cssi/SciSciGPT-SciSciNet huggingface dataset:
Deep tissue fluorescent imaging in scattering specimens using confocal microscopy

In scattering specimens, multiphoton excitation and nondescanned detection improve imaging depth by a factor of 2 or more over confocal microscopy; however, imaging depth is still limited by scattering. We applied the concept of clearing to deep tissue imaging of highly scattering specimens. Clearing is a remarkably effective approach to improving image quality at depth using either confocal or multiphoton microscopy. Tissue clearing appears to eliminate the need for multiphoton excitation for deep tissue imaging.
Visualizing 3D velocity fields near contour surfaces

Vector field rendering is difficult in 3D because the vector icons overlap and hide each other. We propose four different techniques for visualizing vector fields only near surfaces. The first uses motion blurred particles in a thickened region around the surface. The second uses a voxel grid to contain integral curves of the vector field. The third uses many antialiased lines through the surface, and the fourth uses hairs sprouting from the surface and then bending in the direction of the vector field. All the methods use the graphics pipeline, allowing real time rotation and interaction, and the first two methods can animate the texture to move in the flow determined by the velocity field. >
CONTINUUM TOPOLOGY OPTIMIZATION OF BUCKLING-SENSITIVE STRUCTURES

Twoformulationsforcontinuum topologyoptimizationofstructurestakingbucklingconsiderationsinto account are developed, implemented, and compared. In thee rst, the structure undergoing a specie ed loading is modeled as a hyperelastic continuum at e nite deformations and is optimized to maximize the minimum critical buckling load. In the second, the structure under a similar loading is modeled as linear elastic, and the critical buckling load is computed with linearized buckling analysis. Specie c issues addressed include usage of suitable “ mixing rules,” a node-based design variable formulation, techniques for eliminating regions devoid of structural material from the analysis problem, and consistent design sensitivity analysis. The performance of the formulations is demonstrated on the design of different structures. When problems are solved with moderate loads and generous material usage constraints, designs using compression and tension members are realized. Alternatively, when fairly large loads together with very stringent material usage constraints are imposed, structures utilizing primarily tension members result. Issues that arise when designing very light structures with stringent material usage constraints are discussed along with the importance of considering potential geometrical instabilities in the concept design of structural systems.
Scaling algorithms for network problems

This paper gives algorithms for network problems that work by scaling the numeric parameters. Assume all parameters are integers. Let n, m, and N denote the number of vertices, number of edges, and largest parameter of the network, respectively. A scaling algorithm for maximum weight matching on a bipartite graph runs in O(n34m log N) time. For appropriate N this improves the traditional Hungarian method, whose most efficient implementation is O(n(m +n log n)). The speedup results from finding augmenting paths in batches. The matching algorithm gives similar improvements for the following problems: single-source shortest paths for arbitrary edge lengths (Bellman's algorithm); maximum weight degree-constrained subgraph; minimum cost flow on a 0–1 network. Scaling gives a simple maximum value flow algorithm that matches the best known bound (Sleator and Tarjan's algorithm) when log N=O(log n). Scaling also gives a good algorithm for shortest paths on a directed graph with nonnegative edge lengths (Dijkstra's algorithm).
The Role of Problem Representation Shifts in Auditor Decision Processes in Analytical Procedures

In audit analytical procedures, research has shown that auditors have difficulty proposing possible explanations for financial statement discrepancies (Bedard and Biggs 1991a). One source of this difficulty is that auditors may represent analytical procedures problems incorrectly; that is, their mental image of the problem does not contain the underlying cause of the discrepancies. Because shifting initial representations of problems is difficult, auditor decision processes are affected. The purpose of this study is to investigate how problem representation shifts can lead auditors to better insight into possible explanations of discrepancies, and thus improve auditor decision processes in analytical procedures. To accomplish this purpose, verbal protocol data from Bedard and Biggs (1991a) were used to develop a series of problem representations and prompts for the analytical procedures task used in that study. The prompts were given to activate relevant knowledge structures in memory and encourage succes...
Usage control : A vision for next generation access control

The term usage control (UCON) is a generalization of access control to cover obligations, conditions, continuity (ongoing controls) and mutability. Traditionally, access control has dealt only with authorization decisions on a subject’s access to target resources. Obligations are requirements that have to be fulfilled by the subject for allowing access. Conditions are subject and object-independent environmental requirements that have to be satisfied for access. In today’s highly dynamic, distributed environment, obligations and conditions are also crucial decision factors for richer and finer controls on usage of digital resources. Traditional authorization decisions are generally made at the time of request but typically do not recognize ongoing controls for relatively long-lived access or for immediate revocation. Moreover, mutability issues that deal with updates on related subject or object attributes as a consequence of access have not been systematically studied. In this paper we motivate the need for usage control, define a family of ABC models as a core model for usage control and show how it encompasses traditional access control, such as mandatory, discretionary and role-based access control, and more recent requirements such as trust management, and digital rights management. In addition, we also discuss architectures that introduce a new reference monitor for usage control and some variations.
Sparse Fourier Transform via Butterfly Algorithm

