cssi/SciSciGPT-SciSciNet huggingface dataset:
An efficient stereoconvergent synthesis of the 4-ethylamino-2,4-dideoxy-l-threo-pentopyranose component of the calicheamicins and esperamicins

Abstract A stereconvergent synthesis of the 4-ethylamino-2,4-dideoxy-L- threo -pentopyranose coonponent of calicheamicins γ 1 , γ 1 I , α 2 I , and esperamicin A 1b from methyl 2-deoxy-β-D-ribopyranoside is described. The synthesis requires eight steps in each branch. The overall yield is 54%. This synthesis should be adaptable for syntheses of the corresponding 4-methylamino)-2,4-dideoxy- L- threo - and 4-isopropylamino-2.4- dideoxy-L- threo - pentopyranose components of other calicheamicin and esperamicin antibiotics.
Neutral-pion-decay gamma rays from the galaxy and the interstellar gas content

Knowledge of the total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated here using the latest accelerator data on neutral pion production in p-p interactions up to about 1500 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 plus or minus 0.23) times 10 to the -25th power/sec, consistent with the observed upper limit of 1.6 times 10 to the -25th power/sec.
Damage-mitigating control of a reusable rocket engine: Part I-life prediction of the main thrust chamber wall

The goal of damage-mitigating control in reusable rocket engines is to achieve high performance without overstraining the mechanical structures; and the major benefit is an increase in structural durability with no significant loss of performance. This sequence of papers in two parts investigates the feasibility of damage mitigating control of a reusable rocket engine similar to the Space Shuttle Main Engine (SSME). The challenge here is to characterize the thermo-mechanical behavior of the structural materials for damage prediction in conjunction with dynamic performance analysis of the thermo-fluid process in the rocket engine, and then utilize this information in a mathematically and computationally tractable form for synthesizing decision and control algorithms. This paper is the first part and investigates the damage phenomena in the coolant channel ligament of the main thrust chamber of a rocket engine that are characterized by progressive bulging-out and incremental thinning leading to eventual failure by tensile rupture. A creep damage model is analytically derived based on the theories of sandwich beam and viscoplasticity. The objective of this model is to generate a closed-form solution of the wall thin-out in real time where the ligament geometry is continuously updated to account for the resulting deformation. The creep damage model has been examined for both single-cycle and multi-cycle stress-strain behavior, and the results are in agreement with those obtained from the finite element analyses and experimental observation. Due to its computational efficiency, this damage/life prediction model is suitable for on-line applications of decision and control, and also permits parametric studies for off-line synthesis of damage mitigating control systems. The second part, which is a companion paper, develops an optimal policy for damage mitigating control of the rocket engine.
Particle track measurements in lunar regolith breccias

Particle track measurements have been reported for 25 (5%) of the regolith breccias in the collection; they have been reported for 16 breccias (30%) in the reference suite. The most frequently reported measurement for these 25 breccias is the maximum surface exposure age of the compacted rock (48% of the published breccia measurements). Information on the nature of the precompaction regolith is given for 9 rocks (36%) and on the nature of the compaction event for 6 rocks (24%). Most of the breccias appear to have simple post-compaction surface exposure histories (89%). From the few track density frequency distributions (7) that are available and inferring from the low exposure ages of these rocks (75% < 106 yr), it appears that most of these breccias are amenable to studies which separate the contemporary surface exposure age from information about the precompaction regolith. If the number of immature-submature precompaction soils (6 out of 10 of the breccias for which appropriate data are available) represents many regolith breccias, then we can infer that regolith breccias may sample the deeper, less reworked materials in the lunar soil and compliment the samples available from the returned cores.
Ankle-brachial index and the prevalence of age-related maculopathy.

Purpose To examine the association of ankle-brachial blood pressure index (ABI) with prevalence of age-related maculopathy (ARM). Design A cross-sectional cohort study. Methods ABI was measured in 2447 subjects aged 53 to 97 years. ARM was determined from 30-degree color stereoscopic fundus photographs. Results Low ABI (≤0.9) was present in 5.4% of subjects. Early ARM was present in 22.1% of subjects with and 18.8% without low ABI. Late ARM was present in 5.3% of subjects with and 1.7% without low ABI. This result was not statistically significant. Conclusions Low ABI does not appear to be a risk factor for ARM.
A Magnus Theory

An analytical method is developed for predicting Magnus force and moment coefficients for spinning ogive cylinders, cone cylinders, and conical bodies in laminar compressible flow. The contributions to the Magnus coefficients due to boundary-layer displacement thickness distortion and radial pressure gradient effects are included. The boundary-layer theoretical model, which agrees well with experimental boundary-layer velocity profiles, was obtained by applying a compressibility correction and transformations to the Blasius flat plate solution to account for the effects of body shape, angle of attack, and spin. The Magnus theory is shown to agree favorably with experimental data.
Anthropocene changes in desert area: Sensitivity to climate model predictions

