cssi/SciSciGPT-SciSciNet huggingface dataset:
A bridge type optoelectronic sample and hold circuit

A novel bridge type optoelectronic (OE) sample and hold circuit based upon current steering is presented for the first time and experimentally tested. Comparison between this circuit and a more conventional or direct OE sample and hold circuit which draws charge directly from the signal source shows that the bridge type is clearly superior in performance to the direct OE circuit. When a high speed signal is to be sampled with considerable precision, the bridge type OE sample and hold circuit offers high charging capability, much needed isolation, and reduced time jitter, distinct advantages over electronic sample and hold circuits. >
Theory of a Directive Optical Leaky Wave Antenna Integrated into a Resonator and Enhancement of Radiation Control

We provide for the first time the detailed study of the radiation performance of an optical leaky wave antenna (OLWA) integrated into a Fabry-Perot resonator. We show that the radiation pattern can be expressed as the one generated by the interference of two leaky waves counter-propagating in the resonator leading to a design procedure for achieving optimized broadside radiation, i.e., normal to the waveguide axis. We thus report a realizable implementation of the OLWA made of semiconductor and dielectric regions. The theoretical modeling is supported by full-wave simulation results, which are found to be in good agreement. We aim to control the radiation intensity in the broadside direction via excess carrier generation in the semiconductor regions. We show that the presence of the resonator can provide an effective way of enhancing the radiation level modulation, which reaches values as high as 13.5 dB, paving the way for novel promising radiation control capabilities that might allow the generation of very fast optical switches, as an example.
Learning by Doing

This chapter reviews the theoretical and empirical literature on learning by do- ing. Many of the distinctive theoretical implications of learning by doing have been derived under the assumption that the cost-quantity relationships observed in numerous empirical studies are largely the result of passive learning, and some further require that passive learning is unbounded. The empirical literature raises doubts about both assumptions. When observed cost-quantity relationships indicate sustained productivity growth, factors other than passive learning are generally at work. When passive learning is the dominant factor, productivity growth is invariably bounded. Thus, empirically-relevant theories in- corporating learning by doing are hybrid models in which passive learning coexists with other sources of growth. But in such models, many of the distinctive implications of passive learning become unimportant. Moreover, passive learning is often an inessential component of long-run growth; to the contrary, too much learning can lead to stagnation.
Microstructural Development, Densification, and Hot Pressing of Celsian Ceramics from Ion‐Exchanged Zeolite Precursors

Dense monoclinic celsian ceramics (melting point of 1760°C) have been fabricated utilizing zeolite precursors. A sodium zeolite (Na86Al86Si106O384H2O) was ion-exchanged in aqueous solutions to replace Na with Ba ions. The ion-exchanged powders were then heat-treated to effect the collapse of the zeolite structure and formation of an amorphous phase at 627°C, followed by crystallization of the celsian ceramic at 990°C. Inducing viscous flow from a thermal soak above the glass transition temperature was necessary to form a dense body from cold-pressed powders. Hot pressing at a pressure >5 MPa and above the crystallization temperature resulted in densities >90% of theoretical and eliminated the necessity of adding seed particles to form monoclinic celsian. To fabricate shaped bodies, the amorphous phase was molded at a temperature just above the glass transition temperature and then crystallized to monoclinic celsian at 1050°C. This processing technique demonstrates the potential of using zeolites as precursors for the low-temperature fabrication of shaped refractory parts.
Lobular neoplasia on core-needle biopsy—Clinical significance†

BACKGROUND. Approximately 25% of all cases of atypical ductal hyperplasia (ADH) diagnosed on core biopsy of the breast are associated with ductal carcinoma in situ (DCIS) or invasive malignancy at the same site. As a result, surgical excision has become the standard of care for patients with ADH. In contrast, because data on the relation between breast malignancy and lobular neoplasia (LN) detected on core biopsy are limited, clinical management of patients with LN remains controversial. The goal of the current study was to determine the incidence of breast carcinoma at sites of core biopsy exhibiting LN compared with sites of core biopsy exhibiting ADH. METHODS. The results of 2053 core biopsies were reviewed to identify cases of LN and cases of ADH. Follow-up findings on excisional biopsy were categorized as malignancy (DCIS or invasive malignancy) or no malignancy and were compared between the LN group and the ADH group. Mammograms and medical records were reviewed for patients with atypical findings on core biopsy. RESULTS. One hundred six (5.2%) of 2053 biopsy samples exhibited atypia on core biopsy. Among these 106 samples, ADH was found in 49 (46%), LN was found in 45 (42%), and both ADH and LN were found in 12 (12%). Malignant disease was detected on follow-up excisional biopsy in 22% of patients with ADH (9 of 41), 14% of patients with LN (3 of 21), and 33% of patients with both ADH and LN (4 of 12) on core biopsy. In the LN group, two cases of malignant disease were associated with lobular carcinoma in situ, and the third case was associated with atypical lobular hyperplasia. Mammographic and clinical features were unable to distinguish patients with malignant findings on excisional biopsy from patients without malignant findings. CONCLUSIONS. Malignant disease was found in a substantial percentage of excisional biopsy samples (14%) following the detection of LN on core biopsy. Thus, like patients with ADH, patients with LN on core biopsy could be considered candidates for surgical excision, which would allow full assessment of breast carcinoma risk and thereby facilitate the planning of prevention strategies. Cancer 2004;101:242–50. © 2004 American Cancer Society.
On the local interaction of money and credit

