cssi/SciSciGPT-SciSciNet huggingface dataset:
String dualities from Matrix theory

Abstract We suggest that the (2,0) six-dimensional field theory compactified on S1 × K3 is the Matrix model description of both M-theory on K3 and the heterotic string on T3. This proposal is different from existing proposals for the heterotic theory. Different limits of the base-space geometry give the different space-time interpretations, making M-theory/heterotic duality manifest. We also present partial results on heterotic/F-theory duality.
Transform-Both-Sides Approach for Overdispersed Binomial Data When N is Unobserved

Abstract A common complication in analyzing binomial data is overdispersion, where the observed variation exceeds that predicted from the binomial distribution with parameters N and P. We consider the situation where N is not observed and variable. To estimate the regression parameters associated with covariates, we apply the transform-both-sides method. Based on the first-order asymptotic variance stabilizing transformation, we develop the arcsine transformation family indexed by a single parameter. This family includes the square root and the arcsine transformations as special cases. Asymptotic properties of the transformation methods are obtained. Simulation study indicates that the arcsine transformation family is more efficient than the square root and arcsine transformations when there is moderate overdispersion. These approaches are applied to a data set from radiobiology.
DNP enhanced frequency-selective TEDOR experiments in bacteriorhodopsin

We describe a new approach to multiple (13)C-(15)N distance measurements in uniformly labeled solids, frequency-selective (FS) TEDOR. The method shares features with FS-REDOR and ZF- and BASE-TEDOR, which also provide quantitative (15)N-(13)C spectral assignments and distance measurements in U-[(13)C,(15)N] samples. To demonstrate the validity of the FS-TEDOR sequence, we measured distances in [U-(13)C,(15)N]-asparagine which are in good agreement with other methods. In addition, we integrate high frequency dynamic nuclear polarization (DNP) into the experimental protocol and use FS-TEDOR to record a resolved correlation spectrum of the Arg-(13)C(gamma)-(15)N(epsilon) region in [U-(13)C,(15)N]-bacteriorhodopsin. We resolve six of the seven cross-peaks expected based on the primary sequence of this membrane protein.
Optimal Constrained Interest‐Rate Rules

We show that if policymakers compute the optimal unconstrained interest-rate rule within a Taylor-type class, they may be led to rules that generate indeterminacy and/or instability under learning. This problem is compounded by uncertainty about structural parameters since an optimal rule that is determinate and stable under learning for one calibration may be indeterminate or unstable under learning under a different calibration. We advocate a procedure in which policymakers restrict attention to rules constrained to lie in the determinate learnable region for all plausible calibrations, and that minimize the expected loss, computed using structural parameter priors, subject to this constraint.
Problem-solving effort and success in innovation contests: The role of national wealth and national culture

Innovation contests allow firms to harness specialized skills and services from globally dispersed participants for solutions to business problems. Such contests provide a rich setting for operations management (OM) scholars to explore problem solving in global labor markets as firms continue to unbundle their innovation value chains. In this study, we examine the implications of specific types of diversity in innovation contests on problem-solving effort and success. First, we conceptualize diversity among contestants in terms of national wealth (measured as gross domestic product per capita (GDPP) adjusted for purchasing power parity) and national culture (measured using the culture dimensions of performance orientation and uncertainty avoidance) and examine how such factors influence problem-solving effort. Next, we examine how differences between contestants and contest holders in terms of the above factors influence contest outcomes. Using data from a popular online innovation contest platform and country-level archival data, we find that contestants from countries with lower levels of GDPP are more likely to exert greater problem-solving effort compared to other contestants. With regard to national culture, we find that performance orientation and uncertainty avoidance have positive and negative effects, respectively, each of which weakens with increasing levels of GDPP. Finally, our analysis provides evidence of homophily effects indicating that contestants who share greater similarities with the contest holder in terms of national wealth and national culture are more likely to be successful in a contest. We discuss the implications of the study's findings for contest holders and platform owners who organize innovation contests, and for emerging research on innovation contests.
Soil Resistance Predictions From Pile Dynamics