[1] Changes in desert area due to humans have important implications from a local, regional to global level. Here I focus on the latter in order to better understand estimated changes in desert dust aerosols and the associated iron deposition into oceans. Using 17 model simulations from the World Climate Research Programme's Coupled Model Intercomparison Project phase 3 multi-model dataset and the BIOME4 equilibrium vegetation model, I estimate changes in desert dust source areas due to climate change and carbon dioxide fertilization. If I assume no carbon dioxide fertilization, the mean of the model predictions is that desert areas expand from the 1880s to the 2080s, due to increased aridity. If I allow for carbon dioxide fertilization, the desert areas become smaller. Thus better understanding carbon dioxide fertilization is important for predicting desert response to climate. There is substantial spread in the model simulation predictions for regional and global averages.
Heterogeneous distance–elasticities in trade gravity models

Abstract We show that statistically and economically significant heterogeneity exists in the distance elasticity in trade gravity models. Distance elasticities critically depend on whether trading partners belong to the OECD and whether they are Christian or Islam countries.
The impact of educational loan burden on housestaff career decisions

The past decade has seen declining interest in primary care medicine and a dramatic increase in the cost of a medical degree. Seventy-nine percent of housestaff in an internal medicine residency program responded to a survey to determine whether medical school loan burden was related to career choice in a primary care field or specialty area. Overall mean indebtedness was $45,185 (median $40,000). Thirty-eight percent of residents with debts $40,000 (chi square =9.44, p $40,000 stated that financial conditions had a moderate to marked impact on their career decision making. Excessive loan burden has a significant influence on residents’ career decision making and a negative influence on choosing careers in primary care internal medicine.
Radiation-induced collapse of the crystalline structure

Abstract A theory of irradiation-induced amorphization of ordered intermetallic compounds, based on the destabilization of the crystalline structure by excess defect accumulation, has been developed recently. The theory is reviewed starting with its phenomenological basis, where the microstructural evolution of intermetallic compounds that are rendered amorphous by irradiation is emphasized. Next, the analysis of defect buildup that suggests the formation of a stable complex defect consisting of a vacancy-interstitial pair, called a complex, is reviewed. The possibility of a radiation-induced microstructure such as interstitial clusters, in addition to complexes, in intermetallics that undergo the crystalline-to-amorphous transition is incorporated into the theory. A comparison of radiation effects in NiTi and in Zr 3 Al is made using a rate theory approach. In the case of the aluminide, it is found that cluster development can hinder the amorphous transition when the material is irradiated with electrons. However, enhancement of complex production in the collision cascade explains the occurrence of the transition during ion bombardment.
Group strategyproof cost sharing: The role of indifferences

Abstract Every agent reports his willingness to pay for one unit of a good. A mechanism allocates goods and cost shares to some agents. We characterize the group strategyproof (GSP) mechanisms under two alternative continuity conditions interpreted as tie-breaking rules. With the maximalist rule (MAX) an indifferent agent is always served. With the minimalist rule (MIN) an indifferent agent does not get a unit of the good. GSP and MAX characterize the cross-monotonic mechanisms. These mechanisms are appropriate whenever symmetry is required. On the other hand, GSP and MIN characterize the sequential mechanisms. These mechanisms are appropriate whenever there is scarcity of the good. Our results are independent of an underlying cost function; they unify and strengthen earlier results for particular classes of cost functions.
Families of genus 2 curves with small embedding degree

Hyperelliptic curves of small genus have the advantage of providing a group of com- parable size as that of elliptic curves, while working over a field of smaller size. Pairing-friendly hyperelliptic curves are those whose order of the Jacobian is divisible by a large prime, whose em- bedding degree is small enough for computations to be feasible, and whose minimal embedding field is large enough for the discrete logarithm problem in it to be difficult. We give a sequence of Fq-isogeny classes for a family of Jacobians of genus two curves over Fq, for q = 2 m , and their corresponding small embedding degrees. We give examples of the parameters for such curves with embedding degree k < (logq) 2 , such as k = 8,13,16,23,26,37,46,52. For secure and efficient implementation of pairing-based cryptography on genus g curves over Fq, it is desirable that the ratio = g log2 q log2 N be approximately 1, where N is the order of the subgroup with embedding degree k. We show that for our family of curves, is often near 1 and never more than 2. We also give a sequence of Fq-isogeny classes for a family of Jacobians of genus 2 curves over Fq whose minimal embedding field is much smaller than the finite field indicated by the embedding degree k. That is, the extension degrees in this example differ by a factor of m, where q = 2 m , demonstrating that the embedding degree can be a far from accurate measure of security. As a result,
Chiral symmetry breaking for domain wall fermions in quenched lattice QCD

Abstract The domain wall fermion formulation exhibits full chiral symmetry for finite lattice spacing except for the effects of mixing between the domain walls. Close to the continuum limit these symmetry breaking effects should be described by a single residual mass. We determine this mass from the conservation law obeyed by the conserved axial current in quenched simulations with β = 5.7 and 6.0 and domain wall separations varying between 12 and 48 on 83 × 32 and 163 × 32 lattices. Using the resulting values for the residual mass we perform two complete and independent calculations of the pion decay constant. Good agreement is found between these two methods and with experiment.
Massively parallel switch-level simulation: a feasibility study

