cssi/SciSciGPT-SciSciNet huggingface dataset:
A New Estimate of Transaction Costs

Transaction costs are important for a host of empirical analyses from market efficiency to international market research. But transaction costs estimates are not always available, or where available, are cumbersome to use and expensive to purchase. We present a model that requires only the time series of daily security returns to endogenously estimate the effective transaction costs for any firm, exchange, or time period. The feature of the data that allows for the estimation of transaction costs is the incidence of zero returns. Incorporating zero returns in the return-generating process, the model provides continuous estimates of average round-trip transaction costs from 1963 to 1990 that are 1.2% and 10.3% for large and small decile firms, respectively. These estimates are highly correlated (85%), with the most commonly used transaction cost estimators. How much does it cost to trade common stock? The Plexus Group (1996) estimated that trading costs are at least 1.0-2.0% of market value for institutions trading the largest NYSE/AMEX firms. Such trades account for more than 20% of reported trading volume. Stoll and Whaley (1983) reported quoted spread and commission costs of 2.0% for the largest NYSE size decile to 9.0% for the small decile. Bwardwaj and Brooks (1992) reported median quoted spread and commission costs between 2.0% for NYSE securities with prices greater than $20.00 and 12.5% for securities priced less than $5.00. These costs are important in determining investment performance and "can substantially reduce or possibly outweigh the expected value created by an investment strategy" [Keim and Madhavan (1995)]. This article is based on a portion of the first chapter of David A. Lesmond's dissertation entitled: "Trans
The option to withdraw IPOs during the premarket: empirical analysis

Abstract American IPOs are priced after a process of bookbuilding, during which issuers can withdraw at any time. We hypothesize that the option to withdraw reduces underpricing by strengthening the issuers’ bargaining power with respect to investors. Empirical analysis reveals that underpricing is lower when investor perception of an IPO's likelihood of withdrawal is higher. Withdrawing issuers are neither smaller nor less profitable than issuers completing their IPOs, and engage underwriters that are as reputable as those managing completed offerings. Withdrawal is correlated with leverage, intended use of proceeds, expected issue size, venture backing, revenues, NASDAQ returns, and IPO activity.
Ultrafast mid-infrared intra-excitonic response of individualized single-walled carbon nanotubes

We report ultrafast mid-infrared studies of individualized semiconducting carbon nanotubes. Transient spectra of (6,5) and (7,5) nanotubes evidence photoinduced absorption around 200 meV, associated with intra-excitonic transitions that reflect quasi-1D exciton correlations and dynamics.
Who Blinks in Volatile Markets, Individuals or Institutions?

We investigate the relationship between the ownership structure and returns of firms on days when the absolute value of the market's return is two percent or more. We find that a firm's abnormal return on these days is related to the percentage of institutional ownership, that there is abnormally high turnover in the firm's shares on these days, and that this abnormal turnover is significantly related to the percentage of institutional ownership in the firm. Taken together, these results are consistent with positive feedback herding behavior on the part of some institutions, particularly mutual and pension funds. WHO SELLS WHEN THERE IS A LARGE DROP in the stock market, institutional or individual investors? The answer is not clear. One could argue that individual investors are less sophisticated and more risk averse than institutions, so the individual investor is the one who reacts and sells during a sharp market drop. Alternatively, one could argue that institutional investors, although they are more sophisticated, have short horizons. Because of this, they herd together with their peers and sell during a market decline, since "an unprofitable decision is not as bad for reputation when others make the same mistake" (Scharfstein and Stein (1990) and Froot, Scharfstein, and Stein (1992)). Individuals, who may make decisions based on longer-term criteria (Markowitz (1991)), would be less likely to react during short-term market swings. The answer to the question of who sells during large market swings is important since it helps us to understand the dynamics associated with large swings in stock prices and the sources of market volatility. We address this question by examining the returns of stocks on days when the absolute value of the market's return is large, defined as two percent or more. We have four main findings. First, if institutional investors are selling
Inverse probability weighting for covariate adjustment in randomized studies.

Covariate adjustment in randomized clinical trials has the potential benefit of precision gain. It also has the potential pitfall of reduced objectivity as it opens the possibility of selecting “favorable” model that yields strong treatment benefit estimate. Although there is a large volume of statistical literature targeting on the first aspect, realistic solutions to enforce objective inference and improve precision are rare. As a typical randomized trial needs to accommodate many implementation issues beyond statistical considerations, maintaining the objectivity is at least as important as precision gain if not more, particularly from the perspective of the regulatory agencies. In this article, we propose a two-stage estimation procedure based on inverse probability weighting to achieve better precision without compromising objectivity. The procedure is designed in a way such that the covariate adjustment is performed before seeing the outcome, effectively reducing the possibility of selecting a “favorable” model that yields a strong intervention effect. Both theoretical and numerical properties of the estimation procedure are presented. Application of the proposed method to a real data example is presented.
On Explicit Algebraic Stress Models for Complex Turbulent Flows

