Source characterization of major emission sources in the imperial and Mexicali Valleys along the US/Mexico border

Chemical profiles for particle emissions are needed for source apportionment studies using the chemical mass balance (CMB) receptor model. Source measurements of geological sources, motor vehicle exhaust, vegetative burning (e.g. asparagus, field burning, charbroil cooking), and industrial sources (e.g. oil-fueled glass plant, manure-fueled power plants) were acquired as part of the Imperial/Mexicali Valley Cross Border PM10 Transport Study in 1992. Six different source sampling techniques (i.e. hot- and diluted-exhaust sampling, ground-based source sampling, particle sweeping/grab sampling, vacuum sampling, and laboratory resuspension sampling) were applied to acquire filter samples of PM 2.5 and PM10 (particulate matter with aerodynamic diameters < 2.5 and 10 microm, respectively). Filter samples were analyzed for mass by gravimetry, elements (Na to U) by X-ray fluorescence, anions (Cl(-), NO3(-), SO4(=)) by ion chromatography, ammonium (NH4(+)) by automated colorimetry, soluble sodium (Na+) and potassium (K+) by atomic absorption spectrophotometry, and organic and elemental carbon (OC, EC) by thermal/optical reflectance. Concentration data were acquired for a total of approximately 50 chemical species. Elevated abundances of crustal components (Al, Si, K, Ca, Fe) from geological material, carbon (OC, EC) and trace elements (Br, Pb) from vehicle exhausts, carbon (OC, EC) and ions (K(+), Cl(-)) from vegetative burning, ions (SO4(=), NH4(+), Na(+), K(+), Cl(-)) and elements (Cl, Se) from a manure-fueled power plants, and sulfur and trace elements (Na(+), Pb, Se, Ni, V) from an oil-fueled glass plant were found in the resulting source profiles. Abundances of crustal species (e.g. Al, Si, Ca) in the Imperial/Mexicali Valley geological profiles are more than twice those found in central and southern California. Abundances of lead in motor vehicle exhausts indicate different vehicle fleets in border cities. Emission profiles from field burning and charbroil cooking specific to the border area show that a majority (>60%) of emissions are comprised of carbon, with high organic to total carbon ratios (0.93 to 0.97). Abundances of sulfate and ammonium account for nearly 60% of the manure-fueled power plant's emissions. Elevated levels of metals (Na(+), Pb, Cd, Se) and byproducts of petroleum combustion (S, Ni, V) were found in the oil-fueled glass plant's emissions.     

Surface characterization of human hair by atomic force microscopy in the imaging and F-d modes

Surface structure and surface mechanical properties of human hair have been characterized by atomic force microscopy in the imaging mode and by force vs. distance, F-d, analysis. The effects of treatment by commercial conditioner/shampoo or by aqueous exposure have been investigated. The cuticular structure has been imaged at medium resolution; longitudinal striations with lateral spacings of 150-350 nm and vertical corrugations in the range 2-8 nm were observed at higher resolution. The features are similar to those observed for untreated wool fibre. Both adventitious debris/contamination and residues from cosmetic treatment can be imaged with resolution in the low-nanometre range. Removal of the cuticular surface layer from treatment with alkali solution, and subsequent imaging, revealed a fibrous substructure. F-d analysis of the surface is a rich source of spatially resolved mechanical and chemical information. Surface stiffness, and an equivalent Young's Modulus, E, can be inferred from the shape of the 'approach' tip-to-surface contact curve. A value of E of approximately 10 MPa was obtained for untreated hair. During aqueous exposure for 1 h the stiffness and modulus decreased by approximately a factor of 10. The discontinuity seen at 'lift-off' during the retract half-cycle of F-d analysis represents a measure of tip-to-surface adhesion. Adhesion decreased during aqueous exposure and was below the level of detectability after 1 h. Likewise, treatment by conditioner had the effect of lowering adhesion. High resolution F-d data revealed features that are consistent with the presence of a thin and readily compressible surface layer, probably analogous to the surface lipid layer on untreated wool fibre.     

External ring fixators: an overview

External fixation is widely used in the fixation of fractures and limb deformities. The mechanical characteristics of a specific external fixator are major factors in determining the biomechanical environment at a fracture/osteotomy site and, hence, affect the healing process. Although the optimal biomechanical environment for healing of a fracture or an osteotomy is unknown, a specific range of interfragmentary motion exists which promotes healing. It is therefore desirable that the mechanics of an external fixator can be manipulated to enable the surgeon to control the range of interfragmentary motion. The characteristics of an external fixator are defined by a large number of variables. Therefore, to gain control over the degree of interfragmentary motion, an understanding of the effect of each variable and how it interacts with the others to determine the overall characteristics of the device is required. For the past two decades, individual components and whole-frame configurations have been studied in depth. This article provides a summary of previous work concerning the mechanics of external ring fixators and how they affect the biomechanical environment at the fracture/osteotomy site.     

Stress, coping and psychological illness: A cross-cultural study.

