Precision Measurement of Vibrational Quanta in Tritium Hydride (HT)

Saturated absorption measurements of transitions in the (2-0) band of radioactive tritium hydride (HT) are performed with the ultra-sensitive NICE-OHMS intracavity absorption technique in the range 1460-1510 nm. The hyperfine structure of rovibrational transitions of HT, in contrast to that of HD, exhibits a single isolated hyperfine component, allowing for the accurate determination of hyperfineless rovibrational transition frequencies, resulting in R(0) = $203\,396\,426\,692$ (22) kHz and R(1) = $205\,380 \,033 \,644$ (21) kHz. This corresponds to an accuracy three orders of magnitude better than previous measurements in tritiated hydrogen molecules. Observation of an isolated component in P(1) with reversed signal amplitude contradicts models for line shapes in HD based on cross-over resonances.Comment: 6 pages, 4 figures, Accepte

Open thoracic or thoracoabdominal aortic aneurysm repair after previous abdominal aortic aneurysm surgery

ObjectiveThe purpose of this study was to provide insight into the incidence of thoracic and thoracoabdominal aortic aneurysm repair following previous infrarenal abdominal aortic aneurysm (AAA) surgery and to determine whether thoracic or thoracoabdominal aortic aneurysm repair after prior infrarenal AAA surgery is associated with higher mortality and morbidity rates.MethodsMEDLINE, Cochrane Library CENTRAL, and EMBASE databases were searched for relevant articles. Selected articles were critically appraised and meta-analyses were performed.ResultsA total of 12.4% of patients with thoracic aortic aneurysms and 18.7% of patients with thoracoabdominal aortic aneurysms have had prior AAA surgery. The chance of developing a thoracic aortic aneurysm in patients with AAA is 2.2% and 2.5% for developing a thoracoabdominal aortic aneurysm. The mean time interval between prior AAA surgery and subsequent thoracoabdominal aortic aneurysm surgery or detection is 8.0 years with a wide variation between individuals. Surgery in these patients is technically feasible. The 30-day mortality of patients undergoing open thoracoabdominal aortic aneurysm repair does not significantly differ from patients without prior AAA surgery and the 30-day mortality is 11.8%. No data were available about mortality of patients with prior AAA repair undergoing thoracic aortic aneurysm surgery. Morbidity risks are higher in patients with thoracic or thoracoabdominal aortic aneurysms. Prior AAA repair was a significant risk factor for neurological deficit after thoracic or thoracoabdominal aortic aneurysms surgery with relative risks (RRs) of 11.1 (95% confidence interval [CI] 3.8-32.3, P value < .0001) and 2.90 (95% CI 1.26-6.65, P value = .008), respectively. Prior AAA repair was a significant risk factor for developing renal failure in patients undergoing thoracoabdominal aortic aneurysm repair (RR 3.47, 95% CI 1.74-6.91, P value = .0001). Determinants of the prognosis in these patients include distal aortic perfusion, distal extent of the landing zone of the graft, drainage of cerebrospinal fluid for thoracic aortic aneurysm repair and age, history of cardiac diseases, extent of the aneurysm, rupture, amount of estimated blood loss, aortic clamp time, and visceral ischemic times for thoracoabdominal aortic aneurysm repair.ConclusionsA considerable group of patients with thoracic or thoracoabdominal aortic aneurysms have had prior AAA repair. The risk of postoperative morbidity is increased in these patients. Mortality appears to be similar for patients with thoracoabdominal aortic aneurysms. Patients with prior AAA repair undergoing thoracic or thoracoabdominal aortic aneurysm repair should be provided maximum care to protect their spinal cord and renal function

Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopy

The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, which is currently under construction. A custom-made interface is used to connect the tritium containing measurement cell, located inside a glove box, with the Raman setup standing on the outside. A tritium sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more than three weeks with a total throughput of 770 g of tritium. Compositional changes in the sample and the formation of tritiated and deuterated methanes CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen isotope exchange reactions and gas-wall interactions, due to tritium {\beta} decay. A precision of 0.1% was achieved for the monitoring of the T_2 Q_1-branch, which fulfills the requirements for the KATRIN experiment and demonstrates the feasibility of high-precision Raman measurements with tritium inside a glove box

Hysteresis effect due to the exchange Coulomb interaction in short-period superlattices in tilted magnetic fields

We calculate the ground-state of a two-dimensional electron gas in a short-period lateral potential in magnetic field, with the Coulomb electron-electron interaction included in the Hartree-Fock approximation. For a sufficiently short period the dominant Coulomb effects are determined by the exchange interaction. We find numerical solutions of the self-consistent equations that have hysteresis properties when the magnetic field is tilted and increased, such that the perpendicular component is always constant. This behavior is a result of the interplay of the exchange interaction with the energy dispersion and the spin splitting. We suggest that hysteresis effects of this type could be observable in magneto-transport and magnetization experiments on quantum-wire and quantum-dot superlattices.Comment: 3 pages, 3 figures, Revtex, to appear in Phys. Rev.

