This thesis presents measurements of the branching fractions B(Ds -> lvl) and mea- surements of the pseudoscalar decay constant, fDs , using all the data acquired at the BaBar detector at SLAC National Accelerator Laboratory, which were collected from September 1999 to April 2007, and comprised 531 fb-1. The following mea- surements are made: B(Ds -> eve) = (6:11 +/-0:38 +/- 0:33) * 10-3, B(Ds -> tvt) = (5:06 +/- 0:34 +/- 0:50) * 10-2 , and a limit B(Ds -> eve) < 1:46 * 10-4 is obtained. Using these measurements a value of fDs = 252 +/- 6 +/- 7 +/- 1MeV is obtained, where the first uncertainties account for the statistical limitations of the data, the second uncertainties account for the systematic uncertainties, and the third uncertainties account for uncertainties associated with other physical constants (dominated by the lifetime of the Ds meson).

The 87Rb-86Sr system is a widely used long-lived isotope geochronometer. 87Rb, the naturally occurring radioactive isotope of Rb, undergoes beta-decay to stable 87Sr with a half-life of approximately 50 Ga. Decay of 87Rb to 87Sr results in variable 87Sr/86Sr in minerals with different Rb/Sr, and measurement of 87Rb/86Sr and 87Sr/86Sr allows for the determination of the age of the rock. Accurate ages depend both on the quality of the isotopic analysis and on the accuracy of the 87Rb decay constant, lambda87. Although the currently accepted value for lambda87 of 1.42 × 10-11a-1 has been in use for over 30 years, there is growing evidence that it is not accurate. Recent attempts to refine lambda87 and its precision have not reached a consensus. This thesis describes a new experiment to measure lambda87 by 87Sr accumulation over a period of about 30 years, and the preparation of a 84-86Sr double-spike in conjunction with that experiment. Radiogenic 87Sr produced in aliquots of a RbClO4 salt was measured by isotope dilution thermal ionization mass spectrometry. An average of 31 measurements yields a value of 1.398 ± 0.003 × 10-11a-1 . This requires a substantial revision from the previously accepted decay constant and makes Rb-Sr ages calculated with it 1.5% older. A Rb-Sr and U-Pb isotopic chronometry study was carried out on thirteen ordinary chondrites – the most common type of meteorite, the origin and history of which are still unclear. Some meteorites appear disturbed, possibly by recent shock during breakup of the parent body, whereas others yielded accurate and precise U-Pb and Pb-Pb ages. For example, L5 Elenovka yielded distinct ages for silicates (4555 Ma) and phosphates (4535 Ma), allowing the cooling rate of this meteorite from approximately 1055 K to 759 K to be constrained to 15 ± 3 K/Ma. Rb-Sr yielded less precise ages than U-Pb, but using the new decay constant allows accurate comparison between the two methods. This study creates a firm foundation for future studies in thermal history of chondrites and terrestrial metamorphic complexes using Rb-Sr together with other isotopic chronometers.

The 87Rb-86Sr system is a widely used long-lived isotope geochronometer. 87Rb, the naturally occurring radioactive isotope of Rb, undergoes beta-decay to stable 87Sr with a half-life of approximately 50 Ga. Decay of 87Rb to 87Sr results in variable 87Sr/86Sr in minerals with different Rb/Sr, and measurement of 87Rb/86Sr and 87Sr/86Sr allows for the determination of the age of the rock. Accurate ages depend both on the quality of the isotopic analysis and on the accuracy of the 87Rb decay constant, lambda87. Although the currently accepted value for lambda87 of 1.42 × 10-11a-1 has been in use for over 30 years, there is growing evidence that it is not accurate. Recent attempts to refine lambda87 and its precision have not reached a consensus. This thesis describes a new experiment to measure lambda87 by 87Sr accumulation over a period of about 30 years, and the preparation of a 84-86Sr double-spike in conjunction with that experiment. Radiogenic 87Sr produced in aliquots of a RbClO4 salt was measured by isotope dilution thermal ionization mass spectrometry. An average of 31 measurements yields a value of 1.398 ± 0.003 × 10-11a-1 . This requires a substantial revision from the previously accepted decay constant and makes Rb-Sr ages calculated with it 1.5% older. A Rb-Sr and U-Pb isotopic chronometry study was carried out on thirteen ordinary chondrites – the most common type of meteorite, the origin and history of which are still unclear. Some meteorites appear disturbed, possibly by recent shock during breakup of the parent body, whereas others yielded accurate and precise U-Pb and Pb-Pb ages. For example, L5 Elenovka yielded distinct ages for silicates (4555 Ma) and phosphates (4535 Ma), allowing the cooling rate of this meteorite from approximately 1055 K to 759 K to be constrained to 15 ± 3 K/Ma. Rb-Sr yielded less precise ages than U-Pb, but using the new decay constant allows accurate comparison between the two methods. This study creates a firm foundation for future studies in thermal history of chondrites and terrestrial metamorphic complexes using Rb-Sr together with other isotopic chronometers.

