cssi/SciSciGPT-SciSciNet huggingface dataset:
XMCD characterization of the ferromagnetic state of Yb14MnSb11.

X-ray magnetic circular dichroism (XMCD) measurements on Yb14MnSb11 provide experimental evidence of a moment of 5 μB on Mn, with partial cancellation by an opposing moment on the Sb4 cage surrounding each Mn ion. The compound is isostructural to Ca14AlSb11, with Mn occupying the Al site in the AlSb49- discrete tetrahedral, anionic unit. Bulk magnetization measurements indicate a saturation moment of 3.90 ± 0.02 μB/formula unit consistent with four unpaired spins and implying a Mn3+, high-spin d4 state. XMCD measurements reveal that there is strong dichroism in the Mn L23 edge, the Sb M45 edge shows a weak dichroism indicating antialignment to the Mn, and the Yb N45 edge shows no dichroism. Comparisons of the Mn spectra with theoretical models for Mn2+ show excellent agreement. The bulk magnetization can be understood as Mn with a moment of 5 μB and a 2+ configuration, with cancellation of one spin by an antialigned moment from the Sb 5p band of the Sb4 cage surrounding the Mn.
Best-effort scheduling of (m,k)-firm real-time streams in multihop networks

In this paper, we address the problem of best-effort scheduling of (m,k)-firm real-time streams in multihop networks. The existing solutions for the problem ignore scalability considerations because the solutions maintain a separate queue for each stream and maintain per-stream state information. In this context, we propose a scheduling algorithm, Enhanced Distance Based Priority (EDBP), which is scalable (fixed scheduling cost) while offering performance close to that of the existing solutions. The proposed EDBP algorithm achieves this by allowing multiplexing of streams into a fixed number of queues and by using the notion of a look-ahead window. In the EDBP algorithm, at any point of time, the best packet for transmission is selected based on the state of the stream combined with the laxity of the packet. We have conducted extensive simulation studies to evaluate the effectiveness of the proposed EDBP algorithm by comparing it with existing algorithms for the problem. The simulation studies reveal that the dynamic failure performance of the EDBP algorithm is very close to that of the existing algorithms with a significant reduction in scheduling cost.
Testing Cosmological Models and Understanding Cosmological Parameter Determinations with Metaparameters

Cosmological parameters affect observables in physically distinct ways. For example, the baryon density ωb affects the ionization history and also the pressure of the pre-recombination fluid. To investigate the relative importance of different physical effects to the determination of ωb and to test the cosmological model, we artificially split ωb into two "metaparameters": ωbe, which controls the ionization history, and ωbp, which plays the role of ωb for everything else. In our demonstration of the technique we find ωb = 0.0229 ± 0.0012 (with no parameter splitting), ωbp = 0.0238 ± 0.0021, ωbe = 0.0150 ± 0.0034, and ωbp - ωbe = 0.0088 ± 0.0039.
The unstable integral homology of the mapping class groups of a surface with boundary

We construct a graph complex calculating the integral homology of the bordered mapping class groups. We compute the homology of the bordered mapping class groups of the surfaces S 1,1, S 1,2 and S 2,1. Using the circle action on this graph complex, we build a double complex and a spectral sequence converging to the homology of the unbordered mapping class groups. We compute the homology of the punctured mapping class groups associated to the surfaces S 1,1 and S 2,1. Finally, we use Miller’s operad to get the first Kudo–Araki and Browder operations on our graph complex. We also consider an unstable version of the higher Kudo–Araki–Dyer–Lashoff operations.
New observations of the low frequency interplanetary radio emissions

Recent Voyager 1 observations reveal reoccurrences of the low frequency interplanetary radio emissions. Three of the new events are weak transient events which rise in frequency from the range of 2-2.5 kHz to about 3 kHz with drift rates of approximately 1.5 kHz/year. The first of the transient events begins in mid-1989 and the more recent pair of events both were first detected in late 1991. In addition, there is an apparent onset of a 2-kHz component of the emission beginning near day 70 of 1991. The new transient emissions are barely detectable on Voyager 1 and are below the threshold of detectability on Voyager 2, which is less sensitive than Voyager 1. The new activity provides new opportunities to test various theories of the triggering, generation, and propagation of the outer heliospheric radio emissions and may signal a response of the source of the radio emissions to the increased solar activity associated with the recent peak in the solar cycle.
Effects of child support pass-through and disregard policies on in-kind child support

This paper examines whether states’ elimination of child support disregards for welfare payments after welfare reform caused non-custodial parents to increase in-kind support. I use longitudinal data from the Survey of Program Dynamics and take advantage of state and year variation in child support disregard policies before and after the 1996 welfare reform to identify effects of the disregard on in-kind support. I find that a $100 decrease in the disregard corresponds to a 3.2 percentage point increase in the probability a child will receive in-kind child support.
A Compact Low-Power 224-Gb/s DP-16QAM Modulator Module with InP-based Modulator and Linear Driver ICs