This paper introduces a fast algorithm for computing sparse Fourier transforms with spatial and Fourier data supported on curves or surfaces. This problem appears naturally in several important applications of wave scattering, digital signal processing, and reflection seismology. The main idea of the algorithm is that the interaction between a frequency region and a spatial region is approximately low rank if the product of their widths are bounded by the maximum frequency. Based on this property, we can approximate the interaction between these two boxes accurately and compactly using a small number of equivalent sources. The overall structure of the algorithm follows the butterfly algorithm. The computation is further accelerated by exploiting the tensor-product property of the Fourier kernel in two and three dimensions. The proposed algorithm is accurate and has the optimal complexity. We present numerical results in both two and three dimensions.
Memory Trace Compression and Replay for SPMD Systems Using Extended PRSDs

Concurrency levels in large-scale supercomputers are rising exponentially, and shared-memory nodes with hundreds of cores and non-uniform memory access latencies are expected within the next decade. However, even current petascale systems with tens of cores per node suffer from memory bottlenecks. As core counts increase, memory issues will become critical for the performance of large-scale supercomputers. Trace analysis tools are thus vital for diagnosing the root causes of memory problems. However, existing memory tracing tools are expensive due to prohibitively large trace sizes, or they collect only statistical summaries and omit potentially valuable information. In this paper, we present ScalaMemTrace, a novel technique for collecting memory traces in a scalable manner. ScalaMemTrace builds on prior trace methods with aggressive compression techniques to allow lossless representation of memory traces for dense algebraic kernels, with near-constant trace size irrespective of the problem size or the number of threads. We further introduce a replay mechanism for ScalaMemTrace traces, and discuss the results of our prototype implementation on the x86_64 architecture.
Image-Based Stress Recognition Using a Model-Based Dynamic Face Tracking System

Stress recognition from facial image sequences is a subject that has not received much attention although it is an important problem for a host of applications such as security and human-computer interaction. This class of problems and the related software are instances of Dynamic Data Driven Application Systems (DDDAS). This paper presents a method to detect stress from dynamic facial image sequences. The image sequences consist of people subjected to various psychological tests that induce high and low stress situations. We use a model-based tracking system to obtain the deformations of different parts of the face (eyebrows, lips, mouth) in a parameterized form. We train a Hidden Markov Model system using these parameters for stressed and unstressed situations and use this trained system to do recognition of high and low stress situations for an unlabelled video sequence. Hidden Markov Models (HMMs) are an effective tool to model the temporal dependence of the facial movements. The main contribution of this paper is a novel method of stress detection from image sequences of a person’s face.
An effective synthesis of scalemic 3,5,5-trisubstituted pyrrolin-4-ones

Abstract A new two-step method employs the intramolecular cyclization of metalated imino esters for the construction of scalemic 3,5,5-trisubstituted pyrrolin-4-ones (4). The imino esters in turn derive from α-disubstituted amino acids, the latter readily available via a new protocol exploiting the enantioretentive alkylation of oxazolidinones.
An algorithm for the evaluation of radar propagation in the spherical Earth diffraction region

An efficient method for the accurate computation of the Airy function is presented. This method is applied to the calculation of the propagation factor for diffraction around a smooth sphere. These calculations give accurate results well into the visible region. even for high-altitude antennas, extending the useful range of the SEKE low-altitude radar propagation computer model. >
Synthesis of piperazinones and benzopiperazinones from 1,2-diamines and organoboronic acids

Abstract Alkenyl, aryl and heteroaryl boronic acids react with 1,2-diamines and glyoxylic acid to give directly in one step the corresponding piperazinones (2-oxopiperazines). Similarly, the use of monoprotected 1,2-phenylenediamine leads to benzopiperazinones (1,2,3,4-tetrahydroquinoxalin-2-ones).
Monetary Policy for Inattentive Economies

We offer a contribution to the analysis of optimal monetary policy. We begin with a critical assessment of the existing literature, arguing that most work is based on implausible models of inflation–output dynamics. We then suggest that this problem may be solved with some recent behavioral models, which assume that price setters are slow to incorporate macroeconomic information into the prices they set. A specific such model is developed and used to derive optimal policy. In response to shocks to productivity and aggregate demand, optimal policy is price level targeting. Base drift in the price level, which is implicit in the inflation targeting regimes currently used in many central banks, is not desirable in this model. When shocks to desired markups are added, optimal policy is flexible targeting of the price level. That is, the central bank should allow the price level to deviate from its target for a while in response to these supply shocks, but it should eventually return the price level to its target path. Optimal policy can also be described as an elastic price standard: the central bank allows the price level to deviate from its target when output is expected to deviate from its natural rate.
Empirical Investigation of Extreme Single-Particle Behavior of Nuclear Quadrupole Moments in Highly Collective A ∼ 150 Superdeformed Bands

