cssi/SciSciGPT-SciSciNet huggingface dataset:
Ligand-induced coupling versus receptor pre-association: cellular automaton simulations of FGF-2 binding.

Abstract The binding of basic fibroblast growth factor (FGF-2) to its cell surface receptor (CSR) and subsequent signal transduction is known to be enhanced by heparan sulfate proteoglycans (HSPGs). HSPGs bind FGF-2 with low affinity and likely impact CSR-mediated signaling via stabilization of FGF-2–CSR complexes via association with both the ligand and the receptor. What is unknown is whether HSPG associates with CSR in the absence of FGF-2. In this paper, we determine conditions by which pre-association would impact CSR–FGF-2–HSPG triad formation assuming diffusion-limited surface reactions. Using mean-field rate equations, we show that (i) when [HSPG] is much higher than [CSR], the presence of pre-formed complexes does not affect the steady state of FGF-2 binding, and (ii) when the concentrations are comparable, the presence of pre-formed complexes substantially increases the steady-state concentration of FGF-2 bound to CSR. These findings are supported by explicit cellular automaton simulations, which justify the mean-field treatment. We discuss the advantages of such a two-receptor system compared to a single-receptor model, when the parameters are comparable. Further, we speculate that the observed high concentration of HSPG in intact cells ([HSPG]∼100[CSR]) provides a way to ensure that the binding levels of FGF-2 to its signaling receptor remains high, irrespective of the presence of pre-formed CSR–HSPG complexes on the cell surface, while allowing the cell to finely tune the response to FGF-2 via down-regulation of the signaling receptor.
An Integrated Virtual Store-Based Approach for Price Determination Before Product Launch

An integrated model approach is developed to determine market prices for product options that a company can offer consumers before launching a product. The multiple research streams drawn on include pricing, new product launch, on-line experimentation, conjoint analysis, and optimization. The approach incorporates a consumer-response model that considers the cross-price effects of the options as well as the impact of competing product options and prices. Based on the response model, a profit-optimization model framework is applied in an actual market situation involving an on-line video game to be introduced in a foreign market. A description of the stages of the application, from empirical design and data collection to decision-making and postlaunch model validation, demonstrates the usefulness of the approach.
Modeling and Implementation of an Integrated Ramp Metering-Diamond Interchange Control System

Abstract This paper addresses a modeling approach to analyzing an integrated system that includes freeway mainlines, ramp metering, and an upstream signalized diamond interchange. The modeling approach takes into consideration of the various components, their operational characteristics, and their interactions within the system. Strategies are also proposed for real-time operation and possible field implementation. The key element of achieving an integrated operation is to control the ramp feeding the traffic through special signal timings at the diamond interchange. Whenever a long queue is detected at the metered ramp, the signal timing should be adjusted to reduce the traffic flows entering the ramp. In this way, the ramp meter will remain in operation as long as possible, which would delay the onset of queue flush (i.e., termination of ramp meter) and minimize the possibilities of a freeway breakdown. Because a diamond interchange is usually controlled by special signal phasing and timing, the control strategies are specially focused on the special diamond signal phasing schemes. The system design and system architecture are also presented for potential deployment of the system in the field.
Biomedical Applications of Biodegradable Polymers

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.
Surface Chemistry of Supported Chromium Oxide Catalysts

A series of 1% CrO[sub 3] supported on different oxide supports (Al[sub 2]O[sub 3], TiO[sub 2], ZrO[sub 2], Nb[sub 2]O[sub 5], SiO[sub 2], and MgO) was structurally characterized by Raman spectroscopy and chemically probed by methanol oxidation. The Raman results reveal that the polymeric chromium oxide species possessing two terminal Cr[double bond]O bonds preferentially exist on the Al[sub 2]O[sub 3], TiO[sub 2], ZrO[sub 2], and Nb[sub 2]O[sub 5] supports, and isolated chromate species with two Cr[double bond]O bonds predominate on the SiO[sub 2] support. Nonstoichiometric compounds such as Mg[sub x](CrO[sub 4])[sub y] are present on the MgO support due to the strong acid-base interaction of CrO[sup 2[minus]][sub 4] with MgO. The methanol oxidation reaction reveals that the reactivity of the surface chromium oxide species was primarily controlled by the specific oxide support which acts as a ligand, and not the molecular structure of the surface chromium oxide species. The selectivity of the supported chromium oxide catalysts is influenced by the acid-base characteristics of the oxide supports. 33 refs., 2 figs., 1 tab.
DOES EXECUTIVE COMPENSATION AFFECT INVESTMENT

Investment decisions require trading off current expenditures against future revenues. If revenues extend far enough into the future, the executives responsible for designing long-run investment policy may no longer be in office by the time all the revenues are realized. We present evidence that: (1) on average, executives are close to leaving office (relative to the payout period of many investments); (2) bonuses based on accounting earnings constitute an important part of compensation for the typical executive; and (3) executives respond in predictable ways to compensation plans based on accounting measures of earnings. Based on these facts, we hypothesize that existing compensation policy induces executives to reduce investments during their last years in office. In our empirical work, however, we find that investment expenditures on research and development and on advertising tend to be largest in the final years of a CEO's time in office. We offer several possible explanations for this surprising finding(This abstract was borrowed from another version of this item.)
Mass storage: Past, present and future