A compact 224-Gb/s DP-16QAM InP-based modulator module including linear driver ICs and polarization multiplexing micro-optics is demonstrated. A power dissipation is 3.2 W with compatible performance with LiNbO3-based modulator in back-to-back operation.
A NEW STRUCTURAL FORM OF TIN OCTAHEDRALLY COORDINATED IN A DRUM-SHAPED MOLECULE

Abstract Although oligomeric organotin oxycarboxylates based on the composition [RSn(O)O2CR′] n have been known for some time, 2 no indications of their possible structural features are available. As early as 1921 some members of this class were reported3 to be hexameric, e.g., [CH3Sn(O)O2CR]6.
Weak-Lensing Surveys and the Intrinsic Correlation of Galaxy Ellipticities

We explore the possibility that an intrinsic correlation between galaxy ellipticities arising during the galaxy formation process may account for part of the shear signal recently reported by several groups engaged in weak gravitational lensing surveys. Using high-resolution N-body simulations, we measure the projected ellipticities of dark matter halos and their correlations as a function of pair separation. With this simplifying, but not necessarily realistic, assumption (halo shapes as a proxy for galaxy shapes), we find a positive detection of correlations up to scales of at least 20 h-1 Mpc (limited by the box size). The signal is not strongly affected by variations in the halo-finding technique, or by the resolution of the simulations (over the range tested). We translate our three-dimensional results into angular measurements of ellipticity correlation functions and shear variance, which can be directly compared to observational results. We also make simulated angular surveys by projecting our simulation boxes onto the plane of the sky and applying a radial selection function. Measurements from these catalogs are consistent with the analytic projection of the statistics. Interestingly, the shear variance we measure is a small, but not entirely negligible, fraction (from ~10%-20%, depending on the angular scale) of that seen by the observational groups, and the ellipticity correlation functions approximately mimic the functional form expected to be caused by weak lensing. The amplitude of these projected quantities depends strongly on the width in redshift of the galaxy distribution. If in the future photometric redshifts are used to pick out a screen of background galaxies with a small redshift width, then the intrinsic correlation may become comparable to the weak-lensing signal. Although we are dealing with simulated dark matter halos, we might expect there to be a similar sort of signal when real galaxies are used. This could be checked fruitfully using a nearby sample with known redshifts.
Probabilistic query models for transaction data

We investigate the application of Bayesian networks, Markov random fields, and mixture models to the problem of query answering for transaction data sets. We formulate two versions of the querying problem: the query selectivity estimation (i.e., finding exact counts for tuples in a data set) and the query generalization problem (i.e., computing the probability that a tuple will occur in new data). We show that frequent itemsets are useful for reducing the original data to a compressed representation and introduce a method to store them using an ADTree data structure. In an extension of our earlier work on this topic we propose several new schemes for query answering based on the compressed representation that avoid direct scans of the data at query time. Experimental results on real-world transaction data sets provide insights into various tradeoffs involving the offline time for model-building, the online time for query-answering, the memory footprint of the compressed data, and the accuracy of the estimate provided to the query.
Three-dimensional viscous flow analysis for centrifugal impellers

A SPACE-MARCHING Navier-Stokes solver is used to -TjLsimulate three-dimensional viscous flows in centrifugal impellers. This solver employs a finite volume integration procedure for the partially parabolic equations written in arbitrary curvilinear coordinates. The solution is achieved using a multiple-pass forward-marching iteration scheme. The accuracy of the analysis method is verified using impeller intrapassage laser-velocimeter data. The method is demonstrated to predict the jet/wake flows characteristic of centrifugal impellers. The result clearly shows the importance of modeling the blade tip clearance flow accurately.
A Dynamics for Discrete Quantum Gravity

This paper is based on the causal set approach to discrete quantum gravity. We first describe a classical sequential growth process (CSGP) in which the universe grows one element at a time in discrete steps. At each step the process has the form of a causal set (causet) and the “completed” universe is given by a path through a discretely growing chain of causets. We then quantize the CSGP by forming a Hilbert space H on the set of paths. The quantum dynamics is governed by a sequence of positive operators ρ n on H that satisfy normalization and consistency conditions. The pair (H,{ρ n }) is called a quantum sequential growth process (QSGP). We next discuss a concrete realization of a QSGP in terms of a natural quantum action. This gives an amplitude process related to the “sum over histories” approach to quantum mechanics. Finally, we briefly discuss a discrete form of Einstein’s field equation and speculate how this may be employed to compare the present framework with classical general relativity theory.
Synthesis of Disubstituted Phosphinates via Palladium‐Catalyzed Hydrophosphinylation of H‐Phosphinic Acids

The first metal-catalyzed hydrophosphinylation of unsaturated hydrocarbons with H-phosphinic acids is described. A strategy to activate the PH bond through control of the tautomeric equilibrium using ethylene glycol is described. The reactions also avoid chromatographic purification.
Fault-tolerant arithmetic via time-shared TMR

