cssi/SciSciGPT-SciSciNet huggingface dataset:
Random solids and random solidification: what can be learned by exploring systems obeying permanent random constraints?

In many interesting physical settings, such as the vulcanization of rubber, the introduction of permanent random constraints between the constituents of a homogeneous fluid can cause a phase transition to a random solid state. In this random solid state, particles are permanently but randomly localized in space, and a rigidity to shear deformations emerges. Owing to the permanence of the random constraints, this phase transition is an equilibrium transition, which confers on it a simplicity (at least relative to the conventional glass transition) in the sense that it is amenable to treatment by established techniques of equilibrium statistical mechanics. In this paper I shall review recent developments in the theory of random solidification for systems obeying permanent random constraints, with the aim of bringing to the fore the similarities of and differences between such systems and those exhibiting the conventional glass transition. I shall also report new results, obtained in collaboration with Weiqun Peng, on equilibrium correlations and susceptibilities that signal the approach of the random solidification transition, discussing the physical interpretation and values of these quantities both at the Gaussian level of approximation and, via a renormalization-group approach, beyond.
Benchmarking optimization software with performance profiles

We propose performance profiles — distribution functions for a performance metric — as a tool for benchmarking and comparing optimization software. We show that performance profiles combine the best features of other tools for performance evaluation.
Topology Changing Transitions in Bubbling Geometries

Topological transitions in bubbling half-BPS Type IIB geometries with SO(4) x SO(4) symmetry can be decomposed into a sequence of n elementary transitions. The half-BPS solution that describes the elementary transition is seeded by a phase space distribution of fermions filling two diagonal quadrants. We study the geometry of this solution in some detail. We show that this solution can be interpreted as a time dependent geometry, interpolating between two asymptotic pp-waves in the far past and the far future. The singular solution at the transition can be resolved in two different ways, related by the particle-hole duality in the effective fermion description. Some universal features of the topology change are governed by two-dimensional Type 0B string theory, whose double scaling limit corresponds to the Penrose limit of AdS_5 x S^5 at topological transition. In addition, we present the full class of geometries describing the vicinity of the most general localized classical singularity that can occur in this class of half-BPS bubbling geometries.
On graph thickness, geometric thickness, and separator theorems

We investigate the relationship between geometric thickness, thickness, outerthickness, and arboricity of graphs. In particular, we prove that all graphs with arboricity two or outerthickness two have geometric thickness O(logn). The technique used can be extended to other classes of graphs so long as a separator theorem exists. For example, we can apply it to show the known bound that thickness two graphs have geometric thickness O(n), yielding a simple construction in the process.
Effects of light availability and rainfall on leaf production in a moist tropical forest in central Panama

New leaf production in seasonal tropical forests may result from changes in water or light availability. In this study, the relationship between leaf flushing, photosynthetically active radiation (PAR) and rainfall was examined for understorey saplings in a moist tropical forest over one year. During the wet season, weeks with greater PAR were correlated with a greater proportion of sap- lings flushing new leaves during subsequent weeks in nine out of ten species. Rain- fall was negatively correlated with subsequent leafing during the wet season for six of ten species. However, during the dry season, rainfall was positively correlated with leafing during the following weeks for six species, but the relationship was much weaker. PAR in the dry season was negatively correlated with flushing in eight species. These results support the hypothesis that under well-watered condi- tions, light limits leaf production, and peaks in insolation result in greater leaf production.
Ligand-Modulated Palladium-Catalyzed Aerobic Alcohol Oxidations

The discovery and investigation of ligand-modulated Pd-catalyzed aerobic alcohol oxidations is documented. The project has evolved from a simple empirical discovery that (−)-sparteine, in combination with PdII salts, facilitates the aerobic oxidative kinetic resolution of secondary alcohols to an in-depth physical organic investigation that has provided key insights into how new, more effective catalysts can be designed. Mechanistic investigations, the substrate scope for the catalysts developed, and implications to oxidation catalysis are discussed.
SETS WITH MORE SUMS THAN DIFFERENCES

Let A be a finite subset of the integers or, more generally, of any abelian group, written additively. The set A has more sums than di! erences if |A + A| > |A ! A|. A set with this property is called an MSTD set. This paper gives explicit constructions of families of MSTD sets of integers.
On the energy efficiency of orthogonal signaling

In this paper, transmission over the additive white Gaussian noise (AWGN) channel, and coherent and noncoherent fading channels using M-ary orthogonal frequency-shift keying (FSK) or on-off frequency-shift keying (OOFSK) is considered. The receiver is assumed to perform hard-decision detection. In this setting, energy required to reliably send one bit of information is investigated. It is shown that for fixed M and duty cycle, bit energy requirements grow without bound as the signal-to-noise ratio (SNR) vanishes. The minimum bit energy values are numerically obtained for different values of M and the duty cycle. The impact of fading on the energy efficiency is identified. Requirements to approach the minimum bit energy of -1.59 dB are determined.
Angola's infrastructure : a continental perspective

