A Bayesian spatio-temporal model of panel design data: airborne particle number concentration in Brisbane, Australia

This paper outlines a methodology for semi-parametric spatio-temporal modelling of data which is dense in time but sparse in space, obtained from a split panel design, the most feasible approach to covering space and time with limited equipment. The data are hourly averaged particle number concentration (PNC) and were collected, as part of the Ultrafine Particles from Transport Emissions and Child Health (UPTECH) project. Two weeks of continuous measurements were taken at each of a number of government primary schools in the Brisbane Metropolitan Area. The monitoring equipment was taken to each school sequentially. The school data are augmented by data from long term monitoring stations at three locations in Brisbane, Australia. Fitting the model helps describe the spatial and temporal variability at a subset of the UPTECH schools and the long-term monitoring sites. The temporal variation is modelled hierarchically with penalised random walk terms, one common to all sites and a term accounting for the remaining temporal trend at each site. Parameter estimates and their uncertainty are computed in a computationally efficient approximate Bayesian inference environment, R-INLA. The temporal part of the model explains daily and weekly cycles in PNC at the schools, which can be used to estimate the exposure of school children to ultrafine particles (UFPs) emitted by vehicles. At each school and long-term monitoring site, peaks in PNC can be attributed to the morning and afternoon rush hour traffic and new particle formation events. The spatial component of the model describes the school to school variation in mean PNC at each school and within each school ground. It is shown how the spatial model can be expanded to identify spatial patterns at the city scale with the inclusion of more spatial locations.Comment: Draft of this paper presented at ISBA 2012 as poster, part of UPTECH projec

Location of Solution Channels and Sinkholes at Dam Sites and Backwater Areas by Seismic Methods: Part I

The basic concepts associated with the sledge hammer seismic refraction survey are reviewed and a modified version called down hole shooting is discussed. The latter method has distinct advantages for rock surface profiling. These include: calibration at the end points of the survey, measurement of vertical wave propagation velocities directly, and having a refracted wave ray path for almost the entire survey length. The down hole shooting seismic refraction survey has been simulated with the digital computer. The method can handle any shaped rock surface profile and generates corresponding travel time curves for the forward and reverse profile surveys. This program was used to systematically study the effects of anomalies on the travel time curves. A method of data reduction was developed that enables an estimate of the rock surface profile to be made from the travel time data. The procedure involves the use of a reference depth line which connects the end points of a survey and the travel time curves for this reference depth line. Field tests were performed at four sites having soil and rock characteristics different from each other. Typical results are given. Rock surface profiles are estimated from the travel time curves using the procedure developed and these are compared with the depth to rock by proof drilling. Finally, the sources of error are discussed and some limitations of use are presented. For the sledge hammer method to be used for rock surface profiling, the rock surface should be within 25 to 30 ft of the soil surface and the minimum width of solution channel that can be sensed with this method is on the order of two feet. Recommendations for additional research are also given

Heterogeneity in the growth hormone pituitary gland system of rats and humans: Implications to microgravity based research

The cell separation techniques of velocity sedimentation, flow cytometry and continuous flow electrophoresis were used to obtain enriched populations of growth hormone (GH) cells. The goal was to isolate a GH cell subpopulation which releases GH molecules which are very high in biological activity, it was important to use a method which was effective in processing large numbers of cells over a short time span. The techniques based on sedimentation are limited by cell density overlaps and streaming. While flow cytometry is useful in the analytical mode for objectively establishing cell purity, the numbers of cells which can be processed in the sort mode are so small as to make this approach ineffective in terms of the long term goals. It was shown that continuous flow electrophoresis systems (CFES) can separate GH cells from other cell types on the basis of differences in surface charge. The bioreactive producers appear to be more electrophoretically mobile than the low producers. Current ground based CFES efforts are hampered by cell clumping in low ionic strength buffers and poor cell recoveries from the CFES device

Entropic effects on the Size Evolution of Cluster Structure

We show that the vibrational entropy can play a crucial role in determining the equilibrium structure of clusters by constructing structural phase diagrams showing how the structure depends upon both size and temperature. These phase diagrams are obtained for example rare gas and metal clusters.Comment: 5 pages, 3 figure

Krylov-Bogoliubov-Mitropolsky Averaging Used to Construct Effective Hamiltonians in the Theory of Strongly Correlated Electron Systems

We show that the Krylov-Bogoliubov-Mitropolsky averaging in the canonical formulation can be used as a method for constructing effective Hamiltonians in the theory of strongly correlated electron systems. As an example, we consider the transition from the Hamiltonians of the Hubbard and Anderson models to the respective Hamiltonians of the t-J and Kondo models. This is a very general method, has several advantages over other methods, and can be used to solve a wide range of problems in the physics of correlated systems.Comment: 9 page

