Anwendungen des Komplexe-Masse-Renormierungsschemas in effektiver Feldtheorie

Der erste Teil der vorliegenden Dissertation befasst sich mit der Untersuchung der perturbativen Unitarität im Komplexe-Masse-Renormierungsschema (CMS). Zu diesem Zweck wird eine Methode zur Berechnung der Imaginärteile von Einschleifenintegralen mit komplexen Massenparametern vorgestellt, die im Grenzfall stabiler Teilchen auf die herkömmlichen Cutkosky-Formeln führt. Anhand einer Modell-Lagrangedichte für die Wechselwirkung eines schweren Vektorbosons mit einem leichten Fermion wird demonstriert, dass durch Anwendung des CMS die Unitarität der zugrunde liegenden S-Matrix im störungstheoretischen Sinne erfüllt bleibt, sofern die renormierte Kopplungskonstante reell gewählt wird. Der zweite Teil der Arbeit beschäftigt sich mit verschiedenen Anwendungen des CMS in chiraler effektiver Feldtheorie (EFT). Im Einzelnen werden Masse und Breite der Deltaresonanz, die elastischen elektromagnetischen Formfaktoren der Roperresonanz, die elektromagnetischen Formfaktoren des Übergangs vom Nukleon zur Roperresonanz sowie Pion-Nukleon-Streuung und Photo- und Elektropionproduktion für Schwerpunktsenergien im Bereich der Roperresonanz berechnet. Die Wahl passender Renormierungsbedingungen ermöglicht das Aufstellen eines konsistenten chiralen Zählschemas für EFT in Anwesenheit verschiedener resonanter Freiheitsgrade, so dass die aufgeführten Prozesse in Form einer systematischen Entwicklung nach kleinen Parametern untersucht werden können. Die hier erzielten Resultate können für Extrapolationen von entsprechenden Gitter-QCD-Simulationen zum physikalischen Wert der Pionmasse genutzt werden. Deshalb wird neben der Abhängigkeit der Formfaktoren vom quadrierten Impulsübertrag auch die Pionmassenabhängigkeit des magnetischen Moments und der elektromagnetischen Radien der Roperresonanz untersucht. Im Rahmen der Pion-Nukleon-Streuung und der Photo- und Elektropionproduktion werden eine Partialwellenanalyse und eine Multipolzerlegung durchgeführt, wobei die P11-Partialwelle sowie die Multipole M1- und S1- mittels nichtlinearer Regression an empirische Daten angepasst werden.In the first part of the this doctoral thesis the perturbative unitarity in the complex-mass scheme (CMS) is analysed. To that end a procedure for calculating cutting rules for loop integrals containing propagators with finite widths is presented. A toy-model Lagrangian describing the interaction of a heavy vector boson with a light fermion is used to demonstrate that the CMS respects unitarity order by order in perturbation theory provided that the renormalized coupling constant remains real. The second part of the thesis deals with various applications of the CMS to chiral effective field theory (EFT). In particular, mass and width of the delta resonance, elastic electromagnetic form factors of the Roper resonance, form factors of the nucleon-to-Roper transition, pion-nucleon scattering, and pion photo- and electroproduction for center-of-mass energies in the region of the Roper mass are calculated. By choosing appropriate renormalization conditions, a consistent chiral power counting scheme for EFT with resonant degrees of freedom can be established. This allows for a systematic investigation of the above processes in terms of an expansion in small quantities. The obtained results can be applied to the extrapolation of corresponding simulations in the context of lattice QCD to the physical value of the pion mass. Therefore, in addition to the Q^2 dependence of the form factors, also the pion-mass dependence of the magnetic moment and electromagnetic radii of the Roper resonance is explored. Both a partial wave decomposition and a multipole expansion are performed for pion-nucleon scattering and pion photo- and electroproduction, respectively. In this connection the P11 partial wave as well as the M1- and S1- multipoles are fitted via non-linear regression to empirical data.188 S

Narrow band imaging (NBI) during medical thoracoscopy: first impressions

<p>Abstract</p> <p>Background</p> <p>This is the first ever evaluation of narrow band imaging (NBI), an innovative endoscopic imaging procedure, for the visualisation of pleural processes.</p> <p>Methods</p> <p>The pleural cavity was examined in 26 patients with pleural effusions using both white light and narrow band imaging during thoracoscopy under local anaesthesia.</p> <p>Results</p> <p>In the great majority of the patients narrow band imaging depicted the blood vessels more clearly than white light, but failed to reveal any differences in number, shape or size. Only in a single case with pleura thickened by chronic inflammation and metastatic spread of lung cancer did narrow band imaging show vessels that were not detectable under white light.</p> <p>Conclusion</p> <p>It is not yet possible to assess to what extent the evidence provided by NBI is superior to that achieved with white light. Further studies are required, particularly in the early stages of pleural processes.</p

Gemcitabine combined with oxaliplatin in pretreated patients with malignant pleural mesothelioma: an observational study

