Shifted contour auxiliary field Monte Carlo is implemented for molecular electronic structure using a plane-waves basis and norm conserving pseudopotentials. The merits of the method are studied by computing atomization energies of H2,H2, BeH2,BeH2, and Be2.Be2. By comparing with high correlation methods, DFT-based norm conserving pseudopotentials are evaluated for performance in fully correlated molecular computations. Pseudopotentials based on generalized gradient approximation lead to consistently better atomization energies than those based on the local density approximation, and we find there is room for designing pseudopotentials better suited for full valence correlation.
The loss of conformational freedom experienced by lipid chains in the vicinity of one, or two, impenetrable walls, representing the surfaces of hydrophobic transmembrane proteins, is calculated using a mean-field molecular-level chain packing theory. The hydrophobic thickness of the protein is set equal to that of the unperturbed lipid membrane (i.e., no ``hydrophobic mismatch''). The probability distributions of chain conformations, at all distances from the walls, are calculated by generating all conformations according to the rotational-isomeric-state model, and subjecting the system free energy to the requirement that the hydrophobic core of the membrane is liquid-like, and hence uniformly packed by chain segments. As long as the two protein surfaces are far apart, their interaction zones do not overlap, each extending over several molecular diameters. When the interaction zones begin to overlap, inter-protein repulsion sets in. At some intermediate distance the interaction turns strongly attractive, resulting from the depletion of (highly constrained) lipid tails from the volume separating the two surfaces. The chains confined between the hydrophobic surfaces are tilted away from the walls. Their tilt angle decreases monotonically with the distance from the walls, and with the distance between the walls. A nonmonotonic variation of the lipid-mediated interaction free energy between hydrophobic surfaces in membranes is also obtained using a simple, analytical, model in which chain conformations are grouped according to their director (end-to-end vector) orientations.
Investigates the role of the dissociation of phonological, semantic and morphological factors in morphological priming. Priming between morphologically related words in Hebrew determined by higher level linguistic characteristics and not reduced to phonological overlap; Potential of using both masked and cross-modal priming to examine morphological processing.
A solution of poly(4-vinyl-pyridine) in pyridine is converted into a gel over a 3 week period. The spontaneous self-organization is governed by interchain hydrogen bonding. These interactions resulted in a change of polymer's optical properties. Blue, green, and red emissions appear in the gel by appropriate excitation wavelength replacing the initial dark blue emission. Energy transfer between emitting centers is restricted because of the insulating nature of the polymer backbone.
SIR—I have recently read with much interest a paper by Taylor et al. entitled “Staging the Baboon Response to Group A Streptococci Administrated Intramuscularly: Descriptive Study of the Clinical Symptoms and Clinical Chemical Response Patterns” in Clinical Infectious Diseases [1]. While reading through the paper, it became apparent to me that articles published since 1959, which had described in great detail the pathophysiology of group A streptococcal injury (animal models), had not been cited in this article [2–7].
One review had already covered, in detail, many of the aspects related to your article [2], and had described a steep rise in glutamic oxaloacetic transaminase levels, sorbitol dehydro-genase (SOD), and in total lipids in animals injected with extracellular products [6]. In addition, Taylor et al. cite a study (reference 48) on theta toxin. Why not cite studies that show the effects of streptolysins S and O? Furthermore, the possible effects of streptolysin O (reference 52) and cysteine proteinase (reference 53) are mentioned. I would also like to note, for the interest of the readers, a paper by Ginsburg [8] that had shown that tumor cells could be killed and disintegrated, in a synergistic manner, by combining streptolysins S with a proteinase. The cysteine proteinase employed was isolated from streptococci and kindly supplied by Dr. Elliot from the Rockefeller Institute (New York City). Moreover, I would like to draw the attention of the authors to a more recent publication that has discussed in great detail synergistic mechanisms of cell injury. I refer to a review by Ginsburg and Kohen [9].
