cssi/SciSciGPT-SciSciNet huggingface dataset:
Character-aware neural language models

We describe a simple neural language model that relies only on character-level inputs. Predictions are still made at the word-level. Our model employs a convolutional neural network (CNN) and a highway network over characters, whose output is given to a long short-term memory (LSTM) recurrent neural network language model (RNN-LM). On the English Penn Treebank the model is on par with the existing state-of-the-art despite having 60% fewer parameters. On languages with rich morphology (Arabic, Czech, French, German, Spanish, Russian), the model outperforms word-level/morpheme-level LSTM baselines, again with fewer parameters. The results suggest that on many languages, character inputs are sufficient for language modeling. Analysis of word representations obtained from the character composition part of the model reveals that the model is able to encode, from characters only, both semantic and orthographic information.
An Experimental Evaluation of the Best-of-Many Christofides' Algorithm for the Traveling Salesman Problem

Recent papers on approximation algorithms for the traveling salesman problem (TSP) have given a new variant of the well-known Christofides' algorithm for the TSP, called the Best-of-Many Christofides' algorithm. The algorithm involves sampling a spanning tree from the solution to the standard LP relaxation of the TSP, subject to the condition that each edge is sampled with probability at most its value in the LP relaxation. One then runs Christofides' algorithm on the tree by computing a minimum-cost matching on the odd-degree vertices in the tree, and shortcutting a traversal of the resulting Eulerian graph to a tour. In this paper we perform an experimental evaluation of the Best-of-Many Christofides' algorithm to see if there are empirical reasons to believe its performance is better than that of Christofides' algorithm. Furthermore, several different sampling schemes have been proposed; we implement several different schemes to determine which ones might be the most promising for obtaining improved performance guarantees over that of Christofides' algorithm. In our experiments, all of the implemented methods perform significantly better than Christofides' algorithm; an algorithm that samples from a maximum entropy distribution over spanning trees seems to be particularly good, though there are others that perform almost as well.
Absence of the holographic principle in noncommutative Chern-Simons theory

We examine noncommutative Chern-Simons theory on a bounded spatial domain. We argue that upon `turning on' the noncommutativity, the edge observables, which characterized the commutative theory, move into the bulk. We show this to lowest order in the noncommutativity parameter appearing in the Moyal star product. If one includes all orders, the hamiltonian formulation of the gauge theory ceases to exist, indicating that the Moyal star product must be modified in the presence of a boundary. Alternative descriptions are matrix models. We examine one such model, obtained by a simple truncation of Chern-Simons theory on the noncommutative plane, and express its observables in terms of Wilson lines.
Axion dissipation through the mixing of Goldstone bosons

Abstract By coupling axions strongly to a hidden sector, the energy density in coherent axions may be converted to radiative degrees of freedom, alleviating the “axion energy crisis”. The strong coupling is achieved by mixing the axion and some other Goldstone boson through their kinetic energy terms, in a manner reminiscent of paraphoton models. Even with the strong coupling it proves difficult to relax the axion energy density through particle absorption, due to the derivative nature of Goldstone boson couplings and the effect of back reactions on the evolution of the axion number density. However, the distribution of other particle species in the hidden sector will be driven from equilibrium by the axion field oscillations. Restoration of thermal equilibrium results in energy being transferred from the axions to massless particles, where it can redshift harmlessly without causing any cosmological problems.
Comparison Of The Bidirectional Reflectance Distribution Function Of Various Surfaces

This paper describes the development and use of a system to measure the Bidirectional Reflectance Distribution Function (BRDF) of various surfaces. The BRDF measurements will be used in the analysis and design of optical measurement systems, such as laser anemometers. An argon ion laser (514 nm) was the light source. Preliminary results are presented for eight samples: two glossy black paints, two flat black paints, black glass, sand blasted aluminum, unworked aluminum, and a white paint. A BaSO4 white reflectance standard was used as the reference sample throughout the tests. The reflectance characteristics of these surfaces are compared in this paper.
Beryllium in the Hyades F and G Dwarfs from Keck HIRES Spectra

