cssi/SciSciGPT-SciSciNet huggingface dataset:
Influence of ion streaming instabilities on transport near plasma boundaries

Plasma boundary layers are susceptible to electrostatic instabilities driven by ion flows in presheaths and, when present, these instabilities can influence transport. In plasmas with a single species of positive ion, ion-acoustic instabilities are expected under conditions of low pressure and large electron-to-ion temperature ratio ( TT /1 ei � ). In plasmas with two species of positive ions, ion-ion two-stream instabilities can also be excited. The stability phase- space is characterized using the Penrose criterion and approximate linear dispersion relations. Predictions for how these instabilities affect ion and electron transport in presheaths, including rapid thermalization due to instability-enhanced collisions and an instability-enhanced ion-ion friction force, are briefly reviewed. Recent experimental tests of these predictions are discussed along with research needs required for further validation. The calculated stability boundaries provide a guide to determine the experimental conditions at which these effects can be expected.
A local-global principle for isogenies of composite degree

Let $E$ be an elliptic curve over a number field $K$. If for almost all primes of $K$, the reduction of $E$ modulo that prime has rational cyclic isogeny of fixed degree, we can ask if this forces $E$ to have a cyclic isogeny of that degree over $K$. Building upon the work of Sutherland, Anni, and Banwait-Cremona in the case of prime degree, we consider this question for cyclic isogenies of arbitrary degree.
NEUTRON STAR MASSES AND RADII FROM QUIESCENT LOW-MASS X-RAY BINARIES

We perform a systematic analysis of neutron star radius constraints from five quiescent low-mass X-ray binaries and examine how they depend on measurements of their distances and amounts of intervening absorbing material, as well as their assumed atmospheric compositions. We construct and calibrate to published results a semi-analytic model of the neutron star atmosphere which approximates these effects for the predicted masses and radii. Starting from mass and radius probability distributions established from hydrogen-atmosphere spectral fits of quiescent sources, we apply this model to compute alternate sets of probability distributions. We perform Bayesian analyses to estimate neutron star mass-radius curves and equation of state (EOS) parameters that best-fit each set of distributions, assuming the existence of a known low-density neutron star crustal EOS, a simple model for the high-density EOS, causality, and the observation that the neutron star maximum mass exceeds 2 M ☉. We compute the posterior probabilities for each set of distance measurements and assumptions about absorption and composition. We find that, within the context of our assumptions and our parameterized EOS models, some absorption models are disfavored. We find that neutron stars composed of hadrons are favored relative to those with exotic matter with strong phase transitions. In addition, models in which all five stars have hydrogen atmospheres are found to be weakly disfavored. Our most likely models predict neutron star radii that are consistent with current experimental results concerning the nature of the nucleon-nucleon interaction near the nuclear saturation density.
Estimating Total Open Heliospheric Magnetic Flux

Over the solar-activity cycle, there are extended periods where significant discrepancies occur between the spacecraft-observed total (unsigned) open magnetic flux and that determined from coronal models. In this article, the total open heliospheric magnetic flux is computed using two different methods and then compared with results obtained from in-situ interplanetary magnetic-field observations. The first method uses two different types of photospheric magnetic-field maps as input to the Wang–Sheeley–Arge (WSA) model: i) traditional Carrington or diachronic maps, and ii) Air Force Data Assimilative Photospheric Flux Transport model synchronic maps. The second method uses observationally derived helium and extreme-ultraviolet coronal-hole maps overlaid on the same magnetic-field maps in order to compute total open magnetic flux. The diachronic and synchronic maps are both constructed using magnetograms from the same source, namely the National Solar Observatory Kitt Peak Vacuum Telescope and Vector Spectromagnetograph. The results of this work show that the total open flux obtained from observationally derived coronal holes agrees remarkably well with that derived from WSA, especially near solar minimum. This suggests that, on average, coronal models capture well the observed large-scale coronal-hole structure over most of the solar cycle. Both methods show considerable deviations from total open flux deduced from spacecraft data, especially near solar maximum, pointing to something other than poorly determined coronal-hole area specification as the source of these discrepancies.
MODELING THE X-RAYS FROM THE CENTRAL COMPACT OBJECT PSR J1852+0040 IN KESTEVEN 79: EVIDENCE FOR A STRONGLY MAGNETIZED NEUTRON STAR

