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A portable monoenergetic 24 keV neutron source based on the 124Sb-9Be photoneutron reaction and an iron filter has been constructed and characterized. The coincidence of the neutron energy from SbBe and the low interaction cross-section with iron (mean free path up to 29 cm) makes pure iron specially suited to shield against gamma rays from 124Sb decays while letting through the neutrons. To increase the 124Sb activity and thus the neutron flux, a >1 GBq 124Sb source was produced by irradiating a natural Sb metal pellet with a high flux of thermal neutrons in a nuclear reactor. The design of the source shielding structure makes for easy transportation and deployment. A hydrogen gas proportional counter is used to characterize the neutrons emitted by the source and a NaI detector is used for gamma background characterization. At the exit opening of the neutron beam, the characterization determined the neutron flux in the energy range 20-25 keV to be 6.00±0.30 neutrons per cm2 per second and the total gamma flux to be 245±8 gammas per cm2 per second (numbers scaled to 1 GBq activity of the 124Sb source). A liquid scintillator detector is demonstrated to be sensitive to neutrons with incident kinetic energies from 8 to 17 keV, so it can be paired with the source as a backing detector for neutron scattering calibration experiments. This photoneutron source provides a good tool for in-situ low energy nuclear recoil calibration for dark matter experiments and coherent elastic neutrino-nucleus scattering experiments.

We have designed and tested a large-area (0.15 m2) neutron detector based on neutron capture on 6Li. The neutron detector design has been optimized for the purpose of tagging the scattering angle of keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy (

Superfluid He4 is a promising target material for direct detection of light (

We present measurements of the angular distribution of re-emitted light from tetraphenyl butadiene thin films when exposed to 128 nm light, which is the peak of the liquid Argon (LAr) scintillation spectrum, in vacuum. Films ranging from 250 nm to 5.5 μm in thickness are measured. All films were fabricated by evaporation deposition on ultraviolet transmitting (UVT) acrylic substrates. Preliminary comparisons of the angular distribution to that produced by a detailed Monte Carlo model are also presented. The current shortcomings of the model are discussed and future plans briefly outlined.

Abstract Background Chemokines are involved in many biological activities ranging from leukocyte differentiation to neuronal morphogenesis. Despite numerous reports describing chemokine function, little is known about the molecular changes induced by cytokines. Methods We have isolated and identified by differential display analysis 182 differentially expressed cDNAs from CXCR3-transfected Jurkat T cells following treatment with CXCL12 or CXCL10. These chemokine-modulated genes were further verified using quantitative RT-PCR and Western blot analysis. Results One hundred and forty-six of the cDNAs were successfully cloned, sequenced, and identified by BLAST. Following removal of redundant and non-informative clones, seventeen mRNAs were found to be differentially expressed post treatment with either chemokine ligand with several representing known genes with established functions. Twenty-one genes were upregulated in these transfected Jurkat cells following both CXCL12 and CXCL10, four genes displayed a discordant response and seven genes were downregulated upon treatment with either chemokine. Identified genes include geminin (GEM), thioredoxin (TXN), DEAD/H box polypeptide 1 (DDX1), growth hormone inducible transmembrane protein (GHITM), and transcription elongation regulator 1 (TCERG1). Subsequent analysis of several of these genes using semi-quantitative PCR and western blot analysis confirmed their differential expression post ligand treatment. Conclusions Together, these results provide insight into chemokine-induced gene activation and identify potentially novel functions for known genes in chemokine biology.

A superconducting Transition-Edge Sensor (TES) with low- T c is essential in high resolution calorimetric detection. With the motivation of developing sensitive calorimeters for applications in cryogenic neutrinoless double beta decay searches, we have been investigating methods to reduce the T c of an Ir film down to 20 mK. Utilizing the proximity effect between a superconductor and a normal metal, we found two room temperature fabrication recipes for making Ir-based low- T c films. In the first approach, an Ir film sandwiched between two Au films, a Au/Ir/Au trilayer, has a tunable T c in the range of 20-100 mK depending on the relative thicknesses. In the second approach, a paramagnetic Pt thin film is used to create the Ir/Pt bilayer with a tunable T c in the same range. We present a detailed study of fabrication and characterization of Ir-based low- T c films and compare the experimental results to the theoretical models. We show that Ir-based films with a predictable and reproducible critical temperature can be consistently fabricated for use in large scale detector applications.