Although there are extensive observations of Li in field stars of all types and in both open and (recently) globular cluster stars, there are relatively few observations of Be. Because Be is not destroyed as easily as Li, the abundances of Li and Be together can tell us more about the internal physical processes in stars than either element can alone. We have obtained high-resolution (45,000) and high signal-to-noise ratio (typically 90 per pixel) spectra of the Be II resonance lines in 34 Hyades F and G dwarfs with the Keck I telescope and HIRES. In addition we took a spectrum of the daytime sky to use as a surrogate for the solar spectrum so we could determine the value for Be in the Sun, analyzed in the same manner as that for the stars. We have adopted stellar temperatures and some Li abundances for these stars from the literature. For most of the F dwarfs we have rederived Li abundances. The Be abundances have been derived with the spectrum synthesis method. We find that Be is depleted, but detected, in the Li gap in the F stars reaching down to values of A(Be) = 0.60 dex, or a factor of nearly 7 below the meteoritic Be abundance (a factor of 3.5 below the solar value of Chmielewski et al.). There is little or no depletion of Be in stars cooler than 6000 K, in spite of the large depletions (0.5-2.5 dex) in Li. The mean value of A(Be) for the 10 coolest stars is 1.33 ± 0.06, not far from the meteoritic value of 1.42. The pattern in the Be abundances—a Be dip and undepleted Be in the cool stars—is well matched by the predictions of slow mixing due to stellar rotation. We have interpolated the calculations of Deliyannis and Pinsonneault for Be depletion due to rotational mixing to the age of the Hyades; we find excellent agreement of the predictions with the observed Be abundances but less good agreement with the observed Li abundances. Some of our Hyades stars have photometrically determined rotation periods, but there is no relation between Be and rotation period. (Generally, the lower mass stars have less Li and longer periods, which may indicate greater spin-down and thus more Li depletion relative to Be.) The Li and Be abundances are correlated for stars in the temperature range of 5850-6680 K, similar to results from earlier work on Li and Be in F and G field stars. This indicates that the depletions are not just correlated—the only claim that can be made for the field stars—but are probably occurring together during main-sequence evolution. The Hyades G dwarfs have more Be than the Sun; their initial Be may have been larger or they may not be old enough to have depleted much Be. For those Hyades stars that seem to have little or no depletion of Li or Be, the Li/Be ratio is found to be 75 ± 30; the meteoritic ratio Li/Be is 78. The Hyades ratio is a representative value for the initial ratio in the material out of which the Hyades cluster was formed.
Relating aviation service difficulty reports to accident data for safety trend prediction

Abstract Commercial aviation fatalities are predicted (Fulwood et al., ‘Relating aviation service difficulty reports to accident data for safety trend prediction’, BNL Tech. Rpt 63018, March 1996) using linear superposition of the time-dependent spectra of key aircraft systems difficulties reporting in FAA's Service Difficulty Reports (SDR (DOT, FAA, ‘Flight standards service difficulty program’, Order 8010.2, Feb. 22, 1978, reissued 4:5/14/81)) data base. The fitting coefficients are found by a linear regression model (referred to as ‘the model’) to FAA's Accident Incident Data System (AIDS (DOT/FAA, ‘Aviation standards accident/incident data system—AIDS’, Users Guide VS ASAS-D-335, July 1982)) covering 5.5 years beginning January 1990. The model was tested by dividing the data approximately in half, using the first half to calibrate the model for prediction of the second half. A second test did the opposite. A third test used the first 60 months of data to predict the following 6 months. These tests (Fig. 5) showed good agreement between the model and AIDS data. The deficiency frequency of ATA (Aircraft Transportation Association) systems is reported (Table 2). Third-order fitting of the AIDS data was also used for prediction. All methods are compared in Fig. 4. The model was deemed superior because it reflects inspections and may be updated with SDR data from the Internet. The magnitude of the model's fitting coefficients indicate systems importances to the results.
Mental models and software maintenance

Abstract Understanding how a program is constructed and how it functions are significant components of the task of maintaining or enhancing a computer program. We have analyzed vidoetaped protocols of experienced programmers as they enhanced a personnel data base program. Our analysis suggests that there are two strategies for program understanding, the systematic strategy and the as-needed strategy. The programmer using the systematic strategy traces data flow through the program in order to understand global program behavior. The programmer using the as-needed strategy focuses on local program behavior in order to localize study of the program. Our empirical data show that there is a strong relationship between using a systematic approach to acquire knowledge about the program and modifying the program successfully. Programmers who used the systematic approach to study the program constructed successful modifications; programmers who used the as-needed approach failed to construct successful modifications. Programmers who used the systematic strategy gathered knowledge about the causal interactions of the program's functional components . Programmers who used the as-needed strategy did not gather such causal knowledge and therefore failed to detect interactions among components of the program.
Submission Fees and Response Times in Academic Publishing

Both submission fees and response times enable editors to maintain an acceptable refereeing burden by discouraging the submission of articles with low probability of acceptance. When authors differ in their ability or willingness to pay submission fees and deal with delays, journal quality is maximized under a combination of moderate fees and moderate delays.
[(FeIII(OH2)2)3(A-α-PW9O34)2]9- on Cationic Silica Nanoparticles, a New Type of Material and Efficient Heterogeneous Catalyst for Aerobic Oxidations

Polyoxometalates (POMs) electrostatically bind to silica nanoparticles coated with cationic aluminum oxide “(Si/AlO2)n+” to form a new type of material (the anionic POMs replace Cl- counterions associated with the cationic surface sites). Association of a new ∼D3h POM of formula [(FeIII(OH2)2)3(A-α-PW9O34)2]9- (1) with the cationic nanoparticles (to form “K81/(Si/AlO2)”) was studied in detail. Elemental analysis, particle sizes from both laser light scattering and TEM before and after association of 1, the size of 1 from X-ray crystallography, and other methods provide mutually consistent data that indicate about 58 K8[(FeIII(OH2)2)3(A-α-PW9O34)2]- monoanions associate with the average nanoparticle (diameter of the K81/(Si/AlO2) product = ∼17 nm). While heterogeneity of the cationic sites and roughness of the (Si/AlO2)n+ surfaces make the associated POMs structurally nonuniform, the equivalent of ∼1 monolayer of 1 is present in K81/(Si/AlO2). Remarkably, while 1, the precursor (Si/AlO2)n+, and the compone...
Critical Exponent for a Nonlinear Wave Equation with Damping

