Crystal structure of (2Z,5Z)-3-(4-meth­oxy­phen­yl)-2-[(4-meth­oxy­phenyl)­imino]-5-[(E)-3-(2-nitro­phen­yl)allyl­idene]-1,3-thia­zolidin-4-one

PubMed Central

Rahmani, Rachida; Djafri, Ahmed; Daran, Jean-Claude; Djafri, Ayada; Chouaih, Abdelkader; Hamzaoui, Fodil

2016-01-01

In the title compound, C26H21N3O5S, the thia­zole ring is nearly planar with a maximum deviation of 0.017 (2) Å, and is twisted with respect to the three benzene rings, making dihedral angles of 25.52 (12), 85.77 (12) and 81.85 (13)°. In the crystal, weak C—H⋯O hydrogen bonds and C—H⋯π inter­actions link the mol­ecules into a three-dimensional supra­molecular architecture. Aromatic π–π stacking is also observed between the parallel nitro­benzene rings of neighbouring mol­ecules, the centroid-to-centroid distance being 3.5872 (15) Å. PMID:26958377

Orphenadrinium picrate picric acid.

PubMed

Fun, Hoong-Kun; Hemamalini, Madhukar; Siddaraju, B P; Yathirajan, H S; Narayana, B

2010-02-24

The asymmetric unit of the title compound N,N-dimethyl-2-[(2-methyl-phen-yl)phenyl-meth-oxy]ethanaminium picrate picric acid, C(18)H(24)NO(+)·C(6)H(2)N(3)O(7) (-)·C(6)H(3)N(3)O(7), contains one orphenadrinium cation, one picrate anion and one picric acid mol-ecule. In the orphenadrine cation, the two aromatic rings form a dihedral angle of 70.30 (7)°. There is an intra-molecular O-H⋯O hydrogen bond in the picric acid mol-ecule, which generates an S(6) ring motif. In the crystal structure, the orphenadrine cations, picrate anions and picric acid mol-ecules are connected by strong inter-molecular N-H⋯O hydrogen bonds, π⋯π inter-actions between the benzene rings of cations and anions [centroid-centroid distance = 3.5603 (9) Å] and weak C-H⋯O hydrogen bonds, forming a three-dimensional network.

A protein relational database and protein family knowledge bases to facilitate structure-based design analyses.

PubMed

Mobilio, Dominick; Walker, Gary; Brooijmans, Natasja; Nilakantan, Ramaswamy; Denny, R Aldrin; Dejoannis, Jason; Feyfant, Eric; Kowticwar, Rupesh K; Mankala, Jyoti; Palli, Satish; Punyamantula, Sairam; Tatipally, Maneesh; John, Reji K; Humblet, Christine

2010-08-01

The Protein Data Bank is the most comprehensive source of experimental macromolecular structures. It can, however, be difficult at times to locate relevant structures with the Protein Data Bank search interface. This is particularly true when searching for complexes containing specific interactions between protein and ligand atoms. Moreover, searching within a family of proteins can be tedious. For example, one cannot search for some conserved residue as residue numbers vary across structures. We describe herein three databases, Protein Relational Database, Kinase Knowledge Base, and Matrix Metalloproteinase Knowledge Base, containing protein structures from the Protein Data Bank. In Protein Relational Database, atom-atom distances between protein and ligand have been precalculated allowing for millisecond retrieval based on atom identity and distance constraints. Ring centroids, centroid-centroid and centroid-atom distances and angles have also been included permitting queries for pi-stacking interactions and other structural motifs involving rings. Other geometric features can be searched through the inclusion of residue pair and triplet distances. In Kinase Knowledge Base and Matrix Metalloproteinase Knowledge Base, the catalytic domains have been aligned into common residue numbering schemes. Thus, by searching across Protein Relational Database and Kinase Knowledge Base, one can easily retrieve structures wherein, for example, a ligand of interest is making contact with the gatekeeper residue.

Crystal structure and Hirshfeld surface analysis of ethyl 2-{[4-ethyl-5-(quinolin-8-yloxymeth­yl)-4H-1,2,4-triazol-3-yl]sulfan­yl}acetate

PubMed Central

Bahoussi, Rawia Imane; Djafri, Ahmed; Djafri, Ayada

2017-01-01

In the title compound, C18H20N4O3S, the 1,2,4-triazole ring is twisted with respect to the mean plane of quinoline moiety at 65.24 (4)°. In the crystal, mol­ecules are linked by weak C—H⋯O and C—H⋯N hydrogen bonds, forming the three-dimensional supra­molecular packing. π–π stacking between the quinoline ring systems of neighbouring mol­ecules is also observed, the centroid-to-centroid distance being 3.6169 (6) Å. Hirshfeld surface (HS) analyses were performed. PMID:28217336

Crystal structure of di-bromo-meth-oxy-seselin (DBMS), a photobiologically active pyran-ocoumarin.

PubMed

Bauri, A K; Foro, Sabine; Rahman, A F M M

2017-05-01

The title compound, C 15 H 14 Br 2 O 4 [systematic name: rac -(9 S ,10 R )-3,9-dibromo-10-methoxy-8,8-dimethyl-9,10-dihydropyrano[2,3- h ]chromen-2(8 H )-one], is a pyran-ocoumarin derivative formed by the bromination of seselin, which is a naturally occurring angular pyran-ocoumarin isolated from the Indian herb Trachyspermum stictocarpum . In the mol-ecule, the benzo-pyran ring system is essentially planar, with a maximum deviation of 0.044 (2) Å for the O atom. The di-hydro-pyran ring is in a half-chair conformation and the four essentially planar atoms of this ring form a dihedral angle of 4.6 (2)° with the benzo-pyran ring system. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming chains propagating along [010]. In addition, π-π stacking inter-actions, with centroid-centroid distances of 3.902 (2) and 3.908 (2) Å, link the hydrogen-bonded chains into layers parallel to (001).

Anisotropic crystal structure distortion of the monoclinic polymorph of acetaminophen at high hydrostatic pressures.

PubMed

Boldyreva, E V; Shakhtshneider, T P; Vasilchenko, M A; Ahsbahs, H; Uchtmann, H

2000-04-01

The anisotropy of structural distortion of the monoclinic polymorph of acetaminophen induced by hydrostatic pressure up to 4.0 GPa was studied by single-crystal X-ray diffraction in a Merrill-Bassett diamond anvil cell (DAC). The space group (P2(1)/n) and the general structural pattern remained unchanged with pressure. Despite the overall decrease in the molar volume with pressure, the structure expanded in particular crystallographic directions. One of the linear cell parameters (c) passed through a minimum as the pressure increased. The intramolecular bond lengths changed only slightly with pressure, but the changes in the dihedral and torsion angles were very large. The compressibility of the intermolecular hydrogen bonds NH...O and OH...O was measured. NH...O bonds were shown to be slightly more compressible than OH...O bonds. The anisotropy of structural distortion was analysed in detail in relation to the pressure-induced changes in the molecular conformations, to the compression of the hydrogen-bond network, and to the changes in the orientation of molecules with respect to each other in the pleated sheets in the structure. Dirichlet domains were calculated in order to analyse the relative shifts of the centroids of the hydrogen-bonded cycles and of the centroids of the benzene rings with pressure.

2-(4-Hy-droxy-phen-yl)-1H-benzimidazol-3-ium chloride monohydrate.

PubMed

González-Padilla, Jazmin E; Rosales-Hernández, Martha Cecila; Padilla-Martínez, Itzia I; García-Báez, Efren V; Rojas-Lima, Susana

2013-01-01

The title mol-ecular salt, C13H11N2O(+)·Cl(-)·H2O, crystallizes as a monohydrate. In the cation, the phenol and benzimidazole rings are almost coplanar, making a dihedral angle of 3.18 (4)°. The chloride anion and benzimidazole cation are linked by two N(+)-H⋯Cl(-) hydrogen bonds, forming chains propagating along [010]. These chains are linked through O-H⋯Cl hydrogen bonds involving the water mol-ecule and the chloride anion, which form a diamond core, giving rise to the formation of two-dimensional networks lying parallel to (10-2). Two π-π inter-actions involving the imidazolium ring with the benzene and phenol rings [centroid-centroid distances = 3.859 (3) and 3.602 (3) Å, respectively], contribute to this second dimension. A strong O-H⋯O hydrogen bond involving the water mol-ecule and the phenol substituent on the benzimidazole unit links the networks, forming a three-dimensional structure.

2,2'-[2,4-Bis(naphthalen-1-yl)cyclo-butane-1,3-di-yl]bis-(1-methyl-pyridinium) diiodide: thermal-induced [2 + 2] cyclo-addition reaction of a heterostilbene.

PubMed

Chantrapromma, Suchada; Chanawanno, Kullapa; Boonnak, Nawong; Fun, Hoong-Kun

2012-01-01

The asymmetric unit of the title compound, C(36)H(32)N(2) (2+)·2I(-), consists of one half-mol-ecule of the cation and one I(-) anion. The cation is located on an inversion centre. The dihedral angle between the pyridinium ring and the naphthalene ring system in the asymmetric unit is 19.01 (14)°. In the crystal, the cations and the anions are linked by C-H⋯I inter-actions into a layer parallel to the bc plane. Intra- and inter-molecular π-π inter-actions with centroid-centroid distances of 3.533 (2)-3.807 (2) Å are also observed.

Temporal variations in the position of the heliospheric equator

NASA Astrophysics Data System (ADS)

Obridko, V. N.; Shelting, B. D.

2008-08-01

It is shown that the centroid of the heliospheric equator undergoes quasi-periodic oscillations. During the minimum of the 11-year cycle, the centroid shifts southwards (the so-called bashful-ballerina effect). The direction of the shift reverses during the solar maximum. The solar quadrupole is responsible for this effect. The shift is compared with the tilt of the heliospheric current sheet.

1-(2,4-Di-nitro-phen-yl)-2-[(E)-(3,4,5-tri-meth-oxy-benzyl-idene)]hydrazine.

PubMed

Chantrapromma, Suchada; Ruanwas, Pumsak; Boonnak, Nawong; Chidan Kumar, C S; Fun, Hoong-Kun

2014-02-01

Mol-ecules of the title compound, C16H16N4O7, are not planar with a dihedral angle of 5.50 (11)° between the substituted benzene rings. The two meta-meth-oxy groups of the 3,4,5-tri-meth-oxy-benzene moiety lie in the plane of the attached ring [Cmeth-yl-O-C-C torsion angles -0.1 (4)° and -3.7 (3)°] while the para-meth-oxy substituent lies out of the plane [Cmeth-yl-O-C-C, -86.0 (3)°]. An intra-molecular N-H⋯O hydrogen bond involving the 2-nitro substituent generates an S(6) ring motif. In the crystal structure, mol-ecules are linked by weak C-H⋯O inter-actions into screw chains, that are arranged into a sheet parallel to the bc plane. These sheets are connected by π-π stacking inter-actions between the nitro and meth-oxy substituted aromatic rings with a centroid-centroid separation of 3.9420 (13) Å. C-H⋯π contacts further stabilize the two-dimensional network.

N-H.N hydrogen bonding in 4,6-diphenyl-2-pyrimidinylamine isolated from the plant Justicia secunda (Acanthaceae).

PubMed

Gallagher, John F; Goswami, Shyamaprosad; Chatterjee, Baidyanath; Jana, Subrata; Dutta, Kalyani

2004-04-01

The title compound, C(16)H(13)N(3), isolated from Justicia secunda (Acanthaceae), comprises two molecules (which differ slightly in conformation) in the asymmetric unit of space group P-1. Intermolecular N(amino)-H.N(pyrm) interactions (N(pyrm) is a pyrimidine ring N atom) involve only one of the two donor amino H atoms and pyrimidine N atoms per molecule, forming dimeric units via R(2)(2)(8) rings, with N.N distances of 3.058 (2) and 3.106 (3) A, and N-H.N angles of 172.7 (18) and 175.8 (17) degrees. The dimers are linked by C-H.pi(arene) contacts, with an H.centroid distance of 2.77 A and a C-H.centroid angle of 141 degrees.

A recursive technique for adaptive vector quantization

NASA Technical Reports Server (NTRS)

Lindsay, Robert A.

1989-01-01

Vector Quantization (VQ) is fast becoming an accepted, if not preferred method for image compression. The VQ performs well when compressing all types of imagery including Video, Electro-Optical (EO), Infrared (IR), Synthetic Aperture Radar (SAR), Multi-Spectral (MS), and digital map data. The only requirement is to change the codebook to switch the compressor from one image sensor to another. There are several approaches for designing codebooks for a vector quantizer. Adaptive Vector Quantization is a procedure that simultaneously designs codebooks as the data is being encoded or quantized. This is done by computing the centroid as a recursive moving average where the centroids move after every vector is encoded. When computing the centroid of a fixed set of vectors the resultant centroid is identical to the previous centroid calculation. This method of centroid calculation can be easily combined with VQ encoding techniques. The defined quantizer changes after every encoded vector by recursively updating the centroid of minimum distance which is the selected by the encoder. Since the quantizer is changing definition or states after every encoded vector, the decoder must now receive updates to the codebook. This is done as side information by multiplexing bits into the compressed source data.

(2-{[2-(diphenyl­phosphino)phen­yl]thio}­phen­yl)diphenyl­phosphine sulfide

PubMed Central

Alvarez-Larena, Angel; Martinez-Cuevas, Francisco J.; Flor, Teresa; Real, Juli

2012-01-01

In the title compound, C36H28P2S2, the dihedral angle between the central benzene rings is 66.95 (13)°. In the crystal, molecules are linked via Car—H⋯π and π–π inter­actions [shortest centroid–centroid distance between benzene rings = 3.897 (2) Å]. PMID:23284423

Ring Image Analyzer

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry V.

2012-01-01

Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

N-(4-Meth-oxy-phen-yl)-6-methyl-2-phenyl-5-{[4-(tri-fluoro-meth-yl)anilino]meth-yl}pyrimidin-4-amine.

PubMed

Cieplik, Jerzy; Pluta, Janusz; Bryndal, Iwona; Lis, Tadeusz

2013-11-27

The title compound, C26H23F3N4O, crystallizes with two symmetry-independent mol-ecules in the asymmetric unit, denoted A and B, which differ mainly in the rotation of the meth-oxy-phenyl ring. The -CF3 group of mol-ecule B is disordered by rotation, with the F atoms split over two sets of sites; the occupancy factor for the major component is 0.853 (4). The dihedral angles between the pyrimidine ring and the attached phenyl, meth-oxy-phenyl and tri-fluoro-methyl-phenyl rings are 8.1 (2), 37.5 (2) and 70.7 (2)°, respectively, in mol-ecule A, and 9.3 (2), 5.3 (2) and 79.7 (2)° in mol-ecule B. An intra-molecular N-H⋯N hydrogen bond occurs in each mol-ecule. In the crystal, two crystallographically independent mol-ecules associate into a dimer via a pair of N-H⋯N hydrogen bonds, with a resulting R 2 (2)(12) ring motif and π-π stacking inter-actions [centroid-centroid distance = 3.517 (4) Å] between the pyrimidine rings. For the A mol-ecules, there are inter-molecular C-H⋯O hydrogen bonds between an aryl C atom of meth-oxy-phenyl ring and a meth-oxy O atom of an adjacent mol-ecule. A similar inter-action is lacking in the B mol-ecules.

2-(4,5-Dihydro-1H-imidazol-2-yl)­pyridine

PubMed Central

Kia, Reza; Fun, Hoong-Kun; Kargar, Hadi

2009-01-01

In the mol­ecule of the title compound, C8H9N3, a new imidazoline derivative, the six- and five-membered rings are slightly twisted away from each other, forming a dihedral angle of 7.96 (15)°. In the crystal structure, neighbouring mol­ecules are linked together by inter­molecular N—H⋯N hydrogen bonds into extended one-dimensional chains along the a axis. The pyridine N atom is in close proximity to a carbon-bound H atom of the imidazoline ring, with an H⋯N distance of 2.70 Å, which is slightly shorter than the sum of the van der Waals radii of these atoms (2.75 Å). The crystal structure is further stabilized by inter­molecular C—H⋯π and π–π inter­actions (centroid-to-centroid distance 3.853 Å). PMID:21582505

7-Meth­oxy-2-phenyl­chroman-4-one

PubMed Central

Piaskowska, Agata; Hodorowicz, Maciej; Nitek, Wojciech

2013-01-01

In the title compound, C16H14O3, the ring O atom and the two adjacent non-fused C atoms, as well as the attached phenyl ring, exhibit static disorder [occupancy ratio 0.559 (12):0.441 (12)]. The crystal packing features π–π [centroid–centroid distance = 3.912 (1) Å] and C—H⋯π inter­actions. PMID:23424545

3-Methyl-1,4-dioxo-1,4-dihydro­naphthalen-2-yl 4-amino­benzoate

PubMed Central

Bambagiotti-Alberti, Massimo; Bartolucci, Gianluca; Bruni, Bruno; Coran, Silvia; Di Vaira, Massimo

2008-01-01

The crystal structure of the title compound, C18H13NO4, the oxidized form of the drug aminaftone used in venous disease therapy, is characterized by the presence of ribbons of hydrogen-bonded mol­ecules parallel to the [111] crystallographic direction and by stacking inter­actions between rings [centroid–centroid distance between quinone rings = 3.684 (3) Å and between amino­benzoate rings = 4.157 (3) Å] along the ribbons. PMID:21202108

Method of particle trajectory recognition in particle flows of high particle concentration using a candidate trajectory tree process with variable search areas

DOEpatents

Shaffer, Franklin D.

2013-03-12

The application relates to particle trajectory recognition from a Centroid Population comprised of Centroids having an (x, y, t) or (x, y, f) coordinate. The method is applicable to visualization and measurement of particle flow fields of high particle. In one embodiment, the centroids are generated from particle images recorded on camera frames. The application encompasses digital computer systems and distribution mediums implementing the method disclosed and is particularly applicable to recognizing trajectories of particles in particle flows of high particle concentration. The method accomplishes trajectory recognition by forming Candidate Trajectory Trees and repeated searches at varying Search Velocities, such that initial search areas are set to a minimum size in order to recognize only the slowest, least accelerating particles which produce higher local concentrations. When a trajectory is recognized, the centroids in that trajectory are removed from consideration in future searches.

Crystal structure of azilsartan methyl ester ethyl acetate hemisolvate.

PubMed

Li, Zhengyi; Liu, Rong; Zhu, Meilan; Chen, Liang; Sun, Xiaoqiang

2015-02-01

The title compound, C26H22N4O5 (systematic name: methyl 2-eth-oxy-1-{4-[2-(5-oxo-4,5-di-hydro-1,2,4-oxa-diazol-3-yl)phenyl]benz-yl}-1H-1,3-benzo-diazole-7-carboxyl-ate ethyl acetate hemisolvate), was obtained via cyclization of methyl (Z)-2-eth-oxy-1-{(2'-(N'-hy-droxy-carbamimido-yl)-[1,1'-biphen-yl]-4-yl)meth-yl}-1H-benzo[d]imidazole-7-carboxyl-ate with diphen-yl carbonate. There are two independent mol-ecules (A and B) with different conformations and an ethyl acetate solvent mol-ecule in the asymmetric unit. In mol-ecule A, the dihedral angle between the benzene ring and its attached oxa-diazole ring is 59.36 (17); the dihedral angle between the benzene rings is 43.89 (15) and that between the benzene ring and its attached imidazole ring system is 80.06 (11)°. The corres-ponding dihedral angles in mol-ecule B are 58.45 (18), 50.73 (16) and 85.37 (10)°, respectively. The C-O-C-Cm (m = meth-yl) torsion angles for the eth-oxy side chains attached to the imidazole rings in mol-ecules A and B are 93.9 (3) and -174.6 (3)°, respectively. In the crystal, the components are linked by N-H⋯N and C-H⋯O hydrogen bonds, generating a three-dimensional network. Aromatic π-π stacking inter-actions [shortest centroid-centroid separation = 3.536 (3)Å] are also observed.

2-(1,2,3,4-Tetra-hydro-1-naphth-yl)imidazolium chloride monohydrate.

PubMed

Bruni, Bruno; Bartolucci, Gianluca; Ciattini, Samuele; Coran, Silvia

2010-08-18

In the title compound, C(13)H(15)N(2) (+)·Cl(-)·H(2)O, the ions and water mol-ecules are -connected by N-H⋯Cl, O-H⋯Cl, NH⋯Cl⋯HO, NH⋯Cl⋯HN and OH⋯Cl⋯HO inter-actions, forming discrete D(2) and D(2) (1)(3) chains, C(2) (1)(6) chains and R(4) (2)(8) rings, leading to a neutral two-dimensional network. The crystal structure is further stabilized by π-π stacking inter-actions [centroid-centroid distance = 3.652 (11) Å].

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.

2,3-Dimethyl-6-nitro-2H-indazole

PubMed Central

Chen, Yan; Fang, Zheng; Wei, Ping

2009-01-01

In the mol­ecule of the title compound, C9H9N3O2, the indazole ring system is almost planar [maximum deviation = 0.019 (3) Å for the C atom bearing the nitro group]. In the crystal structure, inter­molecular C—H⋯O inter­actions link the mol­ecules into centrosymmetric dimers, forming R 2 2(18) ring motifs. Aromatic π–π contacts between indazole rings [centroid–centroid distances = 3.632 (1) and 3.705 (1) Å] may further stabilize the structure. PMID:21583483

3-Ethyl-5-(4-meth­oxy­phen­oxy)-2-(pyridin-4-yl)-3H-imidazo[4,5-b]pyridine

PubMed Central

Ranjith, S.; SubbiahPandi, A.; Suresh, A. D.; Pitchumani, K.

2011-01-01

In the title compound, C20H18N4O2, the imidazopyridine fused ring system is almost perpendicular to the benzene ring [dihedral angle = 87.6 (5)°]. The pyridine ring makes a dihedral angle of 35.5 (5)° with the mean plane of the imidazopyridine fragment. The crystal structure is stabilized by an aromatic π–π stacking inter­action between the phenyl rings of neighbouring mol­ecules [centroid–centroid distance = 3.772 (2) Å, inter­planar distance = 3.546 (2) Å and slippage = 1.286 (2) Å]. PMID:21837144

1,1'-Bis[bis-(4-meth-oxy-phen-yl)phosphan-yl]ferrocene.

PubMed

Ren, Xinfeng; Wang, Le; Li, Ya

2012-07-01

In the crystal structure of the title substituted ferrocene complex, [Fe(C₁₉H₁₈O₂P)₂], the Fe(II) atom lies on a twofold rotation axis, giving an eclipsed cyclo-penta-dienyl conformation with a ring centroid separation of 3.292 (7) Å and an Fe-C bond-length range of 2.0239 (15)-2.0521 (15) Å. In the ligand, the cyclo-penta-dienyl ring forms dihedral angles of 60.36 (6) and 82.93 (6)° with the two benzene rings of the diphenyl-phosphine group, while the dihedral angle between the benzene rings is 67.4 (5)°.

Crystal structure of a looped-chain CoII coordination polymer: catena-poly[[bis-(nitrato-κO)cobalt(II)]bis-[μ-bis-(pyridin-3-ylmeth-yl)sulfane-κ2N:N'

PubMed

Moon, Suk-Hee; Seo, Joobeom; Park, Ki-Min

2017-11-01

The asymmetric unit of the title compound, [Co(NO 3 ) 2 (C 12 H 12 N 2 S) 2 ] n , contains a bis-(pyridin-3-ylmeth-yl)sulfane ( L ) ligand, an NO 3 - anion and half a Co II cation, which lies on an inversion centre. The Co II cation is six-coordinated, being bound to four pyridine N atoms from four symmetry-related L ligands. The remaining coordination sites are occupied by two O atoms from two symmetry-related nitrate anions in a monodentate manner. Thus, the Co II centre adopts a distorted octa-hedral geometry. Two symmetry-related L ligands are connected by two symmetry-related Co II cations, forming a 20-membered cyclic dimer, in which the Co II atoms are separated by 10.2922 (7) Å. The cyclic dimers are connected to each other by sharing Co II atoms, giving rise to the formation of an infinite looped chain propagating along the [101] direction. Inter-molecular C-H⋯π (H⋯ring centroid = 2.89 Å) inter-actions between one pair of corresponding L ligands and C-H⋯O hydrogen bonds between the L ligands and the nitrate anions occur in the looped chain. In the crystal, adjacent looped chains are connected by inter-molecular π-π stacking inter-actions [centroid-to-centroid distance = 3.8859 (14) Å] and C-H⋯π hydrogen bonds (H⋯ring centroid = 2.65 Å), leading to the formation of layers parallel to (101). These layers are further connected through C-H⋯O hydrogen bonds between the layers, resulting in the formation of a three-dimensional supra-molecular architecture.

(R)-2-[(Dimethyl-amino)-meth-yl]-1,1'-bis-(diphenyl-phosphinothio-yl)ferrocene dichloromethane monsolvate.

PubMed

Philippe, Elisabeth; Manoury, Eric; Daran, Jean-Claude

2012-06-01

In the title compound, [Fe(C(20)H(21)NPS)(C(17)H(14)PS)]·CH(2)Cl(2), both cyclo-penta-dienyl (Cp) rings constituting the ferrocene unit are substituted by a sulfur-protected diphenyl-phosphine. One of the Cp ligands is additionally substituted by a dimethyl-amino-methyl group causing the chirality of the mol-ecule. Surprisingly, although the synthetic procedure yielded the title compound as a racemic mixture, the reported crystal is enanti-omerically pure with the R absolute configuration. The dimethyl-amino group is exo with respect to the Cp ring. Both diphenyl-thio-phosphine groups are trans with respect to the centroid-Fe-centroid direction. Weak intra-molecular C-H⋯S and C-H⋯π inter-actions between symmetry-related mol-ecules are observed. The contribution of the disordered solvent was removed from the refinement using SQUEEZE in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155].

Control of intramolecular π-π stacking interaction in cationic iridium complexes via fluorination of pendant phenyl rings.

PubMed

He, Lei; Ma, Dongxin; Duan, Lian; Wei, Yongge; Qiao, Juan; Zhang, Deqiang; Dong, Guifang; Wang, Liduo; Qiu, Yong

2012-04-16

Intramolecular π-π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)(2)(F2phpzpy)]PF(6) (2) and [Ir(ppy)(2)(F5phpzpy)]PF(6) (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)(2)(phpzpy)]PF(6) (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 Å for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular π-π stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face π-π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π-π stacking interaction remains on the lowest triplet state. © 2012 American Chemical Society

Vibration characteristics of a steadily rotating slender ring

NASA Technical Reports Server (NTRS)

Lallman, F. J.

1980-01-01

Partial differential equations are derived to describe the structural vibrations of a uniform homogeneous ring which is very flexible because the radius is very large compared with the cross sectional dimensions. Elementary beam theory is used and small deflections are assumed in the derivation. Four sets of structural modes are examined: bending and compression modes in the plane of the ring; bending modes perpendicular to the plane of the ring; and twisting modes about the centroid of the ring cross section. Spatial and temporal characteristics of these modes, presented in terms of vibration frequencies and ratios between vibration amplitudes, are demonstrated in several figures. Given a sufficiently high rotational rate, the dynamics of the ring approach those of a vibrating string. In this case, the velocity of traveling wave in the material of the ring approaches in velocity of the material relative to inertial space, resulting in structural modes which are almost stationary in space.

4,4'-Bipyridine-pyroglutamic acid (1/2).

PubMed

Arman, Hadi D; Kaulgud, Trupta; Tiekink, Edward R T

2009-10-31

In the title co-crystal, C(10)H(8)N(2)·2C(5)H(7)NO(3), the 4,4'-bipyridine mol-ecule [dihedral angle between the pyridine rings = 36.33 (11)°] accepts O-H⋯N hydrogen bonds from the two pyroglutamic (pga) acid mol-ecules. The pga mol-ecules at each end of the trimeric aggregate self-associate via centrosymmetric eight-membered amide {⋯HNCO}(2) synthons, so that the crystal structure comprises one-dimensional supra-molecular chains propagating in [13]. C-H⋯O and π-π stacking inter-actions [centroid-centroid separation = 3.590 (2) Å] consolidate the structure.

2-[(E)-2-(4-Eth-oxy-phen-yl)ethen-yl]-1-methyl-quinolinium 4-fluoro-benzene-sulfonate.

PubMed

Fun, Hoong-Kun; Kobkeatthawin, Thawanrat; Ruanwas, Pumsak; Quah, Ching Kheng; Chantrapromma, Suchada

2014-01-01

In the structure of the title salt, C20H20NO(+)·C6H4FO3S(-), the 4-(eth-oxy-phen-yl)ethenyl unit is disordered over two positions with a refined site-occupancy ratio of 0.610 (6):0.390 (6). The cation is nearly planar, the dihedral angle between the quinolinium and benzene rings being 6.7 (4) and 1.7 (7)° for the major and minor components, respectively. The eth-oxy group is essentially coplanar with the benzene ring [C-O-C-Cmethy = 177.1 (8) and 177.8 (12)° for the major and minor components, respectively]. In the crystal, cations and anions are linked into chains along the b-axis direction by C-H⋯Osulfon-yl weak inter-actions. These chains are further connected into sheets parallel to (001) by C-H⋯Osulfon-yl weak inter-actions. The chains are also stacked along the a axis through π-π inter-actions involving the quinolinium and benzene rings [centroid-centroid distances = 3.636 (5) Å for the major component and 3.800 (9) Å for the minor component]. C-H⋯π inter-actions are also present.

2-(Naphthalen-1-yl)-4-(naphthalen-1-yl­methyl­idene)-1,3-oxazol-5(4H)-one

PubMed Central

Gündoğdu, Cevher; Alp, Serap; Ergün, Yavuz; Tercan, Barış; Hökelek, Tuncer

2011-01-01

In the title compound, C24H15NO2, the oxazole ring is oriented at dihedral angles of 10.09 (4) and 6.04 (4)° with respect to the mean planes of the naphthalene ring systems, while the two naphthalene ring systems make a dihedral angle of 4.32 (3)°. Intra­molecular C—H⋯N hydrogen bonds link the oxazole N atom to the naphthalene ring systems. In the crystal, inter­molecular weak C—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. π–π contacts between the oxazole and naphthalene rings and between the naphthalene ring systems [centroid–centroid distances = 3.5947 (9) and 3.7981 (9) Å] may further stabilize the crystal structure. Three weak C—H⋯π inter­actions also occur. PMID:21754548

Crystal structure of bis-(μ-3-nitro-benzoato)-κ3O,O':O;κ3O:O,O'-bis-[bis-(3-cyano-pyridine-κN1)(3-nitro-benzoato-κ2O,O')cadmium].

PubMed

Hökelek, Tuncer; Akduran, Nurcan; Özen, Azer; Uğurlu, Güventürk; Necefoğlu, Hacali

2017-03-01

The asymmetric unit of the title compound, [Cd 2 (C 7 H 4 NO 4 ) 4 (C 6 H 4 N 2 ) 4 ], contains one Cd II atom, two 3-nitro-benzoate (NB) anions and two 3-cyano-pyridine (CPy) ligands. The two CPy ligands act as monodentate N(pyridine)-bonding ligands, while the two NB anions act as bidentate ligands through the carboxyl-ate O atoms. The centrosymmetric dinuclear complex is generated by application of inversion symmetry, whereby the Cd II atoms are bridged by the carboxyl-ate O atoms of two symmetry-related NB anions, thus completing the distorted N 2 O 5 penta-gonal-bipyramidal coordination sphere of each Cd II atom. The benzene and pyridine rings are oriented at dihedral angles of 10.02 (7) and 5.76 (9)°, respectively. In the crystal, C-H⋯N hydrogen bonds link the mol-ecules, enclosing R 2 2 (26) ring motifs, in which they are further linked via C-H⋯O hydrogen bonds, resulting in a three-dimensional network. In addition, π-π stacking inter-actions between parallel benzene rings and between parallel pyridine rings of adjacent mol-ecules [shortest centroid-to-centroid distances = 3.885 (1) and 3.712 (1) Å, respectively], as well as a weak C-H⋯π inter-action, may further stabilize the crystal structure.

5-(4-Bromo­phen­oxy)-1-methyl-3-methyl-1H-pyrazole-4-carbaldehyde-O-[(5-meth­oxy-1,3,4-thia­diazol-2-yl)-meth­yl]oxime

PubMed Central

Fan, Chong-Guang; Chen, Jian-Cun; Dai, Hong; Wei, Yun-Hua; Shi, Yu-Jun

2012-01-01

In the title mol­ecule, C16H16BrN5O3S, the 1,3,4-thia­diazole ring is situated under the benzene ring, forming a dihedral angle of 86.6 (2)°, and with an S⋯Cg (where Cg is the centroid of the benzene ring) distance of 3.312 (3) Å. The benzene and 1,3,4-thia­diazole rings form dihedral angles of 83.8 (3) and 57.7 (2)°, respectively, with the central pyrazole ring. In the absence of classical hydrogen bonds, the crystal packing is stabilized by a C—H⋯π inter­action.. PMID:23284447

(E)-4-Methyl-N′-[(4-oxo-4H-chromen-3-yl)methyl­idene]benzohydrazide

PubMed Central

Ishikawa, Yoshinobu; Watanabe, Kohzoh

2014-01-01

In the title chromone-tethered benzohydrazide derivative, C18H14N2O3, the 4H-chromen-4-one and the –CH=N–NH–CO– units are each essentially planar, with the largest deviations from thei planes being 0.052 (2) and 0.003 (2) Å, respectively. The dihedral angles between the 4H-chromen-4-one and the –CH=N–NH–CO– units, the 4H-chromen-4-one unit and the benzene ring of the 4-tolyl group, and the benzene ring of the 4-tolyl group and the –CH=N–NH–CO– unit are 8.09 (7), 9.94 (5) and 17.97 (8)°, respectively. In the crystal, the mol­ecules form two types of centrosymmetric dimers: one by N—H⋯O hydrogen bonds and the other by π–π stacking inter­actions between the 4H-chromen-4-one unit and the 4-tolyl group [centroid–centroid distance = 3.641 (5) Å]. These dimers form one-dimensional assemblies extending along the a-axis direction. Additional π–π stacking inter­actions between two 4H-chromen-4-one units [centroid–centroid distance = 3.591 (5) Å] and two 4-tolyl groups [centroid–centroid distance = 3.792 (5) Å] organize the mol­ecules into a three-dimensional network. PMID:24860370

(S)-N-[1-(5-Benzyl-sulfan-yl-1,3,4-oxa-diazol-2-yl)-2-phenyl-eth-yl]-4-methyl-benzene-sulfonamide.

PubMed

Syed, Tayyaba; Hameed, Shahid; Jones, Peter G

2011-11-01

The title compound, C(24)H(23)N(3)O(3)S(2), crystallizes with two independent mol-ecules in the asymmetric unit. They differ essentially in the orientation of the tolyl rings, between which there is π-π stacking (centroid-centroid distance = 3.01 Å). The absolute configuration was confirmed by the determination of the Flack parameter [x = 0.008 (9)]. In the crystal, mol-ecules are connected by two classical N-H⋯N hydrogen bonds and two weak but very short C-H⋯O(sulfon-yl) inter-actions, forming layers lying parallel to the bc plane.

N-(Quinolin-8-yl)quinoline-2-carbox­amide

PubMed Central

Li, Yanfeng; Zhou, Hongbo; Shen, Xiaoping

2012-01-01

In the title compound, C19H13N3O, the dihedral angle between the two quinoline systems is 11.54 (3)°. The mol­ecular conformation is stabilized by intra­molecular N—H⋯N and C—H⋯O hydrogen bonds, with N—H⋯N being bifurcated towards the two N atoms of the two quinoline rings. In the crystal, there are weak intermolecular π–π inter­actions present involving the quinoline rings [centroid–centroid distance 3.7351 (14) Å]. PMID:22719482

1-[(3,5-Dimethyl-1H-pyrazol-1-yl)carbon­yl]-5-methyl­indolizine-3-carbo­nitrile

PubMed Central

Gu, Wei-Jin; Xie, Wen-Li; Wang, Ting-Ting

2012-01-01

In the title mol­ecule, C16H14N4O, the indolizine ring system is essentially planar, with a maximum deviation of 0.013 (3) Å, and forms a dihedral angle of 7.52 (12)° with the pyrazole ring. In the crystal, weak C—H⋯O hydrogen bonds and π–π stacking inter­actions, with a centroid–centroid distance of 3.6378 (16) Å, link mol­ecules along [001]. PMID:23476226

(2E)-1-(2,6-Dichloro-3-fluoro-phen-yl)-3-phenyl-prop-2-en-1-one.

PubMed

Praveen, Aletti S; Yathirajan, Hemmige S; Narayana, Badiadka; Gerber, Thomas; Hosten, Eric; Betz, Richard

2012-04-01

In the title compound, C(15)H(9)Cl(2)FO, the F atom shows positional disorder over two positions, with site-occupancy factors of 0.747 (4) and 0.253 (4). The dihedral angle between the rings is 86.37 (10)°. In the crystal, C-H⋯O contacts connect the mol-ecules into chains along the c axis. The shortest inter-centroid distance between two aromatic systems is 3.6686 (12) Å and is apparent between the halogenated rings.

1,1′-Bis[bis­(4-meth­oxy­phen­yl)phosphan­yl]ferrocene

PubMed Central

Ren, Xinfeng; Wang, Le; Li, Ya

2012-01-01

In the crystal structure of the title substituted ferrocene complex, [Fe(C19H18O2P)2], the FeII atom lies on a twofold rotation axis, giving an eclipsed cyclo­penta­dienyl conformation with a ring centroid separation of 3.292 (7) Å and an Fe—C bond-length range of 2.0239 (15)–2.0521 (15) Å. In the ligand, the cyclo­penta­dienyl ring forms dihedral angles of 60.36 (6) and 82.93 (6)° with the two benzene rings of the diphenyl­phosphine group, while the dihedral angle between the benzene rings is 67.4 (5)°. PMID:22807756

From classical to quantum and back: Hamiltonian adaptive resolution path integral, ring polymer, and centroid molecular dynamics

NASA Astrophysics Data System (ADS)

Kreis, Karsten; Kremer, Kurt; Potestio, Raffaello; Tuckerman, Mark E.

2017-12-01

Path integral-based methodologies play a crucial role for the investigation of nuclear quantum effects by means of computer simulations. However, these techniques are significantly more demanding than corresponding classical simulations. To reduce this numerical effort, we recently proposed a method, based on a rigorous Hamiltonian formulation, which restricts the quantum modeling to a small but relevant spatial region within a larger reservoir where particles are treated classically. In this work, we extend this idea and show how it can be implemented along with state-of-the-art path integral simulation techniques, including path-integral molecular dynamics, which allows for the calculation of quantum statistical properties, and ring-polymer and centroid molecular dynamics, which allow the calculation of approximate quantum dynamical properties. To this end, we derive a new integration algorithm that also makes use of multiple time-stepping. The scheme is validated via adaptive classical-path-integral simulations of liquid water. Potential applications of the proposed multiresolution method are diverse and include efficient quantum simulations of interfaces as well as complex biomolecular systems such as membranes and proteins.

N-(3-Chloro-4-eth-oxy-1-methyl-1H-indazol-5-yl)-4-meth-oxy-benzene-sulfonamide.

PubMed

Chicha, Hakima; Rakib, El Mostapha; Hannioui, Abdellah; Saadi, Mohamed; El Ammari, Lahcen

2014-06-01

The indazole ring system of the title compound, C17H18ClN3O4S, is almost planar (r.m.s. deviation = 0.0113 Å) and forms dihedral angles of 32.22 (8) and 57.5 (3)° with the benzene ring and the mean plane through the 4-eth-oxy group, respectively. In the crystal, mol-ecules are connected by pairs of N-H⋯O hydrogen bonds into inversion dimers, which are further linked by π-π inter-actions between the diazole rings [inter-centroid distance = 3.4946 (11) Å], forming chains parallel to [101].

(Nitrato-κ2 O,O′)bis­(1,10-phenanthroline-κ2 N,N′)copper(II) tricyano­methanide

PubMed Central

Lacková, Katarína; Potočňák, Ivan

2012-01-01

The title compound, [Cu(NO3)(C12H8N2)2][C(CN)3], is formed of discrete [Cu(NO3)(phen)2]+ complex cations (phen is 1,10-phenanthroline) and C(CN)3 − counter-anions. The CuII atom has an asymmetric tetragonal–bipyramidal (4 + 1+1) stereochemistry with a pseudo-C 2 symmetry axis bis­ecting the nitrate ligand and passing through the CuII atom between the two phen ligands. The four N atoms of the phen ligands coordinate to the CuII atom with Cu—N distances in the range 1.974 (2)–2.126 (2) Å, while the two O atoms coordinate at substanti­ally different distances [2.154 (2) and 2.586 (2) Å]. The structure is stabilized by C—H⋯O hydrogen bonds and weak π–π inter­actions between nearly parallel benzene and pyridine rings of two adjacent phen mol­ecules, with centroid–centroid distances of 3.684 (2) and 3.6111 (2) Å, and between π-electrons of the tricyano­methanide anion and the pyridine or benzene rings [N⋯(ring centroid) distances = 3.553 (3)–3.875 (3) Å]. PMID:23468758

2-[(4-Chloro­phen­yl)selan­yl]-3,4-di­hydro-2H-benzo[h]chromene-5,6-dione: crystal structure and Hirshfeld analysis

PubMed Central

Prado, Karinne E.; Name, Luccas L.; Jotani, Mukesh M.

2017-01-01

The title organoselenium compound, C19H13ClO3Se {systematic name: 2-[(4-chloro­phen­yl)selan­yl]-2H,3H,4H,5H,6H-naphtho­[1,2-b]pyran-5,6-dione}, has the substituted 2-pyranyl ring in a half-chair conformation with the methyl­ene-C atom bound to the methine-C atom being the flap atom. The dihedral angle between the two aromatic regions of the mol­ecule is 9.96 (9)° and indicates a step-like conformation. An intra­molecular Se⋯O inter­action of 2.8122 (13) Å is noted. In the crystal, π–π contacts between naphthyl rings [inter-centroid distance = 3.7213 (12) Å] and between naphthyl and chloro­benzene rings [inter-centroid distance = 3.7715 (13) Å], along with C—Cl⋯π(chloro­benzene) contacts, lead to supra­molecular layers parallel to the ab plane, which are connected into a three-dimensional architecture via methyl­ene-C—H⋯O(carbon­yl) inter­actions. The contributions of these and other weak contacts to the Hirshfeld surface is described. PMID:28638659

Crystal structure of 2-amino-pyridinium 6-chloro-nicotinate.

PubMed

Jasmine, N Jeeva; Rajam, A; Muthiah, P Thomas; Stanley, N; Razak, I Abdul; Rosli, M Mustaqim

2015-09-01

In the title salt, C5H7N(+)·C6H3ClNO(-), the 2-amino-pyri-din-ium cation inter-acts with the carboxyl-ate group of the 6-chloro-nicotinate anion through a pair of independent N-H⋯O hydrogen bonds, forming an R 2 (2)(8) ring motif. In the crystal, these dimeric units are connected further via N-H⋯O hydrogen bonds, forming chains along [001]. In addition, weak C-H⋯N and C-H⋯O hydrogen bonds, together with weak π-π inter-actions, with centroid-centroid distances of 3.6560 (5) and 3.6295 (5) Å, connect the chains, forming a two-dimensional network parallel to (100).

Crystal structure of 8-hy-droxy-quinolin-ium 2-carboxy-6-nitro-benzoate mono-hydrate.

PubMed

Divya Bharathi, M; Ahila, G; Mohana, J; Chakkaravarthi, G; Anbalagan, G

2015-04-01

In the title hydrated salt, C9H8NO(+)·C8H4NO6 (-)·H2O, the deprotonated carboxyl-ate group is almost normal to its attached benzene ring [dihedral angle = 83.56 (8)°], whereas the protonated carboxyl-ate group is close to parallel [dihedral angle = 24.56 (9)°]. In the crystal, the components are linked by N-H⋯O and O-H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by C-H⋯O and π-π [centroid-to-centroid distances = 3.6408 (9) and 3.6507 (9) Å] inter-actions, which result in a three-dimensional network.

1-(2,4-Dinitro­phen­yl)-2-(1,2,3,4-tetra­hydro­naphthalen-1-yl­idene)hydrazine

PubMed Central

Danish, M.; Hamid, Masood; Tahir, M. Nawaz; Ahmad, Nazir; Ghafoor, Sabiha

2010-01-01

In the title compound, C14H14N4O4, the dihedral angle between the benzene rings is 10.42 (8)°. The nitro groups make dihedral angles of 5.3 (2) and 6.47 (15)° with their parent ring and are oriented at 11.2 (3)° with respect to each other. An intra­molecular N—H⋯O hydrogen bond completes an S(6) ring motif. In the crystal, mol­ecules are linked by C—H⋯O inter­actions, thus forming (010) chains in which R 2 2(13) ring motifs are present. There also exist aromatic π–π stacking inter­actions [centroid–centroid separation = 3.7046 (9) Å]. PMID:21588393

Crystal structure of (7-methyl-2-oxo-2H-chromen-4-yl)methyl piperidine-1-carbo­di­thio­ate

PubMed Central

Roopashree, K. R.; Meenakshi, T. G.; Kumar, K. Mahesh; Kotresh, O.; Devarajegowda, H. C.

2015-01-01

In the title compound, C17H19NO2S2, the 2H-chromene ring system is nearly planar, with a maximum deviation of 0.0383 (28) Å, and the piperidine ring adopts a chair conformation. The 2H-chromene ring makes dihedral angles of 32.89 (16) and 67.33 (8)°, respectively, with the mean planes of the piperidine ring and the carbodi­thio­ate group. In the crystal, C—H⋯O and weak C—H⋯S hydrogen bonds link the mol­ecules into chains along [001]. The crystal structure also features C—H⋯π and π–π inter­actions, with a centroid–centroid distance of 3.7097 (17) Å. PMID:26396821

N-(2-{[5-Bromo-2-(piperidin-1-yl)pyrimidin-4-yl]sulfan­yl}-4-meth­oxy­phen­yl)-4-methyl­benzene­sulfonamide

PubMed Central

Kumar, Mohan; Mallesha, L.; Sridhar, M. A.; Kapoor, Kamini; Gupta, Vivek K.; Kant, Rajni

2012-01-01

In the title compound, C23H25BrN4O3S2, the benzene rings bridged by the sulfonamide group are tilted relative to each other by 69.7 (1)° and the dihedral angle between the sulfur-bridged pyrimidine and benzene rings is 70.4 (1)°. The mol­ecular conformation is stabilized by a weak intra­molecular π–π stacking inter­action between the pyrimidine and the 4-methyl benzene rings [centroid–centroid distance = 3.633 (2) Å]. The piperidine ring adopts a chair conformation. In the crystal, mol­ecules are linked into inversion dimers by pairs of N—H⋯O hydrogen bonds. PMID:23125637

N-(3-Chloro-4-eth­oxy-1-methyl-1H-indazol-5-yl)-4-meth­oxy­benzene­sulfonamide

PubMed Central

Chicha, Hakima; Rakib, El Mostapha; Hannioui, Abdellah; Saadi, Mohamed; El Ammari, Lahcen

2014-01-01

The indazole ring system of the title compound, C17H18ClN3O4S, is almost planar (r.m.s. deviation = 0.0113 Å) and forms dihedral angles of 32.22 (8) and 57.5 (3)° with the benzene ring and the mean plane through the 4-eth­oxy group, respectively. In the crystal, mol­ecules are connected by pairs of N—H⋯O hydrogen bonds into inversion dimers, which are further linked by π–π inter­actions between the diazole rings [inter­centroid distance = 3.4946 (11) Å], forming chains parallel to [101]. PMID:24940259

Dibenzo-18-crown-6–picric acid–water (1/2/3)

PubMed Central

Saleh, Muhammad Idiris; Kusrini, Eny; Rosli, Mohd Mustaqim; Fun, Hoong-Kun

2008-01-01

In the crown ether ring of the title compound, C20H24O6·2C6H3N3O7·3H2O, the O—C(H2)—C(H2)—O torsion angles indicate a gauche conformation of the ethyl­eneoxy units, while the C—O—C—C torsion angles indicate planarity of these segments; the dihedral angle between the two benzene rings is 44.53 (13)°. In both picric acid mol­ecules, one of the nitro groups is twisted away from the attached ring. The mol­ecules are linked into chains along the b axis via inter­molecular O—H⋯O hydrogen bonds. In addition, the crystal structure is stabilized by C—H⋯O hydrogen bonds and π–π inter­actions [centroid–centroid distance between benzene rings = 3.5697 (16) Å]. PMID:21202944

Crystal structure of 8-hy­droxy­quinolin­ium 2-carboxy-6-nitro­benzoate mono­hydrate

PubMed Central

Divya Bharathi, M.; Ahila, G.; Mohana, J.; Chakkaravarthi, G.; Anbalagan, G.

2015-01-01

In the title hydrated salt, C9H8NO+·C8H4NO6 −·H2O, the deprotonated carboxyl­ate group is almost normal to its attached benzene ring [dihedral angle = 83.56 (8)°], whereas the protonated carboxyl­ate group is close to parallel [dihedral angle = 24.56 (9)°]. In the crystal, the components are linked by N—H⋯O and O—H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by C—H⋯O and π–π [centroid-to-centroid distances = 3.6408 (9) and 3.6507 (9) Å] inter­actions, which result in a three-dimensional network. PMID:26029446

(E)-4-Meth­oxy-N′-[(6-methyl-4-oxo-4H-chromen-3-yl)methyl­idene]benzo­hydrazide monohydrate

PubMed Central

Ishikawa, Yoshinobu; Watanabe, Kohzoh

2014-01-01

In the title hydrate, C19H16N2O4·H2O, the 4H-chromen-4-one segment is slightly twisted, with a dihedral angle between the two six-membered rings of 3.30 (5)°. The dihedral angles between the plane of the pyran­one ring and the hydrazide plane and between the planes of the pyran­one ring and the benzene ring of the p-meth­oxy­benzene unit are 26.69 (4) and 2.23 (3)°, respectively. The mol­ecule is connected to the solvent water mol­ecule by an N—H⋯O hydrogen bond. In the crystal, there are π–π stacking inter­actions between centrosymmetrically related pyran­one rings [centroid–centroid distance = 3.5394 (9) Å], as well as bridges formed by the water mol­ecules via O—H⋯O hydrogen bonds. PMID:25161570

Benzene-1,4-diol–5-(1H-imidazol-1-yl)pyrimidine (1/1)

PubMed Central

Jiang, Yan-Ke; Hou, Gui-Ge

2011-01-01

The asymmetric unit of title compound, C7H6N4·C6H6O2, contains one 5-(1H-imidazol-1-yl)pyrimidine mol­ecule and two half benzene-1,4-diol mol­ecules; the benzene-1,4-diol mol­ecules are located on individual inversion centers. In the pyrimidine mol­ecule, the imidazole ring is twisted with respect to the pyrimidine ring at a dihedral angle of 25.73 (7)°. In the crystal, O—H⋯N hydrogen bonds link the mol­ecules to form supra­molecular chains. π–π stacking is also observed in the crystal, the centroid–centroid distance between parallel imdazole rings being 3.5543 (16) Å. PMID:22220081

1-(Prop-2-yn-yl)indoline-2,3-dione.

PubMed

Qachchachi, Fatima-Zahrae; Ouazzani Chahdi, Fouad; Misbahi, Houria; Bodensteiner, Michael; El Ammari, Lahcen

2014-03-01

The structure of the title compound, C11H7NO2, is isotypic to that of its homologue, 1-octylindoline-2,3-dione [Qachchachi et al. (2013 ▶). Acta Cryst. E69, o1801]. The indoline ring and the two carbonyl O atoms are approximately coplanar, the largest deviation from the mean plane being 0.021 (1) Å for one of the O atoms. The mean plane through the fused ring system is nearly perpendicular to the propynyl group, as indicated by the N-C-C-C torsion angle of 77.9 (1)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds and π-π inter-actions between benzene rings [inter-centroid distance = 3.5630 (10) Å], forming a three-dimensional structure.

3,4-Dimethyl-1-phenyl­pyrano[2,3-c]pyrazol-6(1H)-one

PubMed Central

Ahmad, Neman; Tahir, M. Nawaz; Khan, Misbahul Ain; Ather, Abdul Qayyum; Khan, Muhammad Naeem

2011-01-01

In the title compound, C14H12N2O2, the dihedral angle between the phenyl ring and the 3,4-dimethyl­pyrano[2,3-c]pyrazol-6(1H)-one system is 7.28 (6)°. An intra­molecular C—H⋯O inter­action generates an S(6) ring. In the crystal, the mol­ecules are linked by C—H⋯O hydrogen bonds, forming C(8) chains. C–H⋯π and π–π inter­actions [centroid–centroid separation = 3.6374 (12) Å] further consolidate the packing. PMID:21754037

3-(4-Hy­droxy­phen­yl)-7-meth­oxy­chroman-4-one monohydrate

PubMed Central

Xiao, Zhu-Ping; Peng, Zhu-Yun; Luo, Qun; Wu, Ying; Yang, Ye-Ling

2011-01-01

In the title compound, C16H14O4·H2O, the dihedral angle betwen the benzene rings is 71.4 (6)°. The pyran ring is in a sofa conformation. In the crystal, O—H⋯O hydrogen bonds connect the components into a two-dimensional network parallel to (010), incorporating C 2 2(4) and C 2 2(11) chains. In addition, weak C—H⋯O, C—H⋯π and π–π stacking inter­actions [centroid–centroid distance = 3.768 (2) Å] are present. PMID:22199730

Crystal structure of quinolinium 2-carboxy-6-nitro-benzoate monohydrate.

PubMed

Mohana, J; Divya Bharathi, M; Ahila, G; Chakkaravarthi, G; Anbalagan, G

2015-05-01

In the anion of the title hydrated mol-ecular salt, C9H8N(+)·C8H4NO6 (-)·H2O, the protonated carboxyl and nitro groups makes dihedral angles of 27.56 (5) and 6.86 (8)°, respectively, with the attached benzene ring, whereas the deprotonated carb-oxy group is almost orthogonal to it with a dihedral angle of 80.21 (1)°. In the crystal, the components are linked by O-H⋯O and N-H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by weak C-H⋯N and C-H⋯O inter-actions as well as aromatic π-π stacking [centroid-to-centroid distances: 3.7023 (8) & 3.6590 (9)Å] inter-actions, resulting in a three-dimensional network.

Aqua-(3-fluoro-benzoato-κO)(3-fluoro-benzoato-κO,O')(1,10-phenanthroline-κN,N')cobalt(II).

PubMed

Wang, Xiao-Hui; Sun, Li-Mei

2012-01-01

In the title compound, [Co(C(7)H(4)FO(2))(2)(C(12)H(8)N(2))(H(2)O)], the Co(II) ion is coordinated by two O atoms from one 3-fluoro-benzoate (fb) ligand and one O atom from another fb ligand, two N atoms from the 1,10-phenanthroline ligand and a water mol-ecule in a distorted octa-hedral geometry. An intra-molecular O-H⋯O hydrogen bond occurs. Inter-molecular O-H⋯O hydrogen bonds link pairs of mol-ecules into centrosymmetric dimers. Weak inter-molecular C-H⋯O and C-H⋯F hydrogen bonds and π-π inter-actions between the aromatic rings [shortest centroid-centroid distance = 3.4962 (2) Å] further stabilize the crystal packing.

A Comparison of Heuristic Procedures for Minimum within-Cluster Sums of Squares Partitioning

ERIC Educational Resources Information Center

Brusco, Michael J.; Steinley, Douglas

2007-01-01

Perhaps the most common criterion for partitioning a data set is the minimization of the within-cluster sums of squared deviation from cluster centroids. Although optimal solution procedures for within-cluster sums of squares (WCSS) partitioning are computationally feasible for small data sets, heuristic procedures are required for most practical…

Molecular-Scale Description of SPAN80 Desorption from a Squalane-Water Interface.

PubMed

Tan, L; Pratt, L R; Chaudhari, M I

2018-04-05

Extensive all-atom molecular dynamics calculations on the water-squalane interface for nine different loadings with sorbitan monooleate (SPAN80), at T = 300 K, are analyzed for the surface tension equation of state, desorption free-energy profiles as they depend on loading, and to evaluate escape times for adsorbed SPAN80 into the bulk phases. These results suggest that loading only weakly affects accommodation of a SPAN80 molecule by this squalane-water interface. Specifically, the surface tension equation of state is simple through the range of high tension to high loading studied, and the desorption free-energy profiles are weakly dependent on loading here. The perpendicular motion of the centroid of the SPAN80 headgroup ring is well-described by a diffusional model near the minimum of the desorption free-energy profile. Lateral diffusional motion is weakly dependent on loading. Escape times evaluated on the basis of a diffusional model and the desorption free energies are 7 × 10 -2 s (into the squalane) and 3 × 10 2 h (into the water). The latter value is consistent with desorption times of related lab-scale experimental work.

Exciplex and excimer molecular probes: detection of conformational flip in a myo-inositol chair.

PubMed

Kadirvel, Manikandan; Arsic, Biljana; Freeman, Sally; Bichenkova, Elena V

2008-06-07

2-O-tert-Butyldimethylsilyl-4,6-bis-O-pyrenoyl-myo-inositol-1,3,5-orthoformate (6) and 2-O-tert-butyldimethylsilyl-4-O-[4-(dimethylamino)benzoyl]-6-O-pyrenoyl-myo-inositol-1,3,5-orthoacetate (10) adopt conformationally restricted unstable chairs with five axial substituents. In the symmetrical diester 6, the two pi-stacked pyrenoyl groups are electron acceptor-donor partners, giving a strong intramolecular excimer emission. In the mixed ester 10, the pyrenoyl group is the electron acceptor and the 4-(dimethylamino)benzoyl ester is the electron donor, giving a strong intramolecular exciplex emission. The conformation of the mixed ester 10 was assessed using 1H NMR spectroscopy (1H-NOESY) and computational studies. which showed the minimum inter-centroid distance between the two aromatic systems to be approximately 3.9 A. Upon addition of acid, the orthoformate/orthoacetate trigger in 6 and 10 was cleaved, which caused a switch of the conformation of the myo-inositol ring to the more stable penta-equatorial chair, leading to separation of the aromatic ester groups and loss of excimer and exciplex fluorescence, respectively. This study provides proof of principle for the development of novel fluorescent molecular probes.

1-(Prop-2-yn­yl)indoline-2,3-dione

PubMed Central

Qachchachi, Fatima-Zahrae; Ouazzani Chahdi, Fouad; Misbahi, Houria; Bodensteiner, Michael; El Ammari, Lahcen

2014-01-01

The structure of the title compound, C11H7NO2, is isotypic to that of its homologue, 1-octylindoline-2,3-dione [Qachchachi et al. (2013 ▶). Acta Cryst. E69, o1801]. The indoline ring and the two carbonyl O atoms are approximately coplanar, the largest deviation from the mean plane being 0.021 (1) Å for one of the O atoms. The mean plane through the fused ring system is nearly perpendicular to the propynyl group, as indicated by the N—C—C—C torsion angle of 77.9 (1)°. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds and π–π inter­actions between benzene rings [inter­centroid distance = 3.5630 (10) Å], forming a three-dimensional structure. PMID:24765046

3-Chloro-4-methyl­quinolin-2(1H)-one

PubMed Central

Kassem, Mohamed G.; Ghabbour, Hazem A.; Abdel-Aziz, Hatem A.; Fun, Hoong-Kun; Ooi, Chin Wei

2012-01-01

The title compound, C10H8ClNO, is almost planar (r.m.s. deviation for the 13 non-H atoms = 0.023 Å). In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) rings. Weak aromatic π–π stacking inter­actions [centroid–centroid distance = 3.7622 (12) Å] also occur. PMID:22589913

Design and fabrication of a boron reinforced intertank skirt

NASA Technical Reports Server (NTRS)

Henshaw, J.; Roy, P. A.; Pylypetz, P.

1974-01-01

Analytical and experimental studies were performed to evaluate the structural efficiency of a boron reinforced shell, where the medium of reinforcement consists of hollow aluminum extrusions infiltrated with boron epoxy. Studies were completed for the design of a one-half scale minimum weight shell using boron reinforced stringers and boron reinforced rings. Parametric and iterative studies were completed for the design of minimum weight stringers, rings, shells without rings and shells with rings. Computer studies were completed for the final evaluation of a minimum weight shell using highly buckled minimum gage skin. The detail design is described of a practical minimum weight test shell which demonstrates a weight savings of 30% as compared to an all aluminum longitudinal stiffened shell. Sub-element tests were conducted on representative segments of the compression surface at maximum stress and also on segments of the load transfer joint. A 10 foot long, 77 inch diameter shell was fabricated from the design and delivered for further testing.

3-(4-Hy­droxy­phen­yl)-1,5-bis­(pyridin-2-yl)pentane-1,5-dione

PubMed Central

Pan, Lixia; Shi, Huaduan; Ma, Zhen

2013-01-01

In the title mol­ecule, C21H18N2O3, the pyridine rings make a dihedral angle of 13.1 (1)°. The phenyl ring is approximately perpendicular to both of them, forming dihedral angles of 87.4 (1)and 81.9 (1)°. In the crystal, pairs of O—H⋯N hydrogen bonds link the mol­ecules into centrosymmetric dimers. Additional C—H⋯O, π–π [centroid–centroid distance = 3.971 (2) Å] and C—H⋯π inter­actions consolidate the dimers into a three-dimensional network. PMID:24098256

2-[4-(4,5-Dihydro-1H-pyrrol-2-yl)phen­yl]-4,5-dihydro-1H-imidazole

PubMed Central

Kia, Reza; Fun, Hoong-Kun; Kargar, Hadi

2008-01-01

The mol­ecule of the title compound, C12H14N4, lies about a crystallographic inversion centre. The five- and six-membered rings are twisted from each other, forming a dihedral angle of 18.06 (7)°. In the crystal structure, neighbouring mol­ecules are linked by inter­molecular N—H⋯N hydrogen bonds into one-dimensional infinite chains forming 18-membered rings with R 2 2(18) motifs. The crystal structure is further stabilized by weak inter­molecular π–π stacking [centroid–centroid distance = 3.8254 (6) Å] and C—H⋯π inter­actions. PMID:21581375

N-(2-{[5-Bromo-2-(morpholin-4-yl)pyrimidin-4-yl]sulfan­yl}-4-meth­oxy­phen­yl)-4-chloro­benzene­sulfonamide

PubMed Central

Kumar, Mohan; Mallesha, L.; Sridhar, M. A.; Kapoor, Kamini; Gupta, Vivek K.; Kant, Rajni

2012-01-01

In the title compound, C21H20BrClN4O4S2, the benzene rings bridged by the sulfonamide group are tilted relative to each other by a dihedral angle of 70.2 (1)° and the dihedral angle between the sulfur-bridged pyrimidine and benzene rings is 69.5 (1)°. The mol­ecular conformation is stabilized by a weak intra­molecular π–π stacking inter­action between the pyrimidine and the 4-chloro­benzene rings [centroid–centroid distance = 3.978 (2) Å]. The morpholine ring adopts a chair conformation. In the crystal, mol­ecules are linked into inversion dimers by pairs of C—H⋯N hydrogen bonds and these dimers are further connected by N—H⋯O hydrogen bonds, forming a tape along the a axis. PMID:22969673

N-(2-{[5-Bromo-2-(piperidin-1-yl)pyrimidin-4-yl]sulfan­yl}-4-meth­oxy­phen­yl)-2,4,6-trimethyl­benzene­sulfonamide

PubMed Central

Kumar, Mohan; Mallesha, L.; Sridhar, M. A.; Kapoor, Kamini; Gupta, Vivek K.; Kant, Rajni

2012-01-01

In the title compound, C25H29BrN4O3S2, the benzene rings bridged by the sulfonamide group are tilted relative to each other by 63.9 (1)° and the dihedral angle between the sulfur-bridged pyrimidine and benzene rings is 64.9 (1)°. The mol­ecular conformation is stabilized by a weak intra­molecular π–π stacking inter­action between the pyrimidine and the 2,4,6-trimethyl­benzene rings [centroid–centroid distance = 3.766 (2) Å]. The piperidine ring adopts a chair conformation. In the crystal, mol­ecules are linked into inversion dimers by pairs of N—H⋯O hydrogen bonds and these dimers are further linked by C—H⋯O hydrogen bonds into chains propagating along [010]. PMID:22969648

(7-Chloro-2-oxo-2H-chromen-4-yl)methyl pyrrolidine-1-carbodi­thio­ate

PubMed Central

Kotresh, O.; Devarajegowda, H. C.; Shirahatti, Arunkumar; Kumar, K. Mahesh; Mahabhaleshwaraiah, N. M.

