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 impact of seasonal movements by ovigerous American lobsters (Homarus americanus) on egg development and larval release

The American lobster (Homarus americanus) supports one of the most economically successful fisheries in the Gulf of Maine. The continued success of this fishery is attributed in part to vigilant broodstock conservation through the preservation of ovigerous (egg-bearing) females. Previous studies of ovigerous lobster movements indicate that some, if not most, display seasonal inshore-to-offshore movement patterns. While it has been assumed that these movements serve to expose eggs to thermal regimes that are optimal for development, this theory has never been rigorously tested. In Chapter 1, I present results from ultrasonic tracking studies designed to determine if lobsters in coastal New Hampshire waters exhibit this inshore-offshore pattern and also to identify where ovigerous females overwinter. In Chapter 2, I assess how the movements of ovigerous lobsters would influence the temperature regimes they experienced and thus the development of their eggs. I evaluate this question using a combination of laboratory and field experiments that expose animals to seasonally fluctuating water temperatures they would experience if they remained inshore or moved offshore; data from these experiments were then used to determine the influence of these thermal regimes on egg development, time to hatch, and larval survival. Finally, in Chapter 3, I present results from a study using experimental ocean drifters deployed in areas where ovigerous females were located when their eggs hatched, to determine where these larvae might drift. Ultrasonic tracking revealed that most lobsters move offshore in the fall and ovigerous lobsters tend to remain there until after their eggs hatch the following summer (Chapter 1). Eggs exposed to disparate thermal regimes (inshore and offshore) demonstrated that eggs carried by lobsters that moved offshore actually hatched later than those exposed to inshore temperatures (Chapter 2). Finally, most drifters released in offshore hatching locations were carried south or to offshore locations at the time when larvae would settle (Chapter 3). Taken together, these results suggest that seasonal movements of ovigerous lobsters have a strong influence on when and where eggs hatch and, subsequently, where larvae may settle. These findings have significant implications for population connectivity and management of the lobster fishery

A Linear Logic Programming Language for Concurrent Programming over Graph Structures

We have designed a new logic programming language called LM (Linear Meld) for programming graph-based algorithms in a declarative fashion. Our language is based on linear logic, an expressive logical system where logical facts can be consumed. Because LM integrates both classical and linear logic, LM tends to be more expressive than other logic programming languages. LM programs are naturally concurrent because facts are partitioned by nodes of a graph data structure. Computation is performed at the node level while communication happens between connected nodes. In this paper, we present the syntax and operational semantics of our language and illustrate its use through a number of examples.Comment: ICLP 2014, TPLP 201

SOMA A Tool for Synthesizing and Optimizing Memory Accesses in ASICs

Arbitrary memory dependencies and variable latency memory systems are major obstacles to the synthesis of large-scale ASIC systems in high-level synthesis. This paper presents SOMA, a synthesis framework for constructing Memory Access Network (MAN) architectures that inherently enforce memory consistency in the presence of dynamic memory access dependencies. A fundamental bottleneck in any such network is arbitrating between concurrent accesses to a shared memory resource. To alleviate this bottleneck, SOMA uses an application-specific concurrency analysis technique to predict the dynamic memory parallelism profile of the application. This is then used to customize the MAN architecture. Depending on the parallelism profile, the MAN may be optimized for latency, throughput or both. The optimized MAN is automatically synthesized into gate-level structural Verilog using a flexible library of network building blocks. SOMA has been successfully integrated into an automated C-to-hardware synthesis flow, which generates standard cell circuits from unrestricted ANSI-C programs. Post-layout experiments demonstrate that application specific MAN construction significantly improves power and performance

A distributed self-reconfiguration algorithm for cylindrical lattice-based modular robots

International audienceModular self-reconfigurable robots are composed of independent connected modules which can self-rearrange their connectivity using processing, communication and motion capabilities, in order to change the overall robot structure. In this paper, we consider rolling cylindrical modules arranged in a two-dimensional vertical hexagonal lattice. We propose a parallel, asynchronous and fully decentralized distributed algorithm to self-reconfigure robots from an initial configuration to a goal one. We evaluate our algorithm on the millimeter-scale cylindrical robots, developed in the Claytronics project, through simulation of large ensembles composed of up to ten thousand modules. We show the effectiveness of our algorithm and study its performance in terms of communications, movements and execution time. Our observations indicate that the number of communications, the number of movements and the execution time of our algorithm is highly predictable. Furthermore, we observe execution times that are linear in the size of the goal shape

Public attitudes toward larger cigarette pack warnings: Results from a nationally representative U.S. sample