The intrinsic quadrupole moment ${Q}_{0}$ of superdeformed rotational bands in $A\ensuremath{\sim}150$ nuclei depends on the associated single-particle configuration. We have derived an empirical formula based on the additivity of effective quadrupole moments of single-particle orbitals that describes existing measurements from ${}^{142}\mathrm{Sm}$ to ${}^{152}\mathrm{Dy}$. To further test the formula, the predicted ${Q}_{0}$ moments for two superdeformed bands in ${}^{146}\mathrm{Gd}$ of $14.05e\mathrm{b}$ were confronted with a new measurement yielding $13.9\ifmmode\pm\else\textpm\fi{}0.4e\mathrm{b}$ and $13.9\ifmmode\pm\else\textpm\fi{}0.3e\mathrm{b}$, respectively. This excellent agreement provides empirical evidence of extreme single-particle behavior in highly deformed, collective systems.
Terrestrial Vegetation in the Coupled Human-Earth System: Contributions of Remote Sensing

The Earth system and society’s use of ecological resources are tightly coupled through exchanges of water, energy, and nutrients. Terrestrial vegetation transfers materials between the atmosphere, biosphere, and water bodies in the coupled system. Vegetation is also a primary interface between human society and the Earth system through land-cover conversion, cultivation of favorable species, and transfer of organisms between locations. Remote sensing aids analyses of these interactions and, ultimately, contributes information to decision makers for improved management. Multidecadal records from multispectral sensors have been the mainstay for studying terrestrial vegetation at regional and global scales. Representation of vegetation and carbon dynamics is now routine in Earth system models. Challenges remain to incorporate realistic ecological disturbances and human land-use activities based on remote sensing observations. Hyperspectral, LIDAR, and radar systems contribute new capabilities for observing nitrogen fluxes, vegetation stress, canopy structure, and in some cases individual species.
Answering top-k queries over a mixture of attractive and repulsive dimensions

In this paper, we formulate a top-k query that compares objects in a database to a user-provided query object on a novel scoring function. The proposed scoring function combines the idea of attractive and repulsive dimensions into a general framework to overcome the weakness of traditional distance or similarity measures. We study the properties of the proposed class of scoring functions and develop efficient and scalable index structures that index the isolines of the function. We demonstrate various scenarios where the query finds application. Empirical evaluation demonstrates a performance gain of one to two orders of magnitude on querying time over existing state-of-the-art top-k techniques. Further, a qualitative analysis is performed on a real dataset to highlight the potential of the proposed query in discovering hidden data characteristics.
The Masked Sample Covariance Estimator: An Analysis via Matrix Concentration Inequalities

Covariance estimation becomes challenging in the regime where the number p of variables outstrips the number n of samples available to construct the estimate. One way to circumvent this problem is to assume that the covariance matrix is nearly sparse and to focus on estimating only the significant entries. To analyze this approach, Levina and Vershynin (2011) introduce a formalism called masked covariance estimation, where each entry of the sample covariance estimator is reweighted to reflect an a priori assessment of its importance. This paper provides a short analysis of the masked sample covariance estimator by means of a matrix concentration inequality. The main result applies to general distributions with at least four moments. Specialized to the case of a Gaussian distribution, the theory offers qualitative improvements over earlier work. For example, the new results show that n = O(B log^2 p) samples suffice to estimate a banded covariance matrix with bandwidth B up to a relative spectral-norm error, in contrast to the sample complexity n = O(B log^5 p) obtained by Levina and Vershynin.
International benchmarking of Lesotho's infrastructure performance

The author provides a preliminary benchmarking of infrastructure performance in Lesotho in four major sectors--electricity, water and sanitation, information and communication technology, and road transportation--against the relevant group of comparator countries using a new World Bank international data base with objective and perception-based indicators of infrastructure performance from over 200 countries. The results of the benchmarking are revealing of several major, comparative deficiencies in infrastructure performance in Lesotho: (1) extremely low access to electricity and its affordability; (2) poor coverage, quality, and the cost of local (non-cellular) telephony; and (3) poor quality of roads. Infrastructure service delivery in electricity, telephony, and roads is well below what would be expected, on average, for a country in Lesotho's income group. In these sectors, Lesotho also compares unfavorably with many other geographical country groups. Unless addressed, such infrastructure shortfalls are likely to adversely affect the welfare of Lesotho's poor, and the cost competitiveness and growth prospects of a range of economic sectors (such as tourism and trade) that depend critically on a stable and competitive supply of basic infrastructure service. They could also affect the speed and quality of Lesotho's regional economic integration within the South Africa Customs Union (SACU) sub-region with attendant consequences for the long-term growth of regional trade and real output. By contrast, Lesotho's performance is solid in the access to improved water and sanitation, in the aggregate and in both rural and urban areas. Finally, this benchmarking, combined with more in-depth, sector analyses, could provide policymakers in Lesotho a useful guide to the areas of infrastructure performance requiring attention.
A Process Framework of Organizational Politics

