Hexaaquamagnesium(II bis{[N-(4-methoxy-2-oxidobenzylideneglycylglycinato(3−]cuprate(II} hexahydrate
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Jiaxun Jiang
2009-11-01
Full Text Available In the title complex, [Mg(H2O6][Cu(C12H11N2O5]2·6H2O, the CuII atoms lie at the center of the square plane of triple negatively charged O,N,N′,O′-tetradentate Schiff base ligands, which are coordinated by one phenolate O atom, one imine N atom, one deprotonated amide N atom and one carboxylate O atom. The MgII center, which sits on an inversion center, is coordinated by six aqua ligands and exhibits a slightly distorted octahedral conformation. The asymmetric unit consists of an [N-(4-methoxy-2-oxidobenzylideneglycylglycinato]cuprate(II anion, one half of an [Mg(H2O6]2+ cation and three free water molecules. The cations and anions form columns by O—H...O hydrogen bonds.
Hexaaquacobalt(II bis{[N-(4-methoxy-2-oxidobenzylideneglycylglycinato]nickel(II} hexahydrate
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Wenlong Liu
2009-08-01
Full Text Available In the title compound, [Co(H2O6][Ni(C12H11N2O5]2·6H2O, the NiII atom has a nearly square-planar coordination with two N and two O atoms of the N-(4-methoxy-2-oxidobenzylideneglycylglycinate Schiff base ligand (L3−. The CoII atom sits on an inversion center and is coordinated to six aqua ligands in a slightly distorted octahedral geometry. The [Co(H2O6]2+ cations and [NiL]− anions form columns along the a axis by O—H...O hydrogen bonds. Additional hydrogen bonds between the uncoordinated and coordinated water molecules help to consolidate the crystal packing.
catena-Poly[[bis(thiocyanato-κNiron(II]-bis(μ-dipyrazin-2-yl disulfide-κ2N4:N4′
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Susanne Wöhlert
2013-09-01
Full Text Available In the title compound, [Fe(NCS2(C8H6N4S22]n, the FeII cation is coordinated by two terminal N-bonded thiocyanate anions and four bridging N:N′-bridging dipyrazin-2-yl disulfide ligands in an octahedral geometry. The FeII cations are connected via bridging 4,4′-dipyrazine ligands into chains along the b-axis direction. The asymmetric unit consists of one FeII cation located on position with site symmetry 2/m, one thiocyanate anion located on a mirror plane and one disulfide ligand located on a twofold rotation axis.
BKM superalgebras from counting dyons in N=4 supersymmetric type II compactifications
Govindarajan, Suresh; Krishna, K Gopala
2011-01-01
We study the degeneracy of quarter BPS dyons in N =4 type II compactifications of string theory. We find that the genus-two Siegel modular forms generating the degeneracies of the quarter BPS dyons in the type II theories can be expressed in terms of the genus-two Siegel modular forms generating the degeneracies of quarter BPS dyons in the CHL theories and the heterotic string. This helps us in understanding the algebra structure underlying the degeneracy of the quarter BPS states. The Conway group, Co_1, plays a role similar to Mathieu group, M_{24}, in the CHL models with eta quotients appearing in the place of eta products. We construct BKM Lie superalgebra structures corresponding to Z_N (for N=2,3,4) orbifolds of the type II string compactified on a six-torus.
Dinuclear cobalt(II) and copper(II) complexes with a Py2N4S2 macrocyclic ligand.
Núñez, Cristina; Bastida, Rufina; Lezama, Luis; Macías, Alejandro; Pérez-Lourido, Paulo; Valencia, Laura
2011-06-20
The interaction between Co(II) and Cu(II) ions with a Py(2)N(4)S(2)-coordinating octadentate macrocyclic ligand (L) to afford dinuclear compounds has been investigated. The complexes were characterized by microanalysis, conductivity measurements, IR spectroscopy and liquid secondary ion mass spectrometry. The crystal structure of the compounds [H(4)L](NO(3))(4), [Cu(2)LCl(2)](NO(3))(2) (5), [Cu(2)L(NO(3))(2)](NO(3))(2) (6), and [Cu(2)L(μ-OH)](ClO(4))(3)·H(2)O (7) was also determined by single-crystal X-ray diffraction. The [H(4)L](4+) cation crystal structure presents two different conformations, planar and step, with intermolecular face-to-face π,π-stacking interactions between the pyridinic rings. Complexes 5 and 6 show the metal ions in a slightly distorted square-pyramidal coordination geometry. In the case of complex 7, the crystal structure presents the two metal ions joined by a μ-hydroxo bridge and the Cu(II) centers in a slightly distorted square plane or a tetragonally distorted octahedral geometry, taking into account weak interactions in axial positions. Electron paramagnetic resonance spectroscopy is in accordance with the dinuclear nature of the complexes, with an octahedral environment for the cobalt(II) compounds and square-pyramidal or tetragonally elongated octahedral geometries for the copper(II) compounds. The magnetic behavior is consistent with the existence of antiferromagnetic interactions between the ions for cobalt(II) and copper(II) complexes, while for the Co(II) ones, this behavior could also be explained by spin-orbit coupling.
Diaquabis[bis(pyrazin-2-yl sulfide-κN4]bis(thiocyanato-κNiron(II monohydrate
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Susanne Wöhlert
2013-04-01
Full Text Available In the title compound [Fe(NCS2(C8H6N4S2(H2O2]·H2O, the FeII cation is coordinated by two N-bonded thiocyanate anions, two N4-bonded bis(pyrazin-2-yl sulfide ligands and two water molecules in an slightly distorted octahedral geometry. The FeII cation is located on a center of inversion and the lattice water molecule on a twofold rotation axis. The thiocyanate anions, the coordinating water molecules and the sulfide ligands occupy general positions. The complex molecules and lattice water molecules are linked into a three-dimensional network by O—H—N and O—H...O hydrogen bonds.
trans-Dichloridotetrakis[1-(2-hydroxyethyl-1H-tetrazole-κN4]cobalt(II
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Alexander S. Lyakhov
2009-11-01
Full Text Available The title cobalt(II complex, [CoCl2(C3H6N4O4], was obtained from metallic cobalt by direct synthesis. There are two Co atoms in the asymmetric unit, each lying on an inversion centre and adopting a distorted octahedral coordination. Classical and non-classical hydrogen bonds are responsible for formation of a three-dimensional polymeric network in the crystal.
Braverman, Alexander; Nakajima, Hiraku
2016-01-01
Consider the $3$-dimensional $\\mathcal N=4$ supersymmetric gauge theory associated with a compact Lie group $G_c$ and its quaternionic representation $\\mathbf M$. Physicists study its Coulomb branch, which is a noncompact hyper-K\\"ahler manifold with an $\\mathrm{SU}(2)$-action, possibly with singularities. We give a mathematical definition of the Coulomb branch as an affine algebraic variety with $\\mathbb C^\\times$-action when $\\mathbf M$ is of a form $\\mathbf N\\oplus\\mathbf N^*$, as the second step of the proposal given in arXiv:1503.03676.
John, E; Fanwick, P E; McKenzie, A T; Stowell, J G; Green, M A
1989-01-01
Copper(II) pyruvaldehyde bis(N4-methylthiosemicarbazone), Cu(PTSM), has been obtained as a dark red crystalline solid from EtOH-DMSO solvent mixture and structurally characterized by x-ray crystallography. The molecule possesses the expected pseudo-square planar N2S2 metal coordination sphere; however, the copper center also interacts through its axial coordination site with the sulfur atom of an adjacent Cu(PTSM) molecule in the crystal lattice. The structure of this compound is compared with the structures of other metal complexes that have been proposed in the nuclear medicine literature as perfusion tracers.
Dibromidobis(pyrazine-2-carboxylic acid-κN4mercury(II dihydrate
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Guo-Wei Wang
2008-01-01
Full Text Available The asymmetric unit of the title compound, [HgBr2(C5H4N2O22]·2H2O, contains one half-molecule and one water molecule. The HgII ion, lying on a twofold rotation axis, is four-coordinated by two N atoms of pyrazine-2-carboxylic acid ligands and two bromide ions, forming a highly distorted tetrahedral geometry. In the crystal structure, intermolecular O—H...O and O—H...N hydrogen bonds link the molecules.
Solanki, Ankita; Sadhu, Mehul H.; Kumar, Sujit Baran; Mitra, Partho
2014-11-01
A series of six new mononuclear zinc(II) complexes of the type [Zn(X)(dbdmp)]Y (1-6) (X = N3-/NCO-/NCS-, Y = ClO4-/PF6-, and dbdmp = N,N-diethyl-N‧,N‧-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine), two binuclear cadmium(II) complexes [{Cd(dbdmp)}2(μ-N3)2](Y)2 (7-8) and three mononuclear cadmium(II) complexes [Cd(NCO)(dbdmp)]Y (Y = ClO4-/PF6-) (9-10) and [Cd(NCS)2(dbdmp)] (11) have been synthesized and characterized by physico-chemical methods. Crystal structures of the complexes [Zn(N3)(dbdmp)]ClO4 (1), [{Cd(dbdmp)}2(μ-N3)2](ClO4)2 (7), [Cd(NCO)(dbdmp)]ClO4 (9) and [Cd(NCS)2(dbdmp)] (11) have been solved by single crystal X-ray diffraction studies and showed that [Zn(N3)(dbdmp)]ClO4 (1) and [Cd(NCO)(dbdmp)]ClO4 (9) have distorted trigonal bipyramidal geometry, [Cd(NCS)2(dbdmp)] (11) and [(dbdmp)Cd(μ-N3)]2(ClO4)2 (7) have distorted octahedral geometry.
Gerd Neggo stipendiumi sai Rene Nõmmik
2012-01-01
Eesti Tantsuhariduse Liit andis tänavuse Gerd Neggo nimelise tantsuõpetaja stipendiumi Rene Nõmmikule, kes on üks Fine 5 tantsuteatri ja kooli asutajatest ning Tallinna Ülikooli tantsukunsti õppejõud
Widger, Leland R; Jiang, Yunbo; Siegler, Maxime A; Kumar, Devesh; Latifi, Reza; de Visser, Sam P; Jameson, Guy N L; Goldberg, David P
2013-09-16
The known iron(II) complex [Fe(II)(LN3S)(OTf)] (1) was used as starting material to prepare the new biomimetic (N4S(thiolate)) iron(II) complexes [Fe(II)(LN3S)(py)](OTf) (2) and [Fe(II)(LN3S)(DMAP)](OTf) (3), where LN3S is a tetradentate bis(imino)pyridine (BIP) derivative with a covalently tethered phenylthiolate donor. These complexes were characterized by X-ray crystallography, ultraviolet-visible (UV-vis) spectroscopic analysis, (1)H nuclear magnetic resonance (NMR), and Mössbauer spectroscopy, as well as electrochemistry. A nickel(II) analogue, [Ni(II)(LN3S)](BF4) (5), was also synthesized and characterized by structural and spectroscopic methods. Cyclic voltammetric studies showed 1-3 and 5 undergo a single reduction process with E(1/2) between -0.9 V to -1.2 V versus Fc(+)/Fc. Treatment of 3 with 0.5% Na/Hg amalgam gave the monoreduced complex [Fe(LN3S)(DMAP)](0) (4), which was characterized by X-ray crystallography, UV-vis spectroscopic analysis, electron paramagnetic resonance (EPR) spectroscopy (g = [2.155, 2.057, 2.038]), and Mössbauer (δ = 0.33 mm s(-1); ΔE(Q) = 2.04 mm s(-1)) spectroscopy. Computational methods (DFT) were employed to model complexes 3-5. The combined experimental and computational studies show that 1-3 are 5-coordinate, high-spin (S = 2) Fe(II) complexes, whereas 4 is best described as a 5-coordinate, intermediate-spin (S = 1) Fe(II) complex antiferromagnetically coupled to a ligand radical. This unique electronic configuration leads to an overall doublet spin (S(total) = 1/2) ground state. Complexes 2 and 3 are shown to react with O2 to give S-oxygenated products, as previously reported for 1. In contrast, the monoreduced 4 appears to react with O2 to give a mixture of sulfur oxygenates and iron oxygenates. The nickel(II) complex 5 does not react with O2, and even when the monoreduced nickel complex is produced, it appears to undergo only outer-sphere oxidation with O2.
