► Effect of Zr diffusion on the physical, microstructural and superconducting properties of Y123 superconducting sample. ► DC resistivity, transport critical current density, SEM, EDX and XRD ...measurements for characterization of the samples. ► Calculation of diffusion coefficient and activation energy of Zr in Y123 system for the first time. ► Zr diffusion at higher temperatures is found to be much more significant. ► Migration of zirconium primarily proceeds through defects in the polycrystalline samples.
This study reports not only the role of zirconium (Zr) diffusion on the superconducting, physical and microstructural properties of YBa2Cu3O7−δ (Y123) bulk superconductors prepared by the conventional solid-state reaction method with the aid of scanning electron microscopy (SEM), electron dispersive X-ray (EDX), X-ray diffraction (XRD), electrical resistivity (ρ–T) and transport critical current density (Jc) measurements but also the diffusion coefficient and the activation energy of zirconium in Y123 system for the first time. Zr diffusion is examined in the temperature range 500–945°C via the variation of the lattice parameters evaluated from the XRD patterns. It is found that while the room-temperature resistivity reduces in the presence of the Zr ions in the system, the critical transition temperature values measured enhance. The onset (Tconset) and offset (Tcoffset) critical temperatures are found to be about 94.4K and 91.5K for the Zr-diffused sample as against 93.7K and 89.4K, respectively, for the pure sample. The increase in the critical temperatures is due to the improvement of crystallinity and the enhancement in the grain size. Likewise, the presence of the Zr atoms in the system, the Jc value enhances from 128Acm−2 to 160Acm−2 at 77K owing to the increase of the flux pinning mechanism stemming from the stacking faults, planar and micro-defects. Further, XRD measurements display that the samples produced in this work exhibit the polycrystalline superconducting phase with the changing intensity of diffraction lines and contain the Y123 phase only, illustrating the incorporation of Zr atoms into the crystalline structure of the Zr-diffused sample. Based on the refinement of cell parameters done by considering the structural modulation, the Zr diffusion is confirmed by both a reduction of a and b lattice parameters and an enhancement of the cell parameter c (about 0.24%) of the sample in comparison with that of the pure sample. As for the SEM investigations, the crystallinity and grain connectivity improve with the Zr diffusion. According to the results obtained, the Tconset, Tcoffset and Jc values of the samples studied are found to depend strongly on the microstructure. Moreover, EDX measurements indicate that the elements used for the preparation of samples distribute homogeneously. Y3+ and Ba2+ cations may partly be substituted by Zr4+ ions and the substitution at the Cu site is less likely, presenting that the superconducting properties of the Zr-diffused sample are more superior to the pure sample. Further, the diffusion coefficient of the Zr in Y123 system in a range of 500–945°C is determined to change from 4.12×10−10 to 9.77×10−8cm2s−1 with activation energy of about 1.010eV, confirming that the Zr diffusion at lower temperatures is much less significant and the Zr ions primarily proceed through defects in the polycrystalline samples.
OBJECTIVESThe aim of this study was to evaluate the role of the use of fluoroscopy in patients undergoing retrograde intrarenal surgery and the effect on surgical outcomes. MATERIAL AND METHODSThe ...patients who were admitted to our center with the diagnosis of kidney stones were divided into 2groups. In group 1, routine fluoroscopy was used in all cases (n: 58). In group 2, the same procedure was performed without fluoroscopy (n: 67) and the results of the 2groups were compared. RESULTSThere were no statistically significant differences between the 2groups in terms of operation time, stone-free rate, complication rate, need for analgesic and re-treatment requirement and Visual Analogic Scale score. CONCLUSIONThe use of fluoroscopy does not alter the complication frequency and stone-free rate. We think that the use of fluoroscopy is not mandatory in cases in which renal pelvis access is achieved especially with semirigid ureteroscopy and that unnecessary fluoroscopy increases radiation exposure.