The present work extends the application of the force and acceleration records to the calculation of the distribution of soil resistance along the pile. It also shows how the records are used to predict the magnitude of dynamic resistance that the soil applies to the pile, an important factor in choosing efficient hammer characteristics. A method for obtaining a more accurate simplified prediction of total static bearing capacity is also presented. It should be emphasized that the aforementioned predictions are all made from measurements at the pile top only. The work is correlated by presentation of results for 24 pile tests which include construction static load tests as well as specially instrumented load test piles. The application of these results can have considerable impact on foundation costs. Static load tests are very costly and time consuming. In Ohio a single test on a service pile using tension reaction piles (also service piles) typically costs $3,000 to $5,000. This static test provides much useful information about the particular pile which was tested. However, due to variability of soil properties the information may be of less value for other piles in the structure. This is reflected in the large factors of safety commonly used for piles. The proposed dynamic measurements methods can be applied to a substantial number of service piles at less than the cost of a single static load test. The dynamic analysis herein differs from the general dynamics problem in which either the boundary force or acceleration record is given as input and the other record calculated as output. In the present dynamic analysis, both force and acceleration are shown and thus one of the two records can be viewed as redundant information. The second record is, therefore, used in the present analysis to give information on pile resistance effects; e.g., in the absence of soil resistance, the acceleration at the pile top completely determines the force at the top from Newton's and Hooke's laws. The presence of resistance along the pile and at the pile tip affects the force at the top in a precise and predictable manner and makes it possible to compute t e magnitude and location of resistance forces along the pile. A simple soil resistance model is used, which consists of an elastoplastic shear resistance and a linear viscous damper. The dynamic analysis will be reviewed herein to present the basic ideas behind the work. The detailed mathematical expressions are given in Refs. 3 and 9.
Measure the semantic similarity of GO terms using aggregate information content

The rapid development of gene ontology (GO) and huge amount of biomedical data annotated by GO terms necessitate computation of semantic similarity of GO terms and, in turn, measurement of functional similarity of genes based on their annotations. In this paper we propose a novel and efficient method to measure the semantic similarity of GO terms. The proposed method addresses the limitations in existing GO term similarity measurement techniques; it computes the semantic content of a GO term by considering the information content of all of its ancestor terms in the graph. The aggregate information content (AIC) of all ancestor terms of a GO term implicitly reflects the GO term's location in the GO graph and also represents how human beings use this GO term and all its ancestor terms to annotate genes. We show that semantic similarity of GO terms obtained by our method closely matches the human perception. Extensive experimental studies show that this novel method also outperforms all existing methods in terms of the correlation with gene expression data. We have developed web services for measuring semantic similarity of GO terms and functional similarity of genes using the proposed AIC method and other popular methods. These web services are available at http:// bioinformatics.clemson.edu/G-SESAME.
Strong Lensing by Galaxies

Strong lensing is a powerful tool to address three major astrophysical issues: understanding the spatial distribution of mass at kiloparsec and subkiloparsec scale, where baryons and dark matter interact to shape galaxies as we see them; determining the overall geometry, content, and kinematics of the Universe; and studying distant galaxies, black holes, and active nuclei that are too small or too faint to be resolved or detected with current instrumentation. After summarizing strong gravitational lensing fundamentals, I present a selection of recent important results. I conclude by discussing the exciting prospects of strong gravitational lensing in the next decade.
How to catch L 2 -heavy-hitters on sliding windows

Finding heavy-elements (heavy-hitters) in streaming data is one of the central, and well-understood tasks. Despite the importance of this problem, when considering the sliding windows model of streaming (where elements eventually expire) the problem of finding L 2 -heavy elements has remained completely open despite multiple papers and considerable success in finding L 1 -heavy elements.Since the L 2 -heavy element problem doesn't satisfy certain conditions, existing methods for sliding windows algorithms, such as smooth histograms or exponential histograms are not directly applicable to it. In this paper, we develop the first polylogarithmic-memory algorithm for finding L 2 -heavy elements in the sliding window model.Our technique allows us not only to find L 2 -heavy elements, but also heavy elements with respect to any L p with 0 < p ? 2 on sliding windows. By this we completely "close the gap" and resolve the question of finding L p -heavy elements in the sliding window model with polylogarithmic memory, since it is well known that for p 2 this task is impossible.We demonstrate a broader applicability of our method on two additional examples: we show how to obtain a sliding window approximation of the similarity of two streams, and of the fraction of elements that appear exactly a specified number of times within the window (the α-rarity problem). In these two illustrative examples of our method, we replace the current expected memory bounds with worst case bounds.
Behavior of Repeating Earthquake Sequences in Central California and the Implications for Subsurface Fault Creep

Repeating earthquakes (REs) are sequences of events that have nearly identical waveforms and are interpreted to represent fault asperities driven to failure by loading from aseismic creep on the surrounding fault surface at depth. We investigate the occurrence of these REs along faults in central California to determine which faults exhibit creep and the spatiotemporal distribution of this creep. At the juncture of the San Andreas and southern Calaveras–Paicines faults, both faults as well as a smaller secondary fault, the Quien Sabe fault, are observed to produce REs over the observation period of March 1984 through May 2005. REs in this area reflect a heterogeneous creep distribution along the fault plane with significant variations in time. Cumulative slip over the observation period at individual sequence locations is determined to range from 5.5–58.2 cm on the San Andreas fault, from 4.8–14.1 cm on the southern Calaveras–Paicines fault, and from 4.9–24.8 cm on the Quien Sabe fault. Creep at depth appears to mimic the behaviors seen for creep on the surface in that evidence of steady slip, triggered slip, and episodic slip phenomena are also observed in the RE sequences. For comparison, we investigate the occurrence of REs west of the San Andreas fault within the southern Coast Range. Events within these RE sequences occurred only minutes to weeks apart from each other and then did not repeat again over the observation period, suggesting that REs in this area are not produced by steady aseismic creep of the surrounding fault surface.
Chemistry, biological activity, and chemotherapeutic potential of betulinic acid for the prevention and treatment of cancer and HIV infection