Explicit algebraic stress models that are valid for three-dimensional turbulent flows in noninertial frames are systematically derived from a hierarchy of second-order closure models. This represents a generalization of the model derived by Pope who based his analysis on the Launder, Reece, and Rodi model restricted to two-dimensional turbulent flows in an inertial frame. The relationship between the new models and traditional algebraic stress models -- as well as anistropic eddy visosity models -- is theoretically established. The need for regularization is demonstrated in an effort to explain why traditional algebraic stress models have failed in complex flows. It is also shown that these explicit algebraic stress models can shed new light on what second-order closure models predict for the equilibrium states of homogeneous turbulent flows and can serve as a useful alternative in practical computations.
Concise Total Synthesis of (+)-Bionectins A and C.

The concise and efficient total synthesis of (+)-bionectins A and C is described. Our approach to these natural products features a new and scalable method for erythro-β-hydroxytryptophan amino acid synthesis, an intramolecular Friedel–Crafts reaction of a silyl-tethered indole, and a new mercaptan reagent for epipolythiodiketopiperazine (ETP) synthesis that can be unravelled under very mild conditions. In evaluating the impact of C12-hydroxylation, we have identified a unique need for an intramolecular variant of our Friedel–Crafts indolylation chemistry. Several key discoveries including the first example of permanganate-mediated stereoinvertive hydroxylation of the α-stereocenters of diketopiperazines as well as the first example of a direct triketopiperazine synthesis from a parent cyclo-dipeptide are discussed. Finally, the synthesis of (+)-bionectin A and its unambiguous structural assignment through X-ray analysis provides motivation for the reevaluation of its original characterization data and assignment.
The Effect of Winds and Bodily Tides on the Annual Variation in the Length of Day

Summary The effect of winds is to vary the length of day by 0.7 milliseconds between February and August. The bodily tides result largely in a semiannual variation of 0.4 ms. The combined effect of winds and tides is not far out of line with astronomical measurements since 1950. The fluid core of the Earth hardly participates in these variations in angular velocity and there is a half-year slippage of 23 metres between core and mantle at the equator. Eventually the astronomical measurements may provide a basis for determining the Love number h.
Recent conceptual advances in the catalysis science of mixed metal oxide catalytic materials

The catalysis science of mixed metal oxides (supported metal oxides, molecular sieves and bulk mixed metal oxides) has undergone dramatic paradigm changes over the past 25 years as new characterization techniques became available (X-ray absorption spectroscopy (EXAFS/XANES/soft XANES), Raman, solid-state NMR, HR-TEM, UV–vis DRS and LEISS) to catalysis researchers. The major advantages offered by these spectroscopic improvements are that (1) they can detect XRD inactive amorphous surface metal oxide phases as well as crystalline nanophases and (2) their ability to collect information under various environmental conditions. Application of these spectroscopic techniques to the investigation of mixed metal oxide catalysts have provided new fundamental insights into the electronic and molecular structures of mixed metal oxide catalytic active sites and how they control the catalytic activity and selectivity characteristics. The most significant discovery has been that amorphous metal oxide phases are always present and are the catalytic active sites for many applications of mixed metal oxide catalysts. This has resulted in a significant paradigm shift as to how mixed metal oxide catalytic materials function for different applications. This article reviews the instrumental advances and the resulting conceptual advances that have evolved over the past 25 years in the catalysis science of mixed metal oxide catalysts. # 2004 Elsevier B.V. All rights reserved.
VEHICLE DYNAMICS MODEL FOR ESTIMATING MAXIMUM LIGHT-DUTY VEHICLE ACCELERATION LEVELS

A vehicle dynamics model for predicting maximum light-duty vehicle accelerations for use within a microscopic traffic simulation environment is presented and validated. The research also constructs a database of unconstrained vehicle acceleration data for 13 light-duty vehicles and trucks. With the use of the field data, the proposed vehicle dynamics model is validated and compared with a number of state-of-the-art vehicle acceleration models, including the Searle model and the dual-regime, linear decay, and polynomial models. The advantages of the proposed model include its ability to predict vehicle behavior accurately with readily available input parameters and its flexibility in estimating acceleration rates of both large and small vehicles on varied types of terrain.
Lymph Node Ratio Predicts Recurrence in Papillary Thyroid Cancer