This cross-cultural research study aimed to explore the relationship of stress and coping with psychological illness or symptoms among university students in Canada and India. The predictor variables were stress (hassles and life experience), 8 ways of coping (Folkman & Lazarus, 1988), and selected personal-social variables, namely, locus of control, self-esteem, and social support. The criterion variables were 9 psychological symptoms of the Brief Symptom Inventory (BSI; Derogatis & Spencer, 1982). The results revealed that the Indian students reported more psychological symptoms compared to the Canadian students. Stepwise multiple-regression analyses also revealed considerable differences between the 2 samples with respect to the contribution of predictor variables in accounting for variance in the BSI scales. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Status,causes and controls of cyanobacterial blooms in Lake Erie

The Laurentian Great Lakes are among the most prominent sources of fresh water in the world. Lake Erie's infamous cyanobacterial blooms have, however, threatened the health of this valuable freshwater resource for decades. Toxic blooms dominated by the cyanobacterium Microcystis aeruginosa have most recently been one of primary ecological concerns for the lake. These toxic blooms impact the availability of potable water, as well as public health and revenues from the tourism and fishery industries. The socioeconomic effects of these blooms have spurred research efforts to pinpoint factors that drive bloom events. Despite decades of research and mitigation efforts, these blooms have expanded both in size and duration in recent years. However, through continued joint efforts between the Canadian and United States governments, scientists, and environmental managers, identification of the factors that drive bloom events is within reach. This review provides a summary of historical and contemporary research efforts in the realm of Lake Erie's harmful cyanobacterial blooms, both in terms of experimental and management achievements and insufficiencies, as well as future directions on the horizon for the lake's research community.     

On hypoxia and fish kills along the north shore of Lake Erie

Hypoxia is a common feature in the offshore central basin of Lake Erie. In the late summer of 2012, a strong wind-induced upwelling event transported oxygen depleted water to the nearshore zones of northern Lake Erie. Wind speed, duration and direction relative to the shoreline of individual wind events determined the extent of nearshore zone affected by the hypoxic waters. The upwelling event resulted in adverse water quality along some stretches of the northern shoreline of Lake Erie with persistent anoxia, which was mainly responsible for the mortality of fish.     

Analyzing Web-based simulation data

The article deals only with simulation models that have stochastic, or random input. Classical statistical methods for independent observations assume that each observation carries the maximum information, and therefore they compute the smallest confidence interval. Since stationary simulation output data carries less information, the confidence interval resulting from applying classical statistical computations using autocorrelated observations would be too small. This would lead one to conclude the parameter estimate is much more precise than is actually the case. To get around this problem, several methods have been suggested in the output data analysis literature. Two of the most widely accepted methods are: 1) the method of independent replications; and 2) the method of batch means. Both methods try to avoid autocorrelation by breaking the data into “independent” segments. The sample means of these segments are considered i.i.d, and used to calculate confidence intervals. In the first method, several independent runs are executed. In the second method, a long simulation run is executed and divided into several “nearly uncorrelated” batches. The article specifically examines the Java Simulation (JSIM) Web based environment which has evolved to incorporate component based technology. If component based technology succeeds, the long hoped for gains in software development productivity may finally be realized     

Procedural Methods for Urban Modeling

Simulation of our man-made environment, especially cities, is becoming an increasingly important research problem in computer graphics. This special issue captures a good snapshot of work in this emerging area.     

Interaction in Short Rotation Coppice willow,Salix viminalis genotype mixtures

Seven straight Salix viminalis genotypes with different levels of rust (Melampsora epitea) susceptibility were grown as mono-plots as well as being incorporated into a range of mixtures. Two 3-year harvests (2003 and 2006) were taken. Disease progress was followed on each of the individual genotypes throughout each growing season 2001–2006. In 2003 there were small but significant yield increases from the mixtures compared to the yield of individual components grown as mono-plots. These differences were not evident at the second harvest in 2006. No consistent effect of mixtures on reducing rust on the most susceptible genotype, Salix viminalis ‘77082’ were observed. In some years, e.g. 2003, at certain times during the growing season, significant reductions were observed on Salix viminalis ‘77082’ in certain 3-way mixtures compared to mono-plots. These, however, were not repeated consistently in subsequent years. It was concluded that the current commercial practice in many parts of Europe of planting mixtures as a disease control strategy will only be effective if there is sufficient genetic diversity between the Salix genotypes incorporated into the mixture.     

On the constructive orbit problem

Symmetry reduction techniques aim to combat the state-space explosion problem for model checking by restricting search to representative states from equivalence classes with respect to a group of symmetries. The standard approach to representative computation involves converting a state to its minimal image under a permutation group G, before storing the state. This is known as the constructive orbit problem (COP), and is NP{\mathit{NP}} hard. It may be possible to solve the COP efficiently if G is known to have certain structural properties: in particular if G is isomorphic to a full symmetry group, or G is a disjoint/wreath product of subgroups. We extend existing results on solving the COP efficiently for fully symmetric groups, and investigate the problem of automatically classifying an arbitrary permutation group as a disjoint/wreath product of subgroups. We also present an approximate COP strategy based on local search, and some computational group-theoretic optimisations to improve the basic approach of solving the COP by symmetry group enumeration. Experimental results using the TopSPIN symmetry reduction package, which interfaces with the computational group-theoretic system GAP, illustrate the effectiveness of our techniques.