Results from the CDMS II Experiment

I report recent results and the status of the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory in Minnesota, USA. A blind analysis of data taken by 30 detectors between October 2006 and July 2007 found zero events consistent with WIMPs elastically scattering in our Ge detectors. This resulted in an upper limit on the spin-independent, WIMP-nucleon cross section of 6.6 x 10^-44 cm^2 (4.6 x 10^-44 cm^2 when combined with our previous results) at the 90% C.L. for a WIMP of mass 60 GeV/c^2. In March 2009 data taking with CDMS II stopped in order to install the first of 5 SuperTowers of detectors for the SuperCDMS Soudan project. Analysis of data taken between August 2007 and March 2009 is ongoing.Comment: 5 pages, 4 figures, to appear in the proceedings of the TAUP09 conference (Rome, July 1st-5th 2009

Evaluation of Polymer-Filler Interaction Characteristics by Force Microscopy

Silicone polymers are frequently used as cushions and inserts between load bearing parts. In this capacity, they must act to position their associated parts and distribute mechanical force as appropriate. One type of failure is specific to silicones that are filled with high surface area particulates for purposes of tailoring the polymer compressive properties. Additives such as fumed silicon oxide are presumed to have a high degree of surface interaction with the polymer matrix, thus causing the polymer to stiffen and to display greater dimensional stability as a function of temperature. However, it has been observed that the compressive behavior of these materials is not always invariant over long times. There is evidence that suggests changes in humidity and temperature can irreversibly alter the silicone-filler interaction, thereby changing the overall characteristics of parts made from such materials. As before, changes in compressive or shear stability can have serious effects on the ability of these materials to effectively position precision parts or distribute high mechanical loads. We approach the analysis of the filled systems by creating controlled layers of silicone polymers attached to silicon oxide substrates. Straight chain vinyl-silicone polymers identical to those used in the formulation of pads for stockpile systems are chemically appended to a substrate surface, and cross-linked to form a three dimensional network. This type of structure serves as a model of silicone polymer coating a silicon oxide filler particle. We study these model systems first by using Atomic Force Microscopy (AFM) to image the samples with nanometer resolution, and then by measuring the forces of interactions between single model silica filler particles and polymer-coated surfaces. We use normal longitudinal force AFM to measure adhesion, and a relatively newly developed technique, lateral force AFM, to determine the frictional forces between the silica particles and the polymer films. Lateral force AFM is a sophisticated technique that involves observing the torsional deflections of a cantilever that is scanned across a surface perpendicular to the normal mode deflection. For a carefully calibrated system, this gives information on the dynamic frictional component of the particle/polymer interaction. Both force-measuring techniques utilize colloidal silicon oxide probes ranging from 0.6 {micro}m to 2.0 {micro}m in diameter. These probes replace the standard sharp AFM tip on the cantilever with a spherical bead (Figure 1) and are used to examine interactions between the bead material and the sample surface

Coil-Assisted Retrograde Transvenous Obliteration (CARTO) for the Treatment of Portal Hypertensive Variceal Bleeding: Preliminary Results.

ObjectivesTo describe the technical feasibility, safety, and clinical outcomes of coil-assisted retrograde transvenous obliteration (CARTO) in treating portal hypertensive non-esophageal variceal hemorrhage.MethodsFrom October 2012 to December 2013, 20 patients who received CARTO for the treatment of portal hypertensive non-esophageal variceal bleeding were retrospectively evaluated. All 20 patients had at least 6-month follow-up. All patients had detachable coils placed to occlude the efferent shunt and retrograde gelfoam embolization to achieve complete thrombosis/obliteration of varices. Technical success, clinical success, rebleeding, and complications were evaluated at follow-up.ResultsA 100% technical success rate (defined as achieving complete occlusion of efferent shunt with complete thrombosis/obliteration of bleeding varices and/or stopping variceal bleeding) was demonstrated in all 20 patients. Clinical success rate (defined as no variceal rebleeding) was 100%. Follow-up computed tomography after CARTO demonstrated decrease in size with complete thrombosis and disappearance of the varices in all 20 patients. Thirteen out of the 20 had endoscopic confirmation of resolution of varices. Minor post-CARTO complications, including worsening of esophageal varices (not bleeding) and worsening of ascites/hydrothorax, were noted in 5 patients (25%). One patient passed away at 24 days after the CARTO due to systemic and portal venous thrombosis and multi-organ failure. Otherwise, no major complication was noted. No variceal rebleeding was noted in all 20 patients during mean follow-up of 384±154 days.ConclusionsCARTO appears to be a technically feasible and safe alternative to traditional balloon-occluded retrograde transvenous obliteration or transjugular intrahepatic portosystemic shunt, with excellent clinical outcomes in treating portal hypertensive non-esophageal variceal bleeding

Soil organic matter humification under different tillage managements evaluated by Laser Induced Fluorescence (LIF) and C/N ratio

AbstractIn this work is presented the use of the C/N ratio and the Laser Induced Fluorescence (LIF) spectroscopy for determining the humification of soil organic matter (SOM) in an Oxisol under three different long-term tillage managements (no-tillage (NT), reduced tillage (RT) and conventional tillage (CT)). Humification of SOM was evaluated in the soil and its fractions (clay<2μm, silt 2–20μm, sand 20–1000μm). The obtained results show that lower SOM humification was observed in soil under NT, mainly at the surface (0–5cm). In CT, SOM humification values maintained constant for all investigated depths (0–5, 5–10, 10–15 and 15–20cm). Also, clay was the soil fraction that exhibited the lesser humification of SOM. Based on the obtained results it can be said that NT favors the accumulation of SOM on its surface, increasing aggregate stability and presenting samples with lower humification indexes. These results indicate a larger availability of nutrients for the plants in this management

First Results from the Cryogenic Dark Matter Search in the Soudan Underground Lab

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg-d of Ge net exposure after cuts for recoil energies between 10--100 keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. Using the standard dark-matter halo and nuclear-physics WIMP model, these data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross-section for all WIMP masses above 15 GeV, ruling out a significant range of neutralino supersymmetric models. The minimum of this limit curve at the 90% C.L. is 4 x 10^{-43} cm^2 at a WIMP mass of 60 GeV.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett; minor clarifications in response to referee's comment