Abstract In this study we solve the critical exponent problem for the nonlinear wave equation with damping. We show that this critical exponent coincides with the famous Fujita critical exponent for the heat equation. We also observe a futher interesting phenomenon due to the presence of the damping term. The “real” support of the solution is strongly suppressed by the damping and is concentrated in the ball |x| 0 the solution decays exponentially.
Field configurations with half-integer angular momentum in purely bosonic theories without topological charge

Abstract It is shown that purely bosonic field theories can have configurations with half-integral angular momentum even when the topological magnetic charge of the configuration vanishes. This result is applicable whenever there is a non-Abelian gauge theory with particles that transform in the fundamental representation of the non-Abelian symmetry group.
Non-perturbative approaches to magnetism in strongly correlated electron systems

The microscopic basis for the stability of itinerant ferromagnetism in correlated electron systems is examined. To this end several routes to ferromagnetism are explored, using both rigorous methods valid in arbitrary spatial dimensions, as well as Quantum Monte Carlo investigations in the limit of infinite dimensions (dynamical mean-field theory). In particular we discuss the qualitative and quantitative importance of (i) the direct Heisenberg exchange coupling, (ii) band degeneracy plus Hund's rule coupling, and (iii) a high spectral density near the band edges caused by an appropriate lattice structure and/or kinetic energy of the electrons. We furnish evidence of the stability of itinerant ferromagnetism in the pure Hubbard model for appropriate lattices at electronic densities not too close to half-filling and large enough U. Already a weak direct exchange interaction, as well as band degeneracy, is found to reduce the critical value of U above which ferromagnetism becomes stable considerably. Using similar numerical techniques the Hubbard model with an easy axis is studied to explain metamagnetism in strongly anisotropic antiferromagnets from a unifying microscopic point of view.
Postbuckling of long orthotropic plates in combined shear and compression

The nonlinear large-deflection partial differential equations of von karman for orthotropic plates loaded in combined shear and compression are converted into a set of first-order nonlinear ordinary differential equations by assuming trigonometric functions in one direction. These equations are solved numerically using a two point boundary problem solver which makes use of Newton's method. Results are obtained which determine the postbuckling behavior of rectangular plates with loading up to about three times the buckling load. Both isotropic and orthotropic composite plates are considered. Results show that orthotropic plates may behave quite differently than isotropic plates and that in-plane boundary conditions are important for plates loaded in shear.
Accurate low-rank matrix recovery from a small number of linear measurements

We consider the problem of recovering a low-rank matrix M from a small number of random linear measurements. A popular and useful example of this problem is matrix completion, in which the measurements reveal the values of a subset of the entries, and we wish to fill in the missing entries (this is the famous Netflix problem). When M is believed to have low rank, one would ideally try to recover M by finding the minimum-rank matrix that is consistent with the data; this is, however, problematic since this is a nonconvex problem that is, generally, intractable. Nuclear-norm minimization has been proposed as a tractable approach, and past papers have delved into the theoretical properties of nuclear-norm minimization algorithms, establishing conditions under which minimizing the nuclear norm yields the minimum rank solution. We review this spring of emerging literature and extend and refine previous theoretical results. Our focus is on providing error bounds when M is well approximated by a low-rank matrix, and when the measurements are corrupted with noise. We show that for a certain class of random linear measurements, nuclear-norm minimization provides stable recovery from a number of samples nearly at the theoretical lower limit, and enjoys order-optimal error bounds (with high probability).
Nonlinear Dynamics of Traffic Jams

We review current progress and challenges in modeling of nonlinear phenomena in traffic flow. We are particularly interested in the nonlinear dynamics of traffic jams: the transition to instabilities of traffic flow, the formation of traffic jams and the evolution of the traffic jams. A discrete dynamic system approach is proposed. The self- organized oscillatory behavior and chaotic behavior in traffic are identified and formulated. The results can help to explain the appearance of a phantom traffic jam observed in real traffic. It is also proved that coarser resolution results in richer dynamics of the traffic flow including traffic jams. This is exactly what the numerical simulations showed. It is clear that the spatial and temporal resolution affects traffic variable and assumptions in a considerable way. Continuum models run into the limits of describing discrete phenomena in a continuous way. Therefore a combination of continuum and discrete descriptions will be necessary to further improve and declare specific traffic phenomena.
The quantum structure of black holes

We give an elementary review of black holes in string theory. We discuss black hole entropy from string microstates and Hawking radiation from these states. We then review the structure of two-charge microstates and explore how 'fractionation' can lead to quantum effects over macroscopic length scales of the order of the horizon radius.
Performance Testing of a Transit Generator at JPL

