Laserspektroskopie der Grundzustands-Hyperfeinstruktur des lithiumähnlichen 209 Bi 80+

Die theoretische und experimentelle Untersuchung von wasserstoffähnlichen Systemen hat in den letzten hundert Jahren immer wieder sowohl die experimentelle als auch die theoretische Physik entscheidend vorangebracht. Formulierung und Test der Quantenelektrodynamik (QED) standen und stehen in engen Zusammenhang mit der Untersuchung wasserstoffähnlicher Systeme. Gegenwärtig sind besonders wasserstoffähnliche Systeme schwerer Ionen von Interesse, um die QED in den extrem starken Feldern in Kernnähe zu testen. Laserspektroskopische Messungen der Hyperfeinstrukturaufspaltung des Grundzustandes bieten eine hohe Genauigkeit, ihre Interpretation wird jedoch durch die Unsicherheit in der Größe der Kernstruktureffekte erschwert. Beseitigt werden können diese durch die Kombination der Aufspaltung in wasserstoff- und lithiumähnlichen Ionen des gleichen Nuklids. In den letzten zwei Jahrzehnten scheiterten mehrere dadurch motivierte Versuche, den HFS-Übergang in lithiumähnlichen 209Bi80+ zu finden. Im Rahmen dieser Arbeit wurde kollineare Laserspektroskopie bei etwa 70% der Lichtgeschwindigkeit an 209Bi82+ und 209Bi80+ -Ionen im Experimentier- Speicherring an der GSI in Darmstadt durchgeführt. Dabei wurde der Übergang im lithiumähnlichen Bismut erstmals beobachtet und dessen Übergangswellenlänge zu 1554,74(74) nm bestimmt. Ein eigens für dieses Experiment optimiertes Fluoreszenz-Nachweissystem stellte dabei die entscheidende Verbesserung gegenüber den gescheiterten Vorgängerexperimenten dar. Der Wellenlängenfehler ist dominiert von der Unsicherheit der Ionengeschwindigkeit, die für die Transformation in das Ruhesystem der Ionen entscheidend ist. Für deren Bestimmung wurden drei Ansätze verfolgt: Die Geschwindigkeit wurde aus der Elektronenkühlerspannung bestimmt, aus dem Produkt von Orbitlänge und Umlauffrequenz und aus dem relativistischen Dopplereffekt unter Annahme der Korrektheit des früher bestimmten Überganges in wasserstoffähnlichen Bismut. Die Spannungskalibration des Elektronenkühlers wurde im Rahmen dieser Arbeit erstmals kritisch evaluiert und bislang unterschätzte systematische Unsicherheiten aufgezeigt, die derzeit einen aussagekräftigen QED-Test verhindern. Umgekehrt konnte unter Verwendung der QED-Berechnungen eine Ionengeschwindigkeit berechnet werden, die ein genaueres und konsistenteres Resultat für die Übergangswellenlängen beider Ionenspezies liefert. Daraus ergibt sich eine Diskrepanz zu dem früher bestimmten Wert des Überganges in wasserstoffähnlichen Bismut, die es weiter zu untersuchen gilt.

Abituàti a morire: Uno sguardo sulla scena punk-rock siberiana degli anni '80

Il presente elaborato ha lo scopo di fornire una panoramica sul movimento punk siberiano, nato e sviluppatosi a cavallo fra il 1984 e il 1991. L'analisi della poetica di alcuni fra i musicisti principali del cosiddetto "sibpunk" e la traduzione delle loro canzoni più significative costituiscono una prospettiva inusuale e interessante per osservare la Siberia negli anni della Perestrojka.

Peri-ictal correlation dynamics of high-frequency (80-200 Hz) intracranial EEG

To assess (1) how large-scale correlation of intracranial EEG signals in the high-frequency range (80-200Hz) evolves from the pre-ictal, through the ictal into the postictal state and (2) whether the contribution of local neuronal activity to large-scale EEG correlation differentiates epileptogenic from non-epileptogenic brain tissue.

High-dose (80 Gy) intensity-modulated radiation therapy with daily image-guidance as primary treatment for localized prostate cancer

to report acute and late toxicity in prostate cancer patients treated by high-dose intensity-modulated radiation therapy (IMRT) with daily image-guidance.