The feasibility of mapping the COSMOS switch-level simulator onto a computer with thousands of simple processors is addressed. COSMOS preprocesses transistor networks into Boolean behavioral models, capturing the switch-level behavior of a circuit in a set of Boolean formulas. A class of massively parallel computers and a mapping of COSMOS onto these computers are described. The factors affecting the performance of such a massively parallel simulator are discussed, including: the amount of parallelism in the simulation model, performance measures for massively parallel machines, and the impact of event scheduling on simulator performance. Compilation tools that automatically map a MOS circuit onto a massively parallel computer have been developed. Techniques for restructuring Boolean expressions for greater parallelism and mapping Boolean expressions for evaluation on massively parallel machines are described. Massively parallel switch-level simulation is illustrated by a pilot implementation on a 32k-processor Thinking Machines Connection Machine system. >
Communication-Proof Equilibria in Cheap-Talk Games

Abstract We define communication-proof equilibria in simple games of communication. These equilibria satisfy a stability condition guaranteeing that they would not be affected if new opportunities to communicate arose. We look for partitions of possible equilibria into sets of good and bad equilibria. The good equilibria are those that cannot be destabilized by another good equilibrium. The remaining equilibria are bad. An equilibrium for the original game is communication proof if its is a good equilibrium in a partition of this form. We prove that communication-proof equilibria exist and, for a class of common-interest games, communication-proof outcomes are efficient. Journal of Economic Literature Classification Numbers: C72, D80.
An emerging role for the national laboratories in materials research

The mission of the Department of Energy National Laboratories should be expanded to include as an item of high priority collaborative research in support of high technology industry, including the materials industry. There are numerous reasons for doing this. The original missions of the laboratories, other than those of the weapons laboratories, have been deemphasized or disappeared. The laboratories have superior facilities, often unique, and high quality staffs experienced in the interdisciplinary approach to problem solving. Perhaps most important, domestic industry, especially high technology industry, should have this resource available if it is to meet the challenge of remaining competitive.
Market Signals Associated with REIT IPOs

Previous studies have found significant but time-varying valuation effects associated with real estate investment trusts initial public offerings (REIT IPOs). Because REIT IPOs may disclose relevant information about real estate market conditions, they may serve to revalue existing real estate securities. To determine whether REIT IPOs signal information that is impounded into the share prices of other real estate securities, we assess the returns on “rival” portfolios of existing real estate securities upon the issuance of the IPO. On average, the “rival” portfolios experience insignificant effects on the REIT IPO filing date, but negative and significant abnormal returns around the issue date. A cross-sectional analysis of combined effects at the time of the filing date and issue date shows that the negative effects on the “rival” portfolios are more pronounced when (1) the size of the REIT IPO is larger, (2) market conditions are relatively weak, (3) more REIT IPOs come to market, and (4) the IPO is not associated with an umbrella partnership REIT.
Effect of parameters on redistribution and removal of particles from drop surfaces

It was recently shown by us that particles distributed on the surface of a drop can be concentrated at the poles or the equator of the drop by subjecting the latter to a uniform electric field and that such concentrated particles can then be removed from the drop by increasing the electric field intensity. In this paper, we present experimental results for the dependence of the dielectrophoretic force on the parameters of the system such as the particles' and drop's radii and the dielectric properties of the fluids and particles, and define a dimensionless parameter regime for which the technique can work. Specifically, we show that if the drop radius is larger than a critical value, that depends on the physical properties of the drop and ambient fluids and those of the particles, it is not possible to concentrate particles and thus clean the drop of the particles it carries at its surface because the drop breaks or tip-streams at an electric field intensity smaller than that needed for concentrating particles. However, since the dielectrophoretic force varies inversely with the drop radius, the effectiveness of the concentration mechanism increases with decreasing drop size, and therefore the technique (particles concentration followed by drop clean-up or delivery) is guaranteed to work provided the drop radius is sufficiently small. We also show that this concentration method can be used to separate particles experiencing positive dielectrophoresis on the surface of a drop from those experiencing negative dielectrophoresis, and form a composite (Janus) drop by aggregating particles of one type near the poles and of another near the equator. Furthermore, after the two types of particles are separated on the surface of the drop, it is possible to remove the particles concentrated near the poles from the drop by increasing the electric field intensity so that the drop tip-streams, thus leaving only one type of particles at the surface of the drop. This could be useful for having drops selectively deliver, or get rid of, some particles while keeping others.
Value-relevance of nonfinancial information: The wireless communications industry

Abstract We examine the value-relevance to investors of financial (accounting) and nonfinancial information of independent cellular companies and find that, on a stand-alone basis, financial information (earnings, book values, and cash flows) are largely irrelevant for security valuation. Nonfinancial indicators, such as POPS (a growth proxy) and Market Penetration (an operating performance measure), are highly value-relevant. However, combined with nonfinancial information, earnings do contribute to the explanation of prices. The complementarity between financial and nonfinancial data is highlighted in this study.
Electrostatic Tuning of Permeation and Selectivity in Aquaporin Water Channels