3beta-Hydroxy-lup-20(29)-en-28-oic acid (betulinic acid) is a pentacyclic lupane-type triterpene that is widely distributed throughout the plant kingdom. A variety of biological activities have been ascribed to betulinic acid including anti-inflammatory and in vitro antimalarial effects. However, betulinic acid is most highly regarded for its anti-HIV-1 activity and specific cytotoxicity against a variety of tumor cell lines. Interest in developing even more potent anti-HIV agents based on betulinic acid has led to the discovery of a host of highly active derivatives exhibiting greater potencies and better therapeutic indices than some current clinical anti-HIV agents. While its mechanism of action has not been fully determined, it has been shown that some betulinic acid analogs disrupt viral fusion to the cell in a post-binding step through interaction with the viral glycoprotein gp41 whereas others disrupt assembly and budding of the HIV-1 virus. With regard to its anticancer properties, betulinic acid was previously reported to exhibit selective cytotoxicity against several melanoma-derived cell lines. However, more recent work has demonstrated that betulinic acid is cytotoxic against other non-melanoma (neuroectodermal and malignant brain tumor) human tumor varieties. Betulinic acid appears to function by means of inducing apoptosis in cells irrespective of their p53 status. Because of its selective cytotoxicity against tumor cells and favorable therapeutic index, even at doses up to 500 mg/kg body weight, betulinic acid is a very promising new chemotherapeutic agent for the treatment of HIV infection and cancer.
C-H Bond Functionalizations with Palladium(II): Intramolecular Oxidative Annulations of Arenes

Oxidative annulations for the synthesis of carbocycles were developed using a catalytic palladium(II) system. Indoles with pendant olefin tethers were oxidatively cyclized to form annulated products. Electron-rich aromatic systems were also investigated, culminating in the synthesis of benzofurans and dihydrobenzofurans by a similar protocol. These reactions were demonstrated to proceed by an initial C–H bond functionalization event, followed by olefin insertion and β-hydride elimination.
Nonlinear Behavior of a Magnetic Bearing System

This paper describes the result of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bearings and subject to rotating unbalance and feedback control. Geometric coupling between the degrees of freedom leads to a pair of nonlinear ordinary differential equations, which are then solve using both numerical simulation and approximate analytical techniques. The system exhibits a variety of interesting and somewhat unexpected phenomena including various amplitude driven bifurcational events, sensitivity to initial conditions, and the complete loss of stability associated with the escape from the potential well in which the system can be thought to be oscillating. An approximate criterion to avoid this last possibility is developed based on concepts of limiting the response of the system. The present paper may be considered as an extension to an earlier study by the same authors, which described the practical context of the work, free vibration, control aspects, and derivation of the mathematical model.
Development of 4,4‘-Substituted-XylBINAP Ligands for Highly Enantioselective Hydrogenation of Ketones

A family of 4,4‘-substituted-xylBINAPs was synthesized in multistep sequences and characterized by NMR spectroscopy and mass spectrometry. Ru(diphosphine)(diamine)Cl2 complexes based on these 4,4‘-substituted-xylBINAPs and chiral diamines (DPEN and DAIPEN) were synthesized by treatment of [(benzene)RuCl2]2 with 4,4‘-substituted-xylBINAP followed by chiral diamine, and characterized by 1H and 31P NMR spectroscopy and mass spectrometry. These Ru complexes were used for asymmetric hydrogenation of aromatic ketones in a highly enantioselective manner with complete conversion. With 0.1% catalyst loading, complete conversion and enantioselectivity greater than 99% were obtained for most of the aromatic ketones examined. These Ru catalysts thus gave the highest ee for asymmetric hydrogenation of aromatic ketones among all of the catalysts reported in the literature. A single-crystal X-ray diffraction study of Ru[(R)-L4][(R,R)-DPEN]Cl2 indicated that the 4-methyl group of the naphthyl ring and the methyl groups o...
Magnetic dynamo action in two-dimensional turbulent magneto-hydrodynamics

Two-dimensional magnetohydrodynamic turbulence is explored by means of numerical simulation. Previous analytical theory, based on non-dissipative constants of the motion in a truncated Fourier representation, is verified by following the evolution of highly non-equilibrium initial conditions numerically. Dynamo action (conversion of a significant fraction of turbulent kinetic energy into long-wavelength magnetic field energy) is observed. It is conjectured that in the presence of dissipation and external forcing, a dual cascade will be observed for zero-helicity situations. Energy will cascade to higher wave numbers simultaneously with a cascade of mean square vector potential to lower wave numbers, leading to an omni-directional magnetic energy spectrum which varies as 1/k 3 at lower wave numbers, simultaneously with a buildup of magnetic excitation at the lowest wave number of the system. Equipartition of kinetic and magnetic energies is expected at the highest wave numbers in the system.
Did the Work Opportunity Tax Credit Cause Subsidized Worker Substitution