I present modeling of the X-ray pulsations from the central compact object (CCO) PSR J1852+0040 in the Galactic supernova remnant Kesteven 79. In the context of thermal surface radiation from a rotating neutron star (NS), a conventional polar cap model can reproduce the broad, large-amplitude X-ray pulse only with a "pencil plus fan" beam emission pattern, which is characteristic of 1012 G NS atmospheres, much greater than the ~1010 G external dipole field inferred from the pulsar spin-down rate. This discrepancy can be explained by an axially displaced dipole. For other beaming patterns, it is necessary to invoke high-aspect-ratio emitting regions that are greatly longitudinally elongated, possibly due to an extremely offset dipole. For all assumed emission models, the existence of strong internal magnetic fields ( 1014 G) that preferentially channel internal heat to only a portion of the exterior is required to account for the implied high-temperature contrast across the stellar surface. This lends further observational evidence in support of the "hidden" strong magnetic field scenario, in which CCOs possess submerged magnetic fields that are substantially stronger than the external dipole field, presumably due to burial by fallback of supernova ejecta. I also conduct phase-resolved X-ray spectroscopy and find no evidence for prominent spin-phase-dependent absorption features that could be produced by cyclotron absorption/scattering.
Spectroscopy of Infrared Flares from the Microquasar GRS 1915+105

We present near-infrared medium-resolution (R~875) spectra of the microquasar GRS 1915+105 on 1997 August 13-15 UTC from the Hale 5 m telescope. The spectra show broad emission lines of He I (2.058 μm) and H I (2.166 μm; Brγ), which are consistent with previous work. On August 14 UTC, we took spectra with an ~6 minute time resolution during infrared flaring events similar to those reported in Eikenberry et al., which appear to reveal plasma ejection from the system. During the flares, the emission-line fluxes varied in approximately linear proportionality to the IR continuum flux, implying that the lines are radiatively pumped by the flares. We also detected a weak He II (2.189 μm) emission line on August 14 UTC. The nature of the line variability and the presence of the He II feature indicate that the emission lines in GRS 1915+105 arise in an accretion disk around the compact object rather than in the circumstellar disk of a proposed Oe/Be companion. The radiative line pumping also implies that the flare emission originates from ejecta that have moved out of the accretion disk plane.
Action dimensions of some simple complexes of groups

The action dimension of a discrete group $G$ is the minimum dimension of contractible manifold that admits a proper $G$-action. We compute the action dimension of the direct limit of a simple complex of groups for several classes of examples including: 1) Artin groups, 2) graph products of groups, and 3) fundamental groups of aspherical complements of arrangements of affine hyperplanes.
Diffuse 0.5-1 keV X-Rays and Nuclear Gamma Rays from Fast Particles in the Local Hot Bubble

We show that interactions of fast particles with the boundary shell of the local hot bubble could make an important contribution to the 0.5-1 keV diffuse X-ray background observed with ROSAT. The bulk of these nonthermal X-rays are due to line emission from fast O ions of energies around 1 MeV nucleon-1. The unequivocal signature of lines from de-excitations in fast ions is their large width (δE/E0.1 for O lines), which distinguishes them from X-ray lines produced in a hot plasma. If the 0.5-1 keV nonthermal X-rays are produced by accelerated particles with a sufficiently hard energy spectrum, the gamma-ray line emission produced in the boundary shell of the local hot bubble could account for the recently reported COMPTEL observations of nuclear gamma-ray lines from a broad region toward the Galactic center.
Reading the Manual: Event Extraction as Definition Comprehension

We ask whether text understanding has progressed to where we may extract event information through incremental refinement of bleached statements derived from annotation manuals. Such a capability would allow for the trivial construction and extension of an extraction framework by intended end-users through declarations such as, “Some person was born in some location at some time.” We introduce an example of a model that employs such statements, with experiments illustrating we can extract events under closed ontologies and generalize to unseen event types simply by reading new definitions.
The Peculiar Pulsar Population of the Central Parsec

Pulsars orbiting the Galactic center black hole, Sgr A*, would be potential probes of its mass, distance, and spin, and may even be used to test general relativity. Despite predictions of large populations of both ordinary and millisecond pulsars in the Galactic center, none have been detected within 25 pc by deep radio surveys. One explanation has been that hyperstrong temporal scattering prevents pulsar detections, but the recent discovery of radio pulsations from a highly magnetized neutron star (magnetar) within 0.1 pc shows that the temporal scattering is much weaker than predicted. We argue that an intrinsic deficit in the ordinary pulsar population is the most likely reason for the lack of detections to date: a ''missing pulsar problem'' in the Galactic center. In contrast, we show that the discovery of a single magnetar implies efficient magnetar formation in the region. If the massive stars in the central parsec form magnetars rather than ordinary pulsars, their short lifetimes could explain the missing pulsars. Efficient magnetar formation could be caused by strongly magnetized progenitors, or could be further evidence of a top-heavy initial mass function. Furthermore, current high-frequency surveys should already be able to detect bright millisecond pulsars, given the measuredmore » degree of temporal scattering.« less
Spin-diffusions and diffusive molecular dynamics