BACKGROUND Lymph node metastasis occurs in 20%-50% of patients presenting for initial treatment of papillary thyroid cancer (PTC). The significance of lymph node metastases remains controversial, and the aim of this study is to determine how the lymph node ratio (LNR) may predict the likelihood of disease recurrence. METHODS We conducted a retrospective review of patients undergoing total thyroidectomy for PTC at our institution from 2005 to 2010. A total LNR (positive nodes to total nodes) and central lymph node ratio (cLNR) was calculated. Regression was used to determine a threshold LNR that best predicted recurrence. Multivariate logistic regression then determined the influence of LNR on recurrence while accounting for other known predictors of recurrence. Kaplan-Meier analysis and the log-rank test were used to compare differences in disease-free survival. RESULTS Of the 217 patients undergoing total thyroidectomy for PTC, 69 patients had concomitant neck dissections. Sixteen (23.2%) patients developed disease recurrence. When disease-free survival functions were compared, we found that patients with a total LNR ≥0.7 (p < .01) or a cLNR ≥0.86 (p = .04) had significantly worse disease-free survival rates than patients with ratios below these threshold values. Considering other known predictors of recurrence, we found that LNR was significantly associated with recurrence (odds ratio: 19.5, 95% confidence interval: 4.1-22.9; p < .01). CONCLUSIONS Elevated total LNR and cLNR are strongly associated with recurrence of PTC after initial operation. LNR in PTC is a tool that can be used to determine the likelihood of the patient developing recurrent disease and inform postoperative follow-up.
Cyanocarbons—Their History From Conducting to Magnetic Organic Charge Transfer Salts

Abstract A generation ago scientists at Du Pont's Central Research and Development Department sought to prepare, understand, and exploit organic molecules lacking aliphatic hydrogens and possessing a large cyano group to carbon ratio. Like many other ambitious quests the anticipated goal (of commercializing a new family of polymers) was not realized. Nonetheless, the discoveries made during this pursuit have made a permanent mark on the evolution of science. Most notably, the discovery of tetracyanoethylene (TCNE), and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), and the remarkable stability of their radical anions led to an unusual series of charge transfer salts. Many of the TCNQ electron-transfer salts exhibit high, metal-like, dc electrical conductivity. These initial observations led to the evolutionary development of conducting polymers and the realization of molecular based ferromagnets.
Is health recognized in the EU's policy process? An analysis of the European Commission's impact assessments

Background: The European Commission has an Impact Assessment (IA) procedure that aims to inform decision-makers of the all important impacts that decisions may have. This article studies how health is considered in the IA procedure and how it is reflected in the reports: what aspects, whose and simply in what context health is mentioned in the IA reports. Methods: Half of the Commissions IAs from 2006 were studied. The analysis was text based and informed by content analysis. In total, 48 reports by 17 DGs were analysed. Results: Five DGs (29%) and 10 reports (21%) made no reference to human health, public health or health systems. Five DGs were clearly considering health impacts more often than others; DG EMPL, SANCO, AGRI, ELARG and ENV. Health systems/services were most often and human health next most common referred to (39% and 29% of all, respectively). Health impacts were usually referred to in the sections on the definition of problems and the analysis of impacts. Seldom were they reported on in the sections on policy options, comparing options, or in the monitoring and evaluation sections. Conclusion: The results partly support concerns about the potential neglect of health impacts. The results also suggest that health is not considered an important factor when discussing alternative policy choices, and neither does it seem to be an important objective. There is a clear need for further exploration on ways in which health could be more appropriately considered when impacts of other policies are considered by the various DGs.
Parallel repetition: simplifications and the no-signaling case

Consider a game where a refereed chooses (x,y) according to a publiclyknown distribution PXY, sends x to Alice, and y to Bob. Withoutcommunicating with each other, Alice responds with a value "a" and Bobresponds with a value "b". Alice and Bob jointly win if a publiclyknown predicate Q(x,y,a,b) holds. Let such a game be given and assume that the maximum probabilitythat Alice and Bob can win is v
Amplification mechanism in the output section of the harmonic multiplying gyrotron traveling wave amplifier

Summary form only given. Particle-in-cell code simulations have been carried out to investigate the physical mechanism responsible for the wave amplification in the output section of a harmonic-multiplying gyrotron traveling-wave tube. Simulation results demonstrate that the injected signal frequency plays an important role in determining the wave growth process. This is because the initial frequency mismatch in the input section influences the extent of bunching at the entrance of the output section and the slope of the electron phase trajectory. For a small frequency mismatch, the amplification arises entirely from the second harmonic generation due to the bunching at the fundamental frequency. As the mismatch is increased, the bunched electrons start to disperse early in the output section; and the wave amplification is then dominated by the cyclotron maser instability. The electron velocity spread is observed to substantially degrade the device performance. By using the combination of a waveguide input section (L/sub i/, TE/sub 02/) that amplifies the input signal at the fundamental cyclotron frequency, a drift section (L/sub d/), and an output waveguide section (L/sub 0/, TE/sub 03/) that generates the output wave at the second harmonic cyclotron frequency, the bandwidth of the phigtron can be substantially improved. The above harmonic-multiplying scheme made the source for the input signal more readily available, reduces the magnetic weight requirement, and alleviates the stability problem.
The influence of sodium and potassium dynamics on excitability, seizures, and the stability of persistent states: II. Network and glial dynamics

