323 research outputs found
Attenuation and Velocity of Ultrasound Near the Critical Point of Gallium-Bismuth
No full textTitle: Attenuation and Velocity of Ultrasound Near the Critical Point of Gallium-Bismuth, Author: Manfred P. Puls, Location: ThodeAttenuation measurements were performed on a liquid Ga-Bi mixture above its miscibility gap and at the frequencies 16.6, 25.5, 37.6 and 49.7 MHz. The attenuation measurements were made over a composition range from 0.20 to 0.75 weight-fraction Bismuth and in the temperature range 0.3 to 9.9°C above the critical temperature of the mixture. For a mixture at the critical composition, attenuation measurements were also made 27.2°C above the critical temperature. The velocity of sound was measured at 25.5MHz and at each of the above temperature and composition points. The critical temperature and composition of the Ga-Bi system have been determined to improve accuracy as 263.1°C and 0.60 weight-fraction Bismuth, respectively. The attenuation results have been tested against current theories and these theories have been subject to critical analysis.ThesisDoctor of Philosophy (PhD
Heart-type fatty acid-binding protein permits early risk stratification of pulmonary embolism
No full textAims We investigated the value of a novel early biomarker, heart-type fatty acid-binding protein (H-FABP), in risk stratification of patients with acute pulmonary embolism (PE). Methods and results We prospectively included 107 consecutive patients with confirmed PE. The endpoints were (i) PE-related death or major complications and (ii) overall 30-day mortality. Overall, 29 patients (27%) had abnormal (> 6 ng/mL) H-FABP levels at presentation. Of those, 12 (41%) had a complicated course, whereas all patients with normal baseline H-FABP had a favourable 30-day outcome (OR, 71.45; P < 0.0001). At multivariable analysis, H-FABP (P < 0.0001), but not cardiac troponin T (P = 0.13) or N-terminal pro-brain natriuretic peptide (P = 0.36), predicted an adverse outcome. Evaluation of a strategy combining biomarker testing with echocardiography revealed that patients with a negative H-FABP test had an excellent prognosis regardless of echocardiographic findings. In contrast, patients with a positive H-FABP test had a complication rate of 23.1% even in the presence of a normal echocardiogram, and this rose to 57.1% if echocardiography also demonstrated right ventricular dysfunction (OR vs. a negative H-FABP test, 5.6 and 81.4, respectively). Conclusion H-FABP is a promising early indicator of right ventricular injury and dysfunction in acute PE. It may help optimize risk stratification algorithms and treatment strategies
The quality in qualitative methods
No full textQuality concerns play a central role throughout all steps of the research process in qualitative methods, from the inception of a research question and data collection, to the analysis and interpretation of research findings. For instance, the type of instrument or procedure to collect data may be evaluated in relation to quality criteria, and these may be different from those which are used to judge the data obtained from such instruments or procedures. All these may yet again be different from quality criteria that may apply to the qualitative analyses of data. A national resource center for qualitative methods can contribute to the establishment and maintenance of certain quality standards. In this article, we will explore some of these quality criteria and how they can be established and maintained by a national resource center for qualitative methods.