Metastable condensed matter typically fluctuates about local energy minima at the femtosecond time scale before transitioning between local minima after nanoseconds or microseconds. This vast scale separation limits the applicability of classical molecular dynamics methods and has spurned the development of a host of approximate algorithms. One recently proposed method is diffusive molecular dynamics which aims to integrate a system of ordinary differential equations describing the likelihood of occupancy by one of two species, in the case of a binary alloy, while quasistatically evolving the locations of the atoms. While diffusive molecular dynamics has shown to be efficient and provide agreement with observations, it is fundamentally a model, with unclear connections to classical molecular dynamics. In this work, we formulate a spin-diffusion stochastic process and show how it can be connected to diffusive molecular dynamics. The spin-diffusion model couples a classical overdamped Langevin equation to a kinetic Monte Carlo model for exchange amongst the species of a binary alloy. Under suitable assumptions and approximations, spin-diffusion can be shown to lead to diffusive molecular molecular dynamics type models. The key assumptions and approximations include a well defined time scale separation, a choice of spin exchange rates, a low temperature approximation, and a mean field type approximation. We derive several models from different assumptions and show their relationship to diffusive molecular dynamics. Differences and similarities amongst the models are explored in a simple test problem.
Solar sails, optical tweezers, and other light-driven machines

Electromagnetic waves carry energy, linear momentum, and angular momentum. When light (or other electromagnetic radiation) interacts with material media, both energy and momentum are usually exchanged. The force and torque experienced by material bodies in their interactions with the electromagnetic field are such that the energy as well as the linear and angular momenta of the overall system (i.e., the system of field plus matter) are conserved. Radiation forces are now used routinely to trap and manipulate small objects such as glass or plastic micro-beads and biological cells, to drive micro- and nanomachines, and to contemplate interstellar travel with the aid of solar sails. We discuss the properties of the electromagnetic field that enable such wide-ranging applications.
CB1 receptor signaling modulates amygdalar plasticity during context-cocaine memory reconsolidation to promote subsequent cocaine seeking.

Contextual drug-associated memories precipitate craving and relapse in cocaine users. Such associative memories can be weakened through interference with memory reconsolidation, a process by which memories are maintained following memory retrieval-induced destabilization. We hypothesized that cocaine-memory reconsolidation requires cannabinoid type 1 receptor (CB1R) signaling based on the fundamental role of the endocannabinoid system in synaptic plasticity and emotional memory processing. Using an instrumental model of cocaine relapse, we evaluated whether systemic CB1R antagonism (AM251; 3 mg/kg, i.p.) during memory reconsolidation altered (1) subsequent drug context-induced cocaine-seeking behavior as well as (2) cellular adaptations and (3) excitatory synaptic physiology in the basolateral amygdala (BLA) in male Sprague Dawley rats. Systemic CB1R antagonism, during, but not after, cocaine-memory reconsolidation reduced drug context-induced cocaine-seeking behavior 3 d, but not three weeks, later. CB1R antagonism also inhibited memory retrieval-associated increases in BLA zinc finger 268 (zif268) and activity regulated cytoskeletal-associated protein (Arc) immediate-early gene (IEG) expression and changes in BLA AMPA receptor (AMPAR) and NMDA receptor (NMDAR) subunit phosphorylation that likely contribute to increased receptor membrane trafficking and synaptic plasticity during memory reconsolidation. Furthermore, CB1R antagonism increased memory reconsolidation-associated spontaneous EPSC (sEPSC) frequency in BLA principal neurons during memory reconsolidation. Together, these findings suggest that CB1R signaling modulates cellular and synaptic mechanisms in the BLA that may facilitate cocaine-memory strength by enhancing reconsolidation or synaptic reentry reinforcement, or by inhibiting extinction-memory consolidation. These findings identify the CB1R as a potential therapeutic target for relapse prevention. SIGNIFICANCE STATEMENT Drug relapse can be triggered by the retrieval of context-drug memories on re-exposure to a drug-associated environment. Context-drug associative memories become destabilized on retrieval and must be reconsolidated into long-term memory stores to persist. Hence, targeted interference with memory reconsolidation can weaken maladaptive context-drug memories and reduce the propensity for drug relapse. Our findings indicate that cannabinoid type 1 receptor (CB1R) signaling is critical for context-cocaine memory reconsolidation and subsequent drug context-induced reinstatement of cocaine-seeking behavior. Furthermore, cocaine-memory reconsolidation is associated with CB1R-dependent immediate-early gene (IEG) expression and changes in excitatory synaptic proteins and physiology in the basolateral amygdala (BLA). Together, our findings provide initial support for CB1R as a potential therapeutic target for relapse prevention.
Meshing Point Clouds with Predicted Intrinsic-Extrinsic Ratio Guidance