Mass storage as a functional need in computer systems is continually increasing in importance with the growing trend to interactive terminal-oriented systems, serving to store a systems data base and resident programming systems. The associated capacity, plus the ever expanding magnitude of such information, far exceeds the range where "electronic" memory is economically competitive. Included in the product category defined as mass storage are disk, tape, and card-like recording structures. We see in the future the perspective that at a growing number of installations all data will be available on-line under systems control.
Estimations of model parameters for gravity wave spectra observed by MST radar

Abstract The general theory of MST radar observations of gravity wave spectra is developed in this paper. This effort extends the previous results to include anisotropy and Doppler effects for the spectra, as well as the consequences for the multibeam configuration. The relationships between the observed one- or two-dimensional spectra for the line-of-sight velocity in the gravity wave spectra are derived. Expressions for cross spectra, as well as covariances between velocities observed on different beams, are computed. Using these results, studies are carried out to show how model parameters for gravity wave spectra can be estimated from the observed quantities. Model parameters include the variance, power-law indices, anisotropy parameters, Doppler parameters, mean scale sizes, etc. Cases with different numbers of beams will be investigated.
Theory of the (3×2) reconstruction of the GaAs(001) surface

Abstract We discuss an ab initio density functional theory investigation of a (3×2) reconstruction of the Ga-rich GaAs(001) surface. Recent experiments identified this new reconstruction as a stable surface of epitaxially grown GaAs doped with indium or carbon (L. Li, et al., Appl. Phys. A 66 (1998) S501; L. Li, et al., Ultramicroscopy 73 (1998) 229). Using our recently developed real-space pseudopotential density functional code, we investigate this (3×2) reconstruction and evaluate stabilization mechanisms for the model proposed by the experimentalists, which does not satisfy the electron counting rule. In order to study the effect of In substitution, we consider the dependence of the surface energies of competing reconstructions on surface strain and relative chemical potentials. The effects of carbon substitution are modeled using a charged (3×2) reconstruction. These studies support and clarify the proposed structure and stabilization mechanisms. We provide a simple physical explanation for the behavior of the surface energy of the (3×2) reconstruction.
Downscattering Due to Wind Outflows in Compact X-Ray Sources: Theory and Interpretation

A number of recent lines of evidence point towards the presence of hot, outflowing plasma from the central regions of compact Galactic and extragalactic X-ray sources. Additionally, it has long been noted that many of these sources exhibit an "excess" continuum component, above approx. 10 keV, usually attributed to Compton Reflection from a static medium. Motivated by these facts, as well as by recent observational constraints on the Compton reflection models - specifically apparently discrepant variability timescales for line and continuum components in some cases - we consider possible of effects of out-flowing plasma on the high-energy continuum spectra of accretion powered compact objects. We present a general formulation for photon downscattering diffusion which includes recoil and Comptonization effects due to divergence of the flow. We then develop an analytical theory for the spectral formation in such systems that allows us to derive formulae for the emergent spectrum. Finally we perform the analytical model fitting on several Galactic X-ray binaries. Objects which have been modeled with high-covering-fraction Compton reflectors, such as GS1353-64 are included in our analysis. In addition, Cyg X-3, is which is widely believed to be characterized by dense circumstellar winds with temperature of order 10(exp 6) K, provides an interesting test case. Data from INTEGRAL and RXTE covering the approx. 3 - 300 keV range are used in our analysis. We further consider the possibility that the widely noted distortion of the power-law continuum above 10 keV may in some cases be explained by these spectral softening effects.
A comment on models of ion transport across cell membranes.

One usually thinks of ionic flow across membranes as controlled by modulation of the energies needed by an ion to get into a membrane. Examination of these energies shows that they are not only large enough to perturb the ionic distribution but also sufficient to deform a thin membrane. The deformability of a cell membrane may then be related to its control of ionic current.
Extreme slowdowns for one-dimensional excited random walks

Abstract We study the asymptotics of the probabilities of extreme slowdown events for transient one-dimensional excited random walks. That is, if { X n } n ≥ 0 is a transient one-dimensional excited random walk and T n = min { k : X k = n } , we study the asymptotics of probabilities of the form P ( X n ≤ n γ ) and P ( T n γ ≥ n ) with γ 1 . We show that there is an interesting change in the rate of decay of these extreme slowdown probabilities when γ 1 / 2 .
The tax treatment of R&D expenditures of multinational enterprises

Abstract This paper investigates the tax treatment by national governments of R&D expenditures of multinational enterprises. In a noncooperative world, the international tax system is generally shown to discourage R&D investments by multinational firms. For the special case of symmetric corporate tax rates, the multinational is allowed to expense less than the total of its R&D expenses worldwide. Internationalization of the firm's operations and ownership is demonstrated to lead to less generous expensing rules within individual countries, and may even eliminate R&D tax deductions altogether.
Pluri-polarity in almost complex structures

