Effect of sintering temperature on the superconducting properties of MgB2 superconductor co-added with a high concentration of Si and C

In this study, as much as 10 and 15 wt.% nanosized silicon and carbon (Si+C) were reacted with (Mg+2B) at 650°C and 850°C, respectively, for 1 hour. The phase formation, surface morphology and superconducting properties of these samples were evaluated. The relative peak intensity as calculated from the XRD patterns indicates the formation of large Mg2Si volume fraction at low sintering temperature. MgB4 phase was detected in the samples sintered at high temperature as a result of Mg deficiency. The C substitution level as estimated from the lattice parameters, was shown to increase in the samples reacted with a higher amount of (Si+C) at high temperature. Scanning electron micrograph showed that (Si+C) co-addition had refined the grain size and improved the grain coupling of MgB2. The superconducting transition temperature was found to decrease with increasing addition level. The superconducting transition width was also broadened because of a large volume fraction of secondary phases. The improved field dependent critical current density at both 5 K and 20 K is accounted to enhanced scattering by C substitution and grain boundary pinning

X-ray powder diffraction study on the MgB2 superconductor reacted with nano-SiC: the effects of sintering temperature

SiC added MgB2 polycrystalline samples were synthesized at low (650°C) and high (850°C) temperatures in order to study the sintering effect on the phase formation and superconducting properties. The MgB2 bulks with additions of 0wt%, 1wt%, 3wt% and 5wt% SiC were studied with powder X-ray diffraction technique. We observed that MgB2 remained as the primary phase for both sintering temperatures in all samples with the presence of MgO and Mg2Si as the main impurities. Some diffraction peaks associated with unreacted SiC is also noticeable. The relative intensity of the Mg2Si peaks was found to decrease in samples sintered at higher temperature. Temperature dependent magnetic moment measurements showed that the superconducting transition temperature, Tc decreases as the SiC addition level increases while lower sintering temperature degrades Tc to a greater extent. The changes in the physical properties is discussed based on the results of phase formation, full width half maximum (FWHM), lattice parameter and crystallite size

Effects of nano-SiC addition on the superconducting properties of magnesium diboride

In this study, we report the results on phase formation, microstructures, and superconducting properties of a series of MgB2 samples with different level of SiC additions. The polycrystalline samples were prepared via solid state reaction by mixing magnesium, boron and silicone carbide powders according to the ratio of Mg:B:SiC = 1:2:x. XRD spectra showed that MgB2 is the primary phase while Mg2Si, MgO and MgB4, together with some unreacted SiC are the secondary phases as the addition increases. The presence of Mg2Si became more significant as the addition level increased. SEM images showed smaller grains as the addition level increases indicating more grain boundaries were formed. The Tc was as low as 30.5K for x=15wt%. The field dependence of Jc showed that x=1wt% sample gave the best performance at both 5K and 20K

Peripheral T-Cell Lymphoma: Review and Updates of Current Management Strategies

The classification of T-cell and natural-killer- (NK-) cell lymphomas has been updated in the 4th edition of the World Health Organization (WHO) classification of tumors of the haematopoietic and lymphoid tissue published in 2008. Based on recent epidemiological studies, NK-cell lymphomas occur almost exclusively in Asia and South America, although T-cell lymphomas appear to occur in the East as commonly as in the West. Due to the low prevalence of this disease, diagnosis and optimal treatment of patients have not been studied prospectively in large randomized trials. Nevertheless, there has been development in the understanding of T-cell lymphomas and how they should be managed; FDG-PET emerges as an increasingly important tool in diagnosis, gene-expression signatures may aid with prognostication in the future, and novel therapies are currently being studied to improve outcomes in T-cell lymphomas. More work, however, needs to be done, and international collaboration will be pertinent to deriving meaningful results from future clinical studies

Body and Disease 2008: An Integrated Course Teaching Pathology, Pharmacology, Immunology and Microbiology

The Duke-NUS Graduate Medical School Singapore (Duke-NUS) Body and Disease course is a 20-week, integrated course occurring at the end of the first year. The course covers four basic science topics: Pathology, Pharmacology, Immunology, and Microbiology and is modelled after the same course from the Duke University School of Medicine (DSOM) in Durham, North Carolina, USA. The structure of the course, as delivered by DSOM, was adapted to meet the needs and structure of the Duke-NUS programme. In addition, the course was adapted significantly to incorporate the Team-Based Learning methodology. In this paper, we detail how we approached these unique challenges. This paper presents an overview of the course structure, preliminary evaluation, and implications for future implementation

Association between mobility spinal cord independence measure (MSCIM) and period of walking recovery in spinal tuberculosis

This study aimed to identify the association between initial Spinal Cord Independence Measure’s Mobility Sub-score (mSCIM) and the period of walking recovery in Spinal Tuberculosis (STB). This retrospective cohort study divided 36 STB patients into two groups by their initial mSCIM score: ‘mSCIM<13’ and ‘mSCIM≥13’. Both groups were retrospectively followed-up from diagnosis until one year via clinical records. Baseline characteristics, walking outcome and period of walking recovery were recorded. Logical regression tested the association between mSCIM and walking outcome while a timeto-event analysis was done to test the relationship between mSCIM and period of walking recovery. Both ‘mSCIM<13’ and ‘mSCIM≥13’ groups had 18 patients each. Logical regression showed the mSCIM≥13 group had higher probability of recovering their walking ability (p=0.021). Time-to-event analysis showed both groups had significantly different period of walking recovery (p=0.001), averaging 10.44 and 4.94 months in those with mSCIM<13 and mSCIM≥13 respectively. In conclusion, patients with mSCIM≥13 require significantly shorter period of walking recovery

