cssi/SciSciGPT-SciSciNet huggingface dataset:
Coordinated traversal: ( t +1)-round Byzantine agreement in polynomial time

Abstract The problem of efficiently performing Byzantine agreement in t + 1 rounds in the face of arbitrarily malicious failures is a longstanding open problem in fault-tolerant distributed computing. The original paper by Pease, Shostak, and Lamport (J. Assoc. Comput. Mach.27, No.2 (1980), 228-234) presented a (t + 1)-round protocol for the problem that uses exponential-size communication, and many papers in the last decade have labored to improve on that. Whereas efficient (t + 1)-round protocols have been developed for weaker failure models, (t + 1)-round protocols in the Byzantine model have been known only for n = Ω(t2), where n is the number of processors and t is the number of failures tolerated by the protocol. This paper presents a communication-efficient polynomial-time (t + 1)-round Byzantine agreement protocol for n > 8t. The protocol is an "early stopping" protocol, halting in min{t + 1, f + 2} rounds in the worst case, where f is the number of processors that actually fail during the run. This is provably optimal. The protocol is based on a careful combination of early stopping, fault masking, and a new technique called coordinated traversal. The combination of the three provides a powerful method of restricting the damage that a faulty processor, however malicious, can do. One of the byproducts of this protocol is a polynomial-time (t + 1)-round protocol for the Byzantine firing squad problem.
Effect of number of walls on plasmon behavior in carbon nanotubes

Abstract We investigate the physical parameters controlling the low-energy screening in carbon nanotubes via electron energy loss spectroscopy and inelastic X-ray scattering. Two plasmon-like features are observed, one near 9 eV (the so-called π plasmon) and one near 20 eV (the so-called π + σ plasmon). At large nanotube diameters, the π + σ plasmon energies are found to depend on the number of walls and not on the radius or chiral vector. The observed shift with number of walls indicates a change in the strength of the screening and in the effective interaction at inter-atomic distances; thus this result suggests a mechanism for tuning the properties of nanotubes.
Two-Dimensional Computational Model for Wave Rotor Flow Dynamics

A two-dimensional (θ, z) Navier-Stokes solver for multiport wave rotor flow simulation is described. The finite-volume forms of the unsteady thin-layer Navier- Stokes equations are integrated in time on multiblock grids that represent the stationary inlet and outlet ports and the moving rotor passages of the wave rotor. Computed results are compared with three-port wave rotor experimental data. The model is applied to predict the performance of a planned four-port wave rotor experiment. Two-dimensional flow features that reduce machine performance and influence rotor blade and duct wall thermal loads are identified.
Constructing Qubits in Physical Systems

The notion of a qubit is ubiquitous in quantum information processing. In spite of the simple abstract definition of qubits as two-state quantum systems, identifying qubits in physical systems is often unexpectedly difficult. There is an astonishing variety of ways in which qubits can emerge from devices. What essential features are required for an implementation to properly instantiate a qubit? We give three typical examples and propose an operational characterization of qubits based on quantum observables and subsystems.
Supersymmetric color superconductivity

Recent interest in novel phases in high density QCD motivates the study of high density supersymmetric QCD (SQCD), where powerful exact results for supersymmetric gauge theories can be brought to bear in the strongly coupled regime. We begin by describing how a chemical potential can be incorporated into a supersymmetric theory as a spurion vector superfield. We then study supersymmetric SU(Nc) gauge theories with Nf flavors of quarks in the presence of a baryon chemical potential ?, and describe the global symmetry breaking patterns at low energy. Our analysis requires ? > ?. We find that for Nf ?>?c. We also give a qualitative description of the phases in the `conformal window', (3/2)Nc < Nf < 3Nc, at finite density.
The maximal denumerant of a numerical semigroup

Given a numerical semigroup S=〈a 0,a 1,a 2,…,a t 〉 and n∈S, we consider the factorization n=c 0 a 0+c 1 a 1+⋯+c t a t where c i ≥0. Such a factorization is maximal if ∑c i is a maximum over all such factorizations of n. We provide an algorithm for computing the maximum number of maximal factorizations possible for an element in S, which is called the maximal denumerant of S. We also consider various cases that have connections to the Cohen-Macualay and Gorenstein properties of associated graded rings for which this algorithm simplifies.
Estimating lock congestion

We statistically estimate the relationship between lock usage (the number of barges locked) and lock congestion (the average delay and process time incurred) using a fixed-effects regression model that accounts for both lock characteristics and lock heterogeneity. In addition, we exploit the geographical variation in demand patterns for individual locks along the Upper Mississippi River system of locks and dams to avoid simultaneity bias that arises from the use of observed data. Using a panel dataset spanning the years 1993–2010, we find statistically significant evidence of the existence of a quadratic lock congestion function for 600 ft lock technology. While 1,200 ft lock technology on the other hand seemingly operates under free-flow conditions, the presence of an auxiliary chamber significantly mitigates congestion, with the effect being more pronounced for higher levels of traffic. Unscheduled lock outages attenuate lock congestion for both types of lock technology, while lock age (following a U-shaped relationship) affects congestion costs for 600 ft locks only. In addition, we find a tempering effect of scheduled outages in the case of 600 ft locks, and non-commercial vessels in the case of 1,200 ft locks.
A Parametric Level-Set Approach to Simultaneous Object Identification and Background Reconstruction for Dual-Energy Computed Tomography