Reducing Aggressive Responses to TCAS: Evaluation of a TCAS Training Program

The Traffic alert and Collision Avoidance System (TCAS) is an aircraft collision avoidance system designed to prevent mid-air collisions. While responding to a TCAS advisory is generally the safe course of action, instances of overly aggressive responses have resulted in injuries to crew members and passengers as well as disruptions in air traffic operations. However, current training standards do not address the need to mitigate overly aggressive responses. This paper details the design and evaluation of a training program for TCAS which incorporated a learning objective related to mitigating aggressive responses to advisories. The impact of the training program was evaluated by comparing the results of two flight simulator experiments. These experiments examined “trained” and “untrained” pilot responses to TCAS advisories in an integrated flight deck-Air Traffic Control simulator. Overall, the training program had a significant impact on the pilots’ behavior and aggressive responses to TCAS advisories were decreased

Measurement of the Solar Neutrino Capture Rate by the Russian-American Gallium Solar Neutrino Experiment During One Half of the 22-Year Cycle of Solar Activity

We present the results of measurements of the solar neutrino capture rate in gallium metal by the Russian-American Gallium Experiment SAGE during slightly more than half of a 22-year cycle of solar activity. Combined analysis of the data of 92 runs during the 12-year period January 1990 through December 2001 gives a capture rate of solar neutrinos with energy more than 233 keV of 70.8 +5.3/-5.2 (stat.) +3.7/-3.2 (syst.) SNU. This represents only slightly more than half of the predicted standard solar model rate of 128 SNU. We give the results of new runs beginning in April 1998 and the results of combined analysis of all runs since 1990 during yearly, monthly, and bimonthly periods. Using a simple analysis of the SAGE results combined with those from all other solar neutrino experiments, we estimate the electron neutrino pp flux that reaches the Earth to be (4.6 +/- 1.1) E10/(cm^2-s). Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is approximately (7.7 +/- 1.8) E10/(cm^2-s), in agreement with the standard solar model calculation of (5.95 +/- 0.06) E10/(cm^2-s).Comment: English translation of article submitted to Russian journal Zh. Eksp. Teor. Fiz. (JETP); 12 pages, 5 figures. V2: Added winter-summer difference and 2 reference

Molecular dynamics simulations of lead clusters

Molecular dynamics simulations of nanometer-sized lead clusters have been performed using the Lim, Ong and Ercolessi glue potential (Surf. Sci. {\bf 269/270}, 1109 (1992)). The binding energies of clusters forming crystalline (fcc), decahedron and icosahedron structures are compared, showing that fcc cuboctahedra are the most energetically favoured of these polyhedral model structures. However, simulations of the freezing of liquid droplets produced a characteristic form of ``shaved'' icosahedron, in which atoms are absent at the edges and apexes of the polyhedron. This arrangement is energetically favoured for 600-4000 atom clusters. Larger clusters favour crystalline structures. Indeed, simulated freezing of a 6525-atom liquid droplet produced an imperfect fcc Wulff particle, containing a number of parallel stacking faults. The effects of temperature on the preferred structure of crystalline clusters below the melting point have been considered. The implications of these results for the interpretation of experimental data is discussed.Comment: 11 pages, 18 figues, new section added and one figure added, other minor changes for publicatio

Controls Over Foliar N:P Ratios in Tropical Rain Forests

Correlations between foliar nutrient concentrations and soil nutrient availability have been found in multiple ecosystems. These relationships have led to the use of foliar nutrients as an index of nutrient status and to the prediction of broadscale patterns in ecosystem processes. More recently, a growing interest in ecological stoichiometry has fueled multiple analyses of foliar nitrogen : phosphorus (N:P) ratios within and across ecosystems. These studies have observed that N:P values are generally elevated in tropical forests when compared to higher latitude ecosystems, adding weight to a common belief that tropical forests are generally N rich and P poor. However, while these broad generalizations may have merit, their simplicity masks the enormous environmental heterogeneity that exists within the tropics; such variation includes large ranges in soil fertility and climate, as well as the highest plant species diversity of any biome. Here we present original data on foliar N and P concentrations from 150 mature canopy tree species in Costa Rica and Brazil, and combine those data with a comprehensive new literature synthesis to explore the major sources of variation in foliar N:P values within the tropics. We found no relationship between N:P ratios and either latitude or mean annual precipitation within the tropics alone. There is, however, evidence of seasonal controls; in our Costa Rica sites, foliar N:P values differed by 25% between wet and dry seasons. The N:P ratios do vary with soil P availability and/or soil order, but there is substantial overlap across coarse divisions in soil type, and perhaps the most striking feature of the data set is variation at the species level. Taken as a whole, our results imply that the dominant influence on foliar N:P ratios in the tropics is species variability and that, unlike marine systems and perhaps many other terrestrial biomes, the N:P stoichiometry of tropical forests is not well constrained. Thus any use of N:P ratios in the tropics to infer larger-scale ecosystem processes must comprehensively account for the diversity of any given site and recognize the broad range in nutrient requirements, even at the local scale