Infrastructure made a net contribution of around 1 percentage point to Angola's improved per capita growth performance in recent years, despite unreliable power supplies and poor roads, which each holding back growth by 0.2 percentage points. Raising the country's infrastructure endowment to that of the region's middle-income countries (MICs) could boost Angola's annual growth by about 2.9 percentage points. As a resource-rich, postconflict country, Angola has shown an exceptionally strong commitment to financing the reconstruction and expansion of its infrastructure. It has recently expanded its generation capacity, embarked on an ambitious multibillion-dollar road rehabilitation program, begun to make investments aimed at easing congestion at the Port of Luanda, and embarked upon an ambitious rehabilitation program for urban water systems. Numerous challenges remain, however. Angola needs to upgrade its electricity transmission and distribution infrastructure, expand its urban water-supply system, improve efficiency at the Port of Luanda, and make policy and regulatory adjustments across the board. Angola presently spends around $4.3 billion per year on infrastructure, with $1.3 billion lost to inefficiencies. After taking sectoral allocations and inefficiencies into account, a modest funding gap of $115 million per year remains, which could be largely eliminated by focusing on lower-cost water and sanitation options. Angola's infrastructure needs are manageable relative to its fast-growing economy, as long as the country can address inefficiencies.
Lunar missions using advanced chemical propulsion: System design issues

To provide the transportation of lunar base elements to the moon, large high-energy propulsion systems will be required. Advanced propulsion systems for lunar missions can provide significant launch mass reductions and payload increases. These mass reductions and added payload masses can be translated into significant launch cost savings for the lunar base missions. The masses in low Earth orbit (LEO) were compared for several propulsion systems: nitrogen tetroxide/monomethyl hydrazine (NTO/MMH), oxygen/methane (O2/CH4), oxygen/hydrogen (O2/H2), and metallized O2/H2/Al propellants. Also, the payload mass increases enabled with O2/H2 and O2/H2/Al systems were addressed. In addition, many system design issues involving the engine thrust levels, engine commonality between the transfer vehicle and the excursion vehicle, and the number of launches to place the lunar mission vehicles into LEO will be discussed. Analyses of small lunar missions launched from a single STS-C flight are also presented.
Cosmological simulations of intergalactic medium enrichment from galactic outflows

We investigate models of self-consistent chemical enrichment of the intergalactic medium (IGM) from z = 6.0 → 1.5, based on hydrodynamic simulations of structure formation that explicitly incorporate outflows from star-forming galaxies. Our main result is that outflow parametrizations derived from observations of local starburst galaxies, in particular momentum-driven wind scenarios, provide the best agreement with observations of C iv absorption at z ∼ 2-5. Such models sufficiently enrich the high-z IGM to produce a global mass density of Civ absorbers that is relatively invariant from z = 5.5 → 1.5, in agreement with observations. This occurs despite continual IGM enrichment causing an increase in volume-averaged metallicity by ∼ x 5-10 over this redshift range, because energy input accompanying the enriching outflows causes a drop in the global ionization fraction of C iv. Comparisons to observed C IV column density and linewidth distributions and C IV-based pixel optical depth ratios provide significant constraints on wind models. Our best-fitting outflow models show mean IGM temperatures only slightly above our no-outflow case, metal filling factors of just a few per cent with volume-weighted metallicities around 10 -3 at z ∼ 3, significant amounts of collisionally ionized C iv absorption and a metallicity-density relationship that rises rapidly at low overdensities and flattens at higher ones. In general, we find that outflow speeds must be high enough to enrich the low-density IGM at early times but low enough not to overheat it, and concurrently must significantly suppress early star formation while still producing enough early metals. It is therefore non-trivial that locally calibrated momentum-driven wind scenarios naturally yield the desired strength and evolution of outflows, and suggest that such models represent a significant step towards understanding the impact of galactic outflows on galaxies and the IGM across cosmic time.
Parallel‐Series and Series‐Parallel Systems

This article will consider the system reliability of three different systems: series, parallel, and series–parallel systems. Interest is in finding the system reliability when the failure of each component depends on the length of time that the component is observed. Exponentially distributed failure times as well as Weibull failure times will be considered. Keywords: coherent system; competing risks; hazard function; redundancy; system reliability
Dual-core single-mode polymer fiber coupler

We have observed light coupling between dual-core dye-doped polymer optical fibers. The experimentally observed coupling length is consistent with the standard coupled-mode theory for single-mode–single-mode coupling between step-index waveguides [ P. D. McIntyre A. W. Snyder , J. Opt. Soc. Am.63, 1518–1527 (1973)]. We also show that a graded refractive-index profile of such dual-core fibers can be made by controlled dye diffusion. The concentration, as measured by optical absorption, shows a graded profile that matches the refractive-index profile, confirming that dye concentration determines the refractive index.
Do strategic groups differ in reputation