Water permeation and electrostatic interactions between water and channel are investigated in the Escherichia coli glycerol uptake facilitator GlpF, a member of the aquaporin water channel family, by molecular dynamics simulations. A tetrameric model of the channel embedded in a 16:0/18:1c9-palmitoyloleylphosphatidylethanolamine membrane was used for the simulations. During the simulations, water molecules pass through the channel in single file. The movement of the single file water molecules through the channel is concerted, and we show that it can be described by a continuous-time random-walk model. The integrity of the single file remains intact during the permeation, indicating that a disrupted water chain is unlikely to be the mechanism of proton exclusion in aquaporins. Specific hydrogen bonds between permeating water and protein at the channel center (at two conserved Asp-Pro-Ala “NPA” motifs), together with the protein electrostatic fields enforce a bipolar water configuration inside the channel with dipole inversion at the NPA motifs. At the NPA motifs water-protein electrostatic interactions facilitate this inversion. Furthermore, water-water electrostatic interactions are in all regions inside the channel stronger than water-protein interactions, except near a conserved, positively charged Arg residue. We find that variations of the protein electrostatic field through the channel, owing to preserved structural features, completely explain the bipolar orientation of water. This orientation persists despite water translocation in single file and blocks proton transport. Furthermore, we find that for permeation of a cation, ion-protein electrostatic interactions are more unfavorable at the conserved NPA motifs than at the conserved Arg, suggesting that the major barrier against proton transport in aquaporins is faced at the NPA motifs.
Zeroth-order transmission resonance in hyperbolic metamaterials

We describe a novel resonance in planar hyperbolic metamaterials. In conventional Fabry-Perot mode numbering, the resonance corresponds to 0-th order, and can be observed in planar hyperbolic media with arbitrary small thickness.
Polarization smoothing for the National Ignition Facility

Polarization smoothing (PS) is the illumination of the target with two distinct and orthogonally polarized speckle patterns. Since these two polarizations do not interfere, the intensity patterns add incoherently and thus the contrast of the intensity nonuniformity can be reduced by a factor of (root) 2 in addition to any reduction achieved by temporal smoothing techniques. Smoothing by PS is completely effective on an instantaneous basis and is therefore of particular interest for the suppression of laser plasma instabilities, which have a very rapid response time. The various implementations of PS are considered, and their impact, in conjunction with temporal smoothing methods, on the spatial spectrum of the target illumination is analyzed.
Bankable permits for the control of environmental pollution

Abstract Intertemporal trading of emission permits (banking) is often identified as one of three promising market mechanisms for controlling pollution (along with averaging and trading). Surprisingly, the efficiency properties of permit banking systems have not been investigated. Using a simple optimal control model, this paper investigates firms' incentives for banking or borrowing emission permits and compares the emission and output streams firms would choose with the socially optimal solution. We find that in many cases firms will suboptimally choose excessive damage and output levels in early periods and correspondingly too few in later periods if given the opportunity to freely move emissions between time periods. We propose a simple alternative trading scheme we term modified banking that counters this problem and should be no more difficult for an environmental authority to implement than a straigth banking system.
Spatial Diffusion of Stars in the Inner Galactic Bulge

Star formation in the inner few hundred parsecs of the Galactic bulge occurs in a flattened molecular layer called the central molecular zone (CMZ). It has been suggested that star formation in the CMZ has been sustained for the lifetime of the Galaxy and that the resulting agglomeration of stars formed in the CMZ has resulted in the prominent r-2 stellar density cusp at the Galactic center having about the same physical extent as the CMZ. This "central cusp" is somewhat less flat than the CMZ; thus, the population of stars formed in the CMZ appears to have diffused out to larger latitudes. We hypothesize that such vertical diffusion is driven by the scattering of stars off the giant molecular clouds (GMCs) in the CMZ and perform numerical simulations of the scattering between stars and GMCs in the presence of the nonaxisymmetric background potential. The simulation results show that the timescale for an initially flattened stellar population to achieve an aspect ratio of the observed OH/IR stars in the inner bulge, 1-2 Gyr, agrees well with the estimated age of those OH/IR stars.
High-Velocity White Dwarfs: Thick Disk, Not Dark Matter

We present an alternative interpretation of the nature of the extremely cool, high-velocity white dwarfs identified by Oppenheimer et al. in a high-latitude astrometric survey. We argue that the velocities of the majority of the sample are more consistent with the high-velocity tail of a rotating population, probably the thick disk, rather than with a pressure-supported halo system. Indeed, the observed numbers are well matched by predictions based on the kinematics of a complete sample of nearby M dwarfs. Analyzing only stars showing retrograde motion gives a local density close to that expected for white dwarfs in the stellar (R-3.5) halo. Under our interpretation, none of the white dwarfs need be assigned to the dark matter heavy halo. However, luminosity functions derived from observations of these stars can set important constraints on the age of the oldest stars in the Galactic disk.
Atmospheric Entry Test Facilities: Basic Limitations and Proposal for a New Technique