Bisceglie, Franco; Alinovi, Rossella; Pinelli, Silvana; Goldoni, Matteo; Buschini, Annamaria; Franzoni, Susanna; Mutti, Antonio; Tarasconi, Pieralberto; Pelosi, Giorgio
2013-11-01
In this paper we report a study conducted with two analogous complexes, bis(N(4)-ethylmorpholine citronellalthiosemicarbazonate) nickel(II) and -copper(II) on four tumour cell lines (U937, HL60, SK-N-MC and HT29). All cell lines appear to be sensitive to both metal complexes, but while in U937, HL60 and SK-N-MC, apoptosis is the main mode through which cell death occurs, HT29 cells undergo necrosis. Among the cell lines which undergo apoptosis, SK-N-MC response is characterized by the intrinsic pathway, whereas U937 and HL60 involve both the intrinsic and the extrinsic pathways. The redox activity of the two complexes provides experimental evidence that they can modulate reactive oxygen species (ROS) production as a function of both the metal and the cell line used. Among the four cell lines, HL60 does not seem to give a significant response to exposure to both compounds. In the case of the nickel derivative, ROS generation is a relatively early event, and ROS could be the mediator leading to cellular damage. HT29 shows a remarkable and rapid ROS increase and a significant induction of membrane peroxidation that could be correlated to the onset of necrosis.
Berting, Rene
2006-01-01
Keskkriminaalpolitsei menetlusosakonna politseidirektori Rene Bertingu sõnul jätkub Eestis prostitutsiooni seniks, kuni Ida-Virumaal on kehva sotsiaalse seisu tõttu naisi, kes on valmis seda tööd tegema
Berting, Rene
2006-01-01
Keskkriminaalpolitsei menetlusosakonna politseidirektori Rene Bertingu sõnul jätkub Eestis prostitutsiooni seniks, kuni Ida-Virumaal on kehva sotsiaalse seisu tõttu naisi, kes on valmis seda tööd tegema
Elamismudelite otsingul / Leena Torim, Rene Valner
Torim, Leena
2009-01-01
Arhitektid Leena Torim ja Rene Valner on mitu aastat tegelnud lihtsate, tervislike ja keskkonnasõbralike eluasemete projekteerimise ja ehitamisega. Nende eesmärk on luua esmajoones elukvaliteeti ja alles seejärel arhitektuuri. Omadustest, mis peavad olema heal majal. Tulevikuarhitektuurist
Grunert, CM; Schweifer, J; Weinberger, P; Linert, W; Mereiter, K; Hilscher, G; Muller, M; Wiesinger, G; van Koningsbruggen, PJ
2004-01-01
[mu-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF6)(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity a
Radiative Properties of Ceramic Al2O3, AlN and Si3N4—II: Modeling
Yang, Peiyan; Cheng, Qiang; Zhang, Zhuomin
2017-08-01
In Part I of this study (Cheng et al. in Int J Thermophys 37: 62, 2016), the reflectance and transmittance of dense ceramic plates were measured at wavelengths from 0.4 μm to about 20 μm. The samples of Al2O3 and AlN are semitransparent in the wavelength region from 0.4 μm to about 7 μm, where volume scattering dominates the absorption and scattering behaviors. On the other hand, the Si3N4 plate is opaque in the whole wavelength region. In the mid-infrared region, all samples show phonon vibration bands and surface reflection appears to be strong. The present study focuses on modeling the radiative properties and uses an inverse method to obtain the scattering and absorption coefficients of Al2O3 and AlN in the semitransparent region from the measured directional-hemispherical reflectance and transmittance. The scattering coefficient is also predicted using Mie theory for comparison. The Lorentz oscillator model is applied to fit the reflectance spectra of AlN and Si3N4 from 1.6 μm to 20 μm in order to obtain their optical constants. It is found that the phonon modes for Si3N4 are much stronger in the polycrystalline sample studied here than in amorphous films reported previously.
Cho, Yae In; Ward, Meredith L; Rose, Michael J
2016-09-14
We report the synthesis of two fluoride bridged cobalt(ii) dimers - [Co(μ-F)(pnN4-PhCl)2(OH2)(MeCN)](BF4)3 (1) and [Co(μ-F)2(pnN4-PhCl)2](BF4)2 (2) - and related complexes derived from propyl-bridged N4 Schiff base plus pyridine ligands. Notably, the bridging fluoride ion(s) emanate from B-F abstraction processes on the BF4 anions in the starting salt, [Co(H2O)6](BF4)2. Two types of bridging motifs are generated - mono-bridged (μ-F) or di-bridged (μ-F)2- synthetically differentiated by the absence or presence of pyridine, respectively, during metalation. The synergistic roles of pyridine and the (ClPh)N4 ligand in promoting B-F abstraction were clarified by the isolation and crystallization of the simple tetrakis-pyridine monomeric complex [Co(py)4(MeCN)2](BF4)2 (4) [no B-F abstraction]; subsequent addition of the (ClPh)N4 ligand to 4 resulted in formation of the dimeric, di-bridged complex 2. Omission of pyridine during metalation resulted in formation of the mono-bridged dimer 1. The bulky chlorophenyl substituents were obligate for B-F abstraction, as metalation of the unsubstituted N4 ligand resulted in the non-fluoride-bridged dimer, [Co(pnN4)3](BF4)4 (3). In magnetic studies, complexes 1 (μeff = 6.24μB, 298 K) and 2 (μeff = 7.70μB, 298 K) both exhibit antiferromagnetic (AFM) coupling, but to different extents. Temperature-dependent magnetic susceptibility measurements (SQUID, 2 → 300 K) reveal that the linearity of the mono-fluoride bridge in 1 [∠Co-F-Co = 159.47(11)°] results in very strong AFM coupling (J = -14.9 cm(-1)). In contrast, the more acute Co2F2 diamond core [∠Co-F-Co = 98.8(2)°, 99.1(2)°] results in a smaller extent of AFM coupling (J = -2.97 cm(-1)). Overall, the results indicate the 'non-innocence' of the BF4 counterion in cobalt(ii) chemistry, and dimers 1 and 2 affirm the effect of the geometry of the bridging fluoride ion(s) in determining the extent of AFM coupling.
Xu, Zhiqiang; Thompson, Laurence K.; Miller, David O.; Clase, Howard J.; Howard, Judith A. K.; Goeta, Andrés E.
1998-07-13
A series of dinuclear complexes of the tetradentate dipyridyl-diazine ligand PAHAP with Mn(II), Fe(II), Fe(III), Co(III), and Ni(II) salts is reported in which three ligands wrap themselves around the six-coordinate metal centers in a rare spiral-like fashion. A similar Fe(II) complex is found for the dipyrazinyl-diazine ligand PZHPZ. The ligands are severely twisted with dihedral angles between the metal chelate ring mean planes on each ligand in the range 50-70 degrees, values close to the expected twist angle for orthogonality between the bridging nitrogen atom p orbitals. Full structures are reported for the dinuclear complexes [Mn(2)(PAHAP)(3)](ClO(4))(4).5H(2)O (1), [Fe(2)(PAHAP)(3)](NO(3))(4).3H(2)O (2), [Fe(2)(PZHPZ)(3)](NO(3))(4).5H(2)O (5), [Co(2)(PAHAP)(3)](NO(3))(6).5H(2)O (6), and [Ni(2)(PAHAP)(3)][Ni(H(2)O)(6)](NO(3))(6).4.5H(2)O (7). Other derivatives [Fe(2)(PAHAP)(3)](ClO(4))(4).4H(2)O (3), [Fe(2)(PAHAP)(3)](ClO(4))(6).4.5H(2)O (4), [Ni(2)(PAHAP)(3)](ClO(4))(4).5H(2)O (8), and [Fe(PHAAP-H)(H(2)O)(2)(NO(3))](NO(3))(2) (9) are also reported. Complex 1 crystallized in the monoclinic system, space group C2/c, with a = 13.4086(2) Å, b = 32.0249(1) Å, c = 14.3132(2) Å, alpha = 90 degrees, beta = 115.635(1) degrees, gamma = 90 degrees, and Z = 4. Complex 2 crystallized in the cubic system, space group Pa&thremacr;, with a = b = c = 21.0024(1) Å, alpha = beta = gamma = 90 degrees, and Z = 8. Complex 5 crystallized in the monoclinic system, space group P2/n, with a = 14.039(3) Å, b = 11.335(6) Å, c = 14.6517(15) Å, beta = 96.852(11) degrees, and Z = 1. Complex 6 crystallized in the trigonal system, space group R&thremacr;c(h), with a = b = 17.386(2) Å, c = 32.15(2) Å, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 4. Complex 7 crystallized in the trigonal system, space group R&thremacr;c, with a = b = 17.3737(3) Å, c = 33.235(6) Å, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 27. Weak ferromagnetic coupling was observed for 1
Diaquabis[bis(pyrazin-2-yl) sulfide-κN4]bis(thiocyanato-κN)iron(II) monohydrate
National Research Council Canada - National Science Library
Wöhlert, Susanne; Jess, Inke; Näther, Christian
2013-01-01
...) sulfide ligands and two water molecules in an slightly distorted octahedral geometry. The FeII cation is located on a center of inversion and the lattice water molecule on a twofold rotation axis...
Dichloridobis[2-methylsulfanyl-4-(pyridin-2-ylpyrimidine-κ2N3,N4]cobalt(II
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Wen-Na Yang
2011-09-01
Full Text Available The asymmetric unit of the title compound, [CoCl2(C10H9N3S2], contains one half-molecule with the CoII atom situtated on a twofold rotational axis. The CoII atom, in an octahedral enviroment, is coordinated by four N atoms from two 2-methylsulfanyl-4-(pyridin-2-ylpyrimidine ligands and two Cl atoms.
catena-Poly[[bis(pyrazine-2-carboxamide-κN4mercury(II]-di-μ-bromido
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Bahareh Mir Mohammad Sadegh
2010-02-01
Full Text Available In the crystal structure of the title compound, [HgBr2(C5H5N3O2]n, the HgII cation is located on an inversion center and is coordinated by two N atoms from the pyrazine rings and four bridging Br− anions in a distorted octahedral geometry. The Br− anions bridge the HgII cations with significantly different Hg—Br bond distances of 2.4775 (8 and 3.1122 (8 Å, forming polymeric chains running along the a axis. Intermolecular N—H...O and N—H...N hydrogen bonds are effective in the stabilization of the crystal structure.
Poly[bis(μ2-5-n-butyltetrazolato-κ2N1:N4zinc(II
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Xiao-Lan Tong
2008-01-01
Full Text Available In the title complex, [Zn(C5H9N42]n, the ZnII center is coordinated by four N atoms of different tetrazolate ligands with a slightly distorted tetrahedral geometry [Zn—N distances and N—Zn—N angles are in the ranges 1.991 (2–2.007 (2 Å and 104.22 (8–116.13 (8°, respectively]. Each ligand links two ZnII atoms through its 1- and 4-position tetrazole N atoms, forming a single, fully connected three-dimensional framework with a diamond-like topology. In the crystal structure, the Zn...Zn separations across each tetrazole unit are 6.115 (2 and 6.134 (2 Å and the Zn...Zn...Zn angles are in the range 107.77 (8–116.83 (8°.
