376 research outputs found
Experimental evidence of s-wave superconductivity in bulk CaC
The temperature dependence of the in-plane magnetic penetration depth,
, has been measured in a c-axis oriented polycrystalline
CaC bulk sample using a high-resolution mutual inductance technique. A
clear exponential behavior of has been observed at low
temperatures, strongly suggesting isotropic s-wave pairing. Data fit using the
standard BCS theory yields Angstroem and
meV. The ratio
gives indication for a conventional weakly coupled superconductor.Comment: To appear in Phys. Rev. Let
Superconducting gap anisotropy of LuNi2B2C thin films from microwave surface impedance measurements
Surface impedance measurements of LuNi2B2C superconducting thin films as a
function of temperature have been performed down to 1.5 K and at 20 GHz using a
dielectric resonator technique. The magnetic penetration depth closely
reproduces the standard B.C.S. result, but with a reduced value of the energy
gap at low temperature. These data provide evidence for an anisotropic s-wave
character of the order parameter symmetry in LuNi2B2C. From the evaluation of
the real part of complex conductivity, we have observed constructive (type II)
coherence effects in the electromagnetic absorption below Tc.Comment: 15 pages, 4 figure
Alopecia universalis after discontinuation of pegylated interferon and ribavirin combination therapy for hepatitis C: a case report
Abstract For the last decade, the combination therapy of pegylated interferon (Peg-IFN) plus ribavirin (RBV) has been considered as the standard of care treatment for chronic hepatitis C virus (HCV) infection. However, it has been associated with an increased incidence of many adverse cutaneous reactions and emergence of autoantibodies or even autoimmune diseases. We report a case of irreversible alopecia universalis (AU) with complete hair loss extended to the whole body, which started after discontinuation of Peg-IFN/RBV combination therapy for chronic HCV infection. In conclusion, this case represents an uncommon presentation of a common disease. Physicians must be aware of the potential adverse reactions of an antiviral therapy containing IFN, which might occur even after the discontinuation, and fully inform the patient at the beginning of his treatment course. We hope that interferon-free regimens will utterly supplant interferon-based therapy for most or all HCV patients avoiding the emergence of autoimmune manifestations
Hybrid photonic-bandgap accelerating cavities
In a recent investigation, we studied two-dimensional point-defected photonic
bandgap cavities composed of dielectric rods arranged according to various
representative periodic and aperiodic lattices, with special emphasis on
possible applications to particle acceleration (along the longitudinal axis).
In this paper, we present a new study aimed at highlighting the possible
advantages of using hybrid structures based on the above dielectric
configurations, but featuring metallic rods in the outermost regions, for the
design of extremely-high quality factor, bandgap-based, accelerating
resonators. In this framework, we consider diverse configurations, with
different (periodic and aperiodic) lattice geometries, sizes, and
dielectric/metal fractions. Moreover, we also explore possible improvements
attainable via the use of superconducting plates to confine the electromagnetic
field in the longitudinal direction. Results from our comparative studies,
based on numerical full-wave simulations backed by experimental validations (at
room and cryogenic temperatures) in the microwave region, identify the
candidate parametric configurations capable of yielding the highest quality
factor.Comment: 13 pages, 5 figures, 3 tables. One figure and one reference added;
minor changes in the tex
Linear and nonlinear electrodynamic response of bulk CaC6 in the microwave regime
The linear and nonlinear response to a microwave electromagnetic field of two
c-axis oriented polycrystalline samples of the newly discovered superconductor
CaC6 (Tc = 11.5 K) is studied in the superconducting state down to 2 K. The
surface resistance Rs and the third order intermodulation distortion, arising
from a two-tone excitation, have been measured as a function of temperature and
microwave circulating power. Experiments are carried out using a dielectrically
loaded copper cavity operating at 7 GHz in a "hot finger" configuration. The
results confirm recent experimental findings that CaC6 behaves as a
weakly-coupled, fully gapped, superconductor. The weak power dependence of Rs
encourages a further investigation of this novel superconductor as a possible
alternative to Nb in specific microwave applications.Comment: 8 pages, 4 figures, submitted to Appl. Phys. Let
Microwave losses of bulk CaC6
We report a study of the temperature dependence of the surface resistance RS
in the graphite intercalated compound (GIC) CaC6, where superconductivity at
11.5 K was recently discovered. Experiments are carried out using a copper