Modelling the wake effect generated by wind turbines is an essential part for calcu- lating a wind farm’s expected energy production. Operating wind turbines disturb the flow of the wind, which results in decreased production of downwind turbines. The N. O. Jensen model is an industry standard wake model that assumes a linear expansion of the downstream wake. The only adjustable parameter in the model is the wake decay constant (WDC), which has traditionally been derived semi em- pirically from terrain surface roughness. However, the WDC defines the expansion rate of the generated wake, and therefore can be linked to the ambient turbulence intensity (TI): high ambient turbulence leads to a faster decay of the generated wake, and therefore to lower wake losses, and vice-versa. Since the influence of the roughness on the ambient turbulence intensity is expected to be less significant at higher heights, these roughness-based WDC values are rather uncertain for the hub heights employed nowadays. The following study presents the results of a comparison between observed and mod- elled wake losses based on different WDC values. To investigate how a change in height affects the wake modelling, two wake scenarios occurring between two tur- bine sets with different hub heights are selected from an operational wind farm. By modelling the wakes using roughness as well as turbulence intensity-based WDCs, conclusions can be drawn on how the predictive capability of the N.O. Jensen model depends on the selection of a suitable WDC value. Finally it is concluded that the goodness of fit between modelled and observed wake losses shows a clear dependency on the wind speed/power production inter- val. At higher wind speeds, the TI-based WDC resulted in a better accuracy of the modelled wake losses as compared to the roughness-based WDC, while for lower wind speeds the N. O. Jensen model performed most accurately when using WDC = 0.075. However, for the investigated cases the overall accuracy of the modelled wake appears to be higher when choosing WDC = 0.075 instead of a TI-based WDC.

Vernal pools are small, seasonally filling wetlands found throughout forests of north eastern North America. Vernal pools have been proposed as potential 'hot spots' of carbon cycling. A key component of the carbon cycle within vernal pools is the decomposition of leaf litter. I tested the hypothesis that leaf litter decomposition is more rapid within vernal pools than the adjacent upland. Leaf litter mass losses from litterbags incubated in situ within vernal pools and adjacent upland habitat were measured periodically over one year and then again after two years. The experiment was carried out at 24 separate vernal pools, over two replicate years. This is a novel degree of replication in studies of decomposition in temporary wetlands. Factors influencing decomposition, such as duration of flooding, water depth, pH, temperature, and dissolved oxygen were measured. Mass loss was greater within pools than adjacent upland after 6 months, equal after 12 months, and lower within pools than adjacent upland after 24 months. This evidence suggests that vernal pools of Central Ontario are 'hot spots' of decomposition up to 6 months, but not after 12 and 24 months. In the long term, vernal pools may reduce decomposition rates, compared to adjacent uplands.

In der Gitterquantenchromodynamik sind der Einsatz von unphysikalisch großen Quarkmassen und die Extrapolation von Ergebnissen zu physikalischen Massen signifikante systematische Fehlerquellen. In dieser Arbeit wird die praktische Durchführbarkeit numerischer Simulationen der Quantenchromodynamik mit physikalisch leichten up und down Quarkmassen unter Verwendung der Wilson twisted mass Diskretisierung untersucht. Simulationen im Regime physikalisch leichter Quarkmassen sind jedoch einerseits numerisch sehr aufwendig, können andererseits aber auch durch das Auftreten großer Diskretisierungsartefakte nicht praktikabel sein. Anhand von Simulationen mit massendegenerierten dynamischen up und down Quarks wird dargestellt dass die Erweiterung der twisted mass Fermionwirkung durch den Sheikholeslami-Wohlert Term es ermöglicht physikalisch