"Magnetoscan": A Modified Hall Probe Scanning Technique for the Detection of Inhomogeneities in Bulk High Temperature Superconductors

We present a novel technique for the investigation of local variations of the critical current density in large bulk superconductors. In contrast to the usual Hall probe scanning technique, the sample is not magnetized as a whole before the scan, but locally by a small permanent magnet, which is fixed near the Hall probe, during the scanning process. The resulting signal can be interpreted as a qualitative measure of the local shielding currents flowing at the surface.Comment: 8 pages, 4 figure

Direct observation of substitutional Ga after ion implantation in Ge by means of extended x-ray absorption fine structure

We present an experimental lattice location study of Ga atoms in Ge after ion implantation at elevated temperature (250°C). Using extended x-rayabsorption fine structure (EXAFS) experiments and a dedicated sample preparation method, we have studied the lattice location of Ga atoms in Ge with a concentration ranging from 0.5 at. % down to 0.005 at. %. At Ga concentrations ≤0.05 at.%, all Ga dopants are substitutional directly after ion implantation, without the need for post-implantation thermal annealing. At higher Ga concentrations, a reduction in the EXAFS amplitude is observed, indicating that a fraction of the Ga atoms is located in a defective environment. The local strain induced by the Ga atoms in the Ge matrix is independent of the Ga concentration and extends only to the first nearest neighbor Ge shell, where a 1% contraction in bond length has been measured, in agreement with density functional theory calculations.We acknowledge the support from the Research Foundation Flanders, the epi-team from imec, the KU Leuven GOA 09/06 project, the IUAP program P6/42 and the Australian Research Council. S.C. acknowledges support from OCAS NV by an OCAS-endowed chair at Ghent University

Inter- and intragrain currents in bulk melt-grown YBaCuO rings

A simple contactless method suitable to discern between the intergrain (circular) current, which flows in the thin superconducting ring, and the intragrain current, which does not cross the weakest link, has been proposed. At first, we show that the intergrain current may directly be estimated from the magnetic flux density $B(\pm z_0)$ measured by the Hall sensor positioned in the special points $\pm z_0$ above/below the ring center. The experimental and the numerical techniques to determine the value $z_0$ are discussed. Being very promising for characterization of a current flowing across the joints in welded YBaCuO rings (its dependencies on the temperature and the external magnetic field as well as the time dissipation), the approach has been applied to study corresponding properties of the intra- and intergrain currents flowing across the $a$-twisted grain boundaries which are frequent in bulk melt-textured YBaCuO samples. We present experimental data related to the flux penetration inside a bore of MT YBaCuO rings both in the non-magnetized, virgin state and during the field reversal. The shielding properties and their dependence on external magnetic fields are also studied. Besides, we consider the flux creep effects and their influence on the current re-distribution during a dwell.Comment: 13 pages, 16 figures (EPS), RevTeX4. In the revised version, corrections to perturbing effects near the weak links are introduced, one more figure is added. lin

Stimulated perturbation on the neutron flux distribution in the mutually-dependent source-to-absorber geometry

The complexity of the neutron transport phenomenon throws its shadows on every physical system wherever neutron is produced or absorbed. The Monte Carlo N-Particle Transport Code (MCNP) was used to investigate the flux perturbations in the neutron field caused by an absorber. The geometry of the present experiment was designed to reach a simulation of an isotopic neutron field. The neutron source was a ${}^{241}$AmBe with the production physics of neutrons is dependent only on alpha-beryllium interaction and is independent of what happened to the neutron after it was generated. The geometries have been designed to get a volume of uniform neutron densities within a spherical volume of radius 15 cm in every neutron energy group up to 10 MeV. Absorbers of different dimensions were placed within the volume to investigate the field perturbation. Different neutron absorbers were used to correlate the phenomenon to the integral cross-section of the absorber. Flux density inside and outside the absorber samples was determined, while the spatial neutron flux distribution produced by the AmBe source without an absorber was taken as a reference. This study displayed that absorbers of various dimensions perturb the neutron field in a way that is dependent on the absorption and scattering cross-sections, particularly in the neutron resonance region. Unlike the simple picture of reducing the number density of neutrons, the perturbation was found to influence the moderation of neutrons in the medium, significantly above 1 MeV.Comment: 10 pages, 13 figures, 26 reference

Perfil lipídico, compuestos volátiles y estabilidad oxidativa durante el almacenamiento del aceite de semilla de Opuntia ficus-indica marroquí