Theoretical and practical limitations of techniques which are being currently developed for atmospheric entry testing are examined in terms of velocity-altitude duplication, and it is concluded that they cannot provide low-altitude, orbital- to escape-veloci ty capability with sufficiently large models. It is suggested that this capability might be achieved by application of rocket propulsion to aeroballistic range type testing. A multi-stage rocket booster traveling inside a straight tube or tubes evacuated to a low pressure would launch the model into a variable-pressure tank instrumented for aerophysical, erosion, impact, stability, and drag studies. It is estimated that a 10-lb model/sabot package could be launched at 25 kft/sec; a 1-lb package, at 35 kft/sec. The proposed facility is not subject, in the range of interest, to any basic physical limitations, but only to economic constraints. Application of the proposed test technique to lower hypersonic speeds is discussed with particular reference to duplication of high Reynolds number conditions and to hypersonic ramjet testing.
Barriers to screening infants for retinopathy of prematurity after discharge or transfer from a neonatal intensive care unit.

To assess neonatal intensive care unit (NICU) practices affecting screening and follow-up for retinopathy of prematurity (ROP). Retrospective study of infants at risk for ROP, eligible for back transport, admitted to a regional NICU from January 1, 1999 until May 31, 2002. Patients failed to receive needed follow-up for ROP after discharge or transfer from a NICU, if we could not verify their ROP screening follow-up within 1 month. A total of 74 infants were identified to need follow-up eye care. Infants who did not receive the follow-up care had greater mean gestational age (mean SD; 30.7±2.3 vs 29.6±2.5 weeks, p=0.05) and birth weights (mean SD; 1581±366 vs 1360±508 g, p=0.007), compared to infants who received the recommended care. Infants transported back to the community hospital were significantly more likely to miss follow-up eye care compared to infants discharged from the regional center (relative risk 2.81, 95% confidence interval (CI) (1.09 to 7.20)). Infants not screened for ROP in the NICU had greater risk for missing follow-up care compared to infants who had their first retinal examination in the NICU (relative risk 4.25, 95% CI (1.42 to 12.73)). Infants transferred back or discharged from the NICU before ROP screening represent a high-risk group for not receiving follow-up eye care.
The preparation of 1,3,5-tris(1,1′-binaphthoyl)benzene via amine-catalyzed alkyne trimerization

Abstract Three 1,1′-bi-2-naphthol moieties have been positioned about a central aromatic ring by alkyne cyclotrimerization of an optically pure 3-substituted binaphthyl ethynyl ketone. The cyclotrimerization proceeds in good yield and with complete regioselectivity to afford a 1,3,5-substituted arene exclusively.
On the power of poverty orderings

This paper investigates the possibility of increasing the ordering power of additively separable poverty measures beyond the condition of second degree stochastic dominance by considering third degree stochastic dominance. For a fixed poverty line, the ordering power can be significantly enhanced by using the third degree criterion. For a range of poverty lines, the marginal power of the third degree criterion over the second degree depends critically upon the lower bound of the range; if the lower bound poverty line is arbitrarily close to zero, the two criteria coincide. The implications of a strong version of the transfer sensitivity axiom are also considered.
The nose as a stereochemist. Enantiomers and odor.

1. Chirality in BiologysIntroduction 4099 2. Enantioselectivity 4100 3. Proof for Enantioselectivity in Odor 4101 4. Enantioselectivity and Odor Intensity 4102 5. Compounds with More than One Chiral Center 4104 6. Nitrogen Compounds 4106 7. Sulfur Compounds 4107 8. MalodoroussOr Not? 4109 9. A Wider View of the Perception of Enantiomers 4110 10. Practical Applications 4110 11. Acknowledgments 4111 12. References 4111
A Realization of Quantum Groups via Product Valued Quivers

Let C be the symmetrizable generalized Cartan matrix associated to a valued quiver \(\overset{\rightarrow}{\Gamma}\). We show that the whole quantum group associated to C can be realized from the abelian category of the representations of the product valued quiver \(\overset{\rightarrow}{\Gamma^{\pm}}\) of \(\overset{\rightarrow}{\Gamma}\) with the Kronecker quiver. This method can be used to realize the whole generalized Kac–Moody Lie algebra associated to C, as discussed in Li and Lin (submitted for publication, arXiv:math/0610448).
Dynamics of the Segre varieties of a real submanifold in complex space