We study the coexistence of monetary and credit transactions in a model where exchange is decentralized. Agents belong to different locations which are informationally separated. The equilibrium mix of monetary and credit transactions is characterized as a function of the frequency of meetings among agents from different locations. Credit transactions take place only among a small set of “neighbors.” Monetary trades emerge only if interactions with faraway locations are sufficiently frequent. Even in that case, trades among nearby locations remain non-monetized.
A Dirty Word or a Dirty World? Attribute Framing, Political Affiliation, and Query Theory

We explored the effect of attribute framing on choice, labeling charges for environmental costs as either an earmarked tax or an offset. Eight hundred ninety-eight Americans chose between otherwise identical products or services, where one option included a surcharge for emitted carbon dioxide. The cost framing changed preferences for self-identified Republicans and Independents, but did not affect Democrats' preferences. We explain this interaction by means of query theory and show that attribute framing can change the order in which internal queries supporting one or another option are posed. The effect of attribute labeling on query order is shown to depend on the representations of either taxes or offsets held by people with different political affiliations.
Synthesis of a Novel Conformationally Locked Carbocyclic Nucleoside Ring System

A fast and efficient synthetic route to novel Northern locked carbocyclic nucleosides (as precursors of carbocyclic locked nucleic acids or cLNAs) is described. The target nucleoside with a oxabicyclo[2.2.1]heptane ring system was prepared from a simple starting material, diethyl malonate. Ring closure by intramolecular O-alkylation provided the target ring system as the major isomer over the [3.2.0] oxetane system. The adenine moiety was introduced through a reactive triflate after inversion of the stereochemistry of the corresponding alcohol by oxidation and reduction.
Quantizer effects on steady-state error specifications of digital feedback control systems

Suppose that for a linear, time-invariant, single-input single-output (SISO) plant a digital dynamic controller has been designed so that the corresponding discrete-time linear feedback control system will satisfy certain specified steady-state error criteria (e.g., the output v(kT) will follow the input r(kT) within a certain given error bound). Corresponding to this idealized linear system, the digital implementation of the dynamic controller will result in a nonlinear feedback control system. To what extent the resulting nonlinear digital feedback control system satisfies the steady-state-error criteria of the original idealized linear prototype feedback control system is investigated. Digital controller implementations which use fixed-point arithmetic or floating-point arithmetic are considered. Designs which are well scaled are assumed, i.e., overflow nonlinearities in digital controllers are not addressed. >
From fluid relaxations to practical algorithms for job shop scheduling: the makespan objective

We design an algorithm, called the fluid synchronization algorithm (FSA), for the job shop scheduling problem with the objective of minimizing the makespan. We round an optimal solution to a fluid relaxation, in which we replace discrete jobs with the flow of a continuous fluid, and use ideas from fair queueing in the area of communication networks in order to ensure that the discrete schedule is close to the one implied by the fluid relaxation. FSA produces a schedule with makespan at most Cmax +(I +2)Pmax Jmax, where Cmax is the lower bound provided by the fluid relaxation, I is the number of distinct job types, Jmax is the maximum number of stages of any job-type, and Pmax is the maximum processing time over all tasks. We report computational results based on all benchmark instances chosen from the OR library when N jobs from each job-type are present. The results suggest that FSA has a relative error of about 10% for N = 10, 1% for N = 100, 0.01% for N = 1000. In comparison to eight different dispatch rules that have similar running times as FSA, FSA clearly dominates them. In comparison to the shifting bottleneck heuristic whose running time and memory requirements are several orders of magnitude larger than FSA, the shifting bottleneck heuristic produces better schedules for small N (up to 10), but fails to provide a solution for larger values of N.
Scattering models for ultracold atoms

Abstract We present a review of scattering models that can be used to describe the low-energy behavior of identical bosonic atoms. In the simplest models, the only degrees of freedom are atoms in the same spin state. More elaborate models have other degrees of freedom, such as atoms in other spin states or diatomic molecules. The parameters of the scattering models are specified by giving the S-wave phase shifts for scattering of atoms in the spin state of primary interest. The models are formulated as local quantum field theories and the renormalization of their coupling constants is determined. Some of the parameters can be constrained by renormalizability or by the absence of negative-norm states. The Green’s functions that describe the evolution of two-atom states are determined analytically. They are used to determine the T-matrix elements for atom–atom scattering and the binding energies of diatomic molecules. The scattering models all exhibit universal behavior as the scattering length in a specific spin state becomes large.
Incorporating complex data structures into a language for social science research

