cssi/SciSciGPT-SciSciNet huggingface dataset:
Rectilinear short path queries among rectangular obstacles

Abstract Given a set of n disjoint rectangular obstacles in the plane whose edges are either vertical or horizontal, we consider the problem of processing rectilinear approximate shortest path queries between pairs of arbitrary query points. Our goal is to answer each approximate shortest path query quickly by constructing a data structure that captures path information in the obstacle-scattered plane. We present a data structure for rectilinear approximate shortest path queries that requires O(n log2 n) time to construct and O(n log n) space. This data structure enables us to report the length of an approximate shortest path between two arbitrary query points in O(log n) time and the actual path in O(log n + L) time, where L is the number of edges of the output path. If the query points are both obstacle vertices then the length and an actual path can be reported in O(1) and O(L) time respectively. The approximation factor for the approximate shortest paths that we compute is 3. The previously best known solution to this problem requires O(n log3 n) time and O(n log2 n) space to build a data structure, which supports length and actual path queries respectively in O(log2 n) and O(log2 n + L) time (regardless of the types of query points); the approximation factor for paths between arbitrary query points is 7.
Channel Coding over Multiple Coherence Blocks with Queueing Constraints

This paper investigates the performance of wireless systems that employ finite-blocklength channel codes for transmission and operate under queueing constraints in the form of limitations on buffer overflow probabilities. A block fading model, in which fading stays constant in each coherence block and change independently between blocks, is considered. It is assumed that channel coding is performed over multiple coherence blocks. An approximate lower bound on the transmission rate is obtained from Feintein's Lemma. This lower bound is considered as the service rate and is incorporated into the effective capacity formulation, which characterizes the maximum constant arrival rate that can be supported under statistical queuing constraints. Performances of variable-rate and fixed-rate transmissions are studied. The optimum error probability for variable rate transmission and the optimum coding rate for fixed rate transmission are shown to be unique. Moreover, the tradeoff between the throughput and the number of blocks over which channel coding is performed is identified.
UNUSUAL FORMULAE FOR THE EULER CHARACTERISTIC

Everyone knows that the Euler characteristic of a combinatorial manifold is given by the alternating sum of its numbers of simplices. It is shown that there are other linear combinations of the numbers of simplices which are combinatorial invariants, but that all such invariants are multiples of the Euler characteristic.
The relation between hard X-ray and transition-region line emission in solar flares

Observational evidence suggests that both the hard X-ray and ultraviolet emission from the impulsive phase of flares result from an electron beam. We present the results of model calculations that are consistent with this theory. The impulsive phase is envisioned as occurring in many small magnetically confined loops, each of which maintains an electron beam for only a few seconds. This model successfully matches several observed aspects of the impulsive phase. The corona is heated to less than 2 × 106 K, maximum enhanced emission occurs in lines formed near 105 K, and there is only slight enhancement between 105 and 2 × 106 K. The slope of the observed relationship between hard X-ray and Ov 1371 A emission is also matched, but the relative emission is not. The calculations indicate that UV emission lines formed below a temperature of about 105 K will arise predominantly from the chromospheric region heated by the electron beam to transition region temperatures. Emission lines formed at higher temperatures will be produced in the transition region. This should be detectable in density-sensitive line ratios. To account successfully for the impulsive UV emission, the peak temperature in the impulsively heated loops must remain below about 2 × 106 K. Thus our model implies that the impulsive heating takes place in different loops from the hotter gradual phase emission.
Approximating the Minimum Spanning Tree Weight in Sublinear Time

We present a probabilistic algorithm that, given a connected graph G (represented by adjacency lists) of average degree d, with edge weights in the set{1,...,w}, and given a parameter $0<\eps<1/2$, estimates in time $O( dw \varepsilon^{-2} \log{\frac{dw}\varepsilon})$ the weight of the minimum spanning tree (MST) of G with a relative error of at most $\eps$. Note that the running time does not depend on the number of vertices in G. We also prove a nearly matching lower bound of $\Omega( dw \varepsilon^{-2} )$ on the probe and time complexity of any approximation algorithm for MST weight. The essential component of our algorithm is a procedure for estimating in time $O(d\eps^{-2}\log \frac{d}\varepsilon)$ the number of connected components of an unweighted graph to within an additive error of $\varepsilon n$. (This becomes $O(\eps^{-2}\log \frac{1}\varepsilon)$ for $d=O(1)$.) The time bound is shown to be tight up to within the $\log \frac{d}\varepsilon$ factor. Our connected-components algorithm picks $O(1/\varepsilon^2)$ vertices in the graph and then grows "local spanning trees" whose sizes are specified by a stochastic process. From the local information collected in this way, the algorithm is able to infer, with high confidence, an estimate of the number of connected components. We then show how estimates on the number of components in various subgraphs of G can be used to estimate the weight of its MST.
Asymptotic locally optimal detector for large-scale sensor networks under the Poisson regime