leichte Quarkmassen zu erreichen. Es wird gezeigt, dass die Simulationen stabil sind und dass die Parameter der diskretisierten Theorie so gewählt werden können, dass das geladene Pion seine physikalische Masse annimmt. Ferner wird dargestellt, dass auch die Parameter für eine Simulation mit dynamischen massendegenerierten up und down quarks sowie nichtdegenerierten strange und charm Quarks schrittweise auf ihre physkalischen Werte gesetzt werden können. Um das Verhalten von Observablen bei physikalischer Quarkmasse zu untersuchen, werden Massen und Zerfallskonstanten von pseudoskalaren Mesonen mit up, down sowie strange und charm Valenzquarks berechnet. Die Ergebnisse stimmen größtenteils überein mit den phänomenologischen Werten, obwohl weder Kontinuumslimes noch die Extrapolation zu unendlichem Volumen durchgeführt werden. Renormierte leichte, strange und charm Quarkmassen werden über Interpolationen in hadronischen Observablen berechnet und stimmen ebenso größtenteils mit phänomenologischen Werten und anderen Ergebnissen aus der Gitter-QCD überein. / In computer simulations of Lattice Quantum Chromodynamics, the usage of unphysically large quark masses and the subsequent extrapolation of results to the physical value of the quark masses are major sources of systematic uncertainty. In this thesis, the feasibility and practicality of numerical simulations of Quantum Chromodynamics with physically light up and down quarks using the Wilson twisted mass quark discretisation are explored. Working in this regime is complicated firstly by the numerical expense of these simulations and secondly by the presence of potentially large lattice artefacts. The twisted mass discretisation is affected by an unphysical mass difference between the charged and neutral pions, rendering simulations at the physical charged pion mass infeasible if this mass splitting is too large. With the aim of reducing it, the Sheikholeslami-Wohlert term is added to the twisted mass fermion action and simulations with mass degenerate up and down quarks are then performed as a proof of concept. It is demonstrated that these simulations are stable and that the parameters of the lattice theory can be successfully tuned to correspond to the physical charged pion mass. Subsequently, the parameter tuning for simulations with mass degenerate up and down quarks as well as strange and charm quarks is explored and it is shown that it can be carried out in steps. As benchmark observables, the masses and decay constants of pseudoscalar mesons with light, strange and charm valence quarks are calculated and seen to largely reproduce their phenomenological values, even though continuum and infinite volume extrapolations are not performed. Light, strange and charm quark mass estimates are determined based on this data and also seen to coincide with phenomenological and other lattice determinations.

<p>У докторској дисертацији&nbsp; приказани су резултати развијених и примењених коинцидентних метода за временску анализу нуклеарних процеса. Експериментални коинцидентни системи засновани су на&nbsp; HPGe&nbsp; и пластичним сцинтилационим детекторима.&nbsp; Извршена су три експеримента, која су показала примењивост развијених коинцидентних система. Први део експерименталног дела обухвата анализе временских варијација интензитета космичког зрачења посредством нискоенергијских фотона. Показано је да се праћењем интензитета нискоенергијских фотона у току времена у различитим енергијским регионима остварује бољи увид у анализу фонских догађаја, стварајући предуслове за извођење експеримената који трагају за ретким нуклеарним процесима. Поред праћења временских варијација интензитета, метода се може применити и&nbsp; на детекцију периодичних и апериодичних догађаја повезаних са активношћу Сунца. Други део дисертације обухватао је истраживања везана&nbsp; за&nbsp; детекцију потенцијалних&nbsp; флуктуација константе распада 22 Na. Развијен је коинцидентни систем&nbsp; и&nbsp; у току времена је&nbsp; праћен интензитет анихилационе линије, која је резултат анихилације позитрона емитованог распадом 22Na.