Dual-energy computerized tomography has gained great interest because of its ability to characterize the chemical composition of a material rather than simply providing relative attenuation images as in conventional tomography. The purpose of this paper is to introduce a novel polychromatic dual-energy processing algorithm, with an emphasis on detection and characterization of piecewise constant objects embedded in an unknown cluttered background. Physical properties of the objects, particularly the Compton scattering and photoelectric absorption coefficients, are assumed to be known with some level of uncertainty. Our approach is based on a level-set representation of the characteristic function of the object and encompasses a number of regularization techniques for addressing both the prior information we have concerning the physical properties of the object and the fundamental physics-based limitations associated with our ability to jointly recover the Compton scattering and photoelectric absorption properties of the scene. In the absence of an object with appropriate physical properties, our approach returns a null characteristic function and, thus, can be viewed as simultaneously solving the detection and characterization problems. Unlike the vast majority of methods that define the level-set function nonparametrically, i.e., as a dense set of pixel values, we define our level set parametrically via radial basis functions and employ a Gauss-Newton-type algorithm for cost minimization. Numerical results show that the algorithm successfully detects objects of interest, finds their shape and location, and gives an adequate reconstruction of the background.
Benzotriazole-Chromium Trioxide Complex A Versatile Oxidant of Organic Compounds

Abstract Benzotriazole has been found to complex with chromium trioxide to produce a versatile new oxidant. This complex is capable of oxidizing primary alcohols to carboxylic acids, secondary alcohols to ketones, and bringing about the allylic oxidation of olefin substrates.
The Liberation Hypothesis and Racial and Ethnic Disparities in the Application of California's Three Strikes Law

ABSTRACT This paper examines the extent to which racial and ethnic disparities exist in the implementation of California's “Three Strikes and You're Out” law and whether racial and ethnic disparities vary by type of offense. Logistic regression analysis of individual-level data on over 171,000 California prison inmates indicates that African-Americans are more likely than whites and Latinos to receive third-strike sentences, even when legally relevant variables are controlled. The analysis also finds that Latino defendants are significantly less likely to receive third-strike sentences. The results also indicate that the black-white gap is greater for offenses known as “wobblers,” which can be filed as either felonies or misdemeanors than for offenses that must always be charged as felonies. Racial disparities are also greater for property and drug offenses than for violent crimes.
Improving dynamical domain-wall Fermion simulations☆

Abstract We report on studies of the clinical properties of dynamical domain wall fermions combined with the DBW2 gauge action for different gauge couplings and fermion masses. For quenched theories, the DBW2 action gives a residual chiral symmetry breaking much smaller than what was found with more traditional choices for the gauge action. Our goal is to investigate the possibilities which this and further improvements provide for the study of QCD thermodynamics and other simulations at stronger couplings.
Temperature-dependent low-resolution microwave studies of m-iodoanisole, m-bromoanisole, m-nitroanisole and m-anisaldehyde

Abstract Low-resolution microwave spectra of m-iodoanisole and m-bromoanisole, obtained between 290 and 350 K display R-branch a-type band series which are consistent with an anti heavy-atom planar or nearly planar conformer. For both molecules, a second band series, consistent with a species having an effective methoxy group torsional angle between 60° and 120° is observed at temperatures above ambient. Its relative intensity and associated temperature dependence indicate that this series is not due to a stable conformational form and may instead originate from many weakly bound and/or freely rotating torsional satellites with similar rotational constants. The low-resolution microwave spectrum of m-nitroanisole displays two R-branch a-type series, consistent with planar syn and anti conformers. Low-resolution microwave spectra of m-anisaldehyde display three band series consistent with three planar conformational species and an additional band series whose spectral characteristics are consistent with a collection of torsionally excited states with similar B+C values.
Deformations of singularities and variation of GIT quotients

We study the deformations of the minimally elliptic surface sin- gularity N16. A standard argument reduces the study of the deformations of N16 to the study of the moduli space of pairs (C, L) consisting of a plane quintic curve and a line. We construct this moduli space in two ways: via the periods of K3 surfaces and by using geometric invariant theory (GIT). The GIT construction depends on the choice of the linearization. In particular, for one choice of linearization we recover the space constructed via K3 surfaces and for another we obtain the full deformation space of N16. The two spaces are related by a series of explicit flips. In conclusion, by using the flexibil- ity given by GIT and the standard tools of Hodge theory, we obtain a good understanding of the deformations of N16.
A shrinking lemma for indexed languages

Abstract This article presents a lemma in the spirit of the pumping lemma for indexed languages but easier to employ.
Cocycle superrigidity for profinite actions of property (T) Groups

