cssi/SciSciGPT-SciSciNet huggingface dataset:
Inappropriate Detrending and Spurious Cointegration

The empirical literature is abundant with detrended cointegration, where cointegration relationships are tested and estimated with deterministic trend terms. Cointegration is, however, critically dependent on whether time series is detrended or not. A series of Monte Carlo experiments show that inappropriately detrended time series tend to exhibit a spurious cointegration. Although true time series are known not to be cointegrated, inappropriately detrended series tend to be cointegrated. Foreign exchange rates are analyzed to demonstrate the relevance and importance of the inappropriate detrending in the cointegration analysis.
Learning Theory and Algorithms for revenue optimization in second price auctions with reserve

Second-price auctions with reserve play a critical role in the revenue of modern search engine and popular online sites since the revenue of these companies often directly depends on the outcome of such auctions. The choice of the reserve price is the main mechanism through which the auction revenue can be influenced in these electronic markets. We cast the problem of selecting the reserve price to optimize revenue as a learning problem and present a full theoretical analysis dealing with the complex properties of the corresponding loss function. We further give novel algorithms for solving this problem and report the results of several experiments demonstrating their effectiveness.
Cotton Price Policy and New Cereal Technology in the Malian Cotton Zone

During the last decade, cotton production and area have been declining as a result of depleting soil nutrients and low cotton prices in the cotton zone of Mali. This paper shows that the Malian government’s 2011 policy to increase the farm gate cotton price as a response to world cotton price increase enhances farm income but has less impact on cotton than on maize production. A complementary policy of introducing new sorghum technologies would have an equal impact on farmers’ incomes in the cotton zone of Mali.
A real-time, soft robotic patient positioning system for maskless head-and-neck cancer radiotherapy: An initial investigation

We present an initial examination of a novel approach to accurately position a patient during head and neck intensity modulated radiotherapy (IMRT). Position-based visual-servoing of a radio-transparent soft robot is used to control the flexion/extension cranial motion of a manikin head. A Kinect RGB-D camera is used to measure head position and the error between the sensed and desired position is used to control a pneumatic system which regulates pressure within an inflatable air bladder (IAB). Results show that the system is capable of controlling head motion to within 2mm with respect to a reference trajectory. This establishes proof-of-concept that using multiple IABs and actuators can improve cancer treatment.
Measurements of Martian dust devil winds with HiRISE

[1] We report wind measurements within Martian dust devils observed in plan view from the High Resolution Imaging Science Experiment (HiRISE) orbiting Mars. The central color swath of the HiRISE instrument has three separate charge-coupled devices (CCDs) and color filters that observe the surface in rapid cadence. Active features, such as dust devils, appear in motion when observed by this region of the instrument. Our image animations reveal clear circulatory motion within dust devils that is separate from their translational motion across the Martian surface. Both manual and automated tracking of dust devil clouds reveal tangential winds that approach 20–30 m s−1 in some cases. These winds are sufficient to induce a ∼1% decrease in atmospheric pressure within the dust devil core relative to ambient, facilitating dust lifting by reducing the threshold wind speed for particle elevation. Finally, radial velocity profiles constructed from our automated measurements test the Rankine vortex model for dust devil structure. Our profiles successfully reveal the solid body rotation component in the interior, but fail to conclusively illuminate the profile in the outer regions of the vortex. One profile provides evidence for a velocity decrease as a function of r−1/2, instead of r−1, suggestive of surface friction effects. However, other profiles do not support this observation, or do not contain enough measurements to produce meaningful insights.
A kinetic proofreading mechanism for disentanglement of DNA by topoisomerases

Cells must remove all entanglements between their replicated chromosomal DNAs to segregate them during cell division. Entanglement removal is done by ATP-driven enzymes that pass DNA strands through one another, called type II topoisomerases. In vitro, some type II topoisomerases can reduce entanglements much more than expected, given the assumption that they pass DNA segments through one another in a random way1. These type II topoisomerases (of less than 10 nm in diameter) thus use ATP hydrolysis to sense and remove entanglements spread along flexible DNA strands of up to 3,000 nm long. Here we propose a mechanism for this, based on the higher rate of collisions along entangled DNA strands, relative to collision rates on disentangled DNA strands. We show theoretically that if a type II topoisomerase requires an initial ‘activating’ collision before a second strand-passing collision, the probability of entanglement may be reduced to experimentally observed levels. This proposed two-collision reaction is similar to ‘kinetic proofreading’ models of molecular recognition2,3.
Feedback control for communication with non-orthogonal states

