Toughening mechanisms based on the presence of collagen fibrils have long been proposed for mineralized biological tissues like bone and dentin; however, no direct evidence for their precise role has ever been provided. Furthermore, although the anisotropy of mechanical properties of dentin with respect to orientation has been suggested in the literature, accurate measurements to support the effect of orientation on the fracture toughness of dentin are not available. To address these issues, the in vitro fracture toughness of dentin, extracted from elephant tusk, has been characterized using fatigue-precracked compact-tension specimens tested in Hank's balanced salt solution at ambient temperature, with fracture paths perpendicular and parallel to the tubule orientations (and orientations in between) specifically being evaluated. It was found that the fracture toughness was lower where cracking occurred in the plane of the collagen fibers, as compared to crack paths perpendicular to the fibers. The origins of this effect on the toughness of dentin are discussed primarily in terms of the salient toughening mechanisms active in this material; specifically, the role of crack bridging, both from uncracked ligaments and by individual collagen fibrils, is considered. Estimates for the contributions from each of these mechanisms are provided from theoretical models available in the literature.
Many economists are accustomed to thinking about Federal Reserve policy in terms of the institution's “dual mandate,” which refers to price stability and high employment, and in which the exchange rate and other international variables matter only insofar as they influence inflation and the output gap—which is to say, not very much. In fact, this conventional view is heavily shaped by the distinctive and peculiar circumstances of the last three decades, when the influence of international considerations on Fed policy has been limited. In fact, the Federal Reserve paid significant attention to international considerations in its first two decades, followed by relative inattention to such factors in the two-plus decades that followed, then back to renewed attention to international aspects of monetary policy in the 1960s, before the recent period of benign neglect of the international dimension. I argue that in the next few decades, international aspects are likely to play a larger role in Federal Reserve policy making than at present.
Nanofluidic devices incorporating inorganic nanotubes fluidly coupled to channels or nanopores for supplying a fluid containing chemical or bio-chemical species are described. In one aspect, two channels are fluidly interconnected with a nanotube. Electrodes on opposing sides of the nanotube establish electrical contact with the fluid therein. A bias current is passed between the electrodes through the fluid, and current changes are detected to ascertain the passage of select molecules, such as DNA, through the nanotube. In another aspect, a gate electrode is located proximal the nanotube between the two electrodes thus forming a nanofluidic transistor. The voltage applied to the gate controls the passage of ionic species through the nanotube selected as either or both ionic polarities. In either of these aspects the nanotube can be modified, or functionalized, to control the selectivity of detection or passage.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Typically routing is either scalable but inflexible, such as current Internet routing, or flexible but unscalable, such as source routing with with per-flow route discovery. In this paper we argue that to achieve both flexibility and scalability, customized routing should be offered as a service by thirdparty providers. The logical separation of routing from forwarding allows different route selection mechanisms to coexist and to evolve over time as routing requirements change. 1
Detecting edges of objects in their images is a basic problem in computational vision. The authors present the major ideas behind the use of scale space and anisotropic diffusion for edge detection, show that anisotropic diffusion can enhance edges, suggest a network implementation of anisotropic diffusion, and provide design criteria for obtaining networks performing scale space and edge detection. The results of a software implementation are shown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
The preparation and characterization of semiconductive electrodes of MgO doped were investigated. Pellets of MgO doped were sintered at high temperatures between 1300C and 1400C and quenched rapidly in distilled water. The surfaces were analyzed by X-ray diffraction and scanning Auger electron spectroscopy. The surfaces of pellets contained both corundum structure () and spinel structure (). Electrodes made of this material gave comparable anodic and cathodic photocurrents under illumination. The cathodic and anodic photocurrent on these photoelectrodes were verified high at 5-10 wt. percent that is critical doping amounts.
Recent studies suggest that the increased vulnerability of the older person to physical and/or mental breakdown is related to loss or deficiency in the pattern of supportive ties. With increases in the geographical separation of adult children from their parents, and with greater longevity, the needs of the elderly are increasingly being transferred from the family either to public service settings or to voluntary associations. The resource needs depend in part on the individual's existing contacts and state of health, as well as upon the psychological history of the person. Various programs have addressed the differences in social support for older people in markedly different ways. Six different programs are examined to illustrate the importance of attention to health status, ethnicity, and style of life in the provision of social support. By evaluating the offerings of these programs against the concepts of network theory we are able to show how the needs for social support among the elderly are highly differentiated and deserving of equally differentiated forms of response.