2013-01-01

In the title compound, C15H14ClNO2S2, the 2H-chromene ring system is essentially planar, with a maximum deviation of 0.0133 (10) Å. Three C atoms and their attached H atoms of the pyrrolidine ring are disordered [occupany ratio 0.874 (7):0.126 (7)] with both disorder components adopting a twisted conformation. The dihedral angle between the 2H-chromene ring system and the major occupancy component of the pyrrolidine ring is 89.45 (7)°. In the crystal, inversion dimers linked by pairs of C—H⋯S and C—H⋯O inter­actions generate R 2 2(24) and R 2 2(10) loops, respectively. Further C—H⋯O hydrogen bonds link the dimers into [100] chains. C—H⋯π inter­actions also occur and there is very weak π–π stacking [inter­planar spacing = 3.650 (5) Å; centroid–centroid distance = 4.095 (7) Å] between inversion-related chloro­benzene rings. PMID:24454115

Time resolving beam position measurement and analysis of beam unstable movement in PSR

NASA Astrophysics Data System (ADS)

Aleksandrov, A. V.

2000-11-01

Precise measurement of beam centroid movement is very important for understanding the fast transverse instability in the Los Alamos Proton Storage Ring (PSR). Proton bunch in the PSR is long thus different parts of the bunch can have different betatron phase and move differently therefore time resolving position measurement is needed. Wide band strip line BPM can be adequate if proper processing algorithm is used. In this work we present the results of the analysis of unstable transverse beam motion using time resolving processing algorithm. Suggested algorithm allows to calculate transverse position of different parts of the beam on each turn, then beam centroid movement on successive turns can be developed in series of plane travelling waves in the beam frame of reference thus providing important information on instability development. Some general features of fast transverse instability, unknown before, are discovered.

Crystal structure of quinolinium 2-carboxy-6-nitro­benzoate monohydrate

PubMed Central

Mohana, J.; Divya Bharathi, M.; Ahila, G.; Chakkaravarthi, G.; Anbalagan, G.

2015-01-01

In the anion of the title hydrated mol­ecular salt, C9H8N+·C8H4NO6 −·H2O, the protonated carboxyl and nitro groups makes dihedral angles of 27.56 (5) and 6.86 (8)°, respectively, with the attached benzene ring, whereas the deprotonated carb­oxy group is almost orthogonal to it with a dihedral angle of 80.21 (1)°. In the crystal, the components are linked by O—H⋯O and N—H⋯O hydrogen bonds, generating [001] chains. The packing is consolidated by weak C—H⋯N and C—H⋯O inter­actions as well as aromatic π–π stacking [centroid-to-centroid distances: 3.7023 (8) & 3.6590 (9)Å] inter­actions, resulting in a three-dimensional network. PMID:25995899

1-(Hydroxy­meth­yl)pyrene

PubMed Central

Gruber, Tobias; Seichter, Wilhelm; Weber, Edwin

2010-01-01

The asymmetric unit of the title compound, C17H12O, contains two molecules, in which the fused aromatic ring systems are almost planar [maximum deviations = 0.0529 (9) and 0.0256 (9) Å]. In the crystal, aromatic π–π stacking inter­actions (perpendicular distance of centroids of about 3.4 Å) and strong O—H⋯O hydrogen bonds result in a helical arrangement of pyrenyl dimers. PMID:21579858

1-Bromo-1′-(diphenyl­thio­phosphor­yl)­ferrocene

PubMed Central

Štěpnička, Petr; Schulz, Jiří; Císařová, Ivana

2009-01-01

The title compound, [Fe(C5H4Br)(C17H14PS)], crystallizes with two practically undistiguishable mol­ecules in the asymmetric unit, which are related by a non-space-group inversion. The ferrocene-1,1′-diyl units exhibit a regular geometry with negligible tilting and balanced Fe–ring centroid distances, and with the attached substituents assuming conformations close to ideal synclinal eclipsed. PMID:21577736

(E)-1-(2,4-Di­nitro­phen­yl)-2-(3-eth­oxy-4-hy­droxy­benzyl­idene)hydrazine

PubMed Central

Fun, Hoong-Kun; Chantrapromma, Suchada; Ruanwas, Pumsak; Kobkeatthawin, Thawanrat; Chidan Kumar, C. S.

2014-01-01

The mol­ecule of the title hydrazine derivative, C15H14N4O6, is essentially planar, the dihedral angle between the substituted benzene rings being 2.25 (9)°. The eth­oxy and hy­droxy groups are almost coplanar with their bound benzene ring [r.m.s. deviation = 0.0153 (2) Å for the ten non-H atoms]. Intra­molecular N—H⋯O and O—H⋯Oeth­oxy hydrogen bonds generate S(6) and S(5) ring motifs, respectively. In the crystal, mol­ecules are linked by O—H⋯Onitro hydrogen bonds into chains propagating in [010]. Weak aromatic π–π inter­actions, with centroid–centroid distances of 3.8192 (19) and 4.0491 (19) Å, are also observed. PMID:24527018

(2-{[2-(1H-Benzimidazol-2-yl-κN 3)phen­yl]imino­methyl-κN}-5-methyl­phenolato-κO)chloridozinc(II)

PubMed Central

Eltayeb, Naser Eltaher; Teoh, Siang Guan; Chantrapromma, Suchada; Fun, Hoong-Kun

2011-01-01

In the title mononuclear complex, [Zn(C21H16N3O)Cl], the ZnII ion is coordinated in a distorted tetra­hedral geometry by two benzimidazole N atoms and one phenolate O atom from the tridentate Schiff base ligand and a chloride ligand. The benzimidazole ring system forms dihedral angles of 26.68 (9) and 56.16 (9)° with the adjacent benzene ring and the methyl­phenolate group benzene ring, respectively. In the crystal, mol­ecules are linked by N—H⋯Cl hydrogen bonds into chains along [100]. Furthermore, weak C—H⋯O and C—H⋯π inter­actions, in addition to π–π inter­actions with centroid–centroid distances in the range 3.5826 (13)–3.9681 (13) Å, are also observed. PMID:22065469

Dichloridobis(phenanthridine-κN)zinc(II)

PubMed Central

Khoshtarkib, Zeinab; Ebadi, Amin; Alizadeh, Robabeh; Ahmadi, Roya; Amani, Vahid

2009-01-01

In the mol­ecule of the title compound, [ZnCl2(C13H9N)2], the ZnII atom is four-coordinated in a distorted tetra­hedral 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 intra­molecular C—H⋯Cl inter­action 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 inter­actions are also found. PMID:21582680

8-Chloro-6-iodo-2-phenyl­chromeno[4,3-c]pyrazol-4(2H)-one N,N-dimethyl­formamide monosolvate

PubMed Central

Lokhande, Pradeep; Hasanzadeh, Kamal; Khaledi, Hamid; Mohd Ali, Hapipah

2011-01-01

In the title compound, C16H8ClIN2O2·C3H7NO, the fused tricyclic pyrazolo­coumarin ring and the N-phenyl ring are almost coplanar, the dihedral angle between them being 1.86 (9)°. In the crystal, these rings stack on top of each other via π–π inter­actions [centroid–centroid distances = 3.489 (2), 3.637 (2), 3.505 (2) and 3.662 (2) Å], forming infinite chains along the a axis. The chains are connected into layers parallel to ac plane through I⋯O inter­actions [3.0011 (18) Å] between pairs of symmetry-related mol­ecules. The DMF solvent mol­ecules are C—H⋯O bonded to this network. PMID:21837089

1,1′:4′,1′′-Terphenyl-2′,5′-dicarb­oxy­lic acid dimethyl sulfoxide-d 6 disolvate

PubMed Central

Pop, Lucian C.; Preite, Marcelo; Manriquez, Juan Manuel; Vega, Andrés; Chavez, Ivonne

2012-01-01

The asymmetric unit of the title solvate, C20H14O4·2C2D6OS, contains half of the substituted terephthalic acid mol­ecule and one solvent mol­ecule. The centroid of the central benzene ring in the acid mol­ecule is coincident with a crystallographic inversion center. Neither the carboxyl nor the phenyl substituents are coplanar with the central aromatic ring, showing dihedral angles of 53.18 (11) and 47.83 (11)°, respectively. The dimethyl sulfoxide solvent mol­ecules are hydrogen bonded to the carb­oxy­lic acid groups. PMID:22606132

3-Fluoro­salicylaldoxime at 6.5 GPa

PubMed Central

Wood, Peter A.; Forgan, Ross S.; Parsons, Simon; Pidcock, Elna; Tasker, Peter A.

2009-01-01

3-Fluoro­salicylaldoxime, C7H6FNO2, unlike many salicylaldoxime derivatives, forms a crystal structure containing hydrogen-bonded chains rather than centrosymmetric hydrogen-bonded ring motifs. Each chain inter­acts with two chains above and two chains below via π–π stacking contacts [shortest centroid–centroid distance = 3.295 (1) Å]. This structure at 6.5 GPa represents the final point in a single-crystal compression study. PMID:21583672

Crystal structure of 1-iodo-3-{[4-(tert-butyl­sulfan­yl)phen­yl]ethyn­yl}azulene

PubMed Central

Förster, Sebastian; Seichter, Wilhelm; Weber, Edwin

2015-01-01

The title compound, C20H19IS, features a 1,3-disubstituted azulene involving an ethynylene elongated 4-(tert-butyl­sulfanyl)­phenyl sidearm and an iodine atom as the substituents. The azulene ring system is almost planar (r.m.s. deviation = 0.012 Å) and subtends a dihedral angle of 35.7 (1)° with the benzene ring. As a result of the inherent dipole character of the azulene core, a supra­molecular π–π dimer [separation between the centroids of the five- and seven-membered rings = 3.7632 (10) Å] with anti­parallel orientated mol­ecules can be observed in the crystal. The packing is consolidated by an unusual I⋯π(acetyl­ene) contact [I⋯Cg = 3.34 Å, C—I⋯Cg = 173.3°], and a very weak C—H⋯π inter­action is also found in the structure, with the azulene five-membered ring as the acceptor. PMID:26396788

N-[2-(5-Bromo-2-morpholin-4-ylpyrim­idin-4-ylsulfan­yl)-4-meth­oxy­phen­yl]-2,4,6-trimethyl­benzene­sulfonamide

PubMed Central

Kumar, Mohan; Mallesha, L.; Sridhar, M. A.; Kapoor, Kamini; Gupta, Vivek K.; Kant, Rajni

2012-01-01

In the title compound, C24H27BrN4O4S2, the mol­ecule is twisted at the sulfonyl S atom with a C—S(O2)—N(H)—C torsion angle of 62.6 (3)°. The benzene rings bridged by the sulfonamide group are tilted to each other by a dihedral angle of 60.6 (1)°. The dihedral angle between the sulfur-bridged pyrimidine and benzene rings is 62.7 (1)°. The morpholine ring adopts a chair conformation. The mol­ecular conformation is stabilized by a weak intra­molecular π–π stacking inter­action between the pyrimidine and the 2,4,6-trimethyl­benzene rings [centroid–centroid distance = 3.793 (2) Å]. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds into a chain along the b axis. PMID:23284396

N-(2-{[5-Bromo-2-(morpholin-4-yl)pyrimidin-4-yl]sulfan­yl}-4-meth­oxy­phen­yl)-4-methyl­benzene­sulfonamide

PubMed Central

Kant, Rajni; Gupta, Vivek K.; Kapoor, Kamini; Kumar, Mohan; Mallesha, L.; Sridhar, M. A.

2012-01-01

In the title compound, C22H23BrN4O4S2, the benzene rings bridged by the sulfonamide group are tilted relative to each other by 68.9 (1)° and the dihedral angle between the sulfur-bridged pyrimidine and benzene rings is 69.7 (1)°. The mol­ecular conformation is stabilized by a weak intra­molecular π–π stacking inter­action between the pyrimidine and the 4-methylbenzene rings [centroid–centroid distance = 3.934 (2) Å]. The morpholine ring adopts a chair conformation and is disordered over two positions with an occupancy ratio of 0.853 (6):0.147 (6). In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds into chains extending along the a axis and further, through C—H⋯N and C—H⋯O inter­actions, into a three-dimensional supramolecular structure. PMID:22905015

4-{2-[2-(4-Chloro­benzyl­idene)hydrazinyl­idene]-3,6-dihydro-2H-1,3,4-thia­diazin-5-yl}-3-phenyl­sydnone

PubMed Central

Fun, Hoong-Kun; Loh, Wan-Sin; Nithinchandra; Kalluraya, Balakrishna

2011-01-01

The title compound, C18H13ClN6O2S, exists in trans and cis configurations with respect to the acyclic C=N bonds [C=N = 1.2837 (15) and 1.3000 (14) Å, respectively]. The 3,6-dihydro-2H-1,3,4-thia­diazine ring adopts a half-boat conformation. The sydnone ring is approximately planar [maximum deviation = 0.002 (1) Å] and forms dihedral angles of 50.45 (7) and 61.21 (6)° with the aromatic rings. In the crystal, inter­molecular N—H⋯N, C—H⋯Cl and C—H⋯S hydrogen bonds link the mol­ecules into layers parallel to ab plane. The crystal packing is stabilized by C—H⋯π inter­actions and further consolidated by π–π inter­actions involving the phenyl rings [centroid–centroid distance = 3.6306 (7) Å]. PMID:21754481

Crystal structure of 3-{[4-(2-meth-oxy-phen-yl)piperazin-1-yl]meth-yl}-5-(thio-phen-2-yl)-1,3,4-oxa-diazole-2(3H)-thione.

PubMed

Al-Alshaikh, Monirah A; Abuelizz, Hatem A; El-Emam, Ali A; Abdelbaky, Mohammed S M; Garcia-Granda, Santiago

2016-02-01

The title compound, C18H20N4O2S2, is a new 1,3,4-oxa-diazole and a key pharmacophore of several biologically active agents. It is composed of a meth-yl(thio-phen-2-yl)-1,3,4-oxa-diazole-2(3H)-thione moiety linked to a 2-meth-oxy-phenyl unit via a piperazine ring that has a chair conformation. The thio-phene ring mean plane lies almost in the plane of the oxa-diazole ring, with a dihedral angle of 4.35 (9)°. The 2-meth-oxy-phenyl ring is almost normal to the oxa-diazole ring, with a dihedral angle of 84.17 (10)°. In the crystal, mol-ecules are linked by weak C-H⋯S hydrogen bonds and C-H⋯π inter-actions, forming layers parallel to the bc plane. The layers are linked via weak C-H⋯O hydrogen bonds and slipped parallel π-π inter-actions [inter-centroid distance = 3.6729 (10) Å], forming a three-dimensional structure. The thio-phene ring has an approximate 180° rotational disorder about the bridging C-C bond.

Ellipsoids for anomaly detection in remote sensing imagery

NASA Astrophysics Data System (ADS)

Grosklos, Guenchik; Theiler, James

2015-05-01

For many target and anomaly detection algorithms, a key step is the estimation of a centroid (relatively easy) and a covariance matrix (somewhat harder) that characterize the background clutter. For a background that can be modeled as a multivariate Gaussian, the centroid and covariance lead to an explicit probability density function that can be used in likelihood ratio tests for optimal detection statistics. But ellipsoidal contours can characterize a much larger class of multivariate density function, and the ellipsoids that characterize the outer periphery of the distribution are most appropriate for detection in the low false alarm rate regime. Traditionally the sample mean and sample covariance are used to estimate ellipsoid location and shape, but these quantities are confounded both by large lever-arm outliers and non-Gaussian distributions within the ellipsoid of interest. This paper compares a variety of centroid and covariance estimation schemes with the aim of characterizing the periphery of the background distribution. In particular, we will consider a robust variant of the Khachiyan algorithm for minimum-volume enclosing ellipsoid. The performance of these different approaches is evaluated on multispectral and hyperspectral remote sensing imagery using coverage plots of ellipsoid volume versus false alarm rate.

(2,2′-Biquinoline-κ2 N,N′)dichlorido­iron(II)

PubMed Central

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

2009-01-01

In the title compound, [FeCl2(C18H12N2)], the FeII atom is four-coordinated in a distorted tetra­hedral arrangement by an N,N′-bidentate 2,2′-biquinoline ligand and two chloride ions. In the crystal, there are extensive π–π contacts between the pyridine rings [centroid–centroid distances = 3.7611 (3), 3.7603 (4), 3.5292 (4), 3.5336 (5) and 3.6656 (4) Å]. PMID:21578122

Ethyl 5-amino-1-[(4-methyl­phen­yl)sulfon­yl]-1H-pyrazole-4-carboxyl­ate

PubMed Central

Elgazwy, Abdel-Sattar S. Hamad; Nassar, Ibrahim F.; Jones, Peter G.

2013-01-01

In the title mol­ecule, C13H15N3O4S, the benzene and pyrazole rings are inclined to each other at 77.48 (3)°. Two amino H atoms are involved in bifurcated hydrogen bonds, viz. intra­molecular N—H⋯O and inter­molecular N—H⋯O(N). The inter­molecular hydrogen bonds link the mol­ecules related by translation in [100] into chains. A short distance of 3.680 (3) Å between the centroids of benzene and pyrazole rings from neighbouring mol­ecules shows the presence of π–π inter­actions, which link the hydrogen-bonded chains into layers parallel to the ab plane. PMID:24427020

(Carbonato-κ(2)O,O')bis-(5,5'-dimethyl-2,2'-bipyridyl-κ(2)N,N')cobalt(III) bromide trihydrate.

PubMed

Arun Kumar, Kannan; Meera, Parthsarathi; Amutha Selvi, Madhavan; Dayalan, Arunachalam

2012-04-01

In the title complex, [Co(CO(3))(C(12)H(12)N(2))(2)]Br·3H(2)O, the Co(III) cation has a distorted octa-hedral coordination environment. It is chelated by four N atoms of two different 5,5'-dimethyl-2,2'-bipyridyl (dmbpy) ligands in axial and equatorial positions, and by two O atoms of a carbonate anion completing the equatorial positions. Although the water mol-ecules are disordered and their H atoms were not located, there are typical O⋯O distances between 2.8 and 3.0 Å, indicating O-H⋯O hydrogen bonding. The crystal packing is consolidated by C-H⋯O and C-H⋯Br hydrogen bonds, as well as π-π stacking inter-actions between adjacent pyridine rings of the dmbpy ligands, with centroid-centroid distances of 3.694 (3) and 3.7053 (3) Å.

Crystal structure of 3-{1′-[3,5-bis­(tri­fluoro­meth­yl)phen­yl]ferrocenyl}-4-bromo­thio­phene

PubMed Central

Poppitz, Elisabeth A.; Korb, Marcus; Lang, Heinrich

2014-01-01

The mol­ecular structure of the title compound, [Fe(C9H6BrS)(C13H7F6)], consists of a ferrocene backbone with a bis­(tri­fluoro­meth­yl)phenyl group at one cyclo­penta­dienyl ring and a thio­phene heterocycle at the other cyclo­penta­dienyl ring. The latter is disordered over two sets of sites in a 0.6:0.4 ratio. In the crystal structure, intra­molecular π–π inter­actions between the thienyl and the phenyl substituent [centroid–centroid distance 3.695 (4) Å] and additional weak T-shaped π–π inter­actions between the thienyl and the phenyl-substituted cyclo­penta­dienyl ring [4.688 (6) Å] consolidate the crystal packing. PMID:25484662

N-[4-(9-Chloro­quino[3,2-b]benzo[1,4]thia­zin-6-yl)but­yl]acetamide1

PubMed Central

Jeleń, Małgorzata; Suwińska, Kinga; Pluta, Krystian; Morak-Młodawska, Beata

2012-01-01

In the title mol­ecule, C21H20ClN3OS, the tetra­cyclic system is close to planar [r.m.s. deviation = 0.110 (4) Å]. The dihedral angle between the quinoline ring system and the benzene ring is 178.3 (1)° and the angle between two (S—C=C—N) halves of the thia­zine ring is 173.4 (1)°. In the crystal, mol­ecules are arranged via π–π inter­actions [centroid–centroid distances = 3.603 (2)–3.739 (2) Å] into slipped stacks extending along [010]. Inter­molecular N—H⋯O hydrogen bonds link the amide groups of neighbouring mol­ecules along the stack, generating a C(4) motif. The title compound shows promising anti­proliferative and anti­cancer activity. PMID:23476166

Orphenadrinium picrate picric acid

PubMed Central

Fun, Hoong-Kun; Hemamalini, Madhukar; Siddaraju, B. P.; Yathirajan, H. S.; Narayana, B.

2010-01-01

The asymmetric unit of the title compound N,N-dimethyl-2-[(2-methyl­phen­yl)phenyl­meth­oxy]ethanaminium picrate picric acid, C18H24NO+·C6H2N3O7 −·C6H3N3O7, contains one orphenadrinium cation, one picrate anion and one picric acid mol­ecule. In the orphenadrine cation, the two aromatic rings form a dihedral angle of 70.30 (7)°. There is an intra­molecular O—H⋯O hydrogen bond in the picric acid mol­ecule, which generates an S(6) ring motif. In the crystal structure, the orphenadrine cations, picrate anions and picric acid mol­ecules are connected by strong inter­molecular N—H⋯O hydrogen bonds, π⋯π inter­actions between the benzene rings of cations and anions [centroid–centroid distance = 3.5603 (9) Å] and weak C—H⋯O hydrogen bonds, forming a three-dimensional network. PMID:21580426

Accuracy of tree diameter estimation from terrestrial laser scanning by circle-fitting methods

NASA Astrophysics Data System (ADS)

Koreň, Milan; Mokroš, Martin; Bucha, Tomáš

2017-12-01

This study compares the accuracies of diameter at breast height (DBH) estimations by three initial (minimum bounding box, centroid, and maximum distance) and two refining (Monte Carlo and optimal circle) circle-fitting methods The circle-fitting algorithms were evaluated in multi-scan mode and a simulated single-scan mode on 157 European beech trees (Fagus sylvatica L.). DBH measured by a calliper was used as reference data. Most of the studied circle-fitting algorithms significantly underestimated the mean DBH in both scanning modes. Only the Monte Carlo method in the single-scan mode significantly overestimated the mean DBH. The centroid method proved to be the least suitable and showed significantly different results from the other circle-fitting methods in both scanning modes. In multi-scan mode, the accuracy of the minimum bounding box method was not significantly different from the accuracies of the refining methods The accuracy of the maximum distance method was significantly different from the accuracies of the refining methods in both scanning modes. The accuracy of the Monte Carlo method was significantly different from the accuracy of the optimal circle method in only single-scan mode. The optimal circle method proved to be the most accurate circle-fitting method for DBH estimation from point clouds in both scanning modes.

46 CFR 169.549 - Ring lifebuoys and water lights.

Code of Federal Regulations, 2014 CFR

2014-10-01

... chapter and be international orange in color. (2) Each water light must be approved under subpart 161.010... 46 Shipping 7 2014-10-01 2014-10-01 false Ring lifebuoys and water lights. 169.549 Section 169.549... lights. (a)(1) The minimum number of life buoys and the minimum number to which water lights must be...

46 CFR 169.549 - Ring lifebuoys and water lights.

Code of Federal Regulations, 2012 CFR

2012-10-01

... chapter and be international orange in color. (2) Each water light must be approved under subpart 161.010... 46 Shipping 7 2012-10-01 2012-10-01 false Ring lifebuoys and water lights. 169.549 Section 169.549... lights. (a)(1) The minimum number of life buoys and the minimum number to which water lights must be...

Mitigation of time-varying distortions in Nyquist-WDM systems using machine learning

NASA Astrophysics Data System (ADS)

Granada Torres, Jhon J.; Varughese, Siddharth; Thomas, Varghese A.; Chiuchiarelli, Andrea; Ralph, Stephen E.; Cárdenas Soto, Ana M.; Guerrero González, Neil

2017-11-01

We propose a machine learning-based nonsymmetrical demodulation technique relying on clustering to mitigate time-varying distortions derived from several impairments such as IQ imbalance, bias drift, phase noise and interchannel interference. Experimental results show that those impairments cause centroid movements in the received constellations seen in time-windows of 10k symbols in controlled scenarios. In our demodulation technique, the k-means algorithm iteratively identifies the cluster centroids in the constellation of the received symbols in short time windows by means of the optimization of decision thresholds for a minimum BER. We experimentally verified the effectiveness of this computationally efficient technique in multicarrier 16QAM Nyquist-WDM systems over 270 km links. Our nonsymmetrical demodulation technique outperforms the conventional QAM demodulation technique, reducing the OSNR requirement up to ∼0.8 dB at a BER of 1 × 10-2 for signals affected by interchannel interference.

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

Avkshtol, V; Tanny, S; Reddy, K

Purpose: Stereotactic radiation therapy (SRT) provides an excellent alternative to embolization and surgical excision for the management of appropriately selected cerebral arteriovenous malformations (AVMs). The currently accepted standard for delineating AVMs is planar digital subtraction angiography (DSA). DSA can be used to acquire a 3D data set that preserves osseous structures (3D-DA) at the time of the angiography for SRT planning. Magnetic resonance imaging (MRI) provides an alternative noninvasive method of visualizing the AVM nidus with comparable spatial resolution. We utilized 3D-DA and T1 post-contrast MRI data to evaluate the differences in SRT target volumes. Methods: Four patients underwent 3D-DAmore » and high-resolution MRI. 3D T1 post-contrast images were obtained in all three reconstruction planes. A planning CT was fused with MRI and 3D-DA data sets. The AVMs were contoured utilizing one of the image sets at a time. Target volume, centroid, and maximum and minimum dimensions were analyzed for each patient. Results: Targets delineated using post-contrast MRI demonstrated a larger mean volume. AVMs >2 cc were found to have a larger difference between MRI and 3D-DA volumes. Larger AVMs also demonstrated a smaller relative uncertainty in contour centroid position (1 mm). AVM targets <2 cc had smaller absolute differences in volume, but larger differences in contour centroid position (2.5 mm). MRI targets demonstrated a more irregular shape compared to 3D-DA targets. Conclusions: Our preliminary data supports the use of MRI alone to delineate AVM targets >2 cc. The greater centroid stability for AVMs >2 cc ensures accurate target localization during image fusion. The larger MRI target volumes did not result in prohibitively greater volumes of normal brain tissue receiving the prescription dose. The larger centroid instability for AVMs <2 cc precludes the use of MRI alone for target delineation. We recommend incorporating a 3D-DA for these patients.« less

Propagation of an Airy beam through the atmosphere.

PubMed

Ji, Xiaoling; Eyyuboğlu, Halil T; Ji, Guangming; Jia, Xinhong

2013-01-28

In this paper, the effect of thermal blooming of an Airy beam propagating through the atmosphere is examined, and the effect of atmospheric turbulence is not considered. The changes of the intensity distribution, the centroid position and the mean-squared beam width of an Airy beam propagating through the atmosphere are studied by using the four-dimensional (4D) computer code of the time-dependent propagation of Airy beams through the atmosphere. It is shown that an Airy beam can't retain its shape and the structure when the Airy beam propagates through the atmosphere due to thermal blooming except for the short propagation distance, or the short time, or the low beam power. The thermal blooming results in a central dip of the center lobe, and causes the center lobe to spread and decrease. In contrast with the center lobe, the side lobes are less affected by thermal blooming, such that the intensity maximum of the side lobe may be larger than that of the center lobe. However, the cross wind can reduce the effect of thermal blooming. When there exists the cross wind velocity vx in x direction, the dependence of centroid position in x direction on vx is not monotonic, and there exists a minimum, but the centroid position in y direction is nearly independent of vx.

A Standard Law for the Equatorward Drift of the Sunspot Zones

NASA Technical Reports Server (NTRS)

Hathaway, David H.

2012-01-01

The latitudinal location of the sunspot zones in each hemisphere is determined by calculating the centroid position of sunspot areas for each solar rotation from May 1874 to June 2012. When these centroid positions are plotted and analyzed as functions of time from each sunspot cycle maximum there appears to be systematic differences in the positions and equatorward drift rates as a function of sunspot cycle amplitude. If, instead, these centroid positions are plotted and analyzed as functions of time from each sunspot cycle minimum then most of the differences in the positions and equatorward drift rates disappear. The differences that remain disappear entirely if curve fitting is used to determine the starting times (which vary by as much as 8 months from the times of minima). The sunspot zone latitudes and equatorward drift measured relative to this starting time follow a standard path for all cycles with no dependence upon cycle strength or hemispheric dominance. Although Cycle 23 was peculiar in its length and the strength of the polar fields it produced, it too shows no significant variation from this standard. This standard law, and the lack of variation with sunspot cycle characteristics, is consistent with Dynamo Wave mechanisms but not consistent with current Flux Transport Dynamo models for the equatorward drift of the sunspot zones.

1-Methyl-4-(4-nitro­benzo­yl)pyridinium perchlorate

PubMed Central

Gruber, Tobias; Eissmann, Frank; Weber, Edwin; Schüürmann, Gerrit

2011-01-01

In the main mol­ecule of the title compound, C13H11N2O3 +·ClO4 −, the two aromatic rings are twisted by 56.19 (3)° relative to each other and the nitro group is not coplanar with the benzene ring [36.43 (4)°]. The crystal packing is dominated by infinite aromatic stacks in the a-axis direction. These are formed by the benzene units of the mol­ecule featuring an alternating arrangement, which explains the two different distances of 3.3860 (4) and 3.4907 (4) Å for the aromatic units (these are the perpendicular distances of the centroid of one aromatic ring on the mean plane of the other other aromatic ring). Adjacent stacks are connected by π–π stacking between two pyridinium units [3.5949 (4) Å] and weak C—H⋯O inter­actions. The perchlorate anions are accomodated in the lattice voids connected to the cation via weak C—H⋯O contacts between the O atoms of the anion and various aromatic as well as methyl H atoms. PMID:22059070

3-(2,3-Dioxoindolin-1-yl)propane­nitrile

PubMed Central

Qachchachi, Fatima-Zahrae; Kandri Rodi, Youssef; Essassi, El Mokhtar; Bodensteiner, Michael; El Ammari, Lahcen

2014-01-01

The asymmetric unit of the title compound, C11H8N2O2, contains two independent mol­ecules (A and B). Each mol­ecule is build up from fused five- and six-membered rings with the former linked to a cyano­ethyl group. The indoline ring and two carbonyl O atoms of each mol­ecule are nearly coplanar, with the largest deviations from the mean planes being 0.0198 (9) (mol­ecule A) and 0.0902 (9) Å (mol­ecule B), each by a carbonyl O atom. The fused ring system is nearly perpendicular to the mean plane passing through the cyano­ethyl chains, as indicated by the dihedral angles between them of 69.72 (9) (mol­ecule A) and 69.15 (9)° (mol­ecule B). In the crystal, mol­ecules are linked by C—H⋯O and π–π [inter­centroid distance between inversion-related indoline (A) rings = 3.6804 (7) Å] inter­actions into a double layer that stacks along the a-axis direction. PMID:24765047

2,2,2-Trifluoro-1-[3-(2,2,2-trifluoro­acet­yl)azulen-1-yl]ethanone

PubMed Central

Förster, Sebastian; Eissmann, Frank; Seichter, Wilhelm; Weber, Edwin

2011-01-01

There are two mol­ecules in the asymmetric unit of the title compound, C14H6F6O2, in which the azulene systems possess an almost planar geometry with maximum deviations of 0.0438 (15) and 0.0396 (14) Å. Besides intra- and inter­molecular C—H⋯O and C—H⋯F inter­actions, the structure displays three F⋯F contacts [2.793 (2), 2.8820 (17) and 2.9181 (16) Å]. Furthermore, a characteristic azulene π-stacking is observed with an alternating sequence of electron-rich five-membered rings and electron-deficient seven-membered rings [centroid–centroid distances = 3.5413 (12), 3.6847 (12), 3.5790 (12) and 3.7718 (12) Å]. PMID:21754800

Crystal structure of 4-meth-oxy-N-(piperidine-1-carbono-thio-yl)benzamide.

PubMed

Suhud, Khairi; Hasbullah, Siti Aishah; Ahmad, Musa; Heng, Lee Yook; Kassim, Mohammad B

2017-10-01

In the title compound, C 14 H 18 N 2 O 2 S, the piperidine ring has a chair conformation. Its mean plane is twisted with respect to the 4-meth-oxy-benzoyl ring, with a dihedral angle of 63.0 (3)°. The central N-C(=S)-N(H)-C(=O) bridge is twisted with an N-C-N-C torsion angle of 74.8 (6)°. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯O hydrogen bonds, forming chains along the c -axis direction. Adjacent chains are linked by C-H⋯π inter-actions, forming layers parallel to the ac plane. The layers are linked by offset π-π inter-actions [inter-centroid distance = 3.927 (3) Å], forming a supra-molecular three-dimensional structure.

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.

Crystal structure of 1-(3-chloro-phen-yl)piperazin-1-ium picrate-picric acid (2/1).

PubMed

Kavitha, Channappa N; Jasinski, Jerry P; Kaur, Manpreet; Anderson, Brian J; Yathirajan, H S

2014-11-01

The title salt {systematic name: bis-[1-(3-chloro-phen-yl)piperazinium 2,4,6-tri-nitro-phenolate]-picric acid (2/1)}, 2C10H14ClN2 (+)·2C6H5N3O7 (-)·C6H6N3O7, crystallized with two independent 1-(3-chloro-phen-yl)piperazinium cations, two picrate anions and a picric acid mol-ecule in the asymmetric unit. The six-membered piperazine ring in each cation adopts a slightly distorted chair conformation and contains a protonated N atom. In the picric acid mol-ecule, the mean planes of the nitro groups in the ortho-, meta-, and para-positions are twisted from the benzene ring by 31.5 (3), 7.7 (1), and 3.8 (2)°, respectively. In the anions, the dihedral angles between the benzene ring and the ortho-, meta-, and para-nitro groups are 36.7 (1), 5.0 (6), 4.8 (2)°, and 34.4 (9), 15.3 (8), 4.5 (1)°, respectively. The nitro group in one anion is disordered and was modeled with two sites for one O atom with an occupancy ratio of 0.627 (7):0.373 (7). In the crystal, the picric acid mol-ecule inter-acts with the picrate anion through a trifurcated O-H⋯O four-centre hydrogen bond involving an intra-molecular O-H⋯O hydrogen bond and a weak C-H⋯O inter-action. Weak inter-molecular C-H⋯O inter-actions are responsible for the formation of cation-anion-cation trimers resulting in a chain along [010]. In addition, weak C-H⋯Cl and weak π-π inter-actions [centroid-centroid distances of 3.532 (3), 3.756 (4) and 3.705 (3) Å] are observed and contribute to the stability of the crystal packing.

Discrimination of different sub-basins on Tajo River based on water influence factor

NASA Astrophysics Data System (ADS)

Bermudez, R.; Gascó, J. M.; Tarquis, A. M.; Saa-Requejo, A.

2009-04-01

Numeric taxonomy has been applied to classify Tajo basin water (Spain) till Portugal border. Several stations, a total of 52, that estimate 15 water variables have been used in this study. The different groups have been obtained applying a Euclidean distance among stations (distance classification) and a Euclidean distance between each station and the centroid estimated among them (centroid classification), varying the number of parameters and with or without variable typification. In order to compare the classification a log-log relation has been established, between number of groups created and distances, to select the best one. It has been observed that centroid classification is more appropriate following in a more logic way the natural constrictions than the minimum distance among stations. Variable typification doesn't improve the classification except when the centroid method is applied. Taking in consideration the ions and the sum of them as variables, the classification improved. Stations are grouped based on electric conductivity (CE), total anions (TA), total cations (TC) and ions ratio (Na/Ca and Mg/Ca). For a given classification and comparing the different groups created a certain variation in ions concentration and ions ratio are observed. However, the variation in each ion among groups is different depending on the case. For the last group, regardless the classification, the increase in all ions is general. Comparing the dendrograms, and groups that originated, Tajo river basin can be sub dived in five sub-basins differentiated by the main influence on water: 1. With a higher ombrogenic influence (rain fed). 2. With ombrogenic and pedogenic influence (rain and groundwater fed). 3. With pedogenic influence. 4. With lithogenic influence (geological bedrock). 5. With a higher ombrogenic and lithogenic influence added.

Self-Alining Quick-Connect Joint

NASA Technical Reports Server (NTRS)

Lucy, M. H.

1983-01-01

Quick connect tapered joint used with minimum manipulation and force. Split ring retainer holds locking ring in place. Minimal force required to position male in female joint, at which time split-ring retainers are triggered to release split locking rings. Originally developed to assemble large space structures, joint is simple, compact, strong, lightweight, self alining, and has no loose parts.

Synthesis, antityrosinase activity of curcumin analogues, and crystal structure of (1 E,4 E)-1,5-bis(4-ethoxyphenyl)penta-1,4-dien-3-one

NASA Astrophysics Data System (ADS)

Chantrapromma, S.; Ruanwas, P.; Boonnak, N.; Chantrapromma, K.; Fun, H.-K.

2016-12-01

Five derivatives of curcumin analogue ( R = OCH2CH3 ( 1), R = N(CH3)2 ( 2), R = 2,4,5-OCH3 ( 3), R = 2,4,6-OCH3 ( 4), and R = 3,4,5-OCH3 ( 5)) were synthesized and characterized by 1H NMR, FT-IR and UV-Vis spectroscopy. The synthesized derivatives were screened for antityrosinase activity, and found that 4 and 5 possess such activity. The crystal structure of 1 was determined by single crystal X-ray diffraction: monoclinic, sp. gr. P21/ c, a = 17.5728(15) Å, b = 5.9121(5) Å, c = 19.8269(13) Å, β = 121.155(5)°, Z = 4. The molecule 1 is twisted with the dihedral angle between two phenyl rings being 15.68(10)°. In the crystal packing, the molecules 1 are linked into chains by C-H···π interactions and further stacked by π···π interactions with the centroid-centroid distance of 3.9311(13) Å.

Experimental Test of Data Analysis Methods from Staggered Pair X-ray Beam Position Monitors at Bending Magnet Beamlines

NASA Astrophysics Data System (ADS)

Buth, G.; Huttel, E.; Mangold, S.; Steininger, R.; Batchelor, D.; Doyle, S.; Simon, R.

2013-03-01

Different methods have been proposed to calculate the vertical position of the photon beam centroid from the four blade currents of staggered pair X-ray beam position monitors (XBPMs) at bending magnet beamlines since they emerged about 15 years ago. The original difference-over-sum method introduced by Peatman and Holldack is still widely used, even though it has been proven to be rather inaccurate at large beam displacements. By systematically generating bumps in the electron orbit of the ANKA storage ring and comparing synchronized data from electron BPMs and XBPM blade currents, we have been able to show that the log-ratio method by S. F. Lin, B.G. Sun et al. is superior (meaning the characteristic being closer to linear) to the ratio method, which in turn is superior to the difference over sum method. These findings are supported by simulations of the XBPM response to changes of the beam centroid. The heuristic basis for each of the methods is investigated. The implications on using XBPM readings for orbit correction are discussed

Crystal structure of bis-(3-bromo-pyridine-κN)bis-(O-ethyl di-thio-carbonato-κ(2) S,S')nickel(II).

PubMed

Kant, Rajni; Kour, Gurvinder; Anthal, Sumati; Neerupama; Sachar, Renu

2015-01-01

In the title mol-ecular complex, [Ni(C3H5OS2)2(C5H4BrN)2], the Ni(2+) cation is located on a centre of inversion and has a distorted octa-hedral N2S4 environment defined by two chelating xanthate ligands and two monodentate pyridine ligands. The C-S bond lengths of the thio-carboxyl-ate group are indicative of a delocalized bond and the O-Csp (2) bond is considerably shorter than the O-Csp (3) bond, consistent with a significant contribution of one resonance form of the xanthate anion that features a formal C=O+ unit and a negative charge on each of the S atoms. The packing of the mol-ecules is stabilized by C-H⋯S and C-H⋯π inter-actions. In addition, π-π inter-actions between the pyridine rings [centroid-to-centroid distance = 3.797 (3) Å] are also present. In the crystal structure, mol-ecules are arranged in rows along [100], forming layers parallel to (010) and (001).

2-(4-Hy­droxy­phen­yl)-1H-benzimidazol-3-ium chloride monohydrate

PubMed Central

González-Padilla, Jazmin E.; Rosales-Hernández, Martha Cecila; Padilla-Martínez, Itzia I.; García-Báez, Efren V.; Rojas-Lima, Susana

2013-01-01

The title mol­ecular salt, C13H11N2O+·Cl−·H2O, crystallizes as a monohydrate. In the cation, the phenol and benzimidazole rings are almost coplanar, making a dihedral angle of 3.18 (4)°. The chloride anion and benzimidazole cation are linked by two N+—H⋯Cl− hydrogen bonds, forming chains propagating along [010]. These chains are linked through O—H⋯Cl hydrogen bonds involving the water mol­ecule and the chloride anion, which form a diamond core, giving rise to the formation of two-dimensional networks lying parallel to (10-2). Two π–π inter­actions involving the imidazolium ring with the benzene and phenol rings [centroid–centroid distances = 3.859 (3) and 3.602 (3) Å, respectively], contribute to this second dimension. A strong O—H⋯O hydrogen bond involving the water mol­ecule and the phenol substituent on the benzimidazole unit links the networks, forming a three-dimensional structure. PMID:24427105

3,3′′-Bis(9-hy­droxy­fluoren-9-yl)-1,1′:3′,1′′-terphen­yl

PubMed Central

Skobridis, Konstantinos; Theodorou, Vassiliki; Paraskevopoulos, Georgios; Seichter, Wilhelm; Weber, Edwin

2013-01-01

The asymmetric unit of the title compound, C44H30O2, contains two independent mol­ecules in which the terminal rings of the terphenyl element are inclined at angles of 36.3 (1) and 22.5 (1)° with respect to the central ring and the dihedral angles between the fluorenyl units are 72.3 (1) and 62.8 (1)°. In the crystal, pairs of O—H⋯O hydrogen bonds link the mol­ecules into inversion dimers. The hy­droxy H atoms not involved in these hydrogen bonds form O—H⋯π inter­actions in which the central terphenyl rings act as acceptors. Weak C—H⋯O contacts and π–π [centroid–centroid distance = 4.088 (2) Å] stacking inter­actions also occur. Taking into account directed non-covalent bonding between the molecules, the crystal is constructed of supramolecular strands extending along the a-axis direction. PMID:24098206

Quantum optimal control of isomerization dynamics of a one-dimensional reaction-path model dominated by a competing dissociation channel

NASA Astrophysics Data System (ADS)

Kurosaki, Yuzuru; Artamonov, Maxim; Ho, Tak-San; Rabitz, Herschel

2009-07-01

Quantum wave packet optimal control simulations with intense laser pulses have been carried out for studying molecular isomerization dynamics of a one-dimensional (1D) reaction-path model involving a dominant competing dissociation channel. The 1D intrinsic reaction coordinate model mimics the ozone open→cyclic ring isomerization along the minimum energy path that successively connects the ozone cyclic ring minimum, the transition state (TS), the open (global) minimum, and the dissociative O2+O asymptote on the O3 ground-state A1' potential energy surface. Energetically, the cyclic ring isomer, the TS barrier, and the O2+O dissociation channel lie at ˜0.05, ˜0.086, and ˜0.037 hartree above the open isomer, respectively. The molecular orientation of the modeled ozone is held constant with respect to the laser-field polarization and several optimal fields are found that all produce nearly perfect isomerization. The optimal control fields are characterized by distinctive high temporal peaks as well as low frequency components, thereby enabling abrupt transfer of the time-dependent wave packet over the TS from the open minimum to the targeted ring minimum. The quick transition of the ozone wave packet avoids detrimental leakage into the competing O2+O channel. It is possible to obtain weaker optimal laser fields, resulting in slower transfer of the wave packets over the TS, when a reduced level of isomerization is satisfactory.

2,2′-[2,4-Bis(naphthalen-1-yl)cyclo­butane-1,3-di­yl]bis­(1-methyl­pyridinium) diiodide: thermal-induced [2 + 2] cyclo­addition reaction of a heterostilbene1

PubMed Central

Chantrapromma, Suchada; Chanawanno, Kullapa; Boonnak, Nawong; Fun, Hoong-Kun

2012-01-01

The asymmetric unit of the title compound, C36H32N2 2+·2I−, consists of one half-mol­ecule of the cation and one I− anion. The cation is located on an inversion centre. The dihedral angle between the pyridinium ring and the naphthalene ring system in the asymmetric unit is 19.01 (14)°. In the crystal, the cations and the anions are linked by C—H⋯I inter­actions into a layer parallel to the bc plane. Intra- and inter­molecular π–π inter­actions with centroid–centroid distances of 3.533 (2)–3.807 (2) Å are also observed. PMID:22259568

8-Fluoro-4-oxo-4H-chromene-3-carbalde­hyde

PubMed Central

Ishikawa, Yoshinobu

2014-01-01

In the title compound, C10H5FO3, the non-H atoms of the 8-fluoro­chromone unit are essentially coplanar (r.m.s. deviation = 0.0259 Å), with a largest deviation from the mean plane of 0.0660 (12) Å for the chromone carbonyl O atom. The formyl group is twisted with respect to the attached ring [C—C—C—O torsion angles = −11.00 (19) and 170.81 (11)°]. In the crystal, mol­ecules are linked via weak C—H⋯O hydrogen bonds along the a axis and [-101], forming corrugated layers parallel to (010). In addition, π–π stacking inter­actions [centroid–centroid distance between the planes of the pyran and benzene rings = 3.519 (2) Å] are observed between these layers. PMID:25161562

Crystal structure of 4-meth­oxy-N-(piperidine-1-carbono­thio­yl)benzamide

PubMed Central

Suhud, Khairi; Hasbullah, Siti Aishah; Ahmad, Musa; Heng, Lee Yook

2017-01-01

In the title compound, C14H18N2O2S, the piperidine ring has a chair conformation. Its mean plane is twisted with respect to the 4-meth­oxy­benzoyl ring, with a dihedral angle of 63.0 (3)°. The central N—C(=S)—N(H)—C(=O) bridge is twisted with an N—C—N—C torsion angle of 74.8 (6)°. In the crystal, mol­ecules are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming chains along the c-axis direction. Adjacent chains are linked by C—H⋯π inter­actions, forming layers parallel to the ac plane. The layers are linked by offset π–π inter­actions [inter­centroid distance = 3.927 (3) Å], forming a supra­molecular three-dimensional structure. PMID:29250374

Implications of Liebig’s law of the minimum for tree-ring reconstructions of climate

NASA Astrophysics Data System (ADS)

Stine, A. R.; Huybers, P.

2017-11-01

A basic principle of ecology, known as Liebig’s Law of the Minimum, is that plant growth reflects the strongest limiting environmental factor. This principle implies that a limiting environmental factor can be inferred from historical growth and, in dendrochronology, such reconstruction is generally achieved by averaging collections of standardized tree-ring records. Averaging is optimal if growth reflects a single limiting factor and noise but not if growth also reflects locally variable stresses that intermittently limit growth. In this study a collection of Arctic tree ring records is shown to follow scaling relationships that are inconsistent with the signal-plus-noise model of tree growth but consistent with Liebig’s Law acting at the local level. Also consistent with law-of-the-minimum behavior is that reconstructions based on the least-stressed trees in a given year better-follow variations in temperature than typical approaches where all tree-ring records are averaged. Improvements in reconstruction skill occur across all frequencies, with the greatest increase at the lowest frequencies. More comprehensive statistical-ecological models of tree growth may offer further improvement in reconstruction skill.

Molecular and electronic structure, magnetotropicity and absorption spectra of benzene-trinuclear copper(I) and silver(I) trihalide columnar binary stacks.

PubMed

Tsipis, A C; Stalikas, A V

2012-02-20

The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 Å at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 Å) and Ag···C (3.44 Å). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems.

Supercontinent Succession and the Calculation of Absolute Paleolongitude

NASA Astrophysics Data System (ADS)

Mitchell, R. N.; Kilian, T.; Evans, D. A.

2010-12-01

Where will the next supercontinent form? Traditional ‘introversion’ and ‘extraversion’ models of supercontinent succession predict that Super Asia will respectively form whence Pangea was or on the opposite side of the world. We develop the ‘orthoversion’ model whereby a succeeding supercontinent forms 90° away: somewhere along the great circle of subduction encircling its relict predecessor—a mantle topology that arises when supercontinents develop return flow beneath their mature centroids. This centroid defines the minimum moment of inertia (I_min) about which rapid and oscillatory true polar wander occurs owing to the prolate shape of nonhydrostatic Earth. Fitting great circles to each supercontinent’s true polar wander legacy, we determine that the distances between successive supercontinent centers (I_min axes) are 88° and 87° for Nuna→Rodinia and Rodinia→Pangea, respectively—both as predicted by the orthoversion model. Not only can supercontinent centers be pinned back into Precambrian time, they provide fixed points for the calculation of absolute paleolongitude.

Trees, History, and Isotopes - the Late Maunder Minimum (1675-1715) in the Pannonian Basin, Hungary

NASA Astrophysics Data System (ADS)

Kazmer, M.; Demeny, A.; Grynaeus, A.; Racz, L.; Varkonyi, A.

2002-05-01

First results of a comprehensive study on climate change in the Pannonian Basin during the Late Maunder Minimum (1675-1715) are presented. The Pannonian Basin has continental climate, distinctly warm and dry in summer, cold in winter, unlike the Atlantic-type climate of Western Europe. Surrounded by the arc of the Carpathians, exposed to Atlantic, Mediterranean, and Siberian influences, the regional climate displays steep gradients. More than one tree-ring chronology for oak is being built, independent of the south German series. Rethly's rich database of historical sources has been assembled, and completed with recently published letters. Ring-width series are measured on oak, and skeleton plots are logged. Study of hydrogen isotope composition of tree rings is in progress. Tree-ring width faithfully reflects historical indices on spring (i.e. earlywood growth season) precipitation. Generally, precipitation - as shown both by indices and tree-ring width - was high and temperature low during the growth season in the first half of the LMM. The second half has seen a retardation in oak growth and an increase in spring temperature. The decades of the Late Maunder Minimum was a politically turbulent era: it saw the decline and fall of the Ottoman domination in Hungary, followed by a rebellion against Austrian rule, associated with disruption of national economy.

5-(4-Chloro­phen­oxy)-1-methyl-3-tri­fluoro­methyl-1H-pyrazole-4-carbaldehyde O-[(2-chloro­pyridin-5-yl)meth­yl]oxime

PubMed Central

Dai, Hong; Zhu, Peng-Fei; Zhu, Yu-Jun; Fang, Jian-Xin; Shi, Yu-Jun

2011-01-01

In the title mol­ecule, C18H13Cl2F3N4O2, the intra­molecular distance between the centroids of the benzene and pyridine rings is 3.953 (3) Å, and the trifluoro­methyl group is rotationally disordered over two orientations in a 0.678 (19):0.322 (19) ratio. The crystal packing exhibits weak inter­molecular C—H⋯F inter­actions. PMID:22199756

Methyl 4-eth-oxy-2-methyl-2H-1,2-benzothia-zine-3-carboxyl-ate 1,1-dioxide.

PubMed

Zia-Ur-Rehman, Muhammad; Choudary, Jamil Anwar; Elsegood, Mark R J; Akbar, Noshin; Latif Siddiqui, Hamid

2008-07-16

In the crystal structure of the title compound, C(13)H(15)NO(5)S, the mol-ecules exhibit weak S=O⋯H-C and C=O⋯H-C inter-molecular inter-actions and arrange themselves into centrosymmetric dimers by means of π-π inter-actions (ring centroids are separated by 3.619 Å, while the closest C⋯C contacts are 3.514 Å). 1,2-Benzothia-zines of this kind have a range of biological activities and are used as medicines in the treatment of inflammation and rheumatoid arthritis.

2-Amino-4,6-dimethyl­pyrimidin-1-ium chloride

PubMed Central

Hu, Hui-Ling; Yeh, Chun-Wei

2012-01-01

In the title compound, C6H10N3 +·Cl−, the cation is essentially planar with an r.m.s. deviations of the fitted atoms of 0.008 Å. In the crystal, adjacent ions are linked by weak N—H⋯Cl hydrogen bonds involving the pyrimidine and amine N atoms, forming a three-dimensional network. C—H⋯π inter­actions between the methyl and pyrimidine groups and π–π stacking [centroid–centroid distance = 3.474 (1) Å] between parallel pyrimidine ring systems are also observed. PMID:23476204

1-(2,4-Di­nitro­phen­yl)-2-[(E)-(3,4,5-tri­meth­oxy­benzyl­idene)]hydrazine

PubMed Central

Chantrapromma, Suchada; Ruanwas, Pumsak; Boonnak, Nawong; Chidan Kumar, C. S.; Fun, Hoong-Kun

2014-01-01

Mol­ecules of the title compound, C16H16N4O7, are not planar with a dihedral angle of 5.50 (11)° between the substituted benzene rings. The two meta-meth­oxy groups of the 3,4,5-tri­meth­oxy­benzene moiety lie in the plane of the attached ring [Cmeth­yl–O–C–C torsion angles −0.1 (4)° and −3.7 (3)°] while the para-meth­oxy substituent lies out of the plane [Cmeth­yl—O—C—C, −86.0 (3)°]. An intra­molecular N—H⋯O hydrogen bond involving the 2-nitro substituent generates an S(6) ring motif. In the crystal structure, mol­ecules are linked by weak C—H⋯O inter­actions into screw chains, that are arranged into a sheet parallel to the bc plane. These sheets are connected by π–π stacking inter­actions between the nitro and meth­oxy substituted aromatic rings with a centroid–centroid separation of 3.9420 (13) Å. C—H⋯π contacts further stabilize the two-dimensional network. PMID:24764900

Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum.

PubMed

Yamaguchi, Yasuhiko T; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi

2010-11-30

The Maunder Minimum (A.D. 1645-1715) is a useful period to investigate possible sun-climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ(18)O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun-climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ(14)C) and climate (δ(18)O) isotope records derived from annual tree rings. The tree-ring δ(18)O record in Japan shows distinct negative δ(18)O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ(18)O record and the GCR flux reconstructed by an ice-core (10)Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum.

Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum

PubMed Central

Yamaguchi, Yasuhiko T.; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi

2010-01-01

The Maunder Minimum (A.D. 1645–1715) is a useful period to investigate possible sun–climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ18O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun–climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ14C) and climate (δ18O) isotope records derived from annual tree rings. The tree-ring δ18O record in Japan shows distinct negative δ18O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ18O record and the GCR flux reconstructed by an ice-core 10Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum. PMID:21076031

46 CFR 169.549 - Ring lifebuoys and water lights.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Ring lifebuoys and water lights. 169.549 Section 169.549 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Lifesaving and Firefighting Equipment Additional Lifesaving Equipment § 169.549 Ring lifebuoys and water lights. (a)(1) The minimum number of...

46 CFR 169.549 - Ring lifebuoys and water lights.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Ring lifebuoys and water lights. 169.549 Section 169.549 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Lifesaving and Firefighting Equipment Additional Lifesaving Equipment § 169.549 Ring lifebuoys and water lights. (a)(1) The minimum number of...

46 CFR 169.549 - Ring lifebuoys and water lights.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Ring lifebuoys and water lights. 169.549 Section 169.549 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Lifesaving and Firefighting Equipment Additional Lifesaving Equipment § 169.549 Ring lifebuoys and water lights. (a)(1) The minimum number of...

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

DOE PAGES

Theis, Daniel; Ivanic, Joseph; Windus, Theresa L.; ...

2016-03-10

The metastable ring structure of the ozone 1 1A 1 ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two 1A 1 states. In the present work, valence correlated energies of the 1 1A 1 state and the 2 1A 1 state were calculated at the 1 1A 1 open minimum, the 1 1A 1 ring minimum, themore » transition state between these two minima, the minimum of the 2 1A 1 state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of CorrelationEnergy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 11A1 state, the present calculations yield the estimates of (ring minimum—open minimum) ~45–50 mh and (transition state—open minimum) ~85–90 mh. For the (2 1A 1– 1A 1) excitation energy, the estimate of ~130–170 mh is found at the open minimum and 270–310 mh at the ring minimum. At the transition state, the difference (2 1A 1– 1A 1) is found to be between 1 and 10 mh. The geometry of the transition state on the 11A1 surface and that of the minimum on the 2 1A 1 surface nearly coincide. More accurate predictions of the energydifferences also require CI expansions to at least sextuple excitations with respect to the valence space. Furthermore, for every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences.« less

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

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

Theis, Daniel; Ivanic, Joseph; Windus, Theresa L.

The metastable ring structure of the ozone 1 1A 1 ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two 1A 1 states. In the present work, valence correlated energies of the 1 1A 1 state and the 2 1A 1 state were calculated at the 1 1A 1 open minimum, the 1 1A 1 ring minimum, themore » transition state between these two minima, the minimum of the 2 1A 1 state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of CorrelationEnergy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 11A1 state, the present calculations yield the estimates of (ring minimum—open minimum) ~45–50 mh and (transition state—open minimum) ~85–90 mh. For the (2 1A 1– 1A 1) excitation energy, the estimate of ~130–170 mh is found at the open minimum and 270–310 mh at the ring minimum. At the transition state, the difference (2 1A 1– 1A 1) is found to be between 1 and 10 mh. The geometry of the transition state on the 11A1 surface and that of the minimum on the 2 1A 1 surface nearly coincide. More accurate predictions of the energydifferences also require CI expansions to at least sextuple excitations with respect to the valence space. Furthermore, for every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences.« less

6-[3-(p-Tolyl­sulfonyl­amino)­prop­yl]diquino­thia­zine1

PubMed Central

Jeleń, Małgorzata; Shkurenko, Aleksander; Suwińska, Kinga; Pluta, Krystian; Morak-Młodawska, Beata

2013-01-01

In the title mol­ecule {systematic name: N-[3-(diquino[3,2-b;2′,3′-e][1,4]thia­zin-6-yl)prop­yl]-4-methyl­benzene­sulfon­amide}, C28H24N4O2S2, the penta­cyclic system is relatively planar [maximum deviation from the mean plane = 0.242 (1) Å]. The dihedral angle between two quinoline ring systems is 8.23 (2)° and that between the two halves of the 1,4-thia­zine ring is 5.68 (3)°. The conformation adopted by the 3-(p-tolyl­sulfonyl­amino)­propyl substituent allows for the formation of an intra­molecular N—H⋯N hydrogen bond and places the benzene ring of this substituent above one of the quinoline fragments of the penta­cyclic system. In the crystal, mol­ecules are arranged via π–π stacking inter­actions into (0-11) layers [centroid–centroid distances = 3.981 (1)–4.320 (1) Å for the rings in the penta­cyclic system and 3.645 (1) Å for the tolyl benzene rings]. In addition, mol­ecules are involved in weak C—H⋯O, which connect the layers, and C—H⋯S hydrogen bonds. The title compound shows promising anti­cancer activity against renal cancer cell line UO-31. PMID:23795128

Crystal structure of bis­(3-bromo­pyridine-κN)bis­(O-ethyl di­thio­carbonato-κ2 S,S′)nickel(II)

PubMed Central

Kant, Rajni; Kour, Gurvinder; Anthal, Sumati; Neerupama; Sachar, Renu

2015-01-01

In the title mol­ecular complex, [Ni(C3H5OS2)2(C5H4BrN)2], the Ni2+ cation is located on a centre of inversion and has a distorted octa­hedral N2S4 environment defined by two chelating xanthate ligands and two monodentate pyridine ligands. The C—S bond lengths of the thio­carboxyl­ate group are indicative of a delocalized bond and the O—Csp 2 bond is considerably shorter than the O—Csp 3 bond, consistent with a significant contribution of one resonance form of the xanthate anion that features a formal C=O+ unit and a negative charge on each of the S atoms. The packing of the mol­ecules is stabilized by C—H⋯S and C—H⋯π inter­actions. In addition, π–π inter­actions between the pyridine rings [centroid-to-centroid distance = 3.797 (3) Å] are also present. In the crystal structure, mol­ecules are arranged in rows along [100], forming layers parallel to (010) and (001). PMID:25705471

An Integrated Centroid Finding and Particle Overlap Decomposition Algorithm for Stereo Imaging Velocimetry

NASA Technical Reports Server (NTRS)

McDowell, Mark

2004-01-01

An integrated algorithm for decomposing overlapping particle images (multi-particle objects) along with determining each object s constituent particle centroid(s) has been developed using image analysis techniques. The centroid finding algorithm uses a modified eight-direction search method for finding the perimeter of any enclosed object. The centroid is calculated using the intensity-weighted center of mass of the object. The overlap decomposition algorithm further analyzes the object data and breaks it down into its constituent particle centroid(s). This is accomplished with an artificial neural network, feature based technique and provides an efficient way of decomposing overlapping particles. Combining the centroid finding and overlap decomposition routines into a single algorithm allows us to accurately predict the error associated with finding the centroid(s) of particles in our experiments. This algorithm has been tested using real, simulated, and synthetic data and the results are presented and discussed.

2-[(E)-(1,10-Phenanthrolin-5-yl)imino­meth­yl]phenol methanol monosolvate

PubMed Central

Öztürk Yíldírím, Sema; Demirhan, Nebahat; Elmalí, Fikriye; Butcher, Ray J.

2012-01-01

In the title multi-donor Schiff base compound, C19H13N3O·CH3OH, the dihedral angle between the mean planes of the phenanthroline and phenol rings is 59.3 (1)°. The Schiff base mol­ecule is linked to the solvent mol­ecule by an O—H⋯O hydrogen bond. In the crystal, the components are linked by O—H⋯N hydrogen bonds, weak O—H⋯N inter­actions and π–π stacking inter­actions [centroid–centroid distances = 3.701 (1) and 3.656 (1) Å]. PMID:22606116

Dichlorido[2-(phenyl­imino­meth­yl)quinoline-N,N′]palladium(II)

PubMed Central

Motswainyana, William M.; Onani, Martin O.; Madiehe, Abram M.

2012-01-01

In the title complex, [PdCl2(C16H12N2)], the PdII ion is coordinated by two N atoms [Pd—N 2.039 (2), 2.073 (2) Å] from a bidentate ligand and two chloride anions [Pd—Cl 2.2655 (7), 2.2991 (7) Å] in a distorted square-planar geometry. In the crystal, π–π inter­actions between the six-membered rings of the quinoline fragments [centroid–centroid distances = 3.815 (5), 3.824 (5) Å] link two mol­ecules into centrosymmetric dimers. PMID:22589771

2-(1,2,3,4-Tetra­hydro-1-naphth­yl)imidazolium chloride monohydrate

PubMed Central

Bruni, Bruno; Bartolucci, Gianluca; Ciattini, Samuele; Coran, Silvia

2010-01-01

In the title compound, C13H15N2 +·Cl−·H2O, the ions and water mol­ecules are ­connected by N—H⋯Cl, O—H⋯Cl, NH⋯Cl⋯HO, NH⋯Cl⋯HN and OH⋯Cl⋯HO inter­actions, forming discrete D(2) and D 2 1(3) chains, C 2 1(6) chains and R 4 2(8) rings, leading to a neutral two-dimensional network. The crystal structure is further stabilized by π–π stacking inter­actions [centroid–centroid distance = 3.652 (11) Å]. PMID:21588668

N-(2-{[5-Bromo-2-(piperidin-1-yl)pyrimidin-4-yl]sulfan­yl}-4-meth­oxy­phen­yl)benzene­sulfonamide

PubMed Central

Kumar, Mohan; Mallesha, L.; Sridhar, M. A.; Kapoor, Kamini; Gupta, Vivek K.; Kant, Rajni

2012-01-01

The title compound, C22H23BrN4O3S2, crystallizes with two mol­ecules, A and B, in the asymmetric unit. In one of these, the meth­oxy group is disordered over two sets of sites in a 0.565 (9):0.435 (9) ratio. The benzene rings bridged by the sulfonamide group are tilted relative to each other by 37.4 (1) and 56.1 (1)° in mol­ecules A and B, respectively, while the dihedral angles between the sulfur-bridged pyrimidine and benzene rings are 72.4 (1) and 70.2 (1)° for A and B, respectively. The piperidine ring adopts a chair conformation in both mol­ecules. In the crystal, inversion dimers linked by pairs of N—H⋯N hydrogen bonds occur for both A and B; the dimers are linked into [010] chains by C—H⋯O hydrogen bonds. The crystal structure also features inversion-generated aromatic π–π stacking inter­actions between the pyrimidine rings for both mol­ecules [centroid–centroid distances = 3.412 (2) (mol­ecule A) and 3.396 (2) Å (mol­ecule B)]. PMID:23284517

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

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

Theis, Daniel; Windus, Theresa L.; Ruedenberg, Klaus

The metastable ring structure of the ozone 1{sup 1}A{sub 1} ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two {sup 1}A{sub 1} states. In the present work, valence correlated energies of the 1{sup 1}A{sub 1} state and the 2{sup 1}A{sub 1} state were calculated at the 1{sup 1}A{sub 1} open minimum, the 1{sup 1}A{sub 1} ring minimum,more » the transition state between these two minima, the minimum of the 2{sup 1}A{sub 1} state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of Correlation Energy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 1{sup 1}A{sub 1} state, the present calculations yield the estimates of (ring minimum—open minimum) ∼45–50 mh and (transition state—open minimum) ∼85–90 mh. For the (2{sup 1}A{sub 1}–{sup 1}A{sub 1}) excitation energy, the estimate of ∼130–170 mh is found at the open minimum and 270–310 mh at the ring minimum. At the transition state, the difference (2{sup 1}A{sub 1}–{sup 1}A{sub 1}) is found to be between 1 and 10 mh. The geometry of the transition state on the 1{sup 1}A{sub 1} surface and that of the minimum on the 2{sup 1}A{sub 1} surface nearly coincide. More accurate predictions of the energy differences also require CI expansions to at least sextuple excitations with respect to the valence space. For every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences.« less

2,2′-[2,4-Bis(naphthalen-1-yl)cyclo­butane-1,3-di­yl]bis­(1-methyl­pyridinium) bis­(4-chloro­benzene­sulfonate): thermal-induced [2 + 2] cyclo­addition reaction of a heterostilbene

PubMed Central

Chantrapromma, Suchada; Chanawanno, Kullapa; Boonnak, Nawong; Fun, Hoong-Kun

2014-01-01

The asymmetric unit of the title salt, C36H32N2 2+·2C6H4ClO3S−, consists of one anion and one half-cation, the other half being generated by inversion symmetry. The dihedral angle between the pyridinium ring and the napthalene ring system in the asymmetric unit is 42.86 (6)°. In the crystal, cations and anions are linked by weak C—H⋯O inter­actions into chains along [010]. Adjacent chains are further arranged in an anti­parallel manner into sheets parallel to the bc plane. π–π inter­actions are observed involving the cations, with centroid–centroid distances of 3.7664 (8) and 3.8553 (8) Å. PMID:24860326

Diaqua­bis{5-carboxy-2-[(1H-1,2,4-triazol-1-yl)­meth­yl]-1H-imidazole-4-carboxyl­ato}­manganese(II)

PubMed Central

Ding, De-Gang; Tong, Yan

2010-01-01

In the title compound, [Mn(C8H6N5O4)2(H2O)2], the MnII ion is situated on an inversion center and is six-coordinated by two N and two O atoms from two L ligands (HL = 2-[(1H-1,2,4-triazol-1-yl)meth­yl]-1H-imidazole-4,5-dicarboxylic acid) and two water mol­ecules in a distorted octa­hedral geometry. In ligand L, the imidazole and triazole rings form a dihedral angle of 74.25 (8)°. Mol­ecules are assembled into a three-dimensional structure via inter­molecular O—H⋯O, O—H⋯N and N—H⋯N hydrogen-bonds, and π–π inter­actions with a short distance of 3.665 (2) Å between the centroids of the imidazole and triazole rings of neighbouring mol­ecules. PMID:21579014

Resonance of relativistic electrons with electromagnetic ion cyclotron waves

DOE PAGES

Denton, R. E.; Jordanova, V. K.; Bortnik, J.