This article questions whether the implementation of the Work Opportunity Tax Credit (WOTC) created an incentive for employers to substitute subsidized workers for incumbent workers. To see if this substitution occurs, the author uses a differences-in-differences methodology to test whether the implementation of the WOTC caused both an increase in employment from a representative target group and a decrease in employment of a group that is a close substitute for members of the target group. The author finds no evidence that subsidized worker substitution occurred in the period after the WOTC was implemented. There is evidence that the WOTC is effective in increasing the employment rates of long-term welfare recipients.
p38 mitogen-activated protein kinase regulates canonical Wnt–β-catenin signaling by inactivation of GSK3β

The Wnt-beta-catenin canonical signaling pathway is crucial for normal embryonic development, and aberrant expression of components of this pathway results in oncogenesis. Upon scanning for the mitogen-activated protein kinase (MAPK) pathways that might intersect with the canonical Wnt-beta-catenin signaling pathway in response to Wnt3a, we observed a strong activation of p38 MAPK in mouse F9 teratocarcinoma cells. Wnt3a-induced p38 MAPK activation was sensitive to siRNAs against Galpha(q) or Galpha(s), but not against either Galpha(o) or Galpha(11). Activation of p38 MAPK is critical for canonical Wnt-beta-catenin signaling. Chemical inhibitors of p38 MAPK (SB203580 or SB239063) and expression of a dominant negative-version of p38 MAPK attenuate Wnt3a-induced accumulation of beta-catenin, Lef/Tcf-sensitive gene activation, and primitive endoderm formation. Furthermore, epistasis experiments pinpoint p38 MAPK as operating downstream of Dishevelleds. We also demonstrate that chemical inhibition of p38 MAPK restores Wnt3a-attenuated GSK3beta kinase activity. We demonstrate the involvement of G-proteins and Dishevelleds in Wnt3a-induced p38 MAPK activation, highlighting a critical role for p38 MAPK in canonical Wnt-beta-catenin signaling.
Characterization of the nonlinear elastic properties of graphite/epoxy composites using ultrasound

The normalized change in ultrasonic "natural" velocity as a function of stress and temperature was measured in a unidirectional laminate of T300/5208 graphite/epoxy composite using a pulsed phase locked loop ultrasonic interferometer. These measurements were used together with the linear (second order) elastic moduli to calculate some of the nonlinear (third order) moduli of this material.
Activation and coordination patterns of the suprahyoid muscles during swallowing

This study was undertaken to determine the activation and coordination patterns of the three suprahyoid muscles--geniohyoid, mylohyoid, and anterior belly of the digastric muscle--in elevating the larynx during swallowing. Electromyographic activity was also recorded from two intrinsic laryngeal muscles (vocalis and lateral cricoarytenoid) and the anterior genioglossus. Ten adults served as participants. Each participant produced 15 swallows of 15 mL of tap water both normally and with a 12-mm bite block placed between the molars. The electromyographic data were ensemble-averaged with a laboratory computer. Analyses showed that the three suprahyoid muscles were used selectively by different participants. Some participants used all three muscles for hyoid elevation, while others used different pairs of two of the muscles. The activation patterns of the suprahyoid muscles during swallowing also varied with respect to each other and the onset of the laryngeal constrictor muscles; however, use of at least one suprahyoid muscle always preceded the onset of the laryngeal adductors, indicating that larynx elevation consistently preceded glottal adduction. The way in which the muscles responded to the bite block varied considerably both within and among participants. Some maintained temporal stability but increased overall muscle activity; others reorganized temporal relations either with or without corresponding muscle activity adjustments. These findings suggest that the laryngeal elevation system is an adaptive function rather than an immutable action.
'CHROMOSOMAL PUFFING' IN DIPLOID NUCLEI OF DROSOPHILA MELANOGASTER

In situ hybridization has become a powerful technique for dissecting nuclear structure. By localizing nucleic acids with high precision, it is possible to infer the native structure of chromosomes, replication factories and transcript processing complexes. To increase the value of this technique, we have established the limits of resolution of two-color in situ hybridization to chromosomal DNA in diploid chromosomes of Drosophila embryonic nuclei. Using high-resolution 3-dimensional optical microscopy and computational image analysis, we establish that we can distinguish the location of chromosomal sequences that lie 27-29 kb apart within a 40 kb transcription unit with an accuracy of about 100 nm. Contrary to observations made in mammalian tissue culture cells, we find that when the gene is expressed, it assumes an open configuration, and that the extent of decondensation is variable from chromosome to chromosome. Further experiments suggest that variation in gene structure results from asynchrony in transcriptional elongation. We suggest that the phenomenon we observe is the diploid analog to chromosomal puffing that occurs in the transcriptionally active regions of Drosophila polytene chromosomes.
Reframing the Disease Debate and Defending the Biostatistical Theory