Communicating classical information with a quantum system involves the receiver making a measurement on the system so as to distinguish as well as possible the alphabet of states used by the sender. We consider the situation in which this measurement takes an appreciable time. In this case the measurement must be described by a continuous measurement process. We consider a continuous implementation of the optimal measurement for distinguishing between two non-orthogonal states, and show that feedback control can be used during this measurement to increase the rate at which the information regarding the initial preparation is obtained. We show that while the maximum obtainable increase is modest, the effect is purely quantum mechanical in the sense that the enhancement is only possible when the initial states are non-orthogonal. We find further that the enhancement in the rate of information gain is achieved at the expense of reducing the total information which the measurement can extract in the long-time limit.
On the photometric axis of the zodiacal light

A model of the zodiacal cloud is used to predict the position of the photometric axis (the locus of points of maximum brightness) of the zodiacal light at any elongation angle from the sun for any time of the year for various symmetry planes: the orbital planes of Venus, Mars, and Jupiter, the invariable plane, and the solar equatorial plane. Using a scattering function which combines isotropic scattering and Fresnel reflection, the geocentric distance of the dust that contributes most of the brightness at each elongation angle is determined by computing the brightness contribution along the line of sight. A comparison of the predicted and observed positions shows that at elongation angles of 15 to 60 deg, the axis of symmetry appears to be close to the orbital plane of Venus. At angles of less than 10 deg, it is difficult to distinguish among the proposed planes of symmetry. Observations of the photometric axis at angles of 60 to 180 deg are scarce and do not permit precise determination of the axis of symmetry in that region.
Improving the Access to Higher Education for the Poor: Lessons from a Special Admission Program in Chile

This paper presents a higher education special access program for students from disadvantaged socioeconomic backgrounds, custom-designed by the author for one of the leading Chilean universities, and implemented as a pilot during the 2013 and 2014 admission periods. A non-experimental comparison of the academic performance of special and ordinary admission students after enrollment finds evidence that, consistent with Arcidiacono et al (2011), although on average special admission students have comparable final grades than their ordinary admission peers, they tend to perform comparatively worse in "hard" subjects (i.e. those with a strong mathematical component). However, although special admission students seem more likely to decide to withdraw earlier, no significant differences in voluntary withdrawal or dismissal rates are observed between the latter and their ordinary admission peers. Moreover, an initial gap in GPA between special and ordinary admission students is closed by the end of the third semester of enrollment. All this suggests that, with some nuances, students from disadvantaged socioeconomic backgrounds can successfully catch up with their peers when provided with adequate support, and that special admission programs can therefore be an effective tool to improve the access to higher education. Nonetheless, the fact that the program was undersubscribed suggests that, apart from potential information diffusion problems, the minimum requirements set forth for special admission may have been too stringent, and/or that the demand for special admission among the targeted student population may not be as large as predicted.
Server-Side caching strategies for online auction sites

Online auction sites have very specific workloads and user behavior characteristics. Previous studies on workload characterization conducted by the authors showed that i) bidding activity on auctions increases considerably after 90% of an auction’s life time has elapsed, ii) a very large percentage of auctions have a relatively low number of bids and bidders and a very small percentage of auctions have a high number of bids and bidders, iii) prices rise very fast after an auction has lasted more than 90% of its life time. Thus, if bidders are not able to successfully bid at the very last moments of an auction because of site overload, the final price may not be as high as it could be and sellers, and consequently the auction site, may lose revenue. In this paper, we propose server-side caching strategies in which cache placement and replacement policies are based on auction-related parameters such as number of bids placed or percent remaining time till closing time. A main-memory auction cache at the application server can be used to reduce accesses to the back-end database server. Trace-based simulations were used to evaluate these caching strategies in terms of cache hit ratio and cache efficiency.
The National Ignition Facility: status and plans for laser fusion and high-energy-density experimental studies

The National Ignition Facility (NIF), currently under construction at the University of California's Lawrence Livermore National Laboratory is a $2.25B stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, 351-nm laser system. NIF is being built by the National Nuclear Security Agency and when completed will be the world's largest laser system, providing a national center to study inertial confinement fusion and the physics of extreme energy densities and pressures. In NIF up to 192 energetic laser beams will compress small fusion targets to conditions where they will ignite and burn, liberating more energy than is required to initiate the fusion reactions. NIF experiments will allow the study of physical processes at temperatures approaching 100 million K and 100 billion times atmospheric pressure. These conditions exist naturally only in the interior of stars and in nuclear weapons explosions. In the course of designing the world's most energetic laser system, a number of significant technology breakthroughs have been achieved. Research is also underway to develop a shorter pulse capability on NIF for high power applications. We discuss the technology challenges and solutions that have made NIF possible along with enhancements to NIF's design that could lead to exawatt power levels.
Probabilistic Coreference in Information Extraction