We consider distributed detection with a large number of identical binary sensors deployed over a region where the phenomenon of interest (POI) has spatially varying signal strength. Each sensor makes a binary decision based on its own measurement, and the local decision of each sensor is sent to a fusion center using a random access protocol. The fusion center decides whether the event has occurred under a global size constraint in the Neyman-Pearson formulation. Assuming homogeneous Poisson distributed sensors, we show that the distribution of "alarmed" sensors satisfies the local asymptotic normality (LAN). We then derive an asymptotically locally most powerful (ALMP) detector optimized jointly over the fusion form and the local sensor threshold under the Poisson regime. We establish conditions on the spatial signal shape that ensure the existence of the ALMP detector. We show that the ALMP test statistic is a weighted sum of local decisions, the optimal weights being the shape of the spatial signal; the exact value of the signal strength is not required. We also derive the optimal threshold for each sensor. For the case of independent, identically distributed (iid) sensor observations, we show that the counting-based detector is also ALMP under the Poisson regime. The performance of the proposed detector is evaluated through analytic results and Monte Carlo simulations and compared with that of the counting-based detector. The effect of mismatched signal shapes is also investigated.
Optic Tract Injury after Anterior Temporal Lobectomy

Three patients had complete homonymous hemianopia with clinical and neuroimaging characteristics of ipsilateral optic tract infarction after anterior temporal lobectomy for seizure control. This injury presumably resulted from irritative vasospasm of the anterior choroidal artery. The features of this pure optic tract syndrome should be distinguished from the more common compressive optic tract syndrome which generally also impairs ipsilateral optic nerve function.
Digital equalization of ultrafast data using real-time burst sampling

We demonstrate digital equalization of 40Gbps data enabled by use of Real-time Burst Sampling (RBS) with photonic time-stretch A/D converter. Evaluation of a feed-forward equalizer and a decision feedback equalizer is also shown.
Level spacing distributions and the Bessel kernel

Scaling models of randomN×N hermitian matrices and passing to the limitN→∞ leads to integral operators whose Fredholm determinants describe the statistics of the spacing of the eigenvalues of hermitian matrices of large order. For the Gaussian Unitary Ensemble, and for many others'as well, the kernel one obtains by scaling in the “bulk” of the spectrum is the “sine kernel”\(\frac{{\sin \pi (x - y)}}{{\pi (x - y)}}\). Rescaling the GUE at the “edge” of the spectrum leads to the kernel\(\frac{{Ai(x)Ai'(y) - Ai'(x)Ai(y)}}{{x - y}}\), where Ai is the Airy function. In previous work we found several analogies between properties of this “Airy kernel” and known properties of the sine kernel: a system of partial differential equations associated with the logarithmic differential of the Fredholm determinant when the underlying domain is a union of intervals; a representation of the Fredholm determinant in terms of a Painleve transcendent in the case of a single interval; and, also in this case, asymptotic expansions for these determinants and related quantities, achieved with the help of a differential operator which commutes with the integral operator. In this paper we show that there are completely analogous properties for a class of kernels which arise when one rescales the Laguerre or Jacobi ensembles at the edge of the spectrum, namely $$\frac{{J_\alpha (\sqrt x )\sqrt y J'_\alpha (\sqrt y ) - \sqrt x J'_\alpha (\sqrt x )J_\alpha (\sqrt y )}}{{2(x - y)}},$$ , whereJα(z) is the Bessel function of order α. In the cases α=∓1/2 these become, after a variable change, the kernels which arise when taking scaling limits in the bulk of the spectrum for the Gaussian orthogonal and symplectic ensembles. In particular, an asymptotic expansion we derive will generalize ones found by Dyson for the Fredholm determinants of these kernels.
Scalable synchronous queues

In a thread-safe concurrent queue, consumers typically wait for producers to make data available. In a synchronous queue, producers similarly wait for consumers to take the data. We present two new nonblocking, contention-free synchronous queues that achieve high performance through a form of dualism: The underlying data structure may hold both data and, symmetrically, requests. We present performance results on 16-processor SPARC and 4-processor Opteron machines. We compare our algorithms to commonly used alternatives from the literature and from the Java SE 5.0 class java.util.concurrent.SynchronousQueue both directly in synthetic microbenchmarks and indirectly as the core of Java's ThreadPoolExecutor mechanism. Our new algorithms consistently outperform the Java SE 5.0 SynchronousQueue by factors of three in unfair mode and 14 in fair mode; this translates to factors of two and ten for the ThreadPoolExecutor. Our synchronous queues have been adopted for inclusion in Java 6.
Kaon matrix elements in domain-wall QCD with DBW2 gauge action

We present calculations of the decay constants and kaon B-parameter B K as the first stage of RBC Collaboration's quenched numerical simulations using DBW2 gauge action and domain-wall fermions. Some of potential systematic errors and consistency to previous works are discussed.
RG flow on random surfaces with handles and closed string field theory