This paper attempts to advance the study of organizational politics by developing a comprehensive process framework for understanding individual and group political activity. Previous concepts are reviewed and a definition is offered. The process framework is developed through antecedent conditions, operating mechanisms, and outcomes, with operating mechanisms including goals, strategies and tactics, and style and political sensitivity acting as a moderating variable. Suggestions for conducting research are offered.
Two-Dimensional Synthetic Jet Simulation

Direct numerical simulation was used to model an array of two-dimensional synthetic slot jets pulsing into initially quiescent e ow. Such zero-net mass-e ux jets can represent an array of microelectromechanical systems. Fluid ejected by the pulsing jets rolls up into vortex pairs that propagate as a result of their mutually induced velocity andtheinitial momentum given by thepulse.Theeffectsofe uidand geometricparametersontheresulting e owe eld were studied. The results near the slots were compared with experimental data and found to be in good agreement.
Observation of the Uller-Zenneck wave.

The Uller–Zenneck wave has been theoretically predicted to exist at the planar interface of two homogeneous dielectric materials of which only one must be dissipative. Experimental confirmation of this century-old prediction was obtained experimentally by exciting the Uller–Zenneck wave as a Floquet harmonic of nonzero order at the periodically corrugated interface of air and crystalline silicon in the 400-to-900-nm spectral regime. Application for intrachip optical interconnects at 850 nm appears promising.
Comparison of MAPK specificity across the ETS transcription factor family identifies a high-affinity ERK interaction required for ERG function in prostate cells

The RAS/MAPK signaling pathway can regulate gene expression by phosphorylating and altering the function of some, but not all, ETS transcription factors. ETS family transcription factors bind similar DNA sequences and can compete for genomic binding sites. However, MAPK regulation varies across the ETS family. Therefore, changing the ETS factor bound to a cis-regulatory element can alter MAPK regulation of gene expression. To understand RAS/MAPK regulated gene expression programs, comprehensive knowledge of the ETS family members that are MAPK targets and relative MAPK targeting efficiency across the family is needed. An in vitro kinase assay was used to rank-order 27 human ETS family transcription factors based on phosphorylation by ERK2, JNK1, and p38α. Many novel MAPK targets and specificities were identified within the ETS family, including the identification of the prostate cancer oncoprotein ERG as a specific target of ERK2. ERK2 phosphorylation of ERG S215 required a DEF docking domain and was necessary for ERG to activate transcription of cell migration genes and promote prostate cell migration. The ability of ERK2 to bind ERG with higher affinity than ETS1 provided a potential molecular explanation for why ERG overexpression drives migration of prostate cells with low levels of RAS/ERK signaling, while ETS1 has a similar function only when RAS/ERK signaling is high. The rank ordering of ETS transcription factors as MAPK targets provides an important resource for understanding ETS proteins as mediators of MAPK signaling. This is emphasized by the difference in rank order of ERG and ETS1, which allows these factors to have distinct roles based on the level of RAS/ERK signaling present in the cell.
The Design of a Computer Language for Linguistic Information

A considerable body of accumulated knowledge about the design of languages for communicating information to computers has been derived from the subfields of programming language design and semantics. It has been the goal of the PATR group at SRI to utilize a relevant portion of this knowledge in implementing tools to facilitate communication of linguistic information to computers. The PATR-II formalism is our current computer language for encoding linguistic information. This paper, a brief overview of that formalism, attempts to explicate our design decisions in terms of a set of properties that effective computer languages should incorporate.
A method to dramatically improve subcarrier tracking

A method is presented for achieving a considerable improvement in phase tracking of square-wave subcarriers or other square waves. The amplitude of the phase quadrature reference signal is set to zero, except near the zero crossings of the input signal. Without changing the loop bandwidth, the variance of the phase error can be reduced by approximately W sigma /sub 0//sup 2/ where sigma /sub 0//sup 2/ is the phase error variance without windowing and W is the fraction of cycle in which the reference signal has a nonzero value. Simulation results confirm the results of the analysis and establish minimum W versus SNR (signal-to-noise ratio). Typically, the window can be made so narrow as to achieve a phase error variance of 1.5 sigma /sub 0//sup 4/. >
Microfluidic jet injection for delivering macromolecules into cells

We present a microfluidic-based injection system designed to achieve intracellular delivery of macromolecules by directing a picoliter jet of a solution toward the individual cells. After discussing the concept, we present design specification and criteria, elucidate performance and discuss results. The method has the potential to be quantitative and of high throughput, overcoming the limitations of current intracellular delivery protocols.
Planck scale physics and the Peccei-Quinn mechanism

