4,661 research outputs found
The connection between superconducting phase correlations and spin excitations in YBaCuO: A magnetic field study
One of the most striking universal properties of the
high-transition-temperature (high-) superconductors is that they are all
derived from the hole-doping of their insulating antiferromagnetic (AF) parent
compounds. From the outset, the intimate relationship between magnetism and
superconductivity in these copper-oxides has intrigued researchers. Evidence
for this link comes from neutron scattering experiments that show the
unambiguous presence of short-range AF correlations (excitations) in cuprate
superconductors. Even so, the role of such excitations in the pairing mechanism
and superconductivity is still a subject of controversy. For
YBaCuO, where controls the hole-doping level, the most
prominent feature in the magnetic excitations spectra is the ``resonance''.
Here we show that for underdoped YBaCuO, where and
are below the optimal values, modest magnetic fields suppress the resonance
significantly, much more so for fields approximately perpendicular rather than
parallel to the CuO planes. Our results indicate that the resonance
measures pairing and phase coherence, suggesting that magnetism plays an
important role in the superconductivity of cuprates. The persistence of a field
effect above favors mechanisms with preformed pairs in the normal state
of underdoped cuprates.Comment: 12 pages, 4 figures, Nature (in press
Effectiveness of the multidisciplinary Risk Assessment and Management Program for Patients with Diabetes Mellitus (RAMP-DM) for diabetic microvascular complications: A population-based cohort study
Aim: To evaluate the effectiveness of the multidisciplinary Risk Assessment and Management Program for Patients with Diabetes Mellitus (RAMP-DM) in reducing the risks of microvascular complications. Methods: This prospective cohort study was conducted with 29,670 propensity-score-matched RAMP-DM participants and diabetes patients under the usual primary care (14,835 in each group). Study endpoints were the first occurrence of any diabetic microvascular complications, non-proliferative diabetic retinopathy/preproliferative diabetic retinopathy (NPDR/prePDR), sight-threatening diabetic retinopathy (STDR) or blindness, nephropathy, end-stage renal disease (ESRD), neuropathy and lower-limb ulcers or amputation. Log-rank tests and multivariable Cox proportional-hazards regressions were employed to estimate between-group differences in incidences of study endpoints. Results: After a median follow-up of 36 months with>41,000 person-years in each group, RAMP-DM participants had a lower incidence of microvascular complications (760 vs 935; adjusted hazard ratio [HR]: 0.73; 95% confidence interval [CI]: 0.66-0.81; P<0.001) and lower incidences of all specific microvascular complications except neuropathy (adjusted HR: 0.94; 95% CI: 0.61-1.45; P=0.778). Adjusted HRs for the RAMP-DM vs control group for ESRD, STDR or blindness, and lower-limb ulcers or amputation were 0.40 (95% CI: 0.24-0.69; P<0.001), 0.55 (95% CI: 0.39-0.78; P=0.001) and 0.49 (95% CI: 0.30-0.80; P=0.005), respectively. Conclusion: The RAMP-DM intervention was associated with lower incidences of all microvascular complications except neuropathy over a 3-year follow-up. These encouraging results constitute evidence that structured risk assessment and risk-stratified management provided by a multidisciplinary team is effective for reducing microvascular complications in diabetes patients.postprin
Production of α1,3-galactosyltransferase-deficient pigs
The enzyme α1,3-galactosyltransferase (α1,3GT or GGTA1) synthesizes α1,3galactose (α1,3Gal) epitopes (Galα1,3Galβ1,4GlcNAc-R), which are the major xenoantigens causing hyperacute rejection in pig-to-human xenotransplantation. Complete removal of α1,3Gal from pig organs is the critical step toward the success of xenotransplantation. We reported earlier the targeted disruption of one allele of the α1,3GT gene in cloned pigs. A selection procedure based on a bacteria[toxin was used to select for cells in which the second allele of the gene was knocked out. Sequencing analysis demonstrated that knockout of the second allele of the α1,3GT gene was caused by a T-to-G single point mutation at the second base of exon 9, which resulted in inactivation of the α1,3GT protein. Four healthy α1,3GT double-knockout female piglets were produced by three consecutive rounds of cloning. The piglets carrying a point mutation in the α1,3GT gene hold significant value, as they would allow production of α1,3Gal-deficient pigs free of antibiotic-resistance genes and thus have the potential to make a safer product for human use
Facile Synthesis of High Quality Graphene Nanoribbons
Graphene nanoribbons have attracted attention for their novel electronic and
spin transport properties1-6, and because nanoribbons less than 10 nm wide have
a band gap that can be used to make field effect transistors. However,
producing nanoribbons of very high quality, or in high volumes, remains a
challenge. Here, we show that pristine few-layer nanoribbons can be produced by
unzipping mildly gas-phase oxidized multiwalled carbon nanotube using
mechanical sonication in an organic solvent. The nanoribbons exhibit very high
quality, with smooth edges (as seen by high-resolution transmission electron
microscopy), low ratios of disorder to graphitic Raman bands, and the highest
electrical conductance and mobility reported to date (up to 5e2/h and 1500
cm2/Vs for ribbons 10-20 nm in width). Further, at low temperature, the
nanoribbons exhibit phase coherent transport and Fabry-Perot interference,