2015-06-29

Relativistic electrons have been thought to more easily resonate with electromagnetic ion cyclotron EMIC waves if the total density is large. We show that, for a particular EMIC mode, this dependence is weak due to the dependence of the wave frequency and wave vector on the density. A significant increase in relativistic electron minimum resonant energy might occur for the H band EMIC mode only for small density, but no changes in parameters significantly decrease the minimum resonant energy from a nominal value. The minimum resonant energy depends most strongly on the thermal velocity associated with the field line motionmore » of the hot ring current protons that drive the instability. High density due to a plasmasphere or plasmaspheric plume could possibly lead to lower minimum resonance energy by causing the He band EMIC mode to be dominant. We demonstrate these points using parameters from a ring current simulation.« less

Internal V-Band Clamp

DOEpatents

Vaughn, Mark R.; Hafenrichter, Everett S.; Chapa, Agapito C.; Harris, Steven M.; Martinez, Marcus J.; Baty, Roy S.

2006-02-28

A system for clamping two tubular members together in an end-to-end relationship uses a split ring with a V-shaped outer rim that can engage a clamping surface on each member. The split ring has a relaxed closed state where the ends of the ring are adjacent and the outside diameter of the split ring is less than the minimum inside diameter of the members at their ends. The members are clamped when the split ring is spread into an elastically stretched position where the ring rim is pressed tightly against the interior surfaces of the members. Mechanisms are provided for removing the spreader so the split ring will return to the relaxed state, releasing the clamped members.

Photometry of Polar-Ring Galaxies

NASA Astrophysics Data System (ADS)

Godínez-Martínez, A.; Watson, A. M.; Matthews, L. D.; Sparke, L. S.

2007-10-01

We have obtained photometry in B and R for seven confirmed or probable polar-ring galaxies from the Polar-Ring Catalog of Whitmore et al. (1990). The rings show a range of colors from B - R ≈ 0.6 to B - R ≈ 1.7. The bluest rings have bright H II regions, which are direct evidence for recent star formation. The minimum age of the reddest ring, that in PRC B-20, is somewhat uncertain because of a lack of knowledge of the internal reddening and metallicity, but appears to be at least 1.2 Gyr. As such, this ring is likely to be stable for at least several rotation periods. This ring is an excellent candidate for future studies that might better determine if it is truly old.

The minimum alveolar concentration of sevoflurane in ring-tailed lemurs (Lemur catta) and aye-ayes (Daubentonia madagascariensis).

PubMed

Chinnadurai, Sathya K; Williams, Cathy

2016-01-01

To determine the minimum alveolar concentration (MAC) of sevoflurane for ring-tailed lemurs (Lemur catta) and aye-ayes (Daubentonia madagascariensis). Prospective experimental trial. Six adult ring-tailed lemurs, aged 1.3-11.2 years (median age: 8.26) and weighing a mean ± standard deviation (SD) of 2283 ± 254 g. Five adult aye-ayes, aged 4.4-19.3 years (median age: 8.0) and weighing 2712 ± 191 g. Minimum alveolar concentration of sevoflurane was determined using a tail-clamp stimulus. The end-tidal sevoflurane (Fe'Sevo) concentration was increased or decreased by approximately 10% after a positive or negative response to tail clamping, respectively. This procedure was repeated until a positive and negative result were seen on two consecutive trials (i.e. a negative result was achieved and a single 10% decrease in Fe'Sevo concentration resulted in a positive test). The MAC for that animal was determined to be the mean of the concentrations at the two consecutive trials. The mean ± SD MAC of sevoflurane for ring-tailed lemurs was 3.48 ± 0.55% and 1.84 ± 0.17 for aye-ayes. This represents a 47.1% higher MAC in ring-tailed lemurs compared to aye-ayes. The sevoflurane MAC was significantly higher in ring-tailed lemurs, compared to aye-ayes. The MAC of sevoflurane in aye-ayes is consistent with reported MAC values in other species. Extrapolation of sevoflurane anesthetic dose between different species of lemurs could lead to significant errors in anesthetic dosing. © 2015 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

A Tree-Ring Temperature Reconstruction from the Wrangell Mountains, Alaska (1593-1992): Evidence for Pronounced Regional Cooling During the Maunder Minimum

NASA Astrophysics Data System (ADS)

DArrigo, R.; Davi, N.; Jacoby, G.; Wiles, G.

2002-05-01

The Maunder Minimum interval (from the mid-1600s-early 1700s) is believed to have been one of the coldest periods of the past thousand years in the Northern Hemisphere. A maximum latewood density temperature reconstruction for the Wrangell Mountains, southern Alaska (1593-1992) provides information on regional temperature change during the Maunder Minimum and other periods of severe cold over the past four centuries. The Wrangell density record, which reflects warm season (July-September) temperatures, shows an overall cooling over the Maunder Minimum period with annual values reaching as low as -1.8oC below the long-term mean. Ring widths, which can integrate annual as well as summer conditions, also show pronounced cooling at the Wrangell site during this time, as do Arctic and hemispheric-scale temperature reconstructions based on tree rings and other proxy data. Maximum ages of glacial advance based on kill dates from overrun logs (which reflect cooler temperatures) coincide temporally with the cooling seen in the density and ring width records. In contrast, a recent modeling study indicates that during this period there was cold season (November-April) warming over much of Alaska, but cooling over other northern continental regions, as a result of decreased solar irradiance initiating low Arctic Oscillation index conditions. The influence of other forcings on Alaskan climate, the absence of ocean dynamical feedbacks in the model, and the different seasonality represented by the model and the trees may be some of the possible explanations for the different model and proxy results.

Angles-centroids fitting calibration and the centroid algorithm applied to reverse Hartmann test

NASA Astrophysics Data System (ADS)

Zhao, Zhu; Hui, Mei; Xia, Zhengzheng; Dong, Liquan; Liu, Ming; Liu, Xiaohua; Kong, Lingqin; Zhao, Yuejin

2017-02-01

In this paper, we develop an angles-centroids fitting (ACF) system and the centroid algorithm to calibrate the reverse Hartmann test (RHT) with sufficient precision. The essence of ACF calibration is to establish the relationship between ray angles and detector coordinates. Centroids computation is used to find correspondences between the rays of datum marks and detector pixels. Here, the point spread function of RHT is classified as circle of confusion (CoC), and the fitting of a CoC spot with 2D Gaussian profile to identify the centroid forms the basis of the centroid algorithm. Theoretical and experimental results of centroids computation demonstrate that the Gaussian fitting method has a less centroid shift or the shift grows at a slower pace when the quality of the image is reduced. In ACF tests, the optical instrumental alignments reach an overall accuracy of 0.1 pixel with the application of laser spot centroids tracking program. Locating the crystal at different positions, the feasibility and accuracy of ACF calibration are further validated to 10-6-10-4 rad root-mean-square error of the calibrations differences.

Folded Fabry-Perot quasi-optical ring resonator diplexer Theory and experiment

NASA Technical Reports Server (NTRS)

Pickett, H. M.; Chiou, A. E. T.

1983-01-01

Performance of folded Fabry-Perot quasi-optical ring resonator diplexers with different geometries of reflecting surfaces is investigated both theoretically and experimentally. Design of optimum surface geometry for minimum diffraction, together with the figure of merit indicating improvement in performance, are given.

Characterization of the International Linear Collider damping ring optics

NASA Astrophysics Data System (ADS)

Shanks, J.; Rubin, D. L.; Sagan, D.

2014-10-01

A method is presented for characterizing the emittance dilution and dynamic aperture for an arbitrary closed lattice that includes guide field magnet errors, multipole errors and misalignments. This method, developed and tested at the Cornell Electron Storage Ring Test Accelerator (CesrTA), has been applied to the damping ring lattice for the International Linear Collider (ILC). The effectiveness of beam based emittance tuning is limited by beam position monitor (BPM) measurement errors, number of corrector magnets and their placement, and correction algorithm. The specifications for damping ring magnet alignment, multipole errors, number of BPMs, and precision in BPM measurements are shown to be consistent with the required emittances and dynamic aperture. The methodology is then used to determine the minimum number of position monitors that is required to achieve the emittance targets, and how that minimum depends on the location of the BPMs. Similarly, the maximum tolerable multipole errors are evaluated. Finally, the robustness of each BPM configuration with respect to random failures is explored.

Fluctuations in Tree Ring Cellulose d18O during the Little Ice Age Correlate with Solar Activity

NASA Astrophysics Data System (ADS)

Yamaguchi, Y. T.; Yokoyama, Y.; Miyahara, H.; Nakatsuka, T.

2008-12-01

The Maunder Minimum (AD1645-1715), when sunspots became exceedingly rare, is known to coincide with the coldest period during the Little Ice Age. This is a useful period to investigate possible linkage between solar activity and climate because variation in solar activity was different from that of today. The solar cycle length was longer (14 and 28 years) than that of today (11 and 22 years) hence any climate archives that have similar periodic changes could be separated from other internal climate forcing. We have reported that Greenland temperature variations coincided with decadal-scale variability in solar activity during the Maunder Minimum (Miyahara et al. 2008). Here we report interannual and intra-annual relative humidity (RH) variations in central Japan during that period, using tree ring cellulose d18O in a 382-year-old Japanese cedar tree (Cryptomeria japonica). The isotopic composition of tree rings can be a powerful tool to study the relationship between solar activity and climate, because we can directly compare solar activity (D14C) and climate (d18O) with little dating error. The climate proxy obtained using tree ring cellulose d18O is correlated both negatively and positively with RH and d18O in precipitation, respectively. Since d18O in precipitation is negatively correlated with the amount of precipitation in the monsoon area, tree ring cellulose d18O can be a reliable proxy for past RH and/or amount of precipitation in the area of the interest. Tree ring cellulose d18O of the cedar tree during AD1938-1998 in fact correlates significantly with the mean RH in June in central Japan. Tree ring d18O inferred RH variability during the Maunder Minimum shows distinct high RH spikes with an approximate 14-year quasiperiodicity. All nine solar minima during AD1640-1756 deduced from tree ring D14C coincided with high RH spikes, and seven of which coincided within 1-year. Interannual RH variations also coincided with Greenland temperature during this period. These results suggest that weakening of solar activity at solar minima caused distinct hemispheric scale climate change during the Maunder Minimum. We discuss the mechanism in which the solar activity variation caused the climate change, based on intra-annual RH variability and further data analysis of interannual RH variability. H. Miyahara et al., Earth Planet. Sci. Lett. 272, 1-2, 290-295 (2008).

The Particle Size Distribution in Saturn’s C Ring from UVIS and VIMS Stellar Occultations and RSS Radio Occultations

NASA Astrophysics Data System (ADS)

Jerousek, Richard Gregory; Colwell, Josh; Hedman, Matthew M.; French, Richard G.; Marouf, Essam A.; Esposito, Larry; Nicholson, Philip D.

2017-10-01

The Cassini Ultraviolet Imaging Spectrograph (UVIS) and Visual and Infrared Mapping Spectrometer (VIMS) have measured ring optical depths over a wide range of viewing geometries at effective wavelengths of 0.15 μm and 2.9 μm respectively. Using Voyager S and X band radio occultations and the direct inversion of the forward scattered S band signal, Marouf et al. (1982), (1983), and Zebker et al. (1985) determined the power-law size distribution parameters assuming a minimum particle radius of 1 mm. Many further studies have also constrained aspects of the particle size distribution throughout the main rings. Marouf et al. (2008a) determined the smallest ring particles to have radii of 4-5 mm using Cassini RSS data. Harbison et al. (2013) used VIMS solar occultations and also found minimum particle sizes of 4-5 mm in the C ring with q ~ 3.1, where n(a)da=Ca^(-q)da is the assumed differential power-law size distribution for particles of radius a. Recent studies of excess variance in stellar signal by Colwell et al. (2017, submitted) constrain the cross-section-weighted effective particle radius to 1 m to several meters. Using the wide range of viewing geometries available to VIMS and UVIS stellar occultations we find that normal optical depth does not strongly depend on viewing geometry at 10km resolution (which would be the case if self-gravity wakes were present). Throughout the C ring, we fit power-law derived optical depths to those measured by UVIS, VIMS, and by the Cassini Radio Science Subsystem (RSS) at 0.94 and 3.6 cm wavelengths to constrain the four parameters of the size distribution at 10km radial resolution. We find significant amounts of particle size sorting throughout the region with a positive correlation between maximum particles size (amax) and normal optical depth with a mean value of amax ~ 3 m in the background C ring. This correlation is negative in the C ring plateaus. We find an inverse correlation in minimum particle radius with normal optical depth and a mean value of amin ~ 4 mm in the background C ring with slightly larger smallest particles in the C ring plateaus.

Methyl 4-eth­oxy-2-methyl-2H-1,2-benzothia­zine-3-carboxyl­ate 1,1-dioxide

PubMed Central

Zia-ur-Rehman, Muhammad; Choudary, Jamil Anwar; Elsegood, Mark R. J.; Akbar, Noshin; Latif Siddiqui, Hamid

2008-01-01

In the crystal structure of the title compound, C13H15NO5S, the mol­ecules exhibit weak S=O⋯H—C and C=O⋯H—C inter­molecular inter­actions and arrange themselves into centrosymmetric dimers by means of π–π inter­actions (ring centroids are separated by 3.619 Å, while the closest C⋯C contacts are 3.514 Å). 1,2-Benzothia­zines of this kind have a range of biological activities and are used as medicines in the treatment of inflammation and rheumatoid arthritis. PMID:21203217

(E)-3-(2,3,4,5,6-Penta­fluoro­styr­yl)thio­phene

PubMed Central

Clément, Sébastien; Coulembier, Olivier; Meyer, Franck; Zeller, Matthias; Vande Velde, Christophe M. L.

2010-01-01

The reaction of thio­phene-3-carboxaldehyde and perfluoro­benzyl­triphenyl­phospho­nium bromide in the presence of sodium hydride gave the title compound, C12H5F5S, in 70% yield. The thiophene and perfluorophenyl groups form a dihedral angle of 5.4 (2)°. The structure is characterized by a head-to-tail organization in a columnar arrangement due to π–π inter­actions between the thio­phene and penta­fluoro­phenyl rings with centroid–centroid distances in the range 3.698 (2)–3.802 (2) Å. PMID:21580713

4,4′-Bipyridine–pyroglutamic acid (1/2)

PubMed Central

Arman, Hadi D.; Kaulgud, Trupta; Tiekink, Edward R. T.

2009-01-01

In the title co-crystal, C10H8N2·2C5H7NO3, the 4,4′-bipyridine mol­ecule [dihedral angle between the pyridine rings = 36.33 (11)°] accepts O—H⋯N hydrogen bonds from the two pyroglutamic (pga) acid mol­ecules. The pga mol­ecules at each end of the trimeric aggregate self-associate via centrosymmetric eight-membered amide {⋯HNCO}2 synthons, so that the crystal structure comprises one-dimensional supra­molecular chains propagating in [13]. C—H⋯O and π–π stacking inter­actions [centroid–centroid separation = 3.590 (2) Å] consolidate the structure. PMID:21578523

Lyman-alpha observations in the vicinity of Saturn with Copernicus

NASA Technical Reports Server (NTRS)

Barker, E.; Cazes, S.; Emerich, C.; Vidal-Madjar, A.; Owen, T.

1980-01-01

For the first time, high-resolution Ly-alpha observations of the Saturn vicinity were completed with the Princeton spectrometer on board the Copernicus satellite. They showed that near a minimum solar activity the emissions related to several sources are 250 + or - 50 rayleighs for the interplanetary medium in a near-downwind direction, less than 100 rayleighs for the rings, 200 + or - 100 rayleighs for a torus linked to the Titan orbit, and 1400 + or - 450 rayleighs for the disk of Saturn. These results induce some constraints through the corresponding theoretical evaluations: the B ring as the primary source of the atoms for the ring emissions; an efficient production mechanism for hydrogen atoms in the Titan torus; and a slightly larger eddy diffusion coefficient in the Saturn atmosphere than in the Jupiter atmosphere near solar minimum.

catena-Poly[[[di-aqua-bis-[1,2-bis-(pyridin-4-yl)diazene]copper(II)]-μ-1,2-bis-(pyridin-4-yl)diazene] bis-(perchlorate)].

PubMed

Ballestero-Martínez, Ernesto; Campos-Fernández, Cristian Saul; Soto-Tellini, Victor Hugo; Gonzalez-Montiel, Simplicio; Martínez-Otero, Diego

2013-06-01

In the title compound, {[Cu(C10H8N4)3(H2O)2](ClO4)2} n , the coordination environment of the cationic Cu(II) atom is distorted octa-hedral, formed by pairs of symmetry-equivalent 1,2-bis-(pyridin-4-yl)diazene ligands, bridging 1,2-bis-(pyridin-4-yl)diazene ligands and two non-equivalent water mol-ecules. The 1,2-bis-(pyridin-4-yl)diazene mol-ecules form polymeric chains parallel to [-101] via azo bonds which are situated about inversion centres. Since the Cu(II) atom is situated on a twofold rotation axis, the monomeric unit has point symmetry 2. The perchlorate anions are disordered in a 0.536 (9):0.464 (9) ratio and are acceptors of water H atoms in medium-strong O-H⋯O hydrogen bonds with graph set R 4 (4)(12). The water mol-ecules, which are coordinated to the Cu(II) atom and are hydrogen-bonded to the perchlorate anions, form columns parallel to [010]. A π-π inter-action [centroid-centroid distance = 3.913 (2) Å] occurs between pyridine rings, and weak C-H⋯O inter-actions also occur.

21 CFR 172.215 - Coumarone-indene resin.

Code of Federal Regulations, 2011 CFR

2011-04-01

... mixture of indene, indan (hydrindene), substituted benzenes, and related compounds. (2) It contains no... additive meets the following specifications: (1) Softening point, ring and ball: 126 °C minimum as determined by ASTM method E28-67 (Reapproved 1982), “Standard Test Method for Softening Point by Ring-and...

21 CFR 172.215 - Coumarone-indene resin.

Code of Federal Regulations, 2012 CFR

2012-04-01

... mixture of indene, indan (hydrindene), substituted benzenes, and related compounds. (2) It contains no... additive meets the following specifications: (1) Softening point, ring and ball: 126 °C minimum as determined by ASTM method E28-67 (Reapproved 1982), “Standard Test Method for Softening Point by Ring-and...

21 CFR 172.215 - Coumarone-indene resin.

Code of Federal Regulations, 2013 CFR

2013-04-01

... mixture of indene, indan (hydrindene), substituted benzenes, and related compounds. (2) It contains no... additive meets the following specifications: (1) Softening point, ring and ball: 126 °C minimum as determined by ASTM method E28-67 (Reapproved 1982), “Standard Test Method for Softening Point by Ring-and...

Formation and behavior of counter-rotating vortex rings

NASA Astrophysics Data System (ADS)

Sadri, V.; Krueger, P. S.

2017-08-01

Concentric, counter-rotating vortex ring formation by transient jet ejection between concentric cylinders was studied numerically to determine the effects of cylinder gap ratio, Δ R/R, and jet stroke length-to-gap ratio, L/Δ R, on the evolution of the vorticity and the trajectories of the resulting axisymmetric vortex pair. The flow was simulated at a jet Reynolds number of 1000 (based on Δ R and the jet velocity), L/Δ R in the range 1-20, and Δ R/R in the range 0.05-0.25. Five characteristic flow evolution patterns were observed and classified based on L/Δ R and Δ R/R. The results showed that the relative position, relative strength, and radii of the vortex rings during and soon after formation played a prominent role in the evolution of the trajectories of their vorticity centroids at the later time. The conditions on relative strength of the vortices necessary for them to travel together as a pair following formation were studied, and factors affecting differences in vortex circulation following formation were investigated. In addition to the characteristics of the primary vortices, the stopping vortices had a strong influence on the initial vortex configuration and effected the long-time flow evolution at low L/Δ R and small Δ R/R. For long L/Δ R and small Δ R/R, shedding of vorticity was sometimes observed and this shedding was related to the Kelvin-Benjamin variational principle of maximal energy for steadily translating vortex rings.

The Christiansen Effect in Saturn's narrow dusty rings and the spectral identification of clumps in the F ring

USGS Publications Warehouse

Hedman, M.M.; Nicholson, P.D.; Showalter, M.R.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Baines, K.; Sotin, Christophe

2011-01-01

Stellar occultations by Saturn's rings observed with the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft reveal that dusty features such as the F ring and the ringlets in the Encke and the Laplace Gaps have distinctive infrared transmission spectra. These spectra show a narrow optical depth minimum at wavelengths around 2.87??m. This minimum is likely due to the Christiansen Effect, a reduction in the extinction of small particles when their (complex) refractive index is close to that of the surrounding medium. Simple Mie-scattering models demonstrate that the strength of this opacity dip is sensitive to the size distribution of particles between 1 and 100??m across. Furthermore, the spatial resolution of the occultation data is sufficient to reveal variations in the transmission spectra within and among these rings. In both the Encke Gap ringlets and F ring, the opacity dip weakens with increasing local optical depth, which is consistent with the larger particles being concentrated near the cores of these rings. The Encke Gap ringlets also show systematically weaker opacity dips than the F ring and Laplace Gap ringlet, implying that the former has a smaller fraction of grains less than ~30??m across. However, the strength of the opacity dip varies most dramatically within the F ring; certain compact regions of enhanced optical depth lack an opacity dip and therefore appear to have a greatly reduced fraction of grains in the few-micron size range. Such spectrally-identifiable structures probably represent a subset of the compact optically-thick clumps observed by other Cassini instruments. These variations in the ring's particle size distribution can provide new insights into the processes of grain aggregation, disruption and transport within dusty rings. For example, the unusual spectral properties of the F-ring clumps could perhaps be ascribed to small grains adhering onto the surface of larger particles in regions of anomalously low velocity dispersion. ?? 2011 Elsevier Inc.

A centroid model of species distribution with applications to the Carolina wren Thryothorus ludovicianus and house finch Haemorhous mexicanus in the United States

USGS Publications Warehouse

Huang, Qiongyu; Sauer, John R.; Swatantran, Anu; Dubayah, Ralph

2016-01-01

Drastic shifts in species distributions are a cause of concern for ecologists. Such shifts pose great threat to biodiversity especially under unprecedented anthropogenic and natural disturbances. Many studies have documented recent shifts in species distributions. However, most of these studies are limited to regional scales, and do not consider the abundance structure within species ranges. Developing methods to detect systematic changes in species distributions over their full ranges is critical for understanding the impact of changing environments and for successful conservation planning. Here, we demonstrate a centroid model for range-wide analysis of distribution shifts using the North American Breeding Bird Survey. The centroid model is based on a hierarchical Bayesian framework which models population change within physiographic strata while accounting for several factors affecting species detectability. Yearly abundance-weighted range centroids are estimated. As case studies, we derive annual centroids for the Carolina wren and house finch in their ranges in the U.S. We further evaluate the first-difference correlation between species’ centroid movement and changes in winter severity, total population abundance. We also examined associations of change in centroids from sub-ranges. Change in full-range centroid movements of Carolina wren significantly correlate with snow cover days (r = −0.58). For both species, the full-range centroid shifts also have strong correlation with total abundance (r = 0.65, and 0.51 respectively). The movements of the full-range centroids of the two species are correlated strongly (up to r = 0.76) with that of the sub-ranges with more drastic population changes. Our study demonstrates the usefulness of centroids for analyzing distribution changes in a two-dimensional spatial context. Particularly it highlights applications that associate the centroid with factors such as environmental stressors, population characteristics, and progression of invasive species. Routine monitoring of changes in centroid will provide useful insights into long-term avian responses to environmental changes.

A Systematic Approach for Computing Zero-Point Energy, Quantum Partition Function, and Tunneling Effect Based on Kleinert's Variational Perturbation Theory.

PubMed

Wong, Kin-Yiu; Gao, Jiali

2008-09-09

In this paper, we describe an automated integration-free path-integral (AIF-PI) method, based on Kleinert's variational perturbation (KP) theory, to treat internuclear quantum-statistical effects in molecular systems. We have developed an analytical method to obtain the centroid potential as a function of the variational parameter in the KP theory, which avoids numerical difficulties in path-integral Monte Carlo or molecular dynamics simulations, especially at the limit of zero-temperature. Consequently, the variational calculations using the KP theory can be efficiently carried out beyond the first order, i.e., the Giachetti-Tognetti-Feynman-Kleinert variational approach, for realistic chemical applications. By making use of the approximation of independent instantaneous normal modes (INM), the AIF-PI method can readily be applied to many-body systems. Previously, we have shown that in the INM approximation, the AIF-PI method is accurate for computing the quantum partition function of a water molecule (3 degrees of freedom) and the quantum correction factor for the collinear H(3) reaction rate (2 degrees of freedom). In this work, the accuracy and properties of the KP theory are further investigated by using the first three order perturbations on an asymmetric double-well potential, the bond vibrations of H(2), HF, and HCl represented by the Morse potential, and a proton-transfer barrier modeled by the Eckart potential. The zero-point energy, quantum partition function, and tunneling factor for these systems have been determined and are found to be in excellent agreement with the exact quantum results. Using our new analytical results at the zero-temperature limit, we show that the minimum value of the computed centroid potential in the KP theory is in excellent agreement with the ground state energy (zero-point energy) and the position of the centroid potential minimum is the expectation value of particle position in wave mechanics. The fast convergent property of the KP theory is further examined in comparison with results from the traditional Rayleigh-Ritz variational approach and Rayleigh-Schrödinger perturbation theory in wave mechanics. The present method can be used for thermodynamic and quantum dynamic calculations, including to systematically determine the exact value of zero-point energy and to study kinetic isotope effects for chemical reactions in solution and in enzymes.

Structure, stratigraphy, and eruption chronology of the Hanauma Bay Tuff Ring, Oahu, Hawaii

NASA Astrophysics Data System (ADS)

Rottas, K. M.; Houghton, B. F.

2010-12-01

The Hanauma Bay-Koko Head Complex is one of several volcanic landforms along the Koko fissure, in southeastern Oahu, that formed during rejuvenated volcanism. The Hanauma Bay region of the complex is comprised of two nested tuff rings. The internal structure of the inner tuff ring is well exposed due to subsequent breaching and wave erosion and is described in detail here for the first time. The inner tuff ring is currently believed to have formed during a single eruption episode. However, field observations, detailed photography, structural mapping in both the vertical and horizontal planes, extensive measurements of bedding attitudes, and stratigraphic analysis suggest that there were a minimum of five distinct intervals of deposition, which also blanketed the deposits of the outer tuff ring with ejecta. These intervals of sedimentation were separated by significant collapses, generating major unconformities that cross the inner wall of the inner ring. The planes of failure are marked by smaller steep-walled channels and gullies, eroded by rainfall-induced runoff and suggesting the failures were each followed by short time breaks with erosion. Within each pyroclastic sequence there are also smaller slump scars and local unconformities. The inner tuff ring was predominately formed by pyroclastic surges, although the beds of Phase 3 are primarily fall deposits. From ballistic trajectories and bedding features, it is apparent that the eruption locus shifted a minimum of two times during tuff ring growth. Ballistic blocks in the final Phase 5 indicate that the Hanauma Bay eruption was contemporaneous with a separate eruption to the north, most likely that of the Kahauloa tuff ring 880 meters away.

Classification Scheme for Centuries of Reconstructed Streamflow Droughts in Water Resources Planning

NASA Astrophysics Data System (ADS)

Stagge, J.; Rosenberg, D. E.

2017-12-01

New advances in reconstructing streamflow from tree rings have permitted the reconstruction of flows back to the 1400s or earlier at a monthly, rather than annual, time scale. This is a critical step for incorporating centuries of streamflow reconstructions into water resources planning. Expanding the historical record is particularly important where the observed record contains few of these rare, but potentially disastrous extreme events. We present how a paleo-drought clustering approach was incorporated alongside more traditional water management planning in the Weber River basin, northern Utah. This study used newly developed monthly reconstructions of flow since 1430 CE and defined drought events as flow less than the 50th percentile during at least three contiguous months. Characteristics for each drought event included measures of drought duration, severity, cumulative loss, onset, seasonality, recession rate, and recovery rate. Reconstructed drought events were then clustered by hierarchical clustering to determine distinct drought "types" and the historical event that best represents the centroid of each cluster. The resulting 144 reconstructed drought events in the Weber basin clustered into nine distinct types, of which four were severe enough to potentially require drought management. Using the characteristic drought event for each of the severe drought clusters, water managers were able to estimate system reliability and the historical return frequency for each drought type. Plotting drought duration and severity from centuries of historical reconstructed events alongside observed events and climate change projections further placed recent events into a historical context. For example, the drought of record for the Weber River remains the most severe event in the record with regard to minimum flow percentile (1930, 7 years), but is far from the longest event in the longer historical record, where events beginning in 1658 and 1705 both lasted longer than 13 years. The proposed drought clustering approach provides a powerful tool for merging historical reconstructions, observations, and climate change projections in water resources planning, while also providing a framework to make use of valuable and increasingly available tree-ring reconstructions of monthly streamflow.

An analytical investigation of a conceptual design for the station transverse boom rotary joint structure

NASA Technical Reports Server (NTRS)

Lake, M. S.; Bush, H. G.

1986-01-01

A study was conducted to define an annular ring, discrete roller assembly concept for the space station transverse boom rotary joint. The concept was analyzed using closed-form and finite element techniques, to size structural members for a range of joint diameters and to determine necessary equivalent stiffnesses for the roller assemblies. Also, a mass study of the system was conducted to determine its practicality, and maximum loads in the joint were identified. To obtain the optimum balance between high stiffness and low structural mass in the design of the rotary joint, it is necessary to maximize the diameter of the annular ring within operational constraints (i.e., shuttle cargo bay size). Further, a rotary joint designed with the largest possible ring diameter will result in minimum operational loads in both the roller assemblies and the transition truss members while also allowing minimum design stiffnesses for the roller assemblies.

21 CFR 172.215 - Coumarone-indene resin.

Code of Federal Regulations, 2014 CFR

2014-04-01

...), substituted benzenes, and related compounds. (2) It contains no more than 0.25 percent tar bases. (3) 95...) Softening point, ring and ball: 126 °C minimum as determined by ASTM method E28-67 (Reapproved 1982), “Standard Test Method for Softening Point by Ring-and-Ball Apparatus,” which is incorporated by reference...

(E)-2-[2-(4-Carb­oxy­phen­yl)ethen­yl]-8-hydroxy­quinolin-1-ium chloride ethanol monosolvate

PubMed Central

Schulze, Mathias M.; Seichter, Wilhelm; Weber, Edwin

2013-01-01

In the title compound, C18H14NO3 +·Cl−·CH3CH2OH, the dihedral angle formed by the mean planes of the quinolinium and benzene rings is 3.4 (1)°, while the carb­oxy substituent is tilted at an angle of 4.8 (1)° with respect to the benzene ring. There is a short N—H⋯O contact in the cation. In the crystal, due to the planar mol­ecular geometry, two-dimensional aggregates are formed parallel to (221) via C—H⋯O, C—H⋯Cl, O—H⋯Cl and N—H⋯Cl hydrogen bonds. Inter­layer association is accomplished by O—Hethanol⋯Cl and O—H⋯Oethanol hydrogen bonds and π–π stacking inter­actions [centroid–centroid distances vary from 3.6477 (12) to 3.8381 (11) Å]. A supra­molecular three-dimensional architecture results from a stacked arrangement of layers comprising the ionic and hydrogen-bonded components. PMID:24454221

(R)-2-[(Dimethyl­amino)­meth­yl]-1,1′-bis­(diphenyl­phosphinothio­yl)ferrocene dichloromethane monsolvate

PubMed Central

Philippe, Elisabeth; Manoury, Eric; Daran, Jean-Claude

2012-01-01

In the title compound, [Fe(C20H21NPS)(C17H14PS)]·CH2Cl2, both cyclo­penta­dienyl (Cp) rings constituting the ferrocene unit are substituted by a sulfur-protected diphenyl­phosphine. One of the Cp ligands is additionally substituted by a dimethyl­amino­methyl group causing the chirality of the mol­ecule. Surprisingly, although the synthetic procedure yielded the title compound as a racemic mixture, the reported crystal is enanti­omerically pure with the R absolute configuration. The dimethyl­amino group is exo with respect to the Cp ring. Both diphenyl­thio­phosphine groups are trans with respect to the centroid–Fe–centroid direction. Weak intra­molecular C—H⋯S and C—H⋯π inter­actions between symmetry-related mol­ecules are observed. The contribution of the disordered solvent was removed from the refinement using SQUEEZE in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155]. PMID:22719348

2-Amino­benzoic acid–4-(pyridin-4-yl­disulfan­yl)pyridine (1/1)

PubMed Central

Arman, Hadi D.; Kaulgud, Trupta; Tiekink, Edward R. T.

2011-01-01

The title 1:1 co-crystal, C7H7NO2·C10H8N2S2, features a highly twisted 4-(pyridin-4-yldisulfan­yl)pyridine mol­ecule [dihedral angle between the pyridine rings = 89.06 (10)°]. A small twist is evident in the 2-amino­benzoic acid mol­ecule, with the C—C—C—O torsion angle being −7.7 (3)°. An N—H⋯O hydrogen bond occurs in the 2-amino­benzoic acid mol­ecule. In the crystal, mol­ecules are linked by O—H⋯N and N—H⋯N hydrogen bonds into a supra­molecular chain along the b axis. These are connected into layers by π–π inter­actions occurring between pyridine rings [centroid–centroid distance = 3.8489 (15) Å]. The layers are connected along the a axis by C—H⋯O contacts. The crystal studied was a racemic twin. PMID:22199855

Improved measurements of RNA structure conservation with generalized centroid estimators.

PubMed

Okada, Yohei; Saito, Yutaka; Sato, Kengo; Sakakibara, Yasubumi

2011-01-01

Identification of non-protein-coding RNAs (ncRNAs) in genomes is a crucial task for not only molecular cell biology but also bioinformatics. Secondary structures of ncRNAs are employed as a key feature of ncRNA analysis since biological functions of ncRNAs are deeply related to their secondary structures. Although the minimum free energy (MFE) structure of an RNA sequence is regarded as the most stable structure, MFE alone could not be an appropriate measure for identifying ncRNAs since the free energy is heavily biased by the nucleotide composition. Therefore, instead of MFE itself, several alternative measures for identifying ncRNAs have been proposed such as the structure conservation index (SCI) and the base pair distance (BPD), both of which employ MFE structures. However, these measurements are unfortunately not suitable for identifying ncRNAs in some cases including the genome-wide search and incur high false discovery rate. In this study, we propose improved measurements based on SCI and BPD, applying generalized centroid estimators to incorporate the robustness against low quality multiple alignments. Our experiments show that our proposed methods achieve higher accuracy than the original SCI and BPD for not only human-curated structural alignments but also low quality alignments produced by CLUSTAL W. Furthermore, the centroid-based SCI on CLUSTAL W alignments is more accurate than or comparable with that of the original SCI on structural alignments generated with RAF, a high quality structural aligner, for which twofold expensive computational time is required on average. We conclude that our methods are more suitable for genome-wide alignments which are of low quality from the point of view on secondary structures than the original SCI and BPD.

Aeroelastically coupled blades for vertical axis wind turbines

DOEpatents

Paquette, Joshua; Barone, Matthew F.

2016-02-23

Various technologies described herein pertain to a vertical axis wind turbine blade configured to rotate about a rotation axis. The vertical axis wind turbine blade includes at least an attachment segment, a rear swept segment, and optionally, a forward swept segment. The attachment segment is contiguous with the forward swept segment, and the forward swept segment is contiguous with the rear swept segment. The attachment segment includes a first portion of a centroid axis, the forward swept segment includes a second portion of the centroid axis, and the rear swept segment includes a third portion of the centroid axis. The second portion of the centroid axis is angularly displaced ahead of the first portion of the centroid axis and the third portion of the centroid axis is angularly displaced behind the first portion of the centroid axis in the direction of rotation about the rotation axis.

A six hundred-year annual minimum temperature history for the central Tibetan Plateau derived from tree-ring width series

NASA Astrophysics Data System (ADS)

He, Minhui; Yang, Bao; Datsenko, Nina M.

2014-08-01

The recent unprecedented warming found in different regions has aroused much attention in the past years. How temperature has really changed on the Tibetan Plateau (TP) remains unknown since very limited high-resolution temperature series can be found over this region, where large areas of snow and ice exist. Herein, we develop two Juniperus tibetica Kom. tree-ring width chronologies from different elevations. We found that the two tree-ring series only share high-frequency variability. Correlation, response function and partial correlation analysis indicate that prior year annual (January-December) minimum temperature is most responsible for the higher belt juniper radial growth, while more or less precipitation signal is contained by the tree-ring width chronology at the lower belt and is thus excluded from further analysis. The tree growth-climate model accounted for 40 % of the total variance in actual temperature during the common period 1957-2010. The detected temperature signal is further robustly verified by other results. Consequently, a six century long annual minimum temperature history was firstly recovered for the Yushu region, central TP. Interestingly, the rapid warming trend during the past five decades is identified as a significant cold phase in the context of the past 600 years. The recovered temperature series reflects low-frequency variability consistent with other temperature reconstructions over the whole TP region. Furthermore, the present recovered temperature series is associated with the Asian monsoon strength on decadal to multidecadal scales over the past 600 years.

A Doppler centroid estimation algorithm for SAR systems optimized for the quasi-homogeneous source

NASA Technical Reports Server (NTRS)

Jin, Michael Y.

1989-01-01

Radar signal processing applications frequently require an estimate of the Doppler centroid of a received signal. The Doppler centroid estimate is required for synthetic aperture radar (SAR) processing. It is also required for some applications involving target motion estimation and antenna pointing direction estimation. In some cases, the Doppler centroid can be accurately estimated based on available information regarding the terrain topography, the relative motion between the sensor and the terrain, and the antenna pointing direction. Often, the accuracy of the Doppler centroid estimate can be improved by analyzing the characteristics of the received SAR signal. This kind of signal processing is also referred to as clutterlock processing. A Doppler centroid estimation (DCE) algorithm is described which contains a linear estimator optimized for the type of terrain surface that can be modeled by a quasi-homogeneous source (QHS). Information on the following topics is presented: (1) an introduction to the theory of Doppler centroid estimation; (2) analysis of the performance characteristics of previously reported DCE algorithms; (3) comparison of these analysis results with experimental results; (4) a description and performance analysis of a Doppler centroid estimator which is optimized for a QHS; and (5) comparison of the performance of the optimal QHS Doppler centroid estimator with that of previously reported methods.

Analysis of k-means clustering approach on the breast cancer Wisconsin dataset.

PubMed

Dubey, Ashutosh Kumar; Gupta, Umesh; Jain, Sonal

2016-11-01

Breast cancer is one of the most common cancers found worldwide and most frequently found in women. An early detection of breast cancer provides the possibility of its cure; therefore, a large number of studies are currently going on to identify methods that can detect breast cancer in its early stages. This study was aimed to find the effects of k-means clustering algorithm with different computation measures like centroid, distance, split method, epoch, attribute, and iteration and to carefully consider and identify the combination of measures that has potential of highly accurate clustering accuracy. K-means algorithm was used to evaluate the impact of clustering using centroid initialization, distance measures, and split methods. The experiments were performed using breast cancer Wisconsin (BCW) diagnostic dataset. Foggy and random centroids were used for the centroid initialization. In foggy centroid, based on random values, the first centroid was calculated. For random centroid, the initial centroid was considered as (0, 0). The results were obtained by employing k-means algorithm and are discussed with different cases considering variable parameters. The calculations were based on the centroid (foggy/random), distance (Euclidean/Manhattan/Pearson), split (simple/variance), threshold (constant epoch/same centroid), attribute (2-9), and iteration (4-10). Approximately, 92 % average positive prediction accuracy was obtained with this approach. Better results were found for the same centroid and the highest variance. The results achieved using Euclidean and Manhattan were better than the Pearson correlation. The findings of this work provided extensive understanding of the computational parameters that can be used with k-means. The results indicated that k-means has a potential to classify BCW dataset.

From the Line in the Sand: Accounts of USAF Company Grade Officers in Support of Desert Shield/Desert Storm

DTIC Science & Technology

1994-03-01

and target annotated. The threat rings . . . lots of them . . . the wing commander . . . the chaplain reading from the Bible... this was real...Meanwhile, the OPT was already working the next mission. We updated the threat rings , chose a minimum risk route, coordinated defense suppression and...Prove it, Intel! You can’t prove it because you have no imagery backup for electronic intelligence. Okay then, let’s penetrate that ring to mini

Noise estimation of beam position monitors at RHIC

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

Shen, X.; Bai, M.; Lee, S. Y.

2014-02-10

Beam position monitors (BPM) are used to record the average orbits and transverse turn-by-turn displacements of the beam centroid motion. The Relativistic Hadron Ion Collider (RHIC) has 160 BPMs for each plane in each of the Blue and Yellow rings: 72 dual-plane BPMs in the insertion regions (IR) and 176 single-plane modules in the arcs. Each BPM is able to acquire 1024 or 4096 consecutive turn-by-turn beam positions. Inevitably, there are broadband noisy signals in the turn-by-turn data due to BPM electronics as well as other sources. A detailed study of the BPM noise performance is critical for reliable opticsmore » measurement and beam dynamics analysis based on turn-by-turn data.« less

Di­aqua­bis­[2-(2-hy­droxy­eth­yl)pyridine-κ2 N,O]cobalt(II) dichloride

PubMed Central

Zeghouan, Ouahida; Guenifa, Fatiha; Hadjadj, Nasreddine; Bendjeddou, Lamia; Merazig, Hocine

2013-01-01

In the title salt, [Co(C7H9NO)2(H2O)2]Cl2, the CoII cation, located on an inversion center, is N,O-chelated by two hy­droxy­ethyl­pyridine ligands and coordinated by two water mol­ecules in a distorted O4N2 octa­hedral geometry. In the crystal, the Cl− anions link with the complex cations via O—H⋯Cl hydrogen bonds, forming a three-dimensional supra­molecular architecture. π–π stacking is observed between the pyridine rings of adjacent mol­ecules [centroid–centroid distance = 3.5810 (11) Å]. PMID:24109269

Crystal structure of zwitterionic 4-(ammonio­methyl)­benzoate: a simple mol­ecule giving rise to a complex supra­molecular structure

PubMed Central

Atria, Ana María; Garland, Maria Teresa; Baggio, Ricardo

2014-01-01

The asymmetric unit of the title compound, C8H9NO2·H2O consists of an isolated 4-(ammonio­meth­yl)benzoate zwitterion derived from 4-amino­methyl­benzoic acid through the migration of the acidic proton, together with a water molecule of crystallization that is disordered over three sites with occupancy ratios (0.50:0.35:0.15). In the crystal structure, N—H⋯O hydrogen bonds together with π–π stacking of the benzene rings [centroid–centroid distance = 3.8602 (18) Å] result in a strongly linked, compact three-dimensional structure. PMID:25484753

The betainic form of (imidazol-2-yl)phenylphosphinic acid hydrate

PubMed Central

Kunz, Peter C.; Frank, Walter

2010-01-01

Single crystals of the title compound, (imidazolium-2-yl)phenyl­phosphinate monohydrate, C9H9N2O2·H2O, were ob­tained from methanol/water after deprotection and oxidation of bis­(1-diethoxy­methyl­imidazol-2-yl)phenyl­phosphane. In the structure, several N–H⋯O and P—O⋯H–O hydrogen bonds are found. π–π inter­actions between the protonated imidazolyl rings [centroid–centroid distance = 3.977 (2) Å] help to establish the crystal packing. The hydrate water mol­ecule builds hydrogen bridges to three mol­ecules of the phosphinic acid by the O and both H atoms. PMID:21579513

Combustor liner construction

NASA Technical Reports Server (NTRS)

Craig, H. M.; Wagner, W. B.; Strock, W. J. (Inventor)

1983-01-01

A combustor liner is fabricated from a plurality of individual segments each containing counter/parallel Finwall material and are arranged circumferentially and axially to define the combustion zone. Each segment is supported by a hook and ring construction to an opened lattice frame with sufficient tolerance between the hook and ring to permit thermal expansion with a minimum of induced stresses.

CCD centroiding analysis for Nano-JASMINE observation data

NASA Astrophysics Data System (ADS)

Niwa, Yoshito; Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Tazawa, Seiichi; Hanada, Hideo

2010-07-01

Nano-JASMINE is a very small satellite mission for global space astrometry with milli-arcsecond accuracy, which will be launched in 2011. In this mission, centroids of stars in CCD image frames are estimated with sub-pixel accuracy. In order to realize such a high precision centroiding an algorithm utilizing a least square method is employed. One of the advantages is that centroids can be calculated without explicit assumption of the point spread functions of stars. CCD centroiding experiment has been performed to investigate whether this data analysis is available, and centroids of artificial star images on a CCD are determined with a precision of less than 0.001 pixel. This result indicates parallaxes of stars within 300 pc from Sun can be observed in Nano-JASMINE.

The molecular mechanism of fullerene-inhibited aggregation of Alzheimer's β-amyloid peptide fragment

NASA Astrophysics Data System (ADS)

Xie, Luogang; Luo, Yin; Lin, Dongdong; Xi, Wenhui; Yang, Xinju; Wei, Guanghong

2014-07-01

Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of β-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-β (Aβ) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent β-sheet formation of Aβ(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on Aβ(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the β-sheet formation of Aβ(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of β-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and Aβ(16-22) peptides significantly weaken the peptide-peptide interaction that is important for β-sheet formation, thus retarding Aβ(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of Aβ(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease.Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of β-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-β (Aβ) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent β-sheet formation of Aβ(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on Aβ(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the β-sheet formation of Aβ(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of β-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and Aβ(16-22) peptides significantly weaken the peptide-peptide interaction that is important for β-sheet formation, thus retarding Aβ(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of Aβ(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease. Electronic supplementary information (ESI) available: The description of REMD simulations, analysis parameters, and AFM imaging of Aβ(16-22) aggregation with and without C60 nanoparticles, and three figures. The figures show the initial states, the convergence check for all the REMD runs, the PDF of the centroid distance (d) between the aromatic rings of Phe and its closest carbon ring, and the PDF of the angle between the two rings with a centroid distance of d <= 0.65 nm. See DOI: 10.1039/c4nr01005a

Annular ring zoom system using two positive axicons

NASA Astrophysics Data System (ADS)

Dickey, Fred M.; Conner, Jacob D.

2011-10-01

The production of an annular ring of light with a variable diameter has applications in laser material processing and machining, particle manipulation, and corneal surgery. This can readily be accomplished using a positive and negative axicon pair. However, negative axicons are very expensive and difficult to obtain with small diameters. In this paper, we present a design of an annular ring zoom system using two positive axicons. One axicon is placed a distance before a primary lens that is greater than some prescribed minimum, and the second axicon is placed after the primary lens. The position of the second axicon determines the ring diameter. The ring diameter can be zoomed from some maximum design size to a zero diameter ring (spot). Experimental results from a developmental system will be presented.

Bis(N'-{(E)-[(2E)-1,3-di-phenyl-prop-2-en-1-yl-idene]amino}-N-ethyl-carbamimido-thio-ato-κ2N',S)zinc(II): crystal structure and Hirshfeld surface analysis.

PubMed

Tan, Ming Yueh; Crouse, Karen A; Ravoof, Thahira B S A; Jotani, Mukesh M; Tiekink, Edward R T

2017-07-01

The title Zn II complex, [Zn(C 18 H 18 N 3 S) 2 ], (I), features two independent but chemically equivalent mol-ecules in the asymmetric unit. In each, the thio-semicarbazonate monoanion coordinates the Zn II atom via the thiol-ate-S and imine-N atoms, with the resulting N 2 S 2 donor set defining a distorted tetra-hedral geometry. The five-membered ZnSCN 2 chelate rings adopt distinct conformations in each independent mol-ecule, i.e. one ring is almost planar while the other is twisted about the Zn-S bond. In the crystal, the two mol-ecules comprising the asymmetric unit are linked by amine-N-H⋯N(imine) and amine-N-H⋯S(thiol-ate) hydrogen bonds via an eight-membered heterosynthon, {⋯HNCN⋯HNCS}. The dimeric aggregates are further consolidated by benzene-C-H⋯S(thiol-ate) inter-actions and are linked into a zigzag supra-molecular chain along the c axis via amine-N-H⋯S(thiol-ate) hydrogen bonds. The chains are connected into a three-dimensional architecture via phenyl-C-H⋯π(phen-yl) and π-π inter-actions, the latter occurring between chelate and phenyl rings [inter-centroid separation = 3.6873 (11) Å]. The analysis of the Hirshfeld surfaces calculated for (I) emphasizes the different inter-actions formed by the independent mol-ecules in the crystal and the impact of the π-π inter-actions between chelate and phenyl rings.

Crystal structure of 2-((1E)-{2-[bis-(2-methyl-benzyl-sulfan-yl)methyl-idene]hydrazin-1-yl-idene}meth-yl)-6-meth-oxy-phenol.

PubMed

Yusof, Enis Nadia Md; Ravoof, Thahira Begum S A; Tahir, Mohamed Ibrahim Mohamed; Tiekink, Edward R T

2015-04-01

In the title compound, C25H26N2O2S2, the central CN2S2 atoms are almost coplanar (r.m.s. deviation = 0.0058 Å). One phenyl ring clearly lies to one side of the central plane, while the other is oriented in the plane but splayed. Despite the different relative orientations, the phenyl rings form similar dihedral angles of 64.90 (3) and 70.06 (3)° with the central plane, and 63.28 (4)° with each other. The benzene ring is twisted with respect to the central plane, forming a dihedral angle of 13.17 (7)°. The S2C=N, N-N and N-N=C bond lengths of 1.2919 (19), 1.4037 (17) and 1.2892 (19) Å, respectively, suggest limited conjugation over these atoms; the configuration about the N-N=C bond is E. An intra-molecular O-H⋯N hydrogen bond is noted. In the crystal, phen-yl-meth-oxy C-H⋯O and phen-yl-phenyl C-H⋯π inter-actions lead to supra-molecular double chains parallel to the b axis. These are connected into a layer via meth-yl-phenyl C-H⋯π inter-actions, and layers stack along the a axis, being connected by weak π-π inter-actions between phenyl rings [inter-centroid distance = 3.9915 (9) Å] so that a three-dimensional architecture ensues.

Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory.

PubMed

Marsalek, Ondrej; Markland, Thomas E

2016-02-07

Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.

Approximating Matsubara dynamics using the planetary model: Tests on liquid water and ice

NASA Astrophysics Data System (ADS)

Willatt, Michael J.; Ceriotti, Michele; Althorpe, Stuart C.

2018-03-01

Matsubara dynamics is the quantum-Boltzmann-conserving classical dynamics which remains when real-time coherences are taken out of the exact quantum Liouvillian [T. J. H. Hele et al., J. Chem. Phys. 142, 134103 (2015)]; because of a phase-term, it cannot be used as a practical method without further approximation. Recently, Smith et al. [J. Chem. Phys. 142, 244112 (2015)] developed a "planetary" model dynamics which conserves the Feynman-Kleinert (FK) approximation to the quantum-Boltzmann distribution. Here, we show that for moderately anharmonic potentials, the planetary dynamics gives a good approximation to Matsubara trajectories on the FK potential surface by decoupling the centroid trajectory from the locally harmonic Matsubara fluctuations, which reduce to a single phase-less fluctuation particle (the "planet"). We also show that the FK effective frequency can be approximated by a direct integral over these fluctuations, obviating the need to solve iterative equations. This modification, together with use of thermostatted ring-polymer molecular dynamics, allows us to test the planetary model on water (gas-phase, liquid, and ice) using the q-TIP4P/F potential surface. The "planetary" fluctuations give a poor approximation to the rotational/librational bands in the infrared spectrum, but a good approximation to the bend and stretch bands, where the fluctuation lineshape is found to be motionally narrowed by the vibrations of the centroid.

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

Approximating Matsubara dynamics using the planetary model: Tests on liquid water and ice.

PubMed

Willatt, Michael J; Ceriotti, Michele; Althorpe, Stuart C

2018-03-14

Matsubara dynamics is the quantum-Boltzmann-conserving classical dynamics which remains when real-time coherences are taken out of the exact quantum Liouvillian [T. J. H. Hele et al., J. Chem. Phys. 142, 134103 (2015)]; because of a phase-term, it cannot be used as a practical method without further approximation. Recently, Smith et al. [J. Chem. Phys. 142, 244112 (2015)] developed a "planetary" model dynamics which conserves the Feynman-Kleinert (FK) approximation to the quantum-Boltzmann distribution. Here, we show that for moderately anharmonic potentials, the planetary dynamics gives a good approximation to Matsubara trajectories on the FK potential surface by decoupling the centroid trajectory from the locally harmonic Matsubara fluctuations, which reduce to a single phase-less fluctuation particle (the "planet"). We also show that the FK effective frequency can be approximated by a direct integral over these fluctuations, obviating the need to solve iterative equations. This modification, together with use of thermostatted ring-polymer molecular dynamics, allows us to test the planetary model on water (gas-phase, liquid, and ice) using the q-TIP4P/F potential surface. The "planetary" fluctuations give a poor approximation to the rotational/librational bands in the infrared spectrum, but a good approximation to the bend and stretch bands, where the fluctuation lineshape is found to be motionally narrowed by the vibrations of the centroid.

Centroid tracker and aimpoint selection

NASA Astrophysics Data System (ADS)

Venkateswarlu, Ronda; Sujata, K. V.; Venkateswara Rao, B.

1992-11-01

Autonomous fire and forget weapons have gained importance to achieve accurate first pass kill by hitting the target at an appropriate aim point. Centroid of the image presented by a target in the field of view (FOV) of a sensor is generally accepted as the aimpoint for these weapons. Centroid trackers are applicable only when the target image is of significant size in the FOV of the sensor but does not overflow the FOV. But as the range between the sensor and the target decreases the image of the target will grow and finally overflow the FOV at close ranges and the centroid point on the target will keep on changing which is not desirable. And also centroid need not be the most desired/vulnerable point on the target. For hardened targets like tanks, proper aimpoint selection and guidance up to almost zero range is essential to achieve maximum kill probability. This paper presents a centroid tracker realization. As centroid offers a stable tracking point, it can be used as a reference to select the proper aimpoint. The centroid and the desired aimpoint are simultaneously tracked to avoid jamming by flares and also to take care of the problems arising due to image overflow. Thresholding of gray level image to binary image is a crucial step in centroid tracker. Different thresholding algorithms are discussed and a suitable algorithm is chosen. The real-time hardware implementation of centroid tracker with a suitable thresholding technique is presented including the interfacing to a multimode tracker for autonomous target tracking and aimpoint selection. The hardware uses very high speed arithmetic and programmable logic devices to meet the speed requirement and a microprocessor based subsystem for the system control. The tracker has been evaluated in a field environment.

Electronic structure and reactivity of cobalt oxide dimers and their hexacarbonyl complexes: a density functional study.

PubMed

Uzunova, Ellie L; Mikosch, Hans

2012-03-29

The dimers of cobalt oxide (CoO)(2) with cyclic and open bent structure are studied with the B1LYP density functional; the ordering of states is validated by the CCSD(T) method. The D(2h)-symmetry rhombic dioxide Co(2)O(2) with antiferromagnetically ordered electrons on cobalt centers is the global minimum. The cyclic peroxide Co(2)(O(2)) with side-on-bonded dioxygen in (7)B(2) ground state is separated from the global minimum by an energy gap of 3.15 eV. The dioxide is highly reactive as indicated by the high value of proton affinity and chemical reactivity indices. The four-member ring structures are more stable than those with three-member ring or chain configuration. The thermodynamic stability toward dissociation to CoO increases upon carbonylation, whereas proton affinity and reactivity with release of molecular oxygen also increase. The global minimum of Co(2)O(2)(CO)(6) corresponds to a triplet state (3)A" with oxygen atoms shifted above the molecular plane of the rhombic dioxide Co(2)O(2). The SOMO-LUMO gap in the ground-state carbonylated dioxide is wider, compared to the same gap in the bare dicobalt dioxide. The peroxo-isomer Co(2)(O(2))(CO)(6) retains the planar Co(2)(O(2)) ring and is only stable in a high-spin state (7)A". The carbonylated clusters have increased reactivity in both redox and nucleophilic reactions, as a result of the increased electron density in the Co(2)O(2)-ring area.

Adaptive thresholding and dynamic windowing method for automatic centroid detection of digital Shack-Hartmann wavefront sensor.

PubMed

Yin, Xiaoming; Li, Xiang; Zhao, Liping; Fang, Zhongping

2009-11-10

A Shack-Hartmann wavefront sensor (SWHS) splits the incident wavefront into many subsections and transfers the distorted wavefront detection into the centroid measurement. The accuracy of the centroid measurement determines the accuracy of the SWHS. Many methods have been presented to improve the accuracy of the wavefront centroid measurement. However, most of these methods are discussed from the point of view of optics, based on the assumption that the spot intensity of the SHWS has a Gaussian distribution, which is not applicable to the digital SHWS. In this paper, we present a centroid measurement algorithm based on the adaptive thresholding and dynamic windowing method by utilizing image processing techniques for practical application of the digital SHWS in surface profile measurement. The method can detect the centroid of each focal spot precisely and robustly by eliminating the influence of various noises, such as diffraction of the digital SHWS, unevenness and instability of the light source, as well as deviation between the centroid of the focal spot and the center of the detection area. The experimental results demonstrate that the algorithm has better precision, repeatability, and stability compared with other commonly used centroid methods, such as the statistical averaging, thresholding, and windowing algorithms.

Methanol clusters (CH3OH)n: putative global minimum-energy structures from model potentials and dispersion-corrected density functional theory.

PubMed

Kazachenko, Sergey; Bulusu, Satya; Thakkar, Ajit J

2013-06-14

Putative global minima are reported for methanol clusters (CH3OH)n with n ≤ 15. The predictions are based on global optimization of three intermolecular potential energy models followed by local optimization and single-point energy calculations using two variants of dispersion-corrected density functional theory. Recurring structural motifs include folded and/or twisted rings, folded rings with a short branch, and stacked rings. Many of the larger structures are stabilized by weak C-H···O bonds.

Line following using a two camera guidance system for a mobile robot

NASA Astrophysics Data System (ADS)

Samu, Tayib; Kelkar, Nikhal; Perdue, David; Ruthemeyer, Michael A.; Matthews, Bradley O.; Hall, Ernest L.

1996-10-01

Automated unmanned guided vehicles have many potential applications in manufacturing, medicine, space and defense. A mobile robot has been designed for the 1996 Automated Unmanned Vehicle Society competition which was held in Orlando, Florida on July 15, 1996. The competition required the vehicle to follow solid and dashed lines around an approximately 800 ft. path while avoiding obstacles, overcoming terrain changes such as inclines and sand traps, and attempting to maximize speed. The purpose of this paper is to describe the algorithm developed for the line following. The line following algorithm images two windows and locates their centroid and with the knowledge that the points are on the ground plane, a mathematical and geometrical relationship between the image coordinates of the points and their corresponding ground coordinates are established. The angle of the line and minimum distance from the robot centroid are then calculated and used in the steering control. Two cameras are mounted on the robot with a camera on each side. One camera guides the robot and when it loses track of the line on its side, the robot control system automatically switches to the other camera. The test bed system has provided an educational experience for all involved and permits understanding and extending the state of the art in autonomous vehicle design.

Centroid of a Polygon--Three Views.

ERIC Educational Resources Information Center

Shilgalis, Thomas W.; Benson, Carol T.

2001-01-01

Investigates the idea of the center of mass of a polygon and illustrates centroids of polygons. Connects physics, mathematics, and technology to produces results that serve to generalize the notion of centroid to polygons other than triangles. (KHR)

Adjusting resonant wavelengths and spectral shapes of ring resonators using a cladding SiN layer or KOH solution.

PubMed

Park, Sahnggi; Kim, Kap-Joong; Lee, Jong-Moo; Kim, In-Gyoo; Kim, Gyungock

2009-07-06

It is shown that the resonant frequencies and the transmission spectra of ring resonators can be adjusted by depositing or etching the cladding nitride layer on the ring waveguide without introducing an extra loss or extra variations of channel spacing. The cladding nitride layer increases the minimum width of the gap in the coupling region to larger than 150nm which makes it possible to consider photolithography instead of E-beam lithography for the typical design rule of ring filters. KOH silicon etching can also adjust not only the resonance frequencies but also coupling coefficients with a small sacrifice of guiding loss.

Comparison of performance of some common Hartmann-Shack centroid estimation methods

NASA Astrophysics Data System (ADS)

Thatiparthi, C.; Ommani, A.; Burman, R.; Thapa, D.; Hutchings, N.; Lakshminarayanan, V.

2016-03-01

The accuracy of the estimation of optical aberrations by measuring the distorted wave front using a Hartmann-Shack wave front sensor (HSWS) is mainly dependent upon the measurement accuracy of the centroid of the focal spot. The most commonly used methods for centroid estimation such as the brightest spot centroid; first moment centroid; weighted center of gravity and intensity weighted center of gravity, are generally applied on the entire individual sub-apertures of the lens let array. However, these processes of centroid estimation are sensitive to the influence of reflections, scattered light, and noise; especially in the case where the signal spot area is smaller compared to the whole sub-aperture area. In this paper, we give a comparison of performance of the commonly used centroiding methods on estimation of optical aberrations, with and without the use of some pre-processing steps (thresholding, Gaussian smoothing and adaptive windowing). As an example we use the aberrations of the human eye model. This is done using the raw data collected from a custom made ophthalmic aberrometer and a model eye to emulate myopic and hyper-metropic defocus values up to 2 Diopters. We show that the use of any simple centroiding algorithm is sufficient in the case of ophthalmic applications for estimating aberrations within the typical clinically acceptable limits of a quarter Diopter margins, when certain pre-processing steps to reduce the impact of external factors are used.

Magnetic levitation of condensed hydrogen

NASA Technical Reports Server (NTRS)

Paine, C. G.; Seidel, G. M.

1991-01-01

Liquid and solid molecular hydrogen has been levitated using a pair of small superconducting solenoids. The hydrogen samples, up to 3 mm in dimension, were trapped in a magnetic potential having either a discrete minimum or a minimum in the form of a ring 1 cm in diameter. The hydrogen could be moved about in the magnetic trap by applying an electric field.

Antibacterial, antifungal and cytotoxic evaluation of some new quinazolinone derivatives

PubMed Central

Hassanzadeh, F.; Jafari, E.; Hakimelahi, G.H.; Khajouei, M. Rahmani; Jalali, M.; Khodarahmi, G.A.

