär den tibetanska konsttraditionen Thanka och på vilka sätt varierar den? / What involves the tibetan art tradition Thanka and in which ways does it vary?Wallenius, Sandra January 2006 (has links)
Thanka är en tibetansk konsttradition som består av religiösa bilder föreställande en rad gudar och heliga personer ur den buddhistiska tron. Motiven är starkt symbolistiska och strängt traditionsbetingade. Detta arbete beskriver denna företeelse i tre delar där den första är hämtad ur litteratur, jag redogör här för uppkomsten, motiven, tekniken, de religiösa aspekterna och dagens plats. Den andra parten består av intervjuer och den tredje delen sammanfattar processen i den tavlan jag själv målat. Slutsatsen blir att denna konst är mycket komplex och tidskrävande, samt att den i sin lugna precision kontrasterar till den västerländska stressen. Kunskapen om thanka går att applicera i flera av skolans ämnen, så som Historia, Religion och Bild, på grund av sin av tradition befästa plats i det tibetanska samhället. / Thanka is a Tibetan art tradition which consists of religious pictures that portrays several gods, goddesses and holy individuals from the Buddhist faith. The motives are strongly symbolist and strictly traditional. This work describes this occurrence in three parts were the first is taken from literature; I give here an account of the origin, the motives, the technique, the religious aspects and its place today. The second part includes interviews and the third part summarizes the working process in my self-made painting. The conclusion is that this art is very complex and time-demanding, and that its calm precision is contrasting to the Western stress. The knowledge about Thanka is possible to apply in several school subjects such as History, Religion and Art, because of its traditional emplacement in the Tibetan society.
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Évolution de la déformation du prisme Himalayen: de l'imagerie à la modélisationHetényi, György 29 November 2007 (has links) (PDF)
Résumé<br /><br />L'Himalaya et le Plateau Tibétain sont considérés comme l'exemple classique de collision continentale. Cependant, de nombreuses questions fondamentales sur la structure, la rhéologie et les processus physiques liés à l'évolution de la lithosphère de cette région restent ouvertes.<br /><br />Dans le cadre de l'expérience sismologique Hi-CLIMB, un grand nombre de stations large-bande (255) a été déployé pendant trois ans sur un profil de 800 km, à travers l'Himalaya et la moitié sud du Plateau Tibétain. L'espacement serré des stations (~4-9 km), la quantité importante des données (1.5 téraoctets), et l'utilisation de méthodes comme les fonctions récepteurs haute-fréquence ainsi que les conversions multiples ont permis d'obtenir une image détaillée des structures lithosphériques à toute échelle. Ces images permettent un suivi: (1) des failles à faible profondeur (~3-4 km); (2) du chevauchement majeur (MHT) de sa partie superficielle jusqu'à sa continuité profonde et ductile; (3) des zones à vitesses lentes localisées et peu profondes ("bright spots") sous le Tibet en corrélation avec des grabens; (4) de la croûte inférieure indienne sous-plaquée au bloc Lhasa. De plus, nos résultats suggèrent que (5) la lithosphère inférieure indienne avance vers le nord jusqu'au centre du Plateau Tibétain, où elle est opposée au manteau lithosphérique de l'Eurasie; que (6) les sutures en surface n'ont pas de signature marquée en profondeur; et que (7) les discontinuités du manteau supérieur à 410 et 670 km ne sont pas affectées par l'orogenèse. Les informations obtenues sur les géométries sont ensuite utilisées dans deux applications.<br /><br />La rhéologie de la plaque Inde est réévaluée en utilisant l'image améliorée de sa flexure sous le bassin avant-arc. Les résultats des modélisations thermomécaniques montrent que l'épaisseur élastique équivalente diminue du sud au nord dû au découplage lié à l'affaiblissement flexural et thermique. Le support de la topographie du Plateau Tibétain ainsi que l'isostasie régionale en Himalaya nécessitent un manteau résistant.<br /><br />En combinant la géométrie du sous-plaquage avec des anomalies de Bouguer, une densification localisée de la croûte inférieure indienne est mise en évidence à l'endroit où elle atteint sa profondeur maximale. Cette densification est associée à l'éclogitisation. Des analyses du champ thermique et les relations pression--température--densité en supposant différents niveaux d'hydratation sont effectuées par des modélisations thermo-cinématiques et pétrologiques. Les résultats suggèrent que la croûte inférieure indienne est partiellement hydratée, et que l'éclogitisation subit un retard. Ce dernier effet est expliqué par l'absence d'eau libre dans le système, l'éclogitisation n'ayant pas lieu jusqu'à l'occurrence des réactions de déshydratation à des P-T plus élevées que les conditions d'équilibre.<br /><br />En conclusion, cette thèse apporte de nouvelles contraintes sur la géométrie et les propriétés internes de la lithosphère, éléments clés pour mieux évaluer l'importance des différents processus physiques impliqués dans la mise en place des structures et l'évolution de la déformation en Himalaya-Tibet.
