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1

Interactive Molecular Orbital Diagrams  

NSDL National Science Digital Library

Here is an application for constructing the molecular orbital electron configurations of heteronuclear diatomic molecules. Energy level diagrams are given for the two different cases encountered in heteronuclear diatomics of the first short period (Li2 - Ne2). This is a useful tool for having students explore questions of bond order, magnetic properties and numbers of unpaired electrons.

2

Energy Level Diagrams for Black Hole Orbits  

E-print Network

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy to atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy, and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

Janna Levin

2009-07-29

3

ISS EPS Orbital Replacement Unit Block Diagrams  

NASA Technical Reports Server (NTRS)

The attached documents are being provided to Switching Power Magazine for information purposes. This magazine is writing a feature article on the International Space Station Electrical Power System, focusing on the switching power processors. These units include the DC-DC Converter Unit (DDCU), the Bi-directional Charge/Discharge Unit (BCDU), and the Sequential Shunt Unit (SSU). These diagrams are high-level schematics/block diagrams depicting the overall functionality of each unit.

Schmitz, Gregory V.

2001-01-01

4

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

Here is a set of movies that demonstrates heteronuclear diatomic molecular orbital formation. The orbitals start at a distance where there is little or no interatomic interaction and move to the appropriate bond distance. Orbital phase is shown by the different colors.

5

Basic primitives for molecular diagram sketching  

PubMed Central

A collection of primitive operations for molecular diagram sketching has been developed. These primitives compose a concise set of operations which can be used to construct publication-quality 2 D coordinates for molecular structures using a bare minimum of input bandwidth. The input requirements for each primitive consist of a small number of discrete choices, which means that these primitives can be used to form the basis of a user interface which does not require an accurate pointing device. This is particularly relevant to software designed for contemporary mobile platforms. The reduction of input bandwidth is accomplished by using algorithmic methods for anticipating probable geometries during the sketching process, and by intelligent use of template grafting. The algorithms and their uses are described in detail. PMID:20923555

2010-01-01

6

Some Observations on Molecular Orbital Theory  

ERIC Educational Resources Information Center

A few flawed predictions in the context of homonuclear diatomic molecules are presented in order to introduce students to molecular orbital (MO) theory. A common misrepresentation of the relationship between the energy of an atomic orbital and the energy of the MO associated with the atomic orbital is illustrated.

Journal of Chemical Education, 2005

2005-01-01

7

Understanding glycine conformation through molecular orbitals  

NASA Astrophysics Data System (ADS)

The four most stable Cs conformers of glycine have been investigated using a variety of quantum-mechanical methods based on Hartree-Fock theory, density-functional theory (B3LYP and statistical average of orbital potential), and electron propagation (OVGF) treatments. Information obtained from these models were analyzed in coordinate and momentum spaces using dual space analysis to provide insight based on orbitals into the bonding mechanisms of glycine conformers, which are generated by rotation of C-O(H) (II), C-C (III), and C-N (IV) bonds from the global minimum structure (I). Wave functions generated from the B3LYP/TZVP model revealed that each rotation produced a unique set of fingerprint orbitals that correspond to a specific group of outer valence orbitals, generally of a' symmetry. Orbitals 14a', 13a', 12a', and 11a' are identified as the fingerprint orbitals for the C-O(H) (II) rotation, whereas fingerprint orbitals for the C-C (III) bond rotation are located as 16a' [highest occupied molecular orbital (HOMO)], 15a' [next highest molecular occupied molecular orbital (NHOMO)], 14a', and 12a' orbitals. Fingerprint orbitals for IV generated by the combined rotations around the C-C, C-O(H), and C-N bonds are found as 16a', 15a', 14a', 13a', and 11a', as well as in orbitals 2a'' and 1a''. Orbital 14a' is identified as the fingerprint orbital for all three conformational processes, as it is the only orbital in the outer valence region which is significantly affected by the conformational processes regardless rotation of which bond. Binding energies, molecular geometries, and other molecular properties such as dipole moments calculated based on the specified treatments agree well with available experimental measurements and with previous theoretical calculation.

Falzon, Chantal T.; Wang, Feng

2005-12-01

8

A Simple Huckel Molecular Orbital Plotter  

ERIC Educational Resources Information Center

A program is described and presented to readily plot the molecular orbitals from a Huckel calculation. The main features of the program and the scope of its applicability are discussed through some example organic molecules. (Contains 2 figures.)

Ramakrishnan, Raghunathan

2013-01-01

9

Molecular Orbitals of NO, NO[superscript+], and NO[superscript-]: A Computational Quantum Chemistry Experiment  

ERIC Educational Resources Information Center

This computational experiment presents qualitative molecular orbital (QMO) and computational quantum chemistry exercises of NO, NO[superscript+], and NO[superscript-]. Initially students explore several properties of the target molecules by Lewis diagrams and the QMO theory. Then, they compare qualitative conclusions with EHT and DFT calculations…

Orenha, Renato P.; Galembeck, Sérgio E.

2014-01-01

10

Phase diagram of a three-orbital model for high-Tc cuprate superconductors.  

PubMed

We study the phase diagram of an effective three-orbital model of the cuprates using variational Monte Carlo calculations on asymptotically large lattices and exact diagonalization on a 24-site cluster. States with ordered orbital current loops (LC), itinerant antiferromagnetism, d-wave superconductivity, and the Fermi liquid are investigated using appropriate Slater determinants refined by Jastrow functions for on-site and intersite correlations. We find an LC state stable in the thermodynamic limit for a range of parameters compatible with the Fermi surface of a typical hole doped superconductor provided the transfer integrals between the oxygen atoms have signs determined by the effects of indirect transfer through the Cu-4s orbitals as suggested by Andersen. The results of the calculations are that the LC phase gives way at lower dopings to an antiferromagnetism phase, and at larger dopings to superconductivity and Fermi liquid phases. PMID:24702405

Weber, Cédric; Giamarchi, T; Varma, C M

2014-03-21

11

MOPAC: A semiempirical molecular orbital program  

Microsoft Academic Search

Before we start, we need a working definition for MOPAC. The following description has been used many times to describe MOPAC: MOPAC is a general-purpose, semiempirical molecular orbital program for the study of chemical reactions involving molecules, ions, and linear polymers. It implements the semiempirical Hamiltonians MNDO, AM 1, MINDO\\/3, and MNDOPM3, and combir_es the calculations of vibrational spectra, thermodynamic

James J. P. Stewart

1990-01-01

12

Trimer effects in fragment molecular orbital-linear combination of molecular orbitals calculation of one-electron orbitals for biomolecules.  

PubMed

The fragment molecular orbital (FMO)-linear combination of molecular orbitals (LCMO) method incorporates as an efficient post-process calculation of one-electron orbitals of the whole system after the FMO total energy calculation. A straightforward way to increase the accuracy is inclusion of the trimer effect. Here, we derive a comprehensive formulation called the FMO3-LCMO method. To keep the computational costs of the trimer term low enough, we use a matrix-size reduction technique. We evaluated the accuracy and efficiency of the FMO3-LCMO scheme in model biological systems (alanine oligomer and chignolin). The results show that delocalized electronic orbitals with covalent and hydrogen bonds are better described at the trimer level, and the FMO3-LCMO method is applicable to quantitative evaluations of a wide range of frontier orbitals in large biosystems. PMID:24028108

Kobori, Tomoki; Sodeyama, Keitaro; Otsuka, Takao; Tateyama, Yoshitaka; Tsuneyuki, Shinji

2013-09-01

13

Trimer effects in fragment molecular orbital-linear combination of molecular orbitals calculation of one-electron orbitals for biomolecules  

NASA Astrophysics Data System (ADS)

The fragment molecular orbital (FMO)-linear combination of molecular orbitals (LCMO) method incorporates as an efficient post-process calculation of one-electron orbitals of the whole system after the FMO total energy calculation. A straightforward way to increase the accuracy is inclusion of the trimer effect. Here, we derive a comprehensive formulation called the FMO3-LCMO method. To keep the computational costs of the trimer term low enough, we use a matrix-size reduction technique. We evaluated the accuracy and efficiency of the FMO3-LCMO scheme in model biological systems (alanine oligomer and chignolin). The results show that delocalized electronic orbitals with covalent and hydrogen bonds are better described at the trimer level, and the FMO3-LCMO method is applicable to quantitative evaluations of a wide range of frontier orbitals in large biosystems.

Kobori, Tomoki; Sodeyama, Keitaro; Otsuka, Takao; Tateyama, Yoshitaka; Tsuneyuki, Shinji

2013-09-01

14

Angle resolved photoemission from organic semiconductors: orbital imaging beyond the molecular orbital interpretation  

NASA Astrophysics Data System (ADS)

Fascinating pictures that can be interpreted as showing molecular orbitals have been obtained with various imaging techniques. Among these, angle resolved photoemission spectroscopy (ARPES) has emerged as a particularly powerful method. Orbital images have been used to underline the physical credibility of the molecular orbital concept. However, from the theory of the photoemission process it is evident that imaging experiments do not show molecular orbitals, but Dyson orbitals. The latter are not eigenstates of a single-particle Hamiltonian and thus do not fit into the usual simple interpretation of electronic structure in terms of molecular orbitals. In a combined theoretical and experimental study we thus check whether a Dyson-orbital and a molecular-orbital based interpretation of ARPES lead to differences that are relevant on the experimentally observable scale. We discuss a scheme that allows for approximately calculating Dyson orbitals with moderate computational effort. Electronic relaxation is taken into account explicitly. The comparison reveals that while molecular orbitals are frequently good approximations to Dyson orbitals, a detailed understanding of photoemission intensities may require one to go beyond the molecular orbital picture. In particular we clearly observe signatures of the Dyson-orbital character for an adsorbed semiconductor molecule in ARPES spectra when these are recorded over a larger momentum range than in earlier experiments.

Dauth, M.; Wiessner, M.; Feyer, V.; Schöll, A.; Puschnig, P.; Reinert, F.; Kümmel, S.

2014-10-01

15

Tuning molecular orbitals in molecular electronics and spintronics.  

PubMed

With the advance of nanotechnology, a variety of molecules, from single atoms to large-scale structures such as graphene or carbon nanotubes, have been investigated for possible use as molecular devices. Molecular orbitals (MOs) are a key ingredient in determining the transport properties of molecules, because they contain all the quantum mechanical information of molecular electronic structures and offer spatial conduction channels for electron transport. Therefore, the delicate modulation of the MOs enables us to tune the performance of electron transport through the molecule. Electric and magnetic fields are powerful and readily accessible means for that purpose. In this Account, we describe the effects of external fields on molecular electronic and spintronic devices. Quantum transport through a molecule that connects source and drain electrodes depends strongly on the alignment of molecular energy levels with respect to the chemical potentials at both electrodes. This dependence results from the energy levels being exploited in resonant tunneling processes when the molecule is weakly coupled to the electrodes in the molecular junction. Molecular energy levels can be shifted by the Stark effect of an external electric field. For a molecule with no permanent dipole moment, the polarizability is the primary factor determining the energy shift of each MO, according to the second-order Stark effect; more polarizable MOs undergo a larger energy shift. Interestingly, even a small shift may lead to a completely nontrivial result. For example, we show a magnetic on-off switching phenomenon of a molecule controlled by an electric field. If a molecule has a nonmagnetic ground state but a highly polarizable magnetic excited state with an energy slightly above the ground state, the magnetic excited state can have lower energy than the ground state under a sufficiently strong electric field. A magnetic field is normally used to control spin orientation in a ferromagnetic system. Here we show that the magnetic field can also be used to control MOs. A graphene nanoribbon with zig-zag-shaped edges (ZGNR) has a ferromagnetic spin ordering along the edges, and the spin states have unique orbital symmetries. Both spin polarizations and orbital symmetries can simultaneously be controlled by means of an external magnetic field. The ZGNR spin-valve devices incorporating this effect are predicted to show an extreme enhancement (compared with conventional devices) of magnetoresistance due to the double spin-filtering process. In such a system, spins are filtered not only by spin matching-mismatching between both electrodes as in normal spin-valve devices, but also by the orbital symmetry matching-mismatching. Thus, a new type of magnetoresistance, and with extremely large values, so-called super-magnetoresistance (distinct from the conventional tunneling or giant magnetoresistance), is available with this method. MOs are at the heart of understanding and tuning transport properties in molecular systems. Therefore, investigating the effects of external fields on MOs is important not only for understanding fundamental quantum phenomena in molecular devices but also for practical applications in the development of interactive devices. PMID:19769353

Kim, Woo Youn; Kim, Kwang S

2010-01-19

16

Orbital resolution of molecular information channels and stockholder atoms  

Microsoft Academic Search

Within the orbital description of the electronic structure of molecules the variational principles of the entropy deficiency and the entropy\\/information descriptors of the system communication channel are used to establish the orbital-representability (orthonormality) requirements in terms of the relevant conditional probabilities from the superposition principle of quantum mechanics. The orbital resolution of the Hirshfeld (stockholder) partition of the molecular electron

R. F. Nalewajski

2006-01-01

17

Molecular orbital theoretical studies of some organic corrosion inhibitors  

SciTech Connect

Molecular orbital theoretical calculations based on the modified neglect of differential overlap (MNDO) method were performed on some substituted methyl pyridines and substituted ethane derivatives in common use as corrosion inhibitors for iron in acid media. New correlations of corrosion rates with the energy of the highest occupied molecular orbital (E{sub HOMO}), the energy gap or difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital (E{sub LUMO}-E{sub HOMO}), and Hammett`s parameter {sigma} were presented. Absolute electronegativity ({chi}) values and the fraction of electrons ({Delta}N) transferred from substituted pyridine and ethane compounds to iron in the bulk metal were calculated and correlated with corrosion rates for the first time.

Sastri, V.S. [CANMET, Ottawa, Ontario (Canada). Metals Technology Labs.; Perumareddi, J.R. [Florida Atlantic Univ., Boca Raton, FL (United States). Dept. of Chemistry

1997-08-01

18

The rotational barrier in ethane: a molecular orbital study.  

PubMed

The energy change on each Occupied Molecular Orbital as a function of rotation about the C-C bond in ethane was studied using the B3LYP, mPWB95 functional and MP2 methods with different basis sets. Also, the effect of the ZPE on rotational barrier was analyzed. We have found that ? and ? energies contribution stabilize a staggered conformation. The ?(s) molecular orbital stabilizes the staggered conformation while the stabilizes the eclipsed conformation and destabilize the staggered conformation. The ?(z) and molecular orbitals stabilize both the eclipsed and staggered conformations, which are destabilized by the ?(v) and molecular orbitals. The results show that the method of calculation has the effect of changing the behavior of the energy change in each Occupied Molecular Orbital energy as a function of the angle of rotation about the C-C bond in ethane. Finally, we found that if the molecular orbital energy contribution is deleted from the rotational energy, an inversion in conformational preference occurs. PMID:22522396

Quijano-Quiñones, Ramiro F; Quesadas-Rojas, Mariana; Cuevas, Gabriel; Mena-Rejón, Gonzalo J

2012-01-01

19

Muffin-tin orbitals and molecular calculations: General formalism  

Microsoft Academic Search

An account is given of a new formalism for calculating energy levels in molecules using techniques that derive from the band theory of metals. After showing how the molecular potential may be transformed into a cellular potential we define the basis set of muffin-tin orbitals and discuss some of their properties. The relationship between the scattered wave formulation of Johnson,

O. K. Andersen; R. G. Woolley

1973-01-01

20

Conformation effects on the molecular orbitals of serine  

NASA Astrophysics Data System (ADS)

This paper calculates the five most stable conformers of serine with Hartree—Fock theory, density functional theory (B3LYP), Møller—Plesset perturbation theory (MP4(SDQ)) and electron propagation theory with the 6-311++G(2d,2p) basis set. The calculated vertical ionization energies for the valence molecular orbitals of each conformer are in agreement with the experimental data, indicating that a range of molecular conformations would coexist in an equilibrium sample. Information of the five outer valence molecular orbitals for each conformer is explored in coordinate and momentum spaces using dual space analysis to investigate the conformational processes, which are generated from the global minimum conformer Ser1 by rotation of C2-C3 (Ser4), C1-C2 (Ser5) and C1-O2 (Ser2 and Ser3). Orbitals 28a, 27a and 26a are identified as the fingerprint orbitals for all the conformational processes. Project supported by the Doctoral Research Fund of Henan Normal University, China (Grant No. 525449).

Wang, Ke-Dong; Ma, Peng-Fei; Shan, Xu

2011-03-01

21

Chemical bond descriptors from molecular information channels in orbital resolution  

NASA Astrophysics Data System (ADS)

The inter and intraorbital flows of the Fisher and Shannon informations in the molecular communication networks defined in the condensed atomic orbital (AO) resolution are investigated, and the effect of the basis set overlap is examined. The Schrödinger equation is interpreted as solution of the variation principle for the extreme Fisher information, subject to the wave-function-normalization (geometric) and potential-energy (physical) constraints. Its orbital contributions determine the information scattering of the underlying Fisher channel in the adopted AO basis set. This communication network is compared with the associated information system of the Shannon theory of communication. The new set of conditional probabilities between orbitals is compared to that used in the previous, sequential-cascade approach to the effective information promotion of AO in the molecular environment. Both geometrical and physical probabilities are reexamined using the quantum-mechanical superposition principle. The former characterizes the whole orbital space, whereas the latter describes only its occupied part, which determines the system chemical bonds. It is argued that the squares of corresponding elements of the charge and bond-order (CBO) matrix of the LCAO MO theory replace in the physical set of conditional probabilities the corresponding squares of the overlap integrals, which determine the geometrical set. The chain-rule interpretation of conditional probabilities is given. The modified 2-AO channel reproduces fully the earlier predictions from the molecular information channel in atomic resolution. The familiar bond criteria for an effective mixing of AO into molecular orbitals (MO) are shown to remain valid in the communication theory of the chemical bond (CTCB).

Nalewajski, Roman F.

22

Local reactivity descriptors from degenerate frontier molecular orbitals  

NASA Astrophysics Data System (ADS)

Conceptual Density Functional Theory (DFT) has proposed a set of local descriptors to measure the reactivity on specific sites of a molecule, as an example dual descriptor has been successfully used in analyzing interesting systems to understand their local reactivity, however under the frozen orbital approximation (FOA), it is defined from non-degenerate frontier molecular orbitals (FMOs). In this work, the degeneration is taken into account to propose approximated expressions to obtain the dual descriptor, nucleophilic and electrophilic Fukui functions in closed-shell systems. The proposed expressions have been tested on molecules presenting degenerate FMOs.

Martínez, Jorge

2009-08-01

23

Mechanically controlled molecular orbital alignment in single molecule junctions.  

PubMed

Research in molecular electronics often involves the demonstration of devices that are analogous to conventional semiconductor devices, such as transistors and diodes, but it is also possible to perform experiments that have no parallels in conventional electronics. For example, by applying a mechanical force to a molecule bridged between two electrodes, a device known as a molecular junction, it is possible to exploit the interplay between the electrical and mechanical properties of the molecule to control charge transport through the junction. 1,4'-Benzenedithiol is the most widely studied molecule in molecular electronics, and it was shown recently that the molecular orbitals can be gated by an applied electric field. Here, we report how the electromechanical properties of a 1,4'-benzenedithiol molecular junction change as the junction is stretched and compressed. Counterintuitively, the conductance increases by more than an order of magnitude during stretching, and then decreases again as the junction is compressed. Based on simultaneously recorded current-voltage and conductance-voltage characteristics, and inelastic electron tunnelling spectroscopy, we attribute this finding to a strain-induced shift of the highest occupied molecular orbital towards the Fermi level of the electrodes, leading to a resonant enhancement of the conductance. These results, which are in agreement with the predictions of theoretical models, also clarify the origins of the long-standing discrepancy between the calculated and measured conductance values of 1,4'-benzenedithiol, which often differ by orders of magnitude. PMID:22138861

Bruot, Christopher; Hihath, Joshua; Tao, Nongjian

2012-01-01

24

A Simple Demonstration of Atomic and Molecular Orbitals Using Circular Magnets  

ERIC Educational Resources Information Center

A quite simple and inexpensive technique is described here to represent the approximate shapes of atomic orbitals and the molecular orbitals formed by them following the principles of the linear combination of atomic orbitals (LCAO) method. Molecular orbitals of a few simple molecules can also be pictorially represented. Instructors can employ the…

Chakraborty, Maharudra; Mukhopadhyay, Subrata; Das, Ranendu Sekhar

2014-01-01

25

Decomposition Mechanism Studies of Energetic Molecules Using HOMO and LUMO Orbital Energy Driven Molecular Dynamics  

Microsoft Academic Search

In this paper, we present decomposition mechanism studies of energetic molecules using HOMO and LUMO orbital energy gap driven molecular dynamics (MD) method. Under frozen orbital approximation, this is an `electronic excitation' MD, where electrons is excited from HOMO to LUMO orbitals Meanwhile, the HOMO and LUMO orbital energy gap is taken as a biasing potential to accelerate chemical reactions,

Yanhua Dong; Yanfeng Song; Hakima Abou-Rachid

2009-01-01

26

The Fueling Diagram: Linking Galaxy Molecular-to-atomic Gas Ratios to Interactions and Accretion  

NASA Astrophysics Data System (ADS)

To assess how external factors such as local interactions and fresh gas accretion influence the global interstellar medium of galaxies, we analyze the relationship between recent enhancements of central star formation and total molecular-to-atomic (H2/H I) gas ratios, using a broad sample of field galaxies spanning early-to-late type morphologies, stellar masses of 107.2-1011.2 M ?, and diverse stages of evolution. We find that galaxies occupy several loci in a "fueling diagram" that plots H2/H I ratio versus mass-corrected blue-centeredness, a metric tracing the degree to which galaxies have bluer centers than the average galaxy at their stellar mass. Spiral galaxies of all stellar masses show a positive correlation between H2/H I ratio and mass-corrected blue-centeredness. When combined with previous results linking mass-corrected blue-centeredness to external perturbations, this correlation suggests a systematic link between local galaxy interactions and molecular gas inflow/replenishment. Intriguingly, E/S0 galaxies show a more complex picture: some follow the same correlation, some are quenched, and a distinct population of blue-sequence E/S0 galaxies (with masses below key scales associated with transitions in gas richness) defines a separate loop in the fueling diagram. This population appears to be composed of low-mass merger remnants currently in late- or post-starburst states, in which the burst first consumes the H2 while the galaxy center keeps getting bluer, then exhausts the H2, at which point the burst population reddens as it ages. Multiple lines of evidence suggest connected evolutionary sequences in the fueling diagram. In particular, tracking total gas-to-stellar mass ratios within the fueling diagram provides evidence of fresh gas accretion onto low-mass E/S0s emerging from their central starburst episodes. Drawing on a comprehensive literature search, we suggest that virtually all galaxies follow the same evolutionary patterns found in our broad sample.

Stark, David V.; Kannappan, Sheila J.; Wei, Lisa H.; Baker, Andrew J.; Leroy, Adam K.; Eckert, Kathleen D.; Vogel, Stuart N.

2013-05-01

27

Communication: Phase diagram of C36 by atomistic molecular dynamics and thermodynamic integration through coexistence regions  

NASA Astrophysics Data System (ADS)

We report an atomistic molecular dynamics determination of the phase diagram of a rigid-cage model of C36. We first show that free energies obtained via thermodynamic integrations along isotherms displaying "van der Waals loops," are fully reproduced by those obtained via isothermal-isochoric integration encompassing only stable states. We find that a similar result also holds for isochoric paths crossing van der Waals regions of the isotherms, and for integrations extending to rather high densities where liquid-solid coexistence can be expected to occur. On such a basis we are able to map the whole phase diagram of C36, with resulting triple point and critical temperatures about 1770 K and 2370 K, respectively. We thus predict a 600 K window of existence of a stable liquid phase. Also, at the triple point density, we find that the structural functions and the diffusion coefficient maintain a liquid-like character down to 1400-1300 K, this indicating a wide region of possible supercooling. We discuss why all these features might render possible the observation of the melting of C36 fullerite and of its liquid state, at variance with what previously experienced for C60.

Abramo, M. C.; Caccamo, C.; Costa, D.; Munaò, G.

2014-09-01

28

Charge transfer processes: the role of optimized molecular orbitals.  

PubMed

The influence of the molecular orbitals on charge transfer (CT) reactions is analyzed through wave function-based calculations. Characteristic CT processes in the organic radical 2,5-di-tert-butyl-6-oxophenalenoxyl linked with tetrathiafulvalene and the inorganic crystalline material LaMnO3 show that changes in the inner shells must be explicitly taken into account. Such electronic reorganization can lead to a reduction of the CT vertical transition energy up to 66%. A state-specific approach accessible through an adapted CASSCF (complete active space self-consistent field) methodology is capable of reaching good agreement with the experimental spectroscopy of CT processes. A partitioning of the relaxation energy in terms of valence- and inner-shells is offered and sheds light on their relative importance. This work paves the way to the intimate description of redox reactions using quantum chemistry methods. PMID:24781811

Meyer, Benjamin; Domingo, Alex; Krah, Tim; Robert, Vincent

2014-08-01

29

Sulfur at nickel-alumina interfaces - Molecular orbital theory  

NASA Technical Reports Server (NTRS)

Previous studies on Al-Ni alloys containing sulfur as an impurity suggest that, when S is in the interface between a metal and an oxide scale, it weakens the chemical bonding between them. This paper investigates factors responsible for this effect, using a molecular orbital theory to predict sulfur structures and electronic properties on the Ni-Al2O3 interface. It is shown that, in absence of S, the basal plane of Al2O3 will bind strongly through the Al(3+) cation surface to Ni (111). When segregated S impurity is present on the Ni surface, there are too few interfacial AlS bonds to effect good adhesion, leading to an inhibition of the oxide scale adhesion in NiCrAl alloys.

Hong, S. Y.; Anderson, Alfred B.; Smialek, James L.

1990-01-01

30

Ab initio molecular simulations with numeric atom-centered orbitals  

NASA Astrophysics Data System (ADS)

We describe a complete set of algorithms for ab initio molecular simulations based on numerically tabulated atom-centered orbitals (NAOs) to capture a wide range of molecular and materials properties from quantum-mechanical first principles. The full algorithmic framework described here is embodied in the Fritz Haber Institute " ab initio molecular simulations" ( FHI-aims) computer program package. Its comprehensive description should be relevant to any other first-principles implementation based on NAOs. The focus here is on density-functional theory (DFT) in the local and semilocal (generalized gradient) approximations, but an extension to hybrid functionals, Hartree-Fock theory, and MP2/ GW electron self-energies for total energies and excited states is possible within the same underlying algorithms. An all-electron/full-potential treatment that is both computationally efficient and accurate is achieved for periodic and cluster geometries on equal footing, including relaxation and ab initio molecular dynamics. We demonstrate the construction of transferable, hierarchical basis sets, allowing the calculation to range from qualitative tight-binding like accuracy to meV-level total energy convergence with the basis set. Since all basis functions are strictly localized, the otherwise computationally dominant grid-based operations scale as O( N) with system size N. Together with a scalar-relativistic treatment, the basis sets provide access to all elements from light to heavy. Both low-communication parallelization of all real-space grid based algorithms and a ScaLapack-based, customized handling of the linear algebra for all matrix operations are possible, guaranteeing efficient scaling (CPU time and memory) up to massively parallel computer systems with thousands of CPUs.

Blum, Volker; Gehrke, Ralf; Hanke, Felix; Havu, Paula; Havu, Ville; Ren, Xinguo; Reuter, Karsten; Scheffler, Matthias

2009-11-01

31

Use of Molecular Orbital Theory to Interpret X-Ray K-Absorption Spectral Data.  

National Technical Information Service (NTIS)

The paper demonstrates how molecular orbital theory can be useful in obtaining chemical information from x-ray absorption spectra. Basic molecular orbital theory concepts such as symmetry and overlap of wavefunctions are used to explain the K-absorption s...

G. L. Glen, C. G. Dodd

1968-01-01

32

Quantifying the relative molecular orbital alignment for molecular junctions with similar chemical linkage to electrodes.  

PubMed

Estimating the relative alignment between the frontier molecular orbitals (MOs) that dominates the charge transport through single-molecule junctions represents a challenge for theory. This requires approaches beyond the widely employed framework provided by the density functional theory, wherein the Kohn-Sham 'orbitals' are treated as if they were real MOs, which is not the case. In this paper, we report results obtained by means of quantum chemical calculations, including the equation-of-motion coupled-cluster singles and doubles, which is the state-of-the-art of quantum chemistry for medium-size molecules like those considered here. These theoretical results are validated against data on the MO energy offset relative to the electrodes' Fermi energy extracted from experiments for junctions based on 4,4'-bipyridine and 1,4-dicyanobenzene. PMID:25327824

Bâldea, Ioan

2014-11-14

33

Quantifying the relative molecular orbital alignment for molecular junctions with similar chemical linkage to electrodes  

NASA Astrophysics Data System (ADS)

Estimating the relative alignment between the frontier molecular orbitals (MOs) that dominates the charge transport through single-molecule junctions represents a challenge for theory. This requires approaches beyond the widely employed framework provided by the density functional theory, wherein the Kohn–Sham ‘orbitals’ are treated as if they were real MOs, which is not the case. In this paper, we report results obtained by means of quantum chemical calculations, including the equation-of-motion coupled-cluster singles and doubles, which is the state-of-the-art of quantum chemistry for medium-size molecules like those considered here. These theoretical results are validated against data on the MO energy offset relative to the electrodes’ Fermi energy extracted from experiments for junctions based on 4,4’-bipyridine and 1,4-dicyanobenzene.

Bâldea, Ioan

2014-11-01

34

Moving Beyond the Single Center--Ways to Reinforce Molecular Orbital Theory in an Inorganic Course  

ERIC Educational Resources Information Center

It is suggested that molecular theory should be taught earlier in the inorganic chemistry curriculum even in the introductory chemistry course in order to integrate molecular orbital arguments more effectively throughout the curriculum. The method of teaching relies on having access to molecular modeling software as having access to such software…

Cass, Marion E.; Hollingsworth, William E.

2004-01-01

35

Effect of length and geometry on the highest occupied molecular orbital-lowest unoccupied molecular orbital gap of conjugated oligomers: An analytical Hückel model approach  

Microsoft Academic Search

It is shown that the asymptotic behavior of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap of conjugated oligomers of types M?(M)N?2?M and M?(M)N?2?M1 with M = M1?M2, where M, M1, and M2 are alternant but otherwise arbitrary monomers described by the Hu¨ckel Hamiltonian, is ruled by the law ?HL(N)=?HL(?)+const?N?2. On this basis we suggest an approximate expression

Alexander Onipko; Yuriy Klymenko; Lyuba Malysheva

1997-01-01

36

Molecular Orbital Approach to Interpret High Pressure Phenomena – Case of Elusive Gold Monofluoride  

Microsoft Academic Search

\\u000a Usefulness of Molecular Orbital analysis for prediction and interpretation of a variety of high-pressure phenomena will be\\u000a illustrated for the case of elusive gold monofluoride, Au(I)F.

Wojciech Grochala; Dominik Kurzydlowski

2010-01-01

37

Density functional theory, molecular dynamics, and differential scanning calorimetry study of the RbF-CsF phase diagram.  

PubMed

A multiscale modeling approach is developed to compute the phase diagram of the RbF-CsF binary system. The mixing enthalpies of the (Rb,Cs)F solid and liquid solutions are evaluated using density functional theory and classical molecular dynamics calculations, respectively. For the solid solution, 18 different configurations are studied with density functional theory and the surrounded atom model is applied in order to compute the configurational partition function. We also measure the solidus and liquidus equilibria using differential scanning calorimetry. Finally the RbF-CsF phase diagram is constructed using the calculated excess free enthalpies of the solid and liquid solutions and a very good agreement with our experimental data is found. PMID:19355773

Benes, O; Zeller, Ph; Salanne, M; Konings, R J M

2009-04-01

38

Molecular orbital model of optical centers in bismuth-doped glasses.  

PubMed

Spectroscopic properties of optical fibers with a bismuth-doped silicate glass core are explained on the basis of molecular orbital theory and a solution of the Schrödinger equation, which takes into account the exchange, the spin-orbital, and the glass field potential interactions of s, p, and d electron shells of bismuth with s(sigma), p(sigma), and p(pi) orbits of oxygen atoms. The approach can explain the IR luminescence properties of other optical centers formed by other atoms with the same structure of electron shells as the bismuth atom. The model of transitions based on intramolecular charge transfer between molecular orbital and metallic states is proposed. PMID:19448817

Kustov, E F; Bulatov, L I; Dvoyrin, V V; Mashinsky, V M

2009-05-15

39

Orbital symmetry and interference effects in molecular high-order harmonic generation  

SciTech Connect

We investigate harmonic generation from H{sub 2}{sup +} molecules driven by intense few-cycle laser pulses whose linearly polarization axis makes an arbitrary angle {chi} with respect to the molecular axis. The H{sub 2}{sup +} molecule is considered initially in various orbitals with nodal planes. It is found that a strong enhancement of high-order harmonics (HOHs) occurs when the laser polarization axis overlaps with major axes of electron distribution in the active orbital, while broad suppression of HOHs occurs when the laser polarization axis is parallel to a nodal plane of the active molecular orbital. We show that this harmonic suppression is enhanced by destructive interferences when the nodal and the laser polarization axes are parallel to the internuclear axis, which leads to a shortening of the harmonic cutoff. It follows that the orientation dependence of HOHs intensities mimics the electronic density in active orbitals through the angular dependence of ionization and recombination processes.

Lagmago Kamta, G. [Department of Medical Physics, Ottawa Hospital Cancer Centre, Ottawa, Ontario, K1H 8L6 (Canada); Bandrauk, A. D. [Departement de Chimie, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

2009-10-15

40

Diagrams of isoshielding lines of CN bonds and nitrogen and phosphorus lone pairs  

Microsoft Academic Search

Diagrams of isoshielding lines in the vicinity of lone pairs of nitrogen and phosphorus atoms, as well as a C-N bond, have been calculated. The magnetic shielding constants of the protons were calculated by the gauge-invariant atomic-orbital method with the use of localized molecular orbitals and expansions of the atomic wave functions in Gaussian functions. The diagrams of the isoshielding

R. M. Aminova; Yu. Yu. Samitov

1985-01-01

41

Diagrams of isoshielding lines of CN bonds and nitrogen and phosphorus lone pairs  

Microsoft Academic Search

Diagrams of isoshielding lines in the vicinity of lone pairs of nitrogen and phosphorus atoms, as well as a C-N bond, have been calculated. The magnetic shielding constants of the protons were calculated by the gauge-invariant atomic-orbital method with the use of localized molecular orbitals and expansions of the atomic wave functions in Gaussian functions. The diagrams of the isoshielding

R. M. Aminova; Yu. Yu. Samitov

1986-01-01

42

Molecular orbital ordering in titania and the associated semiconducting behavior  

SciTech Connect

RF-sputtered TiO{sub x} layers were thermally treated and the associated thin-film transistor properties were studied. X-ray diffraction and x-ray absorption spectroscopy analyses indicate that as-grown amorphous TiO{sub x} films crystallize to anatase at temperatures above 450 deg. C in air. Thin-film transistors incorporating anatase active layers exhibit n-type behavior, with field effect mobility values near 0.11 cm{sup 2}/Vs when annealed at 550 deg. C. Such a phenomenon is suggested to originate from the ordering of Ti 3d orbitals upon crystallization, and the mobility enhancement at higher annealing temperatures may be attributed to the reduced grain boundary scattering of carriers by virtue of enlarged average grain size.

Park, Joseph; Ok, Kyung-Chul; Park, Jin-Seong [Department of Materials Science and Engineering, Dankook University, Mt. 29, Anseo-Dong, Cheonan 330-714 (Korea, Republic of); Du Ahn, Byung; Hun Lee, Je; Park, Jae-Woo [Samsung Electronics, Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-711 (Korea, Republic of); Chung, Kwun-Bum [Department of Physics, Dankook University, Mt. 29, Anseo-Dong, Cheonan 330-714 (Korea, Republic of)

2011-10-03

43

Phosphate bonding configuration on ferrihydrite based on molecular orbital calculations and XANES fingerprinting  

NASA Astrophysics Data System (ADS)

Sorption of phosphate by Fe(III)- and Al(III)-(hydr)oxide minerals regulates the mobility of this potential water pollutant in the environment. The objective of this research was to determine the molecular configuration of phosphate bound on ferrihydrite at pH 6 by interpreting P K-edge XANES spectra in terms of bonding mode. XANES and UV-visible absorption spectra for aqueous Fe(III)-PO 4 solutions (Fe/P molar ratio = 0-2.0) provided experimental trends for energies of P(3p)-O(2p) and Fe(3d)-O(2p) antibonding molecular orbitals. Molecular orbitals for Fe(III)-PO 4 or Al(III)-PO 4 complexes in idealized monodentate or bidentate bonding mode were generated by conceptual bonding arguments, and Extended-Hückel molecular orbital computations were used to understand and assign XANES spectral features to bound electronic states. The strong white line at the absorption edge in P K-edge XANES spectra for Fe-PO 4 or Al-PO 4 systems is attributable to an electronic transition from a P 1s atomic orbital into P(3p)-O(2p) or P(3p)-O(2p)-Al(3p) antibonding molecular orbitals, respectively. For Fe-PO 4 systems, a XANES peak at 2-5 eV below the edge was assigned to a P 1s electron transition into Fe(4p)-O(2p) antibonding molecular orbitals. Similarly, a shoulder on the low-energy side of the white line for variscite corresponds to a transition into Al(3p)-O(2p) orbitals. In monodentate-bonded phosphate, Fe-O bonding is optimized and P-O bonding is weakened, and the converse is true of bidentate-bonded phosphate. These differences explained an inverse correlation between energies of P(3p)-O(2p) and Fe(3d)-O(2p) antibonding molecular orbitals consistent with a monodentate-to-bidentate transition in aqueous Fe(III)-PO 4 solutions. The intensity of the XANES pre-edge feature in Fe(III)-bonded systems increased with increasing number of Fe(III)-O-P bonds. Based on the similarity of intensity and splitting of the pre-edge feature for phosphate sorbed on ferrihydrite at 750 mmol/kg at pH 6 and aqueous Fe-PO 4 solutions containing predominantly bidentate complexes, XANES results indicated that phosphate adsorbed on ferrihydrite was predominantly a bidentate-binuclear surface complex.

Khare, Nidhi; Martin, James D.; Hesterberg, Dean

2007-09-01

44

Nuclear Molecular Orbital Effects and the Carbon -13 + CARBON13 ---> CARBON12 + CARBON14 Rearrangement Reaction  

Microsoft Academic Search

Collective molecular configurations are observed in nuclei, and of considerable current interest is whether nuclear systems also exhibit single-particle molecular orbital (MO) behavior. An investigation of a heavy-ion single-neutron transfer reaction was carried out for the specific purpose of providing new information concerning the details of the transfer process and to search for evidence of MO effects. The single-neutron transfer

Steven Kenneth Korotky

1980-01-01

45

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis.  

PubMed

We made use of synchrotron radiation to perform near edge X-ray absorption fine structure spectroscopy, NEXAFS, at the carbon K-edge of perylene and perylene-tetracarboxylic-diimide, PTCDI. Reference spectra measured for isolated molecules in the gas phase are compared with polarization dependent NEXAFS spectra measured on highly oriented thin films in order to study the symmetry of the molecular orbitals. The molecular overlayers are grown onto the rutile TiO2(110) surface for which the large anisotropic corrugation effectively drives the molecular orientation, while its dielectric nature prevents the rehybridization of the molecular orbitals. We employed density functional theory, DFT, calculations to disentangle the contribution of specific carbon atoms to the molecular density of states. Numerical simulations correctly predict the observed NEXAFS azimuthal dichroism of the ?* resonances above the ionization threshold, from which we determine the full geometric orientation of the overlayer molecules. A discrepancy observed for the spectral contribution of the imide carbon atom to the calculated unoccupied molecular orbitals has been explained in terms of initial state effects, as determined by Hartree-Fock corrections and in full agreement with the corresponding shift of the C 1s core level measured by X-ray photoelectron spectroscopy, XPS. PMID:24924641

Fratesi, Guido; Lanzilotto, Valeria; Stranges, Stefano; Alagia, Michele; Brivio, Gian Paolo; Floreano, Luca

2014-07-28

46

In pursuit of negative Fukui functions: examples where the highest occupied molecular orbital fails to dominate the chemical reactivity.  

PubMed

In our quest to explore molecules with chemically significant regions where the Fukui function is negative, we explored reactions where the frontier orbital that indicates the sites for electrophilic attack is not the highest occupied molecular orbital. The highest occupied molecular orbital (HOMO) controls the location of the regions where the Fukui function is negative, supporting the postulate that negative values of the Fukui function are associated with orbital relaxation effects and nodal surfaces of the frontier orbitals. Significant negative values for the condensed Fukui function, however, were not observed. PMID:23090502

Echegaray, Eleonora; Cárdenas, Carlos; Rabi, Sandra; Rabi, Nataly; Lee, Sungmin; Zadeh, Farnaz Heidar; Toro-Labbe, Alejandro; Anderson, James S M; Ayers, Paul W

2013-07-01

47

Application of Ab Initio Molecular Orbital and Reaction Rate Theories to Nucleation Kinetics  

Microsoft Academic Search

This paper describes the application of ab initio molecular orbital (MO) theories in conjunction with reaction rate theory to obtain thermochemistry and energetics of nucleation processes. The specific example used for the illustration of this approach is the nucleation of SiO. MO computations on the equilibrium structure have shown the polymers up to the tetramer to be planar rings and

M. R. Zachariah; W. Tsang

1993-01-01

48

A semi-empirical molecular orbital study of freestanding and fullerene-encapsulated Mo nanoclusters  

E-print Network

A semi-empirical molecular orbital study of freestanding and fullerene-encapsulated Mo nanoclusters as implemented in the VAMP module of Materials Studiow , of both freestanding and fullerene by opening of hexagon­hexagon (6­6) carbon bonds that lead eventually to a splitting open of the fullerene

Elliott, James

49

Thermochemistry of Aluminum Species for Combustion Modeling from Ab Initio Molecular Orbital Calculations  

E-print Network

- quence, some of these species have never been introduced into kinetic models. Such species mustThermochemistry of Aluminum Species for Combustion Modeling from Ab Initio Molecular Orbital thermochemical data are also presented for several species never studied experimentally, including AlH2, AlH3, Al

Swihart, Mark T.

50

Methane activation by metals and semiconductors. Molecular orbital theory. Final report, September 1986December 1989  

Microsoft Academic Search

The atom superposition and electron delocalization molecular orbital (ASED-MO) theory and catalyst cluster models as well as ASED-band calculations have been used to study methane CH activation over a diverse set of surfaces. These include metals, oxides, a sulfide, carbide and nitride, a metal with adsorbed O, and a polyoxometallate. CC coupling reactions over molybdenum disulfide and molybdenum carbide have

1990-01-01

51

Numerical estimation of trap depth in polymeric materials using molecular orbital method  

Microsoft Academic Search

Trap depth in polyethylene was numerically estimated using calculation of molecular orbital method. In polymeric material, electric conduction seems to be strongly affected by the existence of carrier traps. Therefore the estimation of trap depth is one of important factors for electrical characterization of polymeric materials. However, there are not so many examples to estimate the trap depth. Therefore, authors

Y. Hayase; T. Osada; T. Takada; Y. Tanaka

2009-01-01

52

ForReview.Confidential-ACS An Effective Hamiltonian Molecular OrbitalValence Bond (MOVB)  

E-print Network

for Chemical Reactions Applied to the Nucleophilic Substitution Reaction of Hydrosulfide Ion and Chloromethane Molecular OrbitalValence Bond (MOVB) Approach for Chemical Reactions Applied to the Nucleophilic evaluated. The EH-MOVB method has been applied to the nucleophilic substitution reaction between

Minnesota, University of

53

The molecular orbital description of SN2 reactions at silicon centres  

Microsoft Academic Search

Bimolecular nucleophilic substitution at a silicon centre has been investigated by the use of ab initio molecular orbital theory in an examination of the attack of hydride and fluoride anions upon silane and silyl fluoride, respectively. In particular, the role of polarization functions in determining the magnitude of reaction barriers was explored. The inclusion of diffuse functions in the calculations

Paul Baybutt

1975-01-01

54

Orbital redistribution in molecular nanostructures mediated by metal-organic bonds.  