A Transit type thermoelectric generator, serial number QM-III, assembled with lightweight Isotec type thermoelectric panels, has been placed on test at the Jet Propulsion Laboratory. In its exterior appearance and main constructive features, generator QM-III is similar to the generator which was flown on the Transit satellite, launched into circular polar orbit on Sept. 2, 1972. The main difference between the flight generator and QM-III is that the flight hardware is heated by radioisotope decay, while QM-III is an ETG and is assembled with three different types of thermoelectric panels. The paper describes the generator and test equipment used and presents the results of the tests performed to date.
On the Incidence of Strong Gravitational Lensing by Clusters in the Las Campanas Distant Cluster Survey

The observed incidence of strongly lensing clusters exceeds the predictions of a ΛCDM model by about a factor of 10. We revisit the observational side of this discrepancy by measuring the incidence of strong lensing in a subsample of clusters drawn from the Las Campanas Distant Cluster Survey (LCDCS). Among clusters with 0.5 ≤ z ≤ 0.7, the redshift range in which we focus our search, we find two strongly lensed systems within an effective search area of 69 deg2. There is at least one other strongly lensed system in the LCDCS outside of this redshift range, where we are less complete. Over all redshifts, the ΛCDM model produces one large arc every 146 deg2. Assuming Poisson statistics, the probability of finding three or more strongly lensing clusters in 69 deg2 is 0.012. The lensing incidence within the LCDCS is in agreement with that derived from an X-ray-selected sample and what has been preliminarily presented from an independent optical cluster survey. The origin of the disagreement between theory and observations, which remains at least at the order-of-magnitude scale for the ΛCDM model, lies either in the concordance cosmological model, in the characteristics of the resulting cluster potentials, or in the adopted source population.
A cohomological approach to the non-abelian Seiberg-Witten map

We present a cohomological method for obtaining the non-abelian Seiberg-Witten map for any gauge group and to any order in θ. By introducing a ghost field, we are able to express the equations defining the Seiberg-Witten map through a coboundary operator, so that they can be solved by constructing a corresponding homotopy operator.
THE ELEMENTAL COMPOSITION OF HIGH-ENERGY COSMIC RAYS: MEASUREMENTS WITH TRACER

TRACER ("Transition Radiation Array for Cosmic Energetic Radiation") is a balloon borne instrument that has been developed to directly measure the composition and energy spectra of individual heavy elements up to 1015 eV particle-1. TRACER achieves a large geometric factor (5 m2 sr) through the use of a Transition Radiation Detector utilizing arrays of single wire proportional tubes. TRACER has measured the energy spectra of the elements O, Ne, Mg, Si, S, Ar, Ca and Fe. The energy spectra reach energies in excess of 1014 eV particle-1 and exhibit nearly the same spectral index (2.65±0.05) for all elements.
Magnetospheric toroidal Alfvén wave harmonics and the field line distribution of mass density

[1] Measurements of electric and magnetic field taken by instruments on the Combined Release and Radiation Effects Satellite (CRRES) spacecraft on 29 July 1991 reveal seven or eight toroidal Alfven wave frequency bands. By using observations of the waves near the magnetic equator and the symmetry of the theoretical modes as a function of magnetic latitude, we can identify which theoretical Alfven wave harmonic corresponds to a particular frequency band. This, along with the L shell frequency dependence, gives convincing evidence that we are in fact observing the toroidal Alfven mode. Because the harmonics of the toroidal Alfven wave have a different response to mass density at different points along a magnetic field line, the frequencies of these harmonics can be used to infer the distribution of mass density along the field line. While there is a significant uncertainty in the results due to the uncertainty in the observed frequencies, it is nevertheless true that both the solution based on the peak (mean) frequencies and the majority of solutions using a Monte Carlo simulation of the effects of uncertainty in frequency show the same result, that there is a local maximum in ρ within about 30° of the magnetic equator. A similar result is found for the wave event observed on 28 August 1990, a local maximum in ρ within about 15° of the magnetic equator. These results imply that heavy ions are preferentially concentrated at the magnetic equator.
Efficiency of (revenue-)optimal mechanisms

We compare the expected efficiency of revenue maximizing (or optimal) mechanisms with that of efficiency maximizing ones. We show that the efficiency of the revenue maximizing mechanism for selling a single item with (k + logeovere-1k + 1) bidders is at least as much as the efficiency of the efficiency-maximizing mechanism with k bidders, when bidder valuations are drawn i.i.d. from a Monotone Hazard Rate distribution. Surprisingly, we also show that this bound is tight within a small additive constant of 4.7. In other words, Θ(log k) extra bidders suffice for the revenue-maximizing mechanism to match the efficiency of the efficiency-maximizing mechanism, while o(log k) do not. This is in contrast to the result of Bulow and Klemperer comparing the revenue of the two mechanisms, where only one extra bidder suffices. More precisely, they show that the revenue of the efficiency-maximizing mechanism with k + 1 bidders is no less than the revenue of the revenue-maximizing mechanism with k bidders.We extend our result for the case of selling t identical items and show that Θ(log k) + t Θ(log log k) extra bidders suffice for the revenue-maximizing mechanism to match the efficiency of the efficiency-maximizing mechanism.In order to prove our results, we do a classification of Monotone Hazard Rate (MHR) distributions and identify a family of MHR distributions, such that for each class in our classification, there is a member of this family that is pointwise lower than every distribution in that class. This lets us prove interesting structural theorems about distributions with Monotone Hazard Rate.
Stochastic Equicontinuity for Unbounded Dependent Heterogeneous Arrays