This paper presents a set of augmentations to the language BEAST (Brookings Economics and Statistical Translator) as part of a continuing effort to define a language for a particular group of computer users, social scientists. In this nebulous group we include professional economists, political scientists, psychologists, sociologists, and a large number of university students in those disciplines. An important assumption underlying our work has been that the cost of not having substantially better software than presently exists is very large and should be measured in terms of researchers' time. The true cost of inappropriate methods of computer utilization should not be measured by staff and computer costs, but by the social cost of the output foregone. When answers to questions of importance for national public policy formation require weeks, months, or even years to obtain, the cost becomes a social cost that we all eventually bear.
The AGS new fast extraction system for the g-2 experiment and RHIC injection

The Alternating Gradient Synchrotron (AGS) requires a new fast extraction beam (NewFEB) system for the muon g-2 experiment and the Relativistic Heavy Ion Collider (RHIC). The conceptual design of the NewFEB system is discussed. The proposed NewFEB system will consist of a new fast multipulsing kicker placed at straight section G 10 and an ejector septum magnet at H 10, together with local orbit bumps generated by powering backleg windings on the AGS main magnets. The new system is capable of performing single bunch multiple extraction as often as every 8ms up to 12 times per AGS cycle, in addition to the standard single-turn fast extraction. >
Setpoint regulation of continuum robots using a fixed camera

In this paper, we investigate the problem of measuring the shape of a continuum robot manipulator using visual information from a fixed camera. Specifically, we capture the motion of a set of fictitious planes, each formed by four or more feature points, defined at various strategic locations along the body of the robot. Then, utilizing expressions for the robot forward kinematics as well as the decomposition of a homography relating a reference image of the robot to the actual robot image, we obtain the three-dimensional shape information continuously. We then use this information to demonstrate the development of a kinematic controller to regulate the manipulator end-effector to a constant desired position and orientation.
1,3-Halogen migration as an entry to aryl coppers from an unintuitive starting material

A copper(I) catalyzed 1,3-halogen migration/borylation migrates a bromine from an sp2 carbon to a benzylic carbon with concomitant borylation of the aryl–bromine bond. This transformation proceeds via an aryl copper intermediate which can be accessed independently and then trapped with electrophiles. As such, copper-catalyzed 1,3-halogen migration provides unique and mild access to an aryl copper species that allows for rapid aromatic functionalization from an unconventional starting material.
Millimeter-wave on-wafer waveform and network measurements using active probes

We have fabricated active probes for on-wafer waveform and network measurements. The probes incorporate GaAs nonlinear transmission line (NLTL) based network analyzer (NWA) integrated circuits and low-loss quartz coplanar-waveguide probe tips. The active probes show step response falltimes of 2.7 ps when excited by a 0.7-ps falltime input, Using these active probes, we demonstrate both waveform measurements with 2.7-ps risetime and network measurements to 200 GHz. We discuss the probe tip and NWA IC design, the hybrid assembly and mechanical design, and system design considerations. On-wafer waveform and S-parameter measurements of monolithic millimeter-wave integrated circuits are demonstrated. >
Facile Oxidation of Aldehydes to Acids and Esters with Oxone

A highly efficient, mild, and simple protocol is presented for the oxidation of aldehydes to carboxylic acids utilizing Oxone as the sole oxidant. Direct conversion of aldehydes in alcoholic solvents to their corresponding ester products is also reported. These reactions may prove to be valuable alternatives to traditional metal-mediated oxidations.
Where Are the M Dwarf Disks Older Than 10 Million Years

We present 11.7 μm observations of nine late-type dwarfs obtained at the Keck I 10 m telescope in 2002 December and 2003 April. Our targets were selected for their youth or apparent IRAS 12 μm excess. For all nine sources, excess infrared emission is not detected. We find that stellar wind drag can dominate the circumstellar grain removal and plausibly explain the dearth of M dwarf systems older than 10 Myr with currently detected infrared excesses. We predict that M dwarfs possess fractional infrared excesses on the order of LIR/L* ~ 10-6 and that this may be detectable with future efforts.
A note on the circuit complexity of PP

In this short note, we show that for any integer k, there are languages in the complexity class PP that do not have Boolean circuits of size nk.
Microbe hunting in the 21st century

A paper from Delwart and colleagues a recent issue of PNAS (1) affords an opportunity not only to discuss a new virus potentially linked to flaccid paralysis but also to review global efforts to eradicate poliovirus, the major cause of flaccid paralysis; recent advances in microbe hunting; and the potential complexity of proving causation when discovering novel microbes.
What’s fit to print: The effect of ownership concentration on product variety in daily newspaper markets

