Spatial Imaging of Charge Transport in Germanium at Low Temperature

The purpose of this experiment is to observe the oblique propagation of electrons through germanium by exciting a point source of charge carriers with a focused laser pulse on one face of a germanium crystal. After the electrons are drifted through the crystal by a uniform electric field, the pattern of charge density arriving on the opposite face is mapped and used to reconstruct the trajectories of the electrons. These measurements will verify in detail the Monte Carlo analysis utilized in the Cryogenic Dark Matter Search to model the transport of charge carriers in high-purity germanium detectors, including both oblique electron propagation and inter-valley scattering.     

Relational aggression, gender, and peer acceptance: Invariance across culture, stability over time, and concordance among informants.

It has been proposed that overt physical and verbal aggression are more prevalent among boys and that covert aggression in the context of interpersonal relationships is more typical of girls. The purpose of this study was to replicate and extend American research on this topic to Italy. Italian elementary school pupils (n?=?314) and their teachers provided nominations for aggression and prosocial behavior on 2 occasions within a single school year. Both peer and teacher nominations were highly stable, though there was very poor concordance between them. Peer nominations for both overt and relational aggression were linked to peer rejection. Contrary to expectations, boys scored higher than girls in both overt and relational aggression. Nevertheless, on the basis of the gender composition of extreme groups, the authors conclude that the distinction between overt and relational aggression is as useful in facilitating research on aggressiveness among girls in Italy as it is in the United States. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detector Development for the Next Phases of the Cryogenic Dark Matter Search: Results from 1 Inch Ge and Si Detectors

The Cryogenic Dark Matter Search (CDMS) experiment is searching for Weakly Interacting Massive Particles (WIMPs) using detectors with the ability to discriminate between candidate (nuclear recoil) and background (electron recoil) events by measuring both phonon and ionization signals from recoils in the detector crystals. As CDMS scales up to greater WIMP sensitivity, it is necessary to increase the detector mass and further improve background discrimination. CDMS is engaged in ongoing fabrication and development of new detector designs in order to meet these criteria for the proposed SuperCDMS experiment. Thicker detector prototypes have been produced with new photolithographic masks. These masks have greater surface coverage of the quasi particle trap and transition edge sensor system to provide superior athermal phonon collection. Results from continuing laboratory tests are presented which already indicate improvement in discrimination parameters.      

Ionization Measurements of SuperCDMS SNOLAB 100 mm Diameter Germanium Crystals

Scaling cryogenic Germanium-based dark matter detectors to probe smaller WIMP-nucleon cross-sections poses significant challenges in the forms of increased labor, cold hardware, warm electronics and heat load. The development of larger crystals alleviates these issues. The results of ionization tests with two 100?mm diameter, 33?mm thick cylindrical detector-grade Germanium crystals are presented here. Through these results the potential of using such crystals in the Super Cryogenic Dark Matter Search (SuperCDMS) SNOLAB experiment is demonstrated.     

Present Status of the SuperCDMS program

The expected final reach of the Weakly Interacting Massive Particle (WIMP) search experiment CDMS-II by the end of 2007 is a WIMP-nucleon cross-section sensitivity of 2.1×10⁻⁴⁴ cm². To proceed further in our search, we have proposed the SuperCDMS Phase A project that would deploy 42 1-inch thick Ge detectors, at a site deeper than the location of CDMS II, and reach a desired sensitivity goal of 1.3×10⁻⁴⁵ cm². These cross-sections are of interest and are complementary to Supersymmetry searches at the Large Hadron Collider (LHC) and future linear colliders. P.L. Brink for the SuperCDMS Collaboration.     

Time Evolution of Electric Fields in CDMS Detectors

The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3″?diameter×1″ thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors, the later providing a ～1?V?cm^?1 electric field in the detector bulk. Cumulative radiation exposure which creates ～200×10⁶ electron-hole pairs could be sufficient to produce a comparable reverse field in the detector thereby degrading the ionization channel performance, if it was not shielded by image charges on the electrodes. To study this, the existing CDMS detector Monte Carlo has been modified to allow for an event by event evolution of the bulk electric field, in three spatial dimensions. Surprisingly, this simple model is not sufficient to explain the degradation of detector performance. Our most recent results and interpretation are discussed.     

Effects of Chronic Red Wine Consumption on the Expression of Vascular Endothelial Growth Factor,Angiopoietin 1, Angiopoietin 2, and Its Receptors in Rat Erectile Tissue

ABSTRACT: Long-term consumption of red wine (RW) apparently confers some protection against cardiovascular diseases due to antiatherosclerotic properties of polyphenols and ethanol (EtOH). There is some evidence indicating that they do so by regulating angiogenesis, but the mechanism and the modulator factors involved are largely unknown. The aim of this study was to evaluate the effects of chronic ingestion of RW in vascular structure and in the pattern of expression of vascular growth factors in the rat corpus cavernosum. Male Wistar rats aged 6 mo were treated with RW or an equivalent EtOH solution, as the only liquid source for 6 mo. Expression of vascular endothelial growth factor (VEGF), angiopoietin 1 and angiopoietin 2, and their receptors (VEGFR1, VEGFR2, and Tie2) in cavernous tissue was assayed by immunofluorescence and Western blotting. A reduction of VEGF and VEGFR2 expression, respectively, in smooth muscle and endothelial cells was observed in RW-treated animals, which was balanced by an increase in angiopoietins/Tie2 expression. In EtOH rats, only a decrease in expression of the receptors VEGFR2 and Tie2 was observed. These results, taken together, suggest that antioxidants present in RW activate selected mechanisms for the maintenance of cavernous tissue vascularization. However, functional studies will be necessary to elucidate if RW is of benefit in the prevention of deleterious vascular events associated with ED.     

Quasiparticle Diffusion in Al Films Coupled to Tungsten Transition Edge Sensors

We report recent results obtained from several W/Al test devices on Si wafers fabricated specifically to better understand energy collection in phonon sensors used for the Cryogenic Dark Matter Search (CDMS) experiment. The devices under study consist of three different lengths of 250 \(\upmu \) m-wide by 300 nm-thick Al absorber films, coupled to 250 \(\upmu \) m x 250 \(\upmu \) m (40 nm thick) W-TESs at each end of the Al film. An \(^{55}\) Fe source was used to excite a NaCl reflector producing 2.6 keV Cl X-rays that were absorbed in our test device after passing through a collimator. The impinging X-rays broke Cooper pairs in the Al film, producing quasiparticles that we detected after they propagated into the W-TESs. We studied the diffusion of these quasiparticles in the Al, trapping effects in the Al film, and energy transmission at the Al/W interfaces.     

Phonon-Mediated Distributed Transition-Edge-Sensor X-Ray Detector with Deep Trenches

We continue our development of a phonon-mediated distributed-TES X-ray detector. X-rays are absorbed in a large silicon or germanium crystal, and the energy is read out by four distributed TESs. This design takes advantage of existing TES technology while overcoming the difficulties of designing spatially large arrays. In this paper, we discuss three detector designs. First, a silicon detector with 220 μm deep trenches through a 350 μm crystal. Second, a germanium detector with 275 μm deep trenches through a 550 μm crystal. Finally another silicon detector with 330 μm deep trenches through a 350 μm crystal. We discuss energy loss mechanisms in the detector and propose a reason for the energy resolution that we observe.