122 research outputs found
Magnetic and thermal properties of the S = 1/2 zig-zag spin-chain compound In2VO5
Static magnetic susceptibility \chi, ac susceptibility \chi_{ac} and specific
heat C versus temperature T measurements on polycrystalline samples of In2VO5
and \chi and C versus T measurements on the isostructural, nonmagnetic compound
In2TiO5 are reported. A Curie-Wiess fit to the \chi(T) data above 175 K for
In2VO5 indicates ferromagnetic exchange between V^{4+} (S = 1/2) moments. Below
150 K the \chi(T) data deviate from the Curie-Weiss behavior but there is no
signature of any long range magnetic order down to 1.8 K. There is a cusp at
2.8 K in the zero field cooled (ZFC) \chi(T) data measured in a magnetic field
of 100 Oe and the ZFC and field cooled (FC) data show a bifurcation below this
temperature. The frequency dependence of the \chi_{ac}(T) data indicate that
below 3 K the system is in a spin-glass state. The difference \Delta C between
the heat capacity of In2VO5 and In2TiO5 shows a broad anomaly peaked at 130 K.
The entropy upto 300 K is more than what is expected for S = 1/2 moments. The
anomaly in \Delta C and the extra entropy suggests that there may be a
structural change below 130 K in In2VO5.Comment: 6 pages, 7 figures, 1 tabl
Search of low-dimensional magnetics on the basis of structural data: spin-1/2 antiferromagnetic zigzag chain compounds In2VO5, beta-Sr(VOAsO4)2,(NH4,K)2VOF4 and alpha-ZnV3O8
A new technique for searching low-dimensional compounds on the basis of
structural data is presented. The sign and strength of all magnetic couplings
at distances up to 12 A in five predicted new antiferromagnetic zigzag spin-1/2
chain compounds In2VO5, beta-Sr(VOAsO4)2, (NH4)2VOF4, K2VOF4 and alpha-ZnV3O8
were calculated. It was stated that in the compound In2VO5 zigzag spin chains
are frustrated, since the ratio (J2/J1) of competing antiferromagnetic (AF)
nearest- (J1) and AF next-to-nearest-neighbour (J2) couplings is equal to 1.68
that exceeds the Majumdar-Ghosh point by 1/2. In other compounds the zigzag
spin chains are AF magnetically ordered single chains as value of ratios J2/J1
is close to zero. The interchain couplings were analyzed in detail.Comment: 14 pages, 6 figure, 1 table, minor change
Triplet Dimerization Crossover Driven by Magnetic Frustration in In2VO5
In2VO5, containing magnetically frustrated zig-zag chains, shows a remarkable
magnetic crossover at 120 K between paramagnetic states with positive (17 K)
and negative (-70 K) Weiss temperatures. Magnetic moment and entropy data show
that the V4+ S = 1/2 spins condense into S = 1 triplet dimers below the
crossover. A further freezing of the antiferromagnetically coupled triplet
dimers into a global singlet state is observed at 2.5 K, with no long range
magnetic order down to 0.42 K and in fields up to 9 T. No structural V-V
dimerization is observed by high-resolution X-ray diffraction down to 10 K, but
a subtle lattice anomaly evidences a spin-lattice coupling in the triplet dimer
state. This is assigned to longitudinal oxygen displacement modes that reduce
frustration within the chains and so couple to the spin dimer fluctuations.Comment: submitted for publicatio
Analysis protocols for MRI mapping of the blood oxygenation-sensitive parameters T(2)* and T(2) in the kidney
Renal hypoxia is generally accepted as a key pathophysiologic event in acute kidney injury of various origins and has also been suggested to play a role in the development of chronic kidney disease. Here we describe step-by-step data analysis protocols for MRI monitoring of renal oxygenation in rodents via the deoxyhemoglobin concentration sensitive MR parameters T(2)* and T(2)-a contrast mechanism known as the blood oxygenation level dependent (BOLD) effect.This chapter describes how to use the analysis tools provided by vendors of animal and clinical MR systems, as well as how to develop an analysis software. Aspects covered are: data quality checks, data exclusion, model fitting, fitting algorithm, starting values, effects of multiecho imaging, and result validation.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis
Effectiveness of interspinous implant surgery in patients with intermittent neurogenic claudication: a systematic review and meta-analysis
Item does not contain fulltextINTRODUCTION: Despite an increasing implantation rate of interspinous process distraction (IPD) devices in the treatment of intermittent neurogenic claudication (INC), definitive evidence on the clinical effectiveness of implants is lacking. The main objective of this review was to perform a meta-analysis of all systematic reviews, randomized clinical trials and prospective cohort series to quantify the effectiveness of IPDs and to evaluate the potential side-effects. METHODS: Data from all studies prospectively describing clinical results based on validated outcome scales and reporting complications of treatment of patients with INC with IPD placement. We searched MEDLINE, EMBASE, Web of Science, Cochrane (CENTRAL), CINAHL, Academic Search Premier, Science Direct up to July 2010. Studies describing patients with INC caused by lumbar stenosis, reporting complication rate and reporting based on validated outcome scores, were eligible. Studies with only instrumented IPD results were excluded. RESULTS: Eleven studies eligible studies were identified. Two independently RCTs and eight prospective cohorts were available. In total 563 patients were treated with IPDs. All studies showed improvement in validated outcome scores after 6 weeks and 1 year. Pooled data based on the Zurich Claudication Questionnaire of the RCTs were more in favor of IPD treatment compared with conservative treatment (pooled estimate 23.2, SD 18.5-27.8). Statistical heterogeneity after pooled data was low (I-squared 0.0, p = 0.930). Overall complication rate was 7%. CONCLUSION: As the evidence is relatively low and the costs are high, more thorough (cost-) effectiveness studies should be performed before worldwide implementation is introduced
The Felix-trial. Double-blind randomization of interspinous implant or bony decompression for treatment of spinal stenosis related intermittent neurogenic claudication
Abstract. Background. Decompressive laminotomy is the standard surgical procedure in the treatment of patients with canal stenosis related intermittent neurogenic claudication. New techniques, such as interspinous process implants, claim a shorter hospital stay, less post-operative pain and equal long-term functional outcome. A comparative (cost-) effectiveness study has not been performed yet. This protocol describes the design of a randomized controlled trial (RCT) on (cost-) effectiveness of the use of interspinous process implants versus conventi
BK virus encephalopathy and sclerosing vasculopathy in a patient with hypohidrotic ectodermal dysplasia and immunodeficiency
IPD without bony decompression versus conventional surgical decompression for lumbar spinal stenosis: 2-year results of a double-blind randomized controlled trial
J. Senegas, Président du parc naturel régional du haut Languedoc
Senegas J. J. Senegas, Président du parc naturel régional du haut Languedoc. In: Revue Juridique de l'Environnement, n°3, 1985. Les parcs naturels régionaux. pp. 257-261
Sur un dispositif simple destiné à la diffractométrie X de poudre à basse température
The apparatus described gives X-rays powder diagram at temperatures precise to ± 0.5 °K in the range of 65 °K to 320 °K.L'appareil décrit permet l'obtention de diffractogrammes de rayons X à des températures régulées à ± 0,5 °K entre 65 °K et 320 °K
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