Mancha Madha, K.; Gurumoorthy, P.; Arul Antony, S.; Ramalakshmi, N.
2017-09-01
A new series of six mononuclear copper(II) complexes were synthesized from N3O2 and N4O2 donors containing Schiff base ligands, and characterized by various spectral methods. The geometry of the complexes was determined using UV-Vis, EPR and DFT calculations. The complexes of N3O2 donors (1-3) adopted square pyramidal geometry and the remaining complexes of N4O2 donors (4-6) show distorted octahedral geometry around copper(II) nuclei. Redox properties of the complexes show a one-electron irreversible reduction process in the cathodic potential (Epc) region from -0.74 to -0.98 V. The complexes show potent antioxidant activity against DPPH radicals. Molecular docking studies of complexes showed σ-π interaction, hydrogen bonding, electrostatic and van der Waals interactions with VEGFR2 kinase receptor. In vitro cytotoxicity of the complexes was tested against human breast cancer (MDA-MB-231) cell lines and one normal human dermal fibroblasts (NHDF) cell line through MTT assay. The morphological assessment data obtained by Hoechst 33258 and AO/EB staining revealed that the complexes induce apoptosis pathway of cell death.
Spot On! Engelske plakater fra mellemkrigsårene - genstandstekster
DEFF Research Database (Denmark)
Christensen, Line Hjorth
2015-01-01
genstandstekster til udstillingen Spot On! Engelske plakater fra mellemkrigsårene. alle tekster oversat til engelsk, men postes her i den danske udgave......genstandstekster til udstillingen Spot On! Engelske plakater fra mellemkrigsårene. alle tekster oversat til engelsk, men postes her i den danske udgave...
Directory of Open Access Journals (Sweden)
Singh Pal Netra
2012-01-01
Full Text Available Mononuclear metal complexes of the type [ML1]Cl2 (where, M = = Cu(II, Co(II or Ni(II and L1 = ligand were synthesized by the reaction of a new N4 coordinating ligand, derived from diacetylbisethylenediamine with benzoic acid, and the corresponding hydrated metal chloride salts. The metal complexes were characterized by elemental analysis, melting point determination, molar conductance and magnetic moment measurements, IR, UV-Vis, 1H- and 13C-NMR, and ESR spectroscopy. The ligand and all the metal complexes were stable in the solid state at room temperature. From the analytical and spectroscopic investigations, the stoichiometry of the complexes was found to be 1:1 (metal:ligand. Based on the electronic spectra and magnetic moment data, the metal complexes had a square planar geometry. The molar conductance values show the 1:2 electrolytic nature of the metal complexes. A cyclic voltammetric study of the Cu(II metal complex has also performed, which showed one electron quasi-reversible reduction around -0.92 to -1.10 V. In vitro biological activities of the ligand and metal complexes was checked against two bacteria Bacillus subtilis and Escherichia coli and two fungi Aspirgillus niger and A. flavus which showed the antibacterial and antifungal properties of the ligand and its metal complexes.
Hogue, Ross W; Feltham, Humphrey L C; Miller, Reece G; Brooker, Sally
2016-05-01
Access to a new family of thioether-linked PSRT ligands, 4-substituted-3,5-bis{[(2-pyridylmethyl)sulfanyl]methyl}-4H-1,2,4-triazoles (analogues of the previously studied amino-linked PMRT ligands), has been established. Four such ligands have been prepared, PSPhT, PS(i)BuT, PS(t-Bu)PhT, and PS(Me)PhT, with R = Ph, (i)Bu, (t-Bu)Ph, and (Me)Ph, respectively. Three dinuclear colorless to pale green iron(II) complexes, [Fe(II)2(PSRT)2](BF4)4·solvent, featuring N4S2 donor sets, were prepared. Single-crystal structure determinations on [Fe(II)2(PSPhT)2](BF4)4·2MeCN·H2O, [Fe(II)2(PSPhT)2](BF4)4·2(1)/2MeCN·(1)/2H2O·THF, [Fe(II)2(PS(Me)PhT)2](BF4)4·2MeCN, and [Fe(II)2(PS(i)BuT)2](BF4)4·4MeCN reveal that all four are stabilized in the [HS-HS] state to 100 K and that both possible binding modes of the bis-terdentate ligands, cis- and trans-axial, are observed. Variable-temperature magnetic susceptibility studies of air-dried crystals (solvatomorphs of the single crystal samples) reveal the first examples of spin crossover (SCO) for a dinuclear iron(II) complex with N4S2 coordination. Specifically, [Fe(II)2(PSPhT)2](BF4)4·2(1)/2H2O undergoes a multistep but complete SCO from [HS-HS] to [LS-LS], whereas [Fe(II)2(PS(Me)PhT)2](BF4)4·1(1)/2MeCN·2H2O exhibits a half-SCO from [HS-HS] to [HS-LS]. In contrast, [Fe(II)2(PS(i)BuT)2](BF4)4·MeCN·H2O remains [HS-HS] down to 50 K. The reflectance spectrum of pale green [Fe(II)2(PSPhT)2](BF4)4·(1)/2CHCl3·2(1)/2H2O (solvatomorph A) reveals a trace of LS character (572 nm band (1)A1g → (1)T1g). Evans' (1)H NMR method and UV-vis spectroscopy studies revealed that on cooling dark green acetonitrile solutions of these complexes from 313 to 233 K, all three undergo SCO centered at or near room temperature. The tendency of the complexes to go LS in solution reflects the electronic impact of R on the σ-donor strength of the PSRT ligand, whereas the opposite trend in stabilization of the LS state is seen in the solid state, where
Solanki, Ankita; Sadhu, Mehul H.; Kumar, Sujit Baran
2015-12-01
Five new mononuclear mixed ligand complexes of the type [Cu(NCCH3)(dbdmp)](ClO4)2, [M(ONO)(dbdmp)]ClO4, [M(pz) (dbdmp)](ClO4)2 where M = Cu(II) and Co(II), pz = 3,5-dimethylpyrazole and dbdmp = N,N-diethyl-N‧,N‧-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine have been synthesized and characterized by physico-chemical and spectroscopy studies. The crystal structures of three copper(II) complexes [Cu(NCCH3)(dbdmp)](ClO4)2, [Cu(ONO)(dbdmp)]ClO4 and [Cu(pz)(dbdmp)](ClO4)2 have been determined by single crystal X-ray diffraction studies. Structural analyses reveal the geometry of [Cu(pz)(dbdmp)](ClO4)2 is distorted square pyramidal and other two copper(II) complexes have distorted trigonal bipyramidal geometry. Molecular composition of cobalt(II) complexes have been determined by mass spectral data. The EPR spectra of copper(II) complexes in frozen acetonitrile solution exhibit axial spectra, characteristic of dx2-y2 ground state. Electrochemical studies of copper(II) complexes using glassy carbon as working electrode in acetonitrile solution show Cu(II)/Cu(I) couple with quasi reversible electron transfer versus Ag/Ag+ reference electrode. Antimicrobial activity of all the synthesized complexes were investigated against two Gram positive and two Gram negative bacterial strains.
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R. V. Parish
2002-02-01
Full Text Available Two potentially heptadentate (N4O3 tripodal Schiff-base ligands: tris(3-(salicylideneiminopropylamine (H3L1 and tris(3-(4Ã¢Â€Â™-hydroxysalicylideneimino-propylamine (H3L2 have been prepared and characterized by various spectroscopic methods (IR, FAB-MS, NMR. They are derived from the condensation reactions of tris(3-aminopropylamine (tpt, with 3 equivalents of either salicylaldehyde or the ringsubstituted salicylaldehyde, 4-hydroxysalicylaldehyde. The nickel(II and copper(II complexes of H3L1 were obtained from the its reactions Ni(II and Cu(II salts in absolute methanol. These complexes were studied by IR and FAB-Mass spectrometry.
Solanki, Ankita; Monfort, Montserrat; Kumar, Sujit Baran
2013-10-01
Two mononuclear nickel(II) complexes [NiL1(NCS)2] (1) and [NiL2(NCS)2] (2) and two azido bridged binuclear nickel(II) complexes [Ni(()2()2] (3) and [Ni(()2()2] (4), where L1, L2, L1‧ and L2‧ are N,N-diethyl-N‧,N‧-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1), N,N-bis((1H-pyrazol-1-yl)methyl)-N‧,N‧-diethylethane-1,2-diamine (L2), N,N-diethyl-N‧-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1‧) and N-((1H-pyrazol-1-yl)methyl)-N‧,N‧-diethylethane-1,2-diamine (L2‧) have been synthesized and characterized by microanalyses and physico-chemical methods. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are mononuclear NCS- containing Ni(II) complex with octahedral geometry and complexes 3 and 4 are end-on (μ-1,1) azido bridged binuclear Ni(II) complexes with distorted octahedral geometry. Variable temperature magnetic studies of the complexes 3 and 4 display ferromagnetic interaction with J values 19 and 32 cm-1, respectively.
Energy Technology Data Exchange (ETDEWEB)
Brennetot, Rene
2009-09-08
The author (Rene Brennetot) recalls his scientific career (diplomas, professional education, teaching activities, expertise, publications), presents his PhD works, his post-PhD works (laser ablation on liquids, sorting of aluminium alloys by laser induced breakdown spectroscopy or LIBS, Mars elemental analysis by LIBS - MALIS), and his current works (elemental and isotopic analyses on irradiated fuels, resolution of interferences in Inductively Coupled Plasma Mass Spectrometry or ICP-MS) and his perspectives and projects (validation of new measurement methods on nuclear matrices, investigation of ion-gas reactions in the collision/reaction cell of ICP-MS)
Abdel Ghani, Nour T; Mansour, Ahmed M
2012-01-01
[MLCl(2)] (L = (1H-benzimidazol-2-ylmethyl)-N-(4-bromo-phenyl)-amine; M = Pd & Pt) and [PdL(OH(2))(2)]∙2X∙zH(2)O (X = Br, I, z = 2; X = SCN, z = 1; X = NO(3), z = 0) complexes have been synthesized as potential anticancer compounds and their structures were elucidated using elemental analysis, spectral, thermal analysis and X-ray powder diffraction. The benzimidazole (L) crystallizes in the space group P2(1)/c with a = 8.6660(3) Å, b = 16.6739(7) Å, c = 9.8611(4) Å and β = 113.505(3) ° and forms an infinite chain structure with a trans-zigzag type along the crystallographic axis "a", through the intermolecular H-bond. FT-IR and (1)H NMR studies revealed that the ligand L is coordinated to the metal ion via the pyridine-type nitrogen (N(py)) of the benzimidazole ring and secondary amino group (NH(sec)). Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, and (1)H NMR of the benzimidazole L and its complexes were carried out by DFT/B3LYP method combined with 6-31G(d) and LANL2DZ basis sets. Natural bond orbital (NBO) analysis and frontier molecular orbitals (FMO) were performed at B3LYP/LANL2DZ level of theory. The benzimidazole L, in comparison to its metal complexes was screened for its antibacterial activity. The complexes showed cyctotoxic effects against human breast cancer (MCF7), hepatocarcinoma (HepG(2)) and colon carcinoma cells (HCT). The platinum complex (6) exhibited a moderate antitumor activity against MCF7 with IC(50) = 10.2 μM comparing to that reported for cis-platin 9.91 μM.