Global-symmetry violating higher-dimension operators, expected to be induced by Planck-scale physics, in general drastically alter the properties of the axion field associated with the Peccei-Quinn solution to the strong-CP problem, and render this solution unnatural. The particle physics and cosmology associated with other global symmetries can also be significantly changed.
Prediction of jump phenomena in roll-coupled maneuvers of airplanes

An easily computerized analytical method is developed for identifying critical airplane maneuvers in which nonlinear rotational coupling effects may cause sudden jumps in the response to pilot's control inputs. Fifth- and ninth-degree polynomials for predicting multiple pseudosteady states of roll-coupled maneuvers are derived. The program calculates the pseudosteady solutions and their stability. The occurrence of jump-like responses for several airplanes and a variety of maneuvers is shown to correlate well with the appearance of multiple stable solutions for critical control combinations. The analysis is extended to include aerodynamics nonlinear in angle of attack. HILLIPS'! original analysis of the roll-coupling problem considered the rotational coupling effects of constant roll rate on the stability of the short-period longitudinal and lateral oscillations. Although the constant rolling constraint is artificial, it is physically realistic for well-behaved airplanes with good damping in roll. Phillips' analysis predicted that divergence-like motions would be expected at certain critical roll rates, when the usual linearized stability analysis predicted perfectly acceptable behavior. This dangerous coupling effect of rapid rolling, leading to large deviations in incidence angles and tail loads, was confirmed in many nonlinear computerized simulations and in flight. In con- nection with these simulation studies, there were many at- tempts to extend Phillips' analysis. The main objective of these studies was to obtain a simplified method for predicting the peak motions in roll-coupled maneuvers. Pinsker2 and Rhoads and Schuler3 showed that Phillips' critical roll rates also could be obtained as steady-state (autorotational) solutions of the approximate equations of motion used by Phillips. This method has the advantages that it also predicts steady-state solutions for the other variables, is more readily generalized, and permits the use of control input values as independent parameters, instead of roll rate. However, attempts to use this method to predict peak disturbances reliably in coupled maneuver were not suc- cessful. In the present study we have returned to this method of calculating the steady states of the approximate equations of motion, which we shall call the pseudosteady-state (PSS) method, because it neglects the effects of varying weight components in body axes. However, instead of trying to predict the magnitudes of response peaks, the method will be used to predict those control input combinations that may cause sudden "jumps" in the response as the motion is "attracted" to a new stable pseudosteady-state.
Automorphic forms and rational homology 3--spheres

We investigate a question of Cooper adjacent to the Virtual Haken Conjecture. Assuming certain conjectures in number theory, we show that there exist hyperbolic rational homology 3–spheres with arbitrarily large injectivity radius. These examples come from a tower of abelian covers of an explicit arithmetic 3–manifold. The conjectures we must assume are the Generalized Riemann Hypothesis and a mild strengthening of results of Taylor et al on part of the Langlands Program for GL2 of an imaginary quadratic field. The proof of this theorem involves ruling out the existence of an irreducible two dimensional Galois representation rho of Gal(Qbar/Qsqrt-2) satisfying certain prescribed ramification conditions. In contrast to similar questions of this form, rho is allowed to have arbitrary ramification at some prime pi of Z[sqrt -2]. In the next paper in this volume, Boston and Ellenberg apply pro–p techniques to our examples and show that our result is true unconditionally. Here, we give additional examples where their techniques apply, including some non-arithmetic examples. Finally, we investigate the congruence covers of twist-knot orbifolds. Our experimental evidence suggests that these topologically similar orbifolds have rather different behavior depending on whether or not they are arithmetic. In particular, the congruence covers of the non-arithmetic orbifolds have a paucity of homology.
On the stability of the Kuramoto model of coupled nonlinear oscillators

We provide an analysis of the classic Kuramoto model of coupled nonlinear oscillators that goes beyond the existing results for all-to-all networks of identical oscillators. Our work is applicable to oscillator networks of arbitrary interconnection topology with uncertain natural frequencies. Using tools from spectral graph theory and control theory, we prove that for couplings above a critical value all the oscillators synchronize, resulting in convergence of all phase differences to a constant value, both in the case of identical natural frequencies as well as uncertain ones. We also provide a series of bounds for the critical values of the coupling strength.
Higher-Dimensional Algebra III: n-Categories and the Algebra of Opetopes

Abstract We give a definition of weak n -categories based on the theory of operads. We work with operads having an arbitrary set S of types, or “ S -operads,” and given such an operad O , we denote its set of operations by elt( O ). Then for any S -operad O there is an elt( O )-operad O + whose algebras are S -operads over O . Letting I be the initial operad with a one-element set of types, and defining I 0+ = I , I ( i +1)+ =( I i + ) + , we call the operations of I ( n −1)+ the “ n -dimensional opetopes.” Opetopes form a category, and presheaves on this category are called “opetopic sets.” A weak n -category is defined as an opetopic set with certain properties, in a manner reminiscent of Street's simplicial approach to weak ω -categories. Similarly, starting from an arbitrary operad O instead of I , we define “ n -coherent O -algebras,” which are n times categorified analogs of algebras of O . Examples include “monoidal n -categories,” “stable n -categories,” “virtual n -functors” and “representable n -prestacks.” We also describe how n -coherent O -algebra objects may be defined in any ( n +1)-coherent O -algebra.
Darkness in Conrad's Heart of Darkness: A Linguistic and Stylistic Analysis