Fault tolerance is increasingly important as society has come to depend on computers for more and more aspects of daily life. The current concern about the Y2K problems indicates just how much we depend on accurate computers. This paper describes work on time- shared TMR, a technique which is used to provide arithmetic operations that produce correct results in spite of circuit faults.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Evidence-based pharmacotherapy for personality disorders

Patients with personality disorders are prescribed psychotropic medications with greater frequency than almost any other diagnostic group. Prescribing practices in these populations are often based on anecdotal evidence rather than rigorous data. Although evidence-based psychotherapy remains an integral part of treatment, Axis II psychopathology is increasingly conceptualized according to neurobiological substrates that correspond to specific psychopharmacological strategies. We summarize the best available evidence regarding medication treatment of personality disordered patients and provide optimal strategies for evidence-based practice. Most available evidence is concentrated around borderline and schizotypal personality disorders, with some additional evidence concerning the treatment of avoidant and antisocial personality disorders. Although maladaptive personality symptoms respond to antidepressants, antipsychotics, mood stabilizers, and other medications, evidence-based pharmacotherapy is most useful in treating circumscribed symptom domains and induces only partial improvement. Most available evidence supports use of medication in reducing impulsivity and aggression, characteristic of borderline and antisocial psychopathology. Efforts have also begun to reduce psychotic-like symptoms and improve cognitive deficits characteristic of schizotypy. Indirect evidence is also provided for psychopharmacological reduction of social anxiety central to avoidant personality disorder. Evidence-based practice requires attention to domains of expected clinical improvement associated with a medication, relative to the potential risks. The development of future rational pharmacotherapy will require increased understanding of the neurobiological underpinnings of personality disorders and their component dimensions. Increasing efforts to translate personality theory and social cognitive neuroscience into increasingly specific neurobiological substrates may provide more effective targets for pharmacotherapy.
Constraints on the Progenitor of Cassiopeia A

We compare a suite of three-dimensional explosion calculations and stellar models incorporating advanced physics with observational constraints on the progenitor of Cassiopeia A. We consider binary and single stars from 16 to 40 M☉ with a range of explosion energies and geometries. The parameter space allowed by observations of nitrogen-rich high-velocity ejecta, ejecta mass, compact remnant mass, and 44Ti and 56Ni abundances individually and as an ensemble is considered. A progenitor of 15-25 M☉ that loses its hydrogen envelope to a binary interaction and undergoes an energetic explosion can match all the observational constraints.
Experiments in Reconstructing Twentieth-Century Sea Levels

One approach to reconstructing historical sea level from the relatively sparse tide-gauge network is to employ Empirical Orthogonal Functions (EOFs) as interpolatory spatial basis functions. The EOFs are determined from independent global data, generally sea-surface heights from either satellite altimetry or a numerical ocean model. The problem is revisited here for sea level since 1900. A new approach to handling the tide-gauge datum problem by direct solution offers possible advantages over the method of integrating sea-level differences, with the potential of eventually adjusting datums into the global terrestrial reference frame. The resulting time series of global mean sea levels appears fairly insensitive to the adopted set of EOFs. In contrast, charts of regional sea level anomalies and trends are very sensitive to the adopted set of EOFs, especially for the sparser network of gauges in the early 20th century. The reconstructions appear especially suspect before 1950 in the tropical Pacific. While this limits some applications of the sea-level reconstructions, the sensitivity does appear adequately captured by formal uncertainties. All our solutions show regional trends over the past five decades to be fairly uniform throughout the global ocean, in contrast to trends observed over the shorter altimeter era. Consistent with several previous estimates, the global sea-level rise since 1900 is 1.70 +/- 0.26 mm/yr. The global trend since 1995 exceeds 3 mm/yr which is consistent with altimeter measurements, but this large trend was possibly also reached between 1935 and 1950.
Discretizing gravity in warped spacetime

We investigate the discretized version of the compact Randall-Sundrum model. By studying the mass eigenstates of the lattice theory, we demonstrate that for warped space, unlike for flat space, the strong coupling scale does not depend on the IR scale and lattice size. However, strong coupling does prevent us from taking the continuum limit of the lattice theory. Nonetheless, the lattice theory works in the manifestly holographic regime and successfully reproduces the most significant features of the warped theory. It is even in some respects better than the KK theory, which must be carefully regulated to obtain the correct physical results. Because it is easier to construct lattice theories than to find exact solutions to GR, we expect lattice gravity to be a useful tool for exploring field theory in curved space.
Strategies for smart control of large structures

Several decades ago, the principles of dynamic systems and controls were directed towards large engineering structures. In more recent years, the use of feedback control systems technology has been introduced to cause a structure to be 'smart,' or to be semi-actively controlled. As structural control matures, and such things as 'intelligent' structures and 'smart' systems methodology become understood and accepted in the broader scientific and technical circles, the uttering of some thoughts in reflection becomes appropriate. The paper recounts the author's personal role and experiences, examines trends and underlying issues in structural control, and concludes with admonitions, recommendations and visions concerning future directions in structural control.
Dynamics of delamination buckling

