cssi/SciSciGPT-SciSciNet huggingface dataset:
Information and entropy

The Landauer cost for erasing information demands that information about a physical system be included in the total entropy, as proposed by Zurek [Nature 341, 119 (1989); Phys. Rev. A 40, 4731 (1989)]. A consequence is that most system states-either classical phase-space distributions or quantum pure states-have total entropy much larger than thermal equilibrium. If total entropy is to be a useful concept, this must imply that work can be extracted in going from equilibrium to a typical system state. The work comes from randomization of a «memory» that holds a record of the system state
Soft gluons and gauge-invariant subtractions in NLO parton-shower Monte Carlo event generators

We address the problem of decomposing graphs in perturbative QCD into terms associated with particular regions. Motivated by asking how to incorporate next-to-leading order (NLO) QCD corrections in parton-shower algorithms, we require that: (a) The integrand for the hard part is to be integrable even if the corrections are applied to a process that is not infrared and collinear safe. (b) The splitting between the terms should be defined gauge-invariantly. (c) The dependence on cut-offs should obey homogeneous evolution equations. In the context of one-gluon-emission graphs for deep inelastic scattering, we explain a subtractive technique that is based on gauge-invariant Wilson-line operators. Appropriate organization of subtractions involving the soft region allows a connection to previous work where evolution equations with respect to the directions of the Wilson lines have been derived.
A chiral SU(N) gauge theory and its non-chiral Spin(8) dual

Abstract We study supersymmetric SU ( N - 4) gauge theories with a symmetric tensor and N antifundamental representations. The theory with W = 0 has a dual description in terms of a non-chiral Spin(8) theory with one spinor and N vectors. This duality flows to the SO ( N ) duality of Seiberg and to a duality proposed by one of us. It also flows to dualities for a number of Spin( m ) theories, m ≤ 8. For N = 6, when an N = 2 SUSY superpotential is added, the singularities of Seiberg and Witten are recovered. For N ≤ 6, a mass for the spinor generates the branches of SO (8) theories found by Intriligator and Seiberg. Other phenomena include a classical constraint mapped to an anomaly equation under duality and an intricate consistency check on the renormalization group flow.
Dynamics for causal sets with matter fields: a Lagrangian-based approach

We present a framework for the dynamics of causal sets and coupled matter fields which is a simplification and generalization of an approach we recently proposed. Given a set of fields including the gravitational one, the main step in implementing our proposal consists in writing their continuum-based action using as variables for the spacetime geometry the causal order and volume element. One then discretizes the resulting expression, with a procedure designed to maintain covariance. After a discussion of the general framework, we treat in detail the case of scalar fields, Yang-Mills gauge fields and the gravitational field.
Order parameter for two-dimensional critical systems with boundaries

Conformal transformations can be used to obtain the order parameter for two-dimensional systems at criticality in finite geometries with fixed boundary conditions on a connected boundary. To the known examples of this class (such as the disk and the infinite strip) we contribute the case of a rectangle. We show that the order parameter profile for simply connected boundaries can be represented as a universal function (independent of the criticality model) raised to the power $\frac{1}{2}\ensuremath{\eta}.$ The universal function can be determined from the Gaussian model or equivalently a problem in two-dimensional electrostatics. We show that fitting the order parameter profile to the theoretical form gives an accurate route to the determination of $\ensuremath{\eta}.$ We perform numerical simulations for the Ising model and percolation for comparison with these analytic predictions, and apply this approach to the study of the planar rotor model.
Multi-level coded caching

Recent work has demonstrated that for content caching, joint design of storage and delivery can yield significant benefits over conventional caching approaches. This is based on storing content in the caches, so as to create coded-multicast opportunities even amongst users with different demands. Such a coded-caching scheme has been shown to be order-optimal for a caching system with single-level content, i.e., all content is uniformly popular. In this work, we consider a system with content divided into multiple levels, based on varying degrees of popularity. The main contribution of this work is the derivation of an information-theoretic outer bound for the multi-level setup, and the demonstration that under some natural regularity conditions, a memory-sharing scheme which operates each level in isolation according to a single-level coded caching scheme, is in fact order-optimal with respect to this outer bound.
Multiple Bonding Between Main-Group And Transition Elements

Abstract The reaction of (Me3Si)2 CHBiCl2 with K2 [W(CO)5] results in tungsten/bismuth cluster compounds. The reaction of (Me3Si)2 CHSbCl)2, with Na2(Fe(CO)4] affords an η2-distibene complex which, in turn, reacts with Fe2(CO)9 to produce Fe2(μ-SbCH(SiMe3),2)(CO)8, a “closed” (i.e. metal-metal bonded) stibinidene complex. The reaction of (2,4,6-t-Bu3C6H2)PCl2 with Na[Co2(μ2-CO)2 (η-C5H5)2] produces 2,4,6-t-Bu3C6H2)-P[Co(CO)(η-C5H5) 2, an “open” phosphinidene complex. The factors affecting the “open” or “closed” nature of dimetallic phosphinidene (or heavier congeneric) complexes are discussed. The discussion is extended from sixteen-electron to fifteen-or fourteen-electron organometallic fragments. The synthesis of Co2 (μ-P(2,4,6-t-Bu3C6H2))(CO)6, a three-membered ring with Co—P multiple bonding is discussed. Finally, the reaction of the phosphaketene, (2,4,6-t-Bu3C6H2)P=C=O, with Fe2 (CO)9 is described.
The Multiple Timescales of Optical Variability of the Blazar 3C 279 during the 2001-2002 Outburst

