cssi/SciSciGPT-SciSciNet huggingface dataset:
Magnetic field variations in interplanetary space

Magnetic field variations and structures in interplanetary space are described and related to the sun. Discrete flare-related effects in the interplanetary medium occur within a large-scale interplanetary sector pattern related to a solar sector pattern that is ordered over a large extent in heliographic latitude and longitude. A random walk transport of photospheric field lines slightly modifies the over-all ordered pattern, but sector boundaries appear to resist the random walk process. There is a delay of approximately one solar rotation between appearance of an active region and its possible effect on the interplanetary sector pattern. A flare occurrence is most probable near a solar sector boundary.
A fully automated framework for control of linear systems from LTL specifications

We consider the following problem: given a linear system and an LTL−−X formula over a set of linear predicates in its state variables, find a feedback control law with polyhedral bounds and a set of initial states so that all trajectories of the closed loop system satisfy the formula. Our solution to this problem consists of three main steps. First, we partition the state space in accordance with the predicates in the formula and construct a transition system over the partition quotient, which captures our capability of designing controllers. Second, using model checking, we determine runs of the transition system satisfying the formula. Third, we generate the control strategy. Illustrative examples are included.
Collective action for public goods provision in low-income groups: a model and evidence from Peru

?Bajo que circunstancias aparece la accion colectiva? ?Cuales son los factores que le dan mayores posibilidades de exito? ?En que medida las comunidades pobres tienen capacidad para organizarse con el objetivo de mejorar sus condiciones de vida? Estas preguntas no son nuevas y se han hecho muchas investigaciones, pero usualmente para el mundo rural. La investigacion sobre la accion colectiva en el mundo urbano parece estar mas desarrollada en la ciencia politica que en la economia. La pregunta fundamental se mantiene: ?como se producen y se mantienen los bienes publicos en comunidades urbanas pobres? Este articulo presenta un conjunto de hipotesis sobre los determinantes de la accion colectiva. La accion colectiva en barrios urbanos pobres enfrentan tres restricciones basicas: el problema olsoniano, el problema de Maslow y el problema de la exclusion. La parte empirica del articulo utiliza datos recolectados en barrios marginales de Lima, Peru, en seis tipos de organizaciones comunales. -- Under what circumstances does collective action arise? What contributes to the likelihood that a particular collective initiative will succeed? To what extent are poor communities capable of organizing themselves to improve their quality of life? These questions are not new, and economic researchers have studied a number of models in rural settings. Yet the research on collective action in urban areas seems to be more in the political sciences, and an economic model is still lacking. The fundamental question remains: How are public goods produced and maintained by poor urban communities? This paper presents a set of hypotheses on collective action determinants. Collective action in poor neighborhoods faces three key barriers to success: the Olsonian free-rider problem, the Maslowian problem, and the exclusion problem. The empirical portion of this paper uses data collected in poor urban and peri-urban areas of Lima, Peru, in six types of community organizations.
G7 Current Account Imbalances: Sustainability and Adjustment

The current account deficit of the United States is more than six percent of its gross domestic product an all-time high. And the rest of the world, including other G7 countries such as Japan and Germany, must collectively run current account surpluses to finance this deficit. How long can such unevenness between imports and exports be sustained, and what form might their eventual reconciliation take? Putting forth scenarios ranging from a gradual correction to a crash landing for the dollar, "G7 Current Account Imbalances" brings together economists from around the globe to consider the origins, status, and future of those disparities. An esteemed group of collaborators here examines the role of the bursting of the dot-com bubble, the history of previous episodes of current account adjustments, and the possibility of the Euro surpassing the dollar as the leading international reserve currency. Though there are areas of broad agreement that the imbalances will ultimately decline and that currency revaluations will be part of the solution many areas of contention remain regarding both the dangers of imbalances and the possible forms of adjustment. This volume will be of tremendous value to economists, politicians, and business leaders alike as they look to the future of the G7 economies. "
Two-Rate Property Tax Effects on Land Development

Economists have long understood that the conventional property tax causes the housing stock to be smaller than it would be in the presence of a nondistortionary tax such as a land or site value tax. This article brings together the results from models of housing development timing and structural density with the results of a modern model of a graded property tax in an urban setting. The combination of results is used to investigate the effects of a community’s movement from a property tax to a two-rate tax system where land is taxed at a higher rate than structures. The conditions under which increasing reliance on a land or site value tax will increase housing structural density and speed of development are identified and examined. Policy implications are drawn.
ALL: Formalizing Access-Limited Reasoning