We are interested in reconstructing the mesh representation of object surfaces from point clouds. Surface reconstruction is a prerequisite for downstream applications such as rendering, collision avoidance for planning, animation, etc. However, the task is challenging if the input point cloud has a low resolution, which is common in real-world scenarios (e.g., from LiDAR or Kinect sensors). Existing learning-based mesh generative methods mostly predict the surface by first building a shape embedding that is at the whole object level, a design that causes issues in generating fine-grained details and generalizing to unseen categories. Instead, we propose to leverage the input point cloud as much as possible, by only adding connectivity information to existing points. Particularly, we predict which triplets of points should form faces. Our key innovation is a surrogate of local connectivity, calculated by comparing the intrinsic/extrinsic metrics. We learn to predict this surrogate using a deep point cloud network and then feed it to an efficient post-processing module for high-quality mesh generation. We demonstrate that our method can not only preserve details, handle ambiguous structures, but also possess strong generalizability to unseen categories by experiments on synthetic and real data.
Ray-tracing a small orbital mission for soft-x-ray polarimetry

X-ray polarimetry is still largely uncharted territory. With the upcoming launch of IXPE, we will learn a lot more about X-ray polarization at energies above 2 keV, but so far no current or accepted mission provides observational capabilities below 2 keV. We present ray-tracing results for a small orbital mission that could be launched within NASA’s Pioneer or SmallSat cost-cap to provide X-ray polarimetry below 2 keV. The design is based on the use of laterally-graded multi-layer (ML) mirrors, a concept that we have developed theoretically for the REDSoX Polarimeter,1 for which most components have been verified in the laboratory. In this contribution, we describe a single channel orbital mission based on the same idea, but modified to the unique cost and space requirements. All results scale up easily to two or more polarimetry channels. Scaling up would simply increase the effective area and reduce the need to rotate the instrument to measure the different polarization directions. In particular, we use the ray-traces to define the maximum size of the dispersion gratings and to determine an alignment budget.
Information Carried by Electromagnetic Radiation Launched from Accelerated Polarization Currents

An unconventional antenna technology can focus the radio waves emitted from the acceleration of polarization currents, aiding use of the waves in communication applications.
Teaching and Learning in Uncertainty

We investigate a simple model for social learning with two agents: a teacher and a student. The teacher’s goal is to teach the student the state of the world; however, the teacher himself is not certain about the state of the world and needs to simultaneously learn this parameter and teach it to the student. We model the teacher’s and student’s uncertainties via noisy transmission channels, and employ two simple decoding strategies for the student. We focus on two teaching strategies: a “low-effort” strategy of simply forwarding information, and a “high-effort” strategy of communicating the teacher’s current best estimate of the world at each time instant, based on his own cumulative learning. Using tools from large deviation theory, we calculate the exact learning rates for these strategies and demonstrate regimes where the low-effort strategy outperforms the high-effort strategy. Finally, we present a conjecture concerning the optimal learning rate for the student over all joint strategies between the student and the teacher.
On the Problem of Modeling the Boat Wake Climate: The Florida Intracoastal Waterway

The impact of boat traffic on the health of coastal ecosystems is a multi-scale process: from minutes (individual wakes) to days (tidal modulation of sediment transport), to seasons and years (traffic is seasonal). A considerable numerical effort, notwithstanding the value of a boat-by-boat numerical modeling approach, is questionable, because of the practical impossibility of specifying the exact type and navigation characteristics for every boat comprising the traffic at any given time. Here, we propose a statistical-mechanics description of the traffic using a joint probability density of the wake population in some characteristic parameter space. We attempt to answer two basic questions: (1) what is the relevant parameter space and (2) how should a numerical model be tested for a wake population? We describe the linear and nonlinear characteristics of wakes observed in the Florida Intracoastal Waters. Adopting provisionally a two-dimensional parameter space (depth- and length-based Froude numbers) we conduct numerical simulations using the open-source FUNWAVE-TVD Boussinesq model. The model performance is excellent for weakly-dispersive, completely specified wakes (e.g., the analytical linear wakes), and also for the range of Froude numbers observed in the field, or for large container ships generating relatively long waves. The model is challenged by the short waves generated by small, slow boats. However, simulations suggest that the problem is confined to the deeper water domain and linear evolution. Nonlinear wake shoaling, essential for modeling wake-induced sediment transport and wake impact on the environment, is described well.
The Global Optimization Geometry of Low-Rank Matrix Optimization