A superconducting Transition-Edge Sensor (TES) with low- T c is essential in high resolution calorimetric detection. With the motivation of developing sensitive calorimeters for applications in cryogenic neutrinoless double beta decay searches, we have been investigating methods to reduce the T c of an Ir film down to 20 mK. Utilizing the proximity effect between a superconductor and a normal metal, we found two room temperature fabrication recipes for making Ir-based low- T c films. In the first approach, an Ir film sandwiched between two Au films, a Au/Ir/Au trilayer, has a tunable T c in the range of 20-100 mK depending on the relative thicknesses. In the second approach, a paramagnetic Pt thin film is used to create the Ir/Pt bilayer with a tunable T c in the same range. We present a detailed study of fabrication and characterization of Ir-based low- T c films and compare the experimental results to the theoretical models. We show that Ir-based films with a predictable and reproducible critical temperature can be consistently fabricated for use in large scale detector applications.

Liquid xenon particle detectors rely on excellent light collection efficiency for their performance. This depends on the high reflectivity of polytetrafluoroethylene (PTFE) at the xenon scintillation wavelength of 178 nm, but the angular dependence of this reflectivity is not well-understood. IBEX is designed to directly measure the angular distribution of xenon scintillation light reflected off PTFE in liquid xenon. These measurements are fully described by a microphysical reflectivity model with few free parameters. Dependence on PTFE type, surface finish, xenon pressure, and wavelength of incident light is explored. Total internal reflection is observed, which results in the dominance of specular over diffuse reflection and a reflectivity near 100% for high angles of incidence.

After the initial infection, bacterial plant pathogens often localize to specific tissues or within certain parts of their hosts. In such cases, it may be possible to clear the infection by removing the infected portion and retraining the plant from the base of the trunk. We tested the efficacy of severe pruning at clearing grapevine infections by Xylella fastidiosa, the causal agent of Pierce’s disease. We surveyed vines in six Northern California vineyards and rated them on a scale of disease severity from 0 to 3. Next, we aggressively pruned vines by removing the trunk 10 cm above the graft union and we monitored their retrained canopies over time. Although 82% (284/346) of severely pruned vines appeared disease free the following season, the prevalence of symptoms in conventionally pruned control vines suggests that more than one-third (112/324) of vines would have recovered without severe pruning—at least those with less advanced symptoms. Moreover, for five of the six vineyards, the majority of severely pruned vines showed symptoms of Pierce’s disease by the time vines were retrained, two seasons after pruning (as high as 81%, 86/106; 71% overall, 245/346). These results suggest that severe pruning does not clear X. fastidiosa infection from grapevines to an extent that would justify its adoption for disease management.

High precision calorimetry using superconducting transition edge sensorsrequires the use of superconducting films with a suitable $T_c$, depending onthe application. To advance high-precision macrocalorimetry, we requirelow-$T_c$ films that are easy to fabricate. A simple and effective way tosuppress $T_c$ of superconducting Iridium through the proximity effect isdemonstrated by using Ir/Pt bilayers as well as Au/Ir/Au trilayers. While Ir/Aufilms fabricated by applying heat to the substrate during Ir deposition havebeen used in the past for superconducting sensors, we present results of $T_c$suppression on Iridium by deposition at room temperature in Au/Ir/Au trilayersand Ir/Pt bilayers in the range of $\sim$20-100~mK. Measurements of therelative impedance between the Ir/Pt bilayers and Au/Ir/Au trilayers fabricatedshow factor of $\sim$10 higher values in the Ir/Pt case. These new films couldplay a key role in the development of scalable superconducting transition edgesensors that require low-$T_c$ films to minimize heat capacity and maximizeenergy resolution, while keeping high-yield fabrication methods.