PubMed

Dicyanovinyl-quinquethiophene (DCV5T-Me2) is a prototype conjugated oligomer for highly efficient organic solar cells. This class of oligothiophenes are built up by an electron-rich donor (D) backbone and terminal electron-deficient acceptor (A) moieties. Here, we investigated its structural and electronic properties when it is adsorbed on a Au(111) surface using low temperature scanning tunneling microscopy/spectroscopy (STM/STS) and atomic force microscopy (AFM). We find that DCV5T-Me2 self-assembles in extended chains, stabilized by intercalated Au atoms. The effect of metal-ligand hybridization with Au adatoms causes an energetic downshift of the DCV5T-Me2 lowest unoccupied molecular orbital (LUMO) with respect to the uncoordinated molecules on the surface. The asymmetric coordination of a gold atom to only one molecular end group leads to an asymmetric localization of the LUMO and LUMO+1 states at opposite sides. Using model density functional theory (DFT) calculations, we explain such orbital reshaping as a consequence of linear combinations of the original LUMO and LUMO+1 orbitals, mixed by the attachment of a bridging Au adatom. Our study shows that the alignment of molecular orbitals and their distribution within individual molecules can be modified by contacting them to metal atoms in specific sites. PMID:25244124

Yang, Zechao; Corso, Martina; Robles, Roberto; Lotze, Christian; Fitzner, Roland; Mena-Osteritz, Elena; Bäuerle, Peter; Franke, Katharina J; Pascual, Jose I

2014-10-28

55

Molecular-orbital description of doubly excited atomic states generalized to arbitrary dimension  

NASA Astrophysics Data System (ADS)

The molecular-orbital description of two-electron atoms [J. M. Feagin and J. S. Briggs, Phys. Rev. A 37, 4599 (1988)], derived from H+2 by interchanging the roles of electrons and nuclei, is generalized to D dimensions. For H+2 itself there exist myriad exact interdimensional degeneracies because D-->D+2 is equivalent to m-->m+1, augmenting by unity the projection of the electronic angular momentum on the internuclear axis. When the molecular orbitals (MO's) are transcribed to treat two-electron motion, additional constraints limit the exact degeneracies to states in D=3 and 5, but many approximate degeneracies persist. Since the MO description emphasizes rotational properties of the two-electron atom, the link between dimension and orbital angular momentum is a pervasive feature. We use this link to classify groups of quasidegenerate doubly excited atomic energies and to explain striking similarities among certain pairs of hyperspherical or molecular-orbital two-electron potential curves.

Rost, J. M.; Sung, S. M.; Herschbach, D. R.; Briggs, J. S.

1992-09-01

56

Molecular-orbital description of doubly excited atomic states generalized to arbitrary dimension  

SciTech Connect

The molecular-orbital description of two-electron atoms (J. M. Feagin and J. S. Briggs, Phys. Rev. A 37, 4599 (1988)), derived from H{sub 2}{sup +} by interchanging the roles of electrons and nuclei, is generalized to {ital D} dimensions. For H{sub 2}{sup +} itself there exist myriad exact interdimensional degeneracies because {ital D}{r arrow}{ital D}+2 is equivalent to {ital m}{r arrow}{ital m}+1, augmenting by unity the projection of the electronic angular momentum on the internuclear axis. When the molecular orbitals (MO's) are transcribed to treat two-electron motion, additional constraints limit the exact degeneracies to states in {ital D}=3 and 5, but many approximate degeneracies persist. Since the MO description emphasizes rotational properties of the two-electron atom, the link between dimension and orbital angular momentum is a pervasive feature. We use this link to classify groups of quasidegenerate doubly excited atomic energies and to explain striking similarities among certain pairs of hyperspherical or molecular-orbital two-electron potential curves.

Rost, J.M.; Sung, S.M.; Herschbach, D.R. (Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138 (United States)); Briggs, J.S. (Fakultaet fuer Physik, Albert-Ludwigs-Universitaet, D-7800 Freiburg (Germany))

1992-09-01

57

The Phase Diagram of MgO from Density Functional Theory and Molecular Dynamics Simulations  

E-print Network

results. This FF, denoted as qMS-Q FF, was then used in molecular dynam- ics (MD) simulations simulations of many other materials. 64.30.+t, 64.70.Kb, 64.70.Dv, 64.90.+b I. INTRODUCTION Magnesium oxide, one of the most abundant oxides in the earth's lower mantle, has been studied extensively, both

Barr, Al

58

The periodic MINDO molecular orbital method as a surface analytical technique  

NASA Astrophysics Data System (ADS)

In previous work we have shown that the periodic LUC-MINDO molecular orbital method with optimized parameters is able to yield a good description of the bulk electronic and elastic properties of the homopolar covalent solids, diamond and silicon. In this paper we consider the extension of this semi-empirical technique to the study of semiconductor surfaces. This surfacemodified, self-consistent molecular orbital method is shown to be a rapidly convergent, computationally viable surface analytical technique which is capable of treating thick slabs and far more complex systems than the corresponding first-principles techniques. When applied to the Si(100)-2 × 1 surface it is shown to correctly predict both the reconstruction (dimerization) of the surface, and the fact that the surface electronic structure is semiconducting. The paper concludes with a brief outline of some proposed applications for this promising technique.

Craig, B. I.; Smith, P. V.

1989-03-01

59

Localized Molecular Orbital Studies of Fullerenes: C60 and C70  

Microsoft Academic Search

Localized molecular orbitals (LMOs) have been calculated for C60 and C70 by using the CNDO\\/2 approximation and the energy-localization scheme of Edmiston-Ruedenberg. It is found that the ?-bonding on the surfaces of the spherical carbon cages is localized into two-centered two-electron (2c2e) and three-centered two-electron (3c2e) bonds with additional charge distributions delocalized in the neighboring atoms. The localized electronic structures,

Jun Li; Chun-Wan Liu; Jia-Xi Lu

1994-01-01

60

Methane activation by metals and semiconductors. Molecular orbital theory. Final report, September 1986-December 1989  

SciTech Connect

The atom superposition and electron delocalization molecular orbital (ASED-MO) theory and catalyst cluster models as well as ASED-band calculations have been used to study methane CH activation over a diverse set of surfaces. These include metals, oxides, a sulfide, carbide and nitride, a metal with adsorbed O, and a polyoxometallate. CC coupling reactions over molybdenum disulfide and molybdenum carbide have been included.

Anderson, A.B.

1990-01-01

61

Linear dichroism in resonant inelastic x-ray scattering to molecular spin-orbit states.  

PubMed

Polarization-dependent resonant inelastic x-ray scattering (RIXS) is shown to be a new probe of molecular-field effects on the electronic structure of isolated molecules. A combined experimental and theoretical analysis explains the linear dichroism observed in Cl 2p RIXS following Cl 1s excitation in HCl and CF3Cl as due to molecular-field effects, including singlet-triplet exchange, indicating polarized-RIXS provides a direct probe of spin-orbit-state populations applicable to any molecule. PMID:18851444

Guillemin, R; Carniato, S; Stolte, W C; Journel, L; Taïeb, R; Lindle, D W; Simon, M

2008-09-26

62

Statistical correction to effective interactions in the fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

A theoretical scheme to evaluate effective, screened interactions between fragments is proposed within the framework of the fragment molecular orbital (FMO) method. In this theory, the presence of implicit, dielectric continuum solvent is not assumed, but only the information on bare, inter-fragment interaction energies obtained through the FMO calculation for explicit, molecular system is employed. The effective interactions with inclusion of entropic effect are then described and optimized as a consequence of inter-fragment correlations on the basis of classical-mechanical many-body theories. Test calculations for a simple model system and a realistic protein system are performed, and their implications are discussed.

Tanaka, Shigenori; Watanabe, Chiduru; Okiyama, Yoshio

2013-01-01

63

Spin-orbital entangled molecular jeff states in lacunar spinel compounds.  

PubMed

The entanglement of the spin and orbital degrees of freedom through the spin-orbit coupling has been actively studied in condensed matter physics. In several iridium oxide systems, the spin-orbital entangled state, identified by the effective angular momentum jeff, can host novel quantum phases. Here we show that a series of lacunar spinel compounds, GaM4X8 (M=Nb, Mo, Ta and W and X=S, Se and Te), gives rise to a molecular jeff state as a new spin-orbital composite on which the low-energy effective Hamiltonian is based. A wide range of electron correlations is accessible by tuning the bandwidth under external and/or chemical pressure, enabling us to investigate the cooperation between spin-orbit coupling and electron correlations. As illustrative examples, a two-dimensional topological insulating phase and an anisotropic spin Hamiltonian are investigated in the weak and strong coupling regimes, respectively. Our finding can provide an ideal platform for exploring jeff physics and the resulting emergent phenomena. PMID:24889209

Kim, Heung-Sik; Im, Jino; Han, Myung Joon; Jin, Hosub

2014-01-01

64

Spin-orbital entangled molecular jeff states in lacunar spinel compounds  

NASA Astrophysics Data System (ADS)

The entanglement of the spin and orbital degrees of freedom through the spin-orbit coupling has been actively studied in condensed matter physics. In several iridium oxide systems, the spin-orbital entangled state, identified by the effective angular momentum jeff, can host novel quantum phases. Here we show that a series of lacunar spinel compounds, GaM4X8 (M=Nb, Mo, Ta and W and X=S, Se and Te), gives rise to a molecular jeff state as a new spin-orbital composite on which the low-energy effective Hamiltonian is based. A wide range of electron correlations is accessible by tuning the bandwidth under external and/or chemical pressure, enabling us to investigate the cooperation between spin-orbit coupling and electron correlations. As illustrative examples, a two-dimensional topological insulating phase and an anisotropic spin Hamiltonian are investigated in the weak and strong coupling regimes, respectively. Our finding can provide an ideal platform for exploring jeff physics and the resulting emergent phenomena.

Kim, Heung-Sik; Im, Jino; Han, Myung Joon; Jin, Hosub

2014-06-01

65

Molecular dynamics of single-particle impacts predicts phase diagrams for large scale pattern formation.  

PubMed

Energetic particle irradiation can cause surface ultra-smoothening, self-organized nanoscale pattern formation or degradation of the structural integrity of nuclear reactor components. A fundamental understanding of the mechanisms governing the selection among these outcomes has been elusive. Here we predict the mechanism governing the transition from pattern formation to flatness using only parameter-free molecular dynamics simulations of single-ion impacts as input into a multiscale analysis, obtaining good agreement with experiment. Our results overturn the paradigm attributing these phenomena to the removal of target atoms via sputter erosion: the mechanism dominating both stability and instability is the impact-induced redistribution of target atoms that are not sputtered away, with erosive effects being essentially irrelevant. We discuss the potential implications for the formation of a mysterious nanoscale topography, leading to surface degradation, of tungsten plasma-facing fusion reactor walls. Consideration of impact-induced redistribution processes may lead to a new design criterion for stability under irradiation. PMID:21505432

Norris, Scott A; Samela, Juha; Bukonte, Laura; Backman, Marie; Djurabekova, Flyura; Nordlund, Kai; Madi, Charbel S; Brenner, Michael P; Aziz, Michael J

2011-01-01

66

A molecular orbital study of bonding and ionization energies in pentavalent uranium imide/amide complexes  

SciTech Connect

Discrete variational local density functional (X{alpha}) calculations on the model complexes ((RN)U(NR{sub 2}){sub 3}) (R = H (1), SiH{sub 3} (2)) have been performed in order to investigate the electronic structure of uranium amido/imido complexes. Special emphasis is placed on the energy ordering of the highest lying levels formed by U 5f orbitals and by out-of-plane N 2p{sub {pi}} orbitals. Orbital relaxations are also estimated by studying the fragments NR and NR{sub 2} with R = H and R = SiMe{sub 3} in order to allow a comparison of the model compounds 1 and 2 with the measured photoelectron spectrum of the complex ((Me{sub 3}SiN)U(N(SiMe{sub 3}){sub 2}){sub 3}). The ionization energies corresponding to the N 2p{sub {pi}} MOs are calculated in the order N 2p{sub {pi}} (amido) < N 2p{sub {pi}} (imido). The calculated level ordering is rationalized by comparing the order of the two types of U-N bonds and the charge distributions of the corresponding ligands. Taking the calculated ordering as well as the character of the molecular orbitals into account, a new assignment of the observed photoelectron spectra is given based on a comparison of He I and He II spectra.

Bowmaker, G.A.; Goerling, A.; Haeberlen, O.; Roesch, N. (Technische Univ. Muenchen, Garching (Germany)); Goodman, G.L. (Argonne National Lab., IL (United States)); Ellis, D.E. (Northwestern Univ., Evanston, IL (United States))

1992-02-19

67

Velocity diagrams  

NASA Technical Reports Server (NTRS)

The selection and design of velocity diagrams for axial flow turbines are considered. Application is treated in two parts which includes: (1) mean-section diagrams, and (2) radial variation of diagrams. In the first part, the velocity diagrams occurring at the mean section are assumed to represent the average conditions encountered by the turbine. The different types of diagrams, their relation to stage efficiency, and their selection when staging is required are discussed. In the second part, it is shown that in certain cases the mean-section diagrams may or may not represent the average flow conditions for the entire blade span. In the case of relatively low hub- to tip-radius ratios, substantial variations in the velocity diagrams are encountered. The radial variations in flow conditions and their effect on the velocity diagrams are considered.

Whitney, W. J.; Stewart, W. L.

1972-01-01

68

An analysis of predictions by the semi-empirical MNDO molecular orbital method for some aspects of molecular energetics  

NASA Astrophysics Data System (ADS)

Calculations using the MNDO HE molecular-orbital method predict that NH 4, PH 4 and H 3S are stable free radicals, and that local minima exist for H 3O and H 2Cl. The tendency of MNDO to overestimate the stability of such systems is traced to its neglect of overlap integrals. Results for H +2 (both ground and excited states) support this conclusion. Stable radicals with formulas BeH 3 and BH 4 are also predicted. Analysis of hydrocarbon thermochemistry indicates that MNDO fails to predict the correct sign for the relative magnitude of bond interactions, whereas ab initio calculations give the correct sign and approximately the correct magnitude. Finally, it is shown that the apparent superiority of MNDO over ab initio MO calculations in predicting molecular energetics is illusory when the methods are compared on the same basis.

Baird, N. Colin; Hadley, Graham C.

1986-07-01

69

X-ray microscopy using the photoexcitation to unoccupied ?*-character molecular orbits  

NASA Astrophysics Data System (ADS)

We studied the possibility of soft x-ray microscopy using unoccupied ?*-character molecular orbits of bases in DNA and RNA. We estimated the photoabsorption cross section of benzene molecule using the atomic base model. Discussion is extended to the case of nuclear acid bases caused by excitation of the 1s electron to the ?* orbit under assumption of the similar electronic transition with the benzene case and found that for the photon energy used in this study it is three times larger than that for the photoionization of the 1s electron at the water window region. We concluded that an image of DNA or RNA in wet biological cells may be observed with good contrast using this proposed method.

Iketaki, Yoshinori; Watanabe, Tsutomu

1995-02-01

70

Molecular orbital evaluation of charge flow dynamics in natural pigments based photosensitizers.  

PubMed

The relationship between structure and photo electrochemical property of ten natural pigments from plants, insects and microbes has been analyzed using density functional theory (DFT) at the B3LYP/6-31G(d) level. The essential parameters for their photoelectrochemical behaviour such as ground state geometries, electronic transition energies and oxidation potentials are computed. The attachment tendency of the anchoring groups, expressed as the deprotonation order, is determined by calculating the proton affinities at different sites of the molecules. A thorough analysis of the charge flow dynamics in the molecular orbitals (HOMO and LUMO) of these molecules has been carried out and presented to emphasize the role of these orbitals in effective charge separation, the important feature of photosensitizers for DSSC. This study highlights that the flexible spatial orientation provided by the bridging aliphatic unsaturation favours the oscillator strength and the hydroxyl anchor group attached to the ring of delocalized pi electron cloud acts as the effective anchor. PMID:19669807

Heera, Thekinneydath Rajan; Cindrella, Louis

2010-03-01

71

Initial elementary processes in tetrafluoroethylene plasma: An ab initio molecular orbital study  

NASA Astrophysics Data System (ADS)

Initial elementary processes in tetrafluoroethylene plasma are studied by using an ab initio molecular orbital method. The energy-surfaces at excited states are obtained by the Hartree-Fock method with a double zeta basis set, plus Rydberg orbitals. A ?-?* transition is low-lying both at singlet and triplet excited states. Vinyl-polymerization-type reactions are expected in the presence of some radical species via these transitions. The C=C bond cleaves via a triplet ?-?* transition to form CF2. The predicted elementary processes via these states are compatible with experimental results that C2F4* and CF2 are primary precursors. No excited states that bring about a C—F bond cleavage are obtained within 10 eV of the ground state. As a path for a C—F bond cleavage, a dissociative electron attachment process is found in a low energy region. This process is considered to be important for producing fluorine anions.

Sato, Kota; Komatsu, Toru; Iwabuchi, Susumu

1993-12-01

72

Detection of a Molecular Disk Orbiting the Nearby, "Old," Classical T Tauri Star MP Mus  

E-print Network

We have used the Atacama Pathfinder Experiment 12 m telescope to detect circumstellar CO emission from MP Mus (K1 IVe), a nearby (D ~ 100 pc), actively accreting, ~7 Myr-old pre-main sequence (pre-MS) star. The CO emission line profile measured for MP Mus is indicative of an orbiting disk with radius ~120 AU, assuming the central star mass is 1.2 solar masses and the disk inclination is ~30 degrees, and the inferred disk molecular gas mass is ~3 Earth masses. MP Mus thereby joins TW Hya and V4046 Sgr as the only late-type (low-mass), pre-MS star systems within ~100 pc of Earth that are known to retain orbiting, molecular disks. We also report the nondetection (with the Institut de Radio Astronomie Millimetrique 30 m telescope) of CO emission from another ten nearby (D ~ 100 pc or less), dusty, young (age ~10-100 Myr) field stars of spectral type A-G. We discuss the implications of these results for the timescales for stellar and Jovian planet accretion from, and dissipation of, molecular disks around young st...

Kastner, Joel H; Sacco, G G; Forveille, Thierry; Zuckerman, B

2010-01-01

73

DETECTION OF A MOLECULAR DISK ORBITING THE NEARBY, 'OLD', CLASSICAL T TAURI STAR MP MUSCAE  

SciTech Connect

We have used the Atacama Pathfinder Experiment 12 m telescope to detect circumstellar CO emission from MP Muscae (MP Mus; K1 IVe), a nearby (D {approx} 100 pc), actively accreting, {approx}7 Myr old pre-main-sequence (pre-MS) star. The CO emission line profile measured for MP Mus is indicative of an orbiting disk with radius {approx}120 AU, assuming that the central star mass is 1.2 M {sub sun} and the disk inclination is i {approx} 30{sup 0}. The inferred disk molecular gas mass is {approx}3 M {sub +}. MP Mus thereby joins TW Hya and V4046 Sgr as the only late-type (low-mass), pre-MS star systems within {approx}100 pc of Earth that are known to retain orbiting, molecular disks. We also report the nondetection (with the Institut de Radio Astronomie Millimetrique 30 m telescope) of CO emission from another 10 nearby (D {approx_lt} 100 pc), dusty, young (age {approx}10-100 Myr) field stars of spectral type A-G. We discuss the implications of these results for the timescales for stellar and Jovian planet accretion from, and dissipation of, molecular disks around young stars.

Kastner, Joel H.; Sacco, G. G. [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Hily-Blant, Pierry; Forveille, Thierry [Laboratoire d'Astrophysique de Grenoble, Universite Joseph Fourier-CNRS, BP 53, 38041 Grenoble Cedex (France); Zuckerman, B., E-mail: jhk@cis.rit.ed [Department of Physics and Astronomy, University of California, Los Angeles 90095, CA (United States)

2010-11-10

74

Fragment molecular orbital calculation using the RI-MP2 method  

NASA Astrophysics Data System (ADS)

The resolution of the identity second-order Møller-Plesset perturbation theory (RI-MP2) was introduced into the fragment molecular orbital (FMO) method, where the program of the RI-MP2 method was newly developed. After some test calculations with a small peptide, the performance of the RI-MP2 method with the FMO scheme was demonstrated for two biomolecular systems: the human immunodeficiency virus type 1 protease with the lopinavir molecule, and the prion protein with the GN8 molecule. These calculations showed the great advantage of FMO calculations using the RI-MP2 method over ordinary FMO calculations.

Ishikawa, Takeshi; Kuwata, Kazuo

2009-05-01

75

An ab initio molecular orbital study of the electron affinity of boron clusters  

NASA Astrophysics Data System (ADS)

The electron affinities of boron clusters were studied using ab initio molecular orbital methods to discuss the phenomenon of clustered boron anions emitted during sputtering. Calculations were performed at the MP4(SDQ)/CBSB5 level. The calculated electron affinities of B, B 2, and B 3 were found to be 0.214, 3.66, and 3.20 eV, respectively. These values are qualitatively consistent with the experimental data of sputtering yield of B -, B 2-, and B 3-.

Takeuchi, T.; Yamamoto, M.; Kiuchi, M.

1999-06-01

76

Reducing the scaling of the fragment molecular orbital method using the multipole method  

NASA Astrophysics Data System (ADS)

The fragment molecular orbital (FMO) method is combined with the multipole method (MM) to reduce the quadratic scaling of the electrostatic terms. MM is applied to the energy and gradient of the well-separated interfragment interactions, and the gradient of the one electron electrostatic potential. The accuracy is controlled using the rigorous criteria based on the multipole expansion. Test calculations on ice surfaces using the 6-31G?? and 6-31++G?? basis sets show that MM is accurate and significantly accelerates FMO, although some quadratically scaling terms remain to be improved.

Choi, Cheol Ho; Fedorov, Dmitri G.

2012-08-01

77

Multicenter molecular integrals for Slater orbitals of higher principal quantum numbers  

NASA Technical Reports Server (NTRS)

As was shown earlier by Tai (1979), by using the Fourier-transform technique and properly coupling a pair of two-center exchange integrals, the multicenter molecular integrals can be cast into a simple expression upon which numerical procedures can be directly applied. In this paper, the procedure of Tai is extended to integrals involving orbitals with arbitrarily higher principal quantum number. The derivation is outlined, and the explicit expressions are presented for a three-center nuclear attraction integral and a four-center two-electron Coulomb repulsion integral of arbitrary higher states.

Tai, H.

1989-01-01

78

An ab initio molecular orbital study of metal nitrosyl bond angles in iron complexes  

E-print Network

] 9 2+ shows it to be similar in both electronic and molecular structure to FeC10) (dtc) (dtc dithiocarbamate) and [Fe(CN)4~DJ; that is all three complexes are square pyramidal structures in which the unpaired electron resides in an orbital which... by Scheidt et al. . For the three complexes Fe(W) ~)- 10 (1-MeIM), l-xmthylimidaaole), Fe(NO) ~) (4-MePip), (4-MePiP = (4-rmthylpiperidine), and Fe pE) (TPP) (4-Yepip): CRC1, he f~~d a linear correlation between nitrosyl stretching frequency' and the Fe...

Hawkins, Tommy Wayne

2012-06-07

79

Simulation of charge transfer and orbital rehybridization in molecular and condensed matter systems  

NASA Astrophysics Data System (ADS)

The mixing and shifting of electronic orbitals in molecules, or between atoms in bulk systems, is crucially important to the overall structure and physical properties of materials. Understanding and accurately modeling these orbital interactions is of both scientific and industrial relevance. Electronic orbitals can be perturbed in several ways. Doping, adding or removing electrons from systems, can change the bond-order and the physical properties of certain materials. Orbital rehybridization, driven by either thermal or pressure excitation, alters the short-range structure of materials and changes their long-range transport properties. Macroscopically, during bond formation, the shifting of electronic orbitals can be interpreted as a charge transfer phenomenon, as electron density may pile up around, and hence, alter the effective charge of, a given atom in the changing chemical environment. Several levels of theory exist to elucidate the mechanisms behind these orbital interactions. Electronic structure calculations solve the time-independent Schrodinger equation to high chemical accuracy, but are computationally expensive and limited to small system sizes and simulation times. Less fundamental atomistic calculations use simpler parameterized functional expressions called force-fields to model atomic interactions. Atomistic simulations can describe systems and time-scales larger and longer than electronic-structure methods, but at the cost of chemical accuracy. In this thesis, both first-principles and phenomenological methods are addressed in the study of several encompassing problems dealing with charge transfer and orbital rehybridization. Firstly, a new charge-equilibration method is developed that improves upon existing models to allow next-generation force-fields to describe the electrostatics of changing chemical environments. Secondly, electronic structure calculations are used to investigate the doping dependent energy landscapes of several high-temperature superconducting materials in order to parameterize the apparently large nonlinear electron-phonon coupling. Thirdly, ab initio simulations are used to investigate the role of pressure-driven structural re-organization in the crystalline-to-amorphous (or, metallic-to-insulating) transition of a common binary phase-change material composed of Ge and Sb. Practical applications of each topic will be discussed. Keywords. Charge-equilibration methods, molecular dynamics, electronic structure calculations, ab initio simulations, high-temperature superconductors, phase-change materials.

Nistor, Razvan A.

80

Envelope molecular-orbital theory of extended systems. I. Electronic states of organic quasilinear nanoheterostructures  

NASA Astrophysics Data System (ADS)

A conceptually appealing and computationally economical course-grained molecular-orbital (MO) theory for extended quasilinear molecular heterostructures is presented. The formalism, which is based on a straightforward adaptation, by including explicitly the vacuum, of the envelope-function approximation widely employed in solid-state physics leads to a mapping of the three-dimensional single-particle eigenvalue equations into simple one-dimensional hole and electron Schrödinger-like equations with piecewise-constant effective potentials and masses. The eigenfunctions of these equations are envelope MO's in which the short-wavelength oscillations present in the full MO's, associated with the atomistic details of the molecular potential, are smoothed out automatically. The approach is illustrated by calculating the envelope MO's of high-lying occupied and low-lying virtual ? states in prototypical nanometric heterostructures constituted by oligomers of polyacetylene and polydiacetylene. Comparison with atomistic electronic-structure calculations reveals that the envelope-MO energies agree very well with the energies of the ? MO's and that the envelope MO's describe precisely the long-wavelength variations of the ? MO's. This envelope MO theory, which is generalizable to extended systems of any dimensionality, is seen to provide a useful tool for the qualitative interpretation and quantitative prediction of the single-particle quantum states in mesoscopic molecular structures and the design of nanometric molecular devices with tailored energy levels and wavefunctions.

Arce, J. C.; Perdomo-Ortiz, A.; Zambrano, M. L.; Mujica-Martínez, C.

2011-03-01

81

An efficient molecular orbital approach for self-consistent calculations of molecular junctions  

Microsoft Academic Search

To model electron transport through a molecular junction, we propose an efficient method using an ab initio self-consistent nonequilibrium Green's function theory combined with density functional theory. We have adopted a model close to the extended molecule approach, due to its flexibility, but have improved on the problems relating to molecule-surface couplings and the long-range potential via a systematic procedure

Hisao Nakamura; Koichi Yamashita

2006-01-01

82

Introductory Molecular Orbital Theory: An Honors General Chemistry Computational Lab as Implemented Using Three-Dimensional Modeling Software  

ERIC Educational Resources Information Center

In this study, a computational molecular orbital theory experiment was implemented in a first-semester honors general chemistry course. Students used the GAMESS (General Atomic and Molecular Electronic Structure System) quantum mechanical software (as implemented in ChemBio3D) to optimize the geometry for various small molecules. Extended Huckel…

Ruddick, Kristie R.; Parrill, Abby L.; Petersen, Richard L.

2012-01-01

83

Massive Star Formation in the Molecular Ring Orbiting the Black Hole at the Galactic Center  

E-print Network

A ring of dense molecular gas extending 2-7 pc orbits the supermassive black hole Sgr A* at the center of our Galaxy. Using the Green Bank Telescope, we detected water maser lines and both narrow (0.35 km/s) and broad (30 - 50 km/s) methanol emission from the molecular ring. Two of the strongest methanol lines at 44 GHz are confirmed as masers by interferometric observations. These class I methanol masers are collisionally excited and are signatures of early phases of massive star formation in the disk of the Galaxy, suggesting that star formation in the molecular ring is in its early phase. Close inspection of the kinematics of the associated molecular clumps in the HCN (J=1-0) line reveals broad red-shifted wings indicative of disturbance by protostellar outflows from young (few times 10^4 yr), massive stars embedded in the clumps. The thermal methanol profile has a similar shape, with a narrow maser line superimposed on a broad, red-shifted wing. Additional evidence for the presence of young massive protostars is provided by shocked molecular hydrogen and a number of striking ionized and molecular linear filaments in the vicinity of methanol sources suggestive of 0.5-pc scale protostellar jets. Given that the circumnuclear molecular ring is kinematically unsettled and thus is likely be the result of a recent capture, the presence of both methanol emission and broad, red-shifted HCN emission suggests that star formation in the circumnuclear ring is in its infancy.

F. Yusef-Zadeh; J. Braatz; M. Wardle; D. Roberts

2008-07-10

84

Analyzing the electric response of molecular conductors using "electron deformation" orbitals and occupied-virtual electron transfer.  

PubMed

The concept of "electron deformation orbitals" (EDOs) is used to investigate the electric response of conducting metals and oligophenyl chains. These orbitals and their eigenvalues are obtained by diagonalization of the deformation density matrix (difference between the density matrices of the perturbed and unperturbed systems) and can be constructed as linear combinations of the unperturbed molecular orbitals within "frozen geometry" conditions. This form of the EDOs allows calculating the part of the electron deformation density associated to an effective electron transfer from occupied to virtual orbitals (valence to conduction band electron transfer in the band model of conductivity). It is found that the "electron deformation" orbitals pair off, displaying the same eigenvalue but opposite sign. Each pair represents an amount of accumulation/depletion of electron charge at different molecular regions. In the oligophenyl systems investigated only one pair contributes effectively to the charge flow between molecular ends, resulting from the promotion of electrons from occupied orbitals to close in energy virtual orbitals of appropriate symmetry and overlapping. Analysis of this pair along explains the differences in conductance of olygophenyl chains based on phenyl units. PMID:24676839

Mandado, Marcos; Ramos-Berdullas, Nicolás

2014-06-30

85

Methane activation by metals and semiconductors. Molecular orbital theory. Annual report, September 1987-August 1988  

SciTech Connect

An atom-superposition and electron delocalization molecular orbital study was made of CHn and CO reactions over coordinatively unsaturated Mo(IV) edge cations in MoS2. Coupling to C2H6 and C2H5(a) proceed with high barriers. CH2(a) coupling to strongly adsorbed ethylene proceeds with a lower barrier, and hydrogenation to ethane is possible. CO binds relatively weakly to 5-fold coordinated Mo and strongly to 4-fold coordinated sites. Over two such sites, CO easily tilts to a di-Sigma bridging orientation and dissociates with a low barrier. In the Fischer-Tropsch process hydrogenation to CH3(ads) and H2O(g) is expected. CO inserts into the Mo-CH3 bond with a low barrier, and subsequent hydrogenations to form C2H6+H2O or CH3CH2OH are favorable. It is proposed that the selectivity toward alcohol formation over alkali-doped MoS2 (the DOW process) may stem from the ability of the alkali cations to stabilize alkoxy intermediates. A second molecular orbital study shows AlN behaves similarly to MgO toward CH4. Stoichiometric AlN is inactive. CH4 is activated by surface N(2-) hole sites, forming surface HN(2-) and methyl radicals.

Anderson, A.B.

1988-09-01

86

The electronic absorption spectra of some acyl azides. Molecular orbital treatment  

NASA Astrophysics Data System (ADS)

The electronic absorption spectra of benzoyl azide and its derivatives: p-methyl, p-methoxy, p-chloro and p-nitrobenzoyl azide were investigated in different solvents. The observed spectra differ basically from the electronic spectra of aryl azides or alkyl azides. Four intense ?-? * transitions were observed in the accessible UV region of the spectrum of each of the studied compounds. The contribution of charge transfer configurations to the observed transitions is rather weak. Shift of band maximum with solvent polarity is minute. On the other hand, band intensity is highly dependent on the solvent used. The observed transitions are delocalized rather than localized ones as in the case with aryl and alkyl azides. The attachment of the C dbnd O group to the azide group in acyl azides has a significant effect on the electronic structure of the molecule. The arrangements as well as energies of the molecular orbitals are different in acyl azides from those in aryl azides. The first electronic transition in phenyl azide is at 276 nm, whereas that of bezoyle azide is at 251 nm. Ab initio molecular orbital calculations using both RHF/6-311G* and B3LYP/6-31+G * levels were carried out on the ground states of the studied compounds. The wave functions of the excited states were calculated using the CIS and the AM1-CI procedures.

Abu-Eittah, Rafie H.; Mohamed, Adel A.; Farag, A. M.; Al Omar, Ahmed M.

2008-06-01

87

Radio Emission Line Surveys of the Molecular Disks Orbiting TW Hya and V4046 Sgr  

NASA Astrophysics Data System (ADS)

We have conducted the first comprehensive mm-wave molecular emission line surveys of the evolved circumstellar disks orbiting the nearby pre-main sequence stars TW Hya (D = 54 pc) and V4046 Sgr AB (D = 73 pc). Both systems have relatively advanced ages of roughly 10 Myr; nevertheless, these disks are known to retain significant residual gaseous components, as evidenced by previous radio and infrared detections of molecular and atomic emission lines and optical/X-ray spectral signatures of ongoing stellar accretion. Our unbiased broad-band radio spectral surveys were performed with the Atacama Pathfinder Experiment (APEX) 12 meter telescope and are intended to yield a complete census of bright molecular emission lines in the 0.85-1.0 mm wavelength range. Here, we present initial results, with particular emphasis on newly detected molecular species and emission lines that are potential diagnostics of the effects of high-energy radiation from pre-main sequence stars on disk gas chemistry and physical conditions. This research is supported by National Science Foundation grant AST-1108950 to RIT.

Kastner, Joel H.; Hily-Blant, P.; Rodriguez, D.; Punzi, K.; Forveille, T.

2013-01-01

88

Equation of state of dense plasmas: Orbital-free molecular dynamics as the limit of quantum molecular dynamics for high-Z elements  

NASA Astrophysics Data System (ADS)

The applicability of quantum molecular dynamics to the calculation of the equation of state of a dense plasma is limited at high temperature by computational cost. Orbital-free molecular dynamics, based on a semiclassical approximation and possibly on a gradient correction, is a simulation method available at high temperature. For a high-Z element such as lutetium, we examine how orbital-free molecular dynamics applied to the equation of state of a dense plasma can be regarded as the limit of quantum molecular dynamics at high temperature. For the normal mass density and twice the normal mass density, we show that the pressures calculated with the quantum approach converge monotonically towards those calculated with the orbital-free approach; we observe a faster convergence when the orbital-free approach includes the gradient correction. We propose a method to obtain an equation of state reproducing quantum molecular dynamics results up to high temperatures where this approach cannot be directly implemented. With the results already obtained for low-Z plasmas, the present study opens the way for reproducing the quantum molecular dynamics pressure for all elements up to high temperatures.

Danel, J.-F.; Blottiau, P.; Kazandjian, L.; Piron, R.; Torrent, M.

2014-10-01

89

Phase Diagrams  

NSDL National Science Digital Library

This problem set challenges students to interpret a simplified temperature-composition phase diagram for the system enstatite (Mg2Si2O6) - diopside (CaMgSi2O6), which are common constituents of peridotites, gabbros, and basalts. Students are provided with the phase diagram and asked to answer 13 questions about it.

90

IMAGING THE MOLECULAR DISK ORBITING THE TWIN YOUNG SUNS OF V4046 Sgr  

SciTech Connect

We have imaged the disk surrounding the nearby (D {approx} 73 pc), {approx}12 Myr, classical T Tauri binary system V4046 Sgr with the Submillimeter Array (SMA) at an angular resolution of {approx}2''. We detect a rotating disk in {sup 12}CO(2-1) and {sup 13}CO(2-1) emission and resolve the continuum emission at 1.3 mm. We infer disk gas and dust masses of {approx}110 and {approx}40 Earth masses, respectively. Fits to a power-law disk model indicate that the molecular disk extends to {approx}370 AU and is viewed at an inclination of between {approx}33{sup 0} and {approx}39{sup 0} for dynamical stellar masses ranging from 1.8 M {sub sun} down to 1.5 M {sub sun} (the range of the total mass previously determined for the central, 2.4 day spectroscopic binary). This range of disk inclination is consistent with that assumed in deducing the central binary mass (i.e., 35{sup 0}), suggesting that the V4046 Sgr binary system and its circumbinary, molecular disk are coplanar. In light of the system's age and binarity, the presence of an extensive molecular disk orbiting V4046 Sgr provides constraints on the timescales of processes related to Jovian planet formation and demonstrates that circumbinary Jovian planets potentially could form around close binary systems.

Rodriguez, David R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Kastner, Joel H. [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Wilner, David; Qi, Chunhua, E-mail: drodrigu@astro.ucla.ed, E-mail: jhk@cis.rit.ed, E-mail: dwilner@cfa.harvard.ed, E-mail: cqi@cfa.harvard.ed [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Mail Stop 42, Cambridge, MA 02138 (United States)

2010-09-10

91

Fourier transform photoelectron diffraction and its application to molecular orbitals and surface structure  

SciTech Connect

Photoemission intensities from the molecular orbitals of c(2x2)CO/Pt(111) over a wide photon energy range were measured and analyzed by the same methods developed for structural studies using core levels. The 4{sigma} orbital center of gravity is found to be concentrated between the C and O atoms, while that of the 5{sigma} orbital lies between the C atom and the Pt surface. The C 1s photoelectron diffraction was used to determine the adsorption geometry. The earlier ambiguity that multiple scattering is needed to correctly model a {chi} curve while single scattering is sufficient for understanding major peaks in the ARPEFS-FTS is clarified by studying the clean Ni(111) surface. In the normal emission case, several different combinations of scattering events have similar path length differences (PLDs), and can either cancel each other or enhance the corresponding FT peak. In the off-normal case the degeneracy is greatly reduced due to the lower degree of symmetry. In normal emission AR PEFS, up to third order multiple scattering is needed to describe fully both the {chi} curve and its FT spectrum. To improve the spectral resolution in the ARPEFS-FT analysis, several new spectral analysis methods are introduced. With both autocorrelation autoregression (ACAR) and autocorrelation eigenvector (ACE), we can produce a reliable power spectrum by following the order-closing procedure. The best spectra are usually obtained when the autocorrelation sequence is computed with lags up to half the data range. A simple way of determining surface adsorption sites is proposed as follows: First use a single scattering cluster for possible adsorption sites to construct the geometrical PLDs from the strong backscattering events; then compare these PLDs with those obtained from the ARPEFS-FT analysis of the experimental data. After the preferred adsorption site is determined, fine tune the interlayer distances according to the positional R-factor.

Zhou, Xin

1998-11-30

92

Oxygen evolution on a SrFeO3 anode - Mechanistic considerations from molecular orbital theory  

NASA Technical Reports Server (NTRS)

Various pathways proposed in the literature for the evolution of O2 in electrochemical oxidations are explored using the atom superposition and electron delocalization molecular orbital (ASED-MO) theory and the cluster models of the SrFeO3 surface as a prototype material. Calculations indicate that oxygen atoms can be easily formed on the (100) surface as well as on the edge cation sites of a SrFeO3 anode by the discharge of OH(-), followed by its deprotonation and electron transfer to the electrode. The O atoms can form O2 on the edge and corner sites, where the Fe(4+) is coordinated to four and three bulk oxygen anions, respectively. The calculations strongly disfavor mechanisms involving coupling of oxygen atoms adsorbed on different cations as well as a mechanism featuring an ozone intermediate.

Mehandru, S. P.; Anderson, Alfred B.

1989-01-01

93

Mapping Enzymatic Catalysis Using the Effective Fragment Molecular Orbital Method: Towards all ab initio Biochemistry  

PubMed Central

We extend the Effective Fragment Molecular Orbital (EFMO) method to the frozen domain approach where only the geometry of an active part is optimized, while the many-body polarization effects are considered for the whole system. The new approach efficiently mapped out the entire reaction path of chorismate mutase in less than four days using 80 cores on 20 nodes, where the whole system containing 2398 atoms is treated in the ab initio fashion without using any force fields. The reaction path is constructed automatically with the only assumption of defining the reaction coordinate a priori. We determine the reaction barrier of chorismate mutase to be kcal mol?1 for MP2/cc-pVDZ and for MP2/cc-pVTZ in an ONIOM approach using EFMO-RHF/6-31G(d) for the high and low layers, respectively. PMID:23593259

Steinmann, Casper; Fedorov, Dmitri G.; Jensen, Jan H.

2013-01-01

94

?-Frontier molecular orbitals in S = 2 ferryl species and elucidation of their contributions to reactivity  

PubMed Central

S = 2 FeIV?O species are key intermediates in the catalysis of most nonheme iron enzymes. This article presents detailed spectroscopic and high-level computational studies on a structurally-defined S = 2 FeIV?O species that define its frontier molecular orbitals, which allow its high reactivity. Importantly, there are both ?- and ?-channels for reaction, and both are highly reactive because they develop dominant oxyl character at the transition state. These ?- and ?-channels have different orientation dependences defining how the same substrate can undergo different reactions (H-atom abstraction vs. electrophilic aromatic attack) with FeIV?O sites in different enzymes, and how different substrates can undergo different reactions (hydroxylation vs. halogenation) with an FeIV?O species in the same enzyme. PMID:22908238

Srnec, Martin; Wong, Shaun D.; England, Jason; Que, Lawrence; Solomon, Edward I.

2012-01-01

95

Molecular orbital studies in oxidation: Sulfate formation and metal-metal oxide adhesion  

NASA Technical Reports Server (NTRS)

The chemical mechanisms for sulfate formation from sodium chloride and sulfur trioxide, which is a product of jet fuel combustion was determined. Molten sodium sulfate leads to hot corrosion of the protective oxide layers on turbine blades. How yttrium dopants in nidkel-aluminum alloys used in turbine blades reduce the spalling rate of protective alumina films and enhance their adhesion was also determined. Two other fulfate mechanisms were deduced and structure of carbon monoxide on a clean chronium and clean platinum-titanium alloys surfaces was determined. All studies were by use of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. Seven studies were completed. Their titles and abstracts are given.

Anderson, A. B.

1985-01-01

96

The Effective Fragment Molecular Orbital Method for Fragments Connected by Covalent Bonds  

E-print Network

We extend the effective fragment molecular orbital method (EFMO) into treating fragments connected by covalent bonds. The accuracy of EFMO is compared to FMO and conventional ab initio electronic structure methods for polypeptides including proteins. Errors in energy for RHF and MP2 are within 2 kcal/mol for neutral polypeptides and 6 kcal/mol for charged polypeptides similar to FMO but obtained two to five times faster. For proteins, the errors are also within a few kcal/mol of the FMO results. We developed both the RHF and MP2 gradient for EFMO. Compared to ab initio, the EFMO optimized structures had an RMSD of 0.40 and 0.44 {\\AA} for RHF and MP2, respectively.

Steinmann, Casper; Jensen, Jan H

2012-01-01

97

Mapping Enzymatic Catalysis using the Effective Fragment Molecular Orbital Method: Towards all ab initio Biochemistry  

E-print Network

We extend the Effective Fragment Molecular Orbital (EFMO) method to the frozen domain approach where only the geometry of an active part is optimized, while the many-body polarization effects are considered for the whole system. The new approach efficiently mapped out the entire reaction path of chorismate mutase in less than four days using 80 cores on 20 nodes, where the whole system containing 2398 atoms is treated in the ab initio fashion without using any force fields. The reaction path is constructed automatically with the only assumption of defining the reaction coordinate a priori. We determine the reaction barrier of chorismate mutase to be $18.3\\pm 3.6$ kcal mol$^{-1}$ using ONIOM with MP2/cc-pVDZ and EFMO/6-31G(d) for the high and low layers, respectively.

Steinmann, Casper; Jensen, Jan H

2012-01-01

98

Anomalous molecular orbital variation upon adsorption on a wide band gap insulator  

NASA Astrophysics Data System (ADS)

It is commonly believed that organic molecules are physisorbed on the ideal nonpolar surfaces of wide band gap insulators with limited variation in the electronic properties of the adsorbate molecule. On the basis of first principles calculations within density functional theory (DFT) and GW approximation, we show that this is not generally true. We find that the molecular frontier orbitals undergo significant changes when a hydroxy acid (here we chose gluconic acid) is adsorbed on MgSO4.H2O(100) surface due to the complex interaction between the molecule and the insulating surface. The predicted trend of the adsorption effect on the energy gap obtained by DFT is reversed when the surface polarization effect is taken into account via the many-body corrections.

Chen, Wei; Tegenkamp, Christoph; Pfnür, Herbert; Bredow, Thomas

2010-06-01

99

?-Bromo-2,6-dichlorotoluene: Molecular structure, vibrational spectroscopy, natural bond orbital analysis and NMR studies  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectra of ?-bromo-2,6-dichlorotoluene (?BDCT) have been recorded. The structural and spectroscopic data of the molecule in the ground state have been calculated using Hartree Fock (HF) and Density Functional Theory (DFT)/B3LYP with the standard 6-31++G(d,p) basis set. The optimized molecular geometry, vibrational frequencies and atomic charges in the ground state are calculated. With the help of specific scaling procedures, the observed vibrational wavenumbers in FT-IR and FT-Raman spectra have been analyzed and assigned to different normal modes of the molecule. A detailed interpretation of the infrared and Raman spectra of ?BDCT is also reported based on total energy distribution (TED). The 1H and 13C NMR chemical shifts have been calculated by gauge-including atomic orbital method with B3LYP/6-31++G(d,p) approach. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The theoretical results agree well with the observed spectra.

