421 research outputs found
Liver fat in adults with GH deficiency: comparison to matched controls and the effect of GH replacement
CONTEXT:
Existing data regarding the association between growth hormone deficiency (GHD) and liver fat content are conflicting.
OBJECTIVE:
We aimed i) to assess intrahepatocellular lipid (IHCL) content in hypopituitary adults with GHD compared to matched controls and ii) to evaluate the effect of growth hormone (GH) replacement on IHCL content.
DESIGN:
Cross-sectional comparison and controlled intervention study.
PATIENTS, PARTICIPANTS:
Cross-sectional comparison: 22 hypopituitary adults with GHD and 44 healthy controls matched for age, BMI, gender and ethnicity. Intervention study: 9 GHD patients starting GH replacement (GH Rx group), 9 GHD patients not starting replacement therapy (non-GH Rx group).
INTERVENTION:
Intervention study:GH replacement for 6 months in the GH Rx group, dosage was titrated to achieve normal IGF-1 levels.
MAIN OUTCOME MEASURES:
IHCL content determined by proton magnetic resonance spectroscopy (1 H MRS).
RESULTS:
Cross-sectional comparison: There was no difference in IHCL content between GHD patients and healthy controls (1.89% (0.30, 4.03) vs. 1.14% (0.22, 2.32); p=0.2), the prevalence of patients with hepatic steatosis (IHCL of ≥ 5.56%) was similar in the two groups (22.7% vs. 15.9%; chi square probability = 0.4). Intervention study: The change in IHCL content over 6 months did not differ between the GH Rx group and the non-GH Rx group (-0.63 ± 4.53% vs. +0.11 ± 1.46%; p=0.6).
CONCLUSIONS:
In our study liver fat content and the prevalence of hepatic steatosis did not differ between hypopituitary adults with GHD and matched controls. In GHD patients GH replacement had no effect on liver fat content
Evidence for Shape Co-existence at medium spin in 76Rb
Four previously known rotational bands in 76Rb have been extended to moderate
spins using the Gammasphere and Microball gamma ray and charged particle
detector arrays and the 40Ca(40Ca,3pn) reaction at a beam energy of 165 MeV.
The properties of two of the negative-parity bands can only readily be
interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model
calculations if they have the same configuration in terms of the number of g9/2
particles, but they result from different nuclear shapes (one near-oblate and
the other near-prolate). These data appear to constitute a unique example of
shape co-existing structures at medium spins.Comment: Accepted for publication in Physics Letters
A Monte Carlo Study of Correlations in Quantum Spin Ladders
We study antiferromagnetic spin--1/2 Heisenberg ladders, comprised of
chains () with ratio of inter-- to
intra--chain couplings. From measurements of the correlation function we deduce
the correlation length . For even , the static structure factor
exhibits a peak at a temperature below the corresponding spin gap. Results for
isotropically coupled ladders () are compared to those for
the single chain and the square lattice. For , the
correlation function of the two--chain ladder is in excellent agreement with
analytic results from conformal field theory, and exhibits simple
scaling behavior.Comment: 4 pages, 5 EPS figures, submitted to Phys. Rev. Let
On the Application of the Non Linear Sigma Model to Spin Chains and Spin Ladders
We review the non linear sigma model approach (NLSM) to spin chains and spin
ladders, presenting new results. The generalization of the Haldane's map to
ladders in the Hamiltonian approach, give rise to different values of the
parameter depending on the spin S, the number of legs and
the choice of blocks needed to built up the NLSM fields. For rectangular blocks
we obtain or depending on wether , is even or
odd, while for diagonal blocks we obtain . Both
results agree modulo , and yield the same prediction, namely that even (
resp. odd) ladders are gapped (resp. gapless). For even legged ladders we show
that the spin gap collapses exponentially with and we propose a
finite size correction to the gap formula recently derived by Chakravarty using
the 2+1 NSLM, which gives a good fit of numerical results. We show the
existence of a Haldane phase in the two legged ladder using diagonal blocks and
finally we consider the phase diagram of dimerized ladders.Comment: 25 pages, Latex, 7 figures in postscript files, Proc. of the 1996 El
Escorial Summer School on "Strongly Correlated Magnetic and Superconducting
Systems". Some more references are adde
Elementary Excitations in Dimerized and Frustrated Heisenberg Chains
We present a detailed numerical analysis of the low energy excitation
spectrum of a frustrated and dimerized spin Heisenberg chain. In
particular, we show that in the commensurate spin--Peierls phase the ratio of
the singlet and triplet excitation gap is a universal function which depends on
the frustration parameter only. We identify the conditions for which a second
elementary triplet branch in the excitation spectrum splits from the continuum.
We compare our results with predictions from the continuum limit field theory .