Abstract Access-limited logic (ALL) is a language for knowledge representation that formalizes the access limitations inherent in a network-structured knowledge base. Where a classical deductive method or logic programming language would retrieve all assertions that satisfy a given pattern, an access-limited logic retrieves all assertions reachable by following an available access path. The complexity of inference is thus independent of the size of the knowledge base and depends only on its local connectivity. Access-limited logic, though incomplete, still has a well-defined semantics and a weakened form of completeness, Socratic completeness , which guarantees that for any query that is a logical consequence of the knowledge base, there exists a series of queries after which the original query will succeed. This chapter presents an overview of ALL, and sketches the proofs of its Socratic completeness and polynomial time complexity.
A Note on the Consistency of Game Theory

It has been claimed in the literature that classical game theory is inconsistent, since it (implicitly) assumes that all players are rational and that this is common knowledge among them, while these two assumptions seem to be contradictory. The purpose of this note is to suggest a framework which allows the formalization of these implicit axioms in a consistent way. The main idea is to distinguish between conceivable and possible states of the world, while both exist as formal objects in the theory. Thus we may require that the players would make rational choices only at possible states of the world, and that this fact be common knowledge at all (conceivable) states, where the impossible ones are present in the model for the sole purpose of formally presenting the players' reasoning. It seems that the new concept of possible states of the world is an analytical tool which may have further (theoretical) applications.
Mansour's Conjecture is True for Random DNF Formulas

In 1994, Y. Mansour conjectured that for every DNF formula on n variables with t terms there exists a polynomial p with t O(log(1/ǫ)) non-zero coefficients such that Ex2{0,1}n[(p(x) − f(x)) 2 ] ≤ ǫ. We make the first progress on this conjecture and show that it is t rue for several natural subclasses of DNF formulas including randomly chosen DNF formulas and read-k DNF formulas for constant k. Our result yields the first polynomial-time query algorithm for agnostically learning these subclasses of DNF formulas with respect to the uniform distribution on {0,1} n (for any constant error parameter). Applying recent work on sandwiching polynomials, our results imply that a t O(log 1/ǫ) -biased distribution fools the above subclasses of DNF formulas. This gives pseudorandom generators for these subclasses with shorter seed length than all previous work.
A method for solving distributed service allocation problems

We present a method for solving service allocation problems in which a set of services must be allocated to a set of agents so as to maximize a global utility. The method is completely distributed so it can scale to any number of services without degradation. We first formalize the service allocation problem and then present a simple hill-climbing, a global hill-climbing, and a bidding-protocol algorithm for solving it. We analyze the expected performance of these algorithms as a function of various problem parameters such as the branching factor and the number of agents. Finally, we use the sensor allocation problem, an instance of a service allocation problem, to show the bidding protocol at work. The simulations also show that phase transition on the expected quality of the solution exists as the amount of communication between agents increases.
Managing unilateral market power in electricity

This paper first describes those features of the electricity supply industry that make a prospective market monitoring process essential to a well-functioning wholesale market. Some of these features are shared with the securities industry, although the technology of electricity production and delivery make a reliable transmission network a necessary condition for an efficient wholesale market. These features of the electricity supply industry also make antitrust or competition law alone an inadequate foundation for an electricity market monitoring process. This paper provides examples of both the successes and failures of market monitoring from several international markets. More than 10 years of experience with the electricity industry restructuring process has shown that market failures are more likely and substantially more harmful to consumers than other market failures because of how electricity is produced and delivered and the crucial role it plays in the modern economy. Wholesale market meltdowns of varying magnitudes and durations have occurred in electricity markets around the world, and many of them could have been prevented if a prospective market monitoring process backed by the prevailing regulatory authority had been in place at the start of the market.
Feedback Invariants for Nonlinear Systems

Abstract The problem of finding invariants under nonlinear feedback for systems of the form x ˙ = f ( x ) + ∑ u i g i ( x ) ; f ( 0 ) = 0 is investigated in this paper and we establish certain generalizations of the earlier work on linear systems. We are concerned here with the local theory in the neighborhood of an equilibrium point; global questions are not investigated. Even so the study of invariants under feedback is considerably more complicated in this setting and a completely satisfactory theory is given here only in certain cases. The invariants found here describe a degree of intrinsic nonlinearity of a control system, i.e., they characterize nonlinearity which cannot be removed by feedback compensation. We work only with f’s and g’s that are real analytic. It appears to be possible to relax this hypothesis somewhat but a certain amount of smoothness is essential to our approach.
Cooperation and Reciprocity in Carbon Sequestration Contracts

This paper studies the role of cooperation and reciprocity on the structure of self-enforcing carbon sequestration contracts. The optimal contract is derived as a result of the optimizing actions of purely self-interested agents, and agents that act according to social or egoistic preferences. The analysis finds that buyers' preferences do not affect contract structure unless the buyer is averse to inequality. In contrast, the optimal payment rule is directly related to the seller's preferences as the payment must motivate the seller to comply with forest conservation. It also finds that the presence of altruistic or warm glow preferences increases the likelihood of cooperation in the long-term relationship relative to the case of selfish parties. These results imply that agencies or organizations that are not only concerned about carbon sequestration but also have objectives related to the economic development of small land holders may be more successful in the implementation contracts to reduce emissions from deforestation and forest degradation.
Energy-Efficient Transaction Management for Real-Time Mobile Databases in Ad-Hoc Network Environments