Karunakaran, V.; Balachandran, V.

2012-09-01

100

Design principle for increasing charge mobility of ?-conjugated polymers using regularly localized molecular orbitals  

PubMed Central

The feasibility of using ?-conjugated polymers as next-generation electronic materials is extensively studied; however, their charge mobilities are lower than those of inorganic materials. Here we demonstrate a new design principle for increasing the intramolecular charge mobility of ?-conjugated polymers by covering the ?-conjugated chain with macrocycles and regularly localizing ?-molecular orbitals to realize an ideal orbital alignment for charge hopping. Based on theoretical predictions, insulated wires containing meta-junctioned poly(phenylene–ethynylene) as the backbone units were designed and synthesized. The zigzag wires exhibited higher intramolecular charge mobility than the corresponding linear wires. When the length of the linear region of the zigzag wires was increased to 10 phenylene–ethynylene units, the intramolecular charge mobility increased to 8.5?cm2?V?1?s?1. Theoretical analysis confirmed that this design principle is suitable for obtaining ideal charge mobilities in ?-conjugated polymer chains and that it provides the most effective pathways for inter-site hopping processes. PMID:23575695

Terao, Jun; Wadahama, Akihisa; Matono, Akitoshi; Tada, Tomofumi; Watanabe, Satoshi; Seki, Shu; Fujihara, Tetsuaki; Tsuji, Yasushi

2013-01-01

101

Estimation of Molecular Acidity via Electrostatic Potential at the Nucleus and Valence Natural Atomic Orbitals  

PubMed Central

An effective approach of estimating molecular pKa values from simple density functional calculations is proposed in this work. Both the molecular electrostatic potential (MEP) at the nucleus of the acidic atom and the sum of valence natural atomic orbitals are employed for three categories of compounds, amines and anilines, carbonyl acids and alcohols, and sulfonic acids and thiols. A strong correlation between experimental pKa values and each of these two quantities for each of the three categories has been discovered. Moreover, if the MEP is subtracted by the isolated atomic MEP for each category of compounds, we observe a single unique linear relationship between the resultant MEP difference and experimental pKa data of amines, anilines, carbonyl acids, alcohols, sulfonic acids, thiols, and their substituents. These results can generally be utilized to simultaneously estimate pKa values at multiple sites with a single calculation for either relatively small molecules in drug design or amino acids in proteins and macromolecules. PMID:19317439

Liu, Shubin; Pedersen, Lee G.

2009-01-01

102

Communication: Superatom molecular orbitals: new types of long-lived electronic states.  

PubMed

We present ab initio calculations of the quasiparticle decay times in a Buckminsterfullerene based on the many-body perturbation theory. A particularly lucid representation arises when the broadening of the quasiparticle states is plotted in the angular momentum (l) and energy (?) coordinates. In this representation the main spectroscopic features of the fullerene consist of two occupied nearly parabolic bands, and delocalized plane-wave-like unoccupied states with a few long-lived electronic states (the superatom molecular orbitals, SAMOs) embedded in the continuum of Fermi-liquid states. SAMOs have been recently uncovered experimentally by Feng et al. [Science 320, 359 (2008)] using scanning tunneling spectroscopy. The present calculations offer an explanation of their unusual stability and unveil their long-lived nature making them good candidates for applications in the molecular electronics. From the fundamental point of view these states illustrate a concept of the Fock-space localization [B. L. Altshuler, Y. Gefen, A. Kamenev, and L. S. Levitov, Phys. Rev. Lett. 78, 2803 (1997)] with properties drastically different from the Fermi-liquid excitations. PMID:22128920

Pavlyukh, Y; Berakdar, J

2011-11-28

103

Ab initio molecular orbital study of adsorption of oxygen, nitrogen, and ethylene on silver-zeolite and silver halides  

SciTech Connect

An ab initio molecular orbital study is undertaken on the adsorption of N{sub 2}, O{sub 2}, and C{sub 2}H{sub 4} (adsorbate) on Ag-zeolite and Ag halides (adsorbent). Geometry optimization is performed at the HF/3-21G level, while MP2/3-21G with natural bond orbital calculations are performed to obtain energies, atomic charges, orbital energies, and orbital populations (occupancies). The bonding of adsorbate to adsorbent is discussed in the context of {sigma}-donation (i.e., overlap of the 2p orbitals of the adsorbate molecule with the 5s orbital of Ag) and d-{pi}* back donation (i.e., overlap of the 4d{sub yz} orbitals of Ag with the 2p* antibonding orbitals of the adsorbate). For all adsorbate-adsorbent pairs, the ratio of {sigma}-donation to d-{pi}* back donation is approximately 3:1. Results on occupancy analysis indicate that a considerable electron redistribution from the 4d{sub zy} orbitals to the 4d{sub yz} orbitals occurs in Ag during adsorption and that this redistribution has possibly enhanced the d-{pi}* back donation. Net charge and energy gap ({Delta}{epsilon}) analyses indicate that it is slightly easier for N{sub 2} than O{sub 2} to adsorb, whereas a comparison of N{sub 2} and O{sub 2} adsorption from calculations of the energies of adsorption is inconclusive. However, a fair agreement is obtained in comparison of theory and experiment for energy of adsorption of N{sub 2} and C{sub 2}J{sub 4} on Ag-zeolite. The dispersion energies of adsorption, based on the MP2 correlation energies, are nearly the same for all adsorption pairs, i.e,, approximately 4--5 kcal/mol.

Chen, N.; Yang, R.T. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering] [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering

1996-11-01

104

A Monte Carlo study of the influence of molecular flexibility on the phase diagram of a fused hard sphere model  

Microsoft Academic Search

A study of a rigid fully flexible fused hard sphere model [C. McBride, C. Vega, and L. G. MacDowell, Phys. Rev. E 64, 011703 (2001)] is extended to the smectic and solid branches of the phase diagram. Computer simulations have been performed for a completely rigid model composed of 15 fused hard spheres (15+0), a model of 15 fused hard

Carl McBride; Carlos Vega

2002-01-01

105

Molecular Orbital Study of the First Excited State of the OLED Material Tris(8-hydroxyquinoline)aluminum(III)  

E-print Network

Molecular Orbital Study of the First Excited State of the OLED Material Tris(8-hydroxyquinoline)aluminum(III), Alq3, is used in organic light-emitting diodes (OLEDs) as an electron transport material and emitting. Introduction Organic light-emitting diodes (OLEDs) are currently under intense investigation for application

Schlegel, H. Bernhard

106

Silicon nanorings and nanotubes: a full-potential linear-muffin-tin-orbital molecular-dynamics method study  

Microsoft Academic Search

Using full-potential linear-muffin-tin-orbital molecular-dynamics method, we have studied the geometric and electronic structures of short possible silicon nanotube consisting of silicon rings. All atoms in the ring structures have fourfold coordination. The stacked tubes are stable.

Bao-xing Li; Pei-lin Cao

2004-01-01

107

On the room-temperature phase diagram of high pressure hydrogen: an ab initio molecular dynamics perspective and a diffusion Monte Carlo study.  

PubMed

The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results. PMID:25028021

Chen, Ji; Ren, Xinguo; Li, Xin-Zheng; Alfè, Dario; Wang, Enge

2014-07-14

108

On the room-temperature phase diagram of high pressure hydrogen: An ab initio molecular dynamics perspective and a diffusion Monte Carlo study  

NASA Astrophysics Data System (ADS)

The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results.

Chen, Ji; Ren, Xinguo; Li, Xin-Zheng; Alfè, Dario; Wang, Enge

2014-07-01

109

Analyzing molecular properties calculated with two-component relativistic methods using spin-free natural bond orbitals: NMR spin-spin coupling constants  

Microsoft Academic Search

An analysis method for static linear response properties employing two-component (spin-orbit) relativistic density functional theory along with scalar relativistic ``natural localized molecular orbitals'' (NLMOs) and ``natural bond orbitals'' (NBOs) has been developed. The spin-orbit NLMO\\/NBO analysis has been applied to study the indirect spin-spin coupling (J-coupling) constants in Tl-I, PbH4, and a dinuclear Pt-Tl bonded complex with a very large

Jochen Autschbach

2007-01-01

110

Molecular Orbital Calculation of the Elastic Modulus and the Dielectric Constant for Ultra Low-k Organic Polymers  

NASA Astrophysics Data System (ADS)

We propose a new theoretical calculation method for estimating the (Young’s) elastic modulus E as well as the dielectric constant k of low-k films using a molecular orbital method. Co-oligomers of tricyclo[6.2.0.03,6]deca-1(8),2,6-triene (TCDT) and divinylbenzene (DVB) were investigated by applying this new calculation method to evaluate both k and E. It is shown that organic low-k films with k<2.0 and high elastic modulus are synthesized through the copolymerization reactions of TCDT and para-DVB. The molecular orbital method was demonstrated as a powerful tool for designing molecular structures of ultra low-k films with high elastic modulus.

Uera, Kazuyoshi; Kawahara, Jun; Miyoshi, Hidenori; Hata, Nobuhiro; Kikkawa, Takamaro

2004-02-01

111

Lattice relaxation, electronic screening, and spin and orbital phase diagram of LaTiO3/SrTiO3 superlattices  

NASA Astrophysics Data System (ADS)

The effect of lattice relaxation on the electronic charge density, band structure, and phase diagram in oxide heterostructure, LaTiO3/SrTiO3 superlattices, the structure grown and measured by Ohtomo et al.[1], is investigated using density functional theory LDA and LDA+U (VASP implementation). We observe substantial ferroelectric-like distortion of TiO6 octahedra at the nearest-to-La region which screens the electrostatic force originating from La^3+ ion reducing the charge density in the La-rich region. We determine the changes in the low energy electronic Hamiltonian caused by the lattice relaxation and investigate the consequences for the ground state phase diagram using the Hartree-Fock approximation. Finally, we present a detailed comparison with previous calculations which neglected the lattice effect. [2] Support from DOE ER 46169. [1]Ohtomo et al., Nature 419, 378 (2002). [2]Okamoto and Millis, Nature (London) 428, 630 (2004), and Phys. Rev. B 70, 195120 (2004).

Okamoto, Satoshi; Millis, Andrew; Spaldin, Nicola

2006-03-01

112

Molecular structure and conformational composition of methyl chloroacetate: An electron-diffraction and ab initio molecular orbital investigation  

NASA Astrophysics Data System (ADS)

The molecular structure and conformational composition of methyl chloroacetate, H 2ClC sbnd C( dbnd O) sbnd O sbnd CH 3, have been determined by gas-phase electron-diffraction (GED), using results from ab initio molecular orbital calculations (HF, MP2 and MP3/6-311+G(d,p)) to obtain constraints on some of the structural parameters. The molecules exist in the gas-phase at 25 °C as a mixture of two stable conformers: syn with C sbnd Cl eclipsing C dbnd O and gauche with C sbnd H approximately eclipsing C dbnd O. In both of these conformers O sbnd CH 3 is also eclipsing C dbnd O. The experimentally observed conformational composition at 25 °C was 36(8)% syn and 64(8)% gauche (parenthesised values are 2 ?), corresponding to a free energy difference between conformers of ?Gexp° = 1.4(9) kJ/mol. The corresponding theoretical values obtained for ? G° are 1.1 kJ/mol (HF), 2.3 kJ/mol (MP2), and 2.4 kJ/mol (MP3). The results for the principal distances ( rh1) and angles ( ?h1) for the major gauche conformer obtained from the combined GED/ ab initio study (2 ? uncertainties) are r(CO sbnd CCl) = 1.502(9) Å, r(C sbnd H) = 1.084(6) Å (average value), r(C sbnd Cl) = 1.782(4) Å, r(C dbnd O) = 1.213(4) Å, r(CO sbnd O) = 1.346(4) Å, r(CH 3sbnd O) = 1.468(10) Å, ?C sbnd C sbnd Cl = 110.0(6)°, ?C sbnd C dbnd O = 124.7(6)°, ?C sbnd C sbnd O = 108.3(10)°, ?C sbnd O sbnd C = 115.9(8)°, ?(Cl sbnd C sbnd C dbnd O) = 111(2)°, ?(C sbnd O sbnd C dbnd O) = 3(3)°.

Aarset, Kirsten; Boldermo, Kjell Gunnar; Hagen, Kolbjørn

2010-08-01

113

Spin-orbit interactionsand magnetic field in antiferromagnetic triangular molecular magnets  

NASA Astrophysics Data System (ADS)

Frustrated triangular molecular magnets such as Cu3 are characterized by a doubly generate S=1/2 ground-state (GS) with opposite chirality. Recently it has been proposed theoretically [1] and verified by ab-initio calculations [2] that an external electric field can efficiently couple these two chiral spin states, even in the absence of spin-orbit interaction (SOI). SOIs are nevertheless important, since they introduce a splitting in the GS manifold. In this talk we will discuss different schemes on how to evaluate within spin density functional theory the effect of the SOIs on the chiral states. The connection between SOI and the Dzyalozhinsky-Moriya interaction will be discussed. We will also present calculations of the energy dependence on an external magnetic field, whose presence is important to achieve full control of the spin-electric coupling within the manifold of the GS chiral doublets. [4pt] [1] M. Trif et. al. Phys. Rev. B 82, 045429 (2010) and M. Trif et. al. Phys. Rev. Lett. 101, 217201 (2008) [0pt] [2] F. Islam et. al. Phys. Rev. B 82, 155446 (2010)

Nossa, J. F.; Islam, M. F.; Canali, C. M.; Pederson, M. R.

2011-03-01

114

Potential energy surface of the HNO + NO reaction. An ab initio molecular orbital study  

SciTech Connect

The potential energy surface of the HNO + NO reaction has been investigated by ab initio molecular orbital calculations at the QCISD(T)/6-311G(d,p)//UMP2/6-311G(d,p) + ZPE[UMP2/6-311G(d,p)] and Gaussian-2 (G2) levels of theory. The initial reaction step is NO association with the N atom of the HNO molecule to form the HN(O)NO intermediate, 2, overcoming the barrier 1[prime] of 9.5 kcal/mol. The reaction proceeds further by 1,3-hydrogen migration in HN(O)NO from nitrogen to oxygen via the transition state 3, which is much more favorable than 1,2-shift. This step is shown to be rate-determining, having a barrier of 21.6 kcal/mol. After the H shift, trans,cis-HONNO ([sup 2]A[double prime]) intermediate, 5a, is formed, which rearranges to trans,trans-HONNO ([sup 2]A[prime]), 7b. Finally, the latter dissociates to give the reaction products H[sub 2]O + OH. The energies of the transition states for internal rearrangements of HONNO as well as the transition state for HONNO ([sup 2]A[prime]) dissociation are calculated to be significantly lower than the rate-determining barrier for 1,3-hydrogen migration in HN(O)NO. 23 refs., 2 figs., 3 tabs.

Mebel, A.M.; Morokuma, K.; Lin, M.C. (Emory Univ., Atlanta, GA (United States)); Melius, C.F. (Sandia National Lab., Livermore, CA (United States))

1995-02-16

115

Molecular-orbital description of the states of two-electron systems  

SciTech Connect

The molecular-orbital (MO) method introduced previously by us (Phys. Rev. Lett. 57, 984 (1986)) to treat two-electron atoms is developed further. The states of systems consisting of two electrons and one positively charged particle are analyzed with use of the interelectronic distance as an adiabatic coordinate in analogy to the interprotonic distance in H/sub 2//sup +/. The motion of two electrons then separates into rotational, vibrational, and internal motion, the latter being described by MO, exactly as in molecules. Indeed, adiabatic MO potential curves for atomic systems are obtained by scaling the corresponding curves for H/sub 2//sup +/. Approximate quantum numbers for two-electron states, derived previously by empirical methods or from an ad hoc rovibrational model, arise naturally since the two-center Coulomb problem is exactly separable in MO coordinates and the corresponding nodal surfaces are conserved for all interelectronic separations. In addition, the gerade-ungerade symmetry of MO is exactly preserved and appears as a fundamental symmetry of two-electron states.

Feagin, J.M.; Briggs, J.S.

1988-06-15

116

Venn diagrams  

NSDL National Science Digital Library

These online resources offer varied opportunities to work with Venn diagrams, one of many tools used in logic and reasoning. Their use is especially helpful in learning foundational notions of definition and set theory. One of the five Process Standards promoted by NCTM, Reasoning and Proof requires middle school students to sharpen such skills as they learn to develop mathematical argument.

National Science Digital Library (NSDL) Middle School Portal Staff

2008-03-10

117

Prediction of quantum interference in molecular junctions using a parabolic diagram: Understanding the origin of Fano and anti- resonances  

NASA Astrophysics Data System (ADS)

Recently the interest in quantum interference (QI) phenomena in molecular devices (molecular junctions) has been growing due to the unique features observed in the transmission spectra. In order to design single molecular devices exploiting QI effects as desired, it is necessary to provide simple rules for predicting the appearance of QI effects such as anti-resonances or Fano line shapes and for controlling them. In this study, we derive a transmission function of a generic molecular junction with a side group (T-shaped molecular junction) using a minimal toy model. We developed a simple method to predict the appearance of quantum interference, Fano resonances or anti- resonances, and its position in the conductance spectrum by introducing a simple graphical representation (parabolic model). Using it we can easily visualize the relation between the key electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. We also demonstrate Fano and anti-resonance in T-shaped molecular junctions using a simple tight-binding model. This parabolic model enables one to infer on-site energies of T-shaped molecules and the coupling between side group and main conduction channel from transmission spectra.

Nozaki, Daijiro; Avdoshenko, Stanislav M.; Sevinçli, Hâldun; Gutierrez, Rafael; Cuniberti, Gianaurelio

2013-03-01

118

The Space Shuttle Orbiter molecular environment induced by the supplemental flash evaporator system  

NASA Technical Reports Server (NTRS)

The water vapor environment of the Space Shuttle Orbiter induced by the supplemental flash evaporator during the on-orbit flight phase has been analyzed based on Space II model predictions and orbital flight measurements. Model data of local density, column density, and return flux are presented. Results of return flux measurements with a mass spectrometer during STS-2 and of direct flux measurements during STS-4 are discussed and compared with model predictions.

Ehlers, H. K. F.

1985-01-01

119

Theoretical Chemistry of The 7p Series of Superheavy Elements II. The Relativistic Molecular Orbital and Kappa Valence Methods  

Microsoft Academic Search

The relativistic generalizations of both molecular orbital and spin-valence (the Kappa valence method) theories are used to investigate the covalent bonds that can be formed by the ground relativistic configuration of a heavy element containing a non-closed subshell of {p} or p valence electrons. Both theories predict that {p}-H and p-H bonds are not greatly weakened compared with normal covalent

N. C. Pyper

1982-01-01

120

Ionization Potential, Electron Affinity, Electronegativity, Hardness, and Electron Excitation Energy: Molecular Properties from Density Functional Theory Orbital Energies  

Microsoft Academic Search

Representative atomic and molecular systems, including various inorganic and organic molecules with covalent and ionic bonds, have been studied by using density functional theory. The calculations were done with the commonly used exchange-correlation functional B3LYP followed by a comprehensive analysis of the calculated highest-occupied and lowest-unoccupied Kohn-Sham orbital (HOMO and LUMO) energies. The basis set dependence of the DFT results

Chang-Guo Zhan; Jeffrey A. Nichols; David A. Dixon

2003-01-01

121

Reduced explicitly correlated Hartree-Fock approach within the nuclear-electronic orbital framework: applications to positronic molecular systems.  

PubMed

In the application of the nuclear-electronic orbital (NEO) method to positronic systems, all electrons and the positron are treated quantum mechanically on the same level. Explicit electron-positron correlation can be included using Gaussian-type geminal functions within the variational self-consistent-field procedure. In this paper, we apply the recently developed reduced explicitly correlated Hartree-Fock (RXCHF) approach to positronic molecular systems. In the application of RXCHF to positronic systems, only a single electronic orbital is explicitly correlated to the positronic orbital. We apply NEO-RXCHF to three systems: positron-lithium, lithium positride, and positron-lithium hydride. For all three of these systems, the RXCHF approach provides accurate two-photon annihilation rates, average contact densities, electronic and positronic single-particle densities, and electron-positron contact densities. Moreover, the RXCHF approach is significantly more accurate than the original XCHF approach, in which all electronic orbitals are explicitly correlated to the positronic orbital in the same manner, because the RXCHF wavefunction is optimized to produce a highly accurate description of the short-ranged electron-positron interaction that dictates the annihilation rates and other local properties. Furthermore, RXCHF methods that neglect or approximate the electronic exchange interactions between the geminal-coupled electronic orbital and the regular electronic orbitals lead to virtually identical annihilation rates and densities as the fully antisymmetric RXCHF method but offer substantial advantages in computational tractability. Thus, NEO-RXCHF is a promising, computationally practical approach for studying larger positron-containing systems. PMID:23883006

Sirjoosingh, Andrew; Pak, Michael V; Swalina, Chet; Hammes-Schiffer, Sharon

2013-07-21

122

Using Atomic Orbitals and Kinesthetic Learning to Authentically Derive Molecular Stretching Vibrations  

ERIC Educational Resources Information Center

The stretching modes of ML[subscript "x"] complexes have the same symmetry as the atomic orbitals on M that are used to form its s bonds. In the exercise suggested here, the atomic orbitals are used to derive the form of the stretching modes without the need for formal group theory. The analogy allows students to help understand many…

Bridgeman, Adam J.; Schmidt, Timothy W.; Young, Nigel A.

2013-01-01

123

Using Molecular Models To Show Steric Clash in Peptides: An Illustration of Two Disallowed Regions in the Ramachandran Diagram  

ERIC Educational Resources Information Center

In this activity, students manipulate three-dimensional molecular models of the Ala-Ala-Ala tripeptide, where Ala is alanine. They rotate bonds to show that the pairs of dihedral angles phi = 0 degrees, psi = 180 degrees, and phi = 0 degrees, psi = 0 degrees lead to unfavorable interactions among the main chain atoms of the tripeptide. This…

Halkides, Christopher J.

2013-01-01

124

Negative differential resistance in a hybrid silicon-molecular system: resonance between the intrinsic surface-states and the molecular orbital.  

PubMed

It has been a long-term desire to fabricate hybrid silicon-molecular devices by taking advantages of organic molecules and the existing silicon-based technology. However, one of the challenging tasks is to design applicable functions on the basis of the intrinsic properties of the molecules, as well as the silicon substrates. Here we demonstrate a silicon-molecular system that produces negative differential resistance (NDR) by making use of the well-defined intrinsic surface-states of the Si (111)-?3 × ?3-Ag (R3-Ag/Si) surface and the molecular orbital of cobalt(II)-phthalocyanine (CoPc) molecules. From our experimental results obtained using scanning tunneling microscopy/spectroscopy, we find that NDR robustly appears at the Co(2+) ion centers of the CoPc molecules, independent of the adsorption configuration of the CoPc molecules and irrespective of doping type and doping concentration of the silicon substrates. Joint with first principle calculations, we conclude that NDR is originated from the resonance between the intrinsic surface-state band S(1) of the R3-Ag/Si surface and the localized unoccupied Co(2+)d(z(2)) orbital of the adsorbed CoPc molecules. We expect that such a mechanism can be generally used in other silicon-molecular systems. PMID:22793258

Wang, Weihua; Ji, Yongfei; Zhang, Hui; Zhao, Aidi; Wang, Bing; Yang, Jinlong; Hou, J G

2012-08-28

125

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region  

NASA Astrophysics Data System (ADS)

Context. It is well known that the kinetic temperatures, Tkin, of the molecular clouds in the Galactic center region are higher than in typical disk clouds. However, the Tkin of the molecular complexes found at higher latitudes towards the giant molecular loops in the central region of the Galaxy is so far unknown. The gas of these high-latitude molecular clouds (hereafter referred to as "halo clouds") is located in a region where the gas in the disk may interact with the gas in the halo in the Galactic center region. Aims: To derive Tkin in the molecular clouds at high latitude and understand the physical process responsible for the heating of the molecular gas both in the central molecular zone (the concentration of molecular gas in the inner ~500 pc) and in the giant molecular loops. Methods: We measured the metastable inversion transitions of NH3 from (J,K) = (1,1) to (6,6) toward six positions selected throughout the Galactic central disk and halo. We used rotational diagrams and large velocity gradient (LVG) modeling to estimate the kinetic temperatures toward all the sources. We also observed other molecules like SiO, HNCO, CS, C34S, C18O, and 13CO, to derive the densities and to trace different physical processes (shocks, photodissociation, dense gas) expected to dominate the heating of the molecular gas. Results: We derive for the first time Tkin of the high-latitude clouds interacting with the disk in the Galactic center region. We find high rotational temperatures in all the observed positions. We derive two kinetic temperature components (~150 K and ~40 K) for the positions in the central molecular zone, and only the warm kinetic temperature component for the clouds toward the giant molecular loops. The fractional abundances derived from the different molecules suggest that shocks provide the main heating mechanism throughout the Galactic center, also at high latitudes. Appendices A and B are available in electronic form at http://www.aanda.org

Riquelme, D.; Amo-Baladrón, M. A.; Martín-Pintado, J.; Mauersberger, R.; Martín, S.; Bronfman, L.

2013-01-01

126

Photoelectron spectra and molecular orbital calculations of dicarbonyl- and dinitrosyl-bridged cobalt, rhodium and iridium cyclopentadienyl dimers and of disulfido- and diselenido-nonacarbonyltriosmium  

E-print Network

PHOTOELECTRON SPECTRA AND MOLECULAR ORBITAL CALCULATIONS OF DICARBONYL- AND DINITROSYL-BRIDGED COBALT, RHODIUM AND IRIDIUM CYCLOPENTADIENYL DIMERS AND OF DISULFIDO- AND DISELENIDO-NONACARBONYLTRIOSMIUM. A Thesis by GREG LEWIS GRIEWE Submitted... to the Craduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1987 Major Subject: Chemistry PHOTOELECTRON SPECTRA AND MOLECULAR ORBITAL CALCULATIONS OF DICARBONYL- AND DINITROSYL...

Griewe, Greg Lewis

2012-06-07

127

Core molecule dependence of energy migration in phenylacetylene nanostar dendrimers: Ab initio molecular orbital-configuration interaction based quantum master equation study  

Microsoft Academic Search

The core molecule dependence of energy (exciton) migration in phenylacetylene nanostar dendrimers is investigated using the ab initio molecular orbital (MO)-configuration interaction based quantum master equation approach. We examine three kinds of core molecular species, i.e., benzene, anthracene, and pentacene, with different highest occupied MO-lowest unoccupied MO (HOMO-LUMO) gaps, which lead to different orbital interactions between the dendron parts and

Ryohei Kishi; Takuya Minami; Hitoshi Fukui; Hideaki Takahashi; Masayoshi Nakano

2008-01-01

128

Role of the virtual orbitals and HOMO-LUMO gap in mean-field approximations to the conductance of molecular junctions  

Microsoft Academic Search

We investigate the role of virtual orbitals on the molecular conductance at the static mean-field level of approximation in the nonequilibrium Green's functions (NEGFs) formalism, within a model system with wide-band leads. We use a projector operator formalism to define corrections to the molecular Hamiltonian that solely act on its virtual-orbital subspace, leaving ground-state properties invariant. In its most trivial

A. Cehovin; H. Mera; J. H. Jensen; K. Stokbro; T. B. Pedersen

2008-01-01

129

Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals  

SciTech Connect

Ab initio effective core potentials (ECP's) have been generated to replace the innermost core electron for third-row (K--Au), fourth-row (Rb--Ag), and fifth-row (Cs--Au) atoms. The outermost core orbitals: corresponding to the ns/sup 2/np/sup 6/ configuration for the three rows here: are not replaced by the ECP but are treated on an equal footing with the nd, (n+1)s and (n+1)p valence orbitals. These ECP's have been derived for use in molecular calculations where these outer core orbitals need to be treated explicitly rather than to be replaced by an ECP. The ECP's for the forth and fifth rows also incorporate the mass--velocity and Darwin relativistic effects into the potentials. Analytic fits to the potentials are presented for use in multicenter integral evaluation. Gaussian orbital valence basis sets are developed for the (3s, 3p, 3d, 4s, 4p), (4s, 4p, 4d, 5s, 5p), and (5s, 5p, 5d, 6s, 6p) ortibals of the three respective rows.

Hay, P.J.; Wadt, W.R.

1985-01-01

130

Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states  

NASA Astrophysics Data System (ADS)

The metal L-edge (2p ? 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d5) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6]3- with ligand donor bonding, and low-spin [Fe(CN)6]3- that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

Pinjari, Rahul V.; Delcey, Mickaël G.; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

2014-09-01

131

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.  

PubMed

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol?acetonitrile?acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials. PMID:23822250

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

132

Formation of giant molecular clouds in global spiral structures: The role of orbital dynamics and cloud-cloud collisions  

NASA Technical Reports Server (NTRS)

The different roles played by orbital dynamics and dissipative cloud-cloud collisions in the formation of giant molecular clouds (GMCs) in a global spiral structure are investigated. The interstellar medium (ISM) is simulated by a system of particles, representing clouds, which orbit in a spiral-perturbed, galactic gravitational field. The overall magnitude and width of the global cloud density distribution in spiral arms is very similar in the collisional and collisionless simulations. The results suggest that the assumed number density and size distribution of clouds and the details of individual cloud-cloud collisions have relatively little effect on these features. Dissipative cloud-cloud collisions play an important steadying role for the cloud system's global spiral structure. Dissipative cloud-cloud collisions also damp the relative velocity dispersion of clouds in massive associations and thereby aid in the effective assembling of GMC-like complexes.

Roberts, W. W., Jr.; Stewart, G. R.

1987-01-01

133

Unrestricted absolutely localized molecular orbitals for energy decomposition analysis: Theory and applications to intermolecular interactions involving radicals  

NASA Astrophysics Data System (ADS)

Radical-closed shell and radical-radical intermolecular interactions are less well-understood than those between closed shell species. With the objective of gaining additional insight, this work reports a generalization of the absolutely localized molecular orbital (ALMO) energy decomposition analysis (EDA) to open shell fragments, described by self-consistent field methods, such as standard density functional theory. The ALMO-EDA variationally partitions an intermolecular interaction energy into three separate contributions; frozen orbital interactions, polarization, and charge transfer. The first examples involve comparison of the interactions of alkanes and alkyl radicals (methyl radical, methane, tertiary butyl radical, and isobutane) with sodium, potassium, hydronium, and ammonium cations. A second series of examples involve benzene cation interacting with a series of nucleophiles in both on-top and side-on geometries. The ALMO-EDA yields a variety of interesting insights into the relative roles of its component contributions as the interacting partners and their geometries are changed.

Horn, Paul R.; Sundstrom, Eric Jon; Baker, Thomas A.; Head-Gordon, Martin

2013-04-01

134

Molecular structure, vibrational spectroscopic, hyperpolarizability, natural bond orbital analysis, frontier molecular orbital analysis and thermodynamic properties of 2,3,4,5,6-pentafluorophenylacetic acid  

NASA Astrophysics Data System (ADS)

The FT-IR (4000-400 cm-1) and FT-Raman spectra (3500-100 cm-1) of 2,3,4,5,6-pentafluorophenylacetic acid (PAA) have been recorded. Density functional theory calculation with LSDA/6-31+G(d,p) and B3LYP/6-31+G(d,p) basis sets have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman intensities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of PAA are calculated using B3LYP/6-31+G(d,p) method on the finite-field approach. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within this molecule. Mulliken population analysis on atomic charges is also calculated. Thermodynamic properties (heat capacity, enthalpy, Gibb's free energy and entropy) of the title compound at different temperatures were calculated.

Balachandran, V.; Karunakaran, V.

2014-06-01

135

Molecular orbital studies of the bonding in heavy element organometallics: Progress report  

SciTech Connect

Areas in which progress has been made in understanding the bonding in heavy element complexes are: general bonding scheme for mononuclear organoactinide complexes; bonding in unsupported actinide heterobimetallic complexes; f-orbital to carbonyl 2..pi.. backbonding; bonding at the Cp/sub 3/U binding site; direct actinide-to-actinide bonding.

Bursten, B.E.

1987-04-23

136

Growth diagram of N-face GaN (0001¯) grown at high rate by plasma-assisted molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

N-face GaN was grown on free-standing GaN (0001¯) substrates at a growth rate of 1.5 ?m/h using plasma-assisted molecular beam epitaxy. Difference in growth rate between (0001¯) and (0001) oriented GaN depends on nitrogen plasma power, and the (0001¯) oriented GaN had only 70% of the growth rate of the (0001) oriented GaN at 300 W. Unintentional impurity concentrations of silicon, carbon, and oxygen were 2 × 1015, 2 × 1016, and 7 × 1016 cm-3, respectively. A growth diagram was constructed that shows the dependence of the growth modes on the difference in the Ga and active nitrogen flux, ?Ga - ?N*, and the growth temperature. At high ?Ga - ?N* (?Ga ? ?N*), two-dimensional (step-flow and layer-by-layer) growth modes were realized. High growth temperature (780 °C) expanded the growth window of the two-dimensional growth modes, achieving a surface with rms roughness of 0.48 nm without Ga droplets.

Okumura, Hironori; McSkimming, Brian M.; Huault, Thomas; Chaix, Catherine; Speck, James S.

2014-01-01

137

Shielded-orbital model for quasimolecule analysis of ion--atom collisions  

Microsoft Academic Search

A method is proposed for calculating diadiabatic correlation diagrams of the orbitals of diatomic quasimolecules formed in collisions of atoms. The screening of the nuclei by the electrons in the quasimolecule is taken into account by specifying an empirical one-electron molecular potential for which separation of variables is possible for the Schroedinger equation written in spheroidal coordinates. As a result

V. K. Nikulin; N. A. Gushchina

1978-01-01

138

Beyond the spin model: exchange coupling in molecular magnets with unquenched orbital angular momenta.  

PubMed

In this critical review we review the problem of exchange interactions in polynuclear metal complexes involving orbitally degenerate metal ions. The key feature of these systems is that, in general, they carry an unquenched orbital angular momentum that manifests itself in all their magnetic properties. Thus, interest in degenerate systems involves fundamental problems related to basic models in magnetism. In particular, the conventional Heisenberg-Dirac-Van Vleck model becomes inapplicable even as an approximation. In the first part we attempt to answer two key questions, namely which theoretical tools are to be used in the case of degeneracy, and how these tools can be employed. We demonstrate that the exchange interaction between orbitally degenerate metal ions can be described by the so-called orbitally-dependent exchange Hamiltonian. This approach has shown to reveal an anomalously strong magnetic anisotropy that can be considered as the main physical manifestation of the unquenched orbital angular momentum in magnetic systems. Along with the exchange coupling, a set of other interactions (such as crystal field effects, spin-orbit and Zeeman coupling), which are specific for the degenerate systems, need to be considered. All these features will be discussed in detail using a pseudo-spin-1/2 Hamiltonian approach. In the second part, the described theoretical background will be used to account for the magnetic properties of several magnetic metal clusters and low-dimensional systems: (i) the dinuclear face-sharing unit [Ti(2)Cl(9)](3-), which exhibits a large magnetic anisotropy; (ii) the rare-earth compounds Cs(3)Yb(2)Cl(9) and Cs(3)Yb(2)Br(9), which, surprisingly, exhibit a full magnetic isotropy; (iii) a zig-zag Co(II) chain exhibiting unusual combination of single-chain magnet behavior and antiferromagnetic exchange coupling; (iv) a trigonal bipyramidal Ni(3)Os(2) complex; (v) various Co(II) clusters encapsulated by polyoxometalate ligands. In the two last examples a pseudospin-1/2 Hamiltonian approach is applied to account for the presence of exchange anisotropy (150 references). PMID:21431145

Palii, Andrei; Tsukerblat, Boris; Klokishner, Sophia; Dunbar, Kim R; Clemente-Juan, Juan M; Coronado, Eugenio

2011-06-01

139

Continuous corrections to the molecular Kohn-Sham gap and virtual orbitals  

Microsoft Academic Search

We use projector operators to correct the Kohn-Sham Hamiltonian of density functional theory (KS-DFT) so that the resulting mean-field scheme yields, in finite systems, virtual orbitals and energy gaps in better agreement with those predicted by quasiparticle theory. The proposed correction term is a scissors-like operator of the form $(\\\\hat{I}-\\\\hat{\\\\rho})\\\\delta \\\\hat{H}(\\\\hat{I}-\\\\hat{\\\\rho})$, where $\\\\hat{I}$ is the identity operator, $\\\\hat{\\\\rho}$ the density

Hector Mera

2008-01-01

140

Inner valence molecular orbitals and structure of the X-ray O 4,5(Th,U) emission spectra in thorium and uranium oxides  

Microsoft Academic Search

In the present work, the possibility of an influence of the chemical environment on the structure of O4,5(Th,U) emission spectra of thorium and uranium oxides was studied. It is noted that the fine structure in such spectra is caused by the formation of inner valence molecular orbitals, involving relatively deep Th(U) 6p and O(F) 2s atomic orbitals of the neighbouring

Yu. A Teterin; V. A Terekhov; A. Yu Teterin; K. E Ivanov; I. O Utkin; A. M Lebedev; L Vukchevich

1998-01-01

141

Localized and Spectroscopic Orbitals: Squirrel Ears on Water.  

ERIC Educational Resources Information Center

Reexamines the electronic structure of water considering divergent views. Discusses several aspects of molecular orbital theory using spectroscopic molecular orbitals and localized molecular orbitals. Gives examples for determining lowest energy spectroscopic orbitals. (ML)

Martin, R. Bruce

1988-01-01

142

First Results from a Radio Emission Line Survey of the Molecular Disk Orbiting LkCa 15  

NASA Astrophysics Data System (ADS)

We have conducted the first comprehensive mm-wave molecular emission line survey of the circumstellar disk orbiting the nearby pre-main sequence star LkCa 15 (D = 140 pc). The disk around this young 3-5 Myr) solar analog appears to have a planetary-mass companion (LkCa 15b) within its central cavity. The outer disk is chemically rich, with numerous previous detections of molecular emission lines revealing a significant gas mass. Hence -- like the TW Hya and V4046 Sgr disks (Kastner et al. 2012, this meeting) -- LkCa 15 is an excellent target for an unbiased radio spectroscopic survey intended to produce a full census of the detectable molecular species within an evolved, protoplanetary disk. Our survey of LkCa 15 was conducted with the Institute de Radioastronomie Millimétrique (IRAM) 30 meter telescope over the 1.1-1.4 mm wavelength range. Here, we present initial results, including first-time detections of C18O, CS, and many transitions of previously detected molecules such as H2CO and CCH. This research is supported by National Science Foundation grant AST-1108950 to RIT.

Punzi, Kristina M.; Kastner, J. H.; Hily-Blant, P.; Forveille, T.; Sacco, G.

2013-01-01

143

Proposed Alteration of Images of Molecular Orbitals Obtained Using a Scanning Tunneling Microscope as a Probe of Electron Correlation  

NASA Astrophysics Data System (ADS)

Scanning tunneling spectroscopy (STS) allows us to image single molecules decoupled from the supporting substrate. The obtained images are routinely interpreted as the square moduli of molecular orbitals, dressed by the mean-field electron-electron interaction. Here we demonstrate that the effect of electron correlation beyond the mean field qualitatively alters the uncorrelated STS images. Our evidence is based on the ab initio many-body calculation of STS images of planar molecules with metal centers. We find that many-body correlations alter significantly the image spectral weight close to the metal center of the molecules. This change is large enough to be accessed experimentally, surviving to molecule-substrate interactions.

Toroz, Dimitrios; Rontani, Massimo; Corni, Stefano

2013-01-01

144

Re-evaluation of cytotoxicity and iron chelation activity of three beta-diketones by semiempirical molecular orbital method.  

PubMed

We investigated the chelating effect of FeCl3 on three beta-diketones, curcumin [1], (-)-3-(trifluoroacetyl)camphor [2] and 3-formylchromone [3], as judged by changes in their cytotoxicity and absorption spectra. Addition of an equimolar concentration of FeCl3 almost completely abrogated the cytotoxicity and changed the pattern of absorption spectra (decrease in the peak height at 430 nm) of [1], without affecting those of [2] and [3]. A semiempirical molecular orbital method (CAChe), based on these experimental data, proposed the estimated structure of [1] chelated with FeCl3 at 1:1 molar ratio. The present study suggests that [1], but not [2] and [3], is an iron chelator. PMID:15796163

Ishihara, Mariko; Sakagami, Hiroshi

2005-01-01

145

Complete determination of molecular orbitals by measurement of phase symmetry and electron density.  

PubMed

Several experimental methods allow measuring the spatial probability density of electrons in atoms, molecules and solids, that is, the absolute square of the respective single-particle wave function. But it is an intrinsic problem of the measurement process that the information about the phase is generally lost during the experiment. The symmetry of this phase, however, is a crucial parameter for the knowledge of the full orbital information in real space. Here, we report on a key experiment that demonstrates that the phase symmetry can be derived from a strictly experimental approach from the circular dichroism in the angular distribution of photoelectrons. In combination with the electron density derived from the same experiment, the full quantum mechanical wave function can thus be determined experimentally. PMID:24910256

Wießner, M; Hauschild, D; Sauer, C; Feyer, V; Schöll, A; Reinert, F

2014-01-01

146

Roles of K151 and D180 in L-2-haloacid dehalogenase from Pseudomonas sp. YL: analysis by molecular dynamics and ab initio fragment molecular orbital calculations.  

PubMed

L-2-haloacid dehalogenase (L-DEX) catalyzes the hydrolytic dehalogenation of L-2-haloalkanoic acids to produce the corresponding D-2-hydroxyalkanoic acids. This enzyme is expected to be applicable to the bioremediation of environments contaminated with halogenated organic compounds. We analyzed the reaction mechanism of L-DEX from Pseudomonas sp. YL (L-DEX YL) by using molecular modeling. The complexes of wild-type L-DEX YL and its K151A and D180A mutants with its typical substrate, L-2-chloropropionate, were constructed by docking simulation. Subsequently, molecular dynamics (MD) and ab initio fragment molecular orbital (FMO) calculations of the complexes were performed. The ab initio FMO method was applied at the MP2/6-31G level to estimate interfragment interaction energies. K151 and D180, which are experimentally shown to be important for enzyme activity, interact particularly strongly with L-2-chloropropionate, catalytic water, nucleophile (D10), and with each other. Our calculations suggest that K151 stabilizes substrate orientation and balances the charge around the active site, while D180 stabilizes the rotation of the nucleophile D10, fixes catalytic water around D10, and prevents K151 from approaching D10. Further, D180 may activate catalytic water on its own or with K151, S175, and N177. These roles are consistent with the previous results. Thus, MD and ab initio FMO calculations are powerful tools for the elucidation of the mechanism of enzymatic reaction at the molecular level and can be applied to other catalytically important residues. The results obtained here will play an important role in elucidating the reaction mechanism and rational design of L-DEX YL with improved enzymatic activity or substrate specificity. PMID:19373895

Nakamura, Takashi; Yamaguchi, Azusa; Kondo, Hirotaka; Watanabe, Hirofumi; Kurihara, Tatsuo; Esaki, Nobuyoshi; Hirono, Shuichi; Tanaka, Shigenori

2009-12-01

147

True Phase Diagrams  

NASA Astrophysics Data System (ADS)

With the use of today's computer softwares, phase diagrams can readily be plotted with a wide choice of variables on the axes. Hillert defined a true phase diagram as a diagram where each point uniquely defines the stable phases. He also showed that not all choices of axis variables give true phase diagrams. In this note we will demonstrate that although the rules stated by Hillert are necessary they are not sufficient to have true phase diagrams.

Ågren, John; Schmid-Fetzer, Rainer

2014-10-01

148

Structural Characterization of MAO and Related Aluminum Complexes. 1. Solid-State 27 Al NMR with Comparison to EFG Tensors from ab Initio Molecular Orbital Calculations  

SciTech Connect

Aminato and propanolato aluminum clusters with 3-, 4-, and 6-coordinate aluminum sites are studied with three 27Al NMR techniques optimized for large 27Al Quadrupole coupling constants: field-swept, frequency-stepped, and high-field MAS NMR. The 27Al quadrupole coupling constants and asymmetry parameters of molecular species, both experimental and derived from ab initio molecular orbital calculations, are correlated with structure.

Bryant, Pamela L.; Harwell, Chris; Mrse, Anthony A.; Emery, Earl F.; Gan, Zhedong; Caldwell, Tod; Reyes, Arneil P.; Kuhns, Philip; Hoyt, David W.; Simeral, Larry S.; Hall, Randall W.; Butler, Leslie G.

2001-11-07

149

Communication: Localized molecular orbital analysis of the effect of electron correlation on the anomalous isotope effect in the NMR spin-spin coupling constant in methane.  