Let M ⊂ C be a smooth (C∞) real submanifold of codimension d with 0 ∈ M . We choose smooth real-valued functions r = (r1, . . . , rd), with differentials dr1, . . . , drd linearly independent at 0, so thatM is defined by r = 0 near the origin. If the complex differentials ∂r1, . . . , ∂rd are also linearly independent at 0, thenM is called generic (near the origin). If M is a real-analytic, generic submanifold, there is a family of complex submanifolds of C , called the Segre varieties associated to M , which carry a great deal of information about the local geometry of M . The Segre varieties have been used by many mathematicians to study mappings between generic submanifolds. (See the end of this introduction for some specific references.) In this paper, we shall consider an algebraic substitute for these varieties for the case of smooth manifolds by introducing a formal mapping which, in the realanalytic case, parametrizes the Segre varieties. Our main objective is to study iterations of this mapping and relate these iterations to the local CR geometry of the manifold. If r is a local defining function of a smooth generic submanifold M as above, then we denote by ρj(Z, Z) the Taylor series of rj at 0. We write ρ = (ρ1, . . . , ρd). We consider ρj(Z, ζ) as a formal power series in the 2N indeterminates (Z, ζ). We shall denote the ring of such power series with complex coefficients by C[[Z, ζ]]. By a formal mapping F : (C, 0) → (C, 0), we shall mean a p-tuple F (x) = (F1(x), . . . , Fp(x)), where x = (x1, . . . , xk), of formal power series Fj ∈ C[[x]] without constant terms. The rank of F , RkF , is defined as the rank of the Jacobian matrix ∂F/∂x regarded as a Kx-linear mapping Kx → Kx, where Kx denotes the field of fractions of C[[x]]. Hence RkF is the largest integer s such that there is an s× s minor of the matrix ∂F/∂x which is not 0 as a formal power series in x. Let γ(ζ, t), where ζ = (ζ1, . . . ζN), t = (t1, . . . , tn), and n = N − d, be a formal mapping (C × C, 0)→ (C , 0) such that
A Newtonian model for the quantum gravitational back reaction on inflation

Abstract Quantum gravitational back-reaction offers a simultaneous explanation for why the cosmological constant is so small and a natural model of inflation in which scalars play no role. In this talk I review previous work and present a simple model of the mechanism in which the induced stress tensor behaves like negative vacuum energy with a density proportional to - Λ/8πG · (GΛ)2·Ht. The model also highlights the essential role of causality in back-reaction.
Deflagrations, hot spots, and the transition to detonation

A series of multidimensional numerical simulations were used to investigate how, through a series of shock-flame interactions, a turbulent flame may suddenly evolve into a detonation, the process o...
Constrained Optimal Nonlinear Regulators for Single-State Feedback

This work considers the regulator problem for single input-output linear plants in which only the plant output is available for control. A method is presented to specify an optimal nonlinear controller characteristic, constrained to lie within a given Popov sector, that yields improved performance over that obtained by proportional controllers. System performance is measured by a quadratic performance index, and performance is compared with that of both proportional and optimum linear state regulators.
Weak matrix elements on the lattice - circa 1995

Status of weak matrix elements is reviewed. In particular, e{prime}/e, B {yields} K*{gamma}, B{sub B} and B{sub B}, are discussed and the overall situation with respect to the lattice effort and some of its phenomenological implications are summarised. For e{prime}/e the need for the relevant matrix elements is stressed in view of the forthcoming improved experiments. For some of the operators, (e.g. O{sub 6}), even bound on their matrix elements would be very helpful. On B {yields} K{degrees}{gamma}, a constant behavior of T{sub 2} appears disfavored although dependence of T{sub 2} could, of course, be milder than a simple pole. Improved data is badly needed to settle this important issue firmly, especially in view of its ramification for extractions of V{sub td} from B {yields} {rho}{gamma}. On B{sub {kappa}}, the preliminary result from JLQCD appears to contradict Sharpe et al. JLQCD data seems to fit very well to linear {alpha} dependence and leads to an appreciably lower value of B{sub {kappa}}. Four studies of B{sub {kappa}} in the {open_quotes}full{close_quotes} (n{sub f} = 2) theory indicate very little quenching effects on B{sub {kappa}}; the full theory value seems to be just a little less than the quenched result. Based on expectations from HQET, analysis of B-parameter (B{sub h}{ell}) for the heavy-light mesons via B{sub h}{ell}) = constant + constants{prime}/m{sub h}{ell} is suggested. A summary of an illustrative sample of hadron matrix elements is given and constraints on CKM parameters (e.g. V{sub td}/V{sub ts}, on the unitarity triangle and on x{sub s}/x{sub d}, emerging from the lattice calculations along with experimental results are briefly discussed. In quite a few cases, for the first time, some indication of quenching errors on weak matrix elements are now becoming available.
Modular Chemical Descriptor Language (MCDL): composition, connectivity, and supplementary modules.