This paper establishes stochastic equicontinuity for classes of mixingales. Attention is restricted to Lipschitz-continuous parametric functions. Unlike some other empirical process theory for dependent data, our results do not require bounded functions, stationary processes, or restrictive dependence conditions. Applications are given to martingale difference arrays, strong mixing arrays, and near-epoch dependent arrays.
Asymmetric Allylboration of Aldehydes with Pinacol Allylboronates Catalyzed by 1,1′‐Spirobiindane‐7,7′‐diol (SPINOL) Based Phosphoric Acids

The asymmetric allylboration of aldehydes with pinacolallylboronates catalyzed by 1,1′-spirobiindane-7,7′-diol (SPINOL) based phosphoric acids is described. 6,6′-Bis(2,4,6-triisopropylphenyl)SPINOL-based phosphoric acid was found to be a general, highly enantioselective catalyst for such allylboration reactions and excellent enantioselectivities were obtained for different types of aldehydes including aromatic aldehydes, α,β-unsaturated aldehydes, propargylic aldehydes, and aliphatic aldehydes.
Testing cosmological models against the abundance of damped Lyman-alpha absorbers

We calculate the number of damped Lyα absorbers expected in various popular cosmological models as a function of redshift and compare our predictions with observed abundances. The Press-Schechter formalism is used to obtain the distribution of halos with circular velocity in different cosmologies, and we calibrate the relation between circular velocity and absorption cross section using detailed gasdynamical simulations of a standard cold dark matter (CDM) model. Because of this calibration, our approach makes more realistic assumptions about the absorption properties of collapsed objects than previous, analytic calculations of the damped Lyα abundance. CDM models with Ω0 = 1, H0 = 50 km s-1 Mpc-1, baryon density Ωb = 0.05, and scale-invariant primeval fluctuations reproduce the observed incidence and redshift evolution of damped Lyα absorption to within observational uncertainty, for both COBE normalization (σ8 = 1.2) and a lower normalization (σ8 = 0.7) that better matches the observed cluster abundance at z = 0. A tilted (n = 0.8, σ8 = 0.7) CDM model tends to underproduce absorption, especially at z = 4. With COBE normalization, a CDM model with Ω0 = 0.4, ΩΛ = 0.6 gives an acceptable fit to the observed absorption; an open CDM model is marginally acceptable if Ω0 ≥ 0.4 and is strongly inconsistent with the z = 4 data if Ω0 = 0.3. Mixed dark matter models tend not to produce sufficient absorption, being roughly comparable to tilted CDM models if Ων = 0.2 and failing drastically if Ων = 0.3.
Centroid finding method for position-sensitive detectors

Abstract A new centroid finding method for all detectors where the signal charge is collected or induced on strips or wires, or on subdivided resistive electrodes, is presented. The centroid of charge is determined by convolution of the sequentially switched outputs from these subdivisions or from the strips with a linear centroid finding filter . The position line width is inversely proportional to N 3 2 , where N is the number of subdivisions.
A simple polarizable electrode for EEG audiometry.

Electroencephalic energy transmission as a function of frequency for solder electrodes was investigated since this type of polarizable electrode has an economic advantage over commercial non-polarizable types. The electrode's characteristics were measured and replicated at infrasonic frequencies in saline solution. The results of the investigation revealed that values of linearity, frequency response and phase response were acceptable for evoked response audiometry.
Color or Multispectral Laser Recording on Black and White Film

Color-encoded images can be recorded on black-and-white film through the use of synthetically generated diffraction gratings. This technique has applications in the display and interpretation of multispectral information generated by airborne or spaceborne line scan sensors and color scanners in facsimile systems. A color facsimile system based on this principle has been implemented using a white light color transparency scanner and a laser beam recorder. In system tests, good color recognition, 20-line pair/millimeter resolution, and 7, grey level steps have been achieved.
Computation of the nucleolus of some bilateral market games

This paper gives a simple algorithm for computing the nucleolus of bilateral markets with two complementary commodities.
The superconducting proximity effect as a tool to investigate metal films and interfaces

The superconducting proximity effect is measured in sandwiches of thin Pb films and the alkali metals Cs, Rb, K and Na. The T c -dependence provides information about the interface barriers between Pb and the alkalis. Such a barrier is particularly large in Pb/Cs sandwiches. It is not due to impurities or oxydation. In the presence of a sufficiently strong barrier a special form of the Cooper limit can be applied to calculate the transition temperature of the sandwich.
Atmospheric ammonia measurements in Houston, TX using an external-cavity quantum cascade laser-based sensor