(1,4,7,10-Tetraazacyclododecane-κ4N1,N4,N7,N10(tetraoxidomolybdato-κOcopper(II monohydrate
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Dorothea Rohde
2010-08-01
Full Text Available In the title compound, [CuMoO4(C8H20N4]·H2O, the CuII atom is coordinated by four N atoms of the 1,4,7,10-tetraazacyclododecane (cyclen ligand and one O atom of the molybdate unit in a distorted square-pyramidal environment. The water molecules are linked to the complex unit to form centrosymmetric dimers [R44(12 and R44(16] and discrete D32(9, D33(11 and D33(13 chains by O—H...O and N—H...O interactions. Additionally, the complex molecules are linked into C44(18 chain motifs by N—H...O interactions. As a result [(cyclenCuMoO4] units and water molecules are linked to layers that are oriented parallel to the ac plane. The stacking of the layers in the b-axis direction is supported by weak C—H...O hydrogen bridges.
Institute of Scientific and Technical Information of China (English)
FU Ding-Wei; SONG Ji-Rong; REN Ying-Hui; YAN Biao; L(U) Xing-Qiang; HU Huai-Ming
2008-01-01
A copper(Ⅱ) complex Cu(L)2(NO3)2 constructed by the L (L = N-(4,6-dime- thoxylpyrimidin)-N'-(ethoxycarbonyl)thiourea) ligand crystallizes in monoclinic, space group C2/c with a = 16.2416(16), b = 9.1385(7), c = 22.0008(18) (A),β = 108.077(2)°, V ＝ 3104.3(5)(A)3, Dc = 1.627 g/cm3, Z = 4, C20H28CuN10O14S2, Mr = 760.18, μ(MoKα) = 0.920 mm-1, F(000) = 1564, R = 0.0471 and wR = 0.1284 for 2239 observed reflections (I > 2σ(I)). X-ray diffraction shows the existence of weak complementary intramolecular N-H…O (DA) hydrogen bonds which further strengthen the coordination from the two L ligands with the Cu(II) ion, intermolecular C-H…O hydrogen bonds and weak π…π stacking interactions, leading to the formation of a multi-dimen- sional supramolecular network.
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Md. Serajul Haque Faizi
2015-02-01
Full Text Available In the mononuclear title complex, [HgCl2(C22H17N3], synthesized from the quinoline-derived Schiff base N1-phenyl-N4-[(quinolin-2-ylmethylidene]benzene-1,4-diamine (PQMBD and HgCl2, the coordination sphere around the Hg2+ atom is distorted tetrahedral, comprising two Cl atoms [Hg—Cl = 2.3487 (14 and 2.4490 (15 Å] and two N atom donors from the PQMBD ligand, viz. the quinolyl and the imine N atom [Hg—N = 2.270 (4 and 2.346 (4 Å, respectively]. The dihedral angle between the two benzene rings attached to the amino group is 43.7 (3°. In the crystal, N—H...Cl and C—H...Cl hydrogen bonds, as well as π–π stacking interactions between one phenyl ring and the pyridine ring of the quinoline moiety of an adjacent molecule [centroid-to-centroid separation = 3.617 (4 Å] are observed, resulting in a three-dimensional network.
Grunert, C Matthias; Schweifer, Johannes; Weinberger, Peter; Linert, Wolfgang; Mereiter, Kurt; Hilscher, Gerfried; Müller, Martin; Wiesinger, Günter; van Koningsbruggen, Petra J
2004-01-12
[micro-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF(6))(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T(1/2) = 174 K and a hysteresis of about 4 K between T(1/2) and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, (57)Fe-Mössbauer spectroscopy, and variable temperature far and midrange FTIR spectroscopy. The title compound crystallizes in the trigonal space group P3 (No. 147) with a unit cell content of one formula unit plus a small amount of disordered solvent. The lattice parameters were determined by X-ray diffraction at several temperatures between 100 and 300 K. Complete crystal structures were resolved for 9 of these temperatures between 100 (only low spin, LS) and 300 K (only high spin, HS), Z = 1 [Fe(btzb)(3)](PF(6))(2): 300 K (HS), a = 11.258(6) A, c = 8.948(6) A, V = 982.2(10) A(3); 100 K (LS), a = 10.989(3) A, c = 8.702(2) A, V = 910.1(4) A(3). The molecular structure consists of octahedral coordinated iron(II) centers bridged by six N4,N4' coordinating bis(tetrazole) ligands to form three 3-dimensional networks. Each of these three networks is symmetry related and interpenetrates each other within a unit cell to form the interlocked structure. The Fe-N bond lengths change between 1.993(1) A at 100 K in the LS state and 2.193(2) A at 300 K in the HS state. The nearest Fe separation is along the c-axis and identical with the lattice parameter c.
Poly[bis[μ2-1,4-bis(1,2,4-triazol-1-ylmethylbenzene-κ2N4:N4′]bis(nitrito-κOcobalt(II
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Xia Zhu
2010-01-01
Full Text Available The CoII atom in the title complex, [Co(NO22(C12H12N62]n, lies on an inversion center and is coordinated by four N atoms from the triazole rings of two symmetry-related pairs of 1,4-bis(1,2,4-triazol-1-ylmethylbenzene (bbtz ligands and two O atoms from two symmetry-related monodentate nitrate ligands in a distorted octahedral geometry. The Co atoms are bridged by four bbtz ligands, forming a two-dimensional (4,4 network parallel to (102.
Powder metallurgy Rene 95 rotating turbine engine parts, volume 2
Wilbers, L. G.; Redden, T. K.
1981-01-01
A Rene 95 alloy as-HIP high pressure turbine aft shaft in the CF6-50 engine and a HIP plus forged Rene 95 compressor disk in the CFM56 engine were tested. The CF6-50 engine test was conducted for 1000 C cycles and the CFM56 test for 2000 C cycles. Post test evaluation and analysis of the CF6-50 shaft and the CFM56 compressor disk included visual, fluorescent penetrant, and dimensional inspections. No defects or otherwise discrepant conditions were found. These parts were judged to have performed satisfactorily.
Writing, Teaching, and Researching: An Interview with Rene Saldana, Jr.
Saldana, Rene, Jr.; Moore, David W.
2010-01-01
Rene Saldana, Jr., an assistant professor at Texas Tech University, is a writer of short stories, poetry, and novels. In order to get his storytelling right, he has relied on his memory when writing memoirs and consulted popular culture and family when writing fiction. In order to get his university teaching right, he reads seminal texts on…
God has moved. Long live the God! / Rene Fischer
Fischer, Rene
2004-01-01
Reklaamifirma Tank senine shveitslasest loovjuht Rene Fischer oma tööst ettevõttes, firma edukuse võimalikest põhjustest, olukorrast Baltimaade reklaamiturul, Läti reklaamifirma Bates/Red Cell loovjuhiks lahkumise põhjustest ning eesmärkidest uuel töökohal. Lisad: Other stuff; Technical data
God has moved. Long live the God! / Rene Fischer
Fischer, Rene
2004-01-01
Reklaamifirma Tank senine shveitslasest loovjuht Rene Fischer oma tööst ettevõttes, firma edukuse võimalikest põhjustest, olukorrast Baltimaade reklaamiturul, Läti reklaamifirma Bates/Red Cell loovjuhiks lahkumise põhjustest ning eesmärkidest uuel töökohal. Lisad: Other stuff; Technical data
Rene Valner ja Mikk Suursild - lihtsa elu tegelased / Susan Lahesalu
Lahesalu, Susan
2007-01-01
Arhitekt Rene Valner ja Mikk Suursild - tandem nimega UNITe - ehitavad ökonoomseid ja ökoloogilisi looduslikest materjalidest maju. Nende koostöös on valminud ka Peipsi ääres Nina külas 3 põhumaja. Ott Kadariku, Margit Mutso ja Kuido Kartau kommentaarid
Rene Magritte, Constructivism, and the Researcher as Interpreter.
Stake, Robert; Kerr, Dale
1995-01-01
This paper examines the art of Rene Magritte to illustrate how artworks provide a number of dimensions for realizing experience, for creating knowledge, and for a changed role of interpretation in educational research. The paper argues that works of art provide new gestalts and new grounds for confidence. (JB)
Aqua(3-carboxybenzoato-κO1(nitrato-κO(dipyrido[3,2-a:2′,3′-c]phenazine-κ2N4,N5copper(II
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Yan-Sheng Yin
2008-10-01
Full Text Available The title complex, [Cu(C8H5O4(NO3(C18H10N4(H2O], was synthesized by reacting Cu(NO32, isophthalic acid and dipyridophenazine under hydrothermal conditions. The CuII ion is in a slightly distorted square-pyramidal coordination environment. In the crystal structure, intermolecular O—H...O hydrogen bonds connect complex molecules into chains along [001].
Diaqua-bis-[bis-(pyrazin-2-yl) sulfide-κN (4)]bis-(thio-cyanato-κN)iron(II) monohydrate
National Research Council Canada - National Science Library
Wöhlert, Susanne; Jess, Inke; Näther, Christian
2013-01-01
...) sulfide ligands and two water mol-ecules in an slightly distorted octa-hedral geometry. The Fe(II) cation is located on a center of inversion and the lattice water mol-ecule on a twofold rotation axis...
Chicherin, Dmitry
2017-03-09
We study the multipoint super-correlation functions of the full non-chiral stress-tensor multiplet in N=4 super-Yang-Mills theory in the Born approximation. We derive effective supergraph Feynman rules for them. Surprisingly, the Feynman rules for the non-chiral correlators differ only slightly from those for the chiral correlators. We rely on the formulation of the theory in Lorentz harmonic chiral (LHC) superspace elaborated in the twin paper \\cite{PartI}. In this approach only the chiral half of the supersymmetry is manifest. The other half is realized by nonlinear and nonlocal transformations of the LHC superfields. However, at Born level only the simple linear part of the transformations is relevant. It corresponds to effectively working in the self-dual sector of the theory. Our method is also applicable to a wider class of supermultiplets like all the half-BPS operators and the Konishi multiplet.
catena-Poly[[diaquabis(formato-κOnickel(II]-μ-2,4,6-tris(4-pyridyl-1,3,5-triazine-κ2N2:N4
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Miao Feng
2011-05-01
Full Text Available In the title compound, [Ni(CHO22(C18H12N6(H2O2]n, the NiII ion, lying on a crystallographic inversion center, has a distorted octahedral coordination comprising two water ligands, two O-atom donors from formate ligands and two N-atom donors from the 2,4,6-tris(4-pyridyl-1,3,5-triazine ligands. These ligands bridge the NiII complex units, forming zigzag chains along the c axis. Adjacent chains are linked by O—H...O hydrogen bonds, forming a three-dimensional supramolecular network.
Tetra-μ-acetato-κ8O:O′-bis{[N-(4-methylphenylpyridin-2-amine-κN1]copper(II}(Cu—Cu
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Zainal Abidin Fairuz
2011-11-01
Full Text Available The complete dinuclear molecule of the title complex, [Cu2(CH3COO4(C12H12N22], is generated by a centre of inversion. The CuII atoms are connected [Cu—Cu = 2.6329 (16 Å] and bridged by four acetate ligands. The distorted octahedral coordination geometry is completed by a terminal pyridine N atom. The amine H atom forms an intramolecular N—H...O hydrogen bond.
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Julio Cesar da Rocha
2015-01-01
Full Text Available Herein we report on the synthesis and single crystal X-ray structure characterization of [{Cu2(tidf(μ-NO3}∞]ClO4 (tidf = a Robson type macrocyclic ligand obtained upon condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane. The coordination geometry around the copper(II is square-pyramidal and has [Cu2(tidf]2+ units connected to each other through nitrate bridges extending as a one-dimension coordination polymer. The compound exhibits an extensive supramolecular structure supported by nonclassic hydrogen bonding between C-H⋯Operchlorate and C-H⋯Onitrate.