While most strategic group research has focused on performance implications, we consider the relationship between strategic group membership and reputation. Using strategic group identity and domain consensus concepts, we propose strategic groups have different reputations. We find significant differences exist in reputation across three identified strategic groups of U.S. property/casualty insurers, supporting our contention that reputation is a multilevel concept. Post hoc analyses suggest strategic groups with higher reputation also have higher performance on some critical measures, indicating reputation may be a mobility barrier beneficial to members of certain groups. Practitioner implications include challenges of within-group differentiation in firm reputation. Copyright © 2000 John Wiley & Sons, Ltd.
The Development of Versatile Methods for Palladium-Catalyzed Coupling Reactions of Aryl Electrophiles through the Use of P(t-Bu)3 and PCy3 as Ligands

Metal-catalyzed coupling reactions of aryl electrophiles with organometallics and with olefins serve as unusually effective tools for forming new carbon−carbon bonds. By 1998, researchers had developed catalysts that achieved reactions of aryl iodides, bromides, and triflates. Nevertheless, many noteworthy challenges remained; among them were couplings of aryl iodides, bromides, and triflates under mild conditions (at room temperature, for example), couplings of hindered reaction partners, and couplings of inexpensive aryl chlorides. This Account highlights some of the progress that has been made in our laboratory over the past decade, largely through the appropriate choice of ligand, in achieving these synthetic objectives. In particular, we have established that palladium in combination with a bulky trialkylphosphine accomplishes a broad spectrum of coupling processes, including Suzuki, Stille, Negishi, and Heck reactions. These methods have been applied in a wide array of settings, such as natural-prod...
The future of electric two-wheelers and electric vehicles in China

The method of force field analysis is used to examine the future technological and market evolution of electric two-wheelers (E2W) in China. The authors identify key forces driving and resisting future E2W market growth, root causes behind these forces, and important insights about the likelihood of a wide shift to larger three- and four-wheel electric vehicles (EV). The authors conclude that the key forces driving E2W market growth are: improvements in E2W and battery technology due to product modularity and modular industry structure, strong local regulatory support in the form of gasoline-powered motorcycle bans and loose enforcement of E2W standards, and deteriorating bus public transit service. The largest forces resisting E2W market growth are strong demand for gasoline-powered motorcycles, bans on E2Ws due to safety concerns in urban areas, and growing support for public transit. The balance of these forces appears to favor E2W market growth. This growth will likely drive vehicle electrification through continued innovation in batteries and motors, the switch from lead-acid to Li-ion batteries in E2Ws, and the development of larger E2Ws and EVs. There are however strong forces resisting vehicle electrification, including battery cost, charging infrastructure, and inherent complications with large battery systems.
When is foreign aid policy credible : aid dependence and conditionality

The author studies foreign aid policy within a principal-agent framework. He shows that one reason for foreign aid's poor overall record may be a moral hazard problem that shapes the aid recipient s incentive to undertake structural reform. The model's basic prediction is a two-way relationship: Disbursements of foreign aid are guided (in part) by the needs of the poor. Anticipating this, recipients have little incentive to improve the welfare of the poor. Preliminary econometric work shows that the data support this hypothesis. In principle, conditionality could partly solve this problem, but only if the donor can make a binding commitment to increase disbursements in good relative to bad states. Without such a commitment technology, aid disbursements remain guided by the needs of the poor and recipient countries maintain a low effort to reduce poverty. Contrary to the conventional wisdom found in the aid literature, the author shows that the welfare of all parties might be improved by using tied project aid or by delegating part of the aid budget to an (international) agency with less aversion to poverty.
High-Speed Optical Photometry of the Ultracompact X-Ray Binary 4U 1626–67

Rapid UBVRI photometry of the ultracompact low-mass X-ray binary (LMXB) pulsar 4U 1626-67/KZ TrA has detected 130.4 mHz (7.67 s) optical pulsations in all five bands. The optical pulsations, at the same frequency as the X-ray pulsations caused by rotation of the highly magnetized accreting neutron star primary, can be understood as a reprocessing of the pulsed X-ray emission in the accretion disk. The optical pulsed fraction is roughly 6%, independent of wavelength, indicating that the optical emission is dominated by X-ray reprocessing. A weaker (1.5%) sideband, downshifted 0.395(15) mHz from the main optical pulsation, is also present. This is consistent with a previously reported sideband downshifted 0.4011(21) mHz from the main pulsation, corroborating the 42 minute binary period proposed by Middleditch et al. A 0.048 Hz optical quasi-periodic oscillation (QPO), corresponding to a previously reported X-ray feature, was also detected in some of the observations, with a fractional rms amplitude of 3%-5%. This is the first measurement of an optical QPO in an X-ray binary pulsar. I discuss constraints on the nature of the mass donor and show that mass transfer via a radiatively driven wind is inconsistent with the optical data. I also review the basic theory of X-ray-heated accretion disks and show that such models provide a good fit to the optical photometry. If the effective X-ray albedo of LMXB accretion disks is as high as recently reported (ηd 0.9), then the optical data imply a distance of ~8 kpc and an X-ray luminosity of ≈ 1037 ergs s-1.
Quantitative theory of nanowire and nanotube antenna performance