During 2001-2002 the optically violent variable blazar 3C 279 underwent the most intense outburst seen during the entire 14 yr period that this quasar has been studied at Colgate University's Foggy Bottom Observatory. This study concentrates on ~1600 R-filter images taken during this period of activity. This data set includes 29 nights of microvariability coverage. The outburst began in 2001 March, after 3C 279 had faded to its faintest level, R = 15.5, in 4 yr. The source reached its brightest level, R = 12.5, in the 14 yr of our study in 2001 August, at which time it became unobservable due to its proximity to the Sun. On becoming observable again in 2001 mid-December, 3C 279 fluctuated between R = 13.9 and 14.7, until a dramatic decrease in flux level in 2002 June-July brought the source back down to a level comparable to its preoutburst state. The source exhibited numerous week-long flares of approximately 1 mag during the outburst period. Superposed on these flares were night-to-night variations of up to 0.5 mag and intranight microvariability of up to 0.13 mag in 3 hr. We use visual inspection of the light curve, as well as numerical timescale analysis tools (the autocorrelation function, the structure function, and the power spectrum), to characterize the multiple timescales of variability ranging from 1.5 yr to several hours.
Synthetic studies toward the microtubule-stabilizing agent laulimalide: synthesis of the C15–C28 fragment

Abstract The C 15 –C 28 fragment of the paclitaxel-like antimicrotubule agent laulimalide has been synthesized in 12 linear steps with an overall yield of 14%. The methyldihydropyran ring of the side chain was efficiently prepared using ring-closing olefin metathesis chemistry and the 19,20- syn -diol was generated through the addition of a mixed vinyl zincate to a protected α-hydroxyaldehyde.
Unipotent flows and isotropic quadratic forms in positive characteristic

The analogous statement to Oppenheim conjecture over a local field of positive characteristic is proved. The dynamical argument is most involved in the case of characteristic 3.
Effect of Coolant Ejection in Rectangular and Trapezoidal Trailing-Edge Cooling Passages

Heat transfer coefficients are experimentally determined in various trailing-edge cooling channels. A rectangular channel (AR = 3:1) with fully developed flow is used as a baseline for the study, with the Reynolds number varying from 20,000 to 80,000. The heat transfer coefficients in this channel are compared with those in a similar rectangular channel with coolant extraction, which would likely be encountered in a trailing-edge cooling passage. The heat transfer trends in the rectangular channel are compared with those obtained in a passage with a trapezoidal (or wedge-shaped) cross section. The heat transfer coefficients are also obtained in the channel without coolant extraction and with extraction from the narrow side of the channel. The effect of V-shaped rib turbulators is also considered in the rectangular and trapezoidal cooling passages. In addition, the effect of entrance condition is considered with the wedge-shaped channel. Heat transfer coefficients obtained with hydrodynamically developed flow are compared with those with flow through a contraction into the heated section of the channel. In the rectangular channel without ejection, the heat transfer coefficients are uniform across the span of the channel; however, with coolant ejection, the heat transfer coefficients increase near the ejection slots. In addition, in the trapezoidal channels, the heat transfer coefficients are uniform across the cross section of the smooth channel. When coolant is extracted for trailing-edge ejection, the outer surface sees the most significant heat transfer enhancement. The outer surface of the smooth trapezoidal channel is most profoundly affected by the entrance condition, and the effect of the entrance condition is marginal in trapezoidal channels with ribs and ejection.
Polarimetry and Unification of Low-Redshift Radio Galaxies

We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or P{alpha}.The BLRGs in ourmore » sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise steeply to the blue. Strong rotations of the electric vector position angle across H{alpha} in 3C 227 and 3C 445 may be explained by systematic orbital motions in an equatorial broad-line region. (c) (c) 1999. The American Astronomical Society.« less
The Effectiveness of University Technology Transfer

In recent years, there have been numerous studies of the effectiveness of university technology transfer. Such technology transfer mechanisms include licensing agreements between the university and private firms, science parks, incubators, and university-based startups. We review and synthesize these papers and present some pointed recommendations on how to enhance effectiveness. Implementation of these recommendations will depend on the mechanisms that universities choose to stress, based on their technology transfer “strategy.” For example, institutions that emphasize the entrepreneurial dimension of technology transfer must address skill deficiencies in technology transfer offices, reward systems that are inconsistent with enhanced entrepreneurial activity and the lack of training for faculty members, post-docs, and graduate students in starting new ventures or interacting with entrepreneurs. Universities will also have to confront a set of issues related to ethics and social responsibility, as they more aggressively pursue technology commercialization. Finally, we suggest some possible theoretical frameworks for additional research.
Stereoselective radical-radical disproportionation

