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

NASA-FAA helicopter Microwave Landing System curved path flight test

An ongoing series of joint NASA/FAA helicopter Microwave Landing System (MLS) flight tests was conducted at Ames Research Center. This paper deals with tests done from the spring through the fall of 1983. This flight test investigated and developed solutions to the problem of manually flying curved-path and steep glide slope approaches into the terminal area using the MLS and flight director guidance. An MLS-equipped Bell UH-1H helicopter flown by NASA test pilots was used to develop approaches and procedures for flying these approaches. The approaches took the form of Straight-in, U-turn, and S-turn flightpaths with glide slopes of 6 deg, 9 deg, and 12 deg. These procedures were evaluated by 18 pilots from various elements of the helicopter community, flying a total of 221 hooded instrument approaches. Flying these curved path and steep glide slopes was found to be operationally acceptable with flight director guidance using the MLS

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

Texas Salt Domes--Aspects, Affecting Disposal of Toxic-Chemical Waste in Solution-Mined Caverns

This report represents Phase II of a one-year contract aimed at analyzing technical considerations linked to the potential isolation of toxic chemical waste within solution-mined caverns situated in Texas salt domes. A key objective of Phase II research was to characterize the properties of salt domes that could impact this form of waste disposal.Bureau of Economic Geolog

Technical Issues for Chemical Waste Isolation in Solution-Mined Caverns in Salt Domes

Many factors contribute to assessing the technical viability of isolating chemical waste in solution-mined caverns within salt domes. Our investigation highlights several key factors of primary importance, including geohydrology, engineering considerations, and the stability of the geologic isolation system, encompassing the cavern, cap rock, and surrounding strata. These factors are largely interconnected and mutually dependent. An essential initial step involves detailed mapping of the domal system, including the cap rock, salt stock, and surrounding domed strata, a level of detail often lacking in public sources and geological literature. Postulated release scenarios typically involve waste transport via groundwater, making the direction and rates of groundwater flow critical. Groundwater flow is influenced by various factors such as rock matrix composition, depositional systems, sand-body geometry, and fault patterns. The cap rock serves as a focal point for many domal processes and is a dynamically changing region of a salt dome. Studies on cap-rock properties can help determine whether salt domes are undergoing uplift or dissolution. The cap rock plays a crucial role in either facilitating or impeding dome dissolution and cavern stability. Further research on salt domes should focus on defining the geometry and structure of cap rocks, identifying cap-rock lost-circulation zones, understanding the geometry, structure, and stratigraphy of salt stocks and caverns, assessing salt-cavern stability, and investigating domal geohydrology. In the following sections, we discuss various issues that need to be addressed to evaluate the technical feasibility of isolating chemical waste in solution-mined caverns within salt domes.Bureau of Economic Geolog

Live high-train low altitude training: responders and non-responders

Objective: Investigate differences between athletes that responded (improved performance) compared to those that did not, after a 20-day “live high-train low” (LHTL) altitude training camp. Methods: Ten elite triathletes completed 20 days of live high (1545-1650 m), train low (300 m) training. The athletes underwent (i), two 800-m swimming time trials at sea-level (1 week prior to and 1 week after the altitude camp) and (ii) two 10-min standardised submaximal cycling tests at altitude on day 1 and day 20 of the altitude camp. Acute mountain sickness (AMS) was also measured during the camp. Based on their 800-m swimming time trial performances, athletes were divided into responders (improved by 3.2 ± 2.2%, mean ± SD, n=6) and non-responders (decreased by 1.8 ± 1.2%, n=4). Results: Compared to non-responders, the responders had lower exercise heart rates (-6.3 ± 7.8%, mean ± 90% CL, and higher oxygen saturations (1.2 ± 1.3%) at the end of the 10-min submaximal test after the camp. Compared to the responders, the non-responders had substantially higher VE and VE/VO₂ during the submaximal test on day 1 of the altitude training camp, and a substantially higher RER during the submaximal test on day 20 of the camp. As a result of the altitude training, exercise economy of the non-responders compared to the responders deteriorated (i.e., non-responders required more oxygen per watt). Non-responders were 3.0 times (90% CL=0.5-16.6) more likely to suffer symptoms of acute mountain sickness during first 5 days of altitude compared to responders. Conclusion: Changes in SpO₂, heart rate and some respiratory variables during exercise and resting AMS scores may help determine athletes that respond to LHTL altitude training camps from athletes that fail to respond to such training

Texas Salt Domes: Natural Resources, Storage Caverns, and Extraction Technology

This report reviews natural resources associated with salt domes in Texas. Salt domes provide a broad spectrum of the nation's industrial needs including fuel, minerals, chemical feedstock, and efficient storage space. This report focuses on the development, technology, uses, and problems associated with solution-mined caverns in salt domes. One proposed new use for salt domes is the permanent isolation of toxic chemical waste in solution-mined caverns. As the Texas Department of Water Resources (TDWR) is the State authority responsible for issuing permits for waste disposal in Texas, TDWR funded this report to judge better the technical merits of toxic waste disposal in domes and to gain a review of the state of the art of applicable technology. Salt domes are among the most interesting and intensively studied structural-stratigraphic geologic features. Individual domes may be the largest autochthonous structures on earth. Yet many aspects of salt-dome genesis and evolution, geometry, internal structure, and stratigraphy are problematic. Details of both external and internal geometry of salt stocks and their cap rocks are vague, and information is restricted to the shallow parts of the structure. These facts are all the more surprising considering that salt diapirs dominate the fabric of the Gulf Coastal Province, which is one of the most explored and best known geologic regions on earth. This report includes information on present and past uses of Texas salt domes, their production histories, and extractive technologies (see also Halbouty, 1979; Hawkins and Jirik, 1966; and Jirik and Weaver, 1976). Natural resources associated with salt domes are dominated by petroleum that is trapped in cap rocks and in strata flanking and overlying salt structures. Sulfur occurs in the cap rock of many domes. Some cap rocks also host potentially valuable Mississippi Valley-type sulfide and silver deposits. Salt is produced both by underground mining of rock salt and by solution brining. The caverns created in salt by solution mining also represent a natural resource. The relative stability, economics, location, and size of these caverns make them valuable storage vessels for various petroleum products and chemical feedstocks.Bureau of Economic Geolog