Abstract The renormalization group flow in two-dimensional field theories that are coupled to gravity has unusual features: First, the flow equations are second order in derivatives. Second, in the presence of handles the flow has quantum mechanical properties. Third, the beta functions contain the elementary higher-genus vertices of closed string field theory. This is demonstrated at simple examples and is applied to derive various results about gravitationally dressed beta functions. The possibility of interpreting closed string field theory as the theory of the renormalization group on random surfaces with random topology is considered.
Evolution of intermediate and low mass binary systems

Abstract There are a number of binaries, fairly wide and with one or even two evolved giant components, that do not agree very well with conventional stellar evolution: the secondaries are substantially larger (‘oversized’) than they should be because their masses are quite low compared with the primaries. I discuss the possibility that these binaries are former triples, in which a merger has occurred fairly recently in a short-period binary sub-component. Some mergers are expected, and may follow a phase of contact evolution. I suggest that in contact there is substantial transfer of luminosity between the components due to differential rotation, of the character observed by helioseismology in the Sun’s surface convection zone.
On the Hardness of Counting and Sampling Center Strings

Given a set S of n strings, each of length \ell , and a nonnegative value d , we define a center string as a string of length \ell that has Hamming distance at most d from each string in S . The \#{\rm CLOSEST STRING} problem aims to determine the number of center strings for a given set of strings S and input parameters n , \ell , and d . We show \#{\rm CLOSEST STRING} is impossible to solve exactly or even approximately in polynomial time, and that restricting \#{\rm CLOSEST STRING} so that any one of the parameters n , \ell , or d is fixed leads to a fully polynomial-time randomized approximation scheme (FPRAS). We show equivalent results for the problem of efficiently sampling center strings uniformly at random (u.a.r.).
Intense magnetic fields in astrophysics

In this paper we summarize the current knowledge of research on the influence of intense magnetic fields on physical processes. The contents are summarized in the enclosed Table of Contents.
Cooling Active Region Loops Observed with SXT and TRACE

An impulsive heating multiple strand (IHMS) model is able to reproduce the observational characteristics of EUV (~1 MK) active region loops. This model implies that some of the loops must reach temperatures where X-ray filters are sensitive (>2.5 MK) before they cool to EUV temperatures. Hence, some bright EUV loops must be preceded by bright X-ray loops. Previous analyses of X-ray and EUV active region observations, however, have concluded that EUV loops are not the result of cooling X-ray loops. In this paper, we examine two active regions observed in both X-ray and EUV filters and analyze the evolution of five loops over several hours. These loops first appear bright in the X-ray images and later appear bright in the EUV images. The delay between the appearance of the loops in the X-ray and EUV filters is as little as 1 hr and as much as 3 hr. All five loops appear as single "monolithic" structures in the X-ray images but are resolved into many smaller structures in the (higher resolution) EUV images. The positions of the loops appear to shift during cooling, implying that the magnetic field is changing as the loops evolve. There is no correlation between the brightness of the loop in the X-ray and EUV filters, meaning that a bright X-ray loop does not necessarily cool to a bright EUV loop, and vice versa. The progression of the loops from X-ray images to EUV images and the observed substructure is qualitatively consistent with the IHMS model.
Tachyonic field theory and neutrino mass running

In this paper three things are done. (i) We investigate the analogues of Cerenkov radiation for the decay of a superluminal neutrino and calculate the Cerenkov angles for the emission of a photon through a W loop, and for a collinear electron-positron pair, assuming the tachyonic dispersion relation for the superluminal neutrino. The decay rate of a freely propagating neutrino is found to depend on the shape of the assumed dispersion relation, and is found to decrease with decreasing tachyonic mass of the neutrino. (ii)We discuss a few properties of the tachyonic Dirac equation (symmetries and plane-wave solutions), which may be relevant for the description of superluminal neutrinos seen by the OPERA experiment, and discuss the calculation of the tachyonic propagator. (iii) In the absence of a commonly accepted tachyonic field theory, and in view of an apparent “running” of the observed neutrino mass with the energy, we write down a model Lagrangian, which describes a Yukawa-type interaction of a neutrino coupling to a scalar background field via a scalar-minus-pseudoscalar interaction. This constitutes an extension of the standard model. If the interaction is strong, then it leads to a substantial renormalization-group “running” of the neutrino mass and could potentially explain the experimental observations.
Optofluidic circular grating distributed feedback dye laser

We demonstrate a surface emitting optofluidic dye laser using a second order circular grating distributed feedback resonator. The optofluidic dye laser offers a low-cost and integrated coherent light source for lab-on-a-chip spectroscopy systems.
Improved capacity approximations for Gaussian relay networks