In an ad-hoc mobile network architecture, all the mobile hosts (MHs) are connected with each other through a wireless network that has a frequently changing topology. This type of architecture is used in many applications such as battlefields and disaster recovery where it is difficult or not feasible to depend on a static wired communication infrastructure. These applications are usually time-critical where many of their transactions must not only be executed correctly but also within their deadlines. In addition, the MHs in this environment are not connected to unlimited power supplies and may store data that can be shared by other MHs. Existing mobile database transaction management techniques do not consider the ad-hoc network characteristics, real-time constraints and energy limitation. This paper identifies the issues that need to be addressed in this new environment and proposes approaches for solutions.
Molecular structure determination on a computational and data Grid

The focus of this paper is on the design and implementation of a critical program in structural biology onto two computational and data Grids. The first is the Buffalo-based ACDC Grid, which uses facilities at SUNY-Buffalo and several research institutions that are under distinct control. The second is Grid2003, the iVDGL Grid established late in 2003 primarily for physics and astronomy applications. In this paper, we prevent an overview of the ACDC Grid and Grid2003, focusing on the implementation of several new ACDC computational and Grid tools.
IGF-I restores satellite cell proliferative potential in immobilized old skeletal muscle

One of the key factors responsible for the age-associated reduction in muscle mass may be that satellite cell proliferation potential (number of doublings contained within each cell) could become r...
Distinguishing between observationally equivalent theories of crises

The objective of this paper is to empirically test across alternative, apparently observationally equivalent theories of currency crises. Theories of crises are often difficult to distinguish from each other based on the behavior of commonly used predictors. Using a comprehensive data set on gross external assets and liabilities for 167 countries created by the World Bank's Latin America and the Caribbean Region and the Development Research Group, this study is able to make a significant move toward redressing this shortcoming. It focuses on identifying potential crisis predictors, as well as testing the validity of the distinct transmission mechanisms implied by various theories of currency crisis. Evidence is presented in support of insurance-based models, suggesting that proxies for contingent liability accumulation are effective crisis predictors.
Light Responses and Morphology of bNOS-Immunoreactive Neurons in the Mouse Retina

Nitric oxide (NO), produced by NO synthase (NOS), modulates the function of all retinal neurons and ocular blood vessels and participates in the pathogenesis of ocular diseases. To further understand the regulation of ocular NO release, we systematically studied the morphology, topography, and light responses of NOS-containing amacrine cells (NOACs) in dark-adapted mouse retina. Immunohistological staining for neuronal NOS (bNOS), combined with retrograde labeling of ganglion cells (GCs) with Neurobiotin (NB, a gap junction permeable dye) and Lucifer yellow (LY, a less permeable dye), was used to identify NOACs. The light responses of ACs were recorded under whole-cell voltage clamp conditions and cell morphology was examined with a confocal microscope. We found that in dark-adapted conditions bNOS-immunoreactivity (IR) was present primarily in the inner nuclear layer and the ganglion cell layer. bNOS-IR somas were negative for LY, thus they were identified as ACs; nearly 6% of the cells were labeled by NB but not by LY, indicating that they were dye-coupled with GCs. Three morphological subtypes of NOACs (NI, NII, and displaced) were identified. The cell density, intercellular distance, and the distribution of NOACs were studied in whole retinas. Light evoked depolarizing highly sensitive ON-OFF responses in NI cells and less sensitive OFF responses in NII cells. Frequent (1–2 Hz) or abrupt change of light intensity evoked larger peak responses. The possibility for light to modify NO release from NOACs is discussed. J. Comp. Neurol. 518:2456–2474, 2010.
The iPod Model

We introduce a Voter Model variant, inspired by social evolution of musical preferences. In our model, agents have preferences over a set of songs and upon meeting update their own preferences incrementally towards those of the other agents they meet. Using the spectral gap of an associated Markov chain, we give a geometry dependent result on the asymptotic consensus time of the model.
A polynomial-time algorithm for deciding Markov equivalence of directed cyclic graphical models

Although the concept of d-separation was originally defined for directed acyclic graphs (see Pearl 1988), there is a natural extension of the concept to directed cyclic graphs. When exactly the same set of d-separation relations hold in two directed graphs, no matter whether respectively cyclic or acyclic, we say that they are Markov equivalent. In other words, when two directed cyclic graphs are Markov equivalent, the set of distributions that satisfy a natural extension of the Global Directed Markov Condition (Lauritzen et al. 1990) is exactly the same for each graph. There is an obvious exponential (in the number of vertices) time algorithm for deciding Markov equivalence of two directed cyclic graphs; simply check all of the d-separation relations in each graph. In this paper I state a theorem that gives necessary and sufficient conditions for the Markov equivalence of two directed cyclic graphs, where each of the conditions can be checked in polynomial time. Hence, the theorem can be easily adapted into a polynomial time algorithm for deciding the Markov equivalence of two directed cyclic graphs. Although space prohibits inclusion of correctness proofs, they are fully described in Richardson (1994b).
Studies of autoionizing states relevant to dielectronic recombination