J-Holomorphic curves are −∞ sets of J-plurisubharmonic functions, with a singularity of LogLog type, but it is shown that in general they are not −∞ sets of J-plurisubharmonic functions with Logarithmic singularity (i.e. non-zero Lelong number). Some few additional remarks on pluripolarity in almost complex structures are made.
Characterizing Laser-Generated Hot Spots for Receptivity Studies

Simple, well-characterized experimental perturbations are needed to validate CFD simulations of supersonic and hypersonic boundary-layer receptivity. A laser-generated hot-spot perturbation has been characterized and modeled, based on experiments in the Purdue University Mach-4 quiet-flow Ludwieg tube. The model provides a detailed density profile and time evolution for the perturbation, which consists of a hot spot and the surrounding weak shock. The model is validated by comparing simulated optical path differences to measurements from a high-sensitivity, high-bandwidth laser differential interferometer. CFD simulations are compared with receptivity experiments on a hemisphere to illustrate the usefulness of the perturbation model.
Biaxial load effects in fracture mechanics

Abstract Our investigation into the effects of load biaxiality thus far, has produced several findings which, in our opinion, are deemed to be important. 1. (a) The standard expressions for elastic stress and displacement in the crack-tip region, i.e. the so-called “singular-solution’, cannot be considered to be approximations that are acceptable in a completely general sense. 2. (b) This conclusion is best illustrated in the instance of a biaxially loaded infinite sheet with a flat (horizontal) central crack, wherein the effect of the load applied parallel to the plane of the crack appears entirely in the second terms of the series representations for local stress and displacement. Omission of these contributions, which is the usual practice, is tantamount therefore to denial of the physical presence of the horizontal load. Thus, in calculations of stress, displacement and related quantities of interest in the crack border region by means of the standard expressions, no biaxial load effects will appear, leading thereby to the erroneous impression that load applied parallel to the plane of the crack can have no influence with regard to the fracture problem. 3. (c) For the infinite sheet problem with a horizontal central crack, our analytical analysis shows significant biaxial load effect on crack border region and crack edge displacement, on local maximum shear stress, on the pattern of maximum shear isostats, on the angle of initial crack extension, and on local elastic strain energy density and strain energy rate. On the other hand, both the elastic stress intensity factor (as to be expected) and the J -integral show no sensitivity whatsoever to the presence of the horizontal load. 4. (d) The analytical results referred to above for the infinite sheet are also seen in the results obtained for a finite sheet using finite element numerical analysis. 5. (e) A nonlinear finite element analysis of the same biaxially loaded finite specimen geometry, designed to simulate elastic-plastic material behavior under conditions of no unloading, shows that the global energy rate, the J -integral, the plastic stress and strain intensity factors (in the sense of Hilton and Hutchinson), and the size of the crack border region plastic yield, all have pronounced biaxial load dependency.
Electrical Conductivity in Heavily Doped n -Type Germanium: Temperature and Stress Dependence

Investigations of the piezoresistance of heavily doped $n$-type germanium were made to determine (1) the nature of the carrier scattering mechanisms in degenerate materials and (2) any modification of the conduction-band edge resulting from the large number of impurity states. Stresses large enough to alter the resistivity well beyond the range of linear piezoresistance were applied; saturation of the resistivity at the larger stresses was attained in samples with as many as ${10}^{19}$ carriers per cc. Resistivity was measured with extensive parametric variation of dopant, carrier concentration, temperature, and applied stress. The Hall coefficient was also measured as a function of stress for several concentrations. The data are interpreted qualitatively by a four-valley model with a parabolic conduction-band edge, and deviations from this model are discussed. Electron-electron interactions and the temperature dependence of screening contribute significantly to the temperature dependence of the resistivity. The variation of the screening with the relative population of the valley must be considered in interpreting the results of the piezoresistance experiments; in the case of arsenic doping, intervalley scattering is also significant. The mobility anisotropy for screened Coulomb scattering in one valley, as determined from resistivity measurements on antimony-doped samples with large $〈111〉$ stress, varies with concentration from 5.5 at 1\ifmmode\times\else\texttimes\fi{}${10}^{18}$ per cc to 3.8 at 1\ifmmode\times\else\texttimes\fi{}${10}^{19}$ per cc. Evidence for the existence of tail states extending \ensuremath{\approx}0.04 eV below the conduction-band edge is presented.
Probabilities of Sentences about Very Sparse Random Graphs

We consider random graphs with edge probability βn−α, where n is the number of vertices of the graph, β > 0 is fixed, and α = 1 or α = (l + 1) /l for some fixed positive integer l. We prove that for every first-order sentence, the probability that the sentence is true for the random graph has an asymptotic limit. © 1992 Wiley Periodicals, Inc.
Thrust vector control design for a liquid upper stage spacecraft