Abstract Radicals α to the carbonyl of ethyl 3,4,4-trimethylpentanoate couple with little stereoselectivity while analogous tertiary radicals derived from ethyl 2,3,4,4-tetramethylpentanoate disproportionate at 25°C to give the corresponding alkene and alkane. The alkane is formed by disproportionation with a diastereoselectivity of greater than 20:1.
Parallel Computation of the Phonon Boltzmann Transport Equation

The performance of a parallel implementation of the phonon Boltzmann transport equation (BTE) is tested. Two three-phonon scattering models, the full-scattering model and the anisotropic relaxation-time model, are considered. The finite-volume method is used to solve the BTE numerically. Two strategies are explored: spatial domain decomposition and phonon band decomposition. The parallel computations are validated. Overall parallel performance, as measured by speed-up, is presented for the two BTE models using the two decomposition strategies on two architectures: the IBM Power 4+, and a cluster of 8-core Dell 1950 systems with Gigabit Ethernet and Infiniband.
Two bromotyrosine-cysteine derived metabolites from a sponge

Abstract The structures of a dimeric and a tetrameric degraded dipeptide, derivable from bromotyrosine and cysteine, have been elucidated. Both compounds inhibit the growth of Bacillus subtilis and Staphylococcus aureus.
Marketing processes in developing latin American societies

Past economic development efforts have overemphasized production problems and neglected marketing problems. The thesis of this article is that marketing “barriers” exist which impede economic growt...
Modular Adaptive Control of a Nonlinear Aeroelastic System

The paper treats the question of adaptive control of prototypical aeroelastic wing sections with structural nonlinearity. The chosen dynamic model describes the nonlinear plunge and pitch motion of a wing. The model has both the plunge and pitch structural nonlinearities, and a single control surface is used for the purpose of control. It is assumed that only the sign of the coefficient of the control input and the lower bound on its absolute value are known, and the remaining parameters of the model are completely unknown. Modular adaptive control systems based on estimation-based design are derived for the control of the pitch angle and the plunge displacement. Unlike the direct adaptive controllers available in the literature, an input-to-state stabilizing control law is used herein. This control law accomplishes input-to-state stability with respect to parameter estimation error treated as a disturbance input. The control system includes a passive identifier (an observer and an adaptation law) for the parameter estimation. In the closed-loop system asymptotic stabilization of the plunge and pitch motion is accomplished. Simulation results are presented to show that the modular adaptive control systems accomplish flutter suppression in spite of the large uncertainties in the system. Simulation results also show that the closed-loop system without parameter adaptation fails to suppress flutter, but the input-to-state-stabilizing controller is effective in keeping the pitch and plunge responses bounded.
2,3-Dihydroimidazo[1,2-a]pyridines: A New Class of Enantioselective Acyl Transfer Catalysts and Their Use in Kinetic Resolution of Alcohols

The long-known, but previously unexplored 2,3-dihydroimidazo[1,2-a]pyridine (DHIP) has been shown to be a competent acyl transfer catalyst. Its chiral 2-phenyl derivatives obtainable in two steps from commercially available starting materials have proved to be effective acylation catalysts, giving high levels of enantioselectivity (s = 20−85) in kinetic resolution of secondary benzylic alcohols. A transition state model explaining the observed selectivity has been proposed.
Polarization of 129Xe with high power external-cavity laser diode arrays

We demonstrate narrowing of a 2 W, broad area laser diode array and present calculations of the resulting improvement of 129Xe polarization by spin exchange with laser optically pumped Rb vapor. This improvement significantly impacts both medical imaging with laser polarized noble gas and spin-exchange pumped noble gas maser research.
Use of the Automatic Surgical Stapler for Intestinal Anastomosis Associated with Gynecologic Malignancy: Review of 283 Procedures

Abstract Between the years 1974 and 1980, 283 intestinal stapling procedures involving the large and small bowel have been performed on the Gynecologic Oncology service. The automatic surgical staplers used in this series were: the gastrointestinal anastomosis (GIA), the thoracoabdominal (TA-55/30), and the end-to-end anastomosis (EEA) stapler (United States Surgical Corp., Stamford, Conn.). The 283 stapling operations were performed on 162 patients. Fifty-three of the patients had received pelvic irradiation prior to the intestinal operations. The complication rate was low, and compared very favorably with other techniques of gastrointestinal anastomosis which were performed by the same authors. There was one disruption of a small-bowel anastomosis, temporary stricture in three anastomoses of rectum to colon, a leak in a low colonie-rectal anastomosis which resulted in a pelvic abscess, and a rectovaginal fistula. Fifty-two patients underwent urinary diversion by bowel conduit. In all of these cases the conduit was fashioned with the aid of the automatic stapler. The low complication rate in gastrointestinal anastomoses performed with the automatic surgical staplers supports the conclusion that this is a technically superior method which provides better utilization of operating time on radical pelvic procedures.
Exploring B4: A Pulsating sdB Star, in a Binary, in the Open Cluster NGC 6791