In these companion papers, we study how the interrelated dynamics of sodium and potassium affect the excitability of neurons, the occurrence of seizures, and the stability of persistent states of activity. We seek to study these dynamics with respect to the following compartments: neurons, glia, and extracellular space. We are particularly interested in the slower time-scale dynamics that determine overall excitability, and set the stage for transient episodes of persistent oscillations, working memory, or seizures. In this second of two companion papers, we present an ionic current network model composed of populations of Hodgkin-Huxley type excitatory and inhibitory neurons embedded within extracellular space and glia, in order to investigate the role of micro-environmental ionic dynamics on the stability of persistent activity. We show that these networks reproduce seizure-like activity if glial cells fail to maintain the proper micro-environmental conditions surrounding neurons, and produce several experimentally testable predictions. Our work suggests that the stability of persistent states to perturbation is set by glial activity, and that how the response to such perturbations decays or grows may be a critical factor in a variety of disparate transient phenomena such as working memory, burst firing in neonatal brain or spinal cord, up states, seizures, and cortical oscillations.
Automatic data structure choice in a language of very high level

SETL is a set-theoretically oriented language of very high level whose repertoire of semantic objects includes finite sets, ordered n-tuples, and sets of ordered n-tuples useable as mappings. This paper sets forth techniques for the logical analysis and optimization of SETL programs. The techniques described allow relations of inclusion and membership to be established, the domains and ranges of (tabulated) mappings to be estimated from above and below, and the singlevaluedness of (tabulated) mappings to be proved. Once facts of this kind have been established, automatic choice of data structures becomes possible. The methods employed are based upon, and extend, known techniques of data-flow analysis.
All-optical retrieval of the global phase for two-dimensional Fourier-transform spectroscopy

A combination of spatial interference patterns and spectral interferometry are used to find the global phase for non-collinear two-dimensional Fourier-transform (2DFT) spectra. Results are compared with those using the spectrally resolved transient absorption (STRA) method to find the global phase when excitation is with co-linear polarization. Additionally cross-linear polarized 2DFT spectra are correctly “phased” using the all-optical technique, where the SRTA is not applicable.
Reflecting on the Rule of Law: Its Reciprocal Relation with Rights, Legitimacy, and Other Concepts and Institutions

Arguments concerning law and social change call for a relationship between legitimacy, the rule of law, and respect for rights. To the extent that a government is subject to the rule of law, the human and civil rights of its citizens are advanced. When citizens can bring disputes concerning rights to court rather than fight in the streets, the rule of law is enhanced. Respect for rights and the rule of law are likely to make a government more acceptable and hence more legitimate. A basic requirement of legitimacy is that government advance everyone's share of primary social goods, their opportunity to participate in society and hence their basic rights. Rights are not only statements of ideals or entitlements but goals and tools for pursuit of those goals, means for pursuing law reform, advancing the rule of law, and enhancing society's legitimacy.
Finite difference computation of acoustic scattering by small surface inhomogeneities and discontinuities

The use of finite difference schemes to compute the scattering of acoustic waves by surfaces made up of different materials with sharp surface discontinuities at the joints would, invariably, result in the generations of spurious reflected waves of numerical origin. Spurious scattered waves are produced even if a high-order scheme capable of resolving and supporting the propagation of the incident wave is used. This problem is of practical importance in jet engine duct acoustic computation. In this work, the basic reason for the generation of spurious numerical waves is first examined. It is known that when the governing partial differential equations of acoustics are discretized, one should only use the long waves of the computational scheme to represent or simulate the physical waves. The short waves of the computational scheme have entirely different propagation characteristics. They are the spurious numerical waves. A method by which high wave number components (short waves) in the wave scattering process is intentionally removed so as to minimize the scattering of spurious numerical waves is proposed. This method is implemented in several examples from computational aeroacoustics to illustrate its effectiveness, accuracy and efficiency. This method is also employed to compute the scattering of acoustic waves by scatterers, such as rigid wall acoustic liner splices, with width smaller than the computational mesh size. Good results are obtained when comparing with computed results using much smaller mesh size. The method is further extended for applications to computations of acoustic wave reflection and scattering by very small surface inhomogeneities with simple geometries.
Asymmetric Diels-Alder Reactions Catalyzed by a Triflic Acid Activated Chiral Oxazaborolidine

This paper reports a new method for the generation of chiral Lewis superacids by protonation of a non-Lewis acidic oxazaborolidine (1) with triflic acid. The resulting cationic species (3) are powerful and highly enantioselective catalysts for the Diels−Alder reaction of various 1,3-dienes with α,β-enals. An optimization study (see Table 1) led to the selection of reaction conditions and catalysts (6A and 6B) which are very effective. The reactions are simple to conduct, reproducible, and economical, since only ca. 6 mol % of catalyst is required. In addition, the chiral catalyst precursor is readily recovered for reuse (>95% efficiency) and is commercially available. The broad scope of the process is documented by the 14 examples listed in Table 2. The absolute stereochemical course of the Diels−Alder reactions catalyzed by 6A and 6B was successfully predicted on the basis of the mechanistic principles which have recently been formulated for this type of catalytic enantioselective reaction involving re-f...
Simple models of the protein folding problem