Abstract This paper examines the effect of ownership concentration on product position, product variety and circulation in the US daily newspaper market. The effects of consolidation in differentiated product markets cannot be determined solely from theory. Because multi-product firms internalize business stealing, mergers may encourage firms to reposition products, leading to more, not less, variety. Using data on the assignment of reporters to topical areas at 706 newspapers in 1993, 1999 and 2004, results show that both differentiation and variety increase with ownership concentration. Moreover, greater concentration increases variety over a range of topics and does not reduce readership.
Failure to Refinance

Households that fail to refinance their mortgage when interest rates decline can lose out on substantial savings. Based on a large random sample of outstanding U.S. mortgages in December of 2010, we estimate that approximately 20% of households for whom refinancing would be optimal and who appeared unconstrained to do so, had not taken advantage of the lower rates. We estimate the present-discounted cost to the median household who fails to refinance to be approximately $11,500.
Throughput and Delay in Random Wireless Networks With Restricted Mobility

Grossglauser and Tse (2001) introduced a mobile random network model where each node moves independently on a unit disk according to a stationary uniform distribution and showed that a throughput of Theta(1) is achievable. El Gamal, Mammen, Prabhakar, and Shah (2004) showed that the delay associated with this throughput scales as Theta(nlogn), when each node moves according to an independent random walk. In a later work, Diggavi, Grossglauser, and Tse (2002) considered a random network on a sphere with a restricted mobility model, where each node moves along a randomly chosen great circle on the unit sphere. They showed that even with this one-dimensional restriction on mobility, constant throughput scaling is achievable. Thus, this particular mobility restriction does not affect the throughput scaling. This raises the question whether this mobility restriction affects the delay scaling. This correspondence studies the delay scaling at Theta(1) throughput for a random network with restricted mobility. First, a variant of the scheme presented by Diggavi, Grossglauser, and Tse (2002) is presented and it is shown to achieve Theta(1) throughput using different (and perhaps simpler) techniques. The exact order of delay scaling for this scheme is determined, somewhat surprisingly, to be of Theta(nlogn), which is the same as that without the mobility restriction. Thus, this particular mobility restriction does not affect either the maximal throughput scaling or the corresponding delay scaling of the network. This happens because under this 1-D restriction, each node is in the proximity of every other node in essentially the same manner as without this restriction
Repair Optimal Erasure Codes Through Hadamard Designs

In distributed storage systems that employ erasure coding, the issue of minimizing the total communication required to exactly rebuild a storage node after a failure arises. This repair bandwidth depends on the structure of the storage code and the repair strategies used to restore the lost data. Designing high-rate maximum-distance separable (MDS) codes that achieve the optimum repair communication has been a well-known open problem. Our work resolves, in part, this open problem. In this study, we use Hadamard matrices to construct the first explicit two-parity MDS storage code with optimal repair properties for all single node failures, including the parities. Our construction relies on a novel method of achieving perfect interference alignment over finite fields with a finite number of symbol extensions. We generalize this construction to design $m$ -parity MDS codes that achieve the optimum repair communication for single systematic node failures.
Lateral compaction effects in braided structures

This paper addresses the phenomenology of strand interaction in biaxial non-embedded braided textile structures under uniaxial tension. The specific interest in the development of new braided textile structures is a result of the shortcomings of current rope, belt, and cable performance under large strain controlled conditions. However, this work also holds particular significance in the area of textile composite preforms. In composites forming, the lateral strand compaction mechanism, which drives braid behavior under tension, may be applied to woven fabrics for predicting wrinkling during forming processes. Additionally, manufacturing models produced in this study may be used to predict shape and size limitations of braided composite preforms. In this paper, a generalized model is developed for these structures with the intent of characterizing and predicting mechanical behavior. The methodology consists of a modular framework, which includes the prediction of manufacturing parameters. Lateral strand compaction tests were performed to generate constitutive material curves for use in analytical geometric models. Model predictions correlate well with data generated from braid uniaxial tension tests. Results suggest that lateral strand strain drives braid tensile behavior.
Breakup of Al/Al2O3 agglomerates in accelerating flowfields

Aluminized propdlrnts often p~uce large AI/AIP03 qglomentes which burn slowly compwd to rocket motor stay times. Two-phase llow velocity lags in the nozzle cause breakup of suffickntly Iargt aggIomentcs and thereby permit msonaMe combustion eftickacks to be achieved. High-spd photogmphs of the agglomerate pmxsses in a windowed rocket motor were used to obtain data on bmkup as a function of agglomerate size and two-phase flow vclocitics. The breakup process produces a cloud of much smaller droplets. A cemlation of the minimum qgglomerate size for bnakup was obtained in terms of the do of AI/AI2O3 surface tension and shear forces. Generally, agglomerotr: breakup occurs when the Weber number exceeds the range of 20 to 30. Nomenclature C,, = drag coefficient d,, = diameter of agglomerate, m F = drag force on agglomerate, N M = Mach number Red = Reynolds number based on diameter of agglomerate u = velocity, m/s We = Weber number p = density, kg/m rr = surface tension, N/m Subscripts performance compared with the theoretical would occur. Studies of the overall combustion efficiency of aluminized propellants burning in rocket motors reveal the performance losses due to incomplete combustion of aluminum and particle lag. It has been hypothesized that the two-phase flow processes in the nozzle produce breakup of sufficiently large agglomerates and thereby permit reasonable combustion efficiencies to be achieved. However, until now, direct observations of agglomerate breakup dnder rocket motor nozzle flow conditions did ,- ot exist.
Final results from the high-current, high-action closing switch test program at Sandia National Laboratories