Abstract The dynamics of delamination growth in layered plates as a result of delamination buckling is studied in the context of the model problem of a two layer circular plate with an initial penny-shaped delaminalion subject to a time dependent radial compressive load. The interaction of delamination buckling and normal impact is modeled through the application of a uniform transverse tension pulse, simulating the effect of a wave front passing through the layer interface, in conjunction with the radial loading. In addition three types of radial loading functions are considered independently and characcteristic features of the response are observed. Comparison is made with growth predictions made using a quasi-static analysis.
Long-Short Strategies may not be Factor-Neutral

This is an examination of three long-short investment strategies that may be used by investment managers. The factor strategy is long in small size and high book-equity/market equity (BE/ME) stocks and short in large size and low BE/ME stocks. The relative return strategy is long in stocks with the highest past returns and short in stocks with the lowest past returns. The relative earnings surprise strategy is long in stocks with the greatest (positive) earnings surprise and short in stocks with the worst earnings surprise. Only the relative return and relative earnings surprise strategies provide significant risk-adjusted returns; none of the three strategies is size and BE/ME-neutral. This suggests that other simple long-short strategies probably are not size and BE/ME-neutral. Investors should not equate long/short portfolios with the absence of systematic risk.
Hearing Results With Cartilage Tympanoplasty

Cartilage has shown promise as a graft material to close perforations in the tympanic membrane (TM), particularly in cases of advanced middle ear pathology. Although it is similar to fascia, its more rigid quality tends to resist resorption and retraction. However, it is this rigid quality that has led many to anticipate a significant conductive hearing loss when using cartilage to reconstruct the TM. Because little has been reported in the literature comparing hearing results using cartilage with results using other grafting materials, this retrospective study was conducted to compare the hearing results of patients with cartilage tympanoplasty with results in patients who underwent revision tympanoplasty using perichondrium. Both series of patients had undergone type I tympanoplasty, and the middle ear pathology was considered to be similar between the two groups. TM closure was achieved in all 22 patients undergoing cartilage reconstruction, but three of the 20 patients undergoing perichondrium reconstruction had a recurrent perforation during the follow-up period (approximately 1 year). The average pre- and postoperative pure-tone average air-bone gap (PTA-ABG) was 21.1 dB and 6.8 dB for the cartilage group and 17.9 dB and 7.7 dB for the perichondrium group, respectively. These gains in hearing were statistically significant (P < 0.001 in each case), but there was no statistically significant difference in hearing results between the two groups. Analysis of the PTA-ABG as a function of percentage of TM reconstructed showed no statistically significant difference in hearing results due to percentage of cartilage used. These results indicate that cartilage tympanoplasty offers the possibility of a rigorous TM reconstruction with excellent postoperative hearing results.
The effect of condensates on the characterization of transiting planet atmospheres with transmission spectroscopy

Through a simple physical argument we show that the slant optical depth through the atmosphere of a ‘hot Jupiter’ planet is ∼35‐90 times greater than the normal optical depth. This not unexpected result has direct consequences for the method of transmission spectroscopy for characterizing the atmospheres of transiting giant planets. The atmospheres of these planets likely contain minor condensates and hazes, which at normal viewing geometry have negligible optical depth, but at slant viewing geometry have appreciable optical depth that can obscure absorption features of gaseous atmospheric species. We identify several possible condensates. We predict that this is a general masking mechanism for all planets, not just for HD 209458b, and will lead to weaker than expected or undetected absorption features. Constraints on an atmosphere from transmission spectroscopy are not the same as constraints on an atmosphere at normal viewing geometry. Ke yw ords: radiative transfer ‐ planetary systems.
Fast: A Transducer-Based Language for Tree Manipulation

Tree automata and transducers are used in a wide range of applications in software engineering. While these formalisms are of immense practical use, they can only model finite alphabets. To overcome this problem we augment tree automata and transducers with symbolic alphabets represented as parametric theories. Admitting infinite alphabets makes these models more general and succinct than their classic counterparts. Despite this, we show how the main operations, such as composition and language equivalence, remain computable given a decision procedure for the alphabet theory. We introduce a high-level language called Fast that acts as a front-end for the preceding formalisms.
Convergence and divergence in tagging systems: an examination of tagging practices over a four year period

This paper analyses the tagging patterns on delicious.com for a set of documents (URLs) over a 4 year period using informetrics methods to assess how collaborative tagging supports and enhances traditional document indexing. Results of the study show that there is still a mix of consensus and divergence in tagging term use and tagging patterns. While some of the chosen URLs maintained or even increased their popularity, others experienced a severe drop in popularity. Tag usage showed some measures of influence between taggers, but users continued to use their own tags and the proportions of unique and untagged items has increased. Proportions of tags used showed fluctuations with islands of stability over a 4 year period. Patterns in the usage of tags assigned to these documents also highlighted practices related to personal and collective information organisation which conventional systems are unable to facilitate.
Regularization of fields for self-force problems in curved spacetime: Foundations and a time-domain application

