The target for the new plasma/wall experiment Magnum-PSI

The construction of Magnum-PSI is in its final stage. The aim is to provide a controlled and highly accessible linear plasma device to perform the basic plasma-surface interaction research needed for the design of the plasma facing components of future fusion devices. This contribution will focus on the thermal challenges imposed by those extreme conditions on the design of the target holder of Magnum-PSI. The target holder is designed to allow the exposure of large size targets with variable inclination angles with respect to the magnetic field. A test set up was made to test different interlayers (grafoil (R), soft metal sheets) and improve the thermal contact between the target and the heat sink. In addition, a modular target holder for sequential exposure of smaller size targets has been designed. Finite element modeling using the ANSYS code was used to optimize the cooling geometry and to predict the temperature profiles due to the heat load of the plasma. Experiments were done on the Pilot-PSI linear device to validate the thermal calculations. Calorimetry and infrared thermography were used to experimentally measure the temperature profile on the target and the heat deposition. (C) 2011 Elsevier B.V. All rights reserved

Transcriptomic analysis of PPARalpha-dependent alterations during cardiac hypertrophy.

Peroxisome proliferator-activated receptor alpha (PPARalpha) regulates lipid metabolism at the transcriptional level and modulates the expression of genes involved in inflammation, cell proliferation and differentiation. Although PPARalpha has been shown to mitigate cardiac hypertrophy, knowledge about underlying mechanisms and nature of signalling pathways involved is fragmentary and incomplete. The aim of this study was to identify the processes and signalling pathways regulated by PPARalpha in hearts challenged by a chronic pressure overload by means of whole genome transcriptomic analysis. Thereto, PPARalpha-/- and wild-type mice were subjected to transverse aortic constriction (TAC) for 28 days and left ventricular gene expression profile was determined using Affymetrix GeneChip Mouse Genome 430 2.0 arrays containing over 45,000 probe sets. In unchallenged hearts, the mere lack of PPARalpha resulted in 821 differentially expressed genes, many of which were related to lipid metabolism and immune response. TAC resulted in a more pronounced cardiac hypertrophy and more extensive changes in gene expression (1910 and 312 differentially expressed genes, respectively) in PPARalpha-/- mice than in wild-type mice. Many of the hypertrophy related genes were related to development, signal transduction, actin filament organization, and collagen synthesis. Compared to wild-type hypertrophied hearts, PPARalpha-/- hypertrophied hearts revealed enrichment of gene clusters related to extracellular matrix remodelling, immune response, oxidative stress, and inflammatory signalling pathways. The present study demonstrates therefore that, in addition to lipid metabolism, PPARalpha is an important modulator of the immune- and inflammatory response in the cardiac muscle. Key words: microarray, lipid metabolism, inflammation, immune response

Thermal effects and component cooling in Magnum-PSI

Magnum-PSI is a linear plasma generator, built at the FOM-Institute for Plasma Physics Rijnhuizen. Subject of study will be the interaction of plasma with a diversity of surface materials. The machine is designed to provide an environment with a steady state high-flux plasma (up to 10(24) H(+) ions/m(2) s) in a 3T magnetic field with an exposed surface of 80 cm(2) up to 10 MW/m(2). Magnum-PSI will provide new insights in the complex physics and chemistry that will occur in the divertor region of the future experimental fusion reactor ITER and reactors beyond ITER. The conditions at the surface of the sample can be varied over a wide range, such as plasma temperature, beam diameter, particle flux, inclination angle of the target, background pressure and magnetic field. An important subject of attention in the design of the machine was thermal effects originating in the excess heat and gas flow from the plasma source and radiation from the target. (C) 2011 Elsevier B.V. All rights reserved

Operational status of the Magnum-PSI linear plasma device

The construction phase of the linear plasma generator Magnum-PSI at the FOM institute DIFFER has been completed and the facility has been officially opened in March 2012. The scientific program to gain more insight in the plasma–wall interactions relevant for ITER and future fusion reactors has started. In Magnum-PSI, targets of a wide range of materials and shapes can be exposed to high particle, high heat flux plasmas (>1024 ions m−2 s−1; >10 MW/m2). For magnetization of the plasma, oil-cooled electromagnets are temporarily installed to enable pulsed operation until the device is upgraded with a superconducting magnet. The magnets generate a field of up to 1.9 T close to the plasma source for a duration of 6 s. Longer exposure times are available for lower field settings. Plasma characterizations were done with a variety of gases (H, D, He, Ne and Ar) to determine the machine performance and prepare for subsequent scientific experiments. Thomson scattering and optical emission spectroscopy were used to determine the plasma parameters while infrared thermography and target calorimetry were used to determine the power loads to the surface. This paper reports on the status of Magnum-PSI and its diagnostic systems. In addition, an overview of the plasma parameters that can be achieved in the present state will be given

Folate and vitamin B12-related biomarkers in relation to brain volumes

Aim: We investigated cross-sectional associations between circulating homocysteine, folate, biomarkers of vitamin B12 status and brain volumes. We furthermore compared brain volumes of articipants who received daily folic acid and vitamin B12 supplementation with participants who did not. Methods: Participants of the B-PROOF study (n = 2919) were assigned to 400 μg folic acid and 500 μg vitamin B12, or a placebo. After two years of intervention, T1-weighted magnetic resonance imaging (MRI) scans were made in a random subsample (n = 218) to obtain grey and white matter volume, and total brain volume (TBV). Plasma homocysteine, serum folate, vitamin B12, holotranscobalamin, and methylmalonic acid concentrations were measured. Results: Multiple linear regression analyses showed inverse associations between plasma homocysteine with TBV (β = -0.91, 95% CI-1.85-0.03, p = 0.06) and between serum folate and TBV (β = -0.20, 95% CI -0.38, -0.02, p = 0.03). No significant associations were observed for serum vitamin B12 and holotranscobalamin. Fully adjusted ANCOVA models showed that the group that received B-vitamins had a lower TBV (adjusted mean 1064, 95% CI 1058-1069 mL) than the non-supplemented group (1072, 95% CI 1067-1078 mL, p = 0.03). Conclusions: Results were contradictory, with higher Hcy levels associated with lower TBV, but also with higher folate levels associated with lower TBV. In addition, the lack of a baseline measurement withholds us from giving recommendations on whether folic acid and vitamin B12 supplementation will be beneficial above and beyond normal dietary intake for brain health

Operational characteristics of the high flux plasma generator Magnum-PSI

Abstract In Magnum-PSI (MAgnetized plasma Generator and \{NUMerical\} modeling for Plasma Surface Interactions), the high density, low temperature plasma of a wall stabilized dc cascaded arc is confined to a magnetized plasma beam by a quasi-steady state axial magnetic field up to 1.3 T. It aims at conditions that enable fundamental studies of plasma surface interactions in the regime relevant for fusion reactors such as ITER: 1023-1025 m−2 s−1 hydrogen plasma flux densities at 1-5 eV. To study the effects of transient heat loads on a plasma-facing surface, a high power pulsed magnetized arc discharge has been developed. Additionally, the target surface can be transiently heated with a pulsed laser system during plasma exposure. In this contribution, the current status, capabilities and performance of Magnum-PSI are presented