This paper considers general rank-constrained optimization problems that minimize a general objective function ${f}( {X})$ over the set of rectangular ${n}\times {m}$ matrices that have rank at most r. To tackle the rank constraint and also to reduce the computational burden, we factorize $ {X}$ into $ {U} {V} ^{\mathrm {T}}$ where $ {U}$ and $ {V}$ are ${n}\times {r}$ and ${m}\times {r}$ matrices, respectively, and then optimize over the small matrices $ {U}$ and $ {V}$ . We characterize the global optimization geometry of the nonconvex factored problem and show that the corresponding objective function satisfies the robust strict saddle property as long as the original objective function f satisfies restricted strong convexity and smoothness properties, ensuring global convergence of many local search algorithms (such as noisy gradient descent) in polynomial time for solving the factored problem. We also provide a comprehensive analysis for the optimization geometry of a matrix factorization problem where we aim to find ${n}\times {r}$ and ${m}\times {r}$ matrices $ {U}$ and $ {V}$ such that $ {U} {V} ^{\mathrm {T}}$ approximates a given matrix $ {X}^\star $ . Aside from the robust strict saddle property, we show that the objective function of the matrix factorization problem has no spurious local minima and obeys the strict saddle property not only for the exact-parameterization case where $\mathrm {rank}( {X}^\star) = {r}$ , but also for the over-parameterization case where $\mathrm {rank}( {X}^\star) and the under-parameterization case where $\mathrm {rank}( {X}^\star) > {r}$ . These geometric properties imply that a number of iterative optimization algorithms (such as gradient descent) converge to a global solution with random initialization.
Investment Plans and Stock Returns

When the discount rate falls, investment should rise. Thus with time-varying discount rates and instantly changing investment, investment should positively covary with current stock returns and negatively covary with future stock returns. Aggregate nonresidential U.S. investment contradicts both these implications, probably because of investment lags. Investment plans, however, satisfy both implications. These investment plans, from a U.S. government survey of firms, are highly informative measures of expected investment and explain more than threequarters of the variation in real annual aggregate investment growth. Plans have substantial forecasting power for excess stock returns, showing that time-varying risk premia affect investment. A BASIC IDEA IN ECONOMICS and finance is that when the discount rate falls, investment should rise. If discount rates move over time and investment instantly adjusts, then the idea has two implications. First, investment and stock returns should positively covary over time. This positive contemporaneous covariation occurs because when discount rates fall, firms increase investment (since the hurdle rate on investment falls) and stock prices rise (since the discounted sum of future cash flows rises). Second, investment and future stock returns should negatively covary over time. This negative covariation occurs because when discount rates are low, investment today is high and future expected returns are low. Post-war annual aggregate U.S. data on stock returns and nonresidential investment growth contradict these implications. Investment and stock returns have a significant negative contemporaneous covariation, and investment and future stock returns have a covariation that is not statistically different from zero. The significant negative contemporaneous covariation is particularly puzzling since it seems to suggest that firms perversely cut investment when stock prices go up.
NEGLECTED STORIES AND CIVIC SPACE

Professor Davis argues that millions of hours of struggle by people in the overlapping categories labeled African American, woman, and abolitionist warrant recognition as contributions to our Constitutional tradition. and explains why this recognition would enrich the United States’ civic and constitutional culture.
Where the Heart Is: Information Production and the Home Bias

This paper tests whether home bias exists among information producers. We find that credit analysts are more generous when rating issuers from their home states compared with (a) benchmark analysts...
Public information releases, private information arrival and volatility in the foreign exchange market

Abstract This paper estimates the impact of market activity and news on the volatility of returns in the exchange market for Japanese Yen and US dollars. We examine the effects of news on volatility before, during and after news arrival, using three categories of news. Market activity is proxied by quote arrival, separated into a predictable seasonal component and an unexpected component. Results indicate that both components of market activity, as well as news releases, affect volatility levels. We conclude that both private information and news effects are important determinants of exchange rate volatility. Our finding that unexpected quote arrival positively impacts foreign exchange rate volatility is consistent with the interpretation that unexpected quote arrival serves as a measure of informed trading. Corroborating this interpretation is regression analysis, which indicates that spreads increase in the surprise component of the quote arrival rate, but not in the expected component. The estimated impact of a unit increase in unexpected quote arrival and the range of values observed for this variable imply an important volatility conditioning role for informed trading.
Nepa and Environmental Justice: Integration, Implementation, and Judicial Review

The purpose of the National Environmental Policy Act (NEPA) is to assure “for all Americans safe, healthful, productive, and esthetically and culturally pleasing surroundings,” a goal that is essential to environmental justice. Although NEPA provides the structure for federal environmental decisionmaking, is it effective as a tool for addressing environmental justice concerns? This Essay addresses NEPA’s limitations and potential for this purpose, and assesses the role of case law and judicial review in shaping this integrative process. To do so, it considers the environmental justice implications of NEPA’s structural gaps—including exemptions, categorical exclusions, and so-called “functional equivalents”— and evaluates judicial review of agencies’ environmental justice analyses
An evaluation of alternative proxies for the market's assessment of unexpected earnings☆