Abstract. In order to improve the current understanding of the dynamics of ammonia (NH3) in a major industrial and urban area, intensive measurements of atmospheric NH3 were conducted in Houston during two sampling periods (12 February 2010–1 March 2010 and 5 August 2010–25 September 2010). The measurements were performed with a 10.4-μm external cavity quantum cascade laser (EC-QCL)-based sensor employing conventional photo-acoustic spectroscopy. The mixing ratio of NH3 ranged from 0.1 to 8.7 ppb with a mean of 2.4 ± 1.2 ppb in winter and ranged from 0.2 to 27.1 ppb with a mean of 3.1 ± 2.9 ppb in summer. The larger levels in summer probably are due to higher ambient temperature. A notable morning increase and a mid-day decrease were observed in the diurnal profile of NH3 mixing ratios. Motor vehicles were found to be major contributors to the elevated levels during morning rush hours in winter. However, changes in vehicular catalytic converter performance and other local or regional emission sources from different wind directions governed the behavior of NH3 during morning rush hours in summer. There was a large amount of variability, particularly in summer, with several episodes of elevated NH3 mixing ratios that could be linked to industrial facilities. A considerable discrepancy in NH3 mixing ratios existed between weekdays and weekends. This study suggests that NH3 mixing ratios in Houston occasionally exceeded previous modeling predictions when sporadic and substantial enhancements occurred, potentially causing profound effects on particulate matter formation and local air quality.
Advances and Prospects in Reversed Field Pinch Research

The reactor attributes of the compact, high beta RFP are as needed today as when the RFP was conceived. Confinement is a dominant scientific issue at present. In the past several years magnetic fluctuations have been shown experimentally to drive anomalous transport. From an understanding of the cause of transport, it is expected that flattening of the current density profile should suppress fluctuations and transport. Inductive current profile control has succeeded in reducing the fluctuations, and doubling the energy and particle confinement times. For steady state current profile control, electrostatic current injection (dc helicity injection) is under preparation and rf current drive (fast wave and lower hybrid) has been shown to be feasible. 16 refs., 2 figs.
Function of Escherichia coli MsbA, an Essential ABC Family Transporter, in Lipid A and Phospholipid Biosynthesis

The Escherichia coli msbA gene, first identified as a multicopy suppressor of htrB mutations, has been proposed to transport nascent core-lipid A molecules across the inner membrane (Polissi, A., and Georgopoulos, C. (1996) Mol. Microbiol. 20, 1221–1233). msbA is an essentialE. coli gene with high sequence similarity to mammalian Mdr proteins and certain types of bacterial ABC transporters.htrB is required for growth above 32 °C and encodes the lauroyltransferase that acts after Kdo addition during lipid A biosynthesis (Clementz, T., Bednarski, J., and Raetz, C. R. H. (1996) J. Biol. Chem. 271, 12095–12102). By using a quantitative new 32Pi labeling technique, we demonstrate that hexa-acylated species of lipid A predominate in the outer membranes of wild type E. coli labeled for several generations at 42 °C. In contrast, in htrB mutants shifted to 42 °C for 3 h, tetra-acylated lipid A species and glycerophospholipids accumulate in the inner membrane. Extra copies of the cloned msbA gene restore the ability ofhtrB mutants to grow at 42 °C, but they do not increase the extent of lipid A acylation. However, a significant fraction of the tetra-acylated lipid A species that accumulate in htrBmutants are transported to the outer membrane in the presence of extra copies of msbA. E. coli strains in which msbA synthesis is selectively shut off at 42 °C accumulate hexa-acylated lipid A and glycerophospholipids in their inner membranes. Our results support the view that MsbA plays a role in lipid A and possibly glycerophospholipid transport. The tetra-acylated lipid A precursors that accumulate in htrB mutants may not be transported as efficiently by MsbA as are penta- or hexa-acylated lipid A species.
The chemical diversity and distribution of glucosinolates and isothiocyanates among plants

Glucosinolates (beta-thioglucoside-N-hydroxysulfates), the precursors of isothiocyanates, are present in sixteen families of dicotyledonous angiosperms including a large number of edible species. At least 120 different glucosinolates have been identified in these plants, although closely related taxonomic groups typically contain only a small number of such compounds. Glucosinolates and/or their breakdown products have long been known for their fungicidal, bacteriocidal, nematocidal and allelopathic properties and have recently attracted intense research interest because of their cancer chemoprotective attributes. Numerous reviews have addressed the occurrence of glucosinolates in vegetables, primarily the family Brassicaceae (syn. Cruciferae; including Brassica spp and Raphanus spp). The major focus of much previous research has been on the negative aspects of these compounds because of the prevalence of certain "antinutritional" or goitrogenic glucosinolates in the protein-rich defatted meal from widely grown oilseed crops and in some domesticated vegetable crops. There is, however, an opposite and positive side of this picture represented by the therapeutic and prophylactic properties of other "nutritional" or "functional" glucosinolates. This review addresses the complex array of these biologically active and chemically diverse compounds many of which have been identified during the past three decades in other families. In addition to the Brassica vegetables, these glucosinolates have been found in hundreds of species, many of which are edible or could provide substantial quantities of glucosinolates for isolation, for biological evaluation, and potential application as chemoprotective or other dietary or pharmacological agents.
Patent Litigation with Endogenous Disputes