We present quantitative predictions of the performance of nanotubes and nanowires as antennas, including the radiation resistance, the input reactance and resistance, and antenna efficiency, as a function of frequency and nanotube length. Particular attention is paid to the quantum capacitance and kinetic inductance. We develop models for both far-field antenna patterns as well as near-field antenna-to-antenna coupling. In so doing, we also develop a circuit model for a transmission line made of two parallel nanotubes, which has applications for nanointerconnect technology. Finally, we derive an analog of Hallen's integral equation appropriate for single-walled carbon nanotube antennas
An Efficient Exact-Least-Squares Fractionally Spaced Equalizer Using Intersymbol Interpolation

An efficient exact-least-squares procedure is presented specifically for the adaptive adjustment of a fractionally spaced equalizer (FSE). The intersymbol interpolation of the desired training sequence is used by this new procedure to reduce computational requirements and to improve convergence. For a T/p FSE ( 1/T being the data symbol rate and p the number of taps that span one symbol period), a factor of p improvement in "start-up" time is attained by this new procedure in comparison to the multichannel FSE versions of the "fast-Kalman" leastsquares algorithms of Falconer and Ljung [7] and in comparison to the Ling-Proakis [10] simplification for multichannel versions of the "fastlattice" least-squares algorithms of Satorius and Pack [8 ]Substantial reductions in computational and storage requirements are also achieved by the new procedure through the elimination of the inversion of p \times p matrices in these multichannel versions. Additional reductions in computational requirements are achieved by a special exact-least-squares modification for the passband "Nyquist" FSE structure of Mueller and Werner [6]. The procedure is shown to be most efficiently implemented using a transversal-filter realization of the fast exact-least-squares algorithmns. The per-iteration and per-unit-time computational requirements of the new procedure ( T/4 FSE) are found to be approximately the same as those of the more conventional, but much slower converging, ( T/2 ) tap-leakage stochastic-gradient algorithms of Gitlin, Meadors, and Weinstein [15]. Finally, simulations are conducted to verify the operation of the new procedure for both the training and decision-directed modes of operation.
Preparation of Orthorhombic Ba2YCu3O7 Powder by Single-Step Calcining

A single calcination step, solid-state process that provides orthohombic Ba2YCu3O7 powder is described. BaCO3, Y2O3, and CuO are used as precursor materials. The only phase identifiable by X-ray diffraction is the orthorhombic Ba2YCu3O7. The use of a vacuum during the inital stages of the calcining process promotes complete decomposition of the carbonate, and no residual carbonate is observed. An oxygen atmosphere during the later stages of calcining ensures proper oxidation to Ba2YCu3O7. The use of a similar combination vacuum-oxygen calcining schedule should also be beneficial in the preparation of chemically derived powders.
The Speed of Information Revelation and Eventual Price Quality in Markets with Insiders: Comparing Two Theories*

Two theoretical literatures, one using Bayesian Nash equilibrium (BNE), and the other using noisy rational expectations equilibrium (NREE), both provide a foundation for understanding how private information is impounded into asset prices, yet some of their predictions are conflicting. Here, we compare for the first time, the two theories using data from carefully controlled laboratory asset markets. In the dynamics, we find strong evidence for BNE theory, although final prices support predictions of the NREE theory. Finally, we document that price volatility increases when information is being impounded in prices.
Household Food Expenditures, Parental Time Allocation, and Childhood Obesity

The increased prevalence of childhood obesity is a major concern for society. This study aims at exploring the influence of the parents (especially parental time allocation choices) on childrens obesity-related health outcomes and examining the potential differences between the fathers and the mothers marginal effects. A household with two parents and one child is modeled. The household production theory and the collective household modeling structure are combined. The model treats the mother, the father and the child as three separate agents with individual preferences. The two parents interaction is modeled within the collective model framework by assuming that they will reach Pareto efficient resource allocation between them. In order to capture the dynamics between parents and the child, parents-child interaction is modeled in a two-stage Stackleberg game structure where the child is allowed to have certain decision choices of his/her own. This game structure allows us to explore the parental influence on the childs health outcomes while allowing the child to have influencing power in the household decision-making process. Based on this theoretical model, a general triangular system with one childs health production equation and five health inputs demand equations is derived and estimated. The empirical estimation is performed for three systems: pooled model, the younger children model (of age 9 to 11), and the older children model (of age 13 to 15). The empirical results shows positive relationship between total household monthly food expenditure and the childs BMI outcome. Both parents time spent with the child are important and both show negatively significant impact on the childs BMI outcomes in all models and the pool model confirms the statistical difference between paternal and maternal time spent with the child. Other mother-related variables show more influence on the childrens BMI. There exists a complementary relationship between mothers income and fathers time allocation. Fathers have more significant influence on household food expenditure compared to mothers. In general, mothers show more significant influence on the parental time allocation compared to fathers. The main contribution of this study is that it develops a general theoretical framework to capture the dynamics in parents-child interaction. Based on this theoretical model, empirical analysis and future work can be conducted in a theoretically consistent way.
Shuttle Subscale Ablative Nozzle Tests