Diagnostic accuracy of pulmonary CT angiography at low tube voltage: intraindividual comparison of a normal-dose protocol at 120 kVp and a low-dose protocol at 80 kVp using reduced amount of contrast medium in a simulation study

The purpose of this study was to simulate pulmonary emboli (PE) and image quality at low tube energy and reduced contrast material volume in normal-dose pulmonary CT angiography (CTA) images and to analyze the diagnostic accuracy with normal- and low-dose pulmonary CTA.

Genome-Wide Survey of Pseudogenes in 80 Fully Re-sequenced Arabidopsis thaliana Accessions

Pseudogenes (Ψs), including processed and non-processed Ψs, are ubiquitous genetic elements derived from originally functional genes in all studied genomes within the three kingdoms of life. However, systematic surveys of non-processed Ψs utilizing genomic information from multiple samples within a species are still rare. Here a systematic comparative analysis was conducted of Ψs within 80 fully re-sequenced Arabidopsis thaliana accessions, and 7546 genes, representing ~28% of the genomic annotated open reading frames (ORFs), were found with disruptive mutations in at least one accession. The distribution of these Ψs on chromosomes showed a significantly negative correlation between Ψs/ORFs and their local gene densities, suggesting a higher proportion of Ψs in gene desert regions, e.g. near centromeres. On the other hand, compared with the non-Ψ loci, even the intact coding sequences (CDSs) in the Ψ loci were found to have shorter CDS length, fewer exon number and lower GC content. In addition, a significant functional bias against the null hypothesis was detected in the Ψs mainly involved in responses to environmental stimuli and biotic stress as reported, suggesting that they are likely important for adaptive evolution to rapidly changing environments by pseudogenization to accumulate successive mutations.

Patient exposure and image quality of low-dose pulmonary computed tomography angiography: comparison of 100- and 80-kVp protocols

OBJECTIVE: Measures to reduce radiation exposure and injected iodine mass are becoming more important with the widespread and often repetitive use of pulmonary CT angiography (CTA) in patients with suspected pulmonary embolism. In this retrospective study, we analyzed the capability of 2 low-kilovoltage CTA-protocols to achieve these goals. MATERIALS AND METHODS: Ninety patients weighing less than 100 kg were examined by a pulmonary CTA protocol using either 100 kVp (group A) or 80 kVp (group B). Volume and flow rate of contrast medium were reduced in group B (75 mL at 3 mL/s) compared with group A (100 mL at 4 mL/s). Attenuation was measured in the central and peripheral pulmonary arteries, and the contrast-to-noise ratios (CNR) were calculated. Entrance skin dose was estimated by measuring the surface dose in an ovoid-cylindrical polymethyl methacrylate chest phantom with 2 various dimensions corresponding to the range of chest diameters in our patients. Quantitative image parameters, estimated effective dose, and skin dose in both groups were compared by the t test. Arterial enhancement, noise, and overall quality were independently assessed by 3 radiologists, and results were compared between the groups using nonparametric tests. RESULTS: Mean attenuation in the pulmonary arteries in group B (427.6 +/- 116 HU) was significantly higher than in group A (342.1 +/- 87.7 HU; P < 0.001), whereas CNR showed no difference (group A, 20.6 +/- 7.3 and group B, 22.2 +/- 7.1; P = 0.302). Effective dose was lower by more than 40% with 80 kVp (1.68 +/- 0.23 mSv) compared with 100 kVp (2.87 +/- 0.88 mSv) (P < 0.001). Surface dose was significantly lower at 80 kVp compared with 100 kVp at both phantom dimensions (2.75 vs. 3.22 mGy; P = 0.027 and 2.22 vs. 2.73 mGy; P = 0.005, respectively). Image quality did not differ significantly between the groups (P = 0.151). CONCLUSIONS: Using 80 kVp in pulmonary CTA permits reduced patient exposure by 40% and CM volume by 25% compared with 100 kVp without deterioration of image quality in patients weighing less than 100 kg.

Detection of pulmonary emboli with CT angiography at reduced radiation exposure and contrast material volume: comparison of 80 kVp and 120 kVp protocols in a matched cohort

The detection rate of pulmonary emboli (PE) with computed tomography angiography (CTA) using either a standard or a low-dose protocol, combining reduced radiation exposure and iodine delivery rate, was retrospectively analyzed in a matched cohort of 120 patients.