868 research outputs found
Evolution of the Fermi surface of BiTeCl with pressure
We report measurements of Shubnikov-de Haas oscillations in the giant Rashba
semiconductor BiTeCl under applied pressures up to ~2.5 GPa. We observe two
distinct oscillation frequencies, corresponding to the Rashba-split inner and
outer Fermi surfaces. BiTeCl has a conduction band bottom that is split into
two sub-bands due to the strong Rashba coupling, resulting in two
spin-polarized conduction bands as well as a Dirac point. Our results suggest
that the chemical potential lies above this Dirac point, giving rise to two
Fermi surfaces. We use a simple two-band model to understand the pressure
dependence of our sample parameters. Comparing our results on BiTeCl to
previous results on BiTeI, we observe similar trends in both the chemical
potential and the Rashba splitting with pressure.Comment: 6 pages, 5 figure
Efficient room temperature cw Yb:glass laser pumped by a 946nm Nd:YAG laser
By pumping with a cw diode-pumped Nd:YAG laser operating at 946nm laser operation of a new Yb-doped phosphate glass with 440mW cw output power and a slope efficiency of 48% with respect to the absorbed pump power was achieved at room temperature
Studies of superconductivity and structure for CaC6 to pressures above 15 GPa
The dependence of the superconducting transition temperature Tc of CaC6 has
been determined as a function of hydrostatic pressure in both helium-loaded gas
and diamond-anvil cells to 0.6 and 32 GPa, respectively. Following an initial
increase at the rate +0.39(1) K/GPa, Tc drops abruptly from 15 K to 4 K at 10
GPa. Synchrotron x-ray measurements to 15 GPa point to a structural transition
near 10 GPa from a rhombohedral to a higher symmetry phase
Pressure-induced superconductivity in the giant Rashba system BiTeI
At ambient pressure, BiTeI is the first material found to exhibit a giant
Rashba splitting of the bulk electronic bands. At low pressures, BiTeI
undergoes a transition from trivial insulator to topological insulator. At
still higher pressures, two structural transitions are known to occur. We have
carried out a series of electrical resistivity and AC magnetic susceptibility
measurements on BiTeI at pressure up to ~40 GPa in an effort to characterize
the properties of the high-pressure phases. A previous calculation found that
the high-pressure orthorhombic P4/nmm structure BiTeI is a metal. We find that
this structure is superconducting with Tc values as high as 6 K. AC magnetic
susceptibility measurements support the bulk nature of the superconductivity.
Using electronic structure and phonon calculations, we compute Tc and find that
our data is consistent with phonon-mediated superconductivity.Comment: 7 pages, 7 figure
Hypoxic repeat sprint training improves rugby player's repeated sprint but not endurance performance
This study aims to investigate the performance changes in 19 well-trained male rugby players after repeat-sprint training (six sessions of four sets of 5 Ă 5 s sprints with 25 s and 5 min of active recovery between reps and sets, respectively) in either normobaric hypoxia (HYP; n = 9; FâOâ = 14.5%) or normobaric normoxia (NORM; n = 10; FâOâ = 20.9%). Three weeks after the intervention, 2 additional repeat-sprint training sessions in hypoxia (FâOâ = 14.5%) was investigated in both groups to gauge the efficacy of using "top-up" sessions for previously hypoxic-trained subjects and whether a small hypoxic dose would be beneficial for the previously normoxic-trained group. Repeated sprint (8 Ă 20 m) and Yo-Yo Intermittent Recovery Level 1 (YYIR1) performances were tested twice at baseline (Pre 1 and Pre 2) and weekly after (Post 1-3) the initial intervention (intervention 1) and again weekly after the second "top-up" intervention (Post 4-5). After each training set, heart rate, oxygen saturation, and rate of perceived exertion were recorded. Compared to baseline (mean of Pre 1 and Pre 2), both the hypoxic and normoxic groups similarly lowered fatigue over the 8 sprints 1 week after the intervention (Post 1: -1.8 ± 1.6%, -1.5 ± 1.4%, mean change ± 90% CI in HYP and NORM groups, respectively). However, from Post 2 onwards, only the hypoxic group maintained the performance improvement compared to baseline (Post 2: -2.1 ± 1.8%, Post 3: -2.3 ± 1.7%, Post 4: -1.9 ± 1.8%, and Post 5: -1.2 ± 1.7%). Compared to the normoxic group, the hypoxic group was likely to have substantially less fatigue at Post 3-5 (-2.0 ± 2.4%, -2.2 ± 2.4%, -1.6 ± 2.4% Post 3, Post 4, Post 5, respectively). YYIR1 performances improved throughout the recovery period in both groups (13-37% compared to baseline) with unclear differences found between groups. The addition of two sessions of "top-up" training after intervention 1, had little effect on either group. Repeat-sprint training in hypoxia for six sessions increases repeat sprint ability but not YYIR1 performance in well-trained rugby players
