Spatial Distributions of Legacy Contaminants in Sediments of Lakes Huron and Superior

The sediments of Lake Superior, Lake Huron, and Georgian Bay were sampled in 2001 and 2002 in order to evaluate the extent of surficial sediment contamination of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs), polycyclic aromatic hydrocarbons (PAHs), and metals. Sediment concentrations of PCBs, OCs, PAHs, and mercury were generally low and up to 2 orders of magnitude less than in Lakes Erie and Ontario. In contrast, concentrations of metals such as arsenic, copper, and nickel were comparable to those in Lakes Erie and Ontario. These elevated Lakes Superior and Huron metal concentrations were attributed to naturally occurring metals within the bedrock, soil, and sediment of the study region. Concentrations of all contaminants were typically below the Canadian Sediment Quality Probable Effect Level (PEL) guidelines. With regard to spatial patterns, most contaminants were focused primarily in the depositional basins and atmospheric deposition was likely the major source of these chemicals to the lakes. The major exception was for metals (not including mercury) whose patterns were also influenced by natural sources as well as extensive mining activity. A comparison between surficial sediment contamination of samples collected as part of this survey and those collected in the late 1960s/early 1970s using similar methods showed that concentrations of DDT, PCB, lead, and mercury were generally similar between these two time periods. These results are not consistent with production and usage patterns that have declined substantially in the past 3 decades. We hypothesize that the lack of temporal trends is an artifact due to slow sediment accumulation rates as well as differences in analytical protocols between the two time periods.     

Extracellular matrix regenerated: tissue engineering via electrospun biomimetic nanofibers

While electrospinning had seen intermittent use in the textile industry from the early twentieth century, it took the explosion of the field of tissue engineering, and its pursuit of biomimetic extracellular matrix (ECM) structures, to create an electrospinning renaissance. Over the past decade, a growing number of researchers in the tissue engineering community have embraced electrospinning as a polymer processing technique that effectively and routinely produces non‐woven structures of nanoscale fibers (sizes of 80 nm to 1.5 µm). These nanofibers are of physiological significance as they closely resemble the structure and size scale of the native ECM (fiber diameters of 50 to 500 nm). Attempts to replicate the many roles of native ECM have led to the electrospinning of a wide array of polymers, both synthetic (poly(glycolic acid), poly(lactic acid), polydioxanone, polycaprolactone, etc.) and natural (collagen, fibrinogen, elastin, etc.) in origin, for a multitude of different tissue applications. With various compositions, fiber dimensions and fiber orientations, the biological, chemical and mechanical properties of the electrospun materials can be tailored. In this review we highlight the role of electrospinning in the engineering of different tissues and applications (skin/wound healing, cartilage, bone, vascular tissue, urological tissues, nerve, and ligament), and discuss its potential role in future work. Copyright © 2007 Society of Chemical Industry     

Toughening and weakening in ferroelectric ceramics by domain-switching process under mixed electric and mechanical loading

The structural reliability of ferroelectric ceramics calls for a better understanding of the mechanism of fracture. For a ferroelectric ceramic under mechanical and electric loadings, the intensified stress and electric fields in the vicinity of a crack tip lead to polarization switching. The switched zone induces an incompatible strain and, consequently, changes the stress intensities and the apparent fracture toughness. This article investigates the effects on fracture parameters of an initially poled ferroelectric ceramic induced by polarization switching in the case of small-scale switching. The changes of stress intensities and energy release rate at the crack tip induced by the switched zone are calculated when the specimen is under both electric and mechanical loadings. Our results show that a switched zone usually produces both mode I and mode II stress intensities at the crack tip, and the increments are strongly dependent on the initial poling direction and electric-field strength. With certain initial poling directions, the material could be toughened, whereas, with other directions, be weakened. Generally, high-magnitude electric fields (both positive and negative) decrease the material toughness when both the mechanical and electric fields at the crack tip are singular.     

A low cost,one-piece nitrogen burst processing rack for 3¼× 4 inches and 4×5 inches TEM and SEM negatives

A processing rack designed with a built-in nitrogen burst plenum to accommodate 3¼ × 4 in. and 4 × 5 in. negative can be inexpensively constructed from plexiglass.     

Induction Skull Melting of Titanium and Other Reactive Alloys

Along with discussing the development history of the induction-slag process for melting titanium, zirconium, and other reactive alloys, this paper examines a recent modification to the process which eliminates calcium fluoride slag, producing inclusion-free metal. Also considered are the application and commercialization of this technology. In addition, some of the mechanical properties and structure of induction skull melted Ti-6Al-4V, including very good fatigue strengths, are reported.     

Blood-alcohol level feedback: A failure to deter impaired driving.

In an attempt to decrease the incidence of driving under the influence of alcohol (DUI), some alcohol-serving establishments have installed blood-alcohol level (BAL) feedback devices. These devices are meant to increase awareness of intoxication and result in the avoidance of DUI. However, studies in the US, Canada, and New Zealand (e.g., J. F. Oates, 1976; J. Calvert-Boyanowsky and E. O. Boyanowsky, 1980; P. M. Hurst and P. G. Wright, 1981) indicate that BAL feedback does not deter intoxicated individuals from DUI. Moreover, there is some evidence that it may increase alcohol consumption. The education of alcohol servers about effective techniques they can use to prevent DUI is suggested as a more effective means of preventing DUI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bistability and hysteresis in the organization of apparent motion patterns.

In a paradigm for which 2 distinct patterns are perceived for the same stimulus, perceptual hysteresis (persistence of a percept despite parameter change to values favoring the alternative pattern) and temporal stability (persistence despite intrinsic propensities toward spontaneous change) are interdependent. Greater persistence during parameter change reduces temporal stability, slowing the rate of parameter change reduces hysteresis by increasing opportunity for spontaneous change, and increasing temporal stability (by enlarging the stimulus) increases hysteresis. Hysteresis results in the perception of parametrically disfavored patterns; a parameter can influence a percept without specifying it. The visual system thus exhibits time-dependent behavior analogous to dynamical behavior observed in other systems, both physical and biological, for which there is competition among alternative patterns that vary in relative stability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further delineation of spondylo-meta-epiphyseal dysplasia, short limb-abnormal calcification type, with emphasis on diagnostic features

Further delineation of a generalized bone dysplasia which we call spondylo-meta-epiphyseal dysplasia, short limb-abnormal calcification type is presented. This dwarfing condition has several serious complications, with the most common cause of death being spinal cord damage secondary to atlantoaxial instability. It is a heritable condition with an autosomal recessive mode of transmission. Radiologic diagnostic criteria are developed on the basis of studies in 8 patients with the oldest being between 4 and 5 years old. The condition is clinically and radiographically apparent neonatally or in early infancy, and it is probable that all or almost all affected individuals will come to medical attention in the age range screened by this study.