Consider a free ergodic measure-preserving profinite action Γ↷X (i.e., an inverse limit of actions Γ↷Xn, with Xn finite) of a countable property (T) group Γ (more generally, of a group Γ which admits an infinite normal subgroup Γ0 such that the inclusion Γ0⊂Γ has relative property (T) and Γ/Γ0 is finitely generated) on a standard probability space X. We prove that if w:Γ×X→Λ is a measurable cocycle with values in a countable group Λ, then w is cohomologous to a cocycle w′ which factors through the map Γ×X→Γ×Xn, for some n. As a corollary, we show that any orbit equivalence of Γ↷X with any free ergodic measure-preserving action Λ↷Y comes from a (virtual) conjugacy of actions.
Abelian non-global logarithms from soft gluon clustering

Most recombination-style jet algorithms cluster soft gluons in a complex way. This leads to previously identified correlations in the soft gluon phase space and introduces logarithmic corrections to jet cross sections, which are known as clustering logarithms. The leading Abelian clustering logarithms occur at least at next-to leading logarithm (NLL) in the exponent of the distribution. Using the framework of Soft Collinear Effective Theory (SCET), we show that new clustering effects contributing at NLL arise at each order. While numerical resummation of clustering logs is possible, it is unlikely that they can be analytically resummed to NLL. Clustering logarithms make the anti-kT algorithm theoretically preferred, for which they are power suppressed. They can arise in Abelian and non-Abelian terms, and we calculate the Abelian clustering logarithms at O $$ \left( {\alpha_s^2} \right) $$ for the jet mass distribution using the Cambridge/Aachen and kT algorithms, including jet radius dependence, which extends previous results. We find that clustering logarithms can be naturally thought of as a class of non-global logarithms, which have traditionally been tied to non-Abelian correlations in soft gluon emission.
Fast Neutron Radiation Damage of High-Purity Germanium Detectors

Seven high resolution, high-purity planar germanium and two lithium-drifted germanium detectors have been exposed to fluences of monoenergetic fast neutrons of 1.4, 5.5 and 16.4 MeV to study radiation damage effects. Seven of the exposures were made at 5.5 MeV using detectors made from both LBL and General Electric Company material. Initial degradation of 60Co energy resolution was generally observed after fluences of 3 × 10+9 n/cm2. After fluences of 1010 n/cm2, the detector resolutions were all affected, and replacement would be required in most gamma ray spectrometry; these results are consistent with previous damage studies on germanium detectors. Considerable variability in neutron damage threshold between detectors was observed within this fluence range which must be attributable to a material parameter that is not yet fully determined. This is the major finding in this study. After irradiation, a significant increase in material resistivity was observed as a series resistance in the diodes undepleted region at low biases. The observations were made by capacitance effects and lengthened pulse rise time. Annealing of damage was observed during storage at LN2 temperature after irradiation; resulting, in some cases, in improvement of resolution and in others, further degradation. Drastic resolution degradation was observed on cycling detectors to dry ice temperatures, (200° K) with the loss of the high series resistance and an increase in acceptor concentration. Further cycling to room temperature for periods of hours resulted in improvement of the energy resolution compared with the 200° K value.
Abelian Subgroups of the Torelli Group

Let S be a closed oriented surface of genus g > 2, and let T denote its Torelli group. First, given a set E of homotopically nontrivial, pairwise disjoint, pairwise nonisotopic simple closed curves on S, we determine precisely when a multitwist on E is an element of T by defining an equivalence relation on E and then applying graph theory. Second, we prove that an arbitrary Abelian subgroup of T has rank ≤ 2g - 3.
On fundamental groups of quotient spaces

Abstract In classical covering space theory, a covering map induces an injection of fundamental groups. This paper reveals a dual property for certain quotient maps having connected fibers, with applications to orbit spaces of vector fields and leaf spaces in general.
Party On! A call for entrepreneurship research that is more interactive, activity based, cognitively hot, compassionate, and prosocial

It is the Journal of Business Venturing's (JBV) 30th birthday. Although the community of entrepreneurship scholars deserves to celebrate JBV's achievements over the last 30 years (and congratulate the journal's parents—Ian Macmillan and S. Venkataraman), my focus is more on the future of entrepreneurship (and by extension JBV). A focus on entrepreneurship is both timeless and timely. On the one hand, entrepreneurship is timeless given the long-recognized importance of entrepreneurs to economies and societies (e.g., Jean Baptiste who supposedly coined the term in about 1800). On the other hand, a discussion of entrepreneurship is timely because now that the field of entrepreneurship has achieved legitimacy, it faces both opportunities and threats. It is thus timely to acknowledge the threats and think about opportunities to advance the field. A discussion of entrepreneurship is also timely because society faces a number of grand challenges (including the durability of poverty, environmental degradation [ Dorado and Ventresca, 2013]), challenges well suited to entrepreneurial responses...
Speculative attacks and currency crises: The Mexican experience

