cssi/SciSciGPT-SciSciNet huggingface dataset:
The simulation of continuous arteriovenous hemodialysis with a mathematical model

Simulation of continuous arteriovenous hemodialysis with a mathematical model. We have developed a mathematical model that predicts the performance of continuous arteriovenous hemodialysis. Given patient (plasma protein concentration, hematocrit, mean arterial pressure, central venous pressure) and circuit (flow resistance, membrane hydraulic permeability, dialyzer mass transfer coefficient, ultrafiltrate column height, dialysate flow rate) characteristics as inputs, predictions of hydraulic and oncotic pressure distribution, filtration rate, blood flow, total, diffusive, and convective urea clearances are provided. The model was tested by perfusing a circuit with bovine blood under conditions of pure ultrafiltration, zero net ultrafiltration and dialysis, or combined ultrafiltration and dialysis (countercurrent dialysate flow at rates of 10, 20, and 30 ml/min). In order to permit computation, membrane hydraulic permeability and flow resistances were measured. Dialyzer mass transfer coefficient for urea could not be measured directly and so was determined by fitting model predictions to measured urea clearances. For all conditions of operation, a urea mass transfer coefficient of 0.014 cm/min successfully simulated the data. Predictions of blood flow, filtrate generation rate, and circuit pressure distribution were accurate. At lower dialysate flow rates, urea clearance approximated the sum of dialysate flow and filtration rate. At higher dialysate flows, however, departure from this ideal blood-dialysate equilibrium was observed. Model predictions regarding the relative contributions of diffusion and convection to urea clearance were explored. Under conditions of nearly perfect equilibration of urea between blood and dialysate at the blood inlet, the model predicts that the diffusive clearance of urea will increase with increasing rate of filtration and may exceed the rate of dialysate inflow.
Investigation of the Charge Compensation Mechanism on the Electrochemically Li-Ion Deintercalated Li1-xCo1/3Ni1/3Mn1/3O2 Electrode System by Combination of Soft and Hard X-ray Absorption Spectroscopy

In situ hard X-ray absorption spectroscopy (XAS) at metal K-edges and soft XAS at O K-edge and metal L-edges have been carried out during the first charging process for the layered Li1-xCo1/3Ni1/3Mn1/3O2 cathode material. The metal K-edge XANES results show that the major charge compensation at the metal site during Li-ion deintercalation is achieved by the oxidation of Ni2+ ions, while the manganese ions and the cobalt ions remain mostly unchanged in the Mn4+ and Co3+ state. These conclusions are in good agreement with the results of the metal K-edge EXAFS data. Metal L-edge XAS results at different charge states in both the FY and PEY modes show that, unlike Mn and Co ions, Ni ions at the surface are oxidized to Ni3+ during charge, whereas Ni ions in the bulk are further oxidized to Ni4+ during charge. From the observation of O K-edge XAS results, we can conclude that a large portion of the charge compensation during Li-ion deintercalation is achieved in the oxygen site. By comparison to our earlier res...
Informed consent in emergency settings.

It is often difficult for emergency physicians to comply with the doctrine of informed consent. Patients suffering true emergencies require immediate treatment, and patients who are unable to give consent, because they are either incompetent or underage, are seen frequently in emergency departments. We examine the legal requirements of informed consent in emergency settings, with specific examples illustrated by Connecticut statutes. General guidelines for developing departmental policies are suggested.
Metallacarboranes: New synthetic strategies and structural patterns

A summary of the latest results in the authors' laboratories covering three areas is presented. The results of the controlled syntheses of oxide ion encapsulating lanthana- carboranes, by the introduction of stoichiometric amounts of H 2 O in the synthesis reactions, and the strictures of the resulting compounds were discussed. The scope and limitations of a general method for the synthesis of the open pentadienyl complexes were presented. In ad- dition, the results of a systematic study of the reactions of the (2,n-(SiMe 3 ) 2 -nido- 2,n-C 2 B 4 H 4 ) 2- (n = 3, 4) with the late transition-metal salts MCl 2 (M = Fe, Co, Ni) were dis- cussed.
Quickly bounding diagonal edge lengths in tessellated bilinear patches

We present QuickBound, an algorithm for quickly determining whether a uniformly tessellated grid derived from a bilinear patch satisfies a maximum edge length threshold. Our approach generalizes the well-known technique of bounding the length of all horizontal and vertical edges in the uniformly tessellated grid by checking only a small, constant number of edges. We generalize this technique to apply to all diagonal edges. Our approach, called Quick-Bound, reduces the time complexity of determining whether an (m face x n face) grid satisfies the edge length threshold from O(mxn) to O(1). We provide a proof of correctness for QuickBound and also measure its effectiveness in a real-time bilinear patch visualizer.
Peru's return toward an open economy: Macroeconomic complications and structural questions