This paper presents a preliminary thrust vector control design for a liquid-bipropellant upper stage spacecraft. The intent here is to describe an analytical design procedure as well as a systematic way of specifying the system requirements during the early phases of the new upper stage development. Maintaining the thrust vector pointing and overall stability under significant uncertainties of center-of-mass location and propellant sloshing was a major concern in the thrust vector control design. Mission requirements, dynamic modeling of propellant slosh, guidance and control loop design, and specification of the requirements are discussed. Because of the Shuttleoptimized configuration (short longitudinal length), the lateral center-of-mass location uncertainty is shown to be the most critical parameter in the thrust vector control design.
Finite volume partition functions and Itzykson-Zuber integrals

Abstract We find the finite volume QCD partition function for different quark masses. This is a generalization of a result obtained by Leutwyler and Smilga for equal quark masses. Our result is derived in the sector of zero topological charge using a generalization of the Itzykson-Zuber integral appropriate for arbitrary complex matrices. We present a conjecture regarding the result for arbitrary topological charge which reproduces the Leutwyler-Smilga result in the limit of equal quark masses. We derive a formula of the Itzykson-Zuber type for arbitrary rectangular complex matrices, extending the result of Guhr and Wettig obtained for square matrices.
A Spitzer White Dwarf Infrared Survey

We present mid-infrared photometry of 124 white dwarf stars with the Spitzer Space Telescope. Objects were observed simultaneously at 4.5 and 8.0 μm with sensitivities better than 0.1 mJy. This data set can be used to test models of white dwarf atmospheres in a new wavelength regime, as well as to search for planetary companions and debris disks.
An Offset Seyfert 2 Nucleus in the Minor Merger System NGC 3341

We present the discovery of a triplet of emission-line nuclei in the disturbed disk galaxy NGC 3341, based on archival data from the Sloan Digital Sky Survey and new observations from the Keck Observatory. This galaxy contains two offset nuclei within or projected against its disk, at projected distances of 5.1 and 8.4 kpc from its primary nucleus and at radial velocity separation of less than 200 km s−1 from the primary. These appear to be either dwarf ellipticals or the bulges of low-mass spirals whose disks have already been stripped off while merging into the primary galaxy. The inner offset nucleus has a Seyfert 2 spectrum and a stellar velocity dispersion of 70 ± 7 km s−1. The outer offset nucleus has very weak emission lines consistent with a LINER classification, and the primary nucleus has an emission-line spectrum close to the boundary between LINER/H II composite systems and H II nuclei; both may contain accreting massive black holes, but the optical classifications alone are ambiguous. The detection of an offset active nucleus in NGC 3341 provides a strong suggestion that black hole accretion episodes during minor mergers can be triggered in the nuclei of dwarf secondary galaxies as well as in the primary.
Rearrangement of bis[(2, 4, 6-trimethylphenyl)methanoyl]bicyclo[2.2.1]hept-5-enes to 2-oxabicyclo[3.3.0]octa-3, 7-dienes

Abstract 2- endo -3- endo - and 2- endo -3- exo -bis(2, 4, 6-trimethylphenyl)]methanoylbicyclo[2.2.1]hept-5-ene ( 6 and 7 ) rearrange in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and bis(trimethylsilyl) sulfide to 3-(2, 4, 6-trimethylphenyl)-4-[(2, 4, 6-trimethylphenyl)methyl]-2-oxabicyclo[3.3.0]octa-3, 7-diene ( 8 ) and 3-(2, 4, 6-trimethylphenyl)-4-[(Z-1-(2, 4, 6-trimethylphenyl)-1-(trimethylsiloxy)ethenyl]-2-oxabicyclo[3.3.0]octa-3, 7-diene ( 9 ). No reaction occurs under these experimental conditions with 2- endo -3- endo - and 2- endo -3- exo -bis[(2, 4, 6-trimethylphenyl)methanoyl]bicyclo[2.2.1]heptane ( 10 and 11 ). Download full-size image
An analytic model for buoyancy resonances in protoplanetary disks

Zhu et al. found in three-dimensional shearing box simulations a new form of planet-disk interaction that they attributed to a vertical buoyancy resonance in the disk. We describe an analytic linear model for this interaction. We adopt a simplified model involving azimuthal forcing that produces the resonance and permits an analytic description of its structure. We derive an analytic expression for the buoyancy torque and show that the vertical torque distribution agrees well with the results of the Athena simulations and a Fourier method for linear numerical calculations carried out with the same forcing. The buoyancy resonance differs from the classic Lindblad and corotation resonances in that the resonance lies along tilted planes. Its width depends on damping effects and is independent of the gas sound speed. The resonance does not excite propagating waves. At a given large azimuthal wavenumber ky > h –1 (for disk thickness h), the buoyancy resonance exerts a torque over a region that lies radially closer to the corotation radius than the Lindblad resonance. Because the torque is localized to the region of excitation, it is potentially subject to the effects of nonlinear saturation. In addition, the torque can be reduced by the effects of radiative heat transfer between the resonant region and its surroundings. For each azimuthal wavenumber, the resonance establishes a large scale density wave pattern in a plane within the disk.
Synthesis of the naphthoic acid component of kedarcidin chromophore by routes employing photochemical and thermal electrocyclic ring closure reactions