In the past year we have focused most of our effort on the study of the 3pnl autoionizing states of Mg. Specifically, we have measured the angular distributions of electrons ejected from these states, we have carried out theoretical analyses of the experimentally determined angular distributions, and we have also made measurements of the autoionization rates of Mg 3pnk Stark states in electric fields. Finally, we have recorded the spectra of the autoionizing Ba 6pnk Stark states with very high optical powers to see the fine details in the wings of the spectra. Each of these activities is described in more detail in the ensuing paragraphs.
Dynamics of collapsing and exploding Bose–Einstein condensates

When atoms in a gas are cooled to extremely low temperatures, they will-under the appropriate conditions-condense into a single quantum-mechanical state known as a Bose-Einstein condensate. In such systems, quantum-mechanical behaviour is evident on a macroscopic scale. Here we explore the dynamics of how a Bose-Einstein condensate collapses and subsequently explodes when the balance of forces governing its size and shape is suddenly altered. A condensate's equilibrium size and shape is strongly affected by the interatomic interactions. Our ability to induce a collapse by switching the interactions from repulsive to attractive by tuning an externally applied magnetic field yields detailed information on the violent collapse process. We observe anisotropic atom bursts that explode from the condensate, atoms leaving the condensate in undetected forms, spikes appearing in the condensate wavefunction and oscillating remnant condensates that survive the collapse. All these processes have curious dependences on time, on the strength of the interaction and on the number of condensate atoms. Although the system would seem to be simple and well characterized, our measurements reveal many phenomena that challenge theoretical models.
A fusion algorithm for solving Bayesian decision problems

This paper proposes a new method for solving Bayesian decision problems. The method consists of representing a Bayesian decision problem as a valuation-based system and applying a fusion algorithm for solving it. The fusion algorithm is a hybrid of local computational methods for computation of marginals of joint probability distributions and the local computational methods for discrete optimization problems.
Osmoregulation in Plants During Drought

For higher plants, water deficiency is more commonly caused by a lack of sufficient water than by exposure to high concentrations of solutes. Crop production is frequently limited by this factor and certain stages of development are more sensitive than others. A particularly sensitive time is during germination. The plant has little root and is located in a layer of soil that quickly dehydrates. Growth must continue, however, since the plant must become autotrophic. The possibility that osmoregulation may protect against the inhibitory effects of dry soil has not been explored during germination (Meyer and Boyer, 1972). In the present paper, we will describe a highly developed system of osmoregulation that permits seedling growth under dry soil conditions that would otherwise be lethal for the plant.
Corrigendum to “High Dose Dexmedetomidine: Effective as a Sole Agent Sedation for Children Undergoing MRI”

A previous study conducted at the same institution, with a patient population of 77, concluded that high dose dexmedetomidine can be successfully used for MRI sedation in children, with 29% of patients requiring additional agents for optimal sedation [19]. In our study, over the course of five years, the patient cohort was larger (544 patients) and included the previously reported 77-patient cohort. This larger patient cohort analysis validated previously reported data: 100% success of the existing sedation protocol, rounded up from 99.8% acknowledging one patient failure, with the adjunctive sedative agents used on 21.5% of cases.
Management Buyouts, Efficient Markets, Fair Value, and Soft Information

Leveraged buyouts, particularly by a corporation's management, provide unique opportunities for investors to realize extraordinary profits. In his Article, Professor Repetti examines the potential harm to shareholder interests when management effects a corporate buyout or bailout, and analyzes the effectiveness of current regulatory and common-law protection against that harm. Professor Repetti concludes that the existing regulatory and common law schemes do not adequately protect shareholder interests and proposes as a solution that the Securities and Exchange Commission promulgate rules requiring enhanced disclosure in management buyouts.
Learning Bayesian networks: a unification for discrete and Gaussian domains

We examine Bayesian methods for learning Bayesian networks from a combination of prior knowledge and statistical data. In particular, we unify the approaches we presented at last year's conference for discrete and Gaussian domains. We derive a general Bayesian scoring metric, appropriate for both domains. We then use this metric in combination with well-known statistical facts about the Dirichlet and normal--Wishart distributions to derive our metrics for discrete and Gaussian domains.
Does Eco-Certification Boost Regulatory Compliance in Developing Countries? ISO 14001 in Mexico