Certain applications require that the output of an information extraction system be probabilistic, so that a downstream system can reliably fuse the output with possibly contradictory information from other sources. In this paper we consider the problem of assigning a probability distribution to alternative sets of coreference relationships among entity descriptions. We present the results of initial experiments with several approaches to estimating such distributions in an application using SRI’s FASTUS information extraction system.
Corruption in international business

I analyze corruption in international business, presenting a critical assessment of the topic and providing suggestions for future research. I argue that corruption creates a laboratory for expanding international business studies because its illegal nature, the differences in perception about illegality, and the variation in the enforcement of laws against bribery across countries challenge some of the assumptions upon which arguments have been built, i.e., that managers can choose appropriate actions without major legal implications. Hence, I first provide suggestion for how to analyze the topic of corruption in future studies by analyzing the types, measures, causes, consequences, and controls of corruption. I then provide suggestions for how to extend leading theories of the firm by using corruption as a laboratory that challenges some of the assumptions of these theories: extending agency theory by analyzing the existence of unethical agency relationships; extending transaction cost economics by analyzing illegal transaction costs minimization; extending the resource-based view by studying corporate social irresponsibility capability; extending resource dependency by analyzing the ethical power escape; and extending neo-institutional theory by studying illegal legitimacy.
Ribbon tilings and multidimensional height functions

We fix n and say a square in the two-dimensional grid indexed by (x, y) has color c if x + y ≡ c (mod n). A ribbon tile of order n is a connected polyomino containing exactly one square of each color. We show that the set of order-n ribbon tilings of a simply connected region R is in one-to-one correspondence with a set of height functions from the vertices of R to Z n satisfying certain difference restrictions. It is also in one-to-one correspondence with the set of acyclic orientations of a certain partially oriented graph. Using these facts, we describe a linear (in the area of R) algorithm for determining whether R can be tiled with ribbon tiles of order n and producing such a tiling when one exists. We also resolve a conjecture of Pak by showing that any pair of order-n ribbon tilings of R can be connected by a sequence of local replacement moves. Some of our results are generalizations of known results for order-2 ribbon tilings (a.k.a. domino tilings). We also discuss applications of multidimensional height functions to a broader class of polyomino tiling problems.
Individual differences and correlates of highly superior autobiographical memory

Highly superior autobiographical memory (HSAM) is a recently identified ability that has been difficult to explain with existing memory science. The present study measured HSAM participants’ and age/gender-matched controls’ on a number of behavioural measures to test three main hypotheses: imaginative absorption, emotional arousal, and sleep. HSAM participants were significantly higher than controls on the dispositions absorption and fantasy proneness. These two dispositions also were associated with a measure of HSAM ability within the hyperthymesia participants. The emotional-arousal hypothesis yielded only weak support. The sleep hypothesis was not supported in terms of quantity, but sleep quality may be a small factor worthy of further research. Other individual differences are also documented using a predominantly exploratory analysis. Speculative pathways describing how the tendencies to absorb and fantasise could lead to enhanced autobiographical memory are discussed.
Ligand Binding, Protein Fluctuations, And Allosteric Free Energy

Although the importance of protein dynamics in protein function is generally recognized, the role of protein fluctuations in allosteric effects scarcely has been considered. To address this gap, the Kullback‐Leibler divergence (Dx) between protein conformational distributions before and after ligand binding was proposed as a means of quantifying allosteric effects in proteins. Here, previous applications of Dx to methods for analysis and simulation of proteins are first reviewed, and their implications for understanding aspects of protein function and protein evolution are discussed. Next, equations for Dx suggest that kBTDx should be interpreted as an allosteric free energy — the free energy associated with changing the ligand‐free protein conformational distribution to the ligand‐bound conformational distribution. This interpretation leads to a thermodynamic model of allosteric transitions that unifies existing perspectives on the relation between ligand binding and changes in protein conformational distributions. The definition of Dx is used to explore some interesting mathematical relations among commonly recognized thermodynamic and biophysical quantities, such as the total free energy change upon ligand binding, and ligand‐binding affinities for individual protein conformations. These results represent the beginnings of a theoretical framework for considering the full protein conformational distribution in modeling allosteric transitions. Early applications of the framework have produced results with implications both for methods for coarsed‐grained modeling of proteins, and for understanding the relation between ligand binding and protein dynamics.
A linear approximation method for probabilistic inference

An approximation method is presented for probabilistic inference with continuous random variables. These problems can arise in many practical problems, in particular where there are “second order” probabilities. The approximation, based on the Gaussian influence diagram, iterates over linear approximations to the inference problem.
Anxiety and Related Disorders and Concealment in Sexual Minority Young Adults