PubMed

We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the (1)J(C-H) coupling constant of CH4 using a decomposition into contributions from localized molecular orbitals and compare with the (1)J(N-H) coupling constant in NH3. In particular, we discuss the well known fact that uncorrelated coupled Hartree-Fock (CHF) calculations are not able to reproduce the UDS in methane. For this purpose we have implemented for the first time a localized molecular orbital analysis for the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes-SOPPA(CCSD) in the DALTON program. Comparing the changes in the localized orbital contributions at the correlated SOPPA and SOPPA(CCSD) levels and at the uncorrelated CHF level, we find that the latter overestimates the effect of stretching the bond between the coupled atoms on the contribution to the coupling from the localized bonding orbital between these atoms. This disturbs the subtle balance between the molecular orbital contributions, which lead to the UDS in methane. PMID:25338873

Zarycz, M Natalia C; Sauer, Stephan P A; Provasi, Patricio F

2014-10-21

150

Communication: Localized molecular orbital analysis of the effect of electron correlation on the anomalous isotope effect in the NMR spin-spin coupling constant in methane  

NASA Astrophysics Data System (ADS)

We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the 1J(C-H) coupling constant of CH4 using a decomposition into contributions from localized molecular orbitals and compare with the 1J(N-H) coupling constant in NH3. In particular, we discuss the well known fact that uncorrelated coupled Hartree-Fock (CHF) calculations are not able to reproduce the UDS in methane. For this purpose we have implemented for the first time a localized molecular orbital analysis for the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes—SOPPA(CCSD) in the DALTON program. Comparing the changes in the localized orbital contributions at the correlated SOPPA and SOPPA(CCSD) levels and at the uncorrelated CHF level, we find that the latter overestimates the effect of stretching the bond between the coupled atoms on the contribution to the coupling from the localized bonding orbital between these atoms. This disturbs the subtle balance between the molecular orbital contributions, which lead to the UDS in methane.

Zarycz, M. Natalia C.; Sauer, Stephan P. A.; Provasi, Patricio F.

2014-10-01

151

Protein-specific force field derived from the fragment molecular orbital method can improve protein-ligand binding interactions.  

PubMed

Accurate computational estimate of the protein-ligand binding affinity is of central importance in rational drug design. To improve accuracy of the molecular mechanics (MM) force field (FF) for protein-ligand simulations, we use a protein-specific FF derived by the fragment molecular orbital (FMO) method and by the restrained electrostatic potential (RESP) method. Applying this FMO-RESP method to two proteins, dodecin, and lysozyme, we found that protein-specific partial charges tend to differ more significantly from the standard AMBER charges for isolated charged atoms. We did not see the dependence of partial charges on the secondary structure. Computing the binding affinities of dodecin with five ligands by MM PBSA protocol with the FMO-RESP charge set as well as with the standard AMBER charges, we found that the former gives better correlation with experimental affinities than the latter. While, for lysozyme with five ligands, both charge sets gave similar and relatively accurate estimates of binding affinities. PMID:23420697

Chang, Le; Ishikawa, Takeshi; Kuwata, Kazuo; Takada, Shoji

2013-05-30

152

Studies of the molecular geometry, vibrational spectra, Frontier molecular orbital, nonlinear optical and thermodynamics properties of Aceclofenac by quantum chemical calculations  

NASA Astrophysics Data System (ADS)

The solid phase FT-IR and FT-Raman spectra of 2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl] oxyacetic acid (Aceclofenac) have been recorded in the region 4000-400 and 4000-100 cm-1 respectively. The optimized molecular geometry and fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method and a comparative study between Hartree Fork (HF) method 6-311++G(d,p) level basis set. The calculated harmonic vibrational frequencies were scaled and have been compared with experimental by obtained FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The time dependent DFT method employed to study its absorption energy and oscillator strength. The linear polarizability (?) and the first order hyper polarizability (?) values of the investigated molecule have been computed. The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MESP) were also performed. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

Suresh, S.; Gunasekaran, S.; Srinivasan, S.

153

Studies of the molecular geometry, vibrational spectra, frontier molecular orbital, nonlinear optical and thermodynamics properties of aceclofenac by quantum chemical calculations.  

PubMed

The solid phase FT-IR and FT-Raman spectra of 2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl] oxyacetic acid (Aceclofenac) have been recorded in the region 4000-400 and 4000-100 cm(-1) respectively. The optimized molecular geometry and fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method and a comparative study between Hartree Fork (HF) method 6-311++G(d,p) level basis set. The calculated harmonic vibrational frequencies were scaled and have been compared with experimental by obtained FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The time dependent DFT method employed to study its absorption energy and oscillator strength. The linear polarizability (?) and the first order hyper polarizability (?) values of the investigated molecule have been computed. The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MESP) were also performed. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. PMID:24556133

Suresh, S; Gunasekaran, S; Srinivasan, S

2014-05-01

154

Molecular orbital theory on cellulolytic reactivity between pNP-cellooligosccharides and beta-glucosidase from Cellulomonas uda CS1-1.  

PubMed

A beta-glucosidase with the molecular mass of 160,000 Da was purified to homogeneity from cell extract of a cellulolytic bacterium, Cellulomonas uda CS1-1. The kinetic parameters (Km and Vmax) of the enzyme were determined with pNP-cellooligosccharides (DP 1-5) and cellobiose. The molecular orbital theoretical studies on the cellulolytic reactivity between the pNP-cellooligosaccharides as substrate (S) molecules and the purified beta-glucosidase (E) were conducted by applying the frontier molecular orbital (FMO) interaction theory. The results of the FMO interaction between E and S molecules verified that the first stage of the reaction was induced by exocyclic cleavage, which occurred in an electrophilic reaction based on a strong charge-controlled reaction between the highest occupied molecular orbital (HOMO) energy of the S molecule and the lowest occupied molecular orbital (LUMO) energy of the hydronium ion (H3O+), more than endocyclic cleavage, whereas a nucleophilic substitution reaction was induced by an orbital-controlled reaction between the LUMO energy of the oxonium ion (SH+) protonated to the S molecule and the HOMO energy of the H2O2 molecule. A hypothetic reaction route was proposed with the experimental results in which the enzymatic acid-catalyst hydrolysis reaction of E and S molecules would be progressed via SN1 and SN2 reactions. In addition, the quantitative structure-activity relationships (QSARs) between these kinetic parameters showed that Km has a significant correlation with hydrophobicity (logP), and specific activity has with dipole moment, respectively. PMID:18092462

Yoon, Min-Ho; Nam, Yun-Kyu; Choi, Woo-Young; Sung, Nack-Do

2007-11-01

155

Simplified Voronoi Diagrams  

E-print Network

The Voronoi diagram has proved to be a useful tool in a variety of contexts in computational geometry. Our interest here is in using the diagram to simplify the planning of collision-free paths for a robot among ...

Canny, John

1987-04-01

156

Simplified Voronoi Diagrams  

Microsoft Academic Search

We are interested in Voronoi diagrams as a tool in robot path planning, where thesearch for a path in an r dimensional space may be simplified to a search on an r - 1dimensional Voronoi diagram. We define a Voronoi diagram V based on a measure ofdistance which is not a true metric. This formulation has lower algebraic complexity thanthe

John F. Canny; Bruce Randall Donald

1988-01-01

157

AFM Diagram Quiz  

NSDL National Science Digital Library

This exercise should be used after you think students know what AFM diagrams are and how they work. This is sort of a quiz - to see if they can properly interpret the diagrams. There is no point moving on to real projects that involve AFM diagrams if the students don't understand the basics.

Perkins, Dexter

158

Molecular structure, vibrational spectra (FTIR and FT Raman) and natural bond orbital analysis of 4-Aminomethylpiperidine: DFT study  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectra of 4-Aminomethylpiperidine have been recorded using Perkin Elmer Spectrophotometer and Nexus 670 spectrophotometer. The equilibrium geometrical parameters, various bonding features, the vibrational wavenumbers, the infrared intensities and the Raman scattering activities were calculated using Hartree-Fock and density functional method (B3LYP) with 6-311+G(d,p) basis set. Detailed interpretations of the vibrational spectra have been carried out with the aid of the normal coordinate analysis. The spectroscopic and natural bonds orbital (NBO) analysis confirms the occurrence of intra molecular hydrogen bonds, electron delocalization and steric effects. The changes in electron density in the global minimum and in the energy of hyperconjugative interactions of 4-Aminomethylpiperidine (4AMP) were calculated. The theoretical UV-Visible spectrum of the compound was computed in the region 200-400 nm by time-dependent TD-DFT approach. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. The dipole moment (?) and polarizability (?), anisotropy polarizability (??) and hyperpolarizability (?) of the molecule have been reported.

Mahalakshmi, G.; Balachandran, V.

2014-10-01

159

Ab initio molecular orbital characterization of dimethyl group-III azides as sources for photolytic production of free radical beams  

NASA Astrophysics Data System (ADS)

Use of a beam of biradicaloid such as dialkyl group-III nitrene produced by the method of photodissociation of energetic compound beams (PDECB) is expected to be advantageous to the low-temperature thin-film growth of stoichiometric group-III nitride. Through the clarification of fundamental processes involved in pyrolysis as well as photolysis of dimethylgallium azide [(CH3)2GaN3], dimethylaluminum azide [(CH3)2AlN3], and dimethylboron azide [(CH3)2BN3] based on post-self-consistent field ab initio molecular orbital methods, we discuss the suitability of these possible source compounds for the production of beams of dimethylgalliumnitrene [(CH3)2GaN], dimethylaluminumnitrene [(CH3)2AlN], and dimethylboronnitrene [(CH3)2BN] by the PDECB method. The theoretical results suggested that (CH3)2GaN3 is a promising PDECB source material in that this molecule possesses the nature of unimolecular metastable dye.

Hayashi, Keiji; Kanayama, Takuo; Shimizu, Toyohiro; Kawamura, Yasunori; Kameko, Kenji; Kawakita, Seiji

2002-05-01

160

Calculation of positron binding energies of amino acids with the any-particle molecular-orbital approach  

NASA Astrophysics Data System (ADS)

We report positron binding energies (PBEs) for the 20 standard amino acids in the global minimum, hydrogen-bonded, and zwitterionic forms. The calculations are performed at the any-particle molecular-orbital (APMO) Hartree-Fock (HF), Koopmans' theorem (KT), second-order Möller-Plesset (MP2), and second-order propagator (P2) levels of theory. Our study reveals that the APMO KT and APMO P2 methods generally provide higher PBEs than the APMO HF and APMO MP2 methods, respectively, with only a fraction of the computational costs of the latter. We also discuss the impact of the choice of the positronic center on the PBEs and propose a simple and inexpensive procedure, based on the condensed Fukui functions of the parent molecules, to select the most suitable expansion center. The results reported so far indicate that APMO KT and APMO P2 methods are convenient options for a qualitative or semiquantitative analysis of positron binding in medium to large polyatomic systems.

Charry, J.; Romero, J.; Varella, M. T. do N.; Reyes, A.

2014-05-01

161

Quantitative Structure-Cytotoxicity Relationship of Bioactive Heterocycles by the Semi-empirical Molecular Orbital Method with the Concept of Absolute Hardness  

NASA Astrophysics Data System (ADS)

The relationship between the cytotoxicity of N-heterocycles (13 4-trifluoromethylimidazole, 15 phenoxazine and 12 5-trifluoromethyloxazole derivatives), O-heterocycles (11 3-formylchromone and 20 coumarin derivatives) and seven vitamin K2 derivatives against eight tumor cell lines (HSC-2, HSC-3, HSC-4, T98G, HSG, HepG2, HL-60, MT-4) and a maximum of 15 chemical descriptors was investigated using CAChe Worksystem 4.9 project reader. After determination of the conformation of these compounds and approximation to the molecular form present in vivo (biomimetic) by CONFLEX5, the most stable structure was determined by CAChe Worksystem 4.9 MOPAC (PM3). The present study demonstrates the best relationship between the cytotoxic activity and molecular shape or molecular weight of these compounds. Their biological activities can be estimated by hardness and softness, and by using ?-? activity diagrams.

Ishihara, Mariko; Sakagami, Hiroshi; Kawase, Masami; Motohashi, Noboru

162

Curvature in orbital dynamics  

NASA Astrophysics Data System (ADS)

The physical basis and the geometrical significance of the equation for the orbit of a particle moving under the action of external forces is exhibited by deriving this equation in a coordinate-independent representation in terms of the radius of curvature of the orbit. Although this formulation appeared in Newton's Principia, it has been ignored in contemporary classical mechanics textbooks. For small eccentricities, the orbit equation is used to obtain approximate solutions that illustrate the role of curvature. It is shown that this approach leads to a simple graphical method for determining the orbits for central forces. This method is similar to one attributed to Newton, who applied it to a constant central force, and sent a diagram of the orbit to Hooke in 1679. The result is compared to the corresponding orbit of a ball revolving inside an inverted cone which Hooke described in his response to Newton.

Nauenberg, Michael

2005-04-01

163

Phase Equilibria Diagrams Database  

National Institute of Standards and Technology Data Gateway

SRD 31 NIST/ACerS Phase Equilibria Diagrams Database (PC database for purchase)   The Phase Equilibria Diagrams Database contains commentaries and more than 21,000 diagrams for non-organic systems, including those published in all 21 hard-copy volumes produced as part of the ACerS-NIST Phase Equilibria Diagrams Program (formerly titled Phase Diagrams for Ceramists): Volumes I through XIV (blue books); Annuals 91, 92, 93; High Tc Superconductors I & II; Zirconium & Zirconia Systems; and Electronic Ceramics I. Materials covered include oxides as well as non-oxide systems such as chalcogenides and pnictides, phosphates, salt systems, and mixed systems of these classes.

164

Ab initio molecular orbital study on three feasible mechanisms for substitution of the vinylic carbon in F 2C=C(OMs)BMe 3?  

Microsoft Academic Search

A substitution on 2,2-difluorovinylic carbon was investigated by using ab initio molecular orbital calculations. Three feasible mechanisms, which are the SN1-like, the SN2-type and the addition-elimination mechanisms, were ex- amined for a model borate, 2,2-difluoro-1-mesyloxyvinyl(trimethyl)borate. Four TSs were obtained depending on the position of Li+ around the vinylborate although activation energies in the gas phase are rather high (ca. 30–40

Kenzi Hori; Shohei Fukuda; Junji Ichikawa

1999-01-01

165

A molecular orbital study of a model of the Mg2+ coordination complex of the self splicing reaction of ribosomal RNA  

NASA Technical Reports Server (NTRS)

Recent discoveries have established the fact that RNA is capable of acting as an enzyme. In this study two different types of molecular orbital calculations, INDO and ab initio, were used in an attempt to assess the structural/functional role of the Mg2+ hydrated complex in ribozyme reactions. Preliminary studies indicate that the reaction is multistep and that the Mg2+ complex exerts a stabilizing effect on the intermediate or midpoint of the reaction.

McCourt, M.; Shibata, M.; McIver, J. W.; Rein, R.

1988-01-01

166

Quantitative structure-toxicity relationships for halogenated substituted-benzenes to Vibrio fischeri, using atom-based semi-empirical molecular-orbital descriptors  

Microsoft Academic Search

Quantitative structure-toxicity relationships (QSTR's) are derived for an extensive series of halogenated benzenes, anilines, phenols, nitrobenzenes, toluenes and other substituted benzenes against Vibrio fischeri using a wide range of whole molecule and atom-based descriptors derived from semi-empirical molecular-orbital calculations. In terms of direct statistical correlation with toxicity it was found that the molar refractivity was the most important parameter, closely

M. A. Warne; D. Osborn; J. C. Lindon; J. K. Nicholson

1999-01-01

167

Improved constrained optimization method for reaction-path determination in the generalized hybrid orbital quantum mechanical/molecular mechanical calculations  

NASA Astrophysics Data System (ADS)

The nudged elastic band (NEB) and string methods are widely used to obtain the reaction path of chemical reactions and phase transitions. In these methods, however, it is difficult to define an accurate Lagrangian to generate the conservative forces. On the other hand, the constrained optimization with locally updated planes (CO-LUP) scheme defines target function properly and suitable for micro-iteration optimizations in quantum mechanical/molecular mechanical (QM/MM) systems, which uses the efficient second order QM optimization. However, the method does have problems of inaccurate estimation of reactions and inappropriate accumulation of images around the energy minimum. We introduce three modifications into the CO-LUP scheme to overcome these problems: (1) An improved tangent estimation of the reaction path, which is used in the NEB method, (2) redistribution of images using an energy-weighted interpolation before updating local tangents, and (3) reduction of the number of constraints, in particular translation/rotation constraints, for improved convergence. First, we test the method on the isomerization of alanine dipeptide without QM/MM calculation, showing that the method is comparable to the string method both in accuracy and efficiency. Next, we apply the method for defining the reaction paths of the rearrangement reaction catalyzed by chorismate mutase (CM) and of the phosphoryl transfer reaction catalyzed by cAMP-dependent protein kinase (PKA) using generalized hybrid orbital QM/MM calculations. The reaction energy barrier of CM is in high agreement with the experimental value. The path of PKA reveals that the enzyme reaction is associative and there is a late transfer of the substrate proton to Asp 166, which is in agreement with the recently published result using the NEB method.

Jung, Jaewoon; Re, Suyong; Sugita, Yuji; Ten-no, Seiichiro

2013-01-01

168

Development of glue-type potentials for the Al-Pb system: Phase diagram calculation  

SciTech Connect

Empirical many-body potentials of the glue-type have been constructed for the Al-Pb system using the force matching method. The potentials are fitted to experimental data, physical quantities derived from ab initio linear muffin-tin orbitals calculations and a massive quantum mechanical database of atomic forces generated using ultrasoft pseudopotentials in conjunction with ab initio molecular statics simulations. Monte Carlo simulations using these potentials have been employed to compute an Al-Pb phase diagram which is in fair agreement with experimental data.

Landa, A.; Wynblatt, P.; Siegel, D.J.; Adams, J.B.; Mryasov, O.N.; Liu, X.Y.

2000-05-11

169

On the separability of the extended molecule: Constructing the best localized molecular orbitals for an organic molecule bridging two model electrodes  

NASA Astrophysics Data System (ADS)

Based on a quantum chemical valence formalism that allows the rigorous construction of best-localized molecular orbitals on specific parts of an extended system, we examined the separability of individual components of model systems relevant to the description of electron transport in molecular devices. We started by examining how to construct the maximally localized electronic density at the tip of a realistic model of a gold electrode. By varying the number of gold atoms included in the local region where to project the total electronic density, we quantitatively assess how many molecular orbitals are entirely localized in that region. We then considered a 1,4-benzene-di-thiol molecule connected to two model gold electrodes and examined how to localize the electronic density of the total system in the extended molecule, a fractional entity comprising the organic molecule plus an increasing number of the closest metal atoms. We were able to identify in a rigorous manner the existence of three physically different electronic populations, each one corresponding to a distinct set of molecular orbitals. First, there are those entirely localized in the extended molecule, then there is a second group of those completely distributed in the gold atoms external to that region, and, finally, there are those delocalized over the entire system. This latter group can be associated to the shared electronic population between the extended molecule and the rest of the system. We suggest that the treatment here presented could be useful in the theoretical analysis of the electronic transport in nanodevices whenever the use of localized molecular states are required by the physics of the specific problem, such as in cases of weak coupling and super-exchange limits.

Moreira, Rodrigo A.; de Melo, Celso P.

2014-09-01

170

Venn Diagram Shape Sorter  

NSDL National Science Digital Library

In this activity, students practice placing big and small shapes into Venn diagrams depending on the rules of the diagram. Students can either specify these rules or have the applet assign the rules so they can try to figure them out by placing shapes in the diagram. This activity allows students to explore Venn diagrams and the terms associated with set theory. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

171

Energetic Studies and Phase Diagram of Thioxanthene  

NASA Astrophysics Data System (ADS)

The molecular stability of thioxanthene, a key species from which very important compounds with industrial relevance are derived, has been studied by a combination of several experimental techniques and computational approaches. The standard (p° = 0.1 MPa) molar enthalpy of formation of crystalline thioxanthene (117.4 ± 4.1 kJ·mol-1) was determined from the experimental standard molar energy of combustion, in oxygen, measured by rotating-bomb combustion calorimetry at T = 298.15 K. The enthalpy of sublimation was determined by a direct method, using the vacuum drop microcalorimetric technique, and also by an indirect method, using a static apparatus, where the vapor pressures at different temperatures were measured. The latter technique was used for both crystalline and undercooled liquid samples, and the phase diagram of thioxanthene near the triple point was obtained (triple point coordinates T = 402.71 K and p = 144.7 Pa). From the two methods, a mean value for the standard (p° = 0.1 MPa) molar enthalpy of sublimation, at T = 298.15 K (101.3 ± 0.8 kJ·mol-1), was derived. From the latter value and from the enthalpy of formation of the solid, the standard (p° = 0.1 MPa) enthalpy of formation of gaseous thioxanthene was calculated as 218.7 ± 4.2 kJ·mol-1. Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several homodesmotic reactions in order to derive the standard molar enthalpy of formation of thioxanthene. The ab initio results are in excellent agreement with the experimental data.

Freitas, Vera L. S.; Monte, Manuel J. S.; Santos, Luís M. N. B. F.; Gomes, José R. B.; Ribeiro da Silva, Maria D. M. C.

2009-10-01

172

Constructing Periodic Phase Space Orbits from ab Initio Molecular Dynamics Trajectories to Analyze Vibrational Spectra: Case Study of  

E-print Network

of publications, we used ab initio molecular dynamics (AIMD)1-9 and quantum wavepacket ab initio molecular molecular dynamics allows the "on-the-fly" treatment of electronic structure with simultaneous classical dynamical treatment of nuclei, quantum wavepacket ab initio molecular dynamics, in addition, includes

Iyengar, Srinivasan S.

173

Formalizing Spider Diagrams  

Microsoft Academic Search

Geared to complement UML and to the specification of large software systems by non-mathematicians,spider di- agrams are a visual language that generalizes the popu- lar and intuitive Venn diagrams and Euler circles. The language design emphasized scalability and expressiveness while retaining intuitiveness. In this extended abstract we describe spider diagrams from a mathematical standpoint and show how their formal semantics

Joseph Gil; John Howse; Stuart Kent

1999-01-01

174

Lenses and Ray Diagrams  

NSDL National Science Digital Library

This is the first time that students will draw technical ray diagrams (in previous experiments, they simply sketched the rays). They need a little instruction in drawing ray diagrams before they can do it, so the activity is not purely inquiry. But it is

Horton, Michael

2009-05-30

175

Communication: Systematic shifts of the lowest unoccupied molecular orbital peak in x-ray absorption for a series of 3d metal porphyrins.  

PubMed

Porphyrins are widely used as dye molecules in solar cells. Knowing the energies of their frontier orbitals is crucial for optimizing the energy level structure of solar cells. We use near edge x-ray absorption fine structure (NEXAFS) spectroscopy to obtain the energy of the lowest unoccupied molecular orbital (LUMO) with respect to the N(1s) core level of the molecule. A systematic energy shift of the N(1s) to LUMO transition is found along a series of 3d metal octaethylporphyrins and explained by density functional theory. It is mainly due to a shift of the N(1s) level rather than a shift of the LUMO or a change in the electron-hole interaction of the core exciton. PMID:20969361

García-Lastra, J M; Cook, P L; Himpsel, F J; Rubio, A

2010-10-21

176

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:� Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.� Explain how an object orbits a planet in terms of trajectories and free fall.� Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

177

Quantitative structure-cytotoxicity relationship analysis of 3-formylchromone derivatives by a semiempirical molecular-orbital method with the concept of absolute hardness.  

PubMed

A semiempirical molecular-orbital method (CAChe) was applied to delineate the relationship between the cytotoxicity (evaluated by 50% cytotoxic concentration, CC50) of 11 3-formylchromone derivatives and 15 chemical parameters (descriptors). The most stable conformation of all these compounds was exhibited by the planar structure. Compounds [2], [3], [4] and [9] had additionally protruding branches from the coplanar. In HSG cells, the best correlation coefficient was observed between CC50 and stability of hydration (DeltaH), followed by electron affinity, lowest unoccupied molecular orbital energy (ELUMO), highest occupied molecular orbital energy (EHOMO), ionization potential, absolute electron negativity (chi) and reactivity index (omega). When the value for [1], which was off from the regression line, was omitted, higher correlation coefficients were obtained between CC50 and electron affinity, ELUMO, chi and omega. When CC50 value was plotted vs. log P, a parabolic curve was produced, under the condition that the data for [5] were omitted. In HL-60 cells, moderate correlation was found between CC50 and DeltaH, electron affinity, ELUMO, chi and omega. When the values for [1] and [6], which were off the regression line, were omitted, higher correlation coefficients were obtained between CC50 and these five descriptors. In HSC-3 cells, there was moderate correlation between CC50 and the dipole moment, but not with other descriptors. In HSC-2 and MT-4 cells, there was no clear-cut correlation between CC50 and any of these descriptors. The present study indicates the applicability of HSG cells in searching for more active 3-formylchromone derivatives, using QSAR with the concept of absolute hardness. PMID:18383857

Ishihara, Mariko; Sakagami, Hiroshi

2008-01-01

178

Ab initio molecular orbital calculations of molten salt vapor complexes using Gaussian-2 theory: LiAlF[sub 4] and NaAlF[sub 4  

SciTech Connect

The structures and energies of the molten salt vapor complexes LiAlF[sub 4] and NaAlF[sub 4] are studied using new high level ab initio molecular orbital methods. The structures are determined using Moller-Plesset perturbation theory to second-order and the total energies are determined using a recently introduced modification of Gaussian-2 (G2) theory. The total energies are used to determine relative energies of the corner-, edge-, and face-bridged structures and accurate reaction energies. The results are compared to previous theoretical and experimental studies.

Curtiss, L.A.

1993-01-01

179

Ab initio molecular orbital calculations of molten salt vapor complexes using Gaussian-2 theory: LiAlF{sub 4} and NaAlF{sub 4}  

SciTech Connect

The structures and energies of the molten salt vapor complexes LiAlF{sub 4} and NaAlF{sub 4} are studied using new high level ab initio molecular orbital methods. The structures are determined using Moller-Plesset perturbation theory to second-order and the total energies are determined using a recently introduced modification of Gaussian-2 (G2) theory. The total energies are used to determine relative energies of the corner-, edge-, and face-bridged structures and accurate reaction energies. The results are compared to previous theoretical and experimental studies.

Curtiss, L.A.

1993-04-01

180

Diagram of Computer Keyboard  

NSDL National Science Digital Library

This is a line drawing of a Windows PC keyboard complete with labels for each key. This diagram is used on tests where students are asked to circle the keys that would be used to perform various functions.

Ward, Charles

2011-01-21

181

Voronoi Diagrams and Arrangements  

Microsoft Academic Search

We propose a uniform and general framework for defining and dealing with Voronoi diagrams. In this framework a Voronoi diagram is a partition of a domainD induced by a finite number of real valued functions onD. Valuable insight can be gained when one considers how these real valued functions partitionD ×R. With this view it turns out that the standard

Herbert Edelsbrunner; Raimund Seidel

1986-01-01

182

Induced spin filtering in electron transmission through chiral molecular layers adsorbed on metals with strong spin-orbit coupling  

NASA Astrophysics Data System (ADS)

Recent observations of considerable spin polarization in photoemission from metal surfaces through monolayers of chiral molecules were followed by several efforts to rationalize the results as the effect of spin-orbit interaction that accompanies electronic motion on helical, or more generally strongly curved, potential surfaces. In this paper we (a) argue, using simple models, that motion in curved force-fields with the typical energies used and the characteristic geometry of DNA cannot account for such observations; (b) introduce the concept of induced spin filtering, whereupon selectivity in the transmission of the electron orbital angular momentum can induce spin selectivity in the transmission process provided there is strong spin-orbit coupling in the substrate; and (c) show that the spin polarization in the tunneling current as well as the photoemission current from gold covered by helical adsorbates can be of the observed order of magnitude. Our results can account for most of the published observations that involved gold and silver substrates; however, recent results obtained with an aluminum substrate can be rationalized within the present model only if strong spin-orbit coupling is caused by the built-in electric field at the molecule-metal interface.

Gersten, Joel; Kaasbjerg, Kristen; Nitzan, Abraham

2013-09-01

183

Interaction analysis of HIV-1 antibody 2G12 and Man9GlcNAc2 ligand: Theoretical calculations by fragment molecular orbital and MD methods  

NASA Astrophysics Data System (ADS)

In HIV-1 infection, human antibody 2G12 is capable of recognizing the high-mannose glycans on the HIV-1 surface glycoprotein, gp120. To investigate the ligand binding mechanisms of antibody 2G12 with glycans aiming for the contribution to the medications, we carried out classical molecular dynamics (MD) simulations and ab initio fragment molecular orbital (FMO) calculations on the antibody 2G12 complex with its high-mannose ligand. We found that Mannose D1 of the ligand had the largest binding affinity with the antibody, which was well consistent with experimental reports. Furthermore, significant roles of Mannose 4 and 4? in the ligand binding were theoretically indicated.

Koyama, Yuka; Ueno-Noto, Kaori; Takano, Keiko

2013-07-01

184

Molecular orbital calculations of two-electron states for P-donor solid-state spin qubits  

Microsoft Academic Search

We theoretically study the Hilbert space structure of two neighboring P-donor electrons in silicon-based quantum computer architectures. To use electron spins as qubits, a crucial condition is the isolation of the electron spins from their environment, including the electronic orbital degrees of freedom. We provide detailed electronic structure calculations of both the single donor electron wave function and the two-electron

L. M. Kettle; Hsi-Sheng Goan; Sean C. Smith

2006-01-01

185

Molecular orbital calculations of two-electron states for P-donor solid-state spin qubits  

Microsoft Academic Search

We theoretically study the Hilbert space structure of two neighbouring P\\u000adonor electrons in silicon-based quantum computer architectures. To use\\u000aelectron spins as qubits, a crucial condition is the isolation of the electron\\u000aspins from their environment, including the electronic orbital degrees of\\u000afreedom. We provide detailed electronic structure calculations of both the\\u000asingle donor electron wave function and the

L. M. Kettle; Hsi-Sheng Goan; Sean C. Smith

2006-01-01

186

The projection diagram  

NASA Astrophysics Data System (ADS)

We describe a diagram, named the projection diagram (PD), that can be used for the interpretation of fringe projection operations in a similar way as the Holodiagram is used in holography and other branches in optics. It is obtained as a Moiré pattern between two spoke targets that mimic central projections, the same as those in a projection and observation system or two projection systems. N. Abramson [Academic, London (1981)] has already proposed its use in systems with two observation points (i.e., stereoscopic observation). By using this PD, several interesting features dealing with fringe projection are highlighted. Information on the sensitivity vector and the geometry of the contouring surfaces can be straightforwardly obtained in a graphical way. The effect of defocusing can also be included in the diagram.

Muramatsu, Mikaya; Torroba, Patricia; Cap, Nelly; Rabal, Hector

2003-08-01

187

Diblock copolymer phase diagram  

NSDL National Science Digital Library

Adaptation of the Matsen and Bates BCP phase diagram predicted using Mean-field Theory. * Matsen MW, Bates FS, ''http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/ma951138i Unifying weak- and strong-segregation block copolymer theories. Diblock copolymer phase diagram as calculated using Mean-field Theory by Matsen and Bates, where fA is the Block fraction, Ï is the Flory-Huggins Chi Parameter, and N is the length of the block.

Iacovella, Christopher R.

2006-11-20

188

Natural bond orbital analysis of molecular interactions Theoretical studies of binary complexes of HF, H2O, NH3, O2, F2, CO, and CO2 with HF, H2O, and NH3  

Microsoft Academic Search

Ab initio molecular orbital theory and natural bond orbital analysis were applied to the binary complexes of HF, H2O, NH3, N2, O2, F2, CO and CO2 with HF, H2O and NH3. Both hydrogen-bonded and nonhydrogen-bonded structures were found for complexes involving N2, O2, F2, CO, and CO2; these structures were defined by NBO analysis of charge transfer, which is generally

A. E. Reed; F. Weinhold; L. A. Curtiss; D. J. Pochatko

1986-01-01

189

Natural bond orbital analysis of molecular interactions: Theoretical studies of binary complexes of HF, H2O, NH3, N2, O2, F2, CO, and CO2 with HF, H2O, and NH3  

Microsoft Academic Search

The binary complexes of HF, H2O, NH3, N2, O2, F2, CO, and CO2 with HF, H2O, and NH3 have been studied by abinitio molecular orbital theory and natural bond orbital (NBO) analysis. Most of the complexes involving N2, O2, F2, CO, and CO2 are found to have both hydrogen-bonded and non-hydrogen-bonded structures. The NBO analysis provides a consistent picture of

Alan E. Reed; Frank Weinhold; Larry A. Curtiss; David J. Pochatko

1986-01-01

190

An energy decomposition analysis for intermolecular interactions from an absolutely localized molecular orbital reference at the coupled-cluster singles and doubles level  

SciTech Connect

We propose a wave function-based method for the decomposition of intermolecular interaction energies into chemically-intuitive components, isolating both mean-field- and explicit correlation-level contributions. We begin by solving the locally-projected self-consistent field for molecular interactions equations for a molecular complex, obtaining an intramolecularly polarized reference of self-consistently optimized, absolutely-localized molecular orbitals (ALMOs), determined with the constraint that each fragment MO be composed only of atomic basis functions belonging to its own fragment. As explicit inter-electronic correlation is integral to an accurate description of weak forces underlying intermolecular interaction potentials, namely, coordinated fluctuations in weakly interacting electronic densities, we add dynamical correlation to the ALMO polarized reference at the coupled-cluster singles and doubles level, accounting for explicit dispersion and charge-transfer effects, which map naturally onto the cluster operator. We demonstrate the stability of energy components with basis set extension, follow the hydrogen bond-breaking coordinate in the C{sub s}-symmetry water dimer, decompose the interaction energies of dispersion-bound rare gas dimers and other van der Waals complexes, and examine charge transfer-dominated donor-acceptor interactions in borane adducts. We compare our results with high-level calculations and experiment when possible.

Azar, R. Julian; Head-Gordon, Martin [Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720 (United States) and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2012-01-14

191

Carbon Cycle Diagram  

NSDL National Science Digital Library

This diagram illustrates some of the most abundant stores of carbon and identifies some of the pathways in the carbon cycle along which carbon is transferred from one form to another. Long-term sinks of carbon are labelled in black; shorter-term fluxes are labelled in purple. Amounts are in billions of tons.

2011-07-12

192

Impulse-Momentum Diagrams  

ERIC Educational Resources Information Center

Multiple representations are a valuable tool to help students learn and understand physics concepts. Furthermore, representations help students learn how to think and act like real scientists. These representations include: pictures, free-body diagrams, energy bar charts, electrical circuits, and, more recently, computer simulations and…

Rosengrant, David

2011-01-01

193

Venn Diagrams and Logic  

NSDL National Science Digital Library

This math lesson from Illuminations uses Venn diagrams to illustrate direct, indirect and transitive reasoning. Students will learn the definitions of direct, indirect and transitive reasoning and give examples of each. Several student activity sheets are included. The material is intended for grades 9-12 and should require 2 and a half class periods to complete.

2011-01-04

194

Molecular cloning and characterization of genes for antibodies generated by orbital tissue-infiltrating B-cells in Graves` ophthalmopathy  

SciTech Connect

Graves` ophthalmopathy is a distressing autoimmune disease of unknown etiology. Analysis of the genes for antibodies secreted by orbital tissue-infiltrating plasma cells might provide insight into the pathogenesis of this disease. The authors, therefore, constructed an immunoglobulin heavy (H) chain and an immunoglobulin k light (L) chain cDNA library from the orbital tissue of a patient with active Graves` ophthalmopathy. Analysis of 15 H (IgG1) and 15 L (k) chains revealed a restricted spectrum of variable region genes. Fourteen of 15 variable k genes were about 94% homologous to the closest known germline gene, KL012. Thirteen of 15 H chain genes were 91% and 90% homologous to the closest germline genes, DP10 and hv1263, respectively. Remarkably, these germline genes also code for other autoantibodies to striated muscle (KL012) and thyroid peridase (KL012 and hv1263). These studies raise the possibility that particular germline genes may be associated with autoimmunity in humans. Further, the present study opens the way to identifying ocular autoantigens that may be the target of an humoral immune response. 29 refs., 4 figs., 1 tab.

Jaume, J.C.; Portolano, S.; Prummel, M.F.; McLachlan, S.M.; Rapoport, B. [Univ. of California, San Francisco, CA (United States)] [Univ. of California, San Francisco, CA (United States)

1994-02-01

195

Molecular orbital (SCF-X??-SW) theory of Fe2+-Mn3+, Fe 3+-Mn 2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates  

USGS Publications Warehouse

Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. -from Author

Sherman, D. M.

1990-01-01

196

Yukawa Monte Carlo (YMC) and Orbital Free Molecular Dynamics (OFMD) approaches for the eos of warm dense iron plasma  

Microsoft Academic Search

Yukawa Monte Carlo and Molecular Dynamics simulations are powerful techniques extensively used to compute plasma properties such as EOS or transport coefficients, but are limited to applications where the linear electronic screening assumption is valid (1). Recently we have shown that a modified scheme using density functional theory with a Thomas-Fermi kinetic energy functional for the electrons (OFMD) may be

Dominique Gilles; Flavien Lambert; Jean Clerouin

2008-01-01

197

The tetrazole-azide tautomerism of some nitrotetrazolo [1,5- a]pyridines studied by NMR, IR spectroscopy and molecular orbital calculations  

NASA Astrophysics Data System (ADS)

The 6-nitro- and 8-nitro- groups in the tetrazolo[1,5- a]pyridine molecule exhibit completely different influences on the tetrazole-azide equilibrium. Introduction of the methyl-, nitro-, azido groups or a bromine atom in positions 5, 6, 7 or 8 of the nitrotetrazolopyridine produce changes in the equilibrium constants. Based on the IR spectra taken in the solid state, the tetrazole structure was assigned for almost all the compounds studied. Only one of them, 2,6-diazido-3-nitropyridine, exists in the diazido-form in the solid. The 1H, 13C, 15N, and 17O NMR spectral parameters (coupling constants, chemical shifts) as well as ab initio molecular orbital calculations were used to describe the tetrazole-azide tautomerism in solutions. The differences in the NMR parameters between the neutral compound (6,8-dinitrotetrazolo[1,5- a]pyridine) and its ?-adducts are also included as data for distinguishing between both molecules.

Cmoch, P.; Wiench, J. W.; Stefaniak, L.; Webb, G. A.

1999-11-01

198

Using simple molecular orbital calculations to predict disease: fast DFT methods applied to enzymes implicated in PKU, Parkinson's disease and Obsessive Compulsive Disorder  

NASA Astrophysics Data System (ADS)

Many diseases can be traced to point mutations in the DNA coding for specific enzymes. These point mutations result in the change of one amino acid residue in the enzyme. We have developed a model using simple molecular orbital calculations which can be used to quantitatively determine the change in interaction between the enzyme's active site and necessary ligands upon mutation. We have applied this model to three hydroxylase proteins: phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase, and we have obtained excellent correlation between our results and observed disease symptoms. Furthermore, we are able to use this agreement as a baseline to screen other mutations which may also cause onset of disease symptoms. Our focus is on systems where the binding is due largely to dispersion, which is much more difficult to model inexpensively than pure electrostatic interactions. Our calculations are run in parallel on a sixteen processor cluster of 64-bit Athlon processors.

Hofto, Laura; Hofto, Meghan; Cross, Jessica; Cafiero, Mauricio

2007-09-01

199

Systematic theoretical investigation of a positron binding to amino acid molecules using the ab initio multi-component molecular orbital approach  

NASA Astrophysics Data System (ADS)

The feature of positron binding to twenty neutral amino acid molecules with the global minimum (GM) and intramoleculear hydrogen-bonded (HB) structures was analysed using the ab initio multi-component molecular orbital method. All amino acid molecules in the intramoleculear HB structures have positive positron affinity (PA, the binding energy of a positron) values, which means that a positron can be attached to parent molecules, while in the GM structures only three amino acid molecules of Gln, Trp, and His have positive PA values. Analysing the positronic orbitals of each positronic amino acid molecule and the electrostatic potential maps of the corresponding parent molecules, we found that long-range electrostatic interaction is the most crucial role in positron binding to neutral amino acid molecules. The strong correlation is observed between the PA and dipole moment, that is, a polar molecule with a large dipole moment has a large PA value. The critical dipole moment of neutral amino acid molecules for binding a positron was found at about 3.46 Debye. From the systematic analysis of twenty kinds of amino acid molecule, we theoretically confirmed the possibility of positron binding to conformers of amino acid molecules with strong dipole moment.

Koyanagi, K.; Kita, Y.; Tachikawa, M.

2012-05-01

200

Vibrational spectra, molecular structure, natural bond orbital, first order hyperpolarizability, thermodynamic analysis and normal coordinate analysis of Salicylaldehyde p-methylphenylthiosemicarbazone by density functional method.  

PubMed

The thiosemicarbazone compound, Salicylaldehyde p-methylphenylthiosemicarbazone (abbreviated as SMPTSC) was synthesized and characterized by FTIR, FT-Raman and UV. Density functional (DFT) calculations have been carried out for the title compound by performing DFT level of theory using B3LYP/6-31++G(d,p) basis set. The molecular geometry and vibrational frequencies were calculated and compared with the experimental data. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. The electronic dipole moment (?D) and the first hyperpolarizability (?tot) values of the investigated molecule were computed using density functional theory (DFT/B3LYP) with 6-311++G(d,p) basis set. The stability and charge delocalization of the molecule was studied by natural bond orbital (NBO) analysis. Thearomaticities of the phenyl rings were studied using the standard harmonic oscillator model of aromaticity (HOMA) index. Mulliken population analysis on atomic charges is also calculated. The molecule orbital contributions are studied by density of energy states (DOSs). PMID:25033238

Porchelvi, E Elamurugu; Muthu, S

2015-01-01

201

Molecular structure, Normal Coordinate Analysis, harmonic vibrational frequencies, Natural Bond Orbital, TD-DFT calculations and biological activity analysis of antioxidant drug 7-hydroxycoumarin  

NASA Astrophysics Data System (ADS)

In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the ?* and ?* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.

Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.

2013-01-01

202

An Introduction to Tree Diagrams  

NSDL National Science Digital Library

This brief article describes the use of tree diagrams in calculating probabilities. The author provides examples of how tree diagrams are used to calculate specific probabilities and why the language chosen relates to the operations used to find the probability.

Cork, Stu

2014-01-01

203

Voronoi diagrams for planar shapes  

Microsoft Academic Search

Although many algorithms compute Voronoi diagrams for polygons, few do so for shapes bounded by arbitrary closed curves. The paper presents an algorithm which does this. It also traces the diagrams directly from their differential properties

J. J. Chou

1995-01-01

204

Impulse-Momentum Diagrams  

Microsoft Academic Search

Multiple representations are a valuable tool to help students learn and understand physics concepts.1 Furthermore, representations help students learn how to think and act like real scientists.2 These representations include: pictures, free-body diagrams,3 energy bar charts,4 electrical circuits, and, more recently, computer simulations and animations.5 However, instructors have limited choices when they want to help their students understand impulse and

David Rosengrant

2011-01-01

205

Feynman diagram drawing made easy  

NASA Astrophysics Data System (ADS)

We present a drawing package optimised for Feynman diagrams. These can be constructed interactively with a mouse-driven graphical interface or from a script file, more suitable to work with a diagram generator. It provides most features encountered in Feynman diagrams and allows to modify every part of a diagram after its creation. Special attention has been paid to obtain a high quality printout as easily as possible. This package is written in Tcl/Tk and in C.

Baillargeon, Marc; Nogueira, P.

1997-02-01

206

On-orbit flight control algorithm description  

NASA Technical Reports Server (NTRS)

Algorithms are presented for rotational and translational control of the space shuttle orbiter in the orbital mission phases, which are external tank separation, orbit insertion, on-orbit and de-orbit. The program provides a versatile control system structure while maintaining uniform communications with other programs, sensors, and control effectors by using an executive routine/functional subroutine format. Software functional requirements are described using block diagrams where feasible, and input--output tables, and the software implementation of each function is presented in equations and structured flow charts. Included are a glossary of all symbols used to define the requirements, and an appendix of supportive material.

1975-01-01

207

Ejs Keplerian Orbit Model  

NSDL National Science Digital Library

The Ejs Keplerian Orbit model displays the dynamics of a mass orbiting a much larger mass subject to Newtonian gravity. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial conditions can also be changed by dragging the mass or dragging the black circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Keplerian Orbit model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_kepler.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

208

Molecular determinants for drug-receptor interactions. Part 2. An ab initio molecular orbital and dipole moment study of the novel nootropic agent piracetam (2-oxopyrrolidin-1-ylacetamide)  

NASA Astrophysics Data System (ADS)

From the ab initio molecular energies of the possible conformers and from a classical dipole moment analysis of 2-oxopyrrolidin-l-ylacetamide (? = 4.02 D in dioxan at 30.0°C), the preferred conformation in solution of this novel nootropic agent has been determined. The exocyclic N-CH 2 bond is rotated in one sense by 90° and the exocyclic CH 2-C bond rotated in the same sense by 120° from the "planar" ( OO)- cis conformation. The structures of the two enantiomers in solution differ from that of the crystalline molecule.

