Synthesis, and structural characterization of mixed ligand copper(II) complexes of N,N,N‧,N'-tetramethylethylenediamine incorporating carboxylates

NASA Astrophysics Data System (ADS)

Batool, Syeda Shahzadi; Gilani, Syeda Rubina; Tahir, Muhammad Nawaz; Rüffer, Tobias

2017-11-01

Two ternary copper(II) complexes of N,N,N‧,N'-tetramethylethylenediamine (tmen = C6H16N2) with benzoic acid and p-aminobenzoic acid, having the formula [Cu(tmen)(BA)2(H2O)2] (1), and [Cu(tmen)(pABA)2]. 1/2 CH3OH (2) {(Where BA1- = benzoate1- (C6H5CO21-), pABA1- = p-aminobenzoate1- (p-H2NC6H5CO21-)} have been prepared and characterized by elemental combustion analysis, Uv-Visible spectroscopy, FT-IR spectroscopy, thermal, and single crystal X-ray diffraction analyses. The complex 1 is a monomer with distorted octahedral geometry. In its CuN2O4 chromophore, the Cu(II) centre is coordinated by two N atoms of a symmetrically chelating tmen ligand, by two carboxylate-O atoms from two monodentate benzoate1- anions, and by two apical aqua-O atoms, which define the distorted octahedral structure. The complex 2 is a monomer with a distorted square planar coordination geometry. In CuN2O2 chromophore, tmen is coordinated to Cu(II) ion in a chelating bidentate fashion, while the two p-aminobenzoate1- anions coordinate to Cu(II) centre through their carboxylate-O atoms in a monodentate manner, forming a square planar structure. The observed difference between asymmetric ѵas(OCO) and symmetric ѵs(OCO) stretching IR vibrations of the carboxylate moieties for 1 and 2 is 220 cm-1 and 232 cm-1, respectively, which suggests monodentate coordination mode (Δν OCO>200) of the carboxylate groups to Cu(II) ion. Thermogravimetric studies of 1 indicates removal of two water molecules at 171 °C, elimination of a tmen upto 529 °C and of two benzoate groups upto 931 °C. In tga curve of 2, methanol is lost upto 212 °C, while tmen is lost from 212 to 993 °C. The antibacterial activities of these new compounds against various bacterial strains were also investigated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexandrova, Anastassia N.; Nayhouse, Michael J.; Huynh, Mioy T.

CAl₄²-/- (D₄h, ¹A₁g) is is a cluster ion that has been established to be planar, aromatic, and contain a tetracoordinate planar C atom. Valence isoelectronic substitution of C with Si and Ge in this cluster leads to a radical change of structure toward distorted pentagonal species. We find that this structural change goes together with the cluster acquiring partial covalency of bonding between Si/Ge and Al₄, facilitated by hybridization of the atomic orbitals (AOs). Counter intuitively, for the AAl₄²-/- (A = C, Si, Ge) clusters, hybridization in the dopant atom is strengthened from C, to Si, and to Ge, evenmore » though typically AOs are more likely to hybridize if they are closer in energy (i.e. in earlier elements in the Periodic Table). The trend is explained by the better overlap of the hybrids of the heavier dopants with the orbitals of Al₄. From the thus understood trend, it is inferred that covalency in such clusters can be switched off, by varying the relative sizes of the AOs of the main element and the dopant. Using this mechanism, we then successfully killed covalency in Si, and predicted a new aromatic cluster ion containing a tetracoordinate square planar Si, SiIn₄²-/-.« less

A study of substrate-liquid crystal interaction

NASA Astrophysics Data System (ADS)

Zhang, Baoshe

This thesis concerns the study of substrate-liquid crystal interaction from two different angles. In one approach, we used the IPS (in-plane switching) technique to investigate the liquid crystal alignment by rubbed polyimide films. The IPS mode of liquid crystal cell operation is facilitated through comb electrodes capable of producing planar electric field. We have fabricated comb electrodes with a periodicity of 2 mum in order to confine the planar electric field close to the liquid crystal-substrate interface. Through optical transmittance measurements and comparison with theoretical predictions based on the Ladau-de Gennes formalism, we found the experimental data to be consistent with the physical picture of soft anchoring, in which the liquid crystal director at the substrate interface is rotated azimuthally under the planar electric field. As a result, we were able to obtain the azimuthal anchoring strength as a fitting parameter of the theory. This part of the thesis thus presents evidence(s) for director switching at the liquid crystal-substrate interface, as well as a method for measuring the azimuthal anchoring strength through optical means. In the second approach, we used nano-lithographic technique to fabricate textured two dimensional periodic patterns on silicon wafers, and examined the resulting liquid crystal alignment effect of such textured substrates. It was found that with decreasing periodicity, there exists an orientational transition from a state in which the liquid crystal alignment copies the substrate pattern at larger periodicity, to a state of uniform alignment at smaller periodicity. In our system, this transition occurs at a periodicity between 0.4 mum and 0.8 mum. Through theoretical simulations based on the model of competition between the elastic distortion energy and the interfacial anchoring potential, it was found that there is indeed a first-order abrupt transition when the periodicity is decreased. This is due to the fact that the elastic distortion energy scales as the inverse of the periodicity squared. Hence when the periodicity is decreased, the elastic distortion energy increases rapidly. At the critical periodicity the elastic distortion energy crosses the interfacial anchoring potential, below which the uniform alignment becomes the lower energy state. The uniform-aligned state was confirmed by the excellent theory-experiment agreement on spectral measurements, in conjunction with the optical microscope observations. In the uniform-aligned state, a large pretilt angle (35°) was obtained.

Crystal structure and Hirshfeld surface analysis of aqua-bis-(nicotinamide-κN)bis-(4-sulfamoylbenzoato-κO1)copper(II).

PubMed

Hökelek, Tuncer; Yavuz, Vijdan; Dal, Hakan; Necefoğlu, Hacali

2018-01-01

In the crystal of the title complex, [Cu(C 7 H 6 NO 4 S) 2 (C 6 H 6 N 2 O) 2 (H 2 O)], the Cu II cation and the O atom of the coordinated water mol-ecule reside on a twofold rotation axis. The Cu II ion is coordinated by two carboxyl-ate O atoms of the two symmetry-related 4-sulfamoylbenzoate (SB) anions and by two N atoms of the two symmetry-related nicotinamide (NA) mol-ecules at distances of 1.978 (2) and 2.025 (3) Å, respectively, forming a slightly distorted square-planar arrangement. The distorted square-pyramidal coordination environment is completed by the water O atom in the axial position at a distance of 2.147 (4) Å. In the crystal, the mol-ecules are linked via O-H⋯O and N-H⋯O hydrogen bonds with R 2 2 (8) and R 2 2 (18) ring motifs, forming a three-dimensional architecture. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯O/O⋯H (42.2%), H⋯H (25.7%) and H⋯C/C⋯H (20.0%) inter-actions.

Calculation of optical and K pre-edge absorption spectra for ferrous iron of distorted sites in oxide crystals

NASA Astrophysics Data System (ADS)

Vercamer, Vincent; Hunault, Myrtille O. J. Y.; Lelong, Gérald; Haverkort, Maurits W.; Calas, Georges; Arai, Yusuke; Hijiya, Hiroyuki; Paulatto, Lorenzo; Brouder, Christian; Arrio, Marie-Anne; Juhin, Amélie

2016-12-01

Advanced semiempirical calculations have been performed to compute simultaneously optical absorption and K pre-edge x-ray absorption spectra of Fe2 + in four distinct site symmetries found in minerals. The four symmetries, i.e., a distorted octahedron, a distorted tetrahedron, a square planar site, and a trigonal bipyramidal site, are representative of the Fe2 + sites found in crystals and glasses. A particular attention has been paid to the definition of the p -d hybridization Hamiltonian which occurs for noncentrosymmetric symmetries in order to account for electric dipole transitions. For the different sites under study, an excellent agreement between calculations and experiments was found for both optical and x-ray absorption spectra, in particular in terms of relative intensities and energy positions of electronic transitions. To our knowledge, these are the first calculations of optical absorption spectra on Fe2 + placed in such diverse site symmetries, including centrosymmetric sites. The proposed theoretical model should help to interpret the features of both the optical absorption and the K pre-edge absorption spectra of 3 d transition metal ions and to go beyond the usual fingerprint interpretation.

Synthesis of square-planar aluminum(III) complexes.

PubMed

Thompson, Emily J; Myers, Thomas W; Berben, Louise A

2014-12-15

The synthesis of two four-coordinate and square planar (SP) complexes of aluminum(III) is presented. Reaction of a phenyl-substituted bis(imino)pyridine ligand that is reduced by two electrons, Na2((Ph)I2P(2-)), with AlCl3 afforded five-coordinate [((Ph)I2P(2-))Al(THF)Cl] (1). Square-planar [((Ph)I2P(2-))AlCl] (2) was obtained by performing the same reaction in diethyl ether followed by lyphilization of 2 from benzene. The four-coordinate geometry index for 2, τ4, is 0.22, where 0 would be a perfectly square-planar molecule. The analogous aluminum hydride complex, [((Ph)I2P(2-))AlH] (3), is also square-planar, and was characterized crystallographically and has τ4=0.13. Both 2 and 3 are Lewis acidic and bind 2,6-lutidine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transition Metal d-Orbital Splitting Diagrams: An Updated Educational Resource for Square Planar Transition Metal Complexes

ERIC Educational Resources Information Center

Bo¨rgel, Jonas; Campbell, Michael G.; Ritter, Tobias

2016-01-01

The presentation of d-orbital splitting diagrams for square planar transition metal complexes in textbooks and educational materials is often inconsistent and therefore confusing for students. Here we provide a concise summary of the key features of orbital splitting diagrams for square planar complexes, which we propose may be used as an updated…

[1,2-Bis(diisopropyl­phosphan­yl)ethane-κ2 P,P′](carbonato-κ2 O,O′)nickel(II)

PubMed Central

Morales-Becerril, Illan; Flores-Alamo, Marcos; Garcia, Juventino J.

2013-01-01

In the crystal of the title compound, [Ni(CO3)(C14H32P2)], the metal center in each of three independent mol­ecules shows slight tetra­hedral distortion from ideal square-planar coordination geometry, with angles between the normals to the planes defined by the cis-P—Ni—P and cis-O—Ni—O fragments of 3.92 (17), 0.70 (16) and 2.17 (14)° in the three mol­ecules. In the crystal, there are inter­molecular C—H⋯O hydrogen bonds that show a laminar growth in the ab plane. PMID:23633999

Microwave background distortions from domain walls

NASA Technical Reports Server (NTRS)

Goetz, Guenter; Noetzold, Dirk

1990-01-01

Domain walls arising in a cosmic phase transition after decoupling were recently proposed as seeds for the formation of large scale structure. The distortion induced in the microwave background radiation is calculated in dependence of the wall thickness, surface density, scalar field potential, cosmic redshift and the velocity of the wall. It was found that the maximal redshift distortion for both spherical and planar walls is of the order pi G sigma H(sup -1)(sub 0), where sigma is the surface energy density and H(sup -1)(sub 0) the Hubble parameter. It was also found that, for a wall thickness smaller than the horizon, walls can be treated as infinitely thin, i.e., the redshift distortion is independent of the wall thickness and the specific form of the scalar potential. For planar walls moving with a Lorentz-factor gamma the redshift distortion is enhanced by gamma cubed.

Organic light-emitting diodes from homoleptic square planar complexes

DOEpatents

Omary, Mohammad A

2013-11-12

Homoleptic square planar complexes [M(N.LAMBDA.N).sub.2], wherein two identical N.LAMBDA.N bidentate anionic ligands are coordinated to the M(II) metal center, including bidentate square planar complexes of triazolates, possess optical and electrical properties that make them useful for a wide variety of optical and electrical devices and applications. In particular, the complexes are useful for obtaining white or monochromatic organic light-emitting diodes ("OLEDs"). Improved white organic light emitting diode ("WOLED") designs have improved efficacy and/or color stability at high brightness in single- or two-emitter white or monochrome OLEDs that utilize homoleptic square planar complexes, including bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) ("Pt(ptp).sub.2").

Crystal structure and Hirshfeld surface analysis of aqua­bis­(nicotinamide-κN)bis­(4-sulfamoylbenzoato-κO 1)copper(II)

PubMed Central

Hökelek, Tuncer; Yavuz, Vijdan; Dal, Hakan; Necefoğlu, Hacali

2018-01-01

In the crystal of the title complex, [Cu(C7H6NO4S)2(C6H6N2O)2(H2O)], the CuII cation and the O atom of the coordinated water mol­ecule reside on a twofold rotation axis. The CuII ion is coordinated by two carboxyl­ate O atoms of the two symmetry-related 4-sulfamoylbenzoate (SB) anions and by two N atoms of the two symmetry-related nicotinamide (NA) mol­ecules at distances of 1.978 (2) and 2.025 (3) Å, respectively, forming a slightly distorted square-planar arrangement. The distorted square-pyramidal coordination environment is completed by the water O atom in the axial position at a distance of 2.147 (4) Å. In the crystal, the mol­ecules are linked via O—H⋯O and N—H⋯O hydrogen bonds with R 2 2(8) and R 2 2(18) ring motifs, forming a three-dimensional architecture. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯O/O⋯H (42.2%), H⋯H (25.7%) and H⋯C/C⋯H (20.0%) inter­actions. PMID:29416889

Synthesis and molecular structure of [Cu(NH3)4][Ni(CN)4]: A missing piece in the [Cu(NH3)n][Ni(CN)4] story

NASA Astrophysics Data System (ADS)

Solanki, Dina; Hogarth, Graeme

2015-11-01

Reaction of CuCl2·2H2O and K2[Ni(CN)4]·2H2O in aqueous ammonia gave blue rod-like crystals of [Cu(NH3)4][Ni(CN)4]. An X-ray crystallographic reveals that square-planar anions and cations are weakly associated through coordination of a cis pair of cyanide ligands to copper, with one short and one long contact and thus the copper centre is best described as a square-based pyramid. Crystals lose ammonia readily upon removal from the solvent and this has been probed by TGA and DSC measurements. For comparison we have also re-determined the structure of the related ethylenediamine (en) complex [Cu(en)2][Ni(CN)4] at 150 K. This consists of a 1D chain in which a trans pair of cyanide ligands bind to copper such that the latter has an overall tetragonally distorted octahedral coordination geometry.

Synthesis, spectroscopic characterization, first order nonlinear optical properties and DFT calculations of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with 1,3-diphenyl-4-phenylazo-5-pyrazolone ligand

NASA Astrophysics Data System (ADS)

Abdel-Latif, Samir A.; Mohamed, Adel A.

2018-02-01

Novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions with 1,3-diphenyl-4-phenylazo-5-pyrazolone (L) have been prepared and characterized using different analytical and spectroscopic techniques. 1:1 Complexes of Mn(II), Co(II) and Zn(II) are distorted octahedral whereas Ni(II) complex is square planar and Cu(II) is distorted trigonal bipyramid. 1:2 Complexes of Mn(II), Co(II), Cu(II) and Zn(II) are distorted trigonal bipyramid whereas Ni(II) complex is distorted tetrahedral. All complexes behave as non-ionic in dimethyl formamide (DMF). The electronic structure and nonlinear optical parameters (NLO) of the complexes were investigated theoretically at the B3LYP/GEN level of theory. Molecular stability and bond strengths have been investigated by applying natural bond orbital (NBO) analysis. The geometries of the studied complexes are non-planner. DFT calculations have been also carried out to calculate the global properties; hardness (η), global softness (S) and electronegativity (χ). The calculated small energy gap between HOMO and LUMO energies shows that the charge transfer occurs within the complexes. The total static dipole moment (μtot), the mean polarizability (<α>), the anisotropy of the polarizability (Δα) and the mean first-order hyperpolarizability (<β>) were calculated and compared with urea as a reference material. The complexes show implying optical properties.

Low-spin manganese(II) and high-spin manganese(III) complexes derived from disalicylaldehyde oxaloyldihydrazone: Synthesis, spectral characterization and electrochemical studies

NASA Astrophysics Data System (ADS)

Syiemlieh, Ibanphylla; Kumar, Arvind; Kurbah, Sunshine D.; De, Arjune K.; Lal, Ram A.

2018-01-01

Low-spin manganese(II) complexes [MnII(H2slox)].H2O (1), [MnII(H2slox)(SL)] (where SL (secondary ligand) = pyridine (py, 2), 2-picoline (2-pic, 3), 3-picoline (3-pic, 4), and 4-picoline (4-pic, 5) and high-spin manganese(III) complex Na(H2O)4[MnIII(slox)(H2O)2].2.5H2O have been synthesized from disalicyaldehyde oxaloyldihydrazone in methanolic - water medium. The composition of complexes has been established by elemental analyses and thermoanalytical data. The structures of the complexes have been discussed on the basis of data obtained from molar conductance, UV visible, 1H NMR, infrared spectra, magnetic moment and electron paramagnetic resonance spectroscopic studies. Conductivity measurements in DMF suggest that the complexes (1-5) are non-electrolyte while the complex (6) is 1:1 electrolyte. The electronic spectral studies and magnetic moment data suggest five - coordinate square pyramidal structure for the complexes (2-5) and square planar geometry for manganese(II) in complex (1). In complex (6), both sodium and manganese(III) have six coordinate octahedral geometry. IR spectral studies reveal that the dihydrazone coordinates to the manganese centre in keto form in complexes (1-5) and in enol form in complex (6). In all complexes, the ligand is present in anti-cis configuration. Magnetic moment and EPR studies indicate manganese in +2 oxidation state in complexes (1-5), with low-spin square planar complex (1) and square pyramidal stereochemistries complexes (2-5) while in +3 oxidation state in high-spin distorted octahedral stereochemistry in complex (6). The complex (1) involves significant metal - metal interaction in the solid state. All of the complexes show only one metal centred electron transfer reaction in DMF solution in cyclic voltammetric studies. The complexes (1-5) involve MnII→MnI redox reaction while the complex (6) involves MnIII→MnII redox reaction, respectively.

Reconsidering the advantages of the three-dimensional representation of the interferometric transform for imaging with non-coplanar baselines and wide fields of view

NASA Astrophysics Data System (ADS)

Smith, D. M. P.; Young, A.; Davidson, D. B.

2017-07-01

Radio telescopes with baselines that span thousands of kilometres and with fields of view that span tens of degrees have been recently deployed, such as the Low Frequency Array, and are currently being developed, such as the Square Kilometre Array. Additionally, there are proposals for space-based instruments with all-sky imaging capabilities, such as the Orbiting Low Frequency Array. Such telescopes produce observations with three-dimensional visibility distributions and curved image domains. In most work to date, the visibility distribution has been converted to a planar form to compute the brightness map using a two-dimensional Fourier transform. The celestial sphere is faceted in order to counter pixel distortion at wide angles, with each such facet requiring a unique planar form of the visibility distribution. Under the above conditions, the computational and storage complexities of this approach can become excessive. On the other hand, when using the direct Fourier transform approach, which maintains the three-dimensional shapes of the visibility distribution and celestial sphere, the non-coplanar visibility component requires no special attention. Furthermore, as the celestial samples are placed directly on the curved surface of the celestial sphere, pixel distortion at wide angles is avoided. In this paper, a number of examples illustrate that under these conditions (very long baselines and very wide fields of view) the costs of the direct Fourier transform may be comparable to (or even lower than) methods that utilise the two-dimensional fast Fourier transform.

Synthesis and Characterization of Dimethylbis(2-pyridyl)borate Nickel(II) Complexes: Unimolecular Square-Planar to Square-Planar Rotation around Nickel(II)

PubMed Central

2015-01-01

The syntheses of novel dimethylbis(2-pyridyl)borate nickel(II) complexes 4 and 6 are reported. These complexes were unambiguously characterized by X-ray analysis. In dichloromethane solvent, complex 4 undergoes a unique square-planar to square-planar rotation around the nickel(II) center, for which activation parameters of ΔH⧧ = 12.2(1) kcal mol–1 and ΔS⧧ = 0.8(5) eu were measured via NMR inversion recovery experiments. Complex 4 was also observed to isomerize via a relatively slow ring flip: ΔH⧧ = 15.0(2) kcal mol–1; and ΔS⧧ = −4.2(7) eu. DFT studies support the experimentally measured rotation activation energy (cf. calculated ΔH⧧ = 11.1 kcal mol–1) as well as the presence of a high-energy triplet intermediate (ΔH = 8.8 kcal mol–1). PMID:24882919

Crystal structure of (pyridine-κN)bis(quinolin-2-olato-κ2 N,O)copper(II) monohydrate

PubMed Central

Hawks, Benjamin; Yan, Jingjing; Basa, Prem; Burdette, Shawn

2015-01-01

The title complex, [Cu(C9H6NO)2(C5H4N)]·H2O, adopts a slightly distorted square-pyramidal geometry in which the axial pyridine ligand exhibits a long Cu—N bond of 2.305 (3) Å. The pyridine ligand forms dihedral angles of 79.5 (5) and 88.0 (1)° with the planes of the two quinolin-2-olate ligands, while the dihedral angle between the quinoline groups of 9.0 (3)° indicates near planarity. The water mol­ecule connects adjacent copper complexes through O—H⋯O hydrogen bonds to phenolate O atoms, forming a network inter­connecting all the complexes in the crystal lattice. PMID:25878845

Synthesis and characterization of a novel schiff base of 1,2-diaminopropane with substituted salicyaldehyde and its transition metal complexes: Single crystal structures and biological activities

NASA Astrophysics Data System (ADS)

Tadavi, Samina K.; Yadav, Abhijit A.; Bendre, Ratnamala S.

2018-01-01

A novel schiff base H2L derived from simple condensation of 2-hydroxy-6-isopropyl-3-methyl benzaldehyde and 1,2-diaminopropane in 2:1 M ratio and its [MnL], [CoL] and [NiL]2 complexes have been prepared and characterized by spectroscopic technique, elemental analysis, SEM-EDX analysis, and cyclic voltammetry. Additionally, single crystal X-ray diffraction technique has been applied to the schiff base ligand H2L and its nickel complex. The structure of nickel complex exhibited dimeric form with formula [NiL]2 with distorted square planar geometry around each nickel center. Furthermore, all the synthesized compounds were screened for their antimicrobial and antioxidant and DNA cleavage activities.

Di­chlorido­[N-(N,N-di­methyl­carbamimido­yl)-N′,N′,4-tri­methyl­benzohydrazonamide]­platinum(II) nitro­methane hemisolvate

PubMed Central

Bolotin, Dmitrii S.; Bokach, Nadezha A.; Haukka, Matti

2014-01-01

In the title compound, [PtCl2(C13H21N5)]·0.5CH3NO2, the PtII atom is coordinated in a slightly distorted square-planar geometry by two Cl atoms and two N atoms of the bidentate ligand. The (1,3,5-tri­aza­penta­diene)PtII metalla ring is slightly bent and does not conjugate with the aromatic ring. In the crystal, N—H⋯Cl hydrogen bonds link the complex mol­ecules, forming chains along [001]. The nitromethane solvent molecule shows half-occupancy and is disordered over two sets of sites about an inversion centre. PMID:24826095

Structural characterization and antioxidant properties of Cu(II) and Ni(II) complexes derived from dicyandiamide

NASA Astrophysics Data System (ADS)

Kertmen, Seda Nur; Gonul, Ilyas; Kose, Muhammet

2018-01-01

New Cu(II) and Ni(II) complexes derived from dicyandiamide were synthesized and characterised by spectroscopic and analytical methods. Molecular structures of the complexes were determined by single crystal X-ray diffraction studies. In the complexes, the Cu(II) or Ni(II) ions are four-coordinate with a slight distorted square planar geometry. The ligands (L-nPen and L-iPen) derived from dicyandiamide formed via nucleophilic addition of alcohol solvent molecule in the presence Cu(II) or Ni(II) ions. Complexes were stabilised by intricate array of hydrogen bonding interactions. Antioxidant activity of the complexes was evaluated by DPPH radical scavenging and CUPRAC methods. The complexes exhibit antioxidant activity, however, their activities were much lower than standard antioxidants (Vitamin C and trolox).

Synthesis and crystal structure of the rhodium(I) cyclooctadiene complex with bis(3-tert-butylimidazol-2-ylidene)borate ligand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, F.; Shao, K.-J.; Xiao, Y.-C.

2015-12-15

The rhodium(I) cyclooctadiene complex with the bis(3-tert-butylimidazol-2-ylidene)borate ligand [H{sub 2}B(Im{sup t}Bu){sup 2}]Rh(COD) C{sup 22}H{sup 36}BN{sup 4}Rh, has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal center, which is coordinated by the bidentate H{sup 2}B(Im{sup t}Bu){sub 2} and one cyclooctadiene group. The Rh–C{sub carbene} bond lengths are 2.043(4) and 2.074(4) Å, and the bond angle C–Rh1–C is 82.59°. The dihedral angle between two imidazol-2-ylidene rings is 67.30°.

Analysis of tractable distortion metrics for EEG compression applications.

PubMed

Bazán-Prieto, Carlos; Blanco-Velasco, Manuel; Cárdenas-Barrera, Julián; Cruz-Roldán, Fernando

2012-07-01

Coding distortion in lossy electroencephalographic (EEG) signal compression methods is evaluated through tractable objective criteria. The percentage root-mean-square difference, which is a global and relative indicator of the quality held by reconstructed waveforms, is the most widely used criterion. However, this parameter does not ensure compliance with clinical standard guidelines that specify limits to allowable noise in EEG recordings. As a result, expert clinicians may have difficulties interpreting the resulting distortion of the EEG for a given value of this parameter. Conversely, the root-mean-square error is an alternative criterion that quantifies distortion in understandable units. In this paper, we demonstrate that the root-mean-square error is better suited to control and to assess the distortion introduced by compression methods. The experiments conducted in this paper show that the use of the root-mean-square error as target parameter in EEG compression allows both clinicians and scientists to infer whether coding error is clinically acceptable or not at no cost for the compression ratio.

Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function.

PubMed

Campbell-Washburn, Adrienne E; Xue, Hui; Lederman, Robert J; Faranesh, Anthony Z; Hansen, Michael S

2016-06-01

MRI-guided interventions demand high frame rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real time to interactively deblur spiral images. Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF-predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF-predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 min of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. This real-time distortion correction framework will enable the use of these high frame rate imaging methods for MRI-guided interventions. Magn Reson Med 75:2278-2285, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function

PubMed Central

Campbell-Washburn, Adrienne E; Xue, Hui; Lederman, Robert J; Faranesh, Anthony Z; Hansen, Michael S

2015-01-01

Purpose MRI-guided interventions demand high frame-rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Methods Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real-time to interactively de-blur spiral images. Results Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 minutes of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. Conclusions This real-time distortion correction framework will enable the use of these high frame-rate imaging methods for MRI-guided interventions. PMID:26114951

Wetting of cholesteric liquid crystals.

PubMed

Silvestre, Nuno M; Figueirinhas Pereira, Maria Carolina; Bernardino, Nelson R; Telo da Gama, Margarida M

2016-02-01

We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted, the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal.

Pseudo Jahn-Teller effect in control and rationalization of chemical transformations in two-dimensional compounds

NASA Astrophysics Data System (ADS)

Gorinchoy, N. N.; Bersuker, I. B.

2017-05-01

We show that the pseudo Jahn-Teller effect (PJTE) is instrumental in predicting and rationalizing structural changes in chemical transformations of two-dimensional (2D) molecular systems by means of analyzing the symmetries and electron occupation of the ground and lowest excited electronic states and the energy gap between them, subject to their PJT coupling along the main distortion coordinates. Special attention is paid to rationalizing the PJTE origin of non-planarity of 2D compounds and to the restoration of their planar configurations. Examples of two series of 1,2- and 1,4-dithiin containing tricyclic compounds (carbon sulfide, thianthrene, and antracene and their derivatives) are used to demonstrate in detail the mechanism of (1) enhancement and suppression of the PJTE distortions (puckering) in redox processes, and (2) PJTE induced symmetry breaking and restoration of the planar configuration by chemical substitutions.

Computer controlled performance mapping of thermionic converters: effect of collector, guard-ring potential imbalances on the observed collector current-density, voltage characteristics and limited range performance map of an etched-rhenium, niobium planar converter

NASA Technical Reports Server (NTRS)

Manista, E. J.

1972-01-01

The effect of collector, guard-ring potential imbalance on the observed collector-current-density J, collector-to-emitter voltage V characteristic was evaluated in a planar, fixed-space, guard-ringed thermionic converter. The J,V characteristic was swept in a period of 15 msec by a variable load. A computerized data acquisition system recorded test parameters. The results indicate minimal distortion of the J,V curve in the power output quadrant for the nominal guard-ring circuit configuration. Considerable distortion, along with a lowering of the ignited-mode striking voltage, was observed for the configuration with the emitter shorted to the guard ring. A limited-range performance map of an etched-rhenium, niobium, planar converter was obtained by using an improved computer program for the data acquisition system.

Spectral, biological screening of metal chelates of chalcone based Schiff bases of N-(3-aminopropyl) imidazole.

PubMed

Kalanithi, M; Rajarajan, M; Tharmaraj, P; Sheela, C D

2012-02-15

Tridentate chelate complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the chalcone based ligands 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol(HL(1)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-p-tolylallyl]phenol(HL(2)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol(HL(3)). Microanalytical data, UV-vis spectrophotometric method, magnetic susceptibility measurements, IR, 1H NMR, Mass, and EPR techniques were used to characterize the structure of chelates. The electronic absorption spectra and magnetic susceptibility measurements suggest a distorted square planar geometry for the copper(II) ion. The other metal complexes show distorted tetrahedral geometry. The coordination of the ligands with metal(II) ions was further confirmed by solution fluorescence spectrum. The antimicrobial activity of the ligands and metal(II) complexes against the species Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albigans and Aspergillus niger has been carried out and compared. The electrochemical behavior of copper(II) complex is studied by cyclic voltammetry. Copyright © 2011 Elsevier B.V. All rights reserved.

Real time characterization of hydrodynamics in optically trapped networks of micro-particles.

PubMed

Curran, Arran; Yao, Alison M; Gibson, Graham M; Bowman, Richard; Cooper, Jon M; Padgett, Miles L

2010-04-01

The hydrodynamic interactions of micro-silica spheres trapped in a variety of networks using holographic optical tweezers are measured and characterized in terms of their predicted eigenmodes. The characteristic eigenmodes of the networks are distinguishable within 20-40 seconds of acquisition time. Three different multi-particle networks are considered; an eight-particle linear chain, a nine-particle square grid and, finally, an eight-particle ring. The eigenmodes and their decay rates are shown to behave as predicted by the Oseen tensor and the Langevin equation, respectively. Finally, we demonstrate the potential of using our micro-ring as a non-invasive sensor to the local environmental viscosity, by showing the distortion of the eigenmode spectrum due to the proximity of a planar boundary. ((c) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

A plane wave source with minimal harmonic distortion for investigating nonlinear acoustic properties

PubMed Central

Lloyd, Christopher W.; Wallace, Kirk D.; Holland, Mark R.; Miller, James G.

2008-01-01

The objective of this investigation is to introduce and validate a practical ultrasound source to be used in the investigation of the nonlinear material properties of liquids and soft tissues studied in vitro. Methods based on the progressive distortion of finite amplitude ultrasonic waves in the low megahertz frequency-range are most easily implemented under the assumption of plane wave propagation. However, achieving an approximately planar ultrasonic field over substantial propagation distances can be challenging. Furthermore, undesired harmonic distortion of the ultrasonic field prior to insonification of the specified region of interest represents another serious limitation. This paper introduces an approach based on the use of the ultrasonic field emanating from a stainless-steel delay line. Both simulation and direct experimental measurement demonstrate that such a field exhibits relatively planar wavefronts to a good approximation (such that a 3 mm diameter receiver would be exposed to no more than 3 dB of loss across its face) and is free from the significant harmonic distortion that would occur in a conventional water path. PMID:17614467

Comparison of DWI Methods in the Pediatric Brain: PROPELLER Turbo Spin-Echo Imaging Versus Readout-Segmented Echo-Planar Imaging Versus Single-Shot Echo-Planar Imaging.

PubMed

Kim, Tae-Hyung; Baek, Moon-Young; Park, Ji Eun; Ryu, Young Jin; Cheon, Jung-Eun; Kim, In-One; Choi, Young Hun

2018-06-01

The purpose of this study is to compare DWI for pediatric brain evaluation using single-shot echo-planar imaging (EPI), periodically rotated overlapping parallel lines with enhanced reconstruction (Blade), and readout-segmented EPI (Resolve). Blade, Resolve, and single-shot EPI were performed for 27 pediatric patients (median age, 9 years), and three datasets were independently reviewed by two radiologists. Qualitative analyses were performed for perceptive coarseness, image distortion, susceptibility-related changes, motion artifacts, and lesion conspicuity using a 5-point Likert scale. Quantitative analyses were conducted for spatial distortion and signal uniformity of each sequence. Mean scores were 2.13, 3.17, and 3.76 for perceptive coarseness; 4.85, 3.96, and 2.19 for image distortion; 4.76, 3.96, and 2.30 for susceptibility-related change; 4.96, 3.83, and 4.69 for motion artifacts; and 2.71, 3.75, and 1.92 for lesion conspicuity, for Blade, Resolve, and single-shot EPI, respectively. Blade and Resolve showed better quality than did single-shot EPI for image distortion, susceptibility-related changes, and lesion conspicuity. Blade showed less image distortion, fewer susceptibility-related changes, and fewer motion artifacts than did Resolve, whereas lesion conspicuity was better with Resolve. Blade showed increased signal variation compared with Resolve and single-shot EPI (coefficients of variation were 0.10, 0.08, and 0.05 for lateral ventricle; 0.13, 0.09, and 0.05 for centrum semiovale; and 0.16, 0.09, and 0.06 for pons in Blade, Resolve, and single-shot EPI, respectively). DWI with Resolve or Blade yields better quality regarding distortion, susceptibility-related changes, and lesion conspicuity, compared with single-shot EPI. Blade is less susceptible to motion artifacts than is Resolve, whereas Resolve yields less noise and better lesion conspicuity than does Blade.

Array feed synthesis for correction of reflector distortion and Vernier Beamsteering

NASA Technical Reports Server (NTRS)

Blank, S. J.; Imbriale, W. A.

1986-01-01

An algorithmic procedure for the synthesis of planar array feeds for paraboloidal reflectors is described which simultaneously provides electronic correction of systematic reflector surface distortions as well as a Vernier electronic beamsteering capability. Simple rules of thumb for the optimum choice of planar array feed configuration (i.e., number and type of elements) are derived from a parametric study made using the synthesis procedure. A number of f/D ratios and distortion models were examined that are typical of large paraboloidal reflectors. Numerical results are presented showing that, for the range of distortion models considered, good on-axis gain restoration can be achieved with as few as seven elements. For beamsteering to +/- 1 beamwidth (BW), 19 elements are required. For arrays with either 7 or 19 elements, the results indicate that the use of high-aperture-efficiency elements (e.g., disk-on-rod and short backfire) in the array yields higher system gain than can be obtained with elements having lower aperture efficiency (e.g., open-ended waveguides). With 37 elements, excellent gain and beamsteering performance to +/- 1.5 BW are obtained independent of the assumed effective aperture of the array element. An approximate expression is derived for the focal-plane field distribution of the distorted reflector. Contour plots of the focal-plane fields are also presented for various distortion and beam scan angle cases. The results obtained show the effectiveness of the array feed approach.

Sterically Hindered Square-Planar Nickel(II) Organometallic Complexes: Preparation, Characterization, and Substitution Behavior

ERIC Educational Resources Information Center

Martinez, Manuel; Muller, Guillermo; Rocamora, Merce; Rodriguez, Carlos

2007-01-01

The series of experiments proposed for advanced undergraduate students deal with both standard organometallic preparative methods in dry anaerobic conditions and with a kinetic study of the mechanisms operating in the substitution of square-planar complexes. The preparation of organometallic compounds is carried out by transmetallation or…

Geometric distortion correction in prostate diffusion-weighted MRI and its effect on quantitative apparent diffusion coefficient analysis.

PubMed

Nketiah, Gabriel; Selnaes, Kirsten M; Sandsmark, Elise; Teruel, Jose R; Krüger-Stokke, Brage; Bertilsson, Helena; Bathen, Tone F; Elschot, Mattijs

2018-05-01

To evaluate the effect of correction for B 0 inhomogeneity-induced geometric distortion in echo-planar diffusion-weighted imaging on quantitative apparent diffusion coefficient (ADC) analysis in multiparametric prostate MRI. Geometric distortion correction was performed in echo-planar diffusion-weighted images (b = 0, 50, 400, 800 s/mm 2 ) of 28 patients, using two b 0 scans with opposing phase-encoding polarities. Histology-matched tumor and healthy tissue volumes of interest delineated on T 2 -weighted images were mapped to the nondistortion-corrected and distortion-corrected data sets by resampling with and without spatial coregistration. The ADC values were calculated on the volume and voxel level. The effect of distortion correction on ADC quantification and tissue classification was evaluated using linear-mixed models and logistic regression, respectively. Without coregistration, the absolute differences in tumor ADC (range: 0.0002-0.189 mm 2 /s×10 -3 (volume level); 0.014-0.493 mm 2 /s×10 -3 (voxel level)) between the nondistortion-corrected and distortion-corrected were significantly associated (P < 0.05) with distortion distance (mean: 1.4 ± 1.3 mm; range: 0.3-5.3 mm). No significant associations were found upon coregistration; however, in patients with high rectal gas residue, distortion correction resulted in improved spatial representation and significantly better classification of healthy versus tumor voxels (P < 0.05). Geometric distortion correction in DWI could improve quantitative ADC analysis in multiparametric prostate MRI. Magn Reson Med 79:2524-2532, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Four-Coordinate Iron(II) Diaryl Compounds with Monodentate N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution.

PubMed

Liu, Yuesheng; Luo, Lun; Xiao, Jie; Wang, Lei; Song, You; Qu, Jingping; Luo, Yi; Deng, Liang

2015-05-18

The salt elimination reactions of (IPr2Me2)2FeCl2 (IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with the corresponding aryl Grignard reagents afford [(IPr2Me2)2FeAr2] (Ar = Ph, 3; C6H4-p-Me, 4; C6H4-p-(t)Bu, 5; C6H3-3,5-(CF3)2, 6) in good yields. X-ray crystallographic studies revealed the presence of both tetrahedral and trans square planar isomers for 3 and 6 and the tetrahedral structures for 4 and 5. Magnetic susceptibility and (57)Fe Mössbauer spectrum measurements on the solid samples indicated the high-spin (S = 2) and intermediate-spin (S = 1) nature of the tetrahedral and square planar structures, respectively. Solution property studies, including solution magnetic susceptibility measurement, variable-temperature (1)H and (19)F NMR, and absorption spectroscopy, on 3-6, as well as an (57)Fe Mössbauer spectrum study on a frozen tetrahydrofuran solution of tetrahedral [(IPr2Me2)2(57)FePh2] suggest the coexistence of tetrahedral and trans square planar structures in solution phase. Density functional theory calculations on (IPr2Me2)2FePh2 disclosed that the tetrahedral and trans square planar isomers are close in energy and that the geometry isomerization can occur by spin-change-coupled geometric transformation on four-coordinate iron(II) center.

Prospective and retrospective high order eddy current mitigation for diffusion weighted echo planar imaging.

PubMed

Xu, Dan; Maier, Joseph K; King, Kevin F; Collick, Bruce D; Wu, Gaohong; Peters, Robert D; Hinks, R Scott

2013-11-01

The proposed method is aimed at reducing eddy current (EC) induced distortion in diffusion weighted echo planar imaging, without the need to perform further image coregistration between diffusion weighted and T2 images. These ECs typically have significant high order spatial components that cannot be compensated by preemphasis. High order ECs are first calibrated at the system level in a protocol independent fashion. The resulting amplitudes and time constants of high order ECs can then be used to calculate imaging protocol specific corrections. A combined prospective and retrospective approach is proposed to apply correction during data acquisition and image reconstruction. Various phantom, brain, body, and whole body diffusion weighted images with and without the proposed method are acquired. Significantly reduced image distortion and misregistration are consistently seen in images with the proposed method compared with images without. The proposed method is a powerful (e.g., effective at 48 cm field of view and 30 cm slice coverage) and flexible (e.g., compatible with other image enhancements and arbitrary scan plane) technique to correct high order ECs induced distortion and misregistration for various diffusion weighted echo planar imaging applications, without the need for further image post processing, protocol dependent prescan, or sacrifice in signal-to-noise ratio. Copyright © 2013 Wiley Periodicals, Inc.

Synthesis and crystal structure of the iridium(I) carbene complex with a pair of hydrogen wing tips

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.-Y.; Chen, Z.-M.; Wang, Y.

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im{sup t}Bu){sub 2}Ir(COD)]{sup +}PF{sub 6}{sup −} (C{sub 22}H{sub 32}PF{sub 6}IrN{sub 4}) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im{sup t}Bu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir−C{sub carbene} bond lengths are 2.066(5) and 2.052(5) Å, and the bond angle C−Ir−C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.

Coupled Electronic and Magnetic Phase Transition in the Infinite-Layer Phase LaSrNiRuO4.

PubMed

Patino, Midori Amano; Zeng, Dihao; Bower, Ryan; McGrady, John E; Hayward, Michael A

2016-09-06

Topochemical reduction of the ordered double perovskite LaSrNiRuO6 with CaH2 yields LaSrNiRuO4, an extended oxide phase containing infinite sheets of apex-linked, square-planar Ni(1+)O4 and Ru(2+)O4 units ordered in a checkerboard arrangement. At room temperature the localized Ni(1+) (d(9), S = (1)/2) and Ru(2+) (d(6), S = 1) centers behave paramagnetically. However, on cooling below 250 K the system undergoes a cooperative phase transition in which the nickel spins align ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. Features of the low-temperature crystal structure suggest a symmetry lowering Jahn-Teller distortion could be responsible for the observed diamagnetism of the ruthenium centers.

Copper(II) complexes of tridentate N, N, N', N″, N″-pentamethyldiethylenetriamine: Superoxide dismutase and inhibitory activity against bacteria and fungi

NASA Astrophysics Data System (ADS)

Patel, R. N.; Singh, Nripendra; Gundla, V. L. N.; Chauhan, U. K.

2007-03-01

A series of ternary copper(II) complexes containing same coordination sphere but difference in the counter ions, viz., [Cu(PMDT)(OAc)]PF 6(1); [Cu(PMDT)(OAc)]ClO 4(2); [Cu(PMDT)(OAc)]BF 4(3) and [Cu(PMDT)(OAc)]BPh 4(4) where PMDT = N, N, N', N″, N″-pentamethyldiethylenetriamine, OAc = Acetate ion were synthesized and characterized by means of spectroscopic, magnetic and cyclic voltammetric measurements. In frozen solution e.p.r. spectra, an interesting relation g|| > g⊥ has been observed which is a typical of the axially symmetric d 9 Cu II ( SCu = 1/2) having an unpaired electron in a d orbital. Single crystal X-ray analysis of (1) has revealed the presence of distorted square planar geometry. The influence of the counter ion on the complexes has been examined by performing some biological experiments like superoxide dismutase and anti-microbial activity.

GdPtPb: A noncollinear antiferromagnet with distorted kagome lattice

DOE PAGES

Manni, S.; Bud'ko, Sergey L.; Canfield, Paul C.

2017-08-24

In the spirit of searching for Gd-based, frustrated, rare earth magnets, we have found antiferomagnetism (AF) in GdPtPb, which crystallizes in the ZrNiAl-type structure that has a distorted kagome lattice of Gd triangles. Single crystals were grown and investigated using structural, magnetic, transport, and thermodynamic measurements. GdPtPb orders antiferromagnetically at 15.5 K, arguably with a planar, noncollinear structure. The high temperature magnetic susceptibility data reveal an “anti-frustration” behavior having a frustration parameter, |f| = |Θ|/T N = 0.25, which can be explained by mean field theory within a two-sublattice model. Here, the study of the magnetic phase diagram down tomore » T = 1.8K reveals a change of magnetic structure through a metamagnetic transition at around 20 kOe and the disappearance of the AF ordering near 140 kOe. In total, our work indicates that GdPtPb can serve as an example of a planar, noncollinear AF with a distorted kagome magnetic sublattice.« less

Pd (II) complexes of bidentate chalcone ligands: Synthesis, spectral, thermal, antitumor, antioxidant, antimicrobial, DFT and SAR studies

NASA Astrophysics Data System (ADS)

Gaber, Mohamed; Awad, Mohamed K.; Atlam, Faten M.

2018-05-01

The ligation behavior of two chalcone ligands namely, (E)-3-(4-chlorophenyl)-1-(pyridin-2-yl)prop-2-en-1-one (L1) and (E)-3-(4-methoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one (L2), towards the Pd(II) ion is determined. The structures of the complexes are elucidated by elemental analysis, spectral methods (IR, electronic and NMR spectra) as well as the conductance measurements and thermal analysis. The metal complexes exhibit a square planar geometrical arrangement. The kinetic and thermodynamic parameters for some selected decomposition steps have been calculated. The antimicrobial, antioxidant and anticancer activities of the chalcones and their Pd(II) complexes have been evaluated. Molecular orbital computations are performed using DFT at B3LYP level with 6-31 + G(d) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations are performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry. Thermodynamic parameters for the investigated compounds are also studied. The calculations confirm that the investigated complexes have square planner geometry, which is in a good agreement with the experimental observation.

Synthesis, characterization, single crystal X-ray determination, fluorescence and electrochemical studies of new dinuclear nickel(II) and oxovanadium(IV) complexes containing double Schiff base ligands

NASA Astrophysics Data System (ADS)

Shafaatian, Bita; Ozbakzaei, Zahra; Notash, Behrouz; Rezvani, S. Ahmad

2015-04-01

A series of new bimetallic complexes of nickel(II) and vanadium(IV) have been synthesized by the reaction of the new double bidentate Schiff base ligands with nickel acetate and vanadyl acetylacetonate in 1:1 M ratio. In nickel and also vanadyl complexes the ligands were coordinated to the metals via the imine N and enolic O atoms. The complexes have been found to possess 1:1 metals to ligands stoichiometry and the molar conductance data revealed that the metal complexes were non-electrolytes. The nickel and vanadyl complexes exhibited distorted square planar and square pyramidal coordination geometries, respectively. The emission spectra of the ligands and their complexes were studied in methanol. Electrochemical properties of the ligands and their metal complexes were also investigated in DMSO solvent at 150 mV s-1 scan rate. The ligands and metal complexes showed both quasi-reversible and irreversible processes at this scan rate. The Schiff bases and their complexes have been characterized by FT-IR, 1H NMR, UV/Vis spectroscopies, elemental analysis and conductometry. The crystal structure of the nickel complex has been determined by single crystal X-ray diffraction.

Array feed synthesis for correction of reflector distortion and Vernier beamsteering

NASA Technical Reports Server (NTRS)

Blank, Stephen J.; Imbriale, William A.

1988-01-01

An algorithmic procedure for the synthesis of planar array feeds for paraboloidal reflectors is described which simultaneously provides electronic correction of systematic reflector surface distortions as well as a Vernier electronic beamsteering capability. Simple rules of thumb for the optimum chioce of planar array feed configuration (i.e., the number and type of elements) are derived from a parametric study made using the synthesis procedure. A number of f/D ratios and distortion models were examined that are typical of large paraboloidal reflectors. Numerical results are presented showing that, for the range of distortion models considered, good on-axis gain restoration can be achieved with as few as seven elements. For beamsteering to +/- 1 beamwidth (BW), 19 elements are required. For arrays with either 7 or 19 elements, the results indicate that the use of high-aperture-efficiency elements (e.g., disk-on-rod and short backfire) in the array yields higher system gain than can be obtained with elements having lower aperture efficiency (e.g., open-ended waveguides). With 37 elements, excellent gain and beamsteering performance to +/- 1.5 BW are obtained independent of the assumed effective aperture of the array element. An approximate expression is derived for the focal-plane field distribution of the distorted reflector. Contour plots of the focal-plane fields are also presented for various distortion and beam scan angle cases. The results obtained show the effectiveness of the array feed approach.

PSF mapping-based correction of eddy-current-induced distortions in diffusion-weighted echo-planar imaging.

PubMed

In, Myung-Ho; Posnansky, Oleg; Speck, Oliver

2016-05-01

To accurately correct diffusion-encoding direction-dependent eddy-current-induced geometric distortions in diffusion-weighted echo-planar imaging (DW-EPI) and to minimize the calibration time at 7 Tesla (T). A point spread function (PSF) mapping based eddy-current calibration method is newly presented to determine eddy-current-induced geometric distortions even including nonlinear eddy-current effects within the readout acquisition window. To evaluate the temporal stability of eddy-current maps, calibration was performed four times within 3 months. Furthermore, spatial variations of measured eddy-current maps versus their linear superposition were investigated to enable correction in DW-EPIs with arbitrary diffusion directions without direct calibration. For comparison, an image-based eddy-current correction method was additionally applied. Finally, this method was combined with a PSF-based susceptibility-induced distortion correction approach proposed previously to correct both susceptibility and eddy-current-induced distortions in DW-EPIs. Very fast eddy-current calibration in a three-dimensional volume is possible with the proposed method. The measured eddy-current maps are very stable over time and very similar maps can be obtained by linear superposition of principal-axes eddy-current maps. High resolution in vivo brain results demonstrate that the proposed method allows more efficient eddy-current correction than the image-based method. The combination of both PSF-based approaches allows distortion-free images, which permit reliable analysis in diffusion tensor imaging applications at 7T. © 2015 Wiley Periodicals, Inc.

XAFS study of copper(II) complexes with square planar and square pyramidal coordination geometries

NASA Astrophysics Data System (ADS)

Gaur, A.; Klysubun, W.; Nitin Nair, N.; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2016-08-01

X-ray absorption fine structure of six Cu(II) complexes, Cu2(Clna)4 2H2O (1), Cu2(ac)4 2H2O (2), Cu2(phac)4 (pyz) (3), Cu2(bpy)2(na)2 H2O (ClO4) (4), Cu2(teen)4(OH)2(ClO4)2 (5) and Cu2(tmen)4(OH)2(ClO4)2 (6) (where ac, phac, pyz, bpy, na, teen, tmen = acetate, phenyl acetate, pyrazole, bipyridine, nicotinic acid, tetraethyethylenediamine, tetramethylethylenediamine, respectively), which were supposed to have square pyramidal and square planar coordination geometries have been investigated. The differences observed in the X-ray absorption near edge structure (XANES) features of the standard compounds having four, five and six coordination geometry points towards presence of square planar and square pyramidal geometry around Cu centre in the studied complexes. The presence of intense pre-edge feature in the spectra of four complexes, 1-4, indicates square pyramidal coordination. Another important XANES feature, present in complexes 5 and 6, is prominent shoulder in the rising part of edge whose intensity decreases in the presence of axial ligands and thus indicates four coordination in these complexes. Ab initio calculations were carried out for square planar and square pyramidal Cu centres to observe the variation of 4p density of states in the presence and absence of axial ligands. To determine the number and distance of scattering atoms around Cu centre in the complexes, EXAFS analysis has been done using the paths obtained from Cu(II) oxide model and an axial Cu-O path from model of a square pyramidal complex. The results obtained from EXAFS analysis have been reported which confirmed the inference drawn from XANES features. Thus, it has been shown that these paths from model of a standard compound can be used to determine the structural parameters for complexes having unknown structure.

Pyramidal space frame and associated methods

DOEpatents

Clark, Ryan Michael; White, David; Farr, Jr, Adrian Lawrence

2016-07-19

A space frame having a high torsional strength comprising a first square bipyramid and two planar structures extending outward from an apex of the first square bipyramid to form a "V" shape is disclosed. Some embodiments comprise a plurality of edge-sharing square bipyramids configured linearly, where the two planar structures contact apexes of all the square bipyramids. A plurality of bridging struts, apex struts, corner struts and optional internal bracing struts increase the strength and rigidity of the space frame. In an embodiment, the space frame supports a solar reflector, such as a parabolic solar reflector. Methods of fabricating and using the space frames are also disclosed.

Multiple Aromaticity and Antiaromaticity in Silicon Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Hua JIN.; Kuznetsov, A E.; Boldyrev, Alexander I.

A series of silicon clusters containing four atoms but with different charge states (Si{sub 4}{sup 2+}, Si{sub 4}, Si{sub 4}{sup 2-}, and NaSi{sub 4}{sup -}) were studied by photoelectron spectroscopy and ab initio calculations. Structure evolution and chemical bonding in this series were interpreted in terms of aromaticity and antiaromaticity, which allowed the prediction of how structures of the four-atom silicon clusters change upon addition or removal of two electrons. It is shown that Si{sub 4}{sup 2+} is square-planar, analogous to the recently discovered aromatic Al{sub 4}{sup 2-} cluster. Upon addition of two electrons, neutral Si{sub 4} becomes {sigma}-antiaromatic andmore » exhibits a rhombus distortion. Adding two more electrons to Si{sub 4} leads to two energetically close structures of Si{sub 4}{sup 2-}: either a double antiaromatic parallelogram structure or an aromatic system with a butterfly distortion. Because of the electronic instability of doubly charged Si{sub 4}{sup 2-}, a stabilizing cation (Na{sup +}) was used to produce Si{sub 4}{sup 2-} in the gas phase in the form of Na{sup +}[Si{sub 4}{sup 2-}], which was characterized experimentally by photoelectron spectroscopy. Multiple antiaromaticity in the parallelogram Na{sup +}[Si{sub 4}{sup 2-}] species is highly unusual.« less

Spectroscopic characterization, antioxidant and antitumour studies of novel bromo substituted thiosemicarbazone and its copper(II), nickel(II) and palladium(II) complexes

NASA Astrophysics Data System (ADS)

Jagadeesh, M.; Lavanya, M.; Kalangi, Suresh K.; Sarala, Y.; Ramachandraiah, C.; Varada Reddy, A.

2015-01-01

A new, slightly distorted octahedral complex of copper(II), square planar complexes of nickel(II) and palladium(II) with 2,4‧-dibromoacetophenone thiosemicarbazone (DBAPTSC) are synthesized. The ligand and the complexes are characterized by FT-IR, FT-Raman, powder X-ray diffraction studies. The IR and Raman data are correlated for the presence of the functional groups which specifically helped in the confirmation of the compounds. In addition, the free ligand is unambiguously characterized by 1H and 13C NMR spectroscopy while the copper(II) complex is characterized by electron paramagnetic resonance spectroscopy (EPR). The g values for the same are found to be 2.246 (g1), 2.012 (g2) and 2.005 (g3) which suggested rhombic distortions. The HOMO-LUMO band gap calculations for these compounds are found to be in between 0.5 and 4.0 eV and these compounds are identified as semiconducting materials. The synthesized ligand and its copper(II), nickel(II) and palladium(II) complexes are subjected to antitumour activity against the HepG2 human hepatoblastoma cell lines. Among all the compounds, nickel(II) complex is found to exert better antitumour activity with 57.6% of cytotoxicity.

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

NASA Astrophysics Data System (ADS)

Narang, H. K.; Mahapatra, M. M.; Jha, P. K.; Biswas, P.

2014-05-01

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.

Microscale Synthesis, Reactions, and (Super 1)H NMR Spectroscopic Investigations of Square Planar Macrocyclic, Tetramido-N Co(III) Complexes Relevant to Green Chemistry

ERIC Educational Resources Information Center

Watson, Tanya T.; Uffelman, Erich S.; Lee, Daniel W., III; Doherty, Jonathan R.; Schulze, Carl; Burke, Amy L.; Bonnema, Kristen, R.

2004-01-01

The microscale preparation, characterization, and reactivity of a square planar Co(III) complex that has grown out of a program to introduce experiments of relevance to green chemistry into the undergraduate curriculum is presented. The given experiments illustrate the remarkable redox and aqueous acid-base stability that make the macrocycles very…

Microscale Syntheses, Reactions, and 1H NMR Spectroscopic Investigations of Square Planar Macrocyclic Tetraamido-N Cu(III) Complexes Relevant to Green Chemistry

ERIC Educational Resources Information Center

Uffelman, Erich S.; Doherty, Jonathan R.; Schulze, Carl; Burke, Amy L.; Bonnema, Kristen R.; Watson, Tanya T.; Lee, Daniel W., III

2004-01-01

Microscale fusions, description, and spectroscopic analysis of the reactivity of a square planar Cu(III) complex significant to green chemistry, are presented. The experiment also includes nine focal points on which pre-lab and post-lab questions are based, and the final exams reflect the students' comprehension of these and other features of…

Variation of M···H-C Interactions in Square-Planar Complexes of Nickel(II), Palladium(II), and Platinum(II) Probed by Luminescence Spectroscopy and X-ray Diffraction at Variable Pressure.

PubMed

Poirier, Stéphanie; Lynn, Hudson; Reber, Christian; Tailleur, Elodie; Marchivie, Mathieu; Guionneau, Philippe; Probert, Michael R

2018-06-12

Luminescence spectra of isoelectronic square-planar d 8 complexes with 3d, 4d, and 5d metal centers show d-d luminescence with an energetic order different from that of the spectrochemical series, indicating that additional structural effects, such as different ligand-metal-ligand angles, are important factors. Variable-pressure luminescence spectra of square-planar nickel(II), palladium(II), and platinum(II) complexes with dimethyldithiocarbamate ({CH 3 } 2 DTC) ligands and their deuterated analogues show unexpected variations of the shifts of their maxima. High-resolution crystal structures and crystal structures at variable pressure for [Pt{(CH 3 ) 2 DTC} 2 ] indicate that intermolecular M···H-C interactions are at the origin of these different shifts.

Method of orthogonally splitting imaging pose measurement

NASA Astrophysics Data System (ADS)

Zhao, Na; Sun, Changku; Wang, Peng; Yang, Qian; Liu, Xintong

2018-01-01

In order to meet the aviation's and machinery manufacturing's pose measurement need of high precision, fast speed and wide measurement range, and to resolve the contradiction between measurement range and resolution of vision sensor, this paper proposes an orthogonally splitting imaging pose measurement method. This paper designs and realizes an orthogonally splitting imaging vision sensor and establishes a pose measurement system. The vision sensor consists of one imaging lens, a beam splitter prism, cylindrical lenses and dual linear CCD. Dual linear CCD respectively acquire one dimensional image coordinate data of the target point, and two data can restore the two dimensional image coordinates of the target point. According to the characteristics of imaging system, this paper establishes the nonlinear distortion model to correct distortion. Based on cross ratio invariability, polynomial equation is established and solved by the least square fitting method. After completing distortion correction, this paper establishes the measurement mathematical model of vision sensor, and determines intrinsic parameters to calibrate. An array of feature points for calibration is built by placing a planar target in any different positions for a few times. An terative optimization method is presented to solve the parameters of model. The experimental results show that the field angle is 52 °, the focus distance is 27.40 mm, image resolution is 5185×5117 pixels, displacement measurement error is less than 0.1mm, and rotation angle measurement error is less than 0.15°. The method of orthogonally splitting imaging pose measurement can satisfy the pose measurement requirement of high precision, fast speed and wide measurement range.

High Slew-Rate Head-Only Gradient for Improving Distortion in Echo Planar Imaging: Preliminary Experience

PubMed Central

Tan, Ek T.; Lee, Seung-Kyun; Weavers, Paul T.; Graziani, Dominic; Piel, Joseph E.; Shu, Yunhong; Huston, John; Bernstein, Matt A.; Foo, Thomas K.F.

2016-01-01

Purpose To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in-vivo human brain imaging, with a dedicated, head-only gradient coil. Materials and Methods Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T MRI system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI. Results As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects. Conclusion Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. PMID:26921117

A novel method for correction of temporally- and spatially-variant optical distortion in planar particle image velocimetry

DOE PAGES

Zha, Kan; Busch, Stephen; Park, Cheolwoong; ...

2016-06-24

In-cylinder flow measurements are necessary to gain a fundamental understanding of swirl-supported, light-duty Diesel engine processes for high thermal efficiency and low emissions. Planar particle image velocimetry (PIV) can be used for non-intrusive, in situ measurement of swirl-plane velocity fields through a transparent piston. In order to keep the flow unchanged from all-metal engine operation, the geometry of the transparent piston must adapt the production-intent metal piston geometry. As a result, a temporally- and spatially-variant optical distortion is introduced to the particle images. Here, to ensure reliable measurement of particle displacements, this work documents a systematic exploration of optical distortionmore » quantification and a hybrid back-projection procedure that combines ray-tracing-based geometric and in situ manual back-projection approaches.« less

Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, Gabriel V.; Müller, Erich A.; Jackson, George

2015-03-21

The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derivedmore » for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large system sizes for both the cylindrical and spherical cases. Estimates of the entropic and energetic contributions are also evaluated for the planar and cylindrical geometries and their magnitudes are in line with the expectations of our simple analysis.« less

Crystal structure, thermochromic and magnetic properties of organic-inorganic hybrid compound: (C7H7N2S)2CuCl4

NASA Astrophysics Data System (ADS)

Vishwakarma, Ashok K.; Kumari, Reema; Ghalsasi, Prasanna S.; Arulsamy, Navamoney

2017-08-01

The synthesis, thermal analysis, crystal structure and magnetic properties of (2-aminobenzothiazolium)2CuCl4, organic-inorganic hybrid compound, have been described. The compound crystallizes in the monoclinic space group P21/c with two formula units in a unit cell of dimensions a = 6.9522(4) Å, b = 9.6979(4) Å, c = 13.9633(6) Å, β = 97.849(3)° and volume 930.83(8) Å3 at 150(2) K. The structure consists of isolated nearly square planer [CuC14]2- units, with somewhat longer than normal Cusbnd Cl bond lengths [Cusbnd Cl (average) = 2.2711 Å]. The magnetic measurements of (2-aminobenzothiazolium)2CuCl4 using SQUID magnetometer show paramagnetic nature of the compound. Thermal measurements (TG-DTA and DSC) on this compound showed reversible phase transition at 83 °C. This transition is accompanied by the reversible change in colour of the prismatic crystal from green to dark brown, thermochromic behaviour. Temperature dependent EPR measurements on powdered sample ascertain change in coordination sphere around Cu(II) with shift in g|| = 2.150 and g⊥ = 2.071 at room temperature, typical of square planar, to g|| = 2.201 and g⊥ = 2.182 at 170 °C, typical of distorted tetrahedral geometry.

Multi-projector auto-calibration and placement optimization for non-planar surfaces

NASA Astrophysics Data System (ADS)

Li, Dong; Xie, Jinghui; Zhao, Lu; Zhou, Lijing; Weng, Dongdong

2015-10-01

Non-planar projection has been widely applied in virtual reality and digital entertainment and exhibitions because of its flexible layout and immersive display effects. Compared with planar projection, a non-planar projection is more difficult to achieve because projector calibration and image distortion correction are difficult processes. This paper uses a cylindrical screen as an example to present a new method for automatically calibrating a multi-projector system in a non-planar environment without using 3D reconstruction. This method corrects the geometric calibration error caused by the screen's manufactured imperfections, such as an undulating surface or a slant in the vertical plane. In addition, based on actual projection demand, this paper presents the overall performance evaluation criteria for the multi-projector system. According to these criteria, we determined the optimal placement for the projectors. This method also extends to surfaces that can be parameterized, such as spheres, ellipsoids, and paraboloids, and demonstrates a broad applicability.

Diaqua­bis­(4-meth­oxy­benzoato-κO 1)bis­(nicotinamide-κN 1)cobalt(II) dihydrate

PubMed Central

Hökelek, Tuncer; Dal, Hakan; Tercan, Barış; Tenlik, Erdinç; Necefoğlu, Hacali

2010-01-01

In the mononuclear title compound, [Co(C8H7O3)2(C6H6N2O)2(H2O)2]·2H2O, the CoII ion is located on a crystallographic inversion center. The asymmetric unit is completed by one 4-meth­oxy­benzoate anion, one nicotinamide (NA) ligand and one coordinated and one uncoordinated water mol­ecule. All ligands act in a monodentate mode. The four O atoms in the equatorial plane around the CoII ion form a slightly distorted square-planar arrangement, while the slightly distorted octa­hedral coordination is completed by the two pyridine N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxyl­ate group and the attached benzene ring is 6.47 (7)°, while the pyridine and benzene rings are oriented at a dihedral angle of 72.80 (4)°. An O—H⋯O hydrogen bond links the uncoordinated water mol­ecule to one of the carboxyl­ate groups. In the crystal structure, inter­molecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. PMID:21588149

Synthesis, thermogravimetric, spectroscopic and theoretical characterization of copper(II) complex with 4-chloro-2-nitrobenzenosulfonamide

NASA Astrophysics Data System (ADS)

Camí, G.; Chacón Villalba, E.; Di Santi, Y.; Colinas, P.; Estiu, G.; Soria, D. B.

2011-05-01

4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) complex, [Cu(ClNbsa) 2(NH 3) 2], has been prepared using the sulfonamide as ligand. The thermal behavior of both, the ligand and the Cu(II) complex, was investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT), and the electronic characteristics analyzed by UV-VIS, FTIR, Raman and 1H NMR spectroscopies. The experimental IR, Raman and UV-VIS spectra have been assigned on the basis of DFT calculations at the B3LYP level of theory using the standard (6-31 + G ∗∗) basis set. The geometries have been fully optimized in vacuum and in modeled dimethylsulfoxide (DMSO) solvent, using for the latter a continuum solvation model that reproduced the experimental conditions of the UV-VIS spectroscopy. The theoretical results converged to stable conformations for the free sulfonamide and for the complex, suggesting for the latter a distorted square planar geometry in both environments.

Structure and reactivity of a mononuclear gold(II) complex

NASA Astrophysics Data System (ADS)

Preiß, Sebastian; Förster, Christoph; Otto, Sven; Bauer, Matthias; Müller, Patrick; Hinderberger, Dariush; Hashemi Haeri, Haleh; Carella, Luca; Heinze, Katja

2017-12-01

Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn-Teller distortion enabled by the relativistically lowered 6s orbital of gold. The reactivity of this gold(II) complex towards dioxygen, nitrosobenzene and acids is discussed. This study provides insight on the ionic radius of gold(II), and allows it to be placed within the homologous series of nd9 Cu/Ag/Au divalent ions and the 5d8/9/10 Pt/Au/Hg 'relativistic' triad in the periodic table.

Synthesis, characterization and biological studies of copper(II) complexes with 2-aminobenzimidazole derivatives

NASA Astrophysics Data System (ADS)

Joseph, J.; Suman, A.; Nagashri, K.; Joseyphus, R. Selwin; Balakrishnan, Nisha

2017-06-01

Novel series of four copper(II) complexes with 2-aminobenzimidazole derivatives (obtained from the Knoevenagel condensate of acetylacetone (obtained from acetylacetone and halogen substituted benzaldehydes) and 2-aminobenzimidazole) were synthesized. They were structurally characterized using elemental analysis, molar conductance, FAB mass, FT- IR, 1H &13C-NMR, UV-Vis., and EPR techniques. On the basis of analytical and spectral studies, the distorted square planar geometry was assigned for all the complexes. The antibacterial screening of the ligands and their copper complexes indicated that all the complexes showed higher anti microbial activities than the free ligands. Superoxide dismutase and antioxidant activities of the copper complexes have also been performed. In the electrochemical technique, the shift in ΔEp, E1/2 and Ipc values were explored for the interaction of the complexes with CT-DNA. During the electrolysis process, the present ligand system stabilizes unusual oxidation state of copper in the complexes. It is believed that the copper complexes with curcumin analogs may enhance chemotherapeutic behavior.

Confined Electroconvective and Flexoelectric Instabilities Deep in the Freedericksz State of Nematic CB7CB.

PubMed

Krishnamurthy, Kanakapura S; Palakurthy, Nani Babu; Yelamaggad, Channabasaveshwar V

2017-06-01

We report wormlike flexoelectric structures evolving deep in the Freedericksz state of a nematic layer of the liquid crystal cyanobiphenyl-(CH2) 7 -cyanobiphenyl. They form in the predominantly splay-bend thin boundary layers and are built up of solitary flexoelectric domains of the Bobylev-Pikin type. Their formation is possibly triggered by the gradient flexoelectric surface instability that remains optically discernible up to unusually high frequencies. The threshold voltage at which the worms form scales as square root of the frequency; in their extended state, worms often appear as labyrinthine structures on a section of loops that separate regions of opposite director deviation. Such asymmetric loops are also derived through pincement-like dissociation of ring-shaped walls. Formation of isolated domains of bulk electroconvection precedes the onset of surface instabilities. In essence, far above the Freedericksz threshold, the twisted nematic layer behaves as a combination of two orthogonally oriented planar half-layers destabilized by localized flexoelectric distortion.

Synthesis, characterization and electrochemical studies of heterometallic manganese(IV)-zinc(II) and manganese(IV)-copper(II) complexes derived from bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone

NASA Astrophysics Data System (ADS)

Koch, Angira; Phukan, Arnab; Chanu, Oinam B.; Kumar, A.; Lal, R. A.

2014-02-01

Five manganese(IV) complexes [Mn(L)(bpy)] (1) and heterobimetallic complexes [MMn(L)Cl2(H2O)4]·1.5H2O (M = ZnII(2), CuII(3)) and [MnM(L)(bpy)Cl2] (M = ZnII(4), CuII(5)] have been synthesized from bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone (H4L) in methanol medium. The composition of the complexes have been established based on the data obtained from analytical, thermoanalytical and mass spectral studies. The structures of the complexes have been discussed in the light of molar conductance, magnetic moment, electronic, EPR, IR, FT-IR spectroscopic studies and transmission electron microscopies. The molar conductance values of these complexes in DMSO suggest their non-electrolytic nature. The μeff value for the complexes (1), (2) and (4) fall in the range 3.82-4.12 BM characteristic of the presence of the manganese(IV) in them. The complex (3) has μeff value of 3.70 BM at RT indicating considerable antiferromagnetic interaction between Mn(IV) and Cu(II). The μeff value of 4.72 BM for complex (5) is slightly lower than 4.90 BM for S = 2 ground state. In the complex (1) to (3), the ligand is coordinated to the metal centres as tetradentate ligand while in the complexes (4) and (5) as hexadentate ligand. Manganese(IV) has distorted octahedral stereochemistry in all complexes. Copper(II) has distorted octahedral and square planar stereochemistry in complexes (3) and (5) while zinc has distorted octahedral and tetrahedral stereochemistry, respectively. EPR studies of the complexes are also reported. The electron transfer reactions of the complexes have also been investigated by cyclic voltammetry.

3T diffusion-weighted MRI of the thyroid gland with reduced distortion: preliminary results

PubMed Central

Nagala, S; Priest, A N; McLean, M A; Jani, P; Graves, M J

2013-01-01

Objective: Single-shot diffusion-weighted (DW) echo planar imaging (EPI), which is commonly used for imaging the thyroid, is characterised by severe blurring and distortion. The objectives of this work were: 1, to show that a reduced-field of view (r-FOV) DW EPI technique can improve image quality; and 2, to investigate the effect of different reconstruction strategies on the resulting apparent diffusion coefficients (ADCs). Methods: We implemented a single-shot, r-FOV DW EPI technique with a two-dimensional radiofrequency excitation pulse for DW imaging of the thyroid at 3T. Images were reconstructed using root sum of squares (SOS) and an optimal-B1 reconstruction (OBR). Phantom and in vivo experiments were performed to compare r-FOV and conventional full-FOV DW EPI with root SOS and OBR. Results: r-FOV with OBR substantially improved image quality at 3T. In phantoms, r-FOV gave more accurate ADCs than full-FOV. In vivo r-FOV always gave lower ADC values with respect to the full-FOV technique irrespective of the reconstruction used and whether only two or multiple b-values were used to compute the ADCs. Conclusion: r-FOV DW EPI can reduce image blurring and distortion at the expense of a low signal-to-noise ratio. OBR is a promising reconstruction technique for accurate ADC measurements in lower signal-to-noise ratio regimes, although further studies are needed to characterise its performance. Advances in knowledge: DW imaging of the thyroid at 3T could potentially benefit from r-FOV acquisition strategies, such as the r-FOV DW EPI technique proposed in this paper. PMID:23770539

Formation, stability and crystal structure of mullite-type Al{sub 6−x}B{sub x}O{sub 9}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffmann, K., E-mail: Kristin.Hoffmann@uni-bremen.de; Institut für Anorganische Chemie und Kristallographie, FB02, Leobener Straße/NW2, Universität Bremen, D-28359 Bremen; Hooper, T.J.N.