Abstract The Peruvian program of stabilization and liberalization initiated in August 1990 has been more extreme than those in Mexico in the 1980s or in Chile in the Pinochet period. It has involved exceptionally high costs: potentially constructive changes are interacting with each other in ways adverse for recovery of production, employment, and exports. It could worsen the country's persisting strains of poverty and violence, or could on the contrary help answer them, depending on how liberalization is pursued. Comparisons with other liberalization programs, especially with the two different versions used in Chile, point to alternatives that might be helpful for Peru and for the design of such programs in other countries.
Electron screening in molecular fusion reactions

Abstract Recent laboratory experiments have measured fusion cross sections at center-of-mass energies low enough for the effects of atomic and molecular electrons to be important. To extract the cross section for bare nuclei from these data (as required for astrophysical applications), it is necessary to understand these screening effects. We study electron screening effects in the low-energy collisions of Z = 1 nuclei with hydrogen molecules. Our model is based on a dynamical evolution of the electron wave functions within the TDHF scheme, while the motion of the nuclei is treated classically. We find that at the currently accessible energies the screening effects depend strongly on the molecular orientation. The screening is found to be larger for molecular targets than for atomic targets, due to the reflection symmetry in the latter. The results agree fairly well with data measured for deuteron collisions on molecular deuterium and tritium targets.
k-HYPONORMALITY OF MULTIVARIABLE WEIGHTED SHIFTS

We characterize joint k-hyponormality for 2-variable weighted shifts. Using this characterization we construct a family of examples which establishes and illustrates the gap between k-hyponormality and (k+1)-hyponormality for each k⩾1. As a consequence, we obtain an abstract solution to the Lifting Problem for Commuting Subnormals.
General instability and face wrinkling of sandwich plates - Unified theory and applications.

The governing equations and applicable boundary conditions for sandwich plates with ideally orthotropic cores (honeycomb) are presented. The equations and boundary conditions are the first to be derived variationally with both transverse shear and normal strain effects included. The variational development, based on potential energy and the use of Lagrange multipliers to introduce face-core continuity requirements, leads to the desired results. It is noted that for symmetric buckling there are two multiple-choice boundary conditions per plate edge, and for antisymmetric buckling there are five multiple-choice boundary conditions per plate edge. The theory presented lends itself to certain exact solutions of the governing equations, where boundary conditions permit, and approximate solutions via the Rayleigh-Ritz procedure for more general problems. Buckling criteria are presented in the form of design charts, including both general instability and face wrinkling, for plates with one type of simple support, and for plates with one type of clamped loaded edges and simply supported unloaded edges. The ramifications of the present work relative to existing highly restricted solutions are examined and discussed.
Zeroes of the Jones polynomial

Abstract We study the distribution of zeroes of the Jones polynomial V K ( t ) for a knot K . We have computed numerically the roots of the Jones polynomial for all prime knots with N ⩽10 crossings, and found the zeroes scattered about the unit circle | t |=1 with the average distance to the circle approaching a nonzero value as N increases. For torus knots of the type ( m , n ) we show that all zeroes lie on the unit circle with a uniform density in the limit of either m or n →∞, a fact confirmed by our numerical findings. We have also elucidated the relation connecting the Jones polynomial with the Potts model, and used this relation to derive the Jones polynomial for a repeating chain knot with 3 n crossings for general n . It is found that zeroes of its Jones polynomial lie on three closed curves centered about the points 1,i and −i. In addition, there are two isolated zeroes located one each near the points t ± =e ±2 π i/3 at a distance of the order of 3 −( n +2)/2 . Closed-form expressions are deduced for the closed curves in the limit of n →∞.
Copper(II) catalysis provides cyclohexanone-derived propargylamines free of solvent or excess starting materials: sole by-product is water

A high-yielding three-component reaction proceeds under mild, solvent-free conditions for access to a wide variety of fully-substituted propargylamines. Inexpensive copper(II) chloride catalyzes the coupling of equimolar amounts of amines, alkynes, and cyclohexanone such that the only by-product is one equivalent of water.
Multiple Phases of Gels and Biological Implications

Synthetic polymer gels are known to exist in two phases - swollen and collapsed [1,2]. Volume transition occurs between the phases either continuously or discontinuously. More than two phases are found in gels consisting of copolymers of randomly distributed positively and negatively charged groups. They are characterized by distinct degrees of swelling; the gel can take one of a set of swelling values, but none of the intermediate values. The number of phases depends on the composition of positively and negatively charged monomers: the number decreases from a maximum of seven at a particular composition to one at pure cationic or anionic gel compositions. In these gels, polymer segments interact with each other through attractive or repulsive electrostatic interactions and through hydrogen bonding. The combination of these forces appears to result in multiple phases.The multiple phases seem to have important biological implications. The finding demonstrates that a polymer system can take a stable state o...
Verification of the Heat-Field Concept for Sonic-Boom Alleviation