We discuss the relevance of our data in connection with recent experiments on
, , and .Comment: Corrections to the text + 1 new figure, will appear in PRB (august
98
From nodal liquid to nodal Mottness in a frustrated Hubbard model
We investigate the physics of frustrated 3-leg Hubbard ladders in the band
limit, when hopping across the ladder's rungs (t) is of the same
order as hopping along them (t) much greater than the onsite Coulomb repulsion
(U). We show that this model exhibits a striking electron-hole asymmetry close
to half-filling: the hole-doped system at low temperatures develops a
Resonating Valence Bond (RVB)-like d-wave gap (pseudogap close to (,0))
coinciding with gapless nodal excitations (nodal liquid); in contrast, the
electron-doped system is seen to develop a Mott gap at the nodes, whilst
retaining a metallic character of its majority Fermi surface. At lower
temperatures in the electron-doped case, d-wave superconducting correlations --
here, coexisting with gapped nodal excitations -- are already seen to arise.
Upon further doping the hole-doped case, the RVB-like state yields to d-wave
superconductivity. Such physics is reminiscent of that exhibited by the high
temperature cuprate superconductors--notably electron-hole asymmetry as noted
by Angle Resolved PhotoEmission Spectroscopy (ARPES) and the resistivity
exponents observed. This toy model also reinforces the importance of a more
thorough experimental investigation of the known 3-leg ladder cuprate systems,
and may have some bearing on low dimensional organic superconductors.Comment: 26 pages, 16 figure
Cerebral haemodynamic changes during propofol-remifentanil or sevoflurane anaesthesia: transcranial Doppler study under bispectral index monitoring.
INTRODUCTION: Transcranial Doppler (TCD) can detect the cerebral circulation arrest (CCA) in brain death. TCD is highly specific, but less sensitive because of false-negatives accounting for up to 10%. The aim of the study was to explore the diagnostic accuracy of TCD and to determine whether it can be augmented by strategies such as the insonation of the extracranial internal carotid artery (ICA) and sequential examinations. METHODS: Data of 184 patients, who met clinical criteria of brain death, observed from 1998 through 2006, were retrospectively reviewed. The study of cerebral arteries was performed through the transtemporal approach, suboccipital insonation of the vertebro-basilar system, transorbital insonation of the ICA and ophthalmic artery, and transcervical insonation of the extracranial ICA. Repeated exams were performed in cases of persistent diastolic flow. RESULTS: The specificity of the testing was 100%, no false-positive cases were recorded. The sensitivity of conventional TCD examination was 82.1%. The insonation of the extracranial ICA increased sensitivity to 88% allowing the detection of CCA in those patients lacking temporal windows; serial examinations further increased sensitivity to 95.6%. CONCLUSIONS: The addition of insonation of the cervical ICA and of the siphon increased sensitivity of TCD. Nevertheless, a CCA flow patterns may appear later on those segments. Serial examinations, may be needed in those cases
Assessment of stability and fluctuations of cultured lower airway bacterial communities in people with cystic fibrosis
Background: Routine clinical culture detects a subset of the cystic fibrosis (CF) airways microbiota based on culture-independent (molecular) methods. This study aimed to determine how extended sputum culture of viable bacteria changes over time in relation to clinical status and predicts exacerbations. Methods: Sputa from patients at a baseline stable and up to three subsequent time-points were analysed by extended-quantitative culture; aerobe/anaerobe densities, ecological indexes and community structure were assessed together with clinical outcomes. Results: Eighty patients were prospectively recruited. Sputa were successfully collected and cultured at 199/267 (74.5%) study visits. Eighty-two sputa from 25 patients comprised a complete sample-set for longitudinal analyses. Bacterial density, ecological indexes and clinical outcomes were unchanged in 18 patients with three sequential stable visits. Conversely, in 7 patients who had an exacerbation, total bacterial and aerobe densities differed over four study visits (P < .001) with this difference particularly apparent between the baseline visit and completion of acute antibiotic treatment where a decrease in density was observed. Bacterial communities were more similar within than between patients but stable patients had the least variation in community structure over time. Using logistic regression in a further analysis, baseline features in 37 patients without compared to 15 patients with a subsequent exacerbation showed that clinical measures rather than bacterial density or ecological indexes were independent predictors of an exacerbation. Conclusions: Greater fluctuation in the viable bacterial community during treatment of an exacerbation than between stable visits was observed. Extended-quantitative culture did not provide prognostic information of a future exacerbation
Photoproduction of K+K− meson pairs on the proton
The exclusive reaction γp→pK+K− was studied in the photon energy range 3.0–3.8 GeV and momentum transfer range 0.6<−t<1.3 GeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20 pb−1. The reaction was isolated by detecting the K+ and the proton in CLAS, and reconstructing the K− via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the ϕ meson in the P wave, evidence for S−P interference was found. The differential production cross sections dσ/dt for individual waves in the mass range of the ϕ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the t-dependent cross section of the S-wave contribution to the elastic K+K− photoproduction has been measured
- …