Corning (United States)

This article describes recent technical developments that have made the total-energy pseudopotential the most powerful ab initio quantum-mechanical modeling method presently available. In addition to presenting technical details of the pseudopotential method, the article aims to heighten awareness of the capabilities of the method in order to stimulate its application to as wide a range of problems in as many scientific disciplines as possible.

We present pseudopotential coefficients for the first two rows of the Periodic Table. The pseudopotential is of an analytic form that gives optimal efficiency in numerical calculations using plane waves as a basis set. At most, seven coefficients are necessary to specify its analytic form. It is separable and has optimal decay properties in both real and Fourier space. Because of this property, the application of the nonlocal part of the pseudopotential to a wave function can be done efficiently on a grid in real space. Real space integration is much faster for large systems than ordinary multiplication in Fourier space, since it shows only quadratic scaling with respect to the size of the system. We systematically verify the high accuracy of these pseudopotentials by extensive atomic and molecular test calculations. \textcopyright{} 1996 The American Physical Society.

ABSTRACT Viscosity of Simple Soda‐Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log 10 viscosity amounting to 0.6, those of Washburn et al. , being relatively too high. If correction for this is made, the isothermal curves of log 10 viscosity as a function of soda content are smooth up to 50% Na 2 O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type image where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO 2 , 2Na 2 O) due to Molecular Substitution of CaO, MgO and Al 2 O 3 for Na 2 O The effect is clearly brought out by plotting (from the results of English) the change of log 10 η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T a . If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log 10 η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1 2 O 3 ) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al 2 O 3 ) per 100°. At the aggregation temperature the change of log 10 η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al 2 O 3 . Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log 10 η due to substitution of an oxide for Na 2 O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na 2 O‐CaO‐SiO 2 . Change of Viscosity of Glass (4SiO 2 , 2Na 2 O) due to of Substitution of B 2 O 3 for SiO 2 The change of log 10 η (from the results of English) is plotted as a function of temperature, and also the change of log 10 η per per cent B 2 O 3 . The curves are more complex than for the substitution for Na 2 O.

The confinement of light within a hollow core (a large air hole) in a silica-air photonic crystal fiber is demonstrated. Only certain wavelength bands are confined and guided down the fiber, each band corresponding to the presence of a full two-dimensional band gap in the photonic crystal cladding. Single-mode vacuum waveguides have a multitude of potential applications from ultrahigh-power transmission to the guiding of cold atoms.

Understanding how DNA binding proteins control global gene expression and chromosomal maintenance requires knowledge of the chromosomal locations at which these proteins function in vivo. We developed a microarray method that reveals the genome-wide location of DNA-bound proteins and used this method to monitor binding of gene-specific transcription activators in yeast. A combination of location and expression profiles was used to identify genes whose expression is directly controlled by Gal4 and Ste12 as cells respond to changes in carbon source and mating pheromone, respectively. The results identify pathways that are coordinately regulated by each of the two activators and reveal previously unknown functions for Gal4 and Ste12. Genome-wide location analysis will facilitate investigation of gene regulatory networks, gene function, and genome maintenance.

A surface having a spatial gradient in its surface free energy was capable of causing drops of water placed on it to move uphill. This motion was the result of an imbalance in the forces due to surface tension acting on the liquid-solid contact line on the two opposite sides ("uphill" or "downhill") of the drop. The required gradient in surface free energy was generated on the surface of a polished silicon wafer by exposing it to the diffusing front of a vapor of decyltrichlorosilane, Cl(3)Si(CH(2))(9)CH(3). The resulting surface displayed a gradient of hydrophobicity (with the contact angle of water changing from 97 degrees to 25 degrees ) over a distance of 1 centimeter. When the wafer was tilted from the horizontal plane by 15 degrees , with the hydrophobic end lower than the hydrophilic, and a drop of water (1 to 2 microliters) was placed at the hydrophobic end, the drop moved toward the hydrophilic end with an average velocity of approximately 1 to 2 millimeters per second. In order for the drop to move, the hysteresis in contact angle on the surface had to be low (</=10 degrees ).