We tested a variety of high-current closing switches for lifetime and reliability on a dedicated 2-MJ, 500-kA capacitor bank facility at Sandia National Laboratories. Interest was in a switch capable of one shot every few minutes, switching a critically damped, de-charged 6.2-mF bank at 24 kV, with a peak current of over 500 kA. The desired lifetime is 24000 shots. Typical of high-energy systems, particularly multimodule systems, the primary parameters of interest related to the switch are 1) reliability, meaning absence of both pre-fires and no-fires; 2) total switch lifetime or number of shots between maintenance; 3) cost. Cost was given lower priority at the evaluation stage because there are uncertainties in estimating higher-quantity prices of these devices, most of which have been supplied before in only small quantities. Cost has more importance in choosing between viable candidates after testing The categories of switches tested are vacuum discharge, high-pressure discharge, and solid-state. Each group varies in terms of triggering ease, ease-of-maintenance, and tolerance to faults such as excess current and current reversal. We tested at least two variations of each technology group. The total number of shots on the switch test facility is about 50000. This paper will present the results from the switch testing. The observed lifetime of different switches varied greatly: the shortest life was one shot; one device was still operating after 6000 shots. On several switches, we measured the voltage drop during conduction and calculated energy dissipated in the switch; we will show these data also.
The single audit act: how compliant are nonprofit organizations?

Over the past decade, the accountability of nonprofit organizations has been a concern. Our paper reports one form of accountability, the "A-133" or "single" audit, which is required for nonprofits receiving substantial federal funding. We report on 11,841 audits from 1997 to 1999. Overall, compliance appears to be quite high. Our study indicates that smaller nonprofits, those that are new to government grants, and those with prior audit findings have a significantly higher rate of adverse audit findings. One policy implication of our work might be to provide federal funding specifically for Single Audit Act compliance to these nonprofits.
T-maze learning in weanling lambs.

A major advantage of sheep models in experimental studies of neurodevelopmental disorders (e.g., with prenatal neurotoxicant exposure) is that the equivalent of all three trimesters of human brain development occurs in sheep entirely in utero. However, studies of learning and memory in sheep are limited. The goal of this study was to extend the analysis of spatial learning and memory in adolescent sheep using several traditional T-maze tasks. Both 9- and 14-week-old lambs acquired a delayed nonmatching-to-place task, but the older lambs learned the task significantly faster. In contrast, acquisition of a matching-to-place task was significantly more difficult. Lambs, like rodents, appear to have a predisposition toward learning “win-shift” spatial problems in a T-maze under appetitive motivation. Lambs also rapidly acquired a position habit and showed typical reversal learning curves. These findings support the use of T-maze tasks to assess behavioral outcomes in various sheep models. © 2011 Wiley Periodicals,Inc. Dev Psychobiol 54: 785–797, 2012
Analysis of Fixed Outage Transmission Schemes: A Finer Look at the Full Multiplexing Point

This paper studies the performance of transmission schemes that have rate that increases with average SNR while maintaining a fixed outage probability. This is in contrast to the classical Zheng-Tse diversity-multiplexing tradeoff (DMT) that focuses on increasing rate and decreasing outage probability. Three different systems are explored: antenna diversity systems, time/frequency diversity systems, and automatic repeat request (ARQ) systems. In order to accurately study performance in the fixed outage setting, it is necessary to go beyond the coarse, asymptotic multiplexing gain metric. In the case of antenna diversity and time/frequency diversity, an affine approximation to high SNR outage capacity (i.e., multiplexing gain plus a power/rate offset) accurately describes performance and illustrates the very significant benefits of diversity. ARQ is also seen to provide a significant performance advantage, but even an affine approximation to outage capacity is sometimes unable to capture this advantage and outage capacity must be directly studied in the non-asymptotic regime.
Numerical simulation of turbulent spots in channel and boundary layer flows

The initiation and early growth of spots in channel and boundary layer flows is simulated using a three-dimensional spectral code. The simulated spots show significant agreement with available experimental data for such quantities as growth rates and spreading angles. Disturbances are introduced into the center and edge of the developing channel spots to investigate the relative sensitivity of spots.
Bayesian Nonparametric Inference of Population Size Changes from Sequential Genealogies