The recent explosion of patenting and patent disputes has sparked a growing literature on the economics of patent litigation. Generally, models in this literature take the existence of a dispute as given. This assumption is troubling because it hampers the interpretation of empirical studies of patent litigation and the assessment of many patent policy reforms. Disputes would not arise if all technology adopters obtained ex ante licenses from patent owners. This suggests that two stories could explain the origin of patent disputes. In one, the technology adopter observes a patented technology, but chooses to imitate, “inventing around” and/or hiding the infringement. In the other, the adopter develops his own technology and is unaware of another firm’s putative patent rights. This kind of innocent infringement occurs because patent rights often have uncertain boundaries or questionable validity. In addition, the sheer number of patents facing a typical innovator makes careful assessment quite burdensome. Furthermore, patent claims are often hidden (sometimes strategically) until after firms have made technology investments. These two accounts suggest that a model of disputes should consider the decisions of patent owners to invent, to patent, and to monitor use of the patented technology by others; and the decisions of potential infringers to monitor extant patents, and develop and adopt new technology. Claude Crampes and Corinne Langinier (2002) endogenize disputes by focusing on a patent owner’s monitoring activity and imitative behavior by potential infringers. Our model includes this behavior, but it also includes defendants who “invent around” a patent, and defendants who are unaware of the patented technology. We find that this richer model generates testable implications that better match empirical evidence on patent litigation.
The synthesis of 1-benzyldimethylsilyl-4-phenylthio-1,3-butadiene: A new diene-regenerable diels-alder synthon

Abstract 1-Benzyldimethylsilyl-4-phenylthio-1,3-butadiene ( 1 ), prepared by hydrosilation of propargyl alcohol, oxidation and followed by Wittig-Horner reaction, underwent Diels-Alder reaction with methyl methacrylate. The adduct after oxidation to the sulfone when treated with fluoride gave 5-carbomethoxy-5-methyl-1,3-cyclohexadiene.
Integrable marginal points in the N-cosine model

Abstract The integrability of the N-cosine model, an N-field generalization of the sine-Gordon model, is investigated. We establish to first order in conformal perturbation theory that, for arbitrary N, the model possesses a quantum conserved current of Lorentz spin 3 on a submanifold of the parameter space where the interaction becomes marginal. The integrability of the model on this submanifold is further studied using renormalization techniques. It is shown that for N=2,3, and 4 there exist special points on the marginal manifold at which the N-cosine model is equivalent to models of the Gross–Neveu type and therefore is integrable. In the 2-field case we further argue that the points mentioned above exhaust all integrable cases on the marginal submanifold.
Performance analysis of a guard channel reservation handoff scheme for wireless and mobile networks using smart antennas

In this paper, we propose and analyze a novel wireless and mobile network which employs smart antennas. Using smart antenna techniques, the physical channels (frequency, time slot, code or combinations of them) can be reused in the same cell. In the proposed system, the capacity is increased by reusing channels in a cell. The service quality is improved by inherent properties of smart antennas, such as reducing bit error rate (BER), multipath fading etc. We establish the traffic model and provide an analytical model for the proposed system. The system is modeled and analyzed by a two-dimensional Markov chain. A new algorithm is derived to obtain the equilibrium state probabilities. We also investigate the system in terms of the blocking probability of originating calls and the forced termination probability of handoff calls. As we expect, system capacity and performance are highly improved by employing smart antennas. We believe that the proposed system can be a candidate for future wireless and mobile ne...
Recession, R&D Spending, and the Current Account: Bad News, Bad News, and a Little Encouragement

Coming out of the global recession, it has been suggested that certain United States’ trading partners that have relied on exchange rates policy should switch to the industrial policy, particularly...
Modeling of fluid flow and heat transfer in a hydrothermal crystal growth system: Use of fluid-superposed porous layer theory

Hydrothermal synthesis, which uses aqueous solvents under high pressure and relatively low temperature, is an important technique for difficult to grow crystalline materials. It is a replica of crystal growth under geological conditions. A hydrothermal growth system usually consists of finely divided particles of the nutrient, predetermined volume of a solvent and a suitably oriented crystal seed under very high pressures, generally several thousand bar. The nutrient dissolves at a higher temperature in the lower region, moves to the upper region due to buoyancy-induced convective flows, and deposits on the seed due to lower solubility if the seed region is maintained at a lower temperature. The system can be modeled as a composite fluid and porous layer using the Darcy-Brinkman-Forchheimer flow model in the porous bed. Since the growth process is very slow, the process is considered quasi-steady and the effect of dissolution and growth is neglected. This first study on transport phenomena in a hydrothermal system therefore focuses on the flow and temperature fields without the presence of the seed and mass transfer. A three-dimensional algorithm is used to simulate the flow and heat transfer in a typical autoclave system. An axisymmetric flow pattern at low Grashof numbers becomesmore » three-dimensional at high Grashof numbers. A reduction in the porous bed height for fixed heated and cooled regions can result in oscillatory flows. These results, for the first time, depict the possible flow patterns in a hydrothermal system, that can have far reaching consequences on the growth process and crystal quality.« less
Structural stability of Ni-containing half-Heusler compounds