Sexual minorities face greater exposure to discrimination and rejection than heterosexuals. Given these threats, sexual minorities may engage in sexual orientation concealment in order to avoid danger. This social stigma and minority stress places sexual minorities at risk for anxiety and related disorders. Given that three fourths of anxiety disorder onset occurs before the age of 24, the current study investigated the symptoms of generalized anxiety disorder, social phobia, panic disorder, posttraumatic stress disorder, and depression in sexual minority young adults relative to their heterosexual peers. Secondarily, the study investigated sexual orientation concealment as a predictor of anxiety and related disorders. A sample of 157 sexual minority and 157 heterosexual young adults matched on age and gender completed self-report measures of the aforementioned disorders, and indicated their level of sexual orientation concealment. Results revealed that sexual minority young adults reported greater symptoms relative to heterosexuals across all outcome measures. There were no interactions between sexual minority status and gender, however, women had higher symptoms across all disorders. Sexual minority young women appeared to be at the most risk for clinical levels of anxiety and related disorders. In addition, concealment of sexual orientation significantly predicted symptoms of social phobia. Implications are offered for the cognitive and behavioral treatment of anxiety and related disorders in this population.
Modeling web interactions

Programmers confront a minefield when they design interactive Web programs. Web interactions take place via Web browsers. With browsers, consumers can whimsically navigate among the various stages of a dialog and can thus confuse the most sophisticated corporateWeb sites. In turn,Web services can fault in frustrating and inexplicable ways. The quickening transition from Web scripts toWeb services lends these problems immediacy. To address this programming problem, we develop a foundational model ofWeb interactions and use it to formally describe two classes of errors. The model suggests techniques for detecting both classes of errors. For one class we present an incrementally checked record type system, which effectively eliminates these errors. For the other class, we introduce a dynamic safety check, which catches the mistakes relative to programmers' simple annotations.
Evaluating Public Programs with Close Substitutes: The Case of Head Start

This paper empirically evaluates the cost-effectiveness of Head Start, the largest early- childhood education program in the United States. Using data from the randomized Head Start Impact Study (HSIS), we show that Head Start draws a substantial share of its participants from competing preschool programs that receive public funds. This both attenuates measured experimental impacts on test scores and reduces the program's net social costs. A cost-benefit analysis demonstrates that accounting for the public savings associated with reduced enrollment in other subsidized preschools can reverse negative assessments of the program's social rate of return. Estimates from a semi-parametric selection model indicate that Head Start is about as effective at raising test scores as competing preschools and that its impacts are greater on children from families unlikely to participate in the program. Efforts to expand Head Start to new populations are therefore likely to boost the program's social rate of return, provided that the proposed technology for increasing enrollment is not too costly.
Systemic oversight frameworks in LAC : current practices and reform agenda

The world financial crisis that started in the US housing market in 2008 brought into evidence deep failures of prudential oversight, linked for the most part to a failure to comprehend and handle systemic risk in a way that could prevent systemic crises. This paper summarizes the responses to the joint World Bank -ASBA survey o the state of systemic oversight in the Latin American and Caribbean financial sectors and reflects on some of the challenges identified by respondents. We found that there is broad consensus among regional financial authorities on the need to enhance the current systemic oversight framework. Improving consolidated supervision to mitigate risk-shifting in conglomerates, adjusting prudential regulations to account for the accumulation of systemic risks, redefining the role of the supervisor to make it more proactive, and improving coordination among local supervisors as well as with foreign supervisors figure preeminently in the regional reform agenda.
Automation software for a materials testing laboratory

The software environment in use at the NASA-Lewis Research Center's High Temperature Fatigue and Structures Laboratory is reviewed. This software environment is aimed at supporting the tasks involved in performing materials behavior research. The features and capabilities of the approach to specifying a materials test include static and dynamic control mode switching, enabling multimode test control; dynamic alteration of the control waveform based upon events occurring in the response variables; precise control over the nature of both command waveform generation and data acquisition; and the nesting of waveform/data acquisition strategies so that material history dependencies may be explored. To eliminate repetitive tasks in the coventional research process, a communications network software system is established which provides file interchange and remote console capabilities.
Business Cycles with Revolutions

This paper develops an empirical macroeconomic framework to analyze the relationship between major political disruptions and business cycles of a country. We combine a new dataset of political revolutions (mass domestic political campaigns to remove dictators and juntas) across the world since 1960, with coup data and traditional macro data (of output, investment, trade, inflation and exchange rate). We then build a panel vector-autoregression model with two novel ingredients: (1) political disruptions and (2) an estimated probability of such disruptions. We find that both terms have statistically and economically significant impacts on business cycles. Interestingly, the impacts of the second term dominate those of the first, both statistically and economically. This suggests that our measure of political risk captures an important source of time-varying uncertainty and volatility in many countries.
Instrumentality Tests Revisited