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA Survey of Applications of PolyoxometalatesDimitris E. KatsoulisView Author Information Dow Corning Corporation, Central Research and Development, Midland, Michigan 48686 Cite this: Chem. Rev. 1998, 98, 1, 359–388Publication Date (Web):January 17, 1998Publication History Received2 June 1997Revised8 November 1997Published online17 January 1998Published inissue 1 February 1998https://pubs.acs.org/doi/10.1021/cr960398ahttps://doi.org/10.1021/cr960398aresearch-articleACS PublicationsCopyright © 1998 American Chemical SocietyRequest reuse permissionsArticle Views9001Altmetric-Citations1111LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Anions,Electrodes,Organic polymers,Salts Get e-Alerts

Rapid climate change is likely to impose strong selection pressures on traits important for fitness, and therefore, microevolution in response to climate-mediated selection is potentially an important mechanism mitigating negative consequences of climate change. We reviewed the empirical evidence for recent microevolutionary responses to climate change in longitudinal studies emphasizing the following three perspectives emerging from the published data. First, although signatures of climate change are clearly visible in many ecological processes, similar examples of microevolutionary responses in literature are in fact very rare. Second, the quality of evidence for microevolutionary responses to climate change is far from satisfactory as the documented responses are often - if not typically - based on nongenetic data. We reinforce the view that it is as important to make the distinction between genetic (evolutionary) and phenotypic (includes a nongenetic, plastic component) responses clear, as it is to understand the relative roles of plasticity and genetics in adaptation to climate change. Third, in order to illustrate the difficulties and their potential ubiquity in detection of microevolution in response to natural selection, we reviewed the quantitative genetic studies on microevolutionary responses to natural selection in the context of long-term studies of vertebrates. The available evidence points to the overall conclusion that many responses perceived as adaptations to changing environmental conditions could be environmentally induced plastic responses rather than microevolutionary adaptations. Hence, clear-cut evidence indicating a significant role for evolutionary adaptation to ongoing climate warming is conspicuously scarce.

Iterative diagonalization of the Hamiltonian matrix is required to solve very large electronic-structure problems. Present algorithms are limited in their convergence rates at low wave numbers by stability problems associated with large changes in the Hartree potential, and at high wave numbers with large changes in the kinetic energy. A new method is described which includes the effect of density changes on the potentials and properly scales the changes in kinetic energy. The use of this method has increased the rate of convergence by over an order of magnitude for large problems.

The low-temperature dynamics of ultraviscous liquids hold the key to understanding the nature of glass transition and relaxation phenomena, including the potential existence of an ideal thermodynamic glass transition. Unfortunately, existing viscosity models, such as the Vogel-Fulcher-Tammann (VFT) and Avramov-Milchev (AM) equations, exhibit systematic error when extrapolating to low temperatures. We present a model offering an improved description of the viscosity-temperature relationship for both inorganic and organic liquids using the same number of parameters as VFT and AM. The model has a clear physical foundation based on the temperature dependence of configurational entropy, and it offers an accurate prediction of low-temperature isokoms without any singularity at finite temperature. Our results cast doubt on the existence of a Kauzmann entropy catastrophe and associated ideal glass transition.

A higher-order Poincaré sphere and Stokes parameter representation of the higher-order states of polarization of vector vortex beams that includes radial and azimuthal polarized cylindrical vector beams is presented. The higher-order Poincaré sphere is constructed by naturally extending the Jones vector basis of plane wave polarization in terms of optical spin angular momentum to the total optical angular momentum that includes higher dimensional orbital angular momentum. The salient properties of this representation are illustrated by its ability to describe the higher-order modes of optical fiber waveguides, more exotic vector beams, and a higher-order Pancharatnam-Berry geometric phase.

Measurement-device-independent quantum key distribution (MDIQKD) with the decoy-state method negates security threats of both the imperfect single-photon source and detection losses. Lengthening the distance and improving the key rate of quantum key distribution (QKD) are vital issues in practical applications of QKD. Herein, we report the results of MDIQKD over 404 km of ultralow-loss optical fiber and 311 km of a standard optical fiber while employing an optimized four-intensity decoy-state method. This record-breaking implementation of the MDIQKD method not only provides a new distance record for both MDIQKD and all types of QKD systems but also, more significantly, achieves a distance that the traditional Bennett-Brassard 1984 QKD would not be able to achieve with the same detection devices even with ideal single-photon sources. This work represents a significant step toward proving and developing feasible long-distance QKD.

OVERVIEW:Eight companies that were Process Effectiveness Network members of the Industrial Research Institute attempted to collectively determine the best practices of the Fuzzy Front End (FFE) of innovation. Comparing one company's processes to those of another proved insurmountable because there was neither a common language nor clear and consistent definition of the key elements of the front end. As a result, the group developed a theoretical construct, defined as the New Concept Development (NCD) model, in order to provide a common language and insights on the front end activities. The model consists of three key parts: five front end elements, the engine that powers the elements, and external influencing factors. Proficiency of the FFE was evaluated at 19 companies by using the NCD model. Highly innovative companies were found to be more proficient in the FFE and in several elements of the NCD model.

We present a quantum key distribution system with a 2.5 GHz repetition rate using a three-state time-bin protocol combined with a one-decoy approach. Taking advantage of superconducting single-photon detectors optimized for quantum key distribution and ultralow-loss fiber, we can distribute secret keys at a maximum distance of 421 km and obtain secret key rates of 6.5 bps over 405 km.