2016-11-15

Mullite-type Al{sub 6−x}B{sub x}O{sub 9} compounds were studied by means of powder diffraction and spectroscopic methods. The backbones of this structure are chains of edge-connected AlO{sub 6} octahedra crosslinked by AlO- and BO-polyhedra. Rietveld refinements show that the a and b lattice parameters can be well resolved, thus representing an orthorhombic metric. A continuous decrease of the lattice parameters most pronounced in c-direction indicates a solid solution for Al{sub 6−x}B{sub x}O{sub 9} with 1.09≤x≤2. A preference of boron in 3-fold coordination is confirmed by {sup 11}B MAS NMR spectroscopy and Fourier calculations based on neutron diffraction data collected at 4more » K. Distance Least Squares modeling was performed to simulate a local geometry avoiding long B-O distances linking two octahedral chains by planar BO{sub 3} groups yielding split positions for the oxygen atoms and a strong distortion in the octahedral chains. The lattice thermal expansion was calculated using the Grüneisen first-order equation of state Debye-Einstein-Anharmonicity model. - Graphical abstract: Local distortion induced by boron linking the octahedral chains. - Highlights: • Decreasing lattice parameters indicate a solid solution for Al{sub 6−x}B{sub x}O{sub 9} (1.09≤x≤2). • B-atoms induce a local distortion of neighboring AlO{sub 6} octahedra. • A preference of boron in BO{sub 3} coordination is confirmed by {sup 11}B MAS NMR spectroscopy. • An optimized structural model for Al{sub 6−x}B{sub x}O{sub 9} is presented.« less

High slew-rate head-only gradient for improving distortion in echo planar imaging: Preliminary experience.

PubMed

Tan, Ek T; Lee, Seung-Kyun; Weavers, Paul T; Graziani, Dominic; Piel, Joseph E; Shu, Yunhong; Huston, John; Bernstein, Matt A; Foo, Thomas K F

2016-09-01

To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in vivo human brain imaging, with a dedicated, head-only gradient coil. Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T magnetic resonance imaging (MRI) system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI. As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects. Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. J. Magn. Reson. Imaging 2016;44:653-664. © 2016 International Society for Magnetic Resonance in Medicine.

Using a plenoptic camera to measure distortions in wavefronts affected by atmospheric turbulence

NASA Astrophysics Data System (ADS)

Eslami, Mohammed; Wu, Chensheng; Rzasa, John; Davis, Christopher C.

2012-10-01

Ideally, as planar wave fronts travel through an imaging system, all rays, or vectors pointing in the direction of the propagation of energy are parallel, and thus the wave front is focused to a particular point. If the wave front arrives at an imaging system with energy vectors that point in different directions, each part of the wave front will be focused at a slightly different point on the sensor plane and result in a distorted image. The Hartmann test, which involves the insertion of a series of pinholes between the imaging system and the sensor plane, was developed to sample the wavefront at different locations and measure the distortion angles at different points in the wave front. An adaptive optic system, such as a deformable mirror, is then used to correct for these distortions and allow the planar wave front to focus at the point desired on the sensor plane, thereby correcting the distorted image. The apertures of a pinhole array limit the amount of light that reaches the sensor plane. By replacing the pinholes with a microlens array each bundle of rays is focused to brighten the image. Microlens arrays are making their way into newer imaging technologies, such as "light field" or "plenoptic" cameras. In these cameras, the microlens array is used to recover the ray information of the incoming light by using post processing techniques to focus on objects at different depths. The goal of this paper is to demonstrate the use of these plenoptic cameras to recover the distortions in wavefronts. Taking advantage of the microlens array within the plenoptic camera, CODE-V simulations show that its performance can provide more information than a Shack-Hartmann sensor. Using the microlens array to retrieve the ray information and then backstepping through the imaging system provides information about distortions in the arriving wavefront.

Tuneable reactivity with PPh3 and SnX2 of four- and five-coordinate Pd(II) and Pt(II) complexes containing polyphosphines.

PubMed

Fernández-Anca, Damián; García-Seijo, M Inés; García-Fernández, M Esther

2013-07-28

The reactivity of the unusual d(8) trigonal-bipyramidal systems [MX(PP3)]X (X = Cl: M = Pd(1a), Pt(2a); X = Br: M = Pd(3a), Pt(4a); X = I: M = Pd(5a), Pt(6a); PP3 = tris[2-(diphenylphosphino)ethyl]phosphine) in CHCl3-CH3OH, the square-pyramidal compounds [MCl(NP3)]Cl (M = Pd(7a); Pt(8a); NP3 = tris[2-(diphenylphosphino)ethyl]amine) in CD3OD-DMF and the distorted square-planar mononuclear [MX(PNP)]X (M = Pd: X = Cl(10a); M = Pt: X = I(10b); PNP = bis[2-(diphenylphosphino)ethyl]amine) and the heteronuclear [PdAu2X4(PP3)] [X = I(9a), Cl(14a), Br(15a)] and [MAuX2(PP3)]X [M = Pd: X = Cl(16a); M = Pt: X = Cl(17a), Br(18a)] species in CDCl3 with PPh3 + SnX2 has been explored to establish the factors that influence the nature of the products. With the mononuclear precursors the course of the reaction is strongly dependent on the tripodal or linear arrangement of the polydentate ligand and in the former case on the halogen. Thus, while for chlorides (1a-2a, 7a-8a) and bromides (3a-4a) the reaction led to the trigonal-bipyramidal compounds [M(SnCl3)(AP3)][SnCl3] [A = P: M = Pd(1), Pt(2); A = N: M = Pd(7), Pt(8)], [MBr(PP3)][SnBr3] [M = Pd(4), Pt(6)] containing M-Sn and M-Br bonds, respectively, for iodides (5a-6a) resulted in the unknown neutral square-planar compounds [MI2(PP(PO)2)(SnI2)2] [M = Pd(9) and Pt(10)] bearing two dangling P=O-SnI2 units and P2MI2 environments. However, complexes of the type [PtCl(PP2PO)X]X' [X = SnCl2, X' = [SnCl3](-)(11)] and [M(PP(PO)2)2X4]X'2 [X = SnCl2, X' = [SnCl3](-): M = Pd(12), Pt(13)] showing P=O-SnCl2 arms were obtained by direct reaction of [PtCl(PP2PO)]Cl (11a) and [M(PP(PO)2)2]Cl2 [M = Pd(12a), Pt(13a)] with SnCl2 in CH3OH. Although complex 9 was also prepared by interaction of the heteronuclear iodide 9a with PPh3 + SnI2 in CDCl3, the use of the neutral and ionic heteronuclear chlorides and bromides (14a-18a) as starting materials afforded the distorted square-planar ionic systems [MAuX'(PP3)(PPh3)][SnX3]2 [M = Pd: X = Cl, X' = SnCl3(-)(14); X = Br, X' = SnBr3(-)(15); M = Pt: X = Cl, X' = SnCl3(-)(17); X = Br, X' = SnBr3(-)(18)] containing M-SnX3 and P-Au-PPh3 functionalities. It was found that these reactions where the heteronuclear species are the precursors proceed via the trigonal-bipyramidal halides not only with X = Cl and Br(1a-4a) but also I(5a). When the precursors were 10a and 10b the reaction occurred with formation of [Pd(PNP)(PPh3)][SnCl3]2 (23) and [Pt(PNP)(PPh3)][SnCl2I]2 (24) showing M-PPh3 units and trihalostannato counter anions.

Pseudo-Jahn-Teller Distortion in Two-Dimensional Phosphorus: Origin of Black and Blue Phases of Phosphorene and Band Gap Modulation by Molecular Charge Transfer.

PubMed

Chowdhury, Chandra; Jahiruddin, Sheik; Datta, Ayan

2016-04-07

Phosphorene (Pn) is stabilized as a layered material like graphite, yet it possess a natural direct band gap (Eg = 2.0 eV). Interestingly, unlike graphene, Pn exhibits a much richer phase diagram which includes distorted forms like the stapler-clip (black Pn, α form) and chairlike (blue Pn, β form) structures. The existence of these phases is attributed to pseudo-Jahn-Teller (PJT) instability of planar hexagonal P6(6-) rings. In both cases, the condition for vibronic instability of the planar P6(6-) rings is satisfied. Doping with electron donors like tetrathiafulvalene and tetraamino-tetrathiafulvalene and electron acceptors like tetracyanoquinodimethane and tetracyanoethylene convert blue Pn into N-type and black Pn into efficient P-type semiconductors, respectively. Interestingly, pristine blue Pn, an indirect gap semiconductor, gets converted into a direct gap semiconductor on electron or hole doping. Because of comparatively smaller undulation in blue Pn (with respect to black Pn), the van der Waals interactions between the dopants and blue Pn is stronger. PJT distortions for two-dimensional phosphorus provides a unified understanding of structural features and chemical reactivity in its different phases.

Lattice distortion of square iron nitride monolayers induced by changing symmetry of substrate

NASA Astrophysics Data System (ADS)

Hattori, Takuma; Iimori, Takushi; Miyamachi, Toshio; Komori, Fumio

2018-04-01

Rectangular iron nitride monatomic layers are fabricated on the threefold symmetric Cu(111) substrate by taking advantage of the stability of the square nitride film. Two different ordered structures are observed on the Cu(111) substrate by scanning tunneling microscopy after annealing at 510 K and 580 K. Their chemical composition and lattice symmetry are investigated by x-ray photoelectron spectroscopy and low energy electron diffraction. The monolayer film prepared at 580 K is a distorted Fe2N monolayer analogous to a ferromagnetic square Fe2N monolayer with a clock reconstruction on the Cu(001) substrate. The lattice deformation of the square Fe2N monolayer is induced by using Cu(111) with threefold symmetry.

Role of PROPELLER-DWI of the prostate in reducing distortion and artefact from total hip replacement metalwork.

PubMed

Czarniecki, Marcin; Caglic, Iztok; Grist, James T; Gill, Andrew B; Lorenc, Kamil; Slough, Rhys A; Priest, Andrew N; Barrett, Tristan

2018-05-01

To compare image quality, artefact, and distortion in standard echo-planar imaging (EPI) with periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) for prostate magnetic resonance imaging (MRI) diffusion-weighted imaging (DWI) in patients with previous total hip replacement (THR). 21 male subjects with a clinical suspicion for, or known prostate cancer and previous THR were scanned at 1.5 T using a phased-array body coil. DWI was obtained using single-shot EPI and PROPELLER techniques using fat saturation (PROPELLER-DWI-FS), and without (PROPELLER-DWI-NFS). Image quality (the overall impression of diagnostic quality) was compared to T 2 -weighted (T2WI) imaging using a 5-point Likert scale, with diffusion sequences additionally scored for artefact and distortion according to a 4-point scale, with artefact defined as the amount of prostate affected and distortion as the degree of warping of the organ. The T2W and DW image volumes were compared to produce quantitative distortion maps. A two-sample Wilcoxon test compared the qualitative scores, with inter-reader variability calculated using Cohen's kappa. 21 patients were included in the study, with an average age of 70.4 years and PSA 9.2 ng/ml. Hip metalwork was present bilaterally in 3 patients, left-sided in 9, and right-sided in 9. PROPELLER-DWI-FS significantly improved image quality (p < 0.01) and reduced distortion (p < 0.01) when compared to standard EP-DWI. Artefact was not shown to be significantly improved. The last 5 patients in the study were additionally imaged with PROPELLER-DWI-NFS, which resulted in a significant reduction in artefact compared to EP-DWI (p < 0.05). Quantitative distortion was significantly lower compared to EP-DWI for both PROPELLER with fat saturation (p < 0.01) and without fat saturation (p < 0.01). PROPELLER-DWI demonstrates better image quality and decreases both artefact and distortion compared to conventional echo planar sequences in patients with hip metalwork. Copyright © 2018 Elsevier B.V. All rights reserved.

Magnetic properties of a quasi-two-dimensional S =1/2 Heisenberg antiferromagnet with distorted square lattice

NASA Astrophysics Data System (ADS)

Yamaguchi, Hironori; Tamekuni, Yusuke; Iwasaki, Yoshiki; Otsuka, Rei; Hosokoshi, Yuko; Kida, Takanori; Hagiwara, Masayuki

2017-06-01

We successfully synthesize single crystals of the verdazyl radical α -2 ,3 ,5 -Cl3 -V. Ab initio molecular orbital calculations indicate that the two dominant antiferromagnetic interactions, J1 and J2 (α =J2/J1≃0.56 ), form an S =1 /2 distorted square lattice. We explain the magnetic properties based on the S =1 /2 square lattice Heisenberg antiferromagnet using the quantum Monte Carlo method, and examine the effects of the lattice distortion and the interplane interaction contribution. In the low-temperature regions below 6.4 K, we observe anisotropic magnetic behavior accompanied by a phase transition to a magnetically ordered state. The electron spin resonance signals exhibit anisotropic behavior in the temperature dependence of the resonance field and the linewidth. We explain the frequency dependence of the resonance fields in the ordered phase using a mean-field approximation with out-of-plane easy-axis anisotropy, which causes a spin-flop phase transition at approximately 0.4 T for the field perpendicular to the plane. Furthermore, the anisotropic dipole field provides supporting information regarding the presence of the easy-axis anisotropy. These results demonstrate that the lattice distortion, anisotropy, and interplane interaction of this model are sufficiently small that they do not affect the intrinsic behavior of the S =1 /2 square lattice Heisenberg antiferromagnet.

Nonlinear distortion of thin liquid sheets

NASA Astrophysics Data System (ADS)

Mehring, Carsten Ralf

Thin planar, annular and conical liquid sheets or films are analyzed, in a unified manner, by means of a reduced- dimension approach providing governing equations for the nonlinear motion of planar and swirling annular thin inviscid and incompressible liquid sheets in zero gravity and with axial disturbances only. Temporal analyses of periodically disturbed infinite sheets are considered, as well as spatial analyses of semi-infinite sheets modulated at the nozzle exit. Results on planar and swirling annular or conical sheets are presented for a zero density ambient gas. Here, conical sheets are obtained in the nearfield of the nozzle exit by considering sheets or films with swirl in excess of that needed to stabilize the discharging stream in its annular configuration. For nonswirling annular sheets a spatially and/or temporally constant gas-core pressure is assumed. A model extension considering the influence of aerodynamic effects on planar sheets is proposed. For planar and annular sheets, linear analyses of the pure initial- and pure boundary-value problem provide insight into the propagation characteristics of dilational and sinuous waves, the (linear) coupling between both wave modes, the stability limits for the annular configuration, as well as the appearance of particular waves on semi-infinite modulated sheets downstream from the nozzle exit. Nonlinear steady-state solutions for the conical configuration (without modulation) are illustrated. Comparison between nonlinear and linear numerical and linear analytical solutions for temporally or spatially developing sheets provides detailed information on the nonlinear distortion characteristics including nonlinear wave propagation and mode-coupling for all the considered geometric configurations and for a variety of parameter configurations. Sensitivity studies on the influence of Weber number, modulation frequency, annular radius, forcing amplitude and sheet divergence on breakup or collapse length and times are reported for modulated semi-infinite annular and conical sheets. Comparisons between the different geometric configurations are made. For periodically disturbed planar sheets, accuracy of the employed reduced-dimension approach is demonstrated by comparison with more accurate two-dimensional vortex dynamics simulations.

Least-Squares Camera Calibration Including Lens Distortion and Automatic Editing of Calibration Points

NASA Technical Reports Server (NTRS)

Gennery, D. B.

1998-01-01

A method is described for calibrating cameras including radial lens distortion, by using known points such as those measured from a calibration fixture. The distortion terms are relative to the optical axis, which is included in the model so that it does not have to be orthogonal to the image sensor plane.

Dichlorido[(S,R(S))-1-diphenylphosphino-2-(ethylsulfanylmethyl)ferrocene]palladium(II).

PubMed

Diab, Lisa; Daran, Jean-Claude; Gouygou, Maryse; Manoury, Eric; Urrutigoïty, Martine

2007-12-01

The reaction of enantiomerically pure planar chiral ferrocene phosphine thioether with bis(acetonitrile)dichloridopalladium yields the title square-planar mononuclear palladium complex as an enantiomerically pure single diastereoisomer, [PdFe(C5H5)(C20H20PS)Cl2]. The planar chirality of the ligand is retained in the complex and fully controls the central chirality on the S atom. The absolute configuration, viz. S for the planar chirality and R for the S atom, is unequivocally determined by refinement of the Flack parameter.

Bicollinear antiferromagnetic order, monoclinic distortion, and reversed resistivity anisotropy in FeTe as a result of spin-lattice coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

2016-09-08

The bicollinear antiferromagnetic order experimentally observed in FeTe is shown to be stabilized by the coupling g ~ 12 between monoclinic lattice distortions and the spin-nematic order parameter with B 2g symmetry, within a three-orbital spin-fermion model studied with Monte Carlo techniques. A finite but small value of g ~ 12 is required, with a concomitant lattice distortion compatible with experiments, and a tetragonal-monoclinic transition strongly first order. Remarkably, the bicollinear state found here displays a planar resistivity with the reversed puzzling anisotropy discovered in transport experiments. Orthorhombic distortions are also incorporated, and phase diagrams interpolating between pnictides and chalcogenidesmore » are presented. Here, we conclude that the spin-lattice coupling we introduce is sufficient to explain the challenging properties of FeTe.« less

Insertion of terminal alkyne into Pt-N bond of the square planar [PtI2(Me2phen)] complex.

PubMed

Benedetti, Michele; De Castro, Federica; Lamacchia, Vincenza; Pacifico, Concetta; Natile, Giovanni; Fanizzi, Francesco P

2017-11-21

The reactivity of [PtX 2 (Me 2 phen)] complexes (X = Cl, Br, I; Me 2 phen = 2,9-dimethyl-1,10-phenanthroline) with terminal alkynes has been investigated. Although the dichlorido species [PtCl 2 (Me 2 phen)] exhibits negligible reactivity, the bromido and iodido derivatives lead in short time to the formation of five-coordinate Pt(ii) complexes of the type [PtX 2 (Me 2 phen)(η 2 -CH[triple bond, length as m-dash]CR)] (X = Br, I; R = Ph, n-Bu), in equilibrium with the starting reagents. Similar to analogous complexes with simple acetylene, the five coordinate species can also undergo dissociation of an halido ligand and formation of the transient square-planar cationic species [PtX(Me 2 phen)(η 2 -CH[triple bond, length as m-dash]CR)] + . This latter can further evolve to give an unusual, sparingly soluble square planar product where the former terminal alkyne is converted into a :C[double bond, length as m-dash]C(H)(R) moiety with the α-carbon bridging the Pt(ii) core with one of the two N-donors of coordinated Me 2 phen. The final product [PtX 2 {κ 2 -N,C-(Z)-N[combining low line]1-N10-C[combining low line][double bond, length as m-dash]C(H)(R)}] (N1-N10 = 2,9-dimethyl-1,10-phenanthroline; X = Br, I) contains a Pt-N-C-C-N-C six-membered chelate ring in a square planar Pt(ii) coordination environment.

All substituted nickel porphyrins are highly nonplanar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shelnutt, J.A.; Song, X.Z.; Jentzen, W.

1996-12-31

X-ray crystallographic and resonance Raman studies show that only un-substituted Ni porphine is planar in solution; all substituted Ni porphyrin derivatives either are nonplanar or exist as a mixture of planar and nonplanar conformers in solution. Recent modifications in a molecular mechanics force field improve the ability the MM calculations to predict the X-ray structures of porphyrins and also the planar-nonplanar conformational equilibria in many cases. Calculations using the new force field suggests that all geoporphyrins will be highly nonplanar, especially those having meso substituents. The nonplanarity is expected to influence properties such as solubility and metallation/dematallation reactions. Further, amore » method of quantifying these nonplanar structures has been devised; any porphyrin structure can be decomposed into displacements along the out-of-plane normal coordinates. However, usually distortions along only the lowest-frequency normal modes of each symmetry type are required to adequately describe the structure. The lowest-frequency normal coordinates of b{sub lu}, a{sub 2u}, b{sub 2u}, and e{sub g} symmetries correspond to commonly observed symmetric distortions called ruffling (ruf), doming(dom), saddling (sad), and waving (wav(x), wav(y)). The application of this structural decomposition method to several problems including the influences of steric crowding and protein folding on porphyrin conformation will be described.« less

Influence of the quality of intraoperative fluoroscopic images on the spatial positioning accuracy of a CAOS system.

PubMed

Wang, Junqiang; Wang, Yu; Zhu, Gang; Chen, Xiangqian; Zhao, Xiangrui; Qiao, Huiting; Fan, Yubo

2018-06-01

Spatial positioning accuracy is a key issue in a computer-assisted orthopaedic surgery (CAOS) system. Since intraoperative fluoroscopic images are one of the most important input data to the CAOS system, the quality of these images should have a significant influence on the accuracy of the CAOS system. But the regularities and mechanism of the influence of the quality of intraoperative images on the accuracy of a CAOS system have yet to be studied. Two typical spatial positioning methods - a C-arm calibration-based method and a bi-planar positioning method - are used to study the influence of different image quality parameters, such as resolution, distortion, contrast and signal-to-noise ratio, on positioning accuracy. The error propagation rules of image error in different spatial positioning methods are analyzed by the Monte Carlo method. Correlation analysis showed that resolution and distortion had a significant influence on spatial positioning accuracy. In addition the C-arm calibration-based method was more sensitive to image distortion, while the bi-planar positioning method was more susceptible to image resolution. The image contrast and signal-to-noise ratio have no significant influence on the spatial positioning accuracy. The result of Monte Carlo analysis proved that generally the bi-planar positioning method was more sensitive to image quality than the C-arm calibration-based method. The quality of intraoperative fluoroscopic images is a key issue in the spatial positioning accuracy of a CAOS system. Although the 2 typical positioning methods have very similar mathematical principles, they showed different sensitivities to different image quality parameters. The result of this research may help to create a realistic standard for intraoperative fluoroscopic images for CAOS systems. Copyright © 2018 John Wiley & Sons, Ltd.

Integrated parallel reception, excitation, and shimming (iPRES).

PubMed

Han, Hui; Song, Allen W; Truong, Trong-Kha

2013-07-01

To develop a new concept for a hardware platform that enables integrated parallel reception, excitation, and shimming. This concept uses a single coil array rather than separate arrays for parallel excitation/reception and B0 shimming. It relies on a novel design that allows a radiofrequency current (for excitation/reception) and a direct current (for B0 shimming) to coexist independently in the same coil. Proof-of-concept B0 shimming experiments were performed with a two-coil array in a phantom, whereas B0 shimming simulations were performed with a 48-coil array in the human brain. Our experiments show that individually optimized direct currents applied in each coil can reduce the B0 root-mean-square error by 62-81% and minimize distortions in echo-planar images. The simulations show that dynamic shimming with the 48-coil integrated parallel reception, excitation, and shimming array can reduce the B0 root-mean-square error in the prefrontal and temporal regions by 66-79% as compared with static second-order spherical harmonic shimming and by 12-23% as compared with dynamic shimming with a 48-coil conventional shim array. Our results demonstrate the feasibility of the integrated parallel reception, excitation, and shimming concept to perform parallel excitation/reception and B0 shimming with a unified coil system as well as its promise for in vivo applications. Copyright © 2013 Wiley Periodicals, Inc.

Integrated Parallel Reception, Excitation, and Shimming (iPRES)

PubMed Central

Han, Hui; Song, Allen W.; Truong, Trong-Kha

2013-01-01

Purpose To develop a new concept for a hardware platform that enables integrated parallel reception, excitation, and shimming (iPRES). Theory This concept uses a single coil array rather than separate arrays for parallel excitation/reception and B0 shimming. It relies on a novel design that allows a radiofrequency current (for excitation/reception) and a direct current (for B0 shimming) to coexist independently in the same coil. Methods Proof-of-concept B0 shimming experiments were performed with a two-coil array in a phantom, whereas B0 shimming simulations were performed with a 48-coil array in the human brain. Results Our experiments show that individually optimized direct currents applied in each coil can reduce the B0 root-mean-square error by 62–81% and minimize distortions in echo-planar images. The simulations show that dynamic shimming with the 48-coil iPRES array can reduce the B0 root-mean-square error in the prefrontal and temporal regions by 66–79% as compared to static 2nd-order spherical harmonic shimming and by 12–23% as compared to dynamic shimming with a 48-coil conventional shim array. Conclusion Our results demonstrate the feasibility of the iPRES concept to perform parallel excitation/reception and B0 shimming with a unified coil system as well as its promise for in vivo applications. PMID:23629974

Synthesis and characterization of homoleptic group 10 dithiocarbamate complexes and heteroleptic Ni(II) complexes, and the use of the homoleptic Ni(II) for the preparation of nickel sulphide nanoparticles

NASA Astrophysics Data System (ADS)

Bobinihi, Felicia F.; Onwudiwe, Damian C.; Hosten, Eric C.

2018-07-01

A series of new dithiocarbamate complexes of Ni(II), Pd(II) and Pt(II) of the form [NiL2], [PdL2] and [PtL2] (where L = N-ethyl-N-ethanoldithiocarbamate) have been synthesized and characterized by elemental analysis, FTIR, and 1H and 13C NMR spectroscopy. The nickel complex was utilized to prepare heteroleptic complexes bearing triphenylphosphino (PPh3) and isothiocyanate (sbnd NCS) or isocyanide (sbnd NC) molecules. Furthermore, the structures of the palladium complex and the heteroleptic nickel with PPh3 and NC molecules have been confirmed by X-ray diffraction. The Pd(II) complex indicated a trans arrangement with a distorted square planar geometry around the Pd atom, while the Ni(II) complex revealed a highly distorted geometry with another molecule of triphenylphosphine moiety, held by hydrogen bonding, within the crystal structure. The thermal stability studies of all the complexes conducted by using thermogravimetric analyser (TGA) showed they all have good stability above 200 °C. The nanoparticles synthesized using the homoleptic nickel complex yielded platelets of pure Heazlewoodite phase of Ni3S2 with average size of 7.60 nm. The optical properties of the nanoparticles studied by using UV-vis spectroscopy showed band gap energy of 4.0 eV (355 nm), which was a blue shift of 1.90 eV compared to the bulk and a consequence of quantum confinement effect.

Distortion correction of echo planar images applying the concept of finite rate of innovation to point spread function mapping (FRIP).

PubMed

Nunes, Rita G; Hajnal, Joseph V

2018-06-01

Point spread function (PSF) mapping enables estimating the displacement fields required for distortion correction of echo planar images. Recently, a highly accelerated approach was introduced for estimating displacements from the phase slope of under-sampled PSF mapping data. Sampling schemes with varying spacing were proposed requiring stepwise phase unwrapping. To avoid unwrapping errors, an alternative approach applying the concept of finite rate of innovation to PSF mapping (FRIP) is introduced, using a pattern search strategy to locate the PSF peak, and the two methods are compared. Fully sampled PSF data was acquired in six subjects at 3.0 T, and distortion maps were estimated after retrospective under-sampling. The two methods were compared for both previously published and newly optimized sampling patterns. Prospectively under-sampled data were also acquired. Shift maps were estimated and deviations relative to the fully sampled reference map were calculated. The best performance was achieved when using FRIP with a previously proposed sampling scheme. The two methods were comparable for the remaining schemes. The displacement field errors tended to be lower as the number of samples or their spacing increased. A robust method for estimating the position of the PSF peak has been introduced.

Spline function approximation techniques for image geometric distortion representation. [for registration of multitemporal remote sensor imagery

NASA Technical Reports Server (NTRS)

Anuta, P. E.

1975-01-01

Least squares approximation techniques were developed for use in computer aided correction of spatial image distortions for registration of multitemporal remote sensor imagery. Polynomials were first used to define image distortion over the entire two dimensional image space. Spline functions were then investigated to determine if the combination of lower order polynomials could approximate a higher order distortion with less computational difficulty. Algorithms for generating approximating functions were developed and applied to the description of image distortion in aircraft multispectral scanner imagery. Other applications of the techniques were suggested for earth resources data processing areas other than geometric distortion representation.

Improved volumetric measurement of brain structure with a distortion correction procedure using an ADNI phantom.

PubMed

Maikusa, Norihide; Yamashita, Fumio; Tanaka, Kenichiro; Abe, Osamu; Kawaguchi, Atsushi; Kabasawa, Hiroyuki; Chiba, Shoma; Kasahara, Akihiro; Kobayashi, Nobuhisa; Yuasa, Tetsuya; Sato, Noriko; Matsuda, Hiroshi; Iwatsubo, Takeshi

2013-06-01

Serial magnetic resonance imaging (MRI) images acquired from multisite and multivendor MRI scanners are widely used in measuring longitudinal structural changes in the brain. Precise and accurate measurements are important in understanding the natural progression of neurodegenerative disorders such as Alzheimer's disease. However, geometric distortions in MRI images decrease the accuracy and precision of volumetric or morphometric measurements. To solve this problem, the authors suggest a commercially available phantom-based distortion correction method that accommodates the variation in geometric distortion within MRI images obtained with multivendor MRI scanners. The authors' method is based on image warping using a polynomial function. The method detects fiducial points within a phantom image using phantom analysis software developed by the Mayo Clinic and calculates warping functions for distortion correction. To quantify the effectiveness of the authors' method, the authors corrected phantom images obtained from multivendor MRI scanners and calculated the root-mean-square (RMS) of fiducial errors and the circularity ratio as evaluation values. The authors also compared the performance of the authors' method with that of a distortion correction method based on a spherical harmonics description of the generic gradient design parameters. Moreover, the authors evaluated whether this correction improves the test-retest reproducibility of voxel-based morphometry in human studies. A Wilcoxon signed-rank test with uncorrected and corrected images was performed. The root-mean-square errors and circularity ratios for all slices significantly improved (p < 0.0001) after the authors' distortion correction. Additionally, the authors' method was significantly better than a distortion correction method based on a description of spherical harmonics in improving the distortion of root-mean-square errors (p < 0.001 and 0.0337, respectively). Moreover, the authors' method reduced the RMS error arising from gradient nonlinearity more than gradwarp methods. In human studies, the coefficient of variation of voxel-based morphometry analysis of the whole brain improved significantly from 3.46% to 2.70% after distortion correction of the whole gray matter using the authors' method (Wilcoxon signed-rank test, p < 0.05). The authors proposed a phantom-based distortion correction method to improve reproducibility in longitudinal structural brain analysis using multivendor MRI. The authors evaluated the authors' method for phantom images in terms of two geometrical values and for human images in terms of test-retest reproducibility. The results showed that distortion was corrected significantly using the authors' method. In human studies, the reproducibility of voxel-based morphometry analysis for the whole gray matter significantly improved after distortion correction using the authors' method.

Optimized distortion correction technique for echo planar imaging.

PubMed

Chen , N K; Wyrwicz, A M

2001-03-01

A new phase-shifted EPI pulse sequence is described that encodes EPI phase errors due to all off-resonance factors, including B(o) field inhomogeneity, eddy current effects, and gradient waveform imperfections. Combined with the previously proposed multichannel modulation postprocessing algorithm (Chen and Wyrwicz, MRM 1999;41:1206-1213), the encoded phase error information can be used to effectively remove geometric distortions in subsequent EPI scans. The proposed EPI distortion correction technique has been shown to be effective in removing distortions due to gradient waveform imperfections and phase gradient-induced eddy current effects. In addition, this new method retains advantages of the earlier method, such as simultaneous correction of different off-resonance factors without use of a complicated phase unwrapping procedure. The effectiveness of this technique is illustrated with EPI studies on phantoms and animal subjects. Implementation to different versions of EPI sequences is also described. Magn Reson Med 45:525-528, 2001. Copyright 2001 Wiley-Liss, Inc.

Cu(II) salen complex with propylene linkage: An efficient catalyst in the formation of Csbnd X bonds (X = N, O, S) and biological investigations

NASA Astrophysics Data System (ADS)

Azam, Mohammad; Dwivedi, Sourabh; Al-Resayes, Saud I.; Adil, S. F.; Islam, Mohammad Shahidul; Trzesowska-Kruszynska, Agata; Kruszynski, Rafal; Lee, Dong-Ung

2017-02-01

The catalytic property of a mononuclear Cu(II) salen complex in Chan-Lam coupling reaction with phenyl boronic acid at room temperature is reported. The studied complex is found to be potential catalyst in the preparation of carbon-heteroatom bonds with excellent yields. The studied Cu(II) salen complex is monoclinic with cell parameters, a = 9.6807(5) (α 90°), (b = 17.2504(8) (β 112.429 (2), c = 11.1403 (6) (γ = 90°), and has distorted square planar environment around Cu(II) ion. Furthermore, there is no π⋯π interactions in the reported complex due to large distance between the centroid of aromatic rings. In addition, DNA binding study of Cu(II) salen complex by fluorescence and absorption spectroscopy is also reported. Moreover, the reported Cu(II) salen complex exhibits significant anticancer activity against MCF-7 cancer cell lines, and displays potential antimicrobial biofilm activity against P. aeruginosa, suggesting antimicrobial biofilm an important tool for suppression of resistant infections caused by P. aeruginosa.

Bromido({2-[2-(diphenyl­phosphan­yl)benzyl­idene]hydrazin-1-yl­idene}(4-meth­oxy­anilino)methane­thiol­ato)palladium(II) acetone monosolvate

PubMed Central

Mokthar, Khalisah Asilah; Shamsuddin, Mustaffa; Rosli, Mohd Mustaqim; Fun, Hoong-Kun

2012-01-01

In the title compound, [PdBr(C27H23N3OPS)]·C3H6O, the coordination geometry about the PdII atom is distorted square-planar, arising from the attached Br, S, P and N atoms (N and Br are trans), the maximum deviation from the plane being 0.2053 (4) Å for the N atom. The three benzene rings attached to the P atom make dihedral angles of 69.78 (7), 87.05 (7) and 77.50 (7)° with each other. An intra­molecular C—H⋯N hydrogen bond forms an S(6) ring motif. In the crystal, the complex mol­ecules form infinite chains along the a-axis direction through C—H⋯Br inter­actions, and a C—H⋯O inter­action links the main mol­ecule with the acetone solvent mol­ecule. PMID:22807805

Synthesis, crystal structure, theoretical calculations and antimicrobial properties of [Pt(tetramethylthiourea)4] [Pt(CN)4]·4H2O

NASA Astrophysics Data System (ADS)

Sadaf, Haseeba; Isab, Anvarhusein A.; Ahmad, Saeed; Espinosa, Arturo; Mas-Montoya, Míriam; Khan, Islam Ullah; Ejaz; Rehman, Seerat-ur; Ali, Muhammad Akhtar Javed; Saleem, Muhammad; Ruiz, José; Janiak, Christoph

2015-04-01

A new platinum(II) complex, [Pt(Tmtu)4][Pt(CN)4]·4H2O (1) was synthesized by reaction of K2[PtCl4], KCN and tetramethylthiourea (Tmtu). Its structure was determined by X-ray crystallography. The [Pt(CN)4]2- anion shows regular square planar geometry at platinum, while in the [Pt(Tmtu)4]2+ cation the geometry at platinum is somewhat distorted. Hydrogen bonding between water molecules and the cyanide nitrogen of [Pt(CN)4]2- ions stabilizes the structure and leads to a supramolecular 2D network. DFT calculations support the experimentally found dinuclear (homocoordinated) ion-pair structure 1 as the most stable in comparison to noncovalent dimer [Pt(CN)2(Tmtu)2]222 that could, in turn, be involved in the formation sequence of 1. Antimicrobial activities of the complex were evaluated by minimum inhibitory concentration and the results showed that the complex exhibited moderate activities against gram-negative bacteria (Escherichiacoli, Pseudomonas aeruginosa) and molds (Aspergillus niger,Penicilliumcitrinum).

Crystal structure of di-chlorido-{4-[(E)-(meth-oxy-imino-κN)meth-yl]-1,3-thia-zol-2-amine-κN (3)}palladium(II).

PubMed

Dyakonenko, Viktorita V; Zholob, Olga O; Orysyk, Svitlana I; Pekhnyo, Vasily I

2015-01-01

In the title compound, [PdCl2(C5H7N3OS)], the Pd(II) atom adopts a distorted square-planar coordination sphere defined by two N atoms of the bidentate ligand and two Cl atoms. The mean deviation from the coordination plane is 0.029 Å. The methyl group is not coplanar with the plane of the metallacycle [torsion angle C-O-N-C = 20.2 (4)°]. Steric repulsion between the methyl group and atoms of the metallacycle is manifested by shortened intra-molecular H⋯C contacts of 2.27, 2.38 and 2.64 Å, as compared with the sum of the van der Waals radii of 2.87 Å. The amino group participates via one H atom in the formation of an intra-molecular N-H⋯Cl hydrogen bond. In the crystal, the other H atom of the amino group links mol-ecules via bifurcated N-H⋯(Cl,O) hydrogen bonds into chains parallel to [001].

New 15-membered tetraaza (N4) macrocyclic ligand and its transition metal complexes: Spectral, magnetic, thermal and anticancer activity

NASA Astrophysics Data System (ADS)

El-Boraey, Hanaa A.; EL-Gammal, Ohyla A.

2015-03-01

Novel tetraamidemacrocyclic 15-membered ligand [L] i.e. naphthyl-dibenzo[1,5,9,12]tetraazacyclopentadecine-6,10,11,15-tetraoneand its transition metal complexes with Fe(II), Co(II), Ni(II), Cu(II), Ru(III) and Pd(II) have been synthesized and characterized by elemental analysis, spectral, thermal as well as magnetic and molar conductivity measurements. On the basis of analytical, spectral (IR, MS, UV-Vis, 1H NMR and EPR) and thermal studies distorted octahedral or square planar geometry has been proposed for the complexes. The antitumor activity of the synthesized ligand and some complexes against human breast cancer cell lines (MCF-7) and human hepatocarcinoma cell lines (HepG2) has been studied. The complexes (IC50 = 2.27-2.7, 8.33-31.1 μg/mL, respectively) showed potent antitumor activity, towards the former cell lines comparable with their ligand (IC50 = 13, 26 μg/mL, respectively). The results show that the activity of the ligand towards breast cancer cell line becomes more pronounced and significant when coordinated to the metal ion.

Copper(II) complex of new non-innocent O-aminophenol-based ligand as biomimetic model for galactose oxidase enzyme in aerobic oxidation of alcohols

NASA Astrophysics Data System (ADS)

Safaei, Elham; Bahrami, Hadiseh; Pevec, Andrej; Kozlevčar, Bojan; Jagličić, Zvonko

2017-04-01

Mononuclear copper(II) complex of tetra-dentate o-aminophenol-based ligand (H2LBAPP) has been synthesized and characterized. The three dentate precursor (HLBAP) of the final ligand was synthesized first, while the title four-dentate copper bound ligand was synthesized in situ, isolated only in the final copper species [CuLBAPP]. This copper coordination complex reveals a distorted square-planar geometry around the copper(II) centre by one oxygen and three nitrogen atoms from the coordinating ligand. The ligand is thus twice deprotonated via hydroxy and amine groups. The complex is red, non-typical for copper(II), but the effective magnetic moment of 1.86 B M. and a single isotropic symmetry EPR signal with g 2.059 confirm a S = 1/2 diluted spin system, without copper-copper magnetic coupling. Electrochemical oxidation of this complex yields the corresponding Cu(II)-phenyl radical species. Finally, the title complex CuLBAPP has shown good and selective catalytic activity towards alcohol to aldehyde oxidation, at aerobic room temperature conditions, for a set of different alcohols.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chumakov, Yu. M.; Paholnitcaia, A. Yu.; Petrenko, P. A.

Two crystal modifications of nitrato-(2-[2-(1-pyridine-2-ylethylidene)hydrazine]-1,3-benzothiazolo) aquacopper (I and II) and two modifications of chloro-(2-[2-phenyl(pyridine-2-ylethylidene)hydrazine]-1,3-benzothiazolo) copper (III and IV) have been synthesized and studied by X-ray diffraction. In structures I and II, the copper atoms coordinate a monodeprotonated molecule of the organic ligand, nitrate ions, and a water molecule. In crystals of I, the complexes are monomeric, whereas complexes II are linked via nitrate ions to form polymeric chains. In both structures the coordination polyhedron of the copper atom can be described as a distorted tetragonal bipyramid—(4 + 1 + 1) in I and (4 + 2) in II. These coordinationmore » polyherdra have different compositions. In structures III and IV, the metal atoms coordinate a monodeprotonated (2-[2-phenyl(pyridine-2-ylethylidene)hydrazine]-1,3-benzothiazole molecule and chloride ions. In III the complex-forming ion has square-planar coordination geometry, whereas structure IV consists of centrosymmetric dimers with two bridging chlorine atoms. It was found that nitrato-(2-[2-(1-pyridine-2-ylethylidene)hydrazine]-1,3-benzothiazolo) aquacopper possesses antitumor activity.« less

Synthesis, crystal structure and anticancer activity of tetrakis(N-isopropylimidazolidine-2-selenone)platinum(II) chloride

NASA Astrophysics Data System (ADS)

Ahmad, Saeed; Altoum, Ali Osman S.; Vančo, Ján; Křikavová, Radka; Trávníček, Zdeněk; Dvořák, Zdeněk; Altaf, Muhammad; Sohail, Manzar; Isab, Anvarhusein A.

2018-01-01

A Platinum(II) complex of N-isopropylimidazolidine-2-selenone (i-PrImSe), [Pt(i-PrImSe)4]Cl2 (1) was prepared and characterized by elemental analysis, IR and NMR (1H, 13C, 77Se &195Pt) spectroscopy, and X-ray crystallography. The structure of 1 consists of [Pt(i-PrImSe)4]2+ complex ion and chloride counter ions. The platinum(II) atom adopts a distorted square planar geometry. The in vitro antitumor activity of 1 as well as cisplatin, was evaluated by MTT assay against human; ovarian carcinoma A2780 and its cisplatin-resistant subline A2780R, prostate cancer 22Rv1 and breast cancer MCF-7 cell lines. The title complex displayed the activity against the A2780 cells (IC50 = 30.8 μM) at the level comparable to cisplatin (IC50 = 26.8 μM). The interaction studies with sulfur-containing biomolecules revealed its ability to form a variety of intermediates and oxidized species with L-cysteine and reduced glutathione.

Current pulse amplifier transmits detector signals with minimum distortion and attenuation

NASA Technical Reports Server (NTRS)

Bush, N. E.

1967-01-01

Amplifier translates the square pulses generated by a boron-trifluoride neutron sensitive detector located adjacent to a nuclear reactor to slower, long exponential decay pulses. These pulses are transmitted over long coaxial cables with minimum distortion and loss of frequency.

Distorted Carbon Nitride Structure with Substituted Benzene Moieties for Enhanced Visible Light Photocatalytic Activities.

PubMed

Kim, Hyejin; Gim, Suji; Jeon, Tae Hwa; Kim, Hyungjun; Choi, Wonyong

2017-11-22

Carbon nitride (CN) is being intensively investigated as a low-cost visible light active photocatalyst, but its practical applications are limited because of the fast charge pair recombination and low visible light absorption. Here, we introduce a new strategy for enhancing its visible light photocatalytic activity by designing the CN structure in which the nitrogen of tertiary amine is substituted with a benzene molecule connected by three heptazine rings. The intramolecular benzene doping induced the structural changes from planar symmetric structure to distorted geometry, which could be predicted by density functional theory calculation. This structural distortion facilitated the spatial separation of photogenerated charge pairs and retarded charge recombination via exciton dissociation. Such unique properties of the benzene-incorporated CN were confirmed by the photoluminescence (PL) and photoelectrochemical analyses. The optimal loading of benzene doping reduced the PL of the conjugated ring system (π → π* transition) but enhanced the PL of the forbidden n → π* transition at the nitrogen atoms with lone pair electrons due to the distortion from the planar geometry. The photoelectrode of benzene-doped CN exhibited higher photocurrent and lower charge transfer resistance than bare CN electrode, indicating that the photogenerated charge pairs are more efficiently separated. As a result, the benzene-doped CN markedly increased the photocatalytic activity for the degradation of various organic pollutants and that for H 2 O 2 production (via O 2 reduction). This study proposes a simple strategy for chemical structural modification of carbon nitride to boost the visible light photocatalytic activity.

Simultaneous adaptation to size, distance, and curvature underwater.

PubMed

Vernoy, M W

1989-02-01

Perceptual adaptation to underwater size, distance, and curvature distortion was measured for four different adaptation conditions. These conditions consisted of (a) playing Chinese checkers underwater, (b) swimming with eyes open underwater, (c) viewing a square underwater, and (d) an air control. Significant adaptation to underwater distortions was recorded in all except the air control condition. In the viewing square condition a positive correlation between size and distance adaptation was noted. It was suggested that adaptation to curvature may have mediated the positive correlation. Possible applications for the training of divers are discussed.

Catadioptric planar compound eye with large field of view.

PubMed

Deng, Huaxia; Gao, Xicheng; Ma, Mengchao; Li, Yunyang; Li, Hang; Zhang, Jin; Zhong, Xiang

2018-05-14

The planar compound eye has the advantages of simple structure and no requirement for complex relay optical elements, but the field of view (FOV) is very difficult to expand. Overcoming the limitation of FOV, especially with simple structures, is a great challenge for the development of planar compound eyes. Different from the existing designs that only considering refraction, this article proposes a catadioptric planar compound eye based on the reflection and refraction to expand the FOV. In the proposed design, the incident light from a large angle is reflected into the lenslet array by two rotationally symmetric mirrors whose surface equations are optimized by mathematical and optical softwares. The FOV of the proposed catadioptric planar compound eye theoretically can reach 96.6°, which is much wider than the opening record of 70°. Moreover, no distortion of the imaging system can be obtained theoretically in this design. Simulation results show a linearity of better than 99% for the most of the incident angles. The verification experiments show that the FOV of the proposed device can reach 90.7° while the FOV of the corresponding planar compound eye without mirrors is 41.6°. The proposed catadioptric planar compound eye has the great potential in monitoring, detection and virtual reality since the FOV has been widen significantly.

Simulations of absorption spectra of conjugated oligomers: role of planar conformation and aggregation in condensed phase

NASA Astrophysics Data System (ADS)

Yuan, Xiang-Ai; Wen, Jin; Zheng, Dong; Ma, Jing

2018-04-01

This Review highlights the structure/property relationship underlying the morphology modulation through various factors towards the exploration of light-absorbing materials for efficient utilisation of solar power. Theoretical study using a combination of molecular dynamics imulations and the time-dependent density functional theory demonstrated that the planarity plays an important role in tuning spectral properties of oligomer aggregates. The aggregation-induced blue-shift in absorption spectra of oligothiophenes and the red-shift for oligofluorenols were rationalised in a unified way from the reduced (and increased) content of planar conformations in molecular aggregates. The planarity versus non-planarity of oligomers can be modulated by introduction of alkyl side chain or steric bulky substituents. The substitution with various groups in the ortho-position of azobenzene leads to the distorted backbone, breaking symmetry, and hence the red-shift in spectra, expanding the application in biological systems with visible light absorption. The donor-acceptor substituent groups in conjugated oligomers can increase the degree of planarity, electron delocalisation and polarisation, and charge separation, giving rise to the red-shift in spectra and enhancement in polarisability and charge mobility for device applications. The solvent dependent and pH-sensitive properties and intramolecular hydrogen bonds also caused the shift of absorption spectra with the appearance of planar conformers.

Precise calibration of spatial phase response nonuniformity arising in liquid crystal on silicon.

PubMed

Xu, Jingquan; Qin, SiYi; Liu, Chen; Fu, Songnian; Liu, Deming

2018-06-15

In order to calibrate the spatial phase response nonuniformity of liquid crystal on silicon (LCoS), we propose to use a Twyman-Green interferometer to characterize the wavefront distortion, due to the inherent curvature of the device. During the characterization, both the residual carrier frequency introduced by the Fourier transform evaluation method and the lens aberration are error sources. For the tilted phase error introduced by residual carrier frequency, the least mean square fitting method is used to obtain the tilted phase error. Meanwhile, we use Zernike polynomials fitting based on plane mirror calibration to mitigate the lens aberration. For a typical LCoS with 1×12,288 pixels after calibration, the peak-to-valley value of the inherent wavefront distortion is approximately 0.25λ at 1550 nm, leading to a half-suppression of wavefront distortion. All efforts can suppress the root mean squares value of the inherent wavefront distortion to approximately λ/34.

Attenuation of the Squared Canonical Correlation Coefficient under Varying Estimates of Score Reliability

ERIC Educational Resources Information Center

Wilson, Celia M.

2010-01-01

Research pertaining to the distortion of the squared canonical correlation coefficient has traditionally been limited to the effects of sampling error and associated correction formulas. The purpose of this study was to compare the degree of attenuation of the squared canonical correlation coefficient under varying conditions of score reliability.…

Scale interactions of turbulence subjected to a straining relaxation destraining cycle

NASA Astrophysics Data System (ADS)

Chen, Jun; Meneveau, Charles; Katz, Joseph

2006-09-01

The response of turbulence subjected to planar straining and de-straining is studied experimentally, and the impact of the applied distortions on the energy transfer across different length scales is quantified. The data are obtained using planar particle image velocimetry (PIV) in a water tank, in which high-Reynolds-number turbulence with very low mean velocity is generated by an array of spinning grids. Planar straining and de-straining mean flows are produced by pushing and pulling a rectangular piston towards, and away from, the bottom wall of the tank. The data are processed to yield the time evolution of Reynolds stresses, anisotropy tensors, turbulence kinetic energy production, and mean subgrid-scale (SGS) dissipation rate at various scales. During straining, the production rises rapidly. After the relaxation period the small-scale SGS stresses recover isotropy, but the Reynolds stresses still display significant anisotropy. Thus when destraining is applied, a strong negative production (mean backscatter) occurs, i.e. the turbulence returns kinetic energy to the mean flow. The SGS dissipation displays similar behaviour at large filter scales, but the mean backscatter gradually disappears with decreasing filter scales. Energy spectra are compared to predictions of rapid distortion theory (RDT). Good agreement is found for the initial response but, as expected for the time-scale ratios of the experiment, turbulence relaxation causes discrepancies between measurements and RDT at later times.

The Usefulness of Readout-Segmented Echo-Planar Imaging (RESOLVE) for Bio-phantom Imaging Using 3-Tesla Clinical MRI.

PubMed

Yoshimura, Yuuki; Kuroda, Masahiro; Sugiantoc, Irfan; Bamgbosec, Babatunde O; Miyahara, Kanae; Ohmura, Yuichi; Kurozumi, Akira; Matsushita, Toshi; Ohno, Seiichiro; Kanazawa, Susumu; Asaumi, Junichi

2018-02-01

Readout-segmented echo-planar imaging (RESOLVE) is a multi-shot echo-planar imaging (EPI) modality with k-space segmented in the readout direction. We investigated whether RESOLVE decreases the distortion and artifact in the phase direction and increases the signal-to-noise ratio (SNR) in phantoms image taken with 3-tesla (3T) MRI versus conventional EPI. We used a physiological saline phantom and subtraction mapping and observed that RESOLVE's SNR was higher than EPI's. Using RESOLVE, the combination of a special-purpose coil and a large-loop coil had a higher SNR compared to using only a head/neck coil. RESOLVE's image distortioas less than EPI's. We used a 120 mM polyethylene glycol phantom to examine the phase direction artifact.vThe range where the artifact appeared in the apparent diffusion coefficient (ADC) image was shorter with RESOLVE compared to EPI. We used RESOLVE to take images of a Jurkat cell bio-phantom: the cell-region ADC was 856×10-6mm2/sec and the surrounding physiological saline-region ADC was 2,951×10-6mm2/sec. The combination of RESOLVE and the 3T clinical MRI device reduced image distortion and improved SNR and the identification of accurate ADC values due to the phase direction artifact reduction. This combination is useful for obtaining accurate ADC values of bio-phantoms.

Readout-Segmented Echo-Planar Imaging in Diffusion-Weighted MR Imaging in Breast Cancer: Comparison with Single-Shot Echo-Planar Imaging in Image Quality

PubMed Central

Kim, Yun Ju; Kang, Bong Joo; Park, Chang Suk; Kim, Hyeon Sook; Son, Yo Han; Porter, David Andrew; Song, Byung Joo

2014-01-01

Objective The purpose of this study was to compare the image quality of standard single-shot echo-planar imaging (ss-EPI) and that of readout-segmented EPI (rs-EPI) in patients with breast cancer. Materials and Methods Seventy-one patients with 74 breast cancers underwent both ss-EPI and rs-EPI. For qualitative comparison of image quality, three readers independently assessed the two sets of diffusion-weighted (DW) images. To evaluate geometric distortion, a comparison was made between lesion lengths derived from contrast enhanced MR (CE-MR) images and those obtained from the corresponding DW images. For assessment of image parameters, signal-to-noise ratio (SNR), lesion contrast, and contrast-to-noise ratio (CNR) were calculated. Results The rs-EPI was superior to ss-EPI in most criteria regarding the qualitative image quality. Anatomical structure distinction, delineation of the lesion, ghosting artifact, and overall image quality were significantly better in rs-EPI. Regarding the geometric distortion, lesion length on ss-EPI was significantly different from that of CE-MR, whereas there were no significant differences between CE-MR and rs-EPI. The rs-EPI was superior to ss-EPI in SNR and CNR. Conclusion Readout-segmented EPI is superior to ss-EPI in the aspect of image quality in DW MR imaging of the breast. PMID:25053898

Synthesis of Surface-Analogue Square-Planar Tetranuclear Nickel Hydride Clusters and Bonding to μ4-NR, -O and -BH Ligands.

PubMed

Shoshani, Manar M; Beck, Robert; Wang, Xiaoping; McLaughlin, Matthew J; Johnson, Samuel A

2018-03-05

Tetranuclear Ni complexes were synthesized with bonding to BH, NR, and O in atypical surface-like geometries. The previously reported electron-deficient cluster [( i Pr 3 P)Ni] 5 H 6 (1) reacts with N-methylmorpholine oxide to give [( i Pr 3 P)Ni] 4 H 4 (μ 4 -O) (2), which contains O coordinated in the center of a square-plane arrangement of Ni atoms. Reaction of 1 with benzonitrile gave the square-planar tetranuclear Ni cluster [( i Pr 3 P)Ni] 4 H 4 (μ 4 -NCH 2 Ph) (3), which contains an imido donor in a square-based-pyramidal geometry. This reaction also gives [( i Pr 3 P)Ni(N≡CPh)] 3 (4), with bridging benzonitrile ligands. Trimer 4 was independently synthesized from the reaction of Ni(COD) 2 , i Pr 3 P, and PhC≡N. The addition of dihydrogen to a 1:1 mixture of [( i Pr 3 P) 2 Ni] 2 (N 2 ) and ( i Pr 3 P) 2 NiCl 2 yielded [( i Pr 3 P)Ni] 4 (μ 3 -H) 4 (μ 2 -Cl) 2 (5), with a tetrahedral Ni core, in contrast to the square-planar geometries of 2 and 3. The solid-state structure of 5 was determined using both X-ray and neutron diffraction. Reaction of 5 with LiBH 4 gave [( i Pr 3 P)Ni] 4 H 4 (μ 4 -BH) 2 ] (6) via loss of LiCl and H 2 .

Monoclinic distortion and magnetic coupling in the double perovskite Sr{sub 2−x}Ca{sub x}YRuO{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernardo, P.L.; Ghivelder, L.; Eslava, G.G.

2014-12-15

Abstracts: This work investigates in the insulating double perovskites Sr{sub 2−x}Ca{sub x}YRuO{sub 6}. We address the angular dependence of the strength of the magnetic coupling due to the deviation from planarity of the basal layers of the monoclinic structure, characterized by the in-plane angle α<180°, in order to probe the impact of the structural distortions in the magnetic properties of the compounds. High resolution x-ray powder diffraction, susceptibility, and specific heat measurements were performed. The deviation from planarity significantly increases (α=144° for x=1) while the bond distances vary in a complex way as a consequence of the strong monoclinic distortion.more » We found that the magnetic transition temperature, T{sub M}, shows a linear dependence on cos [(π−α)/2]. This result is discussed in terms of t{sub 2g}(π)–e{sub g}(σ) mixing of the magnetic orbitals of the Ru{sup 5+} ions and unbalanced competitive super-exchange interactions. The deleterious effect of Ca doping for the magnetic coupling is confirmed by the reduction in the short-range antiferromagnetic correlations characteristic of the parent compound at T>>T{sub M} and the enhancement of magnetic frustration for T« less

ToF-SIMS measurements with topographic information in combined images.

PubMed

Koch, Sabrina; Ziegler, Georg; Hutter, Herbert

2013-09-01

In 2D and 3D time-of-flight secondary ion mass spectrometric (ToF-SIMS) analysis, accentuated structures on the sample surface induce distorted element distributions in the measurement. The origin of this effect is the 45° incidence angle of the analysis beam, recording planar images with distortion of the sample surface. For the generation of correct element distributions, these artifacts associated with the sample surface need to be eliminated by measuring the sample surface topography and applying suitable algorithms. For this purpose, the next generation of ToF-SIMS instruments will feature a scanning probe microscope directly implemented in the sample chamber which allows the performance of topography measurements in situ. This work presents the combination of 2D and 3D ToF-SIMS analysis with topographic measurements by ex situ techniques such as atomic force microscopy (AFM), confocal microscopy (CM), and digital holographic microscopy (DHM). The concept of the combination of topographic and ToF-SIMS measurements in a single representation was applied to organic and inorganic samples featuring surface structures in the nanometer and micrometer ranges. The correct representation of planar and distorted ToF-SIMS images was achieved by the combination of topographic data with images of 2D as well as 3D ToF-SIMS measurements, using either AFM, CM, or DHM for the recording of topographic data.

Correction of geometric distortion in Propeller echo planar imaging using a modified reversed gradient approach.

PubMed

Chang, Hing-Chiu; Chuang, Tzu-Chao; Lin, Yi-Ru; Wang, Fu-Nien; Huang, Teng-Yi; Chung, Hsiao-Wen

2013-04-01

This study investigates the application of a modified reversed gradient algorithm to the Propeller-EPI imaging method (periodically rotated overlapping parallel lines with enhanced reconstruction based on echo-planar imaging readout) for corrections of geometric distortions due to the EPI readout. Propeller-EPI acquisition was executed with 360-degree rotational coverage of the k-space, from which the image pairs with opposite phase-encoding gradient polarities were extracted for reversed gradient geometric and intensity corrections. The spatial displacements obtained on a pixel-by-pixel basis were fitted using a two-dimensional polynomial followed by low-pass filtering to assure correction reliability in low-signal regions. Single-shot EPI images were obtained on a phantom, whereas high spatial resolution T2-weighted and diffusion tensor Propeller-EPI data were acquired in vivo from healthy subjects at 3.0 Tesla, to demonstrate the effectiveness of the proposed algorithm. Phantom images show success of the smoothed displacement map concept in providing improvements of the geometric corrections at low-signal regions. Human brain images demonstrate prominently superior reconstruction quality of Propeller-EPI images with modified reversed gradient corrections as compared with those obtained without corrections, as evidenced from verification against the distortion-free fast spin-echo images at the same level. The modified reversed gradient method is an effective approach to obtain high-resolution Propeller-EPI images with substantially reduced artifacts.

The Mathematics of Four or More N-Localizers for Stereotactic Neurosurgery.

PubMed

Brown, Russell A

2015-10-13

The mathematics that were originally developed for the N-localizer apply to three N-localizers that produce three sets of fiducials in a tomographic image. Some applications of the N-localizer use four N-localizers that produce four sets of fiducials; however, the mathematics that apply to three sets of fiducials do not apply to four sets of fiducials. This article presents mathematics that apply to four or more sets of fiducials that all lie within one planar tomographic image. In addition, these mathematics are extended to apply to four or more fiducials that do not all lie within one planar tomographic image, as may be the case with magnetic resonance (MR) imaging where a volume is imaged instead of a series of planar tomographic images. Whether applied to a planar image or a volume image, the mathematics of four or more N-localizers provide a statistical measure of the quality of the image data that may be influenced by factors, such as the nonlinear distortion of MR images.

Synthesis and structure of 1,3-dimethyl-5-(p-sulfonamide-phenylazo)-6-aminouracil and its Ni(II) complex: Topological insights and investigation for noncovalent interactions

NASA Astrophysics Data System (ADS)

Debnath, Diptanu; Roy, Subhadip; Purkayastha, Atanu; Bauzá, Antonio; Choudhury, Rupasree; Ganguly, Rakesh; Frontera, Antonio; Misra, Tarun Kumar

2017-08-01

The azo-derivative, 1,3-dimethyl-5-(p-sulfonamide-phenylazo)-6-aminouracil (HL) containing 6-aminouracil (a biomolecule) and sulfonamide functionality (commonly found in sulfa-drugs), and its Ni(II) complex, NiIIL2 were synthesized. Single-crystal X-ray diffraction studies show that the ligand (HL) consists of an E conformation about the azo-linkage with a nearly planar geometry and the complex possesses distorted square planar geometry. The H-bonded underlying networks of HL and NiIIL2 were topologically classified revealing distinct topological types, namely tts and hxl, respectively. Moreover, topology of molecular packings in HL and NiIIL2 has also been discussed. Density functional theory (DFT) calculations, at the M06-2X/def2TZVP level of theory, are employed to characterize a great variety of non-covalent interactions that explicitly show the importance of antiparallel stacking interactions established by π--π+ interactions and H-bonds in the self-assembled dimmers in HL and lp-π/C-H⋯π interactions in NiIIL2. The results of NMR and UV-vis spectroscopies evidence that the ligand exists in hydrazone-imine-keto (B) tautomeric form in solution. The ligand absorption bands consist of the overlapping bands of π→π* and n→π* transitions. The complex experiences electronic transitions that consist of basically ILCT in character with some sort of participation of the atomic d-orbitals of the nickel. The pKa value of the ligand is found to be 4.09.

Image Registration to Compensate for EPI Distortion in Patients with Brain Tumors: An Evaluation of Tract-Specific Effects.

PubMed

Albi, Angela; Meola, Antonio; Zhang, Fan; Kahali, Pegah; Rigolo, Laura; Tax, Chantal M W; Ciris, Pelin Aksit; Essayed, Walid I; Unadkat, Prashin; Norton, Isaiah; Rathi, Yogesh; Olubiyi, Olutayo; Golby, Alexandra J; O'Donnell, Lauren J

2018-03-01

Diffusion magnetic resonance imaging (dMRI) provides preoperative maps of neurosurgical patients' white matter tracts, but these maps suffer from echo-planar imaging (EPI) distortions caused by magnetic field inhomogeneities. In clinical neurosurgical planning, these distortions are generally not corrected and thus contribute to the uncertainty of fiber tracking. Multiple image processing pipelines have been proposed for image-registration-based EPI distortion correction in healthy subjects. In this article, we perform the first comparison of such pipelines in neurosurgical patient data. Five pipelines were tested in a retrospective clinical dMRI dataset of 9 patients with brain tumors. Pipelines differed in the choice of fixed and moving images and the similarity metric for image registration. Distortions were measured in two important tracts for neurosurgery, the arcuate fasciculus and corticospinal tracts. Significant differences in distortion estimates were found across processing pipelines. The most successful pipeline used dMRI baseline and T2-weighted images as inputs for distortion correction. This pipeline gave the most consistent distortion estimates across image resolutions and brain hemispheres. Quantitative results of mean tract distortions on the order of 1-2 mm are in line with other recent studies, supporting the potential need for distortion correction in neurosurgical planning. Novel results include significantly higher distortion estimates in the tumor hemisphere and greater effect of image resolution choice on results in the tumor hemisphere. Overall, this study demonstrates possible pitfalls and indicates that care should be taken when implementing EPI distortion correction in clinical settings. Copyright © 2018 by the American Society of Neuroimaging.

Cationic aza-macrocyclic complexes of germanium(II) and silicon(IV).

PubMed

Everett, Matthew; Jolleys, Andrew; Levason, William; Light, Mark E; Pugh, David; Reid, Gillian

2015-12-28

[GeCl2(dioxane)] reacts with the neutral aza-macrocyclic ligands L, L = Me3tacn (1,4,7-trimethyl-1,4,7-triazacyclononane), Me4cyclen (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) or Me4cyclam (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and two mol. equiv. of Me3SiO3SCF3 in thf solution to yield the unusual and hydrolytically very sensitive [Ge(L)][O3SCF3]2 as white solids in moderate yield. Using shorter reaction times [Ge(Me3tacn)]Cl2 and [Ge(Me3tacn)]Cl[O3SCF3] were also isolated; the preparation of [Ge(Me4cyclen)][GeCl3]2 is also described. The structures of the Me3tacn complexes show κ(3)-coordination of the macrocycle, with the anions interacting only weakly to produce very distorted five- or six-coordination at germanium. In contrast, the structure of [Ge(Me4cyclen)][O3SCF3]2 shows no anion interactions, and a distorted square planar geometry at germanium from coordination to the tetra-aza macrocycle. Crystal structures of the Si(iv) complexes, [SiCl3(Me3tacn)]Y (Y = O3SCF3, BAr(F); [B{3,5-(CF3)2C6H3}4]) and [SiHCl2(Me3tacn)][BAr(F)], obtained from reaction of SiCl4 or SiHCl3 with Me3tacn, followed by addition of either Me3SiO3SCF3 or Na[BAr(F)], contain distorted octahedral cations, with facialκ(3)-coordinated Me3tacn. The open-chain triamine, Me2NCH2CH2N(Me)CH2CH2NMe2 (pmdta), forms [SiCl3(pmdta)][BAr(F)] and [SiBr3(pmdta)][BAr(F)] under similar conditions, containing mer-octahedral cations.

Minimizing eddy currents induced in the ground plane of a large phased-array ultrasound applicator for echo-planar imaging-based MR thermometry.

PubMed

Lechner-Greite, Silke M; Hehn, Nicolas; Werner, Beat; Zadicario, Eyal; Tarasek, Matthew; Yeo, Desmond

2016-01-01

The study aims to investigate different ground plane segmentation designs of an ultrasound transducer to reduce gradient field induced eddy currents and the associated geometric distortion and temperature map errors in echo-planar imaging (EPI)-based MR thermometry in transcranial magnetic resonance (MR)-guided focused ultrasound (tcMRgFUS). Six different ground plane segmentations were considered and the efficacy of each in suppressing eddy currents was investigated in silico and in operando. For the latter case, the segmented ground planes were implemented in a transducer mockup model for validation. Robust spoiled gradient (SPGR) echo sequences and multi-shot EPI sequences were acquired. For each sequence and pattern, geometric distortions were quantified in the magnitude images and expressed in millimeters. Phase images were used for extracting the temperature maps on the basis of the temperature-dependent proton resonance frequency shift phenomenon. The means, standard deviations, and signal-to-noise ratios (SNRs) were extracted and contrasted with the geometric distortions of all patterns. The geometric distortion analysis and temperature map evaluations showed that more than one pattern could be considered the best-performing transducer. In the sagittal plane, the star (d) (3.46 ± 2.33 mm) and star-ring patterns (f) (2.72 ± 2.8 mm) showed smaller geometric distortions than the currently available seven-segment sheet (c) (5.54 ± 4.21 mm) and were both comparable to the reference scenario (a) (2.77 ± 2.24 mm). Contrasting these results with the temperature maps revealed that (d) performs as well as (a) in SPGR and EPI. We demonstrated that segmenting the transducer ground plane into a star pattern reduces eddy currents to a level wherein multi-plane EPI for accurate MR thermometry in tcMRgFUS is feasible.

Li2 B12 and Li3 B12 : Prediction of the Smallest Tubular and Cage-like Boron Structures.

PubMed

Dong, Xue; Jalife, Said; Vásquez-Espinal, Alejandro; Ravell, Estefanía; Pan, Sudip; Cabellos, José Luis; Liang, Wei-Yan; Cui, Zhong-Hua; Merino, Gabriel

2018-04-16

An intriguing structural transition from the quasi-planar form of B 12 cluster upon the interaction with lithium atoms is reported. High-level computations show that the lowest energy structures of LiB 12 , Li 2 B 12 , and Li 3 B 12 have quasi-planar (C s ), tubular (D 6d ), and cage-like (C s ) geometries, respectively. The energetic cost of distorting the B 12 quasi-planar fragment is overcompensated by an enhanced electrostatic interaction between the Li cations and the tubular or cage-like B 12 fragments, which is the main reason of such drastic structural changes, resulting in the smallest tubular (Li 2 B 12 ) and cage-like (Li 3 B 12 ) boron structures reported to date. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transition metal complexes of 2-amino-3,5-dihalopyridines: Syntheses, structures and magnetic properties of (3,5-diCAPH)2CuX4 and (3,5-diBAPH)2CuX4.

PubMed

Tremelling, Grant W; Foxman, Bruce M; Landee, Christopher P; Turnbull, Mark M; Willett, Roger D

2009-12-21

A family of bis(2-amino-3,5-dihalopyridinium)tetrahalocuprate(II) compounds has been synthesized, including (3,5-diCAPH)2CuCl4 (1), (3,5-diCAPH)2CuBr4 (2), (3,5-diBAPH)2CuCl4 (3), and (3,5-diBAPH)2CuBr4 (4) [3,5-diCAPH = 2-amino-3,5-dichloropyridinium; 3,5-diBAPH = 2-amino-3,5-dibromopyridinium]. These complexes have been analyzed through single crystal X-ray diffraction and temperature dependent magnetic susceptibility. Compound 1 crystallizes in the P-1 space group and the tetrachlorocuprate ion is best described as possessing a distorted square planar geometry. Compounds 2-4 are structurally similar and crystallized in the P2(1)/n, P2(1)/c, and P2(1)/n space groups respectively. The tetrahalocuprate ions are best described as distorted tetrahedra. All four compounds show antiferromagnetic interactions and were fit to the uniform chain Heisenberg model with resulting 2J/kB values of -11.71(2) K, -2.21(1) K, -12.43 (2) K, and -1.36(1) K, respectively. The exchange values correlate well with the two-halide exchange pathway parameters. The unusual observation that the chloride complexes show stronger magnetic exchange than the bromide complexes provides strong support that the exchange can be strongly dependent upon the Cu-X...X angles and Cu-X...X-Cu torsion angles.

A Tractography Comparison between Turboprop and Spin-Echo Echo-Planar Diffusion Tensor Imaging

PubMed Central

Gui, Minzhi; Peng, Huiling; Carew, John D.; Lesniak, Maciej S.; Arfanakis, Konstantinos

2008-01-01

The development of accurate, non-invasive methods for mapping white matter fiber-tracts is of critical importance. However, fiber-tracking is typically performed on diffusion tensor imaging (DTI) data obtained with echo-planar-based imaging techniques (EPI), which suffer from susceptibility-related image artifacts, and image warping due to eddy-currents. Thus, a number of white matter fiber-bundles mapped using EPI-based DTI data are distorted and/or terminated early. This severely limits the clinical potential of fiber-tracking. In contrast, Turboprop-MRI provides images with significantly fewer susceptibility and eddy-current-related artifacts than EPI. The purpose of this work was to compare fiber-tracking results obtained from DTI data acquired with Turboprop-DTI and EPI-based DTI. It was shown that, in brain regions near magnetic field inhomogeneities, white matter fiber-bundles obtained with EPI-based DTI were distorted and/or partially detected, when magnetic susceptibility-induced distortions were not corrected. After correction, residual distortions were still present and several fiber-tracts remained partially detected. In contrast, when using Turboprop-DTI data, all traced fiber-tracts were in agreement with known anatomy. The inter-session reproducibility of tractography results was higher for Turboprop than EPI-based DTI data in regions near field inhomogeneities. Thus, Turboprop may be a more appropriate DTI data acquisition technique for tracing white matter fibers near regions with significant magnetic susceptibility differences, as well as in longitudinal studies of such fibers. However, the intra-session reproducibility of tractography results was higher for EPI-based than Turboprop DTI data. Thus, EPI-based DTI may be more advantageous for tracing fibers minimally affected by field inhomogeneities. PMID:18621131

A tractography comparison between turboprop and spin-echo echo-planar diffusion tensor imaging.

PubMed

Gui, Minzhi; Peng, Huiling; Carew, John D; Lesniak, Maciej S; Arfanakis, Konstantinos

2008-10-01

The development of accurate, non-invasive methods for mapping white matter fiber-tracts is of critical importance. However, fiber-tracking is typically performed on diffusion tensor imaging (DTI) data obtained with echo-planar-based imaging techniques (EPI), which suffer from susceptibility-related image artifacts, and image warping due to eddy-currents. Thus, a number of white matter fiber-bundles mapped using EPI-based DTI data are distorted and/or terminated early. This severely limits the clinical potential of fiber-tracking. In contrast, Turboprop-MRI provides images with significantly fewer susceptibility and eddy-current-related artifacts than EPI. The purpose of this work was to compare fiber-tracking results obtained from DTI data acquired with Turboprop-DTI and EPI-based DTI. It was shown that, in brain regions near magnetic field inhomogeneities, white matter fiber-bundles obtained with EPI-based DTI were distorted and/or partially detected, when magnetic susceptibility-induced distortions were not corrected. After correction, residual distortions were still present and several fiber-tracts remained partially detected. In contrast, when using Turboprop-DTI data, all traced fiber-tracts were in agreement with known anatomy. The inter-session reproducibility of tractography results was higher for Turboprop than EPI-based DTI data in regions near field inhomogeneities. Thus, Turboprop may be a more appropriate DTI data acquisition technique for tracing white matter fibers near regions with significant magnetic susceptibility differences, as well as in longitudinal studies of such fibers. However, the intra-session reproducibility of tractography results was higher for EPI-based than Turboprop DTI data. Thus, EPI-based DTI may be more advantageous for tracing fibers minimally affected by field inhomogeneities.