Half-Heusler compounds containing Ni of the form NiMP, where M is a trivalent (Sc) or tetravelent (Ti, Zr, Hf) ion and P is a pnictide or stannide ion (Sb, Sn), are known to form semiconducting phases for $M=\mathrm{Sc}$ and $P=\mathrm{Sb}$ as well as when M=Ti,Zr,Hf and $P=\mathrm{Sn}.$ However, the electronic structure of these compounds depends sensitively on the relative arrangements of the atoms within the unit cell, changing from a narrow-gap semiconductor to a zero-gap semiconductor to a metal, depending on which of the three atoms lies in the octahedrally coordinated pocket of the NaCl substructure formed by the other two atoms. We have carried out extensive calculations of the total energy for these systems using an all-electron, full-potential method within density-functional theory [using both the local-density approximation and the generalized gradient approximation] to clarify some of the conflicts in earlier calculations using pseudopotential and linear muffin-tin orbital--atomic-sphere approximation methods. The minimum-energy configuration for each of these systems occurs when the Ni atom occupies the octahedrally coordinated pocket formed by the other two elements MP. By comparing the energies of the binary compounds arising from different arrangements of the atoms within the unit cell, we find that the stability of the lowest-energy configuration of the ternary system derives from the energy gained from two sources. The largest source is MP forming in the NaCl substructure rather than a diamond substructure, in agreement with the previous pseudopotential calculations of Ogut and Rabe. Also important are the Ni atoms lying in the octahedrally coordinated pockets and bonding with four M and four P nearest-neighbor atoms rather than forming a part of the NaCl substructure itself. The energies of antisite defects have been investigated by studying the supercell $(\mathrm{Ni}\mathit{MP}{)}_{4}$ formed in the simple cubic structure with individual atoms moved from their ideal positions. We find that the idealized half-Heusler structure (formed by three interpenetrating fcc lattices) has the lowest energy ${(E}_{0})$ while structures where Ni atoms move out of a fcc arrangement, but remain within the octahedrally coordinated pockets of MP, have energies of 0.5-eV/unit cell higher than ${E}_{0},$ while structures with disorder in the MP NaCl substructure have energies about 1.5-eV/unit cell higher than ${E}_{0}.$ Since the MP disorder and not the Ni disorder is seen experimentally at low temperatures, this Ni disorder may be annealed out while the MP disorder is quenched.
High pressure percutaneous transtracheal ventilation : the use of large gauge intravenous-type catheters in the totally obstructed airway

Percutaneous transtracheal ventilation using a large gauge intravenous-type catheter can be used successfully in the setting of complete upper airway obstruction in animals. In this study, using a large animal model, satisfactory oxygenation and ventilation was achieved by inversely varying the catheter size and the inspiration to expiration ratio (I:E). Specifically, 30 to 63 kg ruminants with an obstructed upper airway were resuscitated for 30 minutes from a hypoxic, hypercarbic, and acidotic state using 12- and 14-gauge catheters connected to a 50 psi oxygen source via a two-way valve with an I:E of 1:4 and 1:9 seconds, respectively. Shorter expiratory time or increased inspiratory time with these intravenous catheters resulted in significant hemodynamic compromise, barotrauma, inadequate carbon dioxide elimination, acidemia, and frequent death.
Critique of a Large-Scale Organ System Model: Guytonian Cardiovascular Model

This paper reviews Guyton's model, which is large not only in the number of its components but also in the time scale that it spans. The evolution of this model is explained in three stages. To explain short-term regulations of cardiac output Guyton started with a drastically simplified model of the entire cardiovascular system, which emphasized the role of blood volume and the vascular capacity. Guyton's group then directed its efforts toward the analysis of long-term regulation of arterial pressure. Two slow-acting mechanisms were added to the model: (1) the marked increase or decrease of urinary output with only slight increase or decrease in arterial pressure (the renal function curve in the Guytonian model), and (2) long-term vascular autoregulation. This second-stage model explained the transient dynamics and steady equilibrium in renal hypertension. The current version of Guyton's model incorporates a variety of additional endocrine and neural mechanisms that parametrically control the renal function curve. The Guytonian model is a unique venture in modern cardiovascular physiology because of its size and the investigators' incessant efforts to test it against the real system behaviors.
Art Education in Correctional Settings.

This paper identifies aspects of the development and operations of a prison art program, as a series of field notes. Areas of investigation include the organization and maintenance of art instruction, participation of staff and prisoners, planning for continuous program support, training of prison arts specialists, and development of curriculum and instructional strategies for prison art educators. Observations are also made of special problems inherent in a prison setting related to time, space, confinement, and regimentation and their effects on the inmate artist and on the teacher.
Deflation of eigenvalues for iterative methods in lattice QCD

Abstract Work on generalizing the deflated, restarted GMRES algorithm, useful in lattice studies using stochastic noise methods, is reported. We first show how the multi-mass extension of deflated GMRES can be implemented. We then give a deflated GMRES method that can be used on multiple right-hand sides of Aχ = b in an efficient manner. We also discuss and give numerical results on the possibilty of combining deflated GMRES for the first right hand side with a deflated BiCGStab algorithm for the subsequent right hand sides.