We report on Kepler photometry of the hot subdwarf B (sdB) star B4 in the open cluster NGC 6791. We confirm that B4 is a reflection effect binary with an sdB component and a low-mass main-sequence companion with a circular 0.3985 day orbit. The sdB star is a g-mode pulsator (a V1093 Her star) with periods ranging from 2384 s to 7643 s. Several of the pulsation modes show symmetric splitting by 0.62 μHz. Attributing this to rotational splitting, we conclude that the sdB component has a rotation period of approximately 9.63 days, indicating that tidal synchronization has not been achieved in this system. Comparison with theoretical synchronization time provides a discriminant between various theoretical models.
Numerical investigation of three-dimensional active control of boundary-layer transition

A numerical model is developed for the investigation of boundary-layer transition control of spatially evolving instability waves. Active control of a periodically forced boundary layer in an incompressible fluid is simulated using surface beating techniques. The Navier-Stokes and energy equations are solved using a fully implicit finite-difference/spectral method. Temperature perturbations are introduced locally along finite heater strips to directly attenuate instability waves in the flow. A Feedback control loop is employed in which a downstream sensor is used to monitor wall shear stress fluctuations
Process-oriented evaluation of user interactions in integrated system analysis tools

When computer-based tools are used for analysis of complex systems, the design of user interactions and interfaces becomes an essential part of development that determines the overall quality. The objective of this study is to investigate the processes and results of user interactions with integrated analysis tools to synthesize design implications for future tool development. In this study, two space exploration logistics tools are compared in a controlled user experiment. Through a comparative usability analysis, this study evaluated user performance and perception to provide design implications for future integrated analysis tools. For a comprehensive evaluation, multiple methods were used for data collection, including observation, questionnaire and interview. In addition to a result-oriented performance analysis, a process-oriented approach was used for analyzing patterns in user behaviors and errors. Results are presented with reference to the related features embedded in the interfaces of the two tools. Based on the comparative results, synthesized design insights for hierarchical structure, model transparency, automation, and visualization and feedback are discussed for integrated analysis tools in general.
Determinants of interstate migration, by race, 1965–1970

This study examines determinants of gross in-migration by race (white and black) over the 1965-1970 time period. The ordinary least squares results reveal that both white migrants and black migrants have an aversion to cold weather and prefer to move shorter rather than longer distances. White migrants were more likely to move to higher per capita income states. Black migrants manifested a strong aversion to states with a higher unemployment rate; however, unlike white migrants, black migrants appeared to be highly attracted to higher welfare states.
Effect of Ingress Buffering on Self-Similarity of Optical Burst Traffic

ABSTRACT Recently, optical burst switching and aggregated optical packet switching have gained significant exposure as possible future mechanisms for routing aggregated IF traffic over all-optical core networks. However, the limited buffering capacity in all-optical networks presents a major challenge, as current IP traffic displays strong self-similar properties. Reducing the burst loss rate of such long-range dependent traffic can be costly requiring asignificant increase in either the network bandwidth or the buffer size of optical cross connects. In this paper, we revisit the possibility of using buffers to reduce self-similarity before the traffic is routed onto the all-optical core. The aim of this paper is to increase the understanding of the effect of packet/burst aggregation on the self-similarity measure of the traffic. In particular, we implement a simple burst assembly mechanism with twoparameters, the maximum burst length L and the maximum burst delay d, so that incoming traffic is smoothed
State and demographic variation in use of depot antipsychotics by Medicaid beneficiaries with schizophrenia.

ObjectiveThis study examined state and demographic variation in use of depot antipsychotics among Medicaid beneficiaries with schizophrenia.MethodMedicaid claims data (2007) from 21 states and the District of Columbia were analyzed for 102,884 beneficiaries age 18 to 64 with schizophrenia. Rates of receipt of depot antipsychotics were determined for all beneficiaries and for African Americans, Caucasians, and beneficiaries from “all other races.”ResultsAcross study states, a mean of 10% of beneficiaries with schizophrenia received depot antipsychotics. Rates ranged from 1.9% in the District of Columbia to 20.9% in Alabama. In 12 states, African Americans were disproportionately likely to receive these medications compared with beneficiaries of other races.ConclusionsUse of depot antipsychotics varied across state Medicaid programs. African Americans received a disproportionate share in many states. Further research is needed to understand the sources of such variation. These findings underscore the need t...
One-pot conversion of alkynes and alkenes into one-carbon homologated aldehydes via hydrozirconation-isocyanide insertion-hydrolysis