This paper is intended to discuss the concept of "darkness" in Joseph Conrad's Heart of Darkness. It incorporates a fairly detailed linguistic and stylistic analysis of the novel in terms of setting, lexical choices and grammatical choices that all indicate mystery, obscurity, murkiness and then darkness. A linguistic and stylistic analysis of the novel is used to show the literary value of the novel. Most specifically all linguistic and stylistic devices used can not only provide a detailed descriptive basis for interpretation of the novel , but also identify the important linguistic features which may not noticed by critics.
Q-CSMA: queue-length-based CSMA/CA algorithms for achieving maximum throughput and low delay in wireless networks

Recently, it has been shown that carrier-sense multiple access (CSMA)-type random access algorithms can achieve the maximum possible throughput in ad hoc wireless networks. However, these algorithms assume an idealized continuous-time CSMA protocol where collisions can never occur. In addition, simulation results indicate that the delay performance of these algorithms can be quite bad. On the other hand, although some simple heuristics (such as greedy maximal scheduling) can yield much better delay performance for a large set of arrival rates, in general they may only achieve a fraction of the capacity region. In this paper, we propose a discrete-time version of the CSMA algorithm. Central to our results is a discrete-time distributed randomized algorithm that is based on a generalization of the so-called Glauber dynamics from statistical physics, where multiple links are allowed to update their states in a single timeslot. The algorithm generates collision-free transmission schedules while explicitly taking collisions into account during the control phase of the protocol, thus relaxing the perfect CSMA assumption. More importantly, the algorithm allows us to incorporate heuristics that lead to very good delay performance while retaining the throughput-optimality property.
Optimal speckle reduction in polarimetric SAR imagery

Speckle is a major cause of degradation in synthetic aperture radar (SAR) imagery. With the availability of fully polarimetric SAR data, it is possible to use the three complex elements (HH, HV, VV) of the polarimetric scattering matrix to reduce speckle. The optimal method for combining the elements of the scattering matrix to minimize image speckle is derived, and the solution is shown to be a polarimetric whitening filter (PWF). A simulation of spatially correlated, K-distributed, fully polarimetric clutter is then used to compare the PWF with other, suboptimal speckle-reduction methods. Target detection performance of the PWF, span, and single-channel mod HH mod /sup 2/ detectors is compared with that of the optimal polarimetric detector (OPD). A novel, constant-false-alarm-rate (CFAR) detector (the adaptive PWF) is as a simple alternative to the OPD for detecting targets in clutter. This algorithm estimates the polarization covariance of the clutter, uses the covariance to construct the minimum-speckle image, and then tests for the presence of a target. An exact theoretical analysis of the adaptive PWF is presented; the algorithm is shown to have detection performance comparable with that of the OPD. >
Wafer level chip scale packaging (WL-CSP): an overview

Several wafer level chip scale package (WLCSP) technologies have been developed which generate fully packaged and tested chips on the wafer prior to dicing. Many of these technologies are based on simple peripheral pad redistribution technology followed by attachment of 0.3-0.5 mm solder balls. The larger standoff generated by these solder balls result in better reliability for the WLCSP's when underfill is not used than for equivalent flip chip parts. Rambus/sup TM/ RDRAM and integrated passives are two applications that should see wide acceptance of WLCSP packages.
More Social Security, Not Less

The feasibility of a government-sponsored insurance company that would be patterned after the government-sponsored mortgage agencies, and that would be authorized to sell government-insured wage-indexed retirement annuities, is explored. This enterprise would assume the current obligations and cash flows of the U.S. Social Security system in exchange for the exclusive right to sell additional insurance contracts, and may or may not choose to finance itself through the issuance of equity shares. The empirical analysis presented by the author focuses on the stochastic nature of the liabilities faced by such an agency and examines the optimal portfolio of assets required to hedge wage-indexed liabilities.
Simplified Mechanisms with an Application to Sponsored-Search Auctions

Abstract A mechanism can be simplified by restricting its message space. If the restricted message spaces satisfy a certain “outcome closure property,” then the simplification is “tight”: for every e ⩾ 0 , any e-Nash equilibrium of the simplified mechanism is also an e-Nash equilibrium of the unrestricted mechanism. Prominent auction and matching mechanisms are tight simplifications of mechanisms studied in economic theory and often incorporate price-adjustment features that facilitate simplification. The generalized second-price auction used for sponsored-search advertising is a tight simplification of a series of second-price auctions that eliminates the lowest revenue equilibrium outcomes and leaves intact only higher revenue equilibria.
S-duality and the dyon spectrum in N = 2 super Yang-Mills theory

