Mol 7C experiments on local fault propagation in irradiated LMFBR fuel subassemblies

The consequences of local cooling disturbances in irradiated fuel pin bundles of Liquid Metal Fast Breeder Reactors (LMFBRs) were investigated in two in-pile experiments in the BR2 reactor at Mol/Belgium. A porous local blockage was used to initiate the fault. This caused severe local fuel pin damage, but there was no fault propagation to major parts of the bundles during four hours of full power operation. If such events occurred in a LMFBR, the delayed neutron detection (DND) signals generated by the fault would be sufficient to initiate reliable automatic shutdown of the reactor.     

Effects of humor on sentence memory.

Memory for humorous and nonhumorous versions of sentences was compared. Humorous sentences were better remembered than the nonhumorous sentences on both free- and cued-recall tests and on measures of sentence recall and word recall. These effects persisted when Ss were warned that they were about to read a humorous sentence but were attenuated in incidental learning and limited to within-Ss manipulations. In incidental learning, recall was also scored as a function of subjective ratings of humor. Subjective humor affected memory in both within- and between-Ss designs. Attention, arousal, rehearsal, retrieval, and surprise explanations were explored. Results suggest that humorous material receives both increased attention and rehearsal relative to nonhumorous material. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of heat treatments on phase chemistry of the Nickel-Base superalloy SRR 99

The average phase composition of the single-crystal nickel-base alloy SRR 99 after solution treatment, single and double stage annealing, and overaging has been determined by energy dispersive X-ray spectrometry (EDX) (HPGe detector) in a transmission electron microscope (TEM). Calculations of hypothetical nominal compositions for the alloy, using measured compositions ofγ′ phase and matrix as a function of the volume fraction ofγ′ phase, allow determination of the volume fraction ofγ′ phase at the minimum error between nominal composition and hypothetical nominal composition. After single-stage annealing, theγ′ concentrations of W, Al, and Co are higher, and those of Cr, Ta, Ti, and Ni are lower near the phase boundary compared to the average concentration of a precipitate. These concentration gradients and the integral concentrations of element in theγ′ phase are interpreted by the temperature-dependent solubility of elements in theγ′ phase.     

Quantum Criticality and Scaling of the Magnetic Response in CeCu6−x Au x

The heavy-fermion system CeCu_6?x Au _x which exhibits antiferromagnetic order for Au concentrations x>0.1, can be easily tuned to a quantum phase transition, either by chemical composition, i.e., Au concentration, or by an external magnetic field. We present extensive inelastic neutron scattering measurements in order to study the momentum and energy dependence of the critical spin fluctuations for concentration- and magnetic field-tuned CeCu_6?x Au _x . The quasi-2D fluctuations, observed for x=0.1 at the magnetic instability, are already present in pure CeCu₆ and persist to x=0.2, i.e., well into the magnetically ordered regime. This is a strong hint that disorder does not play a major role in this system. The magnetic response for quantum critical CeCu_6?x Au _x exhibits critical slowing down and obeys scaling relations that depend on the tuning parameter. While the E/T scaling of the dynamic susceptibility in concentration-tuned CeCu_5.9Au_0.1 is an indication for local quantum criticality, the E/T ^3/2 scaling in field-tuned CeCu_5.8Au_0.2 points to a conventional spin-density-wave instability.     

Advanced Code-Division Multiplexers for Superconducting Detector Arrays

Multiplexers based on the modulation of superconducting quantum interference devices are now regularly used in multi-kilopixel arrays of superconducting detectors for astrophysics, cosmology, and materials analysis. Over the next decade, much larger arrays will be needed. These larger arrays require new modulation techniques and compact multiplexer elements that fit within each pixel. We present a new in-focal-plane code-division multiplexer that provides multiplexing elements with the required scalability. This code-division multiplexer uses compact lithographic modulation elements that simultaneously multiplex both signal outputs and superconducting transition-edge sensor (TES) detector bias voltages. It eliminates the shunt resistor used to voltage bias TES detectors, greatly reduces power dissipation, allows different dc bias voltages for each TES, and makes all elements sufficiently compact to fit inside the detector pixel area. These in-focal plane code-division multiplexers can be combined with multi-GHz readout based on superconducting microresonators to scale to even larger arrays.     

Temperature characterization of flip-chip packaged piezoresistive barometric pressure sensors

In order to miniaturize piezoresistive barometric pressure sensors, a new flip-chip packaging technology has been developed. The thermal expansions of chip and package are different. So in a standard flip-chip package the strong mechanical coupling by the solder bumps would lead to stress in the sensor chip, which is unacceptable for piezoresistive pressure sensors. To solve this problem, in the new packaging technology the chip is flip-chip bonded on compliant springs to decouple chip and package. As the first step of the packaging process an under bump metallization (UBM) is patterned on the sensor wafer. Then solder bumps are printed. After wafer-dicing the chips are flip-chip bonded on copper springs within a ceramic cavity housing. Due to the compliance of the springs, packaging stress is induced into the sensor chip. As sources of residual stress the UBM and the solder bumps on the sensor chip were identified. Different coefficients of thermal expansion of the silicon chip, the UBM and the solder lead to plastic straining of the aluminum metallization between UBM and chip. As a consequence the measurement accuracy is limited by a temperature hysteresis. The influence of the chip geometry, e.g., the thickness of the chip or the depth of the cavity, on the hysteresis was investigated by simulation and measurements. As a result of this investigation a sensor chip was designed with very low residual stress and a temperature hysteresis which is only slightly larger than the noise of the sensor.     

Schrifttumsberichte

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Bundesanstalt für Forst-und Holzwirtschaft,Reinbek

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Mitochondrial Dysfunction in Spinocerebellar Ataxia Type 3 Is Linked to VDAC1 Deubiquitination

Dysfunctional mitochondria are linked to several neurodegenerative diseases. Metabolic defects, a symptom which can result from dysfunctional mitochondria, are also present in spinocerebellar ataxia type 3 (SCA3), also known as Machado–Joseph disease, the most frequent, dominantly inherited neurodegenerative ataxia worldwide. Mitochondrial dysfunction has been reported for several neurodegenerative disorders and ataxin-3 is known to deubiquitinylate parkin, a key protein required for canonical mitophagy. In this study, we analyzed mitochondrial function and mitophagy in a patient-derived SCA3 cell model. Human fibroblast lines isolated from SCA3 patients were immortalized and characterized. SCA3 patient fibroblasts revealed circular, ring-shaped mitochondria and featured reduced OXPHOS complexes, ATP production and cell viability. We show that wildtype ataxin-3 deubiquitinates VDAC1 (voltage-dependent anion channel 1), a member of the mitochondrial permeability transition pore and a parkin substrate. In SCA3 patients, VDAC1 deubiquitination and parkin recruitment to the depolarized mitochondria is inhibited. Increased p62-linked mitophagy, autophagosome formation and autophagy is observed under disease conditions, which is in line with mitochondrial fission. SCA3 fibroblast lines demonstrated a mitochondrial phenotype and dysregulation of parkin-VDAC1-mediated mitophagy, thereby promoting mitochondrial quality control via alternative pathways.