Similarly to other accounts of disease, Christopher Boorse's Biostatistical Theory (BST) is generally presented and considered as conceptual analysis, that is, as making claims about the meaning of currently used concepts. But conceptual analysis has been convincingly critiqued as relying on problematic assumptions about the existence, meaning, and use of concepts. Because of these problems, accounts of disease and health should be evaluated not as claims about current meaning, I argue, but instead as proposals about how to define and use these terms in the future, a methodology suggested by Quine and Carnap. I begin this article by describing problems with conceptual analysis and advantages of "philosophical explication," my favored approach. I then describe two attacks on the BST that also question the entire project of defining "disease." Finally, I defend the BST as a philosophical explication by showing how it could define useful terms for medical science and ethics.
Big drinkers: how BMI, gender and rules of thumb influence the free pouring of wine.

Abstract Background This research examines free pouring behavior and provides an account of how Body Mass Index (BMI) and gender might lead to the overpouring, and consequently the overconsumption of wine. Methods An observational study with young adults investigated how BMI and gender affect free-pouring of wine over a variety of pouring scenarios, and how rules-of-thumb in pouring affect the quantities of alcohol poured by men and women across BMI categories. Results For men, the amount poured was positively related to BMI. However, BMI did not affect pours by women. The use of the "half glass" rule-of-thumb in pouring reduced the volume of wine poured by over 20% for both men and women. Importantly, this rule-of-thumb substantially attenuated the pours by men at high BMI levels. Conclusion Increasing awareness of pouring biases represents an early and effective step toward curbing alcohol consumption among men, and especially those who are overweight. Additionally, using a simple "half glass" rule-of-thumb may be an effective way to curb overpouring, despite non-standard glass sizes.
Distances of Heegaard splittings

J. Hempel [Topology, 2001] showed that the set of distances of the Heegaard splittings (S;V;h n (V)) is unbounded, as long as the stable and unstable laminations of h avoid the closure of V ‰PML(S). Here h is a pseudo-Anosov homeomorphism of a surface S while V is the set of isotopy classes of simple closed curves in S bounding essential disks in a flxed handlebody. With the same hypothesis we show that the distance of the splitting (S;V;h n (V)) grows linearly with n, answering a question of A. Casson. In addition we prove the converse of Hempel’s theorem. Our method is to study the action of h on the curve complex associated to S . We rely heavily on the result, due to H. Masur and Y. Minsky [Invent. Math., 1999], that the curve complex is Gromov hyperbolic.
Does Plasmodium falciparum have an Achilles' heel?

Plasmodium falciparum is the parasite that causes the most severe form of malaria responsible for nearly a million deaths a year. Currently, science has been established about its cellular structures, its metabolic processes, and even the molecular structures of its intrinsic membrane proteins responsible for transporting water, nutrient, and waste molecules across the Parasite Plasma Membrane (PPM). Based on the molecular structure of the parasite’s membrane and the quantitative mechanics of how erythritol interacts with the multi-functional channel protein expressed in the PPM, I hypothesize that Plasmodium falciparum has an Achilles’ heel that can be attacked with erythritol, the well-known sweetener that is classified as generally safe. Most organisms have in their cell membrane two types of water-channel proteins: aquaporins to maintain hydro-homeostasis across the membrane and aquaglyceroporins to uptake glycerols etc. In contrast, P. falciparum has only one type of such proteins---the multifunctional aquaglyceroporin (PfAQP) expressed in the PPM to do both jobs. Moreover, the parasite also uses PfAQP to excrete its metabolic wastes (ammonia included) produced at a very high rate in the blood stage. This extremely high efficiency of the bug using one protein for multiple essential tasks makes the parasite fatally vulnerable. Erythritol in the blood stream can kill the parasite by clogging up its PfAQP channel that needs to be open for maintaining hydro-homeostasis and for excreting toxic wastes across the bug’s PPM. In vitro tests are to measure the growth/death rate of P. falciparum in blood with various erythritol concentrations. In vivo experiments are to administer groups of infected mice with various doses of erythritol and monitor the parasite growth levels in each group. Moreover, clinic trials can be performed to observe the added effects of administering to patients erythritol along with the known drugs because erythritol was classified as a safe food ingredient.
On Complexity of the Quantum Ising Model