Abstract This study examines the association between abnormal returns and five alternative proxies for the market's assessment of unexpected quarterly earnings. We examine the role that measurement error potentially has in multiple regression tests of abnormal returns (occuring around the time of earnings announcements) on an unexpected earnings proxy and other non-earnings variables. The results indicate a potential measurement error interpretation of such multiple regression tests. We examine three procedures which reduce, to an unknown degree, the measurement error problem. Our procedures appear to be more (less) effective at reducing measurement error for small (large) firms and recent (non-recent) forecasts.
Information Content and Value Relevance of Depreciation: A Cross‐Industry Analysis

ABSTRACT: Funds from Operations (FFO) is the prevailing performance measure in the Real Estate Investment Trust (REIT) industry. However, prior studies are inconclusive about the superiority of FFO over GAAP net income. Because depreciation is the largest reconciling item between FFO and net income, we examine the information content and value relevance of depreciation for both the REIT and non‐REIT industries and report the following findings. First, accumulated depreciation is value‐relevant for the REIT industry, whereas accumulated depreciation has little value relevance for comparably capital‐intensive non‐REIT industries. Second, accounting depreciation deviates from economic depreciation to a greater extent for REITs than for non‐REIT industries. Third, accumulated depreciation has predictive ability for future revenues for REIT firms, but not for non‐REIT firms. Finally, only the REIT industry displays all of these properties. In sum, evidence supports the REIT industry's assertion that GAAP depre...
Liberalization Policies and Welfare in a Financially Repressed Economy

The welfare effects of three types of liberalization policy-financial deregulation, relaxation of capital controls, and trade liberalization-are studied under the realistic assumption that in the short run all markets cannot be liberalized simultaneously. An intertemporal general equilibrium model with two traded goods is used to show that partial reforms, which in the long run are beneficial, may well cause welfare losses in the short run. Contrary to the standard view, raising the deposit rate may reduce welfare if tariffs are present, whereas tariffs can raise welfare when financial repression discourages saving.
Importing, Exporting, and Innovation in Developing Countries

Recent studies have shown that not only exporters but also importers perform better than firms that do not trade. Using a detailed firm level dataset from 43 developing countries, I show that there are persistent differences in evolution of firms when they are grouped according to their trade orientation as: two-way traders (both importing and exporting), only exporters, only importers, and non-traders. Extending the existing models of firm evolution in open economies by incorporating importing decision, I show that: i) globally engaged firms are larger, more productive, and grow faster than non-traders; ii) two-way traders are the fastest growing and most innovative group who are followed by only-exporters; iii) estimating export premium without controlling for import status is likely to overestimate the actual value by capturing the import premium; and iv) R&D investment contributes to growth of traders significantly more than to non-traders. Finally I show the robustness of the findings by providing evidence from the panel data constructed from the original dataset and controlling for variables that are likely to affect firm growth.
The Torpedo Effect Myth or Reality

General evidence indicates that managers manage earnings at three common earnings thresholds: analyst forecasts, prior period earnings, and zero earnings. We examine one market-based motivation suggested for this behavior. If managers perceive the market penalty for barely missing an earnings threshold to be disproportionately high (i.e., a torpedo effect), they may use discretion to manage earnings upward to meet the earnings threshold. This market-based incentive would explain the evidence in favor of earnings management at earnings thresholds. To test the existence of a torpedo effect, we employ a comprehensive model that measures the market’s reaction to reported earnings that barely miss earnings thresholds. This model controls for the level of unexpected earnings and several other firm characteristics known to affect the relation between returns and earnings. Overall, we conclude that there is little evidence of a torpedo effect. This conclusion holds for both low-growth and high-growth firms and is...
Scheduling Homogeneous Impatient Customers

Customer impatience has become an integral component of analyzing services, especially in the context of call centers. Typically, when customers arrive to such systems, they seem identical or homogeneous; however, from the system’s perspective, as they wait in the queue, their residual willingness to wait changes. For instance, a customer who has already waited for 10 minutes may have a different residual willingness to wait compared with a customer who has only waited for 1 minute. In this manner, as time progresses, customers become differentiated on their estimated patience levels. We exploit this dimension of customer heterogeneity to construct scheduling policies in overloaded systems that dynamically prioritize customers based on their time in queue to optimize any given system performance metric. Interestingly, the optimal policy has a very simple structure, and we find that implementing it can lead to significant improvements over the first-come, first-served policy. This paper was accepted by Noa...
Comment on “Aligning the Interests of Lawyers and Clients”