Consider a Gaussian relay network where a number of sources communicate to a destination with the help of several layers of relays. Recent work has shown that a compress-and-forward based strategy at the relays can achieve the capacity of this network within an additive gap. In this strategy, the relays quantize their observations at the noise level and map it to a random Gaussian codebook. The resultant capacity gap is independent of the SNR's of the channels in the network but linear in the total number of nodes. In this paper, we show that if the relays quantize their signals at a resolution decreasing with the number of nodes in the network, the additive gap to capacity can be made logarithmic in the number of nodes for a class of layered, time-varying wireless relay networks. This suggests that the rule-of-thumb to quantize the received signals at the noise level used for compress-and-forward in the current literature can be highly suboptimal.
Stacked Switched Capacitor Energy Buffer Architecture

Electrolytic capacitors are often used for energy buffering applications, including buffering between single-phase ac and dc. While these capacitors have high energy density compared to film and ceramic capacitors, their life is limited. This paper presents a stacked switched capacitor (SSC) energy buffer architecture and some of its topological embodiments, which when used with longer life film capacitors overcome this limitation while achieving effective energy densities comparable to electrolytic capacitors. The architectural approach is introduced along with design and control techniques. A prototype SSC energy buffer using film capacitors, designed for a 320 V dc bus and able to support a 135 W load, has been built and tested with a power factor correction circuit. It is shown that the SSC energy buffer can successfully replace limited-life electrolytic capacitors with much longer life film capacitors, while maintaining volume and efficiency at a comparable level.
Homology surgery and invariants of 3-manifolds.

We introduce a homology surgery problem in dimension 3 which has the property that the vanishing of its algebraic obstruction leads to a canonical class of π–algebraically-split links in 3–manifolds with fundamental group π. Using this class of links, we define a theory of finite type invariants of 3–manifolds in such a way that invariants of degree 0 are precisely those of conventional algebraic topology and surgery theory. When finite type invariants are reformulated in terms of clovers, we deduce upper bounds for the number of invariants in terms of π–decorated trivalent graphs. We also consider an associated notion of surgery equivalence of π–algebraically split links and prove a classification theorem using a generalization of Milnor’s μ–invariants to this class of links.
Ferromagnetic semiconductors: moving beyond (Ga,Mn)As

The recent development of MBE techniques for growth of III–V ferromagnetic semiconductors has created materials with exceptional promise in spintronics, that is, electronics that exploit carrier spin polarization. Among the most carefully studied of these materials is (Ga,Mn)As, in which meticulous optimization of growth techniques has led to reproducible materials properties and ferromagnetic transition temperatures well above 150 K. We review progress in the understanding of this particular material and efforts to address ferromagnetic semiconductors as a class. We then discuss proposals for how these materials might find applications in spintronics. Finally, we propose criteria that can be used to judge the potential utility of newly discovered ferromagnetic semiconductors, and we suggest guidelines that may be helpful in shaping the search for the ideal material.
A quantitative analysis of periorbital aging with three-dimensional surface imaging.

Summary Background Studies of facial aging up to the present have largely been observational and subjective. This study applies state-of-the-art facial imaging and three-dimensional computer modelling to measure changes in the aging female face. The markers of facial aging discussed here go beyond descriptive accounts by individual practitioners and are presented as quantitative measurements of the volume change in the aging periorbital region. Methods Three-dimensional image data sets were acquired of 42 mother–daughter matched pairs (83 individuals). Overall similarity of the faces of the mother–daughter pair were confirmed using best fit analyses prior to further processing of the data. The changes in facial structure secondary to aging were measured using volumetric comparisons of periorbital tissues in the daughter and mother. The age range of the individuals imaged range from 15 to 91 years. Results A consistent pattern of volume difference and regression of soft tissues associated with the medial canthus nasojugal groove was demonstrated in the aged individual of each pair. The volume difference associated with the tear trough ranged from 0.02cc to 1.27cc with median values of 0.38cc and 0.42cc. Volume differences in the adjacent periorbital tissues are also measured. Conclusions Imaging clearly shows a consistent pattern of atrophy and regression of soft tissues associated with the medial canthus and nasojugal groove. Histogram depth analysis of the soft tissue shows greatest atrophy in the medial canthal region and soft tissues caudal to the lower lid. Volumetric analysis of the atrophy of these tissues is a useful adjunct in the accurate rejuvenation of the periorbital region.
Ballistic performance of polyurea-coated armor grade ceramic tiles