By using data from the Mexican economy, this paper estimates a speculative attack model of currency crises in order to identify the role of macroeconomic fundamentals and early warning signals of a potential currency crisis. A deterioration in fundamentals appears to generate high onestep-ahead probabilities for the observed regime changes during the sample period 1982-1994. Particularly, foreign reserve losses, expansionary output, monetary and fiscal policies, an increase in inflation differentials and the share of short-term foreign currency-indexed debt, and an appreciation of the real exchange rate appear to have contributed to the speculative pressures and the associated regime changes.
FREE-FLOATING PLANETS IN STELLAR CLUSTERS: NOT SO SURPRISING

We find that free-floating planets can remain bound to an open cluster for much longer than was previously calculated: of the order of the cluster half-mass relaxation timescale as opposed to the crossing time. This result is based on N-body simulations performed with the new GRAPE-6 special purpose hardware and is important in the context of the preliminary detection of a population of free-floating, substellar objects in the globular cluster M22. The planets in our N-body study are of Jupiter mass and are initially placed in circular orbits of between 0.05 and 50 AU about a parent star whose mass is chosen from a realistic initial mass function. The presence of the free-floating planets is the result of dynamical encounters between planetary systems and the cluster stars. Most planets are liberated from their parent star in, or near, the cluster core, and then drift outward on a timescale of ~108-109 yr. This still implies the existence of many (~100) planets per star if the M22 result is confirmed.
Altering Hydrogen Storage Properties by Hydride Destabilization through Alloy Formation: LiH and MgH2 Destabilized with Si

Alloying with Si is shown to destabilize the strongly bound hydrides LiH and MgH2. For the LiH/Si system, a Li2.35Si alloy forms upon dehydrogenation, causing the equilibrium hydrogen pressure at 490 °C to increase from approximately 5 × 10-5 to 1 bar. For the MgH2/Si system, Mg2Si forms upon dehydrogenation, causing the equilibrium pressure at 300 °C to increase from 1.8 to >7.5 bar. Thermodynamic calculations indicate equilibrium pressures of 1 bar at approximately 20 °C and 100 bar at approximately 150 °C. These conditions indicate that the MgH2/Si system, which has a hydrogen capacity of 5.0 wt %, could be practical for hydrogen storage at reduced temperatures. The LiH/Si system is reversible and can be cycled without degradation. Absorption/desorption isotherms, obtained at 400−500 °C, exhibited two distinct flat plateaus with little hysteresis. The plateaus correspond to formation and decomposition of various Li silicides. The MgH2/Si system was not readily reversible. Hydrogenation of Mg2Si appears...
Ihara's lemma for imaginary quadratic fields

Abstract An analogue over imaginary quadratic fields of a result in algebraic number theory known as Ihara's lemma is established. More precisely, we show that for a prime ideal p of the ring of integers of an imaginary quadratic field F, the kernel of the sum of the two standard p -degeneracy maps between the cuspidal sheaf cohomology H ! 1 ( Y 0 , M ˜ 0 ) 2 → H ! 1 ( Y 1 , M ˜ 1 ) is Eisenstein. Here Y 0 and Y 1 are analogues over F of the modular curves Y 0 ( N ) and Y 0 ( N p ) , respectively. To prove our theorem we use the method of modular symbols and the congruence subgroup property for the group SL 2 ( Z [ 1 / p ] ) which is due to Mennicke [J. Mennicke, On Ihara's modular group, Invent. Math. 4 (1967) 202–228] and Serre [J.-P. Serre, Le probleme des groupes de congruence pour SL 2 , Ann. of Math. (2) 92 (1970) 489–527].
Nuclear dependence in transverse momentum distribution for Drell-Yan pair

Abstract In terms of multiple scattering picture, I compute the nuclear dependence in Drell-Yan transverse momentum distribution, dσ/dQ2dqT2, in hadron-nucleus collisions. I present the results for large qT region and discuss the possible suppression in small qT region.
Limit shapes and the complex Burgers equation

In this paper we study surfaces in R 3 that arise as limit shapes in random surface models related to planar dimers. These limit shapes are surface tension minimizers, that is, they minimize a functional of the form ∫σ(∇h) dx dy among all Lipschitz functions h taking given values on the boundary of the domain. The surface tension σ has singularities and is not strictly convex, which leads to formation of facets and edges in the limit shapes. We find a change of variables that reduces the Euler–Lagrange equation for the variational problem to the complex inviscid Burgers equation (complex Hopf equation). The equation can thus be solved in terms of an arbitrary holomorphic function, which is somewhat similar in spirit to Weierstrass parametrization of minimal surfaces. We further show that for a natural dense set of boundary conditions, the holomorphic function in question is, in fact, algebraic. The tools of algebraic geometry can thus be brought in to study the minimizers and, especially, the formation of their singularities. This is illustrated by several explicitly computed examples.
Production of a short-lived filament by a surge