Sheng, Hua; Frei, Heinz
2016-08-10
In the search for the two-electron-reduced intermediate of the tetraaza catalyst [Co(II)N4H(MeCN)](2+) (N4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene) for CO2 reduction and elementary steps that result in the formation of CO product, rapid-scan FT-IR spectroscopy of the visible-light-sensitized catalysis, using Ir(ppy)3 in wet acetonitrile (CD3CN) solution, led to the observation of two sequential intermediates. The initially formed one-electron-reduced [Co(I)N4H](+)-CO2 adduct was converted by the second electron to a transient [Co(I)N4H](+)-CO2(-) complex that spontaneously converted CO2 to CO in a rate-limiting step on the second time scale in the dark under regeneration of the catalyst (room temperature). The macrocycle IR spectra of the [Co(I)N4H](+)-CO2(-) complex and the preceding one-electron [Co(I)N4H](+)-CO2 intermediate show close similarity but distinct differences in the carboxylate modes, indicating that the second electron resides mainly on the CO2 ligand. Vibrational assignments are corroborated by (13)C isotopic labeling. The structure and stability of the two-electron-reduced intermediate derived from the time-resolved IR study are in good agreement with recent predictions by DFT electronic structure calculations. This is the first observation of an intermediate of a molecular catalyst for CO2 reduction during the bond-breaking step producing CO. The reaction pathway for the Co tetraaza catalyst uncovered here suggests that the competition between CO2 reduction and proton reduction of a macrocyclic multi-electron catalyst is steered toward CO2 activation if the second electron is directly captured by an adduct of CO2 and the one-electron-reduced catalyst intermediate.
Brines, Lisa M; Shearer, Jason; Fender, Jessica K; Schweitzer, Dirk; Shoner, Steven C; Barnhart, David; Kaminsky, Werner; Lovell, Scott; Kovacs, Julie A
2007-10-29
A series of five-coordinate thiolate-ligated complexes [M(II)(tren)N4S(Me2)]+ (M = Mn, Fe, Co, Ni, Cu, Zn; tren = tris(2-aminoethyl)amine) are reported, and their structural, electronic, and magnetic properties are compared. Isolation of dimeric [Ni(II)(SN4(tren)-RS(dang))]2 ("dang"= dangling, uncoordinated thiolate supported by H bonds), using the less bulky [(tren)N4S](1-) ligand, pointed to the need for gem-dimethyls adjacent to the sulfur to sterically prevent dimerization. All of the gem-dimethyl derivatized complexes are monomeric and, with the exception of [Ni(II)(S(Me2)N4(tren)]+, are isostructural and adopt a tetragonally distorted trigonal bipyramidal geometry favored by ligand constraints. The nickel complex uniquely adopts an approximately ideal square pyramidal geometry and resembles the active site of Ni-superoxide dismutase (Ni-SOD). Even in coordinating solvents such as MeCN, only five-coordinate structures are observed. The MII-S thiolate bonds systematically decrease in length across the series (Mn-S > Fe-S > Co-S > Ni-S approximately Cu-S tren)]+, represents a rare example of a stable CuII-thiolate, and models the perturbed "green" copper site of nitrite reductase. In contrast to the intensely colored, low-spin Fe(III)-thiolates, the M(II)-thiolates described herein are colorless to moderately colored and high-spin (in cases where more than one spin-state is possible), reflecting the poorer energy match between the metal d- and sulfur orbitals upon reduction of the metal ion. As the d-orbitals drop in energy proceeding across the across the series M(2+) (M= Mn, Fe, Co, Ni, Cu), the sulfur-to-metal charge-transfer transition moves into the visible region, and the redox potentials cathodically shift. The reduced M(+1) oxidation state is only accessible with copper, and the more oxidized M(+4) oxidation state is only accessible for manganese.
Rev Rene completes 15 years: victories and new challenges
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Maria de Nazaré de Oliveira Fraga
2015-09-01
Full Text Available There are times when we do not know which words to use. They throw themselves on paper, some or many of them without knowing exactly what will result, as a call for help on what they can show. So simple, so flexible, so hard, so complex they are. The request to write an editorial for the Rene Journal gave me the wheel of time. I’m retired of University teaching and research for a decade and a half. I was editor in chief and also section editor in the mental health area of this journal. So I have a lot to remember.
Ferraz, Karina S O; Da Silva, Jeferson G; Costa, Flávia M; Mendes, Bruno M; Rodrigues, Bernardo L; dos Santos, Raquel G; Beraldo, Heloisa
2013-10-01
Complexes [Au(2Ac4oT)Cl][AuCl2] (1), [Au(Hpy2Ac4mT)Cl2]Cl·H2O (2), [Au(Hpy2Ac4pT)Cl2]Cl (3), [Pt(H2Ac4oT)Cl]Cl (4), [Pt(2Ac4mT)Cl]·H2O (5), [Pt(2Ac4pT)Cl] (6) and [Pt(L)Cl2OH], L = 2Ac4mT (7), 2Ac4oT (8), 2Ac4pT (9) were prepared with N(4)-ortho- (H2Ac4oT), N(4)-meta- (H2Ac4mT) and N(4)-para- (H2Ac4pT) tolyl-2-acetylpyridine thiosemicarbazone. The cytotoxic activities of all compounds were assayed against U-87 and T-98 human malignant glioma cell lines. Upon coordination cytotoxicity improved in 2, 5 and 8. In general, the gold(III) complexes were more cytotoxic than those with platinum(II,IV). Several of these compounds proved to be more active than cisplatin and auranofin used as controls. The gold(III) complexes probably act by inhibiting the activity of thioredoxin reductase enzyme whereas the mode of action of the platinum(II,IV) complexes involves binding to DNA. Cells treated with the studied compounds presented morphological changes such as cell shrinkage and blebs formation, which indicate cell death by apoptosis induction.
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Dilovan S. Cati
2014-07-01
Full Text Available The title compound, [Cu(C11H9N4O(CH3CO2]·2H2O (CuL, is a hydrated copper acetate complex of the ligand N-[(pyridin-4-ylmethyl]pyrazine-2-carboxamide (HL. Complex CuL has a metal–organic framework (MOF structure with a 10 (3 network topology. The ligand coordinates in a bidentate and a bis-monodentate manner, bridging three equivalent CuII atoms via the pyridine N atom and the second pyrazine N atom. The CuII atom has a fivefold coordination sphere, CuN4O, being coordinated to three N atoms of the ligand and the acetate O atom in the equatorial plane and to the second pyrazine atom in the apical position. This gives rise to a fairly regular square-pyramidal geometry. In the crystal, the water molecules are linked to each other and to the three-dimensional framework via O—H...O hydrogen bonds. There are also a number of C—H...O hydrogen bonds present within the framework.
Narvas näeb Eesti tantsuauhinna võitnud tantsulavastust / Rene Nõmmik ; intervjueerinud Tiia Linnart
Nõmmik, Rene, 1962-
2015-01-01
Narva kultuurimajas Rugodiv näeb Fine5 tantsuteatri lavastust "...and blue", mis võitis tänavu Eesti teatriauhinna. Etenduse koreograafideks ja lavastajateks on Tiina Ollesk ja Rene Nõmmik, keda on palutud lavastama ka Venemaale. Intervjuu Rene Nõmmikuga
Narvas näeb Eesti tantsuauhinna võitnud tantsulavastust / Rene Nõmmik ; intervjueerinud Tiia Linnart
Nõmmik, Rene, 1962-
2015-01-01
Narva kultuurimajas Rugodiv näeb Fine5 tantsuteatri lavastust "...and blue", mis võitis tänavu Eesti teatriauhinna. Etenduse koreograafideks ja lavastajateks on Tiina Ollesk ja Rene Nõmmik, keda on palutud lavastama ka Venemaale. Intervjuu Rene Nõmmikuga
Viljandi on ideaalne linn vitraažikunsti jaoks. / Renee Aua ; interv. Tiiu Männiste
Aua, Renee
1998-01-01
Vestlus Viljandist pärit vitraažikunstniku Reneé Auaga vitraažikunstist seoses näitusega "Aprillinägu vaatab klaasi" Kilpkonna galeriis Viljandis. Galeriis eksponeeritakse Reneé Aua ja Sofi Arshase minivitraaže ning Reimo Rüntü portreid ja kompositsioone eri tehnikates
21 CFR 177.1020 - Acrylonitrile/butadiene/sty-rene co-polymer.
2010-04-01
... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylonitrile/butadiene/sty-rene co-polymer. 177... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances.../butadiene/sty-rene co-polymer. Acrylonitrile/butadiene/styrene copolymer identified in this section may be...
Rajeshkumar, Thayalan; Annadata, Harshini V; Evangelisti, Marco; Langley, Stuart K; Chilton, Nicholas F; Murray, Keith S; Rajaraman, Gopalan
2015-02-16
Density functional theory (DFT) studies on two polynuclear clusters, [Cu(II)5Gd(III)4O2(OMe)4(teaH)4(O2CC(CH3)3)2(NO3)4] (1) and [Cu5Gd2(OH)4(Br)2-(H2L)2(H3L)2(NO3)2(OH2)4] (2), have been carried out to probe the origin of the large magnetocaloric effect (MCE). The magnetic exchange interactions for 1 and 2 via multiple pathways are estimated using DFT calculations. While the calculated exchange parameters deviate from previous experimental estimates obtained by fitting the magnetic data, the DFT parameter set is found to offer a striking match to the magnetic data for both complexes, highlighting the problem of overparameterization. Magnetostructural correlations for {Cu-Gd} pairs have been developed where both the Cu-O-Gd angles and Cu-O-Gd-O dihedral angles are found to significantly influence the magnitude and sign of the exchange constants. The magnitude of the MCE has been examined as a function of the exchange interactions, and clues on how the effect can be enhanced are discussed.
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Stefan Suckert
2015-12-01
Full Text Available In the crystal structure of the title complex, [Mn(NCS2(C6H8N2(H2O3]·2C6H8N2, the MnII cation is coordinated by two terminally N-bonded thiocyanate anions, three water molecules and one 2,6-dimethylpyrazine ligand within a slightly distorted N3O3 octahedral geometry; the entire complex molecule is generated by the application of a twofold rotation axis. The asymmetric unit also contains an uncoordinating 2,5-dimethylpyrazine ligand in a general position. Obviously, the coordination to the 2,6-dimethylpyrazine ligand is preferred because coordination to the 2,5-dimethylpyrazine is hindered due to the bulky methyl group proximate to the N atom. The discrete complexes are linked by water-O—H...N(2,6-dimethylpyzazine/2,5-dimethylpyzazine hydrogen bonding, forming a three-dimensional network. In the crystal, molecules are arranged in a way that cavities are formed in which unspecified, disordered solvent molecules reside. These were modelled employing the SQUEEZE routine in PLATON [Spek (2015. Acta Cryst. C71, 9–18]. The composition of the unit cell does not take into account the presence of the unspecified solvent.
Leovac, Vukadin M; Vojinović-Jesić, Ljiljana S; Cesljević, Valerija I; Novaković, Sladjana B; Bogdanović, Goran A
2009-09-01
The title compound, [Cu(C(9)H(13)N(5)O(2))(CH(4)O)](NO(3))(2), consists of square-planar cationic complex units where the Cu(II) centre is coordinated by an N,N',O-tridentate pyridoxal-aminoguanidine Schiff base adduct and a methanol molecule. The tridentate ligand is a zwitterion exhibiting an almost planar conformation. The dihedral angles between the mean planes of the pyridoxal ring and the six- and five-membered chelate rings are all less than 2.0 degrees. The charge on the complex cation is neutralized by two nitrate counter-ions. Extensive N-H...O and C-H...O hydrogen bonding connects these ionic species and leads to the formation of layers. The pyridoxal hydroxy groups are the only fragments that deviate significantly from the flat layer structure; these groups are involved in O-H...O hydrogen bonding, connecting the layers into a three-dimensional crystal structure.