Abstract The reaction of monoorganozirconocene chlorides and diorganozirconocenes with relatively unhindered isocyanides, such as n -BuNC, followed by hydrolysis with 50% HOAc or dilute HCl can produce the corresponding aldehydes in good yields.
THE SENSE‐REFERENCE DISTINCTION IN INDIAN PHILOSOPHY OF LANGUAGE

It is generally accepted that Indian philosophers of language do not posit sense as a component of the meaning of an expression in addition to its reference.* There is, for instance, no notion of analyticity of propositions which are true by virtue of meaning alone in Indian philosophy. Likewise no distinction is drawn between contingently and necessarily nonexistent objects: Two stock examples of a nonexistent are the horns of a hare and the son of a barren woman, and these two examples are treated as in all respects alike. We find instead a more or less pure reference theory of meaning: The meaning of an expression is that entity which the expression designates. Here the name-bearer relation seems to reign supreme as the central metaphor of semantics. I shall, however, argue that, predominant though the reference theory might be, certain Indian philosophers of language were nonetheless forced to recognize sense as a distinct element in meaning. That the sense-reference distinction was never extensively made use of by Indian philosophers of language is clear; I shall not be concerned to dispute this or attempt to explain it. Instead I wish to explore how recognition of something sense-like is forced on philosophers working in a tradition dominated by semantic realism. I suspect we may discover something important about the motivation behind the sense reference distinction through such an exploration.
The Panexponential Monocentric Model

Abstract We derive declining exponential rent and density functions for a monocentric city from a new set of assumptions, which place restrictions on commuting costs rather than on the demand for land. The utility function is Cobb–Douglas with unrestricted income expenditure shares for land and for the numeraire good. The marginal commuting cost is assumed to be proportional to income-earning potential and exponentially declining in distance from the center at a particular constant rate. These assumptions capture realistic properties of congested cities. Under these assumptions, equilibrium land rent, residential density, and numeraire consumption all decline exponentially with distance, although at different rates. If it is also assumed that traffic speed at the edge of a city is equal to free-flow speed, then the rates of decline in rent, residential density, and numeraire consumption all increase with the city's physical size. We also suggest a new statistical procedure for estimating negative exponential density functions from a cross section of cities of various sizes.
Sickle Cell MicroRNAs Inhibit the Malaria Parasite

Sickle cell hemoglobin conveys resistance to malaria. In this issue of Cell Host & Microbe, LaMonte et al. (2012) demonstrate a surprising mechanism for this innate immunity. A microRNA enriched in sickle red blood cells is translocated into the parasite, incorporated covalently into P. falciparum mRNAs and inhibits parasite growth.
A scheduling framework for UWB & cellular networks

The max-min fair scheduling problem in wireless ad-hoc networks is a non-convex optimization problem. A general framework is presented for this optimization problem and analyzed to obtain a dual problem, which involves solving a series of optimization sub-problems. In the limit of infinite bandwidth (W → ∞), the scheduling solution reduces to simultaneous transmission (spread spectrum) on all links (Negi and Rajeswaran, INFOCOM '04 (March 2004)). This motivates the analysis of the scheduling problem in the Ultra Wide Band (UWB) regime (W ≫ 1, but finite), a model for certain practical radios. A quadratic (in 1/W) lower bound to the single link capacity function is developed, which simplifies the dual sub-problem to a quadratic optimization (Negi and Rajeswaran, GLOBECOM '04, (Dec. 2004)). The solution to this sub-problem is then obtained under both total power and power spectral density constraints. This solution is utilized to iteratively construct the schedule (sub-band sizes) and power allocation, thus optimally solving the UWB max-min fair scheduling problem, to within any desired precision. Simulations on medium sized networks demonstrate the excellent performance of this scheme. A cellular architecture (not necessarily UWB) may also be considered in this framework. It is proved that Frequency Division Multiple Access is the optimal scheduling for a multi-band cellular architecture.
An efficient Pd-catalyzed route to silyl esters

A one-step, highly selective catalytic route to silyl esters is reported. Commercially available silanes with Si-H functionality were converted to silyl or siloxy esters in the presence of Pd(OAc)2 under mild reaction conditions. This protocol was found to be equally applicable for the modification of multiple silicon centers in one framework and lead to the corresponding polysilyl esters in high yields. A comparison of catalytic efficiency of Pd(OAc)2 versus Pd on carbon was also undertaken.
Temperature and solvent-polarity dependence of the absorption and fluorescence spectra of a fixed-distance symmetric chlorophyll dimer

