411 research outputs found
Carbon Doping of MgB2 by Toluene and Malic-Acid-in-Toluene
The decomposition of malic acid in the presence of Mg and B was studied using
Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA)
which revealed that malic acid reacted with Mg but not B. Also, the addition of
toluene to dissolve malic acid followed by subsequent drying resulted in no
reaction with Mg, indicating that the malic acid had decomposed during the
dissolution/drying stage. The total carbon contributed by toluene versus a
toluene/5 wt% malic acid mixture was measured using a LECO CS600 carbon
analyzer. The toluene sample contained ~0.4 wt% C while the toluene/malic acid
mixture had ~1.5 wt% C, demonstrating that the toluene contributed a
significant amount of carbon to the final product. Resistivity measurements on
powder-in-tube MgB2 monofilamentary wires established that the toluene/malic
acid doped sample had the highest Bc2. However, the toluene-only sample had the
highest transport Jc over most of the magnetic field range (0-9 T), equaled
only by that of toluene/malic acid sample in fields above 9 T.Comment: 17 pages, 6 figures, 1 tabl
On the Quantum Invariant for the Spherical Seifert Manifold
We study the Witten--Reshetikhin--Turaev SU(2) invariant for the Seifert
manifold where is a finite subgroup of SU(2). We show
that the WRT invariants can be written in terms of the Eichler integral of the
modular forms with half-integral weight, and we give an exact asymptotic
expansion of the invariants by use of the nearly modular property of the
Eichler integral. We further discuss that those modular forms have a direct
connection with the polyhedral group by showing that the invariant polynomials
of modular forms satisfy the polyhedral equations associated to .Comment: 36 page
Scintillation Counters for the D0 Muon Upgrade
We present the results of an upgrade to the D0 muon system. Scintillating
counters have been added to the existing central D0 muon system to provide
rejection for cosmic ray muons and out-of-time background, and to provide
additional fast timing information for muons in an upgraded Tevatron.
Performance and results from the 1994-1996 Tevatron run are presented.Comment: 30 pages, 25 postscript figure
Iodine binding to humic acid
The rate of reactions between humic acid (HA) and iodide (I-) and iodate (IO3-) have been investigated in suspensions spiked with 129I at concentrations of 22, 44 and 88 ”g L-1 and stored at 10oC. Changes in the speciation of 129I-, 129IO3- and mixed (129I-+129IO3-) spikes were monitored over 77 days using liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS). In suspensions spiked with 129I- 25% of the added I- was transformed into organic iodine (Org-129I) within 77 days and there was no evidence of 129IO3- formation. By contrast, rapid loss of 129IO3- and increase in both 129I- and Org-129I was observed in 129IO3--spiked suspensions. However, the rate of Org-129I production was greater in mixed systems compared to 129IO3--spiked suspensions with the same total 129I concentration, possibly indicating IO3-âI- redox coupling. Size exclusion chromatography (SEC) demonstrated that Org-129I was present in both high and low molecular weight fractions of the HA although a slight preference to bond with the lower molecular weight fractions was observed indicating that, after 77 days, the spiked isotope had not fully mixed with the native 127I pool. Iodine transformations were modelled using first order rate equations and fitted rate coefficients determined. However, extrapolation of the model to 250 days indicated that a pseudo-steady state would be attained after ~ 200 days but that the proportion of 129I incorporated into HA was less than that of 127I indicating the presence of a recalcitrant pool of 127I that was unavailable for isotopic mixing
Numerical study of the thermoelectric power factor in ultra-thin Si nanowires
Low dimensional structures have demonstrated improved thermoelectric (TE)
performance because of a drastic reduction in their thermal conductivity,
{\kappa}l. This has been observed for a variety of materials, even for
traditionally poor thermoelectrics such as silicon. Other than the reduction in
{\kappa}l, further improvements in the TE figure of merit ZT could potentially
originate from the thermoelectric power factor. In this work, we couple the
ballistic (Landauer) and diffusive linearized Boltzmann electron transport
theory to the atomistic sp3d5s*-spin-orbit-coupled tight-binding (TB)
electronic structure model. We calculate the room temperature electrical
conductivity, Seebeck coefficient, and power factor of narrow 1D Si nanowires
(NWs). We describe the numerical formulation of coupling TB to those transport
formalisms, the approximations involved, and explain the differences in the
conclusions obtained from each model. We investigate the effects of cross
section size, transport orientation and confinement orientation, and the
influence of the different scattering mechanisms. We show that such methodology
can provide robust results for structures including thousands of atoms in the
simulation domain and extending to length scales beyond 10nm, and point towards
insightful design directions using the length scale and geometry as a design
degree of freedom. We find that the effect of low dimensionality on the
thermoelectric power factor of Si NWs can be observed at diameters below ~7nm,
and that quantum confinement and different transport orientations offer the
possibility for power factor optimization.Comment: 42 pages, 14 figures; Journal of Computational Electronics, 201
The association of AGTR2 polymorphisms with preeclampsia and uterine artery bilateral notching is modulated by maternal BMI
On behalf of the SCOPE consortiumIntroductionThis study aimed to determine the association of AGTR1 and AGTR2 polymorphisms with preeclampsia and whether these are affected by environmental factors and fetal sex.MethodsOverall 3234 healthy nulliparous women, their partners and babies were recruited prospectively to the SCOPE study in Adelaide and Auckland. Data analyses were confined to 2121 Caucasian parent-infant trios, among whom 123 had preeclamptic pregnancies. 1185 uncomplicated pregnancies served as controls. DNA was extracted from buffy coats and genotyped by utilizing the Sequenom MassARRAY system. Doppler sonography on the uterine arteries was performed at 20 weeks' gestation.ResultsFour polymorphisms in AGTR1 and AGTR2 genes, including AGTR1 A1166C, AGTR2 C4599A, AGTR2 A1675G and AGTR2 T1134C, were selected and significant associations were predominately observed for AGTR2 C4599A. When the cohort was stratified by maternal BMI, in women with BMIÂ â„Â 25Â kg/m(2), the AGTR2 C4599A AA genotype in mothers and neonates was associated with an increased risk for preeclampsia compared with the CC genotype [adjusted OR 2.1 (95% CI 1.0-4.2) and adjusted OR 3.0 (95% CI 1.4-6.4), respectively]. In the same subset of women, paternal AGTR2 C4599A A allele was associated with an increased risk for preeclampsia and uterine artery bilateral notching at 20 weeks' gestation compared with the C allele [adjusted OR 1.9 (95% CI 1.1-3.3) and adjusted OR 2.1 (95% CI 1.3-3.4), respectively].ConclusionAGTR2 C4599A in mothers, fathers and babies was associated with preeclampsia and this association was only apparent in pregnancies in which the women had a BMIÂ â„Â 25Â kg/m(2), suggesting a gene-environment interaction.A. Zhou, G.A. Dekker, E.R. Lumbers, S.Y. Lee, S.D. Thompson, L.M.E. McCowan, C.T. Robert
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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