Cross, Edward D; MacDonald, Kristen L; McDonald, Robert; Bierenstiel, Matthias
2014-01-01
The reaction of dichlorido(cod)palladium(II) (cod = 1,5-cyclooctadiene) with 2-(benzylsulfanyl)aniline followed by heating in N,N-dimethylformamide (DMF) produces the linear trinuclear Pd3 complex bis(μ2-1,3-benzothiazole-2-thiolato)bis[μ2-2-(benzylsulfanyl)anilinido]dichloridotripalladium(II) N,N-dimethylformamide disolvate, [Pd3(C7H4NS2)2(C13H12NS)2Cl2]·2C3H7NO. The molecule has -1 symmetry and a Pd...Pd separation of 3.2012 (4) Å. The outer Pd(II) atoms have a square-planar geometry formed by an N,S-chelating 2-(benzylsulfanyl)anilinide ligand, a chloride ligand and the thiolate S atom of a bridging 1,3-benzothiazole-2-thiolate ligand, while the central Pd(II) core shows an all N-coordinated square-planar geometry. The geometry is perfectly planar within the PdN4 core and the N-Pd-N bond angles differ significantly [84.72 (15)° for the N atoms of ligands coordinated to the same outer Pd atom and 95.28 (15)° for the N atoms of ligands coordinated to different outer Pd atoms]. This trinuclear Pd3 complex is the first example of one in which 1,3-benzothiazole-2-thiolate ligands are only N-coordinated to one Pd centre. The 1,3-benzothiazole-2-thiolate ligands were formed in situ from 2-(benzylsulfanyl)aniline.
Roo, M. de
1985-01-01
The N = 4 Yang-Mills multiplet is coupled to N = 4 conformal supergravity. The action has a local U(4)Ã—G symmetry, where G is the Yang-Mills gauge group. The action and supersymmetry transformation rules are presented in the PoincarÃ© gauge, and properties of the scalar potential are discussed.
ENPA juht usub Vene arengusse / Rene van der Linden ; interv. Erkki Bahovski
Linden, Rene van der
2006-01-01
Vt. ka Postimees : na russkom jazõke 2. juuni lk. 7. Euroopa Nõukogu Parlamentaarse Assamblee president Rene van der Linden Euroopa Nõukogu (EN) rollist, Venemaa ja Eesti arengutest EN-i liikmena. Lisa: Euroopa parlamentide kogu
ENPA juht usub Vene arengusse / Rene van der Linden ; interv. Erkki Bahovski
Linden, Rene van der
2006-01-01
Vt. ka Postimees : na russkom jazõke 2. juuni lk. 7. Euroopa Nõukogu Parlamentaarse Assamblee president Rene van der Linden Euroopa Nõukogu (EN) rollist, Venemaa ja Eesti arengutest EN-i liikmena. Lisa: Euroopa parlamentide kogu
Eestlane paneb sõiduautod liikuma Transsiberi raudteel / Rene Varek ; interv. Tanel Raig
Varek, Rene, 1972-
2009-01-01
Railtransauto kommertsdirektor Rene Varek vastab küsimustele, mis puudutavad tema igapäevast tööd ettevõttes, seatud eesmärke ja nende täitmist, Mazdade transpordiprojekti, Transsiberi raudtee kasutamise eeliseid, ettevõtte veomahtusid ning Muuga sadama konteinerterminali rajamise edasilükkamise mõju Eesti transpordiettevõtetele. Vt. samas: Rene Varek; Railtransauto Ltd
Eestlane paneb sõiduautod liikuma Transsiberi raudteel / Rene Varek ; interv. Tanel Raig
Varek, Rene, 1972-
2009-01-01
Railtransauto kommertsdirektor Rene Varek vastab küsimustele, mis puudutavad tema igapäevast tööd ettevõttes, seatud eesmärke ja nende täitmist, Mazdade transpordiprojekti, Transsiberi raudtee kasutamise eeliseid, ettevõtte veomahtusid ning Muuga sadama konteinerterminali rajamise edasilükkamise mõju Eesti transpordiettevõtetele. Vt. samas: Rene Varek; Railtransauto Ltd
n = 4 supersymmetric FRW model
Energy Technology Data Exchange (ETDEWEB)
Rosales, J.J.; Pashnev, A. [Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, 141980 (Russian Federation); Tkach, V.I. [Instituto de Fisica, Universidad de Guanajuato, 05315-970 Leon, 66318 Guanajuato (Mexico)]. e-mail: juan@ifug3.ugto.mx, pashnev@thsun1.jinr.ru, vladimir@ifug3.ugto.mx
2003-07-01
In this work we have constructed the n = 4 extended local conformal time supersymmetry for the Friedmann-Robertson-Walker cosmological models. This is based on the superfield construction of the action, which is invariant under world line local n = 4 supersymmetry with SU(2){sub local} X SU(2){sub global} internal subgroup. It is shown that the supersymmetric action has the form of the localized (or superconformal) version of the action for n = 4 supersymmetric quantum mechanics. This superfield procedure provides a well defined scheme for including super matter. (Author)
Directory of Open Access Journals (Sweden)
Monserrat Alfonso
2016-09-01
Full Text Available The reaction of 5,6-bis(pyridin-2-ylpyrazine-2,3-dicarboxylic acid with cadmium dichloride leads to the formation of the title two-dimensional coordination polymer, [Cd(C16H8N4O4(H2O2]n. The metal atom is sevenfold coordinated by one pyrazine and one pyridine N atom, two water O atoms, and by two carboxylate O atoms, one of which bridges two CdII atoms to form a Cd2O2 unit situated about a centre of inversion. Hence, the ligand coordinates to the cadmium atom in an N,N′,O-tridentate and an O-monodentate manner. Within the polymer network, there are a number of O—H...O hydrogen bonds present, involving the water molecules and the carboxylate O atoms. There are also C—H...N and C—H...O hydrogen bonds present. In the crystal, the polymer networks lie parallel to the bc plane. They are aligned back-to-back along the a axis with the non-coordinating pyridine rings directed into the space between the networks.
All N=4 Conformal Supergravities
Butter, Daniel; de Wit, Bernard; Sahoo, Bindusar
2016-01-01
All N=4 conformal supergravities in four space-time dimensions are constructed. These are the only N=4 supergravity theories whose actions are invariant under off-shell supersymmetry. They are encoded in terms of a holomorphic function that is homogeneous of zeroth degree in scalar fields that parametrize an SU(1,1)/U(1) coset space. When this function equals a constant the Lagrangian is invariant under continuous SU(1,1) transformations.
Counting dyons in N=4 string theory
Dijkgraaf, R; Verlinde, Herman L
1997-01-01
We present a microscopic index formula for the degeneracy of dyons in four-dimensional N=4 string theory. This counting formula is manifestly symmetric under the duality group, and its asymptotic growth reproduces the macroscopic Bekenstein-Hawking entropy. We give a derivation of this result in terms of the type II five-brane compactified on K3, by assuming that its fluctuations are described by a closed string theory on its world-volume. We find that the degeneracies are given in terms of the denominator of a generalized super Kac-Moody algebra. We also discuss the correspondence of this result with the counting of D-brane states.
Friedmann, Peretz P.; Johnson, Wayne; Scully, Michael P.
2011-01-01
Rene H. Miller (May 19, 1916 January 28, 2003), Emeritus H. N. Slater Professor of Flight Transportation, was one of the most influential pioneers in rotary wing aeromechanics as well as a visionary whose dream was the development of a tilt-rotor based short haul air transportation system. This paper pays a long overdue tribute to his memory and to his extraordinary contributions.
Emde, Robert N.
1992-01-01
Considers contributions of Sigmund Freud and Rene Spitz to developmental psychology. Freud's contributions include his observations about play, perspectives on developmental processes, and ideas about unconscious mental activity. Spitz's contributions include his assessments of infants, perspectives on developmental processes, and his concept of…
Emde, Robert N.
1992-01-01
Considers contributions of Sigmund Freud and Rene Spitz to developmental psychology. Freud's contributions include his observations about play, perspectives on developmental processes, and ideas about unconscious mental activity. Spitz's contributions include his assessments of infants, perspectives on developmental processes, and his concept of…
Tsaari motopärand Eestimaa teedel / Rene Levoll
Levoll, Rene, 1958-
2016-01-01
Viimane Nikolai II visiit Eestisse toimus 1915. aastal. Oktoobrirevolutsiooni järel sattus tsaari autopark bolševike käsutusse. Kaks autot keiserlikust motopärandist jõudsid ka Maarjamaale. Üks nendest oli varem kuulunud Nikolai II vanemale õele Kseniale
Counting dyons in N=4 string theory
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R. [Amsterdam Univ. (Netherlands). Dept. of Mathematics and Computer Science; Verlinde, E. [TH-Division, CERN, CH-1211 Geneva 23 (Switzerland)]|[Institute for Theoretical Physics, Universtity of Utrecht, 3508 TA Utrecht (Netherlands); Verlinde, H. [Institute for Theoretical Physics, University of Amsterdam, 1018 XE Amsterdam (Netherlands)]|[Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States)
1997-01-27
We present a microscopic index formula for the degeneracy of dyons in four-dimensional N=4 string theory. This counting formula is manifestly symmetric under the duality group, and its asymptotic growth reproduces the macroscopic Bekenstein-Hawking entropy. We give a derivation of this result in terms of the type II five-brane compactified on K3, by assuming that its fluctuations are described by a closed string theory on its world-volume. We find that the degeneracies are given in terms of the denominator of a generalized super Kac-Moody algebra. We also discuss the correspondence of this result with the counting of D-brane states. (orig.).
Farnum, Gregory A.; LaDuca, Robert L.
2008-01-01
In the title compound, {[Cu(C5H6O4)(ClO4)(C16H22N4)]ClO4·2H2O}n, square-pyramidally coordinated Cu atoms with perchlorate and dimethylmalonate ligands are connected into cationic sinusoidal coordination polymer chains by doubly protonated bis(3-pyridylmethyl)piperazine (3-bpmp) ligands. The chains aggregate into pseudo-layers parallel to the (101) crystal planes by N—H⋯O hydrogen bonding. Unligated perchlorate anions and water molecules of crystallization provide additional hydrogen bonding between pseudo-layers. PMID:21581141
Institute of Scientific and Technical Information of China (English)
CHEN Hui; WANG Wen-Guo; ZHANG Xiao-Feng; CHEN Chang-Neng; LIU Qiu-Tian
2006-01-01
A new one-dimensional azido-bridged manganese compound has been prepared and structurally characterized by X-ray diffraction. The complex [Mn(N3)2(H2O)3·C6H12N4]n crystallizes in space group Pnma with a = 6.5252 (5), b = 9.3226(7), c = 22.2070(15)(A), V = 1350.89(17)(A)3, Z = 4, Mr = 333.24, Dc = 1.639 g/cm3, μ= 1.005 mm-1 and F(000) = 692. The final refinement gave R = 0.0328 and wR = 0.0777 for 1085 observed reflections with I > 2σ(I). The structure contains [Mn- (N3)2(H2O)3]n polymeric chains and uncoordinated hexamethylenetetramine (HMTA) molecules with Mn/HMTA molar ratio of 1:1. The Mn atoms are bridged by end-to-end azido ligands to construct one-dimensional zig-zag infinite chains. Each Mn atom is six-coordinated by three N atoms of three azido ligands and three water O atoms, resulting in an octahedral geometry. Extending hydrogen- bonding interactions involving water O atoms, azido and HMTA N atoms link the chains and HMTA molecules into a three-dimensional network.