dielectrically loaded cavity operating at 7 GHz in a "hot finger"
configuration. Bulk CaC6 samples have been synthesized from highly oriented
pyrolytic graphite. Microwave data allows to extract unique information on the
quasiparticle density and on the nature of pairing in superconductors. The
analysis of RS(T) confirms our recent experimental findings that CaC6 behaves
as a weakly-coupled, fully gapped, superconductor.Comment: 2 pages, submitted to Physica C (M2S-HTSC 2006 Proceedings
Evidence of a d to s-wave pairing symmetry transition in the electron-doped cuprate superconductor PrCeCuO
We present point contact spectroscopy (PCS) data for junctions between a
normal metal and the electron doped cuprate superconductor
PrCeCuO (PCCO). For the underdoped compositions of this cuprate
() we observe a peak in the conductance-voltage characteristics of
the point contact junctions. The shape and magnitude of this peak suggests the
presence of Andreev bound states at the surface of underdoped PCCO which is
evidence for a d-wave pairing symmetry. For overdoped PCCO () the
PCS data does not show any evidence of Andreev bound states at the surface
suggesting an s-wave pairing symmetry.Comment: 4 pages Latex, 4 eps figures included. Submitted to Phys. Rev. Let
Phase-sensitive Evidence for d-wave Pairing Symmetry in Electron-doped Cuprate Superconductors
We present phase-sensitive evidence that the electron-doped cuprates
Nd1.85Ce0.15CuO4-y (NCCO) and Pr1.85Ce0.15CuO4-y (PCCO) have d-wave pairing
symmetry. This evidence was obtained by observing the half-flux quantum effect,
using a scanning SQUID microscope, in c-axis oriented films of NCCO or PCCO
epitaxially grown on tricrystal [100] SrTiO3 substrates designed to be
frustrated for a d(x2-y2) order parameter. Samples with two other
configurations, designed to b unfrustrated for a d-wave superconductor, do not
show the half-flux quantum effect.Comment: 4 pages, Latex, 4 figure
Observation of Bound Surface States in Grain Boundary Junctions of High Temperature Superconductors
We have performed a detailed study of the tunneling spectra of bicrystal
grain boundary junctions (GBJs) fabricated from the HTS YBCO, BSCCO, LSCO, and
NCCO. In all experiments the tunneling direction was along the CuO planes. With
the exception of NCCO, for all materials a pronounced zero bias conductance
peak was observed which decreases with increasing temperature and disappears at
the critical temperature. These results can be explained by the presence of a
dominating d-wave symmetry of the order parameter resulting in the formation of
zero energy Andreev bound states at surfaces and interfaces of HTS. The absence
of a ZBCP for NCCO is consistent with a dominating s-wave symmetry of the pair
potential in this material. The observed nonlinear shift of spectral weight to
finite energies by applying a magnetic field is in qualitative agreement with
recent theoretical predictions.Comment: 4 pages, 4 figures, to be published in Phys. Rev.
More anxious than depressed: prevalence and correlates in a 15-nation study of anxiety disorders in people with type 2 diabetes mellitus
Background Anxiety disorder, one of the highly disabling, prevalent and common mental disorders, is known to be more prevalent in persons with type 2 diabetes mellitus (T2DM) than the general population, and the comorbid presence of anxiety disorders is known to have an impact on the diabetes outcome and the quality of life. However, the information on the type of anxiety disorder and its prevalence in persons with T2DM is limited. Aims To assess the prevalence and correlates of anxiety disorder in people with type 2 diabetes in different countries.
Methods People aged 18–65 years with diabetes and treated in outpatient settings were recruited in 15 countries and underwent a psychiatric interview with the Mini-International Neuropsychiatric Interview. Demographic and medical record data were collected. Results A total of 3170 people with type 2 diabetes (56.2% women; with mean (SD) duration of diabetes 10.01 (7.0) years) participated. The overall prevalence of anxiety disorders in type 2 diabetic persons was 18%; however, 2.8% of the study population had more than one type of anxiety disorder. The most prevalent anxiety disorders were generalised anxiety disorder (8.1%) and panic disorder (5.1%). Female gender, presence of diabetic complications, longer duration of diabetes and poorer glycaemic control (HbA1c levels) were significantly associated with comorbid anxiety disorder. A higher prevalence of anxiety disorders was observed in Ukraine, Saudi Arabia and Argentina with a lower prevalence in Bangladesh and India.
Conclusions Our international study shows that people with type 2 diabetes have a high prevalence of anxiety disorders, especially women, those with diabetic complications, those with a longer duration of diabetes and poorer glycaemic control. Early identification and appropriate timely care of psychiatric problems of people with type 2 diabetes is warranted
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