2012-01-01

Quinazolinone ring system is renown because of its wide spectrum of pharmacological activities due to various substitutions on this ring system. In this study, the minimum inhibitory concentration of the synthesized compounds in our laboratory was determined by micro dilution Alamar Blue® Assay against six strains of bacteria (three Gram-positive and three Gram-negative) and three strains of fungi. Following a broth micro dilution minimum inhibitory concentration (MIC) test, Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC) tests were performed. Cytotoxic effects of the compounds were measured using the MTT colorimetric assay on HeLa cell line. Results of antimicrobial screening showed that compounds had better bacteriostatic activity against Gram-negative bacteria. Results from MBC revealed that these compounds had more significant bacteriostatic than bactericidal activities. Nearly all screened compounds showed good activity against C. albicans and A. niger. Results from MFC indicated that these compounds had better fungistatic rather than fungicidal activities. The synthesized target molecules were found to exhibit different cytotoxicity in the range of 10 to 100 μM on HeLa cell line. Compounds 6 and 7 exhibited acceptable cytotoxicity approximately 50% at 10 μM concentration. PMID:23181085

Minimal size of coffee ring structure.

PubMed

Shen, Xiaoying; Ho, Chih-Ming; Wong, Tak-Sing

2010-04-29

A macroscopic evaporating water droplet with suspended particles on a solid surface will form a ring-like structure at the pinned contact line due to induced capillary flow. As the droplet size shrinks, the competition between the time scales of the liquid evaporation and the particle movement may influence the resulting ring formation. When the liquid evaporates much faster than the particle movement, coffee ring formation may cease. Here, we experimentally show that there exists a lower limit of droplet size, D(c), for the successful formation of a coffee ring structure. When the particle concentration is above a threshold value, D(c) can be estimated by considering the collective effects of the liquid evaporation and the particle diffusive motion within the droplet. For suspended particles of size approximately 100 nm, the minimum diameter of the coffee ring structure is found to be approximately 10 microm.

Crystal structure of (E)-4-hy-droxy-N'-(3-meth-oxy-benzyl-idene)benzohydrazide.

PubMed

Chantrapromma, Suchada; Prachumrat, Patcharawadee; Ruanwas, Pumsak; Boonnak, Nawong; Kassim, Mohammad B

2016-09-01

The title compound, C 15 H 14 N 2 O 3 , crystallizes with two independent mol-ecules ( A and B ) in the asymmetric unit that differ in the orientation of the 3-meth-oxy-phenyl group with respect to the methyl-idenebenzohydrazide unit. The dihedral angles between the two benzene rings are 24.02 (10) and 29.30 (9)° in mol-ecules A and B , respectively. In mol-ecule A , the meth-oxy group is twisted slightly relative to its bound benzene ring, with a C meth-yl -O-C-C torsion angle of 14.2 (3)°, whereas it is almost co-planar in mol-ecule B , where the corresponding angle is -2.4 (3)°. In the crystal, the mol-ecules are linked by N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds, as well as by weak C-H⋯O inter-actions, forming sheets parallel to the bc plane. The N-H⋯O hydrogen bond and weak C-H⋯O inter-action link different mol-ecules ( A ⋯ B ) whereas both O-H⋯N and O-H⋯O hydrogen bonds link like mol-ecules ( A ⋯ A ) and ( B ⋯ B ). Pairs of inversion-related B mol-ecules are stacked approximately along the a axis by π-π inter-actions in which the distance between the centroids of the 3-meth-oxy-phenyl rings is 3.5388 (12) Å. The B mol-ecules also participate in weak C-H⋯π inter-actions between the 4-hy-droxy-phenyl and the 3-meth-oxy-phenyl rings.

Crystal structure of 2-((1E)-{2-[bis­(2-methyl­benzyl­sulfan­yl)methyl­idene]hydrazin-1-yl­idene}meth­yl)-6-meth­oxy­phenol

PubMed Central

Yusof, Enis Nadia Md; Ravoof, Thahira Begum S. A.; Tahir, Mohamed Ibrahim Mohamed; Tiekink, Edward R. T.

2015-01-01

In the title compound, C25H26N2O2S2, the central CN2S2 atoms are almost coplanar (r.m.s. deviation = 0.0058 Å). One phenyl ring clearly lies to one side of the central plane, while the other is oriented in the plane but splayed. Despite the different relative orientations, the phenyl rings form similar dihedral angles of 64.90 (3) and 70.06 (3)° with the central plane, and 63.28 (4)° with each other. The benzene ring is twisted with respect to the central plane, forming a dihedral angle of 13.17 (7)°. The S2C=N, N—N and N—N=C bond lengths of 1.2919 (19), 1.4037 (17) and 1.2892 (19) Å, respectively, suggest limited conjugation over these atoms; the configuration about the N—N=C bond is E. An intra­molecular O—H⋯N hydrogen bond is noted. In the crystal, phen­yl–meth­oxy C—H⋯O and phen­yl–phenyl C—H⋯π inter­actions lead to supra­molecular double chains parallel to the b axis. These are connected into a layer via meth­yl–phenyl C—H⋯π inter­actions, and layers stack along the a axis, being connected by weak π–π inter­actions between phenyl rings [inter-centroid distance = 3.9915 (9) Å] so that a three-dimensional architecture ensues. PMID:26029435

Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory

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

Marsalek, Ondrej; Markland, Thomas E., E-mail: tmarkland@stanford.edu

Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding asmore » a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.« less

A Herschel-Resolved Debris Disk Around the Nearby G Star HIP 32480

NASA Technical Reports Server (NTRS)

Stapelfeldt, K.

2011-01-01

The Herschel Space Observatory is providing unprecedented sensitivity and angular resolution in the far-infrared. The DUNES Key Project (DUst around NEarby Stars, PI Carlos Eiroa) has finished its survey of 133 FGK stars within 25 pc of the Sun using the PACS photometer at 100 and 160 microns. We report the detection of a resolved debris ring around HIP 32480, a G0 star 16.5 parsecs distant. The ring is almost 300 AU in diameter and inclined 30 degrees from edge-on. We present a thermal emission model for the system that fits the Spitzer spectroscopy and Herschel images of the system. We find a minimum grainsize of approximately 4 microns in the main ring and a distinct warm dust population interior to it. Faint detached emission features just outside the ring may trace a separate, more distant ring in the system. The non-detection of the ring in archival HST/ACS coronagraphic images limits the dust grain albedo in the ring to be no more than 10%.

A Resolved Debris Disk Around the Nearby G Star HIP 32480

NASA Technical Reports Server (NTRS)

Stapelfeldt, K. R.; Bryden, G. C.; Marshall, J.; Eiroa, C.; Absil, O.; Mora, A.; Krist, J. E.; Su, K. Y. L.

2012-01-01

The Herschel Space Observatory is providing unprecedented sensitivity and angular resolution in the far-infrared. The DUNES Key Project (DUst around NEarby Stars, PI Carlos Eiroa) has finished its survey of 133 FGK stars within 25 pc of the Sun using the PACS photometer at 100 and 160 microns. We report the detection of a resolved debris ring around HIP 32480, a GO star 16.5 parsecs distant. The ring is almost 300 AU in diameter and inclined 30 degrees from edge-on. We present a thermal emission model for the system that fits the Spitzer spectroscopy and Herschel images of the system. We find a minimum grain-size of 4 microns in the main ring and a distinct warm dust population interior to it. Faint detached emission features just outside the ring may trace a separate, more distant ring in the system. The non-detection of the ring in archival HST/ACS coronagraphic images limits the dust grain albedo in the ring to be no more than 10%.

A PET Design Based on SiPM and Monolithic LYSO Crystals: Performance Evaluation

NASA Astrophysics Data System (ADS)

González, Antonio J.; Aguilar, Albert; Conde, Pablo; Hernández, Liczandro; Moliner, Laura; Vidal, Luis F.; Sánchez, Filomeno; Sánchez, Sebastián; Correcher, Carlos; Molinos, César; Barberá, Julio; Lankes, Konrad; Junge, Sven; Bruckbauer, Thomas; Bruyndonckx, Peter; Benlloch, Jose M.

2016-10-01

A new small animal PET based on SiPM and monolithic LYSO crystals has been developed. Eight detector modules form the PET ring, each mounting an array of 12 × 12 SiPMs coupled to a readout providing the summed signals of the pixels on each of the 12 rows and 12 columns of the SiPM array. This design makes it possible to accurately determine the centroid of the scintillation light distribution with about 1.6 mm full width at half maximum (FWHM) resolution without correction for the 1 mm source size, and the photon depth of interaction (DOI) with nearly 2 mm FWHM. This single ring PET system has a homogeneous spatial resolution across the entire 80 mm transaxial field of view (FOV) of about 1 mm FWHM. The noise equivalent count rate (NECR) peak is estimated to occur at around 39.2 MBq with a rate of approximately 82.7 kcps for the mouse-like phantom and 22 kcps at 48.1 MBq for the rat-like phantom. Following the NEMA protocol, the peak absolute sensitivity in the center of the FOV is 2.8% for a 30% peak energy window. A pilot test injecting NaF to a mouse of 20 grams is also presented. Finally, the PET ring has been tested in front of a high field 15.2 T Magnetic Resonance (MR). No significant variation on energy and spatial resolution across the FOV has been observed due to the presence of the magnetic field.

Binding of Alkali Metal Ions with 1,3,5-Tri(phenyl)benzene and 1,3,5-Tri(naphthyl)benzene: The Effect of Phenyl and Naphthyl Ring Substitution on Cation-π Interactions Revealed by DFT Study.

PubMed

Mirchi, Ali; Sizochenko, Natalia; Dinadayalane, Tandabany; Leszczynski, Jerzy

2017-11-22

The effect of substitution of phenyl and naphthyl rings to benzene was examined to elucidate the cation-π interactions involving alkali metal ions with 1,3,5-tri(phenyl)benzene (TPB) and 1,3,5-tri(naphthyl)benzene (TNB). Benzene, TPB, and four TNB isomers (with ααα, ααβ, αββ, and βββ types of fusion) and their complexes with Li + , Na + , K + , Rb + , and Cs + were optimized using DFT approach with B3LYP and M06-2X functionals in conjunction with the def2-QZVP basis set. Higher relative stability of β,β,β-TNB over α,α,α-TNB can be attributed to peri repulsion, which is defined as the nonbonding repulsive interaction between substituents in the 1- and the 8-positions on the naphthalene core. Binding energies, distances between ring centroid and the metal ions, and the distance to metal ions from the center of other six-membered rings were compared for all complexes. Our computational study reveals that the binding affinity of alkali metal cations increases significantly with the 1,3,5-trisubstitution of phenyl and naphthyl rings to benzene. The detailed computational analyses of geometries, partial charges, binding energies, and ligand organization energies reveal the possibility of favorable C-H···M + interactions when a α-naphthyl group exists in complexes of TNB structures. Like benzene-alkali metal ion complexes, the binding affinity of metal ions follows the order: Li + > Na + > K + > Rb + > Cs + for any considered 1,3,5-trisubstituted benzene systems. In case of TNB, we found that the strength of interactions increases as the fusion point changes from α to β position of naphthalene.

Interannual variability of ring formations in the Gulf Stream region

NASA Astrophysics Data System (ADS)

Sasaki, Y. N.

2016-02-01

An oceanic ring in the Gulf Stream (GS) region plays important roles in across-jet transport of heat, salt, momentum, and nutrients. This study examines interannual variability of rings shed from the GS jet and their properties using satellite altimeter observations from 1993 to 2013. An objective method is used to capture a ring shedding from the GS jet and track its movement. A spatial distribution of the ring formations in the GS region showed that both cyclonic (cold-core) and anticyclonic (warm-core) rings were most frequently formed around the New England Seamount chain between 62°-65°W, suggesting the importance of the bottom topography on the pinch-off process. These rings moved westward, although about two-third of these rings was reabsorbed by the GS jet. The number of ring formations, especially cyclonic ring formations, indicated prominent fluctuations on interannual to decadal timescales. The annual maximum number of the pinched-off rings is four times larger than the annual minimum number of the rings. These fluctuations of the ring formations were negatively correlated with the strength of the GS. This situation is similar that in the Kuroshio Extension region. The interannual variability of the number of ring formations is also negatively correlated with the North Atlantic Oscillation (NAO) index with one-year lag (NAO leads). Interannual variations of the propagation tendency and shape of rings are also discussed.

Expected and unexpected products of reactions of 2-hydrazinylbenzo-thia-zole with 3-nitro-benzene-sulfonyl chloride in different solvents.

PubMed

Morscher, Alexandra; de Souza, Marcus V N; Wardell, James L; Harrison, William T A

2018-05-01

The syntheses and crystal structures of 2-[2-(propan-2-yl-idene)hydrazin-yl]-1,3-benzo-thia-zol-3-ium 3-nitro-benzene-sulfonate (C 10 H 12 N 2 S + ·C 6 H 4 NO 5 S - ), (I), 2-[2-(3-nitro-benzene-sulfon-yl)hydrazin-yl]-1,3-benzo-thia-zole (C 13 H 10 N 4 O 4 S 2 ), (II) and 2-[2-(3-nitro-benzene-sulfon-yl)hydrazin-yl]-1,3-benzo-thia-zol-3-ium 3-nitro-benzene-sulfonate (C 13 H 11 N 4 O 4 S 2 + ·C 6 H 4 NO 5 S - ), (III) are reported. Salt (I) arose from an unexpected reaction of 2-hydrazinylbenzo-thia-zole with the acetone solvent in the presence of 3-nitro-benzene-sulfonyl chloride, whereas (II) and (III) were recovered from the equivalent reaction carried out in methanol. The crystal of (I) features ion pairs linked by pairs of N-H⋯O s (s = sulfonate) hydrogen bonds; adjacent cations inter-act by way of short π-π stacking inter-actions between the thia-zole rings [centroid-centroid separation = 3.4274 (18) Å]. In (II), which crystallizes with two neutral mol-ecules in the asymmetric unit, the mol-ecules are linked by N-H⋯N and N-H⋯O n (n = nitro) hydrogen bonds to generate [[Formula: see text]1[Formula: see text

Hot piston ring tests

NASA Technical Reports Server (NTRS)

Allen, David J.; Tomazic, William A.

1987-01-01

As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used. Unlike the conventional rings at the bottom of the piston, these hot rings operated in a high temperature environment (700 C). They were made of a high temperature alloy (Stellite 6B) and a high temperature solid lubricant coating (NASA Lewis-developed PS-200) was applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with hot rings and without to provide a baseline for comparison. Minimum data to assess the potential of both the hot rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency, an increase over and above the friction loss introduced by the hot rings. Seal leakage measurements showed a significant reduction. Wear on both rings and coating was low.

Trophic diversity in the evolution and community assembly of loricariid catfishes

PubMed Central

2012-01-01

Background The Neotropical catfish family Loricariidae contains over 830 species that display extraordinary variation in jaw morphologies but nonetheless reveal little interspecific variation from a generalized diet of detritus and algae. To investigate this paradox, we collected δ13C and δ15N stable isotope signatures from 649 specimens representing 32 loricariid genera and 82 species from 19 local assemblages distributed across South America. We calculated vectors representing the distance and direction of each specimen relative to the δ15N/δ13C centroid for its local assemblage, and then examined the evolutionary diversification of loricariids across assemblage isotope niche space by regressing the mean vector for each genus in each assemblage onto a phylogeny reconstructed from osteological characters. Results Loricariids displayed a total range of δ15N assemblage centroid deviation spanning 4.9‰, which is within the tissue–diet discrimination range known for Loricariidae, indicating that they feed at a similar trophic level and that δ15N largely reflects differences in their dietary protein content. Total range of δ13C deviation spanned 7.4‰, which is less than the minimum range reported for neotropical river fish communities, suggesting that loricariids selectively assimilate a restricted subset of the full basal resource spectrum available to fishes. Phylogenetic regression of assemblage centroid-standardized vectors for δ15N and δ13C revealed that loricariid genera with allopatric distributions in disjunct river basins partition basal resources in an evolutionarily conserved manner concordant with patterns of jaw morphological specialization and with evolutionary diversification via ecological radiation. Conclusions Trophic partitioning along elemental/nutritional gradients may provide an important mechanism of dietary segregation and evolutionary diversification among loricariids and perhaps other taxonomic groups of apparently generalist detritivores and herbivores. Evolutionary patterns among the Loricariidae show a high degree of trophic niche conservatism, indicating that evolutionary lineage affiliation can be a strong predictor of how basal consumers segregate trophic niche space. PMID:22835218

Stirling cycle engine

DOEpatents

Lundholm, Gunnar

1983-01-01

In a Stirling cycle engine having a plurality of working gas charges separated by pistons reciprocating in cylinders, the total gas content is minimized and the mean pressure equalization among the serial cylinders is improved by using two piston rings axially spaced at least as much as the piston stroke and by providing a duct in the cylinder wall opening in the space between the two piston rings and leading to a source of minimum or maximum working gas pressure.

Sizes of the Smallest Particles at Saturn Ring Edges from Diffraction in UVIS Stellar Occultations

NASA Astrophysics Data System (ADS)

Eckert, S.; Colwell, J. E.; Becker, T. M.; Esposito, L. W.

2017-12-01

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has observed more than 150 ring stellar occultations since its arrival at Saturn in 2004. We use stellar occultation data from the UVIS High Speed Photometer (HSP) to identify diffraction signals at ring edges caused by small particles diffracting light into the detector and consequently increasing the signal above that of the unocculted star. The shape of a diffraction signal is indicative of the particle size distribution at the ring edge, which may be a dynamically perturbed region. Becker et al. (2015 Icarus doi:10.1016/j.icarus.2015.11.001) analyzed diffraction signals at the outer edge of the A Ring and the edges of the Encke Gap. We apply the Becker et al. (2015) model to the outer edge of the B Ring as well as the edges of ringlets within the C Ring and Cassini Division. In addition, we analyze diffraction signatures at the A Ring outer edge in 2 new occultations. The best-fit model signals to these occultations are consistent with the findings of Becker et al. (2015) who found an average minimum particle size amin =4.5 mm and average power law slope q=3.2. At the B Ring outer edge, we detect a diffraction signal in 10 of 28 occultations in which the diffraction signal would be observable according to our criteria for star brightness and observation geometry. We find a mean amin =11 mm and a mean q=3.0. At both edges of the so-called "Strange" ringlet (R6) we find a mean amin = 20 mm and mean q values of 3.0 and 2.8 at the inner and outer edges, respectively. In contrast, we do not observe any clear diffraction signals at either edge of the wider Huygens ringlet. This could imply an absence of cm-scale or smaller particles and indicates that collisions here may be less vigorous than at the other ring edges analyzed in this study. We detect diffraction in a small fraction ( 10%) of occultations at 3 ringlets within the Cassini Division: the Herschel ringlet, the Laplace ringlet, and the Barnard ringlet. We also found diffraction signals in only 2 of 30 occultations of the Maxwell ringlet in the C Ring. These ringlet diffraction signals, when present, indicate larger minimum particle sizes than seen in the outer A Ring and B ring edge.

Crystal structure of 10-ethyl-7-(9-ethyl-9H-carbazol-3-yl)-10H-pheno-thia-zine-3-carbaldehyde.

PubMed

Mahalakshmi, Vairavan; Gouthaman, Siddan; Sugunalakshmi, Madurai; Bargavi, Srinivasan; Lakshmi, Srinivasakannan

2017-05-01

The title compound, C 29 H 24 N 2 OS, contains a pheno-thia-zine moiety linked to a planar carbazole unit (r.m.s. deviation = 0.029 Å) by a C-C single bond. The pheno-thia-zine moiety possesses a typical non-planar butterfly structure with a fold angle of 27.36 (9)° between the two benzene rings. The dihedral angle between the mean planes of the carbazole and pheno-thia-zine units is 27.28 (5)°. In the crystal, mol-ecules stack in pairs along the c -axis direction, linked by offset π-π inter-actions [inter-centroid distance = 3.797 (1) Å]. There are C-H⋯π inter-actions present linking these dimers to form a three-dimensional structure.

Fiber Bragg grating sensor interrogators on chip: challenges and opportunities

NASA Astrophysics Data System (ADS)

Marin, Yisbel; Nannipieri, Tiziano; Oton, Claudio J.; Di Pasquale, Fabrizio

2017-04-01

In this paper we present an overview of the current efforts towards integration of Fiber Bragg Grating (FBG) sensor interrogators. Different photonic integration platforms will be discussed, including monolithic planar lightwave circuit technology, silicon on insulator (SOI), indium phosphide (InP) and gallium arsenide (GaAs) material platforms. Also various possible techniques for wavelength metering and methods for FBG multiplexing will be discussed and compared in terms of resolution, dynamic performance, multiplexing capabilities and reliability. The use of linear filters, array waveguide gratings (AWG) as multiple linear filters and AWG based centroid signal processing techniques will be addressed as well as interrogation techniques based on tunable micro-ring resonators and Mach-Zehnder interferometers (MZI) for phase sensitive detection. The paper will also discuss the challenges and perspectives of photonic integration to address the increasing requirements of several industrial applications.

(E)-1,2-Bis(4-methyl­phen­yl)ethane-1,2-dione

PubMed Central

Fun, Hoong-Kun; Kia, Reza

2008-01-01

In the mol­ecule of the title compound, C16H14O2, a substituted benzil, the dicarbonyl unit has an s-trans conformation. This conformation is substanti­ated by the O—C—C—O torsion angle of 108.16 (15)°. The dihedral angle between the two aromatic rings is 72.00 (6)°. In the crystal structure, neighbouring mol­ecules are linked together by weak inter­molecular C—H⋯O hydrogen bonds and weak inter­molecular C—H⋯π inter­actions. In addition, the crystal structure is further stabilized by inter­molecular π–π inter­actions with centroid–centroid distances in the range 3.6000 (8)–3.8341 (8) Å. PMID:21203307

Reliability of an experimental method to analyse the impact point on a golf ball during putting.

PubMed

Richardson, Ashley K; Mitchell, Andrew C S; Hughes, Gerwyn

2015-06-01

This study aimed to examine the reliability of an experimental method identifying the location of the impact point on a golf ball during putting. Forty trials were completed using a mechanical putting robot set to reproduce a putt of 3.2 m, with four different putter-ball combinations. After locating the centre of the dimple pattern (centroid) the following variables were tested; distance of the impact point from the centroid, angle of the impact point from the centroid and distance of the impact point from the centroid derived from the X, Y coordinates. Good to excellent reliability was demonstrated in all impact variables reflected in very strong relative (ICC = 0.98-1.00) and absolute reliability (SEM% = 0.9-4.3%). The highest SEM% observed was 7% for the angle of the impact point from the centroid. In conclusion, the experimental method was shown to be reliable at locating the centroid location of a golf ball, therefore allowing for the identification of the point of impact with the putter head and is suitable for use in subsequent studies.

Correcting the beam centroid motion in an induction accelerator and reducing the beam breakup instability

NASA Astrophysics Data System (ADS)

Coleman, J. E.; Ekdahl, C. A.; Moir, D. C.; Sullivan, G. W.; Crawford, M. T.

2014-09-01

Axial beam centroid and beam breakup (BBU) measurements were conducted on an 80 ns FWHM, intense relativistic electron bunch with an injected energy of 3.8 MV and current of 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the coupling of the beam centroid motion to the BBU instability and validate the theory of this coupling for the first time. Time resolved centroid measurements indicate a reduction in the BBU amplitude, ⟨ξ⟩, of 19% and a reduction in the BBU growth rate (Γ) of 4% by reducing beam centroid misalignments ˜50% throughout the accelerator. An investigation into the contribution of the misaligned elements is made. An alignment algorithm is presented in addition to a qualitative comparison of experimental and calculated results which include axial beam centroid oscillations, BBU amplitude, and growth with different dipole steering.

Performance Analysis of Combined Methods of Genetic Algorithm and K-Means Clustering in Determining the Value of Centroid

NASA Astrophysics Data System (ADS)

Adya Zizwan, Putra; Zarlis, Muhammad; Budhiarti Nababan, Erna

2017-12-01

The determination of Centroid on K-Means Algorithm directly affects the quality of the clustering results. Determination of centroid by using random numbers has many weaknesses. The GenClust algorithm that combines the use of Genetic Algorithms and K-Means uses a genetic algorithm to determine the centroid of each cluster. The use of the GenClust algorithm uses 50% chromosomes obtained through deterministic calculations and 50% is obtained from the generation of random numbers. This study will modify the use of the GenClust algorithm in which the chromosomes used are 100% obtained through deterministic calculations. The results of this study resulted in performance comparisons expressed in Mean Square Error influenced by centroid determination on K-Means method by using GenClust method, modified GenClust method and also classic K-Means.

Modern Optimization Methods in Minimum Weight Design of Elastic Annular Rotating Disk with Variable Thickness

NASA Astrophysics Data System (ADS)

Jafari, S.; Hojjati, M. H.

2011-12-01

Rotating disks work mostly at high angular velocity and this results a large centrifugal force and consequently induce large stresses and deformations. Minimizing weight of such disks yields to benefits such as low dead weights and lower costs. This paper aims at finding an optimal disk thickness profile for minimum weight design using the simulated annealing (SA) and particle swarm optimization (PSO) as two modern optimization techniques. In using semi-analytical the radial domain of the disk is divided into some virtual sub-domains as rings where the weight of each rings must be minimized. Inequality constrain equation used in optimization is to make sure that maximum von Mises stress is always less than yielding strength of the material of the disk and rotating disk does not fail. The results show that the minimum weight obtained for all two methods is almost identical. The PSO method gives a profile with slightly less weight (6.9% less than SA) while the implementation of both PSO and SA methods are easy and provide more flexibility compared with classical methods.

Variable diameter CO₂ laser ring-cutting system adapted to a zoom microscope for applications on polymer tapes.

PubMed

Förster, Erik; Bohnert, Patrick; Kraus, Matthias; Kilper, Roland; Müller, Ute; Buchmann, Martin; Brunner, Robert

2016-11-20

This paper presents the conception and implementation of a variable diameter ring-cutting system for a CO₂ laser with a working wavelength of 10.6 μm. The laser-cutting system is adapted to an observation zoom microscope for combined use and is applicable for the extraction of small circular areas from polymer films, such as forensic adhesive tapes in a single shot. As an important characteristic for our application, the variable diameter ring-cutting system provides telecentricity in the target area. Ring diameters are continuously tunable between 500 μm and 2 mm. A minimum width of less than 20 μm was found for the ring profile edge. The basic characteristics of the system, including telecentricity, were experimentally evaluated and demonstrated by cutting experiments on different polymer tapes and further exemplary samples.

A focal plane metrology system and PSF centroiding experiment

NASA Astrophysics Data System (ADS)

Li, Haitao; Li, Baoquan; Cao, Yang; Li, Ligang

2016-10-01

In this paper, we present an overview of a detector array equipment metrology testbed and a micro-pixel centroiding experiment currently under development at the National Space Science Center, Chinese Academy of Sciences. We discuss on-going development efforts aimed at calibrating the intra-/inter-pixel quantum efficiency and pixel positions for scientific grade CMOS detector, and review significant progress in achieving higher precision differential centroiding for pseudo star images in large area back-illuminated CMOS detector. Without calibration of pixel positions and intrapixel response, we have demonstrated that the standard deviation of differential centroiding is below 2.0e-3 pixels.

High-speed on-chip windowed centroiding using photodiode-based CMOS imager

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor); Sun, Chao (Inventor); Yang, Guang (Inventor); Cunningham, Thomas J. (Inventor); Hancock, Bruce (Inventor)

2003-01-01

A centroid computation system is disclosed. The system has an imager array, a switching network, computation elements, and a divider circuit. The imager array has columns and rows of pixels. The switching network is adapted to receive pixel signals from the image array. The plurality of computation elements operates to compute inner products for at least x and y centroids. The plurality of computation elements has only passive elements to provide inner products of pixel signals the switching network. The divider circuit is adapted to receive the inner products and compute the x and y centroids.

High-speed on-chip windowed centroiding using photodiode-based CMOS imager

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor); Sun, Chao (Inventor); Yang, Guang (Inventor); Cunningham, Thomas J. (Inventor); Hancock, Bruce (Inventor)

2004-01-01

A centroid computation system is disclosed. The system has an imager array, a switching network, computation elements, and a divider circuit. The imager array has columns and rows of pixels. The switching network is adapted to receive pixel signals from the image array. The plurality of computation elements operates to compute inner products for at least x and y centroids. The plurality of computation elements has only passive elements to provide inner products of pixel signals the switching network. The divider circuit is adapted to receive the inner products and compute the x and y centroids.

A Self-Adaptive Fuzzy c-Means Algorithm for Determining the Optimal Number of Clusters

PubMed Central

Wang, Zhihao; Yi, Jing

2016-01-01

For the shortcoming of fuzzy c-means algorithm (FCM) needing to know the number of clusters in advance, this paper proposed a new self-adaptive method to determine the optimal number of clusters. Firstly, a density-based algorithm was put forward. The algorithm, according to the characteristics of the dataset, automatically determined the possible maximum number of clusters instead of using the empirical rule n and obtained the optimal initial cluster centroids, improving the limitation of FCM that randomly selected cluster centroids lead the convergence result to the local minimum. Secondly, this paper, by introducing a penalty function, proposed a new fuzzy clustering validity index based on fuzzy compactness and separation, which ensured that when the number of clusters verged on that of objects in the dataset, the value of clustering validity index did not monotonically decrease and was close to zero, so that the optimal number of clusters lost robustness and decision function. Then, based on these studies, a self-adaptive FCM algorithm was put forward to estimate the optimal number of clusters by the iterative trial-and-error process. At last, experiments were done on the UCI, KDD Cup 1999, and synthetic datasets, which showed that the method not only effectively determined the optimal number of clusters, but also reduced the iteration of FCM with the stable clustering result. PMID:28042291

Coupled low-energy - ring current plasma diffusion in the Jovian magnetosphere

NASA Technical Reports Server (NTRS)

Summers, D.; Siscoe, G. L.

1985-01-01

The outwardly diffusing Iogenic plasma and the simultaneously inwardly diffusing ring current plasma in the Jovian magnetosphere are described using a coupled diffusion model which incorporates the effects of the pressure gradient of the ring current into the cross-L diffusion coefficient. The coupled diffusion coefficient is derived by calculating the total energy available to drive the diffusion process. The condition is imposed that the diffusion coefficient takes on a local minimum value at some point in the region L = 7-8, at which point the gradient of the Io plasma density is specified as ramp value given by Siscoe et al. (1981). The hypothesis that the pressure gradient of the ring current causes the diminution of radial plasma transport is tested, and solution profiles for the Iogenic and ring current plasma densities are obtained which imply that the Io plasma ramp is caused by a high-density, low-energy component of the ring current hitherto unobserved directly.

On the Buckling of Imperfect Anisotropic Shells with Elastic Edge Supports Under Combined Loading Part I:. Pt. 1; Theory and Numerical Analysis

NASA Technical Reports Server (NTRS)

Arbocz, Johann; Hol, J. M. A. M.; deVries, J.

1998-01-01

A rigorous solution is presented for the case of stiffened anisotropic cylindrical shells with general imperfections under combined loading, where the edge supports are provided by symmetrical or unsymmetrical elastic rings. The circumferential dependence is eliminated by a truncated Fourier series. The resulting nonlinear 2-point boundary value problem is solved numerically via the "Parallel Shooting Method". The changing deformation patterns resulting from the different degrees of interaction between the given initial imperfections and the specified end rings are displayed. Recommendations are made as to the minimum ring stiffnesses required for optimal load carrying configurations.

Formulation of state projected centroid molecular dynamics: Microcanonical ensemble and connection to the Wigner distribution.

PubMed

Orr, Lindsay; Hernández de la Peña, Lisandro; Roy, Pierre-Nicholas

2017-06-07

A derivation of quantum statistical mechanics based on the concept of a Feynman path centroid is presented for the case of generalized density operators using the projected density operator formalism of Blinov and Roy [J. Chem. Phys. 115, 7822-7831 (2001)]. The resulting centroid densities, centroid symbols, and centroid correlation functions are formulated and analyzed in the context of the canonical equilibrium picture of Jang and Voth [J. Chem. Phys. 111, 2357-2370 (1999)]. The case where the density operator projects onto a particular energy eigenstate of the system is discussed, and it is shown that one can extract microcanonical dynamical information from double Kubo transformed correlation functions. It is also shown that the proposed projection operator approach can be used to formally connect the centroid and Wigner phase-space distributions in the zero reciprocal temperature β limit. A Centroid Molecular Dynamics (CMD) approximation to the state-projected exact quantum dynamics is proposed and proven to be exact in the harmonic limit. The state projected CMD method is also tested numerically for a quartic oscillator and a double-well potential and found to be more accurate than canonical CMD. In the case of a ground state projection, this method can resolve tunnelling splittings of the double well problem in the higher barrier regime where canonical CMD fails. Finally, the state-projected CMD framework is cast in a path integral form.

Formulation of state projected centroid molecular dynamics: Microcanonical ensemble and connection to the Wigner distribution

NASA Astrophysics Data System (ADS)

Orr, Lindsay; Hernández de la Peña, Lisandro; Roy, Pierre-Nicholas

2017-06-01

A derivation of quantum statistical mechanics based on the concept of a Feynman path centroid is presented for the case of generalized density operators using the projected density operator formalism of Blinov and Roy [J. Chem. Phys. 115, 7822-7831 (2001)]. The resulting centroid densities, centroid symbols, and centroid correlation functions are formulated and analyzed in the context of the canonical equilibrium picture of Jang and Voth [J. Chem. Phys. 111, 2357-2370 (1999)]. The case where the density operator projects onto a particular energy eigenstate of the system is discussed, and it is shown that one can extract microcanonical dynamical information from double Kubo transformed correlation functions. It is also shown that the proposed projection operator approach can be used to formally connect the centroid and Wigner phase-space distributions in the zero reciprocal temperature β limit. A Centroid Molecular Dynamics (CMD) approximation to the state-projected exact quantum dynamics is proposed and proven to be exact in the harmonic limit. The state projected CMD method is also tested numerically for a quartic oscillator and a double-well potential and found to be more accurate than canonical CMD. In the case of a ground state projection, this method can resolve tunnelling splittings of the double well problem in the higher barrier regime where canonical CMD fails. Finally, the state-projected CMD framework is cast in a path integral form.

Optimal design and fabrication of ring resonator composed of Ge02-doped silica waveguides for IOG

NASA Astrophysics Data System (ADS)

Guo, Lijun; Shi, Bangren; Chen, Chen; Lv, Hao; Zhao, Zhenming; Zhao, Meng

2009-07-01

The ring resonator is the core sensing element in the resonant integration optical gyroscope (IOG) . Its performances influence the minimum resolution and the error items of gyroscope directly and it is the key of the design and manufacturing. This paper presents optimal design of ring resonator composed of Ge02 -doped silica waveguides fabricated on silicon substrates using wide angle beam propagation method (WA-BPM). The characteristic of the light propagating across the ring resonator is analyzed. According to the design results, we succeed in fabricating the ring resonator by Plasma Enhanced Chemical Vapor Deposition (PECVD) method and Reactive Ion Etching (RIE) technology. In order to characterize the ring resonator, an optical measurement setup is built, fiber laser line-width is 50 kHz, detector responsibility is 0.95A/W and integral time is 10s. By testing, propagation loss and total loss of ring resonator are 0.02dB/cm and 0.1dB/circuit respectively. Observed from the resonance curve, a finesse of 12.5.

Quiescent and Eruptive Prominences at Solar Minimum: A Statistical Study via an Automated Tracking System

NASA Astrophysics Data System (ADS)

Loboda, I. P.; Bogachev, S. A.

2015-07-01

We employ an automated detection algorithm to perform a global study of solar prominence characteristics. We process four months of TESIS observations in the He II 304Å line taken close to the solar minimum of 2008-2009 and mainly focus on quiescent and quiescent-eruptive prominences. We detect a total of 389 individual features ranging from 25×25 to 150×500 Mm2 in size and obtain distributions of many of their spatial characteristics, such as latitudinal position, height, size, and shape. To study their dynamics, we classify prominences as either stable or eruptive and calculate their average centroid velocities, which are found to rarely exceed 3 km/s. In addition, we give rough estimates of mass and gravitational energy for every detected prominence and use these values to estimate the total mass and gravitational energy of all simultaneously existing prominences (1012 - 1014 kg and 1029 - 1031 erg). Finally, we investigate the form of the gravitational energy spectrum of prominences and derive it to be a power-law of index -1.1 ± 0.2.

Liquid-Oxygen-Compatible Cement for Gaskets

NASA Technical Reports Server (NTRS)

Elmore, N. L.; Neale, B. C.

1984-01-01

Fluorelastomer and metal bonded reliably by new procedure. To cure fluoroelastomer cement, metal plate/gasket assembly placed in vacuum bag evacuated to minimum vacuum of 27 inches (69 cm) of mercury. Vacuum maintained throughout heating process and until assembly returns to ambient room temperature. Used to seal gaskets and O-rings or used to splice layers of elastomer to form non-standard sized O-rings. Another possible use is to apply protective, liquid-oxygen-compatible coating to metal parts.

33 CFR 143.405 - Equipment.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) A minimum of four Coast Guard approved ring life buoys, each equipped with 15 fathoms of line. (10... of 35 degrees north latitude in all other waters. (11) Two boat hooks. (12) A fire monitor with a...

33 CFR 143.405 - Equipment.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) A minimum of four Coast Guard approved ring life buoys, each equipped with 15 fathoms of line. (10... of 35 degrees north latitude in all other waters. (11) Two boat hooks. (12) A fire monitor with a...

33 CFR 143.405 - Equipment.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) A minimum of four Coast Guard approved ring life buoys, each equipped with 15 fathoms of line. (10... of 35 degrees north latitude in all other waters. (11) Two boat hooks. (12) A fire monitor with a...

33 CFR 143.405 - Equipment.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) A minimum of four Coast Guard approved ring life buoys, each equipped with 15 fathoms of line. (10... of 35 degrees north latitude in all other waters. (11) Two boat hooks. (12) A fire monitor with a...

33 CFR 143.405 - Equipment.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) A minimum of four Coast Guard approved ring life buoys, each equipped with 15 fathoms of line. (10... of 35 degrees north latitude in all other waters. (11) Two boat hooks. (12) A fire monitor with a...

4-(Naphthalene-2-carboxamido)­pyridin-1-ium thio­cyanate–N-(pyridin-4-yl)naphthalene-2-carboxamide (1/1)

PubMed Central

Saeed, Sohail; Rashid, Naghmana; Butcher, Ray J.; Öztürk Yildirim, Sema; Hussain, Rizwan

2012-01-01

The asymmetric unit of the title compound, C16H13N2O+·NCS−·C16H12N2O, contains two N-(pyridin-4-yl)naphthalene-2-carboxamide mol­ecules, both are partially protonated in the pyridine moiety, i.e. the H atom attached to the pyridine N atom is partially occupied with an occupancy factor of 0.61 (3) and 0.39 (3), respectively. In the crystal, protonated and neutral N-(pyridin-4-yl)naphthalene-2-carboxamide mol­ecules are linked by N—H⋯N hydrogen bonding; the thio­cyanate counter-ion links with both protonated and neutral N-(pyridin-4-yl)naphthalene-2-carboxamide mol­ecules via N—H⋯S and N—H⋯N hydrogen bonding. The dihedral angles between the pyridine ring and naphthalene ring systems are 11.33 (6) and 9.51 (6)°, respectively. π–π stacking is observed in the crystal structure, the shortest centroid–centroid distance being 3.5929 (8) Å. The crystal structure was determined from a nonmerohedral twin {ratio of the twin components = 0.357 (1):0.643 (1) and twin law [-100 0-10 -101]}. PMID:23125774

(E)-1,2-Bis(4-fluoro­phen­yl)ethane-1,2-dione

PubMed Central

Fun, Hoong-Kun; Kia, Reza

2008-01-01

The title compound, C14H8F2O2, is a substituted benzil with an s-trans conformation of the dicarbonyl unit. This conformation is also shown by the O—C—C—O torsion angle of −110.65 (12)°. An unusual feature of the structure is the length, 1.536 (2) Å, of the central C—C bond connecting the carbonyl units, which is significantly longer than a normal Csp 2—Csp 2 single bond. This is probably the result of decreasing the unfavourable vicinal dipole–dipole inter­actions by increasing the distance between the two electronegative O atoms [O⋯O = 3.1867 (12) Å] and allowing orbital overlap of the dione with the π system of the benzene rings. The dihedral angle between the aromatic rings is 64.74 (5)°. In the crystal structure, neighbouring mol­ecules are linked together by weak inter­molecular C—H⋯O (× 2) hydrogen bonds. In addition, the crystal structure is further stabilized by inter­molecular π–π inter­actions with centroid–centroid distances in the range 3.6416 (6)–3.7150 (7) Å. PMID:21203308

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

Rossi, Mariana; Manolopoulos, David E.; Ceriotti, Michele

Two of the most successful methods that are presently available for simulating the quantum dynamics of condensed phase systems are centroid molecular dynamics (CMD) and ring polymer molecular dynamics (RPMD). Despite their conceptual differences, practical implementations of these methods differ in just two respects: the choice of the Parrinello-Rahman mass matrix and whether or not a thermostat is applied to the internal modes of the ring polymer during the dynamics. Here, we explore a method which is halfway between the two approximations: we keep the path integral bead masses equal to the physical particle masses but attach a Langevin thermostatmore » to the internal modes of the ring polymer during the dynamics. We justify this by showing analytically that the inclusion of an internal mode thermostat does not affect any of the established features of RPMD: thermostatted RPMD is equally valid with respect to everything that has actually been proven about the method as RPMD itself. In particular, because of the choice of bead masses, the resulting method is still optimum in the short-time limit, and the transition state approximation to its reaction rate theory remains closely related to the semiclassical instanton approximation in the deep quantum tunneling regime. In effect, there is a continuous family of methods with these properties, parameterised by the strength of the Langevin friction. Here, we explore numerically how the approximation to quantum dynamics depends on this friction, with a particular emphasis on vibrational spectroscopy. We find that a broad range of frictions approaching optimal damping give similar results, and that these results are immune to both the resonance problem of RPMD and the curvature problem of CMD.« less

CARE AND FEEDING OF FROGS

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

Pan, Margaret; Chiang, Eugene, E-mail: mpan@astro.berkeley.edu

2012-01-15

'Propellers' are features in Saturn's A ring associated with moonlets that open partial gaps. They exhibit non-Keplerian motion (Tiscareno et al.); the longitude residuals of the best-observed propeller, 'Bleriot', appear consistent with a sinusoid of period {approx}4 years. Pan and Chiang proposed that propeller moonlets librate in 'frog resonances' with co-orbiting ring material. By analogy with the restricted three-body problem, they treated the co-orbital material as stationary in the rotating frame and neglected non-co-orbital material. Here we use simple numerical experiments to extend the frog model, including feedback due to the gap's motion, and drag associated with the Lindblad diskmore » torques that cause Type I migration. Because the moonlet creates the gap, we expect the gap centroid to track the moonlet, but only after a time delay t{sub delay}, the time for a ring particle to travel from conjunction with the moonlet to the end of the gap. We find that frog librations can persist only if t{sub delay} exceeds the frog libration period P{sub lib}, and if damping from Lindblad torques balances driving from co-orbital torques. If t{sub delay} << Pl{sub ib}, then the libration amplitude damps to zero. In the case of Bleriot, the frog resonance model can reproduce the observed libration period P{sub lib} {approx_equal} 4 yr. However, our simple feedback prescription suggests that Bleriot's t{sub delay} {approx} 0.01P{sub lib}, which is inconsistent with the observed libration amplitude of 260 km. We urge more accurate treatments of feedback to test the assumptions of our toy models.« less

A 2:1 co-crystal of p-nitro-benzoic acid and N,N'-bis-(pyridin-3-ylmeth-yl)ethanedi-amide: crystal structure and Hirshfeld surface analysis.

PubMed

Syed, Sabrina; Halim, Siti Nadiah Abdul; Jotani, Mukesh M; Tiekink, Edward R T

2016-01-01

The title 2:1 co-crystal, 2C7H5NO4·C14H14N4O2, in which the complete di-amide mol-ecule is generated by crystallographic inversion symmetry, features a three-mol-ecule aggregate sustained by hydroxyl-O-H⋯N(pyrid-yl) hydrogen bonds. The p-nitro-benzoic acid mol-ecule is non-planar, exhibiting twists of both the carb-oxy-lic acid and nitro groups, which form dihedral angles of 10.16 (9) and 4.24 (4)°, respectively, with the benzene ring. The di-amide mol-ecule has a conformation approximating to a Z shape, with the pyridyl rings lying to either side of the central, almost planar di-amide residue (r.m.s. deviation of the eight atoms being 0.025 Å), and forming dihedral angles of 77.22 (6)° with it. In the crystal, three-mol-ecule aggregates are linked into a linear supra-molecular ladder sustained by amide-N-H⋯O(nitro) hydrogen bonds and orientated along [10-4]. The ladders are connected into a double layer via pyridyl- and benzene-C-H⋯O(amide) inter-actions, which, in turn, are connected into a three-dimensional architecture via π-π stacking inter-actions between pyridyl and benzene rings [inter-centroid distance = 3.6947 (8) Å]. An evaluation of the Hirshfeld surfaces confirm the importance of inter-molecular inter-actions involving oxygen atoms as well as the π-π inter-actions.

Ring Current Dynamics in Moderate and Strong Storms: Comparative Analysis of TWINS and IMAGE/HENA Data with the Comprehensive Ring Current Model

NASA Technical Reports Server (NTRS)

Buzulukova, N.; Fok, M.-C.; Goldstein, J.; Valek, P.; McComas, D. J.; Brandt, P. C.

2010-01-01

We present a comparative study of ring current dynamics during strong and moderate storms. The ring current during the strong storm is studied with IMAGE/HENA data near the solar cycle maximum in 2000. The ring current during the moderate storm is studied using energetic neutral atom (ENA) data from the Two Wide-Angle Imaging Neutral- Atom Spectrometers (TWINS) mission during the solar minimum in 2008. For both storms, the local time distributions of ENA emissions show signatures of postmidnight enhancement (PME) during the main phases. To model the ring current and ENA emissions, we use the Comprehensive Ring Current Model (CRCM). CRCM results show that the main-phase ring current pressure peaks in the premidnight-dusk sector, while the most intense CRCM-simulated ENA emissions show PME signatures. We analyze two factors to explain this difference: the dependence of charge-exchange cross section on energy and pitch angle distributions of ring current. We find that the IMF By effect (twisting of the convection pattern due to By) is not needed to form the PME. Additionally, the PME is more pronounced for the strong storm, although relative shielding and hence electric field skewing is well developed for both events.

Comparison of estimates of hardwood bole volume using importance sampling, the centroid method, and some taper equations

Treesearch

Harry V., Jr. Wiant; Michael L. Spangler; John E. Baumgras

2002-01-01

Various taper systems and the centroid method were compared to unbiased volume estimates made by importance sampling for 720 hardwood trees selected throughout the state of West Virginia. Only the centroid method consistently gave volumes estimates that did not differ significantly from those made by importance sampling, although some taper equations did well for most...

Development of welded metal bellows having minimum effective diameter change

NASA Technical Reports Server (NTRS)

Henschel, J. K.; Stevens, J. B.; Harvey, A. C.; Howland, J. S.; Rhee, S. S.

1972-01-01

A program of analysis, design, and fabrication was conducted to develop welded metal bellows having a minimum change in effective diameter for cryogenic turbomachinery face seal applications. Linear analysis of the principle types of bellows provided identification of concepts capable of meeting basic operation requirements. For the 6-inch (.152 m) mean diameter, 1.5-inch free length bellows studied, nonlinear analysis showed that opposed and nested toroidal bellows plates stiffened by means of alternating stiffener rings were capable of maintaining constant effective diameter within 0.3% and 0.1% respectively under the operating conditions of interest. Changes in effective diameter were due principally to bellows axial deflection with pressure differential having a lesser influence. Fabrication problems associated with joining the thin bellows plates to the relatively heavy stiffener rings were encountered and precluded assembly and testing of a bellows core. Fabrication problems are summarized and recommended fabrication methods for future effort are presented.

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

Akparov, V V; Dmitriev, Valentin G; Duraev, V P

A semiconductor ring laser (SRL) with a radiation wavelength of 1540 nm and a fibre ring cavity is developed and studied in several main lasing regimes. An SRL design based on a semiconductor optical travelling-wave amplifier and a ring cavity, composed of a single-mode polarisation-maintaining fibre, is considered. The SRL is studied in the regime of a rotation speed sensor, in which the frequency shift of counterpropagating waves in the SRL is proportional to its rotation speed. The minimum rotation speed that can be detected using the SRL under consideration depends on the cavity length; in our experiment it turnedmore » to be 1deg s{sup -1}. The changes in the threshold current, emission spectrum, and fundamental radiation wavelength upon closing and opening the SRL ring cavity and with a change in its radius are also investigated. (lasers)« less

Doppler centroid estimation ambiguity for synthetic aperture radars

NASA Technical Reports Server (NTRS)

Chang, C. Y.; Curlander, J. C.

1989-01-01

A technique for estimation of the Doppler centroid of an SAR in the presence of large uncertainty in antenna boresight pointing is described. Also investigated is the image degradation resulting from data processing that uses an ambiguous centroid. Two approaches for resolving ambiguities in Doppler centroid estimation (DCE) are presented: the range cross-correlation technique and the multiple-PRF (pulse repetition frequency) technique. Because other design factors control the PRF selection for SAR, a generalized algorithm is derived for PRFs not containing a common divisor. An example using the SIR-C parameters illustrates that this algorithm is capable of resolving the C-band DCE ambiguities for antenna pointing uncertainties of about 2-3 deg.

The active analog approach applied to the pharmacophore identification of benzodiazepine receptor ligands

NASA Astrophysics Data System (ADS)

Tebib, Souhail; Bourguignon, Jean-Jacques; Wermuth, Camille-Georges

1987-07-01

Applied to seven potent benzodiazepine-receptor ligands belonging to chemically different classes, the active analog approach allowed the stepwise identification of the pharmacophoric pattern associated with the recognition by the benzodiazepine receptor. A unique pharmacophore model was derived which involves six critical zones: (a) a π-electron rich aromatic (PAR) zone; (b) two electron-rich zones δ1 and δ2 placed at 5.0 and 4.5 Å respectively from the reference centroid in the PAR zone; (c) a freely rotating aromatic ring (FRA) region; (d) an out-of-plane region (OPR), strongly associated with agonist properties; and (e) an additional hydrophobic region (AHR). The model accommodates all presently known ligands of the benzodiazepine receptor, identifies sensitivity to steric hindrance close to the δ1 zone, accounts for R and S differential affinities and distinguishes requirements for agonist versus non-agonist activity profiles.

N,N′-Bis(3-chloro-2-fluoro­benzyl­idene)ethane-1,2-diamine

PubMed Central

Fun, Hoong-Kun; Kia, Reza

2008-01-01

The mol­ecule of the title centrosymmetric Schiff base compound, C16H12Cl2F2N2, adopts an E configuration with respect to the azomethine C=N bond. The imino groups are coplanar with the aromatic rings. Within the mol­ecule, the planar units are parallel, but extend in opposite directions from the dimethyl­ene bridge. An inter­esting feature of the crystal structure is the short inter­molecular Cl⋯F [3.1747 (5) Å] inter­actions, which are shorter than the sum of the van der Waals radii of these atoms. These inter­actions link neighbouring mol­ecules along the b axis. The crystal structure is further stabilized by π–π inter­actions, with a centroid–centroid distance of 3.5244 (4) Å. PMID:21201124

Thermal quantum time-correlation functions from classical-like dynamics

NASA Astrophysics Data System (ADS)

Hele, Timothy J. H.

2017-07-01

Thermal quantum time-correlation functions are of fundamental importance in quantum dynamics, allowing experimentally measurable properties such as reaction rates, diffusion constants and vibrational spectra to be computed from first principles. Since the exact quantum solution scales exponentially with system size, there has been considerable effort in formulating reliable linear-scaling methods involving exact quantum statistics and approximate quantum dynamics modelled with classical-like trajectories. Here, we review recent progress in the field with the development of methods including centroid molecular dynamics , ring polymer molecular dynamics (RPMD) and thermostatted RPMD (TRPMD). We show how these methods have recently been obtained from 'Matsubara dynamics', a form of semiclassical dynamics which conserves the quantum Boltzmann distribution. We also apply the Matsubara formalism to reaction rate theory, rederiving t → 0+ quantum transition-state theory (QTST) and showing that Matsubara-TST, like RPMD-TST, is equivalent to QTST. We end by surveying areas for future progress.

Bis(acesulfamato-kappaO4)diaquabis(3-methylpyridine-kappaN)nickel(II).

PubMed

Dege, Necmi; Içbudak, Hasan; Adiyaman, Elif

2007-01-01

In the crystal structure of the title compound [systematic name: diaquabis(6-methyl-2,2-dioxo-1,2,3-oxathiazin-4-olato-kappaO4)bis(3-methylpyridine-kappaN)nickel(II)], [Ni(C4H4NO4S)2(C6H7N)2(H2O)2], the Ni(II) centre resides on a centre of symmetry and has a distorted octahedral geometry. The basal plane is formed by two carbonyl O atoms of two monodentate trans-oriented acesulfamate ligands and two trans aqua ligands. The axial positions in the octahedron are occupied by two N atoms of two trans pyridine ligands. Molecules are stacked in columns running along the a axis. There are pi-pi stacking interactions between the molecules in each column, with a distance of 3.623 (2) A between the centroids of the pyridine rings. There are also O-H...O interactions between the columns.

K-Means Algorithm Performance Analysis With Determining The Value Of Starting Centroid With Random And KD-Tree Method

NASA Astrophysics Data System (ADS)

Sirait, Kamson; Tulus; Budhiarti Nababan, Erna

2017-12-01

Clustering methods that have high accuracy and time efficiency are necessary for the filtering process. One method that has been known and applied in clustering is K-Means Clustering. In its application, the determination of the begining value of the cluster center greatly affects the results of the K-Means algorithm. This research discusses the results of K-Means Clustering with starting centroid determination with a random and KD-Tree method. The initial determination of random centroid on the data set of 1000 student academic data to classify the potentially dropout has a sse value of 952972 for the quality variable and 232.48 for the GPA, whereas the initial centroid determination by KD-Tree has a sse value of 504302 for the quality variable and 214,37 for the GPA variable. The smaller sse values indicate that the result of K-Means Clustering with initial KD-Tree centroid selection have better accuracy than K-Means Clustering method with random initial centorid selection.

Characterization of trabecular bone using the backscattered spectral centroid shift.

PubMed

Wear, Keith A

2003-04-01

Ultrasonic attenuation in bone in vivo is generally measured using a through-transmission method at the calcaneus. Although attenuation in calcaneus has been demonstrated to be a useful predictor for osteoporotic fracture risk, measurements at other clinically important sites, such as hip and spine, could potentially contain additional useful diagnostic information. Through-transmission measurements may not be feasible at these sites due to complex bone shapes and the increased amount of intervening soft tissue. Centroid shift from the backscattered signal is an index of attenuation slope and has been used previously to characterize soft tissues. In this paper, centroid shift from signals backscattered from 30 trabecular bone samples in vitro were measured. Attenuation slope also was measured using a through-transmission method. The correlation coefficient between centroid shift and attenuation slope was -0.71. The 95% confidence interval was (-0.86, -0.47). These results suggest that the backscattered spectral centroid shift may contain useful diagnostic information potentially applicable to hip and spine.

Measurements of ultrasonic backscattered spectral centroid shift from spine in vivo: methodology and preliminary results.

PubMed

Garra, Brian S; Locher, Melanie; Felker, Steven; Wear, Keith A

2009-01-01

Ultrasonic backscatter measurements from vertebral bodies (L3 and L4) in nine women were performed using a clinical ultrasonic imaging system. Measurements were made through the abdomen. The location of a vertebra was identified from the bright specular reflection from the vertebral anterior surface. Backscattered signals were gated to isolate signal emanating from the cancellous interiors of vertebrae. The spectral centroid shift of the backscattered signal, which has previously been shown to correlate highly with bone mineral density (BMD) in human calcaneus in vitro, was measured. BMD was also measured in the nine subjects' vertebrae using a clinical bone densitometer. The correlation coefficient between centroid shift and BMD was r = -0.61. The slope of the linear fit was -160 kHz / (g/cm(2)). The negative slope was expected because the attenuation coefficient (and therefore magnitude of the centroid downshift) is known from previous studies to increase with BMD. The centroid shift may be a useful parameter for characterizing bone in vivo.

Extreme pointer years in tree-ring records of Central Spain as evidence of climatic events and the eruption of the Huaynaputina Volcano (Peru, 1600 AD)

NASA Astrophysics Data System (ADS)

Génova, M.

2012-04-01

The study of pointer years of numerous tree-ring chronologies of the central Iberian Peninsula (Sierra de Guadarrama) could provide complementary information about climate variability over the last 405 yr. In total, 64 pointer years have been identified: 30 negative (representing minimum growths) and 34 positive (representing maximum growths), the most significant of these being 1601, 1963 and 1996 for the negative ones, and 1734 and 1737 for the positive ones. Given that summer precipitation was found to be the most limiting factor for the growth of Pinus in the Sierra de Guadarrama in the second half of the 20th century, it is also an explanatory factor in almost 50% of the extreme growths. Furthermore, these pointer years and intervals are not evenly distributed throughout time. Both in the first half of the 17th and in the second half of 20th, they were more frequent and more extreme and these periods are the most notable for the frequency of negative pointer years in Central Spain. The interval 1600-1602 is of special significance, being one of the most unfavourable for tree growth in the centre of Spain, with 1601 representing the minimum index in the regional chronology. We infer that this special minimum annual increase was the effect of the eruption of Huaynaputina, which occurred in Peru at the beginning of 1600 AD. This is the first time that the effects of this eruption in the tree-ring records of Southern Europe have been demonstrated.

The investigation of solar activity signals by analyzing of tree ring chronological scales

NASA Astrophysics Data System (ADS)

Nickiforov, M. G.

2017-07-01

The present study examines the ability of detecting short-cycles and global minima of solar activity by analyzing dendrochronologies. Starting with the study of Douglass, which was devoted to the question of climatic cycles and the growth of trees, it is believed that the analysis of dendrochronologies allows to detect the cycle of Wolf-Schwabe. According to his results, the cycle was absent during Maunder's minimum and appeared after its completion. Having checked Douglass's conclusions by using 10 dendrochronologies of yellow pines from Arizona, which cover the time period from 1600 to 1900, we have come to the opposite results. The verification shows that: a) none of the considered dendroscale allows to detect an 11-year cycle; 2) the behaviour of a short peroid-signal does not undergo significant changes before, during or after Maunder's minimum. A similar attempt to detect global minima of solar activity by using five dendrochronologies from different areas has not led to positive results. On the one hand, the signal of global extremum is not always recorded in dendrochronology, on the other hand, the deep depression of annual rings allows to suppose the existence of a global minimum of solar activity, which is actually absent.

Effects of Recent Minimum Temperature and Water Deficit Increases on Pinus pinaster Radial Growth and Wood Density in Southern Portugal.

PubMed

Kurz-Besson, Cathy B; Lousada, José L; Gaspar, Maria J; Correia, Isabel E; David, Teresa S; Soares, Pedro M M; Cardoso, Rita M; Russo, Ana; Varino, Filipa; Mériaux, Catherine; Trigo, Ricardo M; Gouveia, Célia M

2016-01-01

Western Iberia has recently shown increasing frequency of drought conditions coupled with heatwave events, leading to exacerbated limiting climatic conditions for plant growth. It is not clear to what extent wood growth and density of agroforestry species have suffered from such changes or recent extreme climate events. To address this question, tree-ring width and density chronologies were built for a Pinus pinaster stand in southern Portugal and correlated with climate variables, including the minimum, mean and maximum temperatures and the number of cold days. Monthly and maximum daily precipitations were also analyzed as well as dry spells. The drought effect was assessed using the standardized precipitation-evapotranspiration (SPEI) multi-scalar drought index, between 1 to 24-months. The climate-growth/density relationships were evaluated for the period 1958-2011. We show that both wood radial growth and density highly benefit from the strong decay of cold days and the increase of minimum temperature. Yet the benefits are hindered by long-term water deficit, which results in different levels of impact on wood radial growth and density. Despite of the intensification of long-term water deficit, tree-ring width appears to benefit from the minimum temperature increase, whereas the effects of long-term droughts significantly prevail on tree-ring density. Our results further highlight the dependency of the species on deep water sources after the juvenile stage. The impact of climate changes on long-term droughts and their repercussion on the shallow groundwater table and P. pinaster's vulnerability are also discussed. This work provides relevant information for forest management in the semi-arid area of the Alentejo region of Portugal. It should ease the elaboration of mitigation strategies to assure P. pinaster's production capacity and quality in response to more arid conditions in the near future in the region.

Effects of Recent Minimum Temperature and Water Deficit Increases on Pinus pinaster Radial Growth and Wood Density in Southern Portugal

PubMed Central

Kurz-Besson, Cathy B.; Lousada, José L.; Gaspar, Maria J.; Correia, Isabel E.; David, Teresa S.; Soares, Pedro M. M.; Cardoso, Rita M.; Russo, Ana; Varino, Filipa; Mériaux, Catherine; Trigo, Ricardo M.; Gouveia, Célia M.

2016-01-01

Western Iberia has recently shown increasing frequency of drought conditions coupled with heatwave events, leading to exacerbated limiting climatic conditions for plant growth. It is not clear to what extent wood growth and density of agroforestry species have suffered from such changes or recent extreme climate events. To address this question, tree-ring width and density chronologies were built for a Pinus pinaster stand in southern Portugal and correlated with climate variables, including the minimum, mean and maximum temperatures and the number of cold days. Monthly and maximum daily precipitations were also analyzed as well as dry spells. The drought effect was assessed using the standardized precipitation-evapotranspiration (SPEI) multi-scalar drought index, between 1 to 24-months. The climate-growth/density relationships were evaluated for the period 1958-2011. We show that both wood radial growth and density highly benefit from the strong decay of cold days and the increase of minimum temperature. Yet the benefits are hindered by long-term water deficit, which results in different levels of impact on wood radial growth and density. Despite of the intensification of long-term water deficit, tree-ring width appears to benefit from the minimum temperature increase, whereas the effects of long-term droughts significantly prevail on tree-ring density. Our results further highlight the dependency of the species on deep water sources after the juvenile stage. The impact of climate changes on long-term droughts and their repercussion on the shallow groundwater table and P. pinaster’s vulnerability are also discussed. This work provides relevant information for forest management in the semi-arid area of the Alentejo region of Portugal. It should ease the elaboration of mitigation strategies to assure P. pinaster’s production capacity and quality in response to more arid conditions in the near future in the region. PMID:27570527

Aging of Weapon Seals – An Update on Butyl O-ring Issues

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

Wilson, Mark H.

2011-07-13

During testing under the Enhanced Surveillance Campaign in 2001, preliminary data detected a previously unknown and potentially serious concern with recently procured butyl o-rings on several programs. All butyl o-rings molded from a proprietary formulation throughout the period circa 1999 through 2001 had less than a full cure. Engineering judgment was that under curing is detrimental and could possibly lead to sub-optimum performance or, in the worst case, premature seal failure. An aging study was undertaken to ensure that suspect o-rings installed in the stockpile will retain sufficient sealing force for a minimum ten-year service life. A new prediction modelmore » developed for this study indicates suspect o-rings do not need to be replaced before the ten-year service life. Long-term testing results are reported on a yearly basis to validate the prediction model. This report documents the aging results for the period September 2002 to January 2011.« less

Improvement of the performances of a tandem simulated moving bed chromatography by controlling the yield level of a key product of the first simulated moving bed unit.

PubMed

Mun, Sungyong; Wang, Nien-Hwa Linda

2017-03-10

One of the trustworthy processes for ternary separation is a tandem simulated moving bed (SMB) process, which consists of two subordinate four-zone SMB units (Ring I and Ring II). To take full advantage of a tandem SMB as a means of recovering all three products with high purities and high economical efficiency, it is important to understand how the separation condition in Ring II is affected by that in Ring I, and further to reflect such point in the stage of designing a tandem SMB. In regard to such issue, it was clarified in this study that the Ring I factors affecting the Ring II condition could be represented by the yield level of a key product of Ring I (Y key RingI ). As the Y key RingI level became higher, the amount of the Ring I key-product that was reloaded into Ring II was reduced, which affected favorably the Ring II separation condition. On the other hand, the higher Y key RingI level caused a larger dilution for the stream from Ring I to Ring II, which affected adversely the Ring II separation condition. As a result, a minimum in the desorbent usage of a tandem SMB occurred at the Y key RingI level where the two aforementioned factors could be balanced with each other. If such an optimal Y key RingI level was adopted, the desorbent usage could be reduced by up to 25%. It was also found that as the throughput of a tandem SMB became higher, the factor related to the migration of the Ring I key-product into Ring II was more influential in the performances of a tandem SMB than the factor related to the dilution of the stream from Ring I to Ring II. Copyright © 2016 Elsevier B.V. All rights reserved.

Enriching screening libraries with bioactive fragment space.