URN: urn:nbn:de:0114-fqs050234
The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking
No full textBy drawing together the current theoretical and experimental understanding of the phenomena of delayed hydride cracking (DHC) in zirconium alloys, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking provides a detailed explanation focusing on the properties of hydrogen and hydrides in these alloys. Whilst the focus lies on zirconium alloys, the combination of both the empirical and mechanistic approaches creates a solid understanding that can also be applied to other hydride forming metals. This up-to-date reference focuses on documented research surrounding DHC, including current methodologies for design and assessment of the results of periodic in-service inspections of pressure tubes in nuclear reactors. Emphasis is placed on showing that our understanding of DHC is supported by progress across a broad range of fields. These include hysteresis associated with first-order phase transformations; phase relationships in coherent crystalline metallic solids; diffusion of substitutional and interstitial atoms in crystalline solids; and continuum fracture and solid mechanics. Furthermore, an account of current methodologies is given, illustrating how such understanding of hydrogen, hydrides and DHC in zirconium alloys underpins these methodologies for assessments of real life cases in the Canadian nuclear industry. The all-encompassing approach makes The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Component: Delayed Hydride Cracking an ideal reference source for students, researchers and industry professionals alike
Der Silizium-Vertexdetektor für b-tagging bei Belle II
No full textDas Belle-Experiment am Forschungszentrum KEK (Tsukuba, Japan) lief erfolgreich von 1999 bis 2010, und bestätigte die theoretischen Vorhersagen der CP-Verletzung. Um die Strahlintensität zu erhöhen ist eine Verbesserung des KEKB-Speicherrings vorgesehen, die 2015 in Betrieb geht. Die Luminosität soll auf 8 x 10 35 cm -2 s -1 gesteigert werden, was in etwa das 40-fache des bisherigen Spitzenwerts ist. Die Verbesserung des Beschleunigers bedingt auch Änderungen am Belle-Detektor im Allgemeinen, und am innersten Spurdetektor, dem SVD (Silicon Vertex Detector), im Speziellen. Der SVD wird komplett ersetzt, da er schon bisher an den Grenzen seiner Leistungsfähigkeit gearbeitet hat. Auch alle anderen Subsysteme werden verbessert und angepasst, was zum neuen Belle II-Experiment führt. Das Ziel von Belle II ist die Suche nach Abweichungen vom Standardmodell der Teilchenphysik durch extrem präzise Messungen von seltenen Teilchenzerfällen, was einen komplementären Ansatz zu den direkten Suchen der hochenergetischen Hadronen-Beschleuniger darstellt. Der verbesserte SuperKEKB-Beschleuniger wird Elektronen und Positronen mit einer Energie kollidieren, die einem angeregten Zustand des Y-Teilchens entspricht. Dieses Teilchen zerfällt ausschließlich in ein B-Meson und sein Antiteilchen. Der Zerfallspunkt dieser Mesonen muss präzise bestimmt werden, was die gemeinsame Aufgabe von Belle II SVD, PXD (PiXel Detector) und CDC (Central Drift Chamber) ist. Das erlaubt die Messung von zeitabhängiger, durch Quarkmischungen bedingter CP-Verletzung. Außerdem misst der SVD die Zerfallspunkte von anderen Zerfallskanälen, die D-Mesonen und Tau-Leptonen enthalten. Die Kollisionsenergie ist mit 10 GeV recht klein, weshalb die dabei entstehenden Teilchen niedrigen Impuls aufweisen und damit stark von Vielfachstreuung beeinflusst werden, wenn sie Sensormaterial durchdringen. Deswegen müssen die im Belle II SVD verwendeten Sensoren im Hinblick auf Materialdicke optimiert werden, während Signalausbeute und Positionsgenauigkeit erhalten bleiben müssen. Die Erfüllung dieser Vorgaben ist durch den Einsatz von dünnen, doppelseitigen Silizium-Streifensensoren möglich. Diese Doktorarbeit beschreibt die physikalische Motivation eine hochintensive B-Mesonen-"Fabrik" und einen hochpräzisen Teilchendetektor zu bauen, und gibt eine Einführung in das Belle II-Experiment, wobei alle beteiligten Detektorsysteme kurz nach Zweck und Funktion beschrieben werden. Der Belle II SVD wird detaillierter erklärt, wobei auf die Themen der mechanischen Struktur, der Sensoren, der Ausleseelektronik und der Kühlung eingegangen wird. Weiters werden die Grundlagen der Halbleiterphysik und der Herstellung von Mikroelektronik beleuchtet, und das Prinzip von einseitigen und doppelseitigen Silizium-Streifensensoren wird detailliert erklärt. Die Hauptaufgabe des Autors war die Entwicklung eines trapezförmigen, doppelseitigen Silizium-Streifensensors für den Vorwärtsbereich des Belle II SVD, angefangen bei den CAD-Zeichnungen bis zur Produktion. Der Autor hat ein Programm entwickelt, mit dem schnell und flexibel rechteckige und trapezförmige doppelseitige Silizium-Streifensensoren entworfen werden können. Mit dieser Software wurde ein ganzer Wafer mit einem Sensor im Originalmaßstab, mehreren Testsensoren zur Layoutoptimierung und Teststrukturen bestückt. Die englische Firma Micron Semiconductor Ltd. produzierte in enger Zusammenarbeit mit dem Autor mehrere Lose an Prototyp-Sensoren. Der Wafer enthält kleine Testsensoren, die speziell für die Optimierung der n-seitigen Streifenisolierung entwickelt