The results of an experimental program carried out in the NASA-Langley 4 x 4 ft supersonic pressure tunnel to investigate the validity of the heat-field concept for sonic-boom alleviation are reported herein. The basic idea of the heat-field concept is to heat the flow about a supersonic aircraft in such a manner as to obtain an increase in effective aircraft shape (area distribution) that will result in a shock-free pressure signature on the ground. In the program, pressure signatures were measured below a series of wind-tunnel models to provide a step-by-step verification of the concept. For the key model tested, nitrogen is passed through the near of an off-axis slender fin situated below a representative SST configuration having its lift equivalence in volume. Comparisons of pressure signatures for this model with no flow, cold flow, and heated flow through the fin demonstrated substantial effects due to flow and due to heat, essentially verifying the use of mass flow and heat fields for providing equivalent area in supersonic flow. In addition, the ability of an off-axis slender fin to produce a finite-rise-time signature in the presence of lift was demonstrated by testing a wing-body model both with and without a solid fin.
Computationally fast harmonic balance methods for unsteady aerodynamic predictions of helicopter rotors

A harmonic balance technique for the analysis of unsteady flows about helicopter rotors in forward flight and hover is presented in this paper. The aerodynamics of forward flight are highly nonlinear, with transonic flow on the advancing blade, subsonic flow on the retreating blade, and stalled flow over the inner portion of the rotor. Nevertheless, the unsteady flow is essentially periodic in time making it well suited for frequency domain analysis. The present method uses periodic boundary conditions that allows one to model the flow field on a computational grid around a single helicopter blade, no matter the actual blade count. Using this approach, we compute several solutions, each one corresponding to one of several instants in time over one period. These time levels are coupled to each other through a spectral time derivative operator in the interior of the computational domain and through the far-field and periodic boundary conditions around the boundary of the domain. In this paper, we apply the method to the three-dimensional Euler equations (although the method can also be applied to three-dimensional viscous flows), and examine the steady and unsteady aerodynamics about wings and rotors.
Marginal stability diagrams for infinite-n ballooning modes in quasi-symmetric stellarators

By varying the pressure-gradient and average shear at a selected surface in a given arbitrary stellarator equilibrium and by inducing a coordinate variation such that the perturbed state remains in equilibrium, a family of magnetohydrodynamic equilibria local to the surface is constructed. The equilibria are parameterized by the pressure-gradient and averaged magnetic shear. The geometry of the surface is not changed. The perturbed equilibria are analysed for infinite-n ballooning stability and marginal stability diagrams are constructed that are analogous to the (s, α) diagrams constructed for axisymmetric configurations.The method describes how pressure and rotational-transform gradients influence the local shear, which in turn influences the ballooning stability. Stability diagrams for the quasi-axially symmetric NCSX, a quasi-poloidally symmetric configuration and the quasi-helically symmetric HSX are compared. Regions of second-stability are observed in both NCSX and the quasi-poloidal configuration, whereas no second-stable region is observed for the quasi-helically symmetric device.To explain the different regions of stability, the curvature and local shear of the quasi-poloidal configuration are analysed. The results are seemingly consistent with the following simple explanation: ballooning instability results when the local shear is small in regions of bad curvature with sufficient pressure-gradient. Examples will be given that show that the structure and stability of the ballooning mode is determined by the structure of the potential function arising in the Schrodinger form of the ballooning equation.
Source regions for type II radio bursts

The flares associated with reported type II bursts from 1964–1973 (hereafter abbreviated source-flares) are analyzed with respect to their importance, duration, and heliographic distribution. The source-flares for type II bursts generally are normal to small in area and normal to brilliant in intensity; however, they have slightly longer durations than would be expected from flares with such small areas. Flares associated with type II bursts are distributed uniformly east and west of the central meridian. This implies that type II bursts cannot be narrow-beamed, radially-propagating radio emitters. The latitude of the occurrence of source-flares shows a drift with time that is not significantly different from that of sunspots. The drift rate is a maximum during the period of maximum solar activity. The heliographic distribution of source-flares shows large-scale organization into similarly shaped regions (source-regions) separated by 180° of longitude in each polar hemisphere. The shape of the source-regions differs between the northern and the southern hemispheres. The source-regions exhibit growth and motion characteristics which suggest that their development is due partly to the effects of differential rotation. An analysis of the plage regions which are associated with source-flares shows that relatively few plages ever produce type II bursts, yet certain plages produce type II bursts repeatedly. One active region produced type II bursts on six consecutive disc passages. Since the source-regions for type II bursts are large-scale, persistent solar features that show motion and development related to the solar cycle, an evaluation of the distinctive fluid motion characteristics of these regions appears to be an important step in the determination of specific environmental configurations which can produce solar shock waves.
Bubble Universe Dynamics After Free Passage