Temperature-dependent absorption and fluorescence spectra and line-narrowed fluorescence and excitation spectra are reported for a dimer consisting of two methylpyrochlorophyllide a molecules that share a vinyl group at the 2-position of each macrocycle. The data (obtained for three solvents of widely differing polarity) show that the dimer exists in two conformations (A and B) and that excited-state relaxation from A to B onsets near the glass transition temperature (T{sub g}). Molecular modeling suggests that the two conformations are related by bicycling of the two single bonds joined to the vinyl group linkage. At sufficiently low temperature, the solvent dynamics are rate limiting for the conformational relaxation. For a solvent of sufficiently high polarity (DMF), the excited state of B is shown to access a new radiationless decay channel for T {ge} T{sub g}. A charge-transfer state is suggested to be important for this decay. The model presented is shown to provide a qualitative explanation for the frequency domain and recently obtained picosecond and fluorescence quantum yield room-temperature data.
Effect of Thickness Variation in High-Efficiency Ingan/Gan Light Emitting Diodes

We have found that InxGa(1-x)N/GaN multi-quantum-well (MQW) light emitting diodes (LEDs) having periodic thickness variation (TV) in InxGa(1-x)N active layers exhibit substantially higher optical efficiency than LEDs with uniform InxGa(1-x)N layers. In these nano-structured LEDs, the thickness variation of the active layers is shown to be more important than In composition fluctuation in quantum confinement of excitons (carriers). Detailed STEM-Z contrast analysis, where image contrast is proportional to Z2 (atomic number)2, was carried out to investigate the thickness variation as well as the spatial distribution of In. In the nanostructured LEDs, there are short-range (SR-TV, 3 to 4 nm) and long-range thickness variations (LR-TV, 50 to 100 nm) in InxGa(1-x)N layers. It is envisaged that LR-TV is the key to quantum confinement of the carriers and enhancing the optical efficiency. We propose that the LR-TV thickness variation is caused by two-dimensional strain in the InxGa(1-x)N layer below its critical thickness. The SR-TV may be caused by In composition fluctuation. The observations on thickness variation are in good agreement with model calculations based upon strain effects.
The Voltammetry of Sc3@C82

This paper describes the first electrochemical data for a polymetallic endohedral metallofullerene. The voltammetric behavior of Sc{sub 3}@C{sub 82} resembles that for La@C{sub 82} and Y@C{sub 82}, indicating that the identity of the metal does not influence dramatically the energies of the metallofullerene molecular orbitals. The three Sc atoms, however, transfer more electrons from the encapsulated metals to the cage than the monometallic counterparts, accounting for the differences in the voltammetry for Sc{sub 3}@C{sub 82}. The similarity of the voltammetry of Sc{sub 3}@C{sub 82} with that of the monometallic fullerenes suggests that Sc{sub 3}{sup +4}@C{sub 82}{sup 4-} may describe the formal charges on the Sc trimer and the C{sub 82} cage of these species. Metallofullerene electronic structure and physical properties should be better understood as more metallofullerenes become available for investigation. 31 refs., 1 fig., 1 tab.
Equity and Nonequity Determinants of FHA Single‐Family Mortgage Foreclosures in the 1980s

We examine foreclosures on FHA single-family mortgages insured during the 1975–87 period. The importance of the market value of borrower equity and national house price dispersion support much earlier work emphasizing the key role of negative equity in triggering default. The lower is “mean” market-value equity, and the greater is dispersion, the greater is the fraction of borrowers likely to have negative equity. The unemployment rate and the book value of borrower equity are also shown to be significant determinants of default. Unemployment is one of those events that can force borrowers to move. The moving decision increases the likelihood of default because moving costs no longer deter default, and the costs of selling the house reduce the effective equity in the house. The book value of equity is relevant to this decision because it is what the sellers receive if they move without defaulting. Not only are both of these variables significant determinants of default, but the smaller is book equity, the greater is employment impact (with large book equity, unemployment should not matter because selling the house is preferred to default).
The demersal fish of Narragansett Bay: An analysis of community structure, distribution and abundance☆

Abstract Monthly samples of demersal fish were collected from nine regular and 13 occasional stations in Narragansett Bay, Rhode Island throughout a year. While over 9000 individuals representing 99 species were taken, the 10 most abundant species made up 91% of the catch. Taxonomic composition and dominance of the fish community were generally similar to that reported for adjacent Block Island Sound and Long Island Sound, though diversity was slightly higher in the bay. Winter flounder, Pseudopleuronectes americanus was by far the most abundant species, and accounted for 36% of the total catch. Multiple regression analysis of fish numbers and biomass for total catch and for the dominant flounder indicated that of 14 environmental variables considered, only depth, sediment organic content, temperature and wind speed were significant in explaining distribution within the bay. No clear pattern of fish abundance was apparent, except for higher diversity near the mouth of the bay. The mean annual standing crop of 117 ± 151 fish/acre and 28·5 ± 16·0 lbs/acre (wet weight) was comparable to values reported for a variety of New England coastal and offshore areas. The total biomass of fish remained remarkably constant throughout the year when compared to adjacent coastal environments, while the abundance of particular species varied substantially with season.
The Double-lined Spectroscopic Binary Haro 1-14c

