Hall carrier density and magnetoresistance measurements in thin film vanadium dioxide across the metal-insulator transition

Temperature dependent magneto-transport measurements in magnetic fields of up to 12 Tesla were performed on thin film vanadium dioxide (VO2) across the metal-insulator transition (MIT). The Hall carrier density increases by 4 orders of magnitude at the MIT and accounts almost entirely for the resistance change. The Hall mobility varies little across the MIT and remains low, ~0.1cm2/V sec. Electrons are found to be the major carriers on both sides of the MIT. Small positive magnetoresistance in the semiconducting phase is measured

Deep Traps in AlGaN/GaN Heterostructures Studied by Deep Level Transient Spectroscopy: Effect of Carbon Concentration in GaN Buffer Layers

Electrical properties, including leakage currents, threshold voltages, and deep traps, of AlGaN/GaN heterostructure wafers with different concentrations of carbon in the GaN buffer layer, have been investigated by temperature dependent current-voltage and capacitance-voltage measurements and deep level transient spectroscopy (DLTS), using Schottky barrier diodes (SBDs). It is found that (i) SBDs fabricated on the wafers with GaN buffer layers containing a low concentration of carbon (low-[C] SBD) or a high concentration of carbon (high-[C] SBD) have similar low leakage currents even at 500 K; and (ii) the low-[C] SBD exhibits a larger (negative) threshold voltage than the high-[C] SBD. Detailed DLTS measurements on the two SBDs show that (i) different trap species are seen in the two SBDs: electron traps Ax (0.9 eV), A1 (0.99 eV), and A2 (1.2 eV), and a holelike trap H1 (1.24 eV) in the low-[C] SBD; and electron traps A1, A2, and A3 ( ∼ 1.3 eV), and a holelike trap H2 (\u3e1.3 eV) in the high-[C] SBD; (ii) for both SDBs, in the region close to GaN buffer layer, only electron traps can be detected, while in the AlGaN/GaN interface region, significant holelike traps appear; and iii) all of the deep traps show a strong dependence of the DLTS signal on filling pulse width, which indicates they are associated with extended defects, such as threading dislocations. However, the overall density of electron traps is lower in the low-[C] SBD than in the high-[C] SBD. The different traps observed in the two SBDs are thought to be mainly related to differences in microstructure (grain size and threading dislocation density) of GaN buffer layers grown at different pressures

Effects of annealing in N2 ambient on traps and persistent conduction in hydrothermally grown ZnO

Thermally stimulated current (TSC) spectroscopy and temperature–dependent dark current (DC) measurements have been applied to study traps and photoinduced persistent surface conduction in two hydrothermally grown bulk ZnO samples, as-grown, and annealed at 600 °C in N2 ambient for 30 min, respectively. The as-grown sample had a room-temperature (RT) resistivity of 1.6×103 Ω cm, mobility of 2.1×102 cm2/V s, and carrier concentration of 1.8×1013 cm−3, while the annealed sample was highly resistive, with RT resistivity of 3.6×106 Ω cm, mobility of 4.4 cm2/V s, and carrier concentration of 3.9×1011 cm−3. The as-grown sample showed strong conduction at low temperatures, which has been shown to be due to near-surface carriers in other studies. The annealed sample did not demonstrate this phenomenon. The dominant trap in the as-grown sample had an activation energy of 0.16 eV, was strongest near the surface, and is possibly related to VZn. In the annealed sample, however, the dominant trap had an activation energy of 0.22 eV, was of bulk nature, and is tentatively assigned to LiZn. After several routine TSC measurements, the DC for the as-grown sample increased by more than one order of magnitude at low temperatures (T\u3c180 \u3eK), while for the annealed sample, the DC increased by a factor of 2 at high temperatures (T\u3e200 K). These effects are generated by the TSC trap-filling illumination and can persist for many days under vacuum. At RT, the DC in the annealed sample returns to its equilibrium state if the sample is vented to air

The Effect of Disease Modifying Therapies on Disability Progression in Multiple Sclerosis: A Systematic Overview of Meta-Analyses

Background: Disease modifying therapy (DMT) efficacy trials make an essential contribution to the development of evidence-based clinical treatments and practices for people with multiple sclerosis (MS). Meta-analysis is a critical part of this process and provides a powerful tool to assess the effects of DMT on MS progression. However, although there have been several meta-analyses on the effect of DMT on MS disease progression, they often do not reach the same conclusions.Objective: Our aim was to better understand and contextualize the results of meta-analyses evaluating DMT, identify differences in methodology that might explain their differing conclusions, and highlight areas for future research that will improve our ability to develop clinical recommendations.Methods: We conducted an overview of systematic reviews with meta-analyses assessing the efficacy of DMT on disability progression in people with MS in PubMed (Medline) and the Cochrane Database of Systematic Reviews.Results: We included 22 meta-analyses in this overview: eight general (on >3 DMT), 11 specific (on ≤3 DMT), 2 that evaluated subsets, and 1 that evaluated long-term effects. We found that there is good evidence that DMT improve short-term (≤2–3 years) disability progression outcomes relative to placebo in people with relapsing-remitting MS. However, results varied substantially between meta-analyses, and there is little evidence of their efficacy in other populations or over longer periods. The relative effects of individual DMT also remain unclear. The variance in results between meta-analyses may be related to the substantial differences in inclusion criteria, which was reflected in the limited overlap in included studies, as well as the year of meta-analysis publication. Of the 123 total unique studies included in the general meta-analyses, 77 (62.6%) were included in only one meta-analysis. This incongruence was also evident in the included DMT. Six of the 16 (37.5%) DMT evaluated in the general meta-analyses were only included in one meta-analysis.Conclusions: Translating DMT efficacy studies into evidence-based clinical practice requires greater methodological consistency in meta-analyses, more data on the relative effects of DMT through head-to-head clinical trials, and better reporting of adverse events