A large surge was observed on September 17, 1971, part of which, after travelling 200 000 km through the corona, returned to the surface to form a filament. The filament lasted about 30 min, then rose up and returned to the source of the surge. We interpret this as the filling of a semi-stable magnetic trap. The energetics of radio, X-ray, and surge expulsion are estimated. The radio spectrum and flux correspond to a thermal source of area 4 (arcmin)2, T ∼ 190 000 K, N e 2 V ∼ 7 × 1048, which is optically deep at 8800 MHz. The soft X-ray source has T ∼ 12 × 106 K, N e 2 V ∼ 3 × 1048; and if an equal mass is expelled in the surge, the kinetic energy of the surge is similar to the thermal energy of the X-ray source.
Simple and flexible detection of contiguous repeats using a suffix tree

We study the problem of detecting all occurrences of (primitive) tandem repeats and tandem arrays in a string. We first give a simple time- and space-optimal algorithm to find all tandem repeats, and then modify it to become a time and space-optimal algorithm for finding only the primitive tandem repeats. Both of these algorithms are then extended to handle tandem arrays. The contribution of this paper is both pedagogical and practical, giving simple algorithms and implementations based on a suffix tree, using only standard tree traversal techniques
Cold Dark Matter Substructure and Galactic Disks. I. Morphological Signatures of Hierarchical Satellite Accretion

We conduct dissipationless N-body simulations to investigate the cumulative effect of substructure impacts onto thin disk galaxies in the context of the ΛCDM paradigm. Our simulation campaign is based on a hybrid approach combining cosmological simulations and controlled numerical experiments. Substructure properties are culled from cosmological simulations of galaxy-sized CDM halos. We demonstrate that accretions of massive subhalos onto the central regions of host halos, where the galactic disk resides, since z ~ 1 should be common occurrences. In contrast, extremely few satellites in present-day CDM halos are likely to have a significant impact on the disk structure. One host halo merger history is subsequently used to seed controlled N-body experiments of repeated satellite encounters with an initially thin Milky-Way (MW) type disk galaxy. These simulations track the effects of six dark matter substructures, with initial masses in the range ~(0.7–2) × 1010 M☉ (~20%-60% of the disk mass), crossing the disk in the past ~8 Gyr. We demonstrate that these accretion events produce several distinctive morphological signatures in the disk, including long-lived, low surface brightness, ringlike features in the outskirts; significant flares; bars; and faint filamentary structures above the disk plane. The final distribution of disk stars exhibits a complex vertical structure that is well described by a standard "thin-thick" disk decomposition. We compare one of the resulting ringlike features in our simulations to the Monoceros Ring stellar structure in the MW. The comparison shows quantitative agreement in spatial distribution and kinematics, suggesting that such observed complex stellar components may arise naturally as disk stars are excited by encounters with CDM substructure. We conclude that satellite-disk interactions of the kind expected in ΛCDM models can induce morphological features in galactic disks that are similar to those being discovered in the Milky Way, M31, and other disk galaxies. These results highlight the significant role of CDM substructure in setting the structure of disk galaxies and driving galaxy evolution. Upcoming galactic structure surveys and astrometric satellites may be able to distinguish between competing cosmological models by testing whether the detailed structure of galactic disks is as excited as predicted by the CDM paradigm.
Analytical model accuracy requirements for structural dynamic systems

A test/analysis correlation criterion for the analytical model accuracy requirement has been developed. It is based on the principle of equal errors from the model inaccuracy and the uncertainties of dynamic environments. The forcing functions are idealized to establish the base for uncertainty definition and the maximum allowable errors from these uncertainties are obtained. Then the model accuracy requirement is established by comparing the responses due to the model errors to those due to the forcing function uncertainties.
Angular sensitivity of guided mode resonant filters in classical and conical mounts

The angular sensitivity of guided mode resonant filters (GMRF) is well known. While at times useful for angle tuning of the response, this sensitivity can also be a major detriment as angular changes of tenths of a degree can shift the wavelength response in a narrow bandwidth device by an amount greater than the width of the resonance peak. We identify geometries where the resonance is more angularly stable, demonstrating high reflectivity at the design wavelength for several degrees in both azimuth and inclination angular directions with virtually no change in lineshape of the response. The investigation of GMRFs in both classical and conical mounts through simulation using rigorous coupled wave analysis reveals that there are preferred mounts for greater angular tolerance. We simulate a grating at telecom wavelengths using a design that we have previously fabricated. The identical grating placed in different mounts can exhibit angular tolerances that differ by well over an order of magnitude (60x). The most commonly used classical mount has a much more sensitive angular tolerance than does the conical mount. The lineshape of the resonant response shows only negligible changes across the angular band. The angular band for the sample grating is simulated to be several degrees in the conical mount as opposed to a tenth of a degree in the classical mount. We could thus expand the application space for narrow-band GMRFs into areas where angular tolerance cannot be controlled to the degree that we have believed required in the past.
Late-Time Spectroscopy of SN 2002cx: The Prototype of a New Subclass of Type Ia Supernovae