We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by ‘free passage’ dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.
Why quantum dynamics is linear

A seed George planted 45 years ago is still producing fruit now. In 1961, George set out the fundamental proposition that quantum dynamics is described most generally by linear maps of density matrices. Since the first sprout from George's seed appeared in 1962, we have known that George's fundamental proposition can be used to derive the linear Schrodinger equation in cases where it can be expected to apply. Now we have a proof of George's proposition that density matrices are mapped linearly to density matrices, that there can be no nonlinear generalization of this. That completes the derivation of the linear Schrodinger equation. The proof of George's proposition replaces Wigner's theorem that a symmetry transformation is represented by a linear or antilinear operator. The assumption needed to prove George's proposition is just that the dynamics does not depend on anything outside the system but must allow the system to be described as part of a larger system. This replaces the physically less compelling assumption of Wigner's theorem that absolute values of inner products are preserved. The history of this question is reviewed. Nonlinear generalizations of quantum mechanics have been proposed. They predict small but clear nonlinear effects, which very accurate experiments have not seen. This begs the question. Is there a reason in principle why nonlinearity is not found? Is it impossible? Does quantum dynamics have to be linear? Attempts to prove this have not been decisive, because either their assumptions are not compelling or their arguments are not conclusive. The question has been left unsettled. The simple answer, based on a simple assumption, was found in two steps separated by 44 years.
Minimizing Constant Mean Curvature Hypersurfaces in Hyperbolic Space

We study the constant mean curvature (CMC) hypersurfaces in \(\mathbb{H}^{n+1}\) whose asymptotic boundaries are closed codimension-1 submanifolds in \(S^{n}_{\infty}(\mathbb{H}^{n+1})\). We consider CMC hypersurfaces as generalizations of minimal hypersurfaces. We naturally generalize some notions of minimal hypersurfaces like being area-minimizing, convex hull property, exchange roundoff trick to CMC hypersurface context. We also give a generic uniqueness result for CMC hypersurfaces in hyperbolic space.
Time-invariant structure of nonstationary atmospheric turbulence

where t=(tI + t2)/2 and r = t2 — t1. In airplane preliminary design analyses, this time variability introduces certain analytical difficulties, since in order to incorporate turbulence response characteristics into such analyses the design engineer must make some rather ad hoc assumptions about the nature of the turbulence the aircraft is expected to encounter in its day-to-day flight envelope. Indeed, for any practical engineering results to emerge, the design engineer must impose a particular time variation on C(t,r). The r dependence is usually well known and can be rigorously modeled using the Dry den formulation, viz., exp (- IT I /A) where A— integral scale. A typical time variation imposed by design engineers is the "one-minus-cosine" gust variation. Such variations can often lead to fatigue life problems through nonconservative failure criteria for the aircraft structure, especially if the aircraft ocassionally encounters turbulence whose time variation is something other than the "one-minus-cosine" for which it was designed; such occurrences are not at all uncommon. In this Note, it is established that nonstationary atmospheric turbulence has a distinct well-defined timeinvariant statistical structure. This structure is duly posed in terms of the aircraft response parameters. To the aeronautical design engineer, this time-invariant characteristic suggests that there is a mode in which the effects of nonstationary turbulence can be incorporated into preliminary design analyses in a very unified and cogent fashion. To be sure, the present results remove the need for making arbitrary decisions and/or assumptions about the time dependence of the statistical structure of nonstationary turbulence; simultaneously, they also show how the effects of virtually all types of nonstationary turbulent behavior can be incorporated into a single response statistic.
Re‐conceiving information studies: a quantum approach

Purpose – This paper aims to demonstrate that fundamental aspects of quantum theory can be applied to work in information studies (IS).Design/methodology/approach – The field of information studies is so broad and extensive that it requires similar breadth of epistemic and methodological features in order to fulfill its inherent promise as a human enterprise. Quantum theory holds promise as a way to shape questions and inquiry in information studies (IS).Findings – The revolutionary elements of quantum theory, such as entanglement, nonlocality, etc. can be applied to information, especially language‐based communication.Research limitations/implications – Perhaps most especially, the non‐ or extra‐mathematical components of quantum theory offer ontological and epistemic modes of thought which apply to information. Those modes of thought are ripe with conceptual promise for examination of, for example, information as objective entity and as complex material substance. This paper explores some of the potenti...
Why Are There so Few Magnetic Ferroelectrics

Multiferroic magnetoelectrics are materials that are both ferromagnetic and ferroelectric in the same phase. As a result, they have a spontaneous magnetization that can be switched by an applied magnetic field, a spontaneous polarization that can be switched by an applied electric field, and often some coupling between the two. Very few exist in nature or have been synthesized in the laboratory. In this paper, we explore the fundamental physics behind the scarcity of ferromagnetic ferroelectric coexistence. In addition, we examine the properties of some known magnetically ordered ferroelectric materials. We find that, in general, the transition metal d electrons, which are essential for magnetism, reduce the tendency for off-center ferroelectric distortion. Consequently, an additional electronic or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously.
BACK PAIN IN CHILDREN