PubMed

Zhang, Na; Zhao, Hongtao

2016-08-01

By deconvoluting 238,073 bioactive molecules in the ChEMBL library into extended Murcko ring systems, we identified a set of 2245 ring systems present in at least 10 molecules. These ring systems belong to 2221 clusters by ECFP4 fingerprints with a minimum intracluster similarity of 0.8. Their overlap with ring systems in commercial libraries was further quantified. Our findings suggest that success of a small fragment library is driven by the convergence of effective coverage of bioactive ring systems (e.g., 10% coverage by 1000 fragments vs. 40% by 2million HTS compounds), high enrichment of bioactive ring systems, and low molecular complexity enhancing the probability of a match with the protein targets. Reconciling with the previous studies, bioactive ring systems are underrepresented in screening libraries. As such, we propose a library of virtual fragments with key functionalities via fragmentation of bioactive molecules. Its utility is exemplified by a prospective application on protein kinase CK2, resulting in the discovery of a series of novel inhibitors with the most potent compound having an IC50 of 0.5μM and a ligand efficiency of 0.41kcal/mol per heavy atom. Copyright © 2016 Elsevier Ltd. All rights reserved.

Seasonal variation in Rayleigh-to-Love wave ratio in the secondary microseism

NASA Astrophysics Data System (ADS)

Tanimoto, T.; Hadziioannou, C.; Igel, H.; Wassermann, J. M.; Schreiber, U.; Gebauer, A.; Chow, B.

2015-12-01

The Ring Laser (the G-ring) at Wettzell (WET), Germany, is a rotation-measurement instrument that can monitor tiny variations in seismic noise. It essentially records only SH-type signals. Combined with a co-located seismograph (three-component seismograph STS-2), we can monitor the amount of Love waves from this instrument and that of Rayleigh waves from the STS seismograph. We report on seasonal variation of Rayleigh-to-Love wave ratio in the secondary microseism. The first step in our analysis is to obtain stacked Fourier spectra that were least affected by earthquakes. We used two earthquake catalogues to do this; the GCMT (Global Centroid Moment Tensor, Earthquakes M > 5.5) catalogue and the EMSC (European-Mediterranean Seismic Centre) catalogue for regional earthquakes (distance < 1000 km) with M > 4.5. We then created monthly averages of noise Fourier spectra for the frequency range 0.13-0.30 Hz using both the G-ring and STS data from 2009 to 2015. Monthly spectra show clear seasonal variations for the secondary microseism. We obtained surface vertical acceleration from STS and surface transverse acceleration from G-ring from which we can directly measure the Rayleigh-to-Love wave ratio. The procedure is the same with an account in our recent GRL paper (Tanimoto et al., 2015). Comparison between vertical acceleration and transverse acceleration shows that Rayleigh-wave surface amplitudes are about 20 percent larger than Love waves but in terms of kinetic energy this ratio will be different. We converted these ratios of surface amplitude to those of kinetic energy using an available earth model (Fichtner et al., 2013). The averaged ratio over the frequency band 0.13-0.30 Hz shows is in the range 0.6-0.8 in spring, autumn and winter but it increases to about 1.2 in summer. Except for the summer, the amount of Love waves are higher but the amount of Rayleigh waves increases in summer and appears to exceed that of Love waves.

The influence of image sensor irradiation damage on the tracking and pointing accuracy of optical communication system

NASA Astrophysics Data System (ADS)

Li, Xiaoliang; Luo, Lei; Li, Pengwei; Yu, Qingkui

2018-03-01

The image sensor in satellite optical communication system may generate noise due to space irradiation damage, leading to deviation for the determination of the light spot centroid. Based on the irradiation test data of CMOS devices, simulated defect spots in different sizes have been used for calculating the centroid deviation value by grey-level centroid algorithm. The impact on tracking & pointing accuracy of the system has been analyzed. The results show that both the amount and the position of irradiation-induced defect pixels contribute to spot centroid deviation. And the larger spot has less deviation. At last, considering the space radiation damage, suggestions are made for the constraints of spot size selection.

Fidelity and persistence of Ring-billed (Larus delawarensis) and Herring (Larus argentatus) gulls to wintering sites

USGS Publications Warehouse

Clark, Daniel E.; Koenen, Kiana K. G.; Whitney, Jillian J.; MacKenzie, Kenneth G.; DeStefano, Stephen

2016-01-01

While the breeding ecology of gulls (Laridae) has been well studied, their movements and spatial organization during the non-breeding season is poorly understood. The seasonal movements, winter-site fidelity, and site persistence of Ring-billed (Larus delawarensis) and Herring (L. argentatus) gulls to wintering areas were studied from 2008–2012. Satellite transmitters were deployed on Ring-billed Gulls (n = 21) and Herring Gulls (n = 14). Ten Ring-billed and six Herring gulls were tracked over multiple winters and > 300 wing-tagged Ring-billed Gulls were followed to determine winter-site fidelity and persistence. Home range overlap for individuals between years ranged between 0–1.0 (95% minimum convex polygon) and 0.31–0.79 (kernel utilization distributions). Ringbilled and Herring gulls remained at local wintering sites during the non-breeding season from 20–167 days and 74–161 days, respectively. The probability of a tagged Ring-billed Gull returning to the same site in subsequent winters was high; conversely, there was a low probability of a Ring-billed Gull returning to a different site. Ring-billed and Herring gulls exhibited high winter-site fidelity, but exhibited variable site persistence during the winter season, leading to a high probability of encountering the same individuals in subsequent winters.

Spectrophotometric study of Saturn's main rings by means of Monte Carlo ray-tracing and Hapke's theory

NASA Astrophysics Data System (ADS)

Ciarniello, Mauro; Filacchione, Gianrico; D'Aversa, Emiliano; Cuzzi, Jeffrey N.; Capaccioni, Fabrizio; Hedman, Matthew M.; Dalle Ore, Cristina M.; Nicholson, Philip D.; Clark, Roger Nelson; Brown, Robert H.; Cerroni, Priscilla; Spilker, Linda

2017-10-01

This work is devoted to the investigation of the spectrophotometric properties of Saturn's rings from Cassini-VIMS (Visible and Infrared Mapping Spectrometer) observations. The dataset used for this analysis is represented by ten radial spectrograms of the rings which have been derived in Filacchione et al. (2014) by radial mosaics produced by VIMS. Spectrograms report the measured radiance factor of the main Saturn's rings as a function of both radial distance (from 73.500 to 141.375 km) and wavelength (0.35-5.1 µm) for different observation geometries (phase angle ranging in the 1.9°-132.2° interval). We take advantage of a Monte Carlo ray-tracing routine to characterize the photometric behavior of the rings at each wavelength and derive the spectral Bond albedo of rings particles. This quantity is used to infer the composition of the regolith covering rings particles by applying Hapke's theory. Four different regions, characterized by different optical depths, and respectively located in the C ring, inner B ring, mid B ring and A ring, have been investigated. Results from spectral modeling indicate that rings spectrum can be described by water ice with minimal inclusion of organic materials (tholin, < 1%) mixed with variable amounts of a neutral absorber such as amorphous carbon and amorphous silicates. The abundance of the neutral absorber anti-correlates with the optical depth of the investigated regions, being maximum in the thinnest C ring and minimum in the thickest mid B ring. This distribution of the neutral absorber is interpreted as the result of a contamination by exogenous material, which is more effective in the less dense regions of the rings because of their lower content of pure water ice.

Design and fabrication of engineering model fiber-optics detector

NASA Technical Reports Server (NTRS)

Mcsweeney, A.

1972-01-01

The design and fabrication of an annular ring detector consisting of optical fibers terminated with photodetectors is described. The maximum width of each concentric ring has to be small enough to permit the resolution of a Ronchi ruling transform with a dot spacing of 150 microns. A minimum of 100 concentric rings covering a circular area of 2.54 cm diameter also is necessary. A fiber-optic array consisting of approximately 89,000 fibers of 76 microns diameter was fabricated to meet the above requirements. The fibers within a circular area of 2.5 cm diameter were sorted into 168 adjacent rings concentric with the center fiber. The response characteristics of several photodetectors were measured, and the data used to compare their linearity of response and dynamic range. Also, coupling loss measurements were made for three different methods of terminating the optical fibers with a photodetector.

3β,5α,6β-Trihy­droxy­androstan-17-one

PubMed Central

Andrade, L.C.R.; de Almeida, M.J.B.M.; Paixão, J.A.; Carvalho, J.F.S.; Sá e Melo, M.L.

2011-01-01

The title compound, C19H30O4, is an androstan-17-one derivative synthesized from the dehydro­epiandrosterone through a sequential addition of an oxidant, followed by a trans-diaxial opening of the epoxide generated, with Bi(OTf)3 (OTf is trifluoro­methane­sulfonate). The six-membered rings have a slightly flattened chair conformation, while the five-membered ring adopts a 14-α envelope conformation. All rings are trans fused. In the crystal, the mol­ecules are connected by O—H⋯O hydrogen bonds involving the hydroxyl and carbonyl groups, forming a three-dimensional network. A quantum mechanical ab initio Roothan Hartree–Fock calculation of the free mol­ecule gives bond lengths, valency angles and ring torsion angles of the free molecule at equilibrium geometry (energy minimum) close to the experimental values. PMID:21754383

Density engineering of an oscillating soliton/vortex ring in a Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Levy, Shahar; Shomroni, Itay; Lahoud, Elias; Steinhauer, Jeff

2008-05-01

We study solitons in a Bose-Einstein condensate by engineering a density minimum on the healing length scale, using a far off-resonant laser beam. This results in a pair of counterpropagating solitons, which is the low collisional energy version of the celebrated matter wave interference pattern [M. R. Andrews et al., Science 275, 637 (1997)]. The solitons subsequently evolve into a pair of periodic soliton/vortex rings. We image the vortex rings and solitons in-situ on the healing length scale. This stable periodic evolution is in sharp contrast to the behavior of previous experiments in which the solitons decay irreversibly into vortex rings via the snake instability. The periodic oscillation between two qualitatively different forms seems to be a rare phenomenon in nature. We explain this phenomenon in terms of conservation of mass and energy in a narrow condensate.

Improved ion containment using a ring-cusp ion thruster

NASA Technical Reports Server (NTRS)

Sovey, J. S.

1982-01-01

A 30-centimeter diameter ring-cusp ion thruster is described which operates at inert gas ion beam currents up to about 7 ampere, with significant improvements in discharge chamber performance over conventional divergent-field thrusters. The thruster has strong boundary ring-cusp magnetic fields, a diverging field on the cathode region, and a nearly field-free volume upstream of the ion extraction system. Minimum ion beam production costs of 90 to 100 watts per beam ampere (W/A) were obtained for argon, krypton and xenon. Propellant efficiencies in excess of 0.90 were achieved at 100 to 120 W/A for the three inert gases. The ion beam charge-state was documented with a collimating mass spectrometer probe to allow evaluation of overall thruster efficiencies.

Observational Evidence for the Effect of Amplification Bias in Gravitational Microlensing Experiments

NASA Astrophysics Data System (ADS)

Han, Cheongho; Jeong, Youngjin; Kim, Ho-Il

1998-11-01

Recently Alard, Mao, & Guibert and Alard proposed to detect the shift of a star's image centroid, δx, as a method to identify the lensed source among blended stars. Goldberg & Woźniak actually applied this method to the OGLE-1 database and found that seven of 15 events showed significant centroid shifts of δx >~ 0.2". The amount of centroid shift has been estimated theoretically by Goldberg; however, he treated the problem in general and did not apply it to a particular survey or field and therefore based his estimate on simple toy model luminosity functions (i.e., power laws). In this paper, we construct the expected distribution of δx for Galactic bulge events based on the precise stellar luminosity function observed by Holtzman et al. using the Hubble Space Telescope. Their luminosity function is complete up to MI ~ 9.0 (MV ~ 12), which corresponds to faint M-type stars. In our analysis we find that regular blending cannot produce a large fraction of events with measurable centroid shifts. By contrast, a significant fraction of events would have measurable centroid shifts if they are affected by amplification-bias blending. Therefore, the measurements of large centroid shifts for an important fraction of microlensing events of Goldberg & Woźniak confirm the prediction of Han & Alard that a large fraction of Galactic bulge events are affected by amplification-bias blending.

Improved and Robust Detection of Cell Nuclei from Four Dimensional Fluorescence Images

PubMed Central

Bashar, Md. Khayrul; Yamagata, Kazuo; Kobayashi, Tetsuya J.

2014-01-01

Segmentation-free direct methods are quite efficient for automated nuclei extraction from high dimensional images. A few such methods do exist but most of them do not ensure algorithmic robustness to parameter and noise variations. In this research, we propose a method based on multiscale adaptive filtering for efficient and robust detection of nuclei centroids from four dimensional (4D) fluorescence images. A temporal feedback mechanism is employed between the enhancement and the initial detection steps of a typical direct method. We estimate the minimum and maximum nuclei diameters from the previous frame and feed back them as filter lengths for multiscale enhancement of the current frame. A radial intensity-gradient function is optimized at positions of initial centroids to estimate all nuclei diameters. This procedure continues for processing subsequent images in the sequence. Above mechanism thus ensures proper enhancement by automated estimation of major parameters. This brings robustness and safeguards the system against additive noises and effects from wrong parameters. Later, the method and its single-scale variant are simplified for further reduction of parameters. The proposed method is then extended for nuclei volume segmentation. The same optimization technique is applied to final centroid positions of the enhanced image and the estimated diameters are projected onto the binary candidate regions to segment nuclei volumes.Our method is finally integrated with a simple sequential tracking approach to establish nuclear trajectories in the 4D space. Experimental evaluations with five image-sequences (each having 271 3D sequential images) corresponding to five different mouse embryos show promising performances of our methods in terms of nuclear detection, segmentation, and tracking. A detail analysis with a sub-sequence of 101 3D images from an embryo reveals that the proposed method can improve the nuclei detection accuracy by 9 over the previous methods, which used inappropriate large valued parameters. Results also confirm that the proposed method and its variants achieve high detection accuracies ( 98 mean F-measure) irrespective of the large variations of filter parameters and noise levels. PMID:25020042

Shack-Hartmann wavefront sensor with large dynamic range.

PubMed

Xia, Mingliang; Li, Chao; Hu, Lifa; Cao, Zhaoliang; Mu, Quanquan; Xuan, Li

2010-01-01

A new spot centroid detection algorithm for a Shack-Hartmann wavefront sensor (SHWFS) is experimentally investigated. The algorithm is a kind of dynamic tracking algorithm that tracks and calculates the corresponding spot centroid of the current spot map based on the spot centroid of the previous spot map, according to the strong correlation of the wavefront slope and the centroid of the corresponding spot between temporally adjacent SHWFS measurements. That is, for adjacent measurements, the spot centroid movement will usually fall within some range. Using the algorithm, the dynamic range of an SHWFS can be expanded by a factor of three in the measurement of tilt aberration compared with the conventional algorithm, more than 1.3 times in the measurement of defocus aberration, and more than 2 times in the measurement of the mixture of spherical aberration plus coma aberration. The algorithm is applied in our SHWFS to measure the distorted wavefront of the human eye. The experimental results of the adaptive optics (AO) system for retina imaging are presented to prove its feasibility for highly aberrated eyes.

Electron cooling of a bunched ion beam in a storage ring

NASA Astrophysics Data System (ADS)

Zhao, He; Mao, Lijun; Yang, Jiancheng; Xia, Jiawen; Yang, Xiaodong; Li, Jie; Tang, Meitang; Shen, Guodong; Ma, Xiaoming; Wu, Bo; Wang, Geng; Ruan, Shuang; Wang, Kedong; Dong, Ziqiang

2018-02-01

A combination of electron cooling and rf system is an effective method to compress the beam bunch length in storage rings. A simulation code based on multiparticle tracking was developed to calculate the bunched ion beam cooling process, in which the electron cooling, intrabeam scattering (IBS), ion beam space-charge field, transverse and synchrotron motion are considered. Meanwhile, bunched ion beam cooling experiments have been carried out in the main cooling storage ring (CSRm) of the Heavy Ion Research Facility in Lanzhou, to investigate the minimum bunch length obtained by the cooling method, and study the dependence of the minimum bunch length on beam and machine parameters. The experiments show comparable results to those from simulation. Based on these simulations and experiments, we established an analytical model to describe the limitation of the bunch length of the cooled ion beam. It is observed that the IBS effect is dominant for low intensity beams, and the space-charge effect is much more important for high intensity beams. Moreover, the particles will not be bunched for much higher intensity beam. The experimental results in CSRm show a good agreement with the analytical model in the IBS dominated regime. The simulation work offers us comparable results to those from the analytical model both in IBS dominated and space-charge dominated regimes.

5,8-Bis[bis­(pyridin-2-yl)amino]-1,3,4,6,7,9,9b-hepta­aza­phenalen-2(1H)-one dimethyl sulfoxide monosolvate dihydrate

PubMed Central

Schwarzer, Anke; Kroke, Edwin

2014-01-01

In the asymmetric unit of the title compound, C26H17N13O·C2H6OS·2H2O, there is one independent hepta­zine-based main mol­ecule, one dimethyl sulfoxide mol­ecule and two water mol­ecules as solvents. The tri-s-triazine unit is substituted with two dipyridyl amine moieties and a carbonylic O atom. As indicated by the bond lengths in this acid unit of the hepta­zine derivative [C=O = 1.213 (2) Å, while the adjacent C—N(H) bond = 1.405 (2) Å] it is best described by the keto form. The cyameluric nucleus is close to planar (r.m.s. deviation = 0.061 Å) and the pyridine rings are inclined to its mean plane by dihedral angles varying from 47.47 (5) to 70.22 (5)°. The host and guest mol­ecules are connected via N—H⋯O, O—H⋯O and O—H⋯N hydrogen bonds, forming a four-membered inversion dimer-like arrangement enclosing an R 4 4(24) ring motif. These arrangements stack along [1-10] with a weak π–π inter­action [inter-centroid distance = 3.8721 (12) Å] involving adjacent pyridine rings. There are also C—H⋯N and C—H⋯O hydrogen bonds and C—H⋯π inter­actions present within the host mol­ecule and linking inversion-related mol­ecules, forming a three-dimensional structure. PMID:24826156

[Vertical variability of Pinus sylvestris var. mongolica tree ring delta13C and its relationship with tree ring width in northern Daxing' an Mountains of Northeast China].

PubMed

Shang, Zhi-Yuan; Wang, Jian; Zhang, Wen; Li, Yan-Yan; Cui, Ming-Xing; Chen, Zhen-Ju; Zhao, Xing-Yun

2013-01-01

A measurement was made on the vertical direction tree ring stable carbon isotope ratio (delta13C) and tree ring width of Pinus sylvestris var. mongolica in northern Daxing' an Mountains of Northeast China, with the relationship between the vertical direction variations of the tree ring delta13C and tree ring width analyzed. In the whole ring of xylem, earlywood (EW) and bark endodermis, the delta13C all exhibited an increasing trend from the top to the base at first, with the maximum at the bottom of tree crown, and then, decreased rapidly to the minimum downward. The EW and late-wood (LW) had an increasing ratio of average tree ring width from the base to the top. The average annual sequence of the delta13C in vertical direction had an obvious reverse correspondence with the average annual sequence of tree ring width, and had a trend comparatively in line with the average annual sequence of the tree ring width ratio of EW to LW above tree crown. The variance analysis showed that there existed significant differences in the sequences of tree ring delta13C and ring width in vertical direction, and the magnitude of vertical delta13C variability was basically the same as that of the inter-annual delta13C variability. The year-to-year variation trend of the vertical delta13C sequence was approximately identical. For each sample, the delta13C sequence at the same heights was negatively correlated with the ring width sequence, but the statistical significance differed with tree height.

Concurrent Timbres in Orchestration: a Perceptual Study of Factors Determining "blend"

NASA Astrophysics Data System (ADS)

Sandell, Gregory John

Orchestration often involves selecting instruments for concurrent presentation, as in melodic doubling or chords. One evaluation of the aural outcome of such choices is along the continuum of "blend": whether the instruments fuse into a single composite timbre, segregate into distinct timbral entities, or fall somewhere in between the two extremes. This study investigates, through perceptual experimentation, the acoustical correlates of blend for 15 natural-sounding orchestral instruments presented in concurrently-sounding pairs (e.g. flute-cello, trumpet -oboe, etc.). Ratings of blend showed primary effects for centroid (the location of the midpoint of the spectral energy distribution) and duration of the onset for the tones. Lower average values of both centroid and onset duration for a pair of tones led to increased blends, as did closeness in value for the two factors. Blend decreased (instruments segregated) with higher average values or increased difference in value for the two factors. The musical interval of presentation slightly affected the relative importance of these two mechanisms, with unison intervals determined more by lower average centroid, and minor thirds determined more by closeness in centroid. The contribution of onset in general was slightly more pronounced in the unison conditions than in the minor third condition. Additional factors contributing to blend were correlation of amplitude and centroid envelopes (blend increased as temporal patterns rose and fell in synchrony) and similarity in the overall amount of fundamental frequency perturbation (decreased blend with increasing jitter from both tones). To confirm the importance of centroid as an independent factor determining blend, pairs of tones including instruments with artificially changed centroids were rated for blend. Judgments for several versions of the same instrument pair showed that blend decreased as the altered instrument increased in centroid, corroborating the earlier experiments. Other factors manipulated were amplitude level and the degree of inharmonicity. A survey of orchestration manuals showed many illustrations of "blending" combinations of instruments that were consistent with the results of these experiments. This study's acoustically-based guidelines for blend augment instance-based methods of traditional orchestration teaching, providing underlying abstractions helpful for evaluating the blend of arbitrary combinations of instruments.

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

Mishra, P.; Purdue University, West Lafayette, Indiana 47907; Verma, K.

Borazine is isoelectronic with benzene and is popularly referred to as inorganic benzene. The study of non-covalent interactions with borazine and comparison with its organic counterpart promises to show interesting similarities and differences. The motivation of the present study of the borazine-water interaction, for the first time, stems from such interesting possibilities. Hydrogen-bonded complexes of borazine and water were studied using matrix isolation infrared spectroscopy and quantum chemical calculations. Computations were performed at M06-2X and MP2 levels of theory using 6-311++G(d,p) and aug-cc-pVDZ basis sets. At both the levels of theory, the complex involving an N–H⋯O interaction, where the N–Hmore » of borazine serves as the proton donor to the oxygen of water was found to be the global minimum, in contrast to the benzene-water system, which showed an H–π interaction. The experimentally observed infrared spectra of the complexes corroborated well with our computations for the complex corresponding to the global minimum. In addition to the global minimum, our computations also located two local minima on the borazine-water potential energy surface. Of the two local minima, one corresponded to a structure where the water was the proton donor to the nitrogen of borazine, approaching the borazine ring from above the plane of the ring; a structure that resembled the global minimum in the benzene-water H–π complex. The second local minimum corresponded to an interaction of the oxygen of water with the boron of borazine, which can be termed as the boron bond. Clearly the borazine-water system presents a richer landscape than the benzene-water system.« less

A second triclinic polymorph of azimsulfuron

PubMed Central

Kwon, Eunjin; Kim, Jineun; Park, Hyunjin; Kim, Tae Ho

2016-01-01

The title compound, C13H16N10O5S (systematic name: 1-(4,6-di­meth­oxypyrimidin-2-yl)-3-{[1-methyl-4-(2-methyl-2H-tetra­zol-5-yl)pyrazol-5-yl]sulfonyl}urea), is a second triclinic polymorph of this crystal [for the other, see: Jeon et al., (2015 ▸). Acta Cryst. E71, o470–o471]. There are two mol­ecules, A and B, in the asymmetric unit; the dihedral angles between the pyrazole ring and the tetra­zole and di­meth­oxy­pyrimidine ring planes are 72.84 (10) and 37.24 (14)°, respectively (mol­ecule A) and 84.38 (9) and 26.09 (15)°, respectively (mol­ecule B). Each mol­ecule features an intra­molecular N—H⋯N hydrogen bond. In the crystal, aromatic π–π stacking inter­actions [centroid–centroid separations = 3.9871 (16), 3.4487 (14) and 3.5455 (16) Å] link the mol­ecules into [001] chains. In addition, N—H⋯N, N—H⋯O, C—H⋯O and C—H⋯N hydrogen bonds occur, forming a three-dimensional architecture. We propose that the dimorphism results from differences in conformations and packing owing to different inter­molecular inter­actions, especially aromatic π–π stacking. PMID:27746943

Autumn at Titan's South Pole: The 220 cm-1 Cloud

NASA Astrophysics Data System (ADS)

Jennings, D. E.; Cottini, V.; Achterberg, R. K.; Anderson, C. M.; Flasar, F. M.; de Kok, R. J.; Teanby, N. A.; Coustenis, A.; Vinatier, S.

2015-10-01

Beginning in 2012 an atmospheric cloud known by its far-infrared emission has formed rapidly at Tit an's South Pole [1, 2]. The build-up of this condensate is a result of deepening temperatures and a gathering of gases as Winter approaches. Emission from the cloud in the south has been doubling each year since 2012, in contrast to the north where it has halved every 3.8 years since 2004. The morphology of the cloud in the south is quite different from that in the north. In the north, the cloud has extended over the whole polar region beyond 55 N, whereas in the south the cloud has been confined to within about 10 degrees of the pole. The cloud in the north has had the form of a uniform hood, whereas the southern cloud has been much more complex. A map from December 2014,recorded by the Composite Infrared Spectrometer (CIRS) on Cassini, showed the 220 cm-1 emission coming from a distinct ring with a maximum at about 80 S. In contrast, emissions from the gases HC3N, C4H2 and C6H6 peaked near the pole and had a ring at 70 S. The 220 cm-1 ring at 80 S coincided with the minimum in the gas emission pattern. The80 S condensate ring encompassed the vortex cloud seen by the Cassini Imaging Science Subsystem (ISS) and Visible and Infrared Mapping Spectrometer (VIMS)[3, 4]. Both the 220 cm-1 ring and the gas "bull's-eye" pattern were centered on a point that was shifted from the geographic South Pole by 4 degrees in the direction of the Sun. This corresponds to the overall tilt of Titan's atmosphere discovered from temperature maps early in the Cassini mission by Achterberg et al. [5]. The tilt may be reinforced by the presumably twice-yearly (north and south) spin-up of the atmosphere at the autumnal pole. The bull's-eye pattern of the gas emissions can be explained by the retrieved abundance distributions, which are maximum near the pole and decrease sharply toward lower latitudes, together with temperatures that are minimum at the pole and increase toward lower latitudes. The increasing temperatures overcome the decreasing gas abundances to produce emission in the narrow range around 70 S. This cannot, however, explain the maximum of emission at 80 S from the condensate ring. The coincidence at 80 S of the 220 cm-1 peak with the gas emission minimum may indicate where the condensation is taking place. The central, polar minimum in the cloud emission may be due to faster rain-out and smaller extinction cross-sections. Spectral maps from 2013-15 [6] show that the gas emission pattern has been evolving quickly, with noticeable changes from one flyby to the next (about one month). The bull's-eye structure appears to have been most prominent in early 2014 and by late 2014 the pattern was becoming more uniform. As Titan progresses through late southern Autumn we expect the morphology of the condensate cloud to take on a hood-like distribution similar to that in the north.

Numerical study on the lubrication performance of compression ring-cylinder liner system with spherical dimples

PubMed Central

Liu, Cheng; Zhang, Yong-Fang; Li, Sha; Müller, Norbert

2017-01-01

The effects of surface texture on the lubrication performance of a compression ring-cylinder liner system are studied in this paper. By considering the surface roughness of the compression ring and cylinder liner, a mixed lubrication model is presented to investigate the tribological behaviors of a barrel-shaped compression ring-cylinder liner system with spherical dimples on the liner. In order to determine the rupture and reformulation positions of fluid film accurately, the Jacoboson-Floberg-Olsson (JFO) cavitation boundary condition is applied to the mixed lubrication model for ensuring the mass-conservative law. On this basis, the minimum oil film thickness and average friction forces in the compression ring-cylinder liner system are investigated under the engine-like conditions by changing the dimple area density, radius, and depth. The wear load, average friction forces, and power loss of the compression ring-cylinder liner system with and without dimples are also compared for different compression ring face profiles. The results show that the spherical dimples can produce a larger reduction of friction in mixed lubrication region, and reduce power loss significantly in the middle of the strokes. In addition, higher reduction percentages of average friction forces and wear are obtained for smaller crown height or larger axial width. PMID:28732042

Minimum stiffness criteria for ring frame stiffeners of space launch vehicles

NASA Astrophysics Data System (ADS)

Friedrich, Linus; Schröder, Kai-Uwe

2016-12-01

Frame stringer-stiffened shell structures show high load carrying capacity in conjunction with low structural mass and are for this reason frequently used as primary structures of aerospace applications. Due to the great number of design variables, deriving suitable stiffening configurations is a demanding task and needs to be realized using efficient analysis methods. The structural design of ring frame stringer-stiffened shells can be subdivided into two steps. One, the design of a shell section between two ring frames. Two, the structural design of the ring frames such that a general instability mode is avoided. For sizing stringer-stiffened shell sections, several methods were recently developed, but existing ring frame sizing methods are mainly based on empirical relations or on smeared models. These methods do not mandatorily lead to reliable designs and in some cases the lightweight design potential of stiffened shell structures can thus not be exploited. In this paper, the explicit physical behaviour of ring frame stiffeners of space launch vehicles at the onset of panel instability is described using mechanical substitute models. Ring frame stiffeners of a stiffened shell structure are sized applying existing methods and the method suggested in this paper. To verify the suggested method and to demonstrate its potential, geometrically non-linear finite element analyses are performed using detailed finite element models.

Light-Ring Stability for Ultracompact Objects.

PubMed

Cunha, Pedro V P; Berti, Emanuele; Herdeiro, Carlos A R

2017-12-22

We prove the following theorem: axisymmetric, stationary solutions of the Einstein field equations formed from classical gravitational collapse of matter obeying the null energy condition, that are everywhere smooth and ultracompact (i.e., they have a light ring) must have at least two light rings, and one of them is stable. It has been argued that stable light rings generally lead to nonlinear spacetime instabilities. Our result implies that smooth, physically and dynamically reasonable ultracompact objects are not viable as observational alternatives to black holes whenever these instabilities occur on astrophysically short time scales. The proof of the theorem has two parts: (i) We show that light rings always come in pairs, one being a saddle point and the other a local extremum of an effective potential. This result follows from a topological argument based on the Brouwer degree of a continuous map, with no assumptions on the spacetime dynamics, and, hence, it is applicable to any metric gravity theory where photons follow null geodesics. (ii) Assuming Einstein's equations, we show that the extremum is a local minimum of the potential (i.e., a stable light ring) if the energy-momentum tensor satisfies the null energy condition.

Light-Ring Stability for Ultracompact Objects

NASA Astrophysics Data System (ADS)

Cunha, Pedro V. P.; Berti, Emanuele; Herdeiro, Carlos A. R.

2017-12-01

We prove the following theorem: axisymmetric, stationary solutions of the Einstein field equations formed from classical gravitational collapse of matter obeying the null energy condition, that are everywhere smooth and ultracompact (i.e., they have a light ring) must have at least two light rings, and one of them is stable. It has been argued that stable light rings generally lead to nonlinear spacetime instabilities. Our result implies that smooth, physically and dynamically reasonable ultracompact objects are not viable as observational alternatives to black holes whenever these instabilities occur on astrophysically short time scales. The proof of the theorem has two parts: (i) We show that light rings always come in pairs, one being a saddle point and the other a local extremum of an effective potential. This result follows from a topological argument based on the Brouwer degree of a continuous map, with no assumptions on the spacetime dynamics, and, hence, it is applicable to any metric gravity theory where photons follow null geodesics. (ii) Assuming Einstein's equations, we show that the extremum is a local minimum of the potential (i.e., a stable light ring) if the energy-momentum tensor satisfies the null energy condition.

A dynamical model for gas flows, star formation and nuclear winds in galactic centres

NASA Astrophysics Data System (ADS)

Krumholz, Mark R.; Kruijssen, J. M. Diederik; Crocker, Roland M.

2017-04-01

We present a dynamical model for gas transport, star formation and winds in the nuclear regions of galaxies, focusing on the Milky Way's Central Molecular Zone (CMZ). In our model angular momentum and mass are transported by a combination of gravitational and bar-driven acoustic instabilities. In gravitationally unstable regions the gas can form stars, and the resulting feedback drives both turbulence and a wind that ejects mass from the CMZ. We show that the CMZ is in a quasi-steady state where mass deposited at large radii by the bar is transported inwards to a star-forming, ring-shaped region at ˜100 pc from the Galactic Centre, where the shear reaches a minimum. This ring undergoes episodic starbursts, with bursts lasting ˜5-10 Myr occurring at ˜20-40 Myr intervals. During quiescence the gas in the ring is not fully cleared, but is driven out of a self-gravitating state by the momentum injected by expanding supernova remnants. Starbursts also drive a wind off the star-forming ring, with a time-averaged mass flux comparable to the star formation rate. We show that our model agrees well with the observed properties of the CMZ, and places it near a star formation minimum within the evolutionary cycle. We argue that such cycles of bursty star formation and winds should be ubiquitous in the nuclei of barred spiral galaxies, and show that the resulting distribution of galactic nuclei on the Kennicutt-Schmidt relation is in good agreement with that observed in nearby galaxies.

Unusual centrosymmetric structure of [M(18-crown-6)](+) (M = Rb, Cs and NH4) complexes stabilized in an environment of hexachloridoantimonate(V) anions.

PubMed

Ponomarova, Vira V; Rusanova, Julia A; Rusanov, Eduard B; Domasevitch, Konstantin V

2015-10-01

In (1,4,7,10,13,16-hexaoxacyclooctadecane)rubidium hexachloridoantimonate(V), [Rb(C12H24O6)][SbCl6], (1), and its isomorphous caesium {(1,4,7,10,13,16-hexaoxacyclooctadecane)caesium hexachloridoantimonate(V), [Cs(C12H24O6)][SbCl6]}, (2), and ammonium {ammonium hexachloridoantimonate(V)-1,4,7,10,13,16-hexaoxacyclooctadecane (1/1), (NH4)[SbCl6]·C12H24O6}, (3), analogues, the hexachloridoantimonate(V) anions and 18-crown-6 molecules reside across -3 axes passing through the Sb atoms and the centroids of the 18-crown-6 groups, both of which coincide with centres of inversion. The Rb(+) [in (1)], Cs(+) [in (2)] and NH4(+) [in (3)] cations are situated inside the cavity of the 18-crown-6 ring; they are situated on -3 axes and are equally disordered about centres of inversion, deviating from the centroid of the 18-crown-6 molecule by 0.4808 (13), 0.9344 (7) and 0.515 (8) Å, respectively. Interaction of the ammonium cation and the 18-crown-6 group is supported by three equivalent hydrogen bonds [N...O = 2.928 (3) Å and N-H...O = 162°]. The centrosymmetric structure of [Cs(18-crown-6)](+), with the large Cs(+) cation approaching the centre of the ligand cavity, is unprecedented and accompanied by unusually short Cs-O bonds [2.939 (2) and 3.091 (2) Å]. For all three compounds, the [M(18-crown-6)](+) cations and [SbCl6](-) anions afford linear stacks along the c axis, with the cationic complexes embedded between pairs of inversion-related anions.

Amino acids at water-vapor interfaces: surface activity and orientational ordering.

PubMed

Vöhringer-Martinez, Esteban; Toro-Labbé, Alejandro

2010-10-14

The surface activity and orientational ordering of amino acids at water-vapor interfaces were studied with molecular dynamics simulations in combination with thermodynamic integration and umbrella sampling. Asparagine, representing amino acids with polar side chains, displays no surface activity. Tryptophan, in contrast, with its hydrophobic indole ring as side chain unveils a free energy minimum at the water-vapor interface, which lies 6 kJ/mol under the hydration free energy. To study the orientational ordering of tryptophan along the interface, the order parameter was calculated. At the free energy minimum and at the Gibbs dividing surface, the order parameter reveals a parallel alignment of the indole ring with the water surface exposing the π-system to electrophiles in the hydrophobic phase and indicating polarization dependent spectroscopy. In the vicinity of this position a perpendicular orientation is obtained. The surface excess, calculated from the potential of mean force along the interface, is in excellent agreement with experimental measurements.

Detection and direction discrimination of single vortex rings by harbour seals (Phoca vitulina).

PubMed

Krüger, Yvonne; Hanke, Wolf; Miersch, Lars; Dehnhardt, Guido

2018-04-25

Harbour seals possess highly sensitive vibrissae that enable them to track hydrodynamic trails left behind by a swimming fish. Most of these trails contain vortex rings as a main hydrodynamic component. They may reveal information about their generator as the trails differ depending on the fish species, the fish's body shape, size and swimming style. In addition, fish generate single vortex rings in diverse natural situations. In this study, the ability of blindfolded stationary harbour seals to detect and analyse single vortex rings regarding directional information has been investigated. In three different behavioural experiments, the animals were trained to respond to single artificially generated vortex rings. The results show that harbour seals are able to respond to a variety of different vortex rings upon vibrissal stimulation. The investigation of the minimum hydrodynamically perceivable angle revealed that it is at least as small as 5.7 deg, which was the smallest adjustable angle. Moreover, harbour seals are capable of analysing the travel direction of a vortex ring perceived by the mystacial vibrissae irrespective of whether the vibrissae were stimulated ipsilaterally or contralaterally. In situations in which no complex hydrodynamic trail is available, it is advantageous for a hunting seal to be able to extract information from a single vortex ring. © 2018. Published by The Company of Biologists Ltd.

Basic firefly algorithm for document clustering

NASA Astrophysics Data System (ADS)

Mohammed, Athraa Jasim; Yusof, Yuhanis; Husni, Husniza

2015-12-01

The Document clustering plays significant role in Information Retrieval (IR) where it organizes documents prior to the retrieval process. To date, various clustering algorithms have been proposed and this includes the K-means and Particle Swarm Optimization. Even though these algorithms have been widely applied in many disciplines due to its simplicity, such an approach tends to be trapped in a local minimum during its search for an optimal solution. To address the shortcoming, this paper proposes a Basic Firefly (Basic FA) algorithm to cluster text documents. The algorithm employs the Average Distance to Document Centroid (ADDC) as the objective function of the search. Experiments utilizing the proposed algorithm were conducted on the 20Newsgroups benchmark dataset. Results demonstrate that the Basic FA generates a more robust and compact clusters than the ones produced by K-means and Particle Swarm Optimization (PSO).

Evaluation of a LiF:Mg,Ti thermoluminescent ring dosimeter according to the IEC 62387:2012 Standards

NASA Astrophysics Data System (ADS)

Oliveira, Edyelle L. B.; de Barros, Vinícius S. M.; Asfora, Viviane K.; Khoury, Helen J.

2018-03-01

This work shows results of type testing of a ring radiation dosimeter system under IEC 62387:2012. The personal dosimeter investigated in this work consists of a commercial one element plastic ring which contains an LiF:Mg,Ti thermoluminescent pellet. By applying requirements for statistical fluctuations and linearity, a minimum measurable dose in Hp(0.07) was established. Energy and angular dependence aided in determining energy correction factors and fading requirements were used to select the most appropriate preheat scheme. Type testing of passive radiation monitors was performed in the Radiation Metrology Laboratory (LMRI-DEN/UFPE) of the Federal University of Pernambuco and is a major step in Brazil for the independent evaluation of these dosimeters, currently not available in the country.

Generic Design Procedures for the Repair of Acoustically Damaged Panels

DTIC Science & Technology

2008-12-01

plate for component 1 h2 Thickness of plate for component 2 h3 Thickness of plate for component 3 h13 Distance from centroid of component 1 to centroid...E1 View AA Simply supported/clamped plate h13 Ly Lx y x d3 d1 y 2a Figure 4: Geometry for constrained layer damping of a simply...dimensions, properties and parameters Physical dimensions (Figure 4) Material properties Key parameters h1, h2 , h3 , h13 , Lx , Ly , 2a E1 , E3 , G2

Ambiguity Of Doppler Centroid In Synthetic-Aperture Radar

NASA Technical Reports Server (NTRS)

Chang, Chi-Yung; Curlander, John C.

1991-01-01

Paper discusses performances of two algorithms for resolution of ambiguity in estimated Doppler centroid frequency of echoes in synthetic-aperture radar. One based on range-cross-correlation technique, other based on multiple-pulse-repetition-frequency technique.

Centroid estimation for a Shack-Hartmann wavefront sensor based on stream processing.

PubMed

Kong, Fanpeng; Polo, Manuel Cegarra; Lambert, Andrew

2017-08-10

Using center of gravity to estimate the centroid of the spot in a Shack-Hartmann wavefront sensor, the measurement corrupts with photon and detector noise. Parameters, like window size, often require careful optimization to balance the noise error, dynamic range, and linearity of the response coefficient under different photon flux. It also needs to be substituted by the correlation method for extended sources. We propose a centroid estimator based on stream processing, where the center of gravity calculation window floats with the incoming pixel from the detector. In comparison with conventional methods, we show that the proposed estimator simplifies the choice of optimized parameters, provides a unit linear coefficient response, and reduces the influence of background and noise. It is shown that the stream-based centroid estimator also works well for limited size extended sources. A hardware implementation of the proposed estimator is discussed.

Effects of window size and shape on accuracy of subpixel centroid estimation of target images

NASA Technical Reports Server (NTRS)

Welch, Sharon S.

1993-01-01

A new algorithm is presented for increasing the accuracy of subpixel centroid estimation of (nearly) point target images in cases where the signal-to-noise ratio is low and the signal amplitude and shape vary from frame to frame. In the algorithm, the centroid is calculated over a data window that is matched in width to the image distribution. Fourier analysis is used to explain the dependency of the centroid estimate on the size of the data window, and simulation and experimental results are presented which demonstrate the effects of window size for two different noise models. The effects of window shape were also investigated for uniform and Gaussian-shaped windows. The new algorithm was developed to improve the dynamic range of a close-range photogrammetric tracking system that provides feedback for control of a large gap magnetic suspension system (LGMSS).

Photometric analysis in the Kepler Science Operations Center pipeline

NASA Astrophysics Data System (ADS)

Twicken, Joseph D.; Clarke, Bruce D.; Bryson, Stephen T.; Tenenbaum, Peter; Wu, Hayley; Jenkins, Jon M.; Girouard, Forrest; Klaus, Todd C.

2010-07-01

We describe the Photometric Analysis (PA) software component and its context in the Kepler Science Operations Center (SOC) Science Processing Pipeline. The primary tasks of this module are to compute the photometric flux and photocenters (centroids) for over 160,000 long cadence (~thirty minute) and 512 short cadence (~one minute) stellar targets from the calibrated pixels in their respective apertures. We discuss science algorithms for long and short cadence PA: cosmic ray cleaning; background estimation and removal; aperture photometry; and flux-weighted centroiding. We discuss the end-to-end propagation of uncertainties for the science algorithms. Finally, we present examples of photometric apertures, raw flux light curves, and centroid time series from Kepler flight data. PA light curves, centroid time series, and barycentric timestamp corrections are exported to the Multi-mission Archive at Space Telescope [Science Institute] (MAST) and are made available to the general public in accordance with the NASA/Kepler data release policy.

Photometric Analysis in the Kepler Science Operations Center Pipeline

NASA Technical Reports Server (NTRS)

Twicken, Joseph D.; Clarke, Bruce D.; Bryson, Stephen T.; Tenenbaum, Peter; Wu, Hayley; Jenkins, Jon M.; Girouard, Forrest; Klaus, Todd C.

2010-01-01

We describe the Photometric Analysis (PA) software component and its context in the Kepler Science Operations Center (SOC) pipeline. The primary tasks of this module are to compute the photometric flux and photocenters (centroids) for over 160,000 long cadence (thirty minute) and 512 short cadence (one minute) stellar targets from the calibrated pixels in their respective apertures. We discuss the science algorithms for long and short cadence PA: cosmic ray cleaning; background estimation and removal; aperture photometry; and flux-weighted centroiding. We discuss the end-to-end propagation of uncertainties for the science algorithms. Finally, we present examples of photometric apertures, raw flux light curves, and centroid time series from Kepler flight data. PA light curves, centroid time series, and barycentric timestamp corrections are exported to the Multi-mission Archive at Space Telescope [Science Institute] (MAST) and are made available to the general public in accordance with the NASA/Kepler data release policy.

QPO from the rapid burster

NASA Astrophysics Data System (ADS)

Dotani, T.

1989-11-01

Strong Quasi-Periodic Oscillations (QPO) in type 2 bursts from the rapid burster with Ginga were detected. The QPD have centroid frequency of approximately 5 and 2 Hz during bursts which lasted for approximately 10 and 30 sec, respectively. The QPO observations were analyzed and the following results were obtained: QPO centroid frequencies have some correlation with burst duration and peak count rate, however the correlations are complicated and the burst parameters do not uniquely determine the QPO centroid frequency; the appearance of the QPO is closely related to the so-called timescale-invariant profile of the bursts; the QPO are significant only in the even numbered peaks of the profile and not in the odd numbered peaks; in most cases the QPO centroid frequency decreases up to approximately 25 percent during a burst. The energy spectra at the QPO peaks and valleys were investigated and the QPO peaks were found to have significantely higher blackbody temperature than the QPD valleys.

Application of k-means clustering algorithm in grouping the DNA sequences of hepatitis B virus (HBV)

NASA Astrophysics Data System (ADS)

Bustamam, A.; Tasman, H.; Yuniarti, N.; Frisca, Mursidah, I.

2017-07-01

Based on WHO data, an estimated of 15 millions people worldwide who are infected with hepatitis B (HBsAg+), which is caused by HBV virus, are also infected by hepatitis D, which is caused by HDV virus. Hepatitis D infection can occur simultaneously with hepatitis B (co infection) or after a person is exposed to chronic hepatitis B (super infection). Since HDV cannot live without HBV, HDV infection is closely related to HBV infection, hence it is very realistic that every effort of prevention against hepatitis B can indirectly prevent hepatitis D. This paper presents clustering of HBV DNA sequences by using k-means clustering algorithm and R programming. Clustering processes are started with collecting HBV DNA sequences from GenBank, then performing extraction HBV DNA sequences using n-mers frequency and furthermore the extraction results are collected as a matrix and normalized using the min-max normalization with interval [0, 1] which will later be used as an input data. The number of clusters is two and the initial centroid selected of the cluster is chosen randomly. In each iteration, the distance of every object to each centroid are calculated using the Euclidean distance and the minimum distance is selected to determine the membership in a cluster until two convergent clusters are created. As the result, the HBV viruses in the first cluster is more virulent than the HBV viruses in the second cluster, so the HBV viruses in the first cluster can potentially evolve with HDV viruses that cause hepatitis D.

Fiber-optic annular detector array for large depth of field photoacoustic macroscopy.

PubMed

Bauer-Marschallinger, Johannes; Höllinger, Astrid; Jakoby, Bernhard; Burgholzer, Peter; Berer, Thomas

2017-03-01

We report on a novel imaging system for large depth of field photoacoustic scanning macroscopy. Instead of commonly used piezoelectric transducers, fiber-optic based ultrasound detection is applied. The optical fibers are shaped into rings and mainly receive ultrasonic signals stemming from the ring symmetry axes. Four concentric fiber-optic rings with varying diameters are used in order to increase the image quality. Imaging artifacts, originating from the off-axis sensitivity of the rings, are reduced by coherence weighting. We discuss the working principle of the system and present experimental results on tissue mimicking phantoms. The lateral resolution is estimated to be below 200 μm at a depth of 1.5 cm and below 230 μm at a depth of 4.5 cm. The minimum detectable pressure is in the order of 3 Pa. The introduced method has the potential to provide larger imaging depths than acoustic resolution photoacoustic microscopy and an imaging resolution similar to that of photoacoustic computed tomography.

Fiber-ring laser-based intracavity photoacoustic spectroscopy for trace gas sensing.

PubMed

Wang, Qiang; Wang, Zhen; Chang, Jun; Ren, Wei

2017-06-01

We demonstrated a novel trace gas sensing method based on fiber-ring laser intracavity photoacoustic spectroscopy. This spectroscopic technique is a merging of photoacoustic spectroscopy (PAS) with a fiber-ring cavity for sensitive and all-fiber gas detection. A transmission-type PAS gas cell (resonant frequency f₀=2.68  kHz) was placed inside the fiber-ring laser to fully utilize the intracavity laser power. The PAS signal was excited by modulating the laser wavelength at f₀/2 using a custom-made fiber Bragg grating-based modulator. We used this spectroscopic technique to detect acetylene (C₂H₂) at 1531.6 nm as a proof of principle. With a low Q-factor (4.9) of the PAS cell, our sensor achieved a good linear response (R²=0.996) to C₂H₂ concentration and a minimum detection limit of 390 ppbv at 2-s response time.

Seasonal temperature and precipitation recorded in the intra-annual oxygen isotope pattern of meteoric water and tree-ring cellulose

NASA Astrophysics Data System (ADS)

Schubert, Brian A.; Jahren, A. Hope

2015-10-01

Modern and ancient wood is a valuable terrestrial record of carbon ultimately derived from the atmosphere and oxygen inherited from local meteoric water. Many modern and fossil wood specimens display rings sufficiently thick for intra-annual sampling, and analytical techniques are rapidly improving to allow for precise carbon and oxygen isotope measurements on very small samples, yielding unprecedented resolution of seasonal isotope records. However, the interpretation of these records across diverse environments has been problematic because a unifying model for the quantitative interpretation of seasonal climate parameters from oxygen isotopes in wood is lacking. Towards such a model, we compiled a dataset of intra-ring oxygen isotope measurements on modern wood cellulose (δ18Ocell) from 33 globally distributed sites. Five of these sites represent original data produced for this study, while the data for the other 28 sites were taken from the literature. We defined the intra-annual change in oxygen isotope value of wood cellulose [Δ(δ18Ocell)] as the difference between the maximum and minimum δ18Ocell values determined within the ring. Then, using the monthly-resolved dataset of the oxygen isotope composition of meteoric water (δ18OMW) provided by the Global Network of Isotopes in Precipitation database, we quantified the empirical relationship between the intra-annual change in meteoric water [Δ(δ18OMW)] and Δ(δ18Ocell). We then used monthly-resolved datasets of temperature and precipitation to develop a global relationship between Δ(δ18OMW) and maximum/minimum monthly temperatures and winter/summer precipitation amounts. By combining these relationships we produced a single equation that explains much of the variability in the intra-ring δ18Ocell signal through only changes in seasonal temperature and precipitation amount (R2 = 0.82). We show how our recent model that quantifies seasonal precipitation from intra-ring carbon isotope profiles can be incorporated into the oxygen model above in order to separately quantify both seasonal temperature and seasonal precipitation. Determination of seasonal climate variation using high-resolution isotopes in tree-ring records makes possible a new understanding of the seasonal fluctuations that control the environmental conditions to which organisms are subject, both during recent history and in the geologic past.

Non-linear Min protein interactions generate harmonics that signal mid-cell division in Escherichia coli

PubMed Central

Walsh, James C.; Angstmann, Christopher N.; Duggin, Iain G.

2017-01-01

The Min protein system creates a dynamic spatial pattern in Escherichia coli cells where the proteins MinD and MinE oscillate from pole to pole. MinD positions MinC, an inhibitor of FtsZ ring formation, contributing to the mid-cell localization of cell division. In this paper, Fourier analysis is used to decompose experimental and model MinD spatial distributions into time-dependent harmonic components. In both experiment and model, the second harmonic component is responsible for producing a mid-cell minimum in MinD concentration. The features of this harmonic are robust in both experiment and model. Fourier analysis reveals a close correspondence between the time-dependent behaviour of the harmonic components in the experimental data and model. Given this, each molecular species in the model was analysed individually. This analysis revealed that membrane-bound MinD dimer shows the mid-cell minimum with the highest contrast when averaged over time, carrying the strongest signal for positioning the cell division ring. This concurs with previous data showing that the MinD dimer binds to MinC inhibiting FtsZ ring formation. These results show that non-linear interactions of Min proteins are essential for producing the mid-cell positioning signal via the generation of second-order harmonic components in the time-dependent spatial protein distribution. PMID:29040283

Rock climbing: A local-global algorithm to compute minimum energy and minimum free energy pathways.

PubMed

Templeton, Clark; Chen, Szu-Hua; Fathizadeh, Arman; Elber, Ron

2017-10-21

The calculation of minimum energy or minimum free energy paths is an important step in the quantitative and qualitative studies of chemical and physical processes. The computations of these coordinates present a significant challenge and have attracted considerable theoretical and computational interest. Here we present a new local-global approach to study reaction coordinates, based on a gradual optimization of an action. Like other global algorithms, it provides a path between known reactants and products, but it uses a local algorithm to extend the current path in small steps. The local-global approach does not require an initial guess to the path, a major challenge for global pathway finders. Finally, it provides an exact answer (the steepest descent path) at the end of the calculations. Numerical examples are provided for the Mueller potential and for a conformational transition in a solvated ring system.

Path-integral isomorphic Hamiltonian for including nuclear quantum effects in non-adiabatic dynamics

NASA Astrophysics Data System (ADS)

Tao, Xuecheng; Shushkov, Philip; Miller, Thomas F.

2018-03-01

We describe a path-integral approach for including nuclear quantum effects in non-adiabatic chemical dynamics simulations. For a general physical system with multiple electronic energy levels, a corresponding isomorphic Hamiltonian is introduced such that Boltzmann sampling of the isomorphic Hamiltonian with classical nuclear degrees of freedom yields the exact quantum Boltzmann distribution for the original physical system. In the limit of a single electronic energy level, the isomorphic Hamiltonian reduces to the familiar cases of either ring polymer molecular dynamics (RPMD) or centroid molecular dynamics Hamiltonians, depending on the implementation. An advantage of the isomorphic Hamiltonian is that it can easily be combined with existing mixed quantum-classical dynamics methods, such as surface hopping or Ehrenfest dynamics, to enable the simulation of electronically non-adiabatic processes with nuclear quantum effects. We present numerical applications of the isomorphic Hamiltonian to model two- and three-level systems, with encouraging results that include improvement upon a previously reported combination of RPMD with surface hopping in the deep-tunneling regime.

(E)-2-[4-(Diethyl­amino)­styr­yl]-1-methyl­pyridinium 4-chloro­benzene­sulfonate monohydrate

PubMed Central

Fun, Hoong-Kun; Kaewmanee, Narissara; Chanawanno, Kullapa; Karalai, Chatchanok; Chantrapromma, Suchada

2011-01-01

In the title hydrated mol­ecular salt, C18H23N2 +·C6H4ClO3S−·H2O, which shows moderate biological activity against methicillin-resistant Staphylococcus aureus (MRSA), one ethyl group of the 2-[4-(diethyl­amino)­styr­yl]-1-methyl­pyridinium cation is disordered over two orientations in a 0.604 (13):0.396 (13) ratio. The main part of the cation is nearly planar with a dihedral angle of 4.50 (10)° between the pyridinium and benzene rings. In the crystal, the components are linked by O—H⋯O hydrogen bonds and C—H⋯O weak inter­actions. Aromatic π–π stacking inter­actions with centroid–centroid separations of 3.7363 (12) and 3.7490 (13) Å also occur. PMID:22059040

Optical performances of the FM JEM-X masks

NASA Astrophysics Data System (ADS)

Reglero, V.; Rodrigo, J.; Velasco, T.; Gasent, J. L.; Chato, R.; Alamo, J.; Suso, J.; Blay, P.; Martínez, S.; Doñate, M.; Reina, M.; Sabau, D.; Ruiz-Urien, I.; Santos, I.; Zarauz, J.; Vázquez, J.

2001-09-01

The JEM-X Signal Multiplexing Systems are large HURA codes "written" in a pure tungsten plate 0.5 mm thick. 24.247 hexagonal pixels (25% open) are spread over a total area of 535 mm diameter. The tungsten plate is embedded in a mechanical structure formed by a Ti ring, a pretensioning system (Cu-Be) and an exoskeleton structure that provides the required stiffness. The JEM-X masks differ from the SPI and IBIS masks on the absence of a code support structure covering the mask assembly. Open pixels are fully transparent to X-rays. The scope of this paper is to report the optical performances of the FM JEM-X masks defined by uncertainties on the pixel location (centroid) and size coming from the manufacturing and assembly processes. Stability of the code elements under thermoelastic deformations is also discussed. As a general statement, JEM-X Mask optical properties are nearly one order of magnitude better than specified in 1994 during the ESA instrument selection.

Trichlorido[(meth­yl{2-[meth­yl(2-pyridyl­meth­yl)amino]eth­yl}amino)acetonitrile]iron(III) methanol hemisolvate

PubMed Central

Nielsen, Anne; McKenzie, Christine J.; Bond, Andrew D.

2009-01-01

The title compound, [FeCl3(C12H18N4)]·0.5CH3OH, contains an FeIII ion in a distorted octa­hedral coordination environment. The neutral N,N′,N′′-tridentate ligand adopts a fac coordination mode, and chloride ligands lie trans to each of the three coordinated N atoms. In the crystal, the complexes form columns extending parallel to the approximate local threefold axes of the FeN3Cl3 octa­hedra, and the columns are arranged so that the uncoordinated nitrile groups align in an anti­parallel manner and the pyridyl rings form offset face-to-face arrangements [inter­planar separations = 2.95 (1) and 3.11 (1) Å; centroid–centroid distances = 5.31 (1) and 4.92 (1) Å]. The methanol solvent mol­ecule is disordered about a twofold rotation axis. PMID:21578169

(Carbonato-κ2 O,O′)bis­(5,5′-dimethyl-2,2′-bipyridyl-κ2 N,N′)cobalt(III) bromide trihydrate

PubMed Central

Arun Kumar, Kannan; Meera, Parthsarathi; Amutha Selvi, Madhavan; Dayalan, Arunachalam

2012-01-01

In the title complex, [Co(CO3)(C12H12N2)2]Br·3H2O, the CoIII cation has a distorted octa­hedral coordination environment. It is chelated by four N atoms of two different 5,5′-dimethyl-2,2′-bipyridyl (dmbpy) ligands in axial and equatorial positions, and by two O atoms of a carbonate anion completing the equatorial positions. Although the water mol­ecules are disordered and their H atoms were not located, there are typical O⋯O distances between 2.8 and 3.0 Å, indicating O—H⋯O hydrogen bonding. The crystal packing is consolidated by C—H⋯O and C—H⋯Br hydrogen bonds, as well as π–π stacking inter­actions between adjacent pyridine rings of the dmbpy ligands, with centroid–centroid distances of 3.694 (3) and 3.7053 (3) Å. PMID:22589773

Centroids evaluation of the images obtained with the conical null-screen corneal topographer

NASA Astrophysics Data System (ADS)

Osorio-Infante, Arturo I.; Armengol-Cruz, Victor de Emanuel; Campos-García, Manuel; Cossio-Guerrero, Cesar; Marquez-Flores, Jorge; Díaz-Uribe, José Rufino

2016-09-01

In this work, we propose some algorithms to recover the centroids of the resultant image obtained by a conical nullscreen based corneal topographer. With these algorithms, we obtain the region of interest (roi) of the original image and using an image-processing algorithm, we calculate the geometric centroid of each roi. In order to improve our algorithm performance, we use different settings of null-screen targets, changing their size and number. We also improved the illumination system to avoid inhomogeneous zones in the corneal images. Finally, we report some corneal topographic measurements with the best setting we found.

An Accurate Centroiding Algorithm for PSF Reconstruction

NASA Astrophysics Data System (ADS)

Lu, Tianhuan; Luo, Wentao; Zhang, Jun; Zhang, Jiajun; Li, Hekun; Dong, Fuyu; Li, Yingke; Liu, Dezi; Fu, Liping; Li, Guoliang; Fan, Zuhui

2018-07-01

In this work, we present a novel centroiding method based on Fourier space Phase Fitting (FPF) for Point Spread Function (PSF) reconstruction. We generate two sets of simulations to test our method. The first set is generated by GalSim with an elliptical Moffat profile and strong anisotropy that shifts the center of the PSF. The second set of simulations is drawn from CFHT i band stellar imaging data. We find non-negligible anisotropy from CFHT stellar images, which leads to ∼0.08 scatter in units of pixels using a polynomial fitting method (Vakili & Hogg). When we apply the FPF method to estimate the centroid in real space, the scatter reduces to ∼0.04 in S/N = 200 CFHT-like sample. In low signal-to-noise ratio (S/N; 50 and 100) CFHT-like samples, the background noise dominates the shifting of the centroid; therefore, the scatter estimated from different methods is similar. We compare polynomial fitting and FPF using GalSim simulation with optical anisotropy. We find that in all S/N (50, 100, and 200) samples, FPF performs better than polynomial fitting by a factor of ∼3. In general, we suggest that in real observations there exists anisotropy that shifts the centroid, and thus, the FPF method provides a better way to accurately locate it.

Accuracy of Shack-Hartmann wavefront sensor using a coherent wound fibre image bundle

NASA Astrophysics Data System (ADS)

Zheng, Jessica R.; Goodwin, Michael; Lawrence, Jon

2018-03-01

Shack-Hartmannwavefront sensors using wound fibre image bundles are desired for multi-object adaptive optical systems to provide large multiplex positioned by Starbugs. The use of a large-sized wound fibre image bundle provides the flexibility to use more sub-apertures wavefront sensor for ELTs. These compact wavefront sensors take advantage of large focal surfaces such as the Giant Magellan Telescope. The focus of this paper is to study the wound fibre image bundle structure defects effect on the centroid measurement accuracy of a Shack-Hartmann wavefront sensor. We use the first moment centroid method to estimate the centroid of a focused Gaussian beam sampled by a simulated bundle. Spot estimation accuracy with wound fibre image bundle and its structure impact on wavefront measurement accuracy statistics are addressed. Our results show that when the measurement signal-to-noise ratio is high, the centroid measurement accuracy is dominated by the wound fibre image bundle structure, e.g. tile angle and gap spacing. For the measurement with low signal-to-noise ratio, its accuracy is influenced by the read noise of the detector instead of the wound fibre image bundle structure defects. We demonstrate this both with simulation and experimentally. We provide a statistical model of the centroid and wavefront error of a wound fibre image bundle found through experiment.

[Difference in responses of major tree species growth to climate in the Miyaluo Mountains, western Sichuan, China].

PubMed

Guo, Ming-ming; Zhang, Yuan-dong; Wang, Xiao-chun; Liu, Shi-rong

2015-08-01

To explore the responses of different tree species growth to climate change in the semi-humid region of the eastern Tibetan Plateau, we investigated climate-growth relationships of Tsuga chinensis, Abies faxoniana, Picea purpurea at an altitude of 3000 m (low altitude) and A. faxoniana and Larix mastersiana at an altitude of 4000 m (high altitude) using tree ring-width chronologies (total of 182 cores) developed from Miyaluo, western Sichuan, China. Five residual chronologies were developed from the cross-dated ring width series using the program ARSTAN, and the relationships between monthly climate variables and tree-ring index were analyzed. Results showed that the chronologies of trees at low altitudes were negatively correlated with air temperature but positively with precipitation in April and May. This indicated that drought stress limited tree growth at low altitude, but different tree species showed significant variations. T. chinensis was most severely affected by drought stress, followed by A. faxoniana and P. purpurea. Trees at high altitude were mainly affected by growing season temperature. Tree-ring index of A. faxoniana was positively correlated with monthly minimum temperature in February and July of the current year and monthly maximum temperature in October of the previous year. Radial growth of L. mastersiana was positively correlated with monthly maximum temperature in May, and negatively with monthly mean temperature in February and monthly minimum temperature in March. In recent decadal years, the climate in northeast Tibetan Plateau had a warming and drying trend. If this trend continues, we could deduce that P. purpurea should grow faster than T. chinensis and A. faxoniana at low altitudes, while A. faxoniana would benefit more from global warming at high altitudes.

Branch architecture in Ginkgo biloba: wood anatomy and long shoot-short shoot interactions.

PubMed

Little, Stefan A; Jacobs, Brooke; McKechnie, Steven J; Cooper, Ranessa L; Christianson, Michael L; Jernstedt, Judith A

2013-10-01

Ginkgo, centrally placed in seed plant phylogeny, is considered important in many phylogenetic and evolutionary studies. Shoot dimorphism of Ginkgo has been long noted, but no work has yet been done to evaluate the relationships between overall branch architecture and wood ring characters, shoot growth, and environmental conditions. • Branches, sampled from similar canopy heights, were mapped with the age of each long shoot segment determined by counting annual leaf-scar series on its short shoots. Transverse sections were made for each long shoot segment and an adjacent short shoot; wood ring thickness, number of rings, and number of tracheids/ring were determined. Using branch maps, we identified wood rings for each long shoot segment to year and developmental context of each year (distal short shoot growth only vs. at least one distal long shoot). Climate data were also analyzed in conjunction with developmental context. • Significantly thicker wood rings occur in years with distal long shoot development. The likelihood that a branch produced long shoots in a given year was lower with higher maximum annual temperature. Annual maximum temperature was negatively correlated with ring thickness in microsporangiate trees only. Annual minimum temperatures were correlated differently with ring thickness of megasporangiate and microsporangiate trees, depending on the developmental context. There were no significant effects associated with precipitation. • Overall, developmental context alone predicts wood ring thickness about as well as models that include temperature. This suggests that although climatic factors may be strongly correlated with wood ring data among many gymnosperm taxa, at least for Ginkgo, correlations with climate data are primarily due to changes in proportions of shoot developmental types (LS vs. SS) across branches.

Intraoperative cyclorotation and pupil centroid shift during LASIK and PRK.