Abstract The protein folding problem has attracted an increasing attention from physicists. The problem has a flavor of statistical mechanics, but possesses the most common feature of most biological problems – the profound effects of evolution. I will give an introduction to the problem, and then focus on some recent work concerning the so-called “designability principle”. The designability of a structure is measured by the number of sequences that have that structure as their unique ground state. Structures differ drastically in terms of their designability; highly designable structures emerge with a number of associated sequences much larger than the average. These highly designable structures (1) possess “protein-like” secondary structures and motifs, (2) are thermodynamically more stable, (3) fold faster than other structures. These results suggest that protein structures are selected in nature because they are readily designed and stable against mutations, and that such selection simultaneously leads to thermodynamic stability and foldability. According to this picture, a key to the protein folding problem is to understand the emergence and the properties of the highly desginable structures.
Secrecy coverage in two dimensions

Working in the infinite plane R2, consider a Poisson process of black points with intensity 1, and an independent Poisson process of red points with intensity λ. We grow a disc around each black point until it hits the nearest red point, resulting in a random configuration Aλ, which is the union of discs centered at the black points. Next, consider a fixed disc of area n in the plane. What is the probability pλ(n) that this disc is covered by Aλ? We prove that if λ3nlogn = y then, for sufficiently large n, e-8π2y ≤ pλ(n) ≤ e-2π2y/3. The proofs reveal a new and surprising phenomenon, namely, that the obstructions to coverage occur on a wide range of scales.
Integrating formal verification into an advanced computer architecture course

This paper presents a sequence of three projects on design and formal verification of pipelined and superscalar processors: 1) a single-issue, five-stage DLX (an academic processor used widely for teaching pipelined execution and defined by Hennessy and Patterson in the first edition of their graduate textbook); 2) an extension of the DLX with exceptions and branch prediction; and 3) a dual-issue superscalar DLX. The projects were integrated into two editions of an advanced computer architecture course that was offered at the Georgia Institute of Technology, Atlanta, in the summer and fall 2002 and was taught to 67 students (25 of whom were undergraduates) in a way that required them to have no prior knowledge of formal methods. Preparatory homework problems included an exercise on design and formal verification of a staggered Arithmetic Logic Unit (ALU), pipelined in the style of the integer ALUs in the Intel Pentium 4. The processors were designed and formally verified with a tool flow that was used to formally verify the M/spl middot/CORE processor at Motorola and detected bugs.
Precipitation in neutron-irradiated Fe-Cu and Fe-Cu-Mn model alloys : a comparison of APT and SANS data

Abstract The size, number density and compositions of ultrafine copper–manganese precipitates that form in Fe–0.80at.% Cu and Fe–0.78at.% Cu–1.05at.% Mn model alloys that were neutron irradiated to a fluence of ∼1×1023 nm−2 (E>1 MeV) at 288 °C have been estimated by atom probe tomography and small-angle neutron scattering (SANS) experiments. The number density of precipitates was approximately an order of magnitude higher in the Fe–Cu–Mn alloy than in the Fe–Cu alloy. A direct comparison of the microstructural parameters estimated by each technique revealed good agreement between the radii of gyration and the number densities. However, the copper content in precipitates inferred from SANS was significantly higher than estimated from the atom probe results.
Soliton squeezing at GHz rate in a Sagnac loop

We demonstrate the first all-fiber squeezing experiment at room temperature. A record 6.1+/-0.2 dB of noise reduction below shot noise has been obtained without stabilization. When loss is taken into account, /spl sim/11 dB of squeezing is inferred.
Formation of fullerides and fullerene-based heterostructures.

Two potassium fulleride phases, metallic K3C60 and nonmetallic K6C60, are formed when potassium is incorporated into thin C60 films under ultrahigh vacuum conditions. Phase separation is observed for intermediate stoichiometries. Results obtained for the C60-K3C60 heterostructure demonstrate that it is stable against potassium migration from the K3C60 phase. In contrast, the C60-K6C60 interface is not stable and K3C60 is formed.
An Iterative Algorithm to Build Chinese Language Models

We present an iterative procedure to build a Chinese language model (LM). We segment Chinese text into words based on a word-based Chinese language model. However, the construction of a Chinese LM itself requires word boundaries. To get out of the chicken-and-egg problem, we propose an iterative procedure that alternates two operations: segmenting text into words and building an LM. Starting with an initial segmented corpus and an LM based upon it, we use a Viterbi-liek algorithm to segment another set of data. Then, we build an LM based on the second set and use the resulting LM to segment again the first corpus. The alternating procedure provides a self-organized way for the segmenter to detect automatically unseen words and correct segmentation errors. Our preliminary experiment shows that the alternating procedure not only improves the accuracy of our segmentation, but discovers unseen words suprisingly well. The resulting word-based LM has a perplexity of 188 for a general Chinese corpus.
Deriving Feeder Cattle Pricing Contracts from Fed Cattle Price Grids: Simulation Results of Risk-Sharing Contracts