The fatty acids, sterol, tocopherol and volatile compositions of Moroccan cold-pressed cactus (Opuntia ficus-indica) seed oil were studied. The most abundant fatty acid, tocopherol and sterol were linoleic acid (60.6%), γ-tocopherol (533 mg/kg) and β-sitosterol (6075 mg/kg), respectively. In this study, 23 volatile compounds were identified with perceivable odor attributes for 14 compounds. The oxidative quality of cactus seed oil was monitored over 4 weeks at 50 °C. Increases in PV, K232 and FFA were detected during the first two weeks as well as a decrease in the induction time; whereas no change was reported for the K270 values. The amount of total phenolic content increased until it reached 0.3 mg/kg and then decreased by the end of the storage period; while tocopherols started to decrease after the first week. The fat-free residue extracts showed a very strong effect to reduce the oxidation of linoleic acid. Consequently, the extracts were significantly more effective to bleach β-carotene in the β-carotene-linoleic acid assay in comparison with the control.Se estudiaron los ácidos grasos, esteroles, tocoferoles y la composición volátil del aceite de semilla de cactus marroquí (Opuntia ficus-indica) prensado en frío. Los ácidos grasos, tocoferoles y esteroles más abundantes fueron el ácido linoleico (60,6%), γ-tocoferol (533 mg/kg) y β-sitosterol (6075 mg/kg), respectivamente. En este estudio, se identificaron 23 compuestos volátiles con atributos perceptibles para 14 de ellos. La oxidación del aceite de semilla de cactus fue monitoreada durante 4 semanas a 50°C. Se observó un aumento en el PV, K232 y FFA durante las dos primeras semanas y una disminución en el tiempo de inducción, mientras que no se apreciaron cambios para los valores de K270. La cantidad de fenoles totales aumentó hasta alcanzar 0,3 mg/kg y luego disminuyó al final del almacenamiento, mientras que los tocoferoles comenzaron a disminuir después de la primera semana. Los extractos de residuos libres de grasa mostraron un efecto muy fuerte para reducir la oxidación del ácido linoleico. En consecuencia, los extractos fueron significativamente más efectivos para blanquear el β-caroteno en el ensayo de β-caroteno-ácido linoleico en comparación con el control

Mild Cognitive Impairment among Type II Diabetes Mellitus Patients Attending University Teaching Hospital

BACKGROUND: Type II diabetes mellitus (TIIDM) has been associated with structural and functional changes in the brain. TIIDM is commonly associated with obesity, insulin resistance, hypertension, and dyslipidemia, all of which can have negative impact on brain. AIM: The aim of the study was to study the risk of mild cognitive impairment (MCI) among both diabetics and non-diabetics and to identify risk factors to MCI among both groups. METHODS: Two comparative cross-sectional studies were carried out enrolling 100 diabetics and 100 age, sex, and education matching non-diabetics. Cognitive function was assessed using Montreal Cognitive Assessment (MoCA) test and risk factors for MCI were assessed. RESULTS: The subjective complaint of memory impairment among diabetics was significantly higher (34%) compared to non-diabetics (13.0%), p < 0.05. The mean of objective MoCA score was significantly lower among diabetics (25.9 ± 2.5) compared to non-diabetics (27.4 ± 2.4), p < 0.001. The rate of MCI was significantly higher among TIIDM patients (22%) compared to non-diabetics (9%), p < 0.01 and odds ratio (OR) 2.8 (95% confidence interval 1.2–6.5). Among the two studied groups, the rate of MCI was significantly higher among those aged over 50 years compared to younger age as well as among hypertensive compared to non-hypertensive persons, (p < 0.05). Among diabetics, the MCI was significantly higher among those with secondary education, having heart diseases, longer duration of DM, or repeated hypoglycemia attack, p < 0.05. A healthy diet, brain training, and social activities were found to be significantly associated with normal cognition. Logistic analysis revealed that diabetics aged above 50 was the only significant predicting factor for MCI with an OR 2.9 (95% CI: 3.8–123.3), p < 0.001. CONCLUSION: TIIDM is significantly associated with 3-times increasing risk of having MCI compared to non-diabetics. The age, hypertension, cardiovascular diseases, duration of diabetes, and frequency of hypoglycemic episodes are risk factors for cognitive impairment. A healthy diet, brain training, and social activities were associated with better cognitive function

The AKARI/IRC Mid-Infrared All-Sky Survey

Context : AKARI is the first Japanese astronomical satellite dedicated to infrar ed astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 and 200um during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9um and 18um b ands) of the survey carried out with one of the on-board instruments, the Infrar ed Camera (IRC). Aims : We present unprecedented observational results of the 9 and 18um AKARI al l-sky survey and detail the operation and data processing leading to the point s ource detection and measurements. Methods : The raw data are processed to produce small images for every scan and point sources candidates, above the 5-sigma noise level per single scan, are der ived. The celestial coordinates and fluxes of the events are determined statisti cally and the reliability of their detections is secured through multiple detect ions of the same source within milli-seconds, hours, and months from each other. Results : The sky coverage is more than 90% for both bands. A total of 877,091 s ources (851,189 for 9um, 195,893 for 18um) are confirmed and included in the cur rent release of the point source catalogue. The detection limit for point source s is 50mJy and 90mJy for the 9um and 18um bands, respectively. The position accu racy is estimated to be better than 2". Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9um band and 4% for the 18um ban d. The coordinates and fluxes of detected sources in this survey are also compar ed with those of the IRAS survey and found to be statistically consistent.Comment: Accepted for publication in AandA AKARI special issu