A large body of evidence supports the effectiveness of larger health warnings on cigarette packages. However, there is limited research examining attitudes toward such warning labels, which has potential implications for implementation of larger warning labels. The purpose of the current study was to examine attitudes toward larger warning sizes on cigarette packages and examine variables associated with more favorable attitudes. In a nationally representative survey of U.S. adults (N = 5,014), participants were randomized to different warning size conditions, assessing attitude toward “a health warning that covered (25, 50, 75) % of a cigarette pack.” SAS logistic regression survey procedures were used to account for the complex survey design and sampling weights. Across experimental groups, nearly three-quarters (72%) of adults had attitudes supportive of larger warning labels on cigarette packs. Among the full sample and smokers only (N = 1,511), most adults had favorable attitudes toward labels that covered 25% (78.2% and 75.2%, respectively), 50% (70% and 58.4%, respectively), and 75% (67.9% and 61%, respectively) of a cigarette pack. Young adults, females, racial/ethnic minorities, and non-smokers were more likely to have favorable attitudes toward larger warning sizes. Among smokers only, females and those with higher quit intentions held more favorable attitudes toward larger warning sizes. Widespread support exists for larger warning labels on cigarette packages among U.S. adults, including among smokers. Our findings support the implementation of larger health warnings on cigarette packs in the U.S. as required by the 2009 Tobacco Control Act

Bayesian comparison of cost-effectiveness of different clinical approaches to diagnose coronary artery disease

The objective of this study was to compare the cost-effectiveness of four clinical policies (policies I to IV) in the diagnosis of the presence or absence of coronary artery disease. A model based on Bayes' theorem and published clinical data was constructed to make these comparisons. Effectiveness was denned as either the number of patients with coronary disease diagnosed or as the number of quality-adjusted life years extended by therapy after the diagnosis of coronary disease.The following conclusions arise strictly from analysis of the model and may not necessarily be applicable to all situations. 1) As prevalence of coronary disease in the population increased, it caused a linear increase in cost per patient tested, but a hyperbolic decrease in cost per effect, that is, increased cost-effectiveness. Thus, cost-effectiveness of all policies (I to IV) was poor in populations with a prevalence of disease below 10%, for example, asymptomatic people with no risk factors. 2) Analysis of the model also indicates that at prevalences less than 80%, exercise thallium scintigraphy alone as a first test (policy II) is a more cost-effective initial test than is exercise electrocardiography alone as a first test (policy I) or exercise electrocardiography first combined with thallium imaging as a second test (policy IV). 3) Exercise electrocardiography before thallium imaging (policy IV) is more cost-effective than exercise electrocardiography alone (policy I) at prevalences less than 80%. 4) Noninvasive exercise testing before angiography (policies I, II and IV) is more cost-effective than using coronary angiography as the first and only test (policy III) at prevalences less than 80%. 5) Above a threshold value of prevalence of 80% (for example patients with typical angina), proceeding to angiography as the first test (policy III) was more cost-effective than initial noninvasive exercise tests (policies I, II and IV).One advantage of this quantitative model is that it estimates a threshold value of prevalence (80%) at which the rank order of policies changes. The model also allows substitution of different values for any variable as a way of accounting for the uncertainty inherent in the data. In conclusion, it is essential to consider the prevalence of disease when selecting the most cost-effective clinical approach to making a diagnosis

Orbits Around Black Holes in Triaxial Nuclei

We discuss the properties of orbits within the influence sphere of a supermassive black hole (BH), in the case that the surrounding star cluster is nonaxisymmetric. There are four major orbit families; one of these, the pyramid orbits, have the interesting property that they can approach arbitrarily closely to the BH. We derive the orbit-averaged equations of motion and show that in the limit of weak triaxiality, the pyramid orbits are integrable: the motion consists of a two-dimensional libration of the major axis of the orbit about the short axis of the triaxial figure, with eccentricity varying as a function of the two orientation angles, and reaching unity at the corners. Because pyramid orbits occupy the lowest angular momentum regions of phase space, they compete with collisional loss cone repopulation and with resonant relaxation in supplying matter to BHs. General relativistic advance of the periapse dominates the precession for sufficiently eccentric orbits, and we show that relativity imposes an upper limit to the eccentricity: roughly the value at which the relativistic precession time is equal to the time for torques to change the angular momentum. We argue that this upper limit to the eccentricity should apply also to evolution driven by resonant relaxation, with potentially important consequences for the rate of extreme-mass-ratio inspirals in low-luminosity galaxies. In giant galaxies, we show that capture of stars on pyramid orbits can dominate the feeding of BHs, at least until such a time as the pyramid orbits are depleted; however this time can be of order a Hubble time.Comment: 20 pages, 15 figure