An instrument is a random variable that is uncorrelated with certain (unobserved) error terms and, thus, allows the identification of structural parameters in linear models. In nonlinear models, instrumental variables are useful for deriving bounds on causal effects. Few years ago, Pearl introduced a necessary test for instruments which permits researchers to identify variables that could not serve as instruments. In this paper, we extend Pearl's result in several directions. In particular, we answer in the affirmative an open conjecture about the non-testability of instruments in models with unrestricted variables, and we devise new tests for models with discrete and continuous variables.
Rheology of magnesite

We deformed two natural magnesite aggregates (grain sizes of 1 versus 100 µm) over a wide range of temperatures (400–1000°C) and strain rates (10−7–10−4/s) in order to determine the deformation mechanisms of magnesite and their respective flow laws. Experiments using fine-grained magnesite were performed in a Heard gas confining medium rock deformation apparatus at a constant effective pressure (= confining pressure − CO2 pressure) of 300 MPa. Experiments using coarse-grained magnesite were performed in a Griggs piston-cylinder rock deformation apparatus at a constant effective pressure of 900 MPa. At low temperatures (T < 600°C, strain rate = 10−5/s) both magnesite aggregates deform by crystal plastic mechanisms predominated by dislocation glide. At higher temperatures the coarse-grained magnesite deforms by dislocation creep and the fine-grained magnesite deforms by diffusion creep. The strain rate and temperature dependence of the strength of magnesite deforming by low-temperature plasticity, dislocation creep, and diffusion creep can be described by power law flow laws with stress exponents (n) of 19.7, 3.0, and 1.1 and activation enthalpies of 229, 410, and 209 kJ/mol, respectively. The strength of the low-temperature plasticity data can also be described using an exponential flow law with α = 0.022 MPa−1 with an activation enthalpy of 233 kJ/mol. Extrapolation of the flow laws to natural conditions indicates that magnesite is generally stronger than calcite and dolomite assuming similar grain sizes. However, its strength is orders of magnitude lower than olivine at all conditions in the Earth's mantle and may promote deep-focus earthquakes through ductile instabilities.
Approximating higher-order distances using random projections

We provide a simple method and relevant theoretical analysis for efficiently estimating higher-order lp distances. While the analysis mainly focuses on l4, our methodology extends naturally to p = 6,8,10..., (i.e., when p is even). Distance-based methods are popular in machine learning. In large-scale applications, storing, computing, and retrieving the distances can be both space and time prohibitive. Efficient algorithms exist for estimating lp distances if 0 2 is known to be difficult. Our work partially fills this gap.
Microscale locomotion in a nematic liquid crystal

Microorganisms often encounter anisotropy, for example in mucus and biofilms. We study how anisotropy and elasticity of the ambient fluid affects the speed of a swimming microorganism with a prescribed stroke. Motivated by recent experiments on swimming bacteria in anisotropic environments, we extend a classical model for swimming microorganisms, the Taylor swimming sheet, actuated by small-amplitude traveling waves in a three-dimensional nematic liquid crystal without twist. We calculate the swimming speed and entrained volumetric flux as a function of the swimmer's stroke properties as well as the elastic and rheological properties of the liquid crystal. These results are then compared to previous results on an analogous swimmer in a hexatic liquid crystal, indicating large differences in the cases of small Ericksen number and in a nematic fluid when the tumbling parameter is near the transition to a shear-aligning nematic. We also propose a novel method of swimming or pumping in a nematic fluid by passing a traveling wave of director oscillation along a rigid wall.
An Approximate Dynamic Programming Algorithm for Monotone Value Functions

Many sequential decision problems can be formulated as Markov decision processes MDPs where the optimal value function or cost-to-go function can be shown to satisfy a monotone structure in some or all of its dimensions. When the state space becomes large, traditional techniques, such as the backward dynamic programming algorithm i.e., backward induction or value iteration, may no longer be effective in finding a solution within a reasonable time frame, and thus we are forced to consider other approaches, such as approximate dynamic programming ADP. We propose a provably convergent ADP algorithm called Monotone-ADP that exploits the monotonicity of the value functions to increase the rate of convergence. In this paper, we describe a general finite-horizon problem setting where the optimal value function is monotone, present a convergence proof for Monotone-ADP under various technical assumptions, and show numerical results for three application domains: optimal stopping, energy storage/allocation, and glycemic control for diabetes patients. The empirical results indicate that by taking advantage of monotonicity, we can attain high quality solutions within a relatively small number of iterations, using up to two orders of magnitude less computation than is needed to compute the optimal solution exactly.
Agile Development: Good Process or Bad Attitude?

Agile development methods are gaining adherents in a wide variety of industries. Agile proponents and those who support traditional process improvement have been equally vocal in their disdain for each other. However, it is unclear whether or not agile methods constitute an improvable "process." This paper discusses the relationship between agile methods and process improvement goals and values and evaluates the components of the Capability Maturity Model IntegrationSM (CMMISM) Systems Engineering/Software Engineering/ Integrated Product and Process Model for their support of agile methods.
Eight-French intracardiac echocardiography – safe and effective guidance for transcatheter closure in atrial septal defects –.