Lumbroso, H.; Liégeois, C.; Pappalardo, G. C.; Grassi, A.

209

An optimum strategy for solution chemistry using semiempirical molecular orbital method. II. Primary importance of reproducing electrostatic interaction in the QM/MM framework.  

PubMed

For the purpose of executing direct dynamic and statistical calculation of chemical reactions in solution, we proposed an optimum strategy using semiempirical molecular orbital (MO) method with neglect of diatomic differential overlap (NDDO) approximation with specific solution reaction parameters (SSRPs), that is, the NDDO-SSRP method. It has been further extended to develop the NDDO-MAIS-SSRP method, which is the NDDO-SSRP method reinforced with the method adopted for intermolecular studies (MAIS), to correct the description of the intermolecular core-core repulsion interaction energy. In this strategy, the empirical parameters of the semiempirical MO method are optimized individually for a target chemically reacting molecular system by reference to the ab initio MO calculation data for a lot of instantaneous geometries on the potential energy surface near the reaction path. For demonstration, the NDDO-MAIS-SSRP method was applied, within the QM/MM framework, to a molecular cluster, that is, a couple of a QM solute NH(3)-H(2)O molecule pair and a MM solvent H(2)O molecule. The NDDO-MAIS-SSRP method can reproduce the electrostatic energy in the region R > 4.0 A, though the electrostatic energy shows large difference with those of MP2 level calculations in the region R < 4.0 A in some cases. Both the NDDO-SSRP and the NDDO-MAIS-SSRP methods could promise in the dynamical application to chemical reaction in solution (Takenaka et al., Chem Phys Lett 2010, 485, 119; Koyano et al., Bull Chem Soc Jpn, in press). PMID:20740563

Koyano, Yoshiyuki; Takenaka, Norio; Nakagawa, Yukinori; Nagaoka, Masataka

2010-11-15

210

[Columbia Sensor Diagrams]. Revised  

NASA Technical Reports Server (NTRS)

A two dimensional graphical event sequence of the time history of relevant sensor information located in the left wing and wheel well areas of the Space Shuttle Columbia Orbiter is presented. Information contained in this graphical event sequence include: 1) Sensor location on orbiter and its associated wire bindle in X-Y plane; 2) Wire bundle routing; 3) Description of each anomalous sensor event; 4) Time annotation by (a) GMT, (b) time relative to LOS, (c) time history bar, and (d) ground track; and 5) Graphical display of temperature rise (based on delta temperature from point it is determined to be anomalous).

2003-01-01

211

The molecular structure and conformational characteristics of some specific benzodiazepine receptor ligands: A molecular orbital study of C3-substituted betacarboline derivatives  

SciTech Connect

The molecular structures of the benzodiazepine receptor ligands {beta}-carboline-3-carboxylic acid (BCCA), its methyl, ethyl, and propyl esters (BCCM, BCCE, and BCCP, respectively), and 3-CN-{beta}-carboline (BC-3-CN) have been investigated on a minimal basis STO-3G level of accuracy. For BCCM, BCCE, and BCCP semiempirical AM 1 calculations have also been performed. Fully optimized molecular geometries are reported. Comparisons with available experimental structures indicate that minimal basis results may have a useful predictive value. For the mobile ester side chains, a study of chosen points on the conformational surface was made. Both the STO-3G and the AM 1 results give the planar conformers is the most stable structures with small barriers to internal rotation, provided the ester side chain remains extended. The calculated STO-3G rotational barriers are higher than are the corresponding AM 1 barriers. Partial optimization, i.e., of side-chain structure parameters only, seems sufficient to map the conformational characteristics of these compounds. The orientation of the dipole moment vector and its magnitude may have consequences for possible interaction with a receptor. On the basis of the sidechain internal dynamics, the intramolecular flexibility tends to be confined to certain regions of conformational space.

Konschin, H.; Tylli, H. (Univ. of Helsinki (Finland)); Gynther, J. (Univ. of Kuopio (Finland)); Rouvinen, J. (Univ. of Joensuu (Finland))

1989-01-01

212

The Orbital Acceleration Research Experiment  

NASA Technical Reports Server (NTRS)

The hardware and software of NASA's proposed Orbital Acceleration Research Experiment (OARE) are described. The OARE is to provide aerodynamic acceleration measurements along the Orbiter's principal axis in the free-molecular flow-flight regime at orbital attitude and in the transition regime during reentry. Models considering the effects of electromagnetic effects, solar radiation pressure, orbiter mass attraction, gravity gradient, orbital centripetal acceleration, out-of-orbital-plane effects, orbiter angular velocity, structural noise, mass expulsion signal sources, crew motion, and bias on acceleration are examined. The experiment contains an electrostatically balanced cylindrical proofmass accelerometer sensor with three orthogonal sensing axis outputs. The components and functions of the experimental calibration system and signal processor and control subsystem are analyzed. The development of the OARE software is discussed. The experimental equipment will be enclosed in a cover assembly that will be mounted in the Orbiter close to the center of gravity.

Blanchard, R. C.; Hendrix, M. K.; Fox, J. C.; Thomas, D. J.; Nicholson, J.

1986-01-01

213

Kepler's Orbit  

NASA Video Gallery

Kepler does not orbit the Earth, rather it orbits the Sun in concert with the Earth, slowly drifting away from Earth. Every 61 Earth years, Kepler and Earth will pass by each other. Throughout the ...

214

Impact decision support diagrams  

NASA Astrophysics Data System (ADS)

One way to frame the job of planetary defense is to “find the optimal approach for finding the optimal approach” to NEO mitigation. This requires a framework for defining in advance what should be done under various circumstances. The two-dimensional action matrix from the recent NRC report “Defending Planet Earth” can be generalized to a notional “Impact Decision Support Diagram” by extending it into a third dimension. The NRC action matrix incorporated two important axes: size and time-to-impact, but probability of impact is also critical (it is part of the definitions of both the Torino and Palermo scales). Uncertainty has been neglected, but is also crucial. It can be incorporated by subsuming it into the NEO size axis by redefining size to be three standard deviations greater than the best estimate, thereby providing a built-in conservative margin. The independent variable is time-to-impact, which is known with high precision. The other two axes are both quantitative assessments of uncertainty and are both time dependent. Thus, the diagram is entirely an expression of uncertainty. The true impact probability is either one or zero, and the true size does not change. The domain contains information about the current uncertainty, which changes with time (as opposed to reality, which does not change).

Boslough, Mark

2014-10-01

215

Orbit Program  

NSDL National Science Digital Library

The Orbit program displays the dynamics of multiple massive objects interacting gravitationally. The default scenario shows the figure-eight orbit of three particles first discovered by Montgomery. Additional particles and their initial positions and velocities can be specified using the Display | Switch GUI menu item. Orbit is an Open Source Physics program written for the teaching of classical orbits. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the mech_orbit.jar file will run the program if Java is installed. Other classical mechanics programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or mechanics.

Christian, Wolfgang

2008-05-20

216

Spectroscopic (FT-IR, FT-Raman, NMR and UV-Visible) and quantum chemical studies of molecular geometry, Frontier molecular orbital, NLO, NBO and thermodynamic properties of salicylic acid  

NASA Astrophysics Data System (ADS)

The solid phase FT-IR and FT-Raman spectra of 2-hydroxybenzoic acid (salicylic acid) have been recorded in the region 4000-400 and 4000-100 cm-1 respectively. The optimized molecular geometry and fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method and a comparative study between Hartree Fork (HF) method at 6-311++G(d,p) level basis set. The calculated harmonic vibrational frequencies are scaled and they are compared with experimentally obtained FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The time dependent DFT method is employed to predict its absorption energy and oscillator strength. The linear polarizability (?) and the first order hyper polarizability (?) values of the investigated molecule have been computed. The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) are also performed. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

Suresh, S.; Gunasekaran, S.; Srinivasan, S.

2014-11-01

217

Bound states of positron with simple carbonyl and aldehyde species with configuration interaction multi-component molecular orbital and local vibrational approaches  

NASA Astrophysics Data System (ADS)

Characteristic features of the positron-binding structure of some carbonyl and aldehyde species such as formaldehyde, acetaldehyde, acetone and propionaldehyde are discussed with the configuration interaction scheme of multi-component molecular orbital (MC_MO) calculations. This method can take the electron-positron correlation contribution into account through single electronic-single positronic excitation configurations. Our vertical positron affinity (PA) values of acetaldehyde and acetone with electronic 6-31 + +G(2df,2pd) and positronic [15s15p3d2f1g] basis sets are as 52 and 92 meV, which can be compared to the recent experimental values of 90 and 173 meV by Danielson et al (2010 Phys. Rev. Lett. 104 233201). For formaldehyde we have also found that the PA values are enhanced by including the local C= \\!\\! =O vibrational contribution from the vertical PA value of 15 meV to 17, 21 and 25 meV after averaging over the zeroth, first and second vibrational states, respectively, due to the anharmonicity of the potential.

Tachikawa, Masanori; Kita, Yukiumi; Buenker, Robert J.

2012-03-01

218

Structures, molecular orbitals and UV-vis spectra investigations on methyl 1-benzyl-1H-1,2,3-triazole-4-carboxylate: A computational study  

NASA Astrophysics Data System (ADS)

The methyl 1-benzyl-1H-1,2,3-triazole-4-carboxylate (C11H11N3O2) has been studied by theoretically methods. The structure of this compound is optimized by density functional theory (DFT), the second-order Møller-Plesset perturbation theory (MP2) and G3 theory (G3(MP2)) levels. Our calculation results are in very good agreement with experimental values. Compared to a perfect pentagonal structure, the geometrical structures of C11H11N3O2 show a little distortion of 1,2,3-triazole ring due to the highly electronegativity of substitution groups. In addition, dipole moment and frontier molecular orbitals (FMOs) of the C11H11N3O2 are calculated as well. Because of solvent effect, the HOMO-LUMO energy gap in methanol is predicted to be smaller than in gas phase by 0.367 eV. The simulated UV-vis spectra are investigated by time-dependent density functional theory (TD-DFT), and two obviously absorption features have been predicted. These two absorption features are located between 170 nm and 210 nm, which is in ultraviolet C range. Moreover, the UV absorption features in methanol are predicted to be more intense than in gas phase; besides, the red shift is predicted in methanol as well.

Wang, Tsang-Hsiu; Chu, Hsing-Yu; Wang, I.-Teng

2014-10-01

219

(?, ?) uniform-scale chromaticity diagram  

NASA Astrophysics Data System (ADS)

The non-uniformity of scale in the usual chromaticity diagrams is a very old problem in colour measurements. This program computes the transformation from the CIE 1931 ( x, y) chromaticity diagram to the recent uniform scale (?, ?) diagram and vice-versa. Moreover the program evaluates the most important colorimetric quantities for a comparison with the experimental data. Finally the chromatic gamut needed for TV applications is shown.

Oleari, Claudio; Formaleoni, Guido

1992-02-01

220

Generating function for web diagrams  

NASA Astrophysics Data System (ADS)

We present the description of the exponentiated diagrams in terms of generating function within the universal diagrammatic technique. In particular, we show the exponentiation of the gauge theory amplitudes involving products of an arbitrary number of Wilson lines of arbitrary shapes, which generalizes the concept of web diagrams. The presented method gives a new viewpoint on the web diagrams and proves the non-Abelian exponentiation theorem.

Vladimirov, A. A.

2014-09-01

221

Box diagram in Yukawa theory  

SciTech Connect

We present a light-front calculation of the box diagram in Yukawa theory. The covariant box diagram is finite for the case of spin-1/2 constituents exchanging spin-0 particles. In light-front dynamics, however, individual time-ordered diagrams are divergent. We analyze the corresponding light-front singularities and show the equivalence between the light-front and covariant results by taming the singularities.

Bakker, Bernard L. G.; Boomsma, Jorn K. [Department of Physics and Astrophysics, Vrije Universiteit, De Boelelaan 1081, NL-1081 HV Amsterdam (Netherlands); Ji, Chueng-Ryong [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202 (United States)

2007-03-15

222

Diagonal Slices of 3D Young Diagrams in the Approach of Maya Diagrams  

NASA Astrophysics Data System (ADS)

According to the correspondence between 2D Young diagrams and Maya diagrams and the relation between 2D and 3D Young diagrams, we construct 3D Young diagrams in the approach of Maya diagrams. Moreover, we formulate the generating function of 3D Young diagrams, which is the MacMahon function in terms of Maya diagrams.

Cai, Li-Qiang; Wang, Li-Fang; Wu, Ke; Yang, Jie

2014-09-01

223

Scale Models and Diagrams  

NSDL National Science Digital Library

This is a set of three, one-page problems about the scale of objects in images returned by spacecraft. Learners will measure scaled drawings using high-resolution images of the lunar and martian surfaces. Options are presented so that students may learn about the Lunar Reconnaissance Orbiter (LRO) mission through a NASA press release or by viewing a NASA eClips video [4 min.]. This activity is part of the Space Math multi-media modules that integrate NASA press releases, NASA archival video, and mathematics problems targeted at specific math standards commonly encountered in middle school.

224

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

1969-12-31

225

Geometric Relations Among Voronoi Diagrams  

Microsoft Academic Search

Two general classes of Voronoi diagrams are introduced and, along with their modifications to higher order, are shown to be geometrically related. This geometric background, on one hand, serves to analyze the size and the combinatorial structure, and on the other hand, implies general and efficient methods of construction, for various important types of Voronoi diagrams considered in the literature.

Franz Aurenhammer; Hiroshi Imai

1987-01-01

226

Voronoi diagrams and Delaunay triangulations  

Microsoft Academic Search

IntroductionThe Voronoi diagram of a set of sites partitions space into regions, one per site; theregion for a site s consists of all points closer to s than to any other site. The dual ofthe Voronoi diagram, the Delaunay triangulation, is the unique triangulation so thatthe circumsphere of every triangle contains no sites in its interior. Voronoi diagramsand Delaunay triangulations

Steven Fortune

1995-01-01

227

Potential-pH Diagrams.  

ERIC Educational Resources Information Center

Potential-pH diagrams show the domains of redoxpotential and pH in which major species are most stable. Constructing such diagrams provides students with opportunities to decide what species must be considered, search literature for equilibrium constants and free energies of formation, and practice in using the Nernst equation. (Author/JN)

Barnum, Dennis W.

1982-01-01

228

CONTINUATION OF PERIODIC ORBITS AROUND LAGRANGE POINTS AND AUTO2000  

E-print Network

of bifurcating branches of solutions, so a detailed map of periodic orbits may be computed for each for continuation and bifurcation problems in ordinary di#11;erential equations, originally written in 1980 for such a problem a bifurcation diagram. The computation of such bifurcation diagrams and their singularities, e

Doedel, Eusebius

229

The electronic structure of arene tricarbonyl complexes of group 6 metals: ultraviolet photoelectron spectra and molecular orbital calculations, and the low-temperature X-ray crystal structure of hexamethylbenzene chromium tricarbonyl  

E-print Network

COMPLEXES OF GROUP 6 METALS: ULTRAVIOLET PHOTOELECTRON SPECTRA AND MOLECULAR ORBITAL CALCULATIONS, AND THE LOW-TEMPERATURE X-RAY CRYSTAL STRUCTURE OF HEXAMETHYLBENZENE CHROMIUM TRICARBONYL A Thesis by BRIEN PATRICK BYERS Approved as to style... and content by: cae . a (Chairman) / ar tta . arens o g ( ber) ey . r (Member) cae . a (Head of Department) December 1986 ABSTRACT The Electronic Structure of Arene Tricarbonyl Complexes of Group 6 Metals: Ultraviolet Photoelectron Spectra...

Byers, Brien Patrick

2012-06-07

230

Predicting Allostery Wiring Diagrams within Motor Proteins  

NASA Astrophysics Data System (ADS)

Motor proteins are intricate molecular machines that make use of allostery as a basis of their function. Fundamental questions in trying to understand the operational mechanism of the motors is, therefore, how allostery communicated is within the proteins, what are the pathways that transmit allosteric signals, how to model and predict them. We have proposed a normal-mode analysis based perturbation model that predicts the pathways based on the structure and chemical composition of the molecules. We use the model to investigate allosteric pathways (allostery wiring diagrams) within motor proteins myosin V and VI.

Tehver, Riina

2013-03-01

231

Spider Diagrams: A Diagrammatic Reasoning System  

Microsoft Academic Search

Spider diagrams combine and extend Venn diagrams and Euler circles to express constraints on sets and their relationships with other sets. These diagrams can be used in conjunction with object-oriented modelling notations such as the Unified Modelling Language. This paper summarises the main syntax and semantics of spider diagrams. It also introduces inference rules for reasoning with spider diagrams and

John Howse; Fernando Molina; John Taylor; Stuart Kent; JOSEPH YOSSI GIL

2001-01-01

232

Concrete and abstract Voronoi diagrams  

SciTech Connect

The Voronoi diagram of a set of sites is a partition of the plane into regions, one to each site, such that the region of each site contains all points of the plane that are closer to this site than to the other ones. Such partitions are of great importance to computer science and many other fields. The challenge is to compute Voronoi diagrams quickly. The problem is that their structure depends on the notion of distance and the sort of site. In this book the author proposes a unifying approach by introducing abstract Voronoi diagrams. These are based on the concept of bisecting curves which are required to have some simple properties that are actually possessed by most bisectors of concrete Voronoi diagrams. Abstract Voronoi diagrams can be computed efficiently and there exists a worst-case efficient algorithm of divide-and-conquer type that applies to all abstract Voronoi diagrams satisfying a certain constraint. The author shows that this constraint is fulfilled by the concrete diagrams based no large classes of metrics in the plane.

Klein, R. (Universitat-Gesamthochschule Essen (DE))

1989-01-01

233

Orbiter Autoland reliability analysis  

NASA Technical Reports Server (NTRS)

The Space Shuttle Orbiter is the only space reentry vehicle in which the crew is seated upright. This position presents some physiological effects requiring countermeasures to prevent a crewmember from becoming incapacitated. This also introduces a potential need for automated vehicle landing capability. Autoland is a primary procedure that was identified as a requirement for landing following and extended duration orbiter mission. This report documents the results of the reliability analysis performed on the hardware required for an automated landing. A reliability block diagram was used to evaluate system reliability. The analysis considers the manual and automated landing modes currently available on the Orbiter. (Autoland is presently a backup system only.) Results of this study indicate a +/- 36 percent probability of successfully extending a nominal mission to 30 days. Enough variations were evaluated to verify that the reliability could be altered with missions planning and procedures. If the crew is modeled as being fully capable after 30 days, the probability of a successful manual landing is comparable to that of Autoland because much of the hardware is used for both manual and automated landing modes. The analysis indicates that the reliability for the manual mode is limited by the hardware and depends greatly on crew capability. Crew capability for a successful landing after 30 days has not been determined yet.

Welch, D. Phillip

1993-01-01

234

Natural bond orbital analysis of steric interactions  

Microsoft Academic Search

We describe an ab initio procedure for extracting the Pauli exchange antisymmetry (“steric”) contributions to molecular potential energy in the framework of self-consistent-field molecular orbital (SCFMO) theory. This “natural steric analysis” method is based on natural bond orbital (NBO) representation of the SCFMO wave function, which allows the steric exchange energy to be approximated as an energy difference between “preorthogonal”

J. K. Badenhoop; F. Weinhold

1997-01-01

235

Orbital imaging.  

PubMed

Appropriate axial or coronal computed x-ray tomography is the most inexpensive method to reliably supply detail in orbital disease. Magnetic resonance imaging can provide additional information and may be characteristic in some conditions. Magnetic resonance imaging is imperative for detailed imaging of disease at the orbital apex, optic canal, or chiasm. Color-coded Doppler ultrasonography allows examination of physiological blood flow within orbital vasculature and recent reports have reported the changes of flow in various orbital diseases. Limited results with computed tomographic or video-radiographic investigation of lacrimal outflow obstruction have been presented in several articles, although it remains doubtful whether these techniques are superior to the cheaper, more readily available, conventional macrodacryocystography. Endoscopy of the lacrimal drainage system is proving to be an interesting research tool, but is of uncertain applicability in the treatment of disease. PMID:10146487

Rose, G E

1993-11-01

236

Quantum Diagrams and Quantum Networks  

E-print Network

This paper is an introduction to diagrammatic methods for representing quantum processes and quantum computing. We review basic notions for quantum information and quantum computing. We discuss topological diagrams and some issues about using category theory in representing quantum computing and teleportation. We analyze very carefully the diagrammatic meaning of the usual representation of the Mach-Zehnder interferometer, and we show how it can be generalized to associate to each composition of unitary transformations a "laboratory quantum diagram" such that particles moving though the many alternate paths in this diagram will mimic the quantum process represented by the composition of unitary transformations. This is a finite dimensional way to think about the Feynman Path Integral. We call our representation result the Path Theorem. Then we go back to the basics of networks and matrices and show how elements of quantum measurement can be represented with network diagrams.

Louis H. Kauffman; Samuel J. Lomonaco Jr

2014-04-17

237

Lunar Reconnaissance Orbiter FlatSat  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews the use of FlatSat as a platform for use during flight integration and testing (I&T) of the Lunar Reconnaissance Orbiter (LRO). Included in the presentations are requirements for the facility, a diagram of the LRO FlatSat lab, and discussion of the operational documentation, facility scheduling, and issues and lessons learned.

Wright, Michael

2008-01-01

238

Molecular orbital calculations on the vibrational spectra of Q 3 T-(OH) species and the hydrolysis of a three-membered aluminosilicate ring  

NASA Astrophysics Data System (ADS)

Force constant analyses of the molecules [(H 3SiO) 3Al-(OH)] 1-, Na +[(H 3SiO) 3Al-(OH)] 1-, [((OH) 3SiO) 3Al-(OH)] 1- [(H 3SiO) 3Si-(OH)],[((OH) 3SiO) 3Si-(OH)],[((OH) 3SiO) 2((OH) 3A10)Si(OH)] 1- and Na + [(H 3SiO ) 2 (H 3Al0) Si- (OH)] 1- have been performed with ab initio molecular orbital calculations to determine the frequencies and H-D shifts of T- (OH) vibrations in Q 3 T- (OH) species where T is a So 4+ or Al 3+. Calculated Q 3 Si-(OH) vibrations are close to the observed value in H 2O-bearing Si0 2 glass. The theoretical Al-(OH) stretching frequency in Na +[ (H 3SiO) 3A1-(OH)] 1- matches the 880 cm - shoulder in the vibrational spectra of hydrous albitic glasses within experimental error. Isotopic substitution of deuterium for hydrogen in the T-(OH) bond results in frequency shifts of less than 25 cm -1 in all cases consistent with the small H-D frequency shifts observed in silica (Mysen and Virgo, 1986) and Na-aluminosilicate glasses (McMillan et al., 1993). Hydrolysis of a three-membered aluminosilicate ring into a trimeric chain (i.e., [H 6SiAl 20 9] 2- + H 2O ? [H 8SiAl 20 10] 2-) was also calculated. Hydrolysis occurs through a pentavalent Al 3+ transition state complex. Calculated energies of the reactants and product in the above reaction predict that the chain configuration is in a marginally lower potential energy state (-36 kJ/mol) than the H 2O-ring dimer. An activation energy of + 171 kJ/mol is predicted between the two species for hydrolysis and +207 kJ/mol for the reverse reaction.

Kubicki, J. D.; Sykes, Dan

1995-12-01

239

Conformational structure of gaseous 3-chloropropanoyl chloride by electron diffraction, normal coordinate analysis, and ab initio molecular orbital, and density functional theory calculations.  

PubMed

The molecular and conformational structures of 3-chloropropanoyl chloride (CH(2)Cl-CH(2)-C(=O)Cl) have been studied by using gas-phase electron diffraction (GED) data obtained at 22 degrees C (295 K) and ab initio molecular orbital (MO) and density functional theory (DFT) calculations up to the levels of MP4(SDQ) and B3LYP using larger basis sets. Normal coordinate calculations (NCA) taking into account nonlinear vibrational effects were also used in the analyses. The title compound may have up to four low-energy conformers in the gas phase, labeled according to the position of each of the two chlorine atoms in relation to the CCC propanoyl backbone, labeling the carbonyl chlorine torsion angle first: AA, AG, GG, and GA; where A is anti (ideal C-C-C-Cl torsion angle of approximately 180 degrees) and G is gauche (ideal C-C-C-Cl torsion angle of approximately 60 degrees). It has been judged from the experimental GED data and the theoretical calculations, as well as from previously published infrared (IR) studies on the molecule in both the liquid phase and in argon-trapped matrices at 10 K, that the gas phase consists of a mixture of at least three conformers: AA (most stable), AG, and GG, with the possibility of a smaller contribution (<10%) from the higher-energy GA form. The GA conformer cannot be ruled out by the GED experimental data. Relevant structural parameter values obtained from the GED least-squares refinements, with calculated ab initio MO MP2/6-31+G(2d,p) values used as constraints, were as follows (AA values with estimated 2sigma uncertainties): Bond lengths (r(h1)): r(C-C(=O)) = 1.505(4) A, r(C-CH(2)Cl) = 1.520(4) A, r(C=O) = 1.197(4) A, r(C(=O)-Cl) = 1.789(3) A, and r(C-Cl) = 1.782(3) A. Bond angles (angle(h1)): angle CCC = 111.5(11) degrees , angle CCO = 127.0(5) degrees, angle CC(O)Cl = 112.5(3) degrees, and angle CCCl = 110.3(3) degrees. Torsion angles (phi(C-C) = phi(ClCCC)): for AA, phi(1)(C-C(O)) = phi(2)(C-CH(2)Cl) = 180 degrees (assumed for true C(s) symmetry); for AG, phi(1)(C-C(O)) = -140(5) degrees, phi(2)(C-CH(2)Cl) = 76(13) degrees; for GG, phi(1)(C-C(O)) = 46(8) degrees, phi(2)(C-CH(2)Cl) = 77(14) degrees; for GA, phi(1)(C-C(O)) = 67.9 degrees (assumed), phi(2)(C-CH(2)Cl) = 177.8 degrees (assumed). The non-AA conformers all have chiral C(1) symmetry with twice the statistical weight (multiplicity) of C(s). The MP2/6-31+G(2d,p) calculated composition (%) based on the zero-point energy (ZPE) corrected energy differences, and the statistical weights for conformers: AA/AG/GG/GA = 28/35/28/9 was assumed in the final GED refinement. The more recent literature concerning the title molecule, as well as for several related molecules, has been examined and a survey has been attempted in the present article. The new experimental results for 3-chloropropanoyl chloride are discussed and compared with the previously published findings. PMID:16986848

Johansen, Tore H; Hagen, Kolbjørn

2006-09-28

240

The calculation of heat capacity curves and phase diagrams based on regular solution theory  

Microsoft Academic Search

The intermolecular interactions of molecules within the bilayer are responsible for the lipid organisation, e.g. domain formation, and the interaction and stabilisation of proteins within the lipid matrix. The mixing behaviour of lipids, which reflects the intrinsic molecular interactions, can be deduced from the shape of the phase diagram (temperature vs. mole fraction diagram), which is constructed from the analysis

P. Garidel; C. Johann; A. Blume

2005-01-01

241

Inner valence molecular orbitals and the structure of X-ray O{sub 4,5}(U) emission spectra of uranium in oxides UO{sub 2} and {gamma}-UO{sub 3}  

SciTech Connect

The efficient participation of the relatively low-lying U6p, 6s and Lns atomic orbitals (AOs) of the neighboring ions and ligands (L) in the formation of outer valence and inner valence molecular orbitals (OVMOs and IVMOs, respectively) was first found when interpreting the fine structure of the X-ray photoelectron spectra. However, the first X-ray O{sub 4,5}(U) emission spectra of uranium in oxides, which could prove the formation of IVMO in them, were low-resolution. In this work, the authors obtained, for the first time, high-resolution emission spectra for uranium in dioxide UO{sub 2} and trioxide {gamma}-UO{sub 3} with the aim of interpreting the fine structure using the results of X-ray photoelectron spectroscopy on the IVMOs in these oxides.

Teterin, Yu.A.; Ivanov, K.E. [Kurchatov Institute Russian Research Center, Moscow (Russian Federation); Terekhov, V.A. [Voronezh State Univ. (Russian Federation)

1995-11-01

242

Molecular orbital (SCF-X??-SW) theory of metal-metal charge transfer processes in minerals - II. Application to Fe2+ ??? Ti4+ charge transfer transitions in oxides and silicates  

USGS Publications Warehouse

A molecular orbital description, based on X??-Scattered wave calculations on a (FeTiO10)14- cluster, is given for Fe2+ ??? Ti4+ charge transfer transitions in minerals. The calculated energy for the lowest Fe2+ ??? Ti4+ metal-metal charge transfer transition is 18040 cm-1 in reasonable agreement with energies observed in the optical spectra of Fe-Ti oxides and silicates. As in the case of Fe2+ ??? Fe3+ charge transfer in mixed-valence iron oxides and silicates, Fe2+ ??? Ti4+ charge transfer is associated with Fe-Ti bonding across shared polyhedral edges. Such bonding results from the overlap of the Fe(t2 g) and Ti(t2 g) 3 d orbitals. ?? 1987 Springer-Verlag.

Sherman, D. M.

1987-01-01

243

4,5-Dicyano-3,6-diethylbenzo-1,2-diselenete, a highly stable 1,2-diselenete: its preparation, structural characterization, calculated molecular orbitals, and complexation with tetrakis(triphenylphosphine)palladium.  

PubMed

The first isolable benzo-1,2-diselenete, 4,5-dicyano-3,6-diethylbenzo-1,2-diselenete (4), was prepared by the reaction of 4,5-(o-xylylenediseleno)-3,6-diethylphthalonitrile (3) with aluminum chloride in toluene. X-ray crystallographic analysis demonstrated that 4 contains a trapezoidal diselenide ring rather than a benzo-1,2-diselenone structure. In crystal form, 4 undergoes self-assembly and generates structures based on layered molecular sheets since the unit cell contains only one molecule. While the cyclic voltammogram of 4 exhibited only one irreversible peak (Ep = 1.59 V) during oxidation and two quasireversible couples during reduction, three peaks were observed in the differential pulse voltammogram of the reduction couples (E1/2 = -1.19, -0.75, and -0.69 V). Although a THF solution of 4 in the presence of sodium metal was EPR silent, various signals were readily observed in its (1)H, (13)C, and (77)Se NMR spectra. Molecular orbital calculations for 4 demonstrated that the HOMO orbital is primarily localized at the two selenium atoms and four of the benzene carbon atoms while the LUMO orbital is situated solely on the diselenete ring. It appears that the HOMO and LUMO orbitals of 4 receive significant stabilization from the nitrile groups compared to the level of stabilization in the unsubstituted benzo-1,2-diselenete (BDS). The reaction of 4 with tetrakis(triphenylphosphine)palladium in benzene was found to produce a dinuclear palladium complex (8), and the structure of this complex was determined by X-ray crystallographic analysis. The central four membered ring of 8 consists of the Pd1, Se2, Pd2, and Se3 atoms and is not planar but rather adopts a folded arrangement. PMID:24724937

Kimura, Takeshi; Nakahodo, Tsukasa; Fujihara, Hisashi; Suzuki, Eiichi

2014-05-01

244

Automatically Assessing Graph-Based Diagrams  

ERIC Educational Resources Information Center

To date there has been very little work on the machine understanding of imprecise diagrams, such as diagrams drawn by students in response to assessment questions. Imprecise diagrams exhibit faults such as missing, extraneous and incorrectly formed elements. The semantics of imprecise diagrams are difficult to determine. While there have been…

Thomas, Pete; Smith, Neil; Waugh, Kevin

2008-01-01

245

DRAWING DIAGRAMS IN AN ONLINE EXAMINATION  

Microsoft Academic Search

This paper describes a study into the drawing of diagrams in an online examination. The diagrams were produced by students during an on-line examination using a simple drawing tool. The students' examination answers, which included a diagram, were submitted over the Internet to an automatic marking tool for grading and feedback. This paper describes the diagram drawing tool and discusses

Pete Thomas

246

A frontier orbital study with ab initio molecular dynamics of the effects of solvation on chemical reactivity: solvent-induced orbital control in FeO-activated hydroxylation reactions.  

PubMed

Solvation effects on chemical reactivity are often rationalized using electrostatic considerations: the reduced stabilization of the transition state results in higher reaction barriers and lower reactivity in solution. We demonstrate that the effect of solvation on the relative energies of the frontier orbitals is equally important and may even reverse the trend expected from purely electrostatic arguments. We consider the H abstraction reaction from methane by quintet [EDTAH(n)·FeO]((n-2)+), (n = 0-4) complexes in the gas phase and in aqueous solution, which we examine using ab initio thermodynamic integration. The variation of the charge of the complex with the protonation of the EDTA ligand reveals that the free energy barrier in gas phase increases with the negative charge, varying from 16 kJ mol(-1) for [EDTAH4·FeO](2+) to 57 kJ mol(-1) for [EDTAHn·FeO](2-). In aqueous solution, the barrier for the +2 complex (38 kJ mol(-1)) is higher than in gas phase, as predicted by purely electrostatic arguments. For the negative complexes, however, the barrier is lower than in gas phase (e.g., 45 kJ mol(-1) for the -2 complex). We explain this increase in reactivity in terms of a stabilization of the virtual 3?* orbital of FeO(2+), which acts as the dominant electron acceptor in the H-atom transfer from CH4. This stabilization originates from the dielectric screening caused by the reorientation of the water dipoles in the first solvation shell of the charged solute, which stabilizes the acceptor orbital energy for the -2 complex sufficiently to outweigh the unfavorable electrostatic destabilization of the transition-state relative to the reactants in solution. PMID:23634772

Bernasconi, Leonardo; Baerends, Evert Jan

2013-06-19

247

Orbital Debris  

NASA Technical Reports Server (NTRS)

Earth orbital debris issues and recommended future activities are discussed. The workshop addressed the areas of environment definition, hazards to spacecraft, and space object management. It concluded that orbital debris is a potential problem for future space operations. However, before recommending any major efforts to control the environment, more data are required. The most significant required data are on the population of debris smaller than 4 cm in diameter. New damage criteria are also required. When these data are obtained, they can be combined with hypervelocity data to evaluate the hazards to future spacecraft. After these hazards are understood, then techniques to control the environment can be evaluated.

Kessler, D. J. (compiler); Su, S. Y. (compiler)

1985-01-01

248

Ejs Quartic Potential Orbit Model  

NSDL National Science Digital Library

The Ejs Quartic Potential Orbit model displays the dynamics of a mass orbiting a much larger mass subject to a quartic potential, C/râ´. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial conditions can also be changed by dragging the mass or dragging the pink circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Quartic Potential Orbit model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_quarticpotential.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

249

Vanishing rainbows near orbiting and the energy dependence of rainbow scattering - Relation to properties of the potential. [molecular beam scattering cross sections  

NASA Technical Reports Server (NTRS)

The energy threshold behavior of elastic rainbow scattering near the transition to orbiting is derived. Analysis of the energy dependence of the rainbow angle shows that the full range from high energies down to orbiting can be fitted with two parameters. Thus, measurements of the rainbow angle can give essentially only two pieces of information about the potential. For potentials of common shapes, such measurements are sensitive to regions of the potential just beyond the minimum and give information about the shape of the potential in this range. However, neither a minimum nor a point of inflection in the potential is necessary for rainbow scattering.

Greene, E. F.; Hall, R. B.; Mason, E. A.

1975-01-01

250

Phase diagrams and crystal growth  

NASA Astrophysics Data System (ADS)

Phase diagrams are briefly treated as generalized property-composition relationships, with respect to crystal technology optimization. The treatment is based on mutual interaction of three systems related to semiconductors: (a) the semiconducting material systems, (b0 the data bank, (c) the system of crystallization methods. A model is proposed enabling optimatization on the path from application requirements to the desired material. Further, several examples of the selection as to the composition of LED and laser diode material are given. Some of molten-solution-zone methods are being successfully introduced for this purpose. Common features of these methods, the application of phase diagrams, and their pecularities compared with other crystallization methods are illustrated by schematic diagrams and by examples. LPE methods, particularly the steady-state LPE methods such as Woodall's ISM and Nishizawa's TDM-CVP, and the CAM-S (Crystallization Method Providing Composition Autocontrol in Situ) have been chosen as examples. Another approach of exploiting phase diagrams for optimal material selection and for determination of growth condition before experimentation through a simple calculation is presented on InP-GaP solid solutions. Ternary phase diagrams are visualized in space through calculation and constructions based on the corresponding thermodynamic models and anaglyphs. These make it easy to observe and qualitatively analyze the crystallization of every composition. Phase diagrams can be also used as a powerful tool for the deduction of new crystallization methods. Eutectic crystallization is an example of such an approach where a modified molten-solution-zone method can give a sandwich structure with an abrupt concentration change. The concentration of a component can range from 0 to 100% in the different solid phases.

Venkrbec, Jan

1980-04-01

251

Orbit extrapolation  

Microsoft Academic Search

Orbit extrapolation problems are considered for the following examples: the ARGOS satellite, the SPOT satellite, the D2B and Signe 3 satellites, the Laser satellites, the Transit satellites, and Skylab atmospheric entry. Various extrapolation methods are then described, including analytical (integration and transformation) methods, numerical integration methods (e.g., the Adams-Moulton, Cowell method), and the centering method.

N. Borderies

1980-01-01

252

Mars Orbit  

NSDL National Science Digital Library

This geometry lesson from Illuminations uses the model of the orbits of Mars and Earth relative to the sun to illustrate parametric equations. As an interdisciplinary learning activity, the material may be used in conjunction with astronomy lessons. An interactive applet and student questions are also included. The material is intended for grades 9-12 and should require 1 class period to complete.

2010-12-14

253

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

254

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Horton, Michael

2009-05-30

255

Accurate phase diagram of tetravalent DNA nanostars  

E-print Network

We evaluate, by means of molecular dynamics simulations employing a realistic DNA coarse-grained model, the phase behaviour and the structural and dynamic properties of tetravalent DNA nanostars, i.e. nanoconstructs completely made of DNA. We find that, as the system is cooled down, tetramers undergo a gas--liquid phase separation in a region of concentrations which, if the difference in salt concentration is taken into account, is comparable with the recently measured experimental phase diagram [S. Biffi \\textit{et al}, Proc. Natl. Acad. Sci, \\textbf{110}, 15633 (2013)]. We also present a mean-field free energy for modelling the phase diagram based on the bonding contribution, derived by Wertheim in its studies of associating liquids, combined with mass action law expressions appropriate for DNA binding and a numerically evaluated reference free energy. The resulting free energy qualitatively reproduces the numerical data. Finally, we report information on the nanostar structure, e.g. geometry and flexibility of the single tetramer and of the collective behaviour, providing a useful reference for future small angle scattering experiments, for all investigated temperatures and concentrations.

Lorenzo Rovigatti; Francesca Bomboi; Francesco Sciortino

2014-01-13

256

Molecular orbital studies (hardness, chemical potential, electronegativity and electrophilicity), vibrational spectroscopic investigation and normal coordinate analysis of 5-{1-hydroxy-2-[(propan-2-yl)amino]ethyl}benzene-1,3-diol  

NASA Astrophysics Data System (ADS)

FT-IR and FT-Raman spectra of 5-{1-hydroxy-2-[(propan-2-yl) amino] ethyl} benzene-1,3-diol (abbrevi- 54 ated as HPAEBD) were recorded in the region 4000-450 cm-1 and 4000-100 cm-1 respectively. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (B3LYP) and HF method with 6-31 G(d,p) as basis set. The theoretical wave numbers were scaled and compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated Potential energy distribution (PED). Stability of the molecule arising from hyperconjugation and charge delocalization is confirmed by the natural bond orbital analysis (NBO). The results show that electron density (ED) in the ? antibonding orbitals and E (2) energies confirm the occurrence of intra molecular charge transfer (ICT) within the molecule. The molecule orbital contributions were studied by using the total (TDOS), sum of ? and ? electron (??DOS) density of States. Mulliken population analysis of atomic charges is also calculated. The calculated HOMO and LUMO energy gap shows that charge transfer occurs within the molecule. The electron density-based local reactivity descriptors such as Fukui functions were calculated to explain the chemical selectivity or reactivity site in this compound. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated.

Muthu, S.; Renuga, S.

2014-01-01

257

Molecular orbital studies (hardness, chemical potential, electronegativity and electrophilicity), vibrational spectroscopic investigation and normal coordinate analysis of 5-{1-hydroxy-2-[(propan-2-yl)amino]ethyl}benzene-1,3-diol.  

PubMed

FT-IR and FT-Raman spectra of 5-{1-hydroxy-2-[(propan-2-yl) amino] ethyl} benzene-1,3-diol (abbrevi- 54 ated as HPAEBD) were recorded in the region 4000-450 cm(-1) and 4000-100 cm(-1) respectively. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (B3LYP) and HF method with 6-31 G(d,p) as basis set. The theoretical wave numbers were scaled and compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated Potential energy distribution (PED). Stability of the molecule arising from hyperconjugation and charge delocalization is confirmed by the natural bond orbital analysis (NBO). The results show that electron density (ED) in the ? antibonding orbitals and E (2) energies confirm the occurrence of intra molecular charge transfer (ICT) within the molecule. The molecule orbital contributions were studied by using the total (TDOS), sum of ? and ? electron (??DOS) density of States. Mulliken population analysis of atomic charges is also calculated. The calculated HOMO and LUMO energy gap shows that charge transfer occurs within the molecule. The electron density-based local reactivity descriptors such as Fukui functions were calculated to explain the chemical selectivity or reactivity site in this compound. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated. PMID:24096064

Muthu, S; Renuga, S

2014-01-24

258

Concrete and Abstract Voronoi Diagrams  

Microsoft Academic Search

The Voronoi diagram of a set of sites is a partition of the plane into regions, one to each site, such that the region of each site contains all points of the plane that are closer to this site than to the other ones. Such partitions are of great importance to computer science and many other fields. The challenge is

Rolf Klein

1989-01-01

259

Higher Order City Voronoi Diagrams  

E-print Network

We investigate higher-order Voronoi diagrams in the city metric. This metric is induced by quickest paths in the L1 metric in the presence of an accelerating transportation network of axis-parallel line segments. For the structural complexity of kth-order city Voronoi diagrams of n point sites, we show an upper bound of O(k(n - k) + kc) and a lower bound of {\\Omega}(n + kc), where c is the complexity of the transportation network. This is quite different from the bound O(k(n - k)) in the Euclidean metric. For the special case where k = n - 1 the complexity in the Euclidean metric is O(n), while that in the city metric is {\\Theta}(nc). Furthermore, we develop an O(k^2(n + c) log n)-time iterative algorithm to compute the kth-order city Voronoi diagram and an O(nc log^2(n + c) log n)-time divide-and-conquer algorithm to compute the farthest-site city Voronoi diagram.

Gemsa, Andreas; Liu, Chih-Hung; Wagner, Dorothea

2012-01-01

260

The Hubble diagram for supernovae  

Microsoft Academic Search

The distribution of 47 type I and 13 type II supernovae (SN) in the Hubble diagram is presented and evaluated. Values of the parameter Mpg(100) and the dispersion are determined by least-squares fits to various data subsets, and the results are compared with those of previous studies. Sources of scatter are considered, specifically inaccurate corrections for interstellar extinction in the

D. Branch; C. Bettis

1978-01-01

261

Precipitation and the Sounding Diagram  

NSDL National Science Digital Library

This undergraduate meteorology tutorial deals with the interplay between the vertical temperature structure of the atmosphere and the temperature of the ascending air in the formation of precipitation. Students learn about the dry and moist adiabatic lapse rates, reading and interpreting sounding diagrams, and determining the change in temperature as air parcels rise or sink.

Nielsen-Gammon, John

1996-01-01

262

Animated Diagram: Sedimentary Rock Identification  

NSDL National Science Digital Library

This Flash-enabled diagram provides a scheme for sedimentary rock identification accompanied by pop-up images of the rocks. Rolling the mouse over highlighted boxes links texture, grain size, composition, and map symbols to images of a variety of sedimentary rocks. The animation is downloadable.

263

Index of Animated Phase Diagrams  

NSDL National Science Digital Library

This is a collection of animated phase diagrams by Kenneth Windom at Iowa State University. These short Power Point animations can be used to illustrate equilibrium crystallization concepts. There are slide shows for plagioclase feldspars (albite and anorthite); forsterite, diopside and anorthite; forsterite, enstatite and silica; and diopside and anorthite.

Windom, Kenneth E.; University, Iowa S.

264

ccsd00000445, Making diagrams speak,  

E-print Network

raised by the presence of diagrams in a VIIth century Sanskrit mathematical com- mentary. Exploring di- agrammes dans un commentaire math#19;ematique en langue sanskrite datant du VII#18;eme si#18;ecle: A. Keller is a French CNRS researcher working on medieval sanskrit mathematics but also

265

Payload/orbiter contamination control requirement study  

NASA Technical Reports Server (NTRS)

A study was conducted to determine and quantify the expected particulate and molecular on-orbit contaminant environment for selected space shuttle payloads as a result of major shuttle orbiter contamination sources. Individual payload susceptibilities to contamination are reviewed. The risk of payload degradation is identified and preliminary recommendations are provided concerning the limiting factors which may depend on operational activities associated with the payload/orbiter interface or upon independent payload functional activities. A basic computer model of the space shuttle orbiter which includes a representative payload configuration is developed. The major orbiter contamination sources, locations, and flux characteristics based upon available data have been defined and modeled.

