Nonphotolithographic nanoscale memory density prospects

Technologies are now emerging to construct molecular-scale electronic wires and switches using bottom-up self-assembly. This opens the possibility of constructing nanoscale circuits and memories where active devices are just a few nanometers square and wire pitches may be on the order of ten nanometers. The features can be defined at this scale without using photolithography. The available assembly techniques have relatively high defect rates compared to conventional lithographic integrated circuits and can only produce very regular structures. Nonetheless, with proper memory organization, it is reasonable to expect these technologies to provide memory densities in excess of 10/sup 11/ b/cm/sup 2/ with modest active power requirements under 0.6 W/Tb/s for random read operations

The Legacy of Althusser, 1918-1990: An Introduction

Introduction to the special issue

Althusserian Theory: From Scientific Truth to Institutional History

Scholars have emphasized the scientific and the rationalist features of Althusser\u27s work, but few have noted its post-structuralist aspects, especially its Foucauldian accounts of discourse and power. In the early Pour Marx, Althusser divides ideological practices from objective science and theoretical norms from empirical facts; however, in several later essays Althusser repudiates his earlier faith in theory\u27s normative force as well as his broad distinction between science and ideology. He argues that every discipline establishes its own relationship between its ideological history and its formal, scientific ideals. This argument, together with Althusser\u27s earlier rejection of totalizing approaches, establishes important parallels with Foucault\u27s archaeological studies. The literary theory of Tony Bennett, who develops a Foucauldian critique of traditional and Marxist aesthetics, illuminates the rich implications of these parallels for cultural analyses

Theory, Totality, Critique: The Limits of the Frankfurt School Critical Theory, Marxism and Modernity

Theory, Totality, Critique: The Limits of the Frankfurt School Critical Theory, Marxism and Modernity by Douglas Kellner

Creating a Simple Single Computational Approach to Modeling Rarefied and Continuum Flow About Aerospace Vehicles

We proposed to create a single computational code incorporating methods that can model both rarefied and continuum flow to enable the efficient simulation of flow about space craft and high altitude hypersonic aerospace vehicles. The code was to use a single grid structure that permits a smooth transition between the continuum and rarefied portions of the flow. Developing an appropriate computational boundary between the two regions represented a major challenge. The primary approach chosen involves coupling a four-speed Lattice Boltzmann model for the continuum flow with the DSMC method in the rarefied regime. We also explored the possibility of using a standard finite difference Navier Stokes solver for the continuum flow. With the resulting code we will ultimately investigate three-dimensional plume impingement effects, a subject of critical importance to NASA and related to the work of Drs. Forrest Lumpkin, Steve Fitzgerald and Jay Le Beau at Johnson Space Center. Below is a brief background on the project and a summary of the results as of the end of the grant

Bayes linear analysis for ordinary differential equations

Differential equation models are used in a wide variety of scientific fields to describe the behaviour of physical systems. Commonly, solutions to given systems of differential equations are not available in closed-form; in such situations, the solution to the system is generally approximated numerically. The numerical solution obtained will be systematically different from the (unknown) true solution implicitly defined by the differential equations. Even if it were known, this true solution would be an imperfect representation of the behaviour of the real physical system that it was designed to represent. A Bayesian framework is proposed which handles all sources of numerical and structural uncertainty encountered when using ordinary differential equation (ODE) models to represent real-world processes. The model is represented graphically, and the graph proves to be useful tool, both for deriving a full prior belief specification and for inferring model components given observations of the real system. A general strategy for modelling the numerical discrepancy induced through choice of a particular solver is outlined, in which the variability of the numerical discrepancy is fixed to be proportional to the length of the solver time-step and a grid-refinement strategy is used to study its structure in detail. A Bayes linear adjustment procedure is presented, which uses a junction tree derived from the originally specified directed graphical model to propagate information efficiently between model components, lessening the computational demands associated with the inference. The proposed framework is illustrated through application to two examples: a model for the trajectory of an airborne projectile moving subject to gravity and air resistance, and a model for the coupled motion of a set of ringing bells and the tower which houses them

Teaching Biological Physics

As the ¯eld of Biological Physics expands at breakneck speed within our community and within our departments, the need for both undergraduate and graduate courses grows along with it. Such courses serve not only physics majors, but also students from the life sciences who need to understand the role of physical principles and concepts in understanding the world of biology. Using examples from three universities, we o®er some perspectives on the justi¯cations for departments to move into this area and incorporate biological physics into the standard curriculum, an emerging consensus on the syllabus for introductory and intermediate lecture courses for majors and non-majors in science and engineering, and an example of an advanced interdisciplinary graduate laboratory. PACS numbers: The past few years have seen an unprecedented surge of interest in biological problems by people with physics training, working in Physics departments. A host of new experimental and theoretical techniques has opened up the quantitative study of systems ranging from single molecules to vast networks of simple agents performin

Giant mesenteric lymphatic malformation presenting as small bowel volvulus

Abdominal pain with bilious emesis is an ominous clinical presentation with many possible causes. We describe a previously healthy 4-year-old boy who presented with these symptoms and ultrasound findings of fluid throughout most of the abdominal cavity. Computed tomography imaging revealed a large cystic mass (21-by-13 cm) associated with a small bowel obstruction due to volvulus. A laparoscopic exploration was undertaken, revealing a large mass arising from the small intestinal mesentery and causing a segmental volvulus of the small bowel. Conversion to mini-laparotomy allowed reduction of the volvulus and segmental resection of the small bowel associated with a giant mesenteric lymphatic malformation. This case describes a rare cause of intestinal volvulus due to a mesenteric lymphatic malformation

OBIS-USA: A Data-Sharing Legacy of the Census of Marine Life

This is the publisher's version, also available electronically from http://www.tos.org/oceanography.The United States Geological Survey's Biological Informatics Program hosts OBIS-USA, the US node of the Ocean Biogeographic Information System (OBIS). OBIS-USA gathers, coordinates, applies standard formats to, and makes widely available data on biological collections in marine waters of the United States and other areas where US investigators have collected data and, in some instances, specimens. OBIS-USA delivers its data to OBIS international, which then delivers its data to the Global Biodiversity Information Facility (GBIF) and other Web portals for marine biodiversity data. OBIS-USA currently has 145 data sets from 36 participants, representing over 6.5 million occurrence records of over 83,000 taxa from more than 888,000 locations. OBIS-USA, a legacy of the decade-long (2001–2010) international collaborative Census of Marine Life enterprise, continues to add data, including those from ongoing Census projects. Among the many challenges in creating OBIS, including OBIS-USA, were developing a community of trust and shared value among data providers, and demonstrating to providers the value of making their data accessible to others. Challenges also posed by the diversity of data sets relevant to marine biodiversity stored on thousands of computers, in a variety of formats, not all widely accessible, have been met in OBIS-USA by implementing a uniform standard and publishing platform that is easily accessible to a broad range of users