Children and adolescents occasionally have back symptoms, but rarely come to a physician's office for more severe back pain. When a child or adolescent appears in the clinic with complaints of back pain, a careful detailed evaluation is appropriate. The incidence of findings in children with significant back pain is high; therefore, a detailed history, physical examination, and evaluation are needed. It is also legitimate to continue monitoring children even if no obvious cause is initially identified because often a diagnosis subsequently will be made.
Stochastic Modeling of Service Life of Concrete Structures in Chloride-Laden Environments

Chloride-induced rebar corrosion is a common degradation process for concrete infrastructure, which is a practical concern for cold-climate states and coastal areas. In this work, numeric models based on the FEM are utilized to study service life of concrete structures subject to chloride ingress, where two models are utilized. The first one deals with multiple ionic species in the concrete pore solution, while the second one only accounts for the presence of chloride ions. The stochastic nature of model inputs is taken into consideration because each factor of interest is subject to random variabilities and inherent uncertainties. Specifically, the surface chloride concentrations and concrete cover depth follow the normal distribution; the diffusion coefficients obey the gamma distribution; the actual chloride threshold features the triangular distribution. The nonlinear partial differential equations (PDEs) to characterize the spatial and temporal evolution of ionic species are numerically solved, the results of which were utilized to elucidate the influence of various factors on concrete service life, such as mix design, surface chloride concentrations, cracking level, and coarse aggregate and concrete cover depth.
Adam Smith and Noneconomic Objectives

This note looks at Smith's critiques of bounties (read “subsidies”) on exports. Smith's analysis of bounties foreshadowed the basic trade policy framework of distortions and noneconomic objectives. While Smith did not develop the theory of distortions, he captured the logic of the theory of noneconomic objectives and actually ranked policy alternatives based upon their relative social costs. Corden (1957) first ranked tariffs versus production subsidies within a noneconomic objectives framework, and Johnson (1960) first used the term in its modern sense, but the formulation of the general framework lies with Smith.
A texture synthesis method for liquid animations

Liquid simulation techniques have become a standard tool in production environments, producing extremely realistic liquid motion in a variety of films, commercials, and video games. Surface texturing is an essential computer graphics tool, which gives artists additional control over their results by allowing them to stylize surfaces or add detail to a lowresolution simulations. For example, an artist could use texturing techniques to add the appearance of foam to a wave, bubbles to beer, or fat globules to soup. Unfortunately, texturing liquid surfaces is difficult because the surfaces have no inherent parameterization. Creating a temporally consistent parameterization is extremely difficult for two primary reasons. First, liquid simulations are characterized by their complex and frequent topological changes. These topological changes result in significant discontinuities in any parameter tracked on the surface. Second, liquid surfaces tend to stretch and compress dramatically over the course of a simulation. Similarly, an advected parameterization will also stretch and compress. For these reasons, advected texture coordinates are often unsuitable for texturing liquid surfaces. In this sketch we present a method for generating textures on animated liquid surfaces. Rather than advecting texture coordinates on the surface, we synthesize a new texture at every frame. We initialize the texture with color values advected from the surface at the previous frame. We then run an optimization procedure which attempts to match the surface texture to an input sample texture and, for temporal coherence, the advected colors.
Electronic interactions in strongly correlated systems: what is the glue for high temperature superconductivity?

Recent observation of a "kink" in single-particle dispersion in photoemission experiments on cuprate superconductors has re-initiated a heated debate over the issue of a boson that "mediates" the pairing in cuprates. If the "kink" is indeed caused by interaction with a bosonic excitation, then there are two possible candidates: phonons and spin fluctuations. Here, the role of anti-ferromagnetic spin fluctuations in shaping the phase diagram of cuprate superconductors will be discussed. By using the local (momentum-integrated) dynamic spin susceptibility, recently measured in neutron scattering experiments to high energies, the electronic self-energies are calculated that agree in many aspects with those measured directly in angular resolved photoemission and optical spectroscopies. The spin fluctuations therefore seem to play a role typically played by phonons in renormalizing single particles. The key question emerging from this picture is whether the coupling detected in angle-resolved photoemission spectroscopy (ARPES) reflects the mediating boson, i.e. whether the spin fluctuations may be responsible for superconducting pairing.
Firm performance and knowledge spillovers from academic, industrial and foreign linkages: the case of China

