Torsion nonminimally coupled to the electromagnetic field and birefringence

In conventional Maxwell--Lorentz electrodynamics, the propagation of light is influenced by the metric, not, however, by the possible presence of a torsion T. Still the light can feel torsion if the latter is coupled nonminimally to the electromagnetic field F by means of a supplementary Lagrangian of the type l^2 T^2 F^2 (l = coupling constant). Recently Preuss suggested a specific nonminimal term of this nature. We evaluate the spacetime relation of Preuss in the background of a general O(3)-symmetric torsion field and prove by specifying the optical metric of spacetime that this can yield birefringence in vacuum. Moreover, we show that the nonminimally coupled homogeneous and isotropic torsion field in a Friedmann cosmos affects the speed of light.Comment: Revtex, 12 pages, no figure

Development and test of a 35 kA - HTS CroCo cable demonstrator

The answer to energy-efficient electric power transfer of high currents in the range of several tens of kA can be given by high temperature superconducting (HTS) cables. BSCCO and MgB2 have been used widely for such cables, reaching maximum currents of about 20 kA. REBCO coated conductors are promising for future HTS cables beyond 20 kA and allow the operation based on subcooled liquid nitrogen. Several cabling concepts based on REBCO tapes were developed world-wide to realize such cables. Using the stacked-Tape concept, a scalable semi-industrial process was developed by KIT, called HTS CrossConductor (HTS CroCo). Key aspects of the conceptual design of high-current HTS cables are discussed and the design of a 35 kA DC cable demonstrator made from HTS CroCo strands is presented. Aspects regarding joints, current redistribution between individual strands and electrical stabilization are highlighted. The performance of this demonstrator cable was tested, reaching the envisaged current

Study of the photon flux from the night sky at La Palma and Namibia, in the wavelength region relevant for imaging atmospheric Cherenkov telescopes

The level of the night sky background light at La Palma and Namibia was determined, with emphasis on the wavelength region and solid angle coverage relevant for the operation of imaging atmospheric Cherenkov telescopes. The dependence of the night sky background light both on celestial coordinates (alt, az) and on galactic coordinates (b, l) was measured, with an angular resolution of about 1 degr. Average light levels near the zenith are similar in both locations -- 2.2 x 10^12 to 2.6 x 10^12 photons per sr s m^2 for 300 nm < lambda < 650 nm. With increasing zenith angle the level of background light increases at La Palma, whereas a constant level is measured in Namibia. Near the center of the Milky Way, background light levels are increased by a factor up to 4 and more. Also the level of light backscattered from the ground has been studied.Comment: 21 Pages, 12 figures, Latex, Nucl. Instr. Meth., in pres

Linguistic evaluation of support verb constructions by OpenLogos and google translate

This paper presents a systematic human evaluation of translations of English support verb constructions produced by a rule-based machine translation (RBMT) system (OpenLogos) and a statistical machine translation (SMT) system (Google Translate) for five languages: French, German, Italian, Portuguese and Spanish. We classify support verb constructions by means of their syntactic structure and semantic behavior and present a qualitative analysis of their translation errors. The study aims to verify how machine translation (MT) systems translate fine-grained linguistic phenomena, and how well-equipped they are to produce high-quality translation. Another goal of the linguistically motivated quality analysis of SVC raw output is to reinforce the need for better system hybridization, which leverages the strengths of RBMT to the benefit of SMT, especially in improving the translation of multiword units. Taking multiword units into account, we propose an effective method to achieve MT hybridization based on the integration of semantico-syntactic knowledge into SMT.info:eu-repo/semantics/acceptedVersio

HTS CroCo - A Strand for High Direct Current Applications

High temperature superconductors (HTS) are discussed as energy-efficient solutions for applications needing high direct currents beyond 10 kA e.g. for large high-field magnets or bus bar systems in industrial electrolysis plants. A number of high-current cable concepts based on REBCO tapes were developed such as the Roebel cable, co-axially wound tapes and several stacked-tape arrangements, among them the HTS CrossConductor (HTS CroCo), a stacked-tape conductor with high current density developed at KIT. In this manuscript, the experimental test of a high DC demonstrator, termed Supra-DC-Cable, made from twelve HTS CroCo strands is presented. The demonstrator was tested successfully at T = 77 K, reaching the expected critical current of 33 kA at 77 K and even for a constant-current operation at 36 kA for more than 30 minutes limited by the copper connections, not the superconducting cable. Currents and voltages were measured in all twelve strands individually during the parallel operation in the cable. These measured data allow the experimental validation of the modelled current distribution, based on the individual characterization of the twelve strands

Head of State of Exception

During the escalation of the “German Autumn” in 1977 the Federal German government resorted to a specific form of crisis management that had been described as an undeclared state of exception. It was Federal chancellor Helmut Schmidt in the first place who oversaw the anti-terrorist measures in the situation room where the executive branch ruled for six weeks beyond any parliamentary control. This article examines the role that Helmut Schmidt had played for the creation of a “subjective state of exception” (Julius Hatschek) and how this could be seen as stemming from Schmidt’s earlier experiences and handling of crisis situations dating back to the 1960s. In this regard it has to be asked with Giorgio Agamben, if in the West German case, the state of exception had become the rule

Cranial and ventricular size following shunting or endoscopic third ventriculostomy (ETV) in infants with aqueductal stenosis: further insights from the International Infant Hydrocephalus Study (IIHS)

Purpose: The craniometrics of head circumference (HC) and ventricular size are part of the clinical assessment of infants with hydrocephalus and are often utilized in conjunction with other clinical and radiological parameters to determine the success of treatment. We aimed to assess the effect of endoscopic third ventriculostomy (ETV) and shunting on craniometric measurements during the follow-up of a cohort of infants with symptomatic triventricular hydrocephalus secondary to aqueductal stenosis. Methods: We performed a post hoc analysis of data from the International Infant Hydrocephalus Study (IIHS)—a prospective, multicenter study of infants (\u3c 24 months old) with hydrocephalus from aqueductal stenosis who were treated with either an ETV or shunt. During various stages of a 5-year follow-up period, the following craniometrics were measured: HC, HC centile, HC z-score, and frontal-occipital horn ratio (FOR). Data were compared in an analysis of covariance, adjusting for baseline variables including age at surgery and sex. Results: Of 158 enrolled patients, 115 underwent an ETV, while 43 received a shunt. Both procedures led to improvements in the mean HC centile position and z-score, a trend which continued until the 5-year assessment point. A similar trend was noted for FOR which was measured at 12 months and 3 years following initial treatment. Although the values were consistently higher for ETV compared with shunt, the differences in HC value, centile, and z-score were not significant. ETV was associated with a significantly higher FOR compared with shunting at 12 months (0.52 vs 0.44; p = 0.002) and 3 years (0.46 vs 0.38; p = 0.03) of follow-up. Conclusion: ETV and shunting led to improvements in HC centile, z-score, and FOR measurements during long-term follow-up of infants with hydrocephalus secondary to aqueductal stenosis. Head size did not significantly differ between the treatment groups during follow-up, however ventricle size was greater in those undergoing ETV when measured at 1 and 3 years following treatment