BACKGROUND Intracardiac echocardiography (ICE) was introduced as a new guidance system for transcatheter closure of secundum atrial septal defect (ASD) with Amplatzer septal occluder (ASO). The aim of this study was to investigate the clinical outcome of ICE-guided transcatheter closure of ASD compared with the trans-esophageal echocardiography (TEE)-guided method. METHODS AND RESULTS From May 2003 to April 2010, 560 patients who underwent transcatheter closure of ASD using ASO in a single institute were analyzed retrospectively. In the TEE-guided group (n=237), all the patients underwent general anesthesia. The median age was 24.2 years (range, 14 months-63 years) and the average weight was 42.3 ± 21.6 kg (range, 8.2-82 kg). One patient underwent surgery due to migration of device. The remaining 236 patients underwent the procedure successfully without significant complication. In the ICE-guided group (n=323), the median age was 30.5 years (range, 7 months-75 years). One patient underwent surgery because of mitral valve encroachment by left atrial disk after device placement. Another patient also underwent surgery due to device embolization. The remaining 321 procedures were performed successfully without major complications. Procedure time was 104.2 min and 87.7 min, respectively (P<0.001). CONCLUSIONS ICE-guided ASD occlusion with ASO is safe and effective and provides accurate anatomical information, sufficient to perform the procedure. In addition, there were benefits of avoidance of general anesthesia, and shorter procedure time.
Spectral Efficiency Scaling Laws in Dense Random Wireless Networks With Multiple Receive Antennas

This paper considers large random wireless networks, where transmit-and-receive node pairs communicate within a certain range while sharing a common spectrum. By modeling the spatial locations of nodes as a Poisson point process, analytical expressions for the ergodic spectral efficiency of a typical node pair are derived as a function of the channel state information available at a receiver (CSIR) in terms of relevant system parameters: the density of communication links, the number of receive antennas, the path loss exponent, and the operating signal-to-noise ratio. One key finding is that when the receiver only exploits CSIR for the direct link, the sum spectral efficiency increases linearly with the density, provided the number of receive antennas increases as a certain superlinear function of the density. When each receiver exploits CSIR for a set of dominant interfering links in addition to that of the direct link, the sum spectral efficiency increases linearly with both the density and the path loss exponent if the number of antennas is a linear function of the density. This observation demonstrates that having CSIR for dominant interfering links provides an order gain in the scaling law. It is also shown that this linear scaling holds for direct CSIR when incorporating the effect of the receive antenna correlation, provided that the rank of the spatial correlation matrix scales superlinearly with the density. These scaling laws are derived from integral representations of the distribution of the signal to interference and noise ratio, which are of independent interest and which in turn derived from stochastic geometry and more precisely from the theory of shot noise fields. Simulation results back the scaling laws and the integral representations.
Stress Injuries to Bone in College Athletes: A Retrospective Review of Experience at a Single Institution*

BackgroundNo comprehensive studies have been published on stress injuries to bone in college athletes.PurposeTo review, in a college athlete population, the epidemiologic aspects of stress injuries to bone, and to examine a subset of patients who were treated with a uniform protocol for return to activities, with magnetic resonance imaging as the primary tool for diagnosis.Study TypeRetrospective review.MethodsTen years of medical records from a Division I college institution were reviewed. Location and grade of stress injury to bone and duration of disability were recorded. All injured athletes followed the same treatment program, with the exception of football players, who were excluded from the return to sport analyses.ResultsSeventy-four athletes had lower extremity symptoms consistent with stress injury to bone. Diagnosis was confirmed in 68 of these athletes, 61 via magnetic resonance imaging, 6 via positive radiographs only, and 1 via bone scan only. Distance runners accounted for the most stress i...
Sample Size Adequacy in Surveys

This entry presents concepts involved in determination of sample size adequacy in sample surveys. There is a broad discussion of issues such as stratification, sampling without replacement, finite population corrections, sampling of clusters, sampling in more than one stage, and unequal weighting of observations that have a profound effect on the distribution of estimates and on the sample sizes necessary to construct reliable estimates. We include formulas for determining sample size adequacy for some of the most widely used sample designs and some practical guidelines for statistical consulting on this issue. A set of references to texts and specific articles is included. Keywords: sample size; simple random sampling; stratified random sampling; cluster sampling; precision; estimation
Khovanov-Rozansky homology of two-bridge knots and links