wurden. Diese Sensoren erlauben die Untersuchung der p-stop-Isolierungsmethode (in den drei Ausformungen atoll, common, und einer kombinierten Variante) und der p-spray-Isolierungsmethode. Eingehende Untersuchungen dieser Sensoren in Teilchenstrahlen und bei Gamma-Bestrahlungen zeigten, dass die atoll p-stop Methode am besten geeignet ist für die Anwendung in Belle II. Die trapezoiden Sensoren wurden vom Autor eingehend getestet, sowohl im Halbleiterlabor als auch in Teilchenstrahlen, die Alterungsbeständigkeit der Sensoren wurde durch Bestrahlungen und Wärmelastspiel nachgewiesen. Die Erkenntnisse aus den Messungen der Testsensoren und der großen Sensoren wurden in eine Verbesserung des Sensordesigns gegossen, das nach Produktion eines weiteren Prototypen-Loses wieder eingehend evaluiert wurde. Es konnte gezeigt werden dass der Sensor die Ansprüche des Belle II SVD erfüllt, und das Sensordesign wurde für die Produktion freigegeben. Im Zuge der Sensortests reiste der Autor viermal zu Teilchenstrahl-Experimenten an den CERN, und war für die komplette Analyse der genommenen Daten zuständig.The Belle experiment at KEK (Tsukuba, Japan) was successfully operated from 1999 until 2010 and confirmed the theoretical predictions of CP violation. In order to increase the beam intensity, a major upgrade of the KEKB collider is foreseen until 2015. The final goal is to reach a luminosity of 8 x 10 35 cm -2 s -1, which is about 40 times higher than the previous peak value. This also implies changes to the Belle detector and its innermost tracking subdetector, the SVD (Silicon Vertex Detector), in particular. The SVD will be completely replaced, as it had already operated close to its limits in the past. All other subsystems will also be upgraded. This leads to the new Belle II experiment. The aim of Belle II is to search for deviations from the Standard Model of particle physics by providing extremely precise measurements of rare particle decays, thus representing a complementary approach to the direct searches performed at high energy hadron colliders. The upgraded SuperKEKB machine will collide electrons and positrons at the center-of-mass energy of excited states of the Y-particle, which hereafter decays to a B meson and its anti-particle. The decay vertices of these mesons have to be precisely measured by the Belle II SVD, together with the PXD (PiXel Detector) and the CDC (Central Drift Chamber). This allows the measurement of time-dependent, mixing-induced CP asymmetry. In addition, the SVD measures vertex information in other decay channels involving D meson and tau lepton decays. Since the collision energy is quite low (around 10 GeV), the emerging particles have low momentum and are subject to strong multiple scattering when traversing material. Therefore, all sensors of the Belle II SVD have to be optimised in terms of material thickness, while preserving high signal yield and position measurement accuracy. This will be possible by the development of thin, double-sided silicon microstrip sensors. This PhD thesis includes the physics motivation for building a high luminosity B factory and a high precision particle detector, and an introduction to the Belle II experiment, outlining purpose and working principle of the involved subdetectors. More details are given on the Belle II SVD, including mechanical structure, sensors, electrical readout and cooling. Furthermore, the basics of semiconductor physics and silicon processing are reviewed, and the principles of single-sided and double-sided silicon microstrip sensors are explained in detail. The author's main task was to develop a trapezoidal double-sided silicon microstrip sensor for the forward region of the Belle II SVD, from the initial CAD drawings to the production. He developed a software framework aiming at fast and flexible design of double-sided silicon microstrip sensors, both for rectangular and trapezoidal shapes. Using this framework, a whole wafer was equipped with a full-scale trapezoidal sensor, several test sensors for optimising the layout, and test structures. Several batches of prototype sensors were produced by Micron Semiconductor Ltd. in England, in close collaboration with the author. The wafer contains small test sensors dedicated to investigating the strip insulation on the n-side, featuring the p-stop blocking method (in three geometry patterns: atoll, common and a combined variant) and of the p-spray blocking method. These sensors have been extensively tested by the author in particle beams and gamma irradiations, showing that the atoll p-stop pattern is best suited for application at Belle II. The full-scale prototype sensors were thoroughly tested by the author in the semiconductor laboratory and in particle beams, long-term stability has been demonstrated by irradiation and thermal cycling campaigns. The knowledge gained by examining the test sensors and full-scale sensors led to an update of the design of the full-scale sensor. After production of another prototype batch the updated design was evaluated, compliance with the requirements of the Belle II SVD were shown, and the sensor layout was released for production. In the course of the sensor tests the author went to four beam tests at CERN, and performed the analysis of the data taken
- …