Directory of Open Access Journals (Sweden)
Florina Dumitru
2016-04-01
Full Text Available The title compound, [Co(C5H7O22(C6H12N2]n, was obtained as a one-dimensional coordination polymer from bis(acetylacetonatodiaquacobalt(II, [Co(acac2(OH22], and 1,4-diazabicyclo[2.2.2]octane (DABCO, a diamine with good bridging ability and rod-like spacer function. In the chain complex that extends along the c axis, the CoII atom is six-coordinated, the O-donor atoms of the chelating acac ligands occupying the equatorial positions and the bridging DABCO ligands being in trans-axial positions. In the crystal structure, the DABCO ligand is conformationally disordered in a 50:50 manner as a result of its location across a crystallographic mirror plane. The metal–metal distance is very close to that in a related compound exhibiting weak antiferromagnetic exchange between the CoII ions, and the title compound can thus be useful for obtaining more information about the contribution of different bridges to the magnetic coupling between paramagnetic ions.
Suckert, Stefan; Wöhlert, Susanne; Jess, Inke; Näther, Christian
2015-12-01
In the crystal structure of the title complex, [Mn(NCS)2(C6H8N2)(H2O)3]·2C6H8N2, the Mn(II) cation is coordinated by two terminally N-bonded thio-cyanate anions, three water mol-ecules and one 2,6-di-methyl-pyrazine ligand within a slightly distorted N3O3 octa-hedral geometry; the entire complex mol-ecule is generated by the application of a twofold rotation axis. The asymmetric unit also contains an uncoordinating 2,5-di-methyl-pyrazine ligand in a general position. Obviously, the coordination to the 2,6-di-methyl-pyrazine ligand is preferred because coordination to the 2,5-di-methyl-pyrazine is hindered due to the bulky methyl group proximate to the N atom. The discrete complexes are linked by water-O-H⋯N(2,6-di-methyl-pyzazine/2,5-di-methyl-pyza-zine) hydrogen bonding, forming a three-dimensional network. In the crystal, mol-ecules are arranged in a way that cavities are formed in which unspecified, disordered solvent molecules reside. These were modelled employing the SQUEEZE routine in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18]. The composition of the unit cell does not take into account the presence of the unspecified solvent.
Sun, Wei
2013-02-01
In the title compound, {[Mn(C(15)H(8)O(7))(C(10)H(8)N(2))(H(2)O)(3)]·C(10)H(8)N(2)·2H(2)O}(n), the bridging mode of the coordinating 4,4'-bipyridine ligands leads to the formation of polymeric zigzag chains parallel to [0-11]. The chains are separated by 4,4'-bipyridine and water solvent mol-ecules. Within a chain, the Mn(II) atom is six-coordinated by two N atoms of the bridging 4,4'-bipyridine ligands, three water O atoms and one carboxyl-ate O atom of a single deprotonated 3-(4-carb-oxy-phen-oxy)phthalic acid ligand. Both coordinating and solvent 4,4'-bipyridine mol-ecules are situated on centres of inversion. An intricate network of O-H⋯O and O-H⋯N hydrogen bonds involving the carb-oxy group, the coordinating water mol-ecules and the two types of solvent mol-ecules leads to the formation of a three-dimensional network.
Directory of Open Access Journals (Sweden)
Paul DeBurgomaster
2010-11-01
Full Text Available The title compound [Ni2(C6H6O6P22(C24H16N6(H2O4]·2H2O or [Ni2(tpyprz(1,3-HO3PC6H4PO3H2(H2O4]·2H2O [tpyprz = tetrakis(2-pyridylpyrazine, C24H16N6] is a binuclear complex with a crystallographic inversion center located at the center of the pyrazine ring. The equivalent nickel(II sites exhibit a distorted {NiO3N3} octahedral coordination, with the three nitrogen donors of each terminus of the tpyprz ligand in a meridional orientation. An aqua ligand occupies the position trans to the pyrazine nitrogen donor, while the second aqua ligand is trans to the oxygen donor of the dihydrogen-1,3-phenyldiphosphonate ligand. The Ni—O and Ni—N bond lengths fall in the range 2.011 (3 to 2.089 (3 Å. The protonation sites on the organophosphonate ligand are evident in the significantly longer P—O bonds compared to the unprotonated sites. In the crystal structure, the complex molecules and the solvent water molecules are linked into a three-dimensional hydrogen-bonded framework through O—H...O interactions between the aqua ligands, the protonated organophosphonate oxygen atoms and the water molecules of crystallization. Intramolecular π-stacking between the phenyl group of the phosphonate ligand and a pyridyl group of the tpyprz ligand, at a distance of 3.244 (5 Å between ring centroids, is also observed.
DEFF Research Database (Denmark)
Christiansen, Ask Vest
manistiske dopingforskning og forskningen om cykelsportens kultur, præsenteres. Som baggrund for de følgende analyser, indledes anden del med en redegørelse for moderne cykelsports struktur og organisation. Tre historiske faser afgrænses, og for hver af disse skildres udviklingen indenfor holdorganisation og...
Energy Technology Data Exchange (ETDEWEB)
Li, J. [Laboratory of Laser Materials Processing and Manufacturing, Beihang University (formerly Beijing University of Aeronautics and Astronautics), 37 Xueyuan Road, Beijing 100191 (China); Wang, H.M., E-mail: wanghm@buaa.edu.cn [Laboratory of Laser Materials Processing and Manufacturing, Beihang University (formerly Beijing University of Aeronautics and Astronautics), 37 Xueyuan Road, Beijing 100191 (China); Tang, H.B. [Laboratory of Laser Materials Processing and Manufacturing, Beihang University (formerly Beijing University of Aeronautics and Astronautics), 37 Xueyuan Road, Beijing 100191 (China)
2012-07-30
Highlights: Black-Right-Pointing-Pointer Extensive precipitation of {gamma} Prime particles resulted in high hardness and ductility. Black-Right-Pointing-Pointer Alignment and coalescence of {gamma} Prime precipitates induced decrease in strength. Black-Right-Pointing-Pointer Standard heat treatment for wrought Rene Prime 41 alloy is not suitable for the LMD alloy. - Abstract: Ni-base superalloy Rene Prime 41 was produced by the laser melting deposition (LMD) manufacturing process. The LMD material was solution treated at 1065 Degree-Sign C for 4 h followed by air quenching and aged at 760 Degree-Sign C for 16 h followed by air cooling. Microstructure of the as-deposited, solution treated and solution-aged alloys were characterized by scanning electron microscopy and transmission electron microscopy, and the tensile properties and hardness were tested. The solution-aged Rene Prime 41 superalloy showed high hardness, low strength and low ductility. The extensive precipitation of {gamma} Prime resulted in high hardness and ductility, and the subsequent alignment and coalescence of {gamma} Prime precipitates induced low strength. The structure-property relationships of the alloy under three different heat treating conditions were studied and results indicated that the standard heat treatment recommended for wrought Rene Prime 41 was not suitable for LMD alloy and had to be modified to realize optimum mechanical properties.
Matter coupling in N = 4 supergravity
Roo, M. de
1985-01-01
An arbitrary number of abelian vector multiplets is coupled to N = 4 supergravity. The resulting action is invariant under global SO(n,6), where n is the number of vector multiplets, and under local SU(4) Ã— U(1) transformations. The scalar fields of the theory parametrize the manifold [SO(n,6)/SO(n
Directory of Open Access Journals (Sweden)
Giorgio Baruchello
2014-03-01
Full Text Available Review of: Michele Renee Salzman, Marvina A. Sweeney & William Adler (eds., The Cambridge History of Religions in the Ancient World (2 vols. (New York: Cambridge University Press, 2013
Abelian reductions of deformed N=4 SYM
Directory of Open Access Journals (Sweden)
Carlos Cardona
2015-08-01
Full Text Available Following the work in [1], where the massive ABJM model in 2+1 dimensions was shown to have an abelian reduction to the relativistic Landau–Ginzburg, and motivated by the implications for condensed matter through AdS/CFT, we show that a FI deformation of N=4 SYM in 3+1 dimensions with a mass term can also be reduced to a relativistic Landau–Ginzburg model, with the possibility of coupling it to a real scalar, whereas the simply mass deformed N=4 SYM reduces only to a massive ϕ4 model (scalar QED coupled to a real scalar. We study the classical solutions of the model, in particular vortex solutions.
Gauging isometries in N=4 supersymmetric mechanics
Delduc, F
2008-01-01
This talk summarizes the study of superfield gaugings of isometries of extended supersymmetric mechanics in hep-th/0605211, hep-th/0611247 and arXiv:0706.0706. The gauging procedure provides a manifestly supersymmetric realization of d=1 automorphic dualities which interrelate various irreducible off-shell multiplets of d=1 extended supersymmetry featuring the same number of physical fermions but different divisions of bosonic fields into the physical and auxiliary subsets. We concentrate on the most interesting N=4 case and demonstrate that, with a suitable choice of the symmetry to be gauged, all such multiplets of N=4 supersymmetric mechanics and their generic superfield actions can be obtained from the "root" multiplet (4,4,0) and the appropriate gauged subclasses of the generic superfield action of the latter by a simple universal recipe.
N = 4 l-conformal Galilei superalgebra
Galajinsky, Anton; Masterov, Ivan
2017-08-01
An N = 4 supersymmetric extension of the l-conformal Galilei algebra is constructed. This is achieved by combining generators of spatial symmetries from the l-conformal Galilei algebra and those underlying the most general superconformal group in one dimension D (2 , 1 ; α). The value of the group parameter α is fixed from the requirement that the resulting superalgebra is finite-dimensional. The analysis reveals α = -1/2 thus reducing D (2 , 1 ; α) to OSp (4 | 2).
Rene Thom: de la teoría de Catástrofes a la Metafísica
Espinoza, Miguel
1995-01-01
La Obra De Rene Thom Es Una De Las Contribuciones Mas Significativa Delpensamiento Frances Actual A La Filosofia. Conocido En El Mundo Matematico,Entre Otras Contribuciones, Por Sus Trabajos Sobre Las Variedadesdiferenciables, El Problema Del Cobordismo, La Teoria De Las Singularidades,Thom Es El Autor De La Teoria De Las Catastrofes (Tc). A Traves De Ella, Hapodido Proponer Ideas Pertinentes Al Conjunto De Ciencias Naturales Y Humanas.Sospechosos De La Pretension Universal De La Teoria Y De ...
Energy Technology Data Exchange (ETDEWEB)
Zheng Lei, E-mail: zhenglei_ustb@sina.com [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 10083 (China); Zhang Maicang; Dong Jianxin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 10083 (China)
2010-10-01
The oxidation behaviors of powder metallurgy (PM) Rene95 Ni-based superalloy in the temperature range of 800-1000 deg. C are investigated in air by virtue of isothermal oxidation testing, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the oxidation kinetics follows a square power law as the time extends at each temperature. The oxidation layers are detected to be composed of Cr{sub 2}O{sub 3}, TiO{sub 2} and a small amount of NiCr{sub 2}O{sub 4}. The cross-sectional morphologies indicate that the oxidation layer consists of three parts: Cr-rich oxide layer, Cr and Ti duplex oxide layer, and oxidation affected zone. Theoretical analyses of oxidation kinetics and thicknesses of oxidation layers confirm that the activation energy of oxidation of PM Rene95 superalloy is 165.32 kJ mol{sup -1} and the oxidation process is controlled by diffusions of oxygen, Cr, and Ti. Accordingly, a diffusion-controlled mechanism is suggested to understand the oxidation behaviors of PM Rene95 superalloy at elevated temperatures.