&nbsp; За време трајања&nbsp; аквизиције података, нису пронађена значајна одступања испитиване константе распада од стандардног експоненцијалног закона радиоактивног распада. У трећем делу експерименталног рада, приказана је коинцидентна метода за временско раздвајање догађаја индукованих мионима и неутронима у околини детекторског система. Добијена је временска крива у експерименту и извршена је детаљна анализа различитих временских региона. Извршене су Монте Карло симулације, на основу којих је добијена временска крива. Анализом различитих региона симулиране временске криве, показано је да се ови догађаји могу раздвојити у две велике групе&ndash;брзе и споре догађаје. Међу спорим догађајима, показано је да се може направити разлика између догађаја индукованих мионима, међу којима доминира анихилација, и догађаја индукованих неутронима, који спадају у закаснеле догађаје у групи спорих догађаја. Добијено је да неутрони највише доприносе нискоенергијском региону, првенствено у региону до&nbsp; &asymp;50&nbsp; keV,&nbsp; што их чини&nbsp; нежељеном кариком фонских догађаја у експериментима који трагају за ретким нуклеарним догађајима. На основу резултата симулација, анализирани су електромагнетни и хадронски процеси индуковани мионима и неутронима, као и удели мионске и неутронске компоненте у коинцидентном спектру HPGe&nbsp; детектора и директном спектру пластичног сцинтилационог детектора. Закључено је да нискоенергијском спектру,&nbsp; који је превасходно значајан за ретке нуклеарне процесе,&nbsp; доминантно доприносе неутрони.</p> / <p>U doktorskoj disertaciji&nbsp; prikazani su rezultati razvijenih i primenjenih koincidentnih metoda za vremensku analizu nuklearnih procesa. Eksperimentalni koincidentni sistemi zasnovani su na&nbsp; HPGe&nbsp; i plastičnim scintilacionim detektorima.&nbsp; Izvršena su tri eksperimenta, koja su pokazala primenjivost razvijenih koincidentnih sistema. Prvi deo eksperimentalnog dela obuhvata analize vremenskih varijacija intenziteta kosmičkog zračenja posredstvom niskoenergijskih fotona. Pokazano je da se praćenjem intenziteta niskoenergijskih fotona u toku vremena u različitim energijskim regionima ostvaruje bolji uvid u analizu fonskih događaja, stvarajući preduslove za izvođenje eksperimenata koji tragaju za retkim nuklearnim procesima. Pored praćenja vremenskih varijacija intenziteta, metoda se može primeniti i&nbsp; na detekciju periodičnih i aperiodičnih događaja povezanih sa aktivnošću Sunca. Drugi deo disertacije obuhvatao je istraživanja vezana&nbsp; za&nbsp; detekciju potencijalnih&nbsp; fluktuacija konstante raspada 22 Na. Razvijen je koincidentni sistem&nbsp; i&nbsp; u toku vremena je&nbsp; praćen intenzitet anihilacione linije, koja je rezultat anihilacije pozitrona emitovanog raspadom 22Na.&nbsp; Za vreme trajanja&nbsp; akvizicije podataka, nisu pronađena značajna odstupanja ispitivane konstante raspada od standardnog eksponencijalnog zakona radioaktivnog raspada. U trećem delu eksperimentalnog rada, prikazana je koincidentna metoda za vremensko razdvajanje događaja indukovanih mionima i neutronima u okolini detektorskog sistema. Dobijena je vremenska kriva u eksperimentu i izvršena je detaljna analiza različitih vremenskih regiona. Izvršene su Monte Karlo simulacije, na osnovu kojih je dobijena vremenska kriva. Analizom različitih regiona simulirane vremenske krive, pokazano je da se ovi događaji mogu razdvojiti u dve velike grupe&ndash;brze i spore događaje. Među sporim događajima, pokazano je da se može napraviti razlika između događaja indukovanih mionima, među kojima dominira anihilacija, i događaja indukovanih neutronima, koji spadaju u zakasnele događaje u grupi sporih događaja. Dobijeno je da neutroni najviše doprinose niskoenergijskom regionu, prvenstveno u regionu do&nbsp; &asymp;50&nbsp; keV,&nbsp; što ih čini&nbsp; neželjenom karikom fonskih događaja u eksperimentima koji tragaju za retkim nuklearnim događajima. Na osnovu rezultata simulacija, analizirani su elektromagnetni i hadronski procesi indukovani mionima i neutronima, kao i udeli mionske i neutronske komponente u koincidentnom spektru HPGe&nbsp; detektora i direktnom spektru plastičnog scintilacionog detektora. Zaključeno je da niskoenergijskom spektru,&nbsp; koji je prevashodno značajan za retke nuklearne procese,&nbsp; dominantno doprinose neutroni.