PubMed

Narváez, Julio; Brucks, Matthew; Zimmerman, Grenith; Bekendam, Peter; Bacon, Gregory; Schmid, Kristin

2012-05-01

To determine the degree of cyclorotation and centroid shift in the x and y axis that occurs intraoperatively during LASIK and photorefractive keratectomy (PRK). Intraoperative cyclorotation and centroid shift were measured in 63 eyes from 34 patients with a mean age of 34 years (range: 20 to 56 years) undergoing either LASIK or PRK. Preoperatively, an iris image of each eye was obtained with the VISX WaveScan Wavefront System (Abbott Medical Optics Inc) with iris registration. A VISX Star S4 (Abbott Medical Optics Inc) laser was later used to measure cyclotorsion and pupil centroid shift at the beginning of the refractive procedure and after flap creation or epithelial removal. The mean change in intraoperative cyclorotation was 1.48±1.11° in LASIK eyes and 2.02±2.63° in PRK eyes. Cyclorotation direction changed by >2° in 21% of eyes after flap creation in LASIK and in 32% of eyes after epithelial removal in PRK. The respective mean intraoperative shift in the x axis and y axis was 0.13±0.15 mm and 0.17±0.14 mm, respectively, in LASIK eyes, and 0.09±0.07 mm and 0.10±0.13 mm, respectively, in PRK eyes. Intraoperative centroid shifts >100 μm in either the x axis or y axis occurred in 71% of LASIK eyes and 55% of PRK eyes. Significant changes in cyclotorsion and centroid shifts were noted prior to surgery as well as intraoperatively with both LASIK and PRK. It may be advantageous to engage iris registration immediately prior to ablation to provide a reference point representative of eye position at the initiation of laser delivery. Copyright 2012, SLACK Incorporated.

Filtering effect of SiO2 optical waveguide ring resonator applied to optoelectronic oscillator.

PubMed

Chen, Jiamin; Zheng, Yongqiu; Xue, Chenyang; Zhang, Chengfei; Chen, Yi

2018-05-14

Single-mode oscillation is crucial to the practicality of optoelectronic oscillator (OEO). Due to the limited by bandwidth and precision of radio frequency (RF) filters, it is difficult to be achieved for the OEO based on the long fiber-optic delay line. So instead of the long fiber-optic delay line, SiO 2 optical waveguide ring resonator (OWRR) with high-Q and mode selection is first presented to be applied to OEO. The OEOs based on the minimum loop and SiO 2 OWRR are constructed. The oscillation characteristics of the minimum loop OEO and the transmission characteristics of the SiO 2 OWRR are simulated by MATLAB, respectively. The filtering effect of the SiO 2 OWRR applied to the OEO is verified theoretically by comparing these simulation results. Subsequently, the contrastive experiments of the above two OEOs on oscillation modes are carried out. The oscillation mode spacing of 40.32 MHz and 2.137 GHz are obtained. These results show that the SiO 2 OWRR can function as an excellent 'filter' in the minimum loop of the OEO. Moreover, the side mode suppression ratio and the phase noise of the OEO have been improved. Our experimental results demonstrate that the OEO adopting SiO 2 OWRR is feasible to achieve the single-mode oscillation and obtain better performance microwave signals.

Solar and climate signal records in tree ring width from Chile (AD 1587 1994)

NASA Astrophysics Data System (ADS)

Rodolfo Rigozo, Nivaor; Roger Nordemann, Daniel Jean; Evangelista da Silva, Heitor; Pereira de Souza Echer, Mariza; Echer, Ezequiel

2007-01-01

Tree growth rings represent an important natural record of past climate variations and solar activity effects registered on them. We performed in this study a wavelet analysis of tree ring samples of Pilgerodendron cupressoides species, from Glaciar Pio XI (Lat: 49°12'S; 74°55'W; Alt: 25 m), Chile. We obtained an average chronology of about 400 years from these trees. The 11-yr solar cycle was present during the whole period in tree ring data, being more intense during Maunder minimum (1645-1715). The short-term periods, around 2-7 yr, that were found are more likely associated with ENSO effects. Further, we found significant periods around 52 and 80-100 yr. These periodicities are coincident with the fourth harmonic (52 yr) of the Suess cycle (208 yr) and Gleissberg (˜80-100 yr) solar cycles. Therefore, the present analysis shows evidence of solar activity effect/modulation on climatic conditions that affect tree ring growth. Although we cannot say with the present analysis if this effect is on local, regional or global climate, these results add evidence to an important role of solar activity over terrestrial climate over the past ˜400 yr.

Crystal structure of 2,2′′-bis­(2,7-di­chloro-9-hy­droxy-9H-fluoren-9-yl)-1,1′:4′,1′′-terphenyl tri­ethyl­amine trisolvate

PubMed Central

Klien, Henrik; Seichter, Wilhelm; Weber, Edwin

2015-01-01

In the title solvate, C44H26Cl4O2·3C6H15N, the asymmetric part of the unit cell comprises two halves of the diol mol­ecules, 2,2′′-bis­(2,7-di­chloro-9-hy­droxy-9H-fluoren-9-yl)-1,1′:4′,1′′-terphenyl, and three mol­ecules of tri­ethyl­amine, i. e. the diol mol­ecules are located on crystallographic symmetry centres. Two of the solvent mol­ecules are disordered over two positions [occupancy ratios of 0.567 (3):0.433 (3) and 0.503 (3):0.497 (3)]. In the diol mol­ecules, the outer rings of the 1,1′:4′,1′′-terphenyl elements are twisted with reference to their central arene ring and the mean planes of the fluorenyl moieties are inclined with respect to the terphenyl ring to which they are connected, the latter making dihedral angles of 82.05 (8) and 82.28 (8)°. The presence of two 9-fluoren-9-ol units attached at positions 2 and 2′′ of the terphenyl moiety induces a ‘folded’ geometry which is stabilized by intra­molecular C—H⋯O hydrogen bonds and π–π stacking inter­actions, the latter formed between the fluorenyl units and the central ring of the terphenyl unit [centroid–centroid distances = 3.559 (1) and 3.562 (1) Å]. The crystal is composed of 1:2 complex units, in which the solvent mol­ecules are associated with the diol mol­ecules via O—H⋯N hydrogen bonds, while the remaining solvent mol­ecule is linked to the host by a C—H⋯N hydrogen bond. The given pattern of inter­molecular inter­actions results in formation of chain structures extending along [010]. PMID:26870400

Evaluation of centroiding algorithm error for Nano-JASMINE

NASA Astrophysics Data System (ADS)

Hara, Takuji; Gouda, Naoteru; Yano, Taihei; Yamada, Yoshiyuki

2014-08-01

The Nano-JASMINE mission has been designed to perform absolute astrometric measurements with unprecedented accuracy; the end-of-mission parallax standard error is required to be of the order of 3 milli arc seconds for stars brighter than 7.5 mag in the zw-band(0.6μm-1.0μm) .These requirements set a stringent constraint on the accuracy of the estimation of the location of the stellar image on the CCD for each observation. However each stellar images have individual shape depend on the spectral energy distribution of the star, the CCD properties, and the optics and its associated wave front errors. So it is necessity that the centroiding algorithm performs a high accuracy in any observables. Referring to the study of Gaia, we use LSF fitting method for centroiding algorithm, and investigate systematic error of the algorithm for Nano-JASMINE. Furthermore, we found to improve the algorithm by restricting sample LSF when we use a Principle Component Analysis. We show that centroiding algorithm error decrease after adapted the method.

Reuse of Coconut Shell, Rice Husk, and Coal Ash Blends in Geopolymer Synthesis

NASA Astrophysics Data System (ADS)

Walmiki Samadhi, Tjokorde; Wulandari, Winny; Prasetyo, Muhammad Iqbal; Rizki Fernando, Muhammad

2017-10-01

Mixtures of biomass and coal ashes are likely to be produced in increasing volume as biomass-based energy production is gaining importance in Indonesia. This work highlights the reuse of coconut shell ash (CSA), rice husk ash (RHA), and coal fly ash (FA) for geopolymer synthesis by an activator solution containing concentrated KOH and Na2SiO3. Ash blend compositions are varied according to a simplex-centroid mixture experimental design. Activator to ash mass ratios are varied from 0.8 to 2.0, the higher value being applied for ash compositions with higher Si/Al ratio. The impact of ash blend composition on early strength is adequately modeled by an incomplete quadratic mixture model. Overall, the ashes can produce geopolymer mortars with an early strength exceeding the Indonesian SNI 15-2049-2004 standard minimum value of 2.0 MPa. Good workability of the geopolymer is indicated by their initial setting times which are longer than the minimum value of 45 mins. Geopolymers composed predominantly of RHA composition exhibit poor strength and excessive setting time. FTIR spectroscopy confirms the geopolymerization of the ashes by the shift of the Si-O-Si/Al asymmetric stretching vibrational mode. Overall, these results point to the feasibility of geopolymerization as a reuse pathway for biomass combustion waste.

Automatic extraction of nuclei centroids of mouse embryonic cells from fluorescence microscopy images.

PubMed

Bashar, Md Khayrul; Komatsu, Koji; Fujimori, Toshihiko; Kobayashi, Tetsuya J

2012-01-01

Accurate identification of cell nuclei and their tracking using three dimensional (3D) microscopic images is a demanding task in many biological studies. Manual identification of nuclei centroids from images is an error-prone task, sometimes impossible to accomplish due to low contrast and the presence of noise. Nonetheless, only a few methods are available for 3D bioimaging applications, which sharply contrast with 2D analysis, where many methods already exist. In addition, most methods essentially adopt segmentation for which a reliable solution is still unknown, especially for 3D bio-images having juxtaposed cells. In this work, we propose a new method that can directly extract nuclei centroids from fluorescence microscopy images. This method involves three steps: (i) Pre-processing, (ii) Local enhancement, and (iii) Centroid extraction. The first step includes two variations: first variation (Variant-1) uses the whole 3D pre-processed image, whereas the second one (Variant-2) modifies the preprocessed image to the candidate regions or the candidate hybrid image for further processing. At the second step, a multiscale cube filtering is employed in order to locally enhance the pre-processed image. Centroid extraction in the third step consists of three stages. In Stage-1, we compute a local characteristic ratio at every voxel and extract local maxima regions as candidate centroids using a ratio threshold. Stage-2 processing removes spurious centroids from Stage-1 results by analyzing shapes of intensity profiles from the enhanced image. An iterative procedure based on the nearest neighborhood principle is then proposed to combine if there are fragmented nuclei. Both qualitative and quantitative analyses on a set of 100 images of 3D mouse embryo are performed. Investigations reveal a promising achievement of the technique presented in terms of average sensitivity and precision (i.e., 88.04% and 91.30% for Variant-1; 86.19% and 95.00% for Variant-2), when compared with an existing method (86.06% and 90.11%), originally developed for analyzing C. elegans images.

42 CFR 84.151 - Harness test; minimum requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... withstand a pull of 113 kg. (250 pounds) for 30 minutes without failure. (2) Belts, rings, and attachments... minutes without separating, and the hose attachments shall be arranged so that the pull or drag of the... attachment of the line shall permit dragging the maximum length of hose considered for approval over a...

46 CFR 56.30-30 - Brazed joints.

Code of Federal Regulations, 2010 CFR

2010-10-01

....75). Brazed socket-type joints shall be made with suitable brazing alloys. The minimum socket depth shall be sufficient for the intended service. Brazing alloy shall either be end-fed into the socket or shall be provided in the form of a preinserted ring in a groove in the socket. The brazing alloy shall...

46 CFR 56.30-30 - Brazed joints.

Code of Federal Regulations, 2013 CFR

2013-10-01

....75). Brazed socket-type joints shall be made with suitable brazing alloys. The minimum socket depth shall be sufficient for the intended service. Brazing alloy shall either be end-fed into the socket or shall be provided in the form of a preinserted ring in a groove in the socket. The brazing alloy shall...

46 CFR 56.30-30 - Brazed joints.

Code of Federal Regulations, 2011 CFR

2011-10-01

....75). Brazed socket-type joints shall be made with suitable brazing alloys. The minimum socket depth shall be sufficient for the intended service. Brazing alloy shall either be end-fed into the socket or shall be provided in the form of a preinserted ring in a groove in the socket. The brazing alloy shall...

46 CFR 56.30-30 - Brazed joints.

Code of Federal Regulations, 2014 CFR

2014-10-01

....75). Brazed socket-type joints shall be made with suitable brazing alloys. The minimum socket depth shall be sufficient for the intended service. Brazing alloy shall either be end-fed into the socket or shall be provided in the form of a preinserted ring in a groove in the socket. The brazing alloy shall...

46 CFR 56.30-30 - Brazed joints.

Code of Federal Regulations, 2012 CFR

2012-10-01

....75). Brazed socket-type joints shall be made with suitable brazing alloys. The minimum socket depth shall be sufficient for the intended service. Brazing alloy shall either be end-fed into the socket or shall be provided in the form of a preinserted ring in a groove in the socket. The brazing alloy shall...

16 CFR 1512.6 - Requirements for steering system.

Code of Federal Regulations, 2014 CFR

2014-01-01

... stem insertion mark. Quill-type handlebar stems shall contain a permanent ring or mark which clearly indicates the minimum insertion depth of the handlebar stem into the fork assembly. The insertion mark shall not affect the structural integrity of the stem and shall not be less than 21/2 times the stem...

16 CFR 1512.6 - Requirements for steering system.

Code of Federal Regulations, 2012 CFR

2012-01-01

... stem insertion mark. Quill-type handlebar stems shall contain a permanent ring or mark which clearly indicates the minimum insertion depth of the handlebar stem into the fork assembly. The insertion mark shall not affect the structural integrity of the stem and shall not be less than 21/2 times the stem...

16 CFR 1512.6 - Requirements for steering system.

Code of Federal Regulations, 2010 CFR

2010-01-01

... stem insertion mark. The handlebar stem shall contain a permanent ring or mark which clearly indicates the minimum insertion depth of the handlebar stem into the fork assembly. The insertion mark shall not affect the structural integrity of the stem and shall not be less than 21/2 times the stem diameter from...

16 CFR 1512.6 - Requirements for steering system.

Code of Federal Regulations, 2011 CFR

2011-01-01

... stem insertion mark. The handlebar stem shall contain a permanent ring or mark which clearly indicates the minimum insertion depth of the handlebar stem into the fork assembly. The insertion mark shall not affect the structural integrity of the stem and shall not be less than 21/2 times the stem diameter from...

16 CFR § 1512.6 - Requirements for steering system.

Code of Federal Regulations, 2013 CFR

2013-01-01

... stem insertion mark. Quill-type handlebar stems shall contain a permanent ring or mark which clearly indicates the minimum insertion depth of the handlebar stem into the fork assembly. The insertion mark shall not affect the structural integrity of the stem and shall not be less than 21/2 times the stem...

TORC3: Token-ring clearing heuristic for currency circulation

NASA Astrophysics Data System (ADS)

Humes, Carlos, Jr.; Lauretto, Marcelo S.; Nakano, Fábio; Pereira, Carlos A. B.; Rafare, Guilherme F. G.; Stern, Julio Michael

2012-10-01

Clearing algorithms are at the core of modern payment systems, facilitating the settling of multilateral credit messages with (near) minimum transfers of currency. Traditional clearing procedures use batch processing based on MILP - mixed-integer linear programming algorithms. The MILP approach demands intensive computational resources; moreover, it is also vulnerable to operational risks generated by possible defaults during the inter-batch period. This paper presents TORC3 - the Token-Ring Clearing Algorithm for Currency Circulation. In contrast to the MILP approach, TORC3 is a real time heuristic procedure, demanding modest computational resources, and able to completely shield the clearing operation against the participating agents' risk of default.

Generation of ultrashort pulses with minimum duration of 90\\ {\\text{fs}} in a hybrid mode-locked erbium-doped all-fibre ring laser

NASA Astrophysics Data System (ADS)

Dvoretskiy, D. A.; Sazonkin, S. G.; Voropaev, V. S.; Negin, M. A.; Leonov, S. O.; Pnev, A. B.; Karasik, V. E.; Denisov, L. K.; Krylov, A. A.; Davydov, V. A.; Obraztsova, E. D.

2016-11-01

Regimes of ultrashort pulse generation in an erbium-doped all-fibre ring laser with hybrid mode locking based on single-wall carbon - boron nitride nanotubes and the nonlinear Kerr effect in fibre waveguides are studied. Stable dechirped ultrashort pulses are obtained with a duration of ˜ 90 {\\text{fs}}, a repetition rate of ˜ 42.2 {\\text{MHz}}, and an average output power of ˜ 16.7 {\\text{mW}}, which corresponds to a pulse energy of ˜ 0.4 {\\text{nJ}} and a peak laser power of ˜ 4.4 {\\text{kW}}.

Study of wear between piston ring and cylinder housing of an internal combustion engine by thin layer activation technique

NASA Astrophysics Data System (ADS)

Chowdhury, D. P.; Chaudhuri, Jayanta; Raju, V. S.; Das, S. K.; Bhattacharjee, B. B.; Gangadharan, S.

1989-07-01

The wear analysis of a compression ring and cylinder housing of an Internal Combustion Engine by thin layer activation (TLA) with 40 MeV α-particles from the Variable Energy Cyclotron at Calcutta is reported. The calibration curves have been obtained for Fe and Ni using stacked foil activation technique for determining the absolute wear in these machine parts. It has been possible to determine the pattern of wear on the points along the surface of machine components. The minimum detectable depth in this wear study has been estimated at 0.11 ± 0.04 μm.

Dynamical behavior of Borospherene: A Nanobubble

PubMed Central

Martínez-Guajardo, Gerardo; Luis Cabellos, José; Díaz-Celaya, Andres; Pan, Sudip; Islas, Rafael; Chattaraj, Pratim K.; Heine, Thomas; Merino, Gabriel

2015-01-01

The global minimum structure of borospherene (B40) is a cage, comprising two hexagonal and four heptagonal rings. Born-Oppenheimer Molecular Dynamics simulations show that continuous conversions in between six and seven membered rings take place. The activation energy barrier for such a transformation is found to be 14.3 kcal·mol−1. The completely delocalized σ- and π-frameworks, as well as the conservation of the bonding pattern during rearrangement, facilitate the dynamical behavior of B40. B40 is predicted to act as a support-free spherical two-dimensional liquid at moderate temperature. In other words, B40 could be called as a nanobubble. PMID:26096039

Positron annihilation studies in the field induced depletion regions of metal-oxide-semiconductor structures

NASA Astrophysics Data System (ADS)

Asoka-Kumar, P.; Leung, T. C.; Lynn, K. G.; Nielsen, B.; Forcier, M. P.; Weinberg, Z. A.; Rubloff, G. W.

1992-06-01

The centroid shifts of positron annihilation spectra are reported from the depletion regions of metal-oxide-semiconductor (MOS) capacitors at room temperature and at 35 K. The centroid shift measurement can be explained using the variation of the electric field strength and depletion layer thickness as a function of the applied gate bias. An estimate for the relevant MOS quantities is obtained by fitting the centroid shift versus beam energy data with a steady-state diffusion-annihilation equation and a derivative-gaussian positron implantation profile. Inadequacy of the present analysis scheme is evident from the derived quantities and alternate methods are required for better predictions.

Crystal structure of tetra­aqua­(5,5′-dimethyl-2,2′-bipyridyl-κ2 N,N′)iron(II) sulfate

PubMed Central

Belamri, Yamine; Setifi, Fatima; Francuski, Bojana M.; Novaković, Sladjana B.; Zouaoui, Setifi

2014-01-01

In the title compound, [Fe(C12H12N2)(H2O)4]SO4, the central FeII ion is coordinated by two N atoms from the 5,5′-dimethyl-2,2′-bi­pyridine ligand and four water O atoms in a distorted octa­hedral geometry. The Fe—O coordination bond lengths vary from 2.080 (3) to 2.110 (3) Å, while the two Fe—N coordination bonds have practically identical lengths [2.175 (3) and 2.177 (3) Å]. The chelating N—Fe—N angle of 75.6 (1)° shows the largest deviation from an ideal octa­hedral geometry; the other coordination angles deviate from ideal values by 0.1 (1) to 9.1 (1)°. O—H⋯O hydrogen bonding between the four aqua ligands of the cationic complex and four O-atom acceptors of the anion leads to the formation of layers parallel to the ab plane. Neighbouring layers further inter­act by means of C—H⋯O and π–π inter­actions involving the laterally positioned bi­pyridine rings. The perpen­dicular distance between π–π inter­acting rings is 3.365 (2) Å, with a centroid–centroid distance of 3.702 (3) Å. PMID:25552988

Crystal structures of 3,5-bis-[(E)-3-hy-droxy-benzyl-idene]-1-methyl-piperidin-4-one and 3,5-bis-[(E)-2-chloro-benzyl-idene]-1-methyl-piperidin-4-one.

PubMed

Eryanti, Yum; Zamri, Adel; Herlina, Tati; Supratman, Unang; Rosli, Mohd Mustaqim; Fun, Hoong-Kun

2015-12-01

The title compounds, C20H19NO3, (1), and C20H17Cl2NO, (2), are the 3-hy-droxy-benzyl-idene and 2-chloro-benzyl-idene derivatives, respectively, of curcumin [systematic name: (1E,6E)-1,7-bis-(4-hy-droxy-3-meth-oxy-phen-yl)-1,6-hepta-diene-3,5-dione]. The dihedral angles between the benzene rings in each compound are 21.07 (6)° for (1) and 13.4 (3)° for (2). In both compounds, the piperidinone rings adopt a sofa confirmation and the methyl group attached to the N atom is in an equatorial position. In the crystal of (1), two pairs of O-H⋯N and O-H⋯O hydrogen bonds link the mol-ecules, forming chains along [10-1]. The chains are linked via C-H⋯O hydrogen bonds, forming undulating sheets parallel to the ac plane. In the crystal of (2), mol-ecules are linked by weak C-H⋯Cl hydrogen bonds, forming chains along the [204] direction. The chains are linked along the a-axis direction by π-π inter-actions [inter-centroid distance = 3.779 (4) Å]. For compound (2), the crystal studied was a non-merohedral twin with the refined ratio of the twin components being 0.116 (6):0.886 (6).

Finger vein identification using fuzzy-based k-nearest centroid neighbor classifier

NASA Astrophysics Data System (ADS)

Rosdi, Bakhtiar Affendi; Jaafar, Haryati; Ramli, Dzati Athiar

2015-02-01

In this paper, a new approach for personal identification using finger vein image is presented. Finger vein is an emerging type of biometrics that attracts attention of researchers in biometrics area. As compared to other biometric traits such as face, fingerprint and iris, finger vein is more secured and hard to counterfeit since the features are inside the human body. So far, most of the researchers focus on how to extract robust features from the captured vein images. Not much research was conducted on the classification of the extracted features. In this paper, a new classifier called fuzzy-based k-nearest centroid neighbor (FkNCN) is applied to classify the finger vein image. The proposed FkNCN employs a surrounding rule to obtain the k-nearest centroid neighbors based on the spatial distributions of the training images and their distance to the test image. Then, the fuzzy membership function is utilized to assign the test image to the class which is frequently represented by the k-nearest centroid neighbors. Experimental evaluation using our own database which was collected from 492 fingers shows that the proposed FkNCN has better performance than the k-nearest neighbor, k-nearest-centroid neighbor and fuzzy-based-k-nearest neighbor classifiers. This shows that the proposed classifier is able to identify the finger vein image effectively.

High-Pressure Hot-Gas Self-Acting Floating Ring Shaft Seal for Liquid Rocket Turbopumps. [tapered bore seals

NASA Technical Reports Server (NTRS)

Burcham, R. E.; Diamond, W. A.

1980-01-01

Design analysis, detail design, fabrication, and experimental evaluation was performed on two self acting floating ring shaft seals for a rocket engine turbopump high pressure 24132500 n/sq m (3500 psig) hot gas 533 K 9500 F) high speed 3142 rad/sec (30000 rmp) turbine. The initial design used Rayleigh step hydrodynamic lift pads to assist in centering the seal ring with minimum rubbing contact. The final design used a convergent tapered bore to provide hydrostatic centering force. The Rayleigh step design was tested for 107 starts and 4.52 hours total. The leakage was satisfactory; however, the design was not acceptable due to excessive wear caused by inadequate centering force and failure of the sealing dam caused by erosion damage. The tapered bore design was tested for 370 starts and 15.93 hours total. Satisfactory performance for the required life of 7.5 hours per seal was successfully demonstrated.

Chemicals from Biomass: Combining Ring-Opening Tautomerization and Hydrogenation Reactions to Produce 1,5-Pentanediol from Furfural.

PubMed

Brentzel, Zachary J; Barnett, Kevin J; Huang, Kefeng; Maravelias, Christos T; Dumesic, James A; Huber, George W

2017-04-10

A process for the synthesis of 1,5-pentanediol (1,5-PD) with 84 % yield from furfural is developed, utilizing dehydration/hydration, ring-opening tautomerization, and hydrogenation reactions. Although this process has more reaction steps than the traditional direct hydrogenolysis of tetrahydrofurfuryl alcohol (THFA), techno-economic analyses demonstrate that this process is the economically preferred route for the synthesis of biorenewable 1,5-PD. 2-Hydroxytetrahydropyran (2-HY-THP) is the key reaction pathway intermediate that allows for a decrease in the minimum selling price of 1,5-PD. The reactivity of 2-HY-THP is 80 times greater than that of THFA over a bimetallic hydrogenolysis catalyst. This enhanced reactivity is a result of the ring-opening tautomerization to 5-hydoxyvaleraldehyde and subsequent hydrogenation to 1,5-PD. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure-anti-MRSA activity relationship of macrocyclic bis(bibenzyl) derivatives.

PubMed

Sawada, Hiromi; Onoda, Kenji; Morita, Daichi; Ishitsubo, Erika; Matsuno, Kenji; Tokiwa, Hiroaki; Kuroda, Teruo; Miyachi, Hiroyuki

2013-12-15

We synthesized a series of macrocyclic bis(bibenzyl) derivatives, including riccardin-, isoplagiochin- and marchantin-class structures, and evaluated their antibacterial activity towards methicillin-resistant Staphylococcus aureus (anti-MRSA activity). The structure-activity relationships and the results of molecular dynamics simulations indicated that bis(bibenzyl)s with potent anti-MRSA activity commonly have a 4-hydroxyl group at the D-benzene ring and a 2-hydroxyl group at the C-benzene ring in the hydrophilic part of the molecule, and an unsubstituted phenoxyphenyl group in the hydrophobic part of the molecule containing the A-B-benzene rings. Pharmacological characterization of the bis(bibenzyl) derivatives and 2-phenoxyphenol fragment 25, previously proposed as the minimum structure of riccardin C 1 for anti-MRSA activity, indicated that they have different action mechanisms: the bis(bibenzyl)s are bactericidal, while 25 is bacteriostatic, showing only weak bactericidal activity. Copyright © 2013 Elsevier Ltd. All rights reserved.

X-ray nanoprobes and diffraction-limited storage rings: opportunities and challenges of fluorescence tomography of biological specimens

PubMed Central

de Jonge, Martin D.; Ryan, Christopher G.; Jacobsen, Chris J.

2014-01-01

X-ray nanoprobes require coherent illumination to achieve optic-limited resolution, and so will benefit directly from diffraction-limited storage rings. Here, the example of high-resolution X-ray fluorescence tomography is focused on as one of the most voracious demanders of coherent photons, since the detected signal is only a small fraction of the incident flux. Alternative schemes are considered for beam delivery, sample scanning and detectors. One must consider as well the steps before and after the X-ray experiment: sample preparation and examination conditions, and analysis complexity due to minimum dose requirements and self-absorption. By understanding the requirements and opportunities for nanoscale fluorescence tomography, one gains insight into the R&D challenges in optics and instrumentation needed to fully exploit the source advances that diffraction-limited storage rings offer. PMID:25177992

Magic of Centroids

ERIC Educational Resources Information Center

Ferrarello, Daniela; Mammana, Maria Flavia; Pennisi, Mario

2018-01-01

In this paper, we show some properties of centroids of geometric figures, such as triangles, quadrilaterals and tetrahedra. In particular, we will prove the properties by means of geometric transformations and by introducing extensions of triangles and quadrilaterals, i.e. by adding one, two or three new vertices to the figure. The study of these…

Centroid and Theoretical Rotation: Justification for Their Use in Q Methodology Research

ERIC Educational Resources Information Center

Ramlo, Sue

2016-01-01

This manuscript's purpose is to introduce Q as a methodology before providing clarification about the preferred factor analytical choices of centroid and theoretical (hand) rotation. Stephenson, the creator of Q, designated that only these choices allowed for scientific exploration of subjectivity while not violating assumptions associated with…

Evidence of floods on the Potomac River from anatomical abnormalities in the wood of flood-plain trees

USGS Publications Warehouse

Yanosky, Thomas M.

1983-01-01

Ash trees along the Potomac River flood plain near Washington, D.C., were studied to determine changes in wood anatomy related to flood damage, and anomalous growth was compared to flood records for April 15 to August 31, 1930-79. Collectively, anatomical evidence was detected for 33 of the 34 growing-season floods during the study period. Evidence of 12 floods prior to 1930 was also noted, including catastrophic ones in 1889 and 1924. Trees damaged after the transition from earlywood to latewood growth typically formed ' flood rings ' of enlarged vessels within the latewood zone. Trees damaged near the beginning of the growth year developed flood rings within, or contiguous with, the earlywood. Both patterns are assumed to have developed when flood-damaged trees produced a second crop of leaves. Trees damaged by high-magnitude floods developed well formed flood rings along the entire height and around the entire circumference of the stem. Small floods were generally associated wtih diffuse or discontinuous anomalies restricted to stem apices. Frequency of flood rings was positively related to flood magnitude, and time of flood generation during the tree-growth season was estimated from the radial position of anomalous growth relative to annual ring width. Reconstructing tree heights in a year of flood-ring formation gives a minimum stage estimate along local stream reaches. Some trees provided evidence of numerous floods. Those with the greatest number of flood rings grew on frequently flooded surfaces subject to flood-flow velocities of at least 1 m/s, and more typically greater than 2 m/s. Tree size, more than age, was related to flood-ring formation. Trees kept small by frequent flood damage had more flood rings than taller trees of comparable age. (USGS)

Thin-plate spline analysis of mandibular growth.

PubMed

Franchi, L; Baccetti, T; McNamara, J A

2001-04-01

The analysis of mandibular growth changes around the pubertal spurt in humans has several important implications for the diagnosis and orthopedic correction of skeletal disharmonies. The purpose of this study was to evaluate mandibular shape and size growth changes around the pubertal spurt in a longitudinal sample of subjects with normal occlusion by means of an appropriate morphometric technique (thin-plate spline analysis). Ten mandibular landmarks were identified on lateral cephalograms of 29 subjects at 6 different developmental phases. The 6 phases corresponded to 6 different maturational stages in cervical vertebrae during accelerative and decelerative phases of the pubertal growth curve of the mandible. Differences in shape between average mandibular configurations at the 6 developmental stages were visualized by means of thin-plate spline analysis and subjected to permutation test. Centroid size was used as the measure of the geometric size of each mandibular specimen. Differences in size at the 6 developmental phases were tested statistically. The results of graphical analysis indicated a statistically significant change in mandibular shape only for the growth interval from stage 3 to stage 4 in cervical vertebral maturation. Significant increases in centroid size were found at all developmental phases, with evidence of a prepubertal minimum and of a pubertal maximum. The existence of a pubertal peak in human mandibular growth, therefore, is confirmed by thin-plate spline analysis. Significant morphological changes in the mandible during the growth interval from stage 3 to stage 4 in cervical vertebral maturation may be described as an upward-forward direction of condylar growth determining an overall "shrinkage" of the mandibular configuration along the measurement of total mandibular length. This biological mechanism is particularly efficient in compensating for major increments in mandibular size at the adolescent spurt.

2D wireless sensor network deployment based on Centroidal Voronoi Tessellation

NASA Astrophysics Data System (ADS)

Iliodromitis, Athanasios; Pantazis, George; Vescoukis, Vasileios

2017-06-01

In recent years, Wireless Sensor Networks (WSNs) have rapidly evolved and now comprise a powerful tool in monitoring and observation of the natural environment, among other fields. The use of WSNs is critical in early warning systems, which are of high importance today. In fact, WSNs are adopted more and more in various applications, e.g. for fire or deformation detection. The optimum deployment of sensors is a multi-dimensional problem, which has two main components; network and positioning approach. Although lots of work has dealt with the issue, most of it emphasizes on mere network approach (communication, energy consumption) and not on the topography (positioning) of the sensors in achieving ideal geometry. In some cases, it is hard or even impossible to achieve perfect geometry in nodes' deployment. The ideal and desirable scenario of nodes arranged in square or hexagonal grid would raise extremely the cost of the network, especially in unfriendly or hostile environments. In such environments the positions of the sensors have to be chosen among a list of possible points, which in most cases are randomly distributed. This constraint has to be taken under consideration during the WSN planning. Full geographical coverage is in some applications of the same, if not of greater, importance than the network coverage. Cost is a crucial factor at network planning and given that resources are often limited, what matters, is to cover the whole area with the minimum number of sensors. This paper suggests a deployment method for nodes, in large scale and high density WSNs, based on Centroidal Voronoi Tessellation (CVT). It approximates the solution through the geometry of the random points and proposes a deployment plan, for the given characteristics of the study area, in order to achieve a deployment as near as possible to the ideal one.

Adaptive radiation therapy for postprostatectomy patients using real-time electromagnetic target motion tracking during external beam radiation therapy.

PubMed

Zhu, Mingyao; Bharat, Shyam; Michalski, Jeff M; Gay, Hiram A; Hou, Wei-Hsien; Parikh, Parag J

2013-03-15

Using real-time electromagnetic (EM) transponder tracking data recorded by the Calypso 4D Localization System, we report inter- and intrafractional target motion of the prostate bed, describe a strategy to evaluate treatment adequacy in postprostatectomy patients receiving intensity modulated radiation therapy (IMRT), and propose an adaptive workflow. Tracking data recorded by Calypso EM transponders was analyzed for postprostatectomy patients that underwent step-and-shoot IMRT. Rigid target motion parameters during beam delivery were calculated from recorded transponder positions in 16 patients with rigid transponder geometry. The delivered doses to the clinical target volume (CTV) were estimated from the planned dose matrix and the target motion for the first 3, 5, 10, and all fractions. Treatment adequacy was determined by comparing the delivered minimum dose (Dmin) with the planned Dmin to the CTV. Treatments were considered adequate if the delivered CTV Dmin is at least 95% of the planned CTV Dmin. Translational target motion was minimal for all 16 patients (mean: 0.02 cm; range: -0.12 cm to 0.07 cm). Rotational motion was patient-specific, and maximum pitch, yaw, and roll were 12.2, 4.1, and 10.5°, respectively. We observed inadequate treatments in 5 patients. In these treatments, we observed greater target rotations along with large distances between the CTV centroid and transponder centroid. The treatment adequacy from the initial 10 fractions successfully predicted the overall adequacy in 4 of 5 inadequate treatments and 10 of 11 adequate treatments. Target rotational motion could cause underdosage to partial volume of the postprostatectomy targets. Our adaptive treatment strategy is applicable to post-prostatectomy patients receiving IMRT to evaluate and improve radiation therapy delivery. Copyright © 2013 Elsevier Inc. All rights reserved.

Comparison of fundus autofluorescence with photopic and scotopic fine matrix mapping in patients with retinitis pigmentosa: 4- to 8-year follow-up.

PubMed

Robson, Anthony G; Lenassi, Eva; Saihan, Zubin; Luong, Vy A; Fitzke, Fred W; Holder, Graham E; Webster, Andrew R

2012-09-14

To assess the significance and evolution of parafoveal rings of high-density fundus autofluorescence (AF) in 12 patients with retinitis pigmentosa (RP). Twelve patients with autosomal recessive RP or Usher syndrome type 2 were ascertained who had a parafoveal ring of high-density AF and a visual acuity of 20/30 or better at baseline. Photopic and scotopic fine matrix mapping (FMM) were performed to test sensitivity across the macula. AF imaging and FMM were repeated after 4 to 8 years and optical coherence tomography (OCT) performed. The size of the AF ring reduced over time and disappeared in one subject. Photopic thresholds were normal over the fovea; thresholds were elevated by 0.6 log units over the ring and by 1.2 log units external to the ring at baseline and differed by less than 0.1 log unit at follow-up. Mild photopic losses close to the internal edge of the ring were detected at baseline or follow-up in all. Mean scotopic thresholds over parafoveal areas within the ring were markedly elevated in 8 of 10 at baseline and were severely elevated in 9 of 11 at follow-up. The eccentricity of the inner edge of the AF ring corresponded closely with the lateral extent of the inner segment ellipsoid band in the OCT image. Ring constriction was largely coincident with progressive centripetal photopic threshold elevation led by worsening of rod photoreceptor function. The rate of constriction differed across patients, and a ring may reach a critical minimum before disappearing, at which stage central visual loss occurs. The structural and functional changes associated with rings of increased autofluorescence confirm that they provide an objective index of macular involvement and may aid the management of RP patients and the monitoring of future treatment efficacy.

Ab Initio Path Integral Molecular Dynamics Study of the Nuclear Quantum Effect on Out-of-Plane Ring Deformation of Hydrogen Maleate Anion.

PubMed

Kawashima, Yukio; Tachikawa, Masanori

2014-01-14

Ab initio path integral molecular dynamics (PIMD) simulation was performed to understand the nuclear quantum effect on the out-of-plane ring deformation of hydrogen maleate anion and investigate the existence of a stable structure with ring deformation, which was suggested in experimental observation (Fillaux et al., Chem. Phys. 1999, 120, 387-403). The isotope effect and the temperature effect are studied as well. We first investigated the nuclear quantum effect on the proton transfer. In static calculation and classical ab initio molecular dynamics simulations, the proton in the hydrogen bond is localized to either oxygen atom. On the other hand, the proton is located at the center of two oxygen atoms in quantum ab initio PIMD simulations. The nuclear quantum effect washes out the barrier of proton transfer. We next examined the nuclear quantum effect on the motion of hydrogen maleate anion. Principal component analysis revealed that the out-of-plane ring bending modes have dominant contribution to the entire molecular motion. In quantum ab initio PIMD simulations, structures with ring deformation were the global minimum for the deuterated isotope at 300 K. We analyzed the out-of-plane ring bending mode further and found that there are three minima along a ring distortion mode. We successfully found a stable structure with ring deformation of hydrogen maleate for the first time, to our knowledge, using theoretical calculation. The structures with ring deformation found in quantum simulation of the deuterated isotope allowed the proton transfer to occur more frequently than the planar structure. Static ab initio electronic structure calculation found that the structures with ring deformation have very small proton transfer barrier compared to the planar structure. We suggest that the "proton transfer driven" mechanism is the origin of stabilization for the structure with out-of-plane ring deformation.

An orbit simulation study of a geopotential research mission including satellite-to-satellite tracking and disturbance compensation systems

NASA Technical Reports Server (NTRS)

Antreasian, Peter G.

1988-01-01

Two orbit simulations, one representing the actual Geopotential Research Mission (GRM) orbit and the other representing the orbit estimated from orbit determination techniques, are presented. A computer algorithm was created to simulate GRM's drag compensation mechanism so the fuel expenditure and proof mass trajectories relative to the spacecraft centroid could be calculated for the mission. The results of the GRM DISCOS simulation demonstrated that the spacecraft can essentially be drag-free. The results showed that the centroid of the spacecraft can be controlled so that it will not deviate more than 1.0 mm in any direction from the centroid of the proof mass.

Dynamic imaging model and parameter optimization for a star tracker.

PubMed

Yan, Jinyun; Jiang, Jie; Zhang, Guangjun

2016-03-21

Under dynamic conditions, star spots move across the image plane of a star tracker and form a smeared star image. This smearing effect increases errors in star position estimation and degrades attitude accuracy. First, an analytical energy distribution model of a smeared star spot is established based on a line segment spread function because the dynamic imaging process of a star tracker is equivalent to the static imaging process of linear light sources. The proposed model, which has a clear physical meaning, explicitly reflects the key parameters of the imaging process, including incident flux, exposure time, velocity of a star spot in an image plane, and Gaussian radius. Furthermore, an analytical expression of the centroiding error of the smeared star spot is derived using the proposed model. An accurate and comprehensive evaluation of centroiding accuracy is obtained based on the expression. Moreover, analytical solutions of the optimal parameters are derived to achieve the best performance in centroid estimation. Finally, we perform numerical simulations and a night sky experiment to validate the correctness of the dynamic imaging model, the centroiding error expression, and the optimal parameters.

Two-dimensional shape recognition using oriented-polar representation

NASA Astrophysics Data System (ADS)

Hu, Neng-Chung; Yu, Kuo-Kan; Hsu, Yung-Li

1997-10-01

To deal with such a problem as object recognition of position, scale, and rotation invariance (PSRI), we utilize some PSRI properties of images obtained from objects, for example, the centroid of the image. The corresponding position of the centroid to the boundary of the image is invariant in spite of rotation, scale, and translation of the image. To obtain the information of the image, we use the technique similar to Radon transform, called the oriented-polar representation of a 2D image. In this representation, two specific points, the centroid and the weighted mean point, are selected to form an initial ray, then the image is sampled with N angularly equispaced rays departing from the initial rays. Each ray contains a number of intersections and the distance information obtained from the centroid to the intersections. The shape recognition algorithm is based on the least total error of these two items of information. Together with a simple noise removal and a typical backpropagation neural network, this algorithm is simple, but the PSRI is achieved with a high recognition rate.

Differential computation method used to calibrate the angle-centroid relationship in coaxial reverse Hartmann test

NASA Astrophysics Data System (ADS)

Li, Xinji; Hui, Mei; Zhao, Zhu; Liu, Ming; Dong, Liquan; Kong, Lingqin; Zhao, Yuejin

2018-05-01

A differential computation method is presented to improve the precision of calibration for coaxial reverse Hartmann test (RHT). In the calibration, the accuracy of the distance measurement greatly influences the surface shape test, as demonstrated in the mathematical analyses. However, high-precision absolute distance measurement is difficult in the calibration. Thus, a differential computation method that only requires the relative distance was developed. In the proposed method, a liquid crystal display screen successively displayed two regular dot matrix patterns with different dot spacing. In a special case, images on the detector exhibited similar centroid distributions during the reflector translation. Thus, the critical value of the relative displacement distance and the centroid distributions of the dots on the detector were utilized to establish the relationship between the rays at certain angles and the detector coordinates. Experiments revealed the approximately linear behavior of the centroid variation with the relative displacement distance. With the differential computation method, we increased the precision of traditional calibration 10-5 rad root mean square. The precision of the RHT was increased by approximately 100 nm.

Computational identification of a phospholipidosis toxicophore using (13)C and (15)N NMR-distance based fingerprints.

PubMed

Slavov, Svetoslav H; Wilkes, Jon G; Buzatu, Dan A; Kruhlak, Naomi L; Willard, James M; Hanig, Joseph P; Beger, Richard D

2014-12-01

Modified 3D-SDAR fingerprints combining (13)C and (15)N NMR chemical shifts augmented with inter-atomic distances were used to model the potential of chemicals to induce phospholipidosis (PLD). A curated dataset of 328 compounds (some of which were cationic amphiphilic drugs) was used to generate 3D-QSDAR models based on tessellations of the 3D-SDAR space with grids of different density. Composite PLS models averaging the aggregated predictions from 100 fully randomized individual models were generated. On each of the 100 runs, the activities of an external blind test set comprised of 294 proprietary chemicals were predicted and averaged to provide composite estimates of their PLD-inducing potentials (PLD+ if PLD is observed, otherwise PLD-). The best performing 3D-QSDAR model utilized a grid with a density of 8ppm×8ppm in the C-C region, 8ppm×20ppm in the C-N region and 20ppm×20ppm in the N-N region. The classification predictive performance parameters of this model evaluated on the basis of the external test set were as follows: accuracy=0.70, sensitivity=0.73 and specificity=0.66. A projection of the most frequently occurring bins on the standard coordinate space suggested a toxicophore composed of an aromatic ring with a centroid 3.5-7.5Å distant from an amino-group. The presence of a second aromatic ring separated by a 4-5Å spacer from the first ring and at a distance of between 5.5Å and 7Å from the amino-group was also associated with a PLD+ effect. These models provide comparable predictive performance to previously reported models for PLD with the added benefit of being based entirely on non-confidential, publicly available training data and with good predictive performance when tested in a rigorous, external validation exercise. Published by Elsevier Ltd.

Automated quasi-3D spine curvature quantification and classification

NASA Astrophysics Data System (ADS)

Khilari, Rupal; Puchin, Juris; Okada, Kazunori

2018-02-01

Scoliosis is a highly prevalent spine deformity that has traditionally been diagnosed through measurement of the Cobb angle on radiographs. More recent technology such as the commercial EOS imaging system, although more accurate, also require manual intervention for selecting the extremes of the vertebrae forming the Cobb angle. This results in a high degree of inter and intra observer error in determining the extent of spine deformity. Our primary focus is to eliminate the need for manual intervention by robustly quantifying the curvature of the spine in three dimensions, making it consistent across multiple observers. Given the vertebrae centroids, the proposed Vertebrae Sequence Angle (VSA) estimation and segmentation algorithm finds the largest angle between consecutive pairs of centroids within multiple inflection points on the curve. To exploit existing clinical diagnostic standards, the algorithm uses a quasi-3-dimensional approach considering the curvature in the coronal and sagittal projection planes of the spine. Experiments were performed with manuallyannotated ground-truth classification of publicly available, centroid-annotated CT spine datasets. This was compared with the results obtained from manual Cobb and Centroid angle estimation methods. Using the VSA, we then automatically classify the occurrence and the severity of spine curvature based on Lenke's classification for idiopathic scoliosis. We observe that the results appear promising with a scoliotic angle lying within +/- 9° of the Cobb and Centroid angle, and vertebrae positions differing by at the most one position. Our system also resulted in perfect classification of scoliotic from healthy spines with our dataset with six cases.

360-degrees profilometry using strip-light projection coupled to Fourier phase-demodulation.

PubMed

Servin, Manuel; Padilla, Moises; Garnica, Guillermo

2016-01-11

360 degrees (360°) digitalization of three dimensional (3D) solids using a projected light-strip is a well-established technique in academic and commercial profilometers. These profilometers project a light-strip over the digitizing solid while the solid is rotated a full revolution or 360-degrees. Then, a computer program typically extracts the centroid of this light-strip, and by triangulation one obtains the shape of the solid. Here instead of using intensity-based light-strip centroid estimation, we propose to use Fourier phase-demodulation for 360° solid digitalization. The advantage of Fourier demodulation over strip-centroid estimation is that the accuracy of phase-demodulation linearly-increases with the fringe density, while in strip-light the centroid-estimation errors are independent. Here we proposed first to construct a carrier-frequency fringe-pattern by closely adding the individual light-strip images recorded while the solid is being rotated. Next, this high-density fringe-pattern is phase-demodulated using the standard Fourier technique. To test the feasibility of this Fourier demodulation approach, we have digitized two solids with increasing topographic complexity: a Rubik's cube and a plastic model of a human-skull. According to our results, phase demodulation based on the Fourier technique is less noisy than triangulation based on centroid light-strip estimation. Moreover, Fourier demodulation also provides the amplitude of the analytic signal which is a valuable information for the visualization of surface details.

A comparison of methods for calculating population exposure estimates of daily weather for health research.

PubMed

Hanigan, Ivan; Hall, Gillian; Dear, Keith B G

2006-09-13

To explain the possible effects of exposure to weather conditions on population health outcomes, weather data need to be calculated at a level in space and time that is appropriate for the health data. There are various ways of estimating exposure values from raw data collected at weather stations but the rationale for using one technique rather than another; the significance of the difference in the values obtained; and the effect these have on a research question are factors often not explicitly considered. In this study we compare different techniques for allocating weather data observations to small geographical areas and different options for weighting averages of these observations when calculating estimates of daily precipitation and temperature for Australian Postal Areas. Options that weight observations based on distance from population centroids and population size are more computationally intensive but give estimates that conceptually are more closely related to the experience of the population. Options based on values derived from sites internal to postal areas, or from nearest neighbour sites--that is, using proximity polygons around weather stations intersected with postal areas--tended to include fewer stations' observations in their estimates, and missing values were common. Options based on observations from stations within 50 kilometres radius of centroids and weighting of data by distance from centroids gave more complete estimates. Using the geographic centroid of the postal area gave estimates that differed slightly from the population weighted centroids and the population weighted average of sub-unit estimates. To calculate daily weather exposure values for analysis of health outcome data for small areas, the use of data from weather stations internal to the area only, or from neighbouring weather stations (allocated by the use of proximity polygons), is too limited. The most appropriate method conceptually is the use of weather data from sites within 50 kilometres radius of the area weighted to population centres, but a simpler acceptable option is to weight to the geographic centroid.

Combined quantum chemical density functional theory and spectroscopic Raman and UV-vis-NIR study of oligothienoacenes with five and seven rings.

PubMed

Osuna, Reyes Malavé; Zhang, Xinnan; Matzger, Adam Jay; Hernandez, Víctor; López Navarrete, Juan Teodomiro

2006-04-20

In this article, we report the characterization of novel oligothienoacenes with five and seven fused thiophene rings, materials with potential applications in organic electronics. In contrast to usual alpha-linked oligothiophenes, these fused oligothiophenes have a larger band gap than most semiconductors currently used in the fabrication of organic field-effect transistors (OFETs) and therefore they are expected to be more stable in air. The synthesis of these fused-ring oligomers was motivated by the notion that a more rigid and planar structure should reduce defects (such as torsion about single bonds between alpha-linked units or S-syn defects) and thus improve conjugation for better charge-carrier mobility. The conjugational properties of these two molecular materials have been investigated by means of FT-Raman spectroscopy, revealing that conjugation still increases in passing from the five-ring oligomer to that with seven-rings. DFT and TDDFT quantum chemical calculations have been performed, at the B3LYP/6-31G level, to assess information regarding the minimum-energy molecular structure, topologies, and absolute energies of the frontier molecular orbitals (MOs.) around the gap, vibrational normal modes related to the main Raman features, and vertical one-electron excitations giving rise to the main optical absorptions.

Structure, stratigraphy, and eruption dynamics of a young tuff ring: Hanauma Bay, O'ahu, Hawai'i

NASA Astrophysics Data System (ADS)

Rottas, K. M.; Houghton, B. F.

2012-09-01

The Hanauma Bay-Koko Head complex is one of several young volcanic landforms along the Koko fissure, in southeastern O'ahu. The Hanauma Bay region of the complex comprises two nested tuff rings, inner and outer Hanauma Bay, and multiple smaller vents. The internal structure of the inner tuff ring, well exposed due to subsequent breaching by the ocean and wave erosion, indicates that it formed during a minimum of five distinct phases of deposition that produced five mappable units. Significant inward collapses generated major unconformities that separate the units exposed in the inner wall. The planes of failure are cut by narrow steep-walled, locally overhung channels and gullies, suggesting that the collapse events were each followed by short time breaks during which the deposits were eroded by rainfall runoff. Within each pyroclastic unit, there are many local slump scars and unconformities, suggesting that minor instability of the inner wall was a near-constant feature. From bedding sags and surge bed forms, it is apparent that the vent shifted at least twice during tuff ring growth. Ballistic blocks in the youngest unit indicate that the eruption overlapped in time with a separate eruption to the north, most likely to be that of the Kahauloa tuff ring 880 m away.

Pooled versus separate tree-ring δD measurements, and implications for reconstruction of the Arctic Oscillation in northwestern China.

PubMed

Liu, Xiaohong; An, Wenling; Treydte, Kerstin; Wang, Wenzhi; Xu, Guobao; Zeng, Xiaomin; Wu, Guoju; Wang, Bo; Zhang, Xuanwen

2015-04-01

Stable hydrogen isotope ratios (δD) in tree rings are an attractive but still rarely explored terrestrial archive of past climatic information. Because the preparation of the cellulose nitrate for δD measurements requires more wood and a longer preparation time than preparation techniques for other isotopes in cellulose (δ18O or δ13C), it is challenging to obtain high-resolution records, especially for slow-growing trees at high elevations and in boreal regions. Here, we tested whether annually pooled samples of Qinghai spruce (Picea crassifolia Kom.) trees from northwestern China provided results similar to those derived as the mean of individual measurements of the same trees and whether the resulting chronologies recorded useful climate information. Inter-tree variability of δD was higher than that of measured ring width for the same trees. We found higher and significant coherence between pooled and mean isotope chronologies than that among the individual series. It showed a logarithmic relationship between ring mass and δD; however, accounting for the influence of ring mass on δD values only slightly improved the strength of climatic signals in the pooled records. Tree-ring δD was significantly positively correlated with the mean, maximum, and minimum temperatures during the previous winter and with maximum temperature during the current August, and significantly negatively correlated with precipitation in the previous November to January and the current July. The winter climate signal seems to dominate tree-ring δD through the influence of large-scale atmospheric circulation patterns, i.e. the Arctic Oscillation. These results will facilitate reconstruction of winter atmospheric circulation patterns over northwestern China based on a regional tree-ring δD networks. Copyright © 2015 Elsevier B.V. All rights reserved.

Method of wavefront tilt correction for optical heterodyne detection systems under strong turbulence

NASA Astrophysics Data System (ADS)

Xiang, Jing-song; Tian, Xin; Pan, Le-chun

2014-07-01

Atmospheric turbulence decreases the heterodyne mixing efficiency of the optical heterodyne detection systems. Wavefront tilt correction is often used to improve the optical heterodyne mixing efficiency. But the performance of traditional centroid tracking tilt correction is poor under strong turbulence conditions. In this paper, a tilt correction method which tracking the peak value of laser spot on focal plane is proposed. Simulation results show that, under strong turbulence conditions, the performance of peak value tracking tilt correction is distinctly better than that of traditional centroid tracking tilt correction method, and the phenomenon of large antenna's performance inferior to small antenna's performance which may be occurred in centroid tracking tilt correction method can also be avoid in peak value tracking tilt correction method.

Crystal structures of isomeric 3,5-di-chloro-N-(2,3-di-methyl-phen-yl)benzene-sulfonamide, 3,5-di-chloro-N-(2,6-di-methyl-phen-yl)benzene-sulfonamide and 3,5-di-chloro-N-(3,5-di-methyl-phen-yl)benzene-sulfonamide.

PubMed

Shakuntala, K; Naveen, S; Lokanath, N K; Suchetan, P A

2017-05-01

The crystal structures of three isomeric compounds of formula C 14 H 13 Cl 2 NO 2 S, namely 3,5-di-chloro- N -(2,3-di-methyl-phen-yl)-benzene-sulfonamide (I), 3,5-di-chloro- N -(2,6-di-methyl-phen-yl)benzene-sulfonamide (II) and 3,5-di-chloro- N -(3,5-di-methyl-phen-yl)benzene-sulfonamide (III) are described. The mol-ecules of all the three compounds are U-shaped with the two aromatic rings inclined at 41.3 (6)° in (I), 42.1 (2)° in (II) and 54.4 (3)° in (III). The mol-ecular conformation of (II) is stabilized by intra-molecular C-H⋯O hydrogen bonds and C-H⋯π inter-actions. The crystal structure of (I) features N-H⋯O hydrogen-bonded R 2 2 (8) loops inter-connected via C (7) chains of C-H⋯O inter-actions, forming a three-dimensional architecture. The structure also features π-π inter-actions [ Cg ⋯ Cg = 3.6970 (14) Å]. In (II), N-H⋯O hydrogen-bonded R 2 2 (8) loops are inter-connected via π-π inter-actions [inter-centroid distance = 3.606 (3) Å] to form a one-dimensional architecture running parallel to the a axis. In (III), adjacent C (4) chains of N-H⋯O hydrogen-bonded mol-ecules running parallel to [010] are connected via C-H⋯π inter-actions, forming sheets parallel to the ab plane. Neighbouring sheets are linked via offset π-π inter-actions [inter-centroid distance = 3.8303 (16) Å] to form a three-dimensional architecture.

Estimates of Rayleigh-to-Love wave ratio in microseisms by co-located Ring Laser and STS-2

NASA Astrophysics Data System (ADS)

Tanimoto, Toshiro; Hadziioannou, Céline; Igel, Heiner; Wassermann, Joachim; Schreiber, Ulrich; Gebauer, André

2015-04-01

In older studies of microseisms (seismic noise), it was often assumed that microseisms, especially the secondary microseisms (0.1-0.3 Hz), mainly consist of Rayleigh waves. However, it has become clear that there exists a large amount of Love-wave energy mixed in it (e.g., Nishida et al., 2008). However, its confirmation is not necessarily straightforward and often required an array of seismographs. In this study, we take advantage of two co-located instruments, a Ring Laser and an STS-2 type seismograph, at Wettzell (WET), Germany (Schreiber et al., 2009). The Ring Laser records rotation (its vertical component) and is thus only sensitive to Love waves. The vertical component of STS-2 seismograph is only sensitive to Rayleigh waves. Therefore, a combination of the two instruments provides a unique opportunity to separate Rayleigh waves and Love waves in microseisms. The question we address in this paper is the ratio of Rayleigh waves to Love waves in microseisms. For both instruments, we analyze data from 2009 to 2014. Our basic approach is to create stacked vertical acceleration spectra for Rayleigh waves from STS-2 and stacked transverse acceleration spectra for Love waves from Ring Laser. The two spectra at Earth's surface can then be compared directly by their amplitudes. The first step in our analysis is a selection of time portions (each six-hour long) that are least affected by earthquakes. We do this by examining the GCMT (Global Centroid Moment Tensor) catalogue and also checking the PSDs for various frequency ranges. The second step is to create stacked (averaged) Fourier spectra from those selected time portions. The key is to use the same time portions for the STS-2 and the Ring Laser data so that the two can be directly compared. The vertical spectra from STS-2 are converted to acceleration spectra. The Ring Laser rotation spectra are first obtained in the unit of radians/sec (rotation rate). But as the Ring Laser spectra are dominated by fundamental-mode Love waves, the rotation spectra can be converted to transverse (SH) acceleration by multiplying them by the factor 2xCp where Cp is the Love-wave phase velocity. We used a seismic model by Fichtner et al. (2013) at WET to estimate Love-wave phase velocity. This conversion from rotation to transverse acceleration was first extensively used by Igel et al. (2005) for the analysis of lower frequency Love waves and the same relation holds for our spectral data. The two spectra provide the ratio of surface amplitudes. In the frequency range of secondary microseisms (0.10-0.35 Hz), they are comparable; near the spectral peak (~0.20 Hz), Rayleigh waves are about 20 percent larger in amplitudes but outside this peak region, Love waves have comparable or slightly larger amplitudes than Rayleigh waves. Therefore, the secondary microseisms at WET consist of similar contributions from Rayleigh waves and Love waves.

Reinforcements in avian wing bones: Experiments, analysis, and modeling.

PubMed

Novitskaya, E; Ruestes, C J; Porter, M M; Lubarda, V A; Meyers, M A; McKittrick, J

2017-12-01

Almost all species of modern birds are capable of flight; the mechanical competency of their wings and the rigidity of their skeletal system evolved to enable this outstanding feat. One of the most interesting examples of structural adaptation in birds is the internal structure of their wing bones. In flying birds, bones need to be sufficiently strong and stiff to withstand forces during takeoff, flight, and landing, with a minimum of weight. The cross-sectional morphology and presence of reinforcing structures (struts and ridges) found within bird wing bones vary from species to species, depending on how the wings are utilized. It is shown that both morphology and internal features increases the resistance to flexure and torsion with a minimum weight penalty. Prototypes of reinforcing struts fabricated by 3D printing were tested in diametral compression and torsion to validate the concept. In compression, the ovalization decreased through the insertion of struts, while they had no effect on torsional resistance. An elastic model of a circular ring reinforced by horizontal and vertical struts is developed to explain the compressive stiffening response of the ring caused by differently oriented struts. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

NASA Tech Briefs, June 2006

NASA Technical Reports Server (NTRS)

2006-01-01

Topics covered include: Magnetic-Field-Response Measurement-Acquisition System; Platform for Testing Robotic Vehicles on Simulated Terrain; Interferometer for Low-Uncertainty Vector Metrology; Rayleigh Scattering for Measuring Flow in a Nozzle Testing Facility; "Virtual Feel" Capaciflectors; FETs Based on Doped Polyaniline/Polyethylene Oxide Fibers; Miniature Housings for Electronics With Standard Interfaces; Integrated Modeling Environment; Modified Recursive Hierarchical Segmentation of Data; Sizing Structures and Predicting Weight of a Spacecraft; Stress Testing of Data-Communication Networks; Framework for Flexible Security in Group Communications; Software for Collaborative Use of Large Interactive Displays; Microsphere Insulation Panels; Single-Wall Carbon Nanotube Anodes for Lithium Cells; Tantalum-Based Ceramics for Refractory Composites; Integral Flexure Mounts for Metal Mirrors for Cryogenic Use; Templates for Fabricating Nanowire/Nanoconduit- Based Devices; Measuring Vapors To Monitor the State of Cure of a Resin; Partial-Vacuum-Gasketed Electrochemical Corrosion Cell; Theodolite Ring Lights; Integrating Terrain Maps Into a Reactive Navigation Strategy; Reducing Centroid Error Through Model-Based Noise Reduction; Adaptive Modeling Language and Its Derivatives; Stable Satellite Orbits for Global Coverage of the Moon; and Low-Cost Propellant Launch From a Tethered Balloon

Precision measurement of the mass of the hc(1P1) state of charmonium.

PubMed

Dobbs, S; Metreveli, Z; Seth, K K; Tomaradze, A; Libby, J; Powell, A; Wilkinson, G; Ecklund, K M; Love, W; Savinov, V; Lopez, A; Mendez, H; Ramirez, J; Ge, J Y; Miller, D H; Shipsey, I P J; Xin, B; Adams, G S; Anderson, M; Cummings, J P; Danko, I; Hu, D; Moziak, B; Napolitano, J; He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Yang, F; Artuso, M; Blusk, S; Khalil, S; Li, J; Mountain, R; Nisar, S; Randrianarivony, K; Sultana, N; Skwarnicki, T; Stone, S; Wang, J C; Zhang, L M; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Naik, P; Rademacker, J; Asner, D M; Edwards, K W; Reed, J; Briere, R A; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E; Rosner, J L; Alexander, J P; Cassel, D G; Duboscq, J E; Ehrlich, R; Fields, L; Galik, R S; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Hunt, J M; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Ledoux, J; Mahlke-Krüger, H; Mohapatra, D; Onyisi, P U E; Patterson, J R; Peterson, D; Riley, D; Ryd, A; Sadoff, A J; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Athar, S B; Patel, R; Yelton, J; Rubin, P; Eisenstein, B I; Karliner, I; Mehrabyan, S; Lowrey, N; Selen, M; White, E J; Wiss, J; Mitchell, R E; Shepherd, M R; Besson, D; Pedlar, T K; Cronin-Hennessy, D; Gao, K Y; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Zweber, P

2008-10-31

A precision measurement of the mass of the h_{c}(1P1) state of charmonium has been made using a sample of 24.5x10;{6} psi(2S) events produced in e;{+}e;{-} annihilation at the Cornell Electron Storage Ring (CESR). The reaction used was psi(2S)-->pi;{0}h_{c}, pi;{0}-->gammagamma, h_{c}-->gammaeta_{c}, and the reaction products were detected in the CLEO-c detector. Data have been analyzed both for the inclusive reaction and for the exclusive reactions in which eta_{c} decays are reconstructed in 15 hadronic decay channels. Consistent results are obtained in the two analyses. The averaged results of the present measurements are M(h_{c})=3525.28+/-0.19(stat.)+/-0.12(syst.) MeV, and B(psi(2S)-->pi;{0}h_{c})xB(h_{c}-->gammaeta_{c})=(4.19+/-0.32+/-0.45)x10;{-4}. Using the ;{3}P_{J} centroid mass, DeltaM_{hf}(1P) identical withM(chi_{cJ})-M(h_{c})=+0.02+/-0.19+/-0.13 MeV.

Crystal structure of catena-poly[[[tetra-aqua-zinc(II)]-μ-1,4-bis-[4-(1H-imidazol-1-yl)benzo-yl]piperazine] dinitrate monohydrate].

PubMed

Hou, Chen; Gan, Hong-Mei; Liu, Jia-Cheng

2015-05-01

In the title polymeric complex, {[Zn(C24H22N6O2)(H2O)4](NO3)2·2H2O} n , the Zn(II) cation, located about a twofold rotation axis, is coordinated by two imidazole groups and four water mol-ecules in a distorted N2O4 octa-hedral geometry; among the four coordinate water mol-ecules, two are located on the same twofold rotation axis. The 1,4-bis-[4-(1H-imidazol-1-yl)benzo-yl]piperazine] ligand is centro-symmetric, with the centroid of the piperazine ring located on an inversion center, and bridges the Zn(II) cations, forming polymeric chains propagating along [201]. In the crystal, O-H⋯O and weak C-H⋯O hydrogen bonds link the polymeric chains, nitrate anions and solvent water mol-ecules into a three-dimensional supra-molecular architecture. A short O⋯O contact of 2.823 (13) Å is observed between neighboring nitrate anions.