The use of ceramics as energy absorbents has been studied by many researchers and some improvements in the ballistic performance of ceramic tiles have been made by coating them with different classes of materials (e.g. E-glass/epoxy, carbon-fiber/epoxy, etc.). Using ceramics for energy absorbing applications leads to a significant weight reduction of the system. Therefore, any modification to the ceramic configuration in the system which leads to more energy absorption with the same or less areal density is significant. On the other hand, polyurea has been proved to be an excellent energy dissipating agent in many applications. Inspired by this, we are studying the effect of coating ceramics with polyurea and other materials, on the energy absorption and ballistic performance of the resulting ceramic-based composites. In this study, we investigate the effect of polyurea on ballistic efficiency of ceramic tiles. To this end, we have performed a set of penetration tests on polyurea-ceramic composites. In our experiments, a high velocity projectile is propelled to impact and perforate the ceramic-polyurea composite. The velocity and mass of the projectile are measured before and after the penetration. The change in the kinetic energy of the projectile is evaluated and compared for different polyurea-ceramic configurations (e.g., polyurea on front face, polyurea on back face, polyurea between two ceramic tiles, etc.). The experimental results suggest that polyurea is not as effective as other restraining materials such as E-glass/epoxy and carbon-fiber/epoxy.
A guide to first-passage processes

Preface Errata 1. First-passage fundamentals 2. First passage in an interval 3. Semi-infinite system 4. Illustrations of first passage in simple geometries 5. Fractal and nonfractal networks 6. Systems with spherical symmetry 7. Wedge domains 8. Applications to simple reactions References Index.
The Subprime Turmoil: What's Old, What's New, and What's Next

This article considers the origins of the subprime turmoil and the way the financial system has responded to it. It explains that there are both old and new components in both the origins and the propagation of the subprime shock. Old components include government financial subsidies for bearing risk, accommodative monetary policy, and adverse selection facilitated by asymmetric information. New components include the central role of agency problems in asset management, the ability of financial institutions to raise new capital from external sources, the activist role of the United States Treasury Department and Federal Reserve, and improvements in U.S. financial system diversification resulting from deregulation, consolidation, and globalization. In light of these old and new elements of the origins and propagation of the subprime turmoil, the article concludes by considering the near-term future of financial and macroeconomic performance, and the implications for monetary policy, regulatory policy, and the future of the structure of the financial services industry.
The engineering design of the stretch computer

The Stretch Computer project was started in order to achieve two orders of magnitude of improvement in performance over the then existing 704. Although this computer, like the 704, is aimed at scientific problems such as reactor design, hydrodynamics problems, partial differential equations etc., its instruction set and organization are such that it can handle with ease data-processing problems normally associated with commercial applications, such as processing of alphanumeric fields, sorting, and decimal arithmetic.
Phylogenetic toric varieties on graphs

We define phylogenetic projective toric model of a trivalent graph as a generalization of a binary symmetric model of a trivalent phylogenetic tree. Generators of the projective coordinate ring of the models of graphs with one cycle are explicitly described. The phylogenetic models of graphs with the same topological invariants are deformation-equivalent and share the same Hilbert function. We also provide an algorithm to compute the Hilbert function.
Minimizing phylogenetic number to find good evolutionary trees

Inferring phylogenetic trees is a fundamental problem in computational-biology. We present a new objective criterion, the phylogenetic number, for evaluating evolutionary trees for species defined by biomolecular sequences or other qualitative characters. The phylogenetic number of a tree T is the maximum number of times that any given character state arises in T. By contrast, the classical parsimony criterion measures the total number of times that different character states arise in T. We consider the following related problems: finding the tree with minimum phylogenetic number, and computing the phylogenetic number of a given topology in which only the leaves are labeled by species. When the number of states is bounded (as is the case for biomolecular sequence characters), we can solve the second problem in polynomial time. We can also compute a fixed-topology 2-phylogeny (when one exists) for an arbitrary number of states. This algorithm can be used to further distinguish trees that are equal under parsimony. We also consider a number of other related problems.
The effect of particle coalescence on the surface area of a coagulating aerosol

Abstract The initial stage of particle formation in high temperature processes is characterized by a high density of very small particles undergoing rapid coagulation. When these particles are solid this leads to agglomerates with a high specific surface area. However, at high gas temperatures particle coalescence which is very sensitive to the temperature may reduce the surface area and increase the size of the primary particles. In this paper we generalize the Smoluchowski equation to incorporate the coalescence rate into the aerosol dynamics. Individual agglomerates are characterized by their volume, v , and surface area, a . A Liouville term is added to the coagulation equation determining the movement of the distribution function through a -space due to coalescence. For the rate of coalescence a simple two sphere model has been used. Results for the surface area and the average diameter of the individual primary particles are presented for the case of a collision kernel which is independent of the particle structure. As an example, the theory is applied to fine particle formation in combustion processes under nonisothermal conditions.
Effects of Peclet number on pore‐scale mixing and channeling of a tracer and on directional advective porosity