Abstract We study the dyon spectrum in N = 2 super Yang-Mills theory with gauge group SU (2) coupled to N f matter multiplets in the fundamental representation. For magnetic charge one and two we determine the spectrum explicitly and show that it is in agreement with the duality predictions of Seiberg and Witten. We briefly discuss the extension to higher charge monopoles for the self-dual N f = 4 case and argue that the conjectured spectrum of dyons predicts the existence of certain harmonic spinors on the moduli space of higher charge monopoles.
Ultimate fate of constrained voters

We examine the ultimate fate of individual opinions in a socially interacting population of leftists, centrists and rightists. In an elemental interaction between agents, a centrist and a leftist can both become centrists or both become leftists with equal rates (and similarly for a centrist and a rightist). However leftists and rightists do not interact. This interaction step between pairs of agents is applied repeatedly until the system can no longer evolve. In the mean-field limit, we determine the exact probability that the system reaches consensus (either leftist, rightist or centrist) or a frozen mixture of leftists and rightists as a function of the initial composition of the population. We also determine the mean time until the final state is reached. Some implications of our results for the ultimate fate in a limit of the Axelrod model are discussed.
Role of solution conductivity in reaction induced charge auto-electrophoresis

Catalytic bimetallic Janus particles swim by a bipolar electrochemical propulsion mechanism that results from electroosmotic fluid slip around the particle surface. The flow is driven by electrical body forces which are generated from a coupling of a reaction-induced electric field and net charge in the diffuse layer surrounding the particle. This paper presents simulations, scaling, and physical descriptions of the experimentally observed trend that the swimming speed decays rapidly with increasing solution conductivity. The simulations solve the full Poisson-Nernst-Planck-Stokes equations with multiple ionic species, a cylindrical particle in an infinite fluid, and nonlinear Butler-Volmer boundary conditions to represent the electrochemical surface reactions. The speed of bimetallic particles is reduced in high-conductivity solutions because of reductions in the induced electric field in the diffuse layer near the rod, the total reaction rate, and the magnitude of the rod zeta potential. This work suggests that the auto-electrophoretic mechanism is inherently susceptible to speed reductions in higher ionic strength solutions.
Anisotropy Effects in the Thermal Diffusivity of Si3N4-BN Composites

The thermal diffusivity of silicon nitride-boron nitride composites is shown to exhibit considerable anisotropy with respect to the hot-pressing direction due to the preferred orientation of the boron nitride inclusions.
Compositional competitiveness for distributed algorithms

We define a measure of competitive performance for distributed algorithms based on throughput, the number of tasks that an algorithm can carry out in a fixed amount of work. This new measure complements the latency measure of Ajtai et al. [A theory of competitive analysis for distributed algorithms, in: 35th Annual Symposium on Foundations of Computer Science, Santa Fe, NM, IEEE, 1994, pp. 401-411]. which measures how quickly an algorithm can finish tasks that start at specified times. The novel feature of the throughput measure, which distinguishes it from the latency measure, is that it is compositional: it supports a notion of algorithms that are competitive relative to a class of subroutines, with the property that an algorithm that is k-competitive relative to a class of subroutines, combined with an l-competitive member of that class, gives a combined algorithm that is kl-competitive. In particular, we prove the throughput-competitiveness of a class of algorithms for collect operations, in which each of a group of n processes obtains all values stored in an array of n registers. Collects are a fundamental building block of a wide variety of shared-memory distributed algorithms, and we show that several such algorithms are competitive relative to collects. Inserting a competitive collect in these algorithms gives the first examples of competitive distributed algorithms obtained by composition using a general construction.
Fourier transform representation of the extended Fermi–Dirac and Bose–Einstein functions with applications to the family of the zeta and related functions

On the one hand, the Fermi–Dirac and Bose–Einstein functions have been extended in such a way that they are closely related to the Riemann and other zeta functions. On the other hand, the Fourier transform representation of the gamma and generalized gamma functions proved useful in deriving various integral formulae for these functions. In this paper, we use the Fourier transform representation of the extended functions to evaluate integrals of products of these functions. In particular, we evaluate some integrals containing the Riemann and Hurwitz zeta functions, which had not been evaluated before.
PHYSICISTS ATTEMPT TO SCALE THE IVORY TOWERS OF FINANCE

Physicists have recently begun doing research in finance, and even though this movement is less than five years old, interesting and useful contributions have already emerged. This article reviews these developments in four areas, including empirical statistical properties of prices, random-process models for price dynamics, agent-based modeling, and practical applications.
Contingent Valuation: Controversies and Evidence

Contingent valuation (CV) has become one of the most widely used non-market valuation techniques. CV's prominence is due to its flexibility and ability to estimate total value, including passive use value. Its use and the inclusion of passive use value in benefit-cost analyses and environ- mental litigation are the subject of a contentious debate. This paper discusses key areas of the debate over CV and the validity of passive use value. We conclude that many of the alleged problems with CV can be resolved by careful study design and implementation. We further conclude that claims that empirical CV findings are theoretically inconsistent are not generally supported by the literature. The debate over CV, however, has clarified several key issues related to nonmarket valuation and can provide useful guidance both to CV practitioners and the users of CV results.
Chemoprevention of breast cancer.