Abstract Two different synthetic routes to the naphthoic acid component of kedarcidin chromophore were developed featuring photochemical and thermal electrocyclic ring closure reactions, respectively, as the key step. X-ray crystallographic analysis of the synthetic naphthoic acid confirmed its structure and comparison of 1H and 13C NMR data from its methylamide derivative with those reported for kedarcidin chromophore correspond closely, suggesting that this component of the natural product is correctly assigned.
Equivalent Elmore delay for RLC trees

Closed-form solutions for the 50% delay, rise time, overshoots, and settling time of signals in an RLC tree are presented. These solutions have the same accuracy characteristics of the Elmore delay for RC trees and preserves the simplicity and recursive characteristics of the Elmore delay. Specifically, the complexity of calculating the time domain responses at all the nodes of an RLC tree is linearly proportional to the number of branches in the tree and the solutions are always stable. The closed-form expressions introduced here consider all damping conditions of an RLC circuit including the underdamped response, which is not considered by the Elmore delay due to the nonmonotone nature of the response. The continuous analytical nature of the solutions makes these expressions suitable for design methodologies and optimization techniques. Also, the solutions have significantly improved accuracy as compared to the Elmore delay for an overdamped response. The solutions introduced here for RLC trees can be practically used for the same purposes that the Elmore delay is used for RC trees.
Radiation-induced large-scale structure during the reionization epoch: the autocorrelation function

The structures produced during the epoch of reionization by the action of radiation on neutral hydrogen are in principle different from those that arise through gravitational growth of initially small perturbations. We explore the difference between the two mechanisms using high-resolution cosmological radiative transfer. Our computations use a Monte Carlo code which ray-traces directly through smoothed particle hydrodynamics (SPH) kernels without a grid, preserving the high spatial resolution of the underlying hydrodynamic simulation. Because the properties of the first sources of radiation are uncertain, we simulate a range of models with different source properties and recombination physics. We examine the morphology of the neutral hydrogen distribution and the reionization history in these models. We find that at fixed mean neutral fraction, structures are visually most affected by the existence of a lower limit in source luminosity, then by galaxy mass-to-light ratio, and are minimally affected by changes in the recombination rate and amplitude of mass fluctuations. We concentrate on the autocorrelation function of the neutral hydrogen, ξ Hl (r), as a basic quantitative measure of radiation-induced structure. All the models we test exhibit a characteristic behaviour, with ξ Hl becoming initially linearly antibiased with respect to the matter correlation function, reaching a minimum bias factor b ∼ 0.5 when the universe is ∼ 10-20 per cent ionized. After this ξ Hl increases rapidly in amplitude, overtaking the matter correlation function. It keeps a power-law shape, but flattens considerably, reaching an asymptotic logarithmic slope of γ Hl ≃ -0.5. The growth rate of H i fluctuations is exponentially more rapid than gravitational growth over a brief interval of redshift Δ z ∼ 2-3.
Principals and principles of spectrochemical analysis

The history of science abounds with examples of men who observe natural phenomena but are unable to explain or apply them until a" genius" discovers a generalization, principle or law. Once clearly stated such natural laws seem more or less obvious, and the marvel is that they were not recognized earlier. For example, after thousands of years of accidents, wars, and bloodletting is it not strange that homo ,apienB knew nothing about the circulation of his blood until W ilUam Ha'TfJ6Y discovered it in 1614! Why did the laws of motion and of universal gravitation have to wait for Newton to formulate them during the latter half of the seventeenth century! The ancient Greeks made the first observations on electricity and magnetism but it required 2 % millenniums to produce Farailo,y, Henry, M a:cwelZ, and Hem who perfected the electromagnetic theory. After more than 2000 years of astronomical observation and speculation it remained for Copernicu8 and Kepler to announce the true laws of planetary motion. Since Nature is an open book, for anyone to read who has the wit to understand, it must be concluded that the slowness of scientific progress is at least partly, if not wholly, explained by human stupidity. We owe all progress to the occasional individuals who possess sufficient perseverance, perspicacity, or talents to discover new phenomena or formulate new laws of nature. Only those who have deliberately tried to find such laws know how difficult it is. What have these introductory remarks to do with spectrochemical analysis! According to the Bible, spectroscopy began when the flood ended, but thousands of years elapsed before man made any practical use of a spectrum. Now everyone knows that, in principle, any chemical element can be detected by a characteristic spectral line, and its concentration determined from the intensity of that line. The actual procedure would be simple indeed if all atomic spectra could be excited in the same light source, if each element emitted only one spectrum, and if all spectral lines had nearly the same properties. However, a century or more of experiments in spectroscopy has demonstrated that no single light source can be designed or operated to excite the spectra of all elements, the same
High enantioselective Michael addition of malonates to β,γ-unsaturated α-ketoesters catalyzed by bifunctional thioureas