Field tracer tests indicate that advective porosity, the quantity relating advective velocity to Darcy flux, may exhibit directional dependence. Theory [Neuman, 2005a, 2005b] suggests that directional variations in advective porosity could arise from incomplete mixing of an inert tracer between directional flow channels within a sampling volume of soil or rock that may be hydraulically isotropic or anisotropic, rendering advective porosity a function of Peclet number. Whereas Neuman was able to quantify the process for idealized intersecting fracture sets, his theory is too abstract to allow doing the same for more complex systems of fractures or pores. We use Smoothed Particle Hydrodynamics [e.g. Tartakovsky and Meakin, 2005, 2006] to simulate advective-diffusive transport of a passive tracer in the interior of an idealized pore space between impermeable circular or elliptical solid grains of random sizes, arranged randomly within a square domain. Our numerical experiments reveal a transition from complete mixing of tracer at small Peclet numbers to the gradual evolution of pore-scale channels of tracer which allow less and less mixing as Peclet numbers grow. Advective porosity, computed as the ratio between total water flux across the domain boundaries and migration rate of the tracer center of mass, is found tomore » diminish asymptotically from a value equal to the total porosity at a Peclet number of zero (pure diffusion) to a constant dominated entirely by advection at large Peclet numbers. When total porosity is kept constant, channeling is less pronounced and mixing more prominent when flow takes place parallel to the longer axes of elliptical grains as compared to when the grains are circular. On the other hand, channeling is more pronounced and mixing less so when flow takes place perpendicular to the longer elliptical grain axes. Correspondingly, the rate at which advective porosity diminishes with increasing Peclet number is slower and the asymptote is larger when flow takes place parallel to the longer axes of elliptical grains than when the grains are circular. However, the rate is much faster and the asymptote much smaller when flow takes place perpendicular to the longer elliptical grain axes.« less
ISSUES AND THE PRESIDENTIAL PRIMARY VOTER

Most agree that voting in presidential general elections is largely contingent on the evaluations of the candidates, issues, and parties. Yet inpresidential primary elections the determinants of voter choices are less clear. Partisanship is inconsequential, information about candidate personalities and policy positions is scarce, and a fourth factor, expectations, may influence voters. In this paper, we reconsider the influence ofpolitical issues in presidential primaries. We argue that past work has not adequately considered how issues matter in primary elections. Primaries are intraparty affairs, and the political issues that typically divide the parties are not very relevant in primaries. Instead, we focus on the policy issues each candidate chooses to emphasize in their quest for the nomination, which we call policy priorities. With data gathered about media coverage of the presidential contenders in the 1988 primaries, and using exit poll data from the 1988 Super Tuesday primaries, we show that issues, as policy priorities, do matter in presidential primary elections. This research also implies that primary campaigns matter, since information concerning the policy priorities of the candidates reaches the intended audience.
A Reflexive Approach to Risk and Intervention for Third‐Party Intervenors

In violent contexts, intervenors face dangers and are sometimes targets of violence themselves. Data and discussion about these risks and strategies to address them are missing from the peacebuilding literature. This article begins to address this gap. I argue that existing conflict analysis models provide a foundation for risk analysis, but they do not recognize the interplay between an organization's policies and intervention approaches and its security. I review two generations of conflict analysis frameworks and then present an approach that identifies various dimensions and types of risk and vulnerability for third-party intervenors and integrates easily into existing analytical frameworks.
SUPERMASSIVE BLACK HOLE FORMATION AT HIGH REDSHIFTS VIA DIRECT COLLAPSE: PHYSICAL PROCESSES IN THE EARLY STAGE

We use numerical simulations to explore whether direct collapse can lead to the formation of supermassive black hole (SMBH) seeds at high redshifts. Using the adaptive mesh refinement code ENZO, we follow the evolution of gas within slowly tumbling dark matter (DM) halos of M vir ~ 2 × 108 M ☉ and R vir ~ 1 kpc. For our idealized simulations, we adopt cosmologically motivated DM and baryon density profiles and angular momentum distributions. Our principal goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation which can potentially lead to star formation, decreasing the seed SMBH mass. We find that the collapse proceeds from inside out and leads either to a central runaway or to off-center fragmentation. A disk-like configuration is formed inside the centrifugal barrier, growing via accretion. For models with a more cuspy DM distribution, the gas collapses more and experiences a bar-like perturbation and a central runaway on scales of 1-10 pc. We have followed this inflow down to ~10–4 pc (~10 AU), where it is estimated to become optically thick. The flow remains isothermal and the specific angular momentum, j, is efficiently transferred by gravitational torques in a cascade of nested bars. This cascade is triggered by finite perturbations from the large-scale mass distribution and by gas self-gravity, and supports a self-similar, disk-like collapse where the axial ratios remain constant. The mass accretion rate shows a global minimum on scales of ~1-10 pc at the time of the central runaway. In the collapsing phase, virial supersonic turbulence develops and fragmentation is damped. Models with progressively larger initial DM cores evolve similarly, but the timescales become longer. In models with more organized initial rotation—when the rotation of spherical shells is constrained to be coplanar—a torus forms on scales ~20-50 pc outside the disk, and appears to be supported by turbulent motions driven by accretion from the outside. The overall evolution of the models depends on the competition between two timescales, corresponding to the onset of the central runaway and of off-center fragmentation. In models with less organized rotation—when the rotation of spherical shells is randomized (but the total angular momentum remains unchanged)—the torus is greatly weakened, the central accretion timescale is shortened, and off-center fragmentation is suppressed—triggering the central runaway even in previously "stable" models. The resulting seed SMBH masses is found in the range M • ~ 2 × 104 M ☉-2 × 106 M ☉, substantially higher than the mass range of Population III remnants. We argue that the above upper limit on M • appears to be more realistic, and lies close to the cutoff mass of detected SMBHs. Corollaries of this model include a possible correlation between SMBH and DM halo masses, and similarity between the SMBH and halo mass functions, at time of formation.
Exchange-coupled nanocomposite magnets by nanoparticle self-assembly

