555 research outputs found
Nonlinear ac susceptibility studies of high- rings: Influence of the structuring method and determination of the flux creep exponent
We have studied the influence of the patterning procedure on the critical
current density of high- YBaCuO thin rings using the
nonlinear ac susceptibility method. At no applied dc magnetic field we have
found that laser ablation degrades strongly the critical current density
whereas ion beam etching has only a weak influence on it. From the measurements
at different frequencies and dc magnetic fields we analyzed the influence of
flux creep and obtained the field dependence of the flux creep exponent. Our
data reconfirm the recently observed scaling relation for the nonlinear
susceptibility response of type-II superconductors.Comment: 10 pages, 12 figure
Biophysically motivated efficient estimation of the spatially isotropic R*2 component from a single gradientârecalled echo measurement
Purpose
To propose and validate an efficient method, based on a biophysically motivated signal model, for removing the orientationâdependent part of R*2 using a single gradientârecalled echo (GRE) measurement.
Methods
The proposed method utilized a temporal secondâorder approximation of the hollowâcylinderâfiber model, in which the parameter describing the linear signal decay corresponded to the orientationâindependent part of R*2. The estimated parameters were compared to the classical, monoâexponential decay model for R*2 in a sample of an ex vivo human optic chiasm (OC). The OC was measured at 16 distinct orientations relative to the external magnetic field using GRE at 7T. To show that the proposed signal model can remove the orientation dependence of R*2, it was compared to the established phenomenological method for separating R*2 into orientationâdependent and âindependent parts.
Results
Using the phenomenological method on the classical signal model, the wellâknown separation of R*2 into orientationâdependent and âindependent parts was verified. For the proposed model, no significant orientation dependence in the linear signal decay parameter was observed.
Conclusions
Since the proposed secondâorder model features orientationâdependent and âindependent components at distinct temporal orders, it can be used to remove the orientation dependence of R*2 using only a single GRE measurement
Oblikovanje i vrednovanje plutajuÄih uljnih mikrozrnaca loratadina s produljenim zadrĆŸavanjem u ĆŸelucu
Gastro retentive controlled release system of loratadine was formulated to increase the residence time in stomach and to modulate the release behaviour of the drug. Oil entrapped floating microbeads prepared by emulsion gelation method were optimized by 23 factorial design and a polymer ratio of 2.5:1.5 (pectin: sodium alginate) by mass, 15% (m/v) of oil (mineral oil or castor oil) and 0.45 mol L-1 calcium chloride solution were selected as the optimized processing conditions for the desired buoyancy and physical stability. In vitro drug release in fed state conditions demonstrated sustained release of loratadine for 8 h that best fitted the Peppas model with n < 0.45. The ethylcellulose coating on microbeads optimized by 22 factorial design resulted in controlled release formulation of loratadine that provided zero-order release for 8 h.U radu je opisana priprava plutajuÄih mikrozrnaca za kontrolirano oslobaÄanje loratadina metodom ĆŸeliranja emulzije. Mikrozrnca sadrĆŸe ulja, a njihovo zadrĆŸavanje u ĆŸelucu je produljeno. Priprava mikrozrnaca je optimirana 23 faktorijalnim dizajnom. Pripravci optimalne sposobnosti plutanja i stabilnosti dobiveni su uz omjer masa pektina i natrijevog alginata 2,5:1,5, udio mineralnog ulja ili ulja kastora 15% (m/v) i koncentraciju kalcijevog klorida 0,45 mol L1. Iz tih se mikrozrnaca loratadin oslobaÄa in vitro tijekom 8 h, a oslobaÄanje slijedi Peppasov model ako je n < 0,45. Mikrozrnca presvuÄena etilcelulozom optimirana 22 faktorijalnim dizajnom slijede kinetiku nultog reda tijekom 8 h
Angular dependence of the magnetization relaxation in Co/Pt multilayers
We study the influence of defects in Co/Pt multilayers on the room-temperature magnetization reversal and relaxation mechanisms via angle-dependent magnetic viscosity and coercive field measurements. The data reveal a transition from pinning-dominated domain wall propagation to a sequence of pinning-dominated and uniform switching, with increasing tilt away from the normal direction. The leading role of the dendritic domain wall propagation in the nanogranular exchange-coupled films is corroborated by the scaling of relaxation times, the angular dependence of the coercive field, and Kerr microscopy
Marginal zone lymphomas in children and the young adult population; characterization of genetic aberrations by FISH and RT-PCR
Marginal zone lymphomas present rarely in children and young adults as either primary nodal or extranodal disease and have an excellent prognosis. To date, chromosomal aberrations have not been analyzed in the pediatric and young adult population. We undertook a study to analyze genetic alterations in nodal and extranodal marginal zone lymphomas in children and young adults using fluorescence in situ hybridization (FISH) and RT-PCR. These findings were correlated with clinical features at presentation and immunophenotype. Forty-one cases were identified meeting these criteria. The age range was 1.5-29 years old with 49% of the cases <18 years of age. 73% of the marginal zone lymphoma cases showed evidence of light chain restriction by immunohistochemistry or flow cytometry. CD43 was coexpressed in 83%. 85% of the marginal zone lymphoma cases tested showed evidence of immunoglobulin heavy chain gene rearrangement. Fifty-nine percent of the cases were nodal marginal zone lymphomas with a median age at presentation of 16 years and an M/F ratio of 7:1. Twenty-one percent of the nodal marginal zone lymphoma cases contained genetic aberrations. Seventeen percent contained trisomy 18 with one case containing an additional trisomy 3. A translocation of the immunoglobulin heavy chain gene to an unknown partner gene was present in one case. Forty-one percent of the cases were extranodal marginal zone lymphomas with a median age of 24 years and a M/F ratio of 1.4:1. Eighteen percent of the extranodal marginal zone lymphoma cases contained genetic aberrations. The t(14;18) involving the IGH and MALT1 genes was present in one case, tetraploidy was present in one case, and another case contained trisomy 3. Overall the incidence of genetic aberrations in marginal zone lymphomas in the pediatric and young adult population is low, but the aberrations seen are similar to those seen in the adult population
Biophysically motivated efficient estimation of the spatially isotropic Râ2 component from a single gradient-recalled echo measurement
Purpose To propose and validate an efficient method, based on a biophysically motivated signal model, for removing the orientationâdependent part of Râ2 using a single gradientârecalled echo (GRE) measurement. Methods The proposed method utilized a temporal secondâorder approximation of the hollowâcylinderâfiber model, in which the parameter describing the linear signal decay corresponded to the orientationâindependent part of Râ2. The estimated parameters were compared to the classical, monoâexponential decay model for Râ2 in a sample of an ex vivo human optic chiasm (OC). The OC was measured at 16 distinct orientations relative to the external magnetic field using GRE at 7T. To show that the proposed signal model can remove the orientation dependence of Râ2, it was compared to the established phenomenological method for separating Râ2 into orientationâdependent and âindependent parts. Results Using the phenomenological method on the classical signal model, the wellâknown separation of Râ2 into orientationâdependent and âindependent parts was verified. For the proposed model, no significant orientation dependence in the linear signal decay parameter was observed. Conclusions Since the proposed secondâorder model features orientationâdependent and âindependent components at distinct temporal orders, it can be used to remove the orientation dependence of Râ2 using only a single GRE measurement
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