Least-squares model-based halftoning

NASA Astrophysics Data System (ADS)

Pappas, Thrasyvoulos N.; Neuhoff, David L.

1992-08-01

A least-squares model-based approach to digital halftoning is proposed. It exploits both a printer model and a model for visual perception. It attempts to produce an 'optimal' halftoned reproduction, by minimizing the squared error between the response of the cascade of the printer and visual models to the binary image and the response of the visual model to the original gray-scale image. Conventional methods, such as clustered ordered dither, use the properties of the eye only implicitly, and resist printer distortions at the expense of spatial and gray-scale resolution. In previous work we showed that our printer model can be used to modify error diffusion to account for printer distortions. The modified error diffusion algorithm has better spatial and gray-scale resolution than conventional techniques, but produces some well known artifacts and asymmetries because it does not make use of an explicit eye model. Least-squares model-based halftoning uses explicit eye models and relies on printer models that predict distortions and exploit them to increase, rather than decrease, both spatial and gray-scale resolution. We have shown that the one-dimensional least-squares problem, in which each row or column of the image is halftoned independently, can be implemented with the Viterbi's algorithm. Unfortunately, no closed form solution can be found in two dimensions. The two-dimensional least squares solution is obtained by iterative techniques. Experiments show that least-squares model-based halftoning produces more gray levels and better spatial resolution than conventional techniques. We also show that the least- squares approach eliminates the problems associated with error diffusion. Model-based halftoning can be especially useful in transmission of high quality documents using high fidelity gray-scale image encoders. As we have shown, in such cases halftoning can be performed at the receiver, just before printing. Apart from coding efficiency, this approach permits the halftoner to be tuned to the individual printer, whose characteristics may vary considerably from those of other printers, for example, write-black vs. write-white laser printers.

Tripodal polyphosphine ligands as inductors of chelate ring-opening processes in mononuclear palladium(II) and platinum(II) compounds. The X-ray crystal structure of two derivatives containing dangling phosphorus.

PubMed

Fernández-Anca, Damián; García-Seijo, M Inés; García-Fernández, M Esther

2010-03-07

The reaction of NP(3) (tris[2-(diphenylphosphino)ethyl]amine and PP(3) (tris[2-(diphenylphosphino)ethyl]phosphine) with the five-coordinate complexes [PdCl(NP(3))]Cl (1) and [MX(PP(3))]X [M = Pd: X = Cl(2), Br(3), I(4); M = Pt: X = Cl(5), Br(6), I(7)], respectively, followed by (31)P{(1)H}NMR when X = Cl, led to the formation of unprecedented four-coordinate halides in a 1 : 2 metal to ligand ratio, [M(AP(3))(2)]X(2) [A = N, M = Pd: X = Cl(8); A = P, M = Pd: X = Cl(9), Br(10), I(11); A = P, M = Pt: X = Cl(12), Br(13), I (14)], containing reactive dangling phosphorus. Given the non characterised precursors [M(ONO(2))(PP(3))](NO(3))], the interaction between the heteronuclear species [MAg(NO(3))(3)(PP(3))] [M = Pd(15), Pt(16)] and PP(3) was explored. It was found that the addition of 1 equivalent of phosphine afforded [MAg(NO(3))(PP(3))(2)](NO(3))(2) [M = Pd(15*), Pt(16*)] containing Ag(I) bound to two dangling phosphorus while the reaction with 2 equivalents led to the complexes [M(PP(3))(2)](NO(3))(2) [M = Pd (17), Pt (18)] in coexistence with [Ag(2)(mu-PP(3))(2)](NO(3))(2). The fate of Ag(I) on the reaction of the mixed metal compounds with excess PP(3) consisted of preventing dissociation, observed in solution for halides, and acting as an assistant for crystallization. Colourless single crystals of 18 and 10, studied by X-ray diffraction, were afforded by reaction of 16 with 4 equivalents of PP(3) and from solutions of 10 in chloroform coexisting with red crystals of 3, respectively. The structures revealed the presence of dications [M(PP(3))(2)](2+) that show two five-membered chelate rings to M(II) in a square-planar arrangement and four uncoordinated phosphine arms with the counter anions being symmetrically placed at 4.431 (Br(-)) and 13.823 (NO(3)(-)) A from M(II) above and below its coordination, MP(4), plane. Complexes 9 and 12 were shown to undergo an interesting reactivity in solution versus group 11 monocations. The reactions consisted of conversions of the two five-membered chelate rings to M into three (structure I) or two (structure II) fused five-membered chelate rings, formation of species where Pt(II) retained its square-planar environment with the two dangling phosphine arms of each PP(3) bound to Cu(I) or Ag(I) (structure III) and complexes bearing distorted square-planar (P(2)MCl(2)) and presumably tetrahedral (AuP(4)+ P(2)AuCl(2)) arrangements (structure IV). The processes with Ag(I) salts also gave mixtures of I+III (chloride and nitrate) or II+III (nitrate).

Analysis and application of Fourier transform spectroscopy in atmospheric remote sensing

NASA Technical Reports Server (NTRS)

Park, J. H.

1984-01-01

An analysis method for Fourier transform spectroscopy is summarized with applications to various types of distortion in atmospheric absorption spectra. This analysis method includes the fast Fourier transform method for simulating the interferometric spectrum and the nonlinear least-squares method for retrieving the information from a measured spectrum. It is shown that spectral distortions can be simulated quite well and that the correct information can be retrieved from a distorted spectrum by this analysis technique.

Double-spin-echo diffusion weighting with a modified eddy current adjustment.

PubMed

Finsterbusch, Jürgen

2010-04-01

Magnetic field inhomogeneities like eddy current-related gradient fields cause geometric distortions in echo-planar imaging (EPI). This in particular affects diffusion-weighted imaging where these distortions vary with the direction of the diffusion weighting and hamper the accurate determination of diffusion parameters. The double-spin-echo preparation often used aims to reduce the cumulative eddy current effect by adjusting the diffusion-weighting gradient pulse durations to the time constant of the dominant eddy current contribution. However, eddy currents with a variety of time constants may be present and cause residual distortions. Here, a modification is proposed where the two bipolar gradient pairs of the preparation are adjusted independently to different time constants. At the expense of a slightly prolonged echo time, residual geometric distortions and correspondingly increased values of the diffusion anisotropy can be reduced as is demonstrated in phantoms and the human brain. Thus, it may help to improve the reliability of diffusion-weighted EPI. Copyright 2010 Elsevier Inc. All rights reserved.

On the interaction between turbulence and a planar rarefaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Bryan M.

2014-04-01

The modeling of turbulence, whether it be numerical or analytical, is a difficult challenge. Turbulence is amenable to analysis with linear theory if it is subject to rapid distortions, i.e., motions occurring on a timescale that is short compared to the timescale for nonlinear interactions. Such an approach (referred to as rapid distortion theory) could prove useful for understanding aspects of astrophysical turbulence, which is often subject to rapid distortions, such as supernova explosions or the free-fall associated with gravitational instability. As a proof of principle, a particularly simple problem is considered here: the evolution of vorticity due to amore » planar rarefaction in an ideal gas. Analytical solutions are obtained for incompressive modes having a wave vector perpendicular to the distortion; as in the case of gradient-driven instabilities, these are the modes that couple most strongly to the mean flow. Vorticity can either grow or decay in the wake of a rarefaction front, and there are two competing effects that determine which outcome occurs: entropy fluctuations couple to the mean pressure gradient to produce vorticity via baroclinic effects, whereas vorticity is damped due to the conservation of angular momentum as the fluid expands. Whether vorticity grows or decays depends upon the ratio of entropic to vortical fluctuations at the location of the front; growth occurs if this ratio is of order unity or larger. In the limit of purely entropic fluctuations in the ambient fluid, a strong rarefaction generates vorticity with a turbulent Mach number on the order of the rms of the ambient entropy fluctuations. The analytical results are shown to compare well with results from two- and three-dimensional numerical simulations. Analytical solutions are also derived in the linear regime of Reynolds-averaged turbulence models. This highlights an inconsistency in standard turbulence models that prevents them from accurately capturing the physics of rarefaction-turbulence interaction. In addition to providing physical insight, the solutions derived here can be used to verify algorithms of both the Reynolds-averaged and direct numerical simulation variety. Finally, dimensional analysis of the equations indicates that rapid distortion of turbulence can give rise to two distinct regimes in the turbulent spectrum: a distortion range at large scales where linear distortion effects dominate, and an inertial range at small scales where nonlinear effects dominate.« less

Csbnd H⋯Ni and Csbnd H⋯π(chelate) interactions in nickel(II) complexes involving functionalized dithiocarbamates and triphenylphosphine

NASA Astrophysics Data System (ADS)

Sathiyaraj, E.; Thirumaran, S.; Selvanayagam, S.; Sridhar, B.; Ciattini, Samuele

2018-05-01

New bis(N-benzyl-N-substituted benzyldithiocarbamato-S,S‧)nickel(II) (1-3) and (N-benzyl-N-substituted benzyldithiocarbamato-S,S‧)(isothiocyanato-N)- (triphenylphosphane)nickel(II) (4-6) [where substituted benzyl = 2-HOsbnd C6H4sbnd CH2sbnd (1,4), 3-HOsbnd C6H4sbnd CH2sbnd (2,5), 4-Fsbnd C6H4sbnd CH2sbnd (3,6)] were synthesized and characterized using IR, electronic, and NMR (1H and 13C) spectra. X-ray structural analysis of homoleptic complex (1) and heteroleptic complexes (5 and 6) confirmed the presence of four coordinated nickel in a distorted square planar arrangement with NiS4 and NiS2PN chromophores, respectively. The νC-S stretching vibrations are observed around 990 cm-1 without any splitting supporting the bidentate coordination of the dithiocarbamate ligand. Electronic spectral studies of all the complexes (1-6) indicate that the geometry of the nickel atom is probably square planar. NMR spectra of all homoleptic and heteroleptic complexes (1-6) reveal a weak signal associated with the backbone carbon (N13CS2) in the region 204.0-210.0 ppm with a weak intensity characteristic of the quaternary carbon signals. The greater trans influence of triphenylphosphine in complexes 5 and 6 is supported by the long Nisbnd S distance compared to other Nisbnd S distance which is opposite to the NCS- ligand. In the structure of complex 5, C-H⋯π(chelate) interactions results in polymeric chain. Both structures show intramolecular Ni⋯H interactions but that on 6 is the strongest. C-H⋯π interactions are also found in 1, 5 and 6. Hirshfeld surface analysis and the associated 2D fingerprint plots of 1, 5 and 6 have been studied to evaluate intermolecular interactions. The molecular geometries of complexes 1, 5 and 6 have been optimized by abinitio HF method using LANL2DZ program.

Enantiopure distorted ribbon-shaped nanographene combining two-photon absorption-based upconversion and circularly polarized luminescence.

PubMed

Cruz, Carlos M; Márquez, Irene R; Mariz, Inês F A; Blanco, Victor; Sánchez-Sánchez, Carlos; Sobrado, Jesús M; Martín-Gago, José A; Cuerva, Juan M; Maçôas, Ermelinda; Campaña, Araceli G

2018-04-28

Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push-pull geometry and the extended network of sp 2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results.

Evaluation of the efficacy of rotary vs. hand files in root canal preparation of primary teeth in vitro using CBCT.

PubMed

Musale, P K; Mujawar, S A V

2014-04-01

This in vitro study aimed to evaluate the efficacy of rotary ProFile, ProTaper, Hero Shaper and K-files in shaping ability, cleaning efficacy, preparation time and instrument distortion in primary molars. Sixty extracted primary mandibular second molars were divided into four equal groups: Group I K-file, Group II ProFile, Group III ProTaper file and Group IV Hero Shaper file. The shaping ability was determined by comparing pre- and post-instrumentation CBCT scans and data analysed with SPSS program using the Chi-square test. Cleaning efficacy was evaluated by the degree of India ink removal from the canal walls under stereomicroscopy. Instrumentation times were calculated for each tooth and instrument distortion was visually checked and duly noted. The cleaning efficacy and instrumentation time were determined using ANOVA with Tukey's correction. Instrument distortion was analysed using Chi-square test. The canal taper was significantly more conical for rotary files as compared to K-files with Chi-square test (p < 0.05). Cleaning efficacy of rotary files with average scores (Groups II- 0.68, III- 0.48 and IV- 0.58) was significantly better than K-files (Group I- 0.93) (p < 0.05). Mean instrumentation time with K-file (20.7 min) was significantly higher than rotary files (Groups II 8.9, III 5.6, and IV 8.1 min) (p < 0.05). Instrument distortion was observed in Group I (4.3%), while none of the rotary files were distorted. Rotary files prepared more conical canals in primary teeth than manual instruments. Reduced preparation time with rotary files enhances patient cooperation especially in young children.

Application of Least-Squares Adjustment Technique to Geometric Camera Calibration and Photogrammetric Flow Visualization

NASA Technical Reports Server (NTRS)

Chen, Fang-Jenq

1997-01-01

Flow visualization produces data in the form of two-dimensional images. If the optical components of a camera system are perfect, the transformation equations between the two-dimensional image and the three-dimensional object space are linear and easy to solve. However, real camera lenses introduce nonlinear distortions that affect the accuracy of transformation unless proper corrections are applied. An iterative least-squares adjustment algorithm is developed to solve the nonlinear transformation equations incorporated with distortion corrections. Experimental applications demonstrate that a relative precision on the order of 40,000 is achievable without tedious laboratory calibrations of the camera.

Correction of geometric distortion in Propeller echo planar imaging using a modified reversed gradient approach

PubMed Central

Chang, Hing-Chiu; Chuang, Tzu-Chao; Wang, Fu-Nien; Huang, Teng-Yi; Chung, Hsiao-Wen

2013-01-01

Objective This study investigates the application of a modified reversed gradient algorithm to the Propeller-EPI imaging method (periodically rotated overlapping parallel lines with enhanced reconstruction based on echo-planar imaging readout) for corrections of geometric distortions due to the EPI readout. Materials and methods Propeller-EPI acquisition was executed with 360-degree rotational coverage of the k-space, from which the image pairs with opposite phase-encoding gradient polarities were extracted for reversed gradient geometric and intensity corrections. The spatial displacements obtained on a pixel-by-pixel basis were fitted using a two-dimensional polynomial followed by low-pass filtering to assure correction reliability in low-signal regions. Single-shot EPI images were obtained on a phantom, whereas high spatial resolution T2-weighted and diffusion tensor Propeller-EPI data were acquired in vivo from healthy subjects at 3.0 Tesla, to demonstrate the effectiveness of the proposed algorithm. Results Phantom images show success of the smoothed displacement map concept in providing improvements of the geometric corrections at low-signal regions. Human brain images demonstrate prominently superior reconstruction quality of Propeller-EPI images with modified reversed gradient corrections as compared with those obtained without corrections, as evidenced from verification against the distortion-free fast spin-echo images at the same level. Conclusions The modified reversed gradient method is an effective approach to obtain high-resolution Propeller-EPI images with substantially reduced artifacts. PMID:23630654

Distortion correction for diffusion-weighted MRI tractography and fMRI in the temporal lobes.

PubMed

Embleton, Karl V; Haroon, Hamied A; Morris, David M; Ralph, Matthew A Lambon; Parker, Geoff J M

2010-10-01

Single shot echo-planar imaging (EPI) sequences are currently the most commonly used sequences for diffusion-weighted imaging (DWI) and functional magnetic resonance imaging (fMRI) as they allow relatively high signal to noise with rapid acquisition time. A major drawback of EPI is the substantial geometric distortion and signal loss that can occur due to magnetic field inhomogeneities close to air-tissue boundaries. If DWI-based tractography and fMRI are to be applied to these regions, then the distortions must be accurately corrected to achieve meaningful results. We describe robust acquisition and processing methods for correcting such distortions in spin echo (SE) EPI using a variant of the reversed direction k space traversal method with a number of novel additions. We demonstrate that dual direction k space traversal with maintained diffusion-encoding gradient strength and direction results in correction of the great majority of eddy current-associated distortions in DWI, in addition to those created by variations in magnetic susceptibility. We also provide examples to demonstrate that the presence of severe distortions cannot be ignored if meaningful tractography results are desired. The distortion correction routine was applied to SE-EPI fMRI acquisitions and allowed detection of activation in the temporal lobe that had been previously found using PET but not conventional fMRI. © 2010 Wiley-Liss, Inc.

New copper complexes with bipyrazolic ligands: Synthesis, characterization and evaluation of the antibacterial and catalytic properties

NASA Astrophysics Data System (ADS)

Harit, Tarik; Abouloifa, Houssam; Tillard, Monique; Eddike, Driss; Asehraou, Abdeslam; Malek, Fouad

2018-07-01

The synthesis of new bipyrazolic ligands functionalized by carboxyl groups, namely 3-Bis(3‧-carboxyl-5‧-methyl-l'-pyrazolyl) propan-2-ol (L1) and 1,3-Bis(3‧-carboxyl-5‧-methyl-l '-pyrazolyl),2-methyl propane (L2) is reported. Their corresponding [C13H15CuN4O5] (CuL1) and [C14H16CuN4O4] (CuL2) copper (II) complexes are also elaborated and characterized by elemental analysis, FTIR an UV-visible spectroscopy. The crystal structure of the CuL1 complex confirms that copper atom is 4-coordinated, in a distorted square planar geometry within the molecule, and achieves its coordination through weak intermolecular interactions leading to two dimensional slabs. This geometry is in agreement with UV-visible results which also evidence that structure of complexes are affected in DMSO in contrast to methanol. No antibacterial activity against all the tested bacterial strains has been found for the Cu (II) complexes. By contrast, CuL1 is characterized with good catalytic properties in the air-oxidation of catechol substrate to quinone.

Beyond the structure-property relationship paradigm: influence of the crystal structure and microstructure on the Li+ conductivity of La2/3Li(x)Ti(1-x)Al(x)O3 Oxides.

PubMed

García-Martín, Susana; Morata-Orrantía, Ainhoa; Alario-Franco, Miguel A; Rodríguez-Carvajal, Juan; Amador, Ulises

2007-01-01

The crystal structures of several oxides of the La(2/3)Li(x)Ti(1-x)Al(x)O(3) system have been studied by selected-area electron diffraction, high-resolution transmission electron microscopy, and powder neutron diffraction, and their lithium conductivity has been by complex impedance spectroscopy. The compounds have a perovskite-related structure with a unit cell radical2 a(p)x2 a(p)x radical2 a(p) (a(p)=perovskite lattice parameter) due to the tilting of the (Ti/Al)O(6) octahedra and the ordering of lanthanum and lithium ions and vacancies along the 2 a(p) axis. The Li(+) ions present a distorted square-planar coordination and are located in interstitial positions of the structure, which could explain the very high ionic conductivity of this type of material. The lithium conductivity depends on the oxide composition and its crystal microstructure, which varies with the thermal treatment of the sample. The microstructure of these titanates is complex due to formation of domains of ordering and other defects such as strains and compositional fluctuations.

1D cyanide complexes with 2-pyridinemethanol: Synthesis, crystal structures and spectroscopic properties

NASA Astrophysics Data System (ADS)

Sayın, Elvan; Kürkçüoğlu, Güneş Süheyla; Yeşilel, Okan Zafer; Hökelek, Tuncer

2015-12-01

Two new one-dimensional coordination polymers, [Cu(hmpH)2Pd(μ-CN)2(CN)2]n (1) and [Cu(hmpH)2Pt(μ-CN)2(CN)2]n (2), (hmpH = 2-pyridinemethanol), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. Single crystal X-ray diffraction analysis indicates that complexes 1 and 2 are isomorphous and isostructural, and crystallize in the triclinic system and P-1 space group. The Pd(II) or Pt(II) ions are four coordinated with four cyanide-carbon atoms in a square planar geometry. Cu(II) ion displays a distorted octahedral coordination by two N-atoms and two O-atoms of hmpH ligands, two bridging cyanide groups. In one dimensional structure of the complexes, [M(CN)4]2- (M = Pd(II) or Pt(II)) anions and [Cu(hmpH)2]2+ cations are linked via bridging cyanide ligands. In the complexes, the presence of intramolecular C-H⋯M (M = Pd(II) or Pt(II)) interactions with distance values of 3.00-2.95 Å are established, respectively.

One dimensional coordination polymers: Synthesis, crystal structures and spectroscopic properties

NASA Astrophysics Data System (ADS)

Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Şahin, Onur

2016-11-01

Two new one dimensional (1D) cyanide complexes, namely [M(4-aepy)2(H2O)2][Pt(CN)4], (4-aepy = 4-(2-aminoethyl)pyridine M = Cu(II) (1) or Zn(II) (2)), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The crystallographic analyses reveal that 1 and 2 are isomorphous and isostructural, and crystallize in the monoclinic system and C2 space group. The Pt(II) ions are coordinated by four cyanide-carbon atoms in the square-planar geometry and the [Pt(CN)4]2- ions act as a counter ion. The M(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4-aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. The crystal structures of 1 and 2 are similar each other and linked via intermolecular hydrogen bonding, Pt⋯π interactions to form 3D supramolecular network. Vibration assignments of all the observed bands are given and the spectral features also supported to the crystal structures of the complexes.

The binuclear nickel center in the A-cluster of acetyl-CoA synthase (ACS) and two biomimetic dinickel complexes studied by X-ray absorption and emission spectroscopy

NASA Astrophysics Data System (ADS)

Schrapers, P.; Mebs, S.; Ilina, Y.; Warner, D. S.; Wörmann, C.; Schuth, N.; Kositzki, R.; Dau, H.; Limberg, C.; Dobbek, H.; Haumann, M.

2016-05-01

Acetyl-CoA synthase (ACS) is involved in the bacterial carbon oxide conversion pathway. The binuclear nickel sites in ACS enzyme and two biomimetic synthetic compounds containing a Ni(II)Ni(II) unit (1 and 2) were compared using XAS/XES. EXAFS analysis of ACS proteins revealed similar Ni-N/O/S bond lengths and Ni-Ni/Fe distances as in the crystal structure in oxidized ACS, but elongated Ni-ligand bonds in reduced ACS, suggesting more reduced nickel species. The XANES spectra of ACS and the dinickel complexes showed overall similar shapes, but less resolved pre-edge and edge features in ACS, attributed to more distorted square-planar nickel sites in particular in reduced ACS. DFT calculation of pre-edge absorption and Kβ2,5 emission features reproduced the experimental spectra of the synthetic complexes, was sensitive even to the small geometry differences in 1 and 2, and indicated low-spin Ni(II) sites. Comparison of nickel sites in proteins and biomimetic compounds is valuable for deducing structural and electronic differences in response to ligation and redox changes.

Redetermination of (2,2'-bipyridine-κN,N')dichlorido-palladium(II) dichloro-methane solvate.

PubMed

Kim, Nam-Ho; Hwang, In-Chul; Ha, Kwang

2009-05-07

In the title compound, [PdCl(2)(C(10)H(8)N(2))]·CH(2)Cl(2), the Pd(2+) ion is four-coordinated in a slightly distorted square-planar environment by two N atoms of the 2,2'-bipyridine (bipy) ligand and two chloride ions. The compound displays intra-molecular C-H⋯Cl hydrogen bonds and pairs of complex mol-ecules are connected by inter-molecular C-H⋯Cl hydrogen bonds. Inter-molecular π-π inter-actions are present between the pyridine rings of the ligand, the shortest centroid-centroid distance being 4.096 (3) Å. As a result of the electronic nature of the chelate ring, it is possible to create π-π inter-actions to its symmetry-related counterpart [3.720 (2) Å] and also with a pyridine ring [3.570 (3) Å] of the bipy unit. The present structure is a redetermination of a previous structure [Vicente et al. (1997 ▶). Private communication (refcode PYCXMN02). CCDC, Cambridge, England]. In the new structure refinement all H atoms were located in a difference Fourier synthesis. Their coordinates were refined freely, together with isotropic displacement parameters.

Regulation of planar growth by the Arabidopsis AGC protein kinase UNICORN.

PubMed

Enugutti, Balaji; Kirchhelle, Charlotte; Oelschner, Maxi; Torres Ruiz, Ramón Angel; Schliebner, Ivo; Leister, Dario; Schneitz, Kay

2012-09-11

The spatial coordination of growth is of central importance for the regulation of plant tissue architecture. Individual layers, such as the epidermis, are clonally propagated and structurally maintained by symmetric cell divisions that are oriented along the plane of the layer. The developmental control of this process is poorly understood. The simple cellular basis and sheet-like structure of Arabidopsis integuments make them an attractive model system to address planar growth. Here we report on the characterization of the Arabidopsis UNICORN (UCN) gene. Analysis of ucn integuments reveals localized distortion of planar growth, eventually resulting in an ectopic multicellular protrusion. In addition, ucn mutants exhibit ectopic growth in filaments and petals, as well as aberrant embryogenesis. We further show that UCN encodes an active AGC VIII kinase. Genetic, biochemical, and cell biological data suggest that UCN suppresses ectopic growth in integuments by directly repressing the KANADI transcription factor ABERRANT TESTA SHAPE. Our findings indicate that UCN represents a unique plant growth regulator that maintains planar growth of integuments by repressing a developmental regulator involved in the control of early integument growth and polarity.

Wavefront Correction for Large, Flexible Antenna Reflector

NASA Technical Reports Server (NTRS)

Imbriale, William A.; Jammejad, Vahraz; Rajagopalan, Harish; Xu, Shenheng

2010-01-01

A wavefront-correction system has been proposed as part of an outer-space radio communication system that would include a large, somewhat flexible main reflector antenna, a smaller subreflector antenna, and a small array feed at the focal plane of these two reflector antennas. Part of the wavefront-correction system would reside in the subreflector, which would be a planar patch-element reflectarray antenna in which the phase shifts of the patch antenna elements would be controlled via microelectromechanical systems (MEMS) radio -frequency (RF) switches. The system would include the following sensing-and-computing subsystems: a) An optical photogrammetric subsystem built around two cameras would estimate geometric distortions of the main reflector; b) A second subsystem would estimate wavefront distortions from amplitudes and phases of signals received by the array feed elements; and c) A third subsystem, built around small probes on the subreflector plane, would estimate wavefront distortions from differences among phases of signals received by the probes. The distortion estimates from the three subsystems would be processed to generate control signals to be fed to the MEMS RF switches to correct for the distortions, thereby enabling collimation and aiming of the received or transmitted radio beam to the required precision.

On the use of water phantom images to calibrate and correct eddy current induced artefacts in MR diffusion tensor imaging.

PubMed

Bastin, M E; Armitage, P A

2000-07-01

The accurate determination of absolute measures of diffusion anisotropy in vivo using single-shot, echo-planar imaging techniques requires the acquisition of a set of high signal-to-noise ratio, diffusion-weighted images that are free from eddy current induced image distortions. Such geometric distortions can be characterized and corrected in brain imaging data using magnification (M), translation (T), and shear (S) distortion parameters derived from separate water phantom calibration experiments. Here we examine the practicalities of using separate phantom calibration data to correct high b-value diffusion tensor imaging data by investigating the stability of these distortion parameters, and hence the eddy currents, with time. It is found that M, T, and S vary only slowly with time (i.e., on the order of weeks), so that calibration scans need not be performed after every patient examination. This not only minimises the scan time required to collect the calibration data, but also the computational time needed to characterize these eddy current induced distortions. Examples of how measurements of diffusion anisotropy are improved using this post-processing scheme are also presented.

μ-Carbonato-bis­(bis­{2-[(diethyl­amino)­meth­yl]phen­yl}bis­muth(III))

PubMed Central

Soran, Albert P.; Nema, Mihai G.; Breunig, Hans J.; Silvestru, Cristian

2011-01-01

The mol­ecular structure of the title compound, [Bi2(C11H16N)4(CO3)], consists of a symmetrically bridging carbonato group which binds two [2-Et2NCH2C6H4]2Bi units that are crystallographically related via a twofold rotation axis bis­ecting the carbonate group. The two Bi atoms and two of the C atoms directly bonded to bis­muth are quasi-planar [deviations of 0.323 (1) and 0.330 (9)Å for the Bi and C atoms, respectively] with the carbonate group. The remaining two ligands are in a trans arrangement relative to the quasi-planar (CBi)2CO3 system. The metal atom is strongly coordinated by the N atom of one pendant arm [Bi—N = 2.739 (6) Å], almost trans to the O atom, while the N atom of the other pendant arm exhibits a weaker intra­molecular inter­action [Bi⋯N = 3.659 (7) Å] almost trans to a C atom. If both these intra­molecular N→Bi inter­actions per metal atom are considered, the overall coordination geometry at bis­muth becomes distorted square-pyramidal [(C,N)2BiO cores] and the compound can be described as a hypervalent 12-Bi-5 species. Additional quite short intra­molecular Bi⋯O inter­actions are also present [3.796 (8)–4.020 (9) Å]. Inter­molecular associations through weak η6⋯Bi inter­actions [Bi⋯centroid of benzene ring = 3.659 (1) Å] lead to a ribbon-like supra­molecular association. PMID:21522836

Synthesis and ab initioStructure Determination from Powder X-Ray Diffraction Data of a New Metallic Mixed-Valence Platinum-Lead Oxide PbPt 2O 4

NASA Astrophysics Data System (ADS)

Tancret, N.; Obbade, S.; Bettahar, N.; Abraham, F.

1996-07-01

The mixed-valence PbPt2O4compound was synthesized both by solid state reaction between stoichiometric amounts of PbO and Pt heated at 650-750°C for 1 week and by chemical attack of Pb2PtO4. It decomposes to PbO and Pt at 750°C. The crystal structure was completely solved from direct methods and difference Fourier maps from powder X-ray diffraction data. The unit cell is triclinic (space groupP1,Z= 2) witha= 6.1161(2) Å,b= 6.6504(2) Å,c= 5.5502(2) Å, α = 97.178(2)°, β = 108.803(2)°, and γ = 115.241(2)°. The structural model was refined using the Rietveld profile technique and led to the reliability factorsRwp= 0.118,Rp= 0.086,RBragg= 0.029,RF= 0.018, and χ2= 1.51. The structure of PbPt2O4appears to be a unique one involving both Pt4+in octahedral coordination and Pt2+or partially oxidized platinum in square-planar coordination. The PbPt2O4structure consists of columnar-stacked PtO4groups extending along thecaxis of the unit cell. These columnar stacks are held by other planar PtO4groups to constitute Pt3O8sheets. These sheets are linked together by PtO6octahedra to form a three-dimensional framework. Lead atoms are surrounded by six oxygens forming a distorted octahedron. Metallic conductivity in PbPt2O4is consistent with short Pt-Pt bonds in the columnar stacks of PtO4groups along thecaxis direction (dPt-Pt= 2.78 Å).

μ-Carbonato-bis-(bis-{2-[(diethyl-amino)-meth-yl]phen-yl}bis-muth(III)).

PubMed

Soran, Albert P; Nema, Mihai G; Breunig, Hans J; Silvestru, Cristian

2011-01-12

The mol-ecular structure of the title compound, [Bi(2)(C(11)H(16)N)(4)(CO(3))], consists of a symmetrically bridging carbonato group which binds two [2-Et(2)NCH(2)C(6)H(4)](2)Bi units that are crystallographically related via a twofold rotation axis bis-ecting the carbonate group. The two Bi atoms and two of the C atoms directly bonded to bis-muth are quasi-planar [deviations of 0.323 (1) and 0.330 (9)Å for the Bi and C atoms, respectively] with the carbonate group. The remaining two ligands are in a trans arrangement relative to the quasi-planar (CBi)(2)CO(3) system. The metal atom is strongly coordinated by the N atom of one pendant arm [Bi-N = 2.739 (6) Å], almost trans to the O atom, while the N atom of the other pendant arm exhibits a weaker intra-molecular inter-action [Bi⋯N = 3.659 (7) Å] almost trans to a C atom. If both these intra-molecular N→Bi inter-actions per metal atom are considered, the overall coordination geometry at bis-muth becomes distorted square-pyramidal [(C,N)(2)BiO cores] and the compound can be described as a hypervalent 12-Bi-5 species. Additional quite short intra-molecular Bi⋯O inter-actions are also present [3.796 (8)-4.020 (9) Å]. Inter-molecular associations through weak η(6)⋯Bi inter-actions [Bi⋯centroid of benzene ring = 3.659 (1) Å] lead to a ribbon-like supra-molecular association.

RF Magnetic Field Uniformity of Rectangular Planar Coils for Resonance Imaging

DTIC Science & Technology

2016-02-04

coil with square -shaped overlapping turns along the 135mm length of the coil. This paper compares these two coils to determine which has a more...in which, the coil arrays consist of a few square or circular coils side-by-side or overlapping. Mobile unilateral NMR/MRI scanners were...magnetic field along the length of a normal rectangular coil (NRC) and a rectangular coil with overlapping square -shaped turns (RCOS). The RCOS coil is

Synthesis, X-ray crystallography, and computational analysis of 1-azafenestranes.

PubMed

Denmark, Scott E; Montgomery, Justin I; Kramps, Laurenz A

2006-09-06

The tandem [4+2]/[3+2] cycloaddition of nitroalkenes has been employed in the synthesis of 1-azafenestranes, molecules of theoretical interest because of planarizing distortion of their central carbon atoms. The synthesis of c,c,c,c-[5.5.5.5]-1-azafenestrane was completed in good yield from a substituted nitrocyclopentene, and its borane adduct was analyzed through X-ray crystallography, which showed a moderate distortion from ideal tetrahedral geometry. The syntheses of two members of the [4.5.5.5] family of 1-azafenestranes are also reported, including one with a trans fusion at a bicyclic ring junction which brings about considerable planarization of one of the central angles (16.8 degrees deviation from tetrahedral geometry). While investigating the [4.5.5.5]-1-azafenestranes, a novel dyotropic rearrangement that converts nitroso acetals into tetracyclic aminals was discovered. Through conformational analysis, a means to prevent this molecular reorganization was formulated and realized experimentally with the use of a bulky vinyl ether in the key [4+2] cycloaddition reaction. Finally, DFT calculations on relative strain energy for the 1-azafenestranes, as well as their predicted central angles, are disclosed.

Processing techniques development, volume 3

NASA Technical Reports Server (NTRS)

Landgrebe, D. A. (Principal Investigator); Anuta, P. E.; Hixson, M. M.; Swain, P. H.

1978-01-01

The author has identified the following significant results. Analysis of the geometric characteristics of the aircraft synthetic aperture radar (SAR) relative to LANDSAT indicated that relatively low order polynominals would model the distortions to subpixel accuracy to bring SAR into registration for good quality imagery. Also the area analyzed was small, about 10 miles square, so this is an additional constraint. For the Air Force/ERIM data, none of the tested methods could achieve subpixel accuracy. Reasons for this is unknown; however, the noisy (high scintillation) nature of the data and attendent unrecognizability of features contribute to this error. It is concluded that the quadratic model would adequately provide distortion modeling for small areas, i.e., 10 to 20 miles square.

Capillary Assembly of Colloids: Interactions on Planar and Curved Interfaces

NASA Astrophysics Data System (ADS)

Liu, Iris B.; Sharifi-Mood, Nima; Stebe, Kathleen J.

2018-03-01

In directed assembly, small building blocks are assembled into an organized structure under the influence of guiding fields. Capillary interactions provide a versatile route for structure formation. Colloids adsorbed on fluid interfaces distort the interface, which creates an associated energy field. When neighboring distortions overlap, colloids interact to minimize interfacial area. Contact line pinning, particle shape, and surface chemistry play important roles in structure formation. Interface curvature acts like an external field; particles migrate and assemble in patterns dictated by curvature gradients. We review basic analysis and recent findings in this rapidly evolving literature. Understanding the roles of assembly is essential for tuning the mechanical, physical, and optical properties of the structure.

Well-Defined Chiral Gold(III) Complexes: New Opportunities in Asymmetric Catalysis.

PubMed

Rodriguez, Jessica; Bourissou, Didier

2018-01-08

Square way to heaven: As a result of their square-planar geometry, the reactive site of gold(III) complexes is much closer to the ancillary ligands. This offers new perspectives in asymmetric catalysis, as recently evidenced by the groups of Wong and Toste with well-defined chiral complexes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transmission mode adaptive beamforming for planar phased arrays and its application to 3D ultrasonic transcranial imaging

NASA Astrophysics Data System (ADS)

Shapoori, Kiyanoosh; Sadler, Jeffrey; Wydra, Adrian; Malyarenko, Eugene; Sinclair, Anthony; Maev, Roman G.

2013-03-01

A new adaptive beamforming method for accurately focusing ultrasound behind highly scattering layers of human skull and its application to 3D transcranial imaging via small-aperture planar phased arrays are reported. Due to its undulating, inhomogeneous, porous, and highly attenuative structure, human skull bone severely distorts ultrasonic beams produced by conventional focusing methods in both imaging and therapeutic applications. Strong acoustical mismatch between the skull and brain tissues, in addition to the skull's undulating topology across the active area of a planar ultrasonic probe, could cause multiple reflections and unpredictable refraction during beamforming and imaging processes. Such effects could significantly deflect the probe's beam from the intended focal point. Presented here is a theoretical basis and simulation results of an adaptive beamforming method that compensates for the latter effects in transmission mode, accompanied by experimental verification. The probe is a custom-designed 2 MHz, 256-element matrix array with 0.45 mm element size and 0.1mm kerf. Through its small footprint, it is possible to accurately measure the profile of the skull segment in contact with the probe and feed the results into our ray tracing program. The latter calculates the new time delay patterns adapted to the geometrical and acoustical properties of the skull phantom segment in contact with the probe. The time delay patterns correct for the refraction at the skull-brain boundary and bring the distorted beam back to its intended focus. The algorithms were implemented on the ultrasound open-platform ULA-OP (developed at the University of Florence).

Clinical evaluation of single-shot and readout-segmented diffusion-weighted imaging in stroke patients at 3 T.

PubMed

Morelli, John; Porter, David; Ai, Fei; Gerdes, Clint; Saettele, Megan; Feiweier, Thorsten; Padua, Abraham; Dix, James; Marra, Michael; Rangaswamy, Rajesh; Runge, Val

2013-04-01

Diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI) is most commonly performed utilizing a single-shot echo-planar imaging technique (ss-EPI). Susceptibility artifact and image blur are severe when this sequence is utilized at 3 T. To evaluate a readout-segmented approach to DWI MR in comparison with single-shot echo planar imaging for brain MRI. Eleven healthy volunteers and 14 patients with acute and early subacute infarctions underwent DWI MR examinations at 1.5 and 3T with ss-EPI and readout-segmented echo-planar (rs-EPI) DWI at equal nominal spatial resolutions. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) calculations were made, and two blinded readers ranked the scans in terms of high signal intensity bulk susceptibility artifact, spatial distortions, image blur, overall preference, and motion artifact. SNR and CNR were greatest with rs-EPI (8.1 ± 0.2 SNR vs. 6.0 ± 0.2; P <10(-4) at 3T). Spatial distortions were greater with single-shot (0.23 ± 0.03 at 3T; P <0.001) than with rs-EPI (0.12 ± 0.02 at 3T). Combined with blur and artifact reduction, this resulted in a qualitative preference for the readout-segmented scans overall. Substantial image quality improvements are possible with readout-segmented vs. single-shot EPI - the current clinical standard for DWI - regardless of field strength (1.5 or 3 T). This results in improved image quality secondary to greater real spatial resolution and reduced artifacts from susceptibility in MR imaging of the brain.

Internal process: what is abstraction and distortion process?

NASA Astrophysics Data System (ADS)

Fiantika, F. R.; Budayasa, I. K.; Lukito, A.

2018-03-01

Geometry is one of the branch of mathematics that plays a major role in the development of science and technology. Thus, knowing the geometry concept is needed for students from their early basic level of thinking. A preliminary study showed that the elementary students have difficulty in perceiving parallelogram shape in a 2-dimention of a cube drawing as a square shape. This difficulty makes the students can not solve geometrical problems correctly. This problem is related to the internal thinking process in geometry. We conducted the exploration of students’ internal thinking processes in geometry particularly in distinguishing the square and parallelogram shape. How the students process their internal thinking through distortion and abstraction is the main aim of this study. Analysis of the geometrical test and deep interview are used in this study to obtain the data. The result of this study is there are two types of distortion and abstraction respectively in which the student used in their internal thinking processes.

Distortion correction in EPI at ultra-high-field MRI using PSF mapping with optimal combination of shift detection dimension.

PubMed

Oh, Se-Hong; Chung, Jun-Young; In, Myung-Ho; Zaitsev, Maxim; Kim, Young-Bo; Speck, Oliver; Cho, Zang-Hee

2012-10-01

Despite its wide use, echo-planar imaging (EPI) suffers from geometric distortions due to off-resonance effects, i.e., strong magnetic field inhomogeneity and susceptibility. This article reports a novel method for correcting the distortions observed in EPI acquired at ultra-high-field such as 7 T. Point spread function (PSF) mapping methods have been proposed for correcting the distortions in EPI. The PSF shift map can be derived either along the nondistorted or the distorted coordinates. Along the nondistorted coordinates more information about compressed areas is present but it is prone to PSF-ghosting artifacts induced by large k-space shift in PSF encoding direction. In contrast, shift maps along the distorted coordinates contain more information in stretched areas and are more robust against PSF-ghosting. In ultra-high-field MRI, an EPI contains both compressed and stretched regions depending on the B0 field inhomogeneity and local susceptibility. In this study, we present a new geometric distortion correction scheme, which selectively applies the shift map with more information content. We propose a PSF-ghost elimination method to generate an artifact-free pixel shift map along nondistorted coordinates. The proposed method can correct the effects of the local magnetic field inhomogeneity induced by the susceptibility effects along with the PSF-ghost artifact cancellation. We have experimentally demonstrated the advantages of the proposed method in EPI data acquisitions in phantom and human brain using 7-T MRI. Copyright © 2011 Wiley Periodicals, Inc.

The Assessment of Distortion in Neurosurgical Image Overlay Projection.

PubMed

Vakharia, Nilesh N; Paraskevopoulos, Dimitris; Lang, Jozsef; Vakharia, Vejay N

2016-02-01

Numerous studies have demonstrated the superiority of neuronavigation during neurosurgical procedures compared to non-neuronavigation-based procedures. Limitations to neuronavigation systems include the need for the surgeons to avert their gaze from the surgical field and the cost of the systems, especially for hospitals in developing countries. Overlay projection of imaging directly onto the patient allows localization of intracranial structures. A previous study using overlay projection demonstrated the accuracy of image coregistration for a lesion in the temporal region but did not assess image distortion when projecting onto other anatomical locations. Our aim is to quantify this distortion and establish which regions of the skull would be most suitable for overlay projection. Using the difference in size of a square grid when projected onto an anatomically accurate model skull and a flat surface, from the same distance, we were able to calculate the degree of image distortion when projecting onto the skull from the anterior, posterior, superior, and lateral aspects. Measuring the size of a square when projected onto a flat surface from different distances allowed us to model change in lesion size when projecting a deep structure onto the skull surface. Using 2 mm as the upper limit for distortion, our results show that images can be accurately projected onto the majority (81.4%) of the surface of the skull. Our results support the use of image overlay projection in regions with ≤2 mm distortion to assist with localization of intracranial lesions at a fraction of the cost of existing methods. © The Author(s) 2015.

Effects of image distortions originating from susceptibility variations and concomitant fields on diffusion MRI tractography results

PubMed Central

Irfanoglu, M. Okan; Walker, Lindsay; Sarlls, Joelle; Marenco, Stefano; Pierpaoli, Carlo

2013-01-01

In this work we investigate the effects of echo planar imaging (EPI) distortions on diffusion tensor imaging (DTI) based fiber tractography results. We propose a simple experimental framework that would enable assessing the effects of EPI distortions on the accuracy and reproducibility of fiber tractography from a pilot study on a few subjects. We compare trajectories computed from two diffusion datasets collected on each subject that are identical except for the orientation of phase encode direction, either right–left (RL) or anterior–posterior (AP). We define metrics to assess potential discrepancies between RL and AP trajectories in association, commissural, and projection pathways. Results from measurements on a 3 Tesla clinical scanner indicated that the effects of EPI distortions on computed fiber trajectories are statistically significant and large in magnitude, potentially leading to erroneous inferences about brain connectivity. The correction of EPI distortion using an image-based registration approach showed a significant improvement in tract consistency and accuracy. Although obtained in the context of a DTI experiment, our findings are generally applicable to all EPI-based diffusion MRI tractography investigations, including high angular resolution (HARDI) methods. On the basis of our findings, we recommend adding an EPI distortion correction step to the diffusion MRI processing pipeline if the output is to be used for fiber tractography. PMID:22401760

Assessing the performance of different DTI motion correction strategies in the presence of EPI distortion correction.

PubMed

Taylor, Paul A; Alhamud, A; van der Kouwe, Andre; Saleh, Muhammad G; Laughton, Barbara; Meintjes, Ernesta

2016-12-01

Diffusion tensor imaging (DTI) is susceptible to several artifacts due to eddy currents, echo planar imaging (EPI) distortion and subject motion. While several techniques correct for individual distortion effects, no optimal combination of DTI acquisition and processing has been determined. Here, the effects of several motion correction techniques are investigated while also correcting for EPI distortion: prospective correction, using navigation; retrospective correction, using two different popular packages (FSL and TORTOISE); and the combination of both methods. Data from a pediatric group that exhibited incidental motion in varying degrees are analyzed. Comparisons are carried while implementing eddy current and EPI distortion correction. DTI parameter distributions, white matter (WM) maps and probabilistic tractography are examined. The importance of prospective correction during data acquisition is demonstrated. In contrast to some previous studies, results also show that the inclusion of retrospective processing also improved ellipsoid fits and both the sensitivity and specificity of group tractographic results, even for navigated data. Matches with anatomical WM maps are highest throughout the brain for data that have been both navigated and processed using TORTOISE. The inclusion of both prospective and retrospective motion correction with EPI distortion correction is important for DTI analysis, particularly when studying subject populations that are prone to motion. Hum Brain Mapp 37:4405-4424, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Direct discretization of planar div-curl problems

NASA Technical Reports Server (NTRS)

Nicolaides, R. A.

1989-01-01

A control volume method is proposed for planar div-curl systems. The method is independent of potential and least squares formulations, and works directly with the div-curl system. The novelty of the technique lies in its use of a single local vector field component and two control volumes rather than the other way around. A discrete vector field theory comes quite naturally from this idea and is developed. Error estimates are proved for the method, and other ramifications investigated.

Q-ball imaging with PROPELLER EPI acquisition.

PubMed

Chou, Ming-Chung; Huang, Teng-Yi; Chung, Hsiao-Wen; Hsieh, Tsyh-Jyi; Chang, Hing-Chiu; Chen, Cheng-Yu

2013-12-01

Q-ball imaging (QBI) is an imaging technique that is capable of resolving intravoxel fiber crossings; however, the signal readout based on echo-planar imaging (EPI) introduces geometric distortions in the presence of susceptibility gradients. This study proposes an imaging technique that reduces susceptibility distortions in QBI by short-axis PROPELLER EPI acquisition. Conventional QBI and PROPELLER QBI data were acquired from two 3T MR scans of the brains of five healthy subjects. Prior to the PROPELLER reconstruction, residual distortions in single-blade low-resolution b0 and diffusion-weighted images (DWIs) were minimized by linear affine and nonlinear diffeomorphic demon registrations. Subsequently, the PROPELLER keyhole reconstruction was applied to the corrected DWIs to obtain high-resolution PROPELLER DWIs. The generalized fractional anisotropy and orientation distribution function maps contained fewer distortions in PROPELLER QBI than in conventional QBI, and the fiber tracts more closely matched the brain anatomy depicted by turbo spin-echo (TSE) T2-weighted imaging (T2WI). Furthermore, for fixed T(E), PROPELLER QBI enabled a shorter scan time than conventional QBI. We conclude that PROPELLER QBI can reduce susceptibility distortions without lengthening the acquisition time and is suitable for tracing neuronal fiber tracts in the human brain. Copyright © 2013 John Wiley & Sons, Ltd.

Identification of non-classical C-H···M interactions in early and late transition metal complexes containing the CH(ArO)3 ligand.

PubMed

Lein, Matthias; Harrison, John A; Nielson, Alastair J

2013-08-14

The fully optimised DFT structure of the d(0) complex [{CH(ArO)3}Ti(NEt2)] (2) at the B3LYP level compares well with the distorted tetrahedral geometry shown by the X-ray crystal structure. QTAIM analysis of the electron density associated with the C-H···Ti interaction shows a well defined bond critical point, a bond path between the hydrogen and titanium centres and a negative value for the energy density indicative of covalency. A natural bond orbital (NBO) picture of the interaction shows that the C-H σ bond electron density donates to a d hybrid orbital on the metal in a linear fashion. Calculated IR and NMR data for the components of the interaction are consistent with experiment. The computed structures for [{CH(ArO)3}Ti(OPh)] (3), [{CH(ArO)3}Zr(NEt2)] (4), [{CH(ArO)3}Hf(NEt2)] (5), show tetrahedral geometries and QTAIM and NBO properties similar to (2). [{CH(ArO)3}Mo(NEt2)] (6) shows distortion of the tripodal ligand and a reduced C-H···M bond angle with properties more consistent with a C-H···M side-on donor interaction. In [{CH(ArO)3}Fe(NEt2)] (7) the C-H···M bond angle is linear and involves a donor interaction. An energy minimised structure maintaining the three fold coordination to the tripodal ligand was not obtained for [{CH(ArO)3}Ni(NEt2)](2-) but changing from a diethyl amide ligand to phenolato gave energy minimised [{CH(ArO)3}Ni(OPh)](2-) (8). This structure shows a distorted square planar geometry with a substantially bent phenoxo ligand and a near linear C-H···M covalent interaction with donor and back bonding properties. The work shows that linear C-H···M interactions can have both agostic and weak hydrogen bond-like covalency.

Least squares reconstruction of non-linear RF phase encoded MR data.

PubMed

Salajeghe, Somaie; Babyn, Paul; Sharp, Jonathan C; Sarty, Gordon E

2016-09-01

The numerical feasibility of reconstructing MRI signals generated by RF coils that produce B1 fields with a non-linearly varying spatial phase is explored. A global linear spatial phase variation of B1 is difficult to produce from current confined to RF coils. Here we use regularized least squares inversion, in place of the usual Fourier transform, to reconstruct signals generated in B1 fields with non-linear phase variation. RF encoded signals were simulated for three RF coil configurations: ideal linear, parallel conductors and, circular coil pairs. The simulated signals were reconstructed by Fourier transform and by regularized least squares. The Fourier reconstruction of simulated RF encoded signals from the parallel conductor coil set showed minor distortions over the reconstruction of signals from the ideal linear coil set but the Fourier reconstruction of signals from the circular coil set produced severe geometric distortion. Least squares inversion in all cases produced reconstruction errors comparable to the Fourier reconstruction of the simulated signal from the ideal linear coil set. MRI signals encoded in B1 fields with non-linearly varying spatial phase may be accurately reconstructed using regularized least squares thus pointing the way to the use of simple RF coil designs for RF encoded MRI. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.

Synthesis, structural characterization and DFT calculation on a square-planar Ni(II) complex of a compartmental Schiff base ligand

NASA Astrophysics Data System (ADS)

Biswas, Surajit; Dolai, Malay; Dutta, Arpan; Ali, Mahammad

2016-12-01

Reaction of a symmetric compartmental Schiff-base ligand, (H2L) with nickel(II) perchlorate hexahydrate in 1:1 M ratio in methanol gives rise to a mononuclear nickel(II) compound, NiL (1). The compound has been characterized by C, H, N microanalyses and UV-Vis spectra. The single crystal X-ray diffraction studies reveal a square planar geometry around the Ni(II) center. The compound crystallizes in monoclinic system with space group C2/c with a = 21.6425(6), b = 9.9481(3), c = 13.1958(4) Å, β = 107.728(2)°, V = 2706.16(14) Å3 and Z = 4. Ground state DFT optimization and TDDFT calculations on the ligand and complex were performed to get their UV-Vis spectral pattern.

Fine woody fuel particle diameters for improved planar intersect fuel loading estimates in Southern Rocky Mountain ponderosa pine forests

Treesearch

Emma Vakili; Chad M. Hoffman; Robert E. Keane

2016-01-01

Fuel loading estimates from planar intersect sampling protocols for fine dead down woody surface fuels require an approximation of the mean squared diameter (d2) of 1-h (0-0.63 cm), 10-h (0.63-2.54 cm), and 100-h (2.54-7.62 cm) timelag size classes. The objective of this study is to determine d2 in ponderosa pine (Pinus ponderosa) forests of New Mexico and Colorado,...

Functional modulation of a protein folding landscape via side-chain distortion

PubMed Central

Kelch, Brian A.; Salimi, Neema L.; Agard, David A.

2012-01-01

Ultrahigh-resolution (< 1.0 Å) structures have revealed unprecedented and unexpected details of molecular geometry, such as the deformation of aromatic rings from planarity. However, the functional utility of such energetically costly strain is unknown. The 0.83 Å structure of α-lytic protease (αLP) indicated that residues surrounding a conserved Phe side-chain dictate a rotamer which results in a ∼6° distortion along the side-chain, estimated to cost 4 kcal/mol. By contrast, in the closely related protease Streptomyces griseus Protease B (SGPB), the equivalent Phe adopts a different rotamer and is undistorted. Here, we report that the αLP Phe side-chain distortion is both functional and conserved in proteases with large pro regions. Sequence analysis of the αLP serine protease family reveals a bifurcation separating those sequences expected to induce distortion and those that would not, which correlates with the extent of kinetic stability. Structural and folding kinetics analyses of family members suggest that distortion of this side-chain plays a role in increasing kinetic stability within the αLP family members that use a large Pro region. Additionally, structural and kinetic folding studies of mutants demonstrate that strain alters the folding free energy landscape by destabilizing the transition state (TS) relative to the native state (N). Although side-chain distortion comes at a cost of foldability, it suppresses the rate of unfolding, thereby enhancing kinetic stability and increasing protein longevity under harsh extracellular conditions. This ability of a structural distortion to enhance function is unlikely to be unique to αLP family members and may be relevant in other proteins exhibiting side-chain distortions. PMID:22635267

Estimating maximum instantaneous distortion from inlet total pressure rms and PSD measurements. [Root Mean Square and Power Spectral Density methods

NASA Technical Reports Server (NTRS)

Melick, H. C., Jr.; Ybarra, A. H.; Bencze, D. P.

1975-01-01

An inexpensive method is developed to determine the extreme values of instantaneous inlet distortion. This method also provides insight into the basic mechanics of unsteady inlet flow and the associated engine reaction. The analysis is based on fundamental fluid dynamics and statistical methods to provide an understanding of the turbulent inlet flow and quantitatively relate the rms level and power spectral density (PSD) function of the measured time variant total pressure fluctuations to the strength and size of the low pressure regions. The most probable extreme value of the instantaneous distortion is then synthesized from this information in conjunction with the steady state distortion. Results of the analysis show the extreme values to be dependent upon the steady state distortion, the measured turbulence rms level and PSD function, the time on point, and the engine response characteristics. Analytical projections of instantaneous distortion are presented and compared with data obtained by a conventional, highly time correlated, 40 probe instantaneous pressure measurement system.

Heme Distortions in Sperm-Whale Carbonmonoxy Myoglobin: Correlations between Rotational Strengths and Heme Distortions in MD-Generated Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

KIEFL,CHRISTOPH; SCREERAMA,NARASIMHA; LU,YI

2000-07-13

The authors have investigated the effects of heme rotational isomerism in sperm-whale carbonmonoxy myoglobin using computational techniques. Several molecular dynamics simulations have been performed for the two rotational isomers A and B, which are related by a 180{degree} rotation around the {alpha}-{gamma} axis of the heme, of sperm-whale carbonmonoxy myoglobin in water. Both neutron diffraction and NMR structures were used as starting structures. In the absence of an experimental structure, the structure of isomer B was generated by rotating the heme in the structure of isomer A. Distortions of the heme from planarity were characterized by normal coordinate structural decompositionmore » and by the angle of twist of the pyrrole rings from the heme plane. The heme distortions of the neutron diffraction structure were conserved in the MD trajectories, but in the NMR-based trajectories, where the heme distortions are less well defined, they differ from the original heme deformations. The protein matrix induced similar distortions on the heroes in orientations A and B. The results suggest that the binding site prefers a particular macrocycle conformation, and a 180{degree} rotation of the heme does not significantly alter the protein's preference for this conformation. The intrinsic rotational strengths of the two Soret transitions, separated according to their polarization in the heme plane, show strong correlations with the ruf-deformation and the average twist angle of the pyrrole rings. The total rotational strength, which includes contributions from the chromophores in the protein, shows a weaker correlation with heme distortions.« less

A quantitative comparison of two methods to correct eddy current-induced distortions in DT-MRI.

PubMed

Muñoz Maniega, Susana; Bastin, Mark E; Armitage, Paul A

2007-04-01

Eddy current-induced geometric distortions of single-shot, diffusion-weighted, echo-planar (DW-EP) images are a major confounding factor to the accurate determination of water diffusion parameters in diffusion tensor MRI (DT-MRI). Previously, it has been suggested that these geometric distortions can be removed from brain DW-EP images using affine transformations determined from phantom calibration experiments using iterative cross-correlation (ICC). Since this approach was first described, a number of image-based registration methods have become available that can also correct eddy current-induced distortions in DW-EP images. However, as yet no study has investigated whether separate eddy current calibration or image-based registration provides the most accurate way of removing these artefacts from DT-MRI data. Here we compare how ICC phantom calibration and affine FLIRT (http://www.fmrib.ox.ac.uk), a popular image-based multi-modal registration method that can correct both eddy current-induced distortions and bulk subject motion, perform when registering DW-EP images acquired with different slice thicknesses (2.8 and 5 mm) and b-values (1000 and 3000 s/mm(2)). With the use of consistency testing, it was found that ICC was a more robust algorithm for correcting eddy current-induced distortions than affine FLIRT, especially at high b-value and small slice thickness. In addition, principal component analysis demonstrated that the combination of ICC phantom calibration (to remove eddy current-induced distortions) with rigid body FLIRT (to remove bulk subject motion) provided a more accurate registration of DT-MRI data than that achieved by affine FLIRT.

Multi-element array signal reconstruction with adaptive least-squares algorithms

NASA Technical Reports Server (NTRS)

Kumar, R.

1992-01-01

Two versions of the adaptive least-squares algorithm are presented for combining signals from multiple feeds placed in the focal plane of a mechanical antenna whose reflector surface is distorted due to various deformations. Coherent signal combining techniques based on the adaptive least-squares algorithm are examined for nearly optimally and adaptively combining the outputs of the feeds. The performance of the two versions is evaluated by simulations. It is demonstrated for the example considered that both of the adaptive least-squares algorithms are capable of offsetting most of the loss in the antenna gain incurred due to reflector surface deformations.

Synthesis, Photochemical, and Redox Properties of Gold(I) and Gold(III) Pincer Complexes Incorporating a 2,2′:6′,2″-Terpyridine Ligand Framework

PubMed Central

2015-01-01

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 2,2′:6′,2″-terpyridine (terpy) leads to complex [Au(C6F5)(η1-terpy)] (1). The chemical oxidation of complex (1) with 2 equiv of [N(C6H4Br-4)3](PF6) or using electrosynthetic techniques affords the Au(III) complex [Au(C6F5)(η3-terpy)](PF6)2 (2). The X-ray diffraction study of complex 2 reveals that the terpyridine acts as tridentate chelate ligand, which leads to a slightly distorted square-planar geometry. Complex 1 displays fluorescence in the solid state at 77 K due to a metal (gold) to ligand (terpy) charge transfer transition, whereas complex 2 displays fluorescence in acetonitrile due to excimer or exciplex formation. Time-dependent density functional theory calculations match the experimental absorption spectra of the synthesized complexes. In order to further probe the frontier orbitals of both complexes and study their redox behavior, each compound was separately characterized using cyclic voltammetry. The bulk electrolysis of a solution of complex 1 was analyzed by spectroscopic methods confirming the electrochemical synthesis of complex 2. PMID:26496068

DFT Study of Optical Properties of Pt-based Complexes

NASA Astrophysics Data System (ADS)

Oprea, Corneliu I.; Dumbravǎ, Anca; Moscalu, Florin; Nicolaides, Atnanassios; Gîrţu, Mihai A.

2010-01-01

We report Density Functional Theory (DFT) calculations providing the geometrical and electronic structures, as well as the vibrational and optical properties of the homologous series of Pt-pyramidalized olefin complexes (CH2)n-(C8H10)Pt(PH3)2, where n = 0, 1, and 2, in their neutral and oxidized states. All complexes were geometry optimized for the singlet ground state in vacuum using DFT methods with B3LYP exchange-correlation functional and the Effective Core Potential LANL2DZ basis set, within the frame of Gaussian03 quantum chemistry package. We find the coordination geometry of Pt to be distorted square planar, with dihedral angles ranging from 0°, for n = 0 and 1, which have C2V symmetry to 3.4°, for n = 2 with C2 symmetry. The Mulliken charge analysis allows a discussion of the oxidation state of the Pt ion. Electronic transitions were calculated at the same level of theory by means of Time Dependant-DFT. For n = 2 the electronic absorption bands are located in the UV region of the spectrum, the transitions being assigned to metal to ligand charge transfers. The relevance of these Pt-based compounds as possible pigments for dye-sensitized solar cells is discussed.

Synthesis, structure, spectroscopic and electrochemical properties of (2-amino-4-methylpyrimidine)-(pyridine-2,6-dicarboxylato)copper(II) monohydrate

NASA Astrophysics Data System (ADS)

Uçar, İbrahim; Karabulut, Bünyamin; Bulut, Ahmet; Büyükgüngör, Orhan

2007-05-01

The (2-amino-4-methylpyrimidine)-(pyridine-2,6-dicarboxylato)copper(II) monohydrate complex was synthesized and characterized by spectroscopic (IR, UV/Vis, EPR), thermal (TG/DTA) and electrochemical methods. X-ray structural analysis of the title complex revealed that the copper ion can be considered to have two coordination spheres. In the first coordination sphere the copper ion forms distorted square-planar geometry with trans-N 2O 2 donor set, and also the metal ion is weakly bonded to the amino-nitrogen in the layer over and to the carboxylic oxygen in the layer underneath in the second coordination sphere. The second coordination environment on the copper ion is attributed to pseudo octahedron. The powder EPR spectra of Cu(II) complex at room and liquid nitrogen temperature were recorded. The calculated g and A parameters have indicated that the paramagnetic centre is axially symmetric. The molecular orbital bond coefficients of the Cu(II) ion in d 9 state is also calculated by using EPR and optical absorption parameters. The cyclic voltammogram of the title complex investigated in DMSO (dimethylsulfoxide) solution exhibits only metal centered electroactivity in the potential range -1.25 to 1.5 V versus Ag/AgCl reference electrode.

Synthesis, X-ray structure and electrochemical oxidation of palladium(II) complexes of ferrocenyldiphenylphosphine.

PubMed

Bennett, Martin A; Bhargava, Suresh K; Bond, Alan M; Burgar, Iko M; Guo, Si-Xuan; Kar, Gopa; Privér, Steven H; Wagler, Jörg; Willis, Anthony C; Torriero, Angel A J

2010-10-14

Four new complexes, [PdX(κ(2)-2-C(6)R(4)PPh(2))(PPh(2)Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh(2)Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ(2)-2-C(6)F(4)PPh(2))(μ-I)(μ-2-C(6)F(4)PPh(2))PdI(PPh(2)Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1-4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh(2)Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh(2)Fc; subsequently, the metal-phosphorus bond is cleaved, leading to free PPh(2)Fc(+), which undergoes further chemical and electrochemical reactions.

Structural characterization of two solvates of a luminescent copper(II) bis­(pyridine)-substituted benzimidazole complex

PubMed Central

DeStefano, Matthew R.; Lewis, Robert A.

2017-01-01

Copper(II) complexes of benzimidazole are known to exhibit biological activity that makes them of inter­est for chemotherapeutic and other pharmaceutical uses. The complex bis­(acetato-κO){5,6-dimethyl-2-(pyridin-2-yl)-1-[(pyridin-2-yl)meth­yl]-1H-benzimidazole-κ2 N 2,N 3}copper(II), has been prepared. The absorption spectrum has features attributed to intra­ligand and ligand-field transitions and the complex exhibits ligand-centered room-temperature luminescence in solution. The aceto­nitrile monosolvate, [Cu(C2H3O2)2(C20H18N4)]·C2H3N (1), and the ethanol hemisolvate, [Cu(C2H3O2)2(C20H18N4)]·0.5C2H6O (2), have been structurally characterized. Compound 2 has two copper(II) complexes in the asymmetric unit. In both 1 and 2, distorted square-planar N2O2 coordination geometries are observed and the Cu—N(Im) bond distance is slightly shorter than the Cu—N(py) bond distance. Inter­molecular π–π inter­actions are found in 1 and 2. A weak C—H⋯π inter­action is observed in 1. PMID:29152336

Inner-volume echo volumar imaging (IVEVI) for robust fetal brain imaging.

PubMed

Nunes, Rita G; Ferrazzi, Giulio; Price, Anthony N; Hutter, Jana; Gaspar, Andreia S; Rutherford, Mary A; Hajnal, Joseph V

2018-07-01

Fetal functional MRI studies using conventional 2-dimensional single-shot echo-planar imaging sequences may require discarding a large data fraction as a result of fetal and maternal motion. Increasing the temporal resolution using echo volumar imaging (EVI) could provide an effective alternative strategy. Echo volumar imaging was combined with inner volume (IV) imaging (IVEVI) to locally excite the fetal brain and acquire full 3-dimensional images, fast enough to freeze most fetal head motion. IVEVI was implemented by modifying a standard multi-echo echo-planar imaging sequence. A spin echo with orthogonal excitation and refocusing ensured localized excitation. To introduce T2* weighting and to save time, the k-space center was shifted relative to the spin echo. Both single and multi-shot variants were tested. Acoustic noise was controlled by adjusting the amplitude and switching frequency of the readout gradient. Image-based shimming was used to minimize B 0 inhomogeneities within the fetal brain. The sequence was first validated in an adult. Eight fetuses were scanned using single-shot IVEVI at a 3.5 × 3.5 × 5.0 mm 3 resolution with a readout duration of 383 ms. Multishot IVEVI showed reduced geometric distortions along the second phase-encode direction. Fetal EVI remains challenging. Although effective echo times comparable to the T2* values of fetal cortical gray matter at 3 T could be achieved, controlling acoustic noise required longer readouts, leading to substantial distortions in single-shot images. Although multishot variants enabled us to reduce susceptibility-induced geometric distortions, sensitivity to motion was increased. Future studies should therefore focus on improvements to multishot variants. Magn Reson Med 80:279-285, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

The concerted trimerization of ethyne to benzene revisited

NASA Astrophysics Data System (ADS)

Cioslowski, Jerzy; Liu, Guanghua; Moncrieff, David

2000-01-01

CCSD(T)/6-311G ∗∗//QCISD/6-311G ∗∗ calculations on the concerted [2+2+2] trimerization of ethyne to benzene yield Δ Htrimo (HCCH)=-140.2 kcal/mol and Δ Hacto(HCCH)=53.1 kcal/mol. The corresponding transition state (TS) possesses C 2 symmetry, although both the planar D 3h and nonplanar D 3 structures are negligibly higher in energy, indicating extreme flatness of the potential energy hypersurface along the distortion paths. The analogous trimerizations of HCCCl and ClCCCl are predicted to be considerably more exothermic. As the respective TSs cannot be located and the planar pseudo-TSs that possess several imaginary vibrational frequencies are associated with high reaction barriers, the concerted mechanism can be ruled out for these reactions.

Exactly solved models on planar graphs with vertices in {Z}^3

NASA Astrophysics Data System (ADS)

Kels, Andrew P.

2017-12-01

It is shown how exactly solved edge interaction models on the square lattice, may be extended onto more general planar graphs, with edges connecting a subset of next nearest neighbour vertices of {Z}3 . This is done by using local deformations of the square lattice, that arise through the use of the star-triangle relation. Similar to Baxter’s Z-invariance property, these local deformations leave the partition function invariant up to some simple factors coming from the star-triangle relation. The deformations used here extend the usual formulation of Z-invariance, by requiring the introduction of oriented rapidity lines which form directed closed paths in the rapidity graph of the model. The quasi-classical limit is also considered, in which case the deformations imply a classical Z-invariance property, as well as a related local closure relation, for the action functional of a system of classical discrete Laplace equations.

Zirconocene-iridium hydrido complexes: arene carbon-hydrogen bond activation and formation of a planar square Zr2Ir2 complex.

PubMed

Oishi, Masataka; Suzuki, Hiroharu

2009-03-16

New early-late heterobimetallic hydrides (L(2)ZrCl)(Cp*Ir)(mu-H)(3) (1; L = Cp derivative, Cp* = eta(5)-C(5)Me(5)) were synthesized from zirconocene derivatives (L(2)ZrCl(2)) and LiCp*IrH(3) via a salt elimination reaction and structurally characterized by NMR and X-ray analyses. Upon treatment of 1 with an alkyllithium reagent, hydride abstraction complex 4 underwent thermolytic ligand elimination at the Zr-Ir system to yield a novel planar square complex (L(2)Zr)(2)(Cp*Ir)(2)(mu(3)-H)(4) (2). When a labeling study of the reaction was conducted, it was found that the conversion of 1 to 2 involves rapid aromatic and benzylic C-H activation by a coordinatively unsaturated dinuclear complex (L(2)Zr)(Cp*Ir)(H)(2) (3).

A 5 meter range non-planar CMUT array for Automotive Collision Avoidance

NASA Astrophysics Data System (ADS)

Hernandez Aguirre, Jonathan

A discretized hyperbolic paraboloid geometry capacitive micromachined ultrasonic transducer (CMUT) array has been designed and fabricated for automotive collision avoidance. The array is designed to operate at 40 kHz, beamwidth of 40° with a maximum sidelobe intensity of -10dB. An SOI based fabrication technology has been used for the 5x5 array with 5 sensing surfaces along each x and y axis and 7 elevation levels. An assembly and packaging technique has been developed to realize the non-planar geometry in a PGA-68 package. A highly accurate mathematical method has been presented for analytical characterization of capacitive micromachined ultrasonic transducers (CMUTs) built with square diaphragms. The method uses a new two-dimensional polynomial function to more accurately predict the deflection curve of a multilayer square diaphragm subject to both mechanical and electrostatic pressure and a new capacitance model that takes into account the contribution of the fringing field capacitances.

Strain induced plasmon tuning in planar square-shaped aluminum nanoparticles array

NASA Astrophysics Data System (ADS)

Mokkath, Junais Habeeb

2018-06-01

Metal nanoparticle aggregate is an exciting platform for manipulating light-matter interactions at the nanoscale, thanks to the optically driven free electrons couple electrically across the inter-particle gap region. We use time dependent density functional theory calculations to investigate the optical response modulations in planar square-shaped aluminum nanoparticles array via morphology deformation (varying the inter-particle gap distance in the range of 2-20 Å) separately along one and two directions. We report the surprising observation that irrespective of the different morphology deformations, there exists a unique inter-particle gap distance of 12 Å for which, a maximum optical field enhancement can be achieved. We remark that plasmonic interaction between metal nanoparticles in an aggregate is controlled to a large extent by the size of the inter-particle gap distance. We believe that our quantum mechanical calculations will inspire and contribute to the design, control, and exploitation of aluminum based plasmonic devices.

β-Ketoiminato-based copper(ii) complexes as CVD precursors for copper and copper oxide layer formation.

