733 research outputs found
Low-Background gamma counting at the Kimballton Underground Research Facility
The next generation of low-background physics experiments will require the
use of materials with unprecedented radio-purity. A gamma-counting facility at
the Kimballton Underground Research Facility (KURF) has been commissioned to
perform initial screening of materials for radioactivity primarily from
nuclides in the 238U and 232Th decay chains, 40K and cosmic-ray induced
isotopes. The facility consists of two commercial low-background high purity
germanium (HPGe) detectors. A continuum background reduction better than a
factor of 10 was achieved by going underground. This paper describes the
facility, detector systems, analysis techniques and selected assay results.Comment: 7 pages, 7 figures. Submitted to NIM
Îł-Oryzanol and tocopherol contents in residues of rice bran oil refining
AbstractRice bran oil (RBO) contains significant amounts of the natural antioxidants Îł-oryzanol and tocopherols, which are lost to a large degree during oil refining. This results in a number of industrial residues with high contents of these phytochemicals. With the aim of supporting the development of profitable industrial procedures for Îł-oryzanol and tocopherol recovery, the contents of these phytochemicals in all the residues produced during RBO refining were evaluated. The samples included residues from the degumming, soap precipitation, bleaching earth filtering, dewaxing and deodorisation distillation steps. The highest phytochemical concentrations were found in the precipitated soap for Îł-oryzanol (14.2mggâ1, representing 95.3% of total Îł-oryzanol in crude RBO), and in the deodorisation distillate for tocopherols (576mg100gâ1, representing 6.7% of total tocopherols in crude RBO). Therefore, among the residues of RBO processing, the deodorisation distillate was the best source of tocopherols. As the soap is further processed for the recovery of fatty acids, samples taken from every step of this secondary process, including hydrosoluble fraction, hydrolysed soap, distillation residue and purified fatty acid fraction, were also analyzed. The distillation residue left after fatty acid recovery from soap was found to be the best source of Îł-oryzanol (43.1mggâ1, representing 11.5% of total Îł-oryzanol in crude RBO)
Predicting User-Cell Association in Cellular Networks from Tracked Data
We consider the problem of predicting user location in the form of user-cell association in a cellular wireless network. This is motivated by resource optimization, for example switching base transceiver stations on or off to save on network energy consumption. We use GSM traces obtained from an operator, and compare several prediction methods. First, we find that, on our trace data, user cell sector association can be correctly predicted in ca. 80% of the cases. Second, we propose a new method, called âMARPLâ, which uses Market Basket Analysis to separate patterns where prediction by partial match (PPM) works well from those where repetition of the last known location (LAST) is best. Third, we propose that for network resource optimization, predicting the aggregate location of a user ensemble may be of more interest than separate predictions for all users; this motivates us to develop soft prediction methods, where the prediction is a spatial probability distribution rather than the most likely location. Last, we compare soft predictions methods to a classical time and space analysis (ISTAR). In terms of relative mean square error, MARPL with soft prediction and ISTAR perform better than all other methods, with a slight advantage to MARPL (but the numerical complexity of MARPL is much less than ISTAR)
Methane sources in gas hydrate-bearing cold-seeps : evidence from radiocarbon and stable isotopes
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 115 (2009): 102-109, doi:10.1016/j.marchem.2009.07.001.Fossil methane from the large and dynamic marine gas hydrate reservoir has the potential to influence oceanic and atmospheric carbon pools. However, natural radiocarbon (14C) measurements of gas hydrate methane have been extremely limited, and their use as a source and process indicator has not yet been systematically established. In this study, gas hydrate-bound and dissolved methane recovered from six geologically and geographically distinct high-gas-flux cold seeps was found to be 98 to 100% fossil based on its 14C content. Given this prevalence of fossil methane and the small contribution of gas hydrate (â€1%) to the present-day atmospheric methane flux, non-fossil contributions of gas hydrate methane to the atmosphere are not likely to be quantitatively significant. This conclusion is consistent with contemporary atmospheric methane budget calculations.
In combination with ÎŽ13C- and ÎŽD-methane measurements, we also determine the extent to which the low, but detectable, amounts of 14C (~ 1-2 percent modern carbon, pMC) in methane from two cold seeps might reflect in situ production from near-seafloor sediment organic carbon (SOC). A 14C mass balance approach using fossil methane and 14C-enriched SOC suggests that as much as 8 to 29% of hydrate-associated methane carbon may originate from SOC contained within the upper 6 meters of sediment. These findings validate the assumption of a predominantly fossil carbon source for marine gas hydrate, but also indicate that structural gas hydrate from at least certain cold seeps contains a component of methane produced during decomposition of non-fossil organic matter in near-surface sediment.This work was supported by the Office of Naval Research and Naval Research
Laboratory (NRL). Partial support was also provided by
the USGS Mendenhall Postdoctoral Research Fellowship Program to JWP, and NSF
Chemical Oceanography (OCE-0327423) and Integrated Carbon Cycle Research (EAR-
0403949) program support to JEB
Measurement of the branching fraction
The branching fraction is measured in a data sample
corresponding to 0.41 of integrated luminosity collected with the LHCb
detector at the LHC. This channel is sensitive to the penguin contributions
affecting the sin2 measurement from The
time-integrated branching fraction is measured to be . This is the most precise measurement to
date
Measurement of the CP-violating phase \phi s in Bs->J/\psi\pi+\pi- decays
Measurement of the mixing-induced CP-violating phase phi_s in Bs decays is of
prime importance in probing new physics. Here 7421 +/- 105 signal events from
the dominantly CP-odd final state J/\psi pi+ pi- are selected in 1/fb of pp
collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A
time-dependent fit to the data yields a value of
phi_s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard
Model expectation. No evidence of direct CP violation is found.Comment: 15 pages, 10 figures; minor revisions on May 23, 201
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) and the direct CP asymmetry in B0 -> K*0 gamma
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 phi gamma has been measured using an integrated luminosity of 1.0 fb-1
of pp collision data collected by the LHCb experiment at a centre-of-mass
energy of sqrt(s)=7 TeV. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 ->
phi gamma) = 1.23 +/- 0.06(stat.) +/- 0.04(syst.) +/- 0.10(fs/fd), where the
first uncertainty is statistical, the second is the experimental systematic
uncertainty and the third is associated with the ratio of fragmentation
fractions fs/fd. Using the world average value for BR(B0 -> K*0 gamma), the
branching fraction BR(Bs0 -> phi gamma) is measured to be (3.5 +/- 0.4) x
10^{-5}.
The direct CP asymmetry in B0 -> K*0 gamma decays has also been measured with
the same data and found to be A(CP)(B0 -> K*0 gamma) = (0.8 +/- 1.7(stat.) +/-
0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the
previous experimental results and theoretical expectations.Comment: 21 pages, 3 figues, 4 table
Model-independent search for CP violation in D0âKâK+ÏâÏ+ and D0âÏâÏ+Ï+Ïâ decays
A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states KâK+ÏâÏ+ and ÏâÏ+Ï+Ïâ is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fbâ1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the KâK+ÏâÏ+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the ÏâÏ+Ï+Ïâ final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity
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