Post-slaughter quality-based pricing of cattle is increasingly common. This quality, however, is dependent upon unobservable quality characteristics of the feeder cattle used as inputs. Through stochastic simulation we construct incentive compatible quality risk-sharing contracts based upon final grid-quality schedules that facilitate input quality sorting in the feeder cattle market.
Room‐Temperature KIc Values for Single‐Crystal and Polycrystalline MgAl2O4

The Klc values for (100), (110), and (111) single-crystal MgAl2O4 as well as those for polycrystalline MgAl2O4 with transgranular and intergranular fractures are presented and discussed on the basis of their elastic moduli. It is observed that the single-crystal toughnesses are directly related to the elastic modulus. Polycrystalline and single-crystal toughnesses are comparable; however, the intergranular fracture has the lowest toughness.
Entry regulation as a barrier to entrepreneurship

Abstract Using a comprehensive database of European firms, we study the effect of market entry regulations on the creation of new limited-liability firms, the average size of entrants, and the growth of incumbent firms. We find that costly regulations hamper the creation of new firms, especially in industries that should naturally have high entry. These regulations also force new entrants to be larger and cause incumbent firms in naturally high-entry industries to grow more slowly. Our results hold even when we correct for the availability of financing, the degree of protection of intellectual property, and labor regulations.
Predicting semantic changes in abstraction in tutor responses to students

Post-problem reflective tutorial dialogues between human tutors and students are examined to predict when the tutor changed the level of abstraction from the student's preceding turn (i.e., used more general terms or more specific terms); such changes correlate with learning. Prior work examined lexical changes in abstraction. In this work, we consider semantic changes. Since we are interested in developing a fully-automatic computer-based tutor, we use only automatically-extractable features (e.g., percent of domain words in student turn) or features available in a tutoring system (e.g., correctness). We find patterns that predict tutor changes in abstraction better than a majority class baseline. Generalisation is best-predicted using student and reflection features. Specification is best-predicted using student and problem features.
A Hilbert Space Approach to Effective Resistance Metric

A resistance network is a connected graph (G, c). The conductance function c xy weights the edges, which are then interpreted as conductors of possibly varying strengths. The Dirichlet energy form $${\mathcal E}$$ produces a Hilbert space structure (which we call the energy space $${{\mathcal H}_{\mathcal E}}$$ ) on the space of functions of finite energy. We use the reproducing kernel {v x } constructed in a previous work to analyze the effective resistance R, which is a natural metric for such a network. It is known that when (G, c) supports nonconstant harmonic functions of finite energy, the effective resistance metric is not unique. The two most natural choices for R(x, y) are the “free resistance” R F , and the “wired resistance” R W . We define R F and R W in terms of the functions v x (and certain projections of them). This provides a way to express R F and R W as norms of certain operators, and explain R F ≠ R W in terms of Neumann versus Dirichlet boundary conditions. We show that the metric space (G, R F ) embeds isometrically into $${{\mathcal H}_{\mathcal E}}$$ , and the metric space (G, R W ) embeds isometrically into the closure of the space of finitely supported functions; a subspace of $${{\mathcal H}_{\mathcal E}}$$ . Typically, R F and R W are computed as limits of restrictions to finite subnetworks. A third formulation R tr is given in terms of the trace of the Dirichlet form $${\mathcal E}$$ to finite subnetworks, and is related to R F by a probabilistic argument.
Finite density lattice gauge theories with positive fermion determinants

We perform simulations of (3-colour) QCD with 2 quark flavours at a finite chemical potential μ 1 for isospin (I 3 ), and of 2-colour QCD at a finite chemical potential μ for quark number. At zero temperature, QCD at finite μ I has a mean-field phase transition at μ I = m π to a superfluid state with a charged pion condensate which spontaneously breaks I 3 . We study the finite temperature transition as a function of μ I . For μ I m π this becomes a true phase transition where the pion condensate evaporates. For μ I just above m π the transition seems to be second order, while for larger μ I it appears to become first order. At zero temperature, 2-colour QCD also possesses a superfluid state with a diquark condensate. We study its spectrum of Goldstone and pseudo-Goldstone bosons associated with chiral and quark-number symmetry breaking.
Deriving N=2 S-dualities from scaling for product gauge groups

Abstract S-dualities in scale invariant N=2 supersymmetric field theories with product gauge groups are derived by embedding those theories in asymptotically free theories with higher rank gauge groups. S-duality transformations on the couplings of the scale invariant theory follow from the geometry of the embedding of the scale invariant theory in the Coulomb branch of the asymptotically free theory.
TIME SERIES ANALYSIS AND SIMULTANEOUS EQUATION ECONOMETRIC MODELS

