901 research outputs found
Spectrometry for Analysis of Acylcarnitines in Dried Postmortem Blood Specimens Collected at
7. Feinstein JA, O'Brien K. âAcute metabolic decompensation in an adult patient with isovaleric academia, â South Med J. 2003 May; 96(5): 500-3. 8. Fries, MH, Rinaldo P, Schmidt-Sommerfeld E, Jurecki E, Packman S. âIsovaleric acidemia: Respons
MP2RAGEME: T<sub>1</sub> , T<sub>2</sub><sup>*</sup> , and QSM mapping in one sequence at 7 tesla
Density Matrix Renormalization Group Applied to the Ground State of the XY-Spin-Peierls System
We use the density matrix renormalization group (DMRG) to map out the ground
state of a XY-spin chain coupled to dispersionless phonons of frequency . We confirm the existence of a critical spin-phonon coupling for the onset of the spin gap bearing the signature of
a Kosterlitz-Thouless transition. We also observe a classical-quantum crossover
when the spin-Peierls gap is of order . In the classical
regime, , the mean-field parameters are strongly renormalized
by non-adiabatic corrections. This is the first application of the DMRG to
phonons.Comment: 10 pages, 5 figures. To be published in PR
Triplet Dispersion in CuGeO_3: Perturbative Analysis
We reconsider the 2d model for CuGeO_3 introduced previously (Phys. Rev.
Lett. 79, 163 (1997)). Using a computer aided perturbation method based on flow
equations we expand the 1-triplet dispersion up to 10th order. The expansion is
provided as a polynom in the model parameters. The latter are fixed by fitting
the theoretical result to experimental data obtained by INS. For a dimerization
delta = 0.08(1) we find an excellent agreement with experiment. This value is
at least 2 to 3 times higher than values deduced previously from 1d chain
approaches. For the intrachain frustration alpha_0 we find a smaller value of
0.25(3). The existence of interchain frustration conjectured previously is
confirmed by the analysis of temperature dependent susceptibility.Comment: 8 pages, 10 figures, submitted to Phys. Rev.
The EDELWEISS Experiment : Status and Outlook
The EDELWEISS Dark Matter search uses low-temperature Ge detectors with heat
and ionisation read- out to identify nuclear recoils induced by elastic
collisions with WIMPs from the galactic halo. Results from the operation of 70
g and 320 g Ge detectors in the low-background environment of the Modane
Underground Laboratory (LSM) are presented.Comment: International Conference on Dark Matter in Astro and Particle Physics
(Dark 2000), Heidelberg, Germany, 10-16 Jul 2000, v3 minor revision
Dark Matter Search in the Edelweiss Experiment
Preliminary results obtained with 320g bolometers with simultaneous
ionization and heat measurements are described. After a few weeks of data
taking, data accumulated with one of these detectors are beginning to exclude
the upper part of the DAMA region. Prospects for the present run and the second
stage of the experiment, EDELWEISS-II, using an innovative reversed cryostat
allowing data taking with 100 detectors, are briefly described.Comment: IDM 2000, 3rd International Workshop on the Identification of Dark
Matter, York (GB), 18-22/09/2000, v2.0 minor modification
Background discrimination capabilities of a heat and ionization germanium cryogenic detector
The discrimination capabilities of a 70 g heat and ionization Ge bolometer
are studied. This first prototype has been used by the EDELWEISS Dark Matter
experiment, installed in the Laboratoire Souterrain de Modane, for direct
detection of WIMPs. Gamma and neutron calibrations demonstrate that this type
of detector is able to reject more than 99.6% of the background while retaining
95% of the signal, provided that the background events distribution is not
biased towards the surface of the Ge crystal. However, the 1.17 kg.day of data
taken in a relatively important radioactive environment show an extra
population slightly overlapping the signal. This background is likely due to
interactions of low energy photons or electrons near the surface of the
crystal, and is somewhat reduced by applying a higher charge-collecting inverse
bias voltage (-6 V instead of -2 V) to the Ge diode. Despite this
contamination, more than 98% of the background can be rejected while retaining
50% of the signal. This yields a conservative upper limit of 0.7
event.day^{-1}.kg^{-1}.keV^{-1}_{recoil} at 90% confidence level in the 15-45
keV recoil energy interval; the present sensitivity appears to be limited by
the fast ambient neutrons. Upgrades in progress on the installation are
summarized.Comment: Submitted to Astroparticle Physics, 14 page
Event categories in the EDELWEISS WIMP search experiment
Four categories of events have been identified in the EDELWEISS-I dark matter
experiment using germanium cryogenic detectors measuring simultaneously charge
and heat signals. These categories of events are interpreted as electron and
nuclear interactions occurring in the volume of the detector, and electron and
nuclear interactions occurring close to the surface of the detectors(10-20 mu-m
of the surface). We discuss the hypothesis that low energy surface nuclear
recoils,which seem to have been unnoticed by previous WIMP searches, may
provide an interpretation of the anomalous events recorded by the UKDMC and
Saclay NaI experiments. The present analysis points to the necessity of taking
into account surface nuclear and electron recoil interactions for a reliable
estimate of background rejection factors.Comment: 11 pages, submitted to Phys. Lett.
First Results of the EDELWEISS WIMP Search using a 320 g Heat-and-Ionization Ge Detector
The EDELWEISS collaboration has performed a direct search for WIMP dark
matter using a 320 g heat-and-ionization cryogenic Ge detector operated in a
low-background environment in the Laboratoire Souterrain de Modane. No nuclear
recoils are observed in the fiducial volume in the 30-200 keV energy range
during an effective exposure of 4.53 kg.days. Limits for the cross-section for
the spin-independent interaction of WIMPs and nucleons are set in the framework
of the Minimal Supersymmetric Standard Model (MSSM). The central value of the
signal reported by the experiment DAMA is excluded at 90% CL.Comment: 14 pages, Latex, 4 figures. Submitted to Phys. Lett.
Orthogonally bifunctionalised polyacrylamide nanoparticles: a support for the assembly of multifunctional nanodevices
Polyacrylamide nanoparticles bearing two orthogonal reactive functionalities were prepared by reverse microemulsion polymerisation. Water-soluble photosensitisers and peptide or carbohydrate moieties were sequentially attached to the new nanospecies by orthogonal conjugations based on copper- catalysed azide-alkyne cycloaddition and isothiocyanate chemistry
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