Accurate reference gas mixtures containing tritiated molecules: Their production and raman‐based analysis

Highly accurate, quantitative analyses of mixtures of hydrogen isotopologues—both the stable species, H$_{2}$, D$_{2}$2, and HD, and the radioactive species, T$_{2}$, HT, and DT—are of great importance in fields as diverse as deuterium–tritium fusion, neutrino mass measurements using tritium β-decay, or for photonuclear experiments in which hydrogen–deuterium targets are used. In this publication we describe a production, handling, and analysis facility capable of fabricating well-defined gas samples, which may contain any of the stable and radioactive hydrogen isotopologues, with sub-percent accuracy for the relative species concentrations. The production is based on precise manometric gas mixing of H$_{2}$, D$_{2}$, and T$_{2}$. The heteronuclear isotopologues HD, HT, and DT are generated via controlled, in-line catalytic reaction or by β-induced self-equilibration, respectively. The analysis was carried out using an in-line intensity- and wavelength-calibrated Raman spectroscopy system. This allows for continuous monitoring of the composition of the circulating gas during the self-equilibration or catalytic evolution phases. During all procedures, effects, such as exchange reactions with wall materials, were considered with care. Together with measurement statistics, these and other systematic effects were included in the determination of composition uncertainties of the generated reference gas samples. Measurement and calibration accuracy at the level of 1% was achieved

Light scattering from a periodically modulated two dimensional electron gas with partially filled Landau levels

We study light scattering from a periodically modulated two dimensional electron gas in a perpendicular magnetic field. If a subband is partially filled, the imaginary part of the dielectric function as a function of frequency contains additional discontinuities to the case of completely filled subbands. The positions of the discontinuities may be determined from the partial filling factor and the height of the discontinuity can be directly related to the modulation potential. The light scattering cross section contains a new peak which is absent for integer filling.Comment: RevTex, 4 figures. To appear in Phys. Rev. B as a brief repor

The Dutch version of the Spinal Appearance Questionnaire for adolescents with idiopathic scoliosis:patient-based cross-cultural adaptation and measurement properties evaluation

Purpose: Adolescent idiopathic scoliosis (AIS) affects the appearance of spine and trunk. The Spinal Appearance Questionnaire (SAQ) assesses the perception of appearance in AIS patients. The aim of this study is to translate and culturally adapt the recommended short version of the SAQ into Dutch and to test its measurement properties. Methods: A Dutch SAQ (14-item; appearance and expectations domains) was developed following guidelines for translation and cross-cultural adaptation. The COSMIN Study Design checklist was used for measurement properties evaluation. In this multicenter study, the Dutch SAQ, SRS-22R and NPRS (back pain) were administered to 113 AIS patients (aged 15.4 years [SD 2.2], 21.2% male). Floor and ceiling effects were evaluated for content analysis. For reliability, internal consistency (Cronbach’s alpha) and test–retest reliability (ICC; n = 34) were evaluated. Predefined hypotheses of relationships with other questionnaires and between subgroups based on scoliosis severity (radiological and clinical) were tested for construct validity. Exploratory factor analysis (EFA) was performed to investigate the validity of the underlying structure of this 14-item questionnaire. Results: No floor and ceiling effects were found for domains and total scores. Cronbach’s alpha ranged from 0.84 to 0.89. ICCs varied from 0.76 to 0.77. For construct validity, 89% (8/9) of the predefined hypotheses were confirmed. Significant higher scores for the appearance domain were found for subgroups based on radiological (Cobb angle; &gt; 25.0°) and clinical outcomes. (Angle of Trunk Rotation; &gt; 9.0°). A two-factor structure was found (EV 5.13; 36.63% explained variance). Conclusion: The Dutch SAQ is an adequate, valid and reliable instrument to evaluate patients’ perception of appearance in AIS. Level of evidence: Level I—diagnostic studies.</p

The Quantum Hall Effect of Interacting Electrons in a Periodic Potential

We consider the influence of an external periodic potential on the fractional quantum Hall effect of two-dimensional interacting electron systems. For many electrons on a torus, we find that the splitting of incompressible ground state degeneracies by a weak external potential diminishes as $\exp ( - L/ \xi)$ at large system size $L$. We present numerical results consistent with a scenario in which $\xi$ diverges at continuous phase transitions from fractional to integer quantum Hall states which occur with increasing external potential strength.Comment: 4 pages, REVTeX, 3 epsf-embedded color postscript figures, submitted to PRB (Rapid Comm.), added reference in revised versio

Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields

The magnetoresistivity tensor of an interacting two-dimensional electron system with a lateral and unidirectional electric or magnetic modulation, in a perpendicular quantizing magnetic field, is calculated within the Kubo formalism. The influence of the spin splitting of the Landau bands and of the density of states (DOS) on the internal structure of the Shubnikov-de Haas oscillations is analyzed. The Coulomb electron - electron interaction is responsible for strong screening and exchange effects and is taken into account in a screened Hartree-Fock approximation, in which the exchange contribution is calculated self-consistently with the DOS at the Fermi level. This approximation describes both the exchange enhancement of the spin splitting and the formation of compressible edge strips, unlike the simpler Hartree and Hartree-Fock approximations, which yield either the one or the other.Comment: 20 pages, revtex, 7 ps figures, to appear in Phys. Rev.