Private sector initiatives certifying that producers of goods and services adhere to defined environmental process standards are increasingly popular worldwide. According to proponents, they can circumvent chronic barriers to effective public sector environmental regulation in developing countries. But eco-certification programs will have limited effects on producers’ environmental performance if, as one would expect, they select for those already meeting certification standards. Rigorous evaluations of the environmental effects of eco-certification in developing countries that control for selection bias are rare. We use plant-level data on more than 80,000 Mexican facilities to determine whether ISO 14001 series certification of environmental management systems boosts regulatory compliance. We use propensity score matching to control for nonrandom selection into the program. We find that plants recently fined by environmental regulators were more likely to be certified, all other things equal, but that certified plants were subsequently fined just as often as similar uncertified plants. These results suggest that in Mexico, the ISO 14001 program attracts dirty plants under pressure from regulators—not just relatively clean ones—but does not have a large, lasting impact on their regulatory compliance.
Weather Forecast Based Conditional Pest Management: A Stochastic Optimal Control Investigation

In this paper, we examine conditional, forecast-based dynamic pest management in agricultural crop production given stochastic pest infestations and stochastic climate dynamics throughout the growing season. Using stochastic optimal control we show that correlation between forecast error for climate prediction and forecast error for pest outbreaks can be used to improve pesticide application efficiency. In the general setting, we apply modified Hamiltonian approach to discuss the steady state equilibrium. Given specific functional forms, a closed form solution can be found for the stochastic optimal control problem. Moreover, we find conditions for model parameters so that the optimal pesticide usage path will be monotonically increasing or decreasing in the correlation coefficient between climate forecast errors and pest growth disturbances.
Producing Surface Coatings on Silicon Nitride by Pack Cementation

Pack cementation processing was used to chemically alter the surface of dense silicon nitride materials and form a coating layer. Test samples were examined by XRD, SEM, and optical microscopy to characterize the chemicaland microstructural changes in the materials after processing. The coating that was formed depended on the composition of the reactive powder pack used in the process and on the processing conditions of temperature and furnace atmosphere. Some of the coating compounds identified by XRD, such as Yb 2 Si 2 O 7 , SrAl 2 Si 2 O 8 , and Yb 3 Al 5 O 1 2 , are promising candidate materials for protective environmental barrier coatings. Preliminary exposure testing results in water vapor at high temperature indicate that a Yb 2 Si 2 O 7 coating on NT154 Si 3 N 4 reduces the rate of attack compared to the uncoated material.
Statistical characteristics of particle injections throughout the equatorial magnetotail

Energetic particle injections are critical for supplying particles and energy to the inner magnetosphere. Recent case studies have demonstrated a good correlation between injections and transient, narrow, fast flow channels as well as earthward reconnection (dipolarization) fronts in the magnetotail, but statistical observations beyond geosynchronous orbit (GEO) to verify the findings were lacking. By surveying trans-geosynchronous injections using Time History of Events and Macroscale Interactions during Substorms (THEMIS), we show that their likely origin is the earthward traveling, dipolarizing flux bundles following near-Earth reconnection. The good correlation between injections and fast flows, reconnection fronts and impulsive, dawn-dusk electric field increases is not limited to within 12 RE but extends out to 30 RE. Like near-Earth reconnection, both ion and electron injections are most probable in the premidnight sector. Similar to bursty bulk flows (BBFs), injection-time flow speeds are faster farther from Earth. With faster flows, injection intensity generally increases and extends to higher energy channels. With increased geomagnetic activity, injection occurrence rate increases (akin to that of BBFs) and spectral hardening occurs (κ decreases). The occurrence rate increase within the inner magnetosphere suggests that injections populate the radiation belts more effectively under enhanced activity. Our results are inconsistent with the classical concept of an azimuthally wide injection boundary moving earthward from ~9 to 12 RE to GEO under an enhanced cross-tail electric field. Rather, particle injection and transport occur along a large range of radial distances due to effects from earthward penetrating, azimuthally localized, transient, strong electric fields of recently reconnected, dipolarizing flux bundles.
Linear Relations for a Generalized Tutte Polynomial

Brylawski proved the coefficients of the Tutte polynomial of a matroid satisfy a set of linear relations. We extend these relations to a generalization of the Tutte polynomial that includes greedoids and antimatroids. This leads to families of new identities for antimatroids, including trees, posets, chordal graphs and finite point sets in $\mathbb{R}^n$. It also gives a "new" linear relation for matroids that is implied by Brylawski's identities.
Minor Planet Binaries

The first detailed characterization of a near-Earth binary (2000 DP107) provided significant insights into the formation mechanism, orbital evolution, and physical properties of the system. Near-Earth Asteroid (NEA) binaries are tidally evolved with synchronously rotating secondaries, providing constraints on asteroid mechanical properties (tidal Q and rigidity). It is expected that radar observations will permit measurements of orbital precession, with corresponding implications for the distribution of mass within asteroids.
CO J = 3-2 Emission in the Radio Galaxy 53W002 at z = 2.394