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British, Chinese, and Tibetan representations of the Mission to Tibet of 1904Myatt, Timothy Lloyd January 2011 (has links)
This thesis presents and analyses Chinese, Tibetan, and British sources relating to the British Mission to Tibet of 1904. It balances accounts provided by the British officers and men with modern Chinese sources. It analyses both polarised sides of the history, whilst remaining critical of all sources. British historical accounts analysed in chapter one are balanced with Chinese narratives that present the Mission as an invasion of the Motherland and its unity. Chapter two examines the role of propaganda in modern China, and how different media are used to guide the Tibetan and Chinese populations’ understanding of their history and nation. Chapters three and four provide an original translation of Bod kyi rig gnas lo rgyus dpyad gzhi’i rgyu cha bdams bsgrigs, a textbook written from a Chinese nationalistic perspective. The introductory chapter providing the Chinese narrative of the build-up to the Mission is studied in chapter three, and chapter four analyses the bloody advance into Tibet. The translation and analysis in chapter five of the letters of the Dalai Lama to the King of Nepal, the Tongsa Pönlop, and the Chögyal of Sikkim place the Mission in pan-Himalayan context, and show how the Tibetan Government sought to counter the Mission. It is the first study to provide a historical Tibetan perspective of events. Chapter six analyses the divisive issue of looting during the Mission. It examines the psychology of those who looted Tibet, and the role the items taken play in shaping the image of Tibet in the West. Modern Chinese propaganda sources from the new media are analysed in chapter seven, and demonstrate how they have been used to compliment and propagate the established narrative. The conclusions analyse the impact of the Mission, and the lessons that may be learnt for those that play the ‘New Great Game.’
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Development and Application of a Flow-through Sampler for Semi-volatile Organic Compounds in AirXiao, Hang 18 March 2010 (has links)
The investigation of the atmospheric fate and transport of semi-volatile organic compounds (SOCs) often requires the sampling of large volumes of air (>100 m3) in a relatively short period of time. Conventionally high-volume pumps are not suitable for remote areas without access to reliable network power. We have developed a flow through sampler for such situations. It consists of a horizontally-oriented flow-tube, that can collect gaseous and particle-bound SOCs from large volumes of air by turning into the wind and having the wind blow through a porous sampling medium such as polyurethane foam. Through both indoor and outdoor experiments, we quantified its air sampling rate (through battery operated anemometers inside and outside of the flow tube), its sampling efficiency (by theoretical plate number analysis of the break-though curves for PCBs, PAHs, OCPs and PBDEs), and its accuracy (by comparison of concentrations, time trends, temperature dependences and isomer ratios with those obtained by conventional high-volume sampling) under conditions of constant and variable meteorological conditions (wind speed, temperature). The flow-through sampler was deployed to monitor SOC concentrations at a remote Chinese research station located close to Nam Co Lake, Tibet. During the campaign, fifteen 1 month-long samples were taken, corresponding to sample volumes between 5,000 and 20,000 m3. Despite those large sample volumes, only HCB and HCHs experienced break-through, but application of frontal chromatograph theory allows the estimation of breakthrough-corrected air concentrations even for those relatively volatile SOCs. The pesticide levels at Nam Co are generally very low. Most pesticides had higher levels during summer, resulting in a strong temperature dependence. This is correlated with air mass origin across the Himalayas in the Gangetic plains of India and Bangladesh. The flow through sampler constitutes a feasible method for reliably and quantitatively collecting SOCs from large air volumes.