Introduction Il est classiquement rapporté que 10-15 % des femmes ayant présenté un diabète gestationnel (DG) présentent une dysglycémie 3-6 mois après leur accouchement. Nous avons voulu évaluer ce ...taux lorsque le DG est défini avec les nouveaux critères diagnostiques (IADPSG). Patients et méthodes Nous avons contacté par téléphone 114 femmes ayant été suivies dans notre CHU pour un DG et ayant accouché entre juillet 2013 et janvier 2014. Nous leur avons envoyé une nouvelle ordonnance de charge en glucose 75 g si celle donnée à la sortie de la maternité n’avait pas été réalisée. Résultats À ce jour, 27 femmes ont effectivement réalisé le test, dont 6 après avoir été recontactées. Voici les raisons les plus fréquentes et non exclusives invoquées par 21 femmes ayant explicité pourquoi elles n’avaient pas réalisé le dépistage : manque de temps ( n = 10), perte ou pas d’ordonnance ( n = 9), puis pas d’intérêt ou refus ( n = 5), oubli ( n = 3), nouvelle grossesse ( n = 2). Les tests de dépistage réalisés (27 femmes) étaient 22 charges en glucose, 5 glycémies à jeun dont 1 avec glycémie post-prandiale et 1 avec HbA1c. Une dysglycémie a ainsi été détectée dans 6 cas (22 %) : 1 hyperglycémie à jeun, 2 intolérances au glucose, 1 hyperglycémie à jeun avec intolérance au glucose, 2 diabètes dont un sur la glycémie post-charge seulement. La moitié des dysglycémies n’aurait pas été dépistée si une glycémie à jeun seule avait été effectuée. La proportion de femmes insulinotraitées pendant la grossesse était plus élevée parmi celles avec vs sans dysglycémie du post-partum (3/6 vs 3/21 ; odds ratio 6,0 IC 95 % 0,8-50,0, p = 0,08). Conclusion Nous confirmons dans cette étude pilote la forte prévalence de dysglycémie après un DG défini par les nouveaux critères. Le dépistage apparaît donc primordial sur le plan médical, mais reste cependant peu effectué, même après relance personnalisée. Déclaration d’intérêt Les auteurs déclarent ne pas avoir d’intérêt direct ou indirect (financier ou en nature) avec un organisme privé, industriel ou commercial en relation avec le sujet présenté.
•Lateral and vertical forces in small CHs.•Seed distance and lateral force.•Normalized magnetic flux density distributions of PMGs.
The magnetic levitation force in vertical direction and guidance ...force in lateral direction should be increased for enhancing the loading capacity and stability of Maglev systems, respectively. In this study, we have produced multi‒seeded YBCO (YBa2Cu3O7) superconductors with two seeds and investigated the effect of seed distance on the vertical levitation force and lateral guidance force properties by using different permanent magnetic guideway (PMG) arrangements. Although there are studies in literature related to different distance, orientation and angle of seeds; there is no detailed study investigating the effect of seed distance on the vertical and lateral magnetic force properties of Maglev systems depending on different types of PMGs. In this study, after the sample fabrication, the optimum PMG arrangement were determined by using numerical simulation to obtain magnetic flux density distribution. It is determined that both maximum levitation and guidance force values firstly increased with increasing the seed distance from 0 to 4 mm and then related forces decreased with increasing the seed distance from 4 to 16 mm but still keep the higher force values than the sample with the seed distances of 0 mm. This situation is clarified as the increasing of the seed distance to an optimum value enhances both the levitation and guidance forces simultaneously and this is very important for levitation force applications because it causes to easy control of the Maglev system in vertical and lateral directions.
Corruption of C-band microwave brightness observations by radio-frequency interference (RFI) has been reported in recent data from orbiting radiometers; methods for mitigating these effects are of ...great importance for the design of future spaceborne microwave radiometers. One approach that has been suggested involves the use of multiple subchannels at C-band as opposed to a single channel; the use of multiple subchannels allows RFI to be detected and mitigated by analyzing relationships among subchannel brightnesses. While this approach has been utilized in previous airborne measurements, demonstrations of the RFI mitigation performance achieved have been difficult to obtain. To address this issue, an enhanced airborne system for observing radio-frequency interference effects on C-band microwave radiometers was developed, and is described in this paper. The system includes a traditional microwave radiometer with four C-band subchannels, so that RFI removal is possible using a subchannel mitigation algorithm. In addition, the system includes a digital receiver with the capability of providing high temporal and spectral resolution observations of interference. This high-resolution data allows improved understanding of RFI sources to be obtained, and also allows analysis of subchannel mitigation algorithm performance. Observations using the system in a test flight near Wallops Island, VA are described. Results show the four subchannel approach generally to be effective in mitigating the observed RFI sources, although examples are also illustrated using the digital receiver data to demonstrate failure of this approach. While studies of the digital receiver data alone could be performed to demonstrate further improvements in RFI mitigation, issues with this initial dataset limit the extent of such studies. Nevertheless, the results obtained still demonstrate qualitatively the improved RFI mitigation that can be achieved in brightness observations through the use of digital receivers
Scan blindness phenomenon for finite phased arrays of printed dipoles on material coated, electrically large circular cylinders is investigated. Effects on the scan blindness mechanism of several ...array and supporting structure parameters, including curvature effects, are observed and discussed. A full-wave solution, based on a hybrid method of moments/Green's function technique in the spatial domain, is used to achieve the aforementioned goals. Numerical results show that the curvature affects the surface waves and hence the mutual coupling between array elements. As a result, the array current distribution of arrays mounted on coated cylinders are considerably different compared to similar arrays on planar platforms. Therefore, finite phased arrays of printed dipoles on coated cylinders show different behavior in terms of scan blindness phenomenon compared to their planar counterparts. Furthermore, this phenomenon is completely different for axially and circumferentially oriented printed dipoles on coated cylinders suggesting that particular element types might be important for cylindrical arrays.