Abstract A highly enantioselective Michael addition of malonates to β,γ-unsaturated α-ketoesters was achieved using cinchona alkaloid-derived thioureas as the bifunctional catalyst. The corresponding Michael addition products were obtained in excellent yields (90–99%) and ee values (up to >99% ee) using a quinidine-derived thiourea as the catalyst under neat conditions. The opposite enantiomer may be obtained using a quinine- or cinchonidine-derived thiourea as the catalyst.
Lattice gauge theory: Present status

Lattice gauge theory is our primary tool for the study of non-perturbative phenomena in hadronic physics. In addition to giving quantitative information on confinement, the approach is yielding first-principles calculations of hadronic spectra and matrix elements. After years of confusion, there has been significant recent progress in understanding issues of chiral symmetry on the lattice.
On quiver varieties and affine Grassmannians of type A

Abstract We construct Nakajima's quiver varieties of type A in terms of affine Grassmannians of type A . This gives a compactification of quiver varieties and a decomposition of affine Grassmannians into a disjoint union of quiver varieties. Consequently, singularities of quiver varieties, nilpotent orbits and affine Grassmannians are the same in type A . The construction also provides a geometric framework for skew (GL( m ),GL( n )) duality and identifies the natural basis of weight spaces in Nakajima's construction with the natural basis of multiplicity spaces in tensor products which arises from affine Grassmannians. To cite this article: I. Mirkovic, M. Vybornov, C. R. Acad. Sci. Paris, Ser. I 336 (2003).
Observational Prospects for Afterglows of Short-Duration Gamma-Ray Bursts

If the efficiency for producing gamma rays is the same in short-duration (2 s) gamma-ray bursts (GRBs) as in long-duration GRBs, then the average kinetic energy per solid angle in short GRBs must be ~20 times less than that of long GRBs. Assuming that the relativistic shocks in short- and long-GRB afterglows have similar parameters, we show that the afterglows of short GRBs will be, on average, 10-40 times dimmer than those of long GRBs. We find that the afterglow of a typical short GRB will be below the detection limit (30 μJy) of searches at radio frequencies. The afterglow would also be difficult to observe in the optical, where we predict R 23 10 hr after the burst. The radio and optical afterglows would be even fainter if short GRBs occurred in a low-density medium, as expected in neutron star-neutron star and neutron star-black hole merger models. Early (1 day) observations in X-rays offer the best prospects for detecting short-GRB afterglows.
Effects of Wandering on the Coalescence of Black Hole Binaries in Galactic Centers

We examine whether massive binary black holes in spherically symmetric bulges of galaxies can achieve coalescence through the emission of gravitational radiation under the action of stellar dynamical processes alone. In particular, we address the importance of the Brownian motion of a binary's center of mass to its continued interaction with stellar orbits that allows it to keep hardening. We use an analytical model and N-body simulations to calculate the time required to reach the gravitational radiation-dominated stage. We find that a substantial fraction of all massive binaries in galaxies can coalesce within a Hubble time.
Yohimbine dimers exhibiting binding selectivities for human α2a-versus α2b-adrenergic receptors

Abstract A series of yohimbine dimers was prepared and evaluated at the human α2a- and α2b-adrenergic receptors (ARs) expressed in Chinese hamster ovary (CHO) cells. All dimers display higher binding selectivities for α2a versus α2b subtype than yohimbine, and four compounds ( 3d, 3e, 3g and 3i Download : Download high-res image (60KB) Download : Download full-size image Scheme 1 . ) represent the most potent and α2a- versus α2b-AR selective ligands identified so far.
Dynamical supersymmetry breaking

Abstract I review the motivation for dynamical supersymmetry breaking, the various mechanisms which have been discovered, and the prospects for model building.
On D-wave meson spectroscopy and the K∗ (1410)-K∗ (1680) problem

Abstract The mass spectrum of D-wave mesons is considered in a non-relativistic constituent quark model. The results show a common mass degeneracy of the isovector and isodoublet states of the 1 3D1 and 1 3D3 nonets, and suggest therefore that the K ∗ (1680) cannot be the I = 1 2 member of the 1 3D1 nonet. They also suggest that the η2 (1870), presently omitted from the Meson Summary Table, should be interpreted as the I = 0s s state of the 1 1D2 nonet.
Dynamics of Tropospheric Aerosols

Anthropogenic emissions leading to atmospheric aerosols have increased dramatically over the past century. Airborne particles have been implicated in human health effects, visibility reduction in urban and regional areas, acidic deposition, and altering the earth's radiation balance. The atmosphere subjects aerosol particles to an array of transport and transformation processes that alter their size, number, and composition; the transformation processes include condensation and evaporation, homogeneous nucleation, coagulation, and chemical reactions. A major goal of our research has been to use first principles to gain a predictive understanding of the physical and chemical processes that govern the dynamics, size, and chemical composition of atmospheric aerosols. We review here the current state of our ability to model this atmospheric aerosol behavior.
Endothelial progenitor cell mobilization after percutaneous coronary intervention