Sophisticated inferential tools coupled with the coalescent model have recently emerged for estimating past population sizes from genomic data. Recent methods that model recombination require small sample sizes, make constraining assumptions about population size changes, and do not report measures of uncertainty for estimates. Here, we develop a Gaussian process-based Bayesian nonparametric method coupled with a sequentially Markov coalescent model that allows accurate inference of population sizes over time from a set of genealogies. In contrast to current methods, our approach considers a broad class of recombination events, including those that do not change local genealogies. We show that our method outperforms recent likelihood-based methods that rely on discretization of the parameter space. We illustrate the application of our method to multiple demographic histories, including population bottlenecks and exponential growth. In simulation, our Bayesian approach produces point estimates four times more accurate than maximum-likelihood estimation (based on the sum of absolute differences between the truth and the estimated values). Further, our method's credible intervals for population size as a function of time cover 90% of true values across multiple demographic scenarios, enabling formal hypothesis testing about population size differences over time. Using genealogies estimated with ARGweaver, we apply our method to European and Yoruban samples from the 1000 Genomes Project and confirm key known aspects of population size history over the past 150,000 years.
WIDE AREA DIFFERENTIAL GPS

.GPS has proven to be an extremely accurate positioning sensor for a wide variety of applications. However, in some situations, such as aircraft approach and landing, higher accuracy is required. Wide Area Differential GPS (WADGPS) is a system that could be used to meet such requirements. The WADGPS system comprises a master station, and local monitor stations distributed across the United States. The system calculates and transmits a vector of error corrections to users. This correction vector consists of parameters describing the three-dimensional ephemeris errors, satellite clock offsets, and ionospheric time delay parameters. The master station gathers GPS measurements made at each of the local stations, and estimates the errors using a combination of nonlinear static estimation and batch least squares. The performance of a l&station WADGPS network was investigated by simulation for users at sites across the United States. The monitor stations were located at existing Loran or VOR stations. Simulation results indicate that normal GPS positioning errors can potentially be reduced by more than 95 percent using WADGPS.
The Wealth Effects of Repurchases on Bondholders

Prior research has documented positive abnormal stock returns around the announcements of repurchase programs; several explanations of these returns have been suggested, including signaling, free cash flow, and wealth redistributions. This study analyzes abnormal stock, bond, and firm returns around repurchase announcements to examine these hypotheses. We find evidence consistent with both signaling and wealth redistribution. The loss to bondholders is a function of the size of the repurchase, and the risk of the firm's debt. We also find that bond ratings are twice as likely to be downgraded as upgraded after the announcement of the repurchase program. IN THIS PAPER, WE EXAMINE the impact of open market share repurchase announcements on both stock and bond prices. Positive stock price reactions to the announcement of an open market repurchase program are well documented in the empirical finance literature.1 Several potential explanations of the positive stock returns have been posited in the literature, including signaling, free cash flow, and bondholder wealth expropriation. However, only the signaling and wealth transfer or wealth expropriation hypotheses have implications for the impact of a repurchase program on both stock and bond returns. The signaling hypothesis suggests that bond and stock returns should be positively correlated; the signal provides information regarding the firm as a whole and, consequently, bond and stock prices will move in the same direction depending on the signal.2 Alternatively, the wealth transfer hypothesis suggests that bond and stock value changes should be negatively correlated. Ignoring any dead-weight losses (transactions costs), a wealth transfer is a zero-sum game; any gains to shareholders must come at the expense of bondholders and vice versa.
Untrusted hosts and confidentiality: secure program partitioning

This paper presents secure program partitioning, a language-based technique for protecting confidential data during computation in distributed systems containing mutually untrusted hosts. Confidentiality and integrity policies can be expressed by annotating programs with security types that constrain information flow; these programs can then be partitioned automatically to run securely on heterogeneously trusted hosts. The resulting communicating subprograms collectively implement the original program, yet the system as a whole satisfies the security requirements of participating principals without requiring a universally trusted host machine. The experience in applying this methodology and the performance of the resulting distributed code suggest that this is a promising way to obtain secure distributed computation.
The B-alkyl Suzuki-Miyaura cross-coupling reaction: Development, mechanistic study, and applications in natural product synthesis

The development of new reactions that facilitate the creative and efficient synthesis of molecular structures with desirable properties continues to fascinate chemists. The test of a significant contribution is its acceptance over time by the scientific community. The B-alkyl Suzuki-Miyaura cross-coupling reaction appears to be one such reaction. Since its disclosure by Suzuki and Miyaura in 1986, this reaction has been an attractive solution to challenging synthetic problems.
Chronic hyperoxia alters the early and late phases of the hypoxic ventilatory response in neonatal rats

Chronic hyperoxia during the first 1–4 postnatal weeks attenuates the hypoxic ventilatory response (HVR) subsequently measured in adult rats. Rather than focusing on this long-lasting plasticity, t...
On the rate-distortion efficiency of subband coding

