1,195 research outputs found
Signatures of Inelastic Scattering in Coulomb-Blockade Quantum Dots
We calculate the finite-temperature conductance peak-height distributions in
Coublomb-blockade quantum dots in the limit where the inelastic scattering rate
in the dot is large compared with the mean elastic tunneling rate. The relative
reduction of the standard deviation of the peak-height distribution by a
time-reversal symmetry-breaking magnetic field, which is essentially
temperature-independent in the elastic limit, is enhanced by the inclusion of
inelastic scattering at finite temperature. We suggest this quantity as an
independent experimental probe for inelastic scattering in closed dots.Comment: 4 pages, 3 eps figures, revtex
Inter-study reproducibility of arterial spin labelling magnetic resonance imaging for measurement of renal perfusion in healthy volunteers at 3 Tesla
Background:
Measurement of renal perfusion is a crucial part of measuring kidney function. Arterial spin labelling magnetic resonance imaging (ASL MRI) is a non-invasive method of measuring renal perfusion using magnetised blood as endogenous contrast. We studied the reproducibility of ASL MRI in normal volunteers.<p></p>
Methods:
ASL MRI was performed in healthy volunteers on 2 occasions using a 3.0 Tesla MRI scanner with flow-sensitive alternating inversion recovery (FAIR) perfusion preparation with a steady state free precession (True-FISP) pulse sequence. Kidney volume was measured from the scanned images. Routine serum and urine biochemistry were measured prior to MRI scanning.<p></p>
Results:
12 volunteers were recruited yielding 24 kidneys, with a mean participant age of 44.1 ± 14.6 years, blood pressure of 136/82 mmHg and chronic kidney disease epidemiology formula estimated glomerular filtration rate (CKD EPI eGFR) of 98.3 ± 15.1 ml/min/1.73 m2. Mean kidney volumes measured using the ellipsoid formula and voxel count method were 123.5 ± 25.5 cm3, and 156.7 ± 28.9 cm3 respectively. Mean kidney perfusion was 229 ± 41 ml/min/100 g and mean cortical perfusion was 327 ± 63 ml/min/100 g, with no significant differences between ASL MRIs. Mean absolute kidney perfusion calculated from kidney volume measured during the scan was 373 ± 71 ml/min. Bland Altman plots were constructed of the cortical and whole kidney perfusion measurements made at ASL MRIs 1 and 2. These showed good agreement between measurements, with a random distribution of means plotted against differences observed. The intra class correlation for cortical perfusion was 0.85, whilst the within subject coefficient of variance was 9.2%. The intra class correlation for whole kidney perfusion was 0.86, whilst the within subject coefficient of variance was 7.1%.<p></p>
Conclusions:
ASL MRI at 3.0 Tesla provides a repeatable method of measuring renal perfusion in healthy subjects without the need for administration of exogenous compounds. We have established normal values for renal perfusion using ASL MRI in a cohort of healthy volunteers.<p></p>
Spectral fluctuations effects on conductance peak height statistics in quantum dots
Within random matrix theory for quantum dots, both the dot's one-particle
eigenlevels and the dot-lead couplings are statistically distributed. While the
effect of the latter on the conductance is obvious and has been taken into
account in the literature, the statistical distribution of the one-particle
eigenlevels is generally replaced by a picket-fence spectrum. Here we take the
random matrix theory eigenlevel distribution explicitly into account and
observe significant deviations in the conductance distribution and
magnetoconductance of closed quantum dots at experimentally relevant
temperatures.Comment: 3 pages, 2 figure
Immunomodulatory Therapy for MIS-C.
Studies comparing initial therapy for multisystem inflammatory syndrome in children (MIS-C) provided conflicting results.
To compare outcomes in MIS-C patients treated with intravenous immunoglobulin (IVIG), glucocorticoids, or the combination thereof.
Medline, Embase, CENTRAL and WOS, from January 2020 to February 2022.
Randomized or observational comparative studies including MIS-C patients <21 years.
Two reviewers independently selected studies and obtained individual participant data. The main outcome was cardiovascular dysfunction (CD), defined as left ventricular ejection fraction < 55% or vasopressor requirement ≥ day 2 of initial therapy, analyzed with a propensity score-matched analysis.
