811 research outputs found
Temperature Dependence of the Cyclotron Mass in n-Type CdS
Recent cyclotron resonance experiments in n-type CdS at ultra-high magnetic
fields have revealed a pronounced maximum of the electron cyclotron mass as a
function of temperature. In order to interpret these data, we calculate the
magneto-absorption spectra of polarons in n-CdS using the arbitrary-coupling
approach. We show that in high magnetic fields the polaron effects beyond the
weak-coupling approximation clearly reveal themselves in the magneto-optical
absorption even at relatively small values of the Froehlich coupling constant.
In particular, those effects result in a non-monotonous behaviour of the
cyclotron mass as a function of temperature. We extend the theory to take into
account a combined effect of several scattering mechanisms on the
magneto-absorption spectra. The extended theory allows us to interpret
quantitatively the experimentally observed behaviour of the cyclotron mass in
CdS.Comment: 4 pages, 3 figures, E-mail addresses: [email protected],
[email protected]
Oliguria without serum creatinine increase after living donor liver transplantation is associated with adverse post-operative outcomes
Background: Acute kidney injury (AKI) is a common complication after liver transplantation and is associated with significant morbidity and mortality. Although clinical guidelines recommend defining AKI based on serum creatinine increase and oliguria, the validity and utility of the oliguric component of AKI definition remains largely unexplored. This study examined the incidence and the impact on clinical outcomes of oliguria meeting the urine output criterion of AKI in patients undergoing liver transplantation. The authors hypothesised that oliguria was an independent risk factor for adverse post-operative outcomes. Methods: This study retrospectively examined 320 patients who underwent living donor liver transplantation at our centre. AKI stages were allocated according to recent guidelines based on serum creatinine or urine output within 7 days of surgery. Results: The incidence of oliguria meeting the urine output criterion of AKI was 50.3%. Compared with creatinine criterion alone, incorporating oliguria into the diagnostic criteria dramatically increased the measured incidence of AKI from 39.7% to 62.2%. Compared with patients diagnosed without AKI using either criterion, oliguric patients without serum creatinine increase had significantly longer intensive care unit stays (median: 5 vs. 4 days, P = 0.016), longer hospital stays (median: 60 vs. 49 days, P = 0.014) and lower chronic kidney disease-free survival rate on post-operative day 90 (54.2% vs. 73.3%, P = 0.008). Conclusion: Oliguria is common after liver transplantation, and incorporating oliguria into the diagnostic criteria dramatically increases the measured incidence of AKI. Oliguria without serum creatinine increase was significantly associated with adverse post-operative outcomes
Large Magnetic Susceptibility Anisotropy of Metallic Carbon Nanotubes
Through magnetic linear dichroism spectroscopy, the magnetic susceptibility
anisotropy of metallic single-walled carbon nanotubes has been extracted and
found to be 2-4 times greater than values for semiconducting single-walled
carbon nanotubes. This large anisotropy is consistent with our calculations and
can be understood in terms of large orbital paramagnetism of electrons in
metallic nanotubes arising from the Aharonov-Bohm-phase-induced gap opening in
a parallel field. We also compare our values with previous work for
semiconducting nanotubes, which confirm a break from the prediction that the
magnetic susceptibility anisotropy increases linearly with the diameter.Comment: 4 pages, 4 figure
Possible Phase Transition Deep Inside the Hidden Order Phase of Ultraclean URu2Si2
To elucidate the underlying nature of the hidden order (HO) state in
heavy-fermion compound URu2Si2, we measure electrical transport properties of
ultraclean crystals in a high field/low temperature regime. Unlike previous
studies, the present system with much less impurity scattering resolves a
distinct anomaly of the Hall resistivity at H*=22.5 T well below the
destruction field of the HO phase ~36 T. In addition, a novel quantum
oscillation appears above a magnetic field slightly below H*. These results
indicate an abrupt reconstruction of the Fermi surface, which implies a
possible phase transition well within the HO phase caused by a band-dependent
destruction of the HO parameter. The present results definitely indicate that
the HO transition should be described by an itinerant electron picture.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
Pathological Investigation of Congenital Bicuspid Aortic Valve Stenosis, Compared with Atherosclerotic Tricuspid Aortic Valve Stenosis and Congenital Bicuspid Aortic Valve Regurgitation
Congenital bicuspid aortic valve (CBAV) is the main cause of aortic stenosis (AS) in young adults. However, the histopathological features of AS in patients with CBAV have not been fully investigated.We examined specimens of aortic valve leaflets obtained from patients who had undergone aortic valve re/placement at our institution for severe AS with CBAV (n = 24, CBAV-AS group), severe AS with tricuspid aortic valve (n = 24, TAV-AS group), and severe aortic regurgitation (AR) with CBAV (n = 24, CBAV-AR group). We compared the histopathological features among the three groups. Pathological features were classified using semi-quantitative methods (graded on a scale 0 to 3) by experienced pathologists without knowledge of the patients' backgrounds. The severity of inflammation, neovascularization, and calcium and cholesterol deposition did not differ between the CBAV-AS and TAV-AS groups, and these four parameters were less marked in the CBAV-AR group than in the CBAV-AS (all p<0.01). Meanwhile, the grade of valvular fibrosis was greater in the CBAV-AS group, compared with the TAV-AS and CBAV-AR groups (both p<0.01). In AS patients, thickness of fibrotic lesions was greater on the aortic side than on the ventricular side (both p<0.01). Meanwhile, thickness of fibrotic lesions was comparable between the aortic and ventricular sides in CBAV-AR patients (p = 0.35).Valvular fibrosis, especially on the aortic side, was greater in patients with CBAV-AS than in those without, suggesting a difference in the pathogenesis of AS between CBAV and TAV
Optical Method for Determination of Carrier Density in Modulation Doped Quantum Wells
An optical method is suggested to determine the concentration of
two-dimensional electrons in modulation-doped quantum wells at low and moderate
electron densities between 10^{9} and 2x10^{11} cm^{-2}. The method is based on
an analysis of magneto-reflectivity spectra of charged excitons (trions). The
circular polarization degree and the oscillator strength of the charged
excitons contain information about the density and spin polarization of
two-dimensional electron gas. The method is applied to CdTe/(Cd,Mg)Te and
ZnSe/Zn,Mg)(S,Se) heterostructures
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