Recent subscale nozzle tests have identified new and promising carbon phenolic nozzle ablatives which utilize staple rayon, PAN, and pitch based carbon cloth. A 4-inch throat diameter submerged test nozzle designed for the 48-inch Jet Propulsion Laboratory char motor was used to evaluate five different designs incorporating 20 candidate ablatives. Test results indicate that several pitch and PAN-based carbon phenolic ablatives can provide erosion and char performance equivalent or superior to the present continuous rayon-based SRM ablative.
Summary based structures with improved sublinear recovery for compressed sensing

We introduce a new class of measurement matrices for compressed sensing, using low order summaries over binary sequences of a given length. We prove recovery guarantees for three reconstruction algorithms using the proposed measurements, including l 1 minimization and two combinatorial methods. In particular, one of the algorithms recovers k-sparse vectors of length N in sublinear time poly(k log N), and requires at most O(k log N log log N) measurements. The empirical oversampling constant of the algorithm is significantly better than existing sublinear recovery algorithms such as Chaining Pursuit and Sudocodes. In particular, for 103 ≤ N ≤ 1012 and k = 100, the oversampling factor is between 5 to 25. We provide preliminary insight into how the proposed constructions, and the fast recovery scheme can be used in a number of practical applications such as market basket analysis, and real time compressed sensing implementation.
Solar Proton Events of 1989: Effects on Spacecraft Solar Arrays

Abstract : Three energetic solar proton events occurred in the August to October 1989 time period. The energetic (1-10 MeV proton fluence from these events was among the highest fluence levels observed during the space age. The solar proton events were of sufficient magnitude to produce easily observable (several percent), irreversible losses in solar array output on geosynchronous and polar low-earth-orbiting satellites. The degradation of solar array output was measured on the GOES-5, GOES-6, and GOES-7 satellites and on two other U.S. Government satellites in geosynchronous orbit. The observed solar array degradation was compared with that computed based on knowledge of the solar cell type, cover glass thickness, the operational mode of the array, the observed proton spectrum, and the length of time on orbit for each satellite. In each case, good agreement was obtained between the observed and the computed results. Solar Flares, Radiation Effects.
Constellation Precoded Multiple Beamforming

Beamforming techniques that employ Singular Value Decomposition (SVD) are commonly used in Multi-Input Multi-Output (MIMO) wireless communication systems. In the absence of channel coding, when a single symbol is transmitted, these systems achieve the full diversity order provided by the channel; whereas when multiple symbols are simultaneously transmitted, this property is lost. When channel coding is employed, full diversity order can be achieved. For example, when Bit-Interleaved Coded Modulation (BICM) is combined with this technique, full diversity order of NM in an M x N MIMO channel transmitting S parallel streams is possible, provided a condition on S and the BICM convolutional code rate is satisfied. In this paper, we present constellation precoded multiple beamforming which can achieve the full diversity order both with BICM-coded and uncoded SVD systems. We provide an analytical proof of this property. To reduce the computational complexity of Maximum Likelihood (ML) decoding in this system, we employ Sphere Decoding (SD). We report an SD technique that reduces the computational complexity beyond commonly used approaches to SD. This technique achieves several orders of magnitude reduction in computational complexity not only with respect to conventional ML decoding but also, with respect to conventional SD.
THE SURFACE COMPOSITION OF LARGE KUIPER BELT OBJECT 2007 OR10

We present photometry and spectra of the large Kuiper belt object 2007 OR10. The data show significant near-infrared absorption features due to water ice. While most objects in the Kuiper belt with water ice absorption this prominent have the optically neutral colors of water ice, 2007 OR10 is among the reddest Kuiper belt objects known. One other large Kuiper belt object—Quaoar—has similar red coloring and water ice absorption, and it is hypothesized that the red coloration of this object is due to irradiation of the small amounts of methane able to be retained on Quaoar. 2007 OR10, though warmer than Quaoar, is in a similar volatile retention regime because it is sufficiently larger that its stronger gravity can still retain methane. We propose, therefore, that the red coloration on 2007 OR10 is also caused by the retention of small amounts of methane. Positive detection of methane on 2007 OR10 will require spectra with higher signal to noise. Models for volatile retention on Kuiper belt objects appear to continue to do an excellent job reproducing all of the available observations.
Ant-based computing