Of 2635 studies identified, 3 nonrandomized cohorts were included. The meta-analysis included 958 children. IVIG plus glucocorticoids group as compared with IVIG alone had improved CD (odds ratio [OR] 0.62 [0.42-0.91]). Glucocorticoids alone group as compared with IVIG alone did not have improved CD (OR 0.57 [0.31-1.05]). Glucocorticoids alone group as compared with IVIG plus glucocorticoids did not have improved CD (OR 0.67 [0.24-1.86]). Secondary analyses found better outcomes associated with IVIG plus glucocorticoids compared with glucocorticoids alone (fever ≥ day 2, need for secondary therapies) and better outcomes associated with glucocorticoids alone compared with IVIG alone (left ventricular ejection fraction < 55% ≥ day 2).
Nonrandomized nature of included studies.
In a meta-analysis of MIS-C patients, IVIG plus glucocorticoids was associated with improved CD compared with IVIG alone. Glucocorticoids alone was not associated with improved CD compared with IVIG alone or IVIG plus glucocorticoids
Quantum Chaos in Open versus Closed Quantum Dots: Signatures of Interacting Particles
This paper reviews recent studies of mesoscopic fluctuations in transport
through ballistic quantum dots, emphasizing differences between conduction
through open dots and tunneling through nearly isolated dots. Both the open
dots and the tunnel-contacted dots show random, repeatable conductance
fluctuations with universal statistical proper-ties that are accurately
characterized by a variety of theoretical models including random matrix
theory, semiclassical methods and nonlinear sigma model calculations. We apply
these results in open dots to extract the dephasing rate of electrons within
the dot. In the tunneling regime, electron interaction dominates transport
since the tunneling of a single electron onto a small dot may be sufficiently
energetically costly (due to the small capacitance) that conduction is
suppressed altogether. How interactions combine with quantum interference are
best seen in this regime.Comment: 15 pages, 11 figures, PDF 2.1 format, to appear in "Chaos, Solitons &
Fractals
Optical pumping NMR in the compensated semiconductor InP:Fe
The optical pumping NMR effect in the compensated semiconductor InP:Fe has
been investigated in terms of the dependences of photon energy (E_p), helicity
(sigma+-), and exposure time (tau_L) of infrared lights. The {31}P and {115}In
signal enhancements show large sigma+- asymmetries and anomalous oscillations
as a function of E_p. We find that (i) the oscillation period as a function of
E_p is similar for {31}P and {115}In and almost field independent in spite of
significant reduction of the enhancement in higher fields. (ii) A
characteristic time for buildup of the {31}P polarization under the light
exposure shows strong E_p-dependence, but is almost independent of sigma+-.
(iii) The buildup times for {31}P and {115}In are of the same order (10^3 s),
although the spin-lattice relaxation times (T_1) are different by more than
three orders of magnitude between them. The results are discussed in terms of
(1) discrete energy spectra due to donor-acceptor pairs (DAPs) in compensated
semiconductors, and (2) interplay between {31}P and dipolar ordered indium
nuclei, which are optically induced.Comment: 8 pages, 6 figures, submitted to Physical Review
Dynamic nuclear polarization and spin-diffusion in non-conducting solids
There has been much renewed interest in dynamic nuclear polarization (DNP),
particularly in the context of solid state biomolecular NMR and more recently
dissolution DNP techniques for liquids. This paper reviews the role of spin
diffusion in polarizing nuclear spins and discusses the role of the spin
diffusion barrier, before going on to discuss some recent results.Comment: submitted to Applied Magnetic Resonance. The article should appear in
a special issue that is being published in connection with the DNP Symposium
help in Nottingham in August 200
Single coronary artery from the right sinus of Valsalva
We describe a case of a single coronary artery originating from the right coronary sinus and bifurcating into the left coronary artery (LCA) and right coronary artery (RCA) in a 74-year old woman, with a non-ST elevation acute myocardial infarction (NSTEMI). Diagnosis was made by coronary angiography which ruled out stenosis, and showed normal LCA and RCA branching. The connection path of LCA, with the opposite cusp, was defined retroaortic by multislice computed tomography (CT). The variants of this coronary anomaly, together with their clinical implications and pathophysiology of acute myocardial infarction (AMI) are discussed. Multislice CT is fundamental for clinical decision making
The influence of νh11/2 occupancy on the magnetic moments of collective 21+ states in A∼100 fission fragments
AbstractThe magnetic moments of Iπ=21+ states in even–even A∼100 fission fragments have been measured using the Gammasphere array, using the technique of time-integral perturbed angular correlations. The data are interpreted within the context of the interacting boson model (IBA2) leading to the suggestion of a strong νh11/2 component in the deformed 21+ states of this region
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