Bareiss, L. E.; Rantanen, R. O.; Ress, E. B.

1974-01-01

266

Eye and orbit ultrasound  

MedlinePLUS

Echography - eye orbit; Ultrasound - eye orbit; Ocular ultrasonography; Orbital ultrasonography ... ophthalmology department of a hospital or clinic. Your eye is numbed with medicine (anesthetic drops). The ultrasound ...

267

An ab initio molecular orbital study of the argon hydride molecule-ions, ArH + and ArD +, at the MP4(SDQ)/6-311++G(3df, 3dp) level. I. The dipole moment, charge distribution, energy levels, internuclear distance and potential energy of the X 1?+ ground state of the 40Ar1H+ and 40Ar2D+ molecule-ions  

NASA Astrophysics Data System (ADS)

The X 1?+ state of the 40Ar1H+ and 40Ar2D+ was explored with an ab initio molecular orbital (MO) study (MP4, basis set 6-311++G(3df, 3pd), followed with SDQ): E Total=-527.182 771 62 hartree at R e=1.2767 Å (Exp. 1.280 3730(11)); D e=33 509.189 cm-1; ?=1.9283 D. The potential energy (PE) follows a Morse curve with r2=0.9993. Vibrational term values are G0(ArH +)=1374.95 (ArD +: 964.83) cm-1 and G1(ArH +)=4038.13 (ArD +: 2788.47) cm-1. Rotational constant B=315.406 897 GHz for 40Ar1H+ and 161.70 GHz for 40Ar2D+ (Exp. 158.702 3259(55) GHz). The energy level diagram and the electron density contours are discussed.

Schutte, C. J. H.

2001-09-01

268

Theoretical investigation of the molecular structures and excitation spectra of triphenylamine and its derivatives  

NASA Astrophysics Data System (ADS)

The molecular geometries, electronic structures, and excitation energies of NPh 3, NPh 2Me, NPhMe 2, and NMe 3, were investigated using DFT and post-Hartree Fock methods. When the structural stabilities of these compounds were compared to results obtained by using MP4(SDQ) method, it was confirmed that the optimized geometries by using MP2 method were sufficiently reliable. The excited states with large oscillator strengths consisted of transition components from the HOMO. It should be noted that the orbitals of the nitrogen atom mix with the ?-orbital of the phenyl group in an anti-bonding way in the HOMO, and the orbital energy increases with this mixing. The unoccupied orbitals are generated from bonding and anti-bonding type interactions between the ?-orbitals of the phenyl groups; therefore, the number of phenyl groups strongly affects the energy diagram of the compounds studied. The differences in the energy diagram cause a spectral change in these compounds in the ultraviolet region.

Sumimoto, Michinori; Yokogawa, Daisuke; Komeda, Masahiro; Yamamoto, Hidetoshi; Hori, Kenji; Fujimoto, Hitoshi

2011-10-01

269

Experimental and computational study on molecular structure, natural bond orbital and natural hybrid orbital analysis of non-linear optical material trans-3-(o-hydroxyphenyl-1-phenyl)-2-propen-1-one  

NASA Astrophysics Data System (ADS)

Fourier transform infrared and Fourier transform Raman spectra of trans-3-(o-hydroxyphenyl-1-phenyl)-2-propen-1-one (or simply 2-hydroxychalcone) were recorded in the regions 4000-400 cm-1 and 3500-100 cm-1, respectively in the solid phase. The vibrational frequencies were calculated by Hartee-Fock and density functional B3LYP methods with 6-311++G(d,p) basis set, using Gaussian 09W program package. A detailed interpretation of the infrared and Raman spectra of 2-hydroxychalcone is reported. The thermodynamic functions of the title compound were also studied by the above methods and the basis set. The stability of the molecule arising from hyper conjugative interactions and accompanying charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The linear polarizability (?) and the first order hyperpolarizability (?) values of the investigated molecule have been computed using DFT quantum mechanical calculations. The HOMO and LUMO energy gap reflects the chemical activity of the molecule. The observed and calculated wave numbers are found to be in good agreement.

Karunakaran, V.; Balachandran, V.

2013-12-01

270

Hero's journey in bifurcation diagram  

NASA Astrophysics Data System (ADS)

The hero's journey is a narrative structure identified by several authors in comparative studies on folklore and mythology. This storytelling template presents the stages of inner metamorphosis undergone by the protagonist after being called to an adventure. In a simplified version, this journey is divided into three acts separated by two crucial moments. Here we propose a discrete-time dynamical system for representing the protagonist's evolution. The suffering along the journey is taken as the control parameter of this system. The bifurcation diagram exhibits stationary, periodic and chaotic behaviors. In this diagram, there are transition from fixed point to chaos and transition from limit cycle to fixed point. We found that the values of the control parameter corresponding to these two transitions are in quantitative agreement with the two critical moments of the three-act hero's journey identified in 10 movies appearing in the list of the 200 worldwide highest-grossing films.

Monteiro, L. H. A.; Mustaro, P. N.

2012-06-01

271

Phase Diagrams and Chemographic Projections  

NSDL National Science Digital Library

This exercise is a good way to get students thinking about the phase rule, metastable and stable reactions and phase diagrams. The exercise contains a lot of reading, and is suitable for in-class work or for homework. The idea is that students can do this on their own with little help from their instructor. The students only answer a few questions making this is more of a tutorial than a worksheet.

Perkins, Dexter

272

T-X Phase Diagrams  

NSDL National Science Digital Library

This is a 15 page tutorial and problem set designed to get students familiar with T-X diagrams, their implications, and uses. Students start by reading but, after 10-15 minutes, the room becomes noisy as they work their way through the questions at the end. Often there are "Eureka" moments as they all of a sudden grasp some fundamental principles. It is also interesting to hear them try to explain these insights to others.

Perkins, Dexter

273

Causal diagrams in systems epidemiology  

PubMed Central

Methods of diagrammatic modelling have been greatly developed in the past two decades. Outside the context of infectious diseases, systematic use of diagrams in epidemiology has been mainly confined to the analysis of a single link: that between a disease outcome and its proximal determinant(s). Transmitted causes ("causes of causes") tend not to be systematically analysed. The infectious disease epidemiology modelling tradition models the human population in its environment, typically with the exposure-health relationship and the determinants of exposure being considered at individual and group/ecological levels, respectively. Some properties of the resulting systems are quite general, and are seen in unrelated contexts such as biochemical pathways. Confining analysis to a single link misses the opportunity to discover such properties. The structure of a causal diagram is derived from knowledge about how the world works, as well as from statistical evidence. A single diagram can be used to characterise a whole research area, not just a single analysis - although this depends on the degree of consistency of the causal relationships between different populations - and can therefore be used to integrate multiple datasets. Additional advantages of system-wide models include: the use of instrumental variables - now emerging as an important technique in epidemiology in the context of mendelian randomisation, but under-used in the exploitation of "natural experiments"; the explicit use of change models, which have advantages with respect to inferring causation; and in the detection and elucidation of feedback. PMID:22429606

2012-01-01

274

Mapping the topological phase diagram of multiband semiconductors with supercurrents.  

PubMed

We show that Josephson junctions made of multiband semiconductors with strong spin-orbit coupling carry a critical supercurrent Ic that contains information about the nontrivial topology of the system. In particular, we find that the emergence and annihilation of Majorana bound states in the junction is reflected in strong even-odd effects in Ic at small junction transparency. This effect allows for a mapping between Ic and the topological phase diagram of the junction, thus providing a dc measurement of its topology. PMID:24745449

San-Jose, Pablo; Prada, Elsa; Aguado, Ramón

2014-04-01

275

Designing UML diagrams for technical documentation  

Microsoft Academic Search

This paper presents a framework for improving the presentation of Unified Modeling Language (UML) diagrams, as applied in technical documentation produced at the IBM Toronto Software Laboratory. UML diagrams are a key part of program design. They can enhance understanding of complex programming concepts, and assist in problem analysis and solution design. In turn, UML diagrams can add significant value

Neil MacKinnon; Steve Murphy

2003-01-01

276

Arrows in Comprehending and Producing Mechanical Diagrams  

ERIC Educational Resources Information Center

Mechanical systems have structural organizations--parts, and their relations--and functional organizations--temporal, dynamic, and causal processes--which can be explained using text or diagrams. Two experiments illustrate the role of arrows in diagrams of mechanical systems. In Experiment 1, people described diagrams with or without arrows,…

Heiser, Julie; Tversky, Barbara

2006-01-01

277

Guelph Physics Tutorials: Free Body Diagrams  

NSDL National Science Digital Library

This website offers a tutorial on free body diagrams. The tutorial includes an introduction to free body diagrams, example problems, a series of self-paced questions, and a free body diagram java applet. This is part of series of tutorials on physics and mathematics used in physics classes.

2007-04-23

278

Liftings of diagrams of semilattices by diagrams of dimension groups  

E-print Network

We investigate categorical and amalgamation properties of the functor Idc assigning to every partially ordered abelian group G its semilattice of compact ideals Idc G. Our main result is the following. Theorem 1. Every diagram of finite Boolean semilattices indexed by a finite dismantlable partially ordered set can be lifted, with respect to the Idc functor, by a diagram of pseudo-simplicial vector spaces. Pseudo-simplicial vector spaces are a special kind of finite-dimensional partially ordered vector spaces (over the rationals) with interpolation. The methods introduced make it also possible to prove the following ring-theoretical result. Theorem 2. For any countable distributive join-semilattices S and T and any field K, any (v,0)-homomorphism $f: S\\to T$ can be lifted, with respect to the Idc functor on rings, by a homomorphism $f: A\\to B$ of K-algebras, for countably dimensional locally matricial algebras A and B over K. We also state a lattice-theoretical analogue of Theorem 2 (with respect to the Conc functor, and we provide counterexamples to various related statements. In particular, we prove that the result of Theorem 1 cannot be achieved with simplicial vector spaces alone.

Jiri Tuma; Friedrich Wehrung

2005-01-22

279

Liftings of diagrams of semilattices by diagrams of dimension groups.  

E-print Network

We investigate categorical and amalgamation properties of the functor Idc assigning to every partially ordered abelian group G its semilattice of compact ideals Idc G. Our main result is the following. Theorem 1. Every diagram of finite Boolean semilattices indexed by a finite dismantlable partially ordered set can be lifted, with respect to the Idc functor, by a diagram of pseudo-simplicial vector spaces. Pseudo-simplicial vector spaces are a special kind of finite-dimensional partially ordered vector spaces (over the rationals) with interpolation. The methods introduced make it also possible to prove the following ring-theoretical result. Theorem 2. For any countable distributive join-semilattices S and T and any field K, any (v,0)-homomorphism $f: S\\to T$ can be lifted, with respect to the Idc functor on rings, by a homomorphism $f: A\\to B$ of K-algebras, for countably dimensional locally matricial algebras A and B over K. We also state a lattice-theoretical analogue of Theorem 2 (with respect to the Conc functor, and we provide counterexamples to various related statements. In particular, we prove that the result of Theorem 1 cannot be achieved with simplicial vector spaces alone.

Jiri Tuma (MFF-UK); Friedrich Wehrung (LMNO).; no. 3 (2003) 1--28

280

Correlation of electronic transitions and redox potentials measured for pyrocatechol, resorcinol, hydroquinone, pyrogallol, and gallic acid with results of semi-empirical molecular orbital computations A useful interpretation tool  

NASA Astrophysics Data System (ADS)

Cyclic voltammogram (CV) electrochemical measurements for pyrocatechol, resorcinol, hydroquinone, pyrogallol, and gallic acid in strong alkaline solution produced observable oxidation-reduction potentials for each hydroxy group present except for resorcinol. UV absorption spectra were also observed for the diluted solutions. Semi-empirical molecular orbital computations were conducted for these molecules of C2 v point group symmetry to determine the character and energies to aid interpretation of the experimental results. CV oxidation removed a ?-electron by a radiationless ?-?* transition followed by an electron shift from a negative oxygen to the positive aromatic ?-system indicated by an observable ?-?* transition. Simple semi-empirical computations correlated with measured excited electronic states during electron transfer.

Carter, Melvin Keith

2007-04-01

281

Rhenium oxide as an efficient p-dopant to overcome S-shaped current density-voltage curves in organic photovoltaics with a deep highest occupied molecular orbital level donor layer  

NASA Astrophysics Data System (ADS)

Effect of p-dopants in a p-doped hole transport layer inserted between indium tin oxide and a donor layer of ?,?'-bis(2,2-dicyanovinyl)-quinquethiophene with a deep highest occupied molecular orbital level is reported to remove the S-shape in the organic photovoltaics (OPV) cell. Among the p-dopants of ReO3, MoO3, WO3, and CuI, ReO3 possesses the largest work function and turns out to be the most efficient p-dopant to remove the S-shape of the current density-voltage curve in the OPV cells. The rest of the dopants could not get rid of the S-shape, even with a doping concentration of 25 mol. %. The difference among the dopants can be understood by the different charge generation efficiency of the dopants.

Kim, Dae-Ho; Kim, Tae-Min; Jeong, Won-Ik; Kim, Jang-Joo

2012-10-01

282

Phase diagrams of polyelectrolyte solutions  

NASA Astrophysics Data System (ADS)

We study the phase diagram of polyelectrolyte solutions in salt and salt-free environments. We examine the phase behavior of polyelectrolyte solutions, in the semidilute regime, using different physical models, namely the Random Phase Approximation (RPA) and the cross-linked model. In the RPA, we calculate the electrostatic free energy by summing all the fluctuations of the chains and all present ionic species. Within this approximation, the phase diagrams of salt-free polyelectrolyte solutions show phase separation even without including short-range attractions or ion condensation. We find that the phase behavior of large chains resembles the phase diagram of polymer network solutions. That is, the equilibrium is established between a network phase and a chain-free phase. Upon the addition of salt, the dissociated ions increase the entropy of the system and overcome the energy from the electrostatic fluctuations. When the short-range attraction between monomers is included in the model, the free energy predicts phase segregation for all salt valences at high salt concentrations (1 mol/l and higher). The phenomenon is called salting-out and occurs simply because the addition of salt reduces the quality of the solvent and induces precipitation. However, phase segregation in the presence of multivalent ions in polyelectrolyte solutions occurs at low salt concentrations (less than 1 mol/l). We propose that this phase separation is due to polyions cross-linked by multivalent ions. We constructed a phenomenological two-state model to examine this phenomenon. The two phases coexisting in the solution are a network-like phase and a polymer-free phase. The polymer-free phase is modeled using Debye-Huckel theory. In the cross-linked phase, each condensed multivalent ion attracts an equal number of monomers creating a neutral cluster. The energy of the cluster is evaluated by a simple Coulombic energy. The bare monomer charges between the linkages are treated as line of charges. The cross-linked model solves self-consistently for the fraction of multivalent ions and counterions condensed along the polyions. The calculated phase diagram predicts the precipitation found experimentally; however, it fails to predict the redissolution transition at higher salt concentrations.

Mahdi, Khaled A.

283

Simultaneous analytical optimization of variational parameters in Gaussian-type functions with full configuration interaction of multicomponent molecular orbital method by elimination of translational and rotational motions: Application to isotopomers of the hydrogen molecule  

NASA Astrophysics Data System (ADS)

We have extended the multicomponent molecular orbital (MC_MO) method to the full-configuration interaction (full-CI) fully variational molecular orbital method by elimination of translational and rotational motion components from total Hamiltonian. In the MC_MO scheme, the quantum effects of protons and deuterons as well as electrons can be directly taken into account. All variational parameters in the full-CI scheme, i.e., exponents and centers (? and R) in the Gaussian-type function (GTF) basis set as well as the CI coefficients, are simultaneously optimized by using their analytical gradients. The total energy of the H2 molecule calculated using the electronic [6s3p2d1f] and nuclear [1s1p1d1f] GTFs is -1.161 726 hartree, which can be compared to the energy of -1.164 025 hartree reported using a 512 term-explicitly correlated GTF calculation. Although the d- and f-type nuclear GTFs contribute to the improvement of energy convergence, the convergence of electron-nucleus correlation energy is slower than that of electron-electron one. The nuclear wave functions are delocalized due to the electron-nucleus correlation effect compared to the result of Hartree-Fock level of MC_MO method. In addition, the average internuclear distances of all diatomic molecules are within 0.001 A? of the previously reported experimental results. The dipole moment of the HD molecule estimated by our method is 8.4×10-4 D, which is in excellent agreement with the experimental result of (8-10)×10-4 D.

Ishimoto, Takayoshi; Tachikawa, Masanori; Nagashima, Umpei

2008-04-01

284

Electronic structure of the dioxygen to transition metal bond: generalized molecular orbital calculations on models of manganese, iron, and cobalt porphyrins  

E-print Network

-like character previously reported for the Fe-0 unit in 2 iron dioxygen porphyrins is not observed in the GMO-CI results. The Fe-0 unit appears to be a Fe (S=O)0 (S=O) state in which a pair +2 2 2 of electrons is donated to an Fe atom from the a state...)(N4CZH6)(NH3). . . . . . Compar1son of the Fe-0 ~-Orbital Coeff1cients for 2 the GMO-CI Calculations of Fe(02)(N4CZH6) (NH3) with 0 0 0-0 Bond Lengths of 1. 24A and 1. 21A. . Primary Conf1gur at1ons of the A" Ground-State Wavefunct1on of Co(02)(N...

Newton, James Edward

2012-06-07

285

Analysis of the electronic structure of liquid rubidium by the methods of ab initio molecular dynamics, linear muffin-tin orbitals and recursion.  

PubMed

It is well known that liquid rubidium shows some unusual properties at low densities. The ab initio SIESTA package and the supercell technique within the linear muffin-tin orbital method were used to investigate this phenomenon. Electronic structures of liquid rubidium at different temperatures from the melting point up to the critical point were obtained. The atomic structure for the supercell technique was simulated for a cluster of 4000 atoms by the Schommers method on the basis of experimental structure factors of Rb obtained by Tamura and co-workers at different temperatures (from 373 up to 1973 K). The Kubo-Greenwood formula was applied for the calculations of the melt conductivity. The results obtained indicate that the metal-nonmetal transition in liquid rubidium is not connected to the gap at the Fermi energy in the density of electronic states, but, more likely, with electron localization on some kind of atomic cluster. PMID:21694197

Mirzoev, A A; Mirzoev, A A; Sobolev, A N; Gelchinski, B R

2008-03-19

286

Shapes of d Orbitals  

NSDL National Science Digital Library

Shapes of d Orbitals shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation.Shapes of d Orbitals has a link to D Orbitals in an Octahedral Ligand Field. Here the user may click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable. Orbital phase is shown by the different colors.

287

Early orbit determination  

Microsoft Academic Search

Orbit determination for near real time monitoring of satellite movement based on limited observations is discussed. For geostationary satellites this early orbit determination requirement arises after injection into geostationary transfer orbit, apogee motor firing, and larger orbit maneuvers during the on-station phase. Early orbit determination is hampered by the limited amount of data caused by nonavailability of the tracking system.

S. Pallaschke

1986-01-01

288

LISA Orbits  

NASA Astrophysics Data System (ADS)

The LISA formation is composed of 3 spacecraft in an equilateral triangle formation. The baseline formation has a 5million km radius and lies in a heliocentric orbit 20deg away from the Earth. Earth's gravity induces a perturbation on the nominal Keplerian motion of the formation, generating a change in the relative ranges and thus a Doppler that can be very harmful for the scientific goals of the mission. Zero station keeping options are preferred, so alternative passive solutions have to be found. This paper presents results obtained by optimising the formation design, particularly the orientation of the eccentricity vectors. Formation design optimisation proves to be an effective strategy, succeeding in keeping the relative range rate between any two spacecraft below 13m/s. Another possible source of perturbation arises from the self-acceleration induced on the formation by the imperfect mass distribution on each spacecraft. The effect of this perturbing acceleration on the motion of the formation has been studied, and the formation design has been re-optimised assuming several levels of perturbation. This approach has shown the result that such effect can be even beneficial on the formation stability, provided that the acceleration doesn't exceed 1e-8m/s2. The transfer to the optimal stability formation has then been optimised, assuming a launch window throughout the year. Mission ?v to a specific target is quite sensitive to the launch date: trailing formations are most effectively reached if the launch occurs at Earth's apohelion (summer), while the opposite applies to leading formations. A strategy where leading and trailing formations are alternatively targeted according to the launch date has proved to be the most effective in keeping the ?v as low as possible.

Povoleri, Angelo; Kemble, Stephen

2006-11-01

289

Process Flow Diagrams for Training and Operations  

NASA Astrophysics Data System (ADS)

This paper focuses on the use of process flow diagrams for training first responders who execute search and seizure warrants at electronic crime scenes. A generic process flow framework is presented, and the design goals and layout characteristics of process flow diagrams are discussed. An evaluation of the process flow diagrams used in training courses indicates that they are beneficial to first responders performing searches and seizures, and they speed up investigations, including those conducted by experienced personnel.

Venter, Jacobus

290

ERS orbit control  

NASA Astrophysics Data System (ADS)

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; overhead Venice tower (12.508206 deg east, 45.314222 deg north). The launch, maneuvers for the initial acquisition of the operational orbit, orbit maintenance maneuvers, evaluation of the orbit control, and the drift of the inclination are summarized.

Rosengren, Mats

1991-12-01

291

Hubble's diagram and cosmic expansion  

PubMed Central

Edwin Hubble's classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929) Proc. Natl. Acad. Sci. USA 15, 168–173]. The chief result, that a galaxy's distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble's Law, and the Hubble time, that the article itself is rarely referenced. Even though Hubble's distances have a large systematic error, Hubble's velocities come chiefly from Vesto Melvin Slipher, and the interpretation in terms of the de Sitter effect is out of the mainstream of modern cosmology, this article opened the way to investigation of the expanding, evolving, and accelerating universe that engages today's burgeoning field of cosmology. PMID:14695886

Kirshner, Robert P.

2004-01-01

292

Phase diagram of ammonium nitrate  

NASA Astrophysics Data System (ADS)

Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

Dunuwille, M.; Yoo, C. S.

2014-05-01

293

PHASE DIAGRAMS and MACROMOLECULAR STABILITY  

E-print Network

. Shifts in second derivative UV peak position as a function of pH and temperature. 17 Figure 3. Phase diagram created using high- resolution second derivative UV spectroscopy data. 4 5 6 7 8 pH 10 20 30 40 50 T Ricin- - 2nd Derivative UV Figure 4....25 ?g/mL, circles) and aggregate (19.17 ?g/mL, triangles) species in 25 mM Tris, 300 mM NaCl, 4 mM CaCl2, pH 7 Grillo et al. Biochemistry, 40 (2), 586 -595, 2001 53 (A) Effect of temperature on rhFVIII fluorescence emission intensity at 330 nm. (B...

Middaugh, C. Russell

2006-10-26

294

Some remarks about underused Loedel diagrams  

NASA Astrophysics Data System (ADS)

We emphasize that it can be didactically very useful for students to realize how a space-time diagram of an observer, moving with a constant velocity with respect to another observer, can be obtained easily by means of a standard matrix of rotation, without recourse to imaginary axes and angles. These diagrams were introduced for the first time by Loedel and their main advantage over Minkowski diagrams is that a scale factor is not necessary to convert the units of an observer to those of another observer. We show this well-known property of Loedel diagrams using a new geometric approach.

Benedetto, E.; Capriolo, M.; Feoli, A.; Tucci, D.

2013-01-01

295

Projected seniority-two orbital optimization of the antisymmetric product of one-reference orbital geminal  

NASA Astrophysics Data System (ADS)

We present a new, non-variational orbital-optimization scheme for the antisymmetric product of one-reference orbital geminal wave function. Our approach is motivated by the observation that an orbital-optimized seniority-zero configuration interaction (CI) expansion yields similar results to an orbital-optimized seniority-zero-plus-two CI expansion [L. Bytautas, T. M. Henderson, C. A. Jimenez-Hoyos, J. K. Ellis, and G. E. Scuseria, J. Chem. Phys. 135, 044119 (2011)]. A numerical analysis is performed for the C2 and LiF molecules, for the CH2 singlet diradical as well as for the symmetric stretching of hypothetical (linear) hydrogen chains. For these test cases, the proposed orbital-optimization protocol yields similar results to its variational orbital optimization counterpart, but prevents symmetry-breaking of molecular orbitals in most cases.

Boguslawski, Katharina; Tecmer, Pawe?; Limacher, Peter A.; Johnson, Paul A.; Ayers, Paul W.; Bultinck, Patrick; De Baerdemacker, Stijn; Van Neck, Dimitri

2014-06-01

296

Hydrogen bonding, halogen bonding and lithium bonding: an atoms in molecules and natural bond orbital perspective towards conservation of total bond order, inter- and intra-molecular bonding.  

PubMed

One hundred complexes have been investigated exhibiting D-XA interactions, where X = H, Cl or Li and DX is the 'X bond' donor and A is the acceptor. The optimized structures of all these complexes have been used to propose a generalized 'Legon-Millen rule' for the angular geometry in all these interactions. A detailed Atoms in Molecules (AIM) theoretical analysis confirms an important conclusion, known in the literature: there is a strong correlation between the electron density at the XA bond critical point (BCP) and the interaction energy for all these interactions. In addition, we show that extrapolation of the fitted line leads to the ionic bond for Li-bonding (electrostatic) while for hydrogen and chlorine bonding, it leads to the covalent bond. Further, we observe a strong correlation between the change in electron density at the D-X BCP and that at the XA BCP, suggesting conservation of the bond order. The correlation found between penetration and electron density at BCP can be very useful for crystal structure analysis, which relies on arbitrary van der Waals radii for estimating penetration. Various criteria proposed for shared- and closed-shell interactions based on electron density topology have been tested for H/Cl/Li bonded complexes. Finally, using the natural bond orbital (NBO) analysis it is shown that the D-X bond weakens upon X bond formation, whether it is ionic (DLi) or covalent (DH/DCl) and the respective indices such as ionicity or covalent bond order decrease. Clearly, one can think of conservation of bond order that includes ionic and covalent contributions to both D-X and XA bonds, for not only X = H/Cl/Li investigated here but also any atom involved in intermolecular bonding. PMID:25127185

Shahi, Abhishek; Arunan, Elangannan

2014-10-01

297

Shuttle Orbiter Uplink Text and Graphics System  

NASA Technical Reports Server (NTRS)

This paper presents the definition of requirements for and current design of the Shuttle Orbiter Uplink Text and Graphics System (UT&GS). Beginning in early 1981, the UT&GS will support Shuttle flights by providing the capability of transmitting single-frame imagery from the ground to the orbiting Shuttle vehicle. Such imagery is in the form of maps, text, diagrams, or photographs, and is outputted on the Orbiter as a paper hard copy. Four modes of operation will be provided to minimize the time required to transmit less than full-resolution imagery. This paper discusses the considerations and complications leading to the four modes and associated resolution requirements. The paper also presents the design of the CCD array ground scanner and airborne CRT hardcopier.

Hoover, A. A.; Land, C. K.; Lipoma, P. C.

1978-01-01

298

The use of local orbitals in multireference calculations  

Microsoft Academic Search

CAS-SCF-type algorithms based on molecular orbitals that preserve their physical nature during the iterative process have been proposed recently by our groups. Our approach is based on the iterative partial diagonalization of the one-body reduced density matrix. If localized guess orbitals are used, the locality property is kept by the final orbitals. The use of local orbitals in multiference calculations

Celestino Angeli; Carmen J. Calzado; Renzo Cimiraglia; Stefano Evangelisti; Nathalie Guihéry; Thierry Leininger; Jean-Paul Malrieu; Daniel Maynau; José Vicente Pitarch Ruiz; Manuel Sparta

2003-01-01

299

A DFT study on structures, frontier molecular orbitals and UV-vis spectra of RuX(PPh3)(NHCPh2)L (X=Tp and Cp; L=Cl and N3).  

PubMed

Geometry optimization for RuX(PPh3)(NHCPh2)(L) (X=hydridotris(pyrazolyl)borate (Tp) and cyclopentadiene (Cp); L=Cl and N3) are investigated by using density functional theory (DFT) with DZVP2/DZVP all-electron mixed basis sets and compared with available experimental values, and the calculated structures are in very good agreement with experimental data. The frontier molecular orbitals (FMOs) and electronic transitions have been investigated as well. Our calculations show that the ? electron-rich ligand (N3) may increase the energies of occupied orbitals and reduce the energy gap of the HOMO-LUMO (?EL-H) in these ruthenium based complexes. The simulated UV-vis spectra of these complexes in methanol have been studied with time-dependent density functional theory (TD-DFT), and conductor-like polarizable continuum model (CPCM) was employed to account for the solvent effects. Our results show that a number of absorption peaks are found in the visible region (400-800 nm) with non-zero oscillator strengths. The strongest adsorption feature is associated to a transition from HOMO-2 to LUMO, which is assigned to metal-to-ligand charge transfer (MLCT) or metal/ligand-to-ligand charge transfer (MLCT/LLCT) depending on co-ligands. In addition, the Cp group increases electron-accept ability and results in red shift due to its ? electron-rich and ? donor characters. According to our results, these ruthenium based complexes are good candidates for dye-sensitized solar cell owing to their absorption intensities and rich absorption bands in the visible region. PMID:24366160

Wang, Tsang-Hsiu; Wang, I-Teng; Huang, Wen-Lin; Huang, Li-Yu

2014-01-01

300

Space Math http://spacemath.gsfc.nasa.gov Comparing Planets Orbiting other Stars 2  

E-print Network

Space Math http://spacemath.gsfc.nasa.gov Comparing Planets Orbiting other Stars 2 This diagram shows disks representing the planets discovered in orbit around 8 different stars all drawn to the same the problems below using fraction arithmetic to find out how big these new planets are compared to Earth

301

DECISION DIAGRAMS AND PASS TRANSISTOR LOGIC SYNTHESIS  

E-print Network

DECISION DIAGRAMS AND PASS TRANSISTOR LOGIC SYNTHESIS V. Bertacco S. Minato P. Verplaetse L. Benini by ARPA, under grant No. DABT63-95-C-0049. #12;Decision Diagrams and Pass Transistor Logic Synthesis V transistors and domino logic. The synthesis of these cells is based on BDD and ZBDD representations

De Micheli, Giovanni

302

THE QCD PHASE DIAGRAM AT FINITE DENSITY.  

SciTech Connect

We study the density of states method to explore the phase diagram of the chiral transition on the temperature and quark chemical potential plane. Four quark flavours are used in the analysis. Though the method is quite expensive small lattices show an indication for a triple-point connecting three different phases on the phase diagram.

SCHMIDT, C.; FODOR, Z.; KATZ, S.

2005-07-25

303

Voronoi diagrams based on convex distance functions  

Microsoft Academic Search

We present an “expanding waves” view of Voronoi diagrams that allows such diagrams to be defined for very general metrics and for distance measures that do not qualify as metrics. If a pebble is dropped into a still pond, circular waves move out from the point of impact. If n pebbles are dropped simultaneously, the places where wave fronts meet

L. Paul Chew

1985-01-01

304

Locational optimization problems solved through Voronoi diagrams  

Microsoft Academic Search

This paper reviews a class of continuous locational optimization problems (where an optimal location or an optimal configuration of facilities is found in a continuum on a plane or a network) that can be solved through the Voronoi diagram. Eight types of continuous locational optimization problems are formulated, and these problems are solved through the ordinary Voronoi diagram, the farthest-point

Atsuyuki Okabe; Atsuo Suzuki

1997-01-01

305

A sweepline algorithm for Voronoi diagrams  

Microsoft Academic Search

We present a transformation that can be used to compute Voronoi diagrams with a sweepline technique. The transformation is used to obtain simple algorithms for computing the Voronoi diagram of point sites, of line segment sites, and of weighted point sites. All algorithms have &Ogr;(n log n) worst case running time and use &Ogr;(n) space.

Steven Fortune

1986-01-01

306

Feynman Diagrams and the Quantum Stochastic Calculus  

E-print Network

We present quantum stochastic calculus in terms of diagrams taking weights in the algebra of observables of some quantum system. In particular, we note the absence of non-time-consecutive Goldstien diagrams. We review recent results in Markovian limits in these terms.

John Gough

2004-11-09

307

Visualizing hyperbolic Voronoi diagrams Frank Nielsen  

E-print Network

Visualizing hyperbolic Voronoi diagrams Frank Nielsen Sony Computer Science Laboratories, Japan simultaneously the diagram in the five standard models of hyperbolic geometry: Namely, the Poincar�e disk for personal or classroom use is granted without fee provided that copies are not made or distributed

Nielsen, Frank

308

Hydrogen bonding. Part 77. Molecular orbital study of C H?F hydrogen bonds in tetramethylammonium fluoride; potential effects on solid state structure  

NASA Astrophysics Data System (ADS)

The infrared (IR) spectrum of tetramethylammonium fluoride suggests that it contains the strongest C-H⋯F - hydrogen bonds yet observed. Ab initio 3-21G( ?) calculations were used to examine potential solid state arrangements of cation about anion. The favored state is one in which four cations surround each F - in a D2 d arrangement and four F - surround each cation. Each F - acts as acceptor of four hydrogen bonds of -10.8 kcal mol -1, one from each cation. This arrangement, similar to that of tetramethylammon chloride, is consonant with the IR spectrum of the cation in solid tetramethylammonium fluoride. In the preferred form of the monomeric gas phase ion-pair F - lies against one triangular face of the T d cation with three CHF hydrogen bonds of -11.5 kcal mol -1 each. Constraint of F - in the gas phase ion-pair to interaction with a single cation hydrogen results in a tightly bound molecular complex between HF and trimethylammonium methylide with an interaction energy of -27 kcal mol -1; however, this structure is not seen elsewhere and apparently does not play a role in the solid salt.

Harmon, K. M.; Madeira, S. L.

2001-01-01

309

Operations space diagram for ECRH and ECCD  

NASA Astrophysics Data System (ADS)

A Clemmov-Mullaly-Allis (CMA) type diagram, the ECW-CMA diagram, for representing the operational possibilities of electron cyclotron heating and current drive (ECRH/ECCD) systems for fusion plasmas is presented. In this diagram, with normalized density and normalized magnetic field coordinates, the parameter range in which it is possible to achieve a given task (e.g. O-mode current drive for stabilizing a neoclassical tearing mode) appears as a region. With also the Greenwald density limit shown, this diagram condenses the information on operational possibilities, facilitating the overview required at the design phase. At the operations phase it may also prove useful in setting up experimental scenarios by showing operational possibilities, avoiding the need for survey type ray-tracing at the initial planning stages. The diagram may also serve the purpose of communicating operational possibilities to non-experts. JET and ITER like plasmas are used, but the method is generic.

Bindslev, Henrik

2004-07-01

310

Reading fitness landscape diagrams through HSAB concepts  

NASA Astrophysics Data System (ADS)

Fitness landscapes are conceived as range of mountains, with local peaks and valleys. In terms of potential, such topographic variations indicate places of local instability or stability. The chemical potential, or electronegativity, its value changed of sign, carries similar information. In addition to chemical descriptors defined through hard-soft acid-base (HSAB) concepts and computed through density functional theory (DFT), the principles that rule chemical reactions allow the design of such landscape diagrams. The simplest diagram uses electrophilicity and hardness as coordinates. It allows examining the influence of maximum hardness or minimum electrophilicity principles. A third dimension is introduced within such a diagram by mapping the topography of electronegativity, polarizability or charge exchange. Introducing charge exchange during chemical reactions, or mapping a third parameter (f.i. polarizability) reinforces the information carried by a simple binary diagram. Examples of such diagrams are provided, using data from Earth Sciences, simple oxides or ligands.

Vigneresse, Jean-Louis

2014-10-01

311

Free-Body Diagrams: Necessary or Sufficient?  

NSDL National Science Digital Library

The Rutgers PAER group is working to help students develop various scientific abilities. One of the abilities is to create, understand and learn to use for qualitative reasoning and problem solving different representations of physical processes such as pictorial representations, motion diagrams, free-body diagrams, and energy bar charts. Physics education literature indicates that using multiple representations is beneficial for student understanding of physics ideas and for problem solving. We developed a special approach to construct and utilize free-body diagrams for representing physical phenomena and for problem solving. We will examine whether students draw free-body diagrams in solving problems when they know they will not receive credit for it; the consistency of their use in different conceptual areas; and if students who use free-body diagrams while solving problems in different areas of physics are more successful then those who do not.

Rosengrant, David; Van Heuvelen, A.; Etkina, Eugenia

2009-11-30

312

Working With Orbits  

NSDL National Science Digital Library

This site offers two programs to illustrate how orbits work. The Orbital Elements calculator contains animations to see how the appearance of an orbit depends on the values of the orbital elements which include distance from the Sun, eccentricity, pericenter location and anomaly. This is available in two or three dimensions. The Solar System allows users to watch several planets in our Solar System simultaneously orbit the Sun. An additional object (asteroid or comet) is present and users change the orbital parameters to see what types of orbits are possible for this object.

Hamilton, Douglas

313

Phase diagram of ammonium nitrate  

SciTech Connect

Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ?} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

Dunuwille, Mihindra; Yoo, Choong-Shik, E-mail: csyoo@wsu.edu [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)] [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)

2013-12-07

314

Ab initio molecular orbital study on the excited states of [2.2]-, [3.3]-, and siloxane-bridged paracyclophanes.  

PubMed

Paracyclophanes are simple idealized model molecules for the study of interacting ?-stacking systems. In this study, the excited states of [2.2]paracyclophane ([2.2]PCP), [3.3]paracyclophane ([3.3]PCP), and siloxane-bridged paracyclophane (SiPCP) are systematically investigated using the multiconfiguration quasi-degenerated perturbation theory (MCQDPT) method. The excited states of the alkyl- and silyl-substituted benzene monomers and benzene dimer, which can be regarded as the building blocks of paracyclophanes, are also examined at the same level of theory for more detailed understanding. The accuracy of the time-dependent density functional theory (TD-DFT) method required for excited state geometry optimization of the paracyclophanes is confirmed from calculations of the benzene dimer. The equilibrium distances between the benzene rings of the paracyclophanes in the first excited states are shorter than those in the ground state, and the benzene rings at the excited state optimized geometries are in an almost eclipsed parallel configuration, which indicates excimer formation. The calculated transition energies and oscillator strengths are generally in good agreement with the corresponding experimental results. A clear correlation between the excited state properties and the molecular structures is systematically demonstrated based on the calculation results for the substituted benzene monomers and benzene dimer. The transition energies of SiPCP are close to the corresponding absorption and fluorescence energies of the experimentally studied phenylene-silica hybrids, which indicates that the electronic properties of organic-silica hybrids, which is a new class of material with potential in photofunctional applications, can be approximated by simple siloxane-bridged cyclophane derivatives. PMID:23046357

Shirai, Soichi; Iwata, Suehiro; Maegawa, Yoshifumi; Tani, Takao; Inagaki, Shinji

2012-10-18

315

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

Results from operational OD produced by the NASA Goddard Flight Dynamics Facility for the LRO nominal and extended mission are presented. During the LRO nominal mission, when LRO flew in a low circular orbit, orbit determination requirements were met nearly 100% of the time. When the extended mission began, LRO returned to a more elliptical frozen orbit where gravity and other modeling errors caused numerous violations of mission accuracy requirements. Prediction accuracy is particularly challenged during periods when LRO is in full-Sun. A series of improvements to LRO orbit determination are presented, including implementation of new lunar gravity models, improved spacecraft solar radiation pressure modeling using a dynamic multi-plate area model, a shorter orbit determination arc length, and a constrained plane method for estimation. The analysis presented in this paper shows that updated lunar gravity models improved accuracy in the frozen orbit, and a multiplate dynamic area model improves prediction accuracy during full-Sun orbit periods. Implementation of a 36-hour tracking data arc and plane constraints during edge-on orbit geometry also provide benefits. A comparison of the operational solutions to precision orbit determination solutions shows agreement on a 100- to 250-meter level in definitive accuracy.

Slojkowski, Steven E.

2014-01-01

316

Spectroscopic (FT-IR, FT-Raman, and UV-visible) and quantum chemical studies on molecular geometry, Frontier molecular orbitals, NBO, NLO and thermodynamic properties of 1-acetylindole.  

PubMed

Quantum chemical calculations of ground state energy, geometrical structure and vibrational wavenumbers of 1-acetylindole were carried out using density functional (DFT/B3LYP) method with 6-311++G(d,p) basis set. The FT-IR and FT-Raman spectra were recorded in the condensed state. The fundamental vibrational wavenumbers were calculated and a good correlation between experimental and scaled calculated wavenumbers has been accomplished. Electric dipole moment, polarizability and first static hyperpolarizability values of 1-acetylindole have been calculated at the same level of theory and basis set. The results show that the 1-acetylindole molecule possesses nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-Visible spectrum of the molecule was recorded in the region 200-500nm and the electronic properties like HOMO and LUMO energies and composition were obtained using TD-DFT method. The calculated energies and oscillator strengths are in good correspondence with the experimental data. The thermodynamic properties of the compound under investigation were calculated at different temperatures. PMID:24996206

Shukla, Vikas K; Al-Abdullah, Ebtehal S; El-Emam, Ali A; Sachan, Alok K; Pathak, Shilendra K; Kumar, Amarendra; Prasad, Onkar; Bishnoi, Abha; Sinha, Leena

2014-12-10

317

Direct diabatization of electronic states by the fourfold-way: Including dynamical correlation by multi-configuration quasidegenerate perturbation theory with complete active space self-consistent-field diabatic molecular orbitals  

NASA Astrophysics Data System (ADS)

We propose a new scheme for the direct diabatization of MC-QDPT wave functions. Our new scheme utilizes CASSCF diabatic molecular orbitals (DMOs); this is conceptually simpler than the previous approach and can lead to smoother diabatic potentials. We validated the new diabatization scheme, in comparison to CASSCF diabatization and to the original MC-QDPT diabatization scheme, for two test cases, the dissociation of LiF and the reaction of Li + FH ? LiF + H. The results with our new scheme suggest that the new scheme with CASSCF DMOs would be a good choice for nonadiabatic dynamics studies in the future. where M is the total number of diabatic prototypes in all of the groups. The dominant CSF group lists Gk (with k=1…N) may be used to form templates of the diabatic states ?k, k=1…N, provided that we exclude any CSF that would be prominent in more than one diabatic state as we vary the geometry. One may need to consider more than one potential reference geometry and make dominant CSF lists by taking the union of the dominant CSF lists at each of them. Furthermore, sometimes one needs to add diabatic prototypes to the lists even when they are not identified at potential reference geometries.

Yang, Ke R.; Xu, Xuefei; Truhlar, Donald G.

2013-06-01

318

The Amplituhedron from Momentum Twistor Diagrams  

E-print Network

We propose a new diagrammatic formulation of the all-loop scattering amplitudes/Wilson loops in planar N=4 SYM, dubbed the "momentum-twistor diagrams". These are on-shell-diagrams obtained by gluing trivalent black and white vertices defined in momentum twistor space, which, in the reduced diagram case, are known to be related to diagrams in the original twistor space. The new diagrams are manifestly Yangian invariant, and they naturally represent factorization and forward-limit contributions in the all-loop BCFW recursion relations in momentum twistor space, in a fashion that is completely different from those in momentum space. We show how to construct and evaluate momentum-twistor diagrams, and how to use them to obtain tree-level amplitudes and loop-level integrands; in particular for the latter we identify an isolated bubble-structure for each loop variable, arising from a forward limit, or entangled removal of particles. From a given diagram one can directly read off the C, D matrices via a generalized "boundary measurement"; this in turn determines a cell in the amplituhedron associated with the amplitude, and our diagrammatic representations of the amplitude can provide triangulations of the amplituhedron with generally very intricate geometries. To demonstrate the computational power of the formalism, we give explicit results for general two-loop integrands, and the cells of the complete amplituhedron for two-loop MHV amplitudes.