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Late glacial to Holocene climate and vegetation changes on the Tibetan Plateau inferred from fossil pollen records in lacustrine sedimentsWang, Yongbo January 2011 (has links)
The past climate in central Asia, and especially on the Tibetan Plateau (TP), is of great importance for an understanding of global climate processes and for predicting the future climate. As a major influence on the climate in this region, the Asian Summer Monsoon (ASM) and its evolutionary history are of vital importance for accurate predictions. However, neither the evolutionary pattern of the summer monsoon nor the driving mechanisms behind it are yet clearly understood.
For this research, I first synthesized previously published Late Glacial to Holocene climatic records from monsoonal central Asia in order to extract the general climate signals and the associated summer monsoon intensities. New climate and vegetation sequences were then established using improved quantitative methods, focusing on fossil pollen records recovered from Tibetan lakes and also incorporating new modern datasets. The pollen-vegetation and vegetation-climate relationships on the TP were also evaluated in order to achieve a better understanding of fossil pollen records.
The synthesis of previously published moisture-related palaeoclimate records in monsoonal central Asia revealed generally different temporal patterns for the two monsoonal subsystems, i.e. the Indian Summer Monsoon (ISM) and East Asian Summer Monsoon (EASM). The ISM appears to have experienced maximum wet conditions during the early Holocene, while many records from the area affected by the EASM indicate relatively dry conditions at that time, particularly in north-central China where the maximum moisture levels occurred during the middle Holocene. A detailed consideration of possible driving factors affecting the summer monsoon, including summer solar insolation and sea surface temperatures, revealed that the ISM was primarily driven by variations in northern hemisphere solar insolation, and that the EASM may have been constrained by the ISM resulting in asynchronous patterns of evolution for these two subsystems. This hypothesis is further supported by modern monsoon indices estimated using the NCEP/NCAR Reanalysis data from the last 50 years, which indicate a significant negative correlation between the two summer monsoon subsystems. By analogy with the early Holocene, intensification of the ISM during coming decades could lead to increased aridification elsewhere as a result of the asynchronous nature of the monsoon subsystems, as can already be observed in the meteorological data from the last 15 years.
A quantitative climate reconstruction using fossil pollen records was achieved through analysis of sediment core recovered from Lake Donggi Cona (in the north-eastern part of the TP) which has been dated back to the Last Glacial Maximum (LGM). A new data-set of modern pollen collected from large lakes in arid to semi-arid regions of central Asia is also presented herein. The concept of "pollen source area" was introduced to modern climate calibration based on pollen from large lakes, and was applied to the fossil pollen sequence from Lake Donggi Cona. Extremely dry conditions were found to have dominated the LGM, and a subsequent gradually increasing trend in moisture during the Late Glacial period was terminated by an abrupt reversion to a dry phase that lasted for about 1000 years and coincided with the first Heinrich Event of the northern Atlantic region. Subsequent periods corresponding to the warm Bølling-Allerød period and the Younger Dryas cold event were followed by moist conditions during the early Holocene, with annual precipitation of up to about 400 mm. A slightly drier trend after 9 cal ka BP was then followed by a second wet phase during the middle Holocene that lasted until 4.5 cal ka BP. Relatively steady conditions with only slight fluctuations then dominated the late Holocene, resulting in the present climatic conditions.
In order to investigate the relationship between vegetation and climate, temporal variations in the possible driving factors for vegetation change on the northern TP were examined using a high resolution late Holocene pollen record from Lake Kusai. Moving-window Redundancy Analyses (RDAs) were used to evaluate the correlations between pollen assemblages and individual sedimentary proxies. These analyses have revealed frequent fluctuations in the relative abundances of alpine steppe and alpine desert components, and in particular a decrease in the total vegetation cover at around 1500 cal a BP. The climate was found to have had an important influence on vegetation changes when conditions were relatively wet and stable. However, after the 1500 cal a BP threshold in vegetation cover was crossed the vegetation appears to have been affected more by extreme events such as dust storms or fluvial erosion than by the general climatic trends. In addition, pollen spectra over the last 600 years have been revealed by Procrustes analysis to be significantly different from those recovered from older samples, which is attributed to an increased human impact that resulted in unprecedented changes to the composition of the vegetation.