We present Keck optical spectra of SN 2002cx, the most peculiar known Type Ia supernova (SN Ia), taken 227 and 277 days past maximum light. Astonishingly, the spectra are not dominated by the forbidden emission lines of iron that are a hallmark of thermonuclear SNe in the nebular phase. Instead, we identify numerous P Cygni profiles of Fe II at very low expansion velocities of ~700 km s-1, which are without precedent in SNe Ia. We also report the tentative identification of low-velocity O I in these spectra, suggesting the presence of unburned material near the center of the exploding white dwarf. SN 2002cx is the prototype of a new subclass of SNe Ia, with spectral characteristics that may be consistent with recent pure deflagration models of Chandrasekhar-mass thermonuclear SNe. These are distinct from the majority of SNe Ia, for which an alternative explosion mechanism, such as a delayed detonation, may be required.
The Distance Between Classical and Quantum Systems

In a recent paper, a “distance” function, $$\cal D$$ , was defined which measures the distance between pure classical and quantum systems. In this work, we present a new definition of a “distance”, D, which measures the distance between either pure or impure classical and quantum states. We also compare the new distance formula with the previous formula, when the latter is applicable. To illustrate these distances, we have used 2 × 2 matrix examples and two-dimensional vectors for simplicity and clarity. Several specific examples are calculated.
Combined approach for excision of cervical nerve tumors with dural extension

Tumors of the cervical plexus are rare. Often these tumors are found on routine exam as asymptomatic masses. We present our experience in managing four patients with tumors with dural extension. Three of these lesions were neurilemomas and one was a meningioma. Symptoms and signs included weakness and hypoesthesia. Evaluation included complete neurologic examination with electromyography (EMG). Magnetic resonance imaging (MRI) was the best diagnostic tool to see tumor extent into the epidural and intradural space. Computed tomography (CT) or plain x-rays were used to evaluate the degree of destruction of the cervical spine. The surgical removal of these tumors was performed by a two-team approach. A posterior laminectomy was combined with an anterior neck exploration. Follow-up shows persistent upper extremity weakness in two patients, hypesthesia in three patients, and anesthesia of the anterior chest wall in two patients. Patients with these lesions should be informed of the potential neurologic consequences of removal.
On the log discrepancies in toric Mori contractions

It was conjectured by McKernan and Shokurov that for all Mori contractions from X to Y of given dimensions, for any positive epsilon there is a positive delta, such that if X is epsilon-log terminal, then Y is delta-log terminal. We prove this conjecture in the toric case and discuss the dependence of delta on epsilon, which seems mysterious.
An inequality on the edge lengths of triangular meshes

We give a short proof of the following geometric inequality: for any two triangular meshes A and B of the same polygon C, if the number of vertices in A is at most the number of vertices in B, then the maximum length of an edge in A is at least the minimum distance between two vertices in B. Here the vertices in each triangular mesh include the vertices of the polygon and possibly additional Steiner points. The polygon must not be self-intersecting but may be non-convex and may even have holes. This inequality is useful for many purposes, especially in proving performance guarantees of mesh generation algorithms. For example, a weaker corollary of the inequality confirms a conjecture of Aurenhammer et al. [Theoretical Computer Science 289 (2002) 879-895] concerning triangular meshes of convex polygons, and improves the approximation ratios of their mesh generation algorithm for minimizing the maximum edge length and the maximum triangle perimeter of a triangular mesh.
Mechanical response of random heteropolymers

We present an analytical theory for heteropolymer deformation, as exemplified experimentally by stretching of single protein molecules. Using replica mean-field theory, we determine phase diagrams for stress-induced unfolding of typical random sequences. This transition is sharp in the limit of infinitely long chain molecules. However, for chain lengths relevant to biological macromolecules, partially unfolded conformations prevail over an intermediate range of stress. These necklacelike structures, comprised of alternating compact and extended subunits, are stabilized by quenched variations in the composition of finite chain segments. The most stable arrangements of these subunits are largely determined by preferential extension of segments rich in solvophilic monomers. This predicted significance of necklace structures explains recent observations in protein stretching experiments. We examine the statistical features of select sequences that give rise to mechanical strength and may thus have guided the ...
Studies of the asymmetric [2+2] cycloaddition of silylketenes and aldehydes employing Ti-TADDOL catalysts

Abstract Ti-TADDOL catalysts provide good reactivity and moderate enantioselectivity in the asymmetric [2+2] cycloaddition of silyl ketenes and aldehydes. The effects of potential bidentate chelation of benzyloxy substituted aldehydes and of the steric size of the ketene silyl group were studied.
C-Glycosides to fused polycyclic ethers

This manuscript describes the synthesis of fused polycyclic ethers from the coupling of C-glycoside forming reactions with ring closing metathesis and acid mediated annulation reactions.
Trygve Haavelmo and the Emergence of Causal Calculus

Haavelmo was the first to recognize the capacity of economic models to guide policies. This paper describes some of the barriers that Haavelmo’s ideas have had (and still have) to overcome and lays out a logical framework that has evolved from Haavelmo’s insight and matured into a coherent and comprehensive account of the relationships between theory, data, and policy questions. The mathematical tools that emerge from this framework now enable investigators to answer complex policy and counterfactual questions using simple routines, some by mere inspection of the model’s structure. Several such problems are illustrated by examples, including misspecification tests, nonparametric identification, mediation analysis, and introspection. Finally, we observe that economists are largely unaware of the benefits that Haavelmo’s ideas bestow upon them and, to close this gap, we identify concrete recent advances in causal analysis that economists can utilize in research and education.
Psychopharmacology of attention deficit disorder: pharmacokinetic, neuroendocrine, and behavioral measures following acute and chronic treatment with methylphenidate.