It is shown that for the realizable subband coding of a wide sense stationary Gaussian source, with the implied separate encoding of the subband signals, the encoding performance is generally inferior to the rate-distortion function of the source. It is established that, for small encoding distortion, except for special cases, the subband coding is generally suboptimum. >
Parallel algorithms and architecture for computation of manipulator forward dynamics

Parallel computation of manipulator forward dynamics is investigated. Considering the three classes of algorithms for the problem, the authors show that the O(n/sup 3/) algorithms are the most efficient for parallel computation. Parallel algorithms for computation of inertia matrix, the bias vector, and the linear system solution are developed which can be efficiently implemented on a unique architecture, a triangular array of n(n+1)/2 processors with a nearest neighbor interconnection. This architecture is highly suitable for VLSI and WSI implementation. >
The M theory five-brane and the heterotic string

Brane actions with chiral bosons present special challenges. Recent progress in the description of the two main examples — the M theory five-brane and the heterotic string — is described. Also, double dimensional reduction of the M theory five-brane on K3 is shown to give the heterotic string.
Approximating hereditary discrepancy via small width ellipsoids

The Discrepancy of a hypergraph is the minimum attainable value, over two-colorings of its vertices, of the maximum absolute imbalance of any hyperedge. The Hereditary Discrepancy of a hypergraph, defined as the maximum discrepancy of a restriction of the hypergraph to a subset of its vertices, is a measure of its complexity. Lovasz, Spencer and Vesztergombi (1986) related the natural extension of this quantity to matrices to rounding algorithms for linear programs, and gave a determinant based lower bound on the hereditary discrepancy. Matousek (2011) showed that this bound is tight up to a polylogarithmic factor, leaving open the question of actually computing this bound. Recent work by Nikolov, Talwar and Zhang (2013) showed a polynomial time O(log3n)-approximation to hereditary discrepancy, as a by-product of their work in differential privacy. In this paper, we give a direct simple O(log3/2n)-approximation algorithm for this problem. We show that up to this approximation factor, the hereditary discrepancy of a matrix A is characterized by the optimal value of simple geometric convex program that seeks to minimize the largest l∞ norm of any point in a ellipsoid containing the columns of A. This characterization promises to be a useful tool in discrepancy theory.
Pricing and persuasive advertising in a differentiated market

This paper examines the effects of consumer preferences, firms’ costs, and advertising efficiencies on firms’ pricing and persuasive advertising strategies. We show that as the firms’ horizontal differentiation increases, the firm with a lower value-added product tends to increase persuasive advertising, whereas its competitor tends to reduce advertising. Second, the firm receiving a favorable shock in product valuation will complement the favorable change with additional persuasive advertising rather than reduce advertising spending. Third, an equal improvement in advertising efficiency in the industry will lower the profits for both firms, whereas a decrease in advertising efficiency in the industry can benefit both firms. Fourth, a larger shock that improves a firm’s product valuation or unit cost is more likely to induce higher advertising spending in the industry. Lastly, an exogenous increase in the separation between firms’ product valuations or perceived qualities may actually reduce the price dispersion in the industry.
Universality for the noisy Slepian-Wolf problem via spatial coupling

We consider a noisy Slepian-Wolf problem where two correlated sources are separately encoded and transmitted over two independent binary memoryless symmetric channels. Each channel capacity is assumed to be characterized by a single parameter which is not known at the transmitter. The receiver has knowledge of both the source correlation and the channel parameters. We call a system universal if it retains near-capacity performance without channel knowledge at the transmitter. Kudekar et al. recently showed that terminated low-density parity-check (LDPC) convolutional codes (a.k.a. spatially-coupled LDPC ensembles) can have belief-propagation thresholds that approach their maximum a-posteriori thresholds. This was proven for binary erasure channels and shown empirically for binary memoryless symmetric channels. They also conjectured that the principle of spatial coupling is very general and the phenomenon of threshold saturation applies to a very broad class of graphical models. In this work, we derive an area theorem for the joint decoder and empirically show that threshold saturation occurs for this problem. As a result, we demonstrate near-universal performance for this problem using the proposed spatially-coupled coding system. A similar result is also discussed briefly for the 2-user multiple-access channel.
The X-Ray Binary Population in M33. II. X-Ray Spectra and Variability