We propose an approach for the calculation of self-forces, energy fluxes and waveforms arising from moving point charges in curved spacetimes. As opposed to mode-sum schemes that regularize the self-force derived from the singular retarded field, this approach regularizes the retarded field itself. The singular part of the retarded field is first analytically identified and removed, yielding a finite, differentiable remainder from which the self-force is easily calculated. This regular remainder solves a wave equation which enjoys the benefit of having a nonsingular source. Solving this wave equation for the remainder completely avoids the calculation of the singular retarded field along with the attendant difficulties associated with numerically modeling a delta-function source. From this differentiable remainder one may compute the self-force, the energy flux, and also a waveform which reflects the effects of the self-force. As a test of principle, we implement this method using a 4th-order ($1+1$) code, and calculate the self-force for the simple case of a scalar charge moving in a circular orbit around a Schwarzschild black hole. We achieve agreement with frequency-domain results to $\ensuremath{\sim}0.1%$ or better.
Transition from Clumpy to Smooth Angular Diameter Distances

Distance relations in a locally inhomogeneous universe are expected to behave like the Dyer-Roeder solution on small angular scales and the Friedmann-Robertson-Walker solution on large angular scales. Within a simple compact clump model the transition between these asymptotic behaviors is demonstrated and quantified. The redshift-dependent transition scale is of order a few arcseconds; this implies that it should have little influence on large angular scale cosmological tests such as the volume-redshift relation but possibly significant effects on arcsecond angular diameter measurements of radio galaxies and active galactic nuclei. For example, at z = 2 on arcsecond scales a clumpy flat universe mimics the angular diameter distance of a smooth Ω = 0.27 model.
Generating diagnostic information for behavioral preorders

This paper describes a method for generating diagnostic information that explains why a given finite-state system fails to be greater than its specification with respect to the prebisimulation preorder. The information takes the form of a logical formula satisfied by the specification but not by the system and thus may be used by system designers for debugging purposes. Our technique relies on modifying an algorithm for computing the prebisimulation preorder so that information needed for generating these distinguishing formulas is saved appropriately. As a number of other behavioral preorders may be characterized in terms of prebisimulation preorder, our approach may be used as a basis for computing diagnostic information for these relations as well.
Imaging of low-compressibility strips in the quantum Hall liquid

Using subsurface charge accumulation scanning microscopy, we image strips of low compressibility corresponding to several integer quantum Hall filling factors. We study in detail the strips at Landau level filling factors $\ensuremath{\nu}=2$ and 4. The observed strips appear significantly wider than predicted by theory. We present a model accounting for the discrepancy by considering a disorder-induced nonzero density of states in the cyclotron gap.
A two‐dimensional particle code simulation of inertial Alfvén waves and auroral electron acceleration

[1] A two-dimensional particle code used to simulate the propagation of inertial Alfven waves down auroral field lines. The simulation domain is 20,000 km parallel to the magnetic field and some tens of kilometers perpendicular to the field. Electrons are tied to the magnetic field. Effects of a variable magnetic field and magnetic mirror force are included. A spatially narrow Alfven pulse is launched by application of a variable potential with peak amplitude of 100 V at the top of the simulation domain. If the thickness of the pulse is less than the electron inertial length, the pulse tends to broaden as it propagates down the field line. The result is a parallel electric field considerably smaller than might be expected, assuming a wave whose perpendicular wavelength maps along magnetic field lines. In this model the strongest interaction between the electrons and the Alfven wave occurs in the 3000 to 7000 km altitude range with an energy gain of the order 100 eV. The downward acceleration was strongest when the applied excitation consisted of a moving positive pulse followed by a negative pulse. Strongest upward acceleration was seen when the polarity was reversed. When the magnitude of the driving potential was doubled, there appeared to be some acceleration in the 9000 to 18,000 km altitude range and acceleration of some particles to 1.5 keV.
Optimizing the chiral properties of lattice fermion actions

Abstract We describe a way to optimize the chiral behavior of Wilson-type lattice fermion actions by studying the low energy real eigenmodes of the Dirac operator. We find a candidate action, the clover action with fat links with a tuned clover term. The action shows good scaling behavior at Wilson gauge coupling β = 5.7.
International Capital Mobility and Development Policy in a Dual Economy

This paper introduces international capital mobility in a general-equilibrium model of a small developing economy which is characterized by a dualistic economic structure. The model is then used to analyze the positive and the normative aspects of development policies that are often recommended for achieving employment-related objectives in developing economies.
Kinetics of the Fluorination/Chlorination of 1-Chloro-1,2,2,2-Tetrafluoroethane

The kinetics of the catalytic fluorination and chlorination of 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) by HF and HCl to give pentafluoroethane (HFC-125) and 1,1-dichloro-2,2-trifluoroethane (HCFC-123), respectively, were examined in order to further define the mechanisms of these reactions. An HF-treated preparation of 2% CoCl[sub 2] on Al[sub 2]O[sub 3] was used as a catalyst. Reaction of deuterium-labeled HCFC-124 With HF or HCl showed the deuterium to be retained in both reactant and products, suggesting the absence of carbenoid or olefinic intermediates in these halogenations. Thermodynamic and thermokinetic properties of these halogenations were also determined in order to determine the extent of contributions of reverse reactions to the kinetics of these halogenations. Kinetic studies indicated that these halogenations are consistent with a classical Langmuir-Hinshelwood mechanism where both HX (X = F or Cl) and HCFC-124 are adsorbed on identical active sites of the catalyst in the rate-determining step. 17 refs., 5 figs., 5 tabs.
Voltage-dependent scanning tunneling microscopy imaging of semiconductor surfaces

