Rotational CARS application to simultaneous and multiple-point temperature and concentration determination in a turbulent flow

Coherent anti-Stokes Raman scattering (CARS) from the pure rotational Raman lines of N2 is employed to measure the instantaneous (approximately 10 ns) rotational temperature of N2 gas at room temperature and below with good spatial resolution (0.2 x 0.2 x 3.0 cu mm). A broad bandwidth dye laser is used to obtain the entire rotational spectrum from a single laser pulse; the CARS signal is then dispersed by a spectrograph and recorded on an optical multichannel analyzer. A best fit temperature is found in several seconds with the aid of a computer for each experimental spectrum by a least squares comparison with calculated spectra. The model used to calculate the theoretical spectra incorporates the temperature and pressure dependence of the pressure-broadened rotational Raman lines, includes the nonresonant background susceptibility, and assumes that the pump laser has a finite linewidth. Temperatures are fit to experimental spectra recorded over the temperature range of 135 to 296 K, and over the pressure range of .13 to 15.3 atm

Evolution and chemical consequences of lightning-produced NOx observed in the North Atlantic upper troposphere

Airborne observations of NO during the Subsonics Assessment Ozone and Nitrogen Oxides Experiment (SONEX) reveal episodes of high NOx in the upper troposphere believed to be associated with lightning. Linkage to specific periods of lightning activity is possible through back trajectories and data from the National Lightning Detection Network. Lagrangian model calculations are used to explore the evolution of these high NOx plumes over the 1-2 days between their introduction and subsequent sampling by NASA's DC-8 aircraft. Simulations include expected changes in HNO3, H2O2, CH3OOH, HO2, and OH. Depending on the time of injection and dilution rate, initial NOx concentrations are estimated to range from 1 to 7 ppbv. Similar to many previous studies, simulated HNO3 concentrations tend to be greater than observations. Several possible explanations for this difference are explored. H2O2 observations are shown to be consistent with removal in convective activity. While it is possible that upper tropospheric CH3OOH is enhanced by convection, simulations show such increases in CH3OOH can be short-lived (e.g., < 12 hours) with no perceptible trace remaining at the time of sampling. High NO levels further prevent elevated levels of CH3OOH from propagating into increases in H2O2. HO2 is suppressed through reaction with NO in all cases. Simulated increases in OH exceeded a factor of 2 for some cases, but for the highest NOx levels, loss of OH via OH+NO2 offset production from HO2+NO. Additional increases in OH of 30-60% could result from convection of CH3OOH. A final point of discussion concerns how the chemistry within these plumes, their long-range transport, and their potential importance in sustaining background NOx far from source regions present a challenge to global and regional model simulations. Copyright 2000 by the American Geophysical Union

Rural parents, teenagers and alcohol: what are parents thinking?

INTRODUCTION: The fundamental role of alcohol in the lives of young Australians is mirrored in the level of drinking by adolescents. In 2001, more than one in four Australian adolescents aged 14-19 years consumed alcohol weekly. Teenagers in rural areas are more likely to consume alcohol than their metropolitan counterparts. Parents are key \u27gatekeepers\u27 of adolescent behaviour and as such are a salient group to consider in relation to adolescent alcohol use. The aim of this study was to explore parents\u27 attitudes, beliefs, concerns and receptiveness to harm minimisation strategies with respect to teenage use of alcohol. METHODS: A convenience sample of parents with adolescent children attended a series of focus groups across the north and north-western area of the State of Victoria, Australia. Schools were approached to advertise the project and invite parents to participate. Snowball sampling was used to enhance recruitment. RESULTS: Parents described patterns of alcohol use such as \u27drinking to get drunk\u27 and the influence of both parents and peers on the consumption of alcohol by adolescents. Few parents were concerned about the long-term risks of alcohol use by teenagers; rather they were more concerned about the short-term harms, for example, road trauma and other accidents and risky behaviours such as binge drinking. Parents indicated that they perceived alcohol to be less harmful than other drugs and many indicated that alcohol was often not perceived to be a drug. A number of strategies were adopted by parents to negotiate teenagers\u27 drinking and to minimise the risks associated with alcohol use. These included transporting teenagers to parties, providing teenagers with a mobile phone, setting clear guidelines about alcohol use and/or providing teenagers with a small amount of alcohol. These were seen by parents as strategies for reducing the risks associated with alcohol consumption. Many parents reported that they do not feel well informed about alcohol use and how and when to use harm reduction strategies. CONCLUSIONS: Rural parents are unsure how to respond to teenagers\u27 alcohol use and drunkenness. While some parental strategies for harm reduction (such as supplying adolescents with a small amount of alcohol) may have good face validity in reducing alcohol consumption among adolescents, these strategies are not supported by previous research findings.<br /