We report detection of the low-mass secondary in the spectroscopic binary Haro 1-14c in the Ophiuchus star-forming region. The secondary/primary mass ratio is 0.310 ± 0.014. With an estimated photometric primary mass of 1.2 M☉, the secondary mass is ~0.4 M☉ and the projected semimajor axis is ~1.5 AU. The system is well suited for astrometric mapping of its orbit with the current generation of ground-based IR interferometers. This could yield precision values of the system's component masses and distance.
Sectoral Solow residuals

This paper presents capital utilization corrected measures of technology shocks for aggregate and disaggregated (two-digit Standard Industrial Classification code) industries. We correct for variations in capital utilization by employing industrial electrical use as a measure of capital services. In contrast, the standard measures of technology shocks used in the Real Business Cycle literature are based on economy wide data and assume that capital services are proportional to the stock of measured capital. To assess the impact of these differences, we contrast selected properties of the competing technology shock measures. We argue that the properties of technology shocks for the manufacturing sector are quite different than those used in the RBC literature. We also find that correcting for capital utilization has important implications for the properties of the Solow residual.
Palladium-Catalyzed Acetylation of Arenes

A simple method for the preparation of aryl methyl ketones is reported. The transformation involves the Pd-catalyzed coupling of an acyl anion equivalent, acetyltrimethylsilane, with aryl bromides to afford the corresponding acetylated arenes in synthetically useful yields. The methodology is tolerant of heterocycles and provides a new method for arene functionalization.
Tissue factor expression is increased in cardiac transplant recipients who develop cardiac transplant arteriopathy

and infection (requiring hospitalization) were analyzed. Results: Diabetics had a tendency to be older (mean age 57.1yrs. vs. 51.4yrs, p 0.001), had a greater body mass index (mean 26.7 vs. 24.1, p 0.02) and more commonly had ischemic cardiomyopathy (58% vs. 43%) (p 0.019). There was a trend towards decreased survival for diabetics at 1 year (85.1% vs. 90.9%; p 0.12). Overall 5 year actuarial survival was 81.6% for both diabetics and non diabetics with mean follow up times of 3.53 years and 3.45 years respectively. The proportion of infection within three months was higher among the diabetics (14.0%) compared to the controls (3.0%) (odds ratio, 5.09; 95% CI, 1.59-16.23). Freedom from infection at 4 years was 71.0% for diabetics and 85.0% for non diabetics (p 0.02). Freedom from rejection at 5 years was similar between the two groups (70.6% vs. 73.6%) (p 0.69). Actuarial TCAD free survival at 4 years was 69.5% for diabetics and 81.6% for non diabetics (p 0.23). Serum creatinine 5 years post transplant was 1.6 for diabetics and 1.4 for non diabetics (p 0.18). Conclusion: Survival following heart transplantation for diabetic patients is comparable to that of non diabetic patients. There is an increased risk of serious infections in diabetic patients, particularly early following transplantation. There is a trend towards greater incidence of TCAD and inferior renal function on long term follow up. Multivariate analysis may reveal subgroups of diabetics who present an increased risk for transplantation.
On the Fraction of Quasars with Outflows

Outflows from active galactic nuclei (AGNs) seem to be common and are thought to be important from a variety of perspectives: as an agent of chemical enhancement of the interstellar and intergalactic media, as an agent of angular momentum removal from the accreting central engine, and as an agent limiting star formation in starbursting systems by blowing out gas and dust from the host galaxy. To understand these processes, we must determine what fraction of AGNs feature outflows and understand what forms they take. We examine recent surveys of quasar absorption lines, reviewing the best means to determine if systems are intrinsic and result from outflowing material, and the limitations of approaches taken to date. The surveys reveal that, while the fraction of specific forms of outflows depends on AGN properties, the overall fraction displaying outflows is fairly constant, approximately 60%, over many orders of magnitude in luminosity. We emphasize some issues concerning classification of outflows driven by data type rather than necessarily the physical nature of outflows and illustrate how understanding outflows probably requires a more comprehensive approach than has usually been taken in the past.
The Versatile Phenylthio Group. A Powerful Aid in Synthesis

Abstract The replacement of the phenylthio group by lithium by the use of aromatic radical-anions has become one of the most powerful methods for the production of organolithium compounds. The major reasons for the power of this method are the ease of incorporation of the phenylthio group into molecules, the ability of divalent sulfur to stabilize any electronic arrangement on the atom to which it is attached, the relative ease of reductive cleavage of C-S bonds despite the stability of this type of bond under most other reaction conditions, and the fact that the rate determining step of organolithium production by this method is apparently the formation of a carbon radical. Since the order of stability of radicals in solution is the reverse of that of carbanions, reductive lithiation is capable of producing less stable organolithiums more rapidly and under milder conditions than more stable ones. Recent advances in synthetic and mechanistic chemistry based on carbanions generated by this method are prese...
Finite-Temperature Corrections to the Transport Coefficients of a Normal Fermi Liquid