The Modular Chemical Descriptor Language (MCDL) was developed to address the need for linear representation of structural and other chemical information for chemical databases, E-journals, and the Internet. The current paper describes in detail two major modules of the language: the composition and connectivity modules, which provide a representation of chemical structure. These modules are created using simple hierarchical principles based on ASCII codes and are unique except for stereoisomers and a few special cases (e.g., valence isomers, knot-type compounds). The MCDL also provides for additional information (such as atom coordinates, bond orders, spectra, and physical-chemical characteristics) to be included as a set of supplementary modules.
Synthesis of Dihydrobenzisoxazoles by the [3 + 2] Cycloaddition of Arynes and Oxaziridines

Dihydrobenzisoxazoles are readily prepared in good yields by the [3 + 2] cycloaddition of oxaziridines and arynes. The reaction involves an unusual cleavage of the C−O bond of the oxaziridine and tolerates a variety of substituents on the oxaziridine and the o-(trimethylsilyl)aryl triflate to form aryl-, heteroaryl-, alkyl-, and naphthyl-substituted dihydrobenzisoxazoles. The resulting halogen-substituted dihydrobenzisoxazoles are readily elaborated to more complex products using palladium-catalyzed crossing-coupling processes.
Total reaction cross sections for 20 to 100 MeV deuterons from a microscopic model

Recent extensive measurements of total reaction cross sections $({\ensuremath{\sigma}}_{R})$ for 38, 65, and 97 MeV deuterons on targets from ${}^{9}\mathrm{Be}$ to ${}^{208}\mathrm{Pb}$ were fitted with microscopic model calculations. Using accepted two- and three-parameter Fermi matter distributions for the targets, zero-range nucleon-nucleon forces, and eikonal orbits for the projectile, reasonable fits were obtained when the impact parameter was corrected for Coulomb force effects. Correcting the orbit for nuclear force effects worsened the fits somewhat, as did the use of finite-range nuclear forces; we argue however that it is redundant to make both of these corrections. The results were nearly independent of whether a Hulth\'en, Gartenhaus, or Gaussian form factor was used for the deuteron matter distribution. An attempt to fit older $d+\mathrm{Pb}$ ${\ensuremath{\sigma}}_{R}$ measurements near 25 MeV indicated either a failure of the model at low energies or a need for remeasurement of those data.
Presidential Coequality: The Evolution of a Concept

The assertion that the presidency is coequal in power to the other branches in the American system of government is often heard, has been suggested by all recent presidents, and has even made its way into political science. But tracing the history of the concept demonstrates that this assertion is an invention of quite recent vintage. Those who wrote and favored the Constitution did not make such claims, nor did early presidents. Even Andrew Jackson's famous and, to his generation, shocking assertion of coequality coincident with his censure was not really a claim of equal power between branches. According to our systematic analysis of presidential rhetoric it was Richard Nixon and Gerald Ford who initiated and popularized the idea of interbranch coequality. They did so to defend themselves in two episodes of substantial presidential vulnerability: Watergate and the ensuing midterm elections. Subsequent presidents have elevated something that would have seemed wrong and absurd to any founder into a blithe...
Asymmetric Catalytic Mannich Reactions Catalyzed by Urea Derivatives: Enantioselective Synthesis of β-Aryl-β-Amino Acids

Highly enantioselective addition reactions between silyl ketene acetals and N-Boc aldimines are catalyzed by the thiourea-based catalyst 1c. Extraordinary scope is observed in this methodology with regard to the imine substrate, with aryl and heteroaromatic derivatives generally affording nearly quantitative yields of β-amino ester product in up to 98% enantioselectivity.
The symplectomorphism group of a blow up

We study the relation between the symplectomorphism group Symp M of a closed connected symplectic manifold M and the symplectomorphism and diffeomorphism groups Symp \(\widetilde{M}\) and Diff \(\widetilde{M}\) of its one point blow up \(\widetilde{M}\) . There are three main arguments. The first shows that for any oriented M the natural map from \(\pi_1(M)\) to \(\pi_0({\rm Diff}\widetilde{M})\) is often injective. The second argument applies when M is simply connected and detects nontrivial elements in the homotopy group \(\pi_1({\rm Diff}\widetilde{M})\) that persist into the space of self-homotopy equivalences of \(\widetilde{M}\) . Since it uses purely homological arguments, it applies to c-symplectic manifolds (M, a), that is, to manifolds of dimension 2n that support a class \(a\in H^2(M;{\mathbb{R}})\) such that \(a^n\ne 0\) . The third argument uses the symplectic structure on M and detects nontrivial elements in the (higher) homology of BSymp, M using characteristic classes defined by parametric Gromov–Witten invariants. Some results about many point blow ups are also obtained. For example we show that if M is the four-torus with k-fold blow up \(\widetilde{M}_k\) (where k > 0) then \(\pi_1({\rm Diff} \widetilde{M}_k)\) is not generated by the groups \(\pi_1\left({\rm Symp}\, (\widetilde{M}_k, \widetilde{\omega})\right)\) as \(\widetilde{\omega}\) ranges over the set of all symplectic forms on \(\widetilde{M}_k\) .
Effects of Neutrino-driven Kicks on the Supernova Explosion Mechanism

We show that neutrino-driven pulsar kicks can increase the energy of the supernova shock. The observed large velocities of pulsars are believed to originate in the supernova explosion, either from asymmetries in the ejecta or from an anisotropic emission of neutrinos (or other light particles) from the cooling neutron star. In this paper we assume the velocities are caused by anisotropic neutrino emission and study the effects of these neutrino-driven kicks on the supernova explosion. We find that if the collapsed star is marginally unable to produce an explosion, the neutrino-driven mechanisms can drive the convection to make a successful explosion. The resultant explosion is asymmetric, with the strongest ejecta motion roughly in the direction of the neutron star kick. This is in sharp contrast with the ejecta-driven mechanisms, which predict the motion of the ejecta in the opposite direction. This difference can be used to distinguish between the two mechanisms based on the observations of the supernova remnants.
The impact of Arabic morphological segmentation on broad-coverage English-to-Arabic statistical machine translation