We present voltage-dependent scanning tunneling microscopy (STM) data from various semiconductor surfaces. Different techniques for acquiring the data are demonstrated, and the interpretation of spectroscopic data is discussed. For the Si(111)2 × 1, GaAs (110), and O/ GaAs(110) surfaces, we find that the voltage dependence of constant-current contours provides the most direct method for understanding the electronic and geometric structure of the surface. For the case of oxygen on n-type GaAs, we observe a reversal in the constant-current contours when the polarity of the bias voltage is reversed, which is interpreted in terms of band bending due to a negatively charged adsorbate. Theoretical calculations for a screened Coulomb potential are shown to agree with the observed reversal in the STM contours of the adsorbed oxygen.
A GPU tool for efficient, accurate, and realistic simulation of cone beam CT projections

Purpose: Simulation of x-ray projection images plays an important role in cone beam CT (CBCT) related research projects, such as the design of reconstruction algorithms or scanners. A projection image contains primary signal, scatter signal, and noise. It is computationally demanding to perform accurate and realistic computations for all of these components. In this work, the authors develop a package on graphics processing unit (GPU), called gDRR, for the accurate and efficient computations of x-ray projection images in CBCT under clinically realistic conditions. Methods: The primary signal is computed by a trilinear ray-tracing algorithm. A Monte Carlo (MC) simulation is then performed, yielding the primary signal and the scatter signal, both with noise. A denoising process specifically designed for Poisson noise removal is applied to obtain a smooth scatter signal. The noise component is then obtained by combining the difference between the MC primary and the ray-tracing primary signals, and the difference between the MC simulated scatter and the denoised scatter signals. Finally, a calibration step converts the calculated noise signal into a realistic one by scaling its amplitude according to a specified mAs level. The computations of gDRR include a number of realistic features, e.g., a bowtie filter, a polyenergetic spectrum, and detector response. The implementation is fine-tuned for a GPU platform to yield high computational efficiency. Results: For a typical CBCT projection with a polyenergetic spectrum, the calculation time for the primary signal using the ray-tracing algorithms is 1.2–2.3 s, while the MC simulations take 28.1–95.3 s, depending on the voxel size. Computation time for all other steps is negligible. The ray-tracing primary signal matches well with the primary part of the MC simulation result. The MC simulated scatter signal using gDRR is in agreement with EGSnrc results with a relative difference of 3.8%. A noise calibration process is conducted to calibrate gDRR against a real CBCT scanner. The calculated projections are accurate and realistic, such that beam-hardening artifacts and scatter artifacts can be reproduced using the simulated projections. The noise amplitudes in the CBCT images reconstructed from the simulated projections also agree with those in the measured images at corresponding mAs levels. Conclusions: A GPU computational tool, gDRR, has been developed for the accurate and efficient simulations of x-ray projections of CBCT with realistic configurations.
Effects of Propellant and Electrode Geometry on Pulsed Ablative Plasma Thruster Performance

A performance level compatible with 30% thrust efficiency at 1500 s specific impulse at 1 mlb (4.45 mN) of thrust was demonstrated with the parallel rail pulsed ablative thruster using Teflon propellant. Parametric variations of interelectrod e spacing and included angle were performed. In addition, Teflon was replaced by other thermoplastics and was also seeded with 10% and 30% LiOH and InBr in an evaluation of alternative propellants. Both the conventional breech-fed and later side-feed electrode/propellant configurations were tested. With the same initial conditions it was shown that the breech-fed geometry yields higher thrust efficiency than the side-fed geometry because of the higher specific impulse generated (i.e., up to 5300 s using Teflon). Results of parametric studies indicate that, for high thrust/power and moderately high specific impulse, virgin Teflon propellant with an interelectrode spacing of 3.0 in. (7.62 cm) and zero degree interelectrode included angle in the side-fed configuration are best. A simple semiempirical analytic model is presented where it is shown that the broad range in performance characteristic of this device is related to the degree to which magnetoplasmadynamic and ordinary gasdynamic acceleration mechanisms can be made more or less dominant in the acceleration of the ablated propellant.
Soft-matter physics: Ferromagnetic ferrofluids.