Polinsky and Rubinfeld (2003) propose a novel system for eliminating the conflict of interest between lawyers and clients over how hard the lawyer should work on a given case. In their analysis of the system, however, Polinsky and Rubinfeld implicitly assume that the lawyer's marginal cost of effort is common knowledge. This comment shows that, when this assumption is relaxed, though their scheme does reduce the agency problem relative to the standard contingency fee arrangement, it no longer eliminates it. Copyright 2004, Oxford University Press.
Bringing out the hook: Exit talk in media coverage of Hillary Clinton and past presidential campaigns

In this article the authors measure a phenomenon they name “exit talk”: the undertheorized pressures that second-place contenders for presidential nominations face to exit the race. Content analysis of media exit talk from the 2008 Clinton candidacy compared with that of key comparators from other modern presidential campaigns suggests that Clinton experienced greater levels of exit talk than her historical comparators, though less explicit pressure to exit than was exerted on Ronald Reagan in 1976. The authors also find that a higher percentage of Clinton exit talk was unattributed to its source. They investigate the potential causes for these findings and recommend further study of whether this heightened pressure to exit constitutes an unexamined hurdle for female presidential contenders.
PATENTS AS SIGNALS FOR STARTUP FINANCING

We examine the role of patents as signals used to reduce information asymmetries in entrepreneurial finance. A theoretical model gives conditions for a unique separating equilibrium in which startup founders file for patents to signal invention quality to investors, as well as appropriating value. The theory allows for heterogeneous investors and examines the optimal match of different types of startups, as defined by the quality of their technology, to investors who differ in the amount of non financial capital they provide. The empirical analysis is consistent with the model's predictions using a novel dataset of Israeli startups that received external funding during the period 1994–2011.
Multihoming within Platform Ecosystems: The Strategic Role of Human Capital

Platform ecosystems characterized by a few platform owners and numerous other complementor firms that partner with them have become quite common across industries. Even though there has been considerable research on platform ecosystems, attention has mostly been on the platform owners and their strategies. In this paper, we focus on the complementor firms and try to understand the phenomenon of multihoming, a strategy in which a complementor firm chooses to join multiple platforms rather than one. We build a micro-foundational capability framework based on human capital and test it on a novel dataset from the ERP platform ecosystem. The study has implications for our understanding of platform growth and innovation and contributes toward the literature on platform ecosystems as well as strategic human capital.
Changing nature of North–South linkages: Stylized facts and explanations

Abstract This paper examines the changing nature of growth spillovers between developed economies, the North, and developing countries, the South, driven by the process of globalization—the phenomenon of rising international trade and financial flows. We use a comprehensive database of macroeconomic and sectoral variables for 106 countries over the period 1960–2005. We consider the South to be composed of two groups of countries, the Emerging South and the Developing South, based on the extent of their integration into the global economy. Using a panel regression framework, we find that the impact of the Northern economic activity on the Emerging South has declined during the globalization period (1986–2005). In contrast, the growth linkages between the North and Developing South have been rather stable over time. Our findings also suggest that the North and Emerging South economies have started to exhibit more intensive intra-group growth spillovers.
Minerva unbound: Knowledge stocks, knowledge flows and new knowledge production ☆

Abstract Regional growth of new knowledge in nanotechnology, as measured by counts of articles and patents in the open-access digital library NanoBank, is shown to be positively affected both by the size of existing regional stocks of recorded knowledge in all scientific fields, and the extent to which tacit knowledge in all fields flows between institutions of different organizational types. The level of federal funding has a large, robust impact on both publication and patenting. The data provide support for the cumulative advantage model of knowledge production, and for ongoing efforts to institutionalize channels through which cross-organizational collaboration may be achieved.
Do Kidney Exchanges Improve Patient Outcomes

In this paper, I estimate the number of additional transplants generated by kidney exchanges. To do this, I analyze substitution patterns between exchange transplants and other transplant outcomes. Exploiting variation in patients' exposure to exchange activity across time and place, I find that 64 percent of exchange transplants represent new living donor transplants. Using the same approach, I find that an increase in the probability of receiving an exchange transplant reduces the probability of graft failure and reduces time spent waiting for a kidney. Back-of-the-envelope calculations suggest that each exchange transplant increases social welfare by $300,000 to $700,000.
Rambo as Potted Plant: Local Rulemaking's Preemptive Strike Against Witness-Coaching During Depositions