One in eight women in the United States will develop breast cancer. Family history, hormonal factors and benign breast disease have been identified as key factors in the development of breast cancer. Until recently the only treatment option for women identified as being at high risk of developing breast cancer was bilateral prophylactic mastectomy. Tamoxifen is the treatment of choice for patients with all stages of hormone-responsive breast cancer. Tamoxifen has a proven safety record from analysis of its use in patients with early stage breast cancer and, in postmenopausal women, it maintains bone density and lowers cholesterol levels. Lastly, tamoxifen reduces the incidence of contralateral breast cancer in women with breast cancer. Recently, in a large randomized trial where women at high risk of breast cancer were randomized to tamoxifen or placebo, tamoxifen resulted in a 50% reduction in the incidence of both invasive and non-invasive breast cancers. On the basis of this result, tamoxifen has been approved as a preventive for women at high risk of developing breast cancer. The optimum duration of tamoxifen in the preventive setting is to date unclear, but in the adjuvant setting, tamoxifen continues to have beneficial effects even after it is stopped. Tamoxifen does result in a two- to threefold increase in endometrial cancer, and new antiestrogens, such as raloxifene, are being developed to reduce this risk. The next prevention trial, called Study of Tamoxifen and Raloxifene (STAR), will randomize postmenopausal women to tamoxifen or raloxifene for five years.
Detection of multiple input bridging and stuck-on faults in CMOS logic circuits using current monitoring

Current monitoring is a well-established technique for detecting stuck-on and bridging faults in CMOS logic circuits. When such faults are activated by an appropriate vector, the circuit draws current which is much larger than normal and the fault is detected. The authors first show that any test set, which detects all single stuck-at faults in any irredundant combinational CMOS logic circuit, also detects all multiple stuck-on faults in it using current monitoring. If the constituent gates of the circuit are all primitive CMOS gates (NAND, NOR, NOT) then the authors show that the test set detects all multiple stuck-on and input bridging faults (even if the two types of faults occur simultaneously) with current monitoring. Even when the CMOS circuit is redundant the authors have found that in most cases a test set that detects all detectable single stuck-at faults also has a very high coverage for the multiple stuck-on and input bridging faults and their combinations. >
Spiral evolution applied to legacy avionics systems

The US Department of Defense (DoD), through the Office of the Secretary of Defense (OSD), has determined that evolutionary acquisition is their strategy of choice for future software-intensive systems, and that the spiral development model (SDM) is the preferred method/process for software-intensive development life cycles. Electronic Systems Command (ESC) at Hanscom AFB, Massachusetts, has written a draft handbook on the use of Spiral Development for all future Command and Control (C2) systems, including reference to the DoD 5000 series and Air Force Program Directive 63-1, Acquisition System, which deploys this OSD mandate for future C2 systems. Barry Boehm's continued work on SDM which he conceived in the 1980s, is heavily biased toward development of new systems that are software-intensive, as noted in a workshop he gave at the Software Engineering Institute (SEI) in 2000.
Inflation Stabilization and Welfare: The Case of a Distorted Steady State

This paper considers the appropriate stabilization objectives for monetary policy in a microfounded model with staggered price-setting. Rotemberg and Woodford (1997) and Woodford (2002) have shown that under certain conditions, a local approximation to the expected utility of the representative household in a model of this kind is related inversely to the expected discounted value of a conventional quadratic loss function, in which each period's loss is a weighted average of squared deviations of inflation and an output gap measure from their optimal values (zero). However, those derivations rely on an assumption of the existence of an output or employment subsidy that offsets the distortion due to the market power of monopolistically-competitive price-setters, so that the steady state under a zero-inflation policy involves an efficient level of output. Here we show how to dispense with this unappealing assumption, so that a valid linear-quadratic approximation to the optimal policy problem is possible even when the steady state is distorted to an arbitrary extent (allowing for tax distortions as well as market power), and when, as a consequence, it is necessary to take account of the effects of stabilization policy on the average level of output. We again obtain a welfare-theoretic loss function that involves both inflation and an appropriately defined output gap, though the degree of distortion of the steady state affects both the weights on the two stabilization objectives and the definition of the welfare-relevant output gap. In the light of these results, we reconsider the conditions under which complete price stability is optimal, and find that they are more restrictive in the case of a distorted steady state. We also consider the conditions under which pure randomization of monetary policy can be welfare-improving, and find that this is possible in the case of a sufficiently distorted steady state, though the parameter values required are probably not empirically realistic.