PubMed

Pousaneh, Elaheh; Korb, Marcus; Dzhagan, Volodymyr; Weber, Marcus; Noll, Julian; Mehring, Michael; Zahn, Dietrich R T; Schulz, Stefan E; Lang, Heinrich

2018-06-19

The synthesis of ketoiminato copper(ii) complexes [Cu(OCRCHC(CH3)NCH2CH2X)(μ-OAc)]2 (X = NMe2: 4a, R = Me; 4b, R = Ph. X = OMe: 5, R = Me) and [Cu(OCRCHCMeNCH2CH2NEt2)(OAc)] (6, R = Me) from RC(O)CHC(CH3)N(H)CH2CH2X (X = NMe2: 1a, R = Me; 1b, R = Ph. X = NEt2: 1c, R = Me. X = OMe: 2, R = Me) and [Cu(OAc)2·H2O] (3) is reported. The molecular solid-state structures of 4-6 were determined by single crystal X-ray diffraction studies, showing that 4a,b and 5 are dimers which are set up by two [{Cu(μ-OAc)L}] (L = ketoiminato ligand) units featuring a square-planar Cu2O2 core with a distorted square-pyramidal geometry at Cu(ii). In contrast, 6 is monomeric with a tridentate-coordinated OCMeCHCMeNCH2CH2NEt2 ligand and a σ-bonded acetate group, thus inducing a square-planar environment around Cu(ii). The thermal behavior of all complexes was studied by TG (Thermogravimetry) and DSC (Differential Scanning Calorimetry) under an atmosphere of Ar and O2. Complex 4b shows the highest first onset temperature at 213 °C (under O2) and 239 °C (Ar). PXRD studies confirmed the formation of CuO under an atmosphere of O2 and Cu/Cu2O under Ar. TG-MS studies, exemplarily carried out with 4a, indicate the elimination of the ketoiminato ligands with detectable fragments such as m/z = 15, 28, 43, 44, 45, and 60 at a temperature above 250 °C. Vapor pressure measurements displayed that 5 shows the highest volatility of 3.6 mbar at 70 °C (for comparison, 4a, 1.4; 4b, 1.3; 6, 0.4 mbar) and hence 4a and 5 were used as MOCVD precursors for Cu/Cu2O deposition on Si/SiO2 at substrate temperatures of 450 °C and 510 °C. The deposition experiments were carried out under an atmosphere of nitrogen as well as oxygen. The as-obtained layers were characterized by SEM, EDX, XPS, and PXRD, showing that with oxygen as the reactive gas a mixture of metallic copper and copper(i) oxide without carbon impurities was formed, while under N2 Cu films with 53-68 mol% C contamination were produced. In a deposition experiment using precursor 5 at 510 °C under N2 a pure copper film was obtained.

Maritime Adaptive Optics Beam Control

DTIC Science & Technology

2010-09-01

Liquid Crystal LMS Least Mean Square MIMO Multiple- Input Multiple-Output MMDM Micromachined Membrane Deformable Mirror MSE Mean Square Error...determine how the beam is distorted, a control computer to calculate the correction to be applied, and a corrective element, usually a deformable mirror ...during this research, an overview of the system modification is provided here. Using additional mirrors and reflecting the beam to and from an

Electrochemical-mechanical coupling in composite planar structures that integrate flow channels and ion-conducting membranes

DOE PAGES

Euser, Bryan Jeffry; Zhu, Huayang; Berger, John; ...

2017-01-01

Ceramic oxygen-transport membranes, such as the doped perovskite La 0.6Sr 0.4Co 0.8Fe 0.2O 3-δ(LSCF6482) considered in the present paper, are effective in applications such as air separation. The present paper considers a planar configuration that is composed of a thin (order tens of microns) ion-transport membrane, a relatively thick (order millimeter) porous-ceramic support structure, and millimeter-scale oxygen-collection flow channels. The lattice-scale strain associated with charged defects (oxygen vacancies and small polarons) within ion-transport membranes causes macroscopic stress that could distort or damage the assembly. The modeling approach is based on an extended twodimensional Nernst–Planck–Poisson (NPP) formulation that is developed andmore » applied to evaluate the effects of chemically induced stress within a planar oxygen-separation assembly. The computational model predicts two-dimensional distributions of steady-state defect concentrations, electrostatic potentials, and stress. Parameter studies consider the effects of support-membrane dimensions, materials mechanical properties, and operating conditions. Although the stress is found to have a negligible influence on the defect transport, the defect transport is found to significantly affect the stress distributions. Such results can play important roles in the design and development of planar ion-transport membranes and their support structures.« less

Linear Least Squares for Correlated Data

NASA Technical Reports Server (NTRS)

Dean, Edwin B.

1988-01-01

Throughout the literature authors have consistently discussed the suspicion that regression results were less than satisfactory when the independent variables were correlated. Camm, Gulledge, and Womer, and Womer and Marcotte provide excellent applied examples of these concerns. Many authors have obtained partial solutions for this problem as discussed by Womer and Marcotte and Wonnacott and Wonnacott, which result in generalized least squares algorithms to solve restrictive cases. This paper presents a simple but relatively general multivariate method for obtaining linear least squares coefficients which are free of the statistical distortion created by correlated independent variables.

Effects of atmospheric turbulence on the imaging performance of optical system

NASA Astrophysics Data System (ADS)

Al-Hamadani, Ali H.; Zainulabdeen, Faten Sh.; Karam, Ghada Sabah; Nasir, Eman Yousif; Al-Saedi, Abaas

2018-05-01

Turbulent effects are very complicated and still not entirely understood. Light waves from an astronomical object are distorted as they pass through the atmosphere. The refractive index fluctuations in the turbulent atmosphere induce an optical path difference (OPD) between different parts of the wavefront, distorted wavefronts produce low-quality images and degrade the image beyond the diffraction limit. In this paper the image degradation due to 2-D Gaussian atmospheric turbulence is considered in terms of the point spread function (PSF), and Strehl ratio as an image quality criteria for imaging systems with different apertures using the pupil function teqneque. A general expression for the degraded PSF in the case of circular and square apertures (with half diagonal = √{π/2 } , and 1) diffraction limited and defocused optical system is considered. Based on the derived formula, the effect of the Gaussian atmospheric turbulence on circular and square pupils has been studied with details. Numerical results show that the performance of optical systems with square aperture is more efficient at high levels of atmospheric turbulence than the other apertures.

Reconstructing the vibro-acoustic quantities on a highly non-spherical surface using the Helmholtz equation least squares method.

PubMed

Natarajan, Logesh Kumar; Wu, Sean F

2012-06-01

This paper presents helpful guidelines and strategies for reconstructing the vibro-acoustic quantities on a highly non-spherical surface by using the Helmholtz equation least squares (HELS). This study highlights that a computationally simple code based on the spherical wave functions can produce an accurate reconstruction of the acoustic pressure and normal surface velocity on planar surfaces. The key is to select the optimal origin of the coordinate system behind the planar surface, choose a target structural wavelength to be reconstructed, set an appropriate stand-off distance and microphone spacing, use a hybrid regularization scheme to determine the optimal number of the expansion functions, etc. The reconstructed vibro-acoustic quantities are validated rigorously via experiments by comparing the reconstructed normal surface velocity spectra and distributions with the benchmark data obtained by scanning a laser vibrometer over the plate surface. Results confirm that following the proposed guidelines and strategies can ensure the accuracy in reconstructing the normal surface velocity up to the target structural wavelength, and produce much more satisfactory results than a straight application of the original HELS formulations. Experiment validations on a baffled, square plate were conducted inside a fully anechoic chamber.

Analysis and Optimization of Four-Coil Planar Magnetically Coupled Printed Spiral Resonators.

PubMed

Khan, Sadeque Reza; Choi, GoangSeog

2016-08-03

High-efficiency power transfer at a long distance can be efficiently established using resonance-based wireless techniques. In contrast to the conventional two-coil-based inductive links, this paper presents a magnetically coupled fully planar four-coil printed spiral resonator-based wireless power-transfer system that compensates the adverse effect of low coupling and improves efficiency by using high quality-factor coils. A conformal architecture is adopted to reduce the transmitter and receiver sizes. Both square architecture and circular architectures are analyzed and optimized to provide maximum efficiency at a certain operating distance. Furthermore, their performance is compared on the basis of the power-transfer efficiency and power delivered to the load. Square resonators can produce higher measured power-transfer efficiency (79.8%) than circular resonators (78.43%) when the distance between the transmitter and receiver coils is 10 mm of air medium at a resonant frequency of 13.56 MHz. On the other hand, circular coils can deliver higher power (443.5 mW) to the load than the square coils (396 mW) under the same medium properties. The performance of the proposed structures is investigated by simulation using a three-layer human-tissue medium and by experimentation.

A balloon-borne instrument for high-resolution astrophysical spectroscopy in the 20-8000 keV energy range

NASA Technical Reports Server (NTRS)

Paciesas, W. S.; Baker, R.; Boclet, D.; Brown, S.; Cline, T.; Costlow, H.; Durouchoux, P.; Ehrmann, C.; Gehrels, N.; Hameury, J. M.

1983-01-01

The Low Energy Gamma ray Spectrometer (LEGS) is designed to perform fine energy resolution measurements of astrophysical sources. The instrument is configured for a particular balloon flight with either of two sets of high purity germanium detectors. In one configuration, the instrument uses an array of three coaxial detectors (effective volume equal to or approximately 230 cubic cm) inside an NaI (T1) shield and collimator (field of view equal to or approximately 16 deg FWHM) and operates in the 80 to 8000 keV energy range. In the other configuration, three planar detectors (effective area equal to or approximately square cm) surrounded by a combination of passive Fe and active NaI for shielding and collimation (field of view equal to or approximately 5 deg x 10 deg FWHM) are optimized for the 20 to 200 keV energy range. In a typical one day balloon flight, LEGS sensitivity limit (3 sigma) for narrow line features is less than or approximately .0008 ph/cm/s square (coaxial array: 80 to 2000 keV) and less than or approximately .0003 ph/square cm/s (planar array: 50 to 150 keV).

Quasi-static shape adjustment of a 15 meter diameter space antenna

NASA Technical Reports Server (NTRS)

Belvin, W. Keith; Herstrom, Catherine L.; Edighoffer, Harold H.

1987-01-01

A 15 meter diameter Hoop-Column antenna has been analyzed and tested to study shape adjustment of the reflector surface. The Hoop-Column antenna concept employs pretensioned cables and mesh to produce a paraboloidal reflector surface. Fabrication errors and thermal distortions may significantly reduce surface accuracy and consequently degrade electromagnetic performance. Thus, the ability to adjust the surface shape is desirable. The shape adjustment algorithm consisted of finite element and least squares error analyses to minimize the surface distortions. Experimental results verified the analysis. Application of the procedure resulted in a reduction of surface error by 38 percent. Quasi-static shape adjustment has the potential for on-orbit compensation for a variety of surface shape distortions.

Comparison between Modelled and Measured Magnetic Field Scans of Different Planar Coil Topologies for Stress Sensor Applications.

PubMed

Gibbs, Robert; Moreton, Gregory; Meydan, Turgut; Williams, Paul

2018-03-21

The investigation of planar coils of differing topologies, when combined with a magnetostrictive amorphous ribbon to form a stress-sensitive self-inductor, is an active research area for applications as stress or pressure sensors. Four topologies of planar coil (Circular, Mesh, Meander, and Square) have been constructed using copper track on 30 mm wide PCB substrate. The coils are energized to draw 0.4 A and the resulting magnetic field distribution is observed with a newly developed three-dimensional magnetic field scanner. The system is based on a variably angled Micromagnetics ® STJ-020 tunneling magneto-resistance sensor with a spatial resolution of 5-10 µm and sensitivity to fields of less than 10 A/m. These experimental results are compared with the fields computed by ANSYS Maxwell ® finite element modelling of the same topologies. Measured field shape and strength correspond well with the results of modelling, including direct observation of corner and edge effects. Three-dimensional analysis of the field shape produced by the square coil, isolating the components H ( x ) and H ( z ) , is compared with the three-dimensional field solutions from modelling. The finite element modelling is validated and the accuracy and utility of the new system for three-dimensional scanning of general stray fields is confirmed.

Comparison between Modelled and Measured Magnetic Field Scans of Different Planar Coil Topologies for Stress Sensor Applications

PubMed Central

Moreton, Gregory

2018-01-01

The investigation of planar coils of differing topologies, when combined with a magnetostrictive amorphous ribbon to form a stress-sensitive self-inductor, is an active research area for applications as stress or pressure sensors. Four topologies of planar coil (Circular, Mesh, Meander, and Square) have been constructed using copper track on 30 mm wide PCB substrate. The coils are energized to draw 0.4 A and the resulting magnetic field distribution is observed with a newly developed three-dimensional magnetic field scanner. The system is based on a variably angled Micromagnetics® STJ-020 tunneling magneto-resistance sensor with a spatial resolution of 5–10 µm and sensitivity to fields of less than 10 A/m. These experimental results are compared with the fields computed by ANSYS Maxwell® finite element modelling of the same topologies. Measured field shape and strength correspond well with the results of modelling, including direct observation of corner and edge effects. Three-dimensional analysis of the field shape produced by the square coil, isolating the components H(x) and H(z), is compared with the three-dimensional field solutions from modelling. The finite element modelling is validated and the accuracy and utility of the new system for three-dimensional scanning of general stray fields is confirmed. PMID:29561809

Geometric rectification of camera-captured document images.

PubMed

Liang, Jian; DeMenthon, Daniel; Doermann, David

2008-04-01

Compared to typical scanners, handheld cameras offer convenient, flexible, portable, and non-contact image capture, which enables many new applications and breathes new life into existing ones. However, camera-captured documents may suffer from distortions caused by non-planar document shape and perspective projection, which lead to failure of current OCR technologies. We present a geometric rectification framework for restoring the frontal-flat view of a document from a single camera-captured image. Our approach estimates 3D document shape from texture flow information obtained directly from the image without requiring additional 3D/metric data or prior camera calibration. Our framework provides a unified solution for both planar and curved documents and can be applied in many, especially mobile, camera-based document analysis applications. Experiments show that our method produces results that are significantly more OCR compatible than the original images.

Perfluorocyclobutane containing aromatic ether polymers as planarization materials for alternative magnetic media substrates

NASA Astrophysics Data System (ADS)

Perettie, Donald J.; Judy, Jack; Chen, Qixu; Keirstead, Rick

1994-11-01

Perfluorocyclobutane aromatic ether polymers (PFCB) are being researched as planarization materials for alternative magnetic media substrates allowing smoother surfaces for lower head flying recording. The results of current work reported herein have shown that PFCB can be used to affect surfaces on canasite with R(sub A)'s less than 2 nm. In addition, magnetic media can be produced of a quality comparative to that obtained on standard NiP-coated Al as well as that produced on regular canasite with equivalent coercivities at about 1500-1600 Oe and squarenesses of 0.8 or better. In addition to the above magnetic properties the recording performance was excellent with signal-to-noise ratios of planarized media 3.5 dB higher than that on regular canasite.

trans-Bis(azido-kappaN)bis(pyridine-2-carboxamide-kappa2N1,O2)nickel(II).

PubMed

Daković, Marijana; Popović, Zora

2007-11-01

In the title compound, [Ni(N(3))(2)(C(6)H(6)N(2)O)(2)], the Ni(II) atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N-H...N hydrogen bonds.

Correcting the planar perspective projection in geometric structures applied to forensic facial analysis.

PubMed

Baldasso, Rosane Pérez; Tinoco, Rachel Lima Ribeiro; Vieira, Cristina Saft Matos; Fernandes, Mário Marques; Oliveira, Rogério Nogueira

2016-10-01

The process of forensic facial analysis may be founded on several scientific techniques and imaging modalities, such as digital signal processing, photogrammetry and craniofacial anthropometry. However, one of the main limitations in this analysis is the comparison of images acquired with different angles of incidence. The present study aimed to explore a potential approach for the correction of the planar perspective projection (PPP) in geometric structures traced from the human face. A technique for the correction of the PPP was calibrated within photographs of two geometric structures obtained with angles of incidence distorted in 80°, 60° and 45°. The technique was performed using ImageJ ® 1.46r (National Institutes of Health, Bethesda, Maryland). The corrected images were compared with photographs of the same object obtained in 90° (reference). In a second step, the technique was validated in a digital human face created using MakeHuman ® 1.0.2 (Free Software Foundation, Massachusetts, EUA) and Blender ® 2.75 (Blender ® Foundation, Amsterdam, Nederland) software packages. The images registered with angular distortion presented a gradual decrease in height when compared to the reference. The digital technique for the correction of the PPP is a valuable tool for forensic applications using photographic imaging modalities, such as forensic facial analysis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Electronic structure of trioxide, oxoperoxide, oxosuperoxide, and ozonide clusters of the 3d elements: density functional theory study.

PubMed

Uzunova, Ellie L

2011-03-03

The trioxide clusters with stoichiometry MO3, and the structural isomers with side-on and end-on bonded oxygen atoms, are studied by DFT with the B1LYP functional. For the first half of the 3d elements row (Sc to Cr), pyramidal or distorted pyramidal structures dominate among the trioxide and oxoperoxide ground states, while the remaining elements form planar trioxides, oxoperoxides, oxosuperoxides, and ozonides. Low-lying trioxide clusters are formed by Ti, V, Cr, and Mn, among which the distorted pyramidal VO3 in the (2)A'' state, the pyramidal CrO3 in the (1)A1 state, and the planar MnO3 in the (2)A1' state are global minima. With the exception of the middle-row elements Mn, Fe, and Co, the magnetic moment of the ground-state clusters is formed with a major contribution from unpaired electrons located at the oxygen atoms. The stability of trioxides and oxoperoxides toward release of molecular oxygen is significantly higher for Sc, Ti, and V than for the remaining elements of the row. A trend of increasing the capability to dissociate one oxygen molecule is observed from Cr to Cu, with the exception of OFe(O2) being more reactive than OCo(O2). A gradual increase of reactivity from Ti to Cu is observed for the complete fragmentation reaction M + O + O2.

Synthesis, Structure, Characterization, and Decomposition of Nickel Dithiocarbamates: Effect of Precursor Structure and Processing Conditions on Solid-State Products

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Kulis, Michael J.; McNatt, Jeremiah S.; Duffy, Norman V.; Hoops, Michael D.; Gorse, Elizabeth; Fanwick, Philip E.; Masnovi, John; Cowen, Jonathan E.; Dominey, Raymond N.

2016-01-01

Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)], were determined. Synthetic, spectroscopic, structural, thermal, and sulfide materials studies are discussed in light of prior literature. The spectroscopic results are routine. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogen atoms interact with the CS2 carbons with a bond order of about 1.5, and the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. Thermogravimetric analysis of the homoleptic species under inert atmosphere is consistent with production of 1:1 nickel sulfide phases. Thermolysis of nickel dithiocarbamates under flowing nitrogen produced hexagonal or -NiS as the major phase; thermolysis under flowing forming gas produced millerite (-NiS) at 300 C, godlevskite (Ni9S8) at 325 and 350 C, and heazlewoodite (Ni3S2) at 400 and 450 C. Failure to exclude oxygen results in production of nickel oxide. Nickel sulfide phases produced seem to be primarily influenced by processing conditions, in agreement with prior literature. Nickel dithiocarbamate complexes demonstrate significant promise to serve as single-source precursors to nickel sulfides, a quite interesting family of materials with numerous potential applications.

Calibration of micro-capacitance measurement system for thermal barrier coating testing

NASA Astrophysics Data System (ADS)

Ren, Yuan; Chen, Dixiang; Wan, Chengbiao; Tian, Wugang; Pan, Mengchun

2018-06-01

In order to comprehensively evaluate the thermal barrier coating system of an engine blade, an integrated planar sensor combining electromagnetic coils with planar capacitors is designed, in which the capacitance measurement accuracy of the planar capacitor is a key factor. The micro-capacitance measurement system is built based on an impedance analyzer. Because of the influence of non-ideal factors on the measuring system, there is an obvious difference between the measured value and the actual value. It is necessary to calibrate the measured results and eliminate the difference. In this paper, the measurement model of a planar capacitive sensor is established, and the relationship between the measured value and the actual value of capacitance is deduced. The model parameters are estimated with the least square method, and the calibration accuracy is evaluated with experiments under different dielectric conditions. The capacitance measurement error is reduced from 29% ˜ 46.5% to around 1% after calibration, which verifies the feasibility of the calibration method.

Novel quantitative assessment of metamorphopsia in maculopathy.

PubMed

Wiecek, Emily; Lashkari, Kameran; Dakin, Steven C; Bex, Peter

2014-11-18

Patients with macular disease often report experiencing metamorphopsia (visual distortion). Although typically measured with Amsler charts, more quantitative assessments of perceived distortion are desirable to effectively monitor the presence, progression, and remediation of visual impairment. Participants with binocular (n = 33) and monocular (n = 50) maculopathy across seven disease groups, and control participants (n = 10) with no identifiable retinal disease completed a modified Amsler grid assessment (presented on a computer screen with eye tracking to ensure fixation compliance) and two novel assessments to measure metamorphopsia in the central 5° of visual field. A total of 81% (67/83) of participants completed a hyperacuity task where they aligned eight dots in the shape of a square, and 64% (32/50) of participants with monocular distortion completed a spatial alignment task using dichoptic stimuli. Ten controls completed all tasks. Horizontal and vertical distortion magnitudes were calculated for each of the three assessments. Distortion magnitudes were significantly higher in patients than controls in all assessments. There was no significant difference in magnitude of distortion across different macular diseases. There were no significant correlations between overall magnitude of distortion among any of the three measures and no significant correlations in localized measures of distortion. Three alternative quantifications of monocular spatial distortion in the central visual field generated uncorrelated estimates of visual distortion. It is therefore unlikely that metamorphopsia is caused solely by retinal displacement, but instead involves additional top-down information, knowledge about the scene, and perhaps, cortical reorganization. Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.

Electron paramagnetic resonance and density-functional theory studies of Cu(II)-bis(oxamato) complexes.

PubMed

Bräuer, Björn; Weigend, Florian; Fittipaldi, Maria; Gatteschi, Dante; Reijerse, Edward J; Guerri, Annalisa; Ciattini, Samuele; Salvan, Georgeta; Rüffer, Tobias

2008-08-04

In this work we present the investigation of the influence of electronic and structural variations induced by varying the N,N'-bridge on the magnetic properties of Cu(II)- bis(oxamato) complexes. For this study the complexes [Cu(opba)] (2-) ( 1, opba = o-phenylene- bis(oxamato)), [Cu(nabo)] (2-) ( 2, nabo = 2,3-naphthalene- bis(oxamato)), [Cu(acbo)] (2-) ( 3, acbo = 2,3-anthrachinone- bis(oxamato)), [Cu(pba)] (2-) ( 4, pba = propylene- bis(oxamato)), [Cu(obbo)] (2-) ( 5, obbo = o-benzyl- bis(oxamato)), and [Cu(npbo)] (2-) ( 6, npbo = 1,8-naphthalene- bis(oxamato)), and the respective structurally isomorphic Ni(II) complexes ( 8- 13) have been prepared as ( (n)Bu 4N) (+) salts. The new complex ( (n)Bu 4N) 2[Cu(R-bnbo)].2H 2O ( 7, R-bnbo = (R)-1,1'-binaphthalene-2,2'- bis(oxamato)) was synthesized and is the first chiral complex in the series of Cu(II)-bis(oxamato) complexes. The molecular structure of 7 has been determined by single crystal X-ray analysis. The Cu(II) ions of the complexes 1- 7 are eta (4)(kappa (2) N, kappa (2) O) coordinated with a more or less distorted square planar geometry for 1- 6 and a distorted tetrahedral geometry for 7. Using pulsed Electron Nuclear Double Resonance on complex 6, detailed information about the relative orientation of the hyperfine ( A) and nuclear quadrupole tensors ( Q) of the coordinating nitrogens with respect to the g tensor were obtained. Electron Paramagnetic Resonance studies in the X, Q, and W-band at variable temperatures were carried out to extract g and A values of N ligands and Cu ion for 1- 7. The hyperfine values were interpreted in terms of spin population on the corresponding atoms. The obtained trends of the spin population for the monomeric building blocks were shown to correlate to the trends obtained in the dependence of the exchange interaction of the corresponding trinuclear complexes on their geometry.

Mononuclear Ni(II) complexes of Schiff base ligands formed from unsymmetrical tripodal amines of differing arm lengths: Spectral, X-ray crystal structural, antimicrobial and DNA cleavage activity

NASA Astrophysics Data System (ADS)

Keypour, Hassan; Shayesteh, Maryam; Rezaeivala, Majid; Dhers, Sébastien; Küp, Fatma Öztürk; Güllü, Mithat; Ng, Seikweng

2017-11-01

The synthesis of two unsymmetrical N-capped tripodal amines, 2-((4-aminobutyl)(pyridin-2-ylmethyl)amino)ethanol (3) and 3-((2-aminoethyl)(pyridin-2-ylmethyl)amino)propan-1-ol (4) is reported. They feature a longer, 3-hydroxypropyl or butylamino arm than that in the analogues previously employed. All four tripodal amines, 1-4, are equipped with a 2-methylpyridyl-arm, and either an ethylamino-arm (1 and 4), propylamino-arm (2) or butylamino-arm (3). The amines, 3 and 4, have been employed in one pot condensation reactions with salicylaldehyde and its derivatives in the presence of Ni(II) metal ion. A series of new mononuclear complexes, [NiIILaldi](ClO4) or [NiIILaldi(solvent)](ClO4) with different geometry, of Schiff base ligands were generated. X-ray crystal structure determinations of [NiIILOMe3(H2O)](ClO4)·2H2O and [NiIILOMe4](ClO4) revealed them to be mononuclear. The Ni(II) ion in [NiIILOMe4](ClO4) complex is in a distorted square-planar environment whilst this ion is in distorted octahedral environment in [NiIILOMe3(H2O)](ClO4)·2H2O complex despite the longer arm length of L3. While, in related systems in our previous work, they had led to dimeric complexes. These results clearly showed that the variation of the arm lengths of the ligands and metal ions has a remarkable impact on the formation and structure of the complexes. The cleavage of DNA by all synthesised complexes was examined using gel electrophoresis experiments. Also, the antibacterial effects of components were determined against the three Gram-positive bacteria, and against the three Gram-negative bacteria and against the three yeast Candida albicans ATCC 10231, Candida krusei ATCC 1424 and Candida tropicalis ATCC 13803.

Mononuclear late first row transition metal complexes of ONO donor hydrazone ligand: Synthesis, characterization, crystallographic insight, in vivo and in vitro anti-inflammatory activity

NASA Astrophysics Data System (ADS)

Kendur, Umashri; Chimmalagi, Geeta H.; Patil, Sunil M.; Gudasi, Kalagouda B.; Frampton, Christopher S.; Mangannavar, Chandrashekhar V.; Muchchandi, Iranna S.

2018-02-01

Air and moisture stable coordination compounds of late first row transition metal ions, viz., Co(II), Ni(II), Cu(II) and Zn(II) with a newly designed ligand, (E)-2-amino-N'-(1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)ethylidene)benzohydrazide (H2L) were prepared and extensively characterized using various spectro-analytical techniques. The ligand acts both in mono as well as doubly deprotonated manner. The ligand to metal stoichiometry was found to be 1:2 in case of complexes using chloride salts, whereas 1:1 in case of copper (II) complex using its acetate salt. The molecular structures of H2L, nickel and copper complexes were unambiguously determined by single-crystal X-ray diffraction studies reveal that H2L exists in a zwitterionic form while copper complex has copper centre in a distorted square planar environment. On the other hand, cobalt, nickel and zinc complexes display distorted octahedral coordination around the metal ion. In case of [Ni(HL)2].H2O, intramolecular Csbnd H⋯π stacking interaction were observed between the centroid of five membered chelate ring and phenyl proton C5sbnd H5 and intermolecular Csbnd H⋯π stacking interaction between the centroid of phenyl ring, dehydroacetic acid (DHA) ring and phenyl protons. The [Cu(L)DMF] complex is stabilized by intramolecular hydrogen bonding N1H⋯N2 and by intermolecular hydrogen bonding N1H⋯O4. Intermolecular interactions were investigated by Hirshfeld surfaces. Further, H2L and its metal complexes were screened for their in vivo and in vitro anti-inflammatory activities. The activity of the ligand has enhanced on coordination with transition metals. The tested compounds have shown excellent activity, which is almost equipotent to the standard used in the study.

Effects of EPI distortion correction pipelines on the connectome in Parkinson's Disease

NASA Astrophysics Data System (ADS)

Galvis, Justin; Mezher, Adam F.; Ragothaman, Anjanibhargavi; Villalon-Reina, Julio E.; Fletcher, P. Thomas; Thompson, Paul M.; Prasad, Gautam

2016-03-01

Echo-planar imaging (EPI) is commonly used for diffusion-weighted imaging (DWI) but is susceptible to nonlinear geometric distortions arising from inhomogeneities in the static magnetic field. These inhomogeneities can be measured and corrected using a fieldmap image acquired during the scanning process. In studies where the fieldmap image is not collected, these distortions can be corrected, to some extent, by nonlinearly registering the diffusion image to a corresponding anatomical image, either a T1- or T2-weighted image. Here we compared two EPI distortion correction pipelines, both based on nonlinear registration, which were optimized for the particular weighting of the structural image registration target. The first pipeline used a 3D nonlinear registration to a T1-weighted target, while the second pipeline used a 1D nonlinear registration to a T2-weighted target. We assessed each pipeline in its ability to characterize high-level measures of brain connectivity in Parkinson's disease (PD) in 189 individuals (58 healthy controls, 131 people with PD) from the Parkinson's Progression Markers Initiative (PPMI) dataset. We computed a structural connectome (connectivity map) for each participant using regions of interest from a cortical parcellation combined with DWI-based whole-brain tractography. We evaluated test-retest reliability of the connectome for each EPI distortion correction pipeline using a second diffusion scan acquired directly after the participants' first. Finally, we used support vector machine (SVM) classification to assess how accurately each pipeline classified PD versus healthy controls using each participants' structural connectome.

Retinal image mosaicing using the radial distortion correction model

NASA Astrophysics Data System (ADS)

Lee, Sangyeol; Abràmoff, Michael D.; Reinhardt, Joseph M.

2008-03-01

Fundus camera imaging can be used to examine the retina to detect disorders. Similar to looking through a small keyhole into a large room, imaging the fundus with an ophthalmologic camera allows only a limited view at a time. Thus, the generation of a retinal montage using multiple images has the potential to increase diagnostic accuracy by providing larger field of view. A method of mosaicing multiple retinal images using the radial distortion correction (RADIC) model is proposed in this paper. Our method determines the inter-image connectivity by detecting feature correspondences. The connectivity information is converted to a tree structure that describes the spatial relationships between the reference and target images for pairwise registration. The montage is generated by cascading pairwise registration scheme starting from the anchor image downward through the connectivity tree hierarchy. The RADIC model corrects the radial distortion that is due to the spherical-to-planar projection during retinal imaging. Therefore, after radial distortion correction, individual images can be properly mapped onto a montage space by a linear geometric transformation, e.g. affine transform. Compared to the most existing montaging methods, our method is unique in that only a single registration per image is required because of the distortion correction property of RADIC model. As a final step, distance-weighted intensity blending is employed to correct the inter-image differences in illumination encountered when forming the montage. Visual inspection of the experimental results using three mosaicing cases shows our method can produce satisfactory montages.

The recovery of weak impulsive signals based on stochastic resonance and moving least squares fitting.

PubMed

Jiang, Kuosheng; Xu, Guanghua; Liang, Lin; Tao, Tangfei; Gu, Fengshou

2014-07-29

In this paper a stochastic resonance (SR)-based method for recovering weak impulsive signals is developed for quantitative diagnosis of faults in rotating machinery. It was shown in theory that weak impulsive signals follow the mechanism of SR, but the SR produces a nonlinear distortion of the shape of the impulsive signal. To eliminate the distortion a moving least squares fitting method is introduced to reconstruct the signal from the output of the SR process. This proposed method is verified by comparing its detection results with that of a morphological filter based on both simulated and experimental signals. The experimental results show that the background noise is suppressed effectively and the key features of impulsive signals are reconstructed with a good degree of accuracy, which leads to an accurate diagnosis of faults in roller bearings in a run-to failure test.

SQUARE WAVE AMPLIFIER

DOEpatents

Leavitt, M.A.; Lutz, I.C.

1958-08-01

An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.

Metallic carbon materials

DOEpatents

Cohen, Marvin Lou; Crespi, Vincent Henry; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

1999-01-01

Novel metallic forms of planar carbon are described, as well as methods of designing and making them. Nonhexagonal arrangements of carbon are introduced into a graphite carbon network essentially without destroying the planar structure. Specifically a form of carbon comprising primarily pentagons and heptagons, and having a large density of states at the Fermi level is described. Other arrangements of pentagons and heptagons that include some hexagons, and structures incorporating squares and octagons are additionally disclosed. Reducing the bond angle symmetry associated with a hexagonal arrangement of carbons increases the likelihood that the carbon material will have a metallic electron structure.

Convection-induced distortion of a solid-liquid interface

NASA Technical Reports Server (NTRS)

Schaefer, R. J.; Coriell, S. R.

1984-01-01

Measurements of convective flow fields and solid-liquid interface shapes during the solidification of a pure and a slightly alloyed transparent material reveal that the convective transport of solute can cause a macroscopic depression to develop in the solid-liquid interface. This effect occurs under conditions close to those which are predicted to produce morphological instability of a planar interface. A cellular or dendritic microstructure later develops within the interface depression. The convection is attributed to the effect of radial temperature gradients in the crystal growth apparatus.

Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

DOE PAGES

Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; ...

2014-10-07

The structure of a nanospheric polyhydrido copper cluster, [Cu 20(H) 11{S 2P(O iPr) 2} 9], was determined by single-crystal neutron diffraction. Cu 20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu 2H 5} 3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ 3-hydrides in pyramidal geometry, two μ 4-hydrides in tetrahedral cavity, and three μ 4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal ofmore » the size 0.20 mm x 0.50 mm x 0.65 mm for seven days using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.« less

Unusual ion UO(4)(-) formed upon collision induced dissociation of [UO(2)(NO(3))(3)](-), [UO(2)(ClO(4))(3)](-), [UO(2)(CH(3)COO)(3)](-) ions.

PubMed

Sokalska, Marzena; Prussakowska, Małgorzata; Hoffmann, Marcin; Gierczyk, Błazej; Frański, Rafał

2010-10-01

The following ions [UO(2)(NO(3))(3)](-), [UO(2)(ClO(4))(3)](-), [UO(2)(CH(3)COO)(3)](-) were generated from respective salts (UO(2)(NO(3))(2), UO(2)(ClO(4))(3), UO(2)(CH(3)COO)(2)) by laser desorption/ionization (LDI). Collision induced dissociation of the ions has led, among others, to the formation of UO(4)(-) ion (m/z 302). The undertaken quantum mechanical calculations showed this ion is most likely to possess square planar geometry as suggested by MP2 results or strongly deformed geometry in between tetrahedral and square planar as indicated by DFT results. Interestingly, geometrical parameters and analysis of electron density suggest it is an U(VI) compound, in which oxygen atoms bear unpaired electron and negative charge. Copyright © 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

Using finite element modelling and experimental methods to investigate planar coil sensor topologies for inductive measurement of displacement

NASA Astrophysics Data System (ADS)

Moreton, Gregory; Meydan, Turgut; Williams, Paul

2018-04-01

The usage of planar sensors is widespread due to their non-contact nature and small size profiles, however only a few basic design types are generally considered. In order to develop planar coil designs we have performed extensive finite element modelling (FEM) and experimentation to understand the performance of different planar sensor topologies when used in inductive sensing. We have applied this approach to develop a novel displacement sensor. Models of different topologies with varying pitch values have been analysed using the ANSYS Maxwell FEM package, furthermore the models incorporated a movable soft magnetic amorphous ribbon element. The different models used in the FEM were then constructed and experimentally tested with topologies that included mesh, meander, square coil, and circular coil configurations. The sensors were used to detect the displacement of the amorphous ribbon. A LabView program controlled both the displacement stage and the impedance analyser, the latter capturing the varying inductance values with ribbon displacement. There was good correlation between the FEM models and the experimental data confirming that the methodology described here offers an effective way for developing planar coil based sensors with improved performance.

Microwave structure for the propiolic acid-formic acid complex.

PubMed

Kukolich, Stephen G; Mitchell, Erik G; Carey, Spencer J; Sun, Ming; Sargus, Bryan A

2013-10-03

New microwave spectra were measured to obtain rotational constants and centrifugal distortion constants for the DCCCOOH···HOOCH and HCCCOOD···DOOCH isotopologues. Rotational transitions were measured in the frequency range of 4.9-15.4 GHz, providing accurate rotational constants, which, combined with previous rotational constants, allowed an improved structural fit for the propiolic acid-formic acid complex. The new structural fit yields reasonably accurate orientations for both the propiolic and formic acid monomers in the complex and more accurate structural parameters describing the hydrogen bonding. The structure is planar, with a positive inertial defect of Δ = 1.33 amu Å(2). The experimental structure exhibits a greater asymmetry for the two hydrogen bond lengths than was obtained from the ab initio mp2 calculations. The best-fit hydrogen bond lengths have an r(O1-H1···O4) of 1.64 Å and an r(O3-H2···O2) of 1.87 Å. The average of the two hydrogen bond lengths is r(av)(exp) = 1.76 Å, in good agreement with r(av)(theory) = 1.72 Å. The center of mass separation of the monomers is R(CM) = 3.864 Å. Other structural parameters from the least-squares fit using the experimental rotational constants are compared with theoretical values. The spectra were obtained using two different pulsed beam Fourier transform microwave spectrometers.

catena-Poly[bis(1,3-benzo­thia­zol-3-ium) [[di­chlorido­anti­monate(III)]-di-μ-chlorido-μ-oxido-[chlorido­anti­monate(III)]-μ-chlorido

PubMed Central

Chebout, Oussama; Boudraa, Mhamed; Bouacida, Sofiane; Merazig, Hocine; Boudaren, Chaouki

2016-01-01

The title compound, {(C7H6NS)2[Sb2Cl6O]}n, contains two benzo­thia­zolidium cations and one tri-μ-chlorido-tri­chlorido-μ-oxido-di­anti­monate(III) anion. The structure of the inorganic cation may be described as as being built up from two polyhedra, i.e. a square-pyramidal SbCl4O and a distorted octa­hedral SbOCl5 unit, sharing a common face (comprising the O atom and two Cl atoms). The two benzo­thia­zole cations are quasi-planar and subtend a dihedral angle of 19.93 (5)°. The crystal packing can be described by alternating (100) layers and [001] chains of the organic cations and inorganic anions connected through an extensive three-dimensional network of N—H⋯Cl, C—H⋯O and C—H⋯Cl hydrogen bonds. This is consolidated by slipped π–π stacking, with centroid-to-centroid distances between the benzo­thia­zole rings of 3.7111 (18)–3.8452 (16) Å. These inter­actions link the mol­ecules within the layers and also link the layers together and reinforce the cohesion of the ionic structure. PMID:26958390

Newer mixed ligand Schiff base complexes from aquo-N-(2‧-hydroxy acetophenone) glycinatocopper(II) as synthon: DFT, antimicrobial activity and molecular docking study

NASA Astrophysics Data System (ADS)

Pramanik, Harun A. R.; Das, Dharitri; Paul, Pradip C.; Mondal, Paritosh; Bhattacharjee, Chira R.

2014-02-01

Synthesis of a series of newer mixed ligand copper(II) complexes of aminoacid Schiff base of the type [CuL(X)] (L = N-(2‧-hydroxy acetophenone) glycinate, X = imidazole (im) 2, benzimidazole (benz) 3, pyridine (py) 4, hydrazine (hz) 5,8-hydroxyquinoline (8-hq) 6, pyrrolidine (pyrr) 7, piperidine (pip) 8, and nicotinamide (nic) 9) have been accomplished from the interaction of an aquated Schiff base complex, [CuL(H2O)]·H2O, 1 with some selected neutral nitrogen-donor ligands. The copper(II) Schiff base complex, [CuL(H2O)]·H2O, L = N-(2‧-hydroxy acetophenone) glycinate was synthesized from the reaction of glycine and 2‧ hydroxy acetophenone and copper(II) acetate. The compounds were characterised by elemental analysis, spectral, magnetic and thermal studies. The density functional theory calculations were performed using LANL2DZ and 6-311 G(d, p) basis sets with B3LYP correlation functional to ascertain the stable electronic structure, HOMO-LUMO energy gap, chemical hardness and dipole moment of the mixed ligand complexes. A distorted square planar geometry has been conjectured for the complexes. Antibacterial activities of the ligand and its metal complexes have been tested against selected gram-positive and gram-negative strains and correlated with computational docking scores.

Experimental and numerical investigation of reactive shock-accelerated flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonazza, Riccardo

2016-12-20

The main goal of this program was to establish a qualitative and quantitative connection, based on the appropriate dimensionless parameters and scaling laws, between shock-induced distortion of astrophysical plasma density clumps and their earthbound analog in a shock tube. These objectives were pursued by carrying out laboratory experiments and numerical simulations to study the evolution of two gas bubbles accelerated by planar shock waves and compare the results to available astrophysical observations. The experiments were carried out in an vertical, downward-firing shock tube, 9.2 m long, with square internal cross section (25×25 cm 2). Specific goals were to quantify themore » effect of the shock strength (Mach number, M) and the density contrast between the bubble gas and its surroundings (usually quantified by the Atwood number, i.e. the dimensionless density difference between the two gases) upon some of the most important flow features (e.g. macroscopic properties; turbulence and mixing rates). The computational component of the work performed through this program was aimed at (a) studying the physics of multi-phase compressible flows in the context of astrophysics plasmas and (b) providing a computational connection between laboratory experiments and the astrophysical application of shock-bubble interactions. Throughout the study, we used the FLASH4.2 code to run hydrodynamical and magnetohydrodynamical simulations of shock bubble interactions on an adaptive mesh.« less

Rovibrational constants of the ground state and v8 = 1 state of 13C2HD3 by high-resolution FTIR spectroscopy

NASA Astrophysics Data System (ADS)

Ng, L. L.; Tan, T. L.

2016-06-01

The Fourier transform infrared (FTIR) spectrum of the c-type ν8 band of 13C2HD3 was recorded for the first time at a unapodized resolution of 0.0063 cm-1 in the wavenumber region of 830-1000 cm-1. Through the fitting of a total of 1057 assigned infrared transitions using Watson's A-reduced Hamiltonian in the Ir representation, rovibrational constants for the upper state (v8 = 1) up to five quartic centrifugal distortion terms were derived for the first time with a root-mean-square (rms) deviation of 0.00073 cm-1. The band center of ν8 of 13C2HD3 was found to be 913.011021(55) cm-1. Ground state rovibrational constants up to five quartic terms of 13C2HD3 were also determined from a fit of 453 ground state combination-differences from the present infrared measurements with an rms deviation of 0.00072 cm-1 for the first time. The uncertainty of the measured infrared lines was estimated to be ±0.0012 cm-1. From the ground state rotational constants, the inertial defect of 13C2HD3 was calculated to be 0.06973(16) uÅ2, showing the high planarity of the molecule.

Comparison of methods for quantitative evaluation of endoscopic distortion

NASA Astrophysics Data System (ADS)

Wang, Quanzeng; Castro, Kurt; Desai, Viraj N.; Cheng, Wei-Chung; Pfefer, Joshua

2015-03-01

Endoscopy is a well-established paradigm in medical imaging, and emerging endoscopic technologies such as high resolution, capsule and disposable endoscopes promise significant improvements in effectiveness, as well as patient safety and acceptance of endoscopy. However, the field lacks practical standardized test methods to evaluate key optical performance characteristics (OPCs), in particular the geometric distortion caused by fisheye lens effects in clinical endoscopic systems. As a result, it has been difficult to evaluate an endoscope's image quality or assess its changes over time. The goal of this work was to identify optimal techniques for objective, quantitative characterization of distortion that are effective and not burdensome. Specifically, distortion measurements from a commercially available distortion evaluation/correction software package were compared with a custom algorithm based on a local magnification (ML) approach. Measurements were performed using a clinical gastroscope to image square grid targets. Recorded images were analyzed with the ML approach and the commercial software where the results were used to obtain corrected images. Corrected images based on the ML approach and the software were compared. The study showed that the ML method could assess distortion patterns more accurately than the commercial software. Overall, the development of standardized test methods for characterizing distortion and other OPCs will facilitate development, clinical translation, manufacturing quality and assurance of performance during clinical use of endoscopic technologies.

Structure and Bonding in CE5- (E=Al-Tl) Clusters: Planar Tetracoordinate Carbon versus Pentacoordinate Carbon.

PubMed

Ravell, Estefanía; Jalife, Said; Barroso, Jorge; Orozco-Ic, Mesías; Hernández-Juárez, Gerardo; Ortiz-Chi, Filiberto; Pan, Sudip; Cabellos, José Luis; Merino, Gabriel

2018-03-24

The structure, bonding, and stability of clusters with the empirical formula CE 5 - (E=Al-Tl) have been analyzed by means of high-level computations. The results indicate that, whereas aluminum and gallium clusters have C 2v structures with a planar tetracoordinate carbon (ptC), their heavier homologues prefer three-dimensional C 4v forms with a pentacoordinate carbon center over the ptC one. The reason for such a preference is a delicate balance between the interaction energy of the fifth E atom with CE 4 and the distortion energy. Moreover, bonding analysis shows that the ptC systems can be better described as CE 4 - , with 17-valence electrons interacting with E. The ptC core in these systems exhibits double aromatic (both σ and π) behavior, but the σ contribution is dominating. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental study of strained and destrained turbulence

NASA Astrophysics Data System (ADS)

Chen, Jun; Meneveau, Charles; Katz, Joseph

2003-11-01

Planar Particle Image Velocimetry measurements are performed in a water tank facility in which high Reynolds number turbulence is generated by an array of spinning grids. Straining fields are applied using a piston with rectangular cross-section which is pushed towards the bottom of the tank, setting up a planar straining field there. The facility can also be used to reverse the distortion ("destraining'') by pulling the piston upwards. We present calibration tests characterizing the flow in the facility. The initial turbulent state is characterized by means of ditributions of rms values and energy spectra, and corresponds closely to isotropic, homogeneous turbulence. The applied straining is characterized using high-speed camera and PIV measurements of the mean flow without turbulence. Initial results of turbulence subjected to a sequence of straining and destraining motions are presented, with particular emphasis on the flux of kinetic energy from large to small scales and possible backscatter during destraining.

Precise X-ray and video overlay for augmented reality fluoroscopy.

PubMed

Chen, Xin; Wang, Lejing; Fallavollita, Pascal; Navab, Nassir

2013-01-01

The camera-augmented mobile C-arm (CamC) augments any mobile C-arm by a video camera and mirror construction and provides a co-registration of X-ray with video images. The accurate overlay between these images is crucial to high-quality surgical outcomes. In this work, we propose a practical solution that improves the overlay accuracy for any C-arm orientation by: (i) improving the existing CamC calibration, (ii) removing distortion effects, and (iii) accounting for the mechanical sagging of the C-arm gantry due to gravity. A planar phantom is constructed and placed at different distances to the image intensifier in order to obtain the optimal homography that co-registers X-ray and video with a minimum error. To alleviate distortion, both X-ray calibration based on equidistant grid model and Zhang's camera calibration method are implemented for distortion correction. Lastly, the virtual detector plane (VDP) method is adapted and integrated to reduce errors due to the mechanical sagging of the C-arm gantry. The overlay errors are 0.38±0.06 mm when not correcting for distortion, 0.27±0.06 mm when applying Zhang's camera calibration, and 0.27±0.05 mm when applying X-ray calibration. Lastly, when taking into account all angular and orbital rotations of the C-arm, as well as correcting for distortion, the overlay errors are 0.53±0.24 mm using VDP and 1.67±1.25 mm excluding VDP. The augmented reality fluoroscope achieves an accurate video and X-ray overlay when applying the optimal homography calculated from distortion correction using X-ray calibration together with the VDP.

Computer-assisted map projection research

USGS Publications Warehouse

Snyder, John Parr

1985-01-01

Computers have opened up areas of map projection research which were previously too complicated to utilize, for example, using a least-squares fit to a very large number of points. One application has been in the efficient transfer of data between maps on different projections. While the transfer of moderate amounts of data is satisfactorily accomplished using the analytical map projection formulas, polynomials are more efficient for massive transfers. Suitable coefficients for the polynomials may be determined more easily for general cases using least squares instead of Taylor series. A second area of research is in the determination of a map projection fitting an unlabeled map, so that accurate data transfer can take place. The computer can test one projection after another, and include iteration where required. A third area is in the use of least squares to fit a map projection with optimum parameters to the region being mapped, so that distortion is minimized. This can be accomplished for standard conformal, equalarea, or other types of projections. Even less distortion can result if complex transformations of conformal projections are utilized. This bulletin describes several recent applications of these principles, as well as historical usage and background.

Considerations in high-resolution skeletal muscle diffusion tensor imaging using single-shot echo planar imaging with stimulated-echo preparation and sensitivity encoding.

PubMed

Karampinos, Dimitrios C; Banerjee, Suchandrima; King, Kevin F; Link, Thomas M; Majumdar, Sharmila

2012-05-01

Previous studies have shown that skeletal muscle diffusion tensor imaging (DTI) can noninvasively probe changes in the muscle fiber architecture and microstructure in diseased and damaged muscles. However, DTI fiber reconstruction in small muscles and in muscle regions close to aponeuroses and tendons remains challenging because of partial volume effects. Increasing the spatial resolution of skeletal muscle single-shot diffusion-weighted echo planar imaging (DW-EPI) can be hindered by the inherently low signal-to-noise ratio (SNR) of muscle DW-EPI because of the short muscle T(2) and the high sensitivity of single-shot EPI to off-resonance effects and T(2)* blurring. In this article, eddy current-compensated diffusion-weighted stimulated-echo preparation is combined with sensitivity encoding (SENSE) to maintain good SNR properties and to reduce the sensitivity to distortions and T(2)* blurring in high-resolution skeletal muscle single-shot DW-EPI. An analytical framework is developed to optimize the reduction factor and diffusion weighting time to achieve maximum SNR. Arguments for the selection of the experimental parameters are then presented considering the compromise between SNR, B(0)-induced distortions, T(2)* blurring effects and tissue incoherent motion effects. On the basis of the selected parameters in a high-resolution skeletal muscle single-shot DW-EPI protocol, imaging protocols at lower acquisition matrix sizes are defined with matched bandwidth in the phase-encoding direction and SNR. In  vivo results show that high-resolution skeletal muscle DTI with minimized sensitivity to geometric distortions and T(2)* blurring is feasible using the proposed methodology. In particular, a significant benefit is demonstrated from a reduction in partial volume effects for resolving multi-pennate muscles and muscles with small cross-sections in calf muscle DTI. Copyright © 2011 John Wiley & Sons, Ltd.

Long-range two-dimensional superstructure in the superconducting electron-doped cuprate Pr 0.88 LaCe 0.12 CuO 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, B. J.; Rosenkranz, S.; Kang, H. J.

2015-07-01

Utilizing single-crystal synchrotron x-ray scattering, we observe distorted CuO 2 planes in the electron- doped superconductor Pr 1-xLaCe xCuO 4+δ , x =0.12. Resolution-limited rods of scattering are indicative of a long-range two-dimensional 2√2 × 2√2 superstructure in the a-b plane, adhering to planar space-group symmetry p4gm, which is subject to stacking disorder perpendicular to the planes. This superstructure is present only in annealed, superconducting samples, but not in the as-grown, nonsuperconducting samples. These long-range distortions of the CuO 2 planes, which are generally considered to be detrimental to superconductivity, have avoided detection to date due to the challenges ofmore » observing and interpreting subtle diffuse-scattering features.« less

Jahn-Teller distortion in the phosphorescent excited state of three-coordinate Au(I) phosphine complexes.

PubMed

Barakat, Khaldoon A; Cundari, Thomas R; Omary, Mohammad A

2003-11-26

DFT calculations were used to optimize the phosphorescent excited state of three-coordinate [Au(PR3)3]+ complexes. The results indicate that the complexes rearrange from their singlet ground-state trigonal planar geometry to a T-shape in the lowest triplet luminescent excited state. The optimized structure of the exciton contradicts the structure predicted based on the AuP bonding properties of the ground-state HOMO and LUMO. The rearrangement to T-shape is a Jahn-Teller distortion because an electron is taken from the degenerate e' (5dxy, 5dx2-y2) orbital upon photoexcitation of the ground-state D3h complex. The calculated UV absorption and visible emission energies are consistent with the experimental data and explain the large Stokes' shifts while such correlations are not possible in optimized models that constrained the exciton to the ground-state trigonal geometry.

Surface Design Based on Discrete Conformal Transformations

NASA Astrophysics Data System (ADS)

Duque, Carlos; Santangelo, Christian; Vouga, Etienne

Conformal transformations are angle-preserving maps from one domain to another. Although angles are preserved, the lengths between arbitrary points are not generally conserved. As a consequence there is always a given amount of distortion associated to any conformal map. Different uses of such transformations can be found in various fields, but have been used by us to program non-uniformly swellable gel sheets to buckle into prescribed three dimensional shapes. In this work we apply circle packings as a kind of discrete conformal map in order to find conformal maps from the sphere to the plane that can be used as nearly uniform swelling patterns to program non-Euclidean sheets to buckle into spheres. We explore the possibility of tuning the area distortion to fit the experimental range of minimum and maximum swelling by modifying the boundary of the planar domain through the introduction of different cutting schemes.

Outlier Resistant Predictive Source Encoding for a Gaussian Stationary Nominal Source.

DTIC Science & Technology

1987-09-18

breakdown point and influence function . The proposed sequence of predictive encoders attains strictly positive breakdown point and uniformly bounded... influence function , at the expense of increased mean difference-squared distortion and differential entropy, at the Gaussian nominal source.

Electrohydrodynamic distortion of sample streams in continuous flow electrophoresis

NASA Technical Reports Server (NTRS)

Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

1989-01-01

Continuous flow electrophoresis experiments were carried out, using an electrolyte and a sample both made of aqueous solutions of phosphate buffer (with polystyrene latex added for visibility), to investigate causes of the sample spreading in this procedure. It is shown theoretically that an electric field perpendicular to a circular filament of conducting fluid surrounded by a fluid of different conductivity produces an electrohydrodynamic flow, which distorts the filament into an ellipse. Experimental results were found to be fully consistent with theretical predictions. It was found that the rate of distortion of the sample stream into a ribbon was proportional to the square of the applied voltage gradient. Furthermore, the orientation of the ribbon depends on the ratios of dielectric constant and electrical conductivity between the buffer and the sample.

CMOS chip planarization by chemical mechanical polishing for a vertically stacked metal MEMS integration

NASA Astrophysics Data System (ADS)

Lee, Hocheol; Miller, Michele H.; Bifano, Thomas G.

2004-01-01

In this paper we present the planarization process of a CMOS chip for the integration of a microelectromechanical systems (MEMS) metal mirror array. The CMOS chip, which comes from a commercial foundry, has a bumpy passivation layer due to an underlying aluminum interconnect pattern (1.8 µm high), which is used for addressing individual micromirror array elements. To overcome the tendency for tilt error in the CMOS chip planarization, the approach is to sputter a thick layer of silicon nitride at low temperature and to surround the CMOS chip with dummy silicon pieces that define a polishing plane. The dummy pieces are first lapped down to the height of the CMOS chip, and then all pieces are polished. This process produced a chip surface with a root-mean-square flatness error of less than 100 nm, including tilt and curvature errors.

Addressing challenges of modulation transfer function measurement with fisheye lens cameras

NASA Astrophysics Data System (ADS)

Deegan, Brian M.; Denny, Patrick E.; Zlokolica, Vladimir; Dever, Barry; Russell, Laura

2015-03-01

Modulation transfer function (MTF) is a well defined and accepted method of measuring image sharpness. The slanted edge test, as defined in ISO12233 is a standard method of calculating MTF, and is widely used for lens alignment and auto-focus algorithm verification. However, there are a number of challenges which should be considered when measuring MTF in cameras with fisheye lenses. Due to trade-offs related Petzval curvature, planarity of the optical plane is difficult to achieve in fisheye lenses. It is therefore critical to have the ability to accurately measure sharpness throughout the entire image, particularly for lens alignment. One challenge for fisheye lenses is that, because of the radial distortion, the slanted edges will have different angles, depending on the location within the image and on the distortion profile of the lens. Previous work in the literature indicates that MTF measurements are robust for angles between 2 and 10 degrees. Outside of this range, MTF measurements become unreliable. Also, the slanted edge itself will be curved by the lens distortion, causing further measurement problems. This study summarises the difficulties in the use of MTF for sharpness measurement in fisheye lens cameras, and proposes mitigations and alternative methods.

X-PROP: a fast and robust diffusion-weighted propeller technique.

PubMed

Li, Zhiqiang; Pipe, James G; Lee, Chu-Yu; Debbins, Josef P; Karis, John P; Huo, Donglai

2011-08-01

Diffusion-weighted imaging (DWI) has shown great benefits in clinical MR exams. However, current DWI techniques have shortcomings of sensitivity to distortion or long scan times or combinations of the two. Diffusion-weighted echo-planar imaging (EPI) is fast but suffers from severe geometric distortion. Periodically rotated overlapping parallel lines with enhanced reconstruction diffusion-weighted imaging (PROPELLER DWI) is free of geometric distortion, but the scan time is usually long and imposes high Specific Absorption Rate (SAR) especially at high fields. TurboPROP was proposed to accelerate the scan by combining signal from gradient echoes, but the off-resonance artifacts from gradient echoes can still degrade the image quality. In this study, a new method called X-PROP is presented. Similar to TurboPROP, it uses gradient echoes to reduce the scan time. By separating the gradient and spin echoes into individual blades and removing the off-resonance phase, the off-resonance artifacts in X-PROP are minimized. Special reconstruction processes are applied on these blades to correct for the motion artifacts. In vivo results show its advantages over EPI, PROPELLER DWI, and TurboPROP techniques. Copyright © 2011 Wiley-Liss, Inc.

Eddy current compensated double diffusion encoded (DDE) MRI.

PubMed

Mueller, Lars; Wetscherek, Andreas; Kuder, Tristan Anselm; Laun, Frederik Bernd

2017-01-01

Eddy currents might lead to image distortions in diffusion-weighted echo planar imaging. A method is proposed to reduce their effects on double diffusion encoding (DDE) MRI experiments and the thereby derived microscopic fractional anisotropy (μFA). The twice-refocused spin echo scheme was adapted for DDE measurements. To assess the effect of individual diffusion encodings on the image distortions, measurements of a grid of plastic rods in water were performed. The effect of eddy current compensation on μFA measurements was evaluated in the brains of six healthy volunteers. The use of an eddy current compensation reduced the signal variation. As expected, the distortions caused by the second encoding were larger than those of the first encoding, entailing a stronger need to compensate for them. For an optimal result, however, both encodings had to be compensated. The artifact reduction strongly improved the measurement of the μFA in ventricles and gray matter by reducing the overestimation. An effect of the compensation on absolute μFA values in white matter was not observed. It is advisable to compensate both encodings in DDE measurements for eddy currents. Magn Reson Med 77:328-335, 2017. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Electromagnetic tracking system with reduced distortion using quadratic excitation.

PubMed

Bien, Tomasz; Li, Mengfei; Salah, Zein; Rose, Georg

2014-03-01

Electromagnetic tracking systems, frequently used in minimally invasive surgery, are affected by conductive distorters. The influence of conductive distorters on electromagnetic tracking system accuracy can be reduced through magnetic field modifications. This approach was developed and tested. The voltage induced directly by the emitting coil in the sensing coil without additional influence by the conductive distorter depends on the first derivative of the voltage on the emitting coil. The voltage which is induced indirectly by the emitting coil across the conductive distorter in the sensing coil, however, depends on the second derivative of the voltage on the emitting coil. The electromagnetic tracking system takes advantage of this difference by supplying the emitting coil with a quadratic excitation voltage. The method is adaptive relative to the amount of distortion cause by the conductive distorters. This approach is evaluated with an experimental setup of the electromagnetic tracking system. In vitro testing showed that the maximal error decreased from 10.9 to 3.8 mm when the quadratic voltage was used to excite the emitting coil instead of the sinusoidal voltage. Furthermore, the root mean square error in the proximity of the aluminum disk used as a conductive distorter was reduced from 3.5 to 1.6 mm when the electromagnetic tracking system used the quadratic instead of sinusoidal excitation. Electromagnetic tracking with quadratic excitation is immune to the effects of a conductive distorter, especially compared with sinusoidal excitation of the emitting coil. Quadratic excitation of electromagnetic tracking for computer-assisted surgery is promising for clinical applications.

Adaptively combined FIR and functional link artificial neural network equalizer for nonlinear communication channel.

PubMed

Zhao, Haiquan; Zhang, Jiashu

2009-04-01

This paper proposes a novel computational efficient adaptive nonlinear equalizer based on combination of finite impulse response (FIR) filter and functional link artificial neural network (CFFLANN) to compensate linear and nonlinear distortions in nonlinear communication channel. This convex nonlinear combination results in improving the speed while retaining the lower steady-state error. In addition, since the CFFLANN needs not the hidden layers, which exist in conventional neural-network-based equalizers, it exhibits a simpler structure than the traditional neural networks (NNs) and can require less computational burden during the training mode. Moreover, appropriate adaptation algorithm for the proposed equalizer is derived by the modified least mean square (MLMS). Results obtained from the simulations clearly show that the proposed equalizer using the MLMS algorithm can availably eliminate various intensity linear and nonlinear distortions, and be provided with better anti-jamming performance. Furthermore, comparisons of the mean squared error (MSE), the bit error rate (BER), and the effect of eigenvalue ratio (EVR) of input correlation matrix are presented.

SU-E-J-112: Intensity-Based Pulmonary Image Registration: An Evaluation Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, F; Meyer, J; Sandison, G

2015-06-15

Purpose: Accurate alignment of thoracic CT images is essential for dose tracking and to safely implement adaptive radiotherapy in lung cancers. At the same time it is challenging given the highly elastic nature of lung tissue deformations. The objective of this study was to assess the performances of three state-of-art intensity-based algorithms in terms of their ability to register thoracic CT images subject to affine, barrel, and sinusoid transformation. Methods: Intensity similarity measures of the evaluated algorithms contained sum-of-squared difference (SSD), local mutual information (LMI), and residual complexity (RC). Five thoracic CT scans obtained from the EMPIRE10 challenge database weremore » included and served as reference images. Each CT dataset was distorted by realistic affine, barrel, and sinusoid transformations. Registration performances of the three algorithms were evaluated for each distortion type in terms of intensity root mean square error (IRMSE) between the reference and registered images in the lung regions. Results: For affine distortions, the three algorithms differed significantly in registration of thoracic images both visually and nominally in terms of IRMSE with a mean of 0.011 for SSD, 0.039 for RC, and 0.026 for LMI (p<0.01; Kruskal-Wallis test). For barrel distortion, the three algorithms showed nominally no significant difference in terms of IRMSE with a mean of 0.026 for SSD, 0.086 for RC, and 0.054 for LMI (p=0.16) . A significant difference was seen for sinusoid distorted thoracic CT data with mean lung IRMSE of 0.039 for SSD, 0.092 for RC, and 0.035 for LMI (p=0.02). Conclusion: Pulmonary deformations might vary to a large extent in nature in a daily clinical setting due to factors ranging from anatomy variations to respiratory motion to image quality. It can be appreciated from the results of the present study that the suitability of application of a particular algorithm for pulmonary image registration is deformation-dependent.« less

C60 Recognition from Extended Tetrathiafulvalene Bis-acetylide Platinum(II) Complexes.

PubMed

Bastien, Guillaume; Dron, Paul I; Vincent, Manon; Canevet, David; Allain, Magali; Goeb, Sébastien; Sallé, Marc

2016-11-18

The favorable spatial organization imposed by the square planar 4,4'-di(tert-butyl)-2,2'-bipyridine (dbbpy) platinum(II) complex associated with the electronic and shape complementarity of π-extended tetrathiafulvalene derivatives (exTTF) toward fullerenes is usefully exploited to construct molecular tweezers, which display good affinities for C 60 .

Metal cluster chemistry: Structure and stereochemistry in the polynuclear rhodium hydrides HnRhn[P(OR)3]2n

PubMed Central

Brown, R. K.; Williams, J. M.; Fredrich, M. F.; Day, V. W.; Sivak, A. J.; Muetterties, E. L.

1979-01-01

Crystallographic analyses of x-ray and neutron diffraction data have provided a definitive structural representation of {HRh[P(O-i-C3H7)3]2}2 and {HRh[P(OCH3)3]2}3. These polynuclear hydrides are generated from square planar H2Rh[P(OR)3]2 units by edge (hydrogen atom) sharing and by vertex (hydrogen atom) sharing to form the dimeric and trimeric structures, respectively. The square-planar units are held together through four-center and three-center two-electron Rh—H—Rh bonds in the dimer and trimer, respectively. The dimer and trimer molecules each add one molecule of hydrogen to form H[(i-C3H7O)3P]2RhH3Rh [P(O-i-C3H7)3]2 and H5Rh3[P(OCH3)3]6, respectively. NMR spectral information has served to define the stereochemical features of these polyhydrides. The significance of this chemistry in the metal cluster-metal surface analogy is described. PMID:16592645

Two-Stage Design Method for Enhanced Inductive Energy Transmission with Q-Constrained Planar Square Loops.

PubMed

Eteng, Akaa Agbaeze; Abdul Rahim, Sharul Kamal; Leow, Chee Yen; Chew, Beng Wah; Vandenbosch, Guy A E

2016-01-01

Q-factor constraints are usually imposed on conductor loops employed as proximity range High Frequency Radio Frequency Identification (HF-RFID) reader antennas to ensure adequate data bandwidth. However, pairing such low Q-factor loops in inductive energy transmission links restricts the link transmission performance. The contribution of this paper is to assess the improvement that is reached with a two-stage design method, concerning the transmission performance of a planar square loop relative to an initial design, without compromise to a Q-factor constraint. The first stage of the synthesis flow is analytical in approach, and determines the number and spacing of turns by which coupling between similar paired square loops can be enhanced with low deviation from the Q-factor limit presented by an initial design. The second stage applies full-wave electromagnetic simulations to determine more appropriate turn spacing and widths to match the Q-factor constraint, and achieve improved coupling relative to the initial design. Evaluating the design method in a test scenario yielded a more than 5% increase in link transmission efficiency, as well as an improvement in the link fractional bandwidth by more than 3%, without violating the loop Q-factor limit. These transmission performance enhancements are indicative of a potential for modifying proximity HF-RFID reader antennas for efficient inductive energy transfer and data telemetry links.

Syntheses, structures, and magnetic properties of a family of heterometallic heptanuclear [Cu5Ln2] (Ln = Y(III), Lu(III), Dy(III), Ho(III), Er(III), and Yb(III)) complexes: observation of SMM behavior for the Dy(III) and Ho(III) analogues.

PubMed

Chandrasekhar, Vadapalli; Dey, Atanu; Das, Sourav; Rouzières, Mathieu; Clérac, Rodolphe

2013-03-04

Sequential reaction of the multisite coordination ligand (LH3) with Cu(OAc)2·H2O, followed by the addition of a rare-earth(III) nitrate salt in the presence of triethylamine, afforded a series of heterometallic heptanuclear complexes containing a [Cu5Ln2] core {Ln = Y(1), Lu(2), Dy(3), Ho(4), Er(5), and Yb(6)}. Single-crystal X-ray crystallography reveals that all the complexes are dicationic species that crystallize with two nitrate anions to compensate the charge. The heptanuclear aggregates in 1-6 are centrosymmetrical complexes, with a hexagonal-like arrangement of six peripheral metal ions (two rare-earth and four copper) around a central Cu(II) situated on a crystallographic inversion center. An all-oxygen environment is found to be present around the rare-earth metal ions, which adopt a distorted square-antiprismatic geometry. Three different Cu(II) sites are present in the heptanuclear complexes: two possess a distorted octahedral coordination sphere while the remaining one displays a distorted square-pyramidal geometry. Detailed static and dynamic magnetic properties of all the complexes have been studied and revealed the single-molecule magnet behavior of the Dy(III) and Ho(III) derivatives.

Comparison of Diffusion-Weighted Imaging in the Human Brain Using Readout-Segmented EPI and PROPELLER Turbo Spin Echo With Single-Shot EPI at 7 T MRI.

PubMed

Kida, Ikuhiro; Ueguchi, Takashi; Matsuoka, Yuichiro; Zhou, Kun; Stemmer, Alto; Porter, David

2016-07-01

The purpose of the present study was to compare periodically rotated overlapping parallel lines with enhanced reconstruction-type turbo spin echo diffusion-weighted imaging (pTSE-DWI) and readout-segmented echo planar imaging (rsEPI-DWI) with single-shot echo planar imaging (ssEPI-DWI) in a 7 T human MR system. We evaluated the signal-to-noise ratio (SNR), image distortion, and apparent diffusion coefficient values in the human brain. Six healthy volunteers were included in this study. The study protocol was approved by our institutional review board. All measurements were performed at 7 T using pTSE-DWI, rsEPI-DWI, and ssEPI-DWI sequences. The spatial resolution was 1.2 × 1.2 mm in-plane with a 3-mm slice thickness. Signal-to-noise ratio was measured using 2 scans. The ssEPI-DWI sequence showed significant image blurring, whereas pTSE-DWI and rsEPI-DWI sequences demonstrated high image quality with low geometrical distortion compared with reference T2-weighted, turbo spin echo images. Signal loss in ventral regions near the air-filled paranasal sinus/nasal cavity was found in ssEPI-DWI and rsEPI-DWI but not pTSE-DWI. The apparent diffusion coefficient values for ssEPI-DWI were 824 ± 17 × 10 and 749 ± 25 × 10 mm/s in the gray matter and white matter, respectively; the values obtained for pTSE-DWI were 798 ± 21 × 10 and 865 ± 40 × 10 mm/s; and the values obtained for rsEPI-DWI were 730 ± 12 × 10 and 722 ± 25 × 10 mm/s. The pTSE-DWI images showed no additional distortion comparison to the T2-weighted images, but had a lower SNR than ssEPI-DWI and rsEPI-DWI. The rsEPI-DWI sequence provided high-quality images with minor distortion and a similar SNR to ssEPI-DWI. Our results suggest that the benefits of the rsEPI-DWI and pTSE-DWI sequences, in terms of SNR, image quality, and image distortion, appear to outweigh those of ssEPI-DWI. Thus, pTSE-DWI and rsEPI-DWI at 7 T have great potential use for clinical diagnoses. However, it is noteworthy that both sequences are limited by the scan time required. In addition, pTSE-DWI has limitations on the number of slices due to specific absorption rate. Overall, rsEPI-DWI is a favorable imaging sequence, taking into account the SNR and image quality at 7 T.

Response of turbulence subjected to a straining-relaxation-destraining cycle

NASA Astrophysics Data System (ADS)

Chen, Jun; Meneveau, Charles; Katz, Joseph

2004-11-01

The response of turbulence subjected to planar straining and de-straining is studied experimentally, and the impact of the applied distortions on the energy transfer across different length scales is quantified. The data are obtained using Planar Particle Image Velocimetry (PIV) in a water tank, in which high Reynolds number turbulence with very low mean velocity is generated by an array of spinning grids. Planar straining and de-straining mean flows are produced by pushing and pulling a rectangular piston towards, and away from, the bottom wall of the tank. The data are processed to yield the time evolution of Reynolds stresses, anisotropy tensors, turbulence kinetic energy production, and mean subgrid dissipation rate at various scales. During straining, the production rises rapidly. After the relaxation period the small-scale SGS stresses recover isotropy, but the Reynolds stresses at large scales still display significant anisotropy. When destraining is applied, a strong negative production (back-scattering) is observed, by which turbulence fluctuations return kinetic energy to the mean flow. Reversed energy transfer is also revealed in the vorticity fluctuations history. The experiment allows to disentangle in detail the causes for this global backscatter phenomenon in terms of non-equilibrium conditions of the Reynolds stresses, and to follow the trends as function of scale.

Cyclometalated gold(III) trioxadiborrin complexes: studies of the bonding and excited states.

PubMed

Ayoub, Nicholas A; Browne, Amberle R; Anderson, Bryce L; Gray, Thomas G

2016-03-07

Trioxadiborrins are chelating ligands that assemble in dehydration reactions of boronic acids. They are structurally related to β-diketonate ligands, but have a 2-charge. Little is known of the bonding properties of trioxadiborrin ligands. Presented here are density-functional theory (DFT) studies of cyclometalated gold(III) trioxadiborrins. Substituent effects are evaluated, and comparison is made to the cyclometalating 2-(4-tolyl)pyridine (tpy) ligand on gold. The tpy ligand binds more strongly than any trioxadiborrin ligand considered here, and the two ligands bind competitively to gold. The 1,3-diphenyl trioxadiborrin ligand of 1 has a larger absolute binding enthalpy to gold than its β-diketonate analogue. Conjugation between boron and aryl substituents delocalizes charge and attenuates the trioxadiborrin's binding capacity. Steric effects that disrupt conjugation between boron and aryl substituents cause the trioxadiborrin to chelate more tightly. Fragment bond orders are divided into in-plane and out-of-plane contributions for square planar 1. In-plane bonding accounts for 88% of bond order between (tpy)Au2+ and the trioxadiborrin ligand. Cyclometalated gold(III) trioxadiborrin complexes were previously shown to be phosphorescent. Spin-unrestricted triplet-state geometry optimizations find that the ten largest excited-state distortions all occur on the tpy ligand. A plot of spin density in triplet 1 shows spin to reside predominantly on tpy. The 77 K luminescence spectrum of 1 is reported here. Time-dependent DFT and configuration interaction singles calculations (corrected for doubles excitations) overestimate the emission energy by ∼ 0.12 eV.