Several federal district courts have enacted rules that seek to preempt attorneys from interfering with the discovery process through improper "witness-coaching" by prohibiting an attorney from engaging in off-the-record consultation with his or her client-witness during the course of a deposition. Some argue that such rules intrude into the attorney-client relationship and relegate the role of the attorney to that of a "potted plant" for the sake of curbing the potential for discovery abuse. This article analyzes the varying formulations of the no-consultation rule and discusses how this seemingly innocuous rule is remarkable in two main respects. First, the rule represents much of what critics of local rulemaking have decried. Second, the no-consultation rule represents the nadir of attempts to regulate abusive attorney conduct by assuming that attorneys will act unethically if given the opportunity. Finally, this article discusses the proposition that where the district courts feel compelled to pursue this path, the best approach is the least intrusive one. The goals of the no-consultation rule can be accomplished simply by prohibiting attorney-client consultations while a question is pending. This approach prevents direct coaching of a witness as to a pending question, but allows for the legitimate uses of off-the-record conferences. Therefore, the functions of an attorney serving a client and aiding the tribunal are not unnecessarily supplanted.
The Constitution of Patent Law The Court of Customs and Patent Appeals and the Shape of the Federal Circuit's Jurisprudence

Recent critiques of the Court of Appeals for the Federal Circuit have focused on the court’s reluctance to embrace cohesive policy approaches in its patent jurisprudence, particularly when it comes to questions of patent scope. This Article suggests that the Federal Circuit’s tendency towards more formalistic decision-making derives in part from the jurisprudential heritage of one of its predecessor courts, the Court of Customs and Patent Appeals. The modern doctrines of patent scope were shaped by the CCPA’s decisions in the years following the 1952 Patent Act, especially its decisions interpreting §§ 103 and 112 of the Act. When the Federal Circuit adopted the CCPA’s precedent in its first decision, the CCPA’s law displaced that of other courts previously charged with administering aspects of the patent system. But the CCPA’s patent decisions were uniquely shaped by three imperatives peculiar to the court and its place in the patent system: the nature of the court itself; its need to exert and legitimize its control over Patent Office decisions; and its exclusive focus on patentability rather than patent enforcement. Though the modern Federal Circuit has far different jurisprudential needs than did the CCPA, the CCPA’s legal methodologies are so deeply engrained in patent law that they continue to shape Federal Circuit decision-making today. Those doctrines and methodologies may have served the CCPA well; but they may not answer the needs of the modern patent system.
Reconstructing the Blaine Amendments

In the wake of Zelman v. Simmons-Harris, 1 school choice proponents have turned their attention to state law obstacles, and in particular to the Blaine Amendments. Named after James G. Blaine, a xenophobic member of Congress who served in the House and Senate from 1863 to 1881, the Blaine Amendments are modeled after a federal constitutional amendment that Blaine introduced in the House in 1876. This proposed amendment would have applied the Religion Clauses to the states and prohibited them from allocating state funds and other resources to “sectarian” organizations, particularly religious elementary and secondary schools. 2 Although Congress never passed the federal Blaine Amendment, most of the states enacted similar provisions as part of their constitutions; thirty-seven of these are still on the books.
Joint risk of DB pension underfunding and sponsor termination: incorporating option-based projections and valuations into PIMS *

When a private pension plan sponsor with an underfunded plan becomes insolvent, the difference between the value of the plan's assets and its termination liabilities represents a liability for the Pension Benefit Guaranty Corporation (PBGC). Hence, accurately modeling the joint statistical distribution over time of defined benefit pension underfunding and sponsor terminations is critical for estimating PBGC's prospective cash flows and evaluating its financial position. It appears that the current Pension Insurance Modeling System (PIMS) approach to modeling risk does a reasonable job of capturing its statistical properties effects on PBGC cash flows, although some of the aspects might be improved, and metrics expanded. The present paper outlines, how an option-based approach to modeling the joint distribution of defaults and underfunding in PIMS might be implemented, while preserving the strengths of the current model. Moving to an option-based approach would allow PIMS to be used to estimate the fair values of future liabilities. Such an approach could have a significant effect on the perceived financial position of PBGC.
The Estimation and Determinants of Associations between Returns and Earnings: Evidence from Cross-Industry Comparisons

Associations between accounting earnings and stock returns are modeled and tested by examining relationships between earnings response coefficients and industry structure characteristics. Response coefficients are estimated using a new approach that does not require proxies for market earnings expectations. This approach appears to be well specified relative to a traditional approach and may have wider applicability in other research contexts. A randomization procedure for controlling for returns dependence is also applied. The results suggest that response coefficients differ considerably across industries and that these differences are related to industry entry barriers, product type, growth, financial leverage, and operating leverage.
Bounds on Derivative Prices in an Intertemporal Setting with Proportional Transaction Costs and Multiple Securities

The observed discrepancies of derivative prices from their theoretical, arbitrage-free values are examined in the presence of transaction costs. Analytic upper and lower bounds on the reservation write and purchase prices, respectively, are obtained when an investor's preferences exhibit constant relative risk aversion between zero and one. The economy consists of multiple primary securities with stationary returns, a constant rate of interest, and any number of American or European derivatives with, possibly, path-dependent arbitrary payoffs.