The idea of creating liquids containing magnetic particles that display ferromagnetism has not been realized — until now. Plate-shaped magnets in a liquid crystal have been made that exhibit this property. See Article p.237
Hyperbolic polynomials approach to Van der Waerden/Schrijver-Valiant like conjectures: sharper bounds, simpler proofs and algorithmic applications

Let p(x1,...,xn) = p(X) , X ∈ Rn be a homogeneous polynomial of degree n in n real variables, e = (1,1,..,1) ∈ Rn be a vector of all ones . Such a polynomial p is called e-hyperbolic if for all real vectors X ∈ Rn the univariate polynomial equation p(te - X) = 0 has all real roots λ1(X) ≥ ... ≥ λn(X). The number of nonzero roots |i :λi(X) ≠ 0 | is called Rankp(X). An e-hyperbolic polynomial p is called POS-hyperbolic if roots of vectors X ∈ Rn+ with nonnegative coordinates are also nonnegative (the orthant Rn+ belongs to the hyperbolic cone) and p(e) > 0. Below e1,...,en stands for the canonical orthogonal basis in Rn. The main results of this paper states that if p(x1,x2,...,xn) is a POS-hyperbolic (homogeneous) polynomial of degree n, Rankp (ei) = Ri and p(x1,x2,...,xn) ≥ ∏1 ≤ i ≤ n xi ; xi > 0, 1 ≤ i ≤ n, then the following inequality holds ∂n/∂ x1...∂ xn p(0,...,0) ≥ ∏1 ≤ i ≤ n (Gi-1/Gi)Gi-1, where Gi = min(Ri , n+1-i) . This inequality is a vast (and unifying) generalization of the van der Waerden conjecture on the permanents of doubly stochastic matrices as well as the Schrijver-Valiant conjecture on the number of perfect matchings in k-regular bipartite graphs. These two famous results correspond to the POS-hyperbolic polynomials which are products of linear forms with nonnegative coefficients.Our proof is relatively simple and "noncomputational"; it actually slightly improves Schrijver's lower bound, and uses very basic (more or less centered around Rolle's theorem) properties of hyperbolic polynomials. We present some important algorithmic applications of the result, including a polynomial time deterministic algorithm approximating the permanent of n x n entry-wise non-negative matrices within a multiplicative factor en/nm for any fixed positive m; and a deterministic poly-time algorithm approximating the permanent of n x n matrix A having at most k nonzero entries in each column to within a multiplicative factor (k-1/k)(k-1)n.This paper introduces a new powerful "polynomial" technique , which allows us to simplify and unify hard and key known results as well as to prove new important theorems and get new algorithms.
Field) symmetrization selection rules

QCD and QED exhibit an infinite set of three-point Green's functions that contain only Okubo-Zweig-Iizuka (OZI) rule violating contributions, and (for QCD) are subleading in the large N{sub c} expansion. The Green's functions describe the ''decay'' of a J{sup PC}={l_brace}1,3,5,(hor ellipsis){r_brace}{sup -+} exotic hybrid meson current to two J=0 (hybrid) meson currents with identical P and C. We prove that the QCD amplitude for a neutral hybrid {l_brace}1,3,5,(hor ellipsis){r_brace}{sup -+} exotic current to create {eta}{pi}{sup 0} only comes from OZI rule violating contributions under certain conditions, and is subleading in N{sub c}.
Disturbance Estimation for a STOL Transport During Landing

Transport aircraft can experience dangerously high sink rates if wind shear or thrust loss are encountered during landing approach. This is of special concern for STOL aircraft that use engine thrust for lift augmentation. Such conditions must be detected quickly and available power increased promptly to avoid serious flight path deviations. This study demonstrates the feasibility of designing constant-gain estimators, which use on-board instrumentation, to detect such conditions with sufficient speed and accuracy to provide adequate warning. Estimator design techniques are discussed and simulation results presented.
Ionic inhibitors of human leukocyte elastase: Pyridinium and phenyl carboxylate derivatives of 3‐Alkyl‐N‐hydroxysuccinimide

A series of pyridinium and phenyl carboxylate derivatives of 3-alkyl-N-hydroxysuccinimide has been synthesized; the compounds have been shown to be highly effective, time-dependent inactivators of human leukocyte elastase. The cationic inhibitor having an isobutyl side chain as the P1 residue (3) was found to be the most effective. Human leukocyte cathepsin G and chymotrypsin are also inactivated by these compounds.
Detecting Errors and Imputing Missing Data for Single-Loop Surveillance Systems

Single-loop detectors provide the most abundant source of traffic data in California, but loop data samples are often missing or invalid. A method is described that detects bad data samples and imputes missing or bad samples to form a complete grid of clean data, in real time. The diagnostics algorithm and the imputation algorithm that implement this method are operational on 14,871 loops in six districts of the California Department of Transportation. The diagnostics algorithm detects bad (malfunctioning) single-loop detectors from their volume and occupancy measurements. Its novelty is its use of time series of many samples, instead of basing decisions on single samples, as in previous approaches. The imputation algorithm models the relationship between neighboring loops as linear and uses linear regression to estimate the value of missing or bad samples. This gives a better estimate than previous methods because it uses historical data to learn how pairs of neighboring loops behave. Detection of bad loops and imputation of loop data are important because they allow algorithms that use loop data to perform analysis without requiring them to compensate for missing or incorrect data samples.
Spectrum results with Kogut-Susskind quarks