In this paper we investigate the X-ray spectra and X-ray spectral variability of compact X-ray sources for 3 Chandra observations of the Local Group galaxy M33. The observations are centered on the nucleus and the star-forming re- gionNGC604.Intheobservations,261sourceshavebeendetected.Foratotalof 43sourcesthenumberofnetcounts is above 100, sufficient for a more detailed spectral fitting. Of these sources, 25 have been observed in more than one observation,allowingthestudyofspectralvariabilityontimescalesofmonths.Aquarterofthesourcesarefoundto be variable between observations. However, except for two foreground sources, no source is variable within any observation above the 99% confidence level. Only six sources show significant spectral variability between obser- vations. A comparison of NH values with H i observations shows that X-ray absorption values are consistent with Galactic X-raybinaries and most sources inM33 are intrinsically absorbed.Thepattern of variability and thespectral parameters of these sources are consistent with the M33 X-ray source population being dominated by X-ray binaries: Two-thirds of the 43 bright sources have spectral and timing properties consistent with X-ray binaries; we also find two candidates for supersoft sources and two candidates for quasi-soft sources. Subject headingg galaxies: individual (M33) — Local Group — X-rays: binaries Online material: color figures, extended figure set
Low Energy Electron Beam Lithography

The use of low energy electron beams (<5 keV) to expose polymeric resists has been limited due to worse aberrations, lower available current density, and the difficulties involved in spinning on a very thin continuous resist layer. The first two problems can be eliminated by applying a retarding electric field directly above the workpiece. Computer simulations showing space charge effects on the probe size and improved aberrations coefficients are presented. An inorganic resist, GeSex, is ideally suited for this lithography due to the very shallow active layer ~0.01 um. Experimental results showing the favorable effects due to lower electron landing energy on the required dose and proximity effects are also presented. Lateral scattering in the resist is simulated by Monte Carlo techniques for 2 and 20 keV isolated, unexposed, submicron lines.
Direct oxidative Heck cyclizations: intramolecular Fujiwara-Moritani arylations for the synthesis of functionalized benzofurans and dihydrobenzofurans.

No extra functionalization step is required for palladium(II)-catalyzed oxidative carbocyclizations like that shown, which provide highly substituted benzofuran and dihydrobenzofuran derivatives by net dehydrogenation. The mechanism is similar to that of Heck cyclizations. Products containing quaternary carbon stereocenters can be obtained in diastereomerically pure form.
How Does Child Labor Affect the Demand for Adult Labor?: Evidence from Rural Mexico

Do employers substitute adults for children, or do they treat them as complements? Using data from a Mexican schooling experiment, I find that decreasing child farmwork is accompanied by increasing adult labor demand. This increase was not caused by treatment money reaching farm employers: there were no significant increases in harvest prices and quantities, nonlabor inputs, or nonfarm labor supply. Furthermore, coordinated movements in price and quantity can distinguish this increase in demand from changes in supply induced by the treatment's income effects. Thus, declining child supply caused increasing adult demand: employers substituted adults for children.
A finiteness condition on local cohomology in positive characteristic

Abstract In this paper, we present a condition on a local Cohen–Macaulay F-injective ring of positive characteristic p > 2 , which implies that its top local cohomology module with support in the maximal ideal has finitely many Frobenius compatible submodules.
The pixelflow texture and image subsystem

Abstract Texturing and imaging have become essential tasks for high-speed, high-quality rendering systems. They make possible effects such as photo-textures, environment maps, decals, modulated transparency, shadows, environment maps, and bump maps, to name just a few. These operations all require high-speed access to a large “image” memory closely connected to the rasterizer hardware. The design of such memory systems is challenging because there are many competing constraints: memory bandwidth, memory size, flexibility, and, of course, cost. PixelFlow is an experimental hardware architecture designed to support new levels of geometric complexity and to incorporate realistic rendering effects such as programmable shading. This required an extremely flexible and high-performance texture/image subsystem. This paper describes the PixelFlow texture/image subsystem, the design decisions behind it and its advantages and limitations. Future directions are also described.
The intramolecular asymmetric allylation of aldehydes via organo-SOMO catalysis: A novel approach to ring construction

The intramolecular asymmetric cyclization of aldehydes has been accomplished using singly occupied molecular orbital (SOMO) catalysis. Selective oxidation of chiral enamines (formed by the condensation of an aldehyde and a secondary amine catalyst) leads to the formation of a 3π-electron radical species. These chiral SOMO-activated radical cations undergo enantioselective cyclization with an array of pendent allylsilanes thus efficiently providing a new approach to the construction of five-, six- and seven-membered carbocycles and heterocycles.
Surface photovoltage spectroscopy of minority carrier diffusion lengths in undoped and Si‐doped GaN epitaxial films

Undoped- and Si-doped GaN epitaxial films were grown on sapphire substrates by metal-organic chemical vapor deposition. Variable angle spectroscopic ellipsometry (VASE) and surface photovoltage (SPV) spectroscopy were used to determine the minority carrier diffusion lengths in the films. Both the reflectivity (R) and absorption coefficient (α) could be calculated from the VASE measurements. In the SPV spectra at room temperature, a strong transition with a threshold at 3.42 eV was observed in both films, while an exciton-related absorption was observed only in the undoped GaN. The minority carrier diffusion lengths were measured to be about 200 nm for the undoped GaN and about 20 nm for the Si-doped GaN. Moreover, a large divergence in the range of 1/α in the undoped GaN was found and attributed to a high surface barrier energy. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)