Porous anodic alumina (PAA) masks are employed for the template synthesis of high density silicon nanowire (SiNW) arrays on a silicon substrate by the vapor−liquid−solid method. The uniform-sized ordered arrays of nanopores in the PAA mask anchored to Si(111) substrate are shown to enable the realization of vertically aligned epitaxial SiNWs with uniform diameter and spacing. The average diameter of the wires is 72 nm while the density is 60 wires/μm2. The high packing density and tightly controlled dimensions of SiNWs obtained by this nonlithographic method allow their effective integration into nanodevices for mass production.
Nature abounds with complex patterns and structures emerging from homogeneous media operating far from thermodynamic equilibrium. Such phenomena, which are widely observed in both inanimate (nonbiological) and biological media, can be modeled and studied via the CNN (cellular neural/nonlinear network) paradigm in an in-depth and unified way. Whether a homogeneous medium is capable of exhibiting complexity depends on whether the CNN cells, or its couplings, are locally active in a precise circuit-theoretic sense. This local activity principle is of universal generality and is responsible for all symmetry breaking phenomena observed in a great variety of nonequilibrium media ranging from the nucleation of domain oscillations in bulk semiconductor materials (e.g., gallium arsenide in Gunn diodes) to the emergence of artificial life itself. The long forgotten yet classic P. R. (positive real) criteria is resurrected and given new prominence in this paper by invoking its "negative" version and deriving a set of analytical inequalities for calculating the parameter range necessary for the emergence of a nonhomogeneous static or dynamic pattern in a homogeneous medium operating under an influx of energy and/or matter. The resulting "complexity related" inequalities are applicable to all media, continuous or discrete, which have been mapped into a CNN paradigm.
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.
Abstract What are the origins and nature of today’s most prevalent forms of Western populism? Where do they carry the most risks? This essay offers a brief survey and outlook for populism in Europe and the United States.
This study proposes and develops one way to examine dynamics and performance of voluntary community health partnerships through the development of a social capital index. Selected questions from a pre-existing survey [1] were used to construct three first-order concepts: Trust, Involvement, and Reciprocity. A second-order concept, Social Capital, was then derived. Individual scores were aggregated to the partnership level, and a social capital index was constructed. For validity testing, relationships of the index and accomplishment measures were examined. The index was also related to field notes on three partnerships. The chi-square value of the model indicates the concept of social capital was well captured with survey data. The index is significantly correlated with perceived accomplishment measures. The social capital concept is a viable perspective for examining community health partnerships. Its introduction should enrich our understanding of inter-organizational dynamics and performance. More extensive modeling illustrating the dynamics and performance of partnerships can be developed based on this concept.
One way to motivate hospitals to improve patient safety is to publicly report their rates of hospital-acquired infections, as California is starting to do this year. We conducted a baseline study of California's acute care hospitals just before mandatory reporting of hospital-acquired infection rates to the state began, in 2008. We found variability in many areas: For example, 70.1 percent of hospitals said that they were fully implementing evidence-based guidelines to fight infection by methicillin-resistant Staphylococcus aureus, but 22.8 percent of hospitals had not adopted any. Our analysis showed that rural hospitals, many of which lack resources to implement needed procedures, faced the greatest challenges in reporting and improving infection rates. Our findings should be of interest to Medicare policy makers who will implement the hospital-acquired infection performance measures in the Affordable Care Act, and to leaders in the thirty-eight states that have enacted legislation requiring reports of hospital-acquired infection rates. California's baseline data also present a unique opportunity to assess the impact of mandatory and public reporting laws.
The electrochemistry community provides the largest number of users of experimental information obtained at solid‐liquid interfaces. Molecular scale surface science studies have been carried out mostly at solid‐gas and solid‐vacuum interfaces, although recently several optical and scanning tunneling techniques have become available that can scrutinize solid‐liquid interfaces on the molecular level as well. In order to correlate structure and chemical behavior at solid‐liquid and solid‐gas interfaces, we suggest investigations of the same or similar systems in sequence at the solid‐gas, solid‐liquid, solid‐solvent, and reactant interfaces, and solid‐solvent and reactant interfaces with an external potential. In this paper we review the information accumulated from solid‐gas interface studies on the effect of changing coverage, on bonding, and on trends of bonding across the periodic table. We discuss what is known about the surface structure, the surface chemical bond, the dynamics of surface atoms (diffusion, growth), and the reactivity of metal surfaces from solid‐gas interface studies. In each section the available solid‐liquid interface studies are also indicated. We hope to provide directions for future studies for those interested in correlating phenomena at solid‐liquid and solid‐gas interfaces.