Association between early mobility scim measures and walking function in spinal tuberculosis

Spinal Tuberculosis (STB) often led to walking impairment which could lower a patient’s quality of life. This study aimed to determine the association between the early mobility Spinal Cord Independence Measure (mSCIM) and walking function beyond one year of STB diagnosis. This cross-sectional analytical study was conducted by collecting data via focused history taking, clinical assessment, and clinical notes referencing of STB patients attended the rehabilitation follow-up at Queen Elizabeth Hospital, Kota Kinabalu. A total of 36 patients were recruited and grouped as “walking” or “non-walking” based on ability to achieve a minimal level of 6 based on the Walking Index for Spinal Cord Injury (WISCI). Significant difference in mSCIM between the two groups were analysed using logical regression. The results showed that the mSCIM scores between walking and non-walking patients were significantly different (pvalue=0.021, OR=14.9, 95% CI=1.515-147.404). The results were then compared with previous literature. In conclusion, individuals with a higher mSCIM (a score of more than or equal to 13) have higher likelihood of walking beyond one year of STB diagnosis

Reaction method control of impurity scattering in C-doped MgB2: proving the role of defects besides C substitution level

In this study, Si and C were incorporated into polycrystalline MgB 2 via in situ reaction of Mg and B with either SiC or with separate Si and C (Si+C). The electrical transport and magnetic properties of the two series of samples were compared. The corrected resistivity at 40 K, ρA(40 K), is higher for the samples reacted with SiC regardless of the carbon (C) substitution level, indicating larger intragrain scattering because of the simultaneous reaction between Mg and SiC and carbon substitution during the formation of MgB2. In addition, because of the cleaner reaction route for the samples reacted with SiC, the calculated active area that carries current, AF, is twice that of the (Si+C) samples. On the other hand, the upper critical field, Hc2, was similar for both sets of samples despite their different C substitution levels, which proves the importance of defect scattering in addition to C substitution level. Hence, the form of the precursor reactants is critical for tuning the form of Hc2(T)

Impact of left atrial appendage closure on cardiac functional and structural remodeling: A difference-in-difference analysis of propensity score matched samples

Background: Although the safety and efficacy of left atrial (LA) appendage (LAA) closure (LAAC) in nonvalvular atrial fibrillation (NVAF) patients have been well documented in randomized controlled trials and real-world experience, there are limited data in the literature about the impact of LAAC on cardiac remodeling. The aim of the study was to examine the impact of LAAC on cardiac functional and structural remodeling in NVAF patients. Methods: Between March 2014 and November 2016, 47 NVAF patients who underwent LAAC were included in this study (LAAC group). A control group (non-LAAC group) was formed from 141 NVAF patients without LAAC using propensity score matching. The difference-in-difference analysis was used to evaluate the difference in cardiac remodeling between the two groups at baseline and follow-up evaluations. Results: The LAAC group had a larger increase in LA dimension, volume and volume index than the non-LAAC group (+3.9 mm, p = 0.001; +9.7 mL, p = 0.006 and +5.9 mL/m2, p = 0.011, respectively). Besides, a significant increase in E and E/e’ ratio was also observed in the LAAC group (+14.6 cm/s, p = 0.002 and +2.3, p = 0.028, respectively). Compared with the non-LAAC group, left ventricular (LV) ejection fraction and fractional shortening decreased in LAAC patients, but were statistically insignificant (–3.5%, p = 0.109 and –2.0%, p = 0.167, respectively). Conclusions: There were significant increases in LA size and LV filling pressure among NVAF patients after LAAC. These impacts of LAAC on cardiac functional and structural remodeling may have some clinical implications that need to be addressed in future studies

The One Year Outcome after KTP Laser Vaporization of the Prostate According to the Calculated Vaporized Volume

The aim of this study was to develop a new simple method for measuring the vaporized volume and to evaluate the outcome of high-power potassium-titanyl-phosphate (KTP) photoselective laser vaporization. A total of 65 patients, with a mean age of 67.7 yr (range 53 to 85), were included in the primary analysis. The vaporized volume was calculated as the pre-operative volume minus the immediate post-operative volume plus the volume of the defect. For all patients, the subjective and objective parameters improved significantly after surgery. Six and 12 months after surgery, the group with a smaller vaporized volume (<15 g) had a lower reduction of the mean International Prostate Symptom Score (P=0.006 and P=0.004) and quality of life index (P=0.006 and P=0.004) when compared to the group with a greater vaporized volume (≥15 g). There were no differences in the change of the maximum flow rate and post-void residual based on the vaporized volume. Our findings suggest that the subjective improvement, after a high-power KTP laser vaporization, may be dependent on the vaporized volume obtained after the procedure