We study complexity of several problems related to the Transverse field Ising Model (TIM). First, we consider the problem of estimating the ground state energy known as the Local Hamiltonian Problem (LHP). It is shown that the LHP for TIM on degree-3 graphs is equivalent modulo polynomial reductions to the LHP for general k-local ‘stoquastic’ Hamiltonians with any constant \({k \ge 2}\). This result implies that estimating the ground state energy of TIM on degree-3 graphs is a complete problem for the complexity class \({\mathsf{StoqMA}}\) —an extension of the classical class \({\mathsf{MA}}\). As a corollary, we complete the complexity classification of 2-local Hamiltonians with a fixed set of interactions proposed recently by Cubitt and Montanaro. Secondly, we study quantum annealing algorithms for finding ground states of classical spin Hamiltonians associated with hard optimization problems. We prove that the quantum annealing with TIM Hamiltonians is equivalent modulo polynomial reductions to the quantum annealing with a certain subclass of k-local stoquastic Hamiltonians. This subclass includes all Hamiltonians representable as a sum of a k-local diagonal Hamiltonian and a 2-local stoquastic Hamiltonian.
Dollarization and the Mexican Labor Market

This paper examines how dollarization affects wages and employment in the Mexican labor market. Dollarization is modeled as a fixed real exchange rate and also as a potentially increased inflow of capital from abroad. The effects of dollarization depend upon whether adopting a fixed exchange reduces the rate of return on emigration and helps to attract foreign capital. The paper investigates how Mexican emigration to the United States responds to changes in bilateral economic conditions. The evidence indicates that the flow of illegal immigrants from Mexico into the United States is sensitive to economic conditions and is more volatile when the Mexican monetary authorities have fixed the exchange rate in the past. In contrast, the legal immigrant flow is not sensitive to changes in relative economic conditions.
Geometric ergodicity of a bead–spring pair with stochastic Stokes forcing

We consider a simple model for the uctuating hydrodynamics of a exible polymer in dilute solution, demonstrating geometric ergodicity for a pair of particles that interact with each other through a nonlinear spring potential while being advected by a stochastic Stokes uid velocity field. This is a generalization of previous models which have used linear spring forces as well as white-in-time uid velocity fields. We follow previous work combining control theoretic arguments, Lyapunov functions, and hypo-elliptic diffusion theory to prove exponential convergence via a Harris chain argument. To this, we add the possibility of excluding certain "bad" sets in phase space in which the assumptions are violated but from which the systems leaves with a controllable probability. This allows for the treatment of singular drifts, such as those derived from the Lennard-Jones potential, which is an novel feature of this work.
Using information technology to leverage transport and logistics service operations in the supply chain: an empirical assessment of the interrelation between technology and operations management

Based upon existing work, a synergistic relation between technology and operations management can be assumed. This paper uses a specific focus area to empirically validate this assumption. Within the field of third party logistics operations in the supply chain, technology can be expected to be a critical factor in achieving the often-targeted expansion of service offerings. The empirical research presented in this paper goes beyond existing material in this field, which remains mostly conceptual, qualitative or descriptive, by targeting statistical generalisation, using findings from a multi-annual survey of transport and logistics service operations in the supply chain. Findings show that existing operational arrangements of transport and logistics service providers mostly remain limited to traditional transport and warehouse services but that technology proves an answer to achieving the targeted expansion of third party operations. Case studies of three innovative service providers are used to develop insights into how technology impacts operational relations in the supply chain and how technology can leverage operations management in a synergistic manner.
Stability and Regulation of a Variable-Displacement Vane-Pump

Pressure fluctuations may develop in the hydraulic system of automatic transmissions, even under steady-state conditions. To analyze this phenomenon, a dynamic model was developed for a system which consists of a variable-displacement vane-pump, a regulator, and a resistive load. The model was linearized and reduced to generate a stability criterion for the pressure-regulation circuit. This criterion determines a critical frequency that the natural frequency of the pressure-regulation valve must exceed to assure stability. This critical frequency depends primarily on the daming of the spool of the pressure-regulation valve and on its position; the latter is a function of the regulation-chamber leakage characteristics. The analysis shows that line pressure, flow and leakage, along with production tolerances and different operating conditions, have a significant effect on the stability of the hydraulic system. Test data supports the analysis.
Computing spacetime curvature via differential algebraic equations

The equations that govern the behavior of physical systems can often be solved numerically using a method of lines approach and differential algebraic equation (DAE) solvers. For example, such an approach can be used to solve the Einstein field equations of general relativity, and thereby simulate significant astrophysical events. In this paper, we describe some preliminary work in which two model problems in general relativity are formulated, spatially discretized, and then numerically solved as a DAE. In particular, we seek to reproduce the solution to the spherically symmetric Schwarzschild spacetime. This is an important testbed calculation in numerical relativity since the solution is the steady-state for the collision of two (or more) nonrotating black holes. Moreover, analytic late-time properties of the Schwarzschild spacetime are well known and can be used to verify the accuracy of the simulation.
On subsumption and semiunification in feature algebras