I summarize recent developments in spectrum calculations using Kogut-Susskind quarks. Theoretical developments include one-loop computations with improved actions. I present some recent simulation results, mostly from a MILC collaboration project using three flavors. Effects of dynamical quarks are clearly seen in the isovector 0++ meson propagator and in the mass ratio “J”.
Scale-dependent non-Gaussianity as a generalization of the local model

We generalize the local model of primordial non-Gaussianity by promoting the parameter fNL to a general scale-dependent function fNL(k). We calculate the resulting bispectrum and the eect on the bias of dark matter halos, and thus the extent to which fNL(k) can be measured from the large-scale structure observations. By calculating the principal components of fNL(k), we identify scales where this form of non-Gaussianity is best constrained and estimate the overlap with previously studied local and equilateral non- Gaussian models.
The impact of contingent liability on commercial bank risk taking

Abstract From 1863–1935, regulators imposed contingent liability on bank shareholders to discourage risk taking. Using data from 1900 to 1915, I find that banks subject to stricter liability rules have lower equity and asset volatility, hold a lower proportion of risky assets, and are less likely to increase their investment in risky assets when their net worth declines, consistent with the hypothesis that stricter liability discourages commercial bank risk taking. These findings provide lessons for current bank regulatory policy and show that the shape of the residual claimant's payoff function has a significant impact on managerial incentives and firm performance.
X-ray phase mask: nanostructures

In this paper we report the results of simulations and experiments on application of phase-shifting mask to x-ray lithography (XPM). We have built an XPM with PMMA as a phase shifter; we printed patterns using the XPM and characterized the linewidth dependence on gap and dose. Small lines around 70 nm were printed at 25 micrometer gap. The resist lines have good uniformity, and aspect ratio as high as 4. The characterization experiment was performed on the Karl Suss X- ray Stepper installed at the Center for X-ray Lithography. The results show that the exposure-gap latitude window is obviously increased compared with traditional x-ray mask. XLITH has been used to analyze the aerial image under the XPM and predict linewidth. Different phase shift materials, such as PMMA, Si, SiC and Al have been simulated and characterized with respect to blur, dose and gap. The model predicts a mask contrast 6 - 7, and resolution of 50 nm using gaps around 5 micrometer. XPM is a path to nanostructures with more reasonable process latitudes. We printed sub-0.1 micrometer dots using XPM. The XPM can also be used for gate-level lithography of ultrafast MOS devices to share its high resolution and large process latitude. It is possible to form both of a fine gate line and a contact pad at the same time with the combination of phase and transmission in a single mask. An experimental demonstration of printing unclosed lines is given in this paper. The further combination of phase-edge effects and phase-shifter size can also make it possible to form a wide range of patterns, ranging from line-space to isolated bright or dark areas with varied sizes, in a single exposure.
Measures of per Capita Hours and Their Implications for the Technology‐Hours Debate

Structural vector autoregressions give conflicting results on the effects of technology shocks on hours. The results depend crucially on the assumed data generating process for hours per capita. We show that the standard measure of hours per capita and productivity have significant low-frequency movements that are the source of the conflicting results. Hodrick–Prescott (HP)-filtered hours per capita produce results consistent with those obtained when hours are assumed to have a unit root. We show that important sources of the low-frequency movements in the standard measure are sectoral shifts in hours and the changing age composition of the working-age population. When we control for these low-frequency components to determine the effect of technology shocks on hours using long-run restrictions we get one consistent answer: hours decline in the short run in response to a positive technology shock. We further extend the analysis by examining the effects of demographic controls on the impulse responses to investment-specific technology shocks. Our results are less conclusive.
How Do Mergers Create Value? A Comparison of Taxes, Market Power, and Efficiency Improvements as Explanations for Synergies

There is little evidence in the literature on the relative importance of the underlying sources of merger gains. Prior literature suggests that synergies could arise due to taxes, market power, or efficiency improvements. Based on Value Line forecasts, we estimate the average synergy gains in a broad sample of 264 large mergers to be 10.03% of the combined equity value of the merging firms. The detailed data in Value Line projections allow for the decomposition of these gains into underlying operating and financial synergies. We estimate that tax savings contribute only 1.64% in additional value, while operating synergies account for the remaining 8.38%. Operating synergies are higher in focused mergers, while tax savings constitute a large fraction of the gains in diversifying mergers. The operating synergies are generated primarily by cutbacks in investment expenditures rather than by increased operating profits. Overall, the evidence suggests that mergers generate gains by improving resource allocation rather than by reducing tax payments or increasing the market power of the combined firm.
A quantum neural network computes its own relative phase

Complete characterization of the state of a quantum system made up of subsystems requires determination of relative phase, because of interference effects between the subsystems. For a system of qubits used as a quantum computer this is especially vital, because the entanglement, which is the basis for the quantum advantage in computing, depends intricately on phase. We present here a first step towards that determination, in which we use a two-qubit quantum system as a quantum neural network, which is trained to compute and output its own relative phase.