Synthesis, characterization, antimicrobial activity and carbonic anhydrase enzyme inhibitor effects of salicilaldehyde-N-methyl p-toluenesulfonylhydrazone and its Palladium(II), Cobalt(II) complexes

NASA Astrophysics Data System (ADS)

Alyar, Saliha; Adem, Şevki

2014-10-01

We report the synthesis of the ligand, salicilaldehyde-N-methyl p-toluenesulfonylhydrazone (salptsmh) derived from p-toluenesulfonicacid-1-methylhydrazide (ptsmh) and its Pd(II) and Co(II) metal complexes were synthesized for the first time. The structure of the ligand and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, NMR and LC-MS) measurements. Salptsmh has also been characterized by single crystal X-ray diffraction. 1H and 13C shielding tensors for crystal structure were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The complexes were found to have general composition [ML2]. The results of elemental analysis showed 1:2 (metal/ligand) stoichiometry for all the complex. Magnetic and spectral data indicate a square planar geometry for Pd(II) complex and a distorted tetrahedral geometry for Co(II) complexes. The ligand and its metal chelates have been screened for their antimicrobial activities using the disk diffusion method against the selected Gram positive bacteria: Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Gram negative bacteria: Eschericha coli, Pseudomonas aeruginosa, Klebsiella pneumonia. The inhibition activities of these compounds on carbonic anhydrase II (CA II) and carbonic anhydrase I (CA I) have been investigated by comparing IC50 and Ki values and it has been found that Pd(II) complex have more enzyme inhibition efficiency than salptsmh and Co(II) complex.

Nickel(II) and copper(II) complexes of N,N-dialkyl-N‧-3-chlorobenzoylthiourea: Synthesis, characterization, crystal structures, Hirshfeld surfaces and antimicrobial activity

NASA Astrophysics Data System (ADS)

Binzet, Gun; Gumus, Ilkay; Dogen, Aylin; Flörke, Ulrich; Kulcu, Nevzat; Arslan, Hakan

2018-06-01

We synthesized four new N,N-dialkyl-N‧-3-chlorobenzoylthiourea ligands (Alkyl: Dimethyl, diethyl, di-n-propyl and di-n-butyl) and their metal complexes with copper and nickel atoms. The structure of all synthesized compounds was fully characterized by physicochemical, spectroscopic and single crystal X-ray diffraction analysis techniques. The physical, spectral and analytical data of the newly synthesized metal complexes have shown the formation of 1:2 (metal:ligand) ratio. The benzoylthiourea ligands coordinate with metal atoms through oxygen and sulphur atoms. The metal atoms are in slightly distorted square-planar coordination geometry in Ni(II) or Cu(II) complex. Two oxygen and two sulphur atoms are mutually cis to each other in Ni(II) or Cu(II) complex. The intermolecular contacts in the compounds, which are HL1 and HL3, were examined by Hirshfeld surfaces and fingerprint plots using the data obtained from X-ray single crystal diffraction measurement. Besides these, their antimicrobial activities against Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, Streptococcus pyogenes and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and anti-yeast activity (Candida glabrata, Candida parapsilosis and Candida albicans) were investigated. This exhibited some promising results towards testing organism. Among all the compounds, Ni(L1)2 complex showed high activity against Bacillus subtilis with MIC values at 7.81 μg/mL.

SrFe1‑xMoxO2+δ : parasitic ferromagnetism in an infinite-layer iron oxide with defect structures induced by interlayer oxygen

NASA Astrophysics Data System (ADS)

Guo, Jianhui; Shi, Lei; Zhao, Jiyin; Wang, Yang; Yuan, Xueyou; Li, Yang; Wu, Liang

2018-04-01

The recent discovered compound SrFeO2 is an infinite-layer-structure iron oxide with unusual square-planar coordination of Fe2+ ions. In this study, SrFe1‑xMoxO2+δ (x < 0.12) is obtained by crystal transformation from SrFe1‑xMoxO3‑δ perovskite via low-temperature (≤380 °C) topotactic reduction. The parasitic ferromagnetism of the compound and its relationship to the defect structures are investigated. It is found that substitution of high-valent Mo6+ for Fe2+ results in excess oxygen anions O2‑ inserted at the interlayer sites for charge compensation, which further causes large atomic displacements along the c-axis. Due to the robust but flexible Fe-O-Fe framework, the samples are well crystallized within the ab-plane, but are significantly poorer crystallized along the c-axis. Defect structures including local lattice distortions and edge dislocations responsible for the lowered crystallinity are observed by high resolution transmission electron microscopy. Both the magnetic measurements and electron spin resonance spectra provide the evidence of a parasitic ferromagnetism (FM). The week FM interaction originated from the imperfect antiferromagnetic (AFM) ordering could be ascribed to the introduction of uncompensated magnetic moments due to substitution of Mo6+ (S = 0) for Fe2+ (S = 2) and the canted/frustrated spins resulted from defect structures.

Syntheses, crystal structures and spectroscopic properties of copper(II)-tetracyanometallate(II) complexes with nicotinamide and isonicotinamide ligands

NASA Astrophysics Data System (ADS)

Sayın, Elvan; Kürkçüoğlu, Güneş Süheyla; Yeşilel, Okan Zafer; Hökelek, Tuncer

2015-09-01

Four new one dimensional (1D) cyanide complexes, namely {[Cu(NH3)4(μ-na)][M‧(CN)4]}n and {[Cu(NH3)2(ina)2M‧(μ-CN)2(CN)2]}n (M‧(II) = Pd (1 and 3) or Pt (2 and 4), na:nicotinamide and ina:isonicotinamide) have been synthesized and characterized by elemental, spectral (FT-IR and Raman), and thermal (TG, DTG and DTA) analyses. The crystal structures of complexes 1-3 have been determined by single crystal X-ray diffraction technique. In complexes 1 and 2, na ligand is coordinated to the adjacent Cu(II) ions as a bridging ligand, giving rise to 1D linear cationic chain and the [M‧(CN)4]2- anionic complex acts as a counter ion. Complexes 3 and 4 are also 1D linear chain in which two cyanide ligands bridged neighboring M‧(II) and Cu(II) ions, while ina ligand is coordinated Cu(II) ion through nitrogen atom of pyridine ring. In the complexes, the Cu(II) ions adopt distorted octahedral geometries, while M‧(II) ions are four coordinated with four carbon atoms from cyanide ligands in square-planar geometries. The adjacent chains are further stacked through intermolecular hydrogen bond, Nsbnd Hṡṡṡπ, Csbnd H⋯M‧ and M‧⋯π interactions to form 3D supramolecular networks. Vibration assignments are given for all the observed bands. In addition, thermal stabilities of the compounds are also discussed.

μ-Carbonato-κ(4) O,O':O',O''-bis-{[2'-(di-tert-butyl-phosphan-yl)biphenyl-2-yl-κ(2) P,C (1)]palladium(II)} dichloro-methane monosolvate.

PubMed

Muller, Alfred; Holzapfel, Cedric W

2012-12-01

The title compound, [(μ2-CO3){Pd(P(t-C4H9)2(C12H8)}2]·CH2Cl2, the first CO3-bridged palladium dimer complex reported to date, was obtained while preparing the Pd(0) complex with (2-biphen-yl)P( (t) Bu)2. In the crystal, each palladium dimer is accompanied by a dichloro-methane solvent mol-ecule. Coordination of the carbonate and chelated phosphane ligands gives distorted square-planar environments at the Pd atoms. Important geometrical parameters include Pd-P(av.) = 2.2135 (4) Å, Pd-C(av.) = 1.9648 (16) Å and P-Pd-C = 84.05 (5) and 87.98 (5)°, and O-Pd-O' = 60.56 (4) and 61.13 (4)°. Bonding with the carbonate O atoms shows values of 2.1616 (11) and 2.1452 (11) Å for the Pd-O-Pd bridge, whereas other Pd-O distances are slightly longer at 2.2136 (11) and 2.1946 (11) Å. One of the tert-butyl groups is disordered over two set of sites with an occupancy ratio of 0.723 (6):0.277 (6). Weak C-H⋯O interactions are observed propagating the molecules along the [100] direction.

μ-Carbonato-κ4 O,O′:O′,O′′-bis­{[2′-(di-tert-butyl­phosphan­yl)biphenyl-2-yl-κ2 P,C 1]palladium(II)} dichloro­methane monosolvate

PubMed Central

Muller, Alfred; Holzapfel, Cedric W.

2012-01-01

The title compound, [(μ2-CO3){Pd(P(t-C4H9)2(C12H8)}2]·CH2Cl2, the first CO3-bridged palladium dimer complex reported to date, was obtained while preparing the Pd0 complex with (2-biphen­yl)P(tBu)2. In the crystal, each palladium dimer is accompanied by a dichloro­methane solvent mol­ecule. Coordination of the carbonate and chelated phosphane ligands gives distorted square-planar environments at the Pd atoms. Important geometrical parameters include Pd—P(av.) = 2.2135 (4) Å, Pd—C(av.) = 1.9648 (16) Å and P—Pd—C = 84.05 (5) and 87.98 (5)°, and O—Pd—O′ = 60.56 (4) and 61.13 (4)°. Bonding with the carbonate O atoms shows values of 2.1616 (11) and 2.1452 (11) Å for the Pd—O—Pd bridge, whereas other Pd—O distances are slightly longer at 2.2136 (11) and 2.1946 (11) Å. One of the tert-butyl groups is disordered over two set of sites with an occupancy ratio of 0.723 (6):0.277 (6). Weak C—H⋯O interactions are observed propagating the molecules along the [100] direction. PMID:23468771

a Voxel-Based Metadata Structure for Change Detection in Point Clouds of Large-Scale Urban Areas

NASA Astrophysics Data System (ADS)

Gehrung, J.; Hebel, M.; Arens, M.; Stilla, U.

2018-05-01

Mobile laser scanning has not only the potential to create detailed representations of urban environments, but also to determine changes up to a very detailed level. An environment representation for change detection in large scale urban environments based on point clouds has drawbacks in terms of memory scalability. Volumes, however, are a promising building block for memory efficient change detection methods. The challenge of working with 3D occupancy grids is that the usual raycasting-based methods applied for their generation lead to artifacts caused by the traversal of unfavorable discretized space. These artifacts have the potential to distort the state of voxels in close proximity to planar structures. In this work we propose a raycasting approach that utilizes knowledge about planar surfaces to completely prevent this kind of artifacts. To demonstrate the capabilities of our approach, a method for the iterative volumetric approximation of point clouds that allows to speed up the raycasting by 36 percent is proposed.

Calibration of stereo rigs based on the backward projection process

NASA Astrophysics Data System (ADS)

Gu, Feifei; Zhao, Hong; Ma, Yueyang; Bu, Penghui; Zhao, Zixin

2016-08-01

High-accuracy 3D measurement based on binocular vision system is heavily dependent on the accurate calibration of two rigidly-fixed cameras. In most traditional calibration methods, stereo parameters are iteratively optimized through the forward imaging process (FIP). However, the results can only guarantee the minimal 2D pixel errors, but not the minimal 3D reconstruction errors. To address this problem, a simple method to calibrate a stereo rig based on the backward projection process (BPP) is proposed. The position of a spatial point can be determined separately from each camera by planar constraints provided by the planar pattern target. Then combined with pre-defined spatial points, intrinsic and extrinsic parameters of the stereo-rig can be optimized by minimizing the total 3D errors of both left and right cameras. An extensive performance study for the method in the presence of image noise and lens distortions is implemented. Experiments conducted on synthetic and real data demonstrate the accuracy and robustness of the proposed method.

Arbitrary-Shaped Graphene-Based Planar Sandwich Supercapacitors on One Substrate with Enhanced Flexibility and Integration.

PubMed

Zheng, Shuanghao; Tang, Xingyan; Wu, Zhong-Shuai; Tan, Yuan-Zhi; Wang, Sen; Sun, Chenglin; Cheng, Hui-Ming; Bao, Xinhe

2017-02-28

The emerging smart power source-unitized electronics represent an utmost innovative paradigm requiring dramatic alteration from materials to device assembly and integration. However, traditional power sources with huge bottlenecks on the design and performance cannot keep pace with the revolutionized progress of shape-confirmable integrated circuits. Here, we demonstrate a versatile printable technology to fabricate arbitrary-shaped, printable graphene-based planar sandwich supercapacitors based on the layer-structured film of electrochemically exfoliated graphene as two electrodes and nanosized graphene oxide (lateral size of 100 nm) as a separator on one substrate. These monolithic planar supercapacitors not only possess arbitrary shapes, e.g., rectangle, hollow-square, "A" letter, "1" and "2" numbers, circle, and junction-wire shape, but also exhibit outstanding performance (∼280 F cm -3 ), excellent flexibility (no capacitance degradation under different bending states), and applicable scalability, which are far beyond those achieved by conventional technologies. More notably, such planar supercapacitors with superior integration can be readily interconnected in parallel and series, without use of metal interconnects and contacts, to modulate the output current and voltage of modular power sources for designable integrated circuits in various shapes and sizes.

Edge effects on the fluttering characteristics of freely falling planar particles

NASA Astrophysics Data System (ADS)

Blay Esteban, Luis; Shrimpton, John; Ganapathisubramani, Bharathram

2018-06-01

The effect of particle edge geometry on the descent motion of freely falling planar particles is examined through experiments. Various planar particles, such as disk and polygons, with identical frontal areas (Ap) and different number of edges (or perimeter) are used. All particles are designed such that their values of Galileo number (G ) and dimensionless moment of inertia (I*) correspond to the previously identified fluttering regime of particle motion. Several modes of secondary motion are observed for the same particle and conditions, and these are not equally probable. This probability depends on the particle shape. Disks and heptagons were found to prefer a "planar zig-zag" behavior. These planar motions are composed of gliding sweeps and turning sections. As the number of sides in the polygon decreases, i.e., for hexagons and pentagons, the trajectory transitions to a more three-dimensional form. These trajectories were found to be restricted to one plane per swing, but the subsequent swings are in other planes. Further decrease in number of sides to a square results in the trajectories having a severe out-of-plane motion. These subregimes of particle motion within the fluttering regime are consistent with those reported for disks in previous studies. Based on this information, a length scale that accounts for the frontal area of the particles and its edge geometry (i.e., perimeter) is proposed. This length scale represents an approach to determine an equivalent disk for planar particles such that the phase diagram in the Reynolds number (Re) and dimensionless moment of inertia (I*) domain can be used to characterize the motion of planar particles with different frontal geometries. However, further experiments covering other domains of the regime map are needed to verify its universality.

HOLEGAGE 1.0 - Strain-Gauge Drilling Analysis Program

NASA Technical Reports Server (NTRS)

Hampton, Roy V.

1992-01-01

Interior stresses inferred from changes in surface strains as hole is drilled. Computes stresses using strain data from each drilled-hole depth layer. Planar stresses computed in three ways: least-squares fit for linear variation with depth, integral method to give incremental stress data for each layer, and/or linear fit to integral data. Written in FORTRAN 77.

Influence of the least-squares phase on optical vortices in strongly scintillated beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Mingzhou; Roux, Filippus S.; National Laser Centre, CSIR, P.O. Box 395, Pretoria 0001

2009-07-15

The optical vortices that exist in strongly scintillated beams make it difficult for conventional adaptive optics systems to remove the phase distortions. When the least-squares reconstructed phase is removed, the vortices still remain. However, we found that the removal of the least-squares phase induces a portion of the vortices to be annihilated during subsequent propagation, causing a reduction in the total number of vortices. This can be understood in terms of the restoration of equilibrium between explicit vortices, which are visible in the phase function, and vortex bound states, which are somehow encoded in the continuous phase fluctuations. Numerical simulationsmore » are provided to show that the total number of optical vortices in a strongly scintillated beam can be reduced significantly after a few steps of least-squares phase corrections.« less

Use of ssq rotational invariant of magnetotelluric impedances for estimating informative properties for galvanic distortion

NASA Astrophysics Data System (ADS)

Rung-Arunwan, T.; Siripunvaraporn, W.; Utada, H.

2017-06-01

Several useful properties and parameters—a model of the regional mean one-dimensional (1D) conductivity profile, local and regional distortion indicators, and apparent gains—were defined in our recent paper using two rotational invariants (det: determinant and ssq: sum of squared elements) from a set of magnetotelluric (MT) data obtained by an array of observation sites. In this paper, we demonstrate their characteristics and benefits through synthetic examples using 1D and three-dimensional (3D) models. First, a model of the regional mean 1D conductivity profile is obtained using the average ssq impedance with different levels of galvanic distortion. In contrast to the Berdichevsky average using the average det impedance, the average ssq impedance is shown to yield a reliable estimate of the model of the regional mean 1D conductivity profile, even when severe galvanic distortion is contained in the data. Second, the local and regional distortion indicators were found to indicate the galvanic distortion as expressed by the splitting and shear parameters and to quantify their strengths in individual MT data and in the dataset as a whole. Third, the apparent gain was also shown to be a good approximation of the site gain, which is generally claimed to be undeterminable without external information. The model of the regional mean 1D profile could be used as an initial or a priori model in higher-dimensional inversions. The local and regional distortion indicators and apparent gains could be used to examine the existence and to guess the strength of the galvanic distortion. Although these conclusions were derived from synthetic tests using the Groom-Bailey distortion model, additional tests with different distortion models indicated that these conclusions are not strongly dependent on the choice of distortion model. These galvanic-distortion-related parameters would also assist in judging if a proper treatment is needed for the galvanic distortion when an MT dataset is given. Hence, this information derived from the dataset would be useful in MT data analysis and inversion.

Further evaluation of the constrained least squares electromagnetic compensation method

NASA Technical Reports Server (NTRS)

Smith, William T.

1991-01-01

Technologies exist for construction of antennas with adaptive surfaces that can compensate for many of the larger distortions caused by thermal and gravitational forces. However, as the frequency and size of reflectors increase, the subtle surface errors become significant and degrade the overall electromagnetic performance. Electromagnetic (EM) compensation through an adaptive feed array offers means for mitigation of surface distortion effects. Implementation of EM compensation is investigated with the measured surface errors of the NASA 15 meter hoop/column reflector antenna. Computer simulations are presented for: (1) a hybrid EM compensation technique, and (2) evaluating the performance of a given EM compensation method when implemented with discretized weights.

Aerodynamic influence coefficient method using singularity splines

NASA Technical Reports Server (NTRS)

Mercer, J. E.; Weber, J. A.; Lesferd, E. P.

1974-01-01

A numerical lifting surface formulation, including computed results for planar wing cases is presented. This formulation, referred to as the vortex spline scheme, combines the adaptability to complex shapes offered by paneling schemes with the smoothness and accuracy of loading function methods. The formulation employes a continuous distribution of singularity strength over a set of panels on a paneled wing. The basic distributions are independent, and each satisfied all the continuity conditions required of the final solution. These distributions are overlapped both spanwise and chordwise. Boundary conditions are satisfied in a least square error sense over the surface using a finite summing technique to approximate the integral. The current formulation uses the elementary horseshoe vortex as the basic singularity and is therefore restricted to linearized potential flow. As part of the study, a non planar development was considered, but the numerical evaluation of the lifting surface concept was restricted to planar configurations. Also, a second order sideslip analysis based on an asymptotic expansion was investigated using the singularity spline formulation.

Electrode surface profile and the performance of condenser microphones.

PubMed

Fletcher, N H; Thwaites, S

2002-12-01

Condenser microphones of all types are traditionally made with a planar electrode parallel to an electrically conducting diaphragm, additional diaphragm stiffness at acoustic frequencies being provided by the air enclosed in a cavity behind the diaphragm. In all designs, the motion of the diaphragm in response to an acoustic signal is greatest near its center and reduces to zero at its edges. Analysis shows that this construction leads to less than optimal sensitivity and to harmonic distortion at high sound levels when the diaphragm motion is appreciable compared with its spacing from the electrode. Microphones of this design are also subject to acoustic collapse of the diaphragm under the influence of pressure pulses such as might be produced by wind. A new design is proposed in which the electrode is shaped as a shallow dish, and it is shown that this construction increases the sensitivity by about 4.5 dB, and also completely eliminates harmonic distortion originating in the cartridge.

White matter tractography by means of Turboprop diffusion tensor imaging.

PubMed

Arfanakis, Konstantinos; Gui, Minzhi; Lazar, Mariana

2005-12-01

White matter fiber-tractography by means of diffusion tensor imaging (DTI) is a noninvasive technique that provides estimates of the structural connectivity of the brain. However, conventional fiber-tracking methods using DTI are based on echo-planar image acquisitions (EPI), which suffer from image distortions and artifacts due to magnetic susceptibility variations and eddy currents. Thus, a large percentage of white matter fiber bundles that are mapped using EPI-based DTI data are distorted, and/or terminated early, while others are completely undetected. This severely limits the potential of fiber-tracking techniques. In contrast, Turboprop imaging is a multiple-shot gradient and spin-echo (GRASE) technique that provides images with significantly fewer susceptibility and eddy current-related artifacts than EPI. The purpose of this work was to evaluate the performance of fiber-tractography techniques when using data obtained with Turboprop-DTI. All fiber pathways that were mapped were found to be in agreement with the anatomy. There were no visible distortions in any of the traced fiber bundles, even when these were located in the vicinity of significant magnetic field inhomogeneities. Additionally, the Turboprop-DTI data used in this research were acquired in less than 19 min of scan time. Thus, Turboprop appears to be a promising DTI data acquisition technique for tracing white matter fibers.

Accelerating EPI distortion correction by utilizing a modern GPU-based parallel computation.

PubMed

Yang, Yao-Hao; Huang, Teng-Yi; Wang, Fu-Nien; Chuang, Tzu-Chao; Chen, Nan-Kuei

2013-04-01

The combination of phase demodulation and field mapping is a practical method to correct echo planar imaging (EPI) geometric distortion. However, since phase dispersion accumulates in each phase-encoding step, the calculation complexity of phase modulation is Ny-fold higher than conventional image reconstructions. Thus, correcting EPI images via phase demodulation is generally a time-consuming task. Parallel computing by employing general-purpose calculations on graphics processing units (GPU) can accelerate scientific computing if the algorithm is parallelized. This study proposes a method that incorporates the GPU-based technique into phase demodulation calculations to reduce computation time. The proposed parallel algorithm was applied to a PROPELLER-EPI diffusion tensor data set. The GPU-based phase demodulation method reduced the EPI distortion correctly, and accelerated the computation. The total reconstruction time of the 16-slice PROPELLER-EPI diffusion tensor images with matrix size of 128 × 128 was reduced from 1,754 seconds to 101 seconds by utilizing the parallelized 4-GPU program. GPU computing is a promising method to accelerate EPI geometric correction. The resulting reduction in computation time of phase demodulation should accelerate postprocessing for studies performed with EPI, and should effectuate the PROPELLER-EPI technique for clinical practice. Copyright © 2011 by the American Society of Neuroimaging.

Imaging human brain cyto- and myelo-architecture with quantitative OCT (Conference Presentation)

NASA Astrophysics Data System (ADS)

Boas, David A.; Wang, Hui; Konukoglu, Ender; Fischl, Bruce; Sakadzic, Sava; Magnain, Caroline V.

2017-02-01

No current imaging technology allows us to directly and without significant distortion visualize the microscopic and defining anatomical features of the human brain. Ex vivo histological techniques can yield exquisite planar images, but the cutting, mounting and staining that are required components of this type of imaging induce distortions that are different for each slice, introducing cross-slice differences that prohibit true 3D analysis. We are overcoming this issue by utilizing Optical Coherence Tomography (OCT) with the goal to image whole human brain cytoarchitectural and laminar properties with potentially 3.5 µm resolution in block-face without the need for exogenous staining. From the intrinsic scattering contrast of the brain tissue, OCT gives us images that are comparable to Nissl stains, but without the distortions introduced in standard histology as the OCT images are acquired from the block face prior to slicing and thus without the need for subsequent staining and mounting. We have shown that laminar and cytoarchitectural properties of the brain can be characterized with OCT just as well as with Nissl staining. We will present our recent advances to improve the axial resolution while maintaining contrast; improvements afforded by speckle reduction procedures; and efforts to obtain quantitative maps of the optical scattering coefficient, an intrinsic property of the tissue.

Study of noise propagation and the effects of insufficient numbers of projection angles and detector samplings for iterative reconstruction using planar-integral data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, B.; Zeng, G. L.

2006-09-15

A rotating slat collimator can be used to acquire planar-integral data. It achieves higher geometric efficiency than a parallel-hole collimator by accepting more photons, but the planar-integral data contain less tomographic information that may result in larger noise amplification in the reconstruction. Lodge evaluated the rotating slat system and the parallel-hole system based on noise behavior for an FBP reconstruction. Here, we evaluate the noise propagation properties of the two collimation systems for iterative reconstruction. We extend Huesman's noise propagation analysis of the line-integral system to the planar-integral case, and show that approximately 2.0(D/dp) SPECT angles, 2.5(D/dp) self-spinning angles atmore » each detector position, and a 0.5dp detector sampling interval are required in order for the planar-integral data to be efficiently utilized. Here, D is the diameter of the object and dp is the linear dimension of the voxels that subdivide the object. The noise propagation behaviors of the two systems are then compared based on a least-square reconstruction using the ratio of the SNR in the image reconstructed using a planar-integral system to that reconstructed using a line-integral system. The ratio is found to be proportional to {radical}(F/D), where F is a geometric efficiency factor. This result has been verified by computer simulations. It confirms that for an iterative reconstruction, the noise tradeoff of the two systems is not only dependent on the increase of the geometric efficiency afforded by the planar projection method, but also dependent on the size of the object. The planar-integral system works better for small objects, while the line-integral system performs better for large ones. This result is consistent with Lodge's results based on the FBP method.« less

PREVIEW: Computer Assistance for Visual Management of Forested Landscapes

Treesearch

Erik Myklestad; J. Alan Wagar

1976-01-01

The PREVIEW computer program facilitates visual management of forested landscapes by generating perspective drawings that show proposed timber harvesting and regrowth throughout a rotation. Drawings show how changes would appear from selected viewing points and show landscapes as either a grid of distorted squares or by symbols representing trees, clearings, water,...

Numerical Simulations of Aero-Optical Distortions Around Various Turret Geometries

DTIC Science & Technology

2013-06-12

arbi trary cell topologies. The spatial operator uses the exact Riemann Solver of Gottlieb and Groth, least squares gradient cal- culations using QR...Unstructured Euler/Navier-Stokes Flow Solver ," in A/AA Paper 1999-0786, 1999. [9] J. J. Gottlieb and C. P. T. Groth, "Assessment of Riemann Solvers

High efficiency and stable white OLED using a single emitter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jian

2016-01-18

The ultimate objective of this project was to demonstrate an efficient and stable white OLED using a single emitter on a planar glass substrate. The focus of the project is on the development of efficient and stable square planar phosphorescent emitters and evaluation of such class of materials in the device settings. Key challenges included improving the emission efficiency of molecular dopants and excimers, controlling emission color of emitters and their excimers, and improving optical and electrical stability of emissive dopants. At the end of this research program, the PI has made enough progress to demonstrate the potential of excimer-basedmore » white OLED as a cost-effective solution for WOLED panel in the solid state lighting applications.« less

trans-Bis(1-cyclo­hexyl­pyrrolidin-2-one)dinitratopalladium(II)

PubMed Central

Takahashi, Yuya; Ikeda, Yasuhisa

2009-01-01

In the title compound, [Pd(NO3)2(C10H17NO)2], the PdII centre is located on an inversion center and is coordinated in a square-planar geometry by two O atoms of the monodentate nitrate groups and two carbonyl O atoms of the 1-cyclo­hexyl­pyrrolidin-2-one ligands. PMID:21578576

Structure and magnetic properties of oxychalcogenides A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se) with Fe2O square planar layers representing an antiferromagnetic checkerboard spin lattice.

PubMed

Kabbour, Houria; Janod, Etienne; Corraze, Benoît; Danot, Michel; Lee, Changhoon; Whangbo, Myung-Hwan; Cario, Laurent

2008-07-02

The oxychalcogenides A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se), which contain Fe2O square planar layers of the anti-CuO2 type, were predicted using a modular assembly of layered secondary building units and subsequently synthesized. The physical properties of these compounds were characterized using magnetic susceptibility, electrical resistivity, specific heat, (57)Fe Mossbauer, and powder neutron diffraction measurements and also by estimating their exchange interactions on the basis of first-principles density functional theory electronic structure calculations. These compounds are magnetic semiconductors that undergo a long-range antiferromagnetic ordering below 83.6-106.2 K, and their magnetic properties are well-described by a two-dimensional Ising model. The dominant antiferromagnetic spin exchange interaction between S = 2 Fe(2+) ions occurs through corner-sharing Fe-O-Fe bridges. Moreover, the calculated spin exchange interactions show that the A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se) compounds represent a rare example of a frustrated antiferromagnetic checkerboard lattice.

Numerical investigation of the interaction between a planar shock wave with square and triangular bubbles containing different gases

NASA Astrophysics Data System (ADS)

Igra, Dan; Igra, Ozer

2018-05-01

The interaction between a planar shock wave and square and triangular bubbles containing either SF6, He, Ar, or CO2 is studied numerically. It is shown that, due to the existing large differences in the molecular weight, the specific heat ratio, and the acoustic impedance between these gases, different wave patterns and pressure distribution inside the bubbles are developed during the interaction process. In the case of heavy gases, the velocity of the shock wave propagating along the bubble inner surface is always less than that of the incident shock wave and higher than that of the transmitted shock wave. However, in the case of the light gas (He), the fastest one is the transmitted shock wave and the slowest one is the incident shock wave. The largest pressure jump is witnessed in the SF6 case, while the smallest pressure jump is seen in the helium case. There are also pronounced differences in the deformation of the investigated bubbles; while triangular bubbles filled with either Ar, CO2, or SF6 were deformed to a crescent shape, the helium bubble is deformed to a trapezoidal shape with three pairs of vortices emanating from its surface.

A Hexanuclear Iron(II) Layer with Two Square-Planar FeO4 Units Spanned by Tetrasiloxide Ligands: Mimicking of Minerals and Catalysts.

PubMed

Manicke, N; Hoof, S; Keck, M; Braun-Cula, B; Feist, M; Limberg, C

2017-07-17

A hexanuclear iron(II) siloxide complex has been prepared by reacting an incompletely condensed silsesquioxane first with NaOMe and then with Fe(OTf) 2 . In the process of product formation, the siloxane framework undergoes a transformation and it was shown that this happens already upon addition of base: Treatment of the ligand precursor with NaOMe leads to a completely condensed silsesquioxane cage with 12 Si atoms that is composed of 2 equiv of the tetrasiloxide ligands found in the product complex. Its iron centers form a two-dimensional array reminiscent of the situations found in minerals and two-dimensional oxide films caused by segregation of FeO x and silica. As the hexairon(II) assembly contains two high-spin square-planar FeO 4 units-suggested to represent the active sites in Fe-zeolites, which react with N 2 O to generate strongly oxidizing sites-it was treated with Me 3 NO. This led to the oxidation of two of the iron centers to the oxidation state +III and elimination of one iron ion, so that a pentanuclear, mixed valent iron siloxide was formed. All complexes were fully characterized.

A comparative quantitative analysis of the IDEAL (iterative decomposition of water and fat with echo asymmetry and least-squares estimation) and the CHESS (chemical shift selection suppression) techniques in 3.0 T L-spine MRI

NASA Astrophysics Data System (ADS)

Kim, Eng-Chan; Cho, Jae-Hwan; Kim, Min-Hye; Kim, Ki-Hong; Choi, Cheon-Woong; Seok, Jong-min; Na, Kil-Ju; Han, Man-Seok

2013-03-01

This study was conducted on 20 patients who had undergone pedicle screw fixation between March and December 2010 to quantitatively compare a conventional fat suppression technique, CHESS (chemical shift selection suppression), and a new technique, IDEAL (iterative decomposition of water and fat with echo asymmetry and least squares estimation). The general efficacy and usefulness of the IDEAL technique was also evaluated. Fat-suppressed transverse-relaxation-weighed images and longitudinal-relaxation-weighted images were obtained before and after contrast injection by using these two techniques with a 1.5T MR (magnetic resonance) scanner. The obtained images were analyzed for image distortion, susceptibility artifacts and homogenous fat removal in the target region. The results showed that the image distortion due to the susceptibility artifacts caused by implanted metal was lower in the images obtained using the IDEAL technique compared to those obtained using the CHESS technique. The results of a qualitative analysis also showed that compared to the CHESS technique, fewer susceptibility artifacts and more homogenous fat removal were found in the images obtained using the IDEAL technique in a comparative image evaluation of the axial plane images before and after contrast injection. In summary, compared to the CHESS technique, the IDEAL technique showed a lower occurrence of susceptibility artifacts caused by metal and lower image distortion. In addition, more homogenous fat removal was shown in the IDEAL technique.

Concept Designed and Developed for Distortion- Tolerant, High-Stability Engine Control

NASA Technical Reports Server (NTRS)

1995-01-01

Engine Control Future aircraft turbine engines, both commercial and military, must be able to successfully accommodate expected increased levels of steady-state and dynamic engine-face distortion. Advanced tactical aircraft are likely to use thrust vectoring to enhance their maneuverability. As a result, the engines will see more extreme aircraft angles-of-attack and sideslip levels than are currently encountered with present-day aircraft. Also, the mixed-compression inlets needed for the High Speed Civil Transport will likely encounter disturbances similar to those seen by tactical aircraft, in addition to planar pulse, inlet buzz, and high distortion levels at low flight speed and off-design operation. The current approach of incorporating a sufficient component design stall margin to tolerate these increased levels of distortion would significantly reduce performance. The objective of the High Stability Engine Control (HISTEC) program is to design, develop, and flight demonstrate an advanced, high-stability, integrated engine-control system that uses measurement-based, real-time estimates of distortion to enhance engine stability. The resulting distortion-tolerant control reduces the required design stall margin, with a corresponding increase in performance and decrease in fuel burn. The HISTEC concept has been designed and developed, and the software implementing the concept has successfully accommodated time-varying distortion. The NASA Lewis Research Center is currently overseeing the development and validation of the hardware and software necessary to flight test the HISTEC concept. HISTEC is a contracted effort with Pratt & Whitney of West Palm Beach, Florida. The HISTEC approach includes two major systems: A Distortion Estimation System (DES) and Stability Management Control (SMC). DES is an aircraft-mounted, high-speed processor that estimates the amount and type of distortion present and its effect on the engine. It uses high-response pressure measurements at the engine face to calculate indicators of the type and extent of distortion in real time. From these indicators, DES determines the effects of distortion on the propulsion systems and the corresponding engine match point necessary to accommodate it. DES output consists of fan and compressor pressure ratio trim commands that are passed to the SMC. In addition, DES uses maneuver information, consisting of angle-of-attack and sideslip from the flight control, to anticipate high inlet distortion conditions. The SMC, which is contained in the engine-mounted, Improved Digital Electronic Engine Control (IDEEC), includes advanced control laws to directly control the fan and compressor transient operating line (pressure ratio). These advanced control laws, with a multivariable design, have the potential for higher bandwidth and the resulting more precise control of engine match. The ability to measure and assess the distortion effects in real time coupled with a high-response controller improves engine stability at high levels of distortion. The software algorithms implementing DES have been designed, developed, and demonstrated, and integration testing of the DES and SMC software has been completed. The results show that the HISTEC system will be able to sense inlet distortion, determine the effect on engine stability, and accommodate distortion by maintaining an adequate margin for engine surge. The Pratt &Whitney Comprehensive Engine Diagnostic Unit was chosen as the DES processor. An instrumented inlet case for sensing distortion was designed and fabricated. HISTEC is scheduled for flight test on the ACTIVE F-15 aircraft at the NASA Dryden Flight Research Center in Edwards, California, in late 1996.

Coordination Chemistry of Linear Oligopyrrolic Fragments Inspired by Heme Metabolites

NASA Astrophysics Data System (ADS)

Gautam, Ritika

Linear oligopyrroles are degradation products of heme, which is converted in the presence of heme oxygenase to bile pigments, such as biliverdin and bilirubin. These tetrapyrrolic oligopyrroles are ubiquitously present in biological systems and find applications in the fields of catalysis and sensing. These linear tetrapyrrolic scaffolds are further degraded into linear tripyrrolic and dipyrrolic fragments. Although these lower oligopyrroles are abundantly present, their coordination chemistry requires further characterization. This dissertation focuses mainly on two classes of bioinspired linear oligopyrroles, propentdyopent and tripyrrindione, and their transition metal complexes, which present a rich ligand-based redox chemistry. Chapter 1 offers an overview of heme degradation to different classes of linear oligopyrroles and properties of their transition metal complexes. Chapter 2 is focused on the tripyrrin-1,14-dione scaffold of the urinary pigment uroerythrin, which coordinates divalent transition metals palladium and copper with square planar geometry. Specifically, the tripyrrin-1, 14-dione ligand binds Cu(II) and Pd(II) as a dianionic organic radical under ambient conditions. The electrochemical study confirms the presence of ligand based redox chemistry, and one electron oxidation or reduction reactions do not alter the planar geometry around the metal center. The X-Ray analysis and the electron paramagnetic resonance (EPR) studies of the complexes in the solid and solution phase reveals intermolecular interactions between the ligand based unpaired electrons and therefore formation of neutral pi-pi dimers. In Chapter 3, the antioxidant activity and the fluorescence sensor properties of the tripyrrin-1,14-dione ligand in the presence of superoxide are described. We found that the tripyrrindione ligand undergoes one-electron reduction in the presence of the superoxide radical anion (O2•- ) to form highly fluorescent H3TD1•- radical anion, which emits at 635 nm. This reaction also explains the antioxidant properties of the linear tripyrrin-1,14-dione ligand, which acts as a scavenger of O2•-. In Chapter 4, the zinc binding properties of the tripyrrin-1,14-dione ligand are described. The tripyrrolic ligand coordinates as a dianionic ligand with the divalent Zn(II) ion in both organic and aqueous buffered conditions. The complex formed is highly fluorescent with a long wavelength emission band at 648 nm. The X-Ray crystallography analysis indicates the existence of dinuclear complex [Zn(TD1•)(H2O)]2, featuring a distorted square planar geometry around the Zn(II) center. In Chapter 5, the coordination chemistry of the dipyrrin-1,9-dione fragment of propentdyopent ligand is shown with a series of transition metals like (e.g., Co(II), Ni(II), Cu(II) and Zn(II)), which form homoleptic tetrahedral complexes. The spectroscopic and electrochemical characterization confirms that the complexes shows ligand-based redox chemistry and acts as reservoirs for unpaired electrons. Chapter 6 describes the formation of the fluorescent BODIPY complex of propentdyopent ligand. The dipyrrin-1,9-dione scaffold of heme metabolite propendyopent undergoes a one-pot reaction with borontrifluoride etherate in toluene to form a green fluorescent [(pdp)BF2] complex. Spectroscopic studies reveal that the meso-unsubstituted [(pdp)BF2] complex is stable in tetrahydrofuran and has a quantum yield of 0.13. Electrochemical studies confirm that the complex undergoes ligand-based reduction and acts as a host for an unpaired electron.

Uncertainty based pressure reconstruction from velocity measurement with generalized least squares

NASA Astrophysics Data System (ADS)

Zhang, Jiacheng; Scalo, Carlo; Vlachos, Pavlos

2017-11-01

A method using generalized least squares reconstruction of instantaneous pressure field from velocity measurement and velocity uncertainty is introduced and applied to both planar and volumetric flow data. Pressure gradients are computed on a staggered grid from flow acceleration. The variance-covariance matrix of the pressure gradients is evaluated from the velocity uncertainty by approximating the pressure gradient error to a linear combination of velocity errors. An overdetermined system of linear equations which relates the pressure and the computed pressure gradients is formulated and then solved using generalized least squares with the variance-covariance matrix of the pressure gradients. By comparing the reconstructed pressure field against other methods such as solving the pressure Poisson equation, the omni-directional integration, and the ordinary least squares reconstruction, generalized least squares method is found to be more robust to the noise in velocity measurement. The improvement on pressure result becomes more remarkable when the velocity measurement becomes less accurate and more heteroscedastic. The uncertainty of the reconstructed pressure field is also quantified and compared across the different methods.

Analytical and experimental design and analysis of an optimal processor for image registration

NASA Technical Reports Server (NTRS)

Mcgillem, C. D. (Principal Investigator); Svedlow, M.; Anuta, P. E.

1976-01-01

The author has identified the following significant results. A quantitative measure of the registration processor accuracy in terms of the variance of the registration error was derived. With the appropriate assumptions, the variance was shown to be inversely proportional to the square of the effective bandwidth times the signal to noise ratio. The final expressions were presented to emphasize both the form and simplicity of their representation. In the situation where relative spatial distortions exist between images to be registered, expressions were derived for estimating the loss in output signal to noise ratio due to these spatial distortions. These results are in terms of a reduction factor.

SU-E-I-91: Quantitative Assessment of Early Hepatocellular Carcinoma and Cavernous Hemangioma of Live Using In-Line Phase-Contrast X-Ray Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, J

Purpose: To investigate the potential utility of in-line phase-contrast imaging (ILPCI) technique with synchrotron radiation in detecting early hepatocellular carcinoma and cavernous hemangioma of live using in vitro model system. Methods: Without contrast agents, three typical early hepatocellular carcinoma specimens and three typical cavernous hemangioma of live specimens were imaged using ILPCI. To quantitatively discriminate early hepatocellular carcinoma tissues and cavernous hemangioma tissues, the projection images texture feature based on gray level co-occurrence matrix (GLCM) were extracted. The texture parameters of energy, inertia, entropy, correlation, sum average, sum entropy, difference average, difference entropy and inverse difference moment, were obtained respectively.more » Results: In the ILPCI planar images of early hepatocellular carcinoma specimens, vessel trees were clearly visualized on the micrometer scale. Obvious distortion deformation was presented, and the vessel mostly appeared as a ‘dry stick’. Liver textures appeared not regularly. In the ILPCI planar images of cavernous hemangioma of live specimens, typical vessels had not been found compared with the early hepatocellular carcinoma planar images. The planar images of cavernous hemangioma of live specimens clearly displayed the dilated hepatic sinusoids with the diameter of less than 100 microns, but all of them were overlapped with each other. The texture parameters of energy, inertia, entropy, correlation, sum average, sum entropy, and difference average, showed a statistically significant between the two types specimens image (P<0.01), except the texture parameters of difference entropy and inverse difference moment(P>0.01). Conclusion: The results indicate that there are obvious changes in morphological levels including vessel structures and liver textures. The study proves that this imaging technique has a potential value in evaluating early hepatocellular carcinoma and cavernous hemangioma of live.« less

3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

PubMed

O'Brien, Kieran; Daducci, Alessandro; Kickler, Nils; Lazeyras, Francois; Gruetter, Rolf; Feiweier, Thorsten; Krueger, Gunnar

2013-08-01

Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

Snapshot gradient-recalled echo-planar images of rat brains at long echo time at 9.4 T

PubMed Central

Lei, Hongxia; Mlynárik, Vladimir; Just, Nathalie; Gruetter, Rolf

2009-01-01

With improved B0 homogeneity along with satisfactory gradient performance at high magnetic fields, snapshot gradient-recalled echo-planar imaging (GRE-EPI) would perform at long echo times (TEs) on the order of T2*, which intrinsically allows obtaining strongly T2*-weighted images with embedded substantial anatomical details in ultrashort time. The aim of this study was to investigate the feasibility and quality of long TE snapshot GRE-EPI images of rat brain at 9.4 T. When compensating for B0 inhomogeneities, especially second-order shim terms, a 200×200 μm2 in-plane resolution image was reproducibly obtained at long TE (>25 ms). The resulting coronal images at 30 ms had diminished geometric distortions and, thus, embedded substantial anatomical details. Concurrently with the very consistent stability, such GRE-EPI images should permit to resolve functional data not only with high specificity but also with substantial anatomical details, therefore allowing coregistration of the acquired functional data on the same image data set. PMID:18486393

Van der Waals interactions between planar substrate and tubular lipid membranes undergoing pearling instability

NASA Astrophysics Data System (ADS)

Valchev, G. S.; Djondjorov, P. A.; Vassilev, V. M.; Dantchev, D. M.

2017-10-01

In the current article we study the behavior of the van der Waals force between a planar substrate and an axisymmetric bilayer lipid membrane undergoing pearling instability, caused by uniform hydrostatic pressure difference. To do so, the recently suggested "surface integration approach" is used, which can be considered a generalization of the well known and widely used Derjaguin approximation. The static equilibrium shape after the occurrence of the instability is described in the framework of Helfrich's spontaneous curvature model. Some specific classes of exact analytical solutions to the corresponding shape equation are considered, and the components of the respective position vectors given in terms of elliptic integrals and Jacobi elliptic functions. The mutual orientation between the interacting objects is chosen such that the axis of revolution of the distorted cylinder be parallel to the plane bounding the substrate. Based on the discussed models and approaches we made some estimations for the studied force in real experimentally realizable systems, thus showing the possibility of pearling as an useful technique for reduction of the adhesion in variety of industrial processes using lipid membranes as carriers.

Use of cone beam computed tomography in periodontology

PubMed Central

Acar, Buket; Kamburoğlu, Kıvanç

2014-01-01

Diagnosis of periodontal disease mainly depends on clinical signs and symptoms. However, in the case of bone destruction, radiographs are valuable diagnostic tools as an adjunct to the clinical examination. Two dimensional periapical and panoramic radiographs are routinely used for diagnosing periodontal bone levels. In two dimensional imaging, evaluation of bone craters, lamina dura and periodontal bone level is limited by projection geometry and superpositions of adjacent anatomical structures. Those limitations of 2D radiographs can be eliminated by three-dimensional imaging techniques such as computed tomography. Cone beam computed tomography (CBCT) generates 3D volumetric images and is also commonly used in dentistry. All CBCT units provide axial, coronal and sagittal multi-planar reconstructed images without magnification. Also, panoramic images without distortion and magnification can be generated with curved planar reformation. CBCT displays 3D images that are necessary for the diagnosis of intra bony defects, furcation involvements and buccal/lingual bone destructions. CBCT applications provide obvious benefits in periodontics, however; it should be used only in correct indications considering the necessity and the potential hazards of the examination. PMID:24876918

Enantiopure distorted ribbon-shaped nanographene combining two-photon absorption-based upconversion and circularly polarized luminescence† †Electronic supplementary information (ESI) available: General details, synthesis and spectroscopy data of new compounds. Experimental details on optical, chiroptical, electrochemical and on-surface measurements. Crystal data and structure refinement of compounds 1, and 6. Further details on theoretical calculations and Cartesian coordinates of computed structures. VT-H1NMR, 2D-NMR and HRMS spectra of 1. CCDC 1561552 and 1561553. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8sc00427g

PubMed Central

Cruz, Carlos M.; Márquez, Irene R.; Mariz, Inês F. A.; Blanco, Victor; Sánchez-Sánchez, Carlos; Sobrado, Jesús M.; Martín-Gago, José A.; Cuerva, Juan M.

2018-01-01

Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push–pull geometry and the extended network of sp2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results. PMID:29780523

Reflective afocal broadband adaptive optics scanning ophthalmoscope

PubMed Central

Dubra, Alfredo; Sulai, Yusufu

2011-01-01

A broadband adaptive optics scanning ophthalmoscope (BAOSO) consisting of four afocal telescopes, formed by pairs of off-axis spherical mirrors in a non-planar arrangement, is presented. The non-planar folding of the telescopes is used to simultaneously reduce pupil and image plane astigmatism. The former improves the adaptive optics performance by reducing the root-mean-square (RMS) of the wavefront and the beam wandering due to optical scanning. The latter provides diffraction limited performance over a 3 diopter (D) vergence range. This vergence range allows for the use of any broadband light source(s) in the 450-850 nm wavelength range to simultaneously image any combination of retinal layers. Imaging modalities that could benefit from such a large vergence range are optical coherence tomography (OCT), multi- and hyper-spectral imaging, single- and multi-photon fluorescence. The benefits of the non-planar telescopes in the BAOSO are illustrated by resolving the human foveal photoreceptor mosaic in reflectance using two different superluminescent diodes with 680 and 796 nm peak wavelengths, reaching the eye with a vergence of 0.76 D relative to each other. PMID:21698035

Reflective afocal broadband adaptive optics scanning ophthalmoscope.

PubMed

Dubra, Alfredo; Sulai, Yusufu

2011-06-01

A broadband adaptive optics scanning ophthalmoscope (BAOSO) consisting of four afocal telescopes, formed by pairs of off-axis spherical mirrors in a non-planar arrangement, is presented. The non-planar folding of the telescopes is used to simultaneously reduce pupil and image plane astigmatism. The former improves the adaptive optics performance by reducing the root-mean-square (RMS) of the wavefront and the beam wandering due to optical scanning. The latter provides diffraction limited performance over a 3 diopter (D) vergence range. This vergence range allows for the use of any broadband light source(s) in the 450-850 nm wavelength range to simultaneously image any combination of retinal layers. Imaging modalities that could benefit from such a large vergence range are optical coherence tomography (OCT), multi- and hyper-spectral imaging, single- and multi-photon fluorescence. The benefits of the non-planar telescopes in the BAOSO are illustrated by resolving the human foveal photoreceptor mosaic in reflectance using two different superluminescent diodes with 680 and 796 nm peak wavelengths, reaching the eye with a vergence of 0.76 D relative to each other.

A Readily Accessible Chiral NNN Pincer Ligand with a Pyrrole Backbone and Its Ni(II) Chemistry: Syntheses, Structural Chemistry, and Bond Activations.

PubMed

Wenz, Jan; Kochan, Alexander; Wadepohl, Hubert; Gade, Lutz H

2017-03-20

A new class of chiral C 2 -symmetric N-donor pincer ligands, 2,5-bis(2-oxazolinyldimethylmethyl)pyrroles (PdmBox)H, was synthesized starting from the readily available ethyl 2,2-dimethyl-3-oxobutanoate (1). The synthesis of the ligand backbone was achieved by oxidative enole coupling with CuC1 2 followed by Paal-Knorr-type pyrrole synthesis. The corresponding protioligands ( R PdmBox)H (R = iPr: 5a; Ph: 5b) were obtained by condensation with amino alcohols and subsequent zinc-catalyzed cyclization. Reaction of the lithiated ligands with [NiCl 2 (dme)] yielded the corresponding square-planar nickel(II) complexes [( R PdmBox)NiCl] (6a/b). Salt metathesis of 6a with the corresponding alkali or cesium salts in acetone led to the formation of air- and moisture-stable [( iPr PdmBox)NiX] (X = F (7), X = Br (8), X = I (9), X = N 3 (10), X = OAc (11). Furthermore, the conversion of [( iPr PdmBox)NiF] (7) with hydride transfer reagents such as PhSiH 3 led to the stable hydrido species [( iPr PdmBox)NiH] (27), the stoichiometric transformations of which were studied. Treatment of 6a with organometallic reagents such as ZnEt 2 , PhLi, PhC≡CLi, NsLi, or ( 4F Bn) 2 Mg(THF) 2 gave the corresponding alkyl, alkynyl, or aryl complexes. The availability of the new nonisomerizable PdmBox pincer ligands allowed the comparative study of their ligation to square-planar complexes as helically twisted spectator ligands as opposed to the enforced planar rigidity of their iso-PmBox analogues and the way this influences the reactivity of the Ni complexes.

Syntheses, structural characterization and spectroscopic studies of cadmium(II)-metal(II) cyanide complexes with 4-(2-aminoethyl)pyridine

NASA Astrophysics Data System (ADS)

Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Hökelek, Tuncer

2017-02-01

Three new cadmium(II)-metal(II) cyanide complexes, [Cd(4aepy)2(H2O)2][Ni(CN)4] (1), [Cd(4aepy)2(H2O)2][Pd(CN)4] (2) and [Cd(4aepy)2(H2O)2][Pt(CN)4] (3) [4aepy = 4-(2-aminoethyl)pyridine], have been synthesized and characterized by elemental, thermal, FT-IR and Raman spectral analyses. The crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction technique, in which they crystallize in the monoclinic system and C2/c space group. The M(II) [M(II) = Ni(II), Pd(II) and Pt(II)] ions are coordinated with the carbon atoms of the four cyanide groups in the square planar geometries and the [M(CN)4]2- ions act as counter ions. The Cd(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. 3D supramolecular structures of 1 and 2 were occurred by M⋯π and hydrogen bonding (Nsbnd H⋯N and Osbnd H⋯N) interactions. Vibrational assignments of all the observed bands were given and the spectral properties were also supported the crystal structures of the complexes. A possible decompositions of the complexes were investigated in the temperature range 30-800 °C in the static atmosphere.

Critical Dispersion-Theory Tests of Silicon's IR Refractive Index

NASA Astrophysics Data System (ADS)

Karstens, William; Smith, D. Y.

Silicon strongly absorbs both visible and UV light, but is highly transparent in the IR. Hence, it is a common choice for infrared windows and lenses. However, optical design is hindered by literature index values that disagree by up to 1%. In contrast optical-glass indices are known to 0.01% or better. The most widely available silicon IR indices are based on bulk measurements using either Snell's-Law refraction by a prism or channel-spectra interference of front- and backsurface reflections from a planar sample. To test the physical acceptability of these data, we have developed criteria based on a Taylor expansion of the Kramers-Kronig relation for the index at energies below strong inter-band transitions. These tests require that the coefficients of the series in powers of energy squared must be positive within the region of transparency. This is satisfied by essentially all prism measurements; their small scatter arises primarily from impurities and doping. In contrast, channel-spectra data fail in the second and third coefficients. A review of the experimental analysis indicates three problems besides purity: incorrect channel number arising from a channel-spectra model that neglects spectrum distortion by the weak lattice absorption; use of a series expansion of mixed parity in photon energy to describe the even-parity index; and use of an incorrect absorption energy in the Li-Sellmeier dispersion formula. Recommendations for IR index values for pure silicon will be discussed. Supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC02-06CH11357.

Synthesis, crystal structures and properties of new homoleptic Ni(II)/Pd(II) β-oxodithioester chelates

NASA Astrophysics Data System (ADS)

Yadav, Chote L.; Manar, Krishna K.; Yadav, Manoj K.; Tiwari, Neeraj; Singh, Rakesh K.; Drew, Michael G. B.; Singh, Nanhai

2018-05-01

Six new cis-chelate complexes, [M(L)2] (L = methyl-3-hydroxy-3-(furyl)-2-propenedithioate L1, M = Ni(II) 1, Pd(II) 4; methyl-3-hydroxy-3-(thiophenyl)-2-propenedithioate L2, M = Ni(II) 2, Pd(II) 5 and methyl-3-hydroxy-3-(phenyl)-2-propenedithioate L3, M = Ni(II) 3, Pd(II) 6 have been prepared and characterized by elemental analyses, spectroscopy (IR, UV-Vis., 1H and 13C{1H} NMR). The structures of 2-6 have been revealed by X-ray crystallography. In all the crystal structures, the metal has four-coordinate slightly distorted square planar geometry with a cis-configuration of the ligands. Anti-leishmanial properties of the complexes have been studied; 2, 3 and 6 showed potential anti-promastigote and anti-amastigote activities with IC50 values of 1.70 ± 0.50, 1.62 ± 0.19, 9.20 ± 2.16 μg/mL and IC50 2.50 ± 0.10, 2.05 ± 0.40, 12.84 ± 3.46 μg/mL respectively. Cytotoxicity assays on these complexes showed toxicity on the promastigotes but less toxicity against RAW 264.7 cell lines at different concentrations. Palladium complexes 4, 5 and 6 show luminescent characteristics in CH2Cl2 solution at room temperature. Complexes 1-6 are weakly conducting (σrt = 10-4-10-6 S cm-1, Ea = 0.19-1.13 eV) but show semiconducting behavior in the solid phase.

Rate distortion optimal bit allocation methods for volumetric data using JPEG 2000.

PubMed

Kosheleva, Olga M; Usevitch, Bryan E; Cabrera, Sergio D; Vidal, Edward

2006-08-01

Computer modeling programs that generate three-dimensional (3-D) data on fine grids are capable of generating very large amounts of information. These data sets, as well as 3-D sensor/measured data sets, are prime candidates for the application of data compression algorithms. A very flexible and powerful compression algorithm for imagery data is the newly released JPEG 2000 standard. JPEG 2000 also has the capability to compress volumetric data, as described in Part 2 of the standard, by treating the 3-D data as separate slices. As a decoder standard, JPEG 2000 does not describe any specific method to allocate bits among the separate slices. This paper proposes two new bit allocation algorithms for accomplishing this task. The first procedure is rate distortion optimal (for mean squared error), and is conceptually similar to postcompression rate distortion optimization used for coding codeblocks within JPEG 2000. The disadvantage of this approach is its high computational complexity. The second bit allocation algorithm, here called the mixed model (MM) approach, mathematically models each slice's rate distortion curve using two distinct regions to get more accurate modeling at low bit rates. These two bit allocation algorithms are applied to a 3-D Meteorological data set. Test results show that the MM approach gives distortion results that are nearly identical to the optimal approach, while significantly reducing computational complexity.

Aqua­(1,10-phenanthroline-κ2 N,N′)bis­(trimethyl­acetato)-κ2 O,O′;κO-cobalt(II)

PubMed Central

Chen, Xiao-Dan; Chen, Hong-Xian; Li, Zhong-Shu; Zhang, Huai-Hong; Sun, Bai-Wang

2009-01-01

In the title compound, [Co(C5H9O2)2(C12H8N2)(H2O)], the CoII atom is coordinated in a distorted octahedral environment by three carboxyl O atoms of two trimethyl­acetate ligands, one aqua O atom and two N atoms from 1,10-phen­anthroline. The crystal structure is stabilized by O—H⋯O hydrogen bonds and π–π stacking inter­actions [inter­planar distance between inter­digitating 1,10-phenanthroline ligands = 3.378 (2) Å]. PMID:21583436

A molecular dynamics and ab initio analysis of the electronic structure of single-walled carbon nanotubes adhered to a substrate

NASA Astrophysics Data System (ADS)

Van Der Geest, A. G.; Lu, Z.; Lusk, M. T.; Dunn, M. L.

2011-04-01

Single-wall nanotubes can adhere to planar surfaces via van der Waals forces, and this causes the tubes to deform. We use classical molecular dynamics to estimate this deformation and density functional theory to quantify its impact on electronic band structure. For (n,0) tubes, adhesion causes the maximum bandgap to rise more rapidly with diameter, but the value of the maximum is not affected. The influence of adhesion forces on bandgap was found to correlate with that associated with lateral, uniaxial compression for moderate values of adhesion energy and compressive distortion.

Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovacs, Andras; Ney, A.; Duchamp, Martial

2013-12-23

We have studied planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al2O3) and the Co:ZnO/Al2O3 interface structure at atomic resolution using aberration-corrected transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). Comparing Co:ZnO samples deposited by pulsed laser deposition and reactive magnetron sputtering, both exhibit extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3-4 Co:ZnO layers at the interface.. In addition, we have measured the local strain which reveals the lattice distortion around the stacking faults.

Seamless Image Mosaicking via Synchronization

NASA Astrophysics Data System (ADS)

Santellani, E.; Maset, E.; Fusiello, A.

2018-05-01

This paper proposes an innovative method to create high-quality seamless planar mosaics. The developed pipeline ensures good robustness against many common mosaicking problems (e.g., misalignments, colour distortion, moving objects, parallax) and differs from other works in the literature because a global approach, known as synchronization, is used for image registration and colour correction. To better conceal the mosaic seamlines, images are cut along specific paths, computed using a Voronoi decomposition of the mosaic area and a shortest path algorithm. Results obtained on challenging real datasets show that the colour correction mitigates significantly the colour variations between the original images and the seams on the final mosaic are not evident.

An analysis of optical effects caused by thermally induced mirror deformations.

PubMed

Ogrodnik, R F

1970-09-01

This paper analyzes thermally induced mirror deformations and their resulting wavefront distortions which occur under the conditions of radially nonuniform mirror heating. The analysis is adaptable to heating produced by any radially nonuniform incident radiation. Specific examples of radiation distributions which are considered are the cosine squared and the gaussian and TEM(0, 1) laser distributions. Deformation effects are examined from two aspects, the first of which is the reflected wavefront radial phase distortion profile caused by the thermally induced surface irregularities at the mirror face. These phase distortion effects appear as aberrations in noncoherent optical applications and as the loss of spatial coherence in coherent applications. The second aspect is the gross wavefront bending due to mirror curvature effects. The analysis considers substrate material, geometry, and cooling in order to determine potential deformation controlling factors. Substrate materials are compared, and performance indicators are suggested to aid in selecting an optimum material for a given heating condition. Deformation examples are given for materials of interest and specific absorbed power levels.

Low-cost solar array structure development

NASA Astrophysics Data System (ADS)

Wilson, A. H.

1981-06-01

Early studies of flat-plate arrays have projected costs on the order of $50/square meter for installed array support structures. This report describes an optimized low-cost frame-truss structure that is estimated to cost below $25/square meter, including all markups, shipping an installation. The structure utilizes a planar frame made of members formed from light-gauge galvanized steel sheet and is supposed in the field by treated-wood trusses that are partially buried in trenches. The buried trusses use the overburden soil to carry uplift wind loads and thus to obviate reinforced-concrete foundations. Details of the concept, including design rationale, fabrication and assembly experience, structural testing and fabrication drawings are included.

High resolution hard X-ray spectra of solar and cosmic sources. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Schwartz, R. A.

1984-01-01

High resolution hard X-ray observations of a large solar flare and the Crab Nebula were obtained during balloon flights using an array of cooled germanium planar detectors. In addition, high time resolution high sensitivity measurements were obtained with a 300 square cm NaI/CsI phoswich scintillator. The Crab spectrum from both flights was searched without finding evidence of line emission below 200 keV. In particular, for the 73 keV line previously reported a 3 sigma upper limit for a narrow (1 keV FWHM) line .0019 and .0014 ph square cm/sec for the 1979 and 1980 flights, respectively was obtained.

Low-cost solar array structure development

NASA Technical Reports Server (NTRS)

Wilson, A. H.

1981-01-01

Early studies of flat-plate arrays have projected costs on the order of $50/square meter for installed array support structures. This report describes an optimized low-cost frame-truss structure that is estimated to cost below $25/square meter, including all markups, shipping an installation. The structure utilizes a planar frame made of members formed from light-gauge galvanized steel sheet and is supposed in the field by treated-wood trusses that are partially buried in trenches. The buried trusses use the overburden soil to carry uplift wind loads and thus to obviate reinforced-concrete foundations. Details of the concept, including design rationale, fabrication and assembly experience, structural testing and fabrication drawings are included.

Photogrammetric Method and Software for Stream Planform Identification

NASA Astrophysics Data System (ADS)

Stonedahl, S. H.; Stonedahl, F.; Lohberg, M. M.; Lusk, K.; Miller, D.

2013-12-01

Accurately characterizing the planform of a stream is important for many purposes, including recording measurement and sampling locations, monitoring change due to erosion or volumetric discharge, and spatial modeling of stream processes. While expensive surveying equipment or high resolution aerial photography can be used to obtain planform data, our research focused on developing a close-range photogrammetric method (and accompanying free/open-source software) to serve as a cost-effective alternative. This method involves securing and floating a wooden square frame on the stream surface at several locations, taking photographs from numerous angles at each location, and then post-processing and merging data from these photos using the corners of the square for reference points, unit scale, and perspective correction. For our test field site we chose a ~35m reach along Black Hawk Creek in Sunderbruch Park (Davenport, IA), a small, slow-moving stream with overhanging trees. To quantify error we measured 88 distances between 30 marked control points along the reach. We calculated error by comparing these 'ground truth' distances to the corresponding distances extracted from our photogrammetric method. We placed the square at three locations along our reach and photographed it from multiple angles. The square corners, visible control points, and visible stream outline were hand-marked in these photos using the GIMP (open-source image editor). We wrote an open-source GUI in Java (hosted on GitHub), which allows the user to load marked-up photos, designate square corners and label control points. The GUI also extracts the marked pixel coordinates from the images. We also wrote several scripts (currently in MATLAB) that correct the pixel coordinates for radial distortion using Brown's lens distortion model, correct for perspective by forcing the four square corner pixels to form a parallelogram in 3-space, and rotate the points in order to correctly orient all photos of the same square location. Planform data from multiple photos (and multiple square locations) are combined using weighting functions that mitigate the error stemming from the markup-process, imperfect camera calibration, etc. We have used our (beta) software to mark and process over 100 photos, yielding an average error of only 1.5% relative to our 88 measured lengths. Next we plan to translate the MATLAB scripts into Python and release their source code, at which point only free software, consumer-grade digital cameras, and inexpensive building materials will be needed for others to replicate this method at new field sites. Three sample photographs of the square with the created planform and control points

Single layers and multilayers of GaN and AlN in square-octagon structure: Stability, electronic properties, and functionalization

NASA Astrophysics Data System (ADS)

Gürbüz, E.; Cahangirov, S.; Durgun, E.; Ciraci, S.

2017-11-01

Further to planar single-layer hexagonal structures, GaN and AlN can also form free-standing, single-layer structures constructed from squares and octagons. We performed an extensive analysis of dynamical and thermal stability of these structures in terms of ab initio finite-temperature molecular dynamics and phonon calculations together with the analysis of Raman and infrared active modes. These single-layer square-octagon structures of GaN and AlN display directional mechanical properties and have wide, indirect fundamental band gaps, which are smaller than their hexagonal counterparts. These density functional theory band gaps, however, increase and become wider upon correction. Under uniaxial and biaxial tensile strain, the fundamental band gaps decrease and can be closed. The electronic and magnetic properties of these single-layer structures can be modified by adsorption of various adatoms, or by creating neutral cation-anion vacancies. The single-layer structures attain magnetic moment by selected adatoms and neutral vacancies. In particular, localized gap states are strongly dependent on the type of vacancy. The energetics, binding, and resulting electronic structure of bilayer, trilayer, and three-dimensional (3D) layered structures constructed by stacking the single layers are affected by vertical chemical bonds between adjacent layers. In addition to van der Waals interaction, these weak vertical bonds induce buckling in planar geometry and enhance their binding, leading to the formation of stable 3D layered structures. In this respect, these multilayers are intermediate between van der Waals solids and wurtzite crystals, offering a wide range of tunability.

Orbital angular momentum (OAM) spectrum correction in free space optical communication.

PubMed

Liu, Yi-Dong; Gao, Chunqing; Qi, Xiaoqing; Weber, Horst

2008-05-12

Orbital angular momentum (OAM) of laser beams has potential application in free space optical communication, but it is sensitive against pointing instabilities of the beam, i.e. shift (lateral displacement) and tilt (deflection of the beam). This work proposes a method to correct the distorted OAM spectrum by using the mean square value of the orbital angular momentum as an indicator. Qualitative analysis is given, and the numerical simulation is carried out for demonstration. The results show that the mean square value can be used to determine the beam axis of the superimposed helical beams. The initial OAM spectrum can be recovered.

An Undergraduate Experiment for the Measurement of the Speed of Sound in Air: Phenomena and Discussion

ERIC Educational Resources Information Center

Yang, Hujiang; Zhao, Xiaohong; Wang, Xin; Xiao, Jinghua

2012-01-01

In this paper, we present and discuss some phenomena in an undergraduate experiment for the measurement of the speed of sound in air. A square wave distorts when connected to a piezoelectric transducer. Moreover, the amplitude of the receiving signal varies with the driving frequency. Comparing with the Gibbs phenomenon, these phenomena can be…

Quantitative metrics for evaluating parallel acquisition techniques in diffusion tensor imaging at 3 Tesla.

PubMed

Ardekani, Siamak; Selva, Luis; Sayre, James; Sinha, Usha

2006-11-01

Single-shot echo-planar based diffusion tensor imaging is prone to geometric and intensity distortions. Parallel imaging is a means of reducing these distortions while preserving spatial resolution. A quantitative comparison at 3 T of parallel imaging for diffusion tensor images (DTI) using k-space (generalized auto-calibrating partially parallel acquisitions; GRAPPA) and image domain (sensitivity encoding; SENSE) reconstructions at different acceleration factors, R, is reported here. Images were evaluated using 8 human subjects with repeated scans for 2 subjects to estimate reproducibility. Mutual information (MI) was used to assess the global changes in geometric distortions. The effects of parallel imaging techniques on random noise and reconstruction artifacts were evaluated by placing 26 regions of interest and computing the standard deviation of apparent diffusion coefficient and fractional anisotropy along with the error of fitting the data to the diffusion model (residual error). The larger positive values in mutual information index with increasing R values confirmed the anticipated decrease in distortions. Further, the MI index of GRAPPA sequences for a given R factor was larger than the corresponding mSENSE images. The residual error was lowest in the images acquired without parallel imaging and among the parallel reconstruction methods, the R = 2 acquisitions had the least error. The standard deviation, accuracy, and reproducibility of the apparent diffusion coefficient and fractional anisotropy in homogenous tissue regions showed that GRAPPA acquired with R = 2 had the least amount of systematic and random noise and of these, significant differences with mSENSE, R = 2 were found only for the fractional anisotropy index. Evaluation of the current implementation of parallel reconstruction algorithms identified GRAPPA acquired with R = 2 as optimal for diffusion tensor imaging.

Evaluation of preprocessing steps to compensate for magnetic field distortions due to body movements in BOLD fMRI

PubMed Central

Barry, Robert L.; Williams, Joy M.; Klassen, L. Martyn; Gallivan, Jason P.; Culham, Jody C.

2009-01-01

Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is currently the dominant technique for non-invasive investigation of brain functions. One of the challenges with BOLD fMRI, particularly at high fields, is compensation for the effects of spatiotemporally varying magnetic field inhomogeneities (ΔB0) caused by normal subject respiration, and in some studies, movement of the subject during the scan to perform tasks related to the functional paradigm. The presence of ΔB0 during data acquisition distorts reconstructed images and introduces extraneous fluctuations in the fMRI time series that decrease the BOLD contrast-to-noise ratio. Optimization of the fMRI data-processing pipeline to compensate for geometric distortions is of paramount importance to ensure high quality of fMRI data. To investigate ΔB0 caused by subject movement, echo-planar imaging scans were collected with and without concurrent motion of a phantom arm. The phantom arm was constructed and moved by the experimenter to emulate forearm motions while subjects remained still and observed a visual stimulation paradigm. These data were then subjected to eight different combinations of preprocessing steps. The best preprocessing pipeline included navigator correction, a complex phase regressor, and spatial smoothing. The synergy between navigator correction and phase regression reduced geometric distortions better than either step in isolation, and preconditioned the data to make them more amenable to the benefits of spatial smoothing. The combination of these steps provided a 10% increase in t-statistics compared to only navigator correction and spatial smoothing, and reduced the noise and false activations in regions where no legitimate effects would occur. PMID:19695810

Development of 1-m primary mirror for a spaceborne camera

NASA Astrophysics Data System (ADS)

Kihm, Hagyong; Yang, Ho-Soon; Rhee, Hyug-Gyo; Lee, Yun-Woo

2015-09-01

We present the development of a 1-m lightweight mirror system for a spaceborne electro-optical camera. The mirror design was optimized to satisfy the performance requirements under launch loads and space environment. The mirror made of Zerodur® has pockets at the back surface and three square bosses at the rim. Metallic bipod flexures support the mirror at the bosses and adjust the mirror's surface distortion due to gravity. We also show an analytical formulation of the bipod flexure, where compliance and stiffness matrices of the bipod flexure are derived to estimate theoretical performance and to make initial design guidelines. Optomechanical performances such as surface distortions due to gravity is explained. Environmental verification of the mirror is achieved by vibration tests.

Search for Lorentz Violation in a Short-Range Gravity Experiment

NASA Astrophysics Data System (ADS)

Bennett, D.; Skavysh, V.; Long, J.

2011-12-01

An experimental test of the Newtonian inverse square law at short range has been used to set limits on Lorentz violation in the pure gravity sector of the Standard-Model Extension. On account of the planar test mass geometry, nominally null with respect to 1/r2 forces, the limits derived for the SME coefficients of Lorentz violation are on the order bar sJK ˜ 104 .

Spin transition in a four-coordinate iron oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakami, T.; Sutou, S.; Hirama, H.