Yuntao Bai; Song He

2014-08-11

319

Ejs Non-Newtonian Orbit Model  

NSDL National Science Digital Library

The Ejs Non-Newtonian Orbit model displays the dynamics of a mass orbiting a much larger mass subject to non-Newtonian gravity. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial conditions can also be changed by dragging the mass or dragging the pink circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Non-Newtonian Orbit model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_precession.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

320

Magnetic phase diagram of F2PNNNO  

NASA Astrophysics Data System (ADS)

2-[2',6',-difluoro-4'-(N-tert-butyl-N-oxyamino)phenyl]-4,4,5,5-tetramethyl-4,5- dihydro-1H-imidazol-1-oxyl 3-oxide, F2PNNNO for short, is an organic molecule containing two unpaired electrons. Residing in the N-tert-butyl nitroxide and nitronyl nitroxide groups, the two S=1/2 spins of these electrons are ferromagnetically coupled with an exchange constant of 407 K. In a crystal, two neighboring F2PNNNO molecules form a pair in which the nitronyl-nitroxide spins are coupled antiferromagnetically with an exchange constant of 67 K. The magnetism of F2PNNNO is that of the spin tetramers of these molecular pairs, which in turn are antiferromagnetically coupled with an exchange constant of 7.4 K [1]. Specific-heat and magnetocaloric-effect measurements reveal a highly symmetric boundary of the ordered phase in the phase diagram, with a lower critical field of Hc1=9.46 T and an upper critical field of Hc2=15.37 T. The ordering temperature Tc obeys a power law Tc ˜(H-Hc1)^? near Hc1, with the exponent ? approaching 2/3 in the low-temperature limit, indicative of a Bose-Einstein condensation (BEC) of |S, Sz>=|1,1> tetramers. Near the upper critical field Hc2, where one expects a BEC of singlet |0,0> tetramers in the ``vacuum'' comprising |1,1> tetramers, the corresponding power-law exponent remains around 0.4. Remarkably, the temperature dependence of the specific heat indicates that the magnon dispersion is independent of magnetic field between the two critical fields. This work is in collaboration with H. Tsujii, B. Andraka, Y. Hosokoshi, and K. Inoue. [1] Y. Hosokoshi et al., Phys. Rev. B 60, 12924 (1999).

Takano, Yasu

2007-03-01

321

Phase diagrams of perovskite-type manganese oxides  

NASA Astrophysics Data System (ADS)

In this paper, a competition between a ferromagnetic metal and a charge/orbital-ordered insulator has been investigated for RE1-xAExMnO3 (x=0.45) with RE and AE being rare earth elements, ranging from La to Gd, and alkaline earth elements, Ca, Sr and Ba, respectively. A phase diagram is deduced in the plane of the effective one-electron bandwidth versus the magnitude of quenched disorder, which can be controlled by the averaged value and the variance of the RE/AE ionic radii, respectively. In the vicinity of the phase boundary, the ferromagnetic transition temperature is critically suppressed, and the colossal magnetoresistance (CMR) is enhanced.

Tomioka, Y.; Okimoto, Y.; Jung, J. H.; Kumai, R.; Tokura, Y.

2006-09-01

322

Pilot-wave hydrodynamics in a rotating frame: Exotic orbits  

NASA Astrophysics Data System (ADS)

We present the results of a numerical investigation of droplets walking on a rotating vibrating fluid bath. The drop's trajectory is described by an integro-differential equation, which is simulated numerically in various parameter regimes. As the forcing acceleration is progressively increased, stable circular orbits give way to wobbling orbits, which are succeeded in turn by instabilities of the orbital center characterized by steady drifting then discrete leaping. In the limit of large vibrational forcing, the walker's trajectory becomes chaotic, but its statistical behavior reflects the influence of the unstable orbital solutions. The study results in a complete regime diagram that summarizes the dependence of the walker's behavior on the system parameters. Our predictions compare favorably to the experimental observations of Harris and Bush ["Droplets walking in a rotating frame: from quantized orbits to multimodal statistics," J. Fluid Mech. 739, 444-464 (2014)].

Oza, Anand U.; Wind-Willassen, Øistein; Harris, Daniel M.; Rosales, Rodolfo R.; Bush, John W. M.

2014-08-01

323

Physics Classroom: Drawing Free-Body Diagrams  

NSDL National Science Digital Library

This tutorial explains how free body diagrams are used in solving problems involving Newton's Second Law. This tutorials demonstrates how to draw free body diagrams, what the diagram means to Physics, and includes practice problems for the student. This tutorial also includes other tutorials, animations, and student activities in other concepts of Physics. The Physics Classroom is a set of resources created for learners and teachers of high school physics. It includes comprehensive tutorials, problem sets with solutions, extra help for struggling students, Shockwave animations, multimedia learning modules, labs, and photo gallery.

Henderson, Tom

2011-10-03

324

ProofFlow: Flow Diagrams for Proofs  

E-print Network

We present a light formalism for proofs that encodes their inferential structure, along with a system that transforms these representations into flow-chart diagrams. Such diagrams should improve the comprehensibility of proofs. We discuss language syntax, diagram semantics, and our goal of building a repository of diagrammatic representations of proofs from canonical mathematical literature. The repository will be available online in the form of a wiki at proofflow.org, where the flow chart drawing software will be deployable through the wiki editor. We also consider the possibility of a semantic tagging of the assertions in a proof, to permit data mining.

Kieffer, Steven A

2012-01-01

325

Fibrolipoma of the orbit.  

PubMed

A 47-year-old woman presented with a growing mass on the lateral rim of orbit. Orbital CT revealed a well-circumscribed soft tissue mass in the right lateral orbit, with focal hyperostosis of the adjacent zygomatic bone. MRI showed a lesion of mixed T1-signal intensity, which became hypointense after fat suppression. The lesion was excised, and the diagnosis of orbital fibrolipoma was made by histopathologic examination. There was no evidence of tumor after 12 months of follow-up. Orbital fibrolipoma is a rare variant of lipoma, with only 1 case described previously. It should be considered in the differential diagnosis of orbital mass. PMID:20700070

Kim, Myung Hun; Sa, Ho Seok; Woo, Kyung; Kim, Yoon-Duck

2011-01-01

326

Transneptunian Orbit Computation  

NASA Astrophysics Data System (ADS)

We review the orbit computation problem for the transneptunian population. For these distant objects, the problem is characterized by their short observed orbital arcs, which are known to be coupled with large uncertainties in orbital elements. Currently, the observations of even the best observed objects, such as the first-ever transneptunian object (TNO), Pluto, cover only a fraction of their revolution. Furthermore, of the some 1200 objects discovered since 1992, roughly half have observations from only one opposition. To ensure realistic analyses of the population, e.g., in the derivation of unbiased orbital distributions or correlations between orbital and physical properties, realistic estimation of orbital uncertainties is important. We describe the inverse problem of orbit computation, emphasizing the short-arc problem and its statistical treatment. The complete solution to the problem can be given in terms of the orbital-element probability density function (p.d.f.), which then serves as a starting point for any further analysis, where knowledge of orbital uncertainties is required. We give an overview of the variety of computational techniques developed for TNO orbital uncertainty estimation in the recent years. After presenting the current orbital distribution, we demonstrate their application to several prediction problems, such as classification, ephemeris prediction, and dynamical analysis of objects. We conclude with some future prospects for TNO orbit computation concerning the forthcoming next-generation surveys, including the anticipated evolution of TNO orbital uncertainties over the coming decades.

Virtanen, J.; Tancredi, G.; Bernstein, G. M.; Spahr, T.; Muinonen, K.

327

Architecture flow diagrams under teamwork reg sign  

SciTech Connect

The Teamwork CASE tool allows Data Flow Diagrams (DFDs) to be maintained for structured analysis. Fermilab has extended teamwork under UNIX{trademark} to permit Hatley and Pirbhai Architecture Flow Diagrams (AFDs) to be associated with DFDs and subsequently maintained. This extension, called TWKAFD, allows a user to open an AFD, graphically edit it, and replace it into a TWKAFD maintained library. Other aspects of Hatley and Pirbhai's methodology are supported. This paper presents a quick tutorial on Architecture Diagrams. It then describes the user's view of TWKAFD, the experience incorporating it into teamwork, and the successes with using the Architecture Diagram methodology along with the shortcomings of using the teamwork/TWKAFD tool. 8 refs.

Nicinski, T.

1992-02-01

328

Free energy diagrams for protein function.  

PubMed

Simplified representations can be powerful. Two common examples are sequence logos and ribbon diagrams. Both have been extraordinarily successful in capturing complex static features of sequences and structures. Capturing function is challenging, since activation involves triggered dynamic shifts between ON and OFF states. Here, we show that simple funnel drawings can capture and usefully portray proteins by their cellular triggering mechanism. The funnel shape around the proteins' native states can describe mechanisms of upstream signal integration and downstream response. "Function diagrams" are important: they can combine diverse biochemical data to visually distinguish among activation (or recruitment) mechanisms and tag proteins in cellular networks, clarifying their mechanism at a glance. We create templates for function classification and suggest that they can extend signaling pathway maps. Of note, the diagrams describe free energy landscapes; thus, they can be quantified. We name our dynamic free-energy diagrams dFEDs. PMID:24508196

Nussinov, Ruth; Tsai, Chung-Jung

2014-03-20

329

Recognition of hand drawn chemical diagrams  

E-print Network

Chemists often use hand-drawn structural diagrams to capture and communicate ideas about organic compounds. However, the software available today for specifying these structures to a computer relies on a traditional mouse ...

Ouyang, Tom Yu

2007-01-01

330

Interfaces for creating quantitative conceptual diagrams  

E-print Network

Modern chart-making, illustration, and mathematical tools poorly support the use of conceptual components in quantitative graphs such as Economics diagrams. The substantial time those tools require to achieve the desired ...

Stewart, Robin S. (Robin Scott)

2008-01-01

331

Attribute Reduction Based on Property Pictorial Diagram  

PubMed Central

This paper mainly studies attribute reduction which keeps the lattice structure in formal contexts based on the property pictorial diagram. Firstly, the property pictorial diagram of a formal context is defined. Based on such diagram, an attribute reduction approach of concept lattice is achieved. Then, through the relation between an original formal context and its complementary context, an attribute reduct of complementary context concept lattice is obtained, which is also based on the property pictorial diagram of the original formal context. Finally, attribute reducts in property oriented concept lattice and object oriented concept lattice can be acquired by the relations of attribute reduction between these two lattices and concept lattice of complementary context. In addition, a detailed illustrative example is presented.

Wan, Qing; Wei, Ling

2014-01-01

332

Algebraic decision diagrams and their applications  

Microsoft Academic Search

In this paper we present theory and experiments on the AlgebraicDecision Diagrams (ADD's). These diagrams extend BDD'sby allowing values from an arbitrary finite domain to be associatedwith the terminal nodes. We present a treatment foundedin boolean algebras and discuss algorithms and results in applicationslike matrix multiplication and shortest path algorithms.Furthermore, we outline possible applications of ADD's to logicsynthesis, formal verification,

R. Iris Bahar; Erica A. Frohm; Charles M. Gaona; Gary D. Hachtel; Enrico Macii; Abelardo Pardo; Fabio Somenzi

1993-01-01

333

On the Construction of Abstract Voronoi Diagrams  

Microsoft Academic Search

We show that the abstract Voronoi diagram ofn sites in the plane can be constructed in timeO(n logn) by a randomized algorithm. This yields an alternative, but simpler,O(n logn) algorithm in many previously considered cases and the firstO(n logn) algorithm in some cases, e.g., disjoint convex sites with the Euclidean distance function. Abstract Voronoi diagrams are\\u000a given by a family

Kurt Mehlhorn; Stefan Meiser; Colm Ó'dúnlaing

1991-01-01

334

A Sweepline Algorithm for Voronoi Diagrams  

Microsoft Academic Search

We introduce a geometric transformation that allows Voronoi diagrams to be computed using a sweepline technique. The transformation\\u000a is used to obtain simple algorithms for computing the Voronoi diagram of point sites, of line segment sites, and of weighted\\u000a point sites. All algorithms haveO(n logn) worst-case running time and useO(n) space.

Steven Fortune

1987-01-01

335

Fluctuations and the QCD phase diagram  

SciTech Connect

In this contribution the role of quantum fluctuations for the QCD phase diagram is discussed. This concerns in particular the importance of the matter back-reaction to the gluonic sector. The impact of these fluctuations on the location of the confinement/deconfinement and the chiral transition lines as well as their interrelation are investigated. Consequences of our findings for the size of a possible quarkyonic phase and location of a critical endpoint in the phase diagram are drawn.

Schaefer, B.-J., E-mail: bernd-jochen.schaefer@uni-graz.at [Karl-Franzens-Universitaet, Institut fuer Physik (Austria)

2012-06-15

336

Preliminary Study of Impulse-Momentum Diagrams  

NSDL National Science Digital Library

In this paper we present a new representation to help students learn about momentum, impulse and conservation of momentum which we call an Impulse-Momentum Diagram. We include a description of this diagram as well as examples of how instructors can use them in the classroom. Next we present preliminary quantitative and qualitative data of a study we conducted where students used these representations. Our final analysis shows how students benefited from these representations.

Rosengrant, David; Mzoughi, Taha

2009-01-24

337

An analysis of Newton's projectile diagram  

NASA Astrophysics Data System (ADS)

Newton's famous mountain projectile diagram, reproduced in countless science books, is analysed in detail - mathematically, graphically, and historically - perhaps for the first time. A study of the relationship between this diagram from Newton's On the System of the World and the written texts on projectile motion in this book and in the Principia reveals an ambiguity in Newton's presentation. We propose an explanation of the ambiguity based on an exploration of its roots in Newton's thought.

Topper, D.; Vincent, D. E.

1999-01-01

338

Use of Frequency-Conversion Diagrams  

Microsoft Academic Search

The mathematical difficulties involved in analytical treatment of single-mesh mixer circuits with diodes and crystals lead us to consider other methods for the determination of important mixer characteristics. This paper briefly reviews the rectification-diagram method as applied to large-signal detectors, and presents for consideration the Chaffee conversion-diagram method, which treats mixer circuits in the same way as large-signal detector circuits.

H. Stockman

1944-01-01

339

Elementary diagrams in nuclear and neutron matter  

SciTech Connect

Variational calculations of nuclear and neutron matter are currently performed using a diagrammatic cluster expansion with the aid of nonlinear integral equations for evaluating expectation values. These are the Fermi hypernetted chain (FHNC) and single-operator chain (SOC) equations, which are a way of doing partial diagram summations to infinite order. A more complete summation can be made by adding elementary diagrams to the procedure. The simplest elementary diagrams appear at the four-body cluster level; there is one such E{sub 4} diagram in Bose systems, but 35 diagrams in Fermi systems, which gives a level of approximation called FHNC/4. We developed a novel technique for evaluating these diagrams, by computing and storing 6 three-point functions, S{sub xyz}(r{sub 12}, r{sub 13}, r{sub 23}), where xyz (= ccd, cce, ddd, dde, dee, or eee) denotes the exchange character at the vertices 1, 2, and 3. All 35 Fermi E{sub 4} diagrams can be constructed from these 6 functions and other two-point functions that are already calculated. The elementary diagrams are known to be important in some systems like liquid {sup 3}He. We expect them to be small in nuclear matter at normal density, but they might become significant at higher densities appropriate for neutron star calculations. This year we programmed the FHNC/4 contributions to the energy and tested them in a number of simple model cases, including liquid {sup 3}He and Bethe`s homework problem. We get reasonable, but not exact agreement with earlier published work. In nuclear and neutron matter with the Argonne v{sub 14} interaction these contributions are indeed small corrections at normal density and grow to only 5-10 MeV/nucleon at 5 times normal density.

Wiringa, R.B.

1995-08-01

340

Bifurcation diagrams for two substrate oscillatory systems  

NASA Astrophysics Data System (ADS)

The bifurcation diagrams for the Mn 2+-malonic acid-H 2SO 4-KBrO 3 an Mn 2--oxaloacetic acid-H 2SO 4-KBrO 3 systems have been studied in a stirred tank reactor. Complex oscillations associated with a period-doubling bifurcation were found. Bifurcation diagrams for the two substrate malonic-citric and malonic-oxaloacetic acid systems were also determined.

Mase?ko, Jerzy

1983-08-01

341

Phase diagram of the excitonic insulator  

Microsoft Academic Search

Motivated by recent experiments, which give strong evidence for an excitonic insulating phase in TmSe0.45Te0.55, we developed a scheme to quantitatively construct, for generic two-band models, the phase diagram of an excitonic insulator. As a first application of our approach, we calculated the phase diagram for an effective mass two-band model with long-range Coulomb interaction. The shielded potential approximation is

B. Hülsen; F. X. Bronold; H. Fehske; K. Yonemitsu

2006-01-01

342

Lunar orbiting prospector  

NASA Technical Reports Server (NTRS)

One of the prime reasons for establishing a manned lunar presence is the possibility of using the potential lunar resources. The Lunar Orbital Prospector (LOP) is a lunar orbiting platform whose mission is to prospect and explore the Moon from orbit in support of early lunar colonization and exploitation efforts. The LOP mission is divided into three primary phases: transport from Earth to low lunar orbit (LLO), operation in lunar orbit, and platform servicing in lunar orbit. The platform alters its orbit to obtain the desired surface viewing, and the orbit can be changed periodically as needed. After completion of the inital remote sensing mission, more ambitious and/or complicated prospecting and exploration missions can be contemplated. A refueled propulsion module, updated instruments, or additional remote sensing packages can be flown up from the lunar base to the platform.

1988-01-01

343

Rock-Around Orbits  

E-print Network

. . . . . . . . . . . . . 8 D. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 E. Minimum Distance . . . . . . . . . . . . . . . . . . . . . . 15 III ELLIPTICAL TARGET ORBITS : : : : : : : : : : : : : : : : : 18 A. Acceptable and Compatible Orbits... . . . . . . . . . . . . . 18 B. Eccentricity and Inclination Bounds . . . . . . . . . . . . . 19 C. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 D. Minimum Distance . . . . . . . . . . . . . . . . . . . . . . 26 IV J2 PERTURBATIONS...

Bourgeois, Scott K.

2010-07-14

344

Orbit CT scan  

MedlinePLUS

Massoud TF, Cross JJ. The orbit. In: Adam A, Dixon A, eds. Grainger and Allison's Diagnostic Radiology. 5th ed. Philadelphia, Pa: Elsevier Saunders; 2008:chap 61. Szatmary G. Imaging of the orbit. Neurol Clin . 2008;27:251-284.

345

Preliminary orbital parallax catalog  

NASA Technical Reports Server (NTRS)

The study is undertaken to calibrate the more reliable parallaxes derived from a comparison of visual and spectroscopic orbits and to encourage observational studies of other promising binaries. The methodological techniques used in computing orbital parallaxes are analyzed. Tables summarizing orbital data and derived system properties are then given. Also given is a series of detailed discussions of the 71 individual systems included in the tables. Data are listed for 57 other systems which are considered promising candidates for eventual orbital parallax determination.

Halliwell, M.

1981-01-01

346

Cosmetic orbital surgery  

Microsoft Academic Search

PurposeCurrent indications for orbital surgery primarily aimed at improving cosmesis are considered in the context of subspecialist orbital practice by an ophthalmologist.ScopeThyroid eye disease, orbital vascular anomalies, and dermolipomas are common orbital diseases in which the symptoms can be purely cosmetic. Accurate anatomical awareness, preoperative scanning, control of medical factors including smoking and thyroid status, and endoscopic techniques have all

2006-01-01

347

Mars orbit selection  

NASA Technical Reports Server (NTRS)

Parking orbits for a manned Mars mission are examined for ease of access to the Martian moons. Delta V plots for a variety of burns versus elliptical orbit apoapsis are included. A high elliptical orbit (24 hour period, 500 km periapsis, 20 to 30 deg. inclination) minimizes delta V to the Martian moons and Mars orbit insertion (MOI) and trans-Earth injection (TEI) delta Vs.

Babb, Gus R.; Stump, William R.

1986-01-01

348

Orbiting Binary Stars  

NSDL National Science Digital Library

This simulation demonstrates the path of binary stars' orbit. The user is able to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of two orbiting stars. The observed velocities of the two stars, and the Doppler shifted spectral lines are also shown in the upper right box. The site also includes definitions of terms used, instructions on how to use the simulation and a few examples.

Kolena, John

2007-12-11

349

Five Equivalent d Orbitals  

ERIC Educational Resources Information Center

Amplifies and clarifies a previous paper on pyramidal d orbitals. Discusses two sets of pyramid d orbitals with respect to their maximum bond strength and their symmetry. Authors described the oblate and prolate pentagonal antiprisms arising from the two sets of five equivalent d orbitals. (RR)

Pauling, Linus; McClure, Vance

1970-01-01

350

Mars Reconnaissance Orbiter  

NSDL National Science Digital Library

This is the mission web site for the Mars Reconnaissance Orbiter, which went into orbit around Mars on March 10, 2006. The site provides links to updates and information about the project. The site features links to Mars Reconnaissance Orbiter images, animations, and datasets. Science operations commence in November, 2006.

Laboratory, Jet P.; Administration, National A.

351

SEASAT B orbit synthesis  

NASA Technical Reports Server (NTRS)

Addition were made to Battelle's Interactive Graphics Orbit Selection (IGOS) program; IGOS was exercised via telephone lines from JPL, and candidate SEASAT orbits were analyzed by Battelle. The additions to the program enable clear understanding of the implications of a specific orbit to the diverse desires of the SEASAT user community.

Rea, F. G.; Warmke, J. M.

1976-01-01

352

Diagrams in Architecture: An Examination of Diagram Based Design Methods in Contemporary Urban Architecture Projects.  

E-print Network

??This research explores the relationship between the use of diagrams in architectural production and an architectural outcome which redefines conventional relationships between urban built form… (more)

Shields, Fraser

2012-01-01

353

Synthesis, spectroscopic, molecular orbital calculation, cytotoxic, molecular docking of DNA binding and DNA cleavage studies of transition metal complexes with N-benzylidene-N'-salicylidene-1,1-diaminopropane  

NASA Astrophysics Data System (ADS)

Eight mononuclear chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of Schiff's base ligand were synthesized and determined by different physical techniques. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the eight metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff base is found to act as tridentate ligand using N2O donor set of atoms leading to an octahedral geometry for the complexes around all the metal ions. Quantum chemical calculations were performed with semi-empirical method to find the optimum geometry of the ligand and its complexes. Additionally in silico, the docking studies and the calculated pharmacokinetic parameters show promising futures for application of the ligand and complexes as high potency agents for DNA binding activity. The interaction of the complexes with calf thymus DNA (CT-DNA) has been investigated by UV absorption method, and the mode of CT-DNA binding to the complexes has been explored. Furthermore, the DNA cleavage activity by the complexes was performed. The Schiff base and their complexes have been screened for their antibacterial activity against bacterial strains [Staphylococcus aureus (RCMB010027), Staphylococcus epidermidis (RCMB010024), Bacillis subtilis (RCMB010063), Proteous vulgaris (RCMB 010085), Klebsiella pneumonia (RCMB 010093) and Shigella flexneri (RCMB 0100542)] and fungi [(Aspergillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB 02593) and Candida albicans (RCMB05035)] by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligand.

Al-Mogren, Muneerah M.; Alaghaz, Abdel-Nasser M. A.; Elbohy, Salwa A. H.

2013-10-01

354

OTV orbital tanking systems  

NASA Technical Reports Server (NTRS)

Orbital transfer of cryogenic propellants could benefit spacecraft and Orbital Transfer Vehicle (OTV) missions in the 1980s by supplying main propulsion, attitude control, or other fluid systems. The Space Shuttle can operate as a tanker when equipped with cryogenic propellant storage and orbital transfer systems. The key technologies are multilayer insulation, capillary propellant acquisition, zero-g gaging, orbital chilldown, and possibly large flight weight dewars. The technologies and operations could be realistically demonstrated using a Centaur that has been integrated with the Shuttle. Orbital refueling capability can enhance the usefulness of the whole Shuttle program

Heald, D. A.; Merino, F.

1979-01-01

355

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

LRO definitive and predictive accuracy requirements were easily met in the nominal mission orbit, using the LP150Q lunar gravity model. center dot Accuracy of the LP150Q model is poorer in the extended mission elliptical orbit. center dot Later lunar gravity models, in particular GSFC-GRAIL-270, improve OD accuracy in the extended mission. center dot Implementation of a constrained plane when the orbit is within 45 degrees of the Earth-Moon line improves cross-track accuracy. center dot Prediction accuracy is still challenged during full-Sun periods due to coarse spacecraft area modeling - Implementation of a multi-plate area model with definitive attitude input can eliminate prediction violations. - The FDF is evaluating using analytic and predicted attitude modeling to improve full-Sun prediction accuracy. center dot Comparison of FDF ephemeris file to high-precision ephemeris files provides gross confirmation that overlap compares properly assess orbit accuracy.

Slojkowski, Steven E.

2014-01-01

356

Reactivity index based on orbital energies.  

PubMed

This study shows that the chemical reactivities depend on the orbital energy gaps contributing to the reactions. In the process where a reaction only makes progress through charge transfer with the minimal structural transformation of the reactant, the orbital energy gap gradient (OEGG) between the electron-donating and electron-accepting orbitals is proven to be very low. Using this relation, a normalized reaction diagram is constructed by plotting the normalized orbital energy gap with respect to the normalized intrinsic reaction coordinate. Application of this reaction diagram to 43 fundamental reactions showed that the majority of the forward reactions provide small OEGGs in the initial stages, and therefore, the initial processes of the forward reactions are supposed to proceed only through charge transfer. Conversely, more than 60% of the backward reactions are found to give large OEGGs implying very slow reactions associated with considerable structural transformations. Focusing on the anti-activation-energy reactions, in which the forward reactions have higher barriers than those of the backward ones, most of these reactions are shown to give large OEGGs for the backward reactions. It is also found that the reactions providing large OEGGs in the forward directions inconsistent with the reaction rate constants are classified into SN 2, symmetric, and methyl radical reactions. Interestingly, several large-OEGG reactions are experimentally established to get around the optimum pathways. This indicates that the reactions can take significantly different pathways from the optimum ones provided no charge transfer proceeds spontaneously without the structural transformations of the reactants. PMID:24740548

Tsuneda, Takao; Singh, Raman K

2014-05-30

357

Chemguide: Atomic Orbitals  

NSDL National Science Digital Library

This web page explains what atomic orbitals are in a way that makes it appropriate for pre-college introductory chemistry or physics courses. It goes into detail on s and p orbitals, including their shapes and energies, while devoting less discussion to d and f orbitals. The author uses an analogy comparing an atom to a multi-story house -- with the nucleus on the ground floor and then various rooms (orbitals) on the higher floors occupied by the electrons. A full page debunks the misconception that "orbitals" are like "orbits" (common among beginning students). Beyond this foundation, the tutorial explores how electrons fill orbitals (from low-to-high energy). It concludes with a set of questions, with answers provided, for self-gauging understanding. This page is part of Chemguide, an informational website developed by a veteran high school teacher to promote deeper understanding of concepts in introductory and intermediate-level chemistry.

Clark, Jim

2013-02-20

358

On phase diagrams of magnetic reconnection  

NASA Astrophysics Data System (ADS)

Recently, "phase diagrams" of magnetic reconnection were developed to graphically organize the present knowledge of what type, or phase, of reconnection is dominant in systems with given characteristic plasma parameters. Here, a number of considerations that require caution in using the diagrams are pointed out. First, two known properties of reconnection are omitted from the diagrams: the history dependence of reconnection and the absence of reconnection for small Lundquist number. Second, the phase diagrams mask a number of features. For one, the predicted transition to Hall reconnection should be thought of as an upper bound on the Lundquist number, and it may happen for considerably smaller values. Second, reconnection is never "slow," it is always "fast" in the sense that the normalized reconnection rate is always at least 0.01. This has important implications for reconnection onset models. Finally, the definition of the relevant Lundquist number is nuanced and may differ greatly from the value based on characteristic scales. These considerations are important for applications of the phase diagrams. This is demonstrated by example for solar flares, where it is argued that it is unlikely that collisional reconnection can occur in the corona.

Cassak, P. A.; Drake, J. F.

2013-06-01

359

ASSESSING DIAGRAM QUALITY: MAKING A DIFFERENCE TO REPRESENTATION  

Microsoft Academic Search

The effectiveness of a diagram in problem solving is dependent on its utility as a cognitive tool. In order to develop students' ability to use diagrams as cognitive tools, teachers need to assess the quality of students' diagrams and provide them with the necessary support. However assessing the quality of diagrams is problematic. This paper discusses how theoretical prototypes and

Carmel M Diezmann

360

The Hardness-Duration Diagram of Gamma-Ray Bursts  

Microsoft Academic Search

The hardness-duration diagram for gamma-ray bursts still contains undiscovered important information about the intrinsic properties of these phenomena. We analyze these diagrams for the PHEBUS and BATSE experiments. First, we show that the BATSE diagram is very similar to that for PHEBUS when we restrict the BATSE data set to events observable by PHEBUS. In this case, both diagrams present

J. P. Dezalay; J. P. Lestrade; C. Barat; R. Talon; R. Sunyaev; O. Terekhov; A. Kuznetsov

1996-01-01

361

Fishbone Diagrams: Organize Reading Content with a "Bare Bones" Strategy  

ERIC Educational Resources Information Center

Fishbone diagrams, also known as Ishikawa diagrams or cause-and-effect diagrams, are one of the many problem-solving tools created by Dr. Kaoru Ishikawa, a University of Tokyo professor. Part of the brilliance of Ishikawa's idea resides in the simplicity and practicality of the diagram's basic model--a fish's skeleton. This article describes how…

Clary, Renee; Wandersee, James

2010-01-01

362

The Use of Computational Diagrams and Nomograms in Higher Education.  

ERIC Educational Resources Information Center

The use of computational diagrams and nomographs for the calculations that frequently occur in college administration is examined. Steps in constructing a nomograph and a four-dimensional computational diagram are detailed, and uses of three- and four-dimensional diagrams are covered. Diagrams and nomographs are useful in the following cases: (1)…

Brandenburg, Richard K.; Simpson, William A.

1984-01-01

363

Use of Affinity Diagrams as Instructional Tools in Inclusive Classrooms.  

ERIC Educational Resources Information Center

This article describes how the affinity diagram, a tool for gathering information and organizing it into natural groupings, can be used in inclusive classrooms. It discusses how students can be taught to use an affinity diagram, how affinity diagrams can be used to reflect many voices, and how affinity diagrams can be used to plan class projects.…

Haselden, Polly G.

2003-01-01

364

Picturing Probability: the poverty of Venn diagrams, the richness of  

E-print Network

's name deserves to be attached to these diagrams. Venn diagrams visually ground symbolic logic book Symbolic Logic Venn makes much use of these diagrams, yet in his book on probability, The Logic 1 It is true that Venn's probability book predates his symbolic logic book, however the diagrams

Oldford, R.W.

365

Phase diagram of carbon-oxygen plasma mixtures in white dwarf stars  

NASA Astrophysics Data System (ADS)

The liquid-solid phase-diagram of dense carbon-oxygen plasma mixtures found in white dwarf stars interiors is determined from molecular dynamics (MD) simulations. Our MD simulations consist of boxes with 55296 ions with different carbon to oxygen ratios. Finite size effects are estimated comparing the new MD simulations results to previous smaller simulations. We use bond angle metric to identify whether an ion is in the solid, liquid or interface and study non-equilibrium effects by obtaining the diffusion coefficients in the different phases. Our phase diagram agrees with predictions from Medin and Cumming obtained by an independent method.

Schneider, A. S.; Horowitz, C. J.; Hughto, J.; Berry, D. K.

2012-12-01

366

A Geometric Diagram of Separable States  

E-print Network

This paper present a geometric diagram of a separable state: If a mixed state $\\sigma $ is separable, there are $2^{nS(\\sigma)}$ linearly independant product vectors which span the same Hilbert space as the $2^{nS(\\sigma)}$ ``likely'' strings of $\\sigma ^{\\otimes n}$ do. This diagram results in a criterion for separability which is strictly stronger than the inorder criterion in [M.A. Nielsen and J. Kempe, Phys. Rev. Lett. 86, 5184 (2001)]. This means that the number of product bases of states of a system has close link to the nonlocality of the system.

Ping Xing Chen; Cheng Zu Li

2004-03-02

367

Orbit Determination of the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter (LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than the required 50-100m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences decrease from approx.70m to approx.23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows significantly increased accuracy (approx.20m with only the radiometric data, and approx.14m with the addition of the altimetric crossovers). LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results of the overlap analysis and demonstrate the trajectory accuracy.

Mazarico, Erwan; Rowlands, D. D.; Neumann, G. A.; Smith, D. E.; Torrence, M. H.; Lemoine, F. G.; Zuber, M. T.

2011-01-01

368

PC-402 Pioneer Venus orbiter spacecraft mission operational characteristics document  

NASA Technical Reports Server (NTRS)

The operational characteristics of the Orbiter spacecraft and its subsystems are described. In extensive detail. Description of the nominal phases, system interfaces, and the capabilities and limitations of system level performance are included along with functional and operational descriptions at the subsystem and unit level the subtleties of nominal operation as well as detailed capabilities and limitations beyond nominal performance are discussed. A command and telemetry logic flow diagram for each subsystem is included. Each diagram encountered along each command signal path into, and each telemetry signal path out of the subsystem. Normal operating modes that correspond to the performance of specific functions at the time of specific events in the mission are also discussed. Principal backup means of performing the normal Orbiter operating modes are included.

Barker, F. C.; Butterworth, L. W.; Daniel, R. E.; Drean, R. J.; Filetti, K. A.; Fisher, J. N.; Nowak, L. A.; Porzucki, J.; Salvatore, J. O.; Tadler, G. A.

1978-01-01

369

First-principles pressure-temperature phase diagrams in metals  

SciTech Connect

Using interatomic potentials derived from first-principles generalized pseudopotential theory, finite-temperature phase transitions in both simple and transition metals can be studied through a combination of analytic statistical methods and molecular-dynamics simulation. In the prototype simple metal-Mg, where volume and pair forces adequately describe the energetics, a complete and accurate phase diagram has thereby been obtained to 60 GPa. A rapidly temperature-dependent hcp-bcc phase line is predicted which ends in a triple point on the melting curve near 4 GPa. In central transition metals such as Mo or Fe, on the other hand, the energetics are complicated by d-state interactions which give rise to both many-body angular forces and enhanced electron-thermal contributions. We have made a detailed study of these phenomena and their impact on melting in the prototype case of Mo and a full melting curve to 2 Mbar has been obtained. In the case of Fe, we are examining the high-pressure phase diagram and the question of whether or not there exists a high-pressure, high-temperature solid bcc phase, as has been speculated. To date, we have shown that the bcc structure is both thermodynamically and mechanically unstable at high pressure and zero temperature, with a large and increasing bcc-hcp energy difference under compression.

Moriarty, J.A.

1993-07-01

370

Ghost orbit spectroscopy  

SciTech Connect

Direct periodic-orbit expansions of individual spectral eigenvalues is a new direction in quantum mechanics. Using a unitary S-matrix theory, we present exact, convergent, integral-free ghost orbit expansions of spectral eigenvalues for a step potential in the tunneling regime. We suggest an experiment to extract ghost orbit information from measured spectra in the tunneling regime (ghost orbit spectroscopy). We contrast our unitary, convergent theory with a recently published nonunitary, divergent theory [Yu. Dabaghian and R. Jensen, Eur. J. Phys. 26, 423 (2005)].

Bhullar, A. S.; Bluemel, R. [Department of Physics, Wesleyan University, Middletown, Connecticut 06459-0155 (United States); Koch, P. M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800 (United States)

2006-01-15

371

Magnetospheric Multiscale (MMS) Orbit  

NASA Video Gallery

This animation shows the orbits of Magnetospheric Multiscale (MMS) mission, a Solar-Terrestrial Probe mission comprising of four identically instrumented spacecraft that will study the Earth's magn...

372

Orbital Debris: A Chronology  

NASA Technical Reports Server (NTRS)

This chronology covers the 37-year history of orbital debris concerns. It tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Included are debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

Portree, Davis S. F. (Editor); Loftus, Joseph P., Jr. (Editor)

1999-01-01

373

Using cellular network diagrams to interpret large-scale datasets: past progress and future challenges  

NASA Astrophysics Data System (ADS)

Cellular networks are graphs of molecular interactions within the cell. Thanks to the confluence of genome sequencing and bioinformatics, scientists are now able to reconstruct cellular network models for more than 1,000 organisms. A variety of bioinformatics tools have been developed to support the visualization and navigation of cellular network data. Another important application is the use of cellular network diagrams to visualize and interpret large-scale datasets, such as gene-expression data. We present the Cellular Overview, a network visualization tool developed at SRI International (SRI) to support visualization, navigation, and interpretation of large-scale datasets on metabolic networks. Different variations of the diagram have been generated algorithmically for more than 1,000 organisms. We discuss the graphical design of the diagram and its interactive capabilities.

Karp, Peter D.; Latendresse, Mario; Paley, Suzanne

2011-03-01

374

Liquid-solid phase diagrams of binary carbonates for lithium batteries  

SciTech Connect

The authors present the liquid-solid phase diagrams that they mapped with a differential scanning calorimeter (DSC) for the following seven binary carbonates: dimethyl carbonate (DMC)-ethylene carbonate (EC), ethyl methyl carbonate (EMC)-EC, EMC-propylene carbonate (PC), EMC-dimethyl ethylene carbonate (DMEC), EMC-isobutylene carbonate (iBC), PC-EC, and EMC-DMC. Many of these are among the most frequently used solvent systems for making the nonaqueous electrolytes for lithium batteries. The phase diagrams of these carbonate systems are all of the simple eutectic type but with vastly different particular features. Comparison of these phase diagrams shows that to expand the liquid region of a carbonate system toward low temperature, the two components of the system need to have comparable melting temperatures and compatible molecular structures. These results are consistent with thermodynamic considerations and have significant practical implications.

Ding, M.S.; Xu, K.; Jow, T.R.

2000-05-01

375

Development of a phase diagram to control composite manufacturing using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Fiber reinforced epoxy resins manufactured in autoclaves are expected to continue to dominate the composites market through 2010. However, the ability to obtain consistent mechanical properties from product-to-product remains difficult. This is largely due to the inability to monitor and control epoxy cure, loosely defined as the process of chain extension and cross-linking. Current autoclave process control employs a heat schedule based on a time-temperature-transformation (TTT) phase diagram that is determined by dynamic mechanical rheology. The phase diagram defines epoxy cure in terms of gelation and vitrification. We have been using an FT-Raman spectrometer to develop correlations between molecular (chain extension and cross-linking) and macroscopic (gelation and vitrification) data. The basis of a TTT phase diagram using Raman kinetic data for process control will be presented for several reactions.

Farquharson, Stuart; Carignan, Jessica; Khitrov, Victor; Senador, Antonio; Shaw, Montgomery

2004-03-01

376

Space Station - Infrastructure for radiation measurements in low earth orbit  

NASA Technical Reports Server (NTRS)

The general configuration, development schedule, and capabilities of the NASA International Space Station are reviewed, with an emphasis on the possibilities for long-term measurements of high-energy cosmic and secondary radiation from the main Station spacecraft, coorbiting or polar-orbit platforms, or Station-supported GEO satellites. Also outlined are the organizational structure and the application procedures to be followed by potential users of the Station facilities. Diagrams and drawings are provided.

Meredith, B. D.

1989-01-01

377

Weyl group orbits on Kac–Moody root systems  

NASA Astrophysics Data System (ADS)

Let D be a Dynkin diagram and let \\Pi =\\{{{? }1},...,{{? }\\ell }\\} be the simple roots of the corresponding Kac–Moody root system. Let h denote the Cartan subalgebra, let W denote the Weyl group and let ? denote the set of all roots. The action of W on h, and hence on ?, is the discretization of the action of the Kac–Moody algebra. Understanding the orbit structure of W on ? is crucial for many physical applications. We show that for i\

Carbone, Lisa; Conway, Alexander; Freyn, Walter; Penta, Diego

2014-11-01

378

Segmenting Dot Patterns by Voronoi Diagram Concavity  

Microsoft Academic Search

This correspondence defines a signed distance, called ``internal concavity,'' on paths of the Voronoi diagram of a dot pattern. An algorithm using internal concavity to segment dot patterns is described. The segmentation algorithm produces subsets of the Dirichlet tessellation (Delaunay triangulation) of the dot pattern.

John Fairfield

1983-01-01

379

Neural network design using Voronoi diagrams  

Microsoft Academic Search

A novel approach is proposed which determines the number of layers, the number of neurons in each layer, and their connection weights for a particular implementation of a neural network, with the multilayer feedforward topology, designed to classify patterns in the multidimensional feature space. The approach is based on construction of a Voronoi diagram over the set of points representing

N. K. Bose; Amulya K. Garga

1993-01-01

380

Evaluating formal properties of feature diagram languages  

Microsoft Academic Search

Feature diagrams (FDs) are a family of popular modelling languages, mainly used for managing variability in software product lines. FDs were first introduced by Kang et al. as part of the feature-oriented domain analysis (FODA) method back in 1990. Since then, various extensions of FODA FDs were devised to compensate for purported ambiguity and lack of precision and expressiveness. Recently,

Patrick Heymans; Pierre-yves Schobbens; Jean-christophe Trigaux; Yves Bontemps; Raimundas Matulevicius; Andreas Classen

2008-01-01

381

Nonverbal Poetry: Family Life-Space Diagrams.  

ERIC Educational Resources Information Center

Examines life-space diagrams as a form of nonverbal poetry which taps personal feelings, tells a story, and characterizes a particular life situation, forming a useful therapy technique that provides a family the opportunity to examine its internal family relationships. Offers two case studies, discusses five levels of knowing and awareness, and…

Bardill, Donald R.

2001-01-01

382

Bregman Voronoi Diagrams: Properties, Algorithms and Applications  

E-print Network

entropy of distributions. We define several types of Bregman diagrams, establish correspondences between and Object Modeling -- Geometric algorithms, languages, and systems; F.2.2 [Anal- ysis of Algorithms on Discrete Algorithms (SODA), pp. 746-755, 2007. Related materials are available online at http://www.csl.sony

Nielsen, Frank

383

Ferromagnetic phase diagram of neutron matter  

E-print Network

The magnetic properties of matter under extreme conditions are of particular importance to understanding the neutron star interior. One contributing factor to the magnetic field of a neutron star could be the ferromagnetic phase of nuclear matter. In this letter we present a self-consistent, relativistic description of ferromagnetism in dense matter, within which the ferromagnetic phase diagram for neutron matter is calculated.

J. P. W. Diener; F. G. Scholtz

2010-06-29

384

NFHS Court and Field Diagram Guide.  

ERIC Educational Resources Information Center

This guide contains a comprehensive collection of diagrams and specifications of playing fields and courts used in interscholastic and recreational sports, along with information on how to set up various formats of tournament drawings, how to compute golf handicaps, and how to convert metric-to-English distances. Lists are provided of national…

Gillis, John, Ed.

385

Shockwave Physics Studios: Free Body Diagrams  

NSDL National Science Digital Library

This interactive activity, part of The Physics Classroom tutorial collection, provides self-directed practice in constructing free-body diagrams. Twelve descriptions of physical situations are presented; the goal is to determine the type and relative magnitude of the forces acting upon the described object. Additional help is provided with one click on "Web Help".

Henderson, Tom

2011-09-27

386

Revised state diagram of Laponite dispersions  

Microsoft Academic Search

We propose a state diagram of charged disk-like mineral particle (Laponite) dispersions as a function of the Laponite concentration (C) and the concentration of added salt (Cs), based on simple observation and light-scattering measurements. At low C or high Cs the dispersions separate into two domains due to sedimentation of Laponite aggregates, while at high C and low Cs they

Philippe Mongondry; Jean François Tassin; Taco Nicolai

2005-01-01

387

Shared Variables Interaction Diagrams Rajeev Alur  

E-print Network

of an SVID, an action corresponds to, possibly multiple, reading/writing of shared variables. The actions that the problem can be solved in linear-time when all the variables are read-shared but write- exclusive. BenefitsShared Variables Interaction Diagrams Rajeev Alur Department of Computer and Information Science

Grosu, Radu

388

The Keynesian Diagram: A Cross to Bear?  

ERIC Educational Resources Information Center

In elementary economics courses students are often introduced to the basic concepts of macroeconomics through very simplified static models, and the concept of a macroeconomic equilibrium is generally explained with the help of an aggregate demand/aggregate supply (AD/AS) model and an income/expenditure model (via the Keynesian cross diagram).…

Fleck, Juergen

389

One Parameter Bifurcation Diagram for Chua's Circuit  

E-print Network

One Parameter Bifurcation Diagram for Chua's Circuit MIREILLE E. BROUCKE Abstract -The objective of this letter is to report on the usefulness of a l-dimensional map for characterizing the dynamics of a third-order piece- wise-linear circuit. The map is used to reproduce period-doubling birfurca- tions

Broucke, Mireille E.

390

Testing for monotonicity in the Hubble diagram  

E-print Network

General relativistic kinematics and the cosmological principle alone imply a monotonicity constraint in the Hubble diagram, which we confront to present-day supernova data. We use the running gradient method of statistical inference by Hall & Heckman (2000). We find no significant departure from monotonicity. The method seems well adapted and we recommend its use with future data.

Nicolai Meinshausen; John Rice; Thomas Schücker

2006-12-19

391

Dynamic Tactile Diagram Simplification on Refreshable Displays  

ERIC Educational Resources Information Center

The increasing use of visual diagrams in educational and work environments, and even our daily lives, has created obstacles for individuals who are blind or visually impaired to "independently" access the information they represent. Although physical tactile pictures can be created to convey the visual information, it is typically a slow,…

Rastogi, Ravi; Pawluk, Dianne T. V.

