[I] Terrestrial Ages of Antarctic and Hot Desert Meteorites Using Carbon-14 and Other Cosmogenic Radionuclides

The Tenth Symposium on Polar Science/Special session: [OA] Antarctic meteorites, Thur. 5 Dec. / 3F Multipurpose conference room, National Institute of Polar Researc

Radionuclide measurements by accelerator mass spectrometry at Arizona

Over the past years, Tandem Accelerator Mass Spectrometry (TAMS) has become established as an important method for radionuclide analysis. In the Arizona system the accelerator is operated at a thermal voltage of 1.8MV for C-14 analysis, and 1.6 to 2MV for Be-10. Samples are inserted into a cesium sputter ion source in solid form. Negative ions sputtered from the target are accelerated to about 25kV, and the injection magnet selects ions of a particular mass. Ions of the 3+ charge state, having an energy of about 9MeV are selected by an electrostatic deflector, surviving ions pass through two magnets, where only ions of the desired mass-energy product are selected. The final detector is a combination ionization chamber to measure energy loss (and hence, Z), and a silicon surface-barrier detector which measures residual energy. After counting the trace iosotope for a fixed time, the injected ions are switched to the major isotope used for normalization. These ions are deflected into a Faraday cup after the first high-energy magnet. Repeated measurements of the isotope ratio of both sample and standards results in a measurement of the concentration of the radionuclide. Recent improvements in sample preparation for C-14 make preparation of high-beam current graphite targets directly from CO2 feasible. Except for some measurements of standards and backgrounds for Be-10 measurements to date have been on C-14. Although most results have been in archaeology and quaternary geology, studies have been expanded to include cosmogenic C-14 in meteorites. The data obtained so far tend to confirm the antiquity of Antarctic meteorites from the Allan Hills site. Data on three samples of Yamato meteorites gave terrestrial ages of between about 3 and 22 thousand years

Carbon and oxygen isotope composition of carbonates from an L6 chondrite: Evidence for terrestrial weathering from the Holbrook meteorite

Terrestrial weathering in meteorites is an important process which alters pristine elemental and isotopic abundances. The Holbrook L6 chondrite fell in 1912. Material was recovered at the time of the fall, in 1931, and 1968. The weathering processes operating on the freshly fallen meteorite in a semi-arid region of northeastern Arizona have been studied after a ground residence of 19 and 56 years. It has been shown that a large portion of the carbonate material in 7 Antarctic ordinary chondrites either underwent extensive isotopic exchange with atmospheric CO2, or formed recently in the Antarctic environment. In fact it has been demonstrated that hydrated Mg-carbonates, nesquehonite and hydromagnesite, formed in less than 40 years on LEW 85320. In order to help further constrain the effects of terrestrial weathering in meteorites, the carbon and oxygen isotopes extracted from carbonates of three different samples of Holbrook L6: a fresh sample at the time of the fall in 1912, a specimen collected in 1931, and a third specimen collected at the same site in 1968

Physiotherapy at the XII Commonwealth Games Part II: Injuries and Management

At the XII Commonwealth Games held in Brisbane in 1982, Australian physiotherapists as members of the host nation's medical division, treated the injuries of competitors from the ten sports contested. The nature and incidence of the injuries treated by the host physiotherapists is tabulated and comment is made regarding several significant features. Implications for the management skills of physiotherapists required either to travel with teams or work as host physiotherapists are made. Furthermore, the utilization of equipment is indicated. Overall the paper provides a resource to assist in future planning for such events in respect to physiotherapy manpower, expertise and equipment needs

The exposure history of the Apollo 16 site: An assessment based on methane and hydrolysable carbon

Nineteen soils from eight stations at the Apollo 16 landing site have been analyzed for methane and hydrolysable carbon. These results, in conjunction with published data from photogeology, bulk chemistry, rare gases, primordial and cosmogenic radionuclides, and agglutinate abundances have been interpreted in terms of differing contributions from three components-North and South Ray Crater ejecta and Cayley Plains material

“CLOCK IN THE ROCK” – IN-SITU C-14 ROCK SURFACE EXPOSURE DATING APPLICATIONS

Cosmic rays interact not only with the atmosphere, but also with material at the surface of the Earth. Thus C-14 can be produced directly in a rock surface by the effect of cosmic-ray neutron effects. The goal of the research is to develop the capability of the Hertelendi Laboratory for Environmental Sciences (HEKAL) in the field of cosmogenic radionuclides produced in situ by the action of cosmic radiation. Our aim is to construct a small line for the extraction of cosmogenic C-14 from quartz, making a system compatible with the online capabilities of the new MICADAS accelerator mass spectrometer (AMS) at HEKAL in Debrecen. We have tested the chemical blank level, cross contamination effect and reproducibility of MICADAS gas ion source application in in-situ rock surface exposure dating

Movement-based subgrouping in low back pain: synergy and divergence in approaches

Background Classification systems for low back pain (LBP) aim to guide treatment decisions. In physiotherapy, there are five classification schemes for LBP which consider responses to clinical movement examination. Little is known of the relationship between the schemes