Exchange-spring magnets are nanocomposites that are composed of magnetically hard and soft phases that interact by magnetic exchange coupling. Such systems are promising for advanced permanent magnetic applications, as they have a large energy product--the combination of permanent magnet field and magnetization--compared to traditional, single-phase materials. Conventional techniques, including melt-spinning, mechanical milling and sputtering, have been explored to prepare exchange-spring magnets. However, the requirement that both the hard and soft phases are controlled at the nanometre scale, to ensure efficient exchange coupling, has posed significant preparation challenges. Here we report the fabrication of exchange-coupled nanocomposites using nanoparticle self-assembly. In this approach, both FePt and Fe3O4 particles are incorporated as nanometre-scale building blocks into binary assemblies. Subsequent annealing converts the assembly into FePt-Fe3Pt nanocomposites, where FePt is a magnetically hard phase and Fe3Pt a soft phase. An optimum exchange coupling, and therefore an optimum energy product, can be obtained by independently tuning the size and composition of the individual building blocks. We have produced exchange-coupled isotropic FePt-Fe3Pt nanocomposites with an energy product of 20.1 MG Oe, which exceeds the theoretical limit of 13 MG Oe for non-exchange-coupled isotropic FePt by over 50 per cent.
Design for Test of Asynchronous NULL Convention Logic (NCL) Circuits

Due to the absence of a global clock and the presence of more state holding elements that synchronize the control and data paths, conventional Automatic Test Pattern Generation (ATPG) algorithms fail when applied to asynchronous circuits, leading to poor fault coverage. This paper presents a design for test (DFT) technique for a popular asynchronous design paradigm called NULL Convention Logic (NCL) aimed at making NCL designs testable using existing DFT tools with reasonable gate overhead. The proposed technique performs test points (TPs) insertion using Sandia Controllability and Observability Program (SCOAP) analysis to enhance the controllability of feedback nets and observability for fault sites that are flagged unobservable. An Automatic DFT Insertion Flow (ADIF) algorithm and a custom ATPG NCL primitive gates library are developed. The developed DFT technique has been verified on several NCL benchmark circuits
Parametric analysis of active and passive building thermal storage utilization

Cooling of commercial buildings contributes significantly to the peak demand placed on an electrical utility grid. Time-of-use electricity rates encourage shifting of electrical loads to off-peak periods at night and on weekends. Buildings can respond to these pricing signals by shifting cooling-related thermal loads either by precooling the building's massive structure or by using active thermal energy storage systems such as ice storage. While these two thermal batteries have been engaged separately in the past, this paper investigates the merits of harnessing both storage media concurrently in the context of optimal control for a range of selected parameters. A parametric analysis was conducted utilizing an EnergyPlus-based simulation environment to assess the effects of building mass, electrical utility rates, season and location, economizer operation, central plant size, and thermal comfort. The findings reveal that the cooling-related on-peak electrical demand and utility cost of commercial buildings can be substantially reduced by harnessing both thermal storage inventories using optimal control for a wide range of conditions.
Technique for measuring absorptance and emittance by using cyclic incident radiation

Cyclic radiation technique has been developed for determining absorptance and emittance of metal surfaces. Using this technique both absorptance and emittance can be determined from one set of data, and variable and controlled temperature levels are possible.
The clinical pulmonary infection score poorly predicts pneumonia in patients with burns

The Clinical Pulmonary Infection Score (CPIS) has been reported to be a useful tool in the diagnosis of ventilator-associated pneumonia (VAP) in the critical care setting. However, the systemic inflammation associated with injury may limit the utility of CPIS in patients with burns. The purpose of this study was to determine the potential utility of CPIS in the management of burn patients. A retrospective review was performed on all burn patients who underwent quantitative culture to diagnose VAP from 2003 to 2005. CPIS was retrospectively calculated for each patient on the day of the procedure. The sensitivity, specificity, and predictive values of a CPIS greater than 6 for VAP diagnosis were calculated. In addition, CPIS scores of patients with and without pneumonia were compared using the Mann-Whitney U test. A total of 46 quantitative cultures were obtained in 28 patients during the study period. Average patient age was 45 +/- 19 years, average TBSA was 33 +/- 18%, and the average APACHE II score on admission was 16 +/- 6. Sixty-eight percent of patients had inhalation injury. Twenty-six quantitative cultures were positive, and 20 were negative. Mean CPIS was 5.7 for patients with negative quantitative cultures and 5.5 for patients with positive cultures (P = .41). The sensitivity of CPIS scoring was 0.3, and its specificity was 0.8. CPIS had a positive predictive value of 0.7 and negative predictive value of 0.5. CPIS--a reported reliable indicator of VAP in critically ill patients--did not accurately predict the presence of pneumonia in burn patients. VAP diagnosis in burn patients should still rely on clinical suspicion verified by quantitative culture.
Real-time optical analysis and control of semiconductor epitaxy: Progress and opportunity