A biologically and physically plausible model for ants and pheromones is proposed. It is argued that the mechanisms described in this model are sufficiently powerful to reproduce the necessary components of universal computation. The claim is supported by illustrating the feasibility of designing arbitrary logic circuits, showing that the interactions of ants and pheromones lead to the expected behavior, and presenting computer simulation results to verify the circuits' working. The conclusions of this study can be taken as evidence that coherent deterministic and centralized computation can emerge from the collective behavior of simple distributed Markovian processes such as those followed by biological ants, but also, more generally, by artificial agents with limited computational and communication abilities.
Agricultural Contracting Update: Contracts in 2008

Marketing and production contracts covered 39 percent of the value of U.S. agricultural production in 2008, up from 36 percent in 2001, and a substantial increase over 28 percent in 1991 and 11 percent in 1969. However, aggregate contract use has stabilized in recent years and no longer suggests a strong trend. Contracts between farmers and their buyers are reached prior to harvest (or before the completion stage for livestock) and govern the terms under which products are transferred from the farm. Contracts are far more likely to be used on large farms than on small farms, and they form one element in a package of risk management tools available to farmers. Production contracts are used widely in livestock production, while marketing contracts are important to the production of many crops.
Female-owned firms in Latin America : characteristics, performance, and obstacles to growth

This paper examines the characteristics and performance of female-owned firms in Latin America. Data from firm surveys show that female-owned firms tend to be smaller than male-owned firms in terms of employees, sales, costs, and physical capital. Female-owned firms also have lower profits than male-owned firms, but for larger firms this difference disappears after controlling for labor and capital inputs. Medium-size and large female-owned firms are as productive as male-owned firms of the same size, although micro and small female-owned firms are less productive than male-owned firms. There is no evidence that the differences between female and male-owned firms are due to differences in access to finance or regulatory burdens. However, this paper finds a negative correlation between child care and household obligations and female-owned firm size and performance.
Modeling file system organizations in a local area network environment

This paper presents a modeling methodology for the design of file system organizations in a local area network environment. We first propose a characterization for the workload of typical business transaction systems, and then use this measurable characterization to derive input parameters for the file distribution graph models and the queuing network models that represent two completely different file system organizations, i.e., a file server-based file system and a distributed file system. Total system throughput and mean system response time are the indices used in comparing these two design approaches. An example of this comparison is given. It is shown that this methodology and these models are useful tools for the evaluation of certain design tradeoffs.
Chord theorems on graphs

The Horizontal Chord Theorem states that if a continuous curve connects points A and B in the plane, then for any integer k there are points C and D on the curve such that − − → AB = k − − → CD. In this note, we discuss a few combinatorial-analysis problems related to this theorem and introduce a different formulation that gives way to generalizations on graphs. 1 THE NECKLACE OF PEARLS PROBLEM. Two pirates have a single-strand necklace containing 2N black pearls and 2N white pearls arranged in any order. They would like to cut the necklace into as few pieces as possible so that after dividing the pieces of the necklace between them, each gets exactly N white pearls and N black ones. Using the following theorem, one can show that two cuts are sufficient. V. Totik has discussed several problems, including the above mentioned and the combinatorial-analysis theorem below, in the Monthly paper ‘A Tale of Two Integrals’ [4].
Metric dependence and asymptotic minimization of the expected number of critical points of random holomorphic sections

We prove the main conjecture from Douglas, Shiffman, and Zelditch (2006) concerning the metric dependence and asymptotic minimization of the expected number Ncrit N,hof critical points of random holomorphic sections of the Nth tensor power of a positive line bundle. The first non-topological term in the asymptotic expansion of Ncrit N,h is the Calabi functional multiplied by the constant β 2 (m) which depends only on the dimension of the manifold. We prove that β 2 (m) is strictly positive in all dimensions, showing that the expansion is non-topological for all m, and that the Calabi extremal metric, when it exists, asymptotically minimizes Ncrit N,h.
Population statistics study of radio and gamma-ray pulsars in the Galactic plane

We present results of our pulsar population synthesis of normal and millisecond pulsars in the Galactic plane. Over the past several years, a program has been developed to simulate pulsar birth, evolution and emission using Monte Carlo techniques. We have added to the program the capability to simulate millisecond pulsars, which are old, recycled pulsars with extremely short periods. We model the spatial distribution of the simulated pulsars by assuming that they start with a random kick velocity and then evolve through the Galactic potential. We use a polar cap/slot gap model for γ-ray emission from both millisecond and normal pulsars. From our studies of radio pulsars that have clearly identifiable core and cone components, in which we fit the polarization sweep as well as the pulse profiles in order to constrain the viewing geometry, we develop a model describing the ratio of radio core-to-cone peak fluxes. In this model, short period pulsars are more cone-dominated than in our previous studies. We present the preliminary results of our recent study and the implications for observing these pulsars with GLAST and AGILE.
Recent work on standard solar models