Coupled evolution of BrOx-ClOx-HOx-NOx chemistry during bromine-catalyzed ozone depletion events in the arctic boundary layer

Extensive chemical characterization of ozone (O3) depletion events in the Arctic boundary layer during the TOPSE aircraft mission in March-May 2000 enables analysis of the coupled chemical evolution of bromine (BrOx), chlorine (ClOx), hydrogen oxide (HOx) and nitrogen oxide (NOx) radicals during these events. We project the TOPSE observations onto an O3 chemical coordinate to construct a chronology of radical chemistry during O3 depletion events, and we compare this chronology to results from a photochemical model simulation. Comparison of observed trends in ethyne (oxidized by Br) and ethane (oxidized by Cl) indicates that ClOx chemistry is only active during the early stage Of O3 depletion (O3 &gt; 10 ppbv). We attribute this result to the suppression of BrCl regeneration as O3 decreases. Formaldehyde and peroxy radical concentrations decline by factors of 4 and 2 respectively during O3 depletion and we explain both trends on the basis of the reaction of CH2O with Br. Observed NOx concentrations decline abruptly in the early stages Of O3 depletion and recover as O3 drops below 10 ppbv. We attribute the initial decline to BrNO3 hydrolysis in aerosol, and the subsequent recovery to suppression of BrNO3 formation as O3 drops. Under halogen-free conditions we find that HNO4 heterogeneous chemistry could provide a major NOx sink not included in standard models. Halogen radical chemistry in the model can produce under realistic conditions an oscillatory system with a period of 3 days, which we believe is the fastest oscillation ever reported for a chemical system in the atmosphere

Slippery motion between the limbs of a double tendon graft

Relative motion of tendon limbs of a double tendon graft for the application of anterior cruciate ligament (ACL) reconstruction may affect the mechanical behaviour of a tendon graft structure. The biomechanical data derived from the standard tensile testing machines may not be able to show the relative motion of the graft limbs. This paper uses the non-destructive digital stereo imaging recording system, synchronized with the standard test machine, to precisely determine the biomechanical properties of 10 bovine flexor tendon grafts which hanged from the loop side to the rig and the other end was fixed in a bone block. The study showed there is a relative motion between graft limbs

Performance of an Operating High Energy Physics Data Grid: D0SAR-Grid

The D0 experiment at Fermilab's Tevatron will record several petabytes of data over the next five years in pursuing the goals of understanding nature and searching for the origin of mass. Computing resources required to analyze these data far exceed capabilities of any one institution. Moreover, the widely scattered geographical distribution of D0 collaborators poses further serious difficulties for optimal use of human and computing resources. These difficulties will exacerbate in future high energy physics experiments, like the LHC. The computing grid has long been recognized as a solution to these problems. This technology is being made a more immediate reality to end users in D0 by developing a grid in the D0 Southern Analysis Region (D0SAR), D0SAR-Grid, using all available resources within it and a home-grown local task manager, McFarm. We will present the architecture in which the D0SAR-Grid is implemented, the use of technology and the functionality of the grid, and the experience from operating the grid in simulation, reprocessing and data analyses for a currently running HEP experiment.Comment: 3 pages, no figures, conference proceedings of DPF04 tal