We compute the reduced version of Khovanov and Rozansky's sl(N) homology for two-bridge knots and links. The answer is expressed in terms of the skein polynomial of Hoste, Ocneanu, Millett, Freyd, Lickorish, and Yetter (or HOMFLY polynomial; see [6]) and signature
Advances in isentropic compression experiments (ICE) using high explosive pulsed power

We are developing a prototype high explosive pulsed power (HEPP) system to obtain isentropic Equation of State (EOS) data with the Asay technique. Asay, JR (1999). Our prototype system comprises a flat-plate explosive driven magnetic flux compression generator (FCG), an explosively formed fuse (EFF) opening switch, and a series of explosively-actuated closing switches. The FCG is capable of producing /spl sim/10 MA into suitable loads, and, at a length of 216 mm, the EFF will sustain voltages in excess of 200 kV. The load has an inductance of /spl sim/3 to 10 nH, allowing up to /spl sim/7 MA to be delivered in times of /spl sim/0.5 /spl mu/s. This prototype will produce isentropic compression profiles in excess of 2 Mbar in a material such as tungsten. Our immediate plan is to obtain isentropic EOS data for copper at pressures up to /spl sim/1.5 Mbar with the prototype system; eventually we hope to reach several tens of Mbar with more advanced systems.
THERMAL-INSTABILITY-DRIVEN TURBULENT MIXING IN GALACTIC DISKS. I. EFFECTIVE MIXING OF METALS

Observations show that radial metallicity gradients in disk galaxies are relatively shallow, if not flat, especially at large galactocentric distances and for galaxies in the high-redshift universe. Given that star formation and metal production are centrally concentrated, this requires a mechanism to redistribute metals. However, the nature of this mechanism is poorly understood, let alone quantified. To address this problem, we conduct magnetohydrodynamical simulations of a local shearing sheet of a thin, thermally unstable, gaseous disk driven by a background stellar spiral potential, including metals modeled as passive scalar fields. Contrary to what a simple α prescription for the gas disk would suggest, we find that turbulence driven by thermal instability is very efficient at mixing metals, regardless of the presence or absence of stellar spiral potentials or magnetic fields. The timescale for homogenizing randomly distributed metals is comparable to or less than the local orbital time in the disk. This implies that turbulent mixing of metals is a significant process in the history of chemical evolution of disk galaxies.
Electron and energy transfer from CuI MLCT excited states

Abstract Electron and energy transfer processes from CuI MLCT excited states are reviewed. New results demonstrate clearly that these excited states undergo oxidative electron transfer quenching and energy transfer processes. The yields and dynamics of these processes have been spectroscopically quantified. Interfacial electron transfer from CuI MLCT excited states to wide band gap semiconductors has been observed. When utilized in photoelectrochemical cells, this interfacial electron transfer process provides a means for the conversion of light directly into electrical power.
Multiple model moving horizon estimation approach to prognostics in coupled systems

This article presents a novel MM-MHE algorithm for online prediction of the component survival functions based on their usage profiles. The framework employs Cox PHM based on offline and online data for the RUL prediction. The proposed approach has been validated by way of application to data derived from an automotive ETC system simulator. The MM-MHE algorithm shows excellent performance (R2 and MSE) in the presence of significant measurement noise over all windows and converges to the correct cluster number. The future work includes application of this approach to continuous PID and to account for the uncertainty in RUL estimation. In the near future, by simple transformations, the authors plan on implementing the MM-MHE algorithm for measurements and states between (-∞,∞) and considering the effects of process noise, hence, modifying the cost function accordingly. A potential extension of the Cox PHM framework for prognosis of coupled systems will be to model the coupled survival dynamics as monotone positive linear systems or monotone Markov processes in which the state matrix is a Metzler matrix (i.e., has nonnegative off-diagonal elements).
METAL-FREE GAS SUPPLY AT THE EDGE OF REIONIZATION: LATE-EPOCH POPULATION III STAR FORMATION

While the average metallicity of the intergalactic medium rises above Z 10–3 Z ☉ by the end of the reionization, pockets of metal-free gas can still exist at later times. We quantify the presence of a long tail in the formation rate of metal-free halos during late stages of reionization (redshift z ≈ 6), which might offer the best window to detect Population III stars. Using cosmological simulations for the growth of dark matter halos, coupled with analytical recipes for the metal enrichment of their interstellar medium, we show that pockets of metal-free gas exist at z ≈ 6 even under the assumption of high efficiency in metal pollution via winds. A comoving metal-free halo formation rate d 2 n/dt dV 10–9 Mpc–3 yr–1 is expected at z = 6 for halos with virial temperature T vir ≈ 104 K (mass ~108 M ☉), sufficient to initiate cooling even with strong negative radiative feedback. These halos will appear as absorption systems with a typical hydrogen column density of ~1020 cm–2, a sky covering factor 5 × 10–3 and a number density of 25 arcmin–2 for 5.5 ≤ z ≤ 6.5. Under the assumption of a single Population III supernova (SN) formed per metal-free halo, we expect an observed supernova rate of 2.6 × 10–3 deg–2 yr–1 in the same redshift range. These metal-free stars and their SNe will be isolated and outside galaxies (at distances 150 h –1 kpc) and thus significantly less biased than the general population of ~108 M ☉ halos at z ≈ 6. SN searches for metal-free explosions must thus rely on large area surveys. If metal-free stars produce very luminous SNe, like SN2006gy, then a multi-epoch survey reaching m AB = 27 at 1 μm is sufficient for detecting them at z = 6. While the Large Synoptic Survey Telescope (LSST) will not reach this depth in the z band, it will be able to detect several tens of Population III SNe in the i and r bands at z 5.5, when their observed rate is down to 3-8 × 10–4 deg–2 yr–1.
Perfluoroalkylene-ether triazine elastomers