Theoretical models that have been developed and widely applied to the European area (i.e. the Extended R-Value (ERV) model and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model) have been applied to the high alpine TP ecosystems in order to investigate the pollen-vegetation relationships, as well as for quantitative reconstructions of vegetation abundance. The modern pollen–vegetation relationships for four common pollen species on the TP have been investigated using Poaceae as the reference taxa. The ERV Submodel 2 yielded relatively high PPEs for the steppe and desert taxa (Artemisia Chenopodiaceae), and low PPEs for the Cyperaceae that are characteristic of the alpine Kobresia meadows. The plant abundances on the central and north-eastern TP were quantified by applying these PPEs to four post-Late Glacial fossil pollen sequences. The reconstructed vegetation assemblages for the four pollen sequences always yielded smaller compositional species turnovers than suggested by the pollen spectra, indicating that the strength of the previously-reported vegetation changes may therefore have been overestimated.
In summary, the key findings of this thesis are that (a) the two ASM subsystems show asynchronous patterns during both the Holocene and modern time periods, (b) fossil pollen records from large lakes reflect regional signals for which the pollen source areas need to be taken into account, (c) climate is not always the main driver for vegetation change, and (d) previously reported vegetation changes on the TP may have been overestimated because they ignored inter-species variations in pollen productivity. / Das Paläoklima in Zentralasien, besonders in der Hochebene von Tibet (HT), ist von großer Bedeutung um globale Klimaprozesse zu verstehen und mögliche Voraussagung für die zukunft zu treffen. Als wichtigstes Klimaphänomen nehmen der asiatische Sommermonsun (ASM) und seine Entwicklungsgeschichte eine Schlüsselposition ein. Dennoch sind derzeit weder das Entwicklungsschema noch der antreibende Vorgang ausreichend verstanden. Dies gilt insbesondere für das Holozän, für welches große Kimaschwankungen und regionale Diskrepanzen weithin belegt sind.
Deshalb habe ich zuerst holozäne Klimadaten zusammengefasst. Bereits veröffentlichte Publikationen aus den Monsungebieten Zentralasiens dienten als Grundlage, um die wichtigsten Klimasignale und die zugehörigen Intensitäten des Sommermonsuns heraus zu arbeiten. Anhand von Pollensequenzen aus tibetischen Seen erzeugte ich neue Klima- und Vegetationssequenzen, welche auf verbesserten quantitativen Methoden und rezenten Datensätzen beruhen. Außerdem wurden die Verhältnisse Pollen-Vegetation und Vegetation-Klima bewertet, um Schlussfolgerungen fossiler Pollensequenzen zu verbessern.
Die Zusammenfassung der zuvor veröffentlichten, niederschlagsbezogenen Paläoklimadaten im Monsungebiet Zentralasiens ergab generell unterschiedliche Muster für die zwei Teilsysteme des ASMs, den Indischen Sommermonsun (ISM) und den Ostasiatischen Sommermonsun (OASM). Der ISM weist maximale feuchte Bedingungen während des frühen Holozöns auf, während viele Datensätze aus dem Gebiet des OASMs einen relativ trockenen Zustand anzeigen, besonders im nördlichen Zentralchina, wo maximale Niederschläge während des mittleren Holozäns registriert wurden. Genaue Betrachtungen der Antriebsfaktoren des Sommermonsuns ergaben, dass der ISM hauptsächlich durch Veränderungen der Sonneneinstrahlung auf der Nordhemisphäre angetrieben wird, während der OASM potentiell durch den ISM beherrscht wird - dies führt zu asynchronen Entwicklungen. Diese Hypothese wird durch rezente Monsunindizes gestützt. Sie weisen eine signifikant negative Korrelation zwischen den beiden Sommermonsun-Teilsystemen auf.