We consider a generalization of term subsumption, or matching, to a class of mathematical structures which we call feature algebras. We show how these generalize both first-order terms and the feature structures used in computational linguistics. The notion of term subsumption generalizes to a natural notion of algebra homomorphism. In the setting of feature algebras, unification, corresponds naturally to solving constraints involving equalities between strings of unary function symbols, and semiunification also allows inequalities representing subsumption constraints. Our generalization allows us to show that the semiunification problem for finite feature algebras is undecidable. This implies that the corresponding problem for rational trees (cyclic terms) is also undecidable.
Experimental study of the effect of quantum-well structures on the thermoelectric figure of merit

Experimental investigations have been performed on the thermoelectric properties on the multiple-quantum-well structures of PbTe/Pb/sub 1-x/Eu/sub x/Te grown by molecular beam epitaxy. Our results are found to be consistent with theoretical predictions and indicate that an increase in Z over bulk values may be possible through quantum confinement effects using quantum-well structures.
DETECTION OF CLOSE-IN EXTRASOLAR GIANT PLANETS USING THE FOURIER-KELVIN STELLAR INTERFEROMETER

We evaluate the direct detection of extrasolar giant planets with a two-aperture nulling infrared interferometer, working at angles θ < λ/2B and using a new "ratio-of-two-wavelengths" technique. Simple arguments suggest that interferometric detection and characterization should be quite possible for planets much closer than the conventional inner working angle, or angular resolution limit. We show that the peak signal from a nulling infrared interferometer of baseline 40 m will often occur "inside the null" and that the signal variations from path difference fluctuations will cancel to first order in the ratio of two wavelengths. Using a new interferometer simulation code, we evaluate the detectability of all the known extrasolar planets as observed using this two-color method with the proposed Fourier-Kelvin Stellar Interferometer (FKSI). In its minimum configuration FKSI uses two 0.5 m apertures on a 12.5 m baseline and a ±20° field of regard. We predict that ~7 known extrasolar planets are directly detectable using FKSI, with low-resolution spectroscopy (R ~ 20) being possible in the most favorable cases. Spaceborne direct detection of extrasolar giant planets is possible with ~12 m baselines and does not require the much longer baselines provided by formation flying.
On the minimum size of restricted sumsets in cyclic groups

For positive integers n, m, and h, we let \({\rho\hat (\mathbb{Z}_n, m, h)}\) denote the minimum size of the h-fold restricted sumset among all m-subsets of the cyclic group of order n. The value of \({\rho\hat (\mathbb{Z}_n, m, h)}\) was conjectured for prime values of n and h = 2 by Erdős and Heilbronn in the 1960s; Dias da Silva and Hamidoune proved the conjecture in 1994 and generalized it for an arbitrary h, but little is known about the case when n is composite. Here we exhibit an explicit upper bound for all n, m, and h; our bound is tight for all known cases (including all n, m, and h with \({n \leqq 40}\)). We also provide counterexamples for conjectures made by Plagne and by Hamidoune, Llado, and Serra.
Correlated sources over broadcast channels

An alternative characterization is given for the coding theorem by Han and Costa, which finds a set of admissible source pairs that can be transmitted reliably over the broadcast channel. The associated coding technique is conceptually simpler and the resulting admissible source region can be shown to include the Gray-Wyner distributed source coding region in a straightforward manner. Incidentally, this new characterization illustrates how the common part between the two random sources does not play any role in broadcasting correlated sources, unlike transmission of correlated sources over the multiple access channel.
Optimizing Sequential Cycles Through Shannon Decomposition and Retiming

Optimizing sequential cycles is essential for many types of high-performance circuits, such as pipelines for packet processing. Retiming is a powerful technique for speeding pipelines, but it is stymied by tight sequential cycles. Designers usually attack such cycles by manually combining Shannon decomposition with retiming-effectively a form of speculation-but such manual decomposition is error prone. We propose an efficient algorithm that simultaneously applies Shannon decomposition and retiming to optimize circuits with tight sequential cycles. While the algorithm is only able to improve certain circuits (roughly half of the benchmarks we tried), the performance increase can be dramatic (7%-61%) with only a modest increase in area (1%-12%). The algorithm is also fast, making it a practical addition to a synthesis flow
School choice, student performance, and teacher and school characteristics : the Chilean case

The author explores how schools change in response to increased competition generated by voucher programs in Chile. A unique data set provides information on teacher demographics and labor market characteristics, as well as teachers' perceptions of school management. When teacher data are matched with school-level data on student achievement using a national assessment data set (SIMCE), some teacher and school characteristics affect student performance, but a great deal of unexplained variance among sectors remains important in predicting student outcomes. Teacher education, decentralization of decisionmaking authority, whether the school schedule is strictly enforced, and the extent to which teachers have autonomy in designing teaching plans and implementing projects all appear to affect student outcomes. Interestingly, teacher autonomy has positive effects on student outcomes only when decisionmaking authority is decentralized.
Efficient Bayesian estimates for discrimination among topologically different systems biology models.