Precision Measurement of the Mass of the hc(P11) State of Charmonium

NASA Astrophysics Data System (ADS)

Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tomaradze, A.; Libby, J.; Powell, A.; Wilkinson, G.; Ecklund, K. M.; Love, W.; Savinov, V.; Lopez, A.; Mendez, H.; Ramirez, J.; Ge, J. Y.; Miller, D. H.; Shipsey, I. P. J.; Xin, B.; Adams, G. S.; Anderson, M.; Cummings, J. P.; Danko, I.; Hu, D.; Moziak, B.; Napolitano, J.; He, Q.; Insler, J.; Muramatsu, H.; Park, C. S.; Thorndike, E. H.; Yang, F.; Artuso, M.; Blusk, S.; Khalil, S.; Li, J.; Mountain, R.; Nisar, S.; Randrianarivony, K.; Sultana, N.; Skwarnicki, T.; Stone, S.; Wang, J. C.; Zhang, L. M.; Bonvicini, G.; Cinabro, D.; Dubrovin, M.; Lincoln, A.; Naik, P.; Rademacker, J.; Asner, D. M.; Edwards, K. W.; Reed, J.; Briere, R. A.; Ferguson, T.; Tatishvili, G.; Vogel, H.; Watkins, M. E.; Rosner, J. L.; Alexander, J. P.; Cassel, D. G.; Duboscq, J. E.; Ehrlich, R.; Fields, L.; Galik, R. S.; Gibbons, L.; Gray, R.; Gray, S. W.; Hartill, D. L.; Heltsley, B. K.; Hertz, D.; Hunt, J. M.; Kandaswamy, J.; Kreinick, D. L.; Kuznetsov, V. E.; Ledoux, J.; Mahlke-Krüger, H.; Mohapatra, D.; Onyisi, P. U. E.; Patterson, J. R.; Peterson, D.; Riley, D.; Ryd, A.; Sadoff, A. J.; Shi, X.; Stroiney, S.; Sun, W. M.; Wilksen, T.; Athar, S. B.; Patel, R.; Yelton, J.; Rubin, P.; Eisenstein, B. I.; Karliner, I.; Mehrabyan, S.; Lowrey, N.; Selen, M.; White, E. J.; Wiss, J.; Mitchell, R. E.; Shepherd, M. R.; Besson, D.; Pedlar, T. K.; Cronin-Hennessy, D.; Gao, K. Y.; Hietala, J.; Kubota, Y.; Klein, T.; Lang, B. W.; Poling, R.; Scott, A. W.; Zweber, P.

2008-10-01

A precision measurement of the mass of the hc(P11) state of charmonium has been made using a sample of 24.5×106 ψ(2S) events produced in e+e- annihilation at the Cornell Electron Storage Ring (CESR). The reaction used was ψ(2S)→π0hc, π0→γγ, hc→γηc, and the reaction products were detected in the CLEO-c detector. Data have been analyzed both for the inclusive reaction and for the exclusive reactions in which ηc decays are reconstructed in 15 hadronic decay channels. Consistent results are obtained in the two analyses. The averaged results of the present measurements are M(hc)=3525.28±0.19(stat.)±0.12(syst.)MeV, and B(ψ(2S)→π0hc)×B(hc→γηc)=(4.19±0.32±0.45)×10-4. Using the PJ3 centroid mass, ΔMhf(1P)≡⟨M(χcJ)⟩-M(hc)=+0.02±0.19±0.13MeV.

Geospatial cross-correlation analysis of Oklahoma earthquakes and saltwater disposal volume 2011 - 2016

NASA Astrophysics Data System (ADS)

Pollyea, R.; Mohammadi, N.; Taylor, J. E.

2017-12-01

The annual earthquake rate in Oklahoma increased dramatically between 2009 and 2016, owing in large part to the rapid proliferation of salt water disposal wells associated with unconventional oil and gas recovery. This study presents a geospatial analysis of earthquake occurrence and SWD injection volume within a 68,420 km2 area in north-central Oklahoma between 2011 and 2016. The spatial co-variability of earthquake occurrence and SWD injection volume is analyzed for each year of the study by calculating the geographic centroid for both earthquake epicenter and volume-weighted well location. In addition, the spatial cross correlation between earthquake occurrence and SWD volume is quantified by calculating the cross semivariogram annually for a 9.6 km × 9.6 km (6 mi × 6 mi) grid over the study area. Results from these analyses suggest that the relationship between volume-weighted well centroids and earthquake centroids generally follow pressure diffusion space-time scaling, and the volume-weighted well centroid predicts the geographic earthquake centroid within a 1σ radius of gyration. The cross semivariogram calculations show that SWD injection volume and earthquake occurrence are spatially cross correlated between 2014 and 2016. These results also show that the strength of cross correlation decreased from 2015 to 2016; however, the cross correlation length scale remains unchanged at 125 km. This suggests that earthquake mitigation efforts have been moderately successful in decreasing the strength of cross correlation between SWD volume and earthquake occurrence near-field, but the far-field contribution of SWD injection volume to earthquake occurrence remains unaffected.

The strengths and limitations of effective centroid force models explored by studying isotopic effects in liquid water

NASA Astrophysics Data System (ADS)

Yuan, Ying; Li, Jicun; Li, Xin-Zheng; Wang, Feng

2018-05-01

The development of effective centroid potentials (ECPs) is explored with both the constrained-centroid and quasi-adiabatic force matching using liquid water as a test system. A trajectory integrated with the ECP is free of statistical noises that would be introduced when the centroid potential is approximated on the fly with a finite number of beads. With the reduced cost of ECP, challenging experimental properties can be studied in the spirit of centroid molecular dynamics. The experimental number density of H2O is 0.38% higher than that of D2O. With the ECP, the H2O number density is predicted to be 0.42% higher, when the dispersion term is not refit. After correction of finite size effects, the diffusion constant of H2O is found to be 21% higher than that of D2O, which is in good agreement with the 29.9% higher diffusivity for H2O observed experimentally. Although the ECP is also able to capture the redshifts of both the OH and OD stretching modes in liquid water, there are a number of properties that a classical simulation with the ECP will not be able to recover. For example, the heat capacities of H2O and D2O are predicted to be almost identical and higher than the experimental values. Such a failure is simply a result of not properly treating quantized vibrational energy levels when the trajectory is propagated with classical mechanics. Several limitations of the ECP based approach without bead population reconstruction are discussed.

A JOINT CHANDRA AND SWIFT VIEW OF THE 2015 X-RAY DUST-SCATTERING ECHO OF V404 CYGNI

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

Heinz, S.; Corrales, L.; Neilsen, J.

2016-07-01

We present a combined analysis of the Chandra and Swift observations of the 2015 X-ray echo of V404 Cygni. Using a stacking analysis, we identify eight separate rings in the echo. We reconstruct the soft X-ray light curve of the 2015 June outburst using the high-resolution Chandra images and cross-correlations of the radial intensity profiles, indicating that about 70% of the outburst fluence occurred during the bright flare at the end of the outburst on MJD 57199.8. By deconvolving the intensity profiles with the reconstructed outburst light curve, we show that the rings correspond to eight separate dust concentrations withmore » precise distance determinations. We further show that the column density of the clouds varies significantly across the field of view, with the centroid of most of the clouds shifted toward the Galactic plane, relative to the position of V404 Cyg, invalidating the assumption of uniform cloud column typically made in attempts to constrain dust properties from light echoes. We present a new XSPEC spectral dust-scattering model that calculates the differential dust-scattering cross section for a range of commonly used dust distributions and compositions and use it to jointly fit the entire set of Swift echo data. We find that a standard Mathis–Rumpl–Nordsieck model provides an adequate fit to the ensemble of echo data. The fit is improved by allowing steeper dust distributions, and models with simple silicate and graphite grains are preferred over models with more complex composition.« less

New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data

PubMed Central

Yang, Bao; He, Minhui; Shishov, Vladimir; Tychkov, Ivan; Vaganov, Eugene; Rossi, Sergio; Ljungqvist, Fredrik Charpentier; Bräuning, Achim; Grießinger, Jussi

2017-01-01

Phenological responses of vegetation to climate, in particular to the ongoing warming trend, have received much attention. However, divergent results from the analyses of remote sensing data have been obtained for the Tibetan Plateau (TP), the world’s largest high-elevation region. This study provides a perspective on vegetation phenology shifts during 1960–2014, gained using an innovative approach based on a well-validated, process-based, tree-ring growth model that is independent of temporal changes in technical properties and image quality of remote sensing products. Twenty composite site chronologies were analyzed, comprising about 3,000 trees from forested areas across the TP. We found that the start of the growing season (SOS) has advanced, on average, by 0.28 d/y over the period 1960–2014. The end of the growing season (EOS) has been delayed, by an estimated 0.33 d/y during 1982–2014. No significant changes in SOS or EOS were observed during 1960–1981. April–June and August–September minimum temperatures are the main climatic drivers for SOS and EOS, respectively. An increase of 1 °C in April–June minimum temperature shifted the dates of xylem phenology by 6 to 7 d, lengthening the period of tree-ring formation. This study extends the chronology of TP phenology farther back in time and reconciles the disparate views on SOS derived from remote sensing data. Scaling up this analysis may improve understanding of climate change effects and related phenological and plant productivity on a global scale. PMID:28630302

New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data

NASA Astrophysics Data System (ADS)

Yang, Bao; He, Minhui; Shishov, Vladimir; Tychkov, Ivan; Vaganov, Eugene; Rossi, Sergio; Charpentier Ljungqvist, Fredrik; Bräuning, Achim; Grießinger, Jussi

2017-07-01

Phenological responses of vegetation to climate, in particular to the ongoing warming trend, have received much attention. However, divergent results from the analyses of remote sensing data have been obtained for the Tibetan Plateau (TP), the world’s largest high-elevation region. This study provides a perspective on vegetation phenology shifts during 1960-2014, gained using an innovative approach based on a well-validated, process-based, tree-ring growth model that is independent of temporal changes in technical properties and image quality of remote sensing products. Twenty composite site chronologies were analyzed, comprising about 3,000 trees from forested areas across the TP. We found that the start of the growing season (SOS) has advanced, on average, by 0.28 d/y over the period 1960-2014. The end of the growing season (EOS) has been delayed, by an estimated 0.33 d/y during 1982-2014. No significant changes in SOS or EOS were observed during 1960-1981. April-June and August-September minimum temperatures are the main climatic drivers for SOS and EOS, respectively. An increase of 1 °C in April-June minimum temperature shifted the dates of xylem phenology by 6 to 7 d, lengthening the period of tree-ring formation. This study extends the chronology of TP phenology farther back in time and reconciles the disparate views on SOS derived from remote sensing data. Scaling up this analysis may improve understanding of climate change effects and related phenological and plant productivity on a global scale.

Optimal Doppler centroid estimation for SAR data from a quasi-homogeneous source

NASA Technical Reports Server (NTRS)

Jin, M. Y.

1986-01-01

This correspondence briefly describes two Doppler centroid estimation (DCE) algorithms, provides a performance summary for these algorithms, and presents the experimental results. These algorithms include that of Li et al. (1985) and a newly developed one that is optimized for quasi-homogeneous sources. The performance enhancement achieved by the optimal DCE algorithm is clearly demonstrated by the experimental results.

Automatic localization of the left ventricular blood pool centroid in short axis cardiac cine MR images.

PubMed

Tan, Li Kuo; Liew, Yih Miin; Lim, Einly; Abdul Aziz, Yang Faridah; Chee, Kok Han; McLaughlin, Robert A

2018-06-01

In this paper, we develop and validate an open source, fully automatic algorithm to localize the left ventricular (LV) blood pool centroid in short axis cardiac cine MR images, enabling follow-on automated LV segmentation algorithms. The algorithm comprises four steps: (i) quantify motion to determine an initial region of interest surrounding the heart, (ii) identify potential 2D objects of interest using an intensity-based segmentation, (iii) assess contraction/expansion, circularity, and proximity to lung tissue to score all objects of interest in terms of their likelihood of constituting part of the LV, and (iv) aggregate the objects into connected groups and construct the final LV blood pool volume and centroid. This algorithm was tested against 1140 datasets from the Kaggle Second Annual Data Science Bowl, as well as 45 datasets from the STACOM 2009 Cardiac MR Left Ventricle Segmentation Challenge. Correct LV localization was confirmed in 97.3% of the datasets. The mean absolute error between the gold standard and localization centroids was 2.8 to 4.7 mm, or 12 to 22% of the average endocardial radius. Graphical abstract Fully automated localization of the left ventricular blood pool in short axis cardiac cine MR images.

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

DOE PAGES

Borges, Nicholas; Losko, Adrian; Vogel, Sven

2018-02-13

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

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

Borges, Nicholas; Losko, Adrian; Vogel, Sven

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Automatic detection and quantitative analysis of cells in the mouse primary motor cortex

NASA Astrophysics Data System (ADS)

Meng, Yunlong; He, Yong; Wu, Jingpeng; Chen, Shangbin; Li, Anan; Gong, Hui

2014-09-01

Neuronal cells play very important role on metabolism regulation and mechanism control, so cell number is a fundamental determinant of brain function. Combined suitable cell-labeling approaches with recently proposed three-dimensional optical imaging techniques, whole mouse brain coronal sections can be acquired with 1-μm voxel resolution. We have developed a completely automatic pipeline to perform cell centroids detection, and provided three-dimensional quantitative information of cells in the primary motor cortex of C57BL/6 mouse. It involves four principal steps: i) preprocessing; ii) image binarization; iii) cell centroids extraction and contour segmentation; iv) laminar density estimation. Investigations on the presented method reveal promising detection accuracy in terms of recall and precision, with average recall rate 92.1% and average precision rate 86.2%. We also analyze laminar density distribution of cells from pial surface to corpus callosum from the output vectorizations of detected cell centroids in mouse primary motor cortex, and find significant cellular density distribution variations in different layers. This automatic cell centroids detection approach will be beneficial for fast cell-counting and accurate density estimation, as time-consuming and error-prone manual identification is avoided.

Star centroiding error compensation for intensified star sensors.

PubMed

Jiang, Jie; Xiong, Kun; Yu, Wenbo; Yan, Jinyun; Zhang, Guangjun

2016-12-26

A star sensor provides high-precision attitude information by capturing a stellar image; however, the traditional star sensor has poor dynamic performance, which is attributed to its low sensitivity. Regarding the intensified star sensor, the image intensifier is utilized to improve the sensitivity, thereby further improving the dynamic performance of the star sensor. However, the introduction of image intensifier results in star centroiding accuracy decrease, further influencing the attitude measurement precision of the star sensor. A star centroiding error compensation method for intensified star sensors is proposed in this paper to reduce the influences. First, the imaging model of the intensified detector, which includes the deformation parameter of the optical fiber panel, is established based on the orthographic projection through the analysis of errors introduced by the image intensifier. Thereafter, the position errors at the target points based on the model are obtained by using the Levenberg-Marquardt (LM) optimization method. Last, the nearest trigonometric interpolation method is presented to compensate for the arbitrary centroiding error of the image plane. Laboratory calibration result and night sky experiment result show that the compensation method effectively eliminates the error introduced by the image intensifier, thus remarkably improving the precision of the intensified star sensors.

Fusing Image Data for Calculating Position of an Object

NASA Technical Reports Server (NTRS)

Huntsberger, Terrance; Cheng, Yang; Liebersbach, Robert; Trebi-Ollenu, Ashitey

2007-01-01

A computer program has been written for use in maintaining the calibration, with respect to the positions of imaged objects, of a stereoscopic pair of cameras on each of the Mars Explorer Rovers Spirit and Opportunity. The program identifies and locates a known object in the images. The object in question is part of a Moessbauer spectrometer located at the tip of a robot arm, the kinematics of which are known. In the program, the images are processed through a module that extracts edges, combines the edges into line segments, and then derives ellipse centroids from the line segments. The images are also processed by a feature-extraction algorithm that performs a wavelet analysis, then performs a pattern-recognition operation in the wavelet-coefficient space to determine matches to a texture feature measure derived from the horizontal, vertical, and diagonal coefficients. The centroids from the ellipse finder and the wavelet feature matcher are then fused to determine co-location. In the event that a match is found, the centroid (or centroids if multiple matches are present) is reported. If no match is found, the process reports the results of the analyses for further examination by human experts.

Inner Magnetosphere Modeling at the CCMC: Ring Current, Radiation Belt and Magnetic Field Mapping

NASA Astrophysics Data System (ADS)

Rastaetter, L.; Mendoza, A. M.; Chulaki, A.; Kuznetsova, M. M.; Zheng, Y.

2013-12-01

Modeling of the inner magnetosphere has entered center stage with the launch of the Van Allen Probes (RBSP) in 2012. The Community Coordinated Modeling Center (CCMC) has drastically improved its offerings of inner magnetosphere models that cover energetic particles in the Earth's ring current and radiation belts. Models added to the CCMC include the stand-alone Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model by M.C. Fok, the Rice Convection Model (RCM) by R. Wolf and S. Sazykin and numerous versions of the Tsyganenko magnetic field model (T89, T96, T01quiet, TS05). These models join the LANL* model by Y. Yu hat was offered for instant run earlier in the year. In addition to these stand-alone models, the Comprehensive Ring Current Model (CRCM) by M.C. Fok and N. Buzulukova joined as a component of the Space Weather Modeling Framework (SWMF) in the magnetosphere model run-on-request category. We present modeling results of the ring current and radiation belt models and demonstrate tracking of satellites such as RBSP. Calculations using the magnetic field models include mappings to the magnetic equator or to minimum-B positions and the determination of foot points in the ionosphere.

Use of tree-ring chemistry to document historical ground-water contamination events

USGS Publications Warehouse

Vroblesky, Don A.; Yanosky, Thomas M.

1990-01-01

The annual growth rings of tulip trees (Liriodendron tulipifera L.) appear to preserve a chemical record of ground-water contamination at a landfill in Maryland. Zones of elevated iron and chlorine concentrations in growth rings from trees immediately downgradient from the landfill are closely correlated temporally with activities in the landfill expected to generate iron and chloride contamination in the ground water. Successively later iron peaks in trees increasingly distant from the landfill along the general direction of ground-water flow imply movement of iron-contaminated ground water away from the landfill. The historical velocity of iron movement (2 to 9 m/yr) and chloride movement (at least 40 m/yr) in ground water at the site was estimated from element-concentration trends of trees at successive distances from the landfill. The tree-ring-derived chloride-transport velocity approximates the known ground-water velocity (30 to 80 m/yr). A minimum horizontal hydraulic conductivity (0.01 to .02 cm/s) calculated from chloride velocity agrees well with values derived from aquifer tests (about 0.07 cm/s) and from ground-water modeling results (0.009 to 0.04 cm/s).

Improvement of correlation-based centroiding methods for point source Shack-Hartmann wavefront sensor

NASA Astrophysics Data System (ADS)

Li, Xuxu; Li, Xinyang; wang, Caixia

2018-03-01

This paper proposes an efficient approach to decrease the computational costs of correlation-based centroiding methods used for point source Shack-Hartmann wavefront sensors. Four typical similarity functions have been compared, i.e. the absolute difference function (ADF), ADF square (ADF2), square difference function (SDF), and cross-correlation function (CCF) using the Gaussian spot model. By combining them with fast search algorithms, such as three-step search (TSS), two-dimensional logarithmic search (TDL), cross search (CS), and orthogonal search (OS), computational costs can be reduced drastically without affecting the accuracy of centroid detection. Specifically, OS reduces calculation consumption by 90%. A comprehensive simulation indicates that CCF exhibits a better performance than other functions under various light-level conditions. Besides, the effectiveness of fast search algorithms has been verified.

Research of centroiding algorithms for extended and elongated spot of sodium laser guide star

NASA Astrophysics Data System (ADS)

Shao, Yayun; Zhang, Yudong; Wei, Kai

2016-10-01

Laser guide stars (LGSs) increase the sky coverage of astronomical adaptive optics systems. But spot array obtained by Shack-Hartmann wave front sensors (WFSs) turns extended and elongated, due to the thickness and size limitation of sodium LGS, which affects the accuracy of the wave front reconstruction algorithm. In this paper, we compared three different centroiding algorithms , the Center-of-Gravity (CoG), weighted CoG (WCoG) and Intensity Weighted Centroid (IWC), as well as those accuracies for various extended and elongated spots. In addition, we compared the reconstructed image data from those three algorithms with theoretical results, and proved that WCoG and IWC are the best wave front reconstruction algorithms for extended and elongated spot among all the algorithms.

Trajectory data privacy protection based on differential privacy mechanism

NASA Astrophysics Data System (ADS)

Gu, Ke; Yang, Lihao; Liu, Yongzhi; Liao, Niandong

2018-05-01

In this paper, we propose a trajectory data privacy protection scheme based on differential privacy mechanism. In the proposed scheme, the algorithm first selects the protected points from the user’s trajectory data; secondly, the algorithm forms the polygon according to the protected points and the adjacent and high frequent accessed points that are selected from the accessing point database, then the algorithm calculates the polygon centroids; finally, the noises are added to the polygon centroids by the differential privacy method, and the polygon centroids replace the protected points, and then the algorithm constructs and issues the new trajectory data. The experiments show that the running time of the proposed algorithms is fast, the privacy protection of the scheme is effective and the data usability of the scheme is higher.

Effect of advanced component technology on helicopter transmissions

NASA Technical Reports Server (NTRS)

Lewicki, David G.; Townsend, Dennis P.

1989-01-01

Experimental tests were performed on the NASA/Bell Helicopter Textron (BHT) 500 hp advanced technology transmission (ATT) at the NASA Lewis Research Center. The ATT was a retrofit of the OH-58C helicopter 236 kW (317 hp) main rotor transmission, upgraded to 373 kW (500 hp), with a design goal of retaining long life with a minimum increase in cost, weight, and size. Vibration, strain, efficiency, deflection, and temperature experiments were performed and the results were compared to previous experiments on the OH-58A, OH-58C, and UH-60A transmissions. The high-contact-ratio gears and the cantilevered-mounted, flexible ring gear of the ATT reduced vibration compared to that of the OH-58C. The ATT flexible ring gear improved planetary load sharing compared to that of the rigid ring gear of the UH-60A transmission. The ATT mechanical efficiency was lower than that of the OH-58A transmission, probably due to the high-contact-ratio planetary gears.

Analysis of trends in climate, streamflow, and stream temperature in north coastal California

USGS Publications Warehouse

Madej, Mary Ann; Medley, C. Nicholas; Patterson, Glenn; Parker, Melanie J.

2011-01-01

As part of a broader project analyzing trends in climate, streamflow, vegetation, salmon, and ocean conditions in northern California national park units, we compiled average monthly air temperature and precipitation data from 73 climate stations, streamflow data from 21 river gaging stations, and limited stream temperature data from salmon-bearing rivers in north coastal California. Many climate stations show a statistically significant increase in both average maximum and average minimum air temperature in early fall and midwinter during the last century. Concurrently, average September precipitation has decreased. In many coastal rivers, summer low flow has decreased and summer stream temperatures have increased, which affects summer rearing habitat for salmonids. Nevertheless, because vegetative cover has also changed during this time period, we cannot ascribe streamflow changes to climate change without first assessing water budgets. Although shifts in the timing of the centroid of runoff have been documented in snowmelt-dominated watersheds in the western United States, this was not the case in lower elevation coastal rivers analyzed in this study.

Automated Slicing for a Multi-Axis Metal Deposition System (Preprint)

DTIC Science & Technology

2006-09-01

experimented with different materials like H13 tool steel to build the part. Following the same slicing and scanning toolpath result, there is a geometric...and analysis tool -centroidal axis. Similar to medial axis, it contains geometry and topological information but is significantly computationally...geometry reasoning and analysis tool -centroidal axis. Similar to medial axis, it contains geometry and topological information but is significantly

Video image position determination

DOEpatents

Christensen, Wynn; Anderson, Forrest L.; Kortegaard, Birchard L.

1991-01-01

An optical beam position controller in which a video camera captures an image of the beam in its video frames, and conveys those images to a processing board which calculates the centroid coordinates for the image. The image coordinates are used by motor controllers and stepper motors to position the beam in a predetermined alignment. In one embodiment, system noise, used in conjunction with Bernoulli trials, yields higher resolution centroid coordinates.

Magic of centroids

NASA Astrophysics Data System (ADS)

Ferrarello, Daniela; Mammana, Maria Flavia; Pennisi, Mario

2018-05-01

In this paper, we show some properties of centroids of geometric figures, such as triangles, quadrilaterals and tetrahedra. In particular, we will prove the properties by means of geometric transformations and by introducing extensions of triangles and quadrilaterals, i.e. by adding one, two or three new vertices to the figure. The study of these properties can be used, with profit, in a classroom activity supported by a dynamic geometry system.

SU-F-J-109: Generate Synthetic CT From Cone Beam CT for CBCT-Based Dose Calculation

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

Wang, H; Barbee, D; Wang, W

Purpose: The use of CBCT for dose calculation is limited by its HU inaccuracy from increased scatter. This study presents a method to generate synthetic CT images from CBCT data by a probabilistic classification that may be robust to CBCT noise. The feasibility of using the synthetic CT for dose calculation is evaluated in IMRT for unilateral H&N cancer. Methods: In the training phase, a fuzzy c-means classification was performed on HU vectors (CBCT, CT) of planning CT and registered day-1 CBCT image pair. Using the resulting centroid CBCT and CT values for five classified “tissue” types, a synthetic CTmore » for a daily CBCT was created by classifying each CBCT voxel to obtain its probability belonging to each tissue class, then assigning a CT HU with a probability-weighted summation of the classes’ CT centroids. Two synthetic CTs from a CBCT were generated: s-CT using the centroids from classification of individual patient CBCT/CT data; s2-CT using the same centroids for all patients to investigate the applicability of group-based centroids. IMRT dose calculations for five patients were performed on the synthetic CTs and compared with CT-planning doses by dose-volume statistics. Results: DVH curves of PTVs and critical organs calculated on s-CT and s2-CT agree with those from planning-CT within 3%, while doses calculated with heterogeneity off or on raw CBCT show DVH differences up to 15%. The differences in PTV D95% and spinal cord max are 0.6±0.6% and 0.6±0.3% for s-CT, and 1.6±1.7% and 1.9±1.7% for s2-CT. Gamma analysis (2%/2mm) shows 97.5±1.6% and 97.6±1.6% pass rates for using s-CTs and s2-CTs compared with CT-based doses, respectively. Conclusion: CBCT-synthesized CTs using individual or group-based centroids resulted in dose calculations that are comparable to CT-planning dose for unilateral H&N cancer. The method may provide a tool for accurate dose calculation based on daily CBCT.« less

Energy and Mass Transport of Magnetospheric Plasmas during the November 2003 Magnetic Storm

NASA Technical Reports Server (NTRS)

Fok, Mei-Chging; Moore, Thomas

2008-01-01

Intensive energy and mass transport from the solar wind across the magnetosphere boundary is a trigger of magnetic storms. The storm on 20-21 November 2003 was elicited by a high-speed solar wind and strong southward component of interplanetary magnetic field. This storm attained a minimum Dst of -422 nT. During the storm, some of the solar wind particles enter the magnetosphere and eventually become part of the ring current. At the same time, the fierce solar wind powers strong outflow of H+ and O+ from the ionosphere, as well as from the plasmasphere. We examine the contribution of plasmas from the solar wind, ionosphere and plasmasphere to the storm-time ring current. Our simulation shows, for this particular storm, ionospheric O+ and solar wind ions are the major sources of the ring current particles. The polar wind and plasmaspheric H+ have only minor impacts. In the storm main phase, the strong penetration of solar wind electric field pushes ions from the geosynchronous orbit to L shells of 2 and below. Ring current is greatly intensified during the earthward transport and produces a large magnetic depression in the surface field. When the convection subsides, the deep penetrating ions experience strong charge exchange loss, causing rapid decay of the ring current and fast initial storm recovery. Our simulation reproduces very well the storm development indicated by the Dst index.

Unraveling the strands of Saturn's F ring

USGS Publications Warehouse

Murray, C.D.; Gordon, M.K.; Giuliatti, Winter S.M.

1997-01-01

Several high-resolution Voyager 2 images of Saturn's F ring show that it is composed of at least four separate, non-intersecting strands extending ~45?? in longitude. Voyager 1 images show that the two brightest strands appear to intersect, giving rise to a "braided" morphology. From a study of all available Voyager images the detectable radial structure is cataloged and reviewed. Previous indications that there is fine material interior to the orbit of the F ring are confirmed. Evidence is presented that a model of four strands with comparable eccentricities and nearly aligned perichrones is consistent with all the Voyager observations. The observed perichrone offset of the two brightest strands suggests a minimum radial separation of ~20 km, which implies intersection of these strands when their finite radial widths are taken into account. The longitude range of such an intersection includes that observed in the Voyager 1 "braid" images. The proximity of these two strands at some longitudes may account for the apparent differences in the ring between the Voyager encounters, as well as provide a source for the short-lived features detected in the Hubble Space Telescope images of the F ring. There is no evidence that the locations of the individual strands are determined by resonant perturbations with known satellites. It is proposed that the radial structure is formed by the localized action of small satellites orbiting within the strand region. ?? 1997 Academic Press.

High-Speed Optical Wide-Area Data-Communication Network

NASA Technical Reports Server (NTRS)

Monacos, Steve P.

1994-01-01

Proposed fiber-optic wide-area network (WAN) for digital communication balances input and output flows of data with its internal capacity by routing traffic via dynamically interconnected routing planes. Data transmitted optically through network by wavelength-division multiplexing in synchronous or asynchronous packets. WAN implemented with currently available technology. Network is multiple-ring cyclic shuffle exchange network ensuring traffic reaches its destination with minimum number of hops.

Synthesis and characterization of polymeric materials derived from 2,5-diketopiperazines and pyroglutamic acid

NASA Astrophysics Data System (ADS)

Parrish, Dennis Arch

The research presented in this dissertation describes the investigation of 2,5-diketopiperazines (DKPs) as property modifiers for addition polymers and the self association behavior of pyroglutamic acid derivatives. The first project involved the copolymerization of methyl methacrylate and styrene with DKP-based methacrylate monomers. Low incorporations of serine- and aspartame-based DKPs in the copolymer resulted in dramatic increases in the glass transition temperature (Ts). The research presented in Chapter II focuses on the ring-opening reactions of pyroglutamic diketopiperazine (pyDKP). The original intent was to synthesize polymers containing backbone DKPs through ring-opening polymerization of the five-membered rings. However, it was discovered that regioselective ring-opening occurs at the six-membered ring to give pyroglutamic acid derivatives. Since this reaction had not been reported previously, the focus of research was altered to investigate the scope and limitations of the new reaction. The ring-opening reactions of pyDKP with diamines to give bispyroglutamides is described in Chapter IV. While these materials are not polymeric, they display polymeric behavior. It was found that multi-functional pyroglutamides display Tgs during thermal analysis, exhibit high thermal stability, and form melt-drawn fibers. In contrast, the materials have low solution viscosities and are freely soluble in water, ethanol, and chloroform. This behavior is attributed to non-covalent supramolecular associations. The final part of this dissertation involved the investigation of thermoreversible organic solvent gelators. The ring-opening reaction of pyDKP with long alkyl amines unexpectedly gelled the reaction solvent. A series of analogous gelators were synthesized, and the minimum concentration required for gelation in various solvents was determined. It was found that the nature of the solvent, alkyl chain length, and optical activity of the gelator determined gelator efficiency and gel structure.

Analyzing Bleriot's propeller gaps in Cassini NAC images

NASA Astrophysics Data System (ADS)

Hoffmann, Holger; Chen, Cheng; Seiß, Martin; Albers, Nicole; Spahn, Frank; Nic

2016-10-01

Among the great discoveries of the Cassini mission are the propeller-shaped structures created by small moonlets embedded in Saturn's dense rings. These moonlets are not massive enough to counteract the viscous ring diffusion to open and maintain circumferential gaps, distinguishing them from ring-moons like Pan and Daphnis.Although one of the defining features of propeller structures, well-formed partial gaps have been resolved by the Imaging Science Subsystem Narrow Angle Camera onboard the Cassini spacecraft only for the largest known propeller named Bleriot. We analyze images of the sunlit side of Saturn's outer A ring showing the propeller Bleriot with clearly visible gaps. By fitting a Gaussian to radial brightness profiles at different azimuthal locations, we obtain the evolution of gap minimum and gap width downstream of the moonlet.We report two findings:1) Numerical simulations indicate that the radial separation of the partial propeller gaps is expected to be 4 Hill radii (Spahn and Sremcevic, 2000, A&A). We infer Bleriot's Hill radius to be a few hundred meters, consistent with values given by Sremcevic et al. (2014, DPS) and Hoffmann et al. (2015, Icarus).2) In order to estimate the ring viscosity in the region of Saturn's outer A ring, where Bleriot orbits, we fit several model functions (one example being the analytic solution derived by Sremcevic, Spahn and Duschl, 2002, MNRAS) describing the azimuthal evolution of the surface density in the propeller gap region to the data obtained from the image analysis. We find viscosity values consistent with the parameterization of ring viscosity by Daisaka et al. (2001, Icarus), but significantly lower than the upper limit given by Esposito et al. (1983, Icarus)

THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: BIASES IN z  > 1.46 REDSHIFTS DUE TO QUASAR DIVERSITY

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

Denney, K. D.; Peterson, B. M.; Horne, Keith

We use the coadded spectra of 32 epochs of Sloan Digital Sky Survey (SDSS) Reverberation Mapping Project observations of 482 quasars with z  > 1.46 to highlight systematic biases in the SDSS- and Baryon Oscillation Spectroscopic Survey (BOSS)-pipeline redshifts due to the natural diversity of quasar properties. We investigate the characteristics of this bias by comparing the BOSS-pipeline redshifts to an estimate from the centroid of He ii λ 1640. He ii has a low equivalent width but is often well-defined in high-S/N spectra, does not suffer from self-absorption, and has a narrow component which, when present (the case for aboutmore » half of our sources), produces a redshift estimate that, on average, is consistent with that determined from [O ii] to within the He ii and [O ii] centroid measurement uncertainties. The large redshift differences of ∼1000 km s{sup −1}, on average, between the BOSS-pipeline and He ii-centroid redshifts, suggest there are significant biases in a portion of BOSS quasar redshift measurements. Adopting the He ii-based redshifts shows that C iv does not exhibit a ubiquitous blueshift for all quasars, given the precision probed by our measurements. Instead, we find a distribution of C iv-centroid blueshifts across our sample, with a dynamic range that (i) is wider than that previously reported for this line, and (ii) spans C iv centroids from those consistent with the systemic redshift to those with significant blueshifts of thousands of kilometers per second. These results have significant implications for measurement and use of high-redshift quasar properties and redshifts, and studies based thereon.« less

Spotting stellar activity cycles in Gaia astrometry

NASA Astrophysics Data System (ADS)

Morris, Brett M.; Agol, Eric; Davenport, James R. A.; Hawley, Suzanne L.

2018-06-01

Astrometry from Gaia will measure the positions of stellar photometric centroids to unprecedented precision. We show that the precision of Gaia astrometry is sufficient to detect starspot-induced centroid jitter for nearby stars in the Tycho-Gaia Astrometric Solution (TGAS) sample with magnetic activity similar to the young G-star KIC 7174505 or the active M4 dwarf GJ 1243, but is insufficient to measure centroid jitter for stars with Sun-like spot distributions. We simulate Gaia observations of stars with 10 year activity cycles to search for evidence of activity cycles, and find that Gaia astrometry alone likely cannot detect activity cycles for stars in the TGAS sample, even if they have spot distributions like KIC 7174505. We review the activity of the nearby low-mass stars in the TGAS sample for which we anticipate significant detections of spot-induced jitter.

Use of incomplete energy recovery for the energy compression of large energy spread charged particle beams

DOEpatents

Douglas, David R [Newport News, VA; Benson, Stephen V [Yorktown, VA

2007-01-23

A method of energy recovery for RF-base linear charged particle accelerators that allows energy recovery without large relative momentum spread of the particle beam involving first accelerating a waveform particle beam having a crest and a centroid with an injection energy E.sub.o with the centroid of the particle beam at a phase offset f.sub.o from the crest of the accelerating waveform to an energy E.sub.full and then recovering the beam energy centroid a phase f.sub.o+Df relative to the crest of the waveform particle beam such that (E.sub.full-E.sub.o)(1+cos(f.sub.o+Df))>dE/2 wherein dE=the full energy spread, dE/2=the full energy half spread and Df=the wave form phase distance.

Derivation of the Statistical Distribution of the Mass Peak Centroids of Mass Spectrometers Employing Analog-to-Digital Converters and Electron Multipliers

DOE PAGES

Ipsen, Andreas

2017-02-03

Here, the mass peak centroid is a quantity that is at the core of mass spectrometry (MS). However, despite its central status in the field, models of its statistical distribution are often chosen quite arbitrarily and without attempts at establishing a proper theoretical justification for their use. Recent work has demonstrated that for mass spectrometers employing analog-to-digital converters (ADCs) and electron multipliers, the statistical distribution of the mass peak intensity can be described via a relatively simple model derived essentially from first principles. Building on this result, the following article derives the corresponding statistical distribution for the mass peak centroidsmore » of such instruments. It is found that for increasing signal strength, the centroid distribution converges to a Gaussian distribution whose mean and variance are determined by physically meaningful parameters and which in turn determine bias and variability of the m/z measurements of the instrument. Through the introduction of the concept of “pulse-peak correlation”, the model also elucidates the complicated relationship between the shape of the voltage pulses produced by the preamplifier and the mean and variance of the centroid distribution. The predictions of the model are validated with empirical data and with Monte Carlo simulations.« less

Optimum threshold selection method of centroid computation for Gaussian spot

NASA Astrophysics Data System (ADS)

Li, Xuxu; Li, Xinyang; Wang, Caixia

2015-10-01

Centroid computation of Gaussian spot is often conducted to get the exact position of a target or to measure wave-front slopes in the fields of target tracking and wave-front sensing. Center of Gravity (CoG) is the most traditional method of centroid computation, known as its low algorithmic complexity. However both electronic noise from the detector and photonic noise from the environment reduces its accuracy. In order to improve the accuracy, thresholding is unavoidable before centroid computation, and optimum threshold need to be selected. In this paper, the model of Gaussian spot is established to analyze the performance of optimum threshold under different Signal-to-Noise Ratio (SNR) conditions. Besides, two optimum threshold selection methods are introduced: TmCoG (using m % of the maximum intensity of spot as threshold), and TkCoG ( usingμn +κσ n as the threshold), μn and σn are the mean value and deviation of back noise. Firstly, their impact on the detection error under various SNR conditions is simulated respectively to find the way to decide the value of k or m. Then, a comparison between them is made. According to the simulation result, TmCoG is superior over TkCoG for the accuracy of selected threshold, and detection error is also lower.

Structure and seasonal variations of the nocturnal mesospheric K layer at Arecibo

NASA Astrophysics Data System (ADS)

Yue, Xianchang; Friedman, Jonathan S.; Wu, Xiongbin; Zhou, Qihou H.

2017-07-01

We present the seasonal variations of the nocturnal mesospheric potassium (K) layer at Arecibo, Puerto Rico (18.35°N, 66.75°W) from 160 nights of K Doppler lidar observations between December 2003 and January 2010, during which the solar activity is mostly low. The background temperature is also measured simultaneously by the lidar and shows a strong semiannual oscillation with maxima occurring during equinoxes at all altitudes. The annual mean K density profile is approximately Gaussian with a peak altitude of 91.7 km. The K column abundance and the centroid height have strong semiannual variations, with maxima at the solstices. Both parameters are negatively correlated to the mean background temperature with a correlation coefficient < -0.5. The root-mean-square (RMS) width has a distinct annual oscillation with the largest width occurring in May. The seasonal variation of the centroid height is similar to that of the Fe layer at the same site. The seasonal temperature variation indicates significant enhanced wave-induced downward transport for both species during spring and autumn. This explains the metal layer centroid height and column abundance variations at Arecibo and provides a general mechanism to account for the seasonal variations in the centroid height of all metal species measured at low-latitude and midlatitude sites.

Statistical Properties of Line Centroid Velocity Increments in the rho Ophiuchi Cloud

NASA Technical Reports Server (NTRS)

Lis, D. C.; Keene, Jocelyn; Li, Y.; Phillips, T. G.; Pety, J.

1998-01-01

We present a comparison of histograms of CO (2-1) line centroid velocity increments in the rho Ophiuchi molecular cloud with those computed for spectra synthesized from a three-dimensional, compressible, but non-starforming and non-gravitating hydrodynamic simulation. Histograms of centroid velocity increments in the rho Ophiuchi cloud show clearly non-Gaussian wings, similar to those found in histograms of velocity increments and derivatives in experimental studies of laboratory and atmospheric flows, as well as numerical simulations of turbulence. The magnitude of these wings increases monotonically with decreasing separation, down to the angular resolution of the data. This behavior is consistent with that found in the phase of the simulation which has most of the properties of incompressible turbulence. The time evolution of the magnitude of the non-Gaussian wings in the histograms of centroid velocity increments in the simulation is consistent with the evolution of the vorticity in the flow. However, we cannot exclude the possibility that the wings are associated with the shock interaction regions. Moreover, in an active starforming region like the rho Ophiuchi cloud, the effects of shocks may be more important than in the simulation. However, being able to identify shock interaction regions in the interstellar medium is also important, since numerical simulations show that vorticity is generated in shock interactions.

Derivation of the Statistical Distribution of the Mass Peak Centroids of Mass Spectrometers Employing Analog-to-Digital Converters and Electron Multipliers

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

Ipsen, Andreas

Here, the mass peak centroid is a quantity that is at the core of mass spectrometry (MS). However, despite its central status in the field, models of its statistical distribution are often chosen quite arbitrarily and without attempts at establishing a proper theoretical justification for their use. Recent work has demonstrated that for mass spectrometers employing analog-to-digital converters (ADCs) and electron multipliers, the statistical distribution of the mass peak intensity can be described via a relatively simple model derived essentially from first principles. Building on this result, the following article derives the corresponding statistical distribution for the mass peak centroidsmore » of such instruments. It is found that for increasing signal strength, the centroid distribution converges to a Gaussian distribution whose mean and variance are determined by physically meaningful parameters and which in turn determine bias and variability of the m/z measurements of the instrument. Through the introduction of the concept of “pulse-peak correlation”, the model also elucidates the complicated relationship between the shape of the voltage pulses produced by the preamplifier and the mean and variance of the centroid distribution. The predictions of the model are validated with empirical data and with Monte Carlo simulations.« less

Precision targeting in guided munition using IR sensor and MmW radar

NASA Astrophysics Data System (ADS)

Sreeja, S.; Hablani, H. B.; Arya, H.

2015-10-01

Conventional munitions are not guided with sensors and therefore miss the target, particularly if the target is mobile. The miss distance of these munitions can be decreased by incorporating sensors to detect the target and guide the munition during flight. This paper is concerned with a Precision Guided Munition(PGM) equipped with an infrared sensor and a millimeter wave radar [IR and MmW, for short]. Three-dimensional flight of the munition and its pitch and yaw motion models are developed and simulated. The forward and lateral motion of a target tank on the ground is modeled as two independent second-order Gauss-Markov process. To estimate the target location on the ground and the line-of-sight rate to intercept it an Extended Kalman Filter is composed whose state vector consists of cascaded state vectors of missile dynamics and target dynamics. The line-of-sight angle measurement from the infrared seeker is by centroiding the target image in 40 Hz. The centroid estimation of the images in the focal plane is at a frequency of 10 Hz. Every 10 Hz, centroids of four consecutive images are averaged, yielding a time-averaged centroid, implying some measurement delay. The miss distance achieved by including by image processing delays is 1:45m.

Precision targeting in guided munition using infrared sensor and millimeter wave radar

NASA Astrophysics Data System (ADS)

Sulochana, Sreeja; Hablani, Hari B.; Arya, Hemendra

2016-07-01

Conventional munitions are not guided with sensors and therefore miss the target, particularly if the target is mobile. The miss distance of these munitions can be decreased by incorporating sensors to detect the target and guide the munition during flight. This paper is concerned with a precision guided munition equipped with an infrared (IR) sensor and a millimeter wave radar (MmW). Three-dimensional flight of the munition and its pitch and yaw motion models are developed and simulated. The forward and lateral motion of a target tank on the ground is modeled as two independent second-order Gauss-Markov processes. To estimate the target location on the ground and the line-of-sight (LOS) rate to intercept it, an extended Kalman filter is composed whose state vector consists of cascaded state vectors of missile dynamics and target dynamics. The LOS angle measurement from the IR seeker is by centroiding the target image in 40 Hz. The centroid estimation of the images in the focal plane is at a frequency of 10 Hz. Every 10 Hz, centroids of four consecutive images are averaged, yielding a time-averaged centroid, implying some measurement delay. The miss distance achieved by including image processing delays is 1.45 m.

Management implications of long-term tree growth and mortality rates: A modeling study of big-leaf mahogany (Swietenia macrophylla) in the Brazilian Amazon

Treesearch

C.M. Free; R.M. Landis; J. Grogan; M.D. Schulze; M. Lentini; O. Dunisch; NO-VALUE

2014-01-01

Knowledge of tree age-size relationships is essential towards evaluating the sustainability of harvest regulations that include minimum diameter cutting limits and fixed-length cutting cycles. Although many tropical trees form annual growth rings and can be aged from discs or cores, destructive sampling is not always an option for valuable or threatened species. We...

A PRIMER ON UNIFYING DEBRIS DISK MORPHOLOGIES

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

Lee, Eve J.; Chiang, Eugene, E-mail: evelee@berkeley.edu, E-mail: echiang@astro.berkeley.edu

A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, diskmore » inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.« less

Multi-Criterion Preliminary Design of a Tetrahedral Truss Platform

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey

1995-01-01

An efficient method is presented for multi-criterion preliminary design and demonstrated for a tetrahedral truss platform. The present method requires minimal analysis effort and permits rapid estimation of optimized truss behavior for preliminary design. A 14-m-diameter, 3-ring truss platform represents a candidate reflector support structure for space-based science spacecraft. The truss members are divided into 9 groups by truss ring and position. Design variables are the cross-sectional area of all members in a group, and are either 1, 3 or 5 times the minimum member area. Non-structural mass represents the node and joint hardware used to assemble the truss structure. Taguchi methods are used to efficiently identify key points in the set of Pareto-optimal truss designs. Key points identified using Taguchi methods are the maximum frequency, minimum mass, and maximum frequency-to-mass ratio truss designs. Low-order polynomial curve fits through these points are used to approximate the behavior of the full set of Pareto-optimal designs. The resulting Pareto-optimal design curve is used to predict frequency and mass for optimized trusses. Performance improvements are plotted in frequency-mass (criterion) space and compared to results for uniform trusses. Application of constraints to frequency and mass and sensitivity to constraint variation are demonstrated.

Conformational analysis of (1. -->. 4)-. beta. -D-mannan triacetate

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

Deslandes, Y.; Marchessault, R.H.; Bluhm, T.L.

1983-01-01

In wood, algae, and tubers, glucomannans have varying mannose-to-glucose ratios (M/G). Since diffraction on glucomannans of widely varying M/G do not show significant change in unit-cell base plane dimensions, the authors have suggested that isomorphous replacement may occur in glucomannans. To further investigate this point, it has been undertaken conformational analysis of glucomannan triacetate in which the X-ray fiber diagram suggests that two nonequivalent residues make up the asymmetric unit. X-ray fiber diagrams of the triacetate of glucomannan from Tubera salep show twofold symmetry along the chain axis with a fiber repeat of 1.6 nm. This implies that the asymmetricmore » unit is composed of two pyranose rings since the virtual bond length of a single pyranose ring cannot be greater than approximately 0.54 nm. By using empirical potential functions, it could be shown that the minimum internal energy of a mannan triacetate chain corresponds to a state where contiguous mannose triacetate units are not conformationally equivalent. This supports the hypothesis of mannobiose hexaacetate as the asymmetric unit. Furthermore, introduction of glucose triacetate into the backbone did not change the minimum energy conformation, thereby lending support to the isomorphous replacement concept in crystalline glucomannans. 19 references, 13 figures, 2 tables.« less

Space shuttle Production Verification Motor 1 (PV-1) static fire

NASA Technical Reports Server (NTRS)

1989-01-01

All inspection and instrumentation data indicate that the PV-1 static test firing conducted 18 Aug. 1988 was successful. With the exception of the intentionally flawed joints and static test modifications, PV-1 was flight configuration. Fail-safe flaws guaranteeing pressure to test the sealing capability of primary O-rings were included in the aft field joint, case-to-nozzle joint, and nozzle internal Joint 5. The test was conducted at ambient conditions, with the exception of the field joints and case/nozzle joints which were maintained at a minimum of 75 F. Ballistics performance values were within specification requirements. The PV-1 motor exhibited chamber pressure oscillations similar to previously tested Space Shuttle redesigned solid rocket motors, particularly QM-7. The first longitudinal mode oscillations experienced by PV-1 were the strongest ever measured in a Space Shuttle motor. Investigation into this observation is being conducted. Joint insulation performed as designed with no evidence of gas flow within unflawed forward field joints. The intentionally flawed center and aft case field joint insulation performance was excellent. There was no evidence of hot gas past the center field joint capture feature O-ring, the case-to-nozzle joint primary O-ring, or the aft field joint primary O-ring. O-ring seals and barriers with assured pressure at the flaws showed erosion and heat effect, but all sealed against passage of hot gases with the exception of the aft field joint capture feature O-ring. There was no evidence of erosion, heat effect, or blowby on any O-ring seals or barriers at the unflawed joints. Nozzle performance was nominal with typical erosion. Post-test examination revealed that the forward nose ring was of the old high performance motor design configuration with the 150-deg ply angle. All nozzle components remained intact for post-test evaluation. The thrust vector control system operated correctly. The water deluge system, CO2 quench, and other test equipment performed as planned during all required test operations.

Proposal for an optical multicarrier generator based on single silicon micro-ring modulator

NASA Astrophysics Data System (ADS)

Bhowmik, Bishanka Brata; Gupta, Sumanta

2015-08-01

We propose an optical multicarrier generation technique using silicon micro-ring modulator (MRM) and analyze the scheme. Numerical studies have been done for three types MRMs having different power coupling coefficients. The proposed scheme is found to generate four optical carriers having 12.5 GHz spacing. According to simulation, the maximum side-mode-suppression ratio (SMSR) of ~16.3 dB with flatness of ~0.2 dB is achieved by using this scheme. The minimum extinction ratio (ER) of the generated carriers is found to be more than 35 dB. We also propose modulator driver circuit to generate RF signal, which is needed to generate multicarrier using MRM. The effect of coupling coefficient on the SMSR of the generated carriers is also investigated.

Global Magnetosphere Evolution During 22 June 2015 Geomagnetic Storm as Seen From Multipoint Observations and Comparison With MHD-Ring Rurrent Model

NASA Astrophysics Data System (ADS)

Buzulukova, N.; Moore, T. E.; Dorelli, J.; Fok, M. C. H.; Sibeck, D. G.; Angelopoulos, V.; Goldstein, J.; Valek, P. W.; McComas, D. J.

2015-12-01

On 22-23 June 2015 a severe geomagnetic storm occurred with Dst minimum of approximately -200nT. During this extreme event, multipoint observations of magnetospheric dynamics were obtained by a fleet of Geospace spacecraft including MMS, TWINS, Van-Allen and THEMIS. We present analysis of satellite data during that event, and use a global coupled MHD-ring current model (BATSRUS-CRCM) to connect multipoint observations from different parts of the magnetosphere. The analysis helps to identify different magnetospheric domains from multipoint measurements and various magnetospheric boundary motions. We will explore how the initial disturbance from the solar wind propagates through the magnetosphere causing energization of plasma in the inner magnetosphere and producing an extreme geomagnetic storm.

PyCCF: Python Cross Correlation Function for reverberation mapping studies

NASA Astrophysics Data System (ADS)

Sun, Mouyuan; Grier, C. J.; Peterson, B. M.

2018-05-01

PyCCF emulates a Fortran program written by B. Peterson for use with reverberation mapping. The code cross correlates two light curves that are unevenly sampled using linear interpolation and measures the peak and centroid of the cross-correlation function. In addition, it is possible to run Monto Carlo iterations using flux randomization and random subset selection (RSS) to produce cross-correlation centroid distributions to estimate the uncertainties in the cross correlation results.

Immune Centroids Over-Sampling Method for Multi-Class Classification

DTIC Science & Technology

2015-05-22

recognize to specific antigens . The response of a receptor to an antigen can activate its hosting B-cell. Activated B-cell then proliferates and...modifying N.K. Jerne’s theory. The theory states that in a pre-existing group of lympho- cytes ( specifically B cells), a specific antigen only...the clusters of each small class, which have high data density, called global immune centroids over-sampling (denoted as Global-IC). Specifically

Deep neural network-based domain adaptation for classification of remote sensing images

NASA Astrophysics Data System (ADS)

Ma, Li; Song, Jiazhen

2017-10-01

We investigate the effectiveness of deep neural network for cross-domain classification of remote sensing images in this paper. In the network, class centroid alignment is utilized as a domain adaptation strategy, making the network able to transfer knowledge from the source domain to target domain on a per-class basis. Since predicted labels of target data should be used to estimate the centroid of each class, we use overall centroid alignment as a coarse domain adaptation method to improve the estimation accuracy. In addition, rectified linear unit is used as the activation function to produce sparse features, which may improve the separation capability. The proposed network can provide both aligned features and an adaptive classifier, as well as obtain label-free classification of target domain data. The experimental results using Hyperion, NCALM, and WorldView-2 remote sensing images demonstrated the effectiveness of the proposed approach.

Comparative Analysis of Document level Text Classification Algorithms using R

NASA Astrophysics Data System (ADS)

Syamala, Maganti; Nalini, N. J., Dr; Maguluri, Lakshamanaphaneendra; Ragupathy, R., Dr.

2017-08-01

From the past few decades there has been tremendous volumes of data available in Internet either in structured or unstructured form. Also, there is an exponential growth of information on Internet, so there is an emergent need of text classifiers. Text mining is an interdisciplinary field which draws attention on information retrieval, data mining, machine learning, statistics and computational linguistics. And to handle this situation, a wide range of supervised learning algorithms has been introduced. Among all these K-Nearest Neighbor(KNN) is efficient and simplest classifier in text classification family. But KNN suffers from imbalanced class distribution and noisy term features. So, to cope up with this challenge we use document based centroid dimensionality reduction(CentroidDR) using R Programming. By combining these two text classification techniques, KNN and Centroid classifiers, we propose a scalable and effective flat classifier, called MCenKNN which works well substantially better than CenKNN.

A motion detection system for AXAF X-ray ground testing

NASA Technical Reports Server (NTRS)

Arenberg, Jonathan W.; Texter, Scott C.

1993-01-01

The concept, implementation, and performance of the motion detection system (MDS) designed as a diagnostic for X-ray ground testing for AXAF are described. The purpose of the MDS is to measure the magnitude of a relative rigid body motion among the AXAF test optic, the X-ray source, and X-ray focal plane detector. The MDS consists of a point source, lens, centroid detector, transimpedance amplifier, and computer system. Measurement of the centroid position of the image of the optical point source provides a direct measure of the motions of the X-ray optical system. The outputs from the detector and filter/amplifier are digitized and processed using the calibration with a 50 Hz bandwidth to give the centroid's location on the detector. Resolution of 0.008 arcsec has been achieved by this system. Data illustrating the performance of the motion detection system are also presented.

Assessment of auditory impression of the coolness and warmness of automotive HVAC noise.

PubMed

Nakagawa, Seiji; Hotehama, Takuya; Kamiya, Masaru

2017-07-01

Noise induced by a heating, ventilation and air conditioning (HVAC) system in a vehicle is an important factor that affects the comfort of the interior of a car cabin. Much effort has been devoted to reduce noise levels, however, there is a need for a new sound design that addresses the noise problem from a different point of view. In this study, focusing on the auditory impression of automotive HVAC noise concerning coolness and warmness, psychoacoustical listening tests were performed using a paired comparison technique under various conditions of room temperature. Five stimuli were synthesized by stretching the spectral envelopes of recorded automotive HVAC noise to assess the effect of the spectral centroid, and were presented to normal-hearing subjects. Results show that the spectral centroid significantly affects the auditory impression concerning coolness and warmness; a higher spectral centroid induces a cooler auditory impression regardless of the room temperature.

Depth to the bottom of magnetic sources (DBMS) from aeromagnetic data of Central India using modified centroid method for fractal distribution of sources

NASA Astrophysics Data System (ADS)

Bansal, A. R.; Anand, S. P.; Rajaram, Mita; Rao, V. K.; Dimri, V. P.

2013-09-01

The depth to the bottom of the magnetic sources (DBMS) has been estimated from the aeromagnetic data of Central India. The conventional centroid method of DBMS estimation assumes random uniform uncorrelated distribution of sources and to overcome this limitation a modified centroid method based on scaling distribution has been proposed. Shallower values of the DBMS are found for the south western region. The DBMS values are found as low as 22 km in the south west Deccan trap covered regions and as deep as 43 km in the Chhattisgarh Basin. In most of the places DBMS are much shallower than the Moho depth, earlier found from the seismic study and may be representing the thermal/compositional/petrological boundaries. The large variation in the DBMS indicates the complex nature of the Indian crust.

Experimental and analytical investigation of a modified ring cusp NSTAR engine

NASA Technical Reports Server (NTRS)

Sengupta, Anita

2005-01-01

A series of experimental measurements on a modified laboratory NSTAR engine were used to validate a zero dimensional analytical discharge performance model of a ring cusp ion thruster. The model predicts the discharge performance of a ring cusp NSTAR thruster as a function the magnetic field configuration, thruster geometry, and throttle level. Analytical formalisms for electron and ion confinement are used to predict the ionization efficiency for a given thruster design. Explicit determination of discharge loss and volume averaged plasma parameters are also obtained. The model was used to predict the performance of the nominal and modified three and four ring cusp 30-cm ion thruster configurations operating at the full power (2.3 kW) NSTAR throttle level. Experimental measurements of the modified engine configuration discharge loss compare well with the predicted value for propellant utilizations from 80 to 95%. The theory, as validated by experiment, indicates that increasing the magnetic strength of the minimum closed reduces maxwellian electron diffusion and electrostatically confines the ion population and subsequent loss to the anode wall. The theory also indicates that increasing the cusp strength and minimizing the cusp area improves primary electron confinement increasing the probability of an ionization collision prior to loss at the cusp.

Dense Seismic Recordings of Two Surface-Detonated Chemical Explosions

NASA Astrophysics Data System (ADS)

Koper, K. D.; Hale, J. M.; Burlacu, R.; Goddard, K. J.; Trow, A.; Linville, L. M.; Stein, J. R.; Drobeck, D.; Leidig, M.

2015-12-01

In the summer of 2015 two controlled chemical explosions were carried out near Dugway, Utah. The 2 June 2015 explosion consisted of 30,000 lbs of ammonium nitrate fuel oil (ANFO) and the 22 July 2015 explosion consisted of 60,000 lbs of ANFO. The explosion centroids were 1-2 m above the Earth's surface and both created significant craters in the soft desert alluvium. To better understand the seismic source associated with surface explosions, we deployed an array of wireless, three-component, short-period (5 Hz corner frequency) seismometers for several days around each shot. For the first explosion, 46 receivers were deployed in a "lollipop" geometry that had a sparse ring at a radius of 1 km, and a dense stem with 100 m spacing for distances of 0.5-4.5 km. For the second explosion, 48 receivers were deployed similarly, but with a dense ring spaced in azimuthal increments of 10 degrees at a distance of 1 km, and a sparse stem (~500 m spacing) that extended to a distance of nearly 6 km. A rich variety of phases were recorded including direct P waves, refracted and reflected P waves, nearly monochromatic air-coupled Rayleigh waves, normally dispersed fundamental mode Rayleigh waves (Rg), primary airblast arrivals, some secondary airblast arrivals, and possibly tertiary airblast arrivals. There is also evidence of converted S waves on the radial components and possibly direct S energy on the radial and transverse components, although the transverse energy does not always possess a simple, coherent move-out with distance, implying that it might have a scattering origin. To aid in the phase identification, especially of the apparent SH and Love energy, we are currently performing tau-p, f-k, and particle motion analysis.

Di­aqua­[5,10,15,20-tetra­kis­(4-chloro­phen­yl)porphyrinato-κ4 N]iron(III) tri­fluoro­methane­sulfonate–4-hy­droxy-3-meth­oxy­benzaldehyde–water (1/1/2)

PubMed Central

Ben Haj Hassen, Leila; Ezzayani, Khaireddine; Rousselin, Yoann; Nasri, Habib

2014-01-01

In the title compound, [Fe(C44H24Cl4N4)(H2O)2](SO3CF3)·C8H8O3·2H2O, the FeIII cation is chelated by the four N atoms of the deprotonated tetra­kis­(4-chloro­tetra­phen­yl)porphyrin (TClPP) and further coordinated by two water mol­ecules in a distorted octa­hedral geometry. In the crystal, the cations, anions, 4-hy­droxy-3-meth­oxy­benzaldehyde and water mol­ecules of crystallization are linked by classical O—H⋯O hydrogen bonds and weak C—H⋯O and C—H⋯Cl hydrogen bonds into a three-dimensional supra­molecular architecture. The crystal packing is further stabilized by weak C—H⋯π inter­actions involving pyrrole and benzene rings. π–π stacking between parallel benzene rings of adjacent 4-hy­droxy-3-meth­oxy­benzaldehyde mol­ecules is also observed, the centroid–centroid distance being 3.8003 (13) Å. The three F atoms of the anion are disordered over two sets of sites, with a refined occupancy ratio 0.527 (12):0.473 (12). The O atom of one water mol­ecule of crystallization is also disordered over two positions in an occupancy ratio of 0.68 (5):0.32 (5). PMID:25249880

Correlation between centre offsets and gas velocity dispersion of galaxy clusters in cosmological simulations

NASA Astrophysics Data System (ADS)

Li, Ming-Hua; Zhu, Weishan; Zhao, Dong

2018-05-01

The gas is the dominant component of baryonic matter in most galaxy groups and clusters. The spatial offsets of gas centre from the halo centre could be an indicator of the dynamical state of cluster. Knowledge of such offsets is important for estimate the uncertainties when using clusters as cosmological probes. In this paper, we study the centre offsets roff between the gas and that of all the matter within halo systems in ΛCDM cosmological hydrodynamic simulations. We focus on two kinds of centre offsets: one is the three-dimensional PB offsets between the gravitational potential minimum of the entire halo and the barycentre of the ICM, and the other is the two-dimensional PX offsets between the potential minimum of the halo and the iterative centroid of the projected synthetic X-ray emission of the halo. Haloes at higher redshifts tend to have larger values of rescaled offsets roff/r200 and larger gas velocity dispersion σ v^gas/σ _{200}. For both types of offsets, we find that the correlation between the rescaled centre offsets roff/r200 and the rescaled 3D gas velocity dispersion, σ _v^gas/σ _{200} can be approximately described by a quadratic function as r_{off}/r_{200} ∝ (σ v^gas/σ _{200} - k_2)2. A Bayesian analysis with MCMC method is employed to estimate the model parameters. Dependence of the correlation relation on redshifts and the gas mass fraction are also investigated.

Novel high-resolution computed tomography-based radiomic classifier for screen-identified pulmonary nodules in the National Lung Screening Trial.

PubMed

Peikert, Tobias; Duan, Fenghai; Rajagopalan, Srinivasan; Karwoski, Ronald A; Clay, Ryan; Robb, Richard A; Qin, Ziling; Sicks, JoRean; Bartholmai, Brian J; Maldonado, Fabien

2018-01-01

Optimization of the clinical management of screen-detected lung nodules is needed to avoid unnecessary diagnostic interventions. Herein we demonstrate the potential value of a novel radiomics-based approach for the classification of screen-detected indeterminate nodules. Independent quantitative variables assessing various radiologic nodule features such as sphericity, flatness, elongation, spiculation, lobulation and curvature were developed from the NLST dataset using 726 indeterminate nodules (all ≥ 7 mm, benign, n = 318 and malignant, n = 408). Multivariate analysis was performed using least absolute shrinkage and selection operator (LASSO) method for variable selection and regularization in order to enhance the prediction accuracy and interpretability of the multivariate model. The bootstrapping method was then applied for the internal validation and the optimism-corrected AUC was reported for the final model. Eight of the originally considered 57 quantitative radiologic features were selected by LASSO multivariate modeling. These 8 features include variables capturing Location: vertical location (Offset carina centroid z), Size: volume estimate (Minimum enclosing brick), Shape: flatness, Density: texture analysis (Score Indicative of Lesion/Lung Aggression/Abnormality (SILA) texture), and surface characteristics: surface complexity (Maximum shape index and Average shape index), and estimates of surface curvature (Average positive mean curvature and Minimum mean curvature), all with P<0.01. The optimism-corrected AUC for these 8 features is 0.939. Our novel radiomic LDCT-based approach for indeterminate screen-detected nodule characterization appears extremely promising however independent external validation is needed.

Using Mid-IR Cavity Ring-Down Spectrometry to Simultaneously Measure N2o, CO2, and CH4 Fluxes: Responses to Ammonium Nitrate Additions in Salt Marshes

NASA Astrophysics Data System (ADS)

Brannon, E.; Moseman-Valtierra, S.; Tang, J.; Chen, X.; Martin, R.; Garate, M.