Various optical techniques have been developed in the last few years for real-time analysis of surfaces and near-surface regions during semiconductor epitaxy. These techniques are providing new insights into microscopic mechanisms of crystal growth and new opportunities for several levels of closed-loop feedback control of epitaxy, including control at the product (sample) level. The latter is made possible by new data-reduction algorithms that return the dielectric response of the most recently deposited material even if nothing is known about the underlying sample structure. Examples are provided, and opportunities and challenges discussed.
Rotationally resolved fluorescence excitation spectra of phenol and 4-ethylphenol in a supersonic jet

Abstract The rotationally resolved fluorescence excitation spectra of the electronic origin transitions of phenol and 4-ethylphenol in a supersonic jet have been measured. Analysis of the rotational structure allowed the determination of the rotational constants of the ground and excited electronic states and the measurement of the direction of the transition moment with respect to the inertial axes. From the measured rotational constants possible geometries of the ground and excited states were determined. The geometry of phenol exhibits an appreciable quinoidal character following electronic excitation. The contraction of the carbon-oxygen bond upon electronic excitation supports the theory that the interaction between the lone-pair electrons of the oxygen atom and the π-electrons of the benzene ring is greater in the excited state than in the ground state. The geometrical computations of the molecular conformer structure of 4-ethylphenol confirm our previous assignment and indicate that 4-alkyl-substitution causes an additional shortening of the molecule along the A inertial axis. These experiments provide the groundwork for future high-resolution experiments on para-substituted phenols including the amino acid tyrosine.
Household type and structure, time-use pattern, and trip-chaining behavior

In order to examine time allocation patterns within household-level trip-chaining, simultaneous doubly-censored Tobit models are applied to model time-use behavior within the context of household activity participation. Using the entire sample and a sub-sample of worker households from Tucson's Household Travel Survey, two sets of models are developed to better understand the phenomena of trip-chaining behavior among five types of households: single non-worker households, single worker households, couple non-worker households, couple one-worker households, and couple two-worker households. Durations of out-of-home subsistence, maintenance, and discretionary activities within trip chains are examined. Factors found to be associated with trip-chaining behavior include intra-household interactions with the household types and their structure and household head attributes.
Chemical Characterization of Flowing Polydisperse Aerosols by Raman Spectroscopy

We have applied Raman spectroscopy to the in-situ measurement of chemical composition of polydisperse flowing aerosols. Monodisperse and polydisperse aerosols in the size range 0.3 to 1.8 w m, composed of diethylsebacate (DES) and ammonium sulfate, were generated. The particles were irradiated with 514.5 nm laser light and Raman spectra were collected. The Raman intensities of DES at 2935 cm -1 and ammonium sulfate at 981 cm -1 , normalized by the nitrogen carrier gas Raman intensity at 2313 cm -1 , were approximately proportional to the aerosol mass loading over the particle size range studied. Calculations based on previous theoretical studies support this observation. The mass loading ranged from 0.17 to 12.8 g/m 3 for DES and 20 to 138 mg/m 3 for ammonium sulfate. The method was applied to mixing aerosol streams containing DES and ammonium sulfate in a turbulent jet. The Raman system, with a sensitive volume of 0.02 mm 3 , was used to measure radial and axial concentration profiles in the mixing regio...
Sensitivity of an underwater acoustic array to ultra-high energy neutrinos

Abstract We investigate the possibility of searching for ultra high energy neutrinos in cosmic rays using acoustic techniques in ocean water. The type of information provided by the acoustic detection is complementary to that of other techniques, and the filtering effect of the atmosphere, imposed by the fact that detection only happens if a shower fully develops in water, would provide a clear neutrino identification. We find that it may be possible to implement this technique with very limited resources using existing high frequency underwater hydrophone arrays. We review the expected acoustic signals produced by neutrino-induced showers in water and develop an optimal filtering algorithm able to suppress statistical noise. The algorithm found is computationally appropriate to be used as a trigger for the signal processors available on existing arrays. We estimate the noise rates for a trigger system on a very large size hydrophone array of the US Navy and find that, while a higher density of hydrophones would be desirable, the existing system may already provide useful data.