2009-01-01

The spin transition, or spin crossover, is a manifestation of electronic instability induced by external constraints such as pressure1. Among known examples that exhibit spin transition, 3d ions with d6 electron configurations represent the vast majority, but the spin transition observed thus far has been almost exclusively limited to that between high-spin (S = 2) and low-spin (S = 0) states2-9. Here we report a novel high-spin to intermediate-spin (S = 1) state transition at 33 GPa induced by pressurization of an antiferromagnetic insulator SrFeO2 with a square planar coordination10. The change in spin multiplicity brings to ferromagnetism as wellmore » as metallicity, yet keeping the ordering temperature far above ambient. First-principles calculations attribute the origin of the transition to the strong inlayer hybridization between Fe dx 2 -y 2 O p , leading to a pressure-induced electronic instability toward the depopulation of Fe dx 2 -y 2 O p antibonding states. Furthermore, the ferromagnetic S = 1 state is half-metallic due to the inception of half-occupied spin-down (dxz, dyz) degenerate states upon spin transition. These results highlight the square-planar coordinated iron oxides as a new class of magnetic and electric materials and provide new avenues toward realizing multi-functional sensors and data-storage devices.« less

Measuring the bending of asymmetric planar EAP structures

NASA Astrophysics Data System (ADS)

Weiss, Florian M.; Zhao, Xue; Thalmann, Peter; Deyhle, Hans; Urwyler, Prabitha; Kovacs, Gabor; Müller, Bert

2013-04-01

The geometric characterization of low-voltage dielectric electro-active polymer (EAP) structures, comprised of nanometer thickness but areas of square centimeters, for applications such as artificial sphincters requires methods with nanometer precision. Direct optical detection is usually restricted to sub-micrometer resolution because of the wavelength of the light applied. Therefore, we propose to take advantage of the cantilever bending system with optical readout revealing a sub-micrometer resolution at the deflection of the free end. It is demonstrated that this approach allows us to detect bending of rather conventional planar asymmetric, dielectric EAP-structures applying voltages well below 10 V. For this purpose, we built 100 μm-thin silicone films between 50 nm-thin silver layers on a 25 μm-thin polyetheretherketone (PEEK) substrate. The increase of the applied voltage in steps of 50 V until 1 kV resulted in a cantilever bending that exhibits only in restricted ranges the expected square dependence. The mean laser beam displacement on the detector corresponded to 6 nm per volt. The apparatus will therefore become a powerful mean to analyze and thereby improve low-voltage dielectric EAP-structures to realize nanometer-thin layers for stack actuators to be incorporated into artificial sphincter systems for treating severe urinary and fecal incontinence.

Pyrazolate-based copper(II) and nickel(II) [2 x 2] grid complexes: protonation-dependent self-assembly, structures and properties.

PubMed

Klingele, Julia; Prikhod'ko, Alexander I; Leibeling, Guido; Demeshko, Serhiy; Dechert, Sebastian; Meyer, Franc

2007-05-28

The pyrazole-based diamide ligand N,N'-bis(2-pyridylmethyl)pyrazole-3,5-dicarboxamide (H(3)L) has been structurally characterised and successfully employed in the preparation of [2 x 2] grid-type complexes. Thus, the reaction of H(3)L with Cu(ClO(4))2.6H(2)O or Ni(ClO(4))2.6H(2)O in the presence of added base (NaOH) affords the tetranuclear complexes [M(4)(HL(4))].8H(2)O (1: M = Cu, 2: M = Ni). Employment of a mixture of the two metal salts under otherwise identical reaction conditions leads to the formation of the mixed-metal species [Cu(x)Ni(4-x)(HL)(4)].8H(2)O (x

Modular multi-element high energy particle detector

DOEpatents

Coon, D.D.; Elliott, J.P.

1990-01-02

Multi-element high energy particle detector modules comprise a planar heavy metal carrier of tungsten alloy with planar detector units uniformly distributed over one planar surface. The detector units are secured to the heavy metal carrier by electrically conductive adhesive so that the carrier serves as a common ground. The other surface of each planar detector unit is electrically connected to a feedthrough electrical terminal extending through the carrier for front or rear readout. The feedthrough electrical terminals comprise sockets at one face of the carrier and mating pins projecting from the other face, so that any number of modules may be plugged together to create a stack of modules of any desired number of radiation lengths. The detector units each comprise four, preferably rectangular, p-i-n diode chips arranged around the associated feedthrough terminal to form a square detector unit providing at least 90% detector element coverage of the carrier. Integral spacers projecting from the carriers extend at least partially along the boundaries between detector units to space the p-i-n diode chips from adjacent carriers in a stack. The spacers along the perimeters of the modules are one-half the width of the interior spacers so that when stacks of modules are arranged side by side to form a large array of any size or shape, distribution of the detector units is uniform over the entire array. 5 figs.

Modular multi-element high energy particle detector

DOEpatents

Coon, Darryl D.; Elliott, John P.

1990-01-02

Multi-element high energy particle detector modules comprise a planar heavy metal carrier of tungsten alloy with planar detector units uniformly distributed over one planar surface. The detector units are secured to the heavy metal carrier by electrically conductive adhesive so that the carrier serves as a common ground. The other surface of each planar detector unit is electrically connected to a feedthrough electrical terminal extending through the carrier for front or rear readout. The feedthrough electrical terminals comprise sockets at one face of the carrier and mating pins porjecting from the other face, so that any number of modules may be plugged together to create a stack of modules of any desired number of radiation lengths. The detector units each comprise four, preferably rectangular, p-i-n diode chips arranged around the associated feedthrough terminal to form a square detector unit providing at least 90% detector element coverage of the carrier. Integral spacers projecting from the carriers extend at least partially along the boundaries between detector units to space the p-i-n diode chips from adjacent carriers in a stack. The spacers along the perimeters of the modules are one-half the width of the interior spacers so that when stacks of modules are arranged side by side to form a large array of any size or shape, distribution of the detector units is uniform over the entire array.

Optical absorption enhancement in NH2CH=NH2PbI3 lead halide perovskite solar cells with nanotextures

NASA Astrophysics Data System (ADS)

Xie, Ziang; Sun, Shuren; Xie, Xixi; Hou, Ruixiang; Xu, Wanjin; Li, Yanping; Qin, G. G.

2018-01-01

This article reports, for the first time to our knowledge, that the power conversion efficiencies (PCEs) of planar NH2CH=NH2PbI3 (FAPbI3) lead halide perovskite solar cells (SCs) can be largely improved by fabricating nanotextures on the SC surface. Four kinds of nanotextures are investigated and compared with each other: column hollow (CLH) nanoarrays, cone hollow (CNH) nanoarrays, square prism hollow (SPH) nanoarrays, and pyramid hollow (PYH) nanoarrays. Compared with the PCEs of the planar SCs with the same layer depth d, it is found that when d is in the range of 125-500 nm and when the array period, as well as the filling fraction of the nanotexture, are optimized, the ultimate efficiency increased 29%-50% for the CLH and SPH textured FAPbI3 SCs relative to the planar ones, and 20%-41% for the CNH and PYH textured FAPbI3 SCs relative to the planar ones. When d < 250 nm, the optimized ultimate efficiencies of the CLH and SPH textured FAPbI3 SCs with optimized nanotextures are higher than those of the CNH and PYH ones, and vice versa. The reasons why fabricating nanotextures on SC surfaces can largely improve the PCE of the FAPbI3 SCs are discussed.

Hybrid two-dimensional navigator correction: a new technique to suppress respiratory-induced physiological noise in multi-shot echo-planar functional MRI

PubMed Central

Barry, Robert L.; Klassen, L. Martyn; Williams, Joy M.; Menon, Ravi S.

2008-01-01

A troublesome source of physiological noise in functional magnetic resonance imaging (fMRI) is due to the spatio-temporal modulation of the magnetic field in the brain caused by normal subject respiration. fMRI data acquired using echo-planar imaging is very sensitive to these respiratory-induced frequency offsets, which cause significant geometric distortions in images. Because these effects increase with main magnetic field, they can nullify the gains in statistical power expected by the use of higher magnetic fields. As a study of existing navigator correction techniques for echo-planar fMRI has shown that further improvements can be made in the suppression of respiratory-induced physiological noise, a new hybrid two-dimensional (2D) navigator is proposed. Using a priori knowledge of the slow spatial variations of these induced frequency offsets, 2D field maps are constructed for each shot using spatial frequencies between ±0.5 cm−1 in k-space. For multi-shot fMRI experiments, we estimate that the improvement of hybrid 2D navigator correction over the best performance of one-dimensional navigator echo correction translates into a 15% increase in the volume of activation, 6% and 10% increases in the maximum and average t-statistics, respectively, for regions with high t-statistics, and 71% and 56% increases in the maximum and average t-statistics, respectively, in regions with low t-statistics due to contamination by residual physiological noise. PMID:18024159

Fast susceptibility-weighted imaging with three-dimensional short-axis propeller (SAP)-echo-planar imaging.

PubMed

Holdsworth, Samantha J; Yeom, Kristen W; Moseley, Michael E; Skare, S

2015-05-01

Susceptibility-weighted imaging (SWI) in neuroimaging can be challenging due to long scan times of three-dimensional (3D) gradient recalled echo (GRE), while faster techniques such as 3D interleaved echo-planar imaging (iEPI) are prone to motion artifacts. Here we outline and implement a 3D short-axis propeller echo-planar imaging (SAP-EPI) trajectory as a faster, motion-correctable approach for SWI. Experiments were conducted on a 3T MRI system. The 3D SAP-EPI, 3D iEPI, and 3D GRE SWI scans were acquired on two volunteers. Controlled motion experiments were conducted to test the motion-correction capability of 3D SAP-EPI. The 3D SAP-EPI SWI data were acquired on two pediatric patients as a potential alternative to 2D GRE used clinically. The 3D GRE images had a better target resolution (0.47 × 0.94 × 2 mm, scan time = 5 min), iEPI and SAP-EPI images (resolution = 0.94 × 0.94 × 2 mm) were acquired in a faster scan time (1:52 min) with twice the brain coverage. SAP-EPI showed motion-correction capability and some immunity to undersampling from rejected data. While 3D SAP-EPI suffers from some geometric distortion, its short scan time and motion-correction capability suggest that SAP-EPI may be a useful alternative to GRE and iEPI for use in SWI, particularly in uncooperative patients. © 2014 Wiley Periodicals, Inc.

Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN2-R: Energy Component Analysis of the Pseudo-Jahn-Teller Effect.

PubMed

Toyota, Azumao; Muramatsu, Takashi; Koseki, Shiro

2017-03-23

Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN 2 -R (R = Li, BeH, BH 2 , CH 3 , CN, CCH, C 6 H 5 , NH 2 , OH, and F) (2-11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn-Teller (JT) distortion from a linear C ∞v structure to a C 1 structure via a planar bent C s structure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent C s structure for 2, 3, and 7 and to a C 1 structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1-11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, energy component analyses were carried out at the MCSCF+SOCI level of theory at all of the stationary structures for the relevant molecules. In most of the molecules examined, pseudo-JT stabilizations were classified into two groups, one in which the stability arises from a lowering of the energy of the attractive term V en and the other in which the stability results from a lowering of the energy of the repulsive terms V nn and V ee . In addition to the above two groups, it was also found that the following three groups are responsible for the pseudo-JT stabilizations in a certain stage of the structural changes. Namely, one is a lowering of the energy of the term V ee observed in 6, another is a lowering of the energy of the terms V ee and V en observed in 9-11, and the other is a lowering of the energy of the terms V en and V nn observed in 10. These energetic behaviors were accounted in terms of an elongation or a contraction of the molecular skeleton, a migration of electrons from one part of the molecule to other parts, and the combined effects arising from these two factors.

Automated generation of influence functions for planar crack problems

NASA Technical Reports Server (NTRS)

Sire, Robert A.; Harris, David O.; Eason, Ernest D.

1989-01-01

A numerical procedure for the generation of influence functions for Mode I planar problems is described. The resulting influence functions are in a form for convenient evaluation of stress-intensity factors for complex stress distributions. Crack surface displacements are obtained by a least-squares solution of the Williams eigenfunction expansion for displacements in a cracked body. Discrete values of the influence function, evaluated using the crack surface displacements, are curve fit using an assumed functional form. The assumed functional form includes appropriate limit-behavior terms for very deep and very shallow cracks. Continuous representation of the influence function provides a convenient means for evaluating stress-intensity factors for arbitrary stress distributions by numerical integration. The procedure is demonstrated for an edge-cracked strip and a radially cracked disk. Comparisons with available published results demonstrate the accuracy of the procedure.

Constraints on μ-distortion fluctuations and primordial non-Gaussianity from Planck data

NASA Astrophysics Data System (ADS)

Khatri, Rishi; Sunyaev, Rashid

2015-09-01

We use the Planck HFI channel maps to make an all sky map of μ-distortion fluctuations. Our μ-type distortion map is dominated by the y-type distortion contamination from the hot gas in the low redshift Universe and we can thus only place upper limits on the μ-type distortion fluctuations. For the amplitude of μ-type distortions on 10' scales we get the limit on root mean square (rms) value μrms10'< 6.4× 10-6, a limit 14 times stronger than the COBE-FIRAS (95% confidence) limit on the mean of langle μ rangle<90× 10-6. Using our maps we also place strong upper limits on the auto angular power spectrum of μ, Clμμ and the cross angular power spectrum of μ with the CMB temperature anisotropies, Clμ T. The strongest observational limits are on the largest scales, l(l+1)/(2π)Clμμ|l=2-26<(2.3± 1.0)× 10-12 and l(l+1)/(2π)Clμ T|l=2-26<(2.6± 2.6)× 10-12 K. Our observational limits can be used to constrain new physics which can create spatially varying energy release in the early Universe between redshifts 5× 104lesssim zlesssim 2× 106. We specifically apply our observational results to constrain the primordial non-Gaussianity of the local type, when the source of μ-distortion is Silk damping, for very squeezed configurations with the wavenumber for the short wavelength mode 46 lesssim kS lesssim 104 Mpc-1 and for the long wavelength mode kL≈ 10-3 Mpc-1. Our limits on the primordial non-Gaussianity parameters are fNL<105, τNL<1.4× 1011 for kS/kL≈ 5× 104- 107. We also give a new derivation of the evolution of the μ-distortion fluctuations through the y-distortion era and the recombination epoch until today resulting in very simple expressions for the cross and auto power spectra in the squeezed limit. We also introduce mixing of Bose-Einstein spectra due to Silk damping and yBE-type distortions. The μ-type distortion map and masks are now publicly available.

Distortion of CAD-CAM-fabricated implant-fixed titanium and zirconia complete dental prosthesis frameworks.

PubMed

Al-Meraikhi, Hadi; Yilmaz, Burak; McGlumphy, Edwin; Brantley, William A; Johnston, William M

2018-01-01

Computer-aided design and computer-aided manufacturing (CAD-CAM)-fabricated titanium and zirconia implant-supported fixed dental prostheses have become increasingly popular for restoring patients with complete edentulism. However, the distortion level of these frameworks is not well known. The purpose of this in vitro study was to compare the 3-dimensional (3D) distortion of CAD-CAM zirconia and titanium implant-fixed screw-retained complete dental prostheses. A master edentulous model with 4 implants at the positions of the maxillary first molars and canines was used. Multiunit abutments (Nobel Biocare) secured to the model were digitally scanned using scan bodies and a laboratory scanner (S600 ARTI; Zirkonzahn). Titanium (n=5) and zirconia (n=5) frameworks were milled using a CAD-CAM system (Zirkonzahn M1; Zirkonzahn). All frameworks were scanned using an industrial computed tomography (CT) scanner (Nikon/X-Tek XT H 225kV MCT Micro-Focus). The direct CT scans were reconstructed to generate standard tessellation language (STL) files. To calculate the 3D distortion of the frameworks, STL files of the CT scans were aligned to the CAD model using a sum of the least squares best-fit algorithm. Surface comparison points were placed on the CAD model on the midfacial aspect of all teeth. The 3D distortion of each direct scan to the CAD model was calculated. In addition, color maps of the scan-to-CAD comparison were constructed using a ±0.500 mm color scale range. Both materials exhibited distortion; however, no significant difference was found in the amount of distortion from the CAD model between the materials (P=.747). Absolute values of deviations from the CAD model were evident in the x and y plane and less so in the z direction. Zirconia and titanium frameworks showed similar 3D distortion compared with the CAD model for the tested CAD-CAM and implant systems. The distortion was more pronounced in the horizontal and sagittal plane than in the vertical plane. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Radargrammetric DSM generation in mountainous areas through adaptive-window least squares matching constrained by enhanced epipolar geometry

NASA Astrophysics Data System (ADS)

Dong, Yuting; Zhang, Lu; Balz, Timo; Luo, Heng; Liao, Mingsheng

2018-03-01

Radargrammetry is a powerful tool to construct digital surface models (DSMs) especially in heavily vegetated and mountainous areas where SAR interferometry (InSAR) technology suffers from decorrelation problems. In radargrammetry, the most challenging step is to produce an accurate disparity map through massive image matching, from which terrain height information can be derived using a rigorous sensor orientation model. However, precise stereoscopic SAR (StereoSAR) image matching is a very difficult task in mountainous areas due to the presence of speckle noise and dissimilar geometric/radiometric distortions. In this article, an adaptive-window least squares matching (AW-LSM) approach with an enhanced epipolar geometric constraint is proposed to robustly identify homologous points after compensation for radiometric discrepancies and geometric distortions. The matching procedure consists of two stages. In the first stage, the right image is re-projected into the left image space to generate epipolar images using rigorous imaging geometries enhanced with elevation information extracted from the prior DEM data e.g. SRTM DEM instead of the mean height of the mapped area. Consequently, the dissimilarities in geometric distortions between the left and right images are largely reduced, and the residual disparity corresponds to the height difference between true ground surface and the prior DEM. In the second stage, massive per-pixel matching between StereoSAR epipolar images identifies the residual disparity. To ensure the reliability and accuracy of the matching results, we develop an iterative matching scheme in which the classic cross correlation matching is used to obtain initial results, followed by the least squares matching (LSM) to refine the matching results. An adaptively resizing search window strategy is adopted during the dense matching step to help find right matching points. The feasibility and effectiveness of the proposed approach is demonstrated using Stripmap and Spotlight mode TerraSAR-X stereo data pairs covering Mount Song in central China. Experimental results show that the proposed method can provide a robust and effective matching tool for radargrammetry in mountainous areas.

Scalable L-infinite coding of meshes.

PubMed

Munteanu, Adrian; Cernea, Dan C; Alecu, Alin; Cornelis, Jan; Schelkens, Peter

2010-01-01

The paper investigates the novel concept of local-error control in mesh geometry encoding. In contrast to traditional mesh-coding systems that use the mean-square error as target distortion metric, this paper proposes a new L-infinite mesh-coding approach, for which the target distortion metric is the L-infinite distortion. In this context, a novel wavelet-based L-infinite-constrained coding approach for meshes is proposed, which ensures that the maximum error between the vertex positions in the original and decoded meshes is lower than a given upper bound. Furthermore, the proposed system achieves scalability in L-infinite sense, that is, any decoding of the input stream will correspond to a perfectly predictable L-infinite distortion upper bound. An instantiation of the proposed L-infinite-coding approach is demonstrated for MESHGRID, which is a scalable 3D object encoding system, part of MPEG-4 AFX. In this context, the advantages of scalable L-infinite coding over L-2-oriented coding are experimentally demonstrated. One concludes that the proposed L-infinite mesh-coding approach guarantees an upper bound on the local error in the decoded mesh, it enables a fast real-time implementation of the rate allocation, and it preserves all the scalability features and animation capabilities of the employed scalable mesh codec.

Breast tissue decomposition with spectral distortion correction: A postmortem study

PubMed Central

Ding, Huanjun; Zhao, Bo; Baturin, Pavlo; Behroozi, Farnaz; Molloi, Sabee

2014-01-01

Purpose: To investigate the feasibility of an accurate measurement of water, lipid, and protein composition of breast tissue using a photon-counting spectral computed tomography (CT) with spectral distortion corrections. Methods: Thirty-eight postmortem breasts were imaged with a cadmium-zinc-telluride-based photon-counting spectral CT system at 100 kV. The energy-resolving capability of the photon-counting detector was used to separate photons into low and high energy bins with a splitting energy of 42 keV. The estimated mean glandular dose for each breast ranged from 1.8 to 2.2 mGy. Two spectral distortion correction techniques were implemented, respectively, on the raw images to correct the nonlinear detector response due to pulse pileup and charge-sharing artifacts. Dual energy decomposition was then used to characterize each breast in terms of water, lipid, and protein content. In the meantime, the breasts were chemically decomposed into their respective water, lipid, and protein components to provide a gold standard for comparison with dual energy decomposition results. Results: The accuracy of the tissue compositional measurement with spectral CT was determined by comparing to the reference standard from chemical analysis. The averaged root-mean-square error in percentage composition was reduced from 15.5% to 2.8% after spectral distortion corrections. Conclusions: The results indicate that spectral CT can be used to quantify the water, lipid, and protein content in breast tissue. The accuracy of the compositional analysis depends on the applied spectral distortion correction technique. PMID:25281953

Chaotic mixing in three-dimensional microvascular networks fabricated by direct-write assembly.

PubMed

Therriault, Daniel; White, Scott R; Lewis, Jennifer A

2003-04-01

The creation of geometrically complex fluidic devices is a subject of broad fundamental and technological interest. Here, we demonstrate the fabrication of three-dimensional (3D) microvascular networks through direct-write assembly of a fugitive organic ink. This approach yields a pervasive network of smooth cylindrical channels (approximately 10-300 microm) with defined connectivity. Square-spiral towers, isolated within this vascular network, promote fluid mixing through chaotic advection. These vertical towers give rise to dramatic improvements in mixing relative to simple straight (1D) and square-wave (2D) channels while significantly reducing the device planar footprint. We envisage that 3D microvascular networks will provide an enabling platform for a wide array of fluidic-based applications.

3-Phenyl­pyridinium tetra­chlorido­aurate(III)

PubMed Central

Amani, Vahid; Safari, Nasser; Khavasi, Hamid Reza

2010-01-01

In the title mol­ecular salt, (C11H10N)[AuCl4], the AuIII atom adopts an almost regular square-planar coordination geometry and the dihedral angle between the aromatic rings of the 3-phenyl­pyridinium cation is 23.1 (3)°. In the crystal, the ions inter­act by way of N—H⋯Cl and C—H⋯Cl hydrogen bonds. PMID:21580276

Formal oxidative addition of a C-H bond by a 16e iridium(i) complex involves metal-ligand cooperation.

PubMed

Kumar, Amit; Feller, Moran; Ben-David, Yehoshoa; Diskin-Posner, Yael; Milstein, David

2018-05-10

The first example of oxidative addition of a C-H bond to a square planar d8-Iridium complex, without any external additive, such as an acid, is described. Our mechanistic investigations show that metal-ligand cooperation through aromatization-dearomatization of the lutidine backbone is involved in this process, and that the actual C-H activation step occurs through an Ir(iii) intermediate.

Test of the diffusing-diffusivity mechanism using near-wall colloidal dynamics

NASA Astrophysics Data System (ADS)

Matse, Mpumelelo; Chubynsky, Mykyta V.; Bechhoefer, John

2017-10-01

The mechanism of diffusing diffusivity predicts that, in environments where the diffusivity changes gradually, the displacement distribution becomes non-Gaussian, even though the mean-square displacement grows linearly with time. Here, we report single-particle tracking measurements of the diffusion of colloidal spheres near a planar substrate. Because the local effective diffusivity is known, we have been able to carry out a direct test of this mechanism for diffusion in inhomogeneous media.

Cortical dipole imaging using truncated total least squares considering transfer matrix error.

PubMed

Hori, Junichi; Takeuchi, Kosuke

2013-01-01

Cortical dipole imaging has been proposed as a method to visualize electroencephalogram in high spatial resolution. We investigated the inverse technique of cortical dipole imaging using a truncated total least squares (TTLS). The TTLS is a regularization technique to reduce the influence from both the measurement noise and the transfer matrix error caused by the head model distortion. The estimation of the regularization parameter was also investigated based on L-curve. The computer simulation suggested that the estimation accuracy was improved by the TTLS compared with Tikhonov regularization. The proposed method was applied to human experimental data of visual evoked potentials. We confirmed the TTLS provided the high spatial resolution of cortical dipole imaging.

Computational Study of the Structure of a Sepiolite/Thioindigo Mayan Pigment

PubMed Central

Alvarado, Manuel; Chianelli, Russell C.; Arrowood, Roy M.

2012-01-01

The interaction of thioindigo and the phyllosilicate clay sepiolite is investigated using density functional theory (DFT) and molecular orbital theory (MO). The best fit to experimental UV/Vis spectra occurs when a single thioindigo molecule attaches via Van der Waals forces to a tetrahedrally coordinated Al3+ cation with an additional nearby tetrahedrally coordinated Al3+ also present. The thioindigo molecule distorts from its planar structure, a behavior consistent with a color change. Due to the weak interaction between thioindigo and sepiolite we conclude that the thioindigo molecule must be trapped in a channel, an observation consistent with previous experimental studies. Future computational studies will look at the interaction of indigo with sepiolite. PMID:23193386

Peelle's pertinent puzzle using the Monte Carlo technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawano, Toshihiko; Talou, Patrick; Burr, Thomas

2009-01-01

We try to understand the long-standing problem of the Peelle's Pertinent Puzzle (PPP) using the Monte Carlo technique. We allow the probability density functions to be any kind of form to assume the impact of distribution, and obtain the least-squares solution directly from numerical simulations. We found that the standard least squares method gives the correct answer if a weighting function is properly provided. Results from numerical simulations show that the correct answer of PPP is 1.1 {+-} 0.25 if the common error is multiplicative. The thought-provoking answer of 0.88 is also correct, if the common error is additive, andmore » if the error is proportional to the measured values. The least squares method correctly gives us the most probable case, where the additive component has a negative value. Finally, the standard method fails for PPP due to a distorted (non Gaussian) joint distribution.« less

Cost-Sharing of Ecological Construction Based on Trapezoidal Intuitionistic Fuzzy Cooperative Games.

PubMed

Liu, Jiacai; Zhao, Wenjian

2016-11-08

There exist some fuzziness and uncertainty in the process of ecological construction. The aim of this paper is to develop a direct and an effective simplified method for obtaining the cost-sharing scheme when some interested parties form a cooperative coalition to improve the ecological environment of Min River together. Firstly, we propose the solution concept of the least square prenucleolus of cooperative games with coalition values expressed by trapezoidal intuitionistic fuzzy numbers. Then, based on the square of the distance in the numerical value between two trapezoidal intuitionistic fuzzy numbers, we establish a corresponding quadratic programming model to obtain the least square prenucleolus, which can effectively avoid the information distortion and uncertainty enlargement brought about by the subtraction of trapezoidal intuitionistic fuzzy numbers. Finally, we give a numerical example about the cost-sharing of ecological construction in Fujian Province in China to show the validity, applicability, and advantages of the proposed model and method.

Distortion of liquid film discharging from twin-fluid atomizer

NASA Astrophysics Data System (ADS)

Mehring, C.; Sirignano, W. A.

2001-11-01

The nonlinear distortion and disintegration of a thin liquid film exiting from a two-dimensional twin-fluid atomizer is analyzed numerically. Pulsed gas jets impacting on both sides of the discharging liquid film at the atomizer exit generate dilational and/or sinuous deformations of the film. Both liquid phase and gas phase are inviscid and incompressible. For the liquid phase the so-called long-wavelength approximation is employed yielding a system of unsteady one-dimensional equations for the planar film. Solution of Laplace's equation for the velocity potential yields the gas-phase velocity field on both sides of the liquid stream. Coupling between both phases is described through kinematic and dynamic boundary conditions at the phase interfaces, and includes the solution of the unsteady Bernoulli equation to determine the gas-phase pressure along the interfaces. Both gas- and liquid-phase equations are solved simultaneously. Solution of Laplace's equation for the gas streams is obtained by means of a boundary-element method. Numerical solutions for the liquid phase use the Lax-Wendroff method with Richtmyer splitting. Sheet distortion resulting from the stagnation pressure of the impacting gas jets and subsequent disturbance amplification due to Kelvin-Helmholtz effects are studied for various combinations of gas-pulse timing, gas-jet impact angles, gas-to-liquid-density ratio, liquid-phase Weber number and gas-jet-to-liquid-jet-momentum ratio. Dilational and sinuous oscillations of the liquid are examined and film pinch-off is predicted.

Optimising diffusion-weighted imaging in the abdomen and pelvis: comparison of image quality between monopolar and bipolar single-shot spin-echo echo-planar sequences.

PubMed

Kyriazi, Stavroula; Blackledge, Matthew; Collins, David J; Desouza, Nandita M

2010-10-01

To compare geometric distortion, signal-to-noise ratio (SNR), apparent diffusion coefficient (ADC), efficacy of fat suppression and presence of artefact between monopolar (Stejskal and Tanner) and bipolar (twice-refocused, eddy-current-compensating) diffusion-weighted imaging (DWI) sequences in the abdomen and pelvis. A semiquantitative distortion index (DI) was derived from the subtraction images with b = 0 and 1,000 s/mm(2) in a phantom and compared between the two sequences. Seven subjects were imaged with both sequences using four b values (0, 600, 900 and 1,050 s/mm(2)) and SNR, ADC for different organs and fat-to-muscle signal ratio (FMR) were compared. Image quality was evaluated by two radiologists on a 5-point scale. DI was improved in the bipolar sequence, indicating less geometric distortion. SNR was significantly lower for all tissues and b values in the bipolar images compared with the monopolar (p < 0.05), whereas FMR was not statistically different. ADC in liver, kidney and sacrum was higher in the bipolar scheme compared to the monopolar (p < 0.03), whereas in muscle it was lower (p = 0.018). Image quality scores were higher for the bipolar sequence (p ≤ 0.025). Artefact reduction makes the bipolar DWI sequence preferable in abdominopelvic applications, although the trade-off in SNR may compromise ADC measurements in muscle.

Coordination polyhedron and chemical vapor deposition of Cu(hfacac)2(t-BuNH2).

PubMed

Woo, Kyoungja; Paek, Hojeong; Lee, Wan In

2003-10-06

A new pentacoordinate Cu(II) complex, Cu(hfacac)(2)(t-BuNH(2)) [hfacac = CF(3)C(O)CHC(O)CF(3)(-), t-BuNH(2) = tert-butylamine], has been synthesized and structurally characterized. Interestingly, the structure of a single crystal occurred as square pyramidal with one O atom at the apical position and one N and three O atoms at the basal positions, showing a serious degree of distortion. This contrasts with the square-pyramidal structure of Cu(hfacac)(2)L (L = H(2)O and pyrazine), which has the L ligand at the axial position. In the Cu(hfacac)(2)(t-BuNH(2)) complex, the t-BuNH(2) ligand is placed at an equatorial position with a lowered angle by 19.9(2) degrees from the basal plane. This distortion seems to reduce sigma influence and steric hindrance and so stabilizes the square-pyramidal geometry. This precursor has a lower melting point and superior stability to air, moisture, and heat than the Cu(hfacac)(2)(xH(2)O) precursor. The deposition rate of copper oxide film on a Pt layer above 450 degrees C was nearly constant with increasing temperature, indicating a mass transport limited reaction. Therefore it would be a useful metal organic chemical vapor deposition precursor for the fabrication of copper oxide film or superconducting materials. Crystal data for Cu(hfacac)(2)(t-BuNH(2)): 293(2) K, a = 9.6699(4) A, b = 18.0831(10) A, c = 12.8864(11) A, beta = 111.839(5) degrees, monoclinic, space group P2(1)/c, Z = 4.

TESTS OF LOW-FREQUENCY GEOMETRIC DISTORTIONS IN LANDSAT 4 IMAGES.

USGS Publications Warehouse

Batson, R.M.; Borgeson, W.T.; ,

1985-01-01

Tests were performed to investigate the geometric characteristics of Landsat 4 images. The first set of tests was designed to determine the extent of image distortion caused by the physical process of writing the Landsat 4 images on film. The second was designed to characterize the geometric accuracies inherent in the digital images themselves. Test materials consisted of film images of test targets generated by the Laser Beam Recorders at Sioux Falls, the Optronics* Photowrite film writer at Goddard Space Flight Center, and digital image files of a strip 600 lines deep across the full width of band 5 of the Washington, D. C. Thematic Mapper scene. The tests were made by least-squares adjustment of an array of measured image points to a corresponding array of control points.

Volume and tissue composition preserving deformation of breast CT images to simulate breast compression in mammographic imaging

NASA Astrophysics Data System (ADS)

Han, Tao; Chen, Lingyun; Lai, Chao-Jen; Liu, Xinming; Shen, Youtao; Zhong, Yuncheng; Ge, Shuaiping; Yi, Ying; Wang, Tianpeng; Shaw, Chris C.

2009-02-01

Images of mastectomy breast specimens have been acquired with a bench top experimental Cone beam CT (CBCT) system. The resulting images have been segmented to model an uncompressed breast for simulation of various CBCT techniques. To further simulate conventional or tomosynthesis mammographic imaging for comparison with the CBCT technique, a deformation technique was developed to convert the CT data for an uncompressed breast to a compressed breast without altering the breast volume or regional breast density. With this technique, 3D breast deformation is separated into two 2D deformations in coronal and axial views. To preserve the total breast volume and regional tissue composition, each 2D deformation step was achieved by altering the square pixels into rectangular ones with the pixel areas unchanged and resampling with the original square pixels using bilinear interpolation. The compression was modeled by first stretching the breast in the superior-inferior direction in the coronal view. The image data were first deformed by distorting the voxels with a uniform distortion ratio. These deformed data were then deformed again using distortion ratios varying with the breast thickness and re-sampled. The deformation procedures were applied in the axial view to stretch the breast in the chest wall to nipple direction while shrinking it in the mediolateral to lateral direction re-sampled and converted into data for uniform cubic voxels. Threshold segmentation was applied to the final deformed image data to obtain the 3D compressed breast model. Our results show that the original segmented CBCT image data were successfully converted into those for a compressed breast with the same volume and regional density preserved. Using this compressed breast model, conventional and tomosynthesis mammograms were simulated for comparison with CBCT.

Conformal Pad-Printing Electrically Conductive Composites onto Thermoplastic Hemispheres: Toward Sustainable Fabrication of 3-Cents Volumetric Electrically Small Antennas.

PubMed

Wu, Haoyi; Chiang, Sum Wai; Yang, Cheng; Lin, Ziyin; Liu, Jingping; Moon, Kyoung-Sik; Kang, Feiyu; Li, Bo; Wong, Ching Ping

2015-01-01

Electrically small antennas (ESAs) are becoming one of the key components in the compact wireless devices for telecommunications, defence, and aerospace systems, especially for the spherical one whose geometric layout is more closely approaching Chu's limit, thus yielding significant bandwidth improvements relative to the linear and planar counterparts. Yet broad applications of the volumetric ESAs are still hindered since the low cost fabrication has remained a tremendous challenge. Here we report a state-of-the-art technology to transfer electrically conductive composites (ECCs) from a planar mould to a volumetric thermoplastic substrate by using pad-printing technology without pattern distortion, benefit from the excellent properties of the ECCs as well as the printing-calibration method that we developed. The antenna samples prepared in this way meet the stringent requirement of an ESA (ka is as low as 0.32 and the antenna efficiency is as high as 57%), suggesting that volumetric electronic components i.e. the antennas can be produced in such a simple, green, and cost-effective way. This work can be of interest for the development of studies on green and high performance wireless communication devices.

The Radio Spectra and - Inertial Defects Behavior of Planar Aromatic Heterocycles

NASA Astrophysics Data System (ADS)

McNaughton, Don; Jahn, Michaela K.; Grabow, Jens-Uwe; Godfrey, Peter; Travers, Michael; Wachsmuth, Dennis

2016-06-01

The simplest tricyclic aromatic nitrogen heterocyclic molecules 5,6 benzoquinoline and 7,8 benzoquinoline are possible candidates for detection of aromatic systems in the interstellar medium. Therefore the pure rotational spectra have been recorded using frequency-scanned Stark modulated, jet-cooled millimetre wave absorption spectroscopy (48-87 GHz) and Fourier Transform Microwave (FT MW) spectroscopy (2-26 GHz) of a supersonic rotationally cold molecular jet. Guided by ab initio molecular orbital predictions, spectral analysis of mm wave spectra, and higher resolution FT MW spectroscopy provided accurate rotational and centrifugal distortion constants together with 14N nuclear quadrupole coupling constants for both species. The determined inertial defects, along with those of similar species are used to develop an empirical formula for calculation of inertial defects of aromatic ring systems. The predictive ability of the formula is shown to be excellent for planar species with a number of pronounced out of plane vibrations. The resultant constants are of sufficient accuracy to be used in potential astrophysical searches. We gratefully acknowledge support from the Deutsche Forschungsgemeinschaft, the Deutsche Akademische Austauschdienst, as well as the Land Niedersachsen (J.-U.G). DMcN also thanks the Royal Society of Chemistry for their generous travel support.

Anthraquinones quinizarin and danthron unwind negatively supercoiled DNA and lengthen linear DNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verebová, Valéria; Adamcik, Jozef; Danko, Patrik

2014-01-31

Highlights: • Anthraquinones quinizarin and danthron unwind negatively supercoiled DNA. • Anthraquinones quinizarin and danthron lengthen linear DNA. • Anthraquinones quinizarin and danthron possess middle binding affinity to DNA. • Anthraquinones quinizarin and danthron interact with DNA by intercalating mode. - Abstract: The intercalating drugs possess a planar aromatic chromophore unit by which they insert between DNA bases causing the distortion of classical B-DNA form. The planar tricyclic structure of anthraquinones belongs to the group of chromophore units and enables anthraquinones to bind to DNA by intercalating mode. The interactions of simple derivatives of anthraquinone, quinizarin (1,4-dihydroxyanthraquinone) and danthron (1,8-dihydroxyanthraquinone),more » with negatively supercoiled and linear DNA were investigated using a combination of the electrophoretic methods, fluorescence spectrophotometry and single molecule technique an atomic force microscopy. The detection of the topological change of negatively supercoiled plasmid DNA, unwinding of negatively supercoiled DNA, corresponding to appearance of DNA topoisomers with the low superhelicity and an increase of the contour length of linear DNA in the presence of quinizarin and danthron indicate the binding of both anthraquinones to DNA by intercalating mode.« less

Secondary flow vortical structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

NASA Astrophysics Data System (ADS)

Najjari, Mohammad Reza; Plesniak, Michael W.

2018-01-01

Secondary flow structures in a 180∘ curved pipe model of an artery are studied using particle image velocimetry. Both steady and pulsatile inflow conditions are investigated. In planar curved pipes with steady flow, multiple (two, four, six) vortices are detected. For pulsatile flow, various pairs of vortices, i.e., Dean, deformed-Dean, Lyne-type, and split-Dean, are present in the cross section of the pipe at 90∘ into the bend. The effects of nonplanar curvature (torsion) and vessel dilatation on these vortical structures are studied. Torsion distorts the symmetric secondary flows (which exist in planar curvatures) and can result in formation of more complex vortical structures. For example, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together in pulsatile flow. The vortical structures in elastic vessels with dilatation (0.61%-3.23%) are also investigated and the results are compared with rigid model results. It was found that the secondary flow structures in rigid and elastic models are similar, and hence the local compliance of the vessel does not affect the morphology of secondary flow structures.

JPEG 2000 Encoding with Perceptual Distortion Control

NASA Technical Reports Server (NTRS)

Watson, Andrew B.; Liu, Zhen; Karam, Lina J.

2008-01-01

An alternative approach has been devised for encoding image data in compliance with JPEG 2000, the most recent still-image data-compression standard of the Joint Photographic Experts Group. Heretofore, JPEG 2000 encoding has been implemented by several related schemes classified as rate-based distortion-minimization encoding. In each of these schemes, the end user specifies a desired bit rate and the encoding algorithm strives to attain that rate while minimizing a mean squared error (MSE). While rate-based distortion minimization is appropriate for transmitting data over a limited-bandwidth channel, it is not the best approach for applications in which the perceptual quality of reconstructed images is a major consideration. A better approach for such applications is the present alternative one, denoted perceptual distortion control, in which the encoding algorithm strives to compress data to the lowest bit rate that yields at least a specified level of perceptual image quality. Some additional background information on JPEG 2000 is prerequisite to a meaningful summary of JPEG encoding with perceptual distortion control. The JPEG 2000 encoding process includes two subprocesses known as tier-1 and tier-2 coding. In order to minimize the MSE for the desired bit rate, a rate-distortion- optimization subprocess is introduced between the tier-1 and tier-2 subprocesses. In tier-1 coding, each coding block is independently bit-plane coded from the most-significant-bit (MSB) plane to the least-significant-bit (LSB) plane, using three coding passes (except for the MSB plane, which is coded using only one "clean up" coding pass). For M bit planes, this subprocess involves a total number of (3M - 2) coding passes. An embedded bit stream is then generated for each coding block. Information on the reduction in distortion and the increase in the bit rate associated with each coding pass is collected. This information is then used in a rate-control procedure to determine the contribution of each coding block to the output compressed bit stream.

Estimators of The Magnitude-Squared Spectrum and Methods for Incorporating SNR Uncertainty

PubMed Central

Lu, Yang; Loizou, Philipos C.

2011-01-01

Statistical estimators of the magnitude-squared spectrum are derived based on the assumption that the magnitude-squared spectrum of the noisy speech signal can be computed as the sum of the (clean) signal and noise magnitude-squared spectra. Maximum a posterior (MAP) and minimum mean square error (MMSE) estimators are derived based on a Gaussian statistical model. The gain function of the MAP estimator was found to be identical to the gain function used in the ideal binary mask (IdBM) that is widely used in computational auditory scene analysis (CASA). As such, it was binary and assumed the value of 1 if the local SNR exceeded 0 dB, and assumed the value of 0 otherwise. By modeling the local instantaneous SNR as an F-distributed random variable, soft masking methods were derived incorporating SNR uncertainty. The soft masking method, in particular, which weighted the noisy magnitude-squared spectrum by the a priori probability that the local SNR exceeds 0 dB was shown to be identical to the Wiener gain function. Results indicated that the proposed estimators yielded significantly better speech quality than the conventional MMSE spectral power estimators, in terms of yielding lower residual noise and lower speech distortion. PMID:21886543

[Locally weighted least squares estimation of DPOAE evoked by continuously sweeping primaries].

PubMed

Han, Xiaoli; Fu, Xinxing; Cui, Jie; Xiao, Ling

2013-12-01

Distortion product otoacoustic emission (DPOAE) signal can be used for diagnosis of hearing loss so that it has an important clinical value. Continuously using sweeping primaries to measure DPOAE provides an efficient tool to record DPOAE data rapidly when DPOAE is measured in a large frequency range. In this paper, locally weighted least squares estimation (LWLSE) of 2f1-f2 DPOAE is presented based on least-squares-fit (LSF) algorithm, in which DPOAE is evoked by continuously sweeping tones. In our study, we used a weighted error function as the loss function and the weighting matrixes in the local sense to obtain a smaller estimated variance. Firstly, ordinary least squares estimation of the DPOAE parameters was obtained. Then the error vectors were grouped and the different local weighting matrixes were calculated in each group. And finally, the parameters of the DPOAE signal were estimated based on least squares estimation principle using the local weighting matrixes. The simulation results showed that the estimate variance and fluctuation errors were reduced, so the method estimates DPOAE and stimuli more accurately and stably, which facilitates extraction of clearer DPOAE fine structure.

The cluster Ir4 and its interaction with a hydrogen impurity. A density functional study.

PubMed

Bussai, Chuenchit; Krüger, Sven; Vayssilov, Georgi N; Rösch, Notker

2005-07-07

To contribute to the understanding of how iridium particles act as catalysts for hydrogenation and dehydrogenation of hydrocarbons, we have determined structures and binding energies of various isomers of Ir(4) as well as HIr(4) on the basis of relativistic density functional theory. The most stable isomer of Ir(4) showed a square planar structure with eight unpaired electrons. The tetrahedral structure, experimentally suggested for supported species, was calculated 49 kJ mol(-1) less stable. Hydrogen coordinates preferentially to a single Ir center of the planar cluster with a binding energy of up to 88 kJ mol(-1) with respect to the atom in the H(2) molecule. Terminal interaction of hydrogen with an Ir(4) tetrahedron causes the cluster to open to a butterfly structure. We calculated terminal binding of hydrogen at different Ir(4) isomers to be more stable than bridge coordination, at variance with earlier studies.

A 2 epoch proper motion catalogue from the UKIDSS Large Area Survey

NASA Astrophysics Data System (ADS)

Smith, Leigh; Lucas, Phil; Burningham, Ben; Jones, Hugh; Pinfield, David; Smart, Ricky; Andrei, Alexandre

2013-04-01

The UKIDSS Large Area Survey (LAS) began in 2005, with the start of the UKIDSS program as a 7 year effort to survey roughly 4000 square degrees at high galactic latitudes in Y, J, H and K bands. The survey also included a significant quantity of 2-epoch J band observations, with epoch baselines ranging from 2 to 7 years. We present a proper motion catalogue for the 1500 square degrees of the 2 epoch LAS data, which includes some 800,000 sources with motions detected above the 5σ level. We developed a bespoke proper motion pipeline which applies a source-unique second order polynomial transformation to UKIDSS array coordinates of each source to counter potential local non-uniformity in the focal plane. Our catalogue agrees well with the proper motion data supplied in the current WFCAM Science Archive (WSA) DR9 catalogue where there is overlap, and in various optical catalogues, but it benefits from some improvements. One improvement is that we provide absolute proper motions, using LAS galaxies for the relative to absolute correction. Also, by using unique, local, 2nd order polynomial tranformations, as opposed to the linear transformations in the WSA, we correct better for any local distortions in the focal plane, not including the radial distortion that is removed by their pipeline.

A masked least-squares smoothing procedure for artifact reduction in scanning-EMG recordings.

PubMed

Corera, Íñigo; Eciolaza, Adrián; Rubio, Oliver; Malanda, Armando; Rodríguez-Falces, Javier; Navallas, Javier

2018-01-11

Scanning-EMG is an electrophysiological technique in which the electrical activity of the motor unit is recorded at multiple points along a corridor crossing the motor unit territory. Correct analysis of the scanning-EMG signal requires prior elimination of interference from nearby motor units. Although the traditional processing based on the median filtering is effective in removing such interference, it distorts the physiological waveform of the scanning-EMG signal. In this study, we describe a new scanning-EMG signal processing algorithm that preserves the physiological signal waveform while effectively removing interference from other motor units. To obtain a cleaned-up version of the scanning signal, the masked least-squares smoothing (MLSS) algorithm recalculates and replaces each sample value of the signal using a least-squares smoothing in the spatial dimension, taking into account the information of only those samples that are not contaminated with activity of other motor units. The performance of the new algorithm with simulated scanning-EMG signals is studied and compared with the performance of the median algorithm and tested with real scanning signals. Results show that the MLSS algorithm distorts the waveform of the scanning-EMG signal much less than the median algorithm (approximately 3.5 dB gain), being at the same time very effective at removing interference components. Graphical Abstract The raw scanning-EMG signal (left figure) is processed by the MLSS algorithm in order to remove the artifact interference. Firstly, artifacts are detected from the raw signal, obtaining a validity mask (central figure) that determines the samples that have been contaminated by artifacts. Secondly, a least-squares smoothing procedure in the spatial dimension is applied to the raw signal using the not contaminated samples according to the validity mask. The resulting MLSS-processed scanning-EMG signal (right figure) is clean of artifact interference.

Cyclometalated 6-phenyl-2,2'-bipyridyl (CNN) platinum(II) acetylide complexes: structure, electrochemistry, photophysics, and oxidative- and reductive-quenching studies.

PubMed

Schneider, Jacob; Du, Pingwu; Jarosz, Paul; Lazarides, Theodore; Wang, Xiaoyong; Brennessel, William W; Eisenberg, Richard

2009-05-18

Three cyclometalated 6-phenyl-4-(p-R-phenyl)-2,2'-bipyridyl (CNN-Ph-R) Pt(II) acetylide complexes, Pt(CNN-Ph-R)(CCPh), where R = Me (1), COOMe (2), and P(O)(OEt)(2) (3), have been synthesized and studied. Compounds 1 and 3 have been structurally characterized by single crystal X-ray crystallography and are found to exhibit distorted square planar geometries about the Pt(II) ions. The electrochemical properties of the compounds, as determined by cyclic voltammetry, have also been examined. Complexes 1-3 are brightly emissive in fluid CH(2)Cl(2) solution and in the solid state with lambda(em)(max) of ca. 600 nm and lifetimes on the order of ca. 500 ns in fluid solution. The emissions are assigned to a (3)MLCT transition. The complexes undergo oxidative quenching by MV(2+) with quenching rates near the diffusion-controlled limit (k(q) approximately 1.4 x 10(10) M(-1) s(-1)) in CH(2)Cl(2) solution. Reductive-quenching experiments of complexes 1-3 by the amine donors N,N,N',N'-tetramethylphenylenediamine (TMPD), phenothiazine (PTZ), and N,N,N',N'-tetramethylbenzidine (TMB) follow Stern-Volmer behavior, with very fast quenching rates on the order of 10(9)-10(10) M(-1) s(-1) in CH(2)Cl(2) solution. When the complexes are employed as the sensitizer in multiple component systems containing MV(2+), TEOA, and colloidal Pt in aqueous media, approximately one turnover of H(2) (TN vs mol of chromophore) is produced per hour upon irradiation with lambda > 410 nm but only after at least a 2 h induction period.

Novel Cu(I)-selective chelators based on a bis(phosphorothioyl)amide scaffold.

PubMed

Amir, Aviran; Ezra, Alon; Shimon, Linda J W; Fischer, Bilha

2014-08-04

Bis(dialkyl/aryl-phosphorothioyl)amide (BPA) derivatives are versatile ligands known by their high metal-ion affinity and selectivity. Here, we synthesized related chelators based on bis(1,3,2-dithia/dioxaphospholane-2-sulfide)amide (BTPA/BOPA) scaffolds targeting the chelation of soft metal ions. Crystal structures of BTPA compounds 6 (N(-)R3NH(+)) and 8 (NEt) revealed a gauche geometry, while BOPA compound 7 (N(-)R3NH(+)) exhibited an anti-geometry. Solid-state (31)P magic-angle spinning NMR spectra of BTPA 6-Hg(II) and 6-Zn(II) complexes imply a square planar or tetrahedral geometry of the former and a distorted tetrahedral geometry of the latter, while both BTPA 6-Ni(II) and BOPA 7-Ni(II) complexes possibly form a polymeric structure. In Cu(I)-H2O2 system (Fenton reaction conditions) BTPA compounds 6, 8, and 10 (NCH2Ph) were identified as most potent antioxidants (IC50 32, 56, and 29 μM, respectively), whereas BOPA analogues 7, 9 (NEt), and 11 (NCH2Ph) were found to be poor antioxidants. In Fe(II)-H2O2 system, IC50 values for both BTPA and BOPA compounds exceeded 500 μM indicating high selectivity to Cu(I) versus the borderline Fe(II)-ion. Neither BTPA nor BOPA derivatives showed radical scavenging properties in H2O2 photolysis, implying that inhibition of the Cu(I)-induced Fenton reaction by both BTPA and BOPA analogues occurred predominantly through Cu(I)-chelation. In addition, NMR-monitored Cu(I)- and Zn(II)-titration of BTPA compounds 8 and 10 showed their high selectivity to a soft metal ion, Cu(I), as compared to a borderline metal ion, Zn(II). In summary, lipophilic BTPA analogues are promising highly selective Cu(I) ion chelators.

Microwave spectrum of o-benzyne produced in a discharge nozzle

NASA Astrophysics Data System (ADS)

Kukolich, S. G.; Tanjaroon, C.; McCarthy, M. C.; Thaddeus, P.

2003-08-01

The microwave spectrum for o-benzyne was obtained by passing a dilute (<1%) mixture of benzene in neon through a pulsed-DC discharge nozzle source into a pulsed-beam, Fourier transform spectrometer. Rotational transitions were measured for the normal isotopomer, the two unique single-D isotopomers, and the 13C isotopomer and one of the 13C isotopomers. Benzynes have been known as reactive intermediates in organic reactions for many years, and have recently been implicated in gasoline combustion reactions and antitumor activity of enediynes. Twenty-seven b-type transitions for the normal isotopomer were fit to obtain A=6989.7292(6), B=5706.8062(6), and C=3140.3708(4) MHz, and five centrifugal distortion constants. The inertial defect is Δ=0.069 4 amu Å2, consistent with a planar structure. Hyperfine structure for the D1 (closest to the CtrpbndC bond) and D2 (furthest from the CtrpbndC bond), was analyzed to obtain deuterium quadrupole coupling strengths eQqaa(D1)=185(3) kHz, eQqbb(D1)=-85(2) kHz, eQqaa(D2)=5(13), and eQqbb(D2)=86(13) kHz. The C-D, bond axis quadrupole coupling strengths are compared with values for benzene. Spectra for the 13C6 and one of the 13C1 isotopomers were analyzed to obtain rotational constants. Kraitchman analysis and least-squares fitting provided nearly all of the structural parameters. The preliminary structural analysis yields an acetylenic C≡C bond length of 1.24 Å, in agreement with a recent NMR value. Density functional theory (DFT) calculations were used to obtain structural parameters, and values obtained are in very good agreement with present experimental results.

Interaction between transition metals and phenylalanine: a combined experimental and computational study.

PubMed

Elius Hossain, Md; Mahmudul Hasan, Md; Halim, M E; Ehsan, M Q; Halim, Mohammad A

2015-03-05

Some transition metal complexes of phenylalanine of general formula [M(C9H10NO2)2]; where M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) are prepared in aqueous medium and characterized by spectroscopic, thermo-gravimetric (TG) and magnetic susceptibility analysis. Density functional theory (DFT) has been employed calculating the equilibrium geometries and vibrational frequencies of those complexes at B3LYP level of theory using 6-31G(d) and SDD basis sets. In addition, frontier molecular orbital and time-dependent density functional theory (TD-DFT) calculations are performed with CAM-B3LYP/6-31+G(d,p) and B3LYP/SDD level of theories. Thermo-gravimetric analysis confirms the composition of the complexes by comparing the experimental and calculated data for C, H, N and metals. Experimental and computed IR results predict a significant change in vibrational frequencies of metal-phenylalanine complexes compared to free ligand. DFT calculation confirms that Mn, Co, Ni and Cu complexes form square planar structure whereas Zn adopts distorted tetrahedral geometry. The metal-oxygen bonds in the optimized geometry of all complexes are shorter compared to the metal-nitrogen bonds which is consistent with a previous study. Cation-binding energy, enthalpy and Gibbs free energy indicates that these complexes are thermodynamically stable. UV-vis and TD-DFT studies reveal that these complexes demonstrate representative metal-to-ligand charge transfer (MLCT) and d-d transitions bands. TG analysis and IR spectra of the metal complexes strongly support the absence of water in crystallization. Magnetic susceptibility data of the complexes exhibits that all except Zn(II) complex are high spin paramagnetic. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis, spectroscopic characterization, electrochemical behavior and computational analysis of mixed diamine ligand gold(III) complexes: antiproliferative and in vitro cytotoxic evaluations against human cancer cell lines.

PubMed

Al-Jaroudi, Said S; Monim-ul-Mehboob, M; Altaf, Muhammad; Al-Saadi, Abdulaziz A; Wazeer, Mohammed I M; Altuwaijri, Saleh; Isab, Anvarhusein A

2014-12-01

The gold(III) complexes of the type [(DACH)Au(en)]Cl3, 1,2-Diaminocyclohexane ethylenediamine gold(III) chloride [where 1,2-DACH = cis-, trans-1,2- and S,S-1,2diaminocyclohexane and en = ethylenediamine] have been synthesized and characterized using various analytical and spectroscopic techniques including elemental analysis, UV-Vis and FTIR spectra; and solution as well as solid-state NMR measurements. The solid-state (13)C NMR shows that 1,2-diaminocyclohexane (1,2-DACH) and ethylenediamine (en) are strongly bound to the gold(III) center via N donor atoms. The stability of the mixed diamine ligand gold(III) was determined by (1)H and (13)C NMR spectra. Their electrochemical behavior was studied by cyclic voltammetry. The structural details and relative stabilities of the four possible isomers of the complexes were also reported at the B3LYP/LANL2DZ level of theory. The coordination sphere of these complexes around gold(III) center adopts distorted square planar geometry. The computational study also demonstrates that trans- conformations is slightly more stable than the cis-conformations. The antiproliferative effects and cytotoxic properties of the mixed diamine ligand gold(III) complexes were evaluated in vitro on human gastric SGC7901 and prostate PC3 cancer cells using MTT assay. The antiproliferative study of the gold(III) complexes on PC3 and SGC7901 cells indicate that complex 1 is the most effective antiproliferative agent among mixed ligand based gold(III) complexes 1-3. The IC50 data reveal that the in vitro cytotoxicity of complexes 1 and 3 against SGC7901 cancer cells are fairly better than that of cisplatin.

Crystal structure of a mononuclear Ru(II) complex with a back-to-back terpyridine ligand: [RuCl(bpy)(tpy-tpy)](.).

PubMed

Rein, Francisca N; Chen, Weizhong; Scott, Brian L; Rocha, Reginaldo C

2015-09-01

We report the structural characterization of [6',6''-bis-(pyridin-2-yl)-2,2':4',4'':2'',2'''-quaterpyridine](2,2'-bi-pyridine)-chlorido-ruthenium(II) hexa-fluorido-phosphate, [RuCl(C10H8N2)(C30H20N6)]PF6, which contains the bidentate ligand 2,2'-bi-pyridine (bpy) and the tridendate ligand 6',6''-bis-(pyridin-2-yl)-2,2':4',4'':2'',2'''-quaterpyridine (tpy-tpy). The [RuCl(bpy)(tpy-tpy)](+) monocation has a distorted octa-hedral geometry at the central Ru(II) ion due to the restricted bite angle [159.32 (16)°] of the tridendate ligand. The Ru-bound tpy and bpy moieties are nearly planar and essentially perpendicular to each other with a dihedral angle of 89.78 (11)° between the least-squares planes. The lengths of the two Ru-N bonds for bpy are 2.028 (4) and 2.075 (4) Å, with the shorter bond being opposite to Ru-Cl. For tpy-tpy, the mean Ru-N distance involving the outer N atoms trans to each other is 2.053 (8) Å, whereas the length of the much shorter bond involving the central N atom is 1.936 (4) Å. The Ru-Cl distance is 2.3982 (16) Å. The free uncoordinated moiety of tpy-tpy adopts a trans,trans conformation about the inter-annular C-C bonds, with adjacent pyridyl rings being only approximately coplanar. The crystal packing shows significant π-π stacking inter-actions based on tpy-tpy. The crystal structure reported here is the first for a tpy-tpy complex of ruthenium.

Synthesis, spectroscopic characterization, DFT calculations and biological evaluation of benzothiazole derivative bearing Mn(II) and Ni(II) metal ions

NASA Astrophysics Data System (ADS)

El-Gamel, Nadia E. A.; Ali, Korany A.

2017-11-01

N-(benzo[d]thiazol-2-yl)-3-oxo-3-phenylpropanamide ligand and its Nickel and Manganese complexes have been synthesized and characterized by elemental and thermal analyses, IR, diffuse reflectance, mass and UV-Vis spectra, molar conductance and magnetic moment measurements. The decomposition mechanism and thermal stability of the investigated complexes are interpreted in terms of their structures. The thermal behaviour of the complexes has been studied and different thermodynamic parameters are calculated using Coats-Redfern method. N-(benzo[d]thiazol-2-yl)-3-oxo-3-phenylpropanamide is a neutral bidentate ligand coordinating metal ions via thiazole ring nitrogen and amide carbonyl O forming high spin octahedral complexes with Mn(II) (2) and distorted square planar in case of Ni(II) (1). Natural bond orbital analysis and geometry optimization were carried out at DFT/B3LYP/6-31G(d) level of theory for the ligand and the mentioned complexes. Ab inito computations at the HF/6-31G(d) level of the theory is conducted in order to detect any probability of a hydrogen bond formation in the ligand. The dipole moment of the Ni(II) and Mn(II) complexes is recorded to be 9.69 and 7.39 Debye, respectively, indicating that the complexes are more polarized than the ligand 2.39 Debye. The in vitro biological activity of the metal chelates is screened against the Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli), fungus (Aspergillus flavus, Candida albicans). Ni(II) complexes displayed the highest activity against Candida albicans and Staphylococcus aureus with MIC values of 13, 30 μg/cm3, respectively.

The output least-squares approach to estimating Lamé moduli

NASA Astrophysics Data System (ADS)

Gockenbach, Mark S.

2007-12-01

The Lamé moduli of a heterogeneous, isotropic, planar membrane can be estimated by observing the displacement of the membrane under a known edge traction, and choosing estimates of the moduli that best predict the observed displacement under a finite-element simulation. This algorithm converges to the exact moduli given pointwise measurements of the displacement on an increasingly fine mesh. The error estimates that prove this convergence also show the instability of the inverse problem.

Metal-organic polyhedron based on a Cu(II) paddle-wheel secondary building unit at the truncated octahedron corners.

PubMed

Prakash, M Jaya; Zou, Yang; Hong, Seunghee; Park, Mira; Bui, Minh-Phuong Ngoc; Seong, Gi Hun; Lah, Myoung Soo

2009-02-16

A metal-organic polyhedron of truncated octahedral geometry augmented with a C(4)-symmetric square-planar Cu(II) paddle-wheel node as a secondary building unit can be prepared using a C(3)-symmetric ligand that occupies the face of the octahedral cage, where the three phenyl groups containing a m-carboxylate group in the ligand provide the necessary curvature to form the finite octahedral cage.

Active control of Boundary Layer Separation & Flow Distortion in Adverse Pressure Gradient Flows via Supersonic Microjets

NASA Technical Reports Server (NTRS)

Alvi, Farrukh S.; Gorton, Susan (Technical Monitor)

2005-01-01

Inlets to aircraft propulsion systems must supply flow to the compressor with minimal pressure loss, flow distortion or unsteadiness. Flow separation in internal flows such as inlets and ducts in aircraft propulsion systems and external flows such as over aircraft wings, is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control this flow separation. In particular, the use of supersonic microjets as a means of controlling boundary layer separation was explored. The geometry used for the early part of this study was a simple diverging Stratford ramp, equipped with arrays of supersonic microjets. Initial results, based on the mean surface pressure distribution, surface flow visualization and Planar Laser Scattering (PLS) indicated a reverse flow region. We implemented supersonic microjets to control this separation and flow visualization results appeared to suggest that microjets have a favorable effect, at least to a certain extent. However, the details of the separated flow field were difficult to determine based on surface pressure distribution, surface flow patterns and PLS alone. It was also difficult to clearly determine the exact influence of the supersonic microjets on this flow. In the latter part of this study, the properties of this flow-field and the effect of supersonic microjets on its behavior were investigated in further detail using 2-component (planar) Particle Image Velocimetry (PIV). The results clearly show that the activation of microjets eliminated flow separation and resulted in a significant increase in the momentum of the fluid near the ramp surface. Also notable is the fact that the gain in momentum due to the elimination of flow separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very little mass flow through the microjets.

Topological superfluids confined in a nanoscale slab geometry

NASA Astrophysics Data System (ADS)

Saunders, John

2013-03-01

Nanofluidic samples of superfluid 3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid 3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of 3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe 3He-B with a surface induced planar distortion. 3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter. Supported by EPSRC (UK) GR/J022004/1 and European Microkelvin Consortium, FP7 grant 228464

Evaluation of diffusivity in the anterior lobe of the pituitary gland: 3D turbo field echo with diffusion-sensitized driven-equilibrium preparation.

PubMed

Hiwatashi, A; Yoshiura, T; Togao, O; Yamashita, K; Kikuchi, K; Kobayashi, K; Ohga, M; Sonoda, S; Honda, H; Obara, M

2014-01-01

3D turbo field echo with diffusion-sensitized driven-equilibrium preparation is a non-echo-planar technique for DWI, which enables high-resolution DWI without field inhomogeneity-related image distortion. The purpose of this study was to evaluate the feasibility of diffusion-sensitized driven-equilibrium turbo field echo in evaluating diffusivity in the normal pituitary gland. First, validation of diffusion-sensitized driven-equilibrium turbo field echo was attempted by comparing it with echo-planar DWI. Five healthy volunteers were imaged by using diffusion-sensitized driven-equilibrium turbo field echo and echo-planar DWI. The imaging voxel size was 1.5 × 1.5 × 1.5 mm(3) for diffusion-sensitized driven-equilibrium turbo field echo and 1.5 × 1.9 × 3.0 mm(3) for echo-planar DWI. ADCs measured by the 2 methods in 15 regions of interests (6 in gray matter and 9 in white matter) were compared by using the Pearson correlation coefficient. The ADC in the pituitary anterior lobe was then measured in 10 volunteers by using diffusion-sensitized driven-equilibrium turbo field echo, and the results were compared with those in the pons and vermis by using a paired t test. The ADCs from the 2 methods showed a strong correlation (r = 0.79; P < .0001), confirming the accuracy of the ADC measurement with the diffusion-sensitized driven-equilibrium sequence. The ADCs in the normal pituitary gland were 1.37 ± 0.13 × 10(-3) mm(2)/s, which were significantly higher than those in the pons (1.01 ± 0.24 × 10(-3) mm(2)/s) and the vermis (0.89 ± 0.25 × 10(-3) mm(2)/s, P < .01). We demonstrated that diffusion-sensitized driven-equilibrium turbo field echo is feasible in assessing ADC in the pituitary gland.

Excited-State Conformational/Electronic Responses of Saddle-Shaped N,N'-Disubstituted-Dihydrodibenzo[a,c]phenazines: Wide-Tuning Emission from Red to Deep Blue and White Light Combination.

PubMed

Zhang, Zhiyun; Wu, Yu-Sin; Tang, Kuo-Chun; Chen, Chi-Lin; Ho, Jr-Wei; Su, Jianhua; Tian, He; Chou, Pi-Tai

2015-07-08

A tailored strategy is utilized to modify 5,10-dimethylphenazine (DMP) to donor-acceptor type N,N'-disubstituted-dihydrodibenzo[a,c]phenazines. The representative compounds DMAC (N,N'-dimethyl), DPAC (N,N'-diphenyl), and FlPAC (N-phenyl-N'-fluorenyl) reveal significant nonplanar distortions (i.e., a saddle shape) and remarkably large Stokes-shifted emission independent of the solvent polarity. For DPAC and FlPAC with higher steric hindrance on the N,N'-substituents, normal Stokes-shifted emission also appears, for which the peak wavelength reveals solvent-polarity dependence. These unique photophysical behaviors are rationalized by electronic configuration coupled conformation changes en route to the geometry planarization in the excited state. This proposed mechanism is different from the symmetry rule imposed to explain the anomalously long-wavelength emission for DMP and is firmly supported by polarity-, viscosity-, and temperature-dependent steady-state and nanosecond time-resolved spectroscopy. Together with femtosecond early dynamics and computational simulation of the reaction energy surfaces, the results lead us to establish a sequential, three-step kinetics. Upon electronic excitation of N,N'-disubstituted-dihydrodibenzo[a,c]phenazines, intramolecular charge-transfer takes place, followed by the combination of polarization stabilization and skeletal motion toward the planarization, i.e., elongation of the π-delocalization over the benzo[a,c]phenazines moiety. Along the planarization, DPAC and FlPAC encounter steric hindrance raised by the N,N'-disubstitutes, resulting in a local minimum state, i.e., the intermediate. The combination of initial charge-transfer state, intermediate, and the final planarization state renders the full spectrum of interest and significance in their anomalous photophysics. Depending on rigidity, the N,N'-disubstituted-dihydrodibenzo[a,c]phenazines exhibit multiple emissions, which can be widely tuned from red to deep blue and even to white light generation upon optimization of the surrounding media.

Synthesis of Two New Group 13 Benzoato-Chloro Complexes: A Structural Study of Gallium and Indium Chelating Carboxylates

NASA Technical Reports Server (NTRS)

Duraj, Stan A.; Hepp, Aloysius F.; Woloszynek, Robert; Protasiewicz, John D.; Dequeant, Michael; Ren, Tong

2010-01-01

Two new heteroleptic chelated-benzoato gallium (III) and indium (III) complexes have been prepared and structurally characterized. The molecular structures of [GaCl2(4-Mepy)2(O2CPh)]4-Mepy (1) and [InCl(4-Mepy)2(O2CPh)2]4-Mepy (2) have been determined by single-crystal x-ray diffraction. The gallium compound (1) is a distorted octahedron with cis-chloride ligands co-planar with the chelating benzoate and the 4-methylpyridines trans to each other. This is the first example of a Ga(III) structure with a chelating benzoate. The indium compound (2) is a distorted pentagonal bipyramid with two chelating benzoates, one 4-methylpyridine in the plane and a chloride trans to the other 4-methylpyridine. The indium bis-benzoate is an unusual example of a seven-coordinate structure with classical ligands. Both complexes, which due to the chelates, could also be described as pseudo-trigonal bipyramidal, include a three-bladed motif with three roughly parallel aromatic rings that along with a solvent of crystallization and electron-withdrawing chloride ligand(s) stabilize the solid-state structures.

Referenceless one-dimensional Nyquist ghost correction in multicoil single-shot spatiotemporally encoded MRI.

PubMed

Chen, Ying; Liao, Yupeng; Yuan, Lisha; Liu, Hui; Yun, Seong Dae; Shah, Nadim Joni; Chen, Zhong; Zhong, Jianhui

2017-04-01

Single-shot spatiotemporally encoded (SPEN) MRI is a novel fast imaging method capable of retaining the time efficiency of single-shot echo planar imaging (EPI) but with distortion artifacts significantly reduced. Akin to EPI, the phase inconsistencies between mismatched even and odd echoes also result in the so-called Nyquist ghosts. However, the characteristic of the SPEN signals provides the possibility of obtaining ghost-free images directly from even and odd echoes respectively, without acquiring additional reference scans. In this paper, a theoretical analysis of the Nyquist ghosts manifested in single-shot SPEN MRI is presented, a one-dimensional correction scheme is put forward capable of maintaining definition of image features without blurring when the phase inconsistency along SPEN encoding direction is negligible, and a technique is introduced for convenient and robust correction of data from multi-channel receiver coils. The effectiveness of the proposed processing pipeline is validated by a series of experiments conducted on simulation data, in vivo rats and healthy human brains. The robustness of the method is further verified by implementing distortion correction on ghost corrected data. Copyright © 2016. Published by Elsevier Inc.

Near-field interaction of colloid near wavy walls

NASA Astrophysics Data System (ADS)

Luo, Yimin; Serra, Francesca; Wong, Denise; Steager, Edward; Stebe, Kathleen

Anisotropic media can be used to manipulate colloids, in tandem with carefully designed boundary conditions. For example, in bulk nematic liquid crystal, a wall with homeotropic anchoring repels a colloid with the same anchoring; yet by changing the surface topography from planar to concave, one can turn repulsion into attraction. We explore the behaviors of micro-particles with associated topological defects (hedgehogs or Saturn rings) near wavy walls. The walls locally excite disturbance, which decays into bulk. The range of influence is related to the curvature. The distortion can be used to position particles, either directly on the structure or at a distance away, based on the ``splay-matching'' rules. When distortion becomes stronger through the deepening of the well, the splay field created by the wall can prompt transformation from a Saturn ring to a hedgehog. We combine wells of different wavelength and depth to direct colloid movement. We apply a magnetic field to reset the initial position of ferromagnetic colloids and subsequently release them to probe the elastic energy landscape. Our platform enables manipulation, particle selection, and a detailed study of defect structure under the influence of curvature. Army Research Office.

Circular, confined distribution for charged particle beams

DOEpatents

Garnett, Robert W.; Dobelbower, M. Christian

1995-01-01

A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location.

Circular, confined distribution for charged particle beams

DOEpatents

Garnett, R.W.; Dobelbower, M.C.

1995-11-21

A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location. 26 figs.

JASMINE -- Japan Astrometry Satellite Mission for INfrared Exploration: Data Analysis and Accuracy Assessment with a Kalman Filter

NASA Astrophysics Data System (ADS)

Yamada, Y.; Shimokawa, T.; Shinomoto, S. Yano, T.; Gouda, N.

2009-09-01

For the purpose of determining the celestial coordinates of stellar positions, consecutive observational images are laid overlapping each other with clues of stars belonging to multiple plates. In the analysis, one has to estimate not only the coordinates of individual plates, but also the possible expansion and distortion of the frame. This problem reduces to a least-squares fit that can in principle be solved by a huge matrix inversion, which is, however, impracticable. Here, we propose using Kalman filtering to perform the least-squares fit and implement a practical iterative algorithm. We also estimate errors associated with this iterative method and suggest a design of overlapping plates to minimize the error.