We present a detailed overview of stimulated Brillouin scattering (SBS) in single-mode optical fibers. The review is divided into two parts. In the first part, we discuss the fundamentals of SBS. A particular emphasis is given to analytical calculation of the backreflected power and SBS threshold (SBST) in optical fibers with various index profiles. For this, we consider acousto-optic interaction in the guiding geometry and derive the modal overlap integral, which describes the dependence of the Brillouin gain on the refractive index profile of the optical fiber. We analyze Stokes backreflected power initiated by thermal phonons, compare values of the SBST calculated from different approximations, and discuss the SBST dependence on the fiber length. We also review an analytical approach to calculate the gain of Brillouin fiber amplifiers (BFAs) in the regime of pump depletion. In the high-gain regime, fiber loss is a nonnegligible effect and needs to be accounted for along with the pump depletion. We provide an accurate analytic expression for the BFA gain and show results of experimental validation. Finally, we review methods to suppress SBS including index-controlled acoustic guiding or segmented fiber links. The second part of the review deals with recent advances in fiber-optic applications where SBS is a relevant effect. In particular, we discuss the impact of SBS on the radio-over-fiber technology, enhancement of the SBS efficiency in Raman-pumped fibers, slow light due to SBS and SBS-based optical delay lines, Brillouin fiber-optic sensors, and SBS mitigation in high-power fiber lasers, as well as SBS in multimode and microstructured fibers. A detailed derivation of evolutional equations in the guided wave geometry as well as key physical relations are given in appendices.

This paper reports a simple spin-coating technique for rapidly fabricating three types of technologically important materials--colloidal crystal, macroporous polymer, and polymeric nanocomposite, each with high crystalline qualities and wafer-scale sizes. Dispersion of monodisperse silica colloids in triacrylate monomers is spin-coated onto a variety of substrates. Shear-induced ordering and subsequent polymerization lead to the formation of three-dimensionally (3D) ordered colloidal crystals trapped inside a polymer matrix. The thickness of as-synthesized colloidal crystal-polymer nanocomposite is highly uniform and can be controlled simply by changing the spin speed and time. Selective removal of the polymer matrix and silica spheres lead to the formation of large-area colloidal crystals and macroporous polymers, respectively. The wafer-scale process is compatible with standard semiconductor microfabrication, as multiple micrometer-sized patterns can be created simultaneously for potential device applications. Normal-incidence transmission spectra in the visible and near-infrared regions show distinct peaks due to Bragg diffraction from 3D ordered structures. The spin-coating process opens a new route to the fundamental studies of shear-induced crystallization, melting and relaxation.

Determining the form of key predator-prey relationships is critical for understanding marine ecosystem dynamics. Using a comprehensive global database, we quantified the effect of fluctuations in food abundance on seabird breeding success. We identified a threshold in prey (fish and krill, termed "forage fish") abundance below which seabirds experience consistently reduced and more variable productivity. This response was common to all seven ecosystems and 14 bird species examined within the Atlantic, Pacific, and Southern Oceans. The threshold approximated one-third of the maximum prey biomass observed in long-term studies. This provides an indicator of the minimal forage fish biomass needed to sustain seabird productivity over the long term.

A new etch composed of a dilute aqueous solution of an alkali dichromate and hydrofluoric acid, for suitably revealing dislocations and other lattice defects in (100) planes of silicon, is reported. The etch is fast (typically 5 min), brings out both lineage (low angle grain boundaries) and slip lines, and works over a wide range of resistivities for n‐ and p‐type material. The application of the etch is not restricted to (100) planes; dislocation etch pits are formed on all crystallographic orientations. The same etching characteristics were found with dilute aqueous solutions prepared from various chromium compounds and hydrofluoric acid.

The optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size. Optical absorption, photoluminescence, x-ray diffraction, and transmission electron microscopy are used to examine microcrystallites as a function of composition and development. Results are presented for a series of commercially available CorningR filter glasses with a selenium mole fraction in the range 0.28≤x≤0.74, as well as for several experimental glasses in which the average microcrystallite diameters range from 30 to 80 Å. Optical effects observed in the experimental glasses that are due to electron and hole confinement are not present in the filter glasses considered; variations in optical properties of the filters are due to changes in stoichiometry of the CdSexS1−x mixed anion system. A brief discussion of other microcrystalline phases in glass is also presented. These microcrystallites show room-temperature optical absorption structure analogous to bulk crystal excitons; the temperature dependence of this structure is contrasted with that resulting from quantum confinement in CdSexS1−x glasses.

Abstract Solid‐state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light‐emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state‐of‐the‐art input‐power‐density‐dependent power‐conversion efficiencies; potential improvements both in their peak power‐conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL.