The DRIFT Project: Searching for WIMPS with a Directional Detector

A low pressure time projection chamber for the detection of WIMPs is discussed. Discrimination against Compton electron background in such a device should be very good, and directional information about the recoil atoms would be obtainable. If a full 3-D reconstruction of the recoil tracks can be achieved, Monte Carlo studies indicate that a WIMP signal could be identified with high confidence from as few as 30 detected WIMP-nucleus scattering events.Comment: 5 pages, 3 figures. Presented at Dark 98, Heidelberg, July 1998, and to appear in conference proceeding

Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for the Importance of General Relativistic Effects?

We present results from a simultaneous Chandra HETG and XMM-Newton observation of NGC 3516. We find evidence for several narrow components of Fe Kalpha along with a broad line. We consider the possibility that the lines arise in an blob of material ejected from the nucleus with velocity ~0.25c. We also consider an origin in a neutral accretion disk, suffering enhanced illumination at 35 and 175 gravitational radii, perhaps due to magnetic reconnection. The presence of these narrow features indicates there is no Comptonizing region along the line-of-sight to the nucleus. This in turn is compelling support for the hypothesis that broad Fe Kalpha components are, in general, produced by strong gravity.Comment: 12 pages, 3 color figures. LaTeX with postscript figures. Resubmitted June 7 2002, to Astrophysical Journal Letter

A Randomised, Blinded, Placebo-Controlled, Dose Escalation Study of the Tolerability and Efficacy of Filgrastim for Haemopoietic Stem Cell Mobilisation in Patients With Severe Active Rheumatoid Arthritis

Autologous haemopoietic stem cell transplantation (HSCT) represents a potential therapy for severe rheumatoid arthritis (RA). As a prelude to clinical trails, the safety and efficacy of haemopoietic stem cell (HSC) mobilisation required investigation as colony-stimulating factors (CSFs) have been reported to flare RA. A double-blind, randomised placebo-controlled dose escalation study was performed. Two cohorts of eight patients fulfilling strict eligibility criteria for severe active RA (age median 40 years, range 24-60 years; median disease duration 10.5 years, range 2-18 years) received filgrastim (r-Hu-methionyl granulocyte(G)-(SF) at 5 and 10 microg/kg/day, randomised in a 5:3 ratio with placebo. Patients were unblinded on the fifth day of treatment and those randomised to filgrastim underwent cell harvesting (leukapheresis) daily until 2 X 10^6/kg CD34+ cells (haemopoietic stem and progenitor cells) were obtained. Patients were assessed by clinical and laboratory parameters before, during and after filgrastim administration. RA flare was defined as an increase of 30% or more in two of the following parameters: tender joint count, swollen joint count or pain score. Efficacy was assessed by quantitation of CD34+ cells and CFU-GM. One patient in the 5 microg/kg/day group and two patients in the 10 microg/kg/day group fulfilled criteria for RA flare, although this did not preclude successful stem cell collection. Median changes in swollen and tender joint counts were not supportive of filgrastim consistently causing exacerbation of disease, but administration of filgrastim at 10 microg/kg/day was associated with rises in median C-reactive protein and median rheumatoid factor compared with placebo. Other adverse events were well recognised for filgrastim and included bone pain (80%) and increases in alkaline phosphatase (four-fold) and lactate dehydrogenase (two-fold). With respect to efficacy, filgrastim at 10 microg/kg/day was more efficient with all patients (n = 5) achieving target CD34+ cell counts with a single leukapheresis (median = 2.8, range = 2.3-4.8 X 10^6/kg, median CFU-GM = 22.1, range = 4.2-102.9 X 10^4/kg), whereas 1-3 leukaphereses were necessary to achieve the target yield using 5 microg/kg/day. We conclude that filgrastim may be administered to patients with severe active RA for effective stem cell mobilisation. Flare of RA occurs in a minority of patients and is more likely with 10 than 5 microg/kg/day. However, on balance, 10 microg/kg/day remains the dose of choice in view of more efficient CD34+ cell mobilisation

Autoimmune manifestations in VEXAS: Opportunities for integration and pitfalls to interpretation

VEXAS (Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic) is a novel entity manifesting with a multiplicity of clinical features. Somatic mutations of the UBA1 gene in hematopoietic stem cells constitute the genetic basis of VEXAS. As an X-linked disorder, most cases occur in men, classically developing symptoms during the fifth to sixth decade of life. Considering its multidisciplinary nature involving numerous branches of internal medicine, VEXAS has elicited a wide medical interest and several medical conditions have been associated with this disease. Even so, its recognition in everyday clinical practice is not necessarily straightforward. Close collaboration between different medical specialists is mandatory. Patients with VEXAS may manifest a range of features from manageable cytopenias to disabling and life-threatening autoimmune phenomena with limited responses to therapy, with the potential for progression to hematological malignancies. Diagnostic and treatment guidelines are exploratory and include a range of rheumatological and supportive care treatments. Allogeneic hematopoietic stem cell transplantation is potentially curative, but its risks are significant and its position in the treatment algorithm is yet to be defined. Herein, we present the variegated manifestations of VEXAS, provide practice criteria for diagnostic testing of UBA1, and discuss potential treatment options, including allogeneic hematopoietic stem cell transplantation, current evidence, and future directions

Structural correlations in heterogeneous electron transfer at monolayer and multilayer graphene electrodes

As a new form of carbon, graphene is attracting intense interest as an electrode material with widespread applications. In the present study, the heterogeneous electron transfer (ET) activity of graphene is investigated using scanning electrochemical cell microscopy (SECCM), which allows electrochemical currents to be mapped at high spatial resolution across a surface for correlation with the corresponding structure and properties of the graphene surface. We establish that the rate of heterogeneous ET at graphene increases systematically with the number of graphene layers, and show that the stacking in multilayers also has a subtle influence on ET kinetics. © 2012 American Chemical Society

First measurement of the Head-Tail directional nuclear recoil signature at energies relevant to WIMP dark matter searches

We present first evidence for the so-called Head-Tail asymmetry signature of neutron-induced nuclear recoil tracks at energies down to 1.5 keV/amu using the 1m^3 DRIFT-IIc dark matter detector. This regime is appropriate for recoils induced by Weakly Interacting Massive Particle (WIMPs) but one where the differential ionization is poorly understood. We show that the distribution of recoil energies and directions induced here by Cf-252 neutrons matches well that expected from massive WIMPs. The results open a powerful new means of searching for a galactic signature from WIMPs.Comment: 4 pages, 6 figures, 1 tabl

Dual-barrel conductance micropipet as a new approach to the study of ionic crystal dissolution kinetics

A new approach to the study of ionic crystal dissolution kinetics is described, based on the use of a dual-barrel theta conductance micropipet. The solution in the pipet is undersaturated with respect to the crystal of interest, and when the meniscus at the end of the micropipet makes contact with a selected region of the crystal surface, dissolution occurs causing the solution composition to change. This is observed, with better than 1 ms time resolution, as a change in the ion conductance current, measured across a potential bias between an electrode in each barrel of the pipet. Key attributes of this new technique are: (i) dissolution can be targeted at a single crystal surface; (ii) multiple measurements can be made quickly and easily by moving the pipet to a new location on the surface; (iii) materials with a wide range of kinetics and solubilities are open to study because the duration of dissolution is controlled by the meniscus contact time; (iv) fast kinetics are readily amenable to study because of the intrinsically high mass transport rates within tapered micropipets; (v) the experimental geometry is well-defined, permitting finite element method modeling to allow quantitative analysis of experimental data. Herein, we study the dissolution of NaCl as an example system, with dissolution induced for just a few milliseconds, and estimate a first-order heterogeneous rate constant of 7.5 (±2.5) × 10–5 cm s–1 (equivalent surface dissolution flux ca. 0.5 μmol cm–2 s–1 into a completely undersaturated solution). Ionic crystals form a huge class of materials whose dissolution properties are of considerable interest, and we thus anticipate that this new localized microscale surface approach will have considerable applicability in the future

Low Pressure Negative Ion Drift Chamber for Dark Matter Search

Weakly Interacting Massive Particles (WIMPs) are an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low pressure negative ion drift chamber to search for WIMPs. The innovation of drifting ions, instead of electrons, allows the design of a detector with exceptional sensitivity to, background rejection from, and signature of WIMPs.Comment: 5 pages submitted to PR

Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches

Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches

Open Clusters IC 4665 and Cr 359 and a Probable Birthplace of the Pulsar PSR B1929+10

Based on the epicyclic approximation, we have simulated the motion of the young open star clusters IC 4665 and Collinder 359. The separation between the cluster centers is shown to have been minimal 7 Myr ago, 36 pc. We have established a close evolutionary connection between IC 4665 and the Scorpius-Centaurus association -- the separation between the centers of these structures was $\approx200$ pc 15 Myr ago. In addition, the center of IC 4665 at this time was near two well-known regions of coronal gas: the Local Bubble and the North Polar Spur. The star HIP 86768 is shown to be one of the candidates for a binary (in the past) with the pulsar PSR B1929+10. At the model radial velocity of the pulsar $V_r= 2\pm50$ km s$^{-1}$, a close encounter of this pair occurs in the vicinity of IC 4665 at a time of -1.1 Myr. At the same time, using currently available data for the pulsar B1929+10 at its model radial velocity $V_r=200\pm50$ km s$^{-1}$, we show that the hypothesis of Hoogerwerf et al. (2001) about the breakup of the $\zeta$Oph--B1929+10 binary in the vicinity of Upper Scorpius (US) about 0.9 Myr ago is more plausible.Comment: 19 pages, 8 figure