Abstract Background In animal models, circulating endothelial progenitor cells (EPC) have been shown to participate in repair of damaged or degenerating vascular surfaces. In humans, reduced EPC counts correlate with cardiovascular risk and disease outcome; yet it has been difficult to establish that EPC are in fact mobilized in response to vascular injury as a physiologic response. We therefore studied early ( Methods and results CD34/CD31 positive EPC colony forming units (EPC-CFU) were quantified by a blinded observer in peripheral blood samples from eight control patients with angiographically normal coronary arteries, and in 30 patients with coronary artery lesions before and 12h after PCI. All patients ( n =38) had one or more CV risk factors. Ten patients presented with acute coronary syndrome (PCI ACS ), and the rest ( n =20) underwent elective PCI (PCI Elect ). Despite the presence of an acute coronary syndrome, patients in the PCI ACS group did not present with increased EPC-CFU compared with either the PCI Elect or control groups ( P >0.05). In addition, EPC-CFU (colonies/ml blood) increased significantly in the PCI Elect group after stent placement (11.8+1.6 before versus 16.5+1.9 after, P =0.0009), while in contrast, PCI did not stimulate EPC mobilization in patients in the PCI ACS group (9.6+3.2 before versus 6.5+1.8, P =0.20). We found a higher presenting vascular endothelial growth factor (VEGF) level in the PCI Elect group compared to PCI ACS (78.7+25.2 versus 15.3+7.9pg/ml blood, P =0.02). However, VEGF levels increased after PCI only in the PCI ACS group (15.3+7.9 to 133.3+27.5pg/ml, P =0.003) and not in the PCI Elect group (78.7+25.2 to 79.7+12.2pg/ml, P =0.97). Conclusion Our findings suggest that focal coronary endothelial injury as a result of PCI triggers early mobilization of EPC into the peripheral circulation in patients presenting for an elective PCI, without a corresponding rise in VEGF levels. In contrast, patients with an acute coronary syndrome fail to respond to PCI with early EPC mobilization despite a significant rise in VEGF. The results of the present study may suggest a novel mechanism for early EPC augmentation after PCI.
On residualizing homomorphisms preserving quasiconvexity

ABSTRACT H is called a G-subgroup of a hyperbolic group G if for any finite subset M ⊂ G there exists a homomorphism from G onto a non-elementary hyperbolic group G 1 that is surjective on H and injective on M. In his paper in 1993 A. Ol'shanskii gave a description of all G-subgroups in any given non-elementary hyperbolic group G. Here we show that for the same class of G-subgroups the finiteness assumption on M (under certain natural conditions) can be replaced by an assumption of quasiconvexity.
Alumina as reagent. The one-step conversion of benzyl chloride and bromide into dibenzyl ether

Abstract Benzyl chloride and bromide react with alumina via a two-step mechanism to produce dibenzyl ether in good yield. Chemisorbed benzyloxy is the other major product of the reactions.
A divided Universe: red and blue galaxies and their preferred environments

Making use of scaling relations between the central and the total galaxy luminosity of a dark matter halo as a function of the halo mass, and the scatter in these relations, we present an empirical model to describe the luminosity function (LF) of galaxies. We extend this model to describe relative statistics of early-type (or red) and late-type (or blue) galaxies, with the fraction of early-type galaxies at halo centres, relative to the total sample, determined only by the halo mass; the same fraction in the case of satellites is taken to be dependent on both the halo mass and the satellite galaxy luminosity. This simple model describes the conditional LF (the LF of galaxies as a function of the halo mass) measured with the 2dF galaxy group catalogue from cluster to group mass scales. Given the observational measurements of the LF as a function of the environment using the 2dF, with environment defined by the galaxy overdensity measured over a given volume, we extend our model to describe environmental LFs. Using 2dF measurements, we extract information related to the conditional mass function for haloes from extreme voids to dense regions in terms of the galaxy overdensity. We also calculate the probability distribution function of halo mass, as a function of the galaxy overdensity, and use these probabilities to address preferred environments of red and blue galaxies. Our model also allows us to make predictions, e.g. galaxy bias as a function of the galaxy type and luminosity, the void mass function, and the average galaxy luminosity as a function of the density environment. The extension of the halo model to construct conditional and environmental LFs of galaxies is a powerful approach in the era of wide-field large-scale structure surveys, given the ability to extract information beyond the average LF.
Congruence conditions, parcels, and Tutte polynomials of graphs and matroids

Let G be a matrix and M(G) be the matroid defined by linear dependence on the set E of column vectors of G. Roughly speaking, a parcel is a subset of pairs (f,g) of functions defined on E to a suitable Abelian group A satisfying a coboundary condition (that the difference f-g is a flow over A of G) and a congruence condition (that an algebraic or combinatorial function of f and g, such as the sum of the size of the supports of f and g, satisfies some congruence condition). We prove several theorems of the form: a linear combination of sizes of parcels, with coefficients roots of unity, equals a multiple of an evaluation of the Tutte polynomial of M(G) at a point (u,v), usually with complex coordinates, satisfying (u-1)(v-1)=|A|.
Intrinsic transverse momentum and parton correlations from dynamical chiral symmetry breaking