New process yields product that resists heat and action of oxygen and water. Ring closing step, which gives elastomer its stability, imidoylamidine dinitrile reacts with perfluoroether acide, yielding prepolymer. Prepolymer then treated with ammonia and cured by heating to form polymer. Elastomers are highly resistant to heat, oxidation, and hydrolysis.
QCD and intrinsic heavy quark predictions for leading charm and beauty hadroproduction

Recent experiments at Fermilab and CERN have observed a strong asymmetry between the hadroproduction cross sections of leading D mesons, containing projectile valence quarks, and nonleading charmed mesons, without projectile valence quarks. The observed correlations of the π± N → D± X cross section with the projectile charge violates the usual assumption that heavy quark jet fragmentation factorizes. We examine the asymmetry between leading and nonleading charm production as a function of ηF and pT2 assuming a two-component model combining leading-twist fusion subprocesses and charm production from intrinsic heavy quark Fock states. We predict a sizable asymmetry at low pT2 and high ηF from coalescence of the charm quarks with the comoving spectator quarks of the projectile. An intrinsic cc production cross section of 0.5 μb is sufficient to explain both the magnitude and kinematic dependence of the asymmetry. In contrast, the charm jet hadronization mechanisms contained in PYTHIA predict a sizeable leading charm asymmetry even at low ηF. The two-component model is extended to predict the asymmetry in B meson production in proton-proton and pion-proton interactions.
STAR FORMATION IN DISK GALAXIES. I. FORMATION AND EVOLUTION OF GIANT MOLECULAR CLOUDS VIA GRAVITATIONAL INSTABILITY AND CLOUD COLLISIONS

We investigate the formation and evolution of giant molecular clouds (GMCs) in a Milky-Way-like disk galaxy with a flat rotation curve. We perform a series of three-dimensional adaptive mesh refinement numerical simulations that follow both the global evolution on scales of ~20 kpc and resolve down to scales 10 pc with a multiphase atomic interstellar medium. In this first study, we omit star formation and feedback, and focus on the processes of gravitational instability and cloud collisions and interactions. We define clouds as regions with n H ≥ 100 cm-3 and track the evolution of individual clouds as they orbit through the galaxy from their birth to their eventual destruction via merger or via destructive collision with another cloud. After ~140 Myr a large fraction of the gas in the disk has fragmented into clouds with masses ~106 M ☉ and a mass spectrum similar to that of Galactic GMCs. The disk settles into a quasi-steady-state in which gravitational scattering of clouds keeps the disk near the threshold of global gravitational instability. The cloud collision time is found to be a small fraction, ~1/5, of the orbital time, and this is an efficient mechanism to inject turbulence into the clouds. This helps to keep clouds only moderately gravitationally bound, with virial parameters of order unity. Many other observed GMC properties, such as mass surface density, angular momentum, velocity dispersion, and vertical distribution, can be accounted for in this simple model with no stellar feedback.
Tidal Disruption of a Star by a Black Hole: Observational Signature

We have modeled the time-variable profiles of the Hα emission line from the nonaxisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a 106 M☉ black hole. Two tidal disruption events were simulated using a three-dimensional relativistic smoothed particle hydrodynamics code to describe the early evolution of the debris during the first 50-90 days. We have calculated the physical conditions and radiative processes in the debris using the photoionization code CLOUDY. We model the emission-line profiles in the period immediately after the accretion rate onto the black hole became significant. We find that the line profiles at these very early stages of the evolution of the postdisruption debris do not resemble the double-peaked profiles expected from a rotating disk, since the debris has not yet settled into such a stable structure. As a result of the uneven distribution of the debris and the existence of a tidal tail (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Moreover, the predicted line profiles vary on fairly short timescales (of the order of hours to days). Given the accretion rate onto the black hole, we also model the Hα light curve from the debris and the evolution of the Hα line profiles in time.