Despite the frequent use of methylphenidate (MPH) in school-aged children with disorders of attention, impulsivity, and activity regulation (attention deficit disorder, ADD), little is known of its clinical pharmacology. The pharmacokinetics of MPH as well as its effects on growth hormone and prolactin were examined after oral administration in 14 boys with ADD ranging in age from 7 to 12 years (mean 10.4 years). Peak concentrations determined in these acute studies were compared with concentrations obtained two hours after MPH administration in another group of children with ADD who were receiving MPH chronically. After a lag phase of approximately ½ to 1 hour, MPH reached a peak plasma concentration at 2.5 ± 0.65 hours after 0.34 mg/kg and 1.9 ± 0.82 hours after 0.65 mg/kg (mean ± SD). Terminal half-lives were 2.53 ± 0.59 and 2.61 ± 0.29 hours after administration of 0.34 and 0.65 mg/kg, respectively. Observed maximal concentrations ranged from 11.2 ± 2.7 ng/ml after administration of 0.34, and 20.2 ± 9.1 ng/ml after administration of 0.65 mg/kg. The mean area under the curve after administration of 0.65 mg/kg was approximately double that calculated at 0.34 mg/kg. Plasma growth hormone increased significantly from an initial (pre-MPH) mean concentration of 4.4 to peak at two hours at 10.5 ng/ml. Prolactin concentration declined significantly from a pre-MPH level of 9.5 to a nadir at 1½ hours of 3.80 ng/ml, supporting the notion that MPH is acting via central dopaminergic mechanisms. MPH concentrations in children receiving doses of 0.34 mg/kg chronically averaged 8.00 ± 0.91 at two hours, after medication, approximating the mean concentration at the same time observed in the acute study. The concentration of MPH in single "spot" samples obtained at two to three hours after administration of medication were significantly correlated with the percentage of improvement in the abbreviated Conners rating scale, indicating a relationship between plasma MPH concentration and clinical response.
Selectin ligands: 2,3,4-tri-O-acetyl-6-O-(2-naphthyl)methyl (NAP) α-D-galactopyranosyl imidate as a novel glycosyl donor for the efficient total synthesis of branched mucin core 2-structure containing the NeuAcα2,3(SO3Na-6)Galβ1,3GalNAcα sequence

The stereo- and regioselective total synthesis of branched mucin core 2-structure 2, which contains the NeuAcα- 2,3(SO3Na-6)Galβ1,3GalNAcα sequence, is accomplished through the use of the key glycosyl donor 19.
Adiabatic expansion, early X-ray data and the central engine in GRBs

The Swift satellite early X-ray data show a very steep decay in most of the gamma-ray bursts light curves. This decay is either produced by the rapidly declining continuation of the central engine activity or by some leftover radiation starting right after the central engine shuts off. The latter scenario consists of the emission from an 'ember' that cools via adiabatic expansion and, if the jet angle is larger than the inverse of the source Lorentz factor, the large angle emission. In this work, we calculate the temporal and spectral properties of the emission from such a cooling ember, providing a new treatment for the microphysics of the adiabatic expansion. We use the adiabatic invariance of p 2 ⊥ /B (p ⊥ is the component of the electrons' momentum normal to the magnetic field, B) to calculate the electrons' Lorentz factor during the adiabatic expansion; the electron momentum becomes more and more aligned with the local magnetic field as the expansion develops. We compare the theoretical expectations of the adiabatic expansion (and the large angle emission) with the current observations of the early X-ray data and find that only ∼20 per cent of our sample of 107 bursts are potentially consistent with this model. This leads us to believe that, for most bursts, the central engine does not turn off completely during the steep decay of the X-ray light curve; therefore, this phase is produced by the continued rapidly declining activity of the central engine.
Wideband Fading Channel Capacity With Training and Partial Feedback

We consider the capacity of a wideband fading channel with partial feedback, subject to an average power constraint. The channel is modeled as a set of parallel independent block Rayleigh fading subchannels with finite coherence time (L channel uses). The transmitter probes a subset of subchannels during each coherence time by transmitting pilot sequences for channel estimation. For each subchannel probed, one bit of feedback indicates whether or not the channel gain exceeds a threshold allowing transmission. Our problem is to optimize jointly the training (both length and power), number of subchannels probed (probing bandwidth), and feedback threshold to maximize the achievable rate (lower bound on ergodic capacity) taking into account the subchannel estimation error. Optimizing the probing bandwidth balances diversity against the quality of the subchannel estimate. We show that the achievable rate increases as S log L, where S is the signal-to-noise ratio, and exceeds the capacity with impulsive signaling (given by S) when L exceeds a (positive) threshold value. Moreover, the optimal probing bandwidth scales as SL/log2 L. In contrast, without feedback the optimal probing bandwidth for the probing scheme scales as SL1/3 and the achievable rate converges to S, where the gap diminishes as SL-1/3.
Creating life time value for hardware systems creative maintenance and new market