Abstract Recent results on standard solar models are reviewed. I shall summarize briefly three of the themes that I stressed at the Neutrino '92 Conference: 1) Different solar model codes give the same answers when the same input data are used; 2) Improved calculations of standard solar models include helium diffusion, the Livermore radiative opacity, the meteoritic iron abundance, and a variety of other corrections; and 3) There are a few basic rules that should be followed in using standard solar models. At the Neutrino '92 Conference, I reviewed in more detail the recent work on standard solar models by Marc Pinsonneault and myself. This work has by now appeared in print (Rev. Mod. Phys. 64, 885, 1992, hereafter Paper I, and ApJ Letters, 69, 717, 1992, Paper II). Therefore, there is no need for me to repeat the details here.
Fluorescence Imaging In Vivo at Wavelengths beyond 1500 nm

Compared to imaging in the visible and near-infrared regions below 900 nm, imaging in the second near-infrared window (NIR-II, 1000–1700 nm) is a promising method for deep-tissue high-resolution optical imaging in vivo mainly owing to the reduced scattering of photons traversing through biological tissues. Herein, semiconducting single-walled carbon nanotubes with large diameters were used for in vivo fluorescence imaging in the long-wavelength NIR region (1500–1700 nm, NIR-IIb). With this imaging agent, 3–4 μm wide capillary blood vessels at a depth of about 3 mm could be resolved. Meanwhile, the blood-flow speeds in multiple individual vessels could be mapped simultaneously. Furthermore, NIR-IIb tumor imaging of a live mouse was explored. NIR-IIb imaging can be generalized to a wide range of fluorophores emitting at up to 1700 nm for high-performance in vivo optical imaging.
Stability of Covariant Relativistic Quantum Theory

In this paper we study the relativistic quantum-mechanical interpretation of the solution of the inhomogeneous Euclidean Bethe-Salpeter equation. Our goal is to determine conditions on the input to the Euclidean Bethe-Salpeter equation so the solution can be used to construct a model Hilbert space and a dynamical unitary representation of the Poincare group. We prove three theorems that relate the stability of this construction to properties of the kernel and driving term of the Bethe-Salpeter equation. The most interesting result is that the positivity of the Hilbert space norm in the non-interacting theory is not stable with respect to Euclidean covariant perturbations defined by Bethe-Salpeter kernels. The long-term goal of this work is to understand which model Euclidean Green functions preserve the underlying relativistic quantum theory of the original field theory. Understanding the constraints imposed on the Green functions by the existence of an underlying relativistic quantum theory is an important consideration for formulating field-theory motivated relativistic quantum models.
A temperature dependent SPICE macro-model for power MOSFETs

A power MOSFET SPICE macro-model suitable for use over the temperature range -55 to 125 degrees C has been developed. The model is composed of a single parameter set with temperature dependence accessed through the SPICE.TEMP card. SPICE parameter extraction techniques for the model and model predictive accuracy are discussed. Though complex, the model and approach to parameter extraction are straightforward. As all the parameter extraction algorithms are analytic in nature, automation of the extraction process is straightforward and requires no special optimization routines. The addition of a power MOSFET model to the SPICE code would result in more robust and efficient simulations. >
Palladium‐Catalyzed Chemoselective Allylic Substitution, Suzuki–Miyaura Cross‐Coupling, and Allene Formation of Bifunctional 2‐B(pin)‐Substituted Allylic Acetate Derivatives

A formidable challenge at the forefront of organic synthesis is the control of chemoselectivity to enable the selective formation of diverse structural motifs from a readily available substrate class. Presented herein is a detailed study of chemoselectivity with palladium-based phosphane catalysts and readily available 2-B(pin)-substituted allylic acetates, benzoates, and carbonates. Depending on the choice of reagents, catalysts, and reaction conditions, 2-B(pin)-substituted allylic acetates and derivatives can be steered into one of three reaction manifolds: allylic substitution, Suzuki-Miyaura cross-coupling, or elimination to form allenes, all with excellent chemoselectivity. Studies on the chemoselectivity of Pd catalysts in their reactivity with boron-bearing allylic acetate derivatives led to the development of diverse and practical reactions with potential utility in synthetic organic chemistry.
Non-Parametric Nonlinear System Identification: An Asymptotic Minimum Mean Squared Error Estimator

This paper studies the problem of the minimum mean squared error estimator for non-parametric nonlinear system identification. It is shown that for a wide class of nonlinear systems, the local linear estimator is a linear (in outputs) asymptotic minimum mean squared error estimator. The class of the systems allowed is characterized by a stability condition that is related to many well studied stability notions in the literature. Numerical simulations support the analytical analysis.
Oxygen Depletion in the Interstellar Medium: Implications for Grain Models and the Distribution of Elemental Oxygen