Firm performance may be enhanced by linkages with academic institutions, other firms, and foreign markets that confer knowledge spillovers as well as internal R&D that creates firm-specific knowledge. In particular, firm productivity and innovation may be enhanced by positive externalities from knowledge and technology produced by universities and research institutions (URIs) and diffused to the domestic economy. Productive contributions from such linkages might be particularly expected in China, where policy measures have explicitly supported and facilitated connections between URIs and firms to stimulate economic development and competitiveness. In this paper, we measure the performance impact of such knowledge spillovers in Chinese firms by using a variety of specifications, estimators, and robustness checks, including an “instrumental variable” specification that controls for endogeneity. We find more patent activity in Chinese firms with URI connections and enhanced firm productivity particularly from linkages with research institutions (RIs). Introduction of new products, processes, and new businesses is also positively associated with linkages with research institutions, as well as with linkages with other firms.
Anomaly Matching Conditions in Supersymmetric Gauge Theories

Abstract Sufficient conditions are proven for 't Hooft's consistency conditions to hold at points in the moduli space of supersymmetric gauge theories. Known results for anomaly matching in supersymmetric QCD are rederived as a sample application of the results. The results can be used to show that the anomaly matching conditions hold for s -confining theories.
Chemoselective catalytic oxidation of sulfides to sulfones with tetrapropylammonium perruthenate (TPAP)

Abstract Tetrapropylammonium perruthenate has been found to be an efficient catalyst for the conversion of sulfides to sulfones. The method is highly chemoselective and isolated double bonds are generally unaffected.
New clues to the evolution of dwarf early‐type galaxies

Surface photometry of 18 Virgo cluster dwarf elliptical (dE) and dwarf lenticular (dS0) galaxies, made by Gavazzi et al. in the H band (1.65 μm) and in the B band (0.44 μm), shows that the ratio of the effective radii ofthese stellar systems in the B and H bands, r e B /r e H , ranges between 0.7 and 2.2. In particular, dwarf ellipticals and lenticulars with a red total colour index B - H (i.e. with 3.2 < B- H < 4) have equal effective radii in these two passbands. By contrast, blue (i.e. with 2.5 < B- H < 3.1) dEs and dS0s have B-band effective radii about 50 per cent larger than the H-band ones, on average. Consistently, strong negative gradients in B - H along the galactocentric radius are found to be associated with blue total colours. This trend is not found in a sample of 29 giant E and S0 galaxies of the Coma cluster with analogous data available in the literature. These early-type giants span a broad range in r e b /r e H (0.2-2.2), with a mean r e B /r e H ∼ 1.1, but a narrow range in (red) colour (3.3 < B- H < 4.2). In these stellar systems, colour gradients are usually interpreted as arising either from age/metallicity gradients along the radial coordinate or from dust attenuation, whatever the total colour of the system is. Assuming each of these three distinct interpretations of the origin of colour gradients, we discuss the origin of the association of strong negative colour gradients with blue colours found in the early-type dwarfs under study, in relation with current scenarios of formation and evolution of dE and dS0 galaxies.
Cross-linking of gelatin capsules and its relevance to their in vitro-in vivo performance

The present review deals with the chemistry of gelatin cross-linking under conditions that are relevant to pharmaceutical situations. Mechanistic rationalizations are offered to explain gelatin cross-linking under "stress" conditions. These include elevated temperature and high humidity conditions. In addition, the chemical interactions between gelatin and aldehydes, such as formaldehyde and other formulation excipients, are discussed. The literature on the in vitro and in vivo dissolution and bioavailability of a drug from stressed gelatin capsules and gelatin-coated tablets is reviewed. Cross-linking phenomena, occurring in stressed hard gelatin capsules and gelatin-coated tablets, could cause considerable changes in the in vitro dissolution profiles of drugs. However, in a few cases, the bioavailability of the drug from the stressed capsules is not significantly altered when compared to that obtained from freshly packed capsules. It is concluded that, as with other drug-delivery systems, careful attention should be paid to the purity and chemical reactivity of all excipients that are to be encapsulated in a gelatin shell. It is suggested that in vitro dissolution tests of hard gelatin-containing dosage forms be conducted in two stages, one in a dissolution medium without enzymes and secondly in dissolution media containing enzymes (pepsin at pH 1.2 or pancreatin at pH 7.2, representing gastric and intestinal media, respectively) prior to in vivo evaluation. Such in vitro tests may constitute a better indication of the in vivo behavior of gelatin-encapsulated formulations. Furthermore, testing for contamination with formaldehyde as well as low molecular weight aldehydes should be a standard part of excipient evaluation procedures.
Onset of breakdown and formation of cathode spots

