Cryogenics for an HTS degaussing system demonstrator

This paper describes the design, construction and test results of a high temperature superconducting (HTS) degaussing demonstrator system. Such a system compensates the local disturbance in the earth's magnetic field caused by the ferromagnetic hulls of ships, to prevent detection by active or passive magnetic field sensors. This is done by placing coils around the ship, creating a magnetic field opposing the effect of the earth's magnetic field. Degaussing systems for large naval vessels typically need currents of up to 1 or 2 kAturns, which gives rise to sizeable ohmic losses in conventional copper coils. These losses can be reduced if high temperature superconductors are used, since they have no electrical resistance when cooled down to temperatures below 90 K. For the demonstrator, 3 coils able to generate fields in 2 directions were realized both with HTS and copper to get a representative degaussing performance. A dedicatedly designed cooling system maintains the superconductors at a temperature of 77-85K using (subcooled) liquid nitrogen. Due to the relatively small laboratory scale that this first 1:5m long demonstrator system which was produced, the copper degaussing system is still more efficient than the HTS system because of the cooling power needed. A large fraction of this cooling power is needed to cool away parasitic heat loads, that hardly increases if the size of the system increases. Thereafter the performance of both systems was compared to evaluate on what scale HTS degaussing systems become more efficient than copper degaussing systems

Optical to near-infrared transit observations of super-Earth GJ1214b: water-world or mini-Neptune?

GJ1214b is thought to be either a mini-Neptune with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. In the case of a hydrogen-rich atmosphere, molecular absorption and scattering processes may result in detectable radius variations as a function of wavelength. The aim of this paper is to measure these variations. We have obtained observations of the transit of GJ1214b in the r- and I-band with the INT, in the g, r, i and z bands with the 2.2 meter MPI/ESO telescope, in the Ks-band with the NOT, and in the Kc-band with the WHT. By comparing the transit depth between the the different bands, which is a measure for the planet-to-star size ratio, the atmosphere is investigated. We do not detect clearly significant variations in the planet-to-star size ratio as function of wavelength. Although the ratio at the shortest measured wavelength, in g-band, is 2sigma larger than in the other bands. The uncertainties in the Ks and Kc bands are large, due to systematic features in the light curves. The tentative increase in the planet-to-star size ratio at the shortest wavelength could be a sign of an increase in the effective planet-size due to Rayleigh scattering, which would require GJ1214b to have a hydrogen-rich atmosphere. If true, then the atmosphere has to have both clouds, to suppress planet-size variations at red optical wavelengths, as well as a sub-solar metallicity, to suppress strong molecular features in the near- and mid-infrared. However, star spots, which are known to be present on the hoststar's surface, can (partly) cancel out the expected variations in planet-to-star size ratio, due to the lower surface temperature of the spots . A hypothetical spot-fraction of 10% would be able to raise the infrared points sufficiently with respect to the optical measurements to be inconsistent with a water-dominated atmosphere. [abridged]Comment: 13 pages, 8 figures. Accepted for publication in A&

AMPA Receptor Activation Causes Silencing of AMPA Receptor-Mediated Synaptic Transmission in the Developing Hippocampus

Agonist-induced internalization of transmembrane receptors is a widespread biological phenomenon that also may serve as a mechanism for synaptic plasticity. Here we show that the agonist AMPA causes a depression of AMPA receptor (AMPAR) signaling at glutamate synapses in the CA1 region of the hippocampus in slices from developing, but not from mature, rats. This developmentally restricted agonist-induced synaptic depression is expressed as a total loss of AMPAR signaling, without affecting NMDA receptor (NMDAR) signaling, in a large proportion of the developing synapses, thus creating AMPAR silent synapses. The AMPA-induced AMPAR silencing is induced independently of activation of mGluRs and NMDARs, and it mimics and occludes stimulus-induced depression, suggesting that this latter form of synaptic plasticity is expressed as agonist-induced removal of AMPARs. Induction of long-term potentiation (LTP) rendered the developing synapses resistant to the AMPA-induced depression, indicating that LTP contributes to the maturation-related increased stability of these synapses. Our study shows that agonist binding to AMPARs is a sufficient triggering stimulus for the creation of AMPAR silent synapses at developing glutamate synapses

Ubiquitous molecular substrates for associative learning and activity-dependent neuronal facilitation.