Measurement properties of the Health Literacy Questionnaire in the Understanding Multiple Sclerosis Massive Open Online Course Cohort: A Rasch analysis

Background: Online health education and other electronic health improvement strategies are developing rapidly, highlighting the growing need for valid scales to assess health literacy (HL). One comprehensive HL scale is the Health Literacy Questionnaire (HLQ), but little is known about its measurement properties in online health education cohorts.Objective: The purpose of this study was to determine if the multidimensional HLQ is an appropriate tool to measure HL in a cohort of Understanding Multiple Sclerosis (MS) online course enrollees.Methods: Participants who enrolled in the first two open enrollments of the Understanding MS online course completed the HLQ (N = 1,182) in an online survey prior to beginning course materials. We used Rasch analysis to assess the measurement properties of the HLQ.Key results: The nine Domains of the HLQ each had ordered category function and a good fit with the Rasch model. Each domain was one-dimensional and exhibited good internal consistency and reliability. None of the 44 individual items of the HLQ demonstrated item bias or local dependency. However, while the overall fit was good, few measurement gaps were identified in this cohort for participants in each of the nine Domains, meaning that the HLQ may have low measurement precision in some participants.Conclusion: Our analysis of the HLQ indicated acceptable measurement properties in a cohort of Understanding MS online course enrollees. Although reliable information on nine separate constructs of HL was obtainable in the current study indicating that the HLQ can be used in similar cohorts, its limitations must be also considered

Inheritance of resistance to Sporisorium sorghi in grain sorghum

Greenhouse and field experiments were conducted in 1995, in Kansas, USA, to investigate the inheritance of resistance to covered kernel smut (Sporisorium sorghi) in sorghum cultivars B35-6, SC414 and Sureño. In all crosses, the susceptible parent was BTx623. Crosses were made between resistant and susceptible accessions to determine inheritance. Crosses between resistant accessions were used to determine if they possessed the same genes. Resistant parents remained immune to S. sorghi under both field and greenhouse conditions. The incidence (76%) of smutted panicles of BTx623 grown under greenhouse conditions was substantially higher than that in BTx623 grown in the field (2.3%). The reactions of F1 progenies of the crosses B35-6 × Sureño and Sureño × BTx623 suggest incomplete dominance of resistance. There was a very limited amount of F1 seed from the other resistant × susceptible crosses and therefore no conclusion could be reached on the reactions of their progenies to S. sorghi. A 3:1 ratio of resistant to susceptible plants was obtained in the F2 population of Sureño × BTx623, suggesting incomplete dominance. Higher smut incidence in the F1 progeny of Sureño × BTx623 was observed, indicating incomplete dominance of resistance from Sureno

Reclassification of Subspecies of \u3ci\u3eAcidovorax avenae\u3c/i\u3e as \u3ci\u3eA. Avenae\u3c/i\u3e (Manns 1905) emend., \u3ci\u3eA. cattleyae \u3c/i\u3e (Pavarino, 1911)comb.nov., \u3ci\u3eA. citrulli\u3c/i\u3e Schaad et al.,1978)comb.nov., and proposal of \u3ci\u3eA. oryzae \u3c/i\u3esp. nov.

The bacterium Acidovorax avenae causes disease in a wide range of economically important monocotyledonous and dicotyledonous plants, including corn, rice, watermelon, anthurium, and orchids.Genotypic and phenotypic relatedness among strains of phytopathogenic A. avenae sub sp. avenae, A. avenae sub sp. citrulli, A. avenae subsp. cattleyae and A. konjaci, as well as all other Acidovorax species, including A. facilis, the type strain of Acidovorax, was determined.The16s rDNA sequencing confirmed previous studies showing the environmental species to be very distant from the phytopathogenic species. DNA/DNA reassociation assays on the different strains of A. avenae revealed four(A, B, C, and D) distinct genotypes. Taxon A included six A. avenae subsp. avenaestrains from corn that had a mean reciprocal similarity of 81%; taxon B included six A. avenae sub sp. avenae strains from rice that had a mean reciprocal similarity of 97%; taxon C contained 11 A. avenae sub sp. citrulli strains from cucurbits (cantaloupe, watermelon, and pumpkin) that had a mean reciprocal similarity of 88%, and taxon D contained four A. avenae sub sp. cattleyae strains from orchids that had a mean similarity of 98%