It is discussed if we can change our maintenance to be more creative so as to satisfy our customers expectations that our hardware products would adapt better and work better or would be “customized better” in their present environments and in the present situations, we could create life time value for our hardware systems and could bring more profits in the long run than we try to increase one time values by adding more and higher functions to our systems.
Synthesis and biological applications of collagen-model triple-helical peptides

Triple-helical peptides (THPs) have been utilized as collagen models since the 1960s. The original focus for THP-based research was to unravel the structural determinants of collagen. In the last two decades, virtually all aspects of collagen structural biochemistry have been explored with THP models. More specifically, secondary amino acid analogs have been incorporated into THPs to more fully understand the forces that stabilize triple-helical structure. Heterotrimeric THPs have been utilized to better appreciate the contributions of chain sequence diversity on collagen function. The role of collagen as a cell signaling protein has been dissected using THPs that represent ligands for specific receptors. The mechanisms of collagenolysis have been investigated using THP substrates and inhibitors. Finally, THPs have been developed for biomaterial applications. These aspects of THP-based research are overviewed herein.
Aristotle on Investment Decision Making

In this age of inexpensive and abundant data, investors must remain mindful of the limitations of the data they are using for their investment decisions. Despite widespread problems with the quality, timeliness, and relevance of financial and economic data, many investors accept and react to these data at face value. Often, further analysis of the data and an understanding of the factors that drive the data will lead to increased uncertainty—and may change the analyst's conclusions.
Divergent reactions on racemic mixtures

Methods that furnish enantioenriched products are crucial in modern organic synthesis. An underutilized strategy to arrive at enantioenriched products is to perform divergent reactions on racemic mixtures, where each enantiomer of the starting material reacts with a single chiral reagent to furnish two separable, non-enantiomeric products that are enantioenriched. Stereodivergent, regiodivergent and structurally divergent reactions on racemic mixtures are discussed in this tutorial review.
Network Externalities in Microcomputer Software: An Econometric Analysis of the Spreadsheet Market

Because of network externalities, the success of a software product may depend in part on stalled base and its conformance to industry standards. This research builds a hedonic model to determine the effects of network externalities, standards, intrinsic features and a time trend on microcomputer spreadsheet software prices. When data for a sample of products during the 1987-1992 time period were analyzed using this model, four main results emerged: 1 Network externalities, as measured by the size of a product's installed base, significantly increased the price of spreadsheet products: a one percent increase in a product's installed base was associated with a 0.75% increase in its price. 2 Products which adhered to the dominant standard, the Lotus menu tree interface, commanded prices which were higher by an average of 46%. 3 Although nominal prices increased slightly during this time period, quality-adjusted prices declined by an average of 16% per year. 4 The hedonic model was found to be a good predictor of actual market prices, despite the fact that it was originally estimated using list prices. Several variations of the model were examined, and, while the qualitative findings were robust, the precise estimates of the coefficients varied somewhat depending on the sample of products examined, the weighting of the observations and the functional form used in estimation, suggesting that the use of hedonic methods in this domain is subject to a number of limitations due, inter alia, to the potential for strategic pricing by vendors.
The Genetics of Immunity

In this commentary, Brian P. Lazzaro and David S. Schneider examine the topic of the Genetics of Immunity as explored in this month's issues of GENETICS and G3: Genes|Genomes|Genetics. These inaugural articles are part of a joint Genetics of Immunity collection (ongoing) in the GSA journals.
Strong particle dispersion by weakly dissipative random internal waves

Simple stochastic models and direct nonlinear numerical simulations of three-dimensional internal waves are combined in order to understand the strong horizontal particle dispersion at second-order in wave amplitude that arises when small-amplitude internal waves are exposed to weak dissipation. This is contrasted with the well-known results for perfectly inviscid internal waves, in which such dispersion arises only at fourth-order in wave amplitude.
Do Farmers Hedge Optimally or by Habit? A Bayesian Partial-Adjustment Model of Farmer Hedging

Hedging is one of the most important risk management decisions that farmers make and has a potentially large role in the level of profit eventually earned from farming. Using panel data from a survey of Georgia farmers that recorded their hedging decisions for 4 years on four crops, we examine the role of habit, demographics, farm characteristics, and information sources on the hedging decisions made by 57 different farmers. We find that the role of habit varies widely and that estimation of a single habit effect suffers from aggregation bias. Thus, modeling farmer-level heterogeneity in the examination of habit and hedging is crucial.
The logic programming paradigm and Prolog

This is a tutorial on logic programming and Prolog appropriate for a course on programming languages for students familiar with imperative programming.
Multi-Level Control Systems

A decomposition technique applied to the optimum control problem for interacting dynamic systems is used to generate an equivalent two level hierarchy of sub-problem. Application to the synthesis of controllers is discussed and an important special case for “slack” systems is indicated with an example relating conventional integral action control with coordination.