It is of great concern that the avoidance of citations of “old” and pioneering publications has assumed epidemic dimensions, especially among younger investigators. Today, although without abstracts, MEDLINE already offers citations from 1960 and later; however, a search for “older and obsolete” literature necessitates a review of the Index Medicus. This apparently might be too cumbersome for those who tend to read only titles and abstracts and not the full texts of articles. This dangerous trend in science is self-defeating, unscholarly, unacceptable, and also unethical. Unfortunately, this is how basic observations and ideas are “lost and buried for good.” The phrase “sic transit gloria mundi” is very appropriate. It is even more disturbing that the learned referees of the paper by Taylor et al., who have been expected to be knowledgeable of the older literature on streptococci, have failed to draw their attention to the existence of such “obsolete” and apparently unimportant publications. Unfortunately this is how basic observations are “rediscovered,” leading to the suffocation of the literature with “novel,” but redundant information.
I shall greatly appreciate receiving your comments regarding these issues and am also looking forward to learn what might be the future policies of the editorial board of the journal regarding strategies taken to better cope with lack of appropriate citations to support scientific publications.
Lay summary:
Social scientists have applied new science concepts (from quantum mechanics, chaos theory and new evolutionary biology) to political theory, in particular arguing that the principle of self-organization reflects the dynamics of liberal democracy. The article argues that this view is inaccurate and damaging. The self organizing principle does not depend on or lead to democracy. Furthermore this approach detracts from a focus on democratic institutions as the basis of a stable, healthy democracy.
Publication significance:
Understanding the elements that lead to the formation and maintenance of democratic systems is critical to understand how to nurture emerging democracies and maintain established ones. This article argues that the popular equation of the new sciences' concept of self-organization with the essence of liberal democracy is inaccurate. Instead, it emphasizes a focus on democratic institutions as the elements that shape the character of democratic systems and can ensure their continuity.
With varying aptitudes in different occupations,individuals typically maximize income by specializing in one occupation which promises the highest income. Due to numerous labor market imperfections anduncertainties, the choice of best occupation is accomplished with only partial success. We demonstrate that an income tax that reduces after-tax income differentials across occupations tends to exacerbate the errors of choice made by individuals. Following a model proposed by Tinbergen (1951) and developed by Houthakker (1974), we use Luce’s (1959) multinomial logit approach to evaluate the magnitude of the distortions due to errors in occupational choice caused by income taxation. In an example, we show that the deadweight loss can be as high as a third of total income.
The use of acrylic connecting bars in external fixators has become widespread in veterinary orthopaedics. One of the main advantages of an acrylic connecting bar is the ability to contour it into a curved shape. This allows the surgeon to place the transcortical pins according to safety and convenience considerations, without being bound by the requirement of the standard stainless steel connecting bar, that all transcortical pins be in the same plane.
The purpose of this study was to evaluate the stiffness of unilateral and bilateral medium-sized external fixator frames with different curvatures of acrylic connecting bars. Finite element analysis was used to model the various frames and obtain their stiffness under four types of load: Axial compression, four-point medio-lateral bending, four-point antero-posterior bending and torsion. The analysis also provided the maximal pin stresses occurring in each frame for each loading condition.
Based on the results of this study, curvatures of acrylic connecting bars of up to a maximal angular difference between pins of 25 degrees will result in very similar stiffness and maximal pin stresses to those of the equivalent, uniplanar stainless steel system. In both unilateral and bilateral systems the stiffness decreases slightly as angulation increases for axial compression and medio-lateral bending, increases slightly for torsion and increases substantially for antero-posterior bending.
Improved diffraction efficiency was observed in holograms stored in disordered conjugated polymer/glass composites. The conjugated polymers used were alkoxy substituted poly(phenylenevinylne) analogs and the glass matrices were zirconia-organosilica xerogels. Investigation of the mechanism of hologram formation revealed evidence of a photochromic process consisting of light induced photo-oxidation (bleaching) of the embedded conjugated polymer resulting in the formation of an absorption grating and a phase grating. Investigation of the hologram formation revealed that the process was oxygen dependent. Oxygen removal increases hologram formation time by more than an order of magnitude and halves the total hologram efficiency. The oxygen dependence was also highly correlated with photobleaching of the samples and beam interaction of the writing beams. The chemical transformations upon photobleaching were shown by infrared and Raman spectroscopy to involve chain scission and oxidation of the polymer at the vinylic position of the conjugated polymer. Film preparation of the composites was optimized showing a tenfold improvement in the holographic properties compared to our previous results. The optimized treatment method allows for a high, > 20%, diffraction efficiency, eta, to be obtained for the 2.5-mu m-thick polymer/glass films. Light sensitivity was compared for several polymer/glass composites and was correlated to the absorption curves and holographic diffraction efficiency showing that the new composites and film preparation techniques are promising for holographic materials sensitive in the blue and ultraviolet spectral regions. A method of information fixing by preventing oxygen entry to the composite film resulted in a fourfold increase of the erasure time. These findings suggest that holograms can be fixed for a long term by nonoxygen permeable coating, applied after hologram formation. (C) 2000 American Institute of Physics. [S0021- 8979(00)07114-0].