Magnetic vortex excitation as spin torque oscillator and its unusual trajectories

NASA Astrophysics Data System (ADS)

Natarajan, Kanimozhi; Muthuraj, Ponsudana; Rajamani, Amuda; Arumugam, Brinda

2018-05-01

We report an interesting observation of unusual trajectories of vortex core oscillations in a spin valve pillar. Micromagnetic simulation in the composite free layer spin valve nano-pillar shows magnetic vortex excitation under critical current density. When current density is slightly increased and wave vector is properly tuned, for the first time we observe a star like and square gyration. Surprisingly this star like and square gyration also leads to steady, coherent and sustained oscillations. Moreover, the frequency of gyration is also very high for this unusual trajectories. The power spectral analysis reveals that there is a marked increase in output power and frequency with less distortions. Our investigation explores the possibility of these unusual trajectories to exhibit spin torque oscillations.

Response functions for dimers and square-symmetric molecules in four-wave-mixing experiments with polarized light

NASA Astrophysics Data System (ADS)

Smith, Eric Ryan; Farrow, Darcie A.; Jonas, David M.

2005-07-01

Four-wave-mixing nonlinear-response functions are given for intermolecular and intramolecular vibrations of a perpendicular dimer and intramolecular vibrations of a square-symmetric molecule containing a doubly degenerate state. A two-dimensional particle-in-a-box model is used to approximate the electronic wave functions and obtain harmonic potentials for nuclear motion. Vibronic interactions due to symmetry-lowering distortions along Jahn-Teller active normal modes are discussed. Electronic dephasing due to nuclear motion along both symmetric and asymmetric normal modes is included in these response functions, but population transfer between states is not. As an illustration, these response functions are used to predict the pump-probe polarization anisotropy in the limit of impulsive excitation.

Drawing road networks with focus regions.

PubMed

Haunert, Jan-Henrik; Sering, Leon

2011-12-01

Mobile users of maps typically need detailed information about their surroundings plus some context information about remote places. In order to avoid that the map partly gets too dense, cartographers have designed mapping functions that enlarge a user-defined focus region--such functions are sometimes called fish-eye projections. The extra map space occupied by the enlarged focus region is compensated by distorting other parts of the map. We argue that, in a map showing a network of roads relevant to the user, distortion should preferably take place in those areas where the network is sparse. Therefore, we do not apply a predefined mapping function. Instead, we consider the road network as a graph whose edges are the road segments. We compute a new spatial mapping with a graph-based optimization approach, minimizing the square sum of distortions at edges. Our optimization method is based on a convex quadratic program (CQP); CQPs can be solved in polynomial time. Important requirements on the output map are expressed as linear inequalities. In particular, we show how to forbid edge crossings. We have implemented our method in a prototype tool. For instances of different sizes, our method generated output maps that were far less distorted than those generated with a predefined fish-eye projection. Future work is needed to automate the selection of roads relevant to the user. Furthermore, we aim at fast heuristics for application in real-time systems. © 2011 IEEE

Doping effects on structural and magnetic properties of Heusler alloys Fe2Cr1-xCoxSi

NASA Astrophysics Data System (ADS)

Liu, Yifan; Ren, Lizhu; Zheng, Yuhong; He, Shikun; Liu, Yang; Yang, Ping; Yang, Hyunsoo; Teo, Kie Leong

2018-05-01

In this work, 30nm Fe2Cr1-xCoxSi (FCCS) magnetic films were deposited on Cr buffered MgO (100) substrates by sputtering. Fe2Cr0.5Co0.5Si exhibits the largest magnetization and optimal ordered L21 cubic structure at in-situ annealing temperature (Tia) of 450°C. The Co composition dependence of crystalline structures, surface morphology, defects, lattice distortions and their correlation with the magnetic properties are analyzed in detail. The Co-doped samples show in-plane M-H loops with magnetic squareness ratio of 1 and increasing anisotropy energy density with Co composition. Appropriate Co doping composition promotes L21 phase but higher Co composition converts L21 to B2 phase. Doping effect and lattice mismatch both are proved to increase the defect density. In addition, distortions of the FCCS lattice are found to be approximately linear with Co composition. The largest lattice distortion (c/a) is 0.969 for Fe2Cr0.25Co0.75Si and the smallest is 0.983 for Fe2CrSi. Our analyses suggest that these tetragonal distortions mainly induced by an elastic stress from Cr buffer account for the large in-plane anisotropy energy. This work paves the way for further tailoring the magnetic and structural properties of quaternary Heusler alloys.

Grids in topographic maps reduce distortions in the recall of learned object locations.

PubMed

Edler, Dennis; Bestgen, Anne-Kathrin; Kuchinke, Lars; Dickmann, Frank

2014-01-01

To date, it has been shown that cognitive map representations based on cartographic visualisations are systematically distorted. The grid is a traditional element of map graphics that has rarely been considered in research on perception-based spatial distortions. Grids do not only support the map reader in finding coordinates or locations of objects, they also provide a systematic structure for clustering visual map information ("spatial chunks"). The aim of this study was to examine whether different cartographic kinds of grids reduce spatial distortions and improve recall memory for object locations. Recall performance was measured as both the percentage of correctly recalled objects (hit rate) and the mean distance errors of correctly recalled objects (spatial accuracy). Different kinds of grids (continuous lines, dashed lines, crosses) were applied to topographic maps. These maps were also varied in their type of characteristic areas (LANDSCAPE) and different information layer compositions (DENSITY) to examine the effects of map complexity. The study involving 144 participants shows that all experimental cartographic factors (GRID, LANDSCAPE, DENSITY) improve recall performance and spatial accuracy of learned object locations. Overlaying a topographic map with a grid significantly reduces the mean distance errors of correctly recalled map objects. The paper includes a discussion of a square grid's usefulness concerning object location memory, independent of whether the grid is clearly visible (continuous or dashed lines) or only indicated by crosses.

Stress regularity in quasi-static perfect plasticity with a pressure dependent yield criterion

NASA Astrophysics Data System (ADS)

Babadjian, Jean-François; Mora, Maria Giovanna

2018-04-01

This work is devoted to establishing a regularity result for the stress tensor in quasi-static planar isotropic linearly elastic - perfectly plastic materials obeying a Drucker-Prager or Mohr-Coulomb yield criterion. Under suitable assumptions on the data, it is proved that the stress tensor has a spatial gradient that is locally squared integrable. As a corollary, the usual measure theoretical flow rule is expressed in a strong form using the quasi-continuous representative of the stress.

Lid design for low level waste container

DOEpatents

Holbrook, R.H.; Keener, W.E.

1995-02-28

A container for low level waste includes a shell and a lid. The lid has a frame to which a planar member is welded. The lid frame includes a rectangular outer portion made of square metal tubing, a longitudinal beam extending between axial ends of the rectangular outer portion, and a transverse beam extending between opposite lateral sides of the rectangular outer portion. Two pairs of diagonal braces extend between the longitudinal beam and the four corners of the rectangular outer portion of the frame. 6 figs.

Plasmon resonant cavities in vertical nanowire arrays

DOEpatents

Bora, Mihail; Bond, Tiziana C.; Fasenfest, Benjamin J.; Behymer, Elaine M.

2014-07-15

Tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides are presented. Resonances can be observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides can satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors of over 10.sup.3 are possible due to plasmon focusing in the inter-wire space.

Lid design for low level waste container

DOEpatents

Holbrook, Richard H.; Keener, Wendell E.

1995-01-01

A container for low level waste includes a shell and a lid. The lid has a frame to which a planar member is welded. The lid frame includes a rectangular outer portion made of square metal tubing, a longitudinal beam extending between axial ends of the rectangular outer portion, and a transverse beam extending between opposite lateral sides of the rectangular outer portion. Two pairs of diagonal braces extend between the longitudinal beam and the four corners of the rectangular outer portion of the frame.

A spherical electron-channelling pattern map for use in quartz petrofabric analysis

USGS Publications Warehouse

Lloyd, G.E.; Ferguson, C.C.

1986-01-01

Electron channelling patterns (ECP's) are formed in the scanning electron microscope (SEM) by the interaction between the incident electrons and the lattice of crystalline specimens. The patterns are unique for a particular crystallographic orientation and are therefore of considerable potential in petrofabric studies provided they can be accurately indexed. Indexing requires an ECP-map of the crystallographic stereogram or unit triangle covering all possible orientations and hence ECP patterns. Due to the presence of long-range distortions in planar ECP-maps, it is more convenient to construct the maps over a spherical surface. This also facilitates the indexing of individual ECP's. A spherical ECP-map for quartz is presented together with an example of its use in petrofabric analysis. ?? 1986.

Method for optical pumping of thin laser media at high average power

DOEpatents

Zapata, Luis E [Livermore, CA; Beach, Raymond J [Livermore, CA; Honea, Eric C [Sunol, CA; Payne, Stephen A [Castro Valley, CA

2004-07-13

A thin, planar laser material is bonded to a light guide of an index-matched material forming a composite disk. Diode array or other pump light is introduced into the composite disk through the edges of the disk. Pump light trapped within the composite disk depletes as it multi-passes the laser medium before reaching an opposing edge of the disk. The resulting compound optical structure efficiently delivers concentrated pump light and to a laser medium of minimum thickness. The external face of the laser medium is used for cooling. A high performance cooler attached to the external face of the laser medium rejects heat. Laser beam extraction is parallel to the heat flux to minimize optical distortions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

N, Rekha T.; Rajkumar, Beulah J. M., E-mail: beulah-rajkumar@yahoo.co.in

Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistributionmore » of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices.« less

Real-space visualization of conformation-independent oligothiophene electronic structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taber, Benjamen N.; Kislitsyn, Dmitry A.; Gervasi, Christian F.

2016-05-21

We present scanning tunneling microscopy and spectroscopy (STM/STS) investigations of the electronic structures of different alkyl-substituted oligothiophenes on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes adopted distinct straight and bent conformations. By combining STS maps with STM images, we visualize, in real space, particle-in-a-box-like oligothiophene molecular orbitals. We demonstrate that different planar conformers with significant geometrical distortions of oligothiophene backbones surprisingly exhibit very similar electronic structures, indicating a low degree of conformation-induced electronic disorder. The agreement of these results with gas-phase density functional theory calculations implies that the oligothiophene interaction with the Au(111) surface is generally insensitivemore » to molecular conformation.« less

Axial coordination and conformational heterogeneity of nickel(II) tetraphenylprophyrin complexes with nitrogenous bases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, S.L.; Song, X.Z.; Ma, J.G.

1998-08-24

Axial ligation of nickel(II) 5,10,15,20-tetraphenylporphyrin (NiTPP) with pyrrolidine or piperidine has been investigated using X-ray crystallography, UV-visible spectroscopy, resonance Raman spectroscopy, and molecular mechanics (MM) calculations. Distinct v{sub 4} Raman lines are found for the 4-, 5-, and 6-coordinate species of NiTPP. The equilibrium constants for addition of the first and second pyrrolidine axial ligands are 1.1 and 3.8 M{sup {minus}1}, respectively. The differences in the calculated energies of the conformers having different ligand rotational angles are small so they may coexist in solution. Because of the similarity in macrocyclic structural parameters of these conformers and the free rotation ofmore » the axial ligands, narrow and symmetric v{sub 2} and v{sub 8} Raman lines are observed. Nonetheless, the normal-coordinate structural-decomposition analysis of the nonplanar distortions of the calculated structures and the crystal structure of the bis(piperidine) complex reveals a relationship between the orientations of axial ligand(s) and the macrocyclic distortions. For the 5-coordinate complex with the plane of the axial ligand bisecting the Ni-N{sub pyrrole} bonds, a primarily ruffled deformation results. With the ligand plane eclipsing the Ni-N{sub pyrrole} bonds, a mainly saddled deformation occurs. With the addition of the second axial ligand, the small doming of the 5-coordinate complexes disappears, and ruffling or saddling deformations change depending on the relative orientation of the two axial ligands. The crystal structure of the NiTPP bis(piperidine) complex shows a macrocycle distortion composed of wav(x) and wav(y) symmetric deformations, but no ruffling, saddling, or doming. The difference in the calculated and observed distortions results partly from the phenyl group orientation imposed by crystal packing forces. MM calculations predict three stable conformers (ruf, sad, and planar) for 4-coordinate NiTPP, and resonance Raman evidence for these conformers was given previously.« less

Changes in the geometries of C₂H₂ and C₂H₄ on coordination to CuCl revealed by broadband rotational spectroscopy and ab-initio calculations.

PubMed

Stephens, Susanna L; Bittner, Dror M; Mikhailov, Victor A; Mizukami, Wataru; Tew, David P; Walker, Nicholas R; Legon, Anthony C

2014-10-06

The molecular geometries of isolated complexes in which a single molecule of C2H4 or C2H2 is bound to CuCl have been determined through pure rotational spectroscopy and ab-initio calculations. The C2H2···CuCl and C2H4···CuCl complexes are generated through laser vaporization of a copper rod in the presence of a gas sample undergoing supersonic expansion and containing C2H2 (or C2H4), CCl4, and Ar. Results are presented for five isotopologues of C2H2···CuCl and six isotopologues of C2H4···CuCl. Both of these complexes adopt C(2v), T-shaped geometries in which the hydrocarbon binds to the copper atom through its π electrons such that the metal is equidistant from all H atoms. The linear and planar geometries of free C2H2 and C2H4, respectively, are observed to distort significantly on attachment to the CuCl unit, and the various changes are quantified. The ∠(*-C-H) parameter in C2H2 (where * indicates the midpoint of the C≡C bond) is measured to be 192.4(7)° in the r0 geometry of the complex representing a significant change from the linear geometry of the free molecule. This distortion of the linear geometry of C2H2 involves the hydrogen atoms moving away from the copper atom within the complex. Ab-initio calculations at the CCSD(T)(F12*)/AVTZ level predict a dihedral ∠(HCCCu) angle of 96.05° in C2H4···CuCl, and the experimental results are consistent with such a distortion from planarity. The bonds connecting the carbon atoms within each of C2H2 and C2H4, respectively, extend by 0.027 and 0.029 Å relative to the bond lengths in the isolated molecules. Force constants, k(σ), and nuclear quadrupole coupling constants, χ(aa)(Cu), [χ(bb)(Cu) - χ(cc)(Cu)], χ(aa)(Cl), and [χ(bb)(Cl) - χ(cc)(Cl)], are independently determined for all isotopologues of C2H2···CuCl studied and for four isotopologues of C2H4···CuCl.

Shock-initiated Combustion of a Spherical Density Inhomogeneity

NASA Astrophysics Data System (ADS)

Haehn, Nicholas; Oakley, Jason; Rothamer, David; Anderson, Mark; Ranjan, Devesh; Bonazza, Riccardo

2010-11-01

A spherical density inhomogeneity is prepared using fuel and oxidizer at a stoichiometric ratio and Xe as a diluent that increases the overall density of the bubble mixture (55% Xe, 30% H2, 15% O2). The experiments are performed in the Wisconsin Shock Tube Laboratory in a 9.2 m vertical shock tube with a 25.4 cm x 25.4 cm square cross-section. An injector is used to generate a 5 cm diameter soap film bubble filled with the combustible mixture. The injector retracts flush into the side of the tube releasing the bubble into a state of free fall. The combustible bubble is accelerated by a planar shock wave in N2 (2.0 < M < 2.8). The mismatch of acoustic impedances results in shock-focusing at the downstream pole of the bubble. The shock focusing results in localized temperatures and pressures significantly larger than nominal conditions behind a planar shock wave, resulting in auto-ignition at the focus. Planar Mie scattering and chemiluminescence are used simultaneously to visualize the bubble morphology and combustion characteristics. During the combustion phase, both the span-wise and stream-wise lengths of the bubble are seen to increase compared to the non-combustible scenario. Additionally, smaller instabilities are observed on the upstream surface, which are absent in the non-combustible bubbles.

Experimental Study of Shock-Induced Compression and Vortex Generation in the Shock-Bubble Interaction

NASA Astrophysics Data System (ADS)

Ranjan, Devesh; Motl, Bradley; Niederhaus, John; Oakley, Jason; Anderson, Mark; Bonazza, Riccardo; Greenough, Jeffrey

2006-11-01

Results are presented from experiments studying the interaction of a planar shock wave of strength 1.4

Quaternary rare-earth arsenides REAg{sub 1−x}Zn{sub y}As{sub 2} (RE=La–Nd, Sm, Gd–Dy) with tetragonal SrZnBi{sub 2}- and HfCuSi{sub 2}-type structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramachandran, Krishna K.; Genet, Clément; Mar, Arthur, E-mail: arthur.mar@ualberta.ca

2015-11-15

Reactions of the elements at 800 °C with the nominal compositions REAg{sub 1−x}Zn{sub x}As{sub 2} resulted in quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2} in which the combined Ag and Zn content deviates increasingly from unity in the Zn-richer phases, reflecting the transition from the fully stoichiometric ternary silver-containing arsenides REAgAs{sub 2} to the substoichiometric zinc-containing ones REZn{sub 0.67}As{sub 2}. Powder X-ray diffraction analysis indicated SrZnBi{sub 2}-type (space group I4/mmm, Z=4; RE=La, Ce) and HfCuSi{sub 2}-type structures (space group P4/nmm, Z=2; RE=Pr, Nd, Sm, Gd, Tb, Dy). Single-crystal X-ray diffraction analysis performed on LaAg{sub 0.5}Zn{sub 0.5}As{sub 2}, PrAg{sub 0.5}Zn{sub 0.5}As{sub 2},more » and NdAg{sub 0.5}Zn{sub 0.5}As{sub 2} indicated that the Ag and Zn atoms are disordered within metal-centred tetrahedra and provided no evidence for distortion of the square As nets. The small electron excess tolerated in these quaternary arsenides and the absence of distortion in the square nets can be traced to the occurrence of As–As states that are only weakly antibonding near the Fermi level. PrAg{sub 0.5}Zn{sub 0.5}As{sub 2} and NdAg{sub 0.5}Zn{sub 0.5}As{sub 2} are paramagnetic with effective magnetic moments consistent with trivalent RE species. - Graphical abstract: On proceeding from fully stoichiometric REAgAs{sub 2} to substoichiometric REZn{sub 0.67}As{sub 2}, deficiencies in Zn content become increasingly prominent in quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2}. - Highlights: • Ag and Zn atoms are disordered within quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2}. • In Zn-richer phases, Zn deficiencies develop to counteract electron excess. • Distortions of square As net appear to be suppressed.« less

Cost-Sharing of Ecological Construction Based on Trapezoidal Intuitionistic Fuzzy Cooperative Games

PubMed Central

Liu, Jiacai; Zhao, Wenjian

2016-01-01

There exist some fuzziness and uncertainty in the process of ecological construction. The aim of this paper is to develop a direct and an effective simplified method for obtaining the cost-sharing scheme when some interested parties form a cooperative coalition to improve the ecological environment of Min River together. Firstly, we propose the solution concept of the least square prenucleolus of cooperative games with coalition values expressed by trapezoidal intuitionistic fuzzy numbers. Then, based on the square of the distance in the numerical value between two trapezoidal intuitionistic fuzzy numbers, we establish a corresponding quadratic programming model to obtain the least square prenucleolus, which can effectively avoid the information distortion and uncertainty enlargement brought about by the subtraction of trapezoidal intuitionistic fuzzy numbers. Finally, we give a numerical example about the cost-sharing of ecological construction in Fujian Province in China to show the validity, applicability, and advantages of the proposed model and method. PMID:27834830

Strain-Mediated Modification of Phagraphene Dirac Cones

DOE PAGES

Lopez-Bezanilla, Alejandro

2016-07-07

We present a first-principles study on the electronic and dynamical properties of phagraphene [Nano Lett., 2015, 15 (9), pp 6182]. This carbon allotrope exhibits a square unit cell, Dirac cones, and robustness against uniaxial deformation. By analyzing the contribution of each carbon atom orbital in the formation of the electronic states, we conclude that only the pz orbitals of eight out of the twenty atoms in the square unit cell are responsible of the formation of the nano-structure Dirac cones. Spatial symmetry breaking of the underlying honeycomb-like network upon shear stress application leads to a band gap opening. The analysismore » of the phonon spectra demonstrates that the dynamical stability of phagraphene is guaranteed for small distortion angles. Phagraphene is identified here as the first all-C graphitic monolayer with Dirac cones modifiable by a small and realistic physical deformation. The analysis and conclusions of this study can be applied to other monolayered materials exhibiting Dirac cones in square lattices.« less

Design Rules and Scaling for Solar Sails

NASA Technical Reports Server (NTRS)

Zeiders, Glenn W.

2005-01-01

Useful design rules and simple scaling models have been developed for solar sails. Chief among the conclusions are: 1. Sail distortions contribute to the thrust and moments primarily though the mean squared value of their derivatives (slopes), and the sail behaves like a flat sheet if the value is small. The RMS slope is therefore an important figure of merit, and sail distortion effects on the spacecraft can generally be disregarded if the RMS slope is less than about 10% or so. 2. The characteristic slope of the sail distortion varies inversely with the tension in the sail, and it is the tension that produces the principle loading on the support booms. The tension is not arbitrary, but rather is the value needed to maintain the allowable RMS slope. That corresponds to a halyard force about equal to three times the normal force on the supported sail area. 3. Both the AEC/SRS and L Garde concepts appear to be structurally capable of supporting sail sizes up to a kilometer or more with 1AU solar flux, but select transverse dimensions must be changed to do so. Operational issues such as fabrication, handling, storage and deployment will be the limiting factors.

A new DWT/MC/DPCM video compression framework based on EBCOT

NASA Astrophysics Data System (ADS)

Mei, L. M.; Wu, H. R.; Tan, D. M.

2005-07-01

A novel Discrete Wavelet Transform (DWT)/Motion Compensation (MC)/Differential Pulse Code Modulation (DPCM) video compression framework is proposed in this paper. Although the Discrete Cosine Transform (DCT)/MC/DPCM is the mainstream framework for video coders in industry and international standards, the idea of DWT/MC/DPCM has existed for more than one decade in the literature and the investigation is still undergoing. The contribution of this work is twofold. Firstly, the Embedded Block Coding with Optimal Truncation (EBCOT) is used here as the compression engine for both intra- and inter-frame coding, which provides good compression ratio and embedded rate-distortion (R-D) optimization mechanism. This is an extension of the EBCOT application from still images to videos. Secondly, this framework offers a good interface for the Perceptual Distortion Measure (PDM) based on the Human Visual System (HVS) where the Mean Squared Error (MSE) can be easily replaced with the PDM in the R-D optimization. Some of the preliminary results are reported here. They are also compared with benchmarks such as MPEG-2 and MPEG-4 version 2. The results demonstrate that under specified condition the proposed coder outperforms the benchmarks in terms of rate vs. distortion.

Digital Self-Interference Cancellation for Asynchronous In-Band Full-Duplex Underwater Acoustic Communication.

PubMed

Qiao, Gang; Gan, Shuwei; Liu, Songzuo; Ma, Lu; Sun, Zongxin

2018-05-24

To improve the throughput of underwater acoustic (UWA) networking, the In-band full-duplex (IBFD) communication is one of the most vital pieces of research. The major drawback of IBFD-UWA communication is Self-Interference (SI). This paper presents a digital SI cancellation algorithm for asynchronous IBFD-UWA communication system. We focus on two issues: one is asynchronous communication dissimilar to IBFD radio communication, the other is nonlinear distortion caused by power amplifier (PA). First, we discuss asynchronous IBFD-UWA signal model with the nonlinear distortion of PA. Then, we design a scheme for asynchronous IBFD-UWA communication utilizing the non-overlapping region between SI and intended signal to estimate the nonlinear SI channel. To cancel the nonlinear distortion caused by PA, we propose an Over-Parameterization based Recursive Least Squares (RLS) algorithm (OPRLS) to estimate the nonlinear SI channel. Furthermore, we present the OPRLS with a sparse constraint to estimate the SI channel, which reduces the requirement of the length of the non-overlapping region. Finally, we verify our concept through simulation and the pool experiment. Results demonstrate that the proposed digital SI cancellation scheme can cancel SI efficiently.

Bounds on the performance of a class of digital communication systems

NASA Technical Reports Server (NTRS)

Polk, D. R.; Gupta, S. C.; Cohn, D. L.

1973-01-01

Bounds on the capacity of a class of digital communication channels are derived. Equating the bounds on capacity to rate-distortion functions of (typical) sources in turn produces bounds on the performance of a class of digital communication systems. For ratios of squared quantization level to noise variance much less than one, the power requirements for this class of digital communication systems are shown to be within approximately 3 dB of the theoretical optimum.

Using CMB spectral distortions to distinguish between dark matter solutions to the small-scale crisis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diacoumis, James A.D.; Wong, Yvonne Y.Y., E-mail: j.diacoumis@unsw.edu.au, E-mail: yvonne.y.wong@unsw.edu.au

The dissipation of small-scale perturbations in the early universe produces a distortion in the blackbody spectrum of cosmic microwave background photons. In this work, we propose to use these distortions as a probe of the microphysics of dark matter on scales 1 Mpc{sup -1}∼< k ∼< 10{sup 4} Mpc{sup -1}. We consider in particular models in which the dark matter is kinetically coupled to either neutrinos or photons until shortly before recombination, and compute the photon heating rate and the resultant μ-distortion in both cases. We show that the μ-parameter is generally enhanced relative to ΛCDM for interactions with neutrinos,more » and may be either enhanced or suppressed in the case of interactions with photons. The deviations from the ΛCDM signal are potentially within the sensitivity reach of a PRISM-like experiment if σ{sub DM-γ} ∼> 1.1 × 10{sup -30} (m{sub DM}/GeV) cm{sup 2} and σ{sub DM-ν} ∼> 4.8 × 10{sup -32} (m{sub DM}/GeV) cm{sup 2} for time-independent cross sections, and σ{sup 0}{sub DM-γ} ∼> 1.8 × 10{sup -40} (m{sub DM}/GeV) cm{sup 2} and σ{sup 0}{sub DM-ν} ∼> 2.5 × 10{sup -47} (m{sub DM}/GeV) cm{sup 2} for cross sections scaling as temperature squared, coinciding with the parameter regions in which late kinetic decoupling may serve as a solution to the small-scale crisis. Furthermore, these μ-distortion signals differ from those of warm dark matter (no deviation from ΛCDM) and a suppressed primordial power spectrum (a strongly suppressed or negative μ-parameter), demonstrating that CMB spectral distortion can potentially be used to distinguish between solutions to the small-scale crisis.« less

Millimeter-wave spectroscopy of syn formyl azide (HC(O)N3) in seven vibrational states

NASA Astrophysics Data System (ADS)

Walters, Nicholas A.; Amberger, Brent K.; Esselman, Brian J.; Woods, R. Claude; McMahon, Robert J.

2017-01-01

Millimeter-wave spectra for formyl azide (HC(O)N3) were obtained from 240 to 360 GHz at ambient temperature. For the ground state of syn formyl azide, over 1500 independent rotational transitions were measured and least-squares fit to a complete S-reduced 8th order centrifugal distortion/rigid rotor Hamiltonian. The decomposition of formyl azide was monitored over a period of several hours, the half-life (t½ = 30 min) was determined, and its decomposition products were investigated. Transitions from five vibrational satellites of syn formyl azide (ν9, ν12, 2ν9, ν9 + ν12, and ν11) were observed, measured, and least-squares fit to complete or nearly complete octic centrifugally-distorted, single-state S-reduced models. A less complete single-state fit of 3ν9 (509.3 cm-1) was obtained from an unperturbed subset of its assignable transitions. This state is apparently coupled to the fundamental ν8 (489.4 cm-1) and the overtone 2ν12 (503.6 cm-1), but the coupling remains unanalyzed. Anharmonic CCSD(T)/ANO1 estimates of the vibrational frequencies of syn formyl azide were in close agreement with previously published experimental and computational values. Experimentally determined vibration-rotation interaction (αi) values were in excellent agreement with coupled-cluster predicted αi values for the fundamentals ν9, ν12, and ν11.

The Crystal Structure of Ba 17Sm 10Cl 64

NASA Astrophysics Data System (ADS)

Liu, Guo; Eick, Harry A.

1999-08-01

The structure of Ba17Sm10Cl64, prepared by solvolytic extraction of a program-cooled 1:1 BaCl2:SmCl3 molar mixture sealed in a quartz tube and heated to 750°C, was determined from single-crystal X-ray diffraction data. The compound exhibits cubic symmetry, space group Pa3 (No. 205) with a=21.366(2) Å and Z=4. Refinement effected with I>2σ(I) yielded R1= 0.0926 and wR2=0.216. One Ba atom is 12-coordinated by Cl atoms in a distorted icosahedral arrangement; the three other Ba atoms are 10-coordinated in a distorted bicapped cubic arrangement. There are two Sm atom sites. The coordination around one Sm atom is best described as square antiprismatic, but one Sm-Cl distance is too long for effective bonding. The other Sm atom site, occupied statistically by {1}/{3}Ba and {2}/{3}Sm atoms, is 9-coordinated by Cl atoms in a monocapped square antiprismatic arrangement. The two types of Sm sites combine to form an M6Cl37 cuboctahedral cluster of the composition BaSm5Cl37. It is shown that the cβ phase identified previously in the Yb-F and related fluoride systems is probably isostructural with Ba17Sm10Cl64.

Evaluation of image quality and radiation dose by adaptive statistical iterative reconstruction technique level for chest CT examination.

PubMed

Hong, Sun Suk; Lee, Jong-Woong; Seo, Jeong Beom; Jung, Jae-Eun; Choi, Jiwon; Kweon, Dae Cheol

2013-12-01

The purpose of this research is to determine the adaptive statistical iterative reconstruction (ASIR) level that enables optimal image quality and dose reduction in the chest computed tomography (CT) protocol with ASIR. A chest phantom with 0-50 % ASIR levels was scanned and then noise power spectrum (NPS), signal and noise and the degree of distortion of peak signal-to-noise ratio (PSNR) and the root-mean-square error (RMSE) were measured. In addition, the objectivity of the experiment was measured using the American College of Radiology (ACR) phantom. Moreover, on a qualitative basis, five lesions' resolution, latitude and distortion degree of chest phantom and their compiled statistics were evaluated. The NPS value decreased as the frequency increased. The lowest noise and deviation were at the 20 % ASIR level, mean 126.15 ± 22.21. As a result of the degree of distortion, signal-to-noise ratio and PSNR at 20 % ASIR level were at the highest value as 31.0 and 41.52. However, maximum absolute error and RMSE showed the lowest deviation value as 11.2 and 16. In the ACR phantom study, all ASIR levels were within acceptable allowance of guidelines. The 20 % ASIR level performed best in qualitative evaluation at five lesions of chest phantom as resolution score 4.3, latitude 3.47 and the degree of distortion 4.25. The 20 % ASIR level was proved to be the best in all experiments, noise, distortion evaluation using ImageJ and qualitative evaluation of five lesions of a chest phantom. Therefore, optimal images as well as reduce radiation dose would be acquired when 20 % ASIR level in thoracic CT is applied.

Inverse Band Structure Design via Materials Database Screening: Application to Square Planar Thermoelectrics

DOE PAGES

Isaacs, Eric B.; Wolverton, Chris

2018-02-26

Electronic band structure contains a wealth of information on the electronic properties of a solid and is routinely computed. However, the more difficult problem of designing a solid with a desired band structure is an outstanding challenge. In order to address this inverse band structure design problem, we devise an approach using materials database screening with materials attributes based on the constituent elements, nominal electron count, crystal structure, and thermodynamics. Our strategy is tested in the context of thermoelectric materials, for which a targeted band structure containing both flat and dispersive components with respect to crystal momentum is highly desirable.more » We screen for thermodynamically stable or metastable compounds containing d 8 transition metals coordinated by anions in a square planar geometry in order to mimic the properties of recently identified oxide thermoelectrics with such a band structure. In doing so, we identify 157 compounds out of a total of over half a million candidates. After further screening based on electronic band gap and structural anisotropy, we explicitly compute the band structures for the several of the candidates in order to validate the approach. We successfully find two new oxide systems that achieve the targeted band structure. Electronic transport calculations on these two compounds, Ba 2PdO 3 and La 4PdO 7, confirm promising thermoelectric power factor behavior for the compounds. This methodology is easily adapted to other targeted band structures and should be widely applicable to a variety of design problems.« less

Inverse Band Structure Design via Materials Database Screening: Application to Square Planar Thermoelectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, Eric B.; Wolverton, Chris

Electronic band structure contains a wealth of information on the electronic properties of a solid and is routinely computed. However, the more difficult problem of designing a solid with a desired band structure is an outstanding challenge. In order to address this inverse band structure design problem, we devise an approach using materials database screening with materials attributes based on the constituent elements, nominal electron count, crystal structure, and thermodynamics. Our strategy is tested in the context of thermoelectric materials, for which a targeted band structure containing both flat and dispersive components with respect to crystal momentum is highly desirable.more » We screen for thermodynamically stable or metastable compounds containing d 8 transition metals coordinated by anions in a square planar geometry in order to mimic the properties of recently identified oxide thermoelectrics with such a band structure. In doing so, we identify 157 compounds out of a total of over half a million candidates. After further screening based on electronic band gap and structural anisotropy, we explicitly compute the band structures for the several of the candidates in order to validate the approach. We successfully find two new oxide systems that achieve the targeted band structure. Electronic transport calculations on these two compounds, Ba 2PdO 3 and La 4PdO 7, confirm promising thermoelectric power factor behavior for the compounds. This methodology is easily adapted to other targeted band structures and should be widely applicable to a variety of design problems.« less

Gamma model and its analysis for phase measuring profilometry.

PubMed

Liu, Kai; Wang, Yongchang; Lau, Daniel L; Hao, Qi; Hassebrook, Laurence G

2010-03-01

Phase measuring profilometry is a method of structured light illumination whose three-dimensional reconstructions are susceptible to error from nonunitary gamma in the associated optical devices. While the effects of this distortion diminish with an increasing number of employed phase-shifted patterns, gamma distortion may be unavoidable in real-time systems where the number of projected patterns is limited by the presence of target motion. A mathematical model is developed for predicting the effects of nonunitary gamma on phase measuring profilometry, while also introducing an accurate gamma calibration method and two strategies for minimizing gamma's effect on phase determination. These phase correction strategies include phase corrections with and without gamma calibration. With the reduction in noise, for three-step phase measuring profilometry, analysis of the root mean squared error of the corrected phase will show a 60x reduction in phase error when the proposed gamma calibration is performed versus 33x reduction without calibration.

Role of the local structure in superconductivity of LaO0.5F0.5BiS2-x Se x system

NASA Astrophysics Data System (ADS)

Paris, E.; Mizuguchi, Y.; Hacisalihoglu, M. Y.; Hiroi, T.; Joseph, B.; Aquilanti, G.; Miura, O.; Mizokawa, T.; Saini, N. L.

2017-04-01

We have studied the local structure of LaO0.5F0.5BiS2-x Se x by Bi L1-edge extended x-ray absorption fine structure (EXAFS). We find a significant effect of Se substitution on the local atomic correlations with a gradual elongation of average in-plane Bi-S bondlength. The associated mean square relative displacement, measuring average local distortions in the BiS2 plane, hardly shows any change for small Se substitution, but decreases significantly for x≥slant 0.6 . The Se substitution appears to suppress the local distortions within the BiS2 plane that may optimize in-plane orbital hybridization and hence the superconductivity. The results suggest that the local structure of the BiS2-layer is one of the key ingredients to control the physical properties of the BiS2-based dichalcogenides.

Bonding Thin Mirror Segments Without Distortion for the International X-Ray Observatory

NASA Technical Reports Server (NTRS)

Evans, Tyler C.; Chan, Kai-Wing; Saha, Timo T.

2011-01-01

The International X-Ray Observatory (IXO) uses thin glass optics to maximize large effective area and precise low angular resolution. The thin glass mirror segments must be transferred from their fabricated state to a permanent structure without imparting distortion. IXO will incorporate about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arcseconds. To preserve figure and alignment, the mirror segment must be bonded with sub-micron movement at each corner. Recent advances in technology development have produced significant x-ray test results of a bonded pair of mirrors. Three specific bonding cycles will be described highlighting the improvements in procedure, temperature control, and precision bonding. This paper will highlight the recent advances in alignment and permanent bonding as well as the results they have produced.

A family of chaotic pure analog coding schemes based on baker's map function

NASA Astrophysics Data System (ADS)

Liu, Yang; Li, Jing; Lu, Xuanxuan; Yuen, Chau; Wu, Jun

2015-12-01

This paper considers a family of pure analog coding schemes constructed from dynamic systems which are governed by chaotic functions—baker's map function and its variants. Various decoding methods, including maximum likelihood (ML), minimum mean square error (MMSE), and mixed ML-MMSE decoding algorithms, have been developed for these novel encoding schemes. The proposed mirrored baker's and single-input baker's analog codes perform a balanced protection against the fold error (large distortion) and weak distortion and outperform the classical chaotic analog coding and analog joint source-channel coding schemes in literature. Compared to the conventional digital communication system, where quantization and digital error correction codes are used, the proposed analog coding system has graceful performance evolution, low decoding latency, and no quantization noise. Numerical results show that under the same bandwidth expansion, the proposed analog system outperforms the digital ones over a wide signal-to-noise (SNR) range.

Crosstalk mitigation using pilot assisted least square algorithm in OFDM-carrying orbital angular momentum multiplexed free-space-optical communication links.

PubMed

Sun, Tengfen; Liu, Minwen; Li, Yingchun; Wang, Min

2017-10-16

In this paper, we experimentally investigate the performance of crosstalk mitigation for 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing (16QAM-OFDM) signals carrying orbital angular momentum (OAM) multiplexed free-space-optical communication (FSO) links using the pilot assisted Least Square (LS) algorithm. At the demodulating spatial light modulators (SLMs), we launch the distorted phase holograms which have the information of atmospheric turbulence obeying the modified Hill spectrum. And crosstalk can be introduced by these holograms with the experimental verification. The pilot assisted LS algorithm can efficiently improve the quality of system performance, the points of constellations get closer to the reference points and around two orders of magnitude improvement of bit-error rate (BER) is obtained.

Optical fringe-reflection deflectometry with bundle adjustment

NASA Astrophysics Data System (ADS)

Xiao, Yong-Liang; Li, Sikun; Zhang, Qican; Zhong, Jianxin; Su, Xianyu; You, Zhisheng

2018-06-01

Liquid crystal display (LCD) screens are located outside of a camera's field of view in fringe-reflection deflectometry. Therefore, fringes that are displayed on LCD screens are obtained through specular reflection by a fixed camera. Thus, the pose calibration between the camera and LCD screen is one of the main challenges in fringe-reflection deflectometry. A markerless planar mirror is used to reflect the LCD screen more than three times, and the fringes are mapped into the fixed camera. The geometrical calibration can be accomplished by estimating the pose between the camera and the virtual image of fringes. Considering the relation between their pose, the incidence and reflection rays can be unified in the camera frame, and a forward triangulation intersection can be operated in the camera frame to measure three-dimensional (3D) coordinates of the specular surface. In the final optimization, constraint-bundle adjustment is operated to refine simultaneously the camera intrinsic parameters, including distortion coefficients, estimated geometrical pose between the LCD screen and camera, and 3D coordinates of the specular surface, with the help of the absolute phase collinear constraint. Simulation and experiment results demonstrate that the pose calibration with planar mirror reflection is simple and feasible, and the constraint-bundle adjustment can enhance the 3D coordinate measurement accuracy in fringe-reflection deflectometry.

Interaction of Porosity with a Planar Solid/Liquid Interface

NASA Technical Reports Server (NTRS)

Catalina, Adrian V.; Stefanescu, Doru M.; Sen, Subhayu; Kaukler, William F.

2004-01-01

In this article, an investigation of the interaction between gas porosity and a planar solid/liquid (SL) interface is reported. A two-dimensional numerical model able to accurately track sharp SL interfaces during solidification of pure metals and alloys is proposed. The finite-difference method and a rectangular undeformed grid are used for computation. The SL interface is described through the points of intersection with the grid lines. Its motion is determined by the thermal and solute gradients at each particular point. Changes of the interface temperature because of capillarity or solute redistribution as well as any perturbation of the thermal and solute field produced by the presence of non-metallic inclusions can be computed. To validate the model, the dynamics of the interaction between a gas pore and a solidification front in metal alloys was observed using a state of the art X-ray transmission microscope (XTM). The experiments included observation of the distortion of the SL interface near a pore, real-time measurements of the growth rate, and the change in shape of the porosity during interaction with the SL interface in pure Al and Al-0.25 wt pct Au alloy. In addition, porosity-induced solute segregation patterns surrounding a pore were also quantified.

Brownian dynamics simulations of simplified cytochrome c molecules in the presence of a charged surface

NASA Astrophysics Data System (ADS)

Gorba, C.; Geyer, T.; Helms, V.

2004-07-01

Simulations were performed for up to 150 simplified spherical horse heart cytochrome c molecules in the presence of a charged surface, which serves as an approximate model for a lipid membrane. Screened electrostatic and short-ranged attractive as well as repulsive van der Waals forces for interparticle and particle-membrane interactions are utilized in the simulations. At a distance from the membrane, where particle-membrane interactions are negligible, the simulation is coupled to a noninteraction continuum analogous to a heat bath [Geyer et al., J. Chem. Phys. 120, 4573 (2004)]. From the particles' density profiles perpendicular to the planar surface binding isotherms are derived and compared to experimental results [Heimburg et al. (1999)]. Using a negatively charged structureless membrane surface a saturation effect was found for relatively large particle concentrations. Since biological membranes often contain membrane proteins, we also studied the influence of additional charges on our model membrane mimicking bacterial reaction centers. We find that the onset of the saturation occurs for much lower concentrations and is sensitive to the detailed implementation. Therefore we suggest that local distortion of membrane planarity (undulation), or lipid demixing, or the presence of charged integral membrane proteins create preferential binding sites on the membrane. Only then do we observe saturation at physiological concentrations.

Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demiralp, E.; Dasgupta, S.; Goddard, W.A. III

1995-08-09

The highest T{sub c} organic superconductors all involve the organic molecule bis(ethylenedithio)tetrathiafulvalene (denoted as BEDT-TTF or ET) coupled with an appropriate acceptor. This leads to ET, ET{sup +}, or (ET){sub 2}{sup +} species in the crystal. Using ab initio Hartree-Fock calculations (6-31G** basis set), we show that ET deforms to a boat structure with an energy 28 meV (0.65 kcal/mol) lower than that of planar ET (D{sub 2} symmetry). On the other hand, ET{sup +} is planar. Thus, conduction in this system leads to a coupling between charge transfer and the boat deformation vibrational modes at 20 cm{sup -1} (ET)more » and 28 cm{sup -1} (ET{sup +}). We suggest that this electron-phonon coupling is responsible for the superconductivity and predict the isotope shifts ({delta}T{sub c}) for experimental tests of the electron-transfer boat-vibration (ET-BV) mechanism. The low frequency of this boat mode and its coupling to various lattice modes could explain the sensitivity of T{sub c} to defects, impurities, and pressure. We suggest that new higher temperature organic donors can be sought by finding modifications that change the frequency and stability of this boat distortion mode. 25 refs., 5 figs., 4 tabs.« less

A support-operator method for 3-D rupture dynamics

NASA Astrophysics Data System (ADS)

Ely, Geoffrey P.; Day, Steven M.; Minster, Jean-Bernard

2009-06-01

We present a numerical method to simulate spontaneous shear crack propagation within a heterogeneous, 3-D, viscoelastic medium. Wave motions are computed on a logically rectangular hexahedral mesh, using the generalized finite-difference method of Support Operators (SOM). This approach enables modelling of non-planar surfaces and non-planar fault ruptures. Our implementation, the Support Operator Rupture Dynamics (SORD) code, is highly scalable, enabling large-scale, multiprocessors calculations. The fault surface is modelled by coupled double nodes, where rupture occurs as dictated by the local stress conditions and a frictional failure law. The method successfully performs test problems developed for the Southern California Earthquake Center (SCEC)/U.S. Geological Survey (USGS) dynamic earthquake rupture code validation exercise, showing good agreement with semi-analytical boundary integral method results. We undertake further dynamic rupture tests to quantify numerical errors introduced by shear deformations to the hexahedral mesh. We generate a family of meshes distorted by simple shearing, in the along-strike direction, up to a maximum of 73°. For SCEC/USGS validation problem number 3, grid-induced errors increase with mesh shear angle, with the logarithm of error approximately proportional to angle over the range tested. At 73°, rms misfits are about 10 per cent for peak slip rate, and 0.5 per cent for both rupture time and total slip, indicating that the method (which, up to now, we have applied mainly to near-vertical strike-slip faulting) is also capable of handling geometries appropriate to low-angle surface-rupturing thrust earthquakes. Additionally, we demonstrate non-planar rupture effects, by modifying the test geometry to include, respectively, cylindrical curvature and sharp kinks.

Advantages of soft versus hard constraints in self-modeling curve resolution problems. Alternating least squares with penalty functions.

PubMed

Gemperline, Paul J; Cash, Eric

2003-08-15

A new algorithm for self-modeling curve resolution (SMCR) that yields improved results by incorporating soft constraints is described. The method uses least squares penalty functions to implement constraints in an alternating least squares algorithm, including nonnegativity, unimodality, equality, and closure constraints. By using least squares penalty functions, soft constraints are formulated rather than hard constraints. Significant benefits are (obtained using soft constraints, especially in the form of fewer distortions due to noise in resolved profiles. Soft equality constraints can also be used to introduce incomplete or partial reference information into SMCR solutions. Four different examples demonstrating application of the new method are presented, including resolution of overlapped HPLC-DAD peaks, flow injection analysis data, and batch reaction data measured by UV/visible and near-infrared spectroscopy (NIR). Each example was selected to show one aspect of the significant advantages of soft constraints over traditionally used hard constraints. Incomplete or partial reference information into self-modeling curve resolution models is described. The method offers a substantial improvement in the ability to resolve time-dependent concentration profiles from mixture spectra recorded as a function of time.

Planar Imaging of Hydroxyl in a High Temperature, High Pressure Combustion Facility

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Locke, Randy J.; Anderson, Robert C.; Ockunzzi, Kelly A.

1995-01-01

An optically accessible flame tube combustor is described which has high temperature, pressure, and air flow capabilities. The windows in the combustor measure 3.8 cm axially by 5.1 cm radially, providing 67 percent optical access to the square cross section flow chamber. The instrumentation allows one to examine combusting flows and combustor subcomponents, such as fuel injectors and air swirlers. These internal combustor subcomponents have previously been studied only with physical probes, such as temperature and species rakes. Planar laser-induced fluorescence (PLIF) images of OH have been obtained from this lean burning combustor burning Jet-A fuel. These images were obtained using various laser excitation lines of the OH A yields X (1,0) band for two fuel injector configurations with pressures ranging from 1013 kPa (10 atm) to 1419 kPa (14 atm), and equivalence ratios from 0.41 to 0. 59. Non-uniformities in the combusting flow, attributed to differences in fuel injector configuration, are revealed by these images.

Optimization of planar self-collimating photonic crystals.

PubMed

Rumpf, Raymond C; Pazos, Javier J

2013-07-01

Self-collimation in photonic crystals has received a lot of attention in the literature, partly due to recent interest in silicon photonics, yet no performance metrics have been proposed. This paper proposes a figure of merit (FOM) for self-collimation and outlines a methodical approach for calculating it. Performance metrics include bandwidth, angular acceptance, strength, and an overall FOM. Two key contributions of this work include the performance metrics and identifying that the optimum frequency for self-collimation is not at the inflection point. The FOM is used to optimize a planar photonic crystal composed of a square array of cylinders. Conclusions are drawn about how the refractive indices and fill fraction of the lattice impact each of the performance metrics. The optimization is demonstrated by simulating two spatially variant self-collimating photonic crystals, where one has a high FOM and the other has a low FOM. This work gives optical designers tremendous insight into how to design and optimize robust self-collimating photonic crystals, which promises many applications in silicon photonics and integrated optics.

On-Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles.

PubMed

Chen, Min; Shang, Jian; Wang, Yongfeng; Wu, Kai; Kuttner, Julian; Hilt, Gerhard; Hieringer, Wolfgang; Gottfried, J Michael

2017-01-24

We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C 180 H 120 ) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.

Synthesis, structures and Helicobacter pylori urease inhibitory activity of copper(II) complexes with tridentate aroylhydrazone ligands.

PubMed

Pan, Lin; Wang, Cunfang; Yan, Kai; Zhao, Kedong; Sheng, Guihua; Zhu, Hailiang; Zhao, Xinlu; Qu, Dan; Niu, Fang; You, Zhonglu

2016-06-01

A series of new copper(II) complexes were prepared. They are [CuL(1)(NCS)] (1), [CuClL(1)]·CH3OH (2), [CuClL(2)]·CH3OH (3), [CuL(3)(NCS)]·CH3OH (4), [CuL(4)(NCS)]·0.4H2O (5), and [CuL(5)(bipy)] (6), where L(1), L(2), L(3) and L(4) are the deprotonated form of N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide, 4-bromo-N'-(2-hydroxy-5-methoxybenzylidene)benzohydrazide, N'-(2-hydroxy-5-methoxybenzylidene)-3-methylbenzohydrazide and 2-chloro-N'-(2-hydroxy-5-methoxybenzylidene)benzohydrazide, respectively, L(5) is the dianionic form of N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide, and bipy is 2,2'-bipyridine. The complexes were characterized by infrared and UV-Vis spectra and single crystal X-ray diffraction. The Cu atoms in complexes 1, 2, 3, 4 and 5 are coordinated by the NOO donor set of the aroylhydrazone ligands, and one Cl or thiocyanate N atom, forming square planar coordination. The Cu atom in complex 6 is in a square pyramidal coordination, with the NOO donor set of L(1), and one N atom of bipy defining the basal plane, and with the other N atom of bipy occupying the apical position. Complexes 1, 2, 3, 4 and 5 show effective urease inhibitory activities, with IC50 values of 5.14, 0.20, 4.06, 5.52 and 0.26μM, respectively. Complex 6 has very weak activity against urease, with IC50 value over 100μM. Molecular docking study of the complexes with the Helicobacter pylori urease was performed. The relationship between structures and urease inhibitory activities indicated that copper complexes with square planar coordination are better models for urease inhibition. Copyright © 2016 Elsevier Inc. All rights reserved.

STOP Analysis and Optimization of a Very-Low-Distortion Space Instrument: HST WFC3 Case Study

NASA Technical Reports Server (NTRS)

Kunt, Cengiz; Broduer, Steve (Technical Monitor)

2001-01-01

New generation optical instruments with very demanding stability requirements are being proposed and developed for space applications. STOP (Structural-Thermal-Optical Performance) analysis and optimization is crucial in meeting the very tight distortion budgets of these instruments. This presentation outlines STOP analysis and optimization approach in the context of WFC3 (Wide-Field Camera 3), which is a radial instrument designed to replace the Wide-Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope (HST). WFC3 houses two separate channels, UVIS and IR, and will have greater throughput and sensitivity than WFPC2. WFC3 line-of-sight alignment budget for the UVIS and IR channels are as small as 10 and 20 milli-arcsec, respectively. Its optical bench is the most critical subsystem effecting the optical stability of WFC3 hence our effort concentrates on the design and analysis of the bench and its interfaces. Structural analysis has accompanied the mechanical design of the bench since the initial concept study. A high fidelity structural Finite Element Model (FEM) of the bench has been developed and used for minimizing its thermally induced distortions as well as sizing it to meet the stiffness and strength requirements of a Shuttle launch. The bench is a composite honeycomb panel box structure with a very low planar Coefficient of Thermal Expansion (CTE) of approximately 0.1 ppm/C. Optic components are mounted to super-INVAR inserts bonded into the panels. The bench is kinematically supported on three HST latches via interface struts, which are tailored to exhibit negative CTE to cancel out the thermal motions of the latches. The interface struts also incorporate flexure elements to minimize the mechanical distortions coming into the bench from its enclosure. Bench FEM is coupled with the enclosure FEM to quantify these effects. Short term or on-orbit STOP analysis includes distortion due to the temperature variations of the bench, the struts, and the enclosure. Long term or ground-to-orbit STOP analysis includes distortional effects of gravity release, desorption, and assembly in addition to the ground-to-orbit temperature variations. A rigorous testing program has been implemented for verifying the material properties and the analysis predictions. STOP analysis results demonstrate that both the short-term and the long-term alignment budgets will be met. Presentation will cover design and analysis details that are critical to a successful implementation of the STOP analysis and optimization process.

The research on calibration methods of dual-CCD laser three-dimensional human face scanning system

NASA Astrophysics Data System (ADS)

Wang, Jinjiang; Chang, Tianyu; Ge, Baozhen; Tian, Qingguo; Yang, Fengting; Shi, Shendong

2013-09-01

In this paper, on the basis of considering the performance advantages of two-step method, we combines the stereo matching of binocular stereo vision with active laser scanning to calibrate the system. Above all, we select a reference camera coordinate system as the world coordinate system and unity the coordinates of two CCD cameras. And then obtain the new perspective projection matrix (PPM) of each camera after the epipolar rectification. By those, the corresponding epipolar equation of two cameras can be defined. So by utilizing the trigonometric parallax method, we can measure the space point position after distortion correction and achieve stereo matching calibration between two image points. Experiments verify that this method can improve accuracy and system stability is guaranteed. The stereo matching calibration has a simple process with low-cost, and simplifies regular maintenance work. It can acquire 3D coordinates only by planar checkerboard calibration without the need of designing specific standard target or using electronic theodolite. It is found that during the experiment two-step calibration error and lens distortion lead to the stratification of point cloud data. The proposed calibration method which combining active line laser scanning and binocular stereo vision has the both advantages of them. It has more flexible applicability. Theory analysis and experiment shows the method is reasonable.

C-H activations at iridium(I) square-planar complexes promoted by a fifth ligand.

PubMed

Martín, Marta; Torres, Olga; Oñate, Enrique; Sola, Eduardo; Oro, Luis A

2005-12-28

In the presence of ligands such as acetonitrile, ethylene, or propylene, the Ir(I) complex [Ir(1,2,5,6-eta-C8H12)(NCMe)(PMe3)]BF4 (1) transforms into the Ir(III) derivatives [Ir(1-kappa-4,5,6-eta-C8H12)(NCMe)(L)(PMe3)]BF4 (L = NCMe, 2; eta2-C2H4, 3; eta2-C3H6, 4), respectively, through a sequence of C-H oxidative addition and insertion elementary steps. The rate of this transformation depends on the nature of L and, in the case of NCMe, the pseudo-first-order rate constants display a dependence upon ligand concentration suggesting the formation of five-coordinate reaction intermediates. A similar reaction between 1 and vinyl acetate affords the Ir(III) complex [Ir(1-kappa-4,5,6-eta-C8H12){kappa-O-eta2-OC(Me)OC2H3}(PMe3)]BF4 (7) via the isolable five-coordinate Ir(I) compound [Ir(1,2,5,6-eta-C8H12){kappa-O-eta2-OC(Me)OC2H3}(PMe3)]BF4 (6). DFT (B3LYP) calculations in model complexes show that reactions initiated by acetonitrile or ethylene five-coordinate adducts involve C-H oxidative addition transition states of lower energy than that found in the absence of these ligands. Key species in these ligand-assisted transformations are the distorted (nonsquare-planar) intermediates preceding the intramolecular C-H oxidative addition step, which are generated after release of one cyclooctadiene double bond from the five-coordinate species. The feasibility of this mechanism is also investigated for complexes [IrCl(L)(PiPr3)2] (L = eta2-C2H4, 27; eta2-C3H6, 28). In the presence of NCMe, these complexes afford the C-H activation products [IrClH(CH=CHR)(NCMe)(PiPr3)2] (R = H, 29; Me, 30) via the common cyclometalated intermediate [IrClH{kappa-P,C-P(iPr)2CH(CH3)CH2}(NCMe)(PiPr3)] (31). The most effective C-H oxidative addition mechanism seems to involve three-coordinate intermediates generated by photochemical release of the alkene ligand. However, in the absence of light, the reaction rates display dependences upon NCMe concentration again indicating the intermediacy of five-coordinate acetonitrile adducts.

Image formation in diffusion MRI: A review of recent technical developments

PubMed Central

Miller, Karla L.

2017-01-01

Diffusion magnetic resonance imaging (MRI) is a standard imaging tool in clinical neurology, and is becoming increasingly important for neuroscience studies due to its ability to depict complex neuroanatomy (eg, white matter connectivity). Single‐shot echo‐planar imaging is currently the predominant formation method for diffusion MRI, but suffers from blurring, distortion, and low spatial resolution. A number of methods have been proposed to address these limitations and improve diffusion MRI acquisition. Here, the recent technical developments for image formation in diffusion MRI are reviewed. We discuss three areas of advance in diffusion MRI: improving image fidelity, accelerating acquisition, and increasing the signal‐to‐noise ratio. Level of Evidence: 5 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:646–662 PMID:28194821

Simulated structure and imaging of NTCDI on Si(1 1 1)-7 × 7 : a combined STM, NC-AFM and DFT study

NASA Astrophysics Data System (ADS)

Jarvis, S. P.; Sweetman, A. M.; Lekkas, I.; Champness, N. R.; Kantorovich, L.; Moriarty, P.

2015-02-01

The adsorption of naphthalene tetracarboxylic diimide (NTCDI) on Si(1 1 1)-7 × 7 is investigated through a combination of scanning tunnelling microscopy (STM), noncontact atomic force microscopy (NC-AFM) and density functional theory (DFT) calculations. We show that NTCDI adopts multiple planar adsorption geometries on the Si(1 1 1)-7 × 7 surface which can be imaged with intramolecular bond resolution using NC-AFM. DFT calculations reveal adsorption is dominated by covalent bond formation between the molecular oxygen atoms and the surface silicon adatoms. The chemisorption of the molecule is found to induce subtle distortions to the molecular structure, which are observed in NC-AFM images.

Projection moire for remote contour analysis

NASA Technical Reports Server (NTRS)

Doty, J. L.

1983-01-01

Remote projection and viewing of moire contours are examined analytically for a system employing separate projection and viewing optics, with specific attention paid to the practical limitations imposed by the optical systems. It is found that planar contours are possible only when the optics are telecentric (exit pupil at infinity) but that the requirement for spatial separability of the contour fringes from extraneous fringes is independent of the specific optics and is a function only of the angle separating the two optic axes. In the nontelecentric case, the contour separation near the object is unchanged from that of the telecentric case, although the contours are distorted into low-eccentricity (near-circular) ellipses. Furthermore, the minimum contour spacing is directly related to the depth of focus through the resolution of the optics.

Charge transfer properties of pentacene adsorbed on silver: DFT study

NASA Astrophysics Data System (ADS)

N, Rekha T.; Rajkumar, Beulah J. M.

2015-06-01

Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistribution of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices.

Potassium (2,2'-bipyridine-κN,N')bis-(carbonato-κO,O')cobaltate(III) dihydrate.

PubMed

Wang, Jian-Fei; Lin, Jian-Li

2010-09-30

In the title compound, K[Co(CO(3))(2)(C(10)H(8)N(2))]·2H(2)O, the Co(III) atom is coordinated by two bipyridine N atoms and four O atoms from two bidentate chelating carbonate anions, and thus adopts a distorted octa-hedral N(2)O(4) environment. The [Co(bipy)(CO(3))(2)](-) (bipy is 2,2'-bipyridine) -units are stacked along [100] via π-π stacking inter-actions, with inter-planar distances between the bipyridine rings of 3.36 (4) and 3.44 (6) Å, forming chains. Classical O-H⋯O hydrogen-bonding inter-actions link the chains, forming channels along (100) in which the K(+) ions reside and leading to a three-dimensional supra-molecular architecture.

Zinc ascorbate: a combined experimental and computational study for structure elucidation

NASA Astrophysics Data System (ADS)

Ünaleroǧlu, C.; Zümreoǧlu-Karan, B.; Mert, Y.

2002-03-01

The structure of Zn(HA)2·4H2O (HA=ascorbate) has been examined by a number of techniques (13C NMR, 1H NMR, IR, EI/MS and TGA) and also modeled by the semi-empirical PM3 method. The experimental and computational results agreed on a five-fold coordination around Zn(II) where one ascorbate binds monodentately, the other bidentately and two water molecules occupy the remaining sites of a distorted square pyramid.

Implementation and Evaluation of Two Design Concepts of the Passive Ring Resonator Laser Gyroscope.

DTIC Science & Technology

1983-12-01

The cavity mirrors consist of 23 dielec- tric layers on a Zerodur substrate (Ref 1). The reflectivity of each mirror is 0.99995 (Ref 1). The...Conditions at the Cavity Input Mirror ...II1-8 6 Cavity Power Transmission vs. Frequency.. ........ II-10 7 Spatial Phase Distortion of the Reflected...32 16 Piano-Spherical Square vty.........II3 17 Astigmatism of a Spherical Mirror in a Ring 18 Case Is Circular-Circular Mode Match..........e...II

EXAFS study of some coordination polymers of copper

NASA Astrophysics Data System (ADS)

Deshpande, A. P.

1995-02-01

The EXAFS spectra for (1) azelaic acid bis phenyl hydrazide, (2) azelaic acid bis 2,4 dinitro phenyl hydrazide and (3) sebacic acid bis phenyl hydrazide coordination polymers of copper were obtained using the EXAFS facility of the Daresbury Laboratory. The EXAFS analysis revealed that copper is surrounded by four nitrogen and two oxygen atoms in the first coordination shell, while the second coordination shell consists of two carbon atoms. This information suggests the octahedral geometry for the repeating units of polymeric complexes, in contrast to the square planar geometry previously proposed.

catena-Poly[copper(II)-mu-L-tyrosyl-L-leucinato].

PubMed

Baggio, Ricardo; Casado, Nieves M C; Calvo, Rafael; Rapp, Raul E; Garland, María Teresa

2005-05-01

In the title compound, [Cu(C15H20N2O4)]n, the copper(II) coordination is square planar. The anionic L-tyrosyl-L-leucinate ligand binds in an N,N',O-tridentate mode to one Cu(II) cation on one side and in an O-monodentate mode to a second Cu(II) cation on the other side, thus defining -Cu-O-C-O-Cu'- chains which run along the a axis. These chains are held together by a strong hydrogen bond involving the hydroxy H atom.

Palladium(II)-Catalyzed Annulation between ortho-Alkenylphenols and Allenes. Key Role of the Metal Geometry in Determining the Reaction Outcome.

PubMed

Casanova, Noelia; Del Rio, Karina P; García-Fandiño, Rebeca; Mascareñas, José L; Gulías, Moisés

2016-05-06

2-Alkenylphenols react with allenes, upon treatment with catalytic amounts of Pd(II) and Cu(II), to give benzoxepine products in high yields and with very good regio- and diastereoselectivities. This contrasts with the results obtained with Rh catalysts, which provided chromene-like products through a pathway involving a β-hydrogen elimination step. Computational studies suggest that the square planar geometry of the palladium is critical to favor the reductive elimination process required for the formation of the oxepine products.

Low Noise 1.2 THz SIS Receiver

NASA Technical Reports Server (NTRS)

Karpov, A.; Miller, D.; Rice, F.; Zmuidzinas, J.; Stern, J. A.; Bumble, B.; LeDuc, H. G.

2001-01-01

We present the development of a low noise superconductor insulator superconductor (SIS) mixer for the 1.1 - 1.25 THz heterodyne receiver of FIRST space radiotelescope. The quasi-optical SIS mixer has two NbTiN/AlN/Nb junctions with critical current density 30 kA/sq cm. The individual junction area is close to 0.65 square micrometers. The SIS junctions are coupled to the optical input beam through a planar double slot antenna and a Si hyperhemispherical lens. The minimum DSB receiver noise temperature is 650 K, about 12 hv/k.

Distortion correction of echo-planar diffusion-weighted images of uterine cervix.

PubMed

deSouza, Nandita M; Orton, Matthew; Downey, Kate; Morgan, Veronica A; Collins, David J; Giles, Sharon L; Payne, Geoffrey S

2016-05-01

To investigate the clinical utility of the reverse gradient algorithm in correcting distortions in diffusion-weighted images of the cervix and for increasing diagnostic performance. Forty-one patients ages 25-72 years (mean 40 ± 11 years) with suspected or early stage cervical cancer were imaged at 3T using an endovaginal coil. T2 -weighted (W) and diffusion-weighted images with right and left phase-encode gradient directions were obtained coronal to the cervix (b = 0, 100, 300, 500, 800 s mm(-2) ). Differences in angle of the endocervical canal to the x-axis between T2 W and right-gradient, left-gradient, and corrected images were measured. Uncorrected and corrected images were assessed for diagnostic performance when viewed together with T2 W images by two independent observers against subsequent histology. The angles of the endocervical canal relative to the x-axis were significantly different between the T2 W images and the right-gradient images (P = 0.007), approached significance for left-gradient images (P = 0.055), and were not significantly different after correction (P = 0.95). Corrected images enabled a definitive diagnosis in 34% (n = 14) of patients classified as equivocal on uncorrected images. Tumor volume in this subset was 0.18 ± 0.44 cm(3) (mean ± SD; sensitivity of detection 100% [8/8], specificity 50% [3/6] for an experienced observer). Correction did not improve diagnostic performance for the less-experienced observer. Distortion-corrected diffusion-weighted images improved correspondence with T2 W images and diagnostic performance in a third of cases. © 2015 The Authors Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

String theory of the Regge intercept.

PubMed

Hellerman, S; Swanson, I

2015-03-20

Using the Polchinski-Strominger effective string theory in the covariant gauge, we compute the mass of a rotating string in D dimensions with large angular momenta J, in one or two planes, in fixed ratio, up to and including first subleading order in the large J expansion. This constitutes a first-principles calculation of the value for the order-J(0) contribution to the mass squared of a meson on the leading Regge trajectory in planar QCD with bosonic quarks. For open strings with Neumann boundary conditions, and for closed strings in D≥5, the order-J(0) term in the mass squared is exactly calculated by the semiclassical approximation. This term in the expansion is universal and independent of the details of the theory, assuming only D-dimensional Poincaré invariance and the absence of other infinite-range excitations on the string world volume, beyond the Nambu-Goldstone bosons.

Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section

NASA Astrophysics Data System (ADS)

Zhu, Lianhua; Yang, Xiaofan; Guo, Zhaoli

2017-12-01

Rarefied gas flow in a three-dimensional enclosure induced by nonuniform temperature distribution is numerically investigated. The enclosure has a square channel-like geometry with alternatively heated closed ends and lateral walls with a linear temperature distribution. A recently proposed implicit discrete velocity method with a memory reduction technique is used to numerically simulate the problem based on the nonlinear Shakhov kinetic equation. The Knudsen number dependencies of the vortices pattern, slip velocity at the planar walls and edges, and heat transfer are investigated. The influences of the temperature ratio imposed at the ends of the enclosure and the geometric aspect ratio are also evaluated. The overall flow pattern shows similarities with those observed in two-dimensional configurations in literature. However, features due to the three-dimensionality are observed with vortices that are not identified in previous studies on similar two-dimensional enclosures at high Knudsen and small aspect ratios.

A Comparison Between Jerusalem Cross and Square Patch Frequency Selective Surfaces for Low Profile Antenna Applications

NASA Technical Reports Server (NTRS)

Cure, David; Weller, Thomas; Miranda, Felix A.

2011-01-01

In this paper, a comparison between Jerusalem Cross (JC) and Square Patch (SP) based Frequency Selected Surfaces (FSS) for low profile antenna applications is presented. The comparison is aimed at understanding the performance of low profile antennas backed by high impedance surfaces. In particular, an end loaded planar open sleeve dipole (ELPOSD) antenna is examined due to the various parameters within its configuration, offering significant design flexibility and a wide operating bandwidth. Measured data of the antennas demonstrate that increasing the number of unit cells improves the fractional bandwidth. The antenna bandwidth increased from 0.8% to 1.8% and from 0.8% to 2.7% for the JC and SP structures, respectively. The number of unit cells was increased from 48 to 80 for the JC-FSS and from 24 to 48 for the SP-FSS.

Effects of structural deformations on optical properties of tetrabenzoporphyrins: free-bases and Pd complexes.

PubMed

Lebedev, Artem Y; Filatov, Mikhail A; Cheprakov, Andrei V; Vinogradov, Sergei A

2008-08-21

A recently developed method of synthesis of pi-extended porphyrins made it possible to prepare a series of tetrabenzoporphyrins (TBP) with different numbers of meso-aryl substituents. The photophysical parameters of free-bases and Pd complexes of meso-unsubstituted TBP's, 5,15-diaryl-TBP's (Ar2TBP's) and 5,10,15,20-tetraaryl-TBP's (Ar4TBP's) were measured. For comparison, similarly meso-arylsubstituted porphyrins fused with nonaromatic cyclohexeno-rings, i.e. Ar(n)-tetracyclohexenoporphyrins (Ar(n)TCHP's, n = 0, 2, 4), were also synthesized and studied. Structural information was obtained by ab initio (DFT) calculations and X-ray crystallography. It was found that: 1) Free-base Ar4TBP's are strongly distorted out-of-plane (saddled), possess broadened, red-shifted spectra, short excited-state lifetimes and low fluorescence quantum yields (tau(fl) = 2-3 ns, phi(fl) = 0.02-0.03). These features are characteristic of other nonplanar free-base porphyrins, including Ar4TCHP's. 2) Ar2TBP free-bases possess completely planar geometries, although with significant in-plane deformations. These deformations have practically no effect on the singlet excited-state properties of Ar2TBP's as compared to planar meso-unsubstituted TBP's. Both types of porphyrins retain strong fluorescence (tau(fl) = 10-12 ns, phi(fl) = 0.3-0.4), and their radiative rate constants (k(r)) are 3-4 times higher than those of planar H2TCHP's. 3) Nonplanar deformations dramatically enhance nonradiative decay of triplet states of regular Pd porphyrins. For example, planar PdTCHP phosphoresces with high quantum yield (phi(phos) = 0.45, tau(phos) = 1118 micros), while saddled PdPh4TCHP is practically nonemissive. In contrast, both ruffled and saddled PdAr(n)TBP's retain strong phosphorescence at ambient temperatures (PdPh2TBP: tau(phos) = 496 micros, phi(phos) = 0.15; PdPh4TBP: tau(phos) = 258 micros, phi(phos) = 0.08). It appears that pi-extension is capable of counterbalancing deleterious effects of nonplanar deformations on triplet emissivity of Pd porphyrins.

Effects of Structural Deformations on Optical Properties of Tetrabenzoporphyrins: Free-Bases and Pd Complexes

PubMed Central

Lebedev, Artem Y.; Filatov, Mikhail A.; Cheprakov, Andrei V.; Vinogradov, Sergei A.

2009-01-01

A recently developed method of synthesis of π-extended porphyrins made it possible to prepare a series of tetrabenzoporphyrins (TBP) with different numbers of meso-aryl substituents. The photophysical parameters of free-bases and Pd complexes of meso-unsubstituted TBP’s, 5,15-diaryl-TBP’s (Ar2TBP’s) and 5,10,15,20-tetraaryl-TBP’s (Ar4TBP’s) were measured. For comparison, similarly meso-arylsubstituted porphyrins fused with nonaromatic cyclohexeno-rings, i.e. Arn-tetracyclohexenoporphyrins (ArnTCHP’s, n = 0, 2, 4), were also synthesized and studied. Structural information was obtained by ab initio (DFT) calculations and X-ray crystallography. It was found that: 1) Free-base Ar4TBP’s are strongly distorted out-of-plane (saddled), possess broadened, red-shifted spectra, short excited-state lifetimes and low fluorescence quantum yields (τfl = 2–3 ns, ϕfl = 0.02–0.03). These features are characteristic of other nonplanar free-base porphyrins, including Ar4TCHP’s. 2) Ar2TBP free-bases possess completely planar geometries, although with significant in-plane deformations. These deformations have practically no effect on the singlet excited-state properties of Ar2TBP’s as compared to planar meso-unsubstituted TBP’s. Both types of porphyrins retain strong fluorescence (τfl = 10–12 ns, ϕfl = 0.3–0.4), and their radiative rate constants (kr) are 3–4 times higher than those of planar H2TCHP’s. 3) Nonplanar deformations dramatically enhance nonradiative decay of triplet states of regular Pd porphyrins. For example, planar PdTCHP phosphoresces with high quantum yield (ϕphos = 0.45, τphos = 1118 µs), while saddled PdPh4TCHP is practically nonemissive. In contrast, both ruffled and saddled PdArnTBP’s retain strong phosphorescence at ambient temperatures (PdPh2TBP: τphos = 496 µs, ϕphos = 0.15; PdPh4TBP: τphos = 258 µs, ϕphos = 0.08). It appears that π-extension is capable of counterbalancing deleterious effects of nonplanar deformations on triplet emissivity of Pd porphyrins. PMID:18665576

A library least-squares approach for scatter correction in gamma-ray tomography

NASA Astrophysics Data System (ADS)

Meric, Ilker; Anton Johansen, Geir; Valgueiro Malta Moreira, Icaro

2015-03-01

Scattered radiation is known to lead to distortion in reconstructed images in Computed Tomography (CT). The effects of scattered radiation are especially more pronounced in non-scanning, multiple source systems which are preferred for flow imaging where the instantaneous density distribution of the flow components is of interest. In this work, a new method based on a library least-squares (LLS) approach is proposed as a means of estimating the scatter contribution and correcting for this. The validity of the proposed method is tested using the 85-channel industrial gamma-ray tomograph previously developed at the University of Bergen (UoB). The results presented here confirm that the LLS approach can effectively estimate the amounts of transmission and scatter components in any given detector in the UoB gamma-ray tomography system.