When an increasing diode voltage is applied, enhanced field emission of electrons begins from a growing number of small spots or whiskers on the cathode surface. This stimulates desorption of weakly bound adsorbates from the surface of a whisker. As the diode voltage increases, the 100-V equipotential surface moving toward the cathode is met by the desorbed neutrals moving away from the cathode, resulting in sharp risetime for the onset of ionization of desorbed neutrals by field-emitted electrons. Positive ions produced in the ionization region a few microns from the electron emitting spot are accelerated back to it. This bombardment leads to surface heating of the spot. The onset of breakdown by this mechanism requires much less current than the Joule heating mechanism. The localized buildup of plasma above the electron emitting spot leads to pressure and electric field distributions that ignite unipolar arcs. The high current density of the unipolar arc and the associated surface heating by ions result in the explosive formation of cathode spot plasma. >
The Age and Progenitor Mass of Sirius B

The Sirius AB binary system has masses that are well determined from many decades of astrometric measurements. Because of the well-measured radius and luminosity of Sirius A, we employed the TYCHO stellar evolution code to determine the age of the Sirius AB binary system accurately, at 225-250 Myr. Note that this fit requires the assumption of solar abundance and the use of the new Asplund et al. primordial solar metallicity. No fit to Sirius A's position is possible using the old Grevesse & Sauval scale. Because the Sirius B white dwarf parameters have also been determined accurately from space observations, the cooling age could be determined from recent calculations by Fontaine et al. or Wood to be 124 ± 10 Myr. The difference in the two ages yields the nuclear lifetime and mass of the original primary star, 5.056 M☉. This result yields, in principle, the most accurate data point at relatively high masses for the initial-to-final mass relation. However, the analysis relies on the assumption that the primordial abundance of the Sirius stars was solar, based on membership in the Sirius supercluster. A recent study suggests that its membership in the group is by no means certain.
Development of Soft X-ray Streak Cameras at Lawrence Livermore National Laboratory

Soft x-ray streak cameras are used in conjunction with several instruments for the diagnostic of laser irradiated targets. A program was undertaken to develop cameras satisfying the requirements of the laser facility, to improve the reliability and performance of the camera and to reduce the level of effort required to set and operate each diagnostic. The implemented soft x-ray streak cameras can be operated either manually or automatically.
Synthesis and characterization of new amine-imine ligands based on trans-2,5-disubstituted pyrrolidines

Abstract We present a modular synthesis of a new class of chiral N,N-chelating ligands containing the C2-symmetrictrans-2,5-disubstituted pyrrolidine moiety linked to a pyridine ring. (−)-2-[(2R,5R)-2,5-Dimethylpyrrolidin-1-ylmethyl]pyridine (11, (R,R)-MePMP), (−)-2-[2-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)ethyl]pyridine (12, (R,R)-MePEP), and (+)-2-[(2R,5R)-2,5-diphenylpyrrolidin-1-ylmethyl]pyridine (13, (R,R)-PhPMP) have been prepared. The X-ray structure of the (η3-allyl)Pd complex of (R,R)-MePMP (11) is reported.
Synthesis of 9,10-dihydrosilaanthracenes with substituents ortho to the silicon and methylene bridges

Abstract The generation of 9,10-dihydrosilaanthracenes with substituents on benzo ring carbons, specifically in the 4,5-positions adjacent to the methylene bridge, has been developed. Attempts to prepare the 1-8-isomer where the substituents are adjacent to the silicon bridge are also described. The diarymethane precursors to the substituted 9,10-dihydrosilaanthracenes required the synthesis of 2,3-dihalotoluenes as well as isomeric 2,6-disubstituted benzaldehydes which were then condensed to diarylmethanols through the Grignard reagents. Ring closure to the 4,5-dimethyl-9,9-dialkyl-9,10-dihydro-9-silaanthracene, I, required the use of Rieke magnesium. The structure of I (alkyl = i Pr) was determined and demonstrates that the introduction of substituents adjacent to the methylene bridge causes the dihydrosilaanthracene framework to become nearly planar with a dihedral (or butterfly) angle of 170°C.
Asymmetric allylic alkylation of ketone enolates: an asymmetric Claisen surrogate.

The combination of catalytic palladium(0) and Trost ligand provides an effective catalyst for the rearrangement of allyl β-ketoesters. The mechanism of the transformation involves formation of π-allyl palladium intermediates which undergo enantioselective attack by ketone enolates. Decarboxylation of β-ketocarboxylates allows regiospecific generation of enolates under extremely mild conditions.
Gravitational ionization: a chaotic net in the Kepler system

The long-term nonlinear dynamics of a Keplerian binary system under the combined influences of gravitational radiation damping and external tidal perturbations is analysed. Gravitational radiation reaction leads the binary system towards eventual collapse, while the external periodic perturbations could lead to the ionization of the system via Arnold diffusion. When these two opposing tendencies nearly balance each other, interesting chaotic behaviour occurs which is briefly studied in this paper. It is possible to show that periodic orbits can exist in this system for sufficiently small damping. Moreover, we employ the method of averaging to investigate the phenomenon of capture into resonance.
Skills possessed and skills useful for MIS practitioners: a research report