Recent evidence suggests that many of the molecular cascades and substrates that contribute to learning-related forms of neuronal plasticity may be conserved across ostensibly disparate model systems. Notably, the facilitation of neuronal excitability and synaptic transmission that contribute to associative learning in Aplysia and Hermissenda, as well as associative LTP in hippocampal CA1 cells, all require (or are enhanced by) the convergence of a transient elevation in intracellular Ca2+ with transmitter binding to metabotropic cell-surface receptors. This temporal convergence of Ca2+ and G-protein-stimulated second-messenger cascades synergistically stimulates several classes of serine/threonine protein kinases, which in turn modulate receptor function or cell excitability through the phosphorylation of ion channels. We present a summary of the biophysical and molecular constituents of neuronal and synaptic facilitation in each of these three model systems. Although specific components of the underlying molecular cascades differ across these three systems, fundamental aspects of these cascades are widely conserved, leading to the conclusion that the conceptual semblance of these superficially disparate systems is far greater than is generally acknowledged. We suggest that the elucidation of mechanistic similarities between different systems will ultimately fulfill the goal of the model systems approach, that is, the description of critical and ubiquitous features of neuronal and synaptic events that contribute to memory induction

Capture of exocomets and the erosion of the Oort cloud due to stellar encounters in the Galaxy

Stars and planetary system

Modeling and Characterization of a ReBCO HTS Degaussing Demonstrator

The magnetic modelling and experimental validation of a superconducting degaussing system for maritime vessels is discussed. Degaussing coils compensate for the distortion in the earths’ magnetic field by the magnetized steel hull of a ship, thus rendering it ‘invisible’ for magnetic field sensors. Whereas typical power requirements with copper coils are of the order of 100 kW, a ReBCO HTS degaussing system in principle allows to reduce this by an order of magnitude. In order to validate such efficiency estimates and to demonstrate the required hardware, a table-top test setup was realized with magnetic ship steel. The vessel-imitating cylindrical demonstrator is equipped with six degaussing coils, grouped in three sets that act in two different directions, with each set consisting of one copper and one ReBCO coil, the latter one equipped with a sub-cooled forced-flow liquid nitrogen system. Static magnetic field measurements are reported and compared to both analytical and numeric finite element models. The results illustrate how even relatively simple analytical models can be used as a powerful tool to extrapolate design parameters and thus to predict the power requirements of large-scale degaussing systems

Musculoskeletal Symptoms, Ergonomic Aspects and Psychosocial Factors in Two Different Truck Assembly Concepts

The project was carried out as a multidisciplinary correlational study of two truck-axle assembly systems (System A and B). System A (the old system) could be characterized as an unpaced line assembly system, whereas the change to the new system, System B, involved a parallelized system with longer job cycle time. The study included all permanent assembly workers in the two systems (System A 17 workers, System B 28 workers). The purpose of this study was to evaluate the two systems with respect to ergonomic factors, psychosocial factors and self-reported musculoskeletal symptoms. The job cycles were studied by means of video observation. Each subject answered a questionnaire regarding musculoskeletal symptoms and physical and psychosocial environment. The assemblers in System B were more satisfied with the physical work environment (e.g. noise, air), but less satisfied with the psychosocial environment, and the period prevalence of musculoskeletal symptoms was not lower, compared with the assemblers in System A. Video observation techniques showed that deep forward flexion was less common, but that the work was more hand intense in System B. In System B, neck/shoulder symptoms were associated principally with physical work (load) variables, whereas low back symptoms were associated with psychosocial variables

SAPS3 subunit of protein phosphatase 6 is an AMPK inhibitor and controls metabolic homeostasis upon dietary challenge in male mice.

Inhibition of AMPK is tightly associated with metabolic perturbations upon over nutrition, yet the molecular mechanisms underlying are not clear. Here, we demonstrate the serine/threonine-protein phosphatase 6 regulatory subunit 3, SAPS3, is a negative regulator of AMPK. SAPS3 is induced under high fat diet (HFD) and recruits the PP6 catalytic subunit to deactivate phosphorylated-AMPK, thereby inhibiting AMPK-controlled metabolic pathways. Either whole-body or liver-specific deletion of SAPS3 protects male mice against HFD-induced detrimental consequences and reverses HFD-induced metabolic and transcriptional alterations while loss of SAPS3 has no effects on mice under balanced diets. Furthermore, genetic inhibition of AMPK is sufficient to block the protective phenotype in SAPS3 knockout mice under HFD. Together, our results reveal that SAPS3 is a negative regulator of AMPK and suppression of SAPS3 functions as a guardian when metabolism is perturbed and represents a potential therapeutic strategy to treat metabolic syndromes