Für die quantitative Klimarekonstruktion von Pollensequenzen wurde ein Sedimentkern aus dem See Donggi Cona im Nordosten der HT analysiert, der bis zum letzten glazialen Maximum (LGM) zurückdatiert wurde. Aufgrund der Tatsache, dass Donggi Cona ein relativ großer See ist, wird hiermit ein neuer Pollen-Klima-Kalibrierungsdatensatz auf Grundlage großer Seen in ariden und semiariden Regionen Zentralasiens vorgelegt. Das Konzept des Pollenherkunftsgebietes wurde in diese rezente, pollenbasierte Klimakalibrierung eingebracht und auf die Pollensequenz von Donggi Cona angewendet. Die Auswertung ergab, dass extrem trockene Bedingungen während des LGM (ca. 100 mm/yr) vorherrschten. Ein ansteigender Trend von Niederschlägen während des späten Glazials wurde durch einen abrupten Rückgang zu einer etwa 1000-jährigen Trockenphase beendet, welche mit Heinrich-Ereignis 1 in der Nordatlantik-Region übereinstimmt. Danach entsprechen die Klimaperioden dem warmen Bølling/Allerød und dem Kälteereignis der Jüngeren Dryas. Anschließend herrschten feuchte Bedingungen im frühen Holozän (bis zu 400 mm/yr). Ein etwas trockenerer Trend nach dem Holozänen Klimaoptimum wurde dann von einer zweiten Feuchtphase abgelöst, welche bis 4,5 cal. ka vor heute andauerte. Relativ gleichmäßige Bedingungen dominierten das späte Holozän bis heute. Die Klimadynamik seit dem LGM wurde vor allem durch Entgletscherung und Intensitätsschwankungen des ASM bestimmt.
Bei der Betrachtung des Vegetation-Klima-Verhältnisses habe ich die zeitlichen Variationen der bestimmenden Faktoren hinsichtlich der Vegetationsdynamik auf der nördlichen HT untersucht. Dabei wurden hochauflösende holozäne Pollendaten des Kusai-Sees verwendet. Eine Redundanzanalyse (RDA) wurde angewendet um die Korrelation zwischen Pollenvergesellschaftungen und individuellen sedimentären Klimaanzeigern als auch die damit verbundene Signifikanz zu bewerten. Es stellte sich heraus, dass das Klima einen wichtigen Einfluss auf den Veränderungen in der Vegetation besaß, wenn die Bedingungen relativ warm und feucht waren. Trotzdem scheint es, dass, dass die Vegetation bei zu geringer Bedeckung stärker durch Extremereignisse wie Staubstürme oder fluviale Erosion beeinflusst wurde. Pollenspektren der vergangen 600 Jahre erwiesen sich als signifikant unterschiedlich verglichen mit den älterer Proben, was auf verstärkten anthropogenen Einfluss hindeutet. Dieser resultierte in einem beispiellosen Wandel in der Zusammensetzung der Vegetation.
In Hinsicht auf das Pollen-Vegetation-Verhältnis und der quantitativen Rekonstruktion der Vegetationshäufigkeit habe ich theoretische Modelle, welche für europäische Regionen entwickelt und weithin angewendet wurden, respektive die Modelle "Extended R-Value" (ERV) sowie "Regional Estimates of Vegetation Abundance from Large Sites" (REVEALS), auf die hochalpinen Ökosysteme der HT überführt. Dafür wurden rezente Pollen-Vegetations-Verhältnisse von vier weit verbreiteten Pollen-Arten der HT überprüft. Poaceae wurden als Referenztaxa verwendet. Bei der Anwendung dieser Verhältnisse auf vier Pollensequenzen, welche die Paläoumweltbedingungen seit dem letzten Glazial widerspiegeln, wurden die Häufigkeiten von Pflanzen auf der zentralen und nordöstlichen HT quantifiziert. Anteile von Artimisia und Chenopodiaceae waren dabei im Vergleich zu ihren ursprünglichen Pollenprozenten deutlich verringert. Cyperaceae hingegen wies eine relative Zunahme in dieser Vegetationsrekonstruktion auf. Die rekonstruierten Vegetationsvergesellschaftungen an den Standorten der vier Pollensequenzen ergaben stets geringere Umwälzungen in der Artenzusammensetzung, als durch die Pollenspektren zu vermuten gewesen wäre. Dies kann ein Hinweis darauf sein, dass die Intensität der bislang angenommenen Vegetationsveränderungen überschätzt worden ist.
Zusammengefasst sind die Hauptresultate dieser Dissertation, dass (a) die zwei ASM Teilsysteme asynchrone Muster während des Holozäns und heute aufweisen, dass (b) fossile Pollensequenzen großer Seen regionale Klimasignale widerspiegeln sofern die Herkunftsgebiete der Pollen berücksichtigt werden, dass (c) Klima nicht immer der Haupteinflussfaktor für Vegetationswandel ist und dass (d) das Ausmaß von Vegetationsveränderungen in zuvor veröffentlichten Studien auf der Hochebene von Tibet überschätzt worden sein kann, weil Diskrepanzen der Pollenproduktivität zwischen den Arten nicht einbezogen wurden.
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