2014-12-01

Greenhouse gas emissions from salt marshes, especially of nitrous oxide (N2O), are a central interest because anthropogenic nutrient loads may substantially alter net climatic forcing of these globally significant ecosystems. In a series of lab and field experiments, a new cavity ring down spectrometer (CRDS, Picarro G2508) that uses mid-infrared (mid-IR) frequencies to measure N2O was compared to a near-IR gas analyzer (LGR N2O/CO analyzer). The Picarro G2508 reports N2O as well as CO2 and CH4 concentrations roughly every second at the parts per billion level. Responses of N2O fluxes to experimental ammonium nitrate additions in marsh mesocosms and marsh plots in situ were compared among these analyzers, along with minimum detectable N2O fluxes. At fluxes above 150 μmol N2O m-2 d-1, the Picarro G2508 and LGR analyzers performed similarly in both mesocosm and field plots that had been enriched with ammonium nitrate, however there were significantly lower minimum detectable N2O fluxes (about 1 order of magnitude) for the LGR than for the Picarro. A gas chromatograph (Shimadzu GC 2014) was also used to test calibration of the G2508. These experiments suggest that mid-IR CRDS technology offers a new tool for simultaneous analyses of N2O along with CO2 and CH4, which fills an important need for quantifying the net climatic forcing of ecosystems. However based on relatively high minimum N2O detection levels of the CRDS, it may work best in highly eutrophic environments.

Crystal structure of 1-(3-chloro­phen­yl)piperazin-1-ium picrate–picric acid (2/1)

PubMed Central

Kavitha, Channappa N.; Jasinski, Jerry P.; Kaur, Manpreet; Anderson, Brian J.; Yathirajan, H. S.

2014-01-01

The title salt {systematic name: bis­[1-(3-chloro­phen­yl)piperazinium 2,4,6-tri­nitro­phenolate]–picric acid (2/1)}, 2C10H14ClN2 +·2C6H5N3O7 −·C6H6N3O7, crystallized with two independent 1-(3-chloro­phen­yl)piperazinium cations, two picrate anions and a picric acid mol­ecule in the asymmetric unit. The six-membered piperazine ring in each cation adopts a slightly distorted chair conformation and contains a protonated N atom. In the picric acid mol­ecule, the mean planes of the nitro groups in the ortho-, meta-, and para-positions are twisted from the benzene ring by 31.5 (3), 7.7 (1), and 3.8 (2)°, respectively. In the anions, the dihedral angles between the benzene ring and the ortho-, meta-, and para-nitro groups are 36.7 (1), 5.0 (6), 4.8 (2)°, and 34.4 (9), 15.3 (8), 4.5 (1)°, respectively. The nitro group in one anion is disordered and was modeled with two sites for one O atom with an occupancy ratio of 0.627 (7):0.373 (7). In the crystal, the picric acid mol­ecule inter­acts with the picrate anion through a trifurcated O—H⋯O four-centre hydrogen bond involving an intra­molecular O—H⋯O hydrogen bond and a weak C—H⋯O inter­action. Weak inter­molecular C—H⋯O inter­actions are responsible for the formation of cation–anion–cation trimers resulting in a chain along [010]. In addition, weak C—H⋯Cl and weak π–π inter­actions [centroid–centroid distances of 3.532 (3), 3.756 (4) and 3.705 (3) Å] are observed and contribute to the stability of the crystal packing. PMID:25484834

Temperature tracking by North Sea benthic invertebrates in response to climate change.

PubMed

Hiddink, Jan G; Burrows, Michael T; García Molinos, Jorge

2015-01-01

Climate change is a major threat to biodiversity and distributions shifts are one of the most significant threats to global warming, but the extent to which these shifts keep pace with a changing climate is yet uncertain. Understanding the factors governing range shifts is crucial for conservation management to anticipate patterns of biodiversity distribution under future anthropogenic climate change. Soft-sediment invertebrates are a key faunal group because of their role in marine biogeochemistry and as a food source for commercial fish species. However, little information exists on their response to climate change. Here, we evaluate changes in the distribution of 65 North Sea benthic invertebrate species between 1986 and 2000 by examining their geographic, bathymetric and thermal niche shifts and test whether species are tracking their thermal niche as defined by minimum, mean or maximum sea bottom (SBT) and surface (SST) temperatures. Temperatures increased in the whole North Sea with many benthic invertebrates showing north-westerly range shifts (leading/trailing edges as well as distribution centroids) and deepening. Nevertheless, distribution shifts for most species (3.8-7.3 km yr(-1) interquantile range) lagged behind shifts in both SBT and SST (mean 8.1 km yr(-1)), resulting in many species experiencing increasing temperatures. The velocity of climate change (VoCC) of mean SST accurately predicted both the direction and magnitude of distribution centroid shifts, while maximum SST did the same for contraction of the trailing edge. The VoCC of SBT was not a good predictor of range shifts. No good predictor of expansions of the leading edge was found. Our results show that invertebrates need to shift at different rates and directions to track the climate velocities of different temperature measures, and are therefore lagging behind most temperature measures. If these species cannot withstand a change in thermal habitat, this could ultimately lead to a drop in benthic biodiversity. © 2014 John Wiley & Sons Ltd.

The design of the Spectrometer Ring at the HIAF

NASA Astrophysics Data System (ADS)

Wu, B.; Yang, J. C.; Xia, J. W.; Yan, X. L.; Hu, X. J.; Mao, L. J.; Sheng, L. N.; Wu, J. X.; Yin, D. Y.; Chai, W. P.; Shen, G. D.; Ge, W. W.; Wang, G.; Zhao, H.; Ruan, S.; Ma, X. W.; Wang, M.; Litvinov, S.; Wen, W. Q.; Chen, X. C.; Chen, R. J.; Tang, M. T.; Wu, W.; Luo, C.; Zhao, T. C.; Shi, C. F.; Fu, X.; Liu, J.; Liang, L.

2018-02-01

The Spectrometer Ring (SRing) is an essential part of the High Intensity heavy-ion Accelerator Facility project (HIAF) in China. It is designed as a multi-functional experimental storage ring, which will be able to operate in three ion optical operation modes. The SRing will be used as a time-of-flight mass spectrometer for short-lived, especially neutron-rich nuclei. It will also be used to collect and cool Rare Isotope Beams (RIBs) or highly-charged stable ion beams for nuclear and atomic physics experiments. The design magnetic rigidity is in the range 1.5 to 15 Tm. The beam cooling system consists of stochastic cooling and electron cooling devices. With a help of an electron cooler, stored ions will be decelerated to a minimum energy of 30 MeV/u by RF cavities. The extraction system of the SRing will allow cooled ion beams to be extracted to an external target for further ion manipulations or reaction experiments. The general ion optics design and technical requirements of SRing subsystems are presented and discussed in this paper.

Recent developments in guided wave travel time tomography

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

Zon, Tim van; Volker, Arno

The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography had been developed to create a map of the wall thickness using the travel times of guided waves. It can be used for both monitoring and for inspection of pipe-segments that are difficult to access, for instance at the location of pipe-supports. An important outcome of the tomography is the minimum remaining wall thickness, as this is critical in the scheduling of a replacement of the pipe-segment. In order to improvemore » the sizing accuracy we have improved the tomography scheme. A number of major improvements have been realized allowing to extend the application envelope to pipes with a larger wall thickness and to larger distances between the transducer rings. Simulation results indicate that the sizing accuracy has improved and that is now possible to have a spacing of 8 meter between the source-ring and the receiver-ring. Additionally a reduction of the number of sensors required might be possible as well.« less

Quantum nuclear effects in water using centroid molecular dynamics

NASA Astrophysics Data System (ADS)

Kondratyuk, N. D.; Norman, G. E.; Stegailov, V. V.

2018-01-01

The quantum nuclear effects are studied in water using the method of centroid molecular dynamics (CMD). The aim is the calibration of CMD implementation in LAMMPS. The calculated intramolecular energy, atoms gyration radii and radial distribution functions are shown in comparison with previous works. The work is assumed to be the step toward to solution of the discrepancy between the simulation results and the experimental data of liquid n-alkane properties in our previous works.

Improving experimental phases for strong reflections prior to density modification

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

Uervirojnangkoorn, Monarin; Hilgenfeld, Rolf; Terwilliger, Thomas C.

Experimental phasing of diffraction data from macromolecular crystals involves deriving phase probability distributions. These distributions are often bimodal, making their weighted average, the centroid phase, improbable, so that electron-density maps computed using centroid phases are often non-interpretable. Density modification brings in information about the characteristics of electron density in protein crystals. In successful cases, this allows a choice between the modes in the phase probability distributions, and the maps can cross the borderline between non-interpretable and interpretable. Based on the suggestions by Vekhter [Vekhter (2005), Acta Cryst. D 61, 899–902], the impact of identifying optimized phases for a small numbermore » of strong reflections prior to the density-modification process was investigated while using the centroid phase as a starting point for the remaining reflections. A genetic algorithm was developed that optimizes the quality of such phases using the skewness of the density map as a target function. Phases optimized in this way are then used in density modification. In most of the tests, the resulting maps were of higher quality than maps generated from the original centroid phases. In one of the test cases, the new method sufficiently improved a marginal set of experimental SAD phases to enable successful map interpretation. Lastly, a computer program, SISA, has been developed to apply this method for phase improvement in macromolecular crystallography.« less

Improving experimental phases for strong reflections prior to density modification

DOE PAGES

Uervirojnangkoorn, Monarin; Hilgenfeld, Rolf; Terwilliger, Thomas C.; ...

2013-09-20

Experimental phasing of diffraction data from macromolecular crystals involves deriving phase probability distributions. These distributions are often bimodal, making their weighted average, the centroid phase, improbable, so that electron-density maps computed using centroid phases are often non-interpretable. Density modification brings in information about the characteristics of electron density in protein crystals. In successful cases, this allows a choice between the modes in the phase probability distributions, and the maps can cross the borderline between non-interpretable and interpretable. Based on the suggestions by Vekhter [Vekhter (2005), Acta Cryst. D 61, 899–902], the impact of identifying optimized phases for a small numbermore » of strong reflections prior to the density-modification process was investigated while using the centroid phase as a starting point for the remaining reflections. A genetic algorithm was developed that optimizes the quality of such phases using the skewness of the density map as a target function. Phases optimized in this way are then used in density modification. In most of the tests, the resulting maps were of higher quality than maps generated from the original centroid phases. In one of the test cases, the new method sufficiently improved a marginal set of experimental SAD phases to enable successful map interpretation. Lastly, a computer program, SISA, has been developed to apply this method for phase improvement in macromolecular crystallography.« less

An adaptive tracker for ShipIR/NTCS

NASA Astrophysics Data System (ADS)

Ramaswamy, Srinivasan; Vaitekunas, David A.

2015-05-01

A key component in any image-based tracking system is the adaptive tracking algorithm used to segment the image into potential targets, rank-and-select the best candidate target, and the gating of the selected target to further improve tracker performance. This paper will describe a new adaptive tracker algorithm added to the naval threat countermeasure simulator (NTCS) of the NATO-standard ship signature model (ShipIR). The new adaptive tracking algorithm is an optional feature used with any of the existing internal NTCS or user-defined seeker algorithms (e.g., binary centroid, intensity centroid, and threshold intensity centroid). The algorithm segments the detected pixels into clusters, and the smallest set of clusters that meet the detection criterion is obtained by using a knapsack algorithm to identify the set of clusters that should not be used. The rectangular area containing the chosen clusters defines an inner boundary, from which a weighted centroid is calculated as the aim-point. A track-gate is then positioned around the clusters, taking into account the rate of change of the bounding area and compensating for any gimbal displacement. A sequence of scenarios is used to test the new tracking algorithm on a generic unclassified DDG ShipIR model, with and without flares, and demonstrate how some of the key seeker signals are impacted by both the ship and flare intrinsic signatures.

Depth to the bottom of magnetic sources (DBMS) from aeromagnetic data of Central India using modified centroid method for fractal distribution of sources

NASA Astrophysics Data System (ADS)

Bansal, A. R.; Anand, S.; Rajaram, M.; Rao, V.; Dimri, V. P.

2012-12-01

The depth to the bottom of the magnetic sources (DBMS) may be used as an estimate of the Curie - point depth. The DBMSs can also be interpreted in term of thermal structure of the crust. The thermal structure of the crust is a sensitive parameter and depends on the many properties of crust e.g. modes of deformation, depths of brittle and ductile deformation zones, regional heat flow variations, seismicity, subsidence/uplift patterns and maturity of organic matter in sedimentary basins. The conventional centroid method of DBMS estimation assumes random uniform uncorrelated distribution of sources and to overcome this limitation a modified centroid method based on fractal distribution has been proposed. We applied this modified centroid method to the aeromagnetic data of the central Indian region and selected 29 half overlapping blocks of dimension 200 km x 200 km covering different parts of the central India. Shallower values of the DBMS are found for the western and southern portion of Indian shield. The DBMSs values are found as low as close to middle crust in the south west Deccan trap and probably deeper than Moho in the Chhatisgarh basin. In few places DBMS are close to the Moho depth found from the seismic study and others places shallower than the Moho. The DBMS indicate complex nature of the Indian crust.

Alignment error of mirror modules of advanced telescope for high-energy astrophysics due to wavefront aberrations

NASA Astrophysics Data System (ADS)

Zocchi, Fabio E.

2017-10-01

One of the approaches that is being tested for the integration of the mirror modules of the advanced telescope for high-energy astrophysics x-ray mission of the European Space Agency consists in aligning each module on an optical bench operated at an ultraviolet wavelength. The mirror module is illuminated by a plane wave and, in order to overcome diffraction effects, the centroid of the image produced by the module is used as a reference to assess the accuracy of the optical alignment of the mirror module itself. Among other sources of uncertainty, the wave-front error of the plane wave also introduces an error in the position of the centroid, thus affecting the quality of the mirror module alignment. The power spectral density of the position of the point spread function centroid is here derived from the power spectral density of the wave-front error of the plane wave in the framework of the scalar theory of Fourier diffraction. This allows the defining of a specification on the collimator quality used for generating the plane wave starting from the contribution to the error budget allocated for the uncertainty of the centroid position. The theory generally applies whenever Fourier diffraction is a valid approximation, in which case the obtained result is identical to that derived by geometrical optics considerations.

Advanced Ring-Shaped Microelectrode Assay Combined with Small Rectangular Electrode for Quasi-In vivo Measurement of Cell-to-Cell Conductance in Cardiomyocyte Network

NASA Astrophysics Data System (ADS)

Nomura, Fumimasa; Kaneko, Tomoyuki; Hamada, Tomoyo; Hattori, Akihiro; Yasuda, Kenji

2013-06-01

To predict the risk of fatal arrhythmia induced by cardiotoxicity in the highly complex human heart system, we have developed a novel quasi-in vivo electrophysiological measurement assay, which combines a ring-shaped human cardiomyocyte network and a set of two electrodes that form a large single ring-shaped electrode for the direct measurement of irregular cell-to-cell conductance occurrence in a cardiomyocyte network, and a small rectangular microelectrode for forced pacing of cardiomyocyte beating and for acquiring the field potential waveforms of cardiomyocytes. The advantages of this assay are as follows. The electrophysiological signals of cardiomyocytes in the ring-shaped network are superimposed directly on a single loop-shaped electrode, in which the information of asynchronous behavior of cell-to-cell conductance are included, without requiring a set of huge numbers of microelectrode arrays, a set of fast data conversion circuits, or a complex analysis in a computer. Another advantage is that the small rectangular electrode can control the position and timing of forced beating in a ring-shaped human induced pluripotent stem cell (hiPS)-derived cardiomyocyte network and can also acquire the field potentials of cardiomyocytes. First, we constructed the human iPS-derived cardiomyocyte ring-shaped network on the set of two electrodes, and acquired the field potential signals of particular cardiomyocytes in the ring-shaped cardiomyocyte network during simultaneous acquisition of the superimposed signals of whole-cardiomyocyte networks representing cell-to-cell conduction. Using the small rectangular electrode, we have also evaluated the response of the cell network to electrical stimulation. The mean and SD of the minimum stimulation voltage required for pacing (VMin) at the small rectangular electrode was 166+/-74 mV, which is the same as the magnitude of amplitude for the pacing using the ring-shaped electrode (179+/-33 mV). The results showed that the addition of a small rectangular electrode into the ring-shaped electrode was effective for the simultaneous measurement of whole-cell-network signals and single-cell/small-cluster signals on a local site in the cell network, and for the pacing by electrical stimulation of cardiomyocyte networks.

Climatic Signals from Intra-annual Density Fluctuation Frequency in Mediterranean Pines at a Regional Scale

PubMed Central

Zalloni, Enrica; de Luis, Martin; Campelo, Filipe; Novak, Klemen; De Micco, Veronica; Di Filippo, Alfredo; Vieira, Joana; Nabais, Cristina; Rozas, Vicente; Battipaglia, Giovanna

2016-01-01

Tree rings provide information about the climatic conditions during the growing season by recording them in different anatomical features, such as intra-annual density fluctuations (IADFs). IADFs are intra-annual changes of wood density appearing as latewood-like cells within earlywood, or earlywood-like cells within latewood. The occurrence of IADFs is dependent on the age and size of the tree, and it is triggered by climatic drivers. The variations of IADF frequency of different species and their dependence on climate across a wide geographical range have still to be explored. The objective of this study is to investigate the effect of age, tree-ring width and climate on IADF formation and frequency at a regional scale across the Mediterranean Basin in Pinus halepensis Mill., Pinus pinaster Ait., and Pinus pinea L. The analyzed tree-ring network was composed of P. pinea trees growing at 10 sites (2 in Italy, 4 in Spain, and 4 in Portugal), P. pinaster from 19 sites (2 in Italy, 13 in Spain, and 4 in Portugal), and P. halepensis from 38 sites in Spain. The correlations between IADF frequency and monthly minimum, mean and maximum temperatures, as well as between IADF frequency and total precipitation, were analyzed. A significant negative relationship between IADF frequency and tree-ring age was found for the three Mediterranean pines. Moreover, IADFs were more frequent in wider rings than in narrower ones, although the widest rings showed a reduced IADF frequency. Wet conditions during late summer/early autumn triggered the formation of IADFs in the three species. Our results suggest the existence of a common climatic driver for the formation of IADFs in Mediterranean pines, highlighting the potential use of IADF frequency as a proxy for climate reconstructions with geographical resolution. PMID:27200052

3-Amino­benzoic acid–1,2-bis­(4-pyrid­yl)ethane (1/1)

PubMed Central

Shen, Fwu Ming; Lush, Shie Fu

2010-01-01

The asymmetric unit of the title compound, C12H12N2·C7H7NO2, contains two 3-amino­benzoic acid mol­ecules and two 1,2-bis­(4-pyrid­yl)ethane mol­ecules. In the two 1,2-bis­(4-pyrid­yl)ethane mol­ecules, the dihedral angles between the pyridyl rings are 2.99 (9) and 46.78 (8)°. In the crystal, the mol­ecules associate through amine and carboxyl group N—H⋯O=C inter­actions between one of the 3-amino­benzoic acid mol­ecules and one of the 1,2-bis­(4-pyrid­yl)ethane mol­ecules, generating R 2 2(14) dimers, which are extended head-to-tail via amine and pyridine N—H⋯N hydrogen bonds. Inter­molecular O—H⋯N, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonding are observed in the crystal structure. C—H⋯π and π–π stacking inter­actions [centroid–centroid distance = 3.9985 (10) Å] are also present. PMID:21579186

Synthesis, antityrosinase activity of curcumin analogues, and crystal structure of (1E,4E)-1,5-bis(4-ethoxyphenyl)penta-1,4-dien-3-one

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

Chantrapromma, S., E-mail: suchada.c@psu.ac.th; Ruanwas, P.; Boonnak, N.

2016-12-15

Five derivatives of curcumin analogue (R = OCH{sub 2}CH{sub 3} (1), R = N(CH{sub 3}){sub 2} (2), R = 2,4,5-OCH{sub 3} (3), R = 2,4,6-OCH{sub 3} (4), and R = 3,4,5-OCH{sub 3} (5)) were synthesized and characterized by {sup 1}H NMR, FT-IR and UV–Vis spectroscopy. The synthesized derivatives were screened for antityrosinase activity, and found that 4 and 5 possess such activity. The crystal structure of 1 was determined by single crystal X-ray diffraction: monoclinic, sp. gr. P2{sub 1}/c, a = 17.5728(15) Å, b = 5.9121(5) Å, c = 19.8269(13) Å, β = 121.155(5)°, Z = 4. The molecule 1more » is twisted with the dihedral angle between two phenyl rings being 15.68(10)°. In the crystal packing, the molecules 1 are linked into chains by C−H···π interactions and further stacked by π···π interactions with the centroid–centroid distance of 3.9311(13) Å.« less

Crystal structure of catena-poly[[[tetra­aqua­zinc(II)]-μ-1,4-bis­[4-(1H-imidazol-1-yl)benzo­yl]piperazine] dinitrate monohydrate

PubMed Central

Hou, Chen; Gan, Hong-Mei; Liu, Jia-Cheng

2015-01-01

In the title polymeric complex, {[Zn(C24H22N6O2)(H2O)4](NO3)2·2H2O}n, the ZnII cation, located about a twofold rotation axis, is coordinated by two imidazole groups and four water mol­ecules in a distorted N2O4 octa­hedral geometry; among the four coordinate water mol­ecules, two are located on the same twofold rotation axis. The 1,4-bis­[4-(1H-imidazol-1-yl)benzo­yl]piperazine] ligand is centro-symmetric, with the centroid of the piperazine ring located on an inversion center, and bridges the ZnII cations, forming polymeric chains propagating along [201]. In the crystal, O—H⋯O and weak C—H⋯O hydrogen bonds link the polymeric chains, nitrate anions and solvent water mol­ecules into a three-dimensional supra­molecular architecture. A short O⋯O contact of 2.823 (13) Å is observed between neighboring nitrate anions. PMID:25995894

Technical Note: Using k-means clustering to determine the number and position of isocenters in MLC-based multiple target intracranial radiosurgery.

PubMed

Yock, Adam D; Kim, Gwe-Ya

2017-09-01

To present the k-means clustering algorithm as a tool to address treatment planning considerations characteristic of stereotactic radiosurgery using a single isocenter for multiple targets. For 30 patients treated with stereotactic radiosurgery for multiple brain metastases, the geometric centroids and radii of each met were determined from the treatment planning system. In-house software used this as well as weighted and unweighted versions of the k-means clustering algorithm to group the targets to be treated with a single isocenter, and to position each isocenter. The algorithm results were evaluated using within-cluster sum of squares as well as a minimum target coverage metric that considered the effect of target size. Both versions of the algorithm were applied to an example patient to demonstrate the prospective determination of the appropriate number and location of isocenters. Both weighted and unweighted versions of the k-means algorithm were applied successfully to determine the number and position of isocenters. Comparing the two, both the within-cluster sum of squares metric and the minimum target coverage metric resulting from the unweighted version were less than those from the weighted version. The average magnitudes of the differences were small (-0.2 cm 2 and 0.1% for the within cluster sum of squares and minimum target coverage, respectively) but statistically significant (Wilcoxon signed-rank test, P < 0.01). The differences between the versions of the k-means clustering algorithm represented an advantage of the unweighted version for the within-cluster sum of squares metric, and an advantage of the weighted version for the minimum target coverage metric. While additional treatment planning considerations have a large influence on the final treatment plan quality, both versions of the k-means algorithm provide automatic, consistent, quantitative, and objective solutions to the tasks associated with SRS treatment planning using a single isocenter for multiple targets. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

JASMINE project Instrument design and centroiding experiment

NASA Astrophysics Data System (ADS)

Yano, Taihei; Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki

JASMINE will study the fundamental structure and evolution of the Milky Way Galaxy. To accomplish these objectives, JASMINE will measure trigonometric parallaxes, positions and proper motions of about 10 million stars with a precision of 10 μarcsec at z = 14 mag. In this paper the instrument design (optics, detectors, etc.) of JASMINE is presented. We also show a CCD centroiding experiment for estimating positions of star images. The experimental result shows that the accuracy of estimated distances has a variance of less than 0.01 pixel.

Self-aligning biaxial load frame

DOEpatents

Ward, M.B.; Epstein, J.S.; Lloyd, W.R.

1994-01-18

An self-aligning biaxial loading apparatus for use in testing the strength of specimens while maintaining a constant specimen centroid during the loading operation. The self-aligning biaxial loading apparatus consists of a load frame and two load assemblies for imparting two independent perpendicular forces upon a test specimen. The constant test specimen centroid is maintained by providing elements for linear motion of the load frame relative to a fixed cross head, and by alignment and linear motion elements of one load assembly relative to the load frame. 3 figures.

Self-aligning biaxial load frame

DOEpatents

Ward, Michael B.; Epstein, Jonathan S.; Lloyd, W. Randolph

1994-01-01

An self-aligning biaxial loading apparatus for use in testing the strength of specimens while maintaining a constant specimen centroid during the loading operation. The self-aligning biaxial loading apparatus consists of a load frame and two load assemblies for imparting two independent perpendicular forces upon a test specimen. The constant test specimen centroid is maintained by providing elements for linear motion of the load frame relative to a fixed crosshead, and by alignment and linear motion elements of one load assembly relative to the load frame.

Centroid — moment tensor solutions for July-September 2000

NASA Astrophysics Data System (ADS)

Dziewonski, A. M.; Ekström, G.; Maternovskaya, N. N.

2001-06-01

Centroid-moment tensor (CMT) solutions are presented for 308 earthquakes that occurred during the third quarter of 2000. The solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model SH8/U4L8 of Dziewonski and Woodward [Acoustical Imaging, Vol. 19, Plenum Press, New York, 1992, p. 785]. A model of anelastic attenuation of Durek and Ekström [Bull. Seism. Soc. Am. 86 (1996) 144] is used to predict the decay of the wave forms.

Coupling Correction and Beam Dynamics at Ultralow Vertical Emittance in the ALS

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

Steier, Christoph; Robin, D.; Wolski, A.

2008-03-17

For synchrotron light sources and for damping rings of linear colliders it is important to be able to minimize the vertical emittance and to correct the spurious vertical dispersion. This allows one to maximize the brightness and/or the luminosity. A commonly used tool to measure the skew error distribution is the analysis of orbit response matrices using codes like LOCO. Using the new Matlab version of LOCO and 18 newly installed power supplies for individual skew quadrupoles at the ALS the emittance ratio could be reduced below 0.1% at 1.9 GeV yielding a vertical emittance of about 5 pm. Atmore » those very low emittances, additional effects like intra beam scattering become more important, potentially limiting the minimum emittance for machine like the damping rings of linear colliders.« less

Studies on scintillating fiber response

NASA Astrophysics Data System (ADS)

Albers, D.; Bisplinghoff, J.; Bollmann, R.; Büßer, K.; Cloth, P.; Diehl, O.; Dohrmann, F.; Drüke, V.; Engelhardt, H. P.; Ernst, J.; Eversheim, P. D.; Filges, D.; Gasthuber, M.; Gebel, R.; Greiff, J.; Groß, A.; Groß-Hardt, R.; Heine, A.; Heider, S.; Hinterberger, F.; Igelbrink, M.; Jahn, R.; Jeske, M.; Langkau, R.; Lindlein, J.; Maier, R.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Metsch, B.; Mosel, F.; Müller, M.; Münstermann, M.; Paetz gen. Schieck, H.; Petry, H. R.; Prasuhn, D.; Rohdjeß, H.; Rosendaal, D.; Roß, U.; von Rossen, P.; Scheid, H.; Schirm, N.; Schulz-Rojahn, M.; Schwandt, F.; Scobel, W.; Steeg, B.; Sterzenbach, G.; Trelle, H. J.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.

1996-02-01

Scintillating fibers of type Bicron BCF-12 with 2 × 2 mm 2 cross section, up to 600 mm length, and PMMA cladding have been tested, in conjunction with the multi-channel photomultiplier Hamamatsu R 4760, with minimum ionizing electrons. The impact of cladding, extramural absorbers and/or wrapping on the light attenuation and photoelectron yield is studied in detail. Fibers have been circularly bent with radii of 171 mm and arranged in two layers to bundles forming granulated scintillator rings. Their performance in the EDDA experiment at COSY for detection of high energy protons revealed typically more than 9 (6) photoelectrons per fiber from bundles with (without) mirror on the rear side, guaranteeing detection efficiencies >99% and full compatibility with corresponding solid scintillator rings. The time resolution of 3.4 ns FWHM per fiber read out is essentially due to the R 4760.

Micro-XANES Determination Fe Speciation in Natural Basalts at Mantle-Relevant fO2

NASA Astrophysics Data System (ADS)

Fischer, R.; Cottrell, E.; Lanzirotti, A.; Kelley, K. A.

2007-12-01

We demonstrate that the oxidation state of iron (Fe3+/ΣFe) can be determined with a precision of ±0.02 (10% relative) on natural basalt glasses at mantle-relevant fO2 using Fe K-edge X-ray absorption near edge structure (XANES) spectroscopy. This is equivalent to ±0.25 log unit resolution relative to the QFM buffer. Precise determination of the oxidation state over this narrow range (Fe3+/ΣFe=0.06-0.30) and at low fO2 (down to QFM-2) relies on appropriate standards, high spectral resolution, and highly reproducible methods for extracting the pre-edge centroid position. We equilibrated natural tholeiite powder in a CO/CO2 gas mixing furnace at 1350°C from QFM-3 to QFM+2 to create six glasses of known Fe3+/ΣFe, independently determined by Mössbauer spectroscopy. XANES spectra were collected at station X26A at NSLS, Brookhaven Natl. Lab, in fluorescence mode (9 element Ge array detector) using both Si(111) and Si(311) monochromators. Generally, the energy position of the 1s→3d (pre-edge) transition centroid is the most sensitive monitor of Fe oxidation state using XANES. For the mixture of Fe oxidation states in these glasses and the resulting coordination geometries, the pre-edge spectra are best defined by two multiple 3d crystal field transitions. The Si(311) monochromator, with higher energy resolution, substantially improved spectral resolution for the 1s→3d transition. Dwell times of 5s at 0.1eV intervals across the pre-edge region yielded spectra with the 1s→3d transition peaks clearly resolved. The pre-edge centroid position is highly sensitive to the background subtraction and peak fitting procedures. Differences in fitting models result in small but significant differences in the calculated peak area of each pre-edge multiplet, and the relative contribution of each peak to the calculated centroid. We assessed several schemes and obtained robust centroid positions by simultaneously fitting the background with a damped harmonic oscillator (DHO) function and pre-edge features with two Gaussians over a sub-sample of the pre-edge region (7110-7120 eV). We found that the relation between Fe3+/ΣFe and the centroid energy is non-linear over this fO2 range, which is expected if the coordination environment changes with oxidation state. ΔQFM is linearly related (R2=0.99) to the centroid position. This new calibration allows the oxidation states of natural mantle melts to be discriminated with high spatial resolution (9μm). We apply the new calibration to determination of Fe3+/ΣFe in natural basaltic glasses and olivine-hosted glass inclusions (Cottrell et al. & Kelley et al., this meeting).

The role of collective self-gravity in the nonlinear evolution of viscous overstability in Saturn's rings

NASA Astrophysics Data System (ADS)

Lehmann, M.; Schmidt, J.; Salo, H.

2017-09-01

Observational evidence for the presence of axisymmetric periodic micro-structure on length scales of 100m - 200m in Saturn's A and B rings was revealed by several instruments onboard the Cassini mission to Saturn. The structure was seen in radio occultations performed by the Radio Science Subsystem (RSS) (Thomson et al. (2007)) and stellar occultations carried out with the Ultraviolet Imaging Spectrograph (UVIS) (Colwell et al. (2007)), and the Visual and Infrared Mapping Spectrometer (VIMS) (Hedman et al. (2014)). Up to date, this micro-structure is best explained by the viscous overstability, which arises as a spontaneous oscillatory instability in a dense ring, if certain conditions are met, leading to the formation of axisymmetric density waves with wavelengths on the order of 100m. We investigate the influence of collective self-gravity forces on the nonlinear, large scale evolution of the viscous overstability in Saturn's rings. To this end we numerically solve the nonlinear hydrodynamic model equations for a dense ring, including radial self-gravity and employing values for the transport coefficients (such as the ring's viscosity and heat conductivity) derived by salo et al. (2001). We concentrate on ring optical depths of order unity, which are appropriate to model Saturn's dense rings. Furthermore, local N-body simulations, incorporating vertical and radial collective self-gravity forces are performed. Direct particle-particle forces are omitted, which prevents small scale gravitational instabilities (self-gravity wakes) from forming, an approximation that allows us to study long radial scales of some 10 kilometers and to compare directly the hydrodynamic model and the N-body simulations. Our hydrodynamic model results, in the limit of vanishing self-gravity, compare very well with the studies of Latter & Ogilvie (2010) and Rein & Latter (2013). In contrast, for rings with non-vanishing radial self-gravity we find that the wavelengths of saturated overstable wave trains tend to settle close to the frequency minimum of the nonlinear dispersion relation, i.e. the saturation wavelengths decrease with increasing surface mass density of the ring. Good agreement between hydrodynamics and N-body simulations is found for disks with strong radial self-gravity, while the largest deviations occur in the limit of weak self-gravity. The resulting saturation wavelengths of the viscous overstability for moderate and strong radial self-gravity (100m-300m) agree reasonably well with the length scale of the axisymmetric periodic micro structure in Saturn's inner A ring and the B ring, as found by Cassini.

Three-dimensional ring current decay model

NASA Technical Reports Server (NTRS)

Fok, Mei-Ching; Moore, Thomas E.; Kozyra, Janet U.; Ho, George C.; Hamilton, Douglas C.

1995-01-01

This work is an extension of a previous ring current decay model. In the previous work, a two-dimensional kinetic model was constructed to study the temporal variations of the equatorially mirroring ring current ions, considering charge exchange and Coulomb drag losses along drift paths in a magnetic dipole field. In this work, particles with arbitrary pitch angle are considered. By bounce averaging the kinetic equation of the phase space density, information along magnetic field lines can be inferred from the equator. The three-dimensional model is used to simulate the recovery phase of a model great magnetic storm, similar to that which occurred in early February 1986. The initial distribution of ring current ions (at the minimum Dst) is extrapolated to all local times from AMPTE/CCE spacecraft observations on the dawnside and duskside of the inner magnetosphere spanning the L value range L = 2.25 to 6.75. Observations by AMPTE/CCE of ring current distributions over subsequent orbits during the storm recovery phase are compared to model outputs. In general, the calculated ion fluxes are consistent with observations, except for H(+) fluxes at tens of keV, which are always overestimated. A newly invented visualization idea, designated as a chromogram, is used to display the spatial and energy dependence of the ring current ion differential flux. Important features of storm time ring current, such as day-night asymmetry during injection and drift hole on the dayside at low energies (less than 10 keV), are manifested in the chromogram representation. The pitch angle distribution is well fit by the function, J(sub o)(1 + Ay(sup n)), where y is sine of the equatorial pitch angle. The evolution of the index n is a combined effect of charge exchange loss and particle drift. At low energies (less than 30 keV), both drift dispersion and charge exchange are important in determining n.

A three-dimensional ring current decay model

NASA Technical Reports Server (NTRS)

Fok, Mei-Ching; Moore, Thomas E.; Kozyra, Janet U.; Ho, George C.; Hamilton, Douglas C.

1994-01-01

This work is an extension of a previous ring current decay model. In the previous work, a two-dimensional kinetic model was constructed to study the temporal variations of the equatorially mirroring ring current ions, considering charge exchange and Coulomb drag losses along drift paths in a magnetic dipole field. In this work, particles with arbitrary pitch angle are considered. By bounce averaging the kinetic equation of the phase space density, information along magnetic field lines can be inferred from the equator. The three-dimensional model is used to simulate the recovery phase of a model great magnetic storm, similar to that which occurred in early February 1986. The initial distribution of ring current ions (at the minimum Dst) is extrapolated to all local times from AMPTE/CCE spacecraft observations on the dawn and dusk sides of the inner magnetosphere spanning the L value range L = 2.25 to 6.75. Observations by AMPTE/CCE of ring current distributions over subsequent orbits during the storm recovery phase are compared to model outputs. In general, the calculated ion fluxes are consistent with observations, except for H+ fluxes at tens of keV, which are always over-estimated. A newly-invented visualization idea, designated as a chromogram, is used to display the spatial and energy dependence of the ring current ion differential flux. Important features of storm-time ring current, such as day-night asymmetry during injection and drift hole on the dayside at low energies (less than 10 keV), are manifested in the chromogram representation. The pitch angle distribution is well fit by the function, j(sub o)(1+Ay(exp n)), where y is sine of the equatorial pitch angle. The evolution of the index n is a combined effect of charge exchange loss and particle drift. At low energies (less than 30 keV), both drift dispersion and charge exchange are important in determining n.

HST-STIS Spectra of Saturn's Rings and Implications for Their Reddening Agent

NASA Technical Reports Server (NTRS)

Cuzzi, Jeff

2016-01-01

We obtained HST-STIS spectra of Saturn's main rings in May 2011, using the G230L (and G430L) gratings, with final averaged radial resolution of 160 (and 330) km/pixel. The dataset filled a previous 200-330nm "spectral gap" between Cassini and ground-based spectra. The data provide radial profiles as a function of wavelength, but our most basic product at this point is a set of very low-noise spectra, radially averaged over broad regions of the rings (A, B, C, and Cassini Division). The raw spectra required special processing to remove artifacts due to extended-source grating scatter. We have modeled the spectra using a new particle surface model, which corrects for on-surface shadowing due to the likely very rough ring particle surfaces, and avoids overestimation of intra-mixed "neutral absorber". We correct for non-classical layer effects and finite ring optical depth, and relate our observed reflectivities to the spherical albedos of individual smooth particles. We model these smooth particle albedos using standard Hapke theory for regolith grain mixtures that are either homogeneous and "intramixed" (nonicy absorbers dispersed in water ice regolith grains) or heterogeneous "intimate" mixtures. As candidates for the nonicy contaminants we have considered amorphous carbon, aromatic-rich and aliphatic-rich organic tholins, silicates, hematite and iron metal. For the A and B rings, we find that iron metal (including a new theoretical estimate of the refractive indices of nanometer-sized grains of iron) is not spectrally steep enough in the 200-300nm range, and that aliphatic-rich tholins are either too steep at short wavelengths or too flat at long wavelengths. However, less than 1% by mass of aromatic-rich tholins provides a very good fit across the entire spectral range with no gratuitous "neutral absorber" needed, and a minimum of additional free parameters. The best fits require forward-scattering regolith grains. For the C Ring and Cassini Division, additional absorbers are needed (updated results will be given).

Hartman Testing of X-Ray Telescopes

NASA Technical Reports Server (NTRS)

Saha, Timo T.; Biskasch, Michael; Zhang, William W.

2013-01-01

Hartmann testing of x-ray telescopes is a simple test method to retrieve and analyze alignment errors and low-order circumferential errors of x-ray telescopes and their components. A narrow slit is scanned along the circumference of the telescope in front of the mirror and the centroids of the images are calculated. From the centroid data, alignment errors, radius variation errors, and cone-angle variation errors can be calculated. Mean cone angle, mean radial height (average radius), and the focal length of the telescope can also be estimated if the centroid data is measured at multiple focal plane locations. In this paper we present the basic equations that are used in the analysis process. These equations can be applied to full circumference or segmented x-ray telescopes. We use the Optical Surface Analysis Code (OSAC) to model a segmented x-ray telescope and show that the derived equations and accompanying analysis retrieves the alignment errors and low order circumferential errors accurately.

Centroid-moment tensor inversions using high-rate GPS waveforms

NASA Astrophysics Data System (ADS)

O'Toole, Thomas B.; Valentine, Andrew P.; Woodhouse, John H.

2012-10-01

Displacement time-series recorded by Global Positioning System (GPS) receivers are a new type of near-field waveform observation of the seismic source. We have developed an inversion method which enables the recovery of an earthquake's mechanism and centroid coordinates from such data. Our approach is identical to that of the 'classical' Centroid-Moment Tensor (CMT) algorithm, except that we forward model the seismic wavefield using a method that is amenable to the efficient computation of synthetic GPS seismograms and their partial derivatives. We demonstrate the validity of our approach by calculating CMT solutions using 1 Hz GPS data for two recent earthquakes in Japan. These results are in good agreement with independently determined source models of these events. With wider availability of data, we envisage the CMT algorithm providing a tool for the systematic inversion of GPS waveforms, as is already the case for teleseismic data. Furthermore, this general inversion method could equally be applied to other near-field earthquake observations such as those made using accelerometers.

Spatial pattern recognition of seismic events in South West Colombia

NASA Astrophysics Data System (ADS)

Benítez, Hernán D.; Flórez, Juan F.; Duque, Diana P.; Benavides, Alberto; Lucía Baquero, Olga; Quintero, Jiber

2013-09-01

Recognition of seismogenic zones in geographical regions supports seismic hazard studies. This recognition is usually based on visual, qualitative and subjective analysis of data. Spatial pattern recognition provides a well founded means to obtain relevant information from large amounts of data. The purpose of this work is to identify and classify spatial patterns in instrumental data of the South West Colombian seismic database. In this research, clustering tendency analysis validates whether seismic database possesses a clustering structure. A non-supervised fuzzy clustering algorithm creates groups of seismic events. Given the sensitivity of fuzzy clustering algorithms to centroid initial positions, we proposed a methodology to initialize centroids that generates stable partitions with respect to centroid initialization. As a result of this work, a public software tool provides the user with the routines developed for clustering methodology. The analysis of the seismogenic zones obtained reveals meaningful spatial patterns in South-West Colombia. The clustering analysis provides a quantitative location and dispersion of seismogenic zones that facilitates seismological interpretations of seismic activities in South West Colombia.

Application of the multiple PRF technique to resolve Doppler centroid estimation ambiguity for spaceborne SAR

NASA Technical Reports Server (NTRS)

Chang, C. Y.; Curlander, J. C.

1992-01-01

Estimation of the Doppler centroid ambiguity is a necessary element of the signal processing for SAR systems with large antenna pointing errors. Without proper resolution of the Doppler centroid estimation (DCE) ambiguity, the image quality will be degraded in the system impulse response function and the geometric fidelity. Two techniques for resolution of DCE ambiguity for the spaceborne SAR are presented; they include a brief review of the range cross-correlation technique and presentation of a new technique using multiple pulse repetition frequencies (PRFs). For SAR systems, where other performance factors control selection of the PRF's, an algorithm is devised to resolve the ambiguity that uses PRF's of arbitrary numerical values. The performance of this multiple PRF technique is analyzed based on a statistical error model. An example is presented that demonstrates for the Shuttle Imaging Radar-C (SIR-C) C-band SAR, the probability of correct ambiguity resolution is higher than 95 percent for antenna attitude errors as large as 3 deg.

Optimization of soy isoflavone extraction with different solvents using the simplex-centroid mixture design.

PubMed

Yoshiara, Luciane Yuri; Madeira, Tiago Bervelieri; Delaroza, Fernanda; da Silva, Josemeyre Bonifácio; Ida, Elza Iouko

2012-12-01

The objective of this study was to optimize the extraction of different isoflavone forms (glycosidic, malonyl-glycosidic, aglycone and total) from defatted cotyledon soy flour using the simplex-centroid experimental design with four solvents of varying polarity (water, acetone, ethanol and acetonitrile). The obtained extracts were then analysed by high-performance liquid chromatography. The profile of the different soy isoflavones forms varied with different extractions solvents. Varying the solvent or mixture used, the extraction of different isoflavones was optimized using the centroid-simplex mixture design. The special cubic model best fitted to the four solvents and its combination for soy isoflavones extraction. For glycosidic isoflavones extraction, the polar ternary mixture (water, acetone and acetonitrile) achieved the best extraction; malonyl-glycosidic forms were better extracted with mixtures of water, acetone and ethanol. Aglycone isoflavones, water and acetone mixture were best extracted and total isoflavones, the best solvents were ternary mixture of water, acetone and ethanol.

Development of hardwood seed zones for Tennessee using a geographic information system

USGS Publications Warehouse

Post, L.S.; Schlarbaum, S.E.; Van Manen, F.; Cecich, R.A.; Saxton, A.M.; Schneider, J.F.

2003-01-01

For species that have no or limited information on genetic variation and adaptability to nonnative sites, there is a need for seed collection guidelines based on biological, climatological, and/or geographical criteria. Twenty-eight hardwood species are currently grown for reforestation purposes at the East Tennessee State Nursery. The majority of these species have had no genetic testing to define guidelines for seed collection location and can be distributed to sites that have a very different environment than that of seed origin(s). Poor survival and/or growth may result if seedlings are not adapted to environmental conditions at the planting location. To address this problem, 30 yr of Tennessee county precipitation and minimum temperature data were analyzed and grouped using a centroid hierarchical cluster analysis. The weather data and elevational data were entered into a Geographic Information System (GIS) and separately layered over Bailey's Ecoregions to develop a seed zone system for Tennessee. The seed zones can be used as a practical guideline for collecting seeds to ensure that the resulting seedlings will be adapted to planting environments.

Performance measurements of hybrid PIN diode arrays

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

Jernigan, J.G.; Arens, J.F.; Kramer, G.

We report on the successful effort to develop hybrid PIN diode arrays and to demonstrate their potential as components of vertex detectors. Hybrid pixel arrays have been fabricated by the Hughes Aircraft Co. by bump bonding readout chips developed by Hughes to an array of PIN diodes manufactured by Micron Semiconductor Inc. These hybrid pixel arrays were constructed in two configurations. One array format having 10 {times} 64 pixels, each 120 {mu}m square, and the other format having 256 {times} 256 pixels, each 30 {mu}m square. In both cases, the thickness of the PIN diode layer is 300 {mu}m. Measurementsmore » of detector performance show that excellent position resolution can be achieved by interpolation. By determining the centroid of the charge cloud which spreads charge into a number of neighboring pixels, a spatial resolution of a few microns has been attained. The noise has been measured to be about 300 electrons (rms) at room temperature, as expected from KTC and dark current considerations, yielding a signal-to-noise ratio of about 100 for minimum ionizing particles. 4 refs., 13 figs.« less

Optimization of composite flour biscuits by mixture response surface methodology.

PubMed

Okpala, Laura C; Okoli, Eric C

2013-08-01

Biscuits were produced from blends of pigeon pea, sorghum and cocoyam flours. The study was carried out using mixture response surface methodology as the optimization technique. Using the simplex centroid design, 10 formulations were obtained. Protein and sensory quality of the biscuits were analyzed. The sensory attributes studied were appearance, taste, texture, crispness and general acceptability, while the protein quality indices were biological value and net protein utilization. The results showed that while the addition of pigeon pea improved the protein quality, its addition resulted in reduced sensory ratings for all the sensory attributes with the exception of appearance. Some of the biscuits had sensory ratings, which were not significantly different (p > 0.05) from biscuits made with wheat. Rat feeding experiments indicated that the biological value and net protein utilization values obtained for most of the biscuits were above minimum recommended values. Optimization suggested biscuits containing 75.30% sorghum, 0% pigeon pea and 24.70% cocoyam flours as the best proportion of these components. This sample received good scores for the sensory attributes.

Deactivation via ring opening: A quantum chemical study of the excited states of furan and comparison to thiophene

NASA Astrophysics Data System (ADS)

Gavrilov, Nemanja; Salzmann, Susanne; Marian, Christel M.

2008-06-01

Minimum nuclear arrangements of the ground and low-lying excited electronic states of furan were obtained by means of (time dependent) Kohn-Sham density functional theory. A combined density functional/multi-reference configuration interaction method (DFT/MRCI) was employed to compute the spectral properties at these points. Multiple minima were found on the first excited singlet (S 1) potential energy hypersurface with electronic structures S1, S2, S3 corresponding to the 1 1A 2 (π → 3s-Ryd), 1 1B 2 (π → π ∗), and 2 1A 1 (π → π ∗) states in the vertical absorption spectrum, respectively. In analogy to recently published studies in thiophene [S. Salzmann, M. Kleinschmidt, J. Tatchen, R. Weinkauf, C.M. Marian, Phys. Chem. Chem. Phys. 10 (2008) 380] a deactivation mechanism for electronically excited furan was detected that involves the opening of the pentacyclic ring. We found a nearly barrierless relaxation pathway from the Franck-Condon region along a C-O bond-breaking coordinate. Hereby the initially excited 1B 2 (π → π ∗) state undergoes a conical intersection with a 1B 1 (π → σ ∗) state. The system can return to the electronic ground state through a second conical intersection of the 1(π → σ ∗) state before the minimum of that B 1 state is reached.

Novel method of detecting movement of the interference fringes using one-dimensional PSD.

PubMed

Wang, Qi; Xia, Ji; Liu, Xu; Zhao, Yong

2015-06-02

In this paper, a method of using a one-dimensional position-sensitive detector (PSD) by replacing charge-coupled device (CCD) to measure the movement of the interference fringes is presented first, and its feasibility is demonstrated through an experimental setup based on the principle of centroid detection. Firstly, the centroid position of the interference fringes in a fiber Mach-Zehnder (M-Z) interferometer is solved in theory, showing it has a higher resolution and sensitivity. According to the physical characteristics and principles of PSD, a simulation of the interference fringe's phase difference in fiber M-Z interferometers and PSD output is carried out. Comparing the simulation results with the relationship between phase differences and centroid positions in fiber M-Z interferometers, the conclusion that the output of interference fringes by PSD is still the centroid position is obtained. Based on massive measurements, the best resolution of the system is achieved with 5.15, 625 μm. Finally, the detection system is evaluated through setup error analysis and an ultra-narrow-band filter structure. The filter structure is configured with a one-dimensional photonic crystal containing positive and negative refraction material, which can eliminate background light in the PSD detection experiment. This detection system has a simple structure, good stability, high precision and easily performs remote measurements, which makes it potentially useful in material small deformation tests, refractivity measurements of optical media and optical wave front detection.

Human attention filters for single colors.

PubMed

Sun, Peng; Chubb, Charles; Wright, Charles E; Sperling, George

2016-10-25

The visual images in the eyes contain much more information than the brain can process. An important selection mechanism is feature-based attention (FBA). FBA is best described by attention filters that specify precisely the extent to which items containing attended features are selectively processed and the extent to which items that do not contain the attended features are attenuated. The centroid-judgment paradigm enables quick, precise measurements of such human perceptual attention filters, analogous to transmission measurements of photographic color filters. Subjects use a mouse to locate the centroid-the center of gravity-of a briefly displayed cloud of dots and receive precise feedback. A subset of dots is distinguished by some characteristic, such as a different color, and subjects judge the centroid of only the distinguished subset (e.g., dots of a particular color). The analysis efficiently determines the precise weight in the judged centroid of dots of every color in the display (i.e., the attention filter for the particular attended color in that context). We report 32 attention filters for single colors. Attention filters that discriminate one saturated hue from among seven other equiluminant distractor hues are extraordinarily selective, achieving attended/unattended weight ratios >20:1. Attention filters for selecting a color that differs in saturation or lightness from distractors are much less selective than attention filters for hue (given equal discriminability of the colors), and their filter selectivities are proportional to the discriminability distance of neighboring colors, whereas in the same range hue attention-filter selectivity is virtually independent of discriminabilty.

The Generalized Centroid Difference method for lifetime measurements via γ-γ coincidences using large fast-timing arrays

NASA Astrophysics Data System (ADS)

Régis, J.-M.; Jolie, J.; Mach, H.; Simpson, G. S.; Blazhev, A.; Pascovici, G.; Pfeiffer, M.; Rudigier, M.; Saed-Samii, N.; Warr, N.; Blanc, A.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; Ur, C. A.; Urban, W.; Bruce, A. M.; Drouet, F.; Fraile, L. M.; Ilieva, S.; Korten, W.; Kröll, T.; Lalkovski, S.; Mărginean, S.; Paziy, V.; Podolyák, Zs.; Regan, P. H.; Stezowski, O.; Vancraeyenest, A.

2015-05-01

A novel method for direct electronic "fast-timing" lifetime measurements of nuclear excited states via γ-γ coincidences using an array equipped with N very fast high-resolution LaBr3(Ce) scintillator detectors is presented. The generalized centroid difference method provides two independent "start" and "stop" time spectra obtained without any correction by a superposition of the N(N - 1)/2 calibrated γ-γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ-γ cascade and the centroid difference as the time shift between the centroids of the two time spectra provides a picosecond-sensitive mirror-symmetric observable of the set-up. The energydependent mean prompt response difference between the start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing array mean γ-γ zero-time responses can be determined for 40 keV < Eγ < 1.4 MeV with a precision better than 10 ps using a 152Eu γ-ray source. The new method is described with examples of (n,γ) and (n,f,γ) experiments performed at the intense cold-neutron beam facility PF1B of the Institut Laue-Langevin in Grenoble, France, using 16 LaBr3(Ce) detectors within the EXILL&FATIMA campaign in 2013. The results are discussed with respect to possible systematic errors induced by background contributions.

Empirical Model of Precipitating Ion Oval

NASA Astrophysics Data System (ADS)

Goldstein, Jerry

2017-10-01

In this brief technical report published maps of ion integral flux are used to constrain an empirical model of the precipitating ion oval. The ion oval is modeled as a Gaussian function of ionospheric latitude that depends on local time and the Kp geomagnetic index. The three parameters defining this function are the centroid latitude, width, and amplitude. The local time dependences of these three parameters are approximated by Fourier series expansions whose coefficients are constrained by the published ion maps. The Kp dependence of each coefficient is modeled by a linear fit. Optimization of the number of terms in the expansion is achieved via minimization of the global standard deviation between the model and the published ion map at each Kp. The empirical model is valid near the peak flux of the auroral oval; inside its centroid region the model reproduces the published ion maps with standard deviations of less than 5% of the peak integral flux. On the subglobal scale, average local errors (measured as a fraction of the point-to-point integral flux) are below 30% in the centroid region. Outside its centroid region the model deviates significantly from the H89 integral flux maps. The model's performance is assessed by comparing it with both local and global data from a 17 April 2002 substorm event. The model can reproduce important features of the macroscale auroral region but none of its subglobal structure, and not immediately following a substorm.

Evidence against global attention filters selective for absolute bar-orientation in human vision.

PubMed

Inverso, Matthew; Sun, Peng; Chubb, Charles; Wright, Charles E; Sperling, George

2016-01-01

The finding that an item of type A pops out from an array of distractors of type B typically is taken to support the inference that human vision contains a neural mechanism that is activated by items of type A but not by items of type B. Such a mechanism might be expected to yield a neural image in which items of type A produce high activation and items of type B low (or zero) activation. Access to such a neural image might further be expected to enable accurate estimation of the centroid of an ensemble of items of type A intermixed with to-be-ignored items of type B. Here, it is shown that as the number of items in stimulus displays is increased, performance in estimating the centroids of horizontal (vertical) items amid vertical (horizontal) distractors degrades much more quickly and dramatically than does performance in estimating the centroids of white (black) items among black (white) distractors. Together with previous findings, these results suggest that, although human vision does possess bottom-up neural mechanisms sensitive to abrupt local changes in bar-orientation, and although human vision does possess and utilize top-down global attention filters capable of selecting multiple items of one brightness or of one color from among others, it cannot use a top-down global attention filter capable of selecting multiple bars of a given absolute orientation and filtering bars of the opposite orientation in a centroid task.

An Investigation on the Use of Different Centroiding Algorithms and Star Catalogs in Astro-Geodetic Observations

NASA Astrophysics Data System (ADS)

Basoglu, Burak; Halicioglu, Kerem; Albayrak, Muge; Ulug, Rasit; Tevfik Ozludemir, M.; Deniz, Rasim

2017-04-01

In the last decade, the importance of high-precise geoid determination at local or national level has been pointed out by Turkish National Geodesy Commission. The Commission has also put objective of modernization of national height system of Turkey to the agenda. Meanwhile several projects have been realized in recent years. In Istanbul city, a GNSS/Levelling geoid was defined in 2005 for the metropolitan area of the city with an accuracy of ±3.5cm. In order to achieve a better accuracy in this area, "Local Geoid Determination with Integration of GNSS/Levelling and Astro-Geodetic Data" project has been conducted in Istanbul Technical University and Bogazici University KOERI since January 2016. The project is funded by The Scientific and Technological Research Council of Turkey. With the scope of the project, modernization studies of Digital Zenith Camera System are being carried on in terms of hardware components and software development. Accentuated subjects are the star catalogues, and centroiding algorithm used to identify the stars on the zenithal star field. During the test observations of Digital Zenith Camera System performed between 2013-2016, final results were calculated using the PSF method for star centroiding, and the second USNO CCD Astrograph Catalogue (UCAC2) for the reference star positions. This study aims to investigate the position accuracy of the star images by comparing different centroiding algorithms and available star catalogs used in astro-geodetic observations conducted with the digital zenith camera system.

Ring rolling process simulation for microstructure optimization

NASA Astrophysics Data System (ADS)

Franchi, Rodolfo; Del Prete, Antonio; Donatiello, Iolanda; Calabrese, Maurizio

2017-10-01

Metal undergoes complicated microstructural evolution during Hot Ring Rolling (HRR), which determines the quality, mechanical properties and life of the ring formed. One of the principal microstructure properties which mostly influences the structural performances of forged components, is the value of the average grain size. In the present paper a ring rolling process has been studied and optimized in order to obtain anular components to be used in aerospace applications. In particular, the influence of process input parameters (feed rate of the mandrel and angular velocity of driver roll) on microstructural and on geometrical features of the final ring has been evaluated. For this purpose, a three-dimensional finite element model for HRR has been developed in SFTC DEFORM V11, taking into account also microstructural development of the material used (the nickel superalloy Waspalloy). The Finite Element (FE) model has been used to formulate a proper optimization problem. The optimization procedure has been developed in order to find the combination of process parameters which allows to minimize the average grain size. The Response Surface Methodology (RSM) has been used to find the relationship between input and output parameters, by using the exact values of output parameters in the control points of a design space explored through FEM simulation. Once this relationship is known, the values of the output parameters can be calculated for each combination of the input parameters. Then, an optimization procedure based on Genetic Algorithms has been applied. At the end, the minimum value of average grain size with respect to the input parameters has been found.

Isometries and binary images of linear block codes over ℤ4 + uℤ4 and ℤ8 + uℤ8

NASA Astrophysics Data System (ADS)

Sison, Virgilio; Remillion, Monica

2017-10-01

Let {{{F}}}2 be the binary field and ℤ2 r the residue class ring of integers modulo 2 r , where r is a positive integer. For the finite 16-element commutative local Frobenius non-chain ring ℤ4 + uℤ4, where u is nilpotent of index 2, two weight functions are considered, namely the Lee weight and the homogeneous weight. With the appropriate application of these weights, isometric maps from ℤ4 + uℤ4 to the binary spaces {{{F}}}24 and {{{F}}}28, respectively, are established via the composition of other weight-based isometries. The classical Hamming weight is used on the binary space. The resulting isometries are then applied to linear block codes over ℤ4+ uℤ4 whose images are binary codes of predicted length, which may or may not be linear. Certain lower and upper bounds on the minimum distances of the binary images are also derived in terms of the parameters of the ℤ4 + uℤ4 codes. Several new codes and their images are constructed as illustrative examples. An analogous procedure is performed successfully on the ring ℤ8 + uℤ8, where u 2 = 0, which is a commutative local Frobenius non-chain ring of order 64. It turns out that the method is possible in general for the class of rings ℤ2 r + uℤ2 r , where u 2 = 0, for any positive integer r, using the generalized Gray map from ℤ2 r to {{{F}}}2{2r-1}.

Evolution of the Far-Infrared Cloud at Titan's South Pole

NASA Technical Reports Server (NTRS)

Jennings, Donald E.; Achterberg, R. K.; Cottini, V.; Anderson, C. M.; Flasar, F. M.; Nixon, C. A.; Bjoraker, G. L.; Kunde, V. G.; Carlson, R. C.; Guandique, E.;

TH-CD-209-01: A Greedy Reassignment Algorithm for the PBS Minimum Monitor Unit Constraint

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

Lin, Y; Kooy, H; Craft, D

2016-06-15

Purpose: To investigate a Greedy Reassignment algorithm in order to mitigate the effects of low weight spots in proton pencil beam scanning (PBS) treatment plans. Methods: To convert a plan from the treatment planning system’s (TPS) to a deliverable plan, post processing methods can be used to adjust the spot maps to meets the minimum MU constraint. Existing methods include: deleting low weight spots (Cut method), or rounding spots with weight above/below half the limit up/down to the limit/zero (Round method). An alternative method called Greedy Reassignment was developed in this work in which the lowest weight spot in themore » field was removed and its weight reassigned equally among its nearest neighbors. The process was repeated with the next lowest weight spot until all spots in the field were above the MU constraint. The algorithm performance was evaluated using plans collected from 190 patients (496 fields) treated at our facility. The evaluation criteria were the γ-index pass rate comparing the pre-processed and post-processed dose distributions. A planning metric was further developed to predict the impact of post-processing on treatment plans for various treatment planning, machine, and dose tolerance parameters. Results: For fields with a gamma pass rate of 90±1%, the metric has a standard deviation equal to 18% of the centroid value. This showed that the metric and γ-index pass rate are correlated for the Greedy Reassignment algorithm. Using a 3rd order polynomial fit to the data, the Greedy Reassignment method had 1.8 times better metric at 90% pass rate compared to other post-processing methods. Conclusion: We showed that the Greedy Reassignment method yields deliverable plans that are closest to the optimized-without-MU-constraint plan from the TPS. The metric developed in this work could help design the minimum MU threshold with the goal of keeping the γ-index pass rate above an acceptable value.« less

Assessment of Survivability against Laser Threats. The ASALT-I Computer Program

DTIC Science & Technology

1981-09-01

NUM4ER OF PAGES WHICH DO NOT REPRODUCE LEGIBLY. I - f ~ ~ ’ECUftITt CL.inWCATOM Or TII PAGEL Cu18.. De 3Sawe no"___VISA__________1""I REPORT...subsection. COORDINATE SYSTEMS The four coordinate systems used in the ASALT-I Model are de -I picted in Figure 2-1, where the subscripts on each axis identify...centroid in the Enc,’, inter Coordinate System 2i z-coordinate of the component centroid in the Encounter Coordinate System gy width of the component

X-Ray Properties of Lensing-Selected Clusters

NASA Astrophysics Data System (ADS)

Paterno-Mahler, Rachel; Sharon, Keren; Bayliss, Matthew; McDonald, Michael; Gladders, Michael; Johnson, Traci; Dahle, Hakon; Rigby, Jane R.; Whitaker, Katherine E.; Florian, Michael; Wuyts, Eva

2017-08-01

I will present preliminary results from the Michigan Swift X-ray observations of clusters from the Sloan Giant Arcs Survey (SGAS). These clusters were lensing selected based on the presence of a giant arc visible from SDSS. I will characterize the morphology of the intracluster medium (ICM) of the clusters in the sample, and discuss the offset between the X-ray centroid, the mass centroid as determined by strong lensing analysis, and the BCG position. I will also present early-stage work on the scaling relation between the lensing mass and the X-ray luminosity.

Beam-dynamics codes used at DARHT

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

Ekdahl, Jr., Carl August

Several beam simulation codes are used to help gain a better understanding of beam dynamics in the DARHT LIAs. The most notable of these fall into the following categories: for beam production – Tricomp Trak orbit tracking code, LSP Particle in cell (PIC) code, for beam transport and acceleration – XTR static envelope and centroid code, LAMDA time-resolved envelope and centroid code, LSP-Slice PIC code, for coasting-beam transport to target – LAMDA time-resolved envelope code, LSP-Slice PIC code. These codes are also being used to inform the design of Scorpius.

Preliminary engineering study: Quick opening valve MSFC high Reynolds number wind tunnel

NASA Technical Reports Server (NTRS)

1983-01-01

FluiDyne Engineering Corporation has conducted a preliminary engineering study of a quick-opening valve for the MSFC High Reynolds Number Wind Tunnel under NASA Contract NAS8-35056. The subject valve is intended to replace the Mylar diaphragm system as the flow initiation device for the tunnel. Only valves capable of opening within 0.05 sec. and providing a minimum of 11.4 square feet of flow area were considered. Also, the study focused on valves which combined the quick-opening and tight shutoff features in a single unit. A ring sleeve valve concept was chosen for refinement and pricing. Sealing for tight shutoff, ring sleeve closure release and sleeve actuation were considered. The resulting cost estimate includes the valve and requisite modifications to the facility to accommodate the valve as well as the associated design and development work.

A New Hard X-ray Wiggler for DORIS III

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

Tischer, M.; Gumprecht, L.; Pflueger, J.

2007-01-19

A 4 m long hard X-ray wiggler has been built and installed in the DORIS III storage ring at DESY. The device replaces an old wiggler especially designed for angiography studies. Future use of this beamline at the HARWI straight section has been dedicated to hard X-ray scattering and diffraction experiments for material science and geological investigations. The required energy range is from 30 keV to about 200 keV with emphasis on the {approx}100 keV spectral range. The magnet configuration corresponds to a hybrid structure with additional side magnets to achieve a 2 T peak field for the specified periodmore » length of 110 mm. The wiggler position in the storage ring has been moved 8 m upstream into the next cell which allowed for reduction of the minimum magnetic wiggler gap to 14 mm.« less