Counting dyons in N = 4 string theory
Dijkgraaf, Robbert; Verlinde, Erik; Verlinde, Herman
1997-02-01
We present a microscopic index formula for the degeneracy of dyons in four-dimensional N = 4 string theory. This counting formula is manifestly symmetric under the duality group, and its asymptotic growth reproduces the macroscopic Bekenstein-Hawking entropy. We give a derivation of this result in terms of the type 11 five-brane compactified on K3, by assuming that its fluctuations are described by a closed string theory on its world-volume. We find that the degeneracies are given in terms of the denominator of a generalized super Kac-Moody algebra. We also discuss the correspondence of this result with the counting of D-brane states.
Minimal N=4 topologically massive supergravity
Kuzenko, Sergei M.; Novak, Joseph; Sachs, Ivo
2017-03-01
Using the superconformal framework, we construct a new off-shell model for N=4 topologically massive supergravity which is minimal in the sense that it makes use of a single compensating vector multiplet and involves no free parameter. As such, it provides a counterexample to the common lore that two compensating multiplets are required within the conformal approach to supergravity with eight supercharges in diverse dimensions. This theory is an off-shell N=4 supersymmetric extension of chiral gravity. All of its solutions correspond to non-conformally flat superspaces. Its maximally supersymmetric solutions include the so-called critical (4,0) anti-de Sitter superspace introduced in [25], and well as warped critical (4,0) anti-de Sitter superspaces. We also propose a dual formulation for the theory in which the vector multiplet is replaced with an off-shell hypermultiplet. Upon elimination of the auxiliary fields belonging to the hypermultiplet and imposing certain gauge conditions, the dual action reduces to the one introduced in [20].
INTERACTIONS OF THE INFRARED BUBBLE N4 WITH ITS SURROUNDINGS
Energy Technology Data Exchange (ETDEWEB)
Liu, Hong-Li; Li, Jin-Zeng; Yuan, Jing-Hua; Huang, Maohai; Huang, Ya-Fang; Zhang, Si-Ju [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Wu, Yuefang [Department of Astronomy, Peking University, 100871 Beijing (China); Liu, Tie [Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon, 305-348 (Korea, Republic of); Dubner, G.; Paron, S.; Ortega, M. E. [1Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA), CC 67, Suc. 28, 1428 Buenos Aires (Argentina); Molinari, Sergio [Istituto di Astrofisica e Planetologia Spaziali—IAPS, Istituto Nazionale di Astrofisica—INAF, via Fosso del Cavaliere 100, I-00133 Roma (Italy); Zavagno, Annie; Samal, Manash R., E-mail: hlliu@nao.cas.cn [Aix Marseille Universit, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France)
2016-02-10
The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with H ii regions have been considered to be good samples for investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the H ii region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 × 10{sup 22} cm{sup −2}, mean volume density of about 4.4 × 10{sup 4} cm{sup −3}, and a mean mass of 320 M{sub ⊙}. In addition, from PAH emission seen at 8 μm, free–free emission detected at 20 cm, and a probability density function in special regions, we could identify clear signatures of the influence of the H ii region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source.
Minimal $\\cal N=4$ topologically massive supergravity
Kuzenko, Sergei M; Sachs, Ivo
2016-01-01
Using the superconformal framework, we construct a new off-shell model for topologically massive $\\cal N=4$ supergravity which is minimal in the sense that it makes use of a single compensating vector multiplet. Our theory provides a counterexample to the common lore that two compensating multiplets are required within the conformal approach to supergravity with eight supercharges in diverse dimensions. All solutions in this theory correspond to non-conformally flat superspaces. Its maximally supersymmetric solutions include the so-called critical (4,0) anti-de Sitter superspace introduced in arXiv:1205.4622. Other maximally supersymmetric solutions describe warped critical (4,0) anti-de Sitter superspaces. We also propose a dual formulation for the theory in which the vector multiplet is replaced with an off-shell hypermultiplet. Upon elimination of the auxiliary fields belonging to the hypermultiplet and imposing certain gauge conditions, the dual action reduces to the one introduced in arXiv:1605.00103.
Morphology ofα-Si3N4 in Fe-Si3N4 prepared via flash combustion
Institute of Scientific and Technical Information of China (English)
Bin Li; Jun-hong Chen; Jin-dong Su; Ming-wei Yan; Jia-lin Sun; Yong Li
2015-01-01
The state and formation mechanism ofα-Si3N4 in Fe–Si3N4 prepared by flash combustion were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate thatα-Si3N4 crystals exist only in the Fe–Si3N4 dense areas. When FeSi75 particles react with N2, which generates substantial heat, a large number of Si solid particles evaporate. The prod-uct between Si gas and N2 is a mixture ofα-Si3N4 andβ-Si3N4. At the later stage of the flash combustion process,α-Si3N4 crystals dissolve and reprecipitate asβ-Si3N4 and theβ-Si3N4 crystals grow outward from the dense areas in the product pool. As the temperature decreases, the α-Si3N4 crystals cool before transforming into β-Si3N4 crystals in the dense areas of Fe–Si3N4. The phase composition of flash-combustion-synthesized Fe–Si3N4 is controllable through manipulation of the gas-phase reaction in the early stage and theα→βtrans-formation in the later stage.
Morphology of α-Si3N4 in Fe-Si3N4 prepared via flash combustion
Li, Bin; Chen, Jun-hong; Su, Jin-dong; Yan, Ming-wei; Sun, Jia-lin; Li, Yong
2015-12-01
The state and formation mechanism of α-Si3N4 in Fe-Si3N4 prepared by flash combustion were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that α-Si3N4 crystals exist only in the Fe-Si3N4 dense areas. When FeSi75 particles react with N2, which generates substantial heat, a large number of Si solid particles evaporate. The product between Si gas and N2 is a mixture of α-Si3N4 and β-Si3N4. At the later stage of the flash combustion process, α-Si3N4 crystals dissolve and reprecipitate as β-Si3N4 and the β-Si3N4 crystals grow outward from the dense areas in the product pool. As the temperature decreases, the α-Si3N4 crystals cool before transforming into β-Si3N4 crystals in the dense areas of Fe-Si3N4. The phase composition of flash-combustion-synthesized Fe-Si3N4 is controllable through manipulation of the gas-phase reaction in the early stage and the α→β transformation in the later stage.
Superconformal Chern-Simons-matter theories in N =4 superspace
Kuzenko, Sergei M.; Samsonov, Igor B.
2015-11-01
In three dimensions, every known N =4 supermultiplet has an off-shell completion. However, there is no off-shell N =4 formulation for the known extended superconformal Chern-Simons (CS) theories with eight and more supercharges. To achieve a better understanding of this issue, we provide N =4 superfield realizations for the equations of motion which correspond to various N =4 and N =6 superconformal CS theories, including the Gaiotto-Witten theory and the Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. These superfield realizations demonstrate that the superconformal CS theories with N ≥4 (except for the Gaiotto-Witten theory) require a reducible long N =4 vector multiplet, from which the standard left and right N =4 vector multiplets are obtained by constraining the field strength to be either self-dual or antiself-dual. Such a long multiplet naturally originates upon reduction of any off-shell N >4 vector multiplet to N =4 superspace. For the long N =4 vector multiplet we develop a prepotential formulation. It makes use of two prepotentials being subject to the constraint which defines the so-called hybrid projective multiplets introduced in the framework of N =4 supergravity-matter systems in arXiv:1101.4013. We also couple N =4 superconformal CS theories to N =4 conformal supergravity.
Competing fatigue mechanisms in Nickel-base superalloy Rene 88DT
Chang, Paul N.
Nickel base superalloys exhibit superior high temperature mechanical properties required for aircraft engine components. It has been known that the processing of these alloys by the powder metallurgy route introduces inclusions inside the material. The presence of such inclusions often leads to competing failure modes in fatigue that is described by a step-wise or two distinct S-N curves involving both the surface and internally-initiated cracks, resulting in large uncertainties of fatigue life. A clear understanding of such behavior is yet to be established. The principal objective of this research is to examine the effect of inclusions on the extent of fatigue failure competition from surface and internal initiators at two different specimen test volumes. Experimental fatigue testing has been performed to explore how the presence of inclusions affects the competing fatigue failure modes. In addition, how the competing failure modes will behave with changes in the specimen size was also studied. Two groups of material each with two different specimen sizes were used in this study. It has been shown that the two crack initiation mechanisms occurred in the small unseeded Rene 88DT specimens tested at 650ºC over the stress range tested. Additionally, the fatigue lives were reduced with increase in specimen volume. All fatigue failures in seeded material occurred due to crack initiations from the seeded inclusions. In the fatigue life of seeded material, two competing and separate S-N curves were found in small test volume, whereas, in the large test volume, the regions were separated by a "step" in S-N curve. It has been found that the largest inclusion size observed in metallographic surfaces was smaller than the size determined from the fatigue failure origin. An analysis method based on extreme value statistics developed by Murakami was used to predict the largest size of inclusion in the test volume. The results of this study clearly show that competition for
SEM in-situ investigation on fatigue cracking behavior of P/M Rene95 alloy with surface inclusions
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The low-cycle fatigue behavior of powder metallurgy Rene95 alloy containing surface inclusions was investigated by in-situ observation with scanning electron microscopy (SEM). The process of fatigue crack initiation and early stage of propagation behavior indicates that fatigue crack mainly occurs at the interface between the inclusion and the matrix. The effect of inclusion on the fatigue crack initiation and the early stage of crack growth was very obvious. The fatigue crack growth path in the matrix is similar to the shape of inclusion made on the basis of fatigue fracture image analysis. The empiric relation between the surface and inside crack growth length, near a surface inclusion, can be expressed. Therefore, the fatigue crack growth rate or life of P/M Rene95 alloy including the inclusions can be evaluated on the basis of the measurable surface crack length parameter. In addition, the effect of two inclusions on the fatigue crack initiation behavior was investigated by the in-situ observation with SEM.
Perturbative and Non-Perturbative Partial Supersymmetry Breaking $N=4 \\to N=2 \\to N=1$
Kiritsis, Elias B
1997-01-01
We show the existence of a supersymmetry breaking mechanism in string theory, where N=4 supersymmetry is broken spontaneously to N=2 and N=1 with moduli dependent gravitino masses. The spectrum of the spontaneously broken theory with lower supersymmetry is in one-to-one correspondence with the spectrum of the heterotic N=4 string. The mass splitting of the N=4 spectrum depends on the compactification moduli as well as the three R-symmetry charges. In the large moduli limit a restoration of the N=4 supersymmetry is obtained. As expected the graviphotons and some of the gauge bosons become massive in N=1 vacua. At some special points of the moduli space some of the N=4 states with non-zero winding numbers and with spin 0 and {1/2} become massless chiral superfields of the unbroken N=1 supersymmetry. Such vaccua have a dual type II description, in which there are magnetically charged states with spin 0 and {1/2} that become massless. The heterotic-type II duality suggests some novel non-perturbative transitions ...
Gas-Pressure Sintering of β-Si3N4 and α-Si3N4 with β-Si3N4 Addition%β-Si3N4及添加β-Si3N4的α-Si3N4的气氛加压烧结
Institute of Scientific and Technical Information of China (English)
张宝林; 庄汉锐; 罗新宇; 李文兰
1999-01-01
介绍了β-Si3N4及添加β-Si3N4的α-Si3N4的气氛加压烧结,β-Si3N4在GPS中具有不低于α-Si3N4的烧结活性,而且陶瓷显微结构更容易调节.由GPS β-Si3N4制备的