We report a sensitive search for redshifted CO J = 3-2 emission from the weak radio galaxy 53W002 at z = 2.394. Maps at resolutions of 3'' and 235 km s-1 show a significant emission peak within 05 of the optical and radio continuum peaks. The measured narrowband flux is approximately 10 times the extrapolated centimeter-wavelength nonthermal radio continuum expected at 101.9 GHz and exhibits a spectral profile implying a 540 km s-1 width (FWHM) at a systemic redshift z = 2.394 ± 0.001 for CO (3-2). This emission has a total integrated flux of 1.51 ± 0.2 Jy km s-1, approximately 4 times weaker than that previously seen in the lensed systems FSC 10214+4724 and the Cloverleaf QSO. For a Galactic CO-to-H2 conversion ratio, the implied molecular gas mass is 7.4 × 1010 M☉ (H0 = 75 km s-1 Mpc-1 and q0 = 0.5). The CO emission is elongated at P.A. = 120° with a deconvolved major-axis radius of 15 kpc (28). This extension is along a similar direction to that seen in the centimeter-wave radio continuum and in the optical, but approximately 3 times larger. A velocity gradient is seen along the major axis, and if this structure is a (forming) disk, the implied dynamical mass is (9-22) × 1010 M☉ at r ≤ 15 kpc, assuming inclination i = 0° (edge-on). The magnitude of these masses and the similarity of the high gas-mass fraction are consistent with the host galaxy of 53W002 being a young galactic system but the metallicity (probably ≥0.1 Z☉ in order to produce the CO lines) implies significant heavy-element production prior to z = 2.4. This constitutes the first high redshift molecular gas detected in emission where there is probably no gravitational magnification.
FORWARD AND BACKWARD SIMULATIONS PART II: TIMING-BASED SYSTEMS

A general automaton model for timing-based systems is presented and is used as the context for developing a variety of simulation proof techniques for such systems. As a first step, a comprehensive overview of simulation techniques for simple untimed automata is given. In particular, soundness and completeness results for (1) refinements, (2) forward and backward simulations, (3) forward-backward and backward-forward simulations, and (4) history and prophecy relations are given. History and prophecy relations are new and are abstractions of the history variables of Owicki and Gries and the prophecy variables of Abadi and Lamport, respectively. As a subsequent step, it is shown how most of the results for untimed automata can be carried over to the setting of timed automata. In fact many of the results for the timed case are obtained as consequences of the analogous results for the untimed case.
Electroweak Strings, Sphalerons and Magnetic Fields

In this talk I would like to discuss three main topics. First, I will connect electroweak strings and the sphaleron in a more elaborate manner than that described in my paper with George Field1 and discuss the important issue of the stability of electroweak strings. Secondly, I would like to initiate a discussion of the formation of electroweak strings and their evolution by painting a heuristic picture of the phase transition if the phase transition is weakly first order or second order. Inextricably tied to this picture is a possible scenario for baryogenesis and it is hoped that the present discussion will inspire more rigorous work to either confirm or reject the scenario. Finally, I will make a few comments on the generation of magnetic fields at the electroweak phase transition. Kari Enqvist has already described the basic idea of how this scenario works2 and the purpose of these comments is to clarify some of the issues that have not been addressed in the literature. I will also describe the scenario in an alternate way that makes an interesting connection between electroweak strings and primordial magnetic fields.
Spectroscopic and Variability Surveys for AGN in the Groth Survey Strip

Preliminary results are presented for a spectroscopic survey of the Groth Survey Strip (GSS), a 40 by 3.5 arcminute region of the sky imaged with HST, for which several hundred galaxy spectra have been obtained as part of the DEEP project (this http URL). At least 6 broad-line AGNs (primarily Seyfert 1s) have been detected as well as several narrow-line Seyfert 2 candidates. The Seyfert galaxies detected in our survey have integrated absolute magnitudes extending to M(B)~-17.5, probing fainter magnitudes and higher redshifts than existing optical spectroscopic surveys. We also discuss a variability study of the GSS using the original HST images from 1994 and new images obtained in 2001. The high resolution obtained with HST allows us to isolate and measure variable galactic nuclei too faint to be detected from the ground, reaching nuclear magnitudes of M(B)~-16 in galaxies to z=0.8. The combination of these techniques provides a powerful probe of the population of low-luminosity AGNs at moderate redshifts.
Binaries and Globular Cluster Dynamics