The dynamical breaking of chiral symmetry in QCD is caused by nonperturbative interactions on a distance scale ρ ~ 0.3 fm, much smaller than the typical hadronic size R ~ 1 fm. These short-distance interactions influence the intrinsic transverse momentum distributions of partons and their correlations at a low normalization point. We study this phenomenon in an effective description of the low-energy dynamics in terms of chiral constituent quark degrees of freedom, which refers to the large-N c limit of QCD. The nucleon is obtained as a system of constituent quarks and antiquarks moving in a self-consistent classical chiral field (relativistic mean-field approximation, or chiral quark-soliton model). The calculated transverse momentum distributions of constituent quarks and antiquarks are matched with QCD quarks, antiquarks and gluons at the chiral symmetry-breaking scale ρ −2. We find that the transverse momentum distribution of valence quarks is localized at $ p_T^2\sim {R^{-2 }} $ and roughly of Gaussian shape. The distribution of unpolarized sea quarks exhibits a would-be power-like tail ~ $ {1 \left/ {{p_T^2}} \right.} $ extending up to the chiral symmetry-breaking scale. Similar behavior is observed in the flavor-nonsinglet polarized sea. The high-momentum tails are the result of short-range correlations between sea quarks in the nucleon’s light-cone wave function, which are analogous to short-range N N correlations in nuclei. We show that the nucleon’s light-cone wave function contains correlated pairs of transverse size ρ ≪ R with scalar-isoscalar (Σ) and pseudoscalar-isovector (Π) quantum numbers, whose internal wave functions have a distinctive spin structure and become identical at $ p_T^2\sim {\rho^{-2 }} $ (restoration of chiral symmetry). These features are model-independent and represent an effect of dynamical chiral symmetry breaking on the nucleon’s partonic structure. Our results have numerous implications for the transverse momentum distributions of particles produced in hard scattering processes. Under certain conditions the nonperturbative parton correlations predicted here could be observed in particle correlations between the current and target fragmentation regions of deep-inelastic scattering.
Oil Recovery by Alkaline Waterflooding

Flooding of oil containing organic acids with alkaline water under favorable conditions can result in recovery of around 50% of the residual oil left in a watered-out model. A high recovery efficiency results from the formation of a bank of viscous water-in-oil emulsion as surface active agents (soaps) are created by reactions of base in the water with the organic acids in the oil. The type and amount of organic acids in the oil, the pH and salt content of the water, and the amount of fines in the porous medium are the primary factors which determine the amount of additional oil recovered by this method. Interaction of alkaline water with reservoir rock largely determines the amount of chemical needed to flood a reservoir. Laboratory investigations using synthetic oils and crude oils show the importance of oil-water and liquid-solid interfacial properties to the results of an alkaline waterflood. A small field test demonstrated that emulsion banks can be formed in the reservoir and that chemical costs can be reasonable in selected reservoirs. Although studies have provided many qualitative guide lines for evaluating the feasibility of alkaline waterflooding, the economic attractiveness of the process must be considered on an individual reservoir.
Out of this world supersymmetry breaking

Abstract We show that in a general hidden sector model, supersymmetry breaking necessarily generates at one loop a scalar and gaugino mass as a consequence of the super-Weyl anomaly. We study a scenario in which this contribution dominates. We consider the Standard Model particles to be localized on a (3 + 1)-dimensional subspace or “3-brane” of a higher dimensional space-time, while supersymmetry breaking occurs off the 3-brane, either in the bulk or on another 3-brane. At least one extra dimension is assumed to be compactified roughly one to two orders of magnitude below the four-dimensional Planck scale. This framework is phenomenologically very attractive; it introduces new possibilities for solving the supersymmetric flavor problem, the gaugino mass problem, the supersymmetric CP problem, and the μ-problem. Furthermore, the compactification scale can be consistent with a unification of gauge and gravitational couplings. We demonstrate these claims in a four-dimensional effective theory below the compactification scale that incorporates the relevant features of the underlying higher dimensional theory and the contribution of the super-Weyl anomaly. Naturalness constraints follow not only from symmetries but also from the higher dimensional origins of the theory. We also introduce additional bulk contributions to the MSSM soft masses. This scenario is very predictive: the gaugino masses, squark masses, and A terms are given in terms of MSSM renormalization group functions.
Managing a 21st-Century Library Collection

Matt Goldner, the OCLC Product & Technology Advocate, delivered the keynote address at the MidSouth eResource Symposium, held at Mississippi State University, Mitchell Memorial Libraries on August 11, 2011. From a service provider's perspective, Goldner shared some emergent but critical issues that arise with the electronic revolution and how these issues might affect the future of academic libraries. The focus of this presentation is centered on how librarians should work actively and positively to seek solutions to those issues.