A major effort in systems biology is the development of mathematical models that describe complex biological systems at multiple scales and levels of abstraction. Determining the topology—the set of interactions—of a biological system from observations of the system’s behavior is an important and difficult problem. Here we present and demonstrate new methodology for efficiently computing the probability distribution over a set of topologies based on consistency with existing measurements. Key features of the new approach include derivation in a Bayesian framework, incorporation of prior probability distributions of topologies and parameters, and use of an analytically integrable linearization based on the Fisher information matrix that is responsible for large gains in efficiency. The new method was demonstrated on a collection of four biological topologies representing a kinase and phosphatase that operate in opposition to each other with either processive or distributive kinetics, giving 8–12 parameters for each topology. The linearization produced an approximate result very rapidly (CPU minutes) that was highly accurate on its own, as compared to a Monte Carlo method guaranteed to converge to the correct answer but at greater cost (CPU weeks). The Monte Carlo method developed and applied here used the linearization method as a starting point and importance sampling to approach the Bayesian answer in acceptable time. Other inexpensive methods to estimate probabilities produced poor approximations for this system, with likelihood estimation showing its well-known bias toward topologies with more parameters and the Akaike and Schwarz Information Criteria showing a strong bias toward topologies with fewer parameters. These results suggest that this linear approximation may be an effective compromise, providing an answer whose accuracy is near the true Bayesian answer, but at a cost near the common heuristics.
Emergent quantum near-criticality from baryonic black branes

We find new black 3-brane solutions describing the “conifold gauge theory” at nonzero temperature and baryonic chemical potential. Of particular interest is the lowtemperature limit where we find a new kind of weakly curved near-horizon geometry; it is a warped product $$AdS_{2} \times \mathbb{R}^{3} \times T^{1,1} $$ with warp factors that are powers of the logarithm of the AdS radius. Thus, our solution encodes a new type of emergent quantum near-criticality. We carry out some stability checks for our solutions. We also set up a consistent ansatz for baryonic black 2-branes of M-theory that are asymptotic to AdS 4 × Q 1,1,1.
6-(2-Haloethyl)-2,2-dimethyl-4H-1,3-dioxins: versatile haloethyl vinyl ketone equivalents for carbocycle construction

Abstract 6-(2-Iodoethyl)-2,2-dimethyl-4 H -1,3-dioxin has been prepared in five steps from ethyl acetoacetate. A variety of enolates were then alkylated with this iodide. The resulting 6-alkyl-4 H -1,3-dioxins were either subjected to further transformations and/or heated (or subjected to a Lewis acid) to effect facile retrocycloaddition reactions. The resulting enones were found to smoothly participate in conjugate addition or olefin metathesis reactions to provide various carbocyclic ring systems. Collectively, these examples document the synthetic equivalency of dioxin 2 with iodoethyl vinyl ketone and, moreover, delineate a strategy for accomplishing the sequential reactions with nucleophiles at the β′, followed by the β electrophilic sites.
Institutional Failure in Resource Management

AbstractMany of the world's natural resources are in a state of crisis. The solution to this crisis is to develop effective management institutions, but there is no consensus on what those institutions are. Some economists favor solving resource-management problems through the institution of private property; others advocate central government control; and many anthropologists see local-level management as the solution. In this review, I argue that all these governance structures fail under certain conditions. However, the factors contributing to failure in each of these institutional forms differ radically, and the causes of that failure are not always predicted on the basis of existing theory. This chapter contains a review of the literature on the factors identified as causing the failure of private-property regimes, government-controlled resources, and local-level management. We will have to learn to match the resource problems with governance institutions and specific management techniques if we are ...
Backprojection filtering for variable orbit fan-beam tomography

Backprojection filtering algorithms are presented for three variable orbit fan-beam geometries. Expressions for the fan-beam projection and backprojection operators are given for a flat detector fan-beam geometry with fixed focal length, with variable focal length, and with fixed focal length and off-center focusing. Backprojection operators are derived for each geometry using transformation of coordinates to transform from a parallel geometry backprojector to a fan-beam backprojector for the appropriate geometry. The backprojection operator includes a factor which is a function of the coordinates of the projection ray and the coordinates of the pixel in the backprojected image. The backprojection filtering algorithm first backprojects the variable orbit fan-beam projection data using the appropriately derived backprojector to obtain a 1/r blurring of the original image, then takes the two-dimensional (2D) Fast Fourier Transform (FFT) of the backprojected image, then multiples the transformed image by the 2D ramp filter function, and finally takes the inverse 2D FFT to obtain the reconstructed image. Computer simulations verify that backprojectors with appropriate weighting give artifact free reconstructions of simulated line integral projections. Also, it is shown that it is not necessary to assume a projection model of line integrals, but the projector and backprojector can be defined to model the physics of the imaging detection process. A backprojector for variable orbit fan-beam tomography with fixed focal length is derived which includes an additional factor which is a function of the flux density along the flat detector. It is shown that the impulse response for the composite of the projection and backprojection operations is equal to 1/r. >