Morphologically rich languages pose a challenge for statistical machine translation (SMT). This challenge is magnified when translating into a morphologically rich language. In this work we address this challenge in the framework of a broad-coverage English-to-Arabic phrase based statistical machine translation (PBSMT). We explore the largest-to-date set of Arabic segmentation schemes ranging from full word form to fully segmented forms and examine the effects on system performance. Our results show a difference of 2.31 BLEU points averaged over all test sets between the best and worst segmentation schemes indicating that the choice of the segmentation scheme has a significant effect on the performance of an English-to-Arabic PBSMT system in a large data scenario. We show that a simple segmentation scheme can perform as well as the best and more complicated segmentation scheme. An in-depth analysis on the effect of segmentation choices on the components of a PBSMT system reveals that text fragmentation has a negative effect on the perplexity of the language models and that aggressive segmentation can significantly increase the size of the phrase table and the uncertainty in choosing the candidate translation phrases during decoding. An investigation conducted on the output of the different systems, reveals the complementary nature of the output and the great potential in combining them.
The sparsity gap: Uncertainty principles proportional to dimension

In an incoherent dictionary, most signals that admit a sparse representation admit a unique sparse representation. In other words, there is no way to express the signal without using strictly more atoms. This work demonstrates that sparse signals typically enjoy a higher privilege: each nonoptimal representation of the signal requires far more atoms than the sparsest representation—unless it contains many of the same atoms as the sparsest representation. One impact of this finding is to confer a certain degree of legitimacy on the particular atoms that appear in a sparse representation. This result can also be viewed as an uncertainty principle for random sparse signals over an incoherent dictionary.
Synthesis and receptor binding studies of quinolinic derivatives as melatonin receptor ligands

Abstract We report the development of melatonin receptor ligands containing a quinolinic nucleus. Ligands containing a neutral moiety within the nucleus displayed high affinity for melatonin receptors while those analogs containing a permanently charged nucleus had very low affinity for melatonin receptors.
Electric-field-induced inelastic collisions between magnetically trapped hydroxyl radicals

Inelastic collisions are observed between magnetically trapped neutral hydroxyl (OH•) radicals at a temperature of 45 mK in the presence of an electric field. The collision rate is measured over a range of electric fields from 0.2 to 10 kV/cm. However, the two-body collision rates must be deconvolved from a novel electric-field induced non-adiabatic single particle loss, which arises from Landau–Zener crossings between energy surfaces at the plane where the electric field vector is transverse to the trapping magnetic field. The observed inelastic collision rate follows an approximate quadratic power law in the effective dipole moment.
Natural history of chronic hepatitis C: Identifying a window of opportunity for intervention

ince its discovery in 1989, HCV has emerged as a major cause of chronic liver disease in the United States and around the world. 1 It is estimated that more than 170 million people worldwide and at least 4 million Americans (or 1.8% of the US population) are infected with HCV. 2 Accumulated studies of the last 10 years are now revealing a much clearer picture of the natural history of hepatitis C infection. The hepatitis C “epidemic” occurred at different times and under different circumstances around the world, resulting in different stages of disease in these countries. Recent data indicate that 38% to 43% of infected patients can be “cured” 3,4 and that treatment can potentially interrupt the natural history of hepatitis C‐induced liver fibrosis. 5,6 This review will highlight recent studies that indicate where we stand in the continuing evolution of the burden of disease caused by hepatitis C. NATURAL HISTORY STUDIES The natural history of chronic hepatitis C in various patient cohorts has proved to be difficult to define (Table I). Major obstacles in studying the natural history of hepatitis C infection include biases inherent in referral populations, difficulty in establishing the onset of the infection, and limited periods of follow-up. No prospective studies exist in which an entire population of infected individuals are identified at the time of infection and systematically followed over an adequate time period. The available data indicate that different courses of natural history emerge depending on the population studied, the duration of infection in that population, how the disease was transmitted, and the relative prevalence of cofactors such as gender, age at onset of infection, and alcohol consumption.
Caffeine and headaches

Caffeine is the most widely consumed psychostimulant drug in the world. With intermittent exposures, caffeine may act as a mild analgesic for headache or as an adjuvant for the actions of other analgesics. Chronic repetitive exposures to caffeine increase the risks for development of analgesic-overuse headache, chronic daily headache, and physical dependency. Cessation of caffeine use after chronic exposures leads to a withdrawal syndrome with headache as a dominant symptom. At dosages achieved by common dietary intake, caffeine acts as a potent antagonist of central and peripheral nervous system adenosine receptors. The complex effects of caffeine on headache disorders suggest important roles for adenosine in these disorders and in the induction of caffeine dependency.