We summarize the results of recent theoretical work on the dynamical evolution of globular clusters containing primordial binaries. Even a very small initial binary fraction (e.g., 10%) can play a key role in supporting a cluster against gravothermal collapse for many relaxation times. Inelastic encounters between binaries and single stars or other binaries provide a very significant energy source for the cluster. These dynamical interactions also lead to the production of large numbers of exotic systems such as ultracompact X-ray binaries, recycled radio pulsars, double degenerate systems, and blue stragglers. Our work is based on a new parallel supercomputer code implementing Henon’s Monte Carlo method for simulating the dynamical evolution of dense stellar systems in the Fokker-Planck approximation. This new code allows us to calculate very accurately the evolution of a cluster containing a realistic number of stars (N ~ 105 – 106) in typically a few hours to a few days of computing time. The discrete, star-by-star representation of the cluster in the simulation makes it possible to treat naturally a number of important processes, including single and binary star evolution, all dynamical interactions of single stars and binaries, and tidal interactions with the Galaxy.
Six Years of Chandra Observations of Supernova Remnants

We present a review of the first six years of Chandra X-ray Observatory observations of supernova remnants. From the official “first-light” observation of Cassiopeia A that revealed for the first time the compact remnant of the explosion, to the recent million-second spectrally-resolved observation that revealed new details of the stellar composition and dynamics of the original explosion, Chandra observations have provided new insights into the supernova phenomenon. We present an admittedly biased overview of six years of these observations, highlighting new discoveries made possible by Chandra’s unique capabilities.
Image segmentation in video sequences: a probabilistic approach

"Background subtraction" is an old technique for finding moving objects in a video sequence--for example, cars driving on a freeway. The idea is that subtracting the current image from a time-averaged background image will leave only nonstationary objects. It is, however, a crude approximation to the task of classifying each pixel of the current image; it fails with slow-moving objects and does not distinguish shadows from moving objects. The basic idea of this paper is that we can classify each pixel using a model of how that pixel looks when it is part of different classes. We learn a mixture-of-Gaussians classification model for each pixel using an unsupervised technique--an efficient, incremental version of EM. Unlike the standard image-averaging approach, this automatically updates the mixture component for each class according to likelihood of membership; hence slow-moving objects are handled perfectly. Our approach also identifies and eliminates shadows much more effectively than other techniques such as thresholding. Application of this method as part of the Roadwatch traffic surveillance project is expected to result in significant improvements in vehicle identification and tracking.
The Value of Truth and the Optimal Standard of Proof in Legal Disputes

This article models the fact-finding process as one in which a defendant is accused of violating some legal standard (e.g., exceeding the speed limit). The fact finder cannot observe the actual behavior but observes some variable that is a noisy signal of the truth (e.g., the reading from a radar detector). From this signal it is possible to calculate the probability of guilt. The standard of proof (the minimal probability necessary to convict) that minimizes the expected cost of error is seen as a trade-off between the expected cost of false acquittals and convictions. A simple example shows that a clearer signal of truth (a more reliable radar detector) may not always lower error costs, because the utility of a fact-finding method depends also on the population of defendants and the standard of proof. These results clarify the source of disagreements over different fact-finding procedures. Copyright 1994 by Oxford University Press.
Precision of "target of the day" radiotherapy

We have previously reported that computer-controlled table repositioning can increase the reproducibility of patient setup in 2D using a megavoltage imager and bony anatomy as reference of position. This investigation was extended to daily 3D localization of soft tissue structures ("target of the day" treatment). Research to date has involved liver (under ventilatory immobilization) and prostate patients. Both protocols involve aligning the specified target to the reference position (determined via CT) using a diagnostic imager and alignment software. The liver position is determined by the position of the diaphragm and the spine, the prostate target is automatically localized and positioned through computer-based extraction of 3 implanted gold markers. Adjustments to correct target position are executed using a computer-controlled table. Measuring the residual offset of the target after the corrective action determines the accuracy of measurement and table adjustment, however this uncertainty is also influenced by organ motion between images. For the prostate protocol, the accuracy of the computer-controlled target repositioning is dx:0.56 mm (/spl sigma/=3.69 mm), dy:2.74 mm (/spl sigma/=3.87 mm), dz:2.38 mm (/spl sigma/=4.5 mm) after 24 treatment fractions. For the liver protocol, the accuracy is dx:-0.7 mm (/spl sigma/=1.67 mm), dy:-0.9 mm (/spl sigma/=1.89 mm), dz:-1.0 mm (/spl sigma/=3.18 mm) after 23 treatment fractions. The extra time necessary to image, align, and adjust the target has also been calculated. The average time for the localization and subsequent verification is 12.2 minutes (/spl sigma/=5.7 min).
A direct estimation of high dimensional stationary vector autoregressions