</p> / <p>In&nbsp; this&nbsp; doctoral&nbsp; thesis,&nbsp; the&nbsp; results&nbsp; of&nbsp; the&nbsp; developed and&nbsp; applied&nbsp; coincidence&nbsp;&nbsp; methods&nbsp; on&nbsp; the&nbsp; timeanalysis&nbsp; of&nbsp; nuclear&nbsp; processes&nbsp; are&nbsp; presented. Coincidence systems, used in presented experiments, are&nbsp; based&nbsp; on&nbsp; the&nbsp; HPGe&nbsp; and&nbsp; plastic&nbsp; scintillation detectors.&nbsp; Three&nbsp; experiments&nbsp; were&nbsp; performed,showing&nbsp; a&nbsp; wide&nbsp; application&nbsp; of&nbsp; the&nbsp; developed coincidence&nbsp; systems.&nbsp; The&nbsp; first&nbsp; part&nbsp; of&nbsp; the experimental work involves the analysis of the time&nbsp; variations of cosmic rays via low-energy photons. It was&nbsp; shown&nbsp; that&nbsp; by&nbsp; analyzing&nbsp; the&nbsp; intensity&nbsp; of&nbsp; lowenergy photons better insight into the behavior of thebackground&nbsp; events&nbsp; is&nbsp; provided,&nbsp; which&nbsp; is&nbsp;&nbsp; especially important&nbsp; as&nbsp; a&nbsp; precondition&nbsp; for&nbsp; rare&nbsp; nuclear&nbsp; events experiments.&nbsp; Furthermore,&nbsp; it&nbsp; was&nbsp; shown&nbsp; that&nbsp; this method can be applied in order to search for periodic or aperiodic events resulting from the Sun activity. The&nbsp; second&nbsp; part&nbsp; contains&nbsp; the&nbsp; research&nbsp; of&nbsp; the&nbsp; 22Na decay constant fluctuations. The coincidence system was&nbsp; developed&nbsp; and&nbsp; the&nbsp; intensity&nbsp; of&nbsp; the&nbsp; annihilation line,&nbsp; resulting&nbsp; from&nbsp; annihilation&nbsp; of&nbsp; the&nbsp; positrons emitted from 22Na, was followed with time. During&nbsp; he&nbsp; acquisition&nbsp; time,&nbsp; no&nbsp; significant&nbsp; deviations&nbsp; from the standard exponential radioactive decay law were found. In&nbsp; the&nbsp; third&nbsp; part&nbsp; of&nbsp; the&nbsp; experimental&nbsp; work,&nbsp; the coincidence&nbsp; method&nbsp; for&nbsp; time&nbsp; separation&nbsp; of&nbsp; the events,&nbsp; induced&nbsp; by&nbsp; cosmic&nbsp; muons&nbsp; and&nbsp; neutrons&nbsp; in the&nbsp; vicinity&nbsp; of&nbsp; the&nbsp; detectors&nbsp; system,&nbsp; was&nbsp; presented. The time curve was obtained in the experiment and the&nbsp; detailed&nbsp; analysis&nbsp; of&nbsp; the&nbsp; different&nbsp; time&nbsp; regions was&nbsp; performed.&nbsp; The&nbsp; Monte&nbsp; Carlo&nbsp; simulations&nbsp; were conducted&nbsp; and&nbsp; the&nbsp; time&nbsp; curve&nbsp; from&nbsp; the&nbsp; simulation results was obtained. Analyzing the different regions of the simulated time curve, it was noticed that these events can be separated into two groups&ndash;prompt and delayed.&nbsp; Between&nbsp; delayed&nbsp; events,&nbsp; it&nbsp; was&nbsp; concluded that&nbsp; events&nbsp; induced&nbsp; by&nbsp; muons,&nbsp; dominantly annihilation&nbsp; line,&nbsp; and&nbsp; events&nbsp; induced&nbsp; by&nbsp; neutrons, which&nbsp; may&nbsp; be&nbsp; classified&nbsp; as&nbsp; more&nbsp; delayed&nbsp; events&nbsp; in the&nbsp; group&nbsp; of&nbsp; the&nbsp; delayed&nbsp; events,&nbsp; can&nbsp; be distinguished.&nbsp; It&nbsp; was&nbsp; concluded&nbsp; the&nbsp; neutrons dominantly&nbsp; contribute&nbsp; to&nbsp; the&nbsp; low-energy&nbsp; region, mostly&nbsp; in&nbsp; the&nbsp; region&nbsp; to&nbsp; &asymp;50&nbsp; keV,&nbsp; which&nbsp; makes neutrons&nbsp; an&nbsp; important&nbsp; background&nbsp; in&nbsp; the experiments searching for rare nuclear events. Based on&nbsp; the&nbsp; simulation&nbsp; results,&nbsp; electromagnetic&nbsp; and hadronic processes induced by muons and neutrons, as&nbsp; well&nbsp; as&nbsp; portions&nbsp; of&nbsp; muon&rsquo;s&nbsp; and&nbsp; neutron&rsquo;s component&nbsp; in&nbsp; the&nbsp; coincidence&nbsp; spectrum&nbsp; of&nbsp; HPGe detector&nbsp; and&nbsp; direct&nbsp; spectrum&nbsp; of&nbsp; the&nbsp; plastic scintillation&nbsp; detector&nbsp; were&nbsp; analyzed.&nbsp; It&nbsp; was concluded&nbsp; that&nbsp; in&nbsp; the&nbsp; low-energy&nbsp; part&nbsp; of&nbsp; the spectrum,&nbsp; primarily important for the search for rare nuclear&nbsp; events,&nbsp; dominant&nbsp; influence&nbsp; is&nbsp; originated from cosmic neutrons.</p>