suggesting minimal defects and edge roughness. The yield of nanoribbons was ~2%
of the starting raw nanotube soot material, which was significantly higher than
previous methods capable of producing high quality narrow nanoribbons1. The
relatively high yield synthesis of pristine graphene nanoribbons will make
these materials easily accessible for a wide range of fundamental and practical
applications.Comment: Nature Nanotechnology in pres
The CEACAM1 expression is decreased in the liver of severely obese patients with or without diabetes
<p>Abstract</p> <p>Background</p> <p>Type 2 diabetes is mainly caused by insulin resistance. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is an important candidate for causing insulin resistance.</p> <p>Methods</p> <p>The CEACAM1 expression was evaluated immunohistochemically in the liver tissues of 99 severely obese or non-obese subjects with or without diabetes. The CEACAM1 expression was classified into two categories: a normal expression or a decreased expression.</p> <p>Results</p> <p>The CEACAM1 expression was markedly decreased in the hepatocytes with macrovesicular steatosis. A decreased CEACAM1 expression was noted in 29 (29%) of 99 cases. The incidence of a decreased CEACAM1 expression was significantly higher in high grade fatty liver as well as severe obesity with or without diabetes (p < 0.05). The incidence of a decreased CEACAM1 expression was not different between the diabetic and non-diabetic groups.</p> <p>Conclusions</p> <p>This data supports that a decreased CEACAM1 expression is related to obesity and a fatty liver.</p
Resonances in and
A partial wave analysis is presented of and
from a sample of 58M events in the BES II detector. The
is observed clearly in both sets of data, and parameters of the
Flatt\' e formula are determined accurately: (stat)
(syst) MeV/c, MeV/c, . The data also exhibit a strong peak
centred at MeV/c. It may be fitted with and a
dominant signal made from interfering with a smaller
component. There is evidence that the signal is
resonant, from interference with . There is also a state in with MeV/c and
MeV/c; spin 0 is preferred over spin 2. This state, , is
distinct from . The data contain a strong peak due to
. A shoulder on its upper side may be fitted by interference
between and .Comment: 17 pages, 6 figures, 1 table. Submitted to Phys. Lett.
Search for K_S K_L in psi'' decays
K_S K_L from psi'' decays is searched for using the psi'' data collected by
BESII at BEPC, the upper limit of the branching fraction is determined to be
B(psi''--> K_S K_L) < 2.1\times 10^{-4} at 90% C. L. The measurement is
compared with the prediction of the S- and D-wave mixing model of the
charmonia, based on the measurements of the branching fractions of J/psi-->K_S
K_L and psi'-->K_S K_L.Comment: 5 pages, 1 figur
Resonance in the electron-doped high-Tc superconductor Pr0.88LaCe0.12CuO(4-delta)
In conventional superconductors, the interaction that pairs the electrons to
form the superconducting state is mediated by lattice vibrations (phonons). In
high-transition temperature (high-Tc) copper oxides, it is generally believed
that magnetic excitations play a fundamental role in the superconducting
mechanism because superconductivity occurs when mobile 'electrons' or 'holes'
are doped into the antiferromagnetic parent compounds. Indeed, a sharp magnetic
excitation termed "resonance" has been observed by neutron scattering in a
number of hole-doped materials. The resonance is intimately related to
superconductivity, and its interaction with charged quasi-particles observed by
photoemission, optical conductivity, and tunneling suggests that it plays a
similar role as phonons in conventional superconductors. However, the relevance
of the resonance to high-Tc superconductivity has been in doubt because so far
it has been found only in hole-doped materials. Here we report the discovery of
the resonance in electron-doped superconducting Pr0.88LaCe0.12CuO(4-delta) (Tc
= 24 K). We find that the resonance energy (Er) is proportional to Tc via Er =
5.8kBTc (kB is the Boltzmann's constant) for all high-Tc superconductors
irrespective of electron- or hole-doping (Fig. 1e). Our results demonstrate
that the resonance is a fundamental property of the superconducting copper
oxides and therefore must play an essential role in the mechanism of
superconductivity.Comment: PDF file with 4 Figure
First Measurements of eta_c Decaying into K^+K^-2(pi^+pi^-) and 3(pi^+pi^-)
The decays of eta_c to K^+K^-2(pi^+pi^-) and 3(pi^+pi^-) are observed for the
first time using a sample of 5.8X10^7 J/\psi events collected by the BESII
detector. The product branching fractions are determined to be B(J/\psi-->gamma
eta_c)*B(eta_c-->K^+K^-pi^+pi^-pi^+pi^-)=(1.21+-0.32+-
0.23)X10^{-4}, and (J/\psi-->gamma eta_c)*
B(eta_c-->pi^+pi^-pi^+pi^-pi^+pi^-)= (2.59+-0.32+-0.48)X10^{-4}. The upper
limit for eta_c-->phi pi^+pi^-pi^+pi^- is also obtained as B(J/\psi-->gamma
eta_c)*B(eta_c--> phi pi^+pi^-pi^+pi^-)< 6.03 X10^{-5} at the 90% confidence
level.Comment: 11 pages, 4 figure
Study of psi(2S) decays to X J/psi
Using J/psi -> mu^+ mu^- decays from a sample of approximately 4 million
psi(2S) events collected with the BESI detector, the branching fractions of
psi(2S) -> eta J/psi, pi^0 pi^0 J/psi, and anything J/psi normalized to that of
psi(2S) -> pi^+ pi^- J/psi are measured. The results are B(psi(2S) -> eta
J/psi)/B(psi(2S) -> pi^+ pi^- J/psi) = 0.098 \pm 0.005 \pm 0.010, B(psi(2S) ->
pi^0 pi^0 J/psi)/B(psi(2S) -> pi^+ pi^- J/psi) = 0.570 \pm 0.009 \pm 0.026, and
B(psi(2S) -> anything J/psi)/B(psi(2S) -> pi^+ pi^- J/psi) = 1.867 \pm 0.026
\pm 0.055.Comment: 13 pages, 8 figure
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