Finite-temperature corrections to the limiting low-temperature behavior of the thermal conductivity and spin-diffusion coefficient of a normal Fermi liquid are calculated using a quasiparticle Boltzmann equation which is solved by the variational method. For liquid ${\mathrm{He}}^{3}$ the most important corrections come from small momentum transfer processes, the amplitude for which can be determined exactly by using Landau theory. The expressions obtained are evaluated in detail, assuming that all Landau parameters vanish for $lg~2$, and comparison of theory with experiment yields an estimate for the previously undetermined Landau parameter ${{F}_{1}}^{a}$. The calculations are compared with calculations based on paramagnon theory.
Banana drift diffusion in a tokamak magnetic field with ripples

The drift motions of trapped particles in a tokamak field with ripples lead to a new transport process in large tokamaks in addition to the diffusion process due to particles trapped in the ripples. This problem is studied by solving the bounce-averaged drift kinetic equation with a model collision operator. It is shown that the banana drift diffusion is proportional to the collision frequency when the poloidal banana drift frequency is smaller than the effective collision frequency. This result is contrary to earlier predictions. In a reactor regime, this loss mechanism is shown to be unimportant.
Flow Measurements in a Model Swirl Combustor

Flow measurements in a model combustor composed of two confined coaxial swirling jets under noncombusting conditions are presented. Mean flow results are obtained for five different flow conditions to determine the effect of outer swirl on the recirculation zone (which is used for flame stabilization under combustion conditions). As the outer swirl magnitude is first decreased from maximum counter-swirl to zero and then increased to give co-swirl conditions, the size and the reverse flow velocity in the recirculation zone diminish. Detailed time mean and fluctuating flow measurements are obtained for a co-swirl and a counter-swirl condition with a directional pitot probe and hot-wire anenometry. For these two cases, recirculation zone occurs only with counter-swirl, near the exit of the inner jet. The recirculation zone is in the form of a one celled toroidal vortex having very low swirl velocity. Axial development of fluctuation levels, energy dissipation rates and turbulence length scales are described for the two flow conditions. Spectral analysis reveals periodic oscillations in both flows. The oscillations originate from the inner jet and up to 4 harmonics are observed. The fundamental frequencies are comparable to the rotational frequencies of the inner jets at the exit which are approximately under solid body rotation. The significance of the present results for the combustion process is discussed.
Cold collisions of O 2 with helium

Collision cross sections between oxygen molecules and helium atoms are computed at translational energies between 0.1 K and 10.0 K, motivated by the recently demonstrated cooling of molecules by a helium buffer gas. Detailed calculations based on a rigid-rotor model demonstrate the differences among various isotopic combinations of oxygen atoms and also serve to illustrate resonant features unique to cold molecules. Comparisons of elastic versus spin-changing inelastic collision rates suggest that buffer-gas cooling is likely to be a widely applicable tool for producing cold molecular samples.
Effects of Solubilized Water on the Relaxation Dynamics Surrounding 6-Propionyl-2-(N,N-dimethylamino)naphthalene Dissolved in 1-Butyl-3-methylimidazolium Hexafluorophosphate at 298 K

We report on the picosecond time-resolved fluorescence of 6-propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN) dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) at 298 K as a function of solubilized water in the [bmim][PF6] phase. The observed solvent relaxation dynamics can be described by three components with apparent relaxation times that occur over a large time regime ( 10 ns). The average relaxation dynamics become faster as the water concentration in the [bmim][PF6] phase increases. Libration and vibration, ion ballistic motion, ion local basin exploration, and ion basin hopping, ion diffusion, and/or the ultrafast relaxation from water (or other small molecules/impurities) are suggested as possible reasons for the yet unquantified sub-15-ps dynamics. The sub-nanosecond dynamics are consistent with [PF6] anion relaxation. This process was found to be water-dependent, slowing as the amount of solubilized water in the [bmim][PF6] phase increased. We speculate that this slowing arises from the formation of 1:2 H-bonded [PF6]‚‚‚HOH‚‚‚[PF6] complexes. The nanosecond dynamics are consistent with the cation, decreasing slightly with an increase in the amount of solubilized water. We suggest that the decrease in this relaxation time arises from a decrease in the bulk viscosity on adding water.
A Bargain At Any Price? Child Care Costs and Women′s Employment

Abstract This paper examines how three dimensions of child care costs affect women′s labor supply: (1) women′s perceptions of the price of substitute care, (2) the amount of money that parents spend on child care, and (3) the availability of relatives for providing care. Tobit analyses, using data from the National Child Care Survey 1990, demonstrate that the cost of care has a multidimensional impact on women′s employment. What mothers think about price matters: women′s perceptions of price exert a negative influence on their time spent in paid work. As perceived minimum price increases, women′s labor supply decreases. However, actual price, as indicated by predicted expenditures, affects women′s labor supply in a curvilinear fashion with low-priced and high-priced care discouraging women′s employment time.