The major report setting forth major curricular recommendations for graduate professional programs in information systems appeared in 1972. The context of the report was an information systems environment and developmental process distinguishing between two analyst activities: information analysis and design analysis. Figure 1 seeks to draw the ACM distinction. And that distinction is carried forth into skill sets identified as desirable for graduates. Six clusters or groupings of skills are offered (people, models, systems, computers, organizations, and society) and thirteen courses are proposed to impart those skills. The thirteen courses are set forth as a two-year graduate core curriculum for both information and design analysts.
Nested Bars in Disk Galaxies : No Offset Dust Lanes in Secondary Nuclear Bars

Under certain conditions, subkiloparsec nuclear bars form inside large-scale stellar bars of disk galaxies. These secondary bars spend a fraction of their lifetime in a dynamically decoupled state, tumbling in the gravitational field of the outer bars. We analyze the flow pattern in such nested-bar systems under the conditions of negligible self-gravity and find that secondary bars differ fundamentally from their large-scale counterparts in gas flow pattern and other dynamical properties. In particular, the gas flow across the bar-bar interface in these systems can be more chaotic or more regular in nature and, contrary to predictions, has no difficulty in penetrating the secondary bars along the primary large-scale shocks. The outer parts of both short and long nuclear bars (with respect to their corotation) appear to be depopulated of gas, while deep inside them the flow exhibits low Mach numbers and follows oval-shaped orbits with little dissipation. Long nuclear bars remain gas-rich longer and for this relatively short period of time are largely of a rectangular shape, again with a small dissipation. We find that gas-dominated and star-dominated nuclear bars avoid the bar-bar interface, making both types of bars short relative to their corotation. Furthermore, our earlier work has shown that dynamically coupled secondary bars exhibit a similarly relaxed low-dissipation flow as well. Therefore, no large-scale shocks form in the nuclear bars, and consequently, no offset dust lanes are expected there. We find that offset dust lanes cannot be used in the search for secondary (nuclear) bars. Finally, we discuss the importance of gas self-gravity in the further evolution of these systems.
Superconducting order parameters with sign changes: The density of states and impurity scattering.

We compute ${\mathit{N}}_{\mathit{s}}$(E) for a family of superconducting order parameters with sign changes at the Fermi surface, and find surprising results. We consider all \ensuremath{\Delta}(k^) such that \ensuremath{\Delta}(k^)=+${\mathrm{\ensuremath{\Delta}}}_{0}$ on part of the Fermi surface, and \ensuremath{\Delta}(k^)=-${\mathrm{\ensuremath{\Delta}}}_{0}$ on the rest, yielding an average of 〈\ensuremath{\Delta}(k^)〉=r${\mathrm{\ensuremath{\Delta}}}_{0}$, where 0\ensuremath{\le}r\ensuremath{\le}1. For 0r1, as the impurity concentration increases, the number of low-lying states increases, and the superconductor becomes gapless. As the impurity concentration is further increased, the gap in the spectrum is restored, and ${\mathit{N}}_{\mathit{s}}$(E) approaches the pure limit BCS form, with a renormalized gap. \textcopyright{} 1996 The American Physical Society.
Selective cycloalkanone reductions using aluminum amalgam

Abstract Aluminum amalgam in aqueous tetrahydrofuran reduces cycloalkanones to their respective alcohols. The reaction exhibits sensitivity to the ring size and steric environment of the ketone.
Exponentially stable feedback control of discrete-time nonlinear distributed parameter systems on Banach spaces

Practical engineering systems require feedback control implementation in discrete-time; however, stable control of infinite-dimensional distributed parameter systems (DPS) is not always guaranteed. We introduce two nonlinear controllers, a DPS one and a finite-dimensional one with residual mode filter compensation, which produce local exponential closed-loop stability for nonlinear discrete-time DPS on Banach spaces under appropriate local Lipschitz continuity conditions. Both controllers operate in discrete-time and our results place no restrictions on the smoothness of the initial data in the Banach space.
Phoneme discrimination using connectionist networks

The application of connectionist networks to speech recognition is assessed using a set of eight representative phonetic discrimination problems chosen with respect to a theory of phonetics. A connectionist network model called the temporal flow model (TFM) is defined which represents temporal relationships using delay links and permits general patterns of connectivity. It is argued that the model has properties appropriate for time varying signals such as speech. Networks are trained using gradient descent methods of iterative nonlinear optimization to reduce the mean‐squared error between the actual and the desired response of the output units. Separate network solutions are demonstrated for all eight phonetic discrimination problems for one male speaker. The network solutions are analyzed carefully and are shown in every case to make use of known acoustic phonetic cues. The network solutions vary in the degree to which they make use of context‐dependent cues to achieve phoneme recognition. The network ...