This paper assesses the implications of a recent discovery that atomic oxygen is being depleted from diffuse interstellar gas at a rate that cannot be accounted for by its presence in silicate and metallic oxide particles. To place this discovery in context, the uptake of elemental O into dust is considered over a wide range of environments, from the tenuous intercloud gas and diffuse clouds sampled by the depletion observations to dense clouds where ice mantles and gaseous CO become important reservoirs of O. The distribution of O in these contrasting regions is quantified in terms of a common parameter, the mean number density of hydrogen n H. At the interface between diffuse and dense phases (just before the onset of ice-mantle growth) as much as ~160 ppm of the O abundance is unaccounted for. If this reservoir of depleted oxygen persists to higher densities it has implications for the oxygen budget in molecular clouds, where a shortfall of the same order is observed. Of various potential carriers, the most plausible appears to be a form of O-bearing carbonaceous matter similar to the organics found in cometary particles returned by the Stardust mission. The organic refractory model for interstellar dust is re-examined in the light of these findings, and it is concluded that further observations and laboratory work are needed to determine whether this class of material is present in quantities sufficient to account for a significant fraction of the unidentified depleted oxygen.
Local-testability and self-correctability of q-ary sparse linear codes

We prove that q-ary sparse codes with small bias are self-correctable and locally testable. We generalize a result of Kaufman and Sudan [3] that proves the local testability and correctability of binary sparse codes with small bias. We use properties of q-ary Krawtchouk polynomials and the McWilliams identity -that relates the weight distribution of a code to the weight distribution of its dual- to derive bounds on the error probability of the randomized tester and self-corrector we are analyzing.
Estimation of thickness, complex bulk permittivity and surface conductivity using interdigital dielectrometry

Experiments that are based on theoretical techniques for deducing continuum parameters from the gain-phase response of interdigital electrodes are described. They demonstrate the use of 50- mu m- or 1-mm-wavelength interdigitated electrodes for the absolute measurement of (1) the thickness and voidage of a layer formed by the sedimentation of 41- mu m particles in transformer oil; (2) the thickness and high-frequency bulk permittivity of plasma-deposited bromobenzene and vacuum-deposited parylene, the former in-situ; (3) the complex permittivity of transformer oil without and with a parylene passivation layer to prevent the adsorption of water; (4) the dispersion of oil-impregnated paper having a finite thickness; and (5) the surface conductivity due to adsorption of water on a silicon dioxide substrate. The frequency range for (3)-(5) is 0.005 Hz to 10 kHz. Difficulties that are apparently due to charging effects on the integrated circuitry are discussed. >
Search and Non-Wage Job Characteristics

This paper quantifies the importance of non-wage job characteristics to workers by estimating a structural on-the-job search model. The model generalizes the standard search framework by allowing workers to search for jobs based on both wages and job-specific non-wage utility flows. Within the structure of the search model, data on accepted wages and wage changes at job transitions identify the importance of non-wage utility through revealed preference. The estimates reveal that utility from non-wage job characteristics plays an important role in determining job mobility, the value of jobs to workers, and the gains from job search.
Estimation of rate constants in nonlinear reactions involving chemical inactivation of oxidation catalysts

Over the last decades, copious work has been devoted to the development of small molecule replicas of the peroxidase enzymes that activate hydrogen peroxide in metabolic and detoxifying processes. TAML activators that are the subject of this study are the first full functional, small molecule peroxidase mimics. As an important feature of the catalytic cycle, TAML reactive intermediates (active catalysts, Ac) undergo suicidal inactivation, compromising the functional catalysis. Herein the relationship between suicidal inactivation and productive catalysis is rigorously addressed mathematically and chemically. We focus on a generalized catalytic cycle in which the TAML inactivation step is delineated by its rate constant $$k_{\mathrm{i}}$$ where the revealing data is collected in the regime of incomplete conversion of substrate (S) artificially imposed by the use of very low catalyst concentrations. $$\begin{aligned} \left\{ \begin{array}{l@{\quad }l} \hbox {Resting catalyst (Rc)} + \hbox {Oxidant} \rightarrow \hbox {Ac} &{} (k_{\mathrm{I}})\\ \hbox {Ac + Substrate (S)}\rightarrow \hbox {Rc}+\hbox {Product} &{} (k_{\mathrm{II}})\\ \hbox {Ac} \rightarrow \hbox {Inactive catalyst} &{} (k_{\mathrm{i}}) \end{array} \right. \end{aligned}$$ The system exhibits a nonlinear conservation law and is modeled via a singular perturbation approach, which is used to obtain closed form relationships between system parameters. A new method is derived that allows to compute all the rate constants in the catalytic cycle, $$k_{\mathrm{I}},k_{\mathrm{II}}$$ , and $$k_{\mathrm{i}}$$ , with as little as two linear least squares fits, for the minimal data set collected under any conditions providing that the oxidation of S is incomplete. This method facilitates determination of $$k_{\mathrm{i}}$$ , a critical rate constant that describes the operational lifetime of the catalyst, and greatly reduces the experimental work required to obtain the important rate constants.The approach was applied to the behavior of a new TAML activator, the synthesis and characterization of which are also described.