THU0394â MRI Assessment of Axial Involvement in Inflammatory Bowel Disease-Related SPA: Age at Disease Diagnosis, Not Extent and Severity of Axial Disease, Relates To HLA-B27
A Real-Time Ultrasonic Imaging System (ARIS) for Manual Inspection of Aircraft Composite Structures
Inspection of aircraft composite structures at field site facilities (air bases) is routinely performed using manual ultrasonic testing (UT) techniques. Using these techniques, the examiner detects and sizes defects such as disbonds and delaminations by monitoring and interpreting A-scan waveform signals on a UT instrument display screen. Manual probe manipula- tion permits maximum scanning flexibility and optimization of the ultrasonic signal response by the examiner using manual motions not possible with mechanized scanners. However, the examiner also must be responsible for instrument calibration, signal interpretation, documentation of inspection results, and completeness of coverage. The data reviewer must be able to validate instrument calibration and completeness of coverage, confirm signal interpretation, and compare current UT results to those obtained during previous inspections
Methotrexate-resistant Chinese hamster ovary cells have amplified a 135-kilobase-pair region that includes the dihydrofolate reductase gene.
Systematic Study on Fluorine-doping Dependence of Superconducting and Normal State Properties in LaFePO1-xFx
We have investigated the fluorine-doping dependence of lattice constants,
transports and specific heat for polycrystalline LaFePO1-xFx. F doping slightly
and monotonically decreases the in-plane lattice parameter. In the normal
state, electrical resistivity at low temperature is proportional to the square
of temperature and the electronic specific heat coefficient has large value,
indicating the existence of moderate electron-electron correlation in this
system. Hall coefficient has large magnitude, and shows large temperature
dependence, indicating the low carrier density and multiple carriers in this
system. Temperature dependence of the upper critical field suggests that the
system is a two gap superconductor. The F-doping dependence of these properties
in this system are very weak, while in the FeAs system (LaFeAsO), the F doping
induces the large changes in electronic properties. This difference is probably
due to the different F-doping dependence of the lattice in these two systems.
It has been revealed that a pure effect of electron doping on electronic
properties is very weak in this Fe pnictide compound.Comment: 8 pages, 5 figures, accepted for publication in J. Phys. Soc. Jp
Recommended from our members
Prospectus for a Design Well in the Blessing Area Matagorda County, Texas
In recent years, the Bureau of Economic Geology has conducted regional subsurface studies of the Wilcox Group and Frio Formation of Texas as part of the U. S. Department of Energy's assessment of deep geopressured geothermal resources along the Gulf Coast. These studies resulted in two reports (Bebout and others, 1978; 1979) that describe several areas in Texas where temperatures are greater than 300Ă°F and where the geology and reservoir conditions are suitable for resource testing by a design well.
Throughout the Texas Coastal Plain, the 300Ă°F isotherm generally occurs at depths ranging from 12,000 to 16,000 ft. The overlying geopressured sediments represent a substantial portion of the sedimentary column that contains significant quantities of entrained methane, making them a significant portion of the resource base (Gregory and others, 1980). The lower temperatures and pressures of these shallow geopressured sediments result in lower methane solubility, but drilling costs would be substantially lower, and perhaps reservoir quality would be better in comparison to the deep geopressured intervals. Although the latter condition has not been substantiated, several areas that are geologically favorable for testing shallow geopressured aquifers with temperatures less than 300Ă°F were identified in a recently completed study (Weise and others, 1980) funded by the Gas Research Institute.
The Blessing Prospect (fig. 1), one of the shallow prospects in Matagorda County, Texas, is presented in this prospectus as a candidate for the DOE design well program. The prospectus focuses on the geological and engineering aspects of the test site. Although legal and environmental considerations are mentioned, they have not been studied in detail and additional work would necessarily follow if the prospect is approved for drilling and testing. Likewise, a drilling program and an economic analysis would be necessary before final approval of a design well.Bureau of Economic Geolog
- âŠ