In this work, 2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine (OEP) in its free base form and metalated with iron (III) chloride (FeOEP), magnesium(II) (MgOEP) and cobalt(II) (CoOEP) have been used to ...fabricate Langmuir–Blodgett (LB) thin films. Using the surface pressure–surface area (
Π–
A) isotherm graphs optimum conditions for thin film deposition have been determined and by changing the deposition parameters various thin films have been deposited. Quartz Crystal Microbalance (QCM) system was used to investigate their gas sensing performances during exposure to Volatile Organic Compounds (VOCs) including chloroform, benzene and toluene. The surface properties have been investigated using Atomic Force Microscopy (AFM) and analyzed together with the QCM results to understand the effect of the surface properties on gas sensing mechanism. It is observed that larger surface area leads to higher response in gas sensing applications in terms of resonance frequency change.
The aim of this study was to evaluate the role of the use of fluoroscopy in patients undergoing retrograde intrarenal surgery and the effect on surgical outcomes.
The patients who were admitted to ...our center with the diagnosis of kidney stones were divided into 2groups. In group 1, routine fluoroscopy was used in all cases (n: 58). In group 2, the same procedure was performed without fluoroscopy (n: 67) and the results of the 2groups were compared.
There were no statistically significant differences between the 2groups in terms of operation time, stone-free rate, complication rate, need for analgesic and re-treatment requirement and Visual Analogic Scale score.
The use of fluoroscopy does not alter the complication frequency and stone-free rate. We think that the use of fluoroscopy is not mandatory in cases in which renal pelvis access is achieved especially with semirigid ureteroscopy and that unnecessary fluoroscopy increases radiation exposure.
The effect of coronene (C24H12) addition on the levitation force properties of MgB2 superconductor has been investigated for the first time in this study. The polycrystalline disk-shaped MgB2 + y wt ...% C24H12 samples (y = 0, 2, 4, 6, 8, 10), were synthesized by a pellet/closed tube method at 850 °C under Ar atmosphere, after hot pressing at 200 °C. XRD analysis indicates a decrease in lattice parameters of coronene added samples and confirms substitution of carbon in boron sites. An increase in lattice strain and a decrease in grain size are observed due to the carbon substitution effect. Vertical and lateral levitation force measurements under zero-field-cooled and field-cooled regimes were carried out at different temperatures of 20, 25 and 30 K. It was found that the coronene addition significantly increases the high-field critical current density of MgB2. The Jc values were obtained as 4.6 × 103 Acm−2 and 1.3 × 104 Acm−2 for pure and 4 wt % coronene added samples at 20 K and 4 T. In addition, the levitation force measurements show that 4 wt % coronene adding is very effective in increasing both the vertical and lateral levitation force performances at 20 K. The maximum levitation force for 4 wt % coronene added sample corresponds to 7.58 N/g whereas the reference sample shows 6.73 N/g at 20 K in ZFC regime. The results point out that the hydrocarbon of C24H12 is an effective carbon-containing additive for MgB2 and can be useful for optimizing the levitation performance of MgB2 superconductors for potential applications.
•Effect of coronene addition on levitation force properties of MgB2 was investigated.•The Jc value is obtained as 4.6 × 103 Acm−2 for pure sample at 20 K, 4 T.•The Jc value is obtained as 1.3 × 104 Acm−2 for 4 wt % added sample at 20 K, 4 T.•The levitation force of pure sample corresponds to 6.73 N/g at 20 K in ZFC regime.•Maximum levitation force is 7.58 N/g for 4 wt % added sample at 20 K in ZFC regime.
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