In this paper we take up the analysis of dynamic simultaneous equation models (SEM’s) within the context of general linear multiple time series processes such as studied by Quenouille (1957). As noted by Quenouille, if a set of variables is generated by a multiple time series process, it is often possible to solve for the processes generating individual variables, namely the ‘final equations’ of Tinbergen (1940), and these are in the autoregressive-moving average (ARMA) form. ARMA processes have been studied intensively by Box and Jenkins (1970). Further, if a general multiple time series process is appropriately specialized, we obtain a usual dynamic SEM in structural form. By algebraic manipulations, the associated reduced form and transfer function equation systems can be derived. In what follows, these equation systems are presented and their properties and uses are indicated. It will be shown that assumptions about variables being exogenous, about lags in structural equations of SEM’s, and about serial correlation properties of structural disturbance terms have strong implications for the properties of transfer functions and final equations that can be tested. Further, we show how large sample posterior odds and likelihood ratios can be used to appraise alternative hypotheses. In agreement with Pierce and Mason (1971), we believe that testing the implications of structural assumptions for transfer functions and, we add, final equations is an important element in the process of iterating in on a model that is reasonably in accord with the information in a sample of data. To illustrate these general points and to provide applications of the above methods, a
Distributed wireless channel allocation in networks with mobile base stations

In traditional cellular networks with fixed base stations, the channel reuse pattern is static and deterministic. When the cell layout is dynamic, due to the mobility of base stations, the cluster of cells within cochannel interference range changes with time. Consequently, the channel reuse pattern is highly dynamic. Moreover, base stations also need wireless channels to communicate amongst themselves. A communication session between a pair of nodes may have to switch channels due to the movement of other nodes into the neighborhood. None of the existing dynamic channel allocation algorithms for cellular networks works in such a system. Hence, there is a need for new wireless channel allocation algorithms for virtual cellular networks with mobile base stations. In this paper, principles of mutual exclusion pertaining to distributed computing systems are employed to develop such an algorithm. The inter-base-station wireless links are referred to as backbone links, while the base station to mobile node links are referred to as short-hop links. The proposed algorithm is distributed, dynamic, and deadlock-free. Disjoint sets of channels are used for backbone and short-hop links. The distributed nature of the channel allocation scheme leads to scalability and robustness, as the responsibility is no longer centralized at the mobile telecommunications switching office (MTSO). Instead, it is shared among all the mobile base stations. In addition, the issue of channel rearrangement is addressed. Channel rearrangement is the switching of channels, performed to prevent cochannel interference, when mobile base stations using the same channels, hitherto not in interference range, come within the range of each other. If multiple channels are available to support a communication session, the channel selection policy can have a significant impact on performance. A random selection from the set of available channels yields better performance at low to moderate channel demand. This is in contrast to ordered channel selection (from one end of the spectrum), which always yields the best performance for cellular networks. Results obtained by simulating the algorithm are consistent with the theoretically obtained values.
EIGENCONE, SATURATION AND HORN PROBLEMS FOR SYMPLECTIC AND ODD ORTHOGONAL GROUPS

In this paper we consider the eigenvalue problem, intersection theory of homogeneous spaces (in particular, the Horn problem) and the saturation problem for the symplectic and odd orthogonal groups. The classical embeddings of these groups in the special linear groups play an important role. We deduce properties for these classical groups from the known properties for the special linear groups.
Masked Uncontrolled Hypertension in CKD

Masked uncontrolled hypertension (MUCH) is diagnosed in patients treated for hypertension who are normotensive in the clinic but hypertensive outside. In this study of 333 veterans with CKD, we prospectively evaluated the prevalence of MUCH as determined by ambulatory BP monitoring using three definitions of hypertension (daytime hypertension ≥135/85 mmHg; either nighttime hypertension ≥120/70 mmHg or daytime hypertension; and 24-hour hypertension ≥130/80 mmHg) or by home BP monitoring (hypertension ≥135/85 mmHg). The prevalence of MUCH was 26.7% by daytime ambulatory BP, 32.8% by 24-hour ambulatory BP, 56.1% by daytime or night-time ambulatory BP, and 50.8% by home BP. To assess the reproducibility of the diagnosis, we repeated these measurements after 4 weeks. Agreement in MUCH diagnosis by ambulatory BP was 75-78% (κ coefficient for agreement, 0.44-0.51), depending on the definition used. In contrast, home BP showed an agreement of only 63% and a κ coefficient of 0.25. Prevalence of MUCH increased with increasing clinic systolic BP: 2% in the 90-110 mmHg group, 17% in the 110-119 mmHg group, 34% in the 120-129 mmHg group, and 66% in the 130-139 mmHg group. Clinic BP was a good determinant of MUCH (receiver operating characteristic area under the curve 0.82; 95% confidence interval 0.76-0.87). In diagnosing MUCH, home BP was not different from clinic BP. In conclusion, among people with CKD, MUCH is common and reproducible, and should be suspected when clinic BP is in the prehypertensive range. Confirmation of MUCH diagnosis should rely on ambulatory BP monitoring.
GUTs and exceptional branes in F-theory — I