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to investigate the efficacy and safety of oxaliplatin ± gemcitabine in patients with diffuse malignant pleural mesothelioma (MPM) pretreated with pemetrexed.</p> <p>Methods</p> <p>The study enrolled consecutive patients with relapsed MPM, all of them pretreated with a platin-pemetrexed-based chemotherapy. Oxaliplatin 80 mg/m²was administered as monotherapy or in combination with gemcitabine 1000 mg/m²given on day 1 and 8. Cycles were repeated every 21 days. The primary endpoints were response rate and disease control rate. Secondary endpoints included overall survival (OS), time to tumour progression (TTP), progression-free survival (PFS), time to treatment failure (TTF), and toxicity.</p> <p>Results</p> <p>Between February 2005 and September 2007 29 patients (median age: 65.0 years, World Health Organisation (WHO) performance status: 0–3) were enrolled. The follow-up period encompassed 5.4 to 97.4 weeks (median: 24.3 weeks). Out of these 29 patients, 15 were treated in second, 10 in third, 3 in fourth and 1 in fifth line, respectively. The majority of the patients received the combination oxaliplatin and gemcitabine (n = 25 vs. 4; 86.2 vs. 13.8%).</p> <p>The median overall survival (OS) was 71.7 weeks (30.6–243.3 weeks), whereas survival from the start of oxaliplatin/gemcitabine-treatment was 24.3 weeks (5.4–97.3 weeks). Median time to tumour progression (TTP) was 9.3 weeks (3.0–67.6 weeks).</p> <p>Partial response (PR) was observed in 2 patients (6.9%), stable disease (SD) for at least three courses of treatment in 11 patients (37.9%). Thus, disease control rate was 44.8%, whereas 16 of 29 patients exhibited progressive disease (55.2%).</p> <p>The toxicity profile was favourable, with no WHO grade 4-toxicities, only few dose-reductions were performed due to non-symptomatic haematotoxicities (neutropenia, thrombopenia). Mild WHO grade 2 neurotoxicity was seen in 6 patients.</p> <p>Conclusion</p> <p>Pemetrexed-pretreated patients with progressive MPM may benefit from a consecutive chemotherapy with oxaliplatin and gemcitabine without significant toxicity.</p

Suppressing quasiparticle poisoning with a voltage-controlled filter

We study single-electron charging events in an Al/InAs nanowire hybrid system with deliberately introduced gapless regions. The occupancy of a Coulomb island is detected using a nearby radio-frequency quantum dot as a charge sensor. We demonstrate that a 1 micron gapped segment of the wire can be used to efficiently suppress single electron poisoning of the gapless region and therefore protect the parity of the island while maintaining good electrical contact with a normal lead. In the absence of protection by charging energy, the 1e switching rate can be reduced below 200 per second. In the same configuration, we observe strong quantum charge fluctuations due to exchange of electron pairs between the island and the lead. The magnetic field dependence of the poisoning rate yields a zero-field superconducting coherence length of ~ 90 nm

Dynamics of Majorana-based qubits operated with an array of tunable gates

We study the dynamics of Majorana zero modes that are shuttled via local tuning of the electrochemical potential in a superconducting wire. By performing time-dependent simulations of microscopic lattice models, we show that diabatic corrections associated with the moving Majorana modes are quantitatively captured by a simple Landau-Zener description. We further simulate a Rabi-oscillation protocol in a specific qubit design with four Majorana zero modes in a single wire and quantify constraints on the timescales for performing qubit operations in this setup. Our simulations utilize a Majorana representation of the system, which greatly simplifies simulations of superconductors at the mean-field level.Comment: 12 pages, 8 figures. v2: minor corrections, updated reference

Screening of COPD patients for abdominal aortic aneurysm

Purpose: Screening for abdominal aortic aneurysm (AAA) in “men aged over 65 years who have ever smoked” is a recommended policy. To reduce the number of screenings, it may be of value to define subgroups with a higher prevalence of AAA. Since chronic obstructive pulmonary disease (COPD) and AAA are associated with several common risk factors, this study investigates the prevalence of AAA in COPD patients. Patients and methods: Patients with COPD were identified via the hospital information system. Inclusion criteria were: COPD stage I–IV, ability to give full consent, and age >18 years; exclusion criteria were: patient too obese for an ultrasound check, previously diagnosed AAA, prior surgery for AAA, or ethical grounds such as concomitant advanced malignant or end-stage disease. The primary endpoint of the study was an aortic diameter measured by ultrasound of ≥30 mm. Defined secondary endpoints were evaluated on the basis of medical records and interviews. Results: Of the 1,180 identified COPD patients, 589 were included in this prospective study. In 22 patients (3.70%), the aortic diameter was ≥30 mm, representing an AAA prevalence of 6.72% among males aged >65 years. The risk of AAA increased with the following comorbidities/risk factors: male sex (odds ratio [OR] 2.98), coronary heart disease (OR 2.81), peripheral arterial occlusive disease (OR 2.47), hyperlipoproteinemia (OR 2.77), AAA in the family history (OR 3.95), and COPD stage I/II versus IV (OR 1.81). Conclusion: The overall AAA prevalence of 3.7% in our group of COPD patients is similar to that of the general population aged >65 years. However, the frequency of AAA in male COPD patients aged >65 years is considerably higher (6.72%) and increased further still in those individuals with additional comorbidities/risk factors. Defining subgroups with a higher risk of AAA may increase the efficiency of screening