The vector autoregressive (VAR) model is a powerful tool in learning complex time series and has been exploited in many fields. The VAR model poses some unique challenges to researchers: On one hand, the dimensionality, introduced by incorporating multiple numbers of time series and adding the order of the vector autoregression, is usually much higher than the time series length; On the other hand, the temporal dependence structure naturally present in the VAR model gives rise to extra difficulties in data analysis. The regular way in cracking the VAR model is via "least squares" and usually involves adding different penalty terms (e.g., ridge or lasso penalty) in handling high dimensionality. In this manuscript, we propose an alternative way in estimating the VAR model. The main idea is, via exploiting the temporal dependence structure, formulating the estimating problem to a linear program. There is instant advantage of the proposed approach over the lasso-type estimators: The estimation equation can be decomposed to multiple sub-equations and accordingly can be solved efficiently using parallel computing. Besides that, we also bring new theoretical insights into the VAR model analysis. So far the theoretical results developed in high dimensions (e.g., Song and Bickel, 2011 and Kock and Callot, 2015) are based on stringent assumptions that are not transparent. Our results, on the other hand, show that the spectral norms of the transition matrices play an important role in estimation accuracy and build estimation and prediction consistency accordingly. Moreover, we provide some experiments on both synthetic and real-world equity data. We show that there are empirical advantages of our method over the lasso-type estimators in parameter estimation and forecasting.
A Methodological Framework for Prioritizing Infrastructure Investment

Policy makers are often confronted with a myriad of factors in the investment decision-making process. This issue is particularly acute in infrastructure investment decisions, as these often involve significant financial resources and lock-in technologies. In regions and countries where the infrastructure access gap is large and pubic budgets severely constrained, the importance of considering the different facets of the decision-making process becomes even more relevant. This paper discusses the trade-offs policy makers confront when attempting to prioritize infrastructure investments, in particular with regard to economic growth and welfare, and proposes a methodological framework for prioritizing infrastructure projects and portfolios that holistically equates such trade-offs, among others. The analysis suggests that it is not desirable to have a single methodology, providing a single ranking of infrastructure investments, because of the complexities of infrastructure investments. Rather, a multidisciplinary approach should be taken. Decision makers will also need to account for factors that are often not easily measured. While having techniques that enable logical frameworks in the decision-making process of establishing priorities is highly desirable, they are no substitute for consensus building and political negotiations.
The flat decay phase in the early X-ray afterglows of Swift GRBs

Many Swift GRBs show an early phase of shallow decay in their X-ray afterglows, lasting from t {approx} 10{sup 2.5} s to {approx} 10{sup 4} s after the GRB, where the flux decays as {approx} t{sup -0.2} - t{sup -0.8}. This is perhaps the most mysterious of the new features discovered by Swift in the early X-ray afterglow, since it is still not clear what causes it. I discuss different possible explanations for this surprising new discovery, as well as their potential implications for the gamma-ray efficiency, the afterglow kinetic energy, and perhaps even for the physics of collisionless relativistic shocks.
Optimal relay selection with non-negligible probing time

In this paper an optimal relay selection algorithm with non-negligible probing time is proposed and analyzed for cooperative wireless networks. Relay selection has been introduced to solve the degraded bandwidth efficiency problem in cooperative communication. Yet complete information of relay channels often remain unavailable for complex networks which renders the optimal selection strategies impossible for transmission source without probing the relay channels. Particularly when the number of relay candidate is large, even though probing all relay channels guarantees the finding of the best relays at any time instant, the degradation of bandwidth efficiency due to non-negligible probing times, which was often neglected in past literature, is also significant. In this work, a stopping rule based relay selection strategy is determined for the source node to decide when to stop the probing process and choose one of the probed relays to cooperate with under wireless channels' stochastic uncertainties. This relay selection strategy is further shown to have a simple threshold structure. At the meantime, full diversity order and high bandwidth efficiency can be achieved simultaneously. Both analytical and simulation results are provided to verify the claims.
III-V/Si wafer bonding using transparent, conductive oxide interlayers

We present a method for low temperature plasma-activated direct wafer bonding of III-V materials to Si using a transparent, conductive indium zinc oxide interlayer. The transparent, conductive oxide (TCO) layer provides excellent optical transmission as well as electrical conduction, suggesting suitability for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding temperatures ranging from 100 °C to 350 °C, Ohmic behavior is observed in the sample stacks, with specific contact resistivity below 1 Ω cm2 for samples bonded at 200 °C. Optical absorption measurements show minimal parasitic light absorption, which is limited by the III-V interlayers necessary for Ohmic contact formation to TCOs. These results are promising for Ga0.5In0.5P/Si tandem solar cells operating at 1 sun or low concentration conditions.
Noisy signal recovery via iterative reweighted L1-minimization

Compressed sensing has shown that it is possible to reconstruct sparse high dimensional signals from few linear measurements. In many cases, the solution can be obtained by solving an l 1 -minimization problem, and this method is accurate even in the presence of noise. Recently a modified version of this method, reweighted l 1 -minimization, has been suggested. Although no provable results have yet been attained, empirical studies have suggested the reweighted version outperforms the standard method. Here we analyze the reweighted l 1 -minimization method in the noisy case, and provide provable results showing an improvement in the error bound over the standard bounds.