Motivated by potential phenomenological applications, we develop the necessary tools for building GUT models in F-theory. This approach is quite flexible because the local geometrical properties of singularities in F-theory compactifications encode the physical content of the theory. In particular, we show how geometry determines the gauge group, matter content and Yukawa couplings of a given model. It turns out that these features are beautifully captured by a four-dimensional topologically twisted = 4 theory which has been coupled to a surface defect theory on which chiral matter can propagate. From the vantagepoint of the four-dimensional topological theory, these defects are surface operators. Specific intersection points of these defects lead to Yukawa couplings. We also find that the unfolding of the singularity in the F-theory geometry precisely matches to properties of the topological theory with a defect.
Minimum Energy Tracking Loop With Embedded DC–DC Converter Enabling Ultra-Low-Voltage Operation Down to 250 mV in 65 nm CMOS

Minimizing the energy consumption of battery-powered systems is a key focus in integrated circuit design. This paper presents an energy minimization loop, with on-chip energy sensor circuitry, that can dynamically track the minimum energy operating voltage of arbitrary digital circuits with changing workload and operating conditions. An embedded DC-DC converter which enables this minimum energy operation is designed to deliver load voltages between 0.25 V to 0.7 V. The minimum energy tracking loop along with the DC-DC converter and test circuitry were fabricated in a 65 nm CMOS process. The area overhead of the control loop is only 0.05 mm2. Measured energy savings of the order of 50%-100% are obtained on tracking the minimum energy point (MEP) as it varies with workload and temperature. The DC-DC converter delivers load voltages as low as 250 mV and achieved an efficiency >80% while delivering load powers of the order of 1 muW and higher from a 1.2 V supply.
THE GEOMETRY OF RESONANT SIGNATURES IN DEBRIS DISKS WITH PLANETS

Using simple geometrical arguments, we paint an overview of the variety of resonant structures a single planet with moderate eccentricity (e<approx.0.6) can create in a dynamically cold, optically thin dust disk. This overview may serve as a key for interpreting images of perturbed debris disks and inferring the dynamical properties of the planets responsible for the perturbations. We compare the resonant geometries found in the solar system dust cloud with observations of dust clouds around Vega, Epsilon Eridani, and Fomalhaut.
Political mergers as coalition formation: An analysis of the Heisei municipal amalgamations

In Japan, a formula‐based transfer system resulted in local benefits from municipal mergers differing substantially from national benefits. A change in this transfer policy and the mergers that resulted are analyzed using a structural model involving private consumption, public good quality, and geographic distance, along with an asymmetric information problem between the national and local levels of government. The merger process is modeled using a cooperative form coalition formation game. Parameter estimates are obtained using a moment inequalities approach that requires neither an equilibrium selection assumption nor the enumeration of all possible mergers. Estimates suggest that the actual merger incentives the national government offered were weak relative to the optimal incentives, and the post‐merger number of municipalities were large relative to the optimal number. Municipal amalgamation moment inequalities stable set Japan D71 D82 H77
American Time-Styles: A Finite-Mixture Allocation Model for Time-Use Analysis

Time-use has already been the subject of numerous studies across multiple disciplines such as economics, marketing, sociology, transportation and urban planning. However, most of this research has focused on comparing demographic groups on a few broadly defined activities (e.g., work for pay, leisure, housework, etc.). In this study we take a holistic perspective, identifying a typology of latent “time-styles,” that defines the different ways people allocate the 24 hr in a day across multiple competing daily activities. We propose a finite-mixture time-allocation model that accounts for differences in life priorities across individuals, taking into consideration the fact that we all have the same “budget” of 24 hr to spend every day and that this allocation leads to highly sparse, truncated data. This model is then applied to time-use data from the American Time Use Survey collected by the U.S. Bureau of Labor Statistics in 2006.
A diversity combining DS/CDMA system with convolutional encoding and Viterbi decoding

Averaged diversity combining is applied to an asynchronous DS/CDMA system using convolutional encoding and Viterbi decoding. A cyclic redundancy check (CRC) code is included in the scheme to trigger retransmission requests. Multiple received packets are combined on a bit by bit basis to form a single, more reliable packet. The error correcting decoder operates on the combined packet, as opposed to the most recently received individual packet (e.g., as in a type-I hybrid ARQ protocol), substantially increasing the probability of acceptance with each additional transmission. We show that the proposed technique allows a significant increase in the CDMA system capacity, throughput, and reliability. >
Large-scale electron acceleration by parallel electric fields during magnetic reconnection

Magnetic reconnection is a process by which the field lines of a magnetized plasma undergo dramatic realignment, releasing large amounts of energy. Large-scale simulations of reconnection events in the Earth’s magnetosphere suggest that this process takes place over much greater distances than previously expected.