568 research outputs found
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In Reply - When comparing the infection risks of transparent
vs gauze dressings used on central venous catheters, the
RRs were 1.78 for catheter-tip infection, 1.63 for bacteremia,
and 1.69 for catheter sepsis. These RRs represent the best
assessment of the overall risk associated with the use of
transparent dressings. (For catheter-tip infection, P<.001;
for catheter sepsis, P=.06.) In our discussion we used the
word "trend" in discussing this level of significance. The
choice of .05 as the level of "statistical significance" is arbitrary,
and given the RRs demonstrated in the meta-analysis,
further studies are warranted before accepting transparent
dressings as safe
Synthesis and characterization of atomically-thin graphite films on a silicon carbide substrate
This paper reports the synthesis and detailed characterization of graphite
thin films produced by thermal decomposition of the (0001) face of a 6H-SiC
wafer, demonstrating the successful growth of single crystalline films down to
approximately one graphene layer. The growth and characterization were carried
out in ultrahigh vacuum (UHV) conditions. The growth process and sample quality
were monitored by low-energy electron diffraction, and the thickness of the
sample was determined by core level x-ray photoelectron spectroscopy.
High-resolution angle-resolved photoemission spectroscopy shows constant energy
map patterns, which are very sharp and fully momentum-resolved, but nonetheless
not resolution limited. We discuss the implications of this observation in
connection with scanning electron microscopy data, as well as with previous
studies
Two nonmagnetic impurities in the DSC and DDW state of the cuprate superconductors as a probe for the pseudogap
The quantum interference between two nonmagnetic impurities is studied
numerically in both the d-wave superconducting (DSC) and the d-density wave
(DDW) state. In all calculations we include the tunnelling through excited
states from the CuO planes to the BiO layer probed by the STM tip. Compared
to the single impurity case, a systematic study of the modulations in the
two-impurity local density of states can distinguish between the DSC or DDW
states. This is important if the origin of the pseudogap phase is caused by
preformed pairs or DDW order. Furthermore, in the DSC state the study of the
LDOS around two nonmagnetic impurities provide further tests for the potential
scattering model versus more strongly correlated models.Comment: 6 pages, 6 figure
Current constraints on Cosmological Parameters from Microwave Background Anisotropies
We compare the latest observations of Cosmic Microwave Background (CMB)
Anisotropies with the theoretical predictions of the standard scenario of
structure formation. Assuming a primordial power spectrum of adiabatic
perturbations we found that the total energy density is constrained to be
while the energy density in baryon and Cold Dark
Matter (CDM) are and ,
(all at 68% C.L.) respectively. The primordial spectrum is consistent with
scale invariance, () and the age of the universe is
Gyrs. Adding informations from Large Scale Structure and
Supernovae, we found a strong evidence for a cosmological constant
and a value of the Hubble parameter
. Restricting this combined analysis to flat universes, we put
constraints on possible 'extensions' of the standard scenario. A gravity waves
contribution to the quadrupole anisotropy is limited to be (95%
c.l.). A constant equation of state for the dark energy component is bound to
be (95% c.l.). We constrain the effective relativistic degrees
of freedom and the neutrino chemical potential and (massless neutrinos).Comment: The status of cosmological parameters before WMAP. In press on Phys.
Rev. D., Rapid Communication, 6 pages, 5 figure
A determination of the pairing interaction in the high Tc cuprate superconductor Tl2Ba2CaCu2O8 (Tl2212)
We have measured the near-normal reflectance of Tl2Ba2CaCu2O8 (Tl2212) for
energies from 0.1 to 4.0 eV at room temperature and used a Kramers-Kronig
analysis to find the complex, frequency dependent dielectric function, from
which the optical conductivity was determined. Using
Thermal-Difference-Reflectance (TDR) Spectroscopy the reflectance of the sample
in the normal state just above the superconducting transition, and in the
superconducting state were then obtained. From these data we determined the
ratio of the superconducting- to normal-state optical conductivities. Mattis
and Bardeen had calculated this function within the BCS theory, where the gap
is a fixed energy-independent quantity. Taking into account the retarded nature
of the electron-phonon coupling results in a complex, energy dependent gap
causing deviations from the Mattis-Bardeen plot at energies where the phonon
coupling function is large. We find a typical deviation near the phonon
energies in Tl2212, and in addition, at 1.2 and 1.7eV. The phonon, and these
electronic terms can each be described by a coupling constant. None of which by
itself gives rise to a high transition temperature, but the combination does.
Using Resonant Inelastic X-Ray Scattering (RIXS) we find that the d-to-d
excitations of the cuprate ion in Tl2212 fall at the same energies as the dips
in the Mattis-Bardeen plot. We conclude that the high superconducting
transition temperature of the cuprates is due to the sum of the phonon
interaction, and interactions with the Cu-ion d-shell.Comment: Preprint submitted to Physica C. Paper presented at M2S-HTSC-VIII,
Dresden, Germany, July 9-14,200
Structures associated with feeding in three broad-mouthed, benthic fish groups
The flatheads, toadfishes, and goosefishes discussed here hold certain features in common. All are bottom-living forms with depressed head areas and broad gapes, and all eat large food items: fishes and/or crabs. All have developed structural specializations in association with this diet. The three groups are at most distantly related, and their feeding specializations are different and have evolved from different bases. In flatheads the combination of large food items and depressed head regions seems to have led to the separation of the two halves of the pelvic girdle, a feature in which they differ from their scorpaenoid relatives. Toadfish peculiarities associated with feeding are various but most notable in those that pass crabs they eat through the gape and into the mouth. Goosefish feeding is centered around the use of a lure to attract prey to within striking distance. The three fish groups are discussed separately, but their feeding structures are compared to one another in the final section of the paper.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42639/1/10641_2004_Article_BF00005053.pd
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
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