A novel approach for micropatterning of surfaces with organic and biological microstructures using the scanning electrochemical microscope (SECM) is described. The approach is based on the introduction of the spatial resolution by local deposition of gold particles followed by monolayer formation and functionalization. Specifically, gold patterns were deposited locally on silicon wafers with the SECM as a result of the controlled anodic dissolution of a gold microelectrode. The gold patterns were further used as microsubstrates for assembling cystamine monolayers to which either fluoresceine isothiocyanate (FIT) or glucose oxidase (GOD) were covalently attached. Characterization of the organic monolayers, as well as the biological activity of the enzyme patterns, was carried out by fluorescence microscopy and the SECM, respectively.[on SciFinder (R)]
A novel approach for micropatterning of surfaces with org. and biol. microstructures using the scanning electrochem. microscope (SECM) is described. The approach is based on the introduction of the spatial resoln. by local deposition of Au particles followed by monolayer formation and functionalization. Specifically, Au patterns were deposited locally on Si wafers with the SECM as a result of the controlled anodic dissoln. of a Au microelectrode. The Au patterns were further used as microsubstrates for assembling cystamine monolayers to which either fluoresceine isothiocyanate (FIT) or glucose oxidase (GOD) were covalently attached. Characterization of the org. monolayers, as well as the biol. activity of the enzyme patterns, was carried out by fluorescence microscopy and the SECM, resp. [on SciFinder(R)]
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An electrically controlled holographic switch is proposed as a building block for a free-space optical interconnection network. The switch is based on the voltage-controlled photorefractive effect in KLTN crystals at the paraelectric phase. It is built of electrically controlled Bragg gratings stored in the volume of the crystal. A compact switch that connects four high-speed fiber-optic communication channels with high efficiency is demonstrated experimentally. The switch performance is investigated and optimized. This switch is extremely attractive for cascaded switching arrays such as those found in multistage interconnect networks.
We present a theoretical analysis of the phase behavior of solutions containing DNA, cationic lipids, and nonionic (helper) lipids. Our model allows for five possible structures, treated as incompressible macroscopic phases: two lipid-DNA composite (lipoplex) phases, namely, the lamellar (L-alpha(C)) and hexagonal (H-II(C)) complexes; two binary (cationic/neutral) lipid phases, that is, the bilayer (L-alpha) and inverse-hexagonal (H-II) structures, and uncomplexed DNA. The free energy of the four lipid-containing phases is expressed as a sum of composition-dependent electrostatic, elastic, and mixing terms. The electrostatic free energies of all phases are calculated based on Poisson-Boltzmann theory. The phase diagram of the system is evaluated by minimizing the total free energy of the three-component mixture with respect to all the compositional degrees of freedom. We show that the phase behavior, in particular the preferred lipid-DNA complex geometry, is governed by a subtle interplay between the electrostatic, elastic, and mixing terms, which depend, in turn, on the lipid composition and lipid/DNA ratio. Detailed calculations are presented for three prototypical systems, exhibiting markedly different phase behaviors. The simplest mixture corresponds to a rigid planar membrane as the lipid source, in which case, only lamellar complexes appear in solution. When the membranes are ``soft'' (i.e., low bending modulus) the system exhibits the formation of both lamellar and hexagonal complexes, sometimes coexisting with each other, and with pure lipid or DNA phases. The last system corresponds to a lipid mixture involving helper lipids with strong propensity toward the inverse-hexagonal phase. Here, again, the phase diagram is rather complex, revealing a multitude of phase transitions and coexistences. Lamellar and hexagonal complexes appear, sometimes together, in different regions of the phase diagram.