Symbol signal-to-noise ratio loss in square-wave subcarrier downconversion

NASA Technical Reports Server (NTRS)

Feria, Y.; Statman, J.

1993-01-01

This article presents the simulated results of the signal-to-noise ratio (SNR) loss in the process of a square-wave subcarrier down conversion. In a previous article, the SNR degradation was evaluated at the output of the down converter based on the signal and noise power change. Unlike in the previous article, the SNR loss is defined here as the difference between the actual and theoretical symbol SNR's for the same symbol-error rate at the output of the symbol matched filter. The results show that an average SNR loss of 0.3 dB can be achieved with tenth-order infinite impulse response (IIR) filters. This loss is a 0.2-dB increase over the SNR degradation in the previous analysis where neither the signal distortion nor the symbol detector was considered.

Diagnosing and dealing with multicollinearity.

PubMed

Schroeder, M A

1990-04-01

The purpose of this article was to increase nurse researchers' awareness of the effects of collinear data in developing theoretical models for nursing practice. Collinear data distort the true value of the estimates generated from ordinary least-squares analysis. Theoretical models developed to provide the underpinnings of nursing practice need not be abandoned, however, because they fail to produce consistent estimates over repeated applications. It is also important to realize that multicollinearity is a data problem, not a problem associated with misspecification of a theorectical model. An investigator must first be aware of the problem, and then it is possible to develop an educated solution based on the degree of multicollinearity, theoretical considerations, and sources of error associated with alternative, biased, least-square regression techniques. Decisions based on theoretical and statistical considerations will further the development of theory-based nursing practice.

Weight Vector Fluctuations in Adaptive Antenna Arrays Tuned Using the Least-Mean-Square Error Algorithm with Quadratic Constraint

NASA Astrophysics Data System (ADS)

Zimina, S. V.

2015-06-01

We present the results of statistical analysis of an adaptive antenna array tuned using the least-mean-square error algorithm with quadratic constraint on the useful-signal amplification with allowance for the weight-coefficient fluctuations. Using the perturbation theory, the expressions for the correlation function and power of the output signal of the adaptive antenna array, as well as the formula for the weight-vector covariance matrix are obtained in the first approximation. The fluctuations are shown to lead to the signal distortions at the antenna-array output. The weight-coefficient fluctuations result in the appearance of additional terms in the statistical characteristics of the antenna array. It is also shown that the weight-vector fluctuations are isotropic, i.e., identical in all directions of the weight-coefficient space.

Dynamic multi-coil technique (DYNAMITE) shimming for echo-planar imaging of the human brain at 7 Tesla.

PubMed

Juchem, Christoph; Umesh Rudrapatna, S; Nixon, Terence W; de Graaf, Robin A

2015-01-15

Gradient-echo echo-planar imaging (EPI) is the primary method of choice in functional MRI and other methods relying on fast MRI to image brain activation and connectivity. However, the high susceptibility of EPI towards B0 magnetic field inhomogeneity poses serious challenges. Conventional magnetic field shimming with low-order spherical harmonic (SH) functions is capable of compensating shallow field distortions, but performs poorly for global brain shimming or on specific areas with strong susceptibility-induced B0 distortions such as the prefrontal cortex (PFC). Excellent B0 homogeneity has been demonstrated recently in the human brain at 7 Tesla with the DYNAmic Multi-coIl TEchnique (DYNAMITE) for magnetic field shimming (J Magn Reson (2011) 212:280-288). Here, we report the benefits of DYNAMITE shimming for multi-slice EPI and T2* mapping. A standard deviation of 13Hz was achieved for the residual B0 distribution in the human brain at 7 Tesla with DYNAMITE shimming and was 60% lower compared to conventional shimming that employs static zero through third order SH shapes. The residual field inhomogeneity with SH shimming led to an average 8mm shift at acquisition parameters commonly used for fMRI and was reduced to 1.5-3mm with DYNAMITE shimming. T2* values obtained from the prefrontal and temporal cortices with DYNAMITE shimming were 10-50% longer than those measured with SH shimming. The reduction of the confounding macroscopic B0 field gradients with DYNAMITE shimming thereby promises improved access to the relevant microscopic T2* effects. The combination of high spatial resolution and DYNAMITE shimming allows largely artifact-free EPI and T2* mapping throughout the brain, including prefrontal and temporal lobe areas. DYNAMITE shimming is expected to critically benefit a wide range of MRI applications that rely on excellent B0 magnetic field conditions including EPI-based fMRI to study various cognitive processes and assessing large-scale brain connectivity in vivo. As such, DYNAMITE shimming has the potential to replace conventional SH shim systems in human MR scanners. Copyright © 2014 Elsevier Inc. All rights reserved.

Dynamic Multi-Coil Technique (DYNAMITE) Shimming for Echo-Planar Imaging of the Human Brain at 7 Tesla

PubMed Central

Juchem, Christoph; Rudrapatna, S. Umesh; Nixon, Terence W.; de Graaf, Robin A.

2014-01-01

Gradient-echo echo-planar imaging (EPI) is the primary method of choice in functional MRI and other methods relying on fast MRI to image brain activation and connectivity. However, the high susceptibility of EPI towards B0 magnetic field inhomogeneity poses serious challenges. Conventional magnetic field shimming with low-order spherical harmonic (SH) functions is capable of compensating shallow field distortions, but performs poorly for global brain shimming or on specific areas with strong susceptibility-induced B0 distortions such as the prefrontal cortex (PFC). Excellent B0 homogeneity has been demonstrated recently in the human brain at 7 Tesla with the DYNAmic Multi-coIl TEchnique (DYNAMITE) for magnetic field shimming (Juchem et al., J Magn Reson (2011) 212:280-288). Here, we report the benefits of DYNAMITE shimming for multi-slice EPI and T2* mapping. A standard deviation of 13 Hz was achieved for the residual B0 distribution in the human brain at 7 Tesla with DYNAMITE shimming and was 60% lower compared to conventional shimming that employs static zero through third order SH shapes. The residual field inhomogeneity with SH shimming led to an average 8 mm shift at acquisition parameters commonly used for fMRI and was reduced to 1.5-3 mm with DYNAMITE shimming. T2* values obtained from the prefrontal and temporal cortices with DYNAMITE shimming were 10-50% longer than those measured with SH shimming. The reduction of the confounding macroscopic B0 field gradients with DYNAMITE shimming thereby promises improved access to the relevant microscopic T2* effects. The combination of high spatial resolution and DYNAMITE shimming allows largely artifact-free EPI and T2* mapping throughout the brain, including prefrontal and temporal lobe areas. DYNAMITE shimming is expected to critically benefit a wide range of MRI applications that rely on excellent B0 magnetic field conditions including EPI-based fMRI to study various cognitive processes and assessing large-scale brain connectivity in vivo. As such, DYNAMITE shimming has the potential to replace conventional SH shim systems in human MR scanners. PMID:25462795

Liver imaging at 3.0 T: diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: feasibility study.

PubMed

van den Bos, Indra C; Hussain, Shahid M; Krestin, Gabriel P; Wielopolski, Piotr A

2008-07-01

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced black-blood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers (seven men, seven women; mean age +/- standard deviation, 32.7 years +/- 6.8) were imaged for this purpose. Liver coverage (20 cm, z-axis) was always performed in one 25-second breath hold. Imaging parameters were varied interactively with regard to echo time, diffusion b value, and voxel size. Images were evaluated and compared with fat-suppressed T2-weighted FSE images for image quality, liver delineation, geometric distortions, fat suppression, suppression of the blood signal, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). An optimized short- (25 msec) and long-echo (80 msec) BBEPI provided full anatomic, single breath-hold liver coverage (100 and 50 sections, respectively), with resulting voxel sizes of 3.3 x 2.7 x 2.0 mm and 3.3 x 2.7 x 4.0 mm, respectively. Repetition time was 6300 msec, matrix size was 160 x 192, and an acceleration factor of 2.00 was used. b Values of more than 20 sec/mm(2) showed better suppression of the blood signal but b values of 10 sec/mm(2) provided improved volume coverage and signal consistency. Compared with fat-suppressed T2-weighted FSE, the optimized BBEPI sequence provided (a) comparable image quality and liver delineation, (b) acceptable geometric distortions, (c) improved suppression of fat and blood signals, and (d) high CNR and SNR. BBEPI is feasible for fast, low-SAR, thin-section morphologic imaging of the entire liver in a single breath hold at 3.0 T. (c) RSNA, 2008.

Constraints on μ-distortion fluctuations and primordial non-Gaussianity from Planck data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khatri, Rishi; Sunyaev, Rashid, E-mail: khatri@mpa-garching.mpg.de, E-mail: sunyaev@mpa-garching.mpg.de

2015-09-01

We use the Planck HFI channel maps to make an all sky map of μ-distortion fluctuations. Our μ-type distortion map is dominated by the y-type distortion contamination from the hot gas in the low redshift Universe and we can thus only place upper limits on the μ-type distortion fluctuations. For the amplitude of μ-type distortions on 10' scales we get the limit on root mean square (rms) value μ{sub rms}{sup 10'}< 6.4× 10{sup −6}, a limit 14 times stronger than the COBE-FIRAS (95% confidence) limit on the mean of ( μ )<90× 10{sup −6}. Using our maps we also place strong upper limits on themore » auto angular power spectrum of μ, C{sub ℓ}{sup μμ} and the cross angular power spectrum of μ with the CMB temperature anisotropies, C{sub ℓ}{sup μ T}. The strongest observational limits are on the largest scales, ℓ(ℓ+1)/(2π)C{sub ℓ}{sup μμ}|{sub ℓ=2−26}<(2.3± 1.0)× 10{sup −12} and ℓ(ℓ+1)/(2π)C{sub ℓ}{sup μ T}|{sub ℓ=2−26}<(2.6± 2.6)× 10{sup −12} K. Our observational limits can be used to constrain new physics which can create spatially varying energy release in the early Universe between redshifts 5× 10{sup 4∼<} z∼< 2× 10{sup 6}. We specifically apply our observational results to constrain the primordial non-Gaussianity of the local type, when the source of μ-distortion is Silk damping, for very squeezed configurations with the wavenumber for the short wavelength mode 46 ∼< k{sub S} ∼< 10{sup 4} Mpc{sup −1} and for the long wavelength mode k{sub L}≈ 10{sup −3} Mpc{sup −1}. Our limits on the primordial non-Gaussianity parameters are f{sub NL}<10{sup 5}, τ{sub NL}<1.4× 10{sup 11} for k{sub S}/k{sub L}≈ 5× 10{sup 4}− 10{sup 7}. We also give a new derivation of the evolution of the μ-distortion fluctuations through the y-distortion era and the recombination epoch until today resulting in very simple expressions for the cross and auto power spectra in the squeezed limit. We also introduce mixing of Bose-Einstein spectra due to Silk damping and y{sup BE}-type distortions. The μ-type distortion map and masks are now publicly available.« less

Wireless Power Transfer for Distributed Estimation in Sensor Networks

NASA Astrophysics Data System (ADS)

Mai, Vien V.; Shin, Won-Yong; Ishibashi, Koji

2017-04-01

This paper studies power allocation for distributed estimation of an unknown scalar random source in sensor networks with a multiple-antenna fusion center (FC), where wireless sensors are equipped with radio-frequency based energy harvesting technology. The sensors' observation is locally processed by using an uncoded amplify-and-forward scheme. The processed signals are then sent to the FC, and are coherently combined at the FC, at which the best linear unbiased estimator (BLUE) is adopted for reliable estimation. We aim to solve the following two power allocation problems: 1) minimizing distortion under various power constraints; and 2) minimizing total transmit power under distortion constraints, where the distortion is measured in terms of mean-squared error of the BLUE. Two iterative algorithms are developed to solve the non-convex problems, which converge at least to a local optimum. In particular, the above algorithms are designed to jointly optimize the amplification coefficients, energy beamforming, and receive filtering. For each problem, a suboptimal design, a single-antenna FC scenario, and a common harvester deployment for colocated sensors, are also studied. Using the powerful semidefinite relaxation framework, our result is shown to be valid for any number of sensors, each with different noise power, and for an arbitrarily number of antennas at the FC.

Deconvolution of the PSF of a seismic lens

NASA Astrophysics Data System (ADS)

Yu, Jianhua; Wang, Yue; Schuster, Gerard T.

2002-12-01

We show that if seismic data d is related to the migration image by mmig = LTd. then mmig is a blurred version of the actual reflectivity distribution m, i.e., mmig = (LTL)m. Here L is the acoustic forward modeling operator under the Born approximation where d = Lm. The blurring operator (LTL), or point spread function, distorts the image because of defects in the seismic lens, i.e., small source-receiver recording aperture and irregular/coarse geophone-source spacing. These distortions can be partly suppressed by applying the deblurring operator (LTL)-1 to the migration image to get m = (LTL)-1mmig. This deblurred image is known as a least squares migration (LSM) image if (LTL)-1LT is applied to the data d using a conjugate gradient method, and is known as a migration deconvolved (MD) image if (LTL)-1 is directly applied to the migration image mmig in (kx, ky, z) space. The MD algorithm is an order-of-magnitude faster than LSM, but it employs more restrictive assumptions. We also show that deblurring can be used to filter out coherent noise in the data such as multiple reflections. The procedure is to, e.g., decompose the forward modeling operator into both primary and multiple reflection operators d = (Lprim + Lmulti)m, invert for m, and find the primary reflection data by dprim = Lprimm. This method is named least squares migration filtering (LSMF). The above three algorithms (LSM, MD and LSMF) might be useful for attacking problems in optical imaging.

Measurement of aerosol optical properties by cw cavity enhanced spectroscopy

NASA Astrophysics Data System (ADS)

Jie, Guo; Ye, Shan-Shan; Yang, Xiao; Han, Ye-Xing; Tang, Huai-Wu; Yu, Zhi-Wei

2016-10-01

The CAPS (Cavity Attenuated Phase shift Spectroscopy) system, which detects the extinction coefficients within a 10 nm bandpass centered at 532 nm, comprises a green LED with center wavelength in 532nm, a resonant optical cavity (36 cm length), a Photo Multiplier Tube detector, and a lock in amplifier. The square wave modulated light from the LED passes through the optical cavity and is detected as a distorted waveform which is characterized by a phase shift with respect to the initial modulation. Extinction coefficients are determined from changes in the phase shift of the distorted waveform of the square wave modulated LED light that is transmitted through the optical cavity. The performance of the CAPS system was evaluated by using measurements of the stability and response of the system. The minima ( 0.1 Mm-1) in the Allan plots show the optimum average time ( 100s) for optimum detection performance of the CAPS system. In the paper, it illustrates that extinction coefficient was correlated with PM2.5 mass (0.91). These figures indicate that this method has the potential to become one of the most sensitive on-line analytical techniques for extinction coefficient detection. This work aims to provide an initial validation of the CAPS extinction monitor in laboratory and field environments. Our initial results presented in this paper show that the CAPS extinction monitor is capable of providing state-of-the-art performance while dramatically reducing the complexity of optical instrumentation for directly measuring the extinction coefficients.

Revisiting the polytopal rearrangements in penta-coordinate d7-metallocomplexes: modified Berry pseudorotation, octahedral switch, and butterfly isomerization.

PubMed

Asatryan, Rubik; Ruckenstein, Eli; Hachmann, Johannes

2017-08-01

This paper provides a first-principles theoretical investigation of the polytopal rearrangements and fluxional behavior of five-coordinate d 7 -transition metal complexes. Our work is primarily based on a potential energy surface analysis of the iron tetracarbonyl hydride radical HFe˙(CO) 4 . We demonstrate the existence of distorted coordination geometries in this prototypical system and, for the first time, introduce three general rearrangement mechanisms, which account for the non-ideal coordination. The first of these mechanisms constitutes a modified version of the Berry pseudorotation via a square-based pyramidal C 4v transition state that connects two chemically identical edge-bridged tetrahedral stereoisomers of C 2v symmetry. It differs from the classical Berry mechanism, which involves two regular D 3h equilibrium structures and a C 4v transition state. The second mechanism is related to the famous "tetrahedral jump" hypothesis, postulated by Muetterties for a number of d 6 HML 4 and H 2 ML 4 complexes. Here, our study suggests two fluxional rearrangement pathways via distinct types of C 2v transition states. Both pathways of this mechanism can be described as a single-ligand migration to a vacant position of an "octahedron", thus interchanging (switching) the apical and basal ligands of the initial quasi-square pyramidal isomer, which is considered as an idealized octahedron with a vacancy. Accordingly, we call this mechanism "octahedral switch". The third mechanism follows a butterfly-type isomerization featuring a key-angle deformation, and we thus call it "butterfly isomerization". It connects the quasi-square pyramidal and edge-bridged tetrahedral isomers of HFe˙(CO) 4 through a distorted edge-bridged tetrahedral transition state of C s symmetry. Our paper discusses the overall features of the isomers and rearrangement mechanisms as well as their implications. We rationalize the existence of each stationary point through an electronic structure analysis and argue their relevance for isolobal analogues of HFe˙(CO) 4 .

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoff, M; Rane-Levandovsky, S; Andre, J

Purpose: Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL’s ability to accurately quantify cerebral blood flow (CBF) and assess disease-specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans. Methods: Four subjects were imaged on a 3T Philips Ingenia scanner using a 16-channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field-of-view. An ASL sequence with a pseudo-continuous ASL (pCASL) labeling scheme was employedmore » to acquire thirty dynamics of single-shot EPI data, with control and label datasets for all dynamics, and PLACE gradients applied on odd dynamics. Parameters included a post-labeling delay = 2s, label duration = 1.8s, flip angle = 90°, TR/TE = 5000/23.5ms, and 2.9/2.9/5.0mm (frequency/phase/slice direction) voxel size. “M0” EPI-reference images and T1-weighted spin-echo images with 0.8/1.0/3.3mm (frequency/phase/slice directions) voxel size were also acquired. Complex conjugate image products of pCASL odd and even dynamics were formed, a linear phase ramp applied, and data expanded and smoothed. Data phase was extracted to map control, label, and M0 magnitude image pixels to their undistorted locations, and images were rebinned to original size. All images were corrected for motion artifacts in FSL 5.0. pCASL images were registered to M0 images, and control and label images were subtracted to compute quantitative CBF maps. Results: pCASL image and CBF map distortions were removed by PLACE in all subjects. Corrected images conformed well to the anatomical T1-weighted reference image, and deviations in corrected CBF maps were evident. Conclusion: Eliminating pCASL distortion with PLACE can improve CBF quantification accuracy using minimal pulse sequence modifications and no additional scan time, improving ASL’s clinical applicability.« less

Detecting signatures of cosmological recombination and reionization in the cosmic radio background

NASA Astrophysics Data System (ADS)

Subrahmanyan, Ravi; Shankar Narayana Rao, Udaya; Sathyanarayana Rao, Mayuri; Singh, Saurabh

2015-08-01

Evolution of the baryons during the Epochs of cosmological Recombination and Reionization has left traces in the cosmic radio background in the form of spectral distortions (Sunyaev & Chluba 2008 Astron. Nachrichten, 330, 657; Pritchard & Loeb 2012 Rep Prog Phys 75(8):086901). The spectral signature depends on the evolution in the ionization state in hydrogen and helium and on the spin temperature of hydrogen. These probe the physics of energy release beyond the last scattering surface at redshifts exceeding 1090 and the nature of the first sources and gas evolution down to redshift about 6. The spectral distortions are sensitive to the nature of the first stars, ultra-dwarf galaxies, accreting compact objects, and the evolving ambient radiation field: X-rays and UV from the first sources. Detection of the all-sky or global spectral distortions in the radio background is hence a probe of cosmological recombination and reionization.We present new spectral radiometers that we have purpose designed for precision measurements of spectral distortions at radio wavelengths. New antenna elements include frequency independent and electrically small fat-dipole (Raghunathan et al. 2013 IEEE TAP, 61, 3411) and monopole designs. Receiver configurations have been devised that are self-calibratable (Patra et al. 2013 Expt Astron, 36, 319) so that switching of signal paths and of calibration noise sources provide real time calibration for systematics and receiver noise. Observing strategies (Patra et al. arXiv:1412.7762) and analysis methods (Satyanarayana Rao et al. arXiv:1501.07191) have been evolved that are capable of discriminating between the cosmological signals and the substantially brighter foregrounds. We have also demonstrated the value of system designs that exploit advantages of interferometer detection (Mahesh et al. arXiv:1406.2585) of global spectral distortions.Finally we discuss how the Square Kilometer Array stations may be outfitted with precision spectral radiometer outriggers (Subrahmanyan et al. arXiv:1501.04340) to provide the zero-spacing measurement sets, complement the interferometer visibilities and give the SKA a capability for measurements of cosmic radio background spectral distortions.

(S)-N-{1-[5-(4-Chloro-benzyl-sulfanyl)-1,3,4-oxadiazol-2-yl]eth-yl}-4-methyl-benzene-sulfonamide.

PubMed

Syed, Tayyaba; Hameed, Shahid; Jones, Peter G

2011-10-01

The title compound, C(18)H(18)ClN(3)O(3)S(2), adopts by folding the form of a distorted disc. Inter-planar angles are 29.51 (7) and 63.43 (7)° from the five-membered ring to the aromatic systems and 34.80 (6)° between these two latter rings. The absolute configuration was confirmed by determination of the Flack parameter. In the crystal, the mol-ecules are linked by four hydrogen bonds, one classical (N-H⋯N) and three 'weak' (C-H⋯O), forming layers parallel to the ac plane; these are in turn linked in the third dimension by Cl⋯N [3.1689 (16) Å] and Cl⋯O [3.3148 (13) Å] contacts to the heterocyclic ring.

Dichloridobis(phenanthridine-κN)zinc(II).

PubMed

Khoshtarkib, Zeinab; Ebadi, Amin; Alizadeh, Robabeh; Ahmadi, Roya; Amani, Vahid

2009-06-06

In the mol-ecule of the title compound, [ZnCl(2)(C(13)H(9)N)(2)], the Zn(II) atom is four-coordinated in a distorted tetra-hedral configuration by two N atoms from two phenanthridine ligands and by two terminal Cl atoms. The dihedral angle between the planes of the phenanthridine ring systems is 69.92 (3)°. An intra-molecular C-H⋯Cl inter-action results in the formation of a planar five-membered ring, which is oriented at a dihedral angle of 8.32 (3)° with respect to the adjacent phenanthridine ring system. In the crystal structure, π-π contacts between the phenanthridine systems [centroid-centroid distances = 3.839 (2), 3.617 (1) and 3.682 (1) Å] may stabilize the structure. Two weak C-H⋯π inter-actions are also found.

The shape and location of the sector boundary surface in the inner solar system. [Helios observations

NASA Technical Reports Server (NTRS)

Villante, U.; Bruno, R.; Mariani, F.; Burlaga, L. F.; Ness, N. F.

1979-01-01

Simultaneous observations by Helios-1 and Helios-2 over four solar rotations were used to determine the latitudinal dependence of the polarity of the interplanetary magnetic field within plus or minus 7.23 deg of the solar equator and within 1 AU. The longitudinal and latitudinal positions of the sector boundary crossing are consistent with a warped sector boundary which extended from the sun to 1 AU and was inclined approximately 10 deg with respect to the heliographic equator. This is consistent with simultaneous Pioneer 11 observations, which showed unipolar fields at latitude approximately 16 deg at heliocentric distances greater than 3.5 AU. Two sectors were observed at southern latitudes; however, four sectors were observed at northern latitudes on two rotations, indicating a distortion from planarity of the sectory boundary surface.

CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

NASA Astrophysics Data System (ADS)

Nowak, K. M.; Ohta, T.; Suganuma, T.; Fujimoto, J.; Mizoguchi, H.; Sumitani, A.; Endo, A.

2013-12-01

It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.

A comparative quantitative analysis of magnetic susceptibility artifacts in echo planar and PROPELLER diffusion-weighted images

NASA Astrophysics Data System (ADS)

Cho, Jae-Hwan; Lee, Hae-Kag; Yang, Han-Joon; Lee, Gui-Won; Park, Yong-Soon; Chung, Woon-Kwan

2013-01-01

In this study, the authors investigated whether periodically-rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted imaging (DWI) can remove magnetic susceptibility artifacts and compared apparent diffusion coefficient (ADC) values for PROPELLER DWI and the common echo planar (EP) DWI. Twenty patients that underwent brain MRI with a metal dental implant were selected. A 3.0T MR scanner was then used to obtain EP DWI, PROPELLER DWI, and corresponding apparent diffusion coefficient (ADC) maps for a b-value of 0 and 1,000 s/mm2. The frequencies of magnetic susceptibility artifacts in four parts of the brain (bilateral temporal lobes, pons, and orbit) were selected. In the ADC maps, we measured the ADC values of both sides of the temporal lobe and the pons. According to the study results, the frequency of magnetic susceptibility artifacts in PROPELLER DW images was lower than it was in EP DW images. In ADC maps, the ADC values of the bilateral temporal lobes and the pons were all higher in PROPELLER ADC maps than in EP ADC maps. Our findings show that when a high-field MRI machine is used, magnetic susceptibility artifacts can distort anatomical structures and produce high-intensity signals. Furthermore, our findings suggest that in many cases, PROPELLER DWI would be helpful in terms of achieving a correct diagnosis.

Far-infrared spectra of yttrium-doped gold clusters Au(n)Y (n=1-9).

PubMed

Lin, Ling; Claes, Pieterjan; Gruene, Philipp; Meijer, Gerard; Fielicke, André; Nguyen, Minh Tho; Lievens, Peter

2010-06-21

The geometric, spectroscopic, and electronic properties of neutral yttrium-doped gold clusters Au(n)Y (n=1-9) are studied by far-infrared multiple photon dissociation (FIR-MPD) spectroscopy and quantum chemical calculations. Comparison of the observed and calculated vibrational spectra allows the structures of the isomers present in the molecular beam to be determined. Most of the isomers for which the IR spectra agree best with experiment are calculated to be the energetically most stable ones. Attachment of xenon to the Au(n)Y cluster can cause changes in the IR spectra, which involve band shifts and band splittings. In some cases symmetry changes, as a result of the attachment of xenon atoms, were also observed. All the Au(n)Y clusters considered prefer a low spin state. In contrast to pure gold clusters, which exhibit exclusively planar lowest-energy structures for small sizes, several of the studied species are three-dimensional. This is particularly the case for Au(4)Y and Au(9)Y, while for some other sizes (n=5, 8) the 3D structures have an energy similar to that of their 2D counterparts. Several of the lowest-energy structures are quasi-2D, that is, slightly distorted from planar shapes. For all the studied species the Y atom prefers high coordination, which is different from other metal dopants in gold clusters.

Real-time pose invariant logo and pattern detection

NASA Astrophysics Data System (ADS)

Sidla, Oliver; Kottmann, Michal; Benesova, Wanda

2011-01-01

The detection of pose invariant planar patterns has many practical applications in computer vision and surveillance systems. The recognition of company logos is used in market studies to examine the visibility and frequency of logos in advertisement. Danger signs on vehicles could be detected to trigger warning systems in tunnels, or brand detection on transport vehicles can be used to count company-specific traffic. We present the results of a study on planar pattern detection which is based on keypoint detection and matching of distortion invariant 2d feature descriptors. Specifically we look at the keypoint detectors of type: i) Lowe's DoG approximation from the SURF algorithm, ii) the Harris Corner Detector, iii) the FAST Corner Detector and iv) Lepetit's keypoint detector. Our study then compares the feature descriptors SURF and compact signatures based on Random Ferns: we use 3 sets of sample images to detect and match 3 logos of different structure to find out which combinations of keypoint detector/feature descriptors work well. A real-world test tries to detect vehicles with a distinctive logo in an outdoor environment under realistic lighting and weather conditions: a camera was mounted on a suitable location for observing the entrance to a parking area so that incoming vehicles could be monitored. In this 2 hour long recording we can successfully detect a specific company logo without false positives.

A new type of two-dimensional carbon crystal prepared from 1,3,5-trihydroxybenzene

NASA Astrophysics Data System (ADS)

Du, Qi-Shi; Tang, Pei-Duo; Huang, Hua-Lin; Du, Fang-Li; Huang, Kai; Xie, Neng-Zhong; Long, Si-Yu; Li, Yan-Ming; Qiu, Jie-Shan; Huang, Ri-Bo

2017-01-01

A new two-dimensional (2D) carbon crystal, different from graphene, has been prepared from 1,3,5-trihydroxybenzene, consisting of 4-carbon and 6-carbon rings in 1:1 ratio, named 4-6 carbophene by authors, in which all carbon atoms possess sp2 hybrid orbitals with some distortion, forming an extensive conjugated π-bonding planar structure. The angles between the three σ-bonds of the carbon sp2 orbitals are roughly 120°, 90°, and 150°. Each of the three non-adjacent sides of a 6C-ring is shared with a 4C-ring; and each of the two opposite sides of a 4C-ring is shared with a 6C-ring. Dodecagonal holes with a diameter of approximate 5.8 Å are regularly located throughout the 2D carbon crystal. Even though the bond energies in 4-6 carbophene are weaker than those in the graphene, the new planar crystal is quite stable in ambient conditions. The 4-6 carbophene can be synthetized from 1,3,5-trihydroxybenzene or other benzene derivatives through dehydration and polymerization reactions, and may possess several possible patterns that form a family of 2D carbon crystals. A possible side reaction involving 1,3,5-trihydroxybenzene is also discussed, which may produce a carbon-oxygen two dimensional crystal.

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications

PubMed Central

Shrestha, Suman; Karellas, Andrew; Shi, Linxi; Gounis, Matthew J.; Bellazzini, Ronaldo; Spandre, Gloria; Brez, Alessandro; Minuti, Massimo

2016-01-01

Purpose: High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. Methods: A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. Results: At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Conclusions: Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications. PMID:27147324

Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications.

PubMed

Vedantham, Srinivasan; Shrestha, Suman; Karellas, Andrew; Shi, Linxi; Gounis, Matthew J; Bellazzini, Ronaldo; Spandre, Gloria; Brez, Alessandro; Minuti, Massimo

2016-05-01

High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vedantham, Srinivasan; Shrestha, Suman; Karellas, Andrew, E-mail: andrew.karellas@umassmed.edu

Purpose: High-resolution, photon-counting, energy-resolved detector with fast-framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high-resolution real-time imaging during image-guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon-counting cadmium telluride (CdTe) detector. Methods: A 650 μm thick CdTe Schottky photon-counting detector capable of concurrently acquiring up to two energy-windowed images was operated in a single energy-window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixelmore » pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC-RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image-guided interventional procedures ranging from 1.3 nGy/frame to 91.4 μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge-spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion-free display, the optimal square pixel size was determined by minimizing the root-mean-squared-error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit. Results: At Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line-pairs/mm and qualitative evaluation of a neurovascular nitinol-stent showed the ability to visualize its struts at clinically relevant conditions. Conclusions: Hexagonal pixel array photon-counting CdTe detector provides high spatial resolution in single-photon counting mode. After resampling to optimal square pixel size for distortion-free display, the spatial resolution is preserved. The dual-energy capabilities of the detector could allow for artifact-free subtraction angiography and basis material decomposition. The proposed high-resolution photon-counting detector with energy-resolving capability can be of importance for several image-guided interventional procedures as well as for pediatric applications.« less

Enhancement of the Wear Particle Monitoring Capability of Oil Debris Sensors Using a Maximal Overlap Discrete Wavelet Transform with Optimal Decomposition Depth

PubMed Central

Li, Chuan; Peng, Juan; Liang, Ming

2014-01-01

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements. PMID:24686730

Structural and electrical properties of large area epitaxial VO2 films grown by electron beam evaporation

NASA Astrophysics Data System (ADS)

Théry, V.; Boulle, A.; Crunteanu, A.; Orlianges, J. C.; Beaumont, A.; Mayet, R.; Mennai, A.; Cosset, F.; Bessaudou, A.; Fabert, M.

2017-02-01

Large area (up to 4 squared inches) epitaxial VO2 films, with a uniform thickness and exhibiting an abrupt metal-insulator transition with a resistivity ratio as high as 2.85 × 10 4 , have been grown on (001)-oriented sapphire substrates by electron beam evaporation. The lattice distortions (mosaicity) and the level of strain in the films have been assessed by X-ray diffraction. It is demonstrated that the films grow in a domain-matching mode where the distortions are confined close to the interface which allows growth of high-quality materials despite the high film-substrate lattice mismatch. It is further shown that a post-deposition high-temperature oxygen annealing step is crucial to ensure the correct film stoichiometry and provide the best structural and electrical properties. Alternatively, it is possible to obtain high quality films with a RF discharge during deposition, which hence do not require the additional annealing step. Such films exhibit similar electrical properties and only slightly degraded structural properties.

Arc Second Alignment of International X-Ray Observatory Mirror Segments in a Fixed Structure

NASA Technical Reports Server (NTRS)

Evans, Tyler C.; Chan, Kai-Wing

2009-01-01

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc seconds. These mirror segments are 0.4mm thick, and 200 to 400mm in size, which makes it hard not to impart distortion at the subarc second level. This paper outlines the precise alignment, verification testing, and permanent bonding techniques developed at NASA's Goddard Space Flight Center (GSFC). These techniques are used to overcome the challenge of transferring thin mirror segments from a temporary mount to a fixed structure with arc second alignment and minimal figure distortion. Recent advances in technology development in addition to the automation of several processes have produced significant results. This paper will highlight the recent advances in alignment, testing, and permanent bonding techniques as well as the results they have produced.

A hybrid method for synthetic aperture ladar phase-error compensation

NASA Astrophysics Data System (ADS)

Hua, Zhili; Li, Hongping; Gu, Yongjian

2009-07-01

As a high resolution imaging sensor, synthetic aperture ladar data contain phase-error whose source include uncompensated platform motion and atmospheric turbulence distortion errors. Two previously devised methods, rank one phase-error estimation algorithm and iterative blind deconvolution are reexamined, of which a hybrid method that can recover both the images and PSF's without any a priori information on the PSF is built to speed up the convergence rate by the consideration in the choice of initialization. To be integrated into spotlight mode SAL imaging model respectively, three methods all can effectively reduce the phase-error distortion. For each approach, signal to noise ratio, root mean square error and CPU time are computed, from which we can see the convergence rate of the hybrid method can be improved because a more efficient initialization set of blind deconvolution. Moreover, by making a further discussion of the hybrid method, the weight distribution of ROPE and IBD is found to be an important factor that affects the final result of the whole compensation process.

Geometric accuracy of Landsat-4 and Landsat-5 Thematic Mapper images.

USGS Publications Warehouse

Borgeson, W.T.; Batson, R.M.; Kieffer, H.H.

1985-01-01

The geometric accuracy of the Landsat Thematic Mappers was assessed by a linear least-square comparison of the positions of conspicuous ground features in digital images with their geographic locations as determined from 1:24 000-scale maps. For a Landsat-5 image, the single-dimension standard deviations of the standard digital product, and of this image with additional linear corrections, are 11.2 and 10.3 m, respectively (0.4 pixel). An F-test showed that skew and affine distortion corrections are not significant. At this level of accuracy, the granularity of the digital image and the probable inaccuracy of the 1:24 000 maps began to affect the precision of the comparison. The tested image, even with a moderate accuracy loss in the digital-to-graphic conversion, meets National Horizontal Map Accuracy standards for scales of 1:100 000 and smaller. Two Landsat-4 images, obtained with the Multispectral Scanner on and off, and processed by an interim software system, contain significant skew and affine distortions. -Authors

Temperature-Driven Shape Changes of the Near Earth Asteroid Scout Solar Sail

NASA Technical Reports Server (NTRS)

Stohlman, Olive R.; Loper, Erik R.; Lockett, Tiffany E.

2017-01-01

Near Earth Asteroid Scout (NEA Scout) is a NASA deep space Cubesat, scheduled to launch on the Exploration Mission 1 flight of the Space Launch System. NEA Scout will use a deployable solar sail as its primary propulsion system. The sail is a square membrane supported by rigid metallic tapespring booms, and analysis predicts that these booms will experience substantial thermal warping if they are exposed to direct sunlight in the space environment. NASA has conducted sunspot chamber experiments to confirm the thermal distortion of this class of booms, demonstrating tip displacement of between 20 and 50 centimeters in a 4-meter boom. The distortion behavior of the boom is complex and demonstrates an application for advanced thermal-structural analysis. The needs of the NEA Scout project were supported by changing the solar sail design to keep the booms shaded during use of the solar sail, and an additional experiment in the sunspot chamber is presented in support of this solution.

Spitzer Instrument Pointing Frame (IPF) Kalman Filter Algorithm

NASA Technical Reports Server (NTRS)

Bayard, David S.; Kang, Bryan H.

2004-01-01

This paper discusses the Spitzer Instrument Pointing Frame (IPF) Kalman Filter algorithm. The IPF Kalman filter is a high-order square-root iterated linearized Kalman filter, which is parametrized for calibrating the Spitzer Space Telescope focal plane and aligning the science instrument arrays with respect to the telescope boresight. The most stringent calibration requirement specifies knowledge of certain instrument pointing frames to an accuracy of 0.1 arcseconds, per-axis, 1-sigma relative to the Telescope Pointing Frame. In order to achieve this level of accuracy, the filter carries 37 states to estimate desired parameters while also correcting for expected systematic errors due to: (1) optical distortions, (2) scanning mirror scale-factor and misalignment, (3) frame alignment variations due to thermomechanical distortion, and (4) gyro bias and bias-drift in all axes. The resulting estimated pointing frames and calibration parameters are essential for supporting on-board precision pointing capability, in addition to end-to-end 'pixels on the sky' ground pointing reconstruction efforts.

Arc-Second Alignment of International X-Ray Observatory Mirror Segments in a Fixed Structure

NASA Technical Reports Server (NTRS)

Evans, Tyler C.; Chan, Kai-Wing; Saha, Timo T.

2010-01-01

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it hard not to impart distortion at the subare- second level. This paper outlines the precise alignment, verification testing, and permanent bonding techniques developed at NASA's Goddard Space Flight Center (GSFC). These techniques are used to overcome the challenge of transferring thin mirror segments from a temporary mount to a fixed structure with arc-second alignment and minimal figure distortion. Recent advances in technology development in addition to the automation of several processes have produced significant results. This paper will highlight the recent advances in alignment, testing, and permanent bonding techniques as well as the results they have produced.

Enhancement of the wear particle monitoring capability of oil debris sensors using a maximal overlap discrete wavelet transform with optimal decomposition depth.

PubMed

Li, Chuan; Peng, Juan; Liang, Ming

2014-03-28

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements.

Shearing-induced asymmetry in entorhinal grid cells.

PubMed

Stensola, Tor; Stensola, Hanne; Moser, May-Britt; Moser, Edvard I

2015-02-12

Grid cells are neurons with periodic spatial receptive fields (grids) that tile two-dimensional space in a hexagonal pattern. To provide useful information about location, grids must be stably anchored to an external reference frame. The mechanisms underlying this anchoring process have remained elusive. Here we show in differently sized familiar square enclosures that the axes of the grids are offset from the walls by an angle that minimizes symmetry with the borders of the environment. This rotational offset is invariably accompanied by an elliptic distortion of the grid pattern. Reversing the ellipticity analytically by a shearing transformation removes the angular offset. This, together with the near-absence of rotation in novel environments, suggests that the rotation emerges through non-coaxial strain as a function of experience. The systematic relationship between rotation and distortion of the grid pattern points to shear forces arising from anchoring to specific geometric reference points as key elements of the mechanism for alignment of grid patterns to the external world.

Development of a wavefront sensor for terahertz pulses.

PubMed

Abraham, Emmanuel; Cahyadi, Harsono; Brossard, Mathilde; Degert, Jérôme; Freysz, Eric; Yasui, Takeshi

2016-03-07

Wavefront characterization of terahertz pulses is essential to optimize far-field intensity distribution of time-domain (imaging) spectrometers or increase the peak power of intense terahertz sources. In this paper, we report on the wavefront measurement of terahertz pulses using a Hartmann sensor associated with a 2D electro-optic imaging system composed of a ZnTe crystal and a CMOS camera. We quantitatively determined the deformations of planar and converging spherical wavefronts using the modal Zernike reconstruction least-squares method. Associated with deformable mirrors, the sensor will also open the route to terahertz adaptive optics.

Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.

PubMed

Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V

2015-03-15

Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies. Copyright © 2014 Elsevier B.V. All rights reserved.

The ultimate quantum limits on the accuracy of measurements

NASA Technical Reports Server (NTRS)

Yuen, Horace P.

1992-01-01

A quantum generalization of rate-distortion theory from standard communication and information theory is developed for application to determining the ultimate performance limit of measurement systems in physics. For the estimation of a real or a phase parameter, it is shown that the root-mean-square error obtained in a measurement with a single-mode photon level N cannot do better than approximately N exp -1, while approximately exp(-N) may be obtained for multi-mode fields with the same photon level N. Possible ways to achieve the remarkable exponential performance are indicated.

Propagation of a laser beam in a plasma

NASA Technical Reports Server (NTRS)

Chapman, J. M.; Kevorkian, J.; Steinhauer, L. C.; Vagners, J.

1975-01-01

This paper shows that for a nonabsorbing medium with a prescribed index of refraction, the effects of beam stability, line focusing, and beam distortion can be predicted from simple ray optics. When the paraxial approximation is used, diffraction effects are examined for Gaussian, Lorentzian, and square beams. Most importantly, it is shown that for a Gaussian beam, diffraction effects can be included simply by adding imaginary solutions to the paraxial ray equations. Also presented are several procedures to extend the paraxial approximation so that the solution will have a domain of validity of greater extent.

Theoretical and subjective bit assignments in transform picture

NASA Technical Reports Server (NTRS)

Jones, H. W., Jr.

1977-01-01

It is shown that all combinations of symmetrical input distributions with difference distortion measures give a bit assignment rule identical to the well-known rule for a Gaussian input distribution with mean-square error. Published work is examined to show that the bit assignment rule is useful for transforms of full pictures, but subjective bit assignments for transform picture coding using small block sizes are significantly different from the theoretical bit assignment rule. An intuitive explanation is based on subjective design experience, and a subjectively obtained bit assignment rule is given.

Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91

NASA Technical Reports Server (NTRS)

Baron, N.; Fink, C. L.; Christensen, P. R.; Nickels, J.; Torsteinsen, T.

1972-01-01

The structures of Zr-93 and Zr-91 were studied by the stripping reaction Zr-92(d,p)Zr-93 and the pick-up reaction Zr-92(d,t)Zr-91 using 13 MeV incident deuterons. The reaction product particles were detected by counter telescope. Typical spectra from the reactions were analyzed by a nonlinear least squares peak fitting program which included a background search. Spin and parity assignments to observed excited levels were made by comparing experimental angular distributions with distorted wave Born approximation calculations.

Chloridotetra­kis(pyridine-4-carb­alde­hyde-κN)copper(II) chloride

PubMed Central

Meng, Xiu-Jin; Zhang, Shu-Hua; Yang, Ge-Ge; Huang, Xue-Ren; Jiang, Yi-Min

2009-01-01

In the mol­ecular structure of the title compound, [CuCl(C6H5NO)4]Cl, the CuII atom is coordinated by four N atoms of four pyridine-4-carboxaldehyde ligands and one chloride anion in a slightly distorted square-pyramidal coordination geometry. There is also a non-coordinating Cl− anion in the crystal structure. The CuII atom and both Cl atoms are situated on fourfold rotation axes. A weak C—H⋯Cl inter­action is also present. PMID:21578129

Cyclopalladation of dimesityl selenide: synthesis, reactivity, structural characterization, isolation of an intermediate complex with C-H···Pd intra-molecular interaction and computational studies.

PubMed

Kolay, Siddhartha; Wadawale, Amey; Das, Dasarathi; Kisan, Hemanta K; Sunoj, Raghavan B; Jain, Vimal K

2013-08-14

The reaction of dimesityl selenide (Mes2Se) with either PdCl2(PhCN)2 in toluene or PdCl2 in toluene-acetonitrile yields a chloro-bridged binuclear palladium complex, [Pd2Cl2(μ-Cl)2(Mes2Se)2] (1), whereas with Na2PdCl4 in refluxing ethanol, a cyclometallated palladium complex, [Pd2(μ-Cl)2{MesSeC6H2(Me2)CH2}2] (2) is afforded. 2 can also be obtained when 1 is refluxed in ethanol. On treatment with Pb(Epy)2 in dichloromethane, 2 afforded the Epy-bridged binuclear complexes, [Pd2(μ-Epy)2{MesSeC6H2(Me2)CH2}2] (3; E = S (3a) or Se (3b)). Treatment of 2 with PPh3 yields a bridge-cleaved monomeric complex, [PdCl{MesSeC6H2(Me2)CH2}(PPh3)]. The molecular structures of 1-3 were established by X-ray diffraction analyses. All the complexes are dimeric, with the palladium atoms acquiring a distorted square planar configuration. There are intra-molecular C-H···Pd interactions (d(M-H): 2.75 Å and

Synthesis, spectral and thermal studies of some transition metal mixed ligand complexes: Modeling of equilibrium composition and biological activity

NASA Astrophysics Data System (ADS)

Neelakantan, M. A.; Sundaram, M.; Nair, M. Sivasankaran

2011-09-01

Several mixed ligand Ni(II), Cu(II) and Zn(II) complexes of 2-amino-3-hydroxypyridine (AHP) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) have been synthesized and characterized by elemental and spectral (vibrational, electronic, 1H NMR and EPR) data as well as by magnetic moment values. On the basis of elemental analysis and molar conductance values, all the complexes can be formulated as [MAB]Cl except histidine complexes as MAB. Thermogravimetric studies reveal the presence of coordinated water molecules in most of the complexes. From the magnetic measurements and electronic spectral data, octahedral structure was proposed for Ni(II) and Cu(II)-AHP-his, tetrahedral for Cu(II)-AHP-him/bim/hist, but square planar for the Cu(II)-AHP complex. The g∥/ A∥ calculated supports tetrahedral environment around the Cu(II) in Cu(II)-AHP-him/bim/hist and distorted octahedral for Cu(II)-AHP-his complexes. The morphology of the reported metal complexes was investigated by scanning electron micrographs (SEM). The potentiometric study has been performed in aqueous solution at 37 °C and I = 0.15 mol dm -3 NaClO 4. MABH, MAB and MAB 2 species has been identified in the present systems. Proton dissociation constants of AHP and stability constants of metal complexes were determined using MINIQUAD-75. The most probable structure of the mixed ligand species is discussed based upon their stability constants. The in vitro biological activity of the complexes was tested against the Gram positive and Gram negative bacteria, fungus and yeast. The oxidative DNA cleavage studies of the complexes were performed using gel electrophoresis method. Cu(II) complexes have been found to promote DNA cleavage in presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide.

Flexible printed circuit board actuators

NASA Astrophysics Data System (ADS)

Lee, Junseok; Cha, Youngsu

2017-12-01

Out-of-plane actuators are made possible by the breaking of planar symmetry. In this paper, we present a thin-film out-of-plane electrostatic actuator for a flexible printed circuit board (FPCB) that can be fabricated with a single step of the conventional manufacturing process. No other components are required for actuation except a single sheet of the FPCB, and it works based on the planar asymmetry resulting from asymmetrically patterned top and bottom electrodes on each side of the polyimide film. With the structural asymmetry, the application of a high voltage in the order of kilovolts results in the asymmetry of the electric fields and the body force density, which generates the bending moment that leads to macroscopic deformations. We applied the finite element method to examine the asymmetry induced by the difference in the electrodes. In the experiment, the displacement responses to step input and square wave input of various frequencies were analyzed. It was found that our actuator constitutes an underdamped system, exhibiting resonance characteristics. The maximum oscillatory amplitude was determined at resonance, and the relationship between the displacement and the applied voltage was investigated.

A motif for infinite metal atom wires.

PubMed

Yin, Xi; Warren, Steven A; Pan, Yung-Tin; Tsao, Kai-Chieh; Gray, Danielle L; Bertke, Jeffery; Yang, Hong

2014-12-15

A new motif for infinite metal atom wires with tunable compositions and properties is developed based on the connection between metal paddlewheel and square planar complex moieties. Two infinite Pd chain compounds, [Pd4(CO)4(OAc)4Pd(acac)2] 1 and [Pd4(CO)4(TFA)4Pd(acac)2] 2, and an infinite Pd-Pt heterometallic chain compound, [Pd4(CO)4(OAc)4Pt(acac)2] 3, are identified by single-crystal X-ray diffraction analysis. In these new structures, the paddlewheel moiety is a Pd four-membered ring coordinated by bridging carboxylic ligands and μ2 carbonyl ligands. The planar moiety is either Pd(acac)2 or Pt(acac)2 (acac = acetylacetonate). These moieties are connected by metallophilic interactions. The results showed that these one-dimensional metal wire compounds have photoluminescent properties that are tunable by changing ligands and metal ions. 3 can also serve as a single source precursor for making Pd4Pt bimetallic nanostructures with precise control of metal composition. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Experimental Investigation of Hydrodynamic Forces on Circular Cylinders in Sinusoidal and Random Oscillating Flow

NASA Astrophysics Data System (ADS)

Longoria, Raul Gilberto

An experimental apparatus has been developed which can be used to generate a general time-dependent planar flow across a cylinder. A mass of water enclosed with no free surface within a square cross-section tank and two spring pre-loaded pistons is oscillated using a hydraulic actuator. A circular cylinder is suspended horizontally in the tank by two X-Y force transducers used to simultaneously measure the total in-line and transverse forces. Fluid motion is measured using a differential pressure transducer for instantaneous acceleration and an LVDT for displacement. This investigation provides measurement of forces on cylinders subjected to planar fluid flow velocity with a time (and frequency) dependence which more accurately represent the random conditions encountered in a natural ocean environment. The use of the same apparatus for both sinusoidal and random experiments provides a quantified assessment of the applicability of sinusoidal planar oscillatory flow data in offshore structure design methods. The drag and inertia coefficients for a Morison equation representation of the inline force are presented for both sinusoidal and random flow. Comparison of the sinusoidal results is favorable with those of previous investigations. The results from random experiments illustrates the difference in the force mechanism by contrasting the force transfer coefficients for the inline and transverse forces. It is found that application of sinusoidal results to random hydrodynamic inline force prediction using the Morison equation wrongly weighs the drag and inertia components, and the transverse force is overpredicted. The use of random planar oscillatory flow in the laboratory, contrasted with sinusoidal planar oscillatory flow, quantifies the accepted belief that the force transfer coefficients from sinusoidal flow experiments are conservative for prediction of forces on cylindrical structures subjected to random sea waves and the ensuing forces. Further analysis of data is conducted in the frequency domain to illustrate models used for predicting the power spectral density of the inline force including a nonlinear describing function method. It is postulated that the large-scale vortex activity prominent in sinusoidal oscillatory flow is subdued in random flow conditions.

Roof planes detection via a second-order variational model

NASA Astrophysics Data System (ADS)

Benciolini, Battista; Ruggiero, Valeria; Vitti, Alfonso; Zanetti, Massimo

2018-04-01

The paper describes a unified automatic procedure for the detection of roof planes in gridded height data. The procedure exploits the Blake-Zisserman (BZ) model for segmentation in both 2D and 1D, and aims to detect, to model and to label roof planes. The BZ model relies on the minimization of a functional that depends on first- and second-order derivatives, free discontinuities and free gradient discontinuities. During the minimization, the relative strength of each competitor is controlled by a set of weight parameters. By finding the minimum of the approximated BZ functional, one obtains: (1) an approximation of the data that is smoothed solely within regions of homogeneous gradient, and (2) an explicit detection of the discontinuities and gradient discontinuities of the approximation. Firstly, input data is segmented using the 2D BZ. The maps of data and gradient discontinuities are used to isolate building candidates and planar patches (i.e. regions with homogeneous gradient) that correspond to roof planes. Connected regions that can not be considered as buildings are filtered according to both patch dimension and distribution of the directions of the normals to the boundary. The 1D BZ model is applied to the curvilinear coordinates of boundary points of building candidates in order to reduce the effect of data granularity when the normals are evaluated. In particular, corners are preserved and can be detected by means of gradient discontinuity. Lastly, a total least squares model is applied to estimate the parameters of the plane that best fits the points of each planar patch (orthogonal regression with planar model). Refinement of planar patches is performed by assigning those points that are close to the boundaries to the planar patch for which a given proximity measure assumes the smallest value. The proximity measure is defined to account for the variance of a fitting plane and a weighted distance of a point from the plane. The effectiveness of the proposed procedure is demonstrated by means of its application to urban digital surface models characterized by different spatial resolutions. Results are presented and discussed along with some promising developments.

Understanding the role of A-site and B-site cations on piezoelectric instability in lead--free (1-x) BaTiO3 -- xA(Cu1/3Nb2/3)O3 (A = Sr, Ca, Ba) solid solutions

NASA Astrophysics Data System (ADS)

Maurya, Deepam; Zhou, Yuan; Priya, Shashank

2013-03-01

This study provides fundamental understanding of the enhanced piezoelectric instability in lead-free piezoelectric (1-x) BaTiO3-xA(Cu1/3Nb2/3) O3(A: Sr, Ba and Ca and x = 0.0-0.03) solid solutions. These compositions were found to exhibit large longitudinal piezoelectric constant (d33) of ~330 pC/N and electromechanical planar coupling constant (kp) ~ 46% at room temperature. The X-ray diffraction coupled with atomic pair distribution functions (PDF)s indicated increase in local polarization. Raman scattering and electron paramagnetic resonance (EPR) analysis revealed that substitutions on A and B-site both substantially perturbed the local octahedral dynamics and resulted in localized nano polar regions with lower symmetry. The presence of nano domains and local structural distortions smears the Curie peak resulting in diffuse order-disorder type phase transitions. The effect of these distortions on the variations in physical property was modeled and analyzed within the context of nanodomains and phase transitions. *spriya@vt.edu The financial support from National Science Foundation and Office of Basic Energy Science, Department of Energy (Microscopy analysis) is gratefully acknowledged. The authors would also like to acknowledge the support from KIMS (new piezoelectric)

Origin of stress in radio frequency magnetron sputtered zinc oxide thin films

NASA Astrophysics Data System (ADS)

Menon, Rashmi; Gupta, Vinay; Tan, H. H.; Sreenivas, K.; Jagadish, C.

2011-03-01

Highly c-axis oriented ZnO thin films have been deposited on silicon substrates by planar rf magnetron sputtering under varying pressure (10-50 mTorr) and oxygen percentage (50-100%) in the reactive gas (Ar + O2) mixture. The as-grown films were found to be stressed over a wide range from -1 × 1011 to -2 × 108 dyne/cm2 that in turn depends strongly on the processing conditions, and the film becomes stress free at a unique combination of sputtering pressure and reactive gas composition. Raman spectroscopy and photoluminescence (PL) analyses identified the origin of stress as lattice distortion due to defects introduced in the ZnO thin film. FTIR study reveals that Zn-O bond becomes stronger with the increase in oxygen fraction in the reactive gas mixture. The lattice distortion or stress depends on the type of defects introduced during deposition. PL spectra show the formation of a shoulder in band emission with an increase in the processing pressure and are related to the presence of stress. The ratio of band emission to defect emission decreases with the increase in oxygen percentage from 50 to 100%. The studies show a correlation of stress with the structural, vibrational, and photoluminescence properties of the ZnO thin film. The systematic study of the stress will help in the fabrication of efficient devices based on ZnO film.

WE-G-204-03: Photon-Counting Hexagonal Pixel Array CdTe Detector: Optimal Resampling to Square Pixels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shrestha, S; Vedantham, S; Karellas, A

Purpose: Detectors with hexagonal pixels require resampling to square pixels for distortion-free display of acquired images. In this work, the presampling modulation transfer function (MTF) of a hexagonal pixel array photon-counting CdTe detector for region-of-interest fluoroscopy was measured and the optimal square pixel size for resampling was determined. Methods: A 0.65mm thick CdTe Schottky sensor capable of concurrently acquiring up to 3 energy-windowed images was operated in a single energy-window mode to include ≥10 KeV photons. The detector had hexagonal pixels with apothem of 30 microns resulting in pixel spacing of 60 and 51.96 microns along the two orthogonal directions.more » Images of a tungsten edge test device acquired under IEC RQA5 conditions were double Hough transformed to identify the edge and numerically differentiated. The presampling MTF was determined from the finely sampled line spread function that accounted for the hexagonal sampling. The optimal square pixel size was determined in two ways; the square pixel size for which the aperture function evaluated at the Nyquist frequencies along the two orthogonal directions matched that from the hexagonal pixel aperture functions, and the square pixel size for which the mean absolute difference between the square and hexagonal aperture functions was minimized over all frequencies up to the Nyquist limit. Results: Evaluation of the aperture functions over the entire frequency range resulted in square pixel size of 53 microns with less than 2% difference from the hexagonal pixel. Evaluation of the aperture functions at Nyquist frequencies alone resulted in 54 microns square pixels. For the photon-counting CdTe detector and after resampling to 53 microns square pixels using quadratic interpolation, the presampling MTF at Nyquist frequency of 9.434 cycles/mm along the two directions were 0.501 and 0.507. Conclusion: Hexagonal pixel array photon-counting CdTe detector after resampling to square pixels provides high-resolution imaging suitable for fluoroscopy.« less

Investigating the geometrical preferences of a flexible benzimidazolone-based linker in the synthesis of coordination polymers

PubMed Central

Jones, Corey L.; Marsden, Elizabeth A.; Nevin, Adam C.; Kariuki, Benson M.; Bhadbhade, Mohan M.; Martin, Adam D.

2017-01-01

A series of new group 2 coordination polymers, MgL ={MgL(H2O)(DMF)0.75}∞, CaL = {CaL(DMF)2}∞, SrL = {SrL(H2O)0.5}∞ and BaL = {BaL(H2O)0.5}∞, were synthesized using a flexible benzimidazolone diacetic acid linker (H2L) in which the two carboxylic acid binding sites are connected to a planar core via {–CH2–} spacers that can freely rotate in solution. In a ‘curiosity-led' diversion from group 2 metals, the first row transition metal salts Mn2+, Cu2+ and Zn2+ were also reacted with L to yield crystals of MnL = {MnL(DMF)(H2O)3.33}∞, Cu3L2 = {Cu3L2(DMF)2(CHO2)2}∞ and ZnL = {ZnL(DMF)}∞. Crystal structures were obtained for all seven materials. All structures form as two-dimensional sheets and contain six-coordinate centres, with the exception of ZnL, which displays tetrahedrally coordinated metal centres, and Cu3L2, which contains square planar coordinated metal centres and Cu paddle-wheels. In each structure, the linker adopts one of two distinct conformations, with the carboxylate groups either cis or trans with respect to the planar core. All materials were also characterized by powder X-ray diffraction and thermogravimetric analysis. PMID:29308246

Wing-Fixed PIV and force measurements of a large transverse gust encounter

NASA Astrophysics Data System (ADS)

Perrotta, Gino

2015-11-01

The unsteady aerodynamics of an aspect ratio 4 flat plate wing encountering a large-amplitude transverse gust were investigated using PIV in the wing-fixed reference frame and direct unsteady force measurements. Using a new experimental facility at the University of Maryland, the wing was towed at Reynolds number 20,000 through a 7m-long tank of nominally quiescent water containing a single cross-stream planar jet with velocity equal to the wing's towed velocity - a transverse gust ratio equal to one. The planar jet was created by pumping water through 30 cylindrical nozzles arranged in a single row. PIV confirms that the individual jets converge into a single, narrow, planar gust with a streamwise velocity profile resembling a canonical cosine-squared gust. Forces and fluid velocities of this wing-gust interaction will be presented for two pre-gust conditions: attached flow on the wing and stalled flow over the wing. In both cases, the gust encounter results in a momentary spike in lift coefficient. The peak lift coefficient was measured between 3 and 6 and varies with angle of attack. At low angle of attack, the attached flow wing produces less lift before the gust and much more (non-circulatory) lift during the gust than the stalled wing. Although the flow over the wing at low angle of attack separates during the gust and reattaches afterwards, the recovery time is similar to that of the high angle case, on the order of 10 chord lengths travelled.

Catalytic N 2 Reduction to Silylamines and Thermodynamics of N 2 Binding at Square Planar Fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prokopchuk, Demyan E.; Wiedner, Eric S.; Walter, Eric D.

The geometric constraints imposed by a tetradentate P 4N 2 ligand play an essential role in stabilizing square planar Fe complexes with changes in metal oxidation state. A combination of high-pressure electrochemistry and variable temperature UV-vis spectroscopy were used to obtain these thermodynamic measurements, while X-ray crystallography, 57Fe Mössbauer spectroscopy, and EPR spectroscopy were used to fully characterize these new compounds. Analysis of Fe 0, FeI, and FeII complexes reveals that the free energy of N 2 binding across three oxidation states spans more than 37 kcal mol -1. The square pyramidal Fe0(N 2)(P 4N 2) complex catalyzes the conversionmore » of N 2 to N(SiR 3) 3 (R = Me, Et) at room temperature, representing the highest turnover number (TON) of any Fe-based N 2 silylation catalyst to date (up to 65 equiv N(SiMe 3) 3 per Fe center). Elevated N 2 pressures (> 1 atm) have a dramatic effect on catalysis, increasing N 2 solubility and the thermodynamic N 2 binding affinity at Fe0(N 2)(P 4N 2). Acknowledgment. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences. EPR experiments were performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. DOE. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. The authors thank Prof. Yisong Alex Guo at Carnegie Mellon University for recording Mössbauer data for some complexes and Emma Wellington and Kaye Kuphal for their assistance with the collection of Mössbauer data at Colgate University, Dr. Katarzyna Grubel for X-ray assistance, and Dr. Rosalie Chu for mass spectrometry assistance. The authors also thank Dr. Aaron Appel and Dr. Alex Kendall for helpful discussions.« less

Distortion-free diffusion MRI using an MRI-guided Tri-Cobalt 60 radiotherapy system: Sequence verification and preliminary clinical experience.

PubMed

Gao, Yu; Han, Fei; Zhou, Ziwu; Cao, Minsong; Kaprealian, Tania; Kamrava, Mitchell; Wang, Chenyang; Neylon, John; Low, Daniel A; Yang, Yingli; Hu, Peng

2017-10-01

Monitoring tumor response during the course of treatment and adaptively modifying treatment plan based on tumor biological feedback may represent a new paradigm for radiotherapy. Diffusion MRI has shown great promises in assessing and predicting tumor response to radiotherapy. However, the conventional diffusion-weighted single-shot echo-planar-imaging (DW-ssEPI) technique suffers from limited resolution, severe distortion, and possibly inaccurate ADC at low field strength. The purpose of this work was to develop a reliable, accurate and distortion-free diffusion MRI technique that is practicable for longitudinal tumor response evaluation and adaptive radiotherapy on a 0.35 T MRI-guided radiotherapy system. A diffusion-prepared turbo spin echo readout (DP-TSE) sequence was developed and compared with the conventional diffusion-weighted single-shot echo-planar-imaging sequence on a 0.35 T MRI-guided radiotherapy system (ViewRay). A spatial integrity phantom was used to quantitate and compare the geometric accuracy of the two diffusion sequences for three orthogonal orientations. The apparent diffusion coefficient (ADC) accuracy was evaluated on a diffusion phantom under both 0 °C and room temperature to cover a diffusivity range between 0.40 × 10 -3 and 2.10 × 10 -3 mm 2 /s. Ten room temperature measurements repeated on five different days were conducted to assess the ADC reproducibility of DP-TSE. Two glioblastoma (GBM) and six sarcoma patients were included to examine the in vivo feasibility. The target registration error (TRE) was calculated to quantitate the geometric accuracy where structural CT or MR images were co-registered to the diffusion images as references. ADC maps from DP-TSE and DW-ssEPI were calculated and compared. A tube phantom was placed next to patients not treated on ViewRay, and ADCs of this reference tube were also compared. The proposed DP-TSE passed the spatial integrity test (< 1 mm within 100 mm radius and < 2 mm within 175 mm radius) under the three orthogonal orientations. The detected errors were 0.474 ± 0.355 mm, 0.475 ± 0.287 mm, and 0.546 ± 0.336 mm in the axial, coronal, and sagittal plane. DW-ssEPI, however, failed the tests due to severe distortion and low signal intensity. Noise correction must be performed for the DW-ssEPI to avoid ADC quantitation errors, whereas it is optional for DP-TSE. At 0 °C, the two sequences provided accurate quantitation with < 3% variation with the reference. In the room temperature study, discrepancies between ADCs from DP-TSE and the reference were within 4%, but could be as high as 8% for DW-ssEPI after the noise correction. Excellent ADC reproducibility with a coefficient of variation < 5% was observed among the 10 measurements of DP-TSE, indicating desirable robustness for ADC-based tumor response assessment. In vivo TRE in DP-TSE was less than 1.6 mm overall, whereas it could be greater than 12 mm in DW-ssEPI. For GBM patients, the CSF and brain tissue ADCs from DP-TSE were within the ranges found in literature. ADC differences between the two techniques were within 8% among the six sarcoma patients. For the reference tube that had a relatively low diffusivity, the two diffusion sequences provided matched measurements. A diffusion technique with excellent geometric fidelity, accurate, and reproducible ADC measurement was demonstrated for longitudinal tumor response assessment using a low-field MRI-guided radiotherapy system. © 2017 American Association of Physicists in Medicine.

Family Typology and Appraisal of Preschoolers' Behavior by Female Caregivers.

PubMed

Coke, Sallie P; Moore, Leslie C

2015-01-01

Children with vulnerable caregivers may be at risk for being labeled as having behavior problems when typical behaviors are viewed by their caregivers as problematic, and therefore, research examining the accuracy of the caregivers' perceptions of children's behaviors is needed. The purpose of this study was to use the resiliency model of family stress, adjustment, and adaptation as the theoretical foundation to explore family factors associated with the primary female caregiver's appraisal of her child's behavior, the extent to which the primary female caregiver's appraisal of her child's behavior may be distorted, and the child's level of risk of having a behavioral problem. A cross-sectional, correlational design was used. Data were collected from female caregivers of preschoolers (N = 117). Family factors, demographic characteristics, comfort in parenting, appraisal of behaviors, daily stress, parenting stress, depressive symptoms, social support, ratings of children's behaviors, and distortion in the ratings were measured. Associations were studied using ANOVA, ANCOVA, and chi-squared tests. Family typology was not associated with the female caregiver's appraisals of her child's behavior (p = .31). Distortion of the caregiver's rating of her child's behavior was not associated with family hardiness (high or low; p = .20.) but was associated with having a child with an elevated risk for behavioral problems (p < .01). Families classified as vulnerable were significantly more likely to have a child with elevated risks of having behavioral problems than families classified as secure or regenerative. Findings emphasized the association between family factors (hardiness and coherence) and young children's behaviors. Additional research is needed into how these factors affect the young child's behavior and what causes a caregiver to have a distorted view of her child's behavior.

Wireless visual sensor network resource allocation using cross-layer optimization

NASA Astrophysics Data System (ADS)

Bentley, Elizabeth S.; Matyjas, John D.; Medley, Michael J.; Kondi, Lisimachos P.

2009-01-01

In this paper, we propose an approach to manage network resources for a Direct Sequence Code Division Multiple Access (DS-CDMA) visual sensor network where nodes monitor scenes with varying levels of motion. It uses cross-layer optimization across the physical layer, the link layer and the application layer. Our technique simultaneously assigns a source coding rate, a channel coding rate, and a power level to all nodes in the network based on one of two criteria that maximize the quality of video of the entire network as a whole, subject to a constraint on the total chip rate. One criterion results in the minimal average end-to-end distortion amongst all nodes, while the other criterion minimizes the maximum distortion of the network. Our approach allows one to determine the capacity of the visual sensor network based on the number of nodes and the quality of video that must be transmitted. For bandwidth-limited applications, one can also determine the minimum bandwidth needed to accommodate a number of nodes with a specific target chip rate. Video captured by a sensor node camera is encoded and decoded using the H.264 video codec by a centralized control unit at the network layer. To reduce the computational complexity of the solution, Universal Rate-Distortion Characteristics (URDCs) are obtained experimentally to relate bit error probabilities to the distortion of corrupted video. Bit error rates are found first by using Viterbi's upper bounds on the bit error probability and second, by simulating nodes transmitting data spread by Total Square Correlation (TSC) codes over a Rayleigh-faded DS-CDMA channel and receiving that data using Auxiliary Vector (AV) filtering.

Detector response function of an energy-resolved CdTe single photon counting detector.

PubMed

Liu, Xin; Lee, Hyoung Koo

2014-01-01

While spectral CT using single photon counting detector has shown a number of advantages in diagnostic imaging, knowledge of the detector response function of an energy-resolved detector is needed to correct the signal bias and reconstruct the image more accurately. The objective of this paper is to study the photo counting detector response function using laboratory sources, and investigate the signal bias correction method. Our approach is to model the detector response function over the entire diagnostic energy range (20 keV

Accurate frequency domain measurement of the best linear time-invariant approximation of linear time-periodic systems including the quantification of the time-periodic distortions

NASA Astrophysics Data System (ADS)

Louarroudi, E.; Pintelon, R.; Lataire, J.

2014-10-01

Time-periodic (TP) phenomena occurring, for instance, in wind turbines, helicopters, anisotropic shaft-bearing systems, and cardiovascular/respiratory systems, are often not addressed when classical frequency response function (FRF) measurements are performed. As the traditional FRF concept is based on the linear time-invariant (LTI) system theory, it is only approximately valid for systems with varying dynamics. Accordingly, the quantification of any deviation from this ideal LTI framework is more than welcome. The “measure of deviation” allows us to define the notion of the best LTI (BLTI) approximation, which yields the best - in mean square sense - LTI description of a linear time-periodic LTP system. By taking into consideration the TP effects, it is shown in this paper that the variability of the BLTI measurement can be reduced significantly compared with that of classical FRF estimators. From a single experiment, the proposed identification methods can handle (non-)linear time-periodic [(N)LTP] systems in open-loop with a quantification of (i) the noise and/or the NL distortions, (ii) the TP distortions and (iii) the transient (leakage) errors. Besides, a geometrical interpretation of the BLTI approximation is provided, leading to a framework called vector FRF analysis. The theory presented is supported by numerical simulations as well as real measurements mimicking the well-known mechanical Mathieu oscillator.

Mitigation of Adverse Effects Caused by Shock Wave Boundary Layer Interactions Through Optimal Wall Shaping

NASA Technical Reports Server (NTRS)

Liou, May-Fun; Lee, Byung Joon

2013-01-01

It is known that the adverse effects of shock wave boundary layer interactions in high speed inlets include reduced total pressure recovery and highly distorted flow at the aerodynamic interface plane (AIP). This paper presents a design method for flow control which creates perturbations in geometry. These perturbations are tailored to change the flow structures in order to minimize shock wave boundary layer interactions (SWBLI) inside supersonic inlets. Optimizing the shape of two dimensional micro-size bumps is shown to be a very effective flow control method for two-dimensional SWBLI. In investigating the three dimensional SWBLI, a square duct is employed as a baseline. To investigate the mechanism whereby the geometric elements of the baseline, i.e. the bottom wall, the sidewall and the corner, exert influence on the flow's aerodynamic characteristics, each element is studied and optimized separately. It is found that arrays of micro-size bumps on the bottom wall of the duct have little effect in improving total pressure recovery though they are useful in suppressing the incipient separation in three-dimensional problems. Shaping sidewall geometry is effective in re-distributing flow on the side wall and results in a less distorted flow at the exit. Subsequently, a near 50% reduction in distortion is achieved. A simple change in corner geometry resulted in a 2.4% improvement in total pressure recovery.

Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

PubMed

Lee, Stephen; Hoffmann, Roald

2002-05-01

Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.