2013-01-01

392

Recognition of Hand Drawn Chemical Diagrams  

Microsoft Academic Search

Chemists often use hand-drawn structural diagrams to capture and communicate ideas about organic com- pounds. However, the software available today for spec- ifying these structures to a computer relies on a tra- ditional mouse and keyboard interface, and as a re- sult lacks the ease of use, naturalness, and speed of drawing on paper. In response, we have developed a

Tom Y. Ouyang; Randall Davis

2007-01-01

393

Constructing Causal Diagrams to Learn Deliberation  

ERIC Educational Resources Information Center

Policy problems like "What should we do about global warming?" are ill-defined in large part because we do not agree on a system to represent them the way we agree Algebra problems should be represented by equations. As a first step toward building a policy deliberation tutor, we investigated: (a) whether causal diagrams help students learn to…

Easterday, Matthew W.; Aleven, Vincent; Scheines, Richard; Carver, Sharon M.

2009-01-01

394

Extended Activity Diagrams for Adaptive Workflow Modelling  

Microsoft Academic Search

Activity diagrams are a recognized form of modelling real time systems and have been included in the list of UML techniques for modelling the dynamic aspects of object oriented systems. In this paper, we explain how workflow techniques can be used for developing models of larger chunks of systems. These chunks are expressed through the use of worklets. This can

Elizabeth Chang; E. Gautama; Tharam S. Dillon

2001-01-01

395

Spectrum Analyzer Basics Simplified Block Diagram  

E-print Network

Spectrum Analyzer Basics Simplified Block Diagram Major Controls Frequency Sweep Set Start { Hit MKR-> in the MARKER/LINE CURSOR group. { Use the softkeys to move the marker to the maximum and the CONTmode (it sometimes gets confused and stuck in a single-sweep mode) { If the analyzer complains about

Kuhn, William B.

396

NTNU Java: Free-Body Force Diagram  

NSDL National Science Digital Library

This applet illustrates the forces on a block on an inclined plane. A free-body diagram shows the gravitational, normal, frictional and net force vectors. The weight, angle of the plane, and coefficient of friction can be changed by the user. The user can also apply an external force to the block. The motion resulting from the forces is not shown.

Hwang, Fu-Kwun

2005-02-07

397

Towards Flexible Graphical Communication Using Adaptive Diagrams  

E-print Network

, life- less objects reflecting their origin in print media, the computer of the near future will provide their origin in print media, the computer of the near future will provide more flexible visual computer. There are five main differences between the old print media based view of diagrams and this new view based

Marriott, Kimbal

398

Fog Machines, Vapors, and Phase Diagrams  

ERIC Educational Resources Information Center

A series of demonstrations is described that elucidate the operation of commercial fog machines by using common laboratory equipment and supplies. The formation of fogs, or "mixing clouds", is discussed in terms of the phase diagram for water and other chemical principles. The demonstrations can be adapted for presentation suitable for elementary…

Vitz, Ed

2008-01-01

399

APRICODD: Approximate Policy Construction Using Decision Diagrams  

Microsoft Academic Search

We propose a method of approximate dynamic programming for Markov decision processes (MDPs) using algebraic decision diagrams (ADDs). We produce near-optimal value functions and policies with much lower time and space requirements than exact dynamic programming. Our method reduces the sizes of the intermediate value functions generated during value iteration by replacing the values at the terminals of the ADD

Robert St-aubin; Jesse Hoey; Craig Boutilier

2000-01-01

400

A Diagram Editor for Efficient Biomedical Knowledge Capture and Integration  

PubMed Central

Understanding the molecular mechanisms underlying complex disorders requires the integration of data and knowledge from different sources including free text literature and various biomedical databases. To facilitate this process, we created the Biomedical Concept Diagram Editor (BCDE) to help researchers distill knowledge from data and literature and aid the process of hypothesis development. A key feature of BCDE is the ability to capture information with a simple drag-and-drop. This is a vast improvement over manual methods of knowledge and data recording and greatly increases the efficiency of the biomedical researcher. BCDE also provides a unique concept matching function to enforce consistent terminology, which enables conceptual relationships deposited by different researchers in the BCDE database to be mined and integrated for intelligible and useful results. We hope BCDE will promote the sharing and integration of knowledge from different researchers for effective hypothesis development. PMID:21347131

Yu, Bohua; Jakupovic, Elvis; Wilson, Justin; Dai, Manhong; Xuan, Weijian; Mirel, Barbara; Athey, Brian; Watson, Stanley; Meng, Fan

2008-01-01

401

Glass and liquid phase diagram of a polyamorphic monatomic system  

NASA Astrophysics Data System (ADS)

We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, PLDA-HDA(T) and PHDA-LDA(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, PLPC-HDA(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)], 10.1103/PhysRevE.48.4605 simulations suggest that the PLDA-HDA(T) and PHDA-LDA(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the PLPC-HDA(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the PLDA-HDA(T), PHDA-LDA(T), PLPC-HDA(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the glass phase diagram can be related directly with the liquid phase diagram. However, at our "slow rate," crystallization cannot be prevented at intermediate temperatures, within the glass region. In these cases, multiple crystal-crystal transformations are found upon compression/decompression (polymorphism).

Reisman, Shaina; Giovambattista, Nicolas

2013-02-01

402

Titan Orbiter Aerorover Mission  

NASA Technical Reports Server (NTRS)

We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

2001-01-01

403

Extrapolation of orbits  

Microsoft Academic Search

The use of analytic theory, numerical integration, or a mixed method in the extrapolation of a spacecraft orbit is shown to depend on mission requirements. Parameters to be extrapolated for the ARGOS satellite system, for SPOT satellite, DZB satellite, and for geostationary satellites are among examples cited. Orbit extrapolation for SKYLAB reentry is also covered. Analytic methods include integration of

N. Borderies

1980-01-01

404

Periodic orbits and stability  

Microsoft Academic Search

A review is presented of periodic orbits which are of interest to dynamical astronomy, and their relation to actual systems is considered. In particular, the paper reviews periodic orbits in planetary systems with two or more planets, in the asteroid system, in stellar systems, and in the motion of a star in various types of galaxies. Most systems are close

John D. Hadjidemetriou

1988-01-01

405

Orbital trapdoor fractures  

PubMed Central

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management. PMID:23961006

Phan, Laura T.; Jordan Piluek, W.; McCulley, Timothy J.

2012-01-01

406

Constraint Orbital Branching  

E-print Network

a group of strong constraints on which to base the orbital branching .... that maps each feasible solution onto a feasible solution of the same value. ... For a point z ? Z, the orbit of z under the action of the group ? is the set of all elements of Z to

2008-01-01

407

Orbital Shape Representations.  

ERIC Educational Resources Information Center

Discusses the use of orbital shapes for instructional purposes, emphasizing that differences between polar, contour, and three-dimensional plots must be made clear to students or misconceptions will occur. Also presents three-dimensional contour surfaces for the seven 4f atomic orbitals of hydrogen and discusses their computer generation. (JN)

Kikuchi, Osamu; Suzuki, Keizo

1985-01-01

408

Analyzing Shuttle Orbiter Trajectories  

NASA Technical Reports Server (NTRS)

LRBET4 program best-estimated-of-trajectory (BET) calculation for post-flight trajectory analysis of Shuttle orbiter. Produces estimated measurements for comparing predicted and actual trajectory of Earth-orbiting spacecraft. Kalman filter and smoothing filter applied to input data to estimate state vector, reduce noise, and produce BET. LRBET4 written in FORTRAN IV for batch execution.

Lear, W. M.

1986-01-01

409

Fibrolipoma of the orbit.  

PubMed

Herein we present a retrospective case report of a very rare fibrolipoma originating in the orbit. Lipomas and related variants presenting in the orbit are very rare. Only 2 documented orbital fibrolipomas were noted in our review of literature. A 26-year-old woman presented with a growing mass below the left eyebrow 4 years after suffering facial trauma after being kicked in the face by a horse. CT demonstrated a hypodense nodule adherent to the orbital portion of the left frontal bone that was not encapsulated. An elective left anterior orbitotomy with excisional biopsy was performed, and fibrolipoma was confirmed on histopathologic examination. There was no evidence of tumor after 2-year follow up. The presence of a fibrolipoma in the periosteum of the orbital rim is very rare and might be a result of inflammatory transformation following facial trauma. PMID:23392312

Ali, Sana F; Farber, Martha; Meyer, Dale R

2013-01-01

410

Compare and contrast the reaction coordinate diagrams for chemical reactions and cytoskeletal force generators  

PubMed Central

Reaction coordinate diagrams are used to relate the free energy changes that occur during the progress of chemical processes to the rate and equilibrium constants of the process. Here I briefly review the application of these diagrams to the thermodynamics and kinetics of the generation of force and motion by cytoskeletal motors and polymer ratchets as they mediate intracellular transport, organelle dynamics, cell locomotion, and cell division. To provide a familiar biochemical context for discussing these subcellular force generators, I first review the application of reaction coordinate diagrams to the mechanisms of simple chemical and enzyme-catalyzed reactions. My description of reaction coordinate diagrams of motors and polymer ratchets is simplified relative to the rigorous biophysical treatment found in many of the references that I use and cite, but I hope that the essay provides a valuable qualitative representation of the physical chemical parameters that underlie the generation of force and motility at molecular scales. In any case, I have found that this approach represents a useful interdisciplinary framework for understanding, researching, and teaching the basic molecular mechanisms by which motors contribute to fundamental cell biological processes. PMID:23408787

Scholey, Jonathan M.

2013-01-01

411

Generalized Voronoi Diagrams for a Ladder: II. Efficient Construction of the Diagram  

Microsoft Academic Search

We present a collection of algorithms, all running in timeO(n\\u000a 2 logn ? (n)\\u000a o(?(n)3)) for some fixed integers(where ?(n) is the inverse Ackermann's function), for constructing a skeleton representation of a suitably generalized “Voronoi diagram”\\u000a for a ladder moving in a two-dimensional space bounded by polygonal barriers consisting ofn line segments. This diagram, which is a two-dimensional subcomplex of

Colm Ó'dúnlaing; Micha Sharir; Chee-keng Yap

1987-01-01

412

Natural Orbital Analysis of Ultrafast Multielectron Dynamics of Molecules  

NASA Astrophysics Data System (ADS)

The ionization dynamics of molecules in intense laser fields is investigated by using a time-dependent multiconfiguration theory for propagating the many-electron wave function in a grid space. We use the natural orbitals obtained from the many-electron wave function, i.e., the molecular orbitals obtained by diagonalizing the one-particle electron density matrix, to analyze the ionization process. We eliminate the ionizing portions of orbitals reaching the grid boundaries set far away from the nuclei; the occupation numbers of natural orbitals decrease due to ionization. The ionization probabilities of individual natural orbitals can be obtained from the accumulated reductions in occupation numbers. We also propose a new definition of molecular orbital energy in order to investigate the energetics of natural orbitals. It is shown that when energies are assigned to natural orbitals {{? }j(t)} as chemical potentials {bar{{? }}j(t)}, one can quantify a correction to the total electronic energy that represents electron correlation; that is, time-dependent correlation energy is introduced. Our attempt is illustrated by numerical results on the time-dependence of the spatial density and chemical potential for a H2 molecule interacting with an intense, near-infrared laser field. We compared the energy ? j (t) supplied by the applied field with the net energy gain ? bar{{? }}j(t) in the chemical potential for ? j (t) and found that energy accepting orbitals of ? bar{{? }}j(t) > {? }j(t) exhibit high ionization efficiency.

Kono, Hirohiko; Oyamada, Takayuki; Kato, Tsuyoshi; Koseki, Shiro

413

Photoelectron Spectra and Valence Shell Orbital Structures of Groups V and VI Hydrides  

Microsoft Academic Search

Photoelectron spectra are reported for the hydrides of group V and VI elements. Vibrational structure has been observed in bands associated with all but the inner-most valence orbitals. It has been used to obtain changes in bond angles or bond distances which result from the ionization of successive molecular orbitals. Ionization from the inner (1a1) orbitals of the hydrides has

A. W. Potts; W. C. Price

1972-01-01

414

Fingerprints of spin-orbital entanglement in transition metal oxides  

E-print Network

The concept of spin-orbital entanglement on superexchange bonds in transition metal oxides is introduced and explained on several examples. It is shown that spin-orbital entanglement in superexchange models destabilizes the long-range (spin and orbital) order and may lead either to a disordered spin-liquid state or to novel phases at low temperature which arise from strongly frustrated interactions. Such novel ground states cannot be described within the conventionally used mean field theory which separates spin and orbital degrees of freedom. Even in cases where the ground states are disentangled, spin-orbital entanglement occurs in excited states and may become crucial for a correct description of physical properties at finite temperature. As an important example of this behaviour we present spin-orbital entanglement in the $R$VO$_3$ perovskites, with $R$=La,Pr,...,Yb,Lu, where such finite temperature properties of these compounds can be understood only using entangled states: ($i$) thermal evolution of the optical spectral weights, ($ii$) the dependence of transition temperatures for the onset of orbital and magnetic order on the ionic radius in the phase diagram of the $R$VO$_3$ perovskites, and ($iii$) dimerization observed in the magnon spectra for the $C$-type antiferromagnetic phase of YVO$_3$. Finally, it is shown that joint spin-orbital excitations in an ordered phase with coexisting antiferromagnetic and alternating orbital order introduces topological constraints for the hole propagation and will thus radically modify transport properties in doped Mott insulators where hole motion implies simultaneous spin and orbital excitations.

Andrzej M. Ole?

2012-07-12

415

Ejs Orbiting Mass with Constant Force Model  

NSDL National Science Digital Library

The Ejs Orbiting Mass with Constant Force model displays the dynamics of an orbiting mass due to a constant force (a linear potential energy function). The simulation displays the motion of the mass as well as the effective potential energy. The initial conditions can be changed by dragging the mass or dragging the pink circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Orbiting Mass with Constant Force model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_constant.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-19

416

Orbit Stabilization of Nanosat  

SciTech Connect

An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.

JOHNSON,DAVID J.

1999-12-01

417

The geometry of on-shell diagrams  

NASA Astrophysics Data System (ADS)

The fundamental role of on-shell diagrams in quantum field theory has been recently recognized. On-shell diagrams, or equivalently bipartite graphs, provide a natural bridge connecting gauge theory to powerful mathematical structures such as the Grassmannian. We perform a detailed investigation of the combinatorial and geometric objects associated to these graphs. We mainly focus on their relation to polytopes and toric geometry, the Grassmannian and its stratification. Our work extends the current understanding of these connections along several important fronts, most notably eliminating restrictions imposed by planarity, positivity, reducibility and edge removability. We illustrate our ideas with several explicit examples and introduce concrete methods that considerably simplify computations. We consider it highly likely that the structures unveiled in this article will arise in the on-shell study of scattering amplitudes beyond the planar limit. Our results can be conversely regarded as an expansion in the understanding of the Grassmannian in terms of bipartite graphs.

Franco, Sebastián; Galloni, Daniele; Mariotti, Alberto

2014-08-01

418

More on phase diagram of Laponite  

E-print Network

The phase diagram of a charged colloidal system (Laponite) has been investigated by dynamic light scattering in a previously unexplored range of salt and clay concentrations. Specifically the clay weight and salt molar concentrations have been varied in the ranges Cw=0.004- 0.025, Cs=(1x 10^-3- 5x 10^-3) M respectively. As in the case of free salt water samples (Cs= 1x 10^-4 M) an aging dynamics towards two different arrested phases is found in the whole examined Cw and Cs range. Moreover a transition between these two different regimes is found for each investigated salt concentration. It is clear from these measurements that a revision of the phase diagram is necessary and a new "transition" line between two different arrested states is drawn.

B. Ruzicka; L. Zulian; G. Ruocco

2005-09-09

419

Modeling the Round Earth through Diagrams  

NASA Astrophysics Data System (ADS)

Earlier studies have found that students, including adults, have problems understanding the scientifically accepted model of the Sun-Earth-Moon system and explaining day-to-day astronomical phenomena based on it. We have been examining such problems in the context of recent research on visual-spatial reasoning. Working with middle school students in India, we have developed a pedagogical sequence to build the mental model of the Earth and tried it in three schools for socially and educationally disadvantaged students. This pedagogy was developed on the basis of (1) a reading of current research in imagery and visual-spatial reasoning and (2) students' difficulties identified during the course of pretests and interviews. Visual-spatial tools such as concrete (physical) models, gestures, and diagrams are used extensively in the teaching sequence. The building of a mental model is continually integrated with drawing inferences to understand and explain everyday phenomena. The focus of this article is inferences drawn with diagrams.

Padalkar, Shamin; Ramadas, Jayashree

420

Persistence diagrams of cortical surface data.  

PubMed

We present a novel framework for characterizing signals in images using techniques from computational algebraic topology. This technique is general enough for dealing with noisy multivariate data including geometric noise. The main tool is persistent homology which can be encoded in persistence diagrams. These diagrams visually show how the number of connected components of the sublevel sets of the signal changes. The use of local critical values of a function differs from the usual statistical parametric mapping framework, which mainly uses the mean signal in quantifying imaging data. Our proposed method uses all the local critical values in characterizing the signal and by doing so offers a completely new data reduction and analysis framework for quantifying the signal. As an illustration, we apply this method to a 1D simulated signal and 2D cortical thickness data. In case of the latter, extra homological structures are evident in an control group over the autistic group. PMID:19694279

Chung, Moo K; Bubenik, Peter; Kim, Peter T

2009-01-01

421

Equation of state and phase diagram of ammonia at high pressures from ab initio simulations.  

PubMed

We present an equation of state as well as a phase diagram of ammonia at high pressures and high temperatures derived from ab initio molecular dynamics simulations. The predicted phases of ammonia are characterized by analyzing diffusion coefficients and structural properties. Both the phase diagram and the subsequently computed Hugoniot curves are compared to experimental results. Furthermore, we discuss two methods that allow us to take into account nuclear quantum effects, which are of considerable importance in molecular fluids. Our data cover pressures up to 330 GPa and a temperature range from 500 K to 10,000 K. This regime is of great interest for interior models of the giant planets Uranus and Neptune, which contain, besides water and methane, significant amounts of ammonia. PMID:23802968

Bethkenhagen, Mandy; French, Martin; Redmer, Ronald

2013-06-21

422

Voronoi Diagrams for Pure 1-qubit Quantum States  

E-print Network

1-qubit quantum states form a space called the three-dimensional Bloch ball. To compute Holevo capacity, Voronoi diagrams in the Bloch ball with respect to the quantum divergence have been used as a powerful tool. These diagrams basically treat mixed quantum states corresponding to points in the interior of the Bloch ball. Due to the existence of logarithm in the quantum divergence, the diagrams are not defined on pure quantum states corresponding to points on the two-dimensional sphere. This paper first defines the Voronoi diagrams for pure quantum states on the Bloch sphere by the Fubini-Study distance and the Bures distance. We also introduce other Voronoi diagrams on the sphere obtained by taking a limit of Voronoi diagrams for mixed quantum states by the quantum divergences in the Bloch ball. These diagrams are shown to be equivalent to the ordinary Voronoi diagram on the sphere.

Kimikazu Kato; Mayumi Oto; Hiroshi Imai; Keiko Imai

2006-04-14

423

External Resource: What is orbit?  

NSDL National Science Digital Library

A 5-8 NASA Education reference answering the question, " What is orbit?" Topics include: satellite, ecliptic plane, perigee, apogee, escape velocity, geosynchronous, polar orbits, and low Earth orbit.

1900-01-01

424

Removal of orbital debris  

NASA Technical Reports Server (NTRS)

The several methods presently identified for the reduction of orbital debris populations are broadly classifiable as either preventive or remedial, and fall within distinctive operational regimes. For all particles, (1) in the 250-2000-km altitude band, intelligent sweepers may be used; (2) for large objects, in the 80-250-km altitude band, orbital decay renders removal impractical; (3) for the 250-750-km altitude band, deorbit devices should be used; (4) for 750-2500-km altitude, OMV rendezvous for propulsive deorbit package attachment is foreseeable; and beyond 2500 km, (5) propulsive escape from earth orbit is required.

Petro, Andrew J.; Talent, David L.

1989-01-01

425

Nontraumatic orbital hemorrhage.  

PubMed

Nontraumatic orbital hemorrhage (NTOH) is uncommon. I summarize the published reports of NTOH and offer a classification based on anatomic and etiologic factors. Anatomic patterns of NTOH include diffuse intraorbital hemorrhage, "encysted" hemorrhage (hematic cyst), subperiosteal hemorrhage, hemorrhage in relation to extraocular muscles, and hemorrhage in relation to orbital floor implants. Etiologic factors include vascular malformations and lesions, increased venous pressure, bleeding disorders, infection and inflammation, and neoplastic and nonneoplastic orbital lesions. The majority of NTOH patients can be managed conservatively, but some will have visual compromise and may require operative intervention. Some will suffer permanent visual loss, but a large majority have a good visual outcome. PMID:24359805

McNab, Alan A

2014-01-01

426

The phase diagram YF-GdF  

Microsoft Academic Search

The binary phase diagram YF-GdF was studied by differential scanning calorimetry (DSC). Yttrium fluoride and gadolinium fluoride show complete miscibility in all three phases (orthorhombic room temperature phase, trigonal or hexagonal high temperature phase, liquid). The transformations between room temperature and high temperature phases are of first order and occur at 1338.6 K (YF) or 1174.8 K (GdF). Melting points

D. Klimm; I. M. Ranieri; R. Bertram; S. L. Baldochi

2008-01-01

427

Communicating Phylogeny: Evolutionary Tree Diagrams in Museums  

E-print Network

History Museum 5 Address: University of Kansas, Lawrence, KS 66045-7593, USA 6 7 Second Author: E. O. Wiley 8 Institution: Ecology & Evolutionary Biology and Biodiversity Institute 9 Address: University of Kansas, Lawrence, KS 66045...IN PRESS (EVOLUTION: EDUCATION AND OUTREACH) 1 Title: Communicating Phylogeny: Evolutionary tree diagrams in museums 2 Running Head: Communicating Phylogeny 3 First Author: Teresa MacDonald 4 Institution: University of Kansas Natural...

MacDonald, Teresa; Wiley, Edward O.

2012-01-01

428

Displaying multimedia environmental partitioning by triangular diagrams  

SciTech Connect

It is suggested that equilateral triangular diagrams are a useful method of depicting the equilibrium partitioning of organic chemicals among the three primary environmental media of the atmosphere, the hydrosphere, and the organosphere (natural organic matter and biotic lipids and waxes). The technique is useful for grouping chemicals into classes according to their partitioning tendencies, for depicting the incremental effects of substituents such as alkyl groups and chlorine, and for showing how partitioning changes in response to changes in temperature.

Lee, S.C.; Mackay, D. [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry

1995-11-01

429

Using Diagrams and Models: 2.75  

NSDL National Science Digital Library

This article discusses the importance of abstraction and generalization in being able to use models and diagrams effectively, whether children are creating their own models to represent a situation and explain their thinking, or interpreting a provided model. The resource offers examples to illustrate these ideas as well as teaching strategies and activities in the areas of parity, mental addition, equivalent fractions, and multi-digit multiplication.

2012-09-26

430

Reentrant phase diagram for granular superconductors  

SciTech Connect

The mean-field phase diagram of the self-charging model of a granular superconductor is calculated using the functional-integral formulation. A pronounced reentrance is obtained in quantitative agreement with a previous calculation, involving 2..pi..-antiperiodic eigenstates of the Mathieu equation. It is argued that low-lying, odd-electron-number excitations play a significant role in the thermodynamics of Josephson-junction arrays, for which the Feynman functional-integral formulation holds.

Simanek, E.

1985-07-01

431

Stability diagrams for coupled Mathieu-equations  

Microsoft Academic Search

A method is described for determining stability diagrams for coupled Mathieu-equations. The boundary curves are found by searching for those almost-periodic solutions of the differential equations for which the real part of the characteristic exponent changes from zero to a non-zero value. The method derives analytic expressions for the involved determinants and is able to find the transition curves even

J. Hansen

1985-01-01

432

Mixed wasted integrated program: Logic diagram  

SciTech Connect

The Mixed Waste Integrated Program Logic Diagram was developed to provide technical alternative for mixed wastes projects for the Office of Technology Development`s Mixed Waste Integrated Program (MWIP). Technical solutions in the areas of characterization, treatment, and disposal were matched to a select number of US Department of Energy (DOE) treatability groups represented by waste streams found in the Mixed Waste Inventory Report (MWIR).

Mayberry, J.; Stelle, S. [Science Applications International Corp., Idaho Falls, ID (United States); O`Brien, M. [Univ. of Arizona, Tucson, AZ (United States); Rudin, M. [Univ. of Nevada, Las Vegas, NV (United States); Ferguson, J. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States); McFee, J. [I.T. Corp., Albuquerque, NM (United States)

1994-11-30

433

The plutonium-oxygen phase diagram  

SciTech Connect

Identification of products formed by the reaction of plutonium metal with liquid water at 23{degree}C indicates that the plutonium-oxygen phase diagram is similar to the cerium-oxygen and praseodymium-oxygen diagrams. Quantitative measurements of H{sub 2} formation and analytical data suggest that a sequence of hydrolysis reactions produces oxide hydrides of trivalent plutonium, Pu{sub 2}O{sub 3}, mixed-valent oxides and PuO{sub 2}. The intermediate oxides are the n {equals} 7, 9, 10 and 12 members of the Pu{sub n}O{sub 2n{minus}2} homologous series. Properties of the residue formed by thermal decomposition of the initial hydrolysis product, plutonium monoxide monhydride (PuOH), are consistent with the formation of metastable plutonium monoxide. Crystal-chemical, thermodynamic, and kinetic factors are evaluated, but definitive assignment of the equilibrium Pu-O diagram is not possible. 22 refs., 6 figs., 1 tab.

Haschke, J.M.

1990-01-01

434

Recognition and processing of logic diagrams  

NASA Astrophysics Data System (ADS)

In this paper we present a vision system that is capable of interpreting schematic logic diagrams, i.e. determine the output as a logic function of the inputs. The system is composed of a number of modules each designed to perform a specific subtask. Each module bears a minor contribution in the form of a new mixture of known algorithms or extensions to handle actual real life image imperfections which researchers tend to ignore when they develop their theoretical foundations. The main contribution, thus, is not in any individual module, it is rather in their integration to achieve the target job. The system is organized more or less in a classical fashion. Aside from the image acquisition and preprocessing modules, interesting modules include: the segmenter, the identifier, the connector and the grapher. A good segmentation output is one reason for the success of the presented system. Several novelties exist in the presented approach. Following segmentation the type of each logic gate is determined and its topological connectivity. The logic diagram is then transformed to a directed acyclic graph in which the final node is the output logic gate. The logic function is then determined by backtracking techniques. The system is not only aimed at recognition applications. In fact its main usage may be to target other processing applications such as storage compression and graphics modification and manipulation of the diagram as is explained.

Darwish, Ahmed M.; Bashandy, Ahmed R.

1996-03-01

435

Table of Feynman diagrams of the interacting Fermion Green's function  

NASA Astrophysics Data System (ADS)

The Feynman diagrams of the Green's function expansion of fermions interacting with a nonrelativistic 2-body interaction are displayed in first, second, and third perturbative order of the interaction as 2, 10, and 74 diagrams, respectively. A name convention for the diagrams is proposed and then used to tabulate the diagrams of fourth to seventh order. The Hartree-Fock approximation summons up 2, 8, 40, and 224 of them in first through fourth order.

Mathar, Richard J.

436

Algorithms in electric power system one-line diagram creation  

Microsoft Academic Search

This paper analyzes various algorithms for the automatic generation of electric power system one-line diagrams. Historically these one-line diagrams were created manually. As these diagrams can be large, their manual creation takes a lot of time and resources, and it is also prone to errors. One possible solution to this problem is the automatic generation of one-line diagrams. Automatic visualization

Imre Lendak; Aleksandar Erdeljan; Darko Capko; Srdan Vukmirovic

2010-01-01

437

Indicator diagram of a high pressure pump for cryogenic liquid  

Microsoft Academic Search

sure cycles. The indicator diagram provides a basis for deriving quantitative relationships between pump parameters. To this end we determined experimentally the indicator diagram of a series-produced pump type NZhA-.22M and developed a method of constructing a calculated indicator diagram. It is ,difficult to produce indicator diagrams for high-pressure pumps operating on liquefied gas: ordinary general purpose indicators are unsuitable

E. N. Smirnov; V. I. Epifanova

1969-01-01

438

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual libration point missions. This paper collects both published and unpublished results from four previous libration point missions (ISEE (International Sun-Earth Explorer) -3, SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and MAP (Microwave Anisotropy Probe)) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard range and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using seaboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN (Deep Space Network), missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

439

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual notation point missions. This paper collects both published and unpublished results from four previous notation point missions (ISEE-3, SOHO, ACE and MAP) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard marine and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using onboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN, missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

440

Voronoi Diagrams of Moving Points in the Plane  

Microsoft Academic Search

Consider a set of n points in the Euclidean plane each of which is continuously moving along a given trajectory. At each instant in time, the points define a Voronoi diagram. As the points move, the Voronoi diagram changes continuously, but at certain critical instants in time, topological events occur that cause a change in the Delaunay diagram. In this

Leonidas J. Guibas; Joseph S. B. Mitchell; Thomas Roos

1991-01-01

441

Symbolic Reasoning with Weighted and Normalized Decision Diagrams  

Microsoft Academic Search

Several variants of Bryant's ordered binary decision diagrams have been suggested in the literature to reason about discrete functions. In this paper, we introduce a generic notion of weighted decision diagrams that captures many of them and present criteria for canonic- ity. As a special instance of such weighted diagrams, we introduce a new BDD-variant for real-valued functions, called normalized

Jörn Ossowski; Christel Baier

2006-01-01

442

A vector diagram of Maxwell's equations for chiral media  

Microsoft Academic Search

A vector diagram of Maxwell's time-harmonic equations in homogeneous isotropic media is proposed and derived to include chiral media. This diagram may be used to obtain a number of common relationships between fields, potentials and sources by equating appropriate components of the vectors in it. The construction of the diagram is based on the formal similarity between many theorems of

S. Uckun

1998-01-01

443

Assessing the Comprehension of UML Class Diagrams via Eye Tracking  

Microsoft Academic Search

Eye-tracking equipment is used to assess how well a subject comprehends UML class diagrams. The results of a study are presented in which eye movements are captured in a non-obtrusive manner as users performed various comprehension tasks on UML class diagrams. The goal of the study is to identify specific characteristics of UML class diagrams, such as layout, color, and

Shehnaaz Yusuf; Huzefa H. Kagdi; Jonathan I. Maletic

2007-01-01

444

The Family Diagram and Genogram: Comparisons and Contrasts  

Microsoft Academic Search

The family diagram and its derivative the genogram are widely used in marriage and family therapy, other mental health disciplines, and family medicine. After a brief history of the origins of the family diagram and genogram, several different areas are compared in order to help distinguish differences between family diagrams and genograms. The results of these evaluations illustrate some similarities

John F. Butler

2008-01-01

445

The Classroom as Rhizome: New Strategies for Diagramming Knotted Interactions  

ERIC Educational Resources Information Center

This article calls attention to the unexamined role of diagrams in educational research and offers examples of alternative diagramming practices or tools that shed light on classroom interaction as a rhizomatic process. Drawing extensively on the work of Latour, Deleuze and Guattari, and Chatelet, this article explores the power of diagramming as…

de Freitas, Elizabeth

2012-01-01

446

Density-Enthalpy Phase Diagram 0D Boiler Simulation  

E-print Network

Density-Enthalpy Phase Diagram 0D Boiler Simulation Finite Element Method Further Research Finite Transitions #12;Density-Enthalpy Phase Diagram 0D Boiler Simulation Finite Element Method Further Research;Density-Enthalpy Phase Diagram 0D Boiler Simulation Finite Element Method Further Research Goal

Vuik, Kees

447

DARLS: Differencing and Merging Diagrams Using Dual View, Animation,  

E-print Network

DARLS: Differencing and Merging Diagrams Using Dual View, Animation, Re-Layout, Layers, Animation, Re-Layout, Layers and a Storyboard, short "DARLS". It is targeted at diagrams where node and edge. It presents the union of nodes and edges in figure 1. DARLS showing two versions of a diagram, which

Stürzlinger, Wolfgang

448

Dinosaur Extinction: Causal Loop Diagram of Earth Feedback System  

NSDL National Science Digital Library

This site features a causal loop diagram from system dynamics methodology showing the solar-earth-space energy flow system (the dominant flow system driving earth's surficial systems, including the biosphere) and interactive natural earthly processes that influence it. Also included is a discussion of the diagram, and a link to a page that explains how to read causal loop diagrams.

Mclean, Dewey M.; Tech, Virginia

449

Modelling network problems with power flow equations and diagrams  

Microsoft Academic Search

This paper focuses on the modelling of electrical utility networks, their problems and solutions in a network-planning environment. Equivalent single-line diagrams, vector diagrams and power flow diagrams are derived and used for each specific problem within a specific network

F. J. Rossouw; H. J. Beukes; J. H. R. Enslin

1999-01-01

450

Tethered orbital refueling study  

NASA Technical Reports Server (NTRS)

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazine. One alternative for fuel storage at the space station is a tethered orbital refueling facility (TORF), separated from the space station by a sufficient distance to induce a gravity gradient force that settles the stored fuels. The technical feasibility was examined with the primary focus on the refueling of LO2/LH2 orbital transfer vehicles. Also examined was the tethered facility on the space station. It was compared to a zero-gravity facility. A tethered refueling facility should be considered as a viable alternative to a zero-gravity facility if the zero-gravity fluid transfer technology, such as the propellant management device and no vent fill, proves to be difficult to develop with the required performance.

Fester, Dale A.; Rudolph, L. Kevin; Kiefel, Erlinda R.; Abbott, Peter W.; Grossrode, Pat

1986-01-01

451

Optical orbital debris spotter  

NASA Astrophysics Data System (ADS)

The number of man-made debris objects orbiting the Earth, or orbital debris, is alarmingly increasing, resulting in the increased probability of degradation, damage, or destruction of operating spacecraft. In part, small objects (<10 cm) in Low Earth Orbit (LEO) are of concern because they are abundant and difficult to track or even to detect on a routine basis. Due to the increasing debris population it is reasonable to assume that improved capabilities for on-orbit damage attribution, in addition to increased capabilities to detect and track small objects are needed. Here we present a sensor concept to detect small debris with sizes between approximately 1.0 and 0.01 cm in the vicinity of a host spacecraft for near real time damage attribution and characterization of dense debris fields and potentially to provide additional data to existing debris models.

Englert, Christoph R.; Bays, J. Timothy; Marr, Kenneth D.; Brown, Charles M.; Nicholas, Andrew C.; Finne, Theodore T.

2014-11-01

452

Orbiter entry aerothermodynamics  

NASA Technical Reports Server (NTRS)

The challenge in the definition of the entry aerothermodynamic environment arising from the challenge of a reliable and reusable Orbiter is reviewed in light of the existing technology. Select problems pertinent to the orbiter development are discussed with reference to comprehensive treatments. These problems include boundary layer transition, leeward-side heating, shock/shock interaction scaling, tile gap heating, and nonequilibrium effects such as surface catalysis. Sample measurements obtained from test flights of the Orbiter are presented with comparison to preflight expectations. Numerical and wind tunnel simulations gave efficient information for defining the entry environment and an adequate level of preflight confidence. The high quality flight data provide an opportunity to refine the operational capability of the orbiter and serve as a benchmark both for the development of aerothermodynamic technology and for use in meeting future entry heating challenges.

Ried, R. C.

1985-01-01

453

Imaging in orbital trauma  

PubMed Central

Orbital trauma is one of the most common reasons for ophthalmology specialty consultation in the emergency department setting. We survey the literature from 1990 to present to describe the role of computed tomography (CT), magnetic resonance imaging (MRI) and their associated angiography in some of the most commonly encountered orbital trauma conditions. CT orbit can often detect certain types of foreign bodies, lens dislocation, ruptured globe, choroidal or retinal detachments, or cavernous sinus thrombosis and thus complement a bedside ophthalmic exam that can sometimes be limited in the setting of trauma. CT remains the workhorse for acute orbital trauma owing to its rapidity and ability to delineate bony abnormalities; however MRI remains an important modality in special circumstances such as soft tissue assessment or with organic foreign bodies. PMID:23961028

Lin, Ken Y.; Ngai, Philip; Echegoyen, Julio C.; Tao, Jeremiah P.

2012-01-01

454

Mars parking orbit selection  

NASA Technical Reports Server (NTRS)

For a Mars mission, the selection of a parking orbit is greatly influenced by the precession caused by the oblateness of the planet. This affects the departure condition for earth return, and therefore, the mass required in LEO for a Mars mission. In this investigation, minimum LEO mass penalties were observed for parking orbits characterized by having near-equatorial inclinations, high eccentricities, and requiring a three-dimensional departure burn. However, because near-equatorial inclination orbits have poor planetary coverage characteristics, they are not desirable from a science viewpoint. To enhance these science requirements along with landing-site accessibility, a penalty in initial LEO mass is required. This study shows that this initial LEO mass penalty is reduced for orbits characterized with low to moderate eccentricities, nonequatorial inclinations, and a tangential periapsis arrival and departure burn.

Desai, Prasun N.; Braun, Robert D.

1990-01-01

455

Aerobraking orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

An aerobraking orbital transfer vehicle which includes an aerobraking device which also serves as a heat shield in the shape of a raked-off elliptic or circular cone with a circular or elliptical base, and with an ellipsoid or other blunt shape nose. The aerobraking device is fitted with a toroid-like skirt and is integral with the support structure of the propulsion system and other systems of the space vehicle. The vehicle is intended to be transported in components to a space station in lower earth orbit where it is assembled for use as a transportation system from low earth orbit to geosynchronous earth orbit and return. Conventional guidance means are included for autonomous flight.

Scott, Carl D. (Inventor); Nagy, Kornel (Inventor); Roberts, Barney B. (Inventor); Ried, Robert C. (Inventor); Kroll, Kenneth R. (Inventor); Gamble, Joe (Inventor)

1989-01-01

456

Altimetry, Orbits and Tides  

NASA Technical Reports Server (NTRS)

The nature of the orbit error and its effect on the sea surface heights calculated with satellite altimetry are explained. The elementary concepts of celestial mechanics required to follow a general discussion of the problem are included. Consideration of errors in the orbits of satellites with precisely repeating ground tracks (SEASAT, TOPEX, ERS-1, POSEIDON, amongst past and future altimeter satellites) are detailed. The theoretical conclusions are illustrated with the numerical results of computer simulations. The nature of the errors in this type of orbits is such that this error can be filtered out by using height differences along repeating (overlapping) passes. This makes them particularly valuable for the study and monitoring of changes in the sea surface, such as tides. Elements of tidal theory, showing how these principles can be combined with those pertinent to the orbit error to make direct maps of the tides using altimetry are presented.

Colombo, O. L.

1984-01-01

457

ARTEMIS Orbits Magnetic Moon  

NASA Video Gallery

NASA's THEMIS spacecraft have completed their mission and are still working perfectly, so NASA is re-directing the outermost two spacecraft to special orbits around the Moon. Now called ARTEMIS, th...

458

Habitability study shuttle orbiter  

NASA Technical Reports Server (NTRS)

Studies of the habitability of the space shuttle orbiter are briefly summarized. Selected illustrations and descriptions are presented for: crew compartment, hygiene facilities, food system and galley, and storage systems.

1972-01-01

459

Indian Mars Orbiter Mission  

NASA Astrophysics Data System (ADS)

The Mars Orbiter Mission (MOM) is the first interplanetary mission of India launched by Indian Polar Satellite Launch Vehicle (PSLV-XL) on 5 November 2013. It departed from Earth's orbit on Dec. 1, 2013, on its 300-days journey to Mars. MOM will reach Mars on Sept. 24, 2014. The orbit of MOM around Mars is highly elliptical with periapsis ~370 km and apoapsis ~80000 km, inclination 151 degree, and orbital period 3.15 sols. The spacecraft mass is 1350 kg, with dry mass of 500 kg and science payload mass of 14 kg. The spacecraft carries five science payloads, namely: Methane Sensor for Mars (MSM), Mars Colour Camera (MCC), Lyman Alpha Photometer (LAP), Mars Exospheric Neutral Composition Analyzer (MENCA), TIR Imaging Spectrometer (TIS). This paper will present the details of the instruments, observation plan, and expected science.

Bhardwaj, Anil

460

Orbital dynamics of the gravitational field of stringy black holes  

NASA Astrophysics Data System (ADS)

In this paper, we study the orbital dynamics of the gravitational field of stringy black holes by analyzing the effective potential and the phase plane diagram. By solving the equation of Lagrangian, the general relativistic equations of motion in the gravitational field of stringy black holes are given. It is easy to find that the motion of test particles depends on the energy and angular momentum of the test particles. Using the phase plane analysis method and combining the conditions of the stability, we discuss different types of the test particles' orbits in the gravitational field of stringy black holes. We get the innermost stable circular orbit which occurs at rmin = 5.47422 and when the angular momentum b ? 4.3887 the test particles will fall into the black hole.

Zhang, Yu; Geng, Jin-Ling; Li, En-Kun

2014-09-01

461

Pediatric Orbital Fractures  

PubMed Central

It is wise to recall the dictum “children are not small adults” when managing pediatric orbital fractures. In a child, the craniofacial skeleton undergoes significant changes in size, shape, and proportion as it grows into maturity. Accordingly, the craniomaxillofacial surgeon must select an appropriate treatment strategy that considers both the nature of the injury and the child's stage of growth. The following review will discuss the management of pediatric orbital fractures, with an emphasis on clinically oriented anatomy and development. PMID:24436730

Oppenheimer, Adam J.; Monson, Laura A.; Buchman, Steven R.

2013-01-01

462

Satellites Orbiting Earth  

NSDL National Science Digital Library

In recent years, there has been a push to better understand how Earth works as a system- how land, oceans, air, and life all interact. Satellites in orbit around Earth are a fast and efficient way of gathering remotely sensed data about the planet as a whole. This animated video shows the orbital paths of the satellites in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS), a collection of satellites that work together to study Earth on a wide scale.

463

Orbital Dirofilariasis: MR Findings  

Microsoft Academic Search

Summary: Dirofilariasis is a helminthic zoonosis occurring in many parts of the world. We report the findings in a 61- year-old woman who had painless right exophthalmos caused by orbital dirofilariasis. A vivid worm was embed- ded inside an inflammatory nodule in the right orbit. On T1-weighted MR images, the parasite was visible as a dis- crete, low-intensity, tubular signal

Reinhard Groell; Gerhard Ranner; Martin M. Uggowitzer; Hannes Braun

464

A tapestry of orbits  

SciTech Connect

In this book, the author describes how orbital research developed to yield a rich harvest of knowledge about the earth and its atmosphere. King-Hele relates a personal account of this research based on analysis of satellite orbits between 1957 and 1990 conducted from the Royal Aircraft Establishment in Farnborough England. The early research methods used before the launch of Sputnik in 1957 are discussed.

King-Hele, D.

1992-01-01

465

The Lunar Orbital Prospector  

NASA Technical Reports Server (NTRS)

The establishment of lunar bases will not end the need for remote sensing of the lunar surface by orbiting platforms. Human and robotic surface exploration will necessarily be limited to some proximate distance from the support base. Near real-time, high-resolution, global characterization of the lunar surface by orbiting sensing systems will continue to be essential to the understanding of the Moon's geophysical structure and the location of exploitable minerals and deposits of raw materials. The Lunar Orbital Prospector (LOP) is an orbiting sensing platform capable of supporting a variety of modular sensing packages. Serviced by a lunar-based shuttle, the LOP will permit the exchange of instrument packages to meet evolving mission needs. The ability to recover, modify, and rotate sensing packages allows their reuse in varying combinations. Combining this flexibility with robust orbit modification capabilities and near real-time telemetry links provides considerable system responsiveness. Maintenance and modification of the LOP orbit are accomplished through use of an onboard propulsion system that burns lunar-supplied oxygen and aluminum. The relatively low performance of such a system is more than compensated for by the elimination of the need for Earth-supplied propellants. The LOP concept envisions a continuous expansion of capability through the incorporation of new instrument technologies and the addition of platforms.

Redd, Frank J.; Cantrell, James N.; Mccurdy, Greg

1992-01-01

466

Two Body Orbits Model  

NSDL National Science Digital Library

The Two Body Orbits model for teachers shows the motion of two objects (binary star or moon-planet system) interacting via Newton's law of universal gravitation. It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter). An optional 3D view shows the celestial sphere and and the orbital plane (ecliptic). Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.   An important feature of the ready-to-run Two Body Orbits simulation is that it can be customized by teachers to meet various learning objectives. The teacher sets the ratio of the two masses, their initial positions and velocities, and various visualization and scale parameters. Documentation, such as an exercise or lesson, can be added to the simulation by entering a filename into the Customization dialog. Selecting the âstudentâ checkbox creates a ready-to-run package with the new configuration without the Customization dialog. The Two Body Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run Java archive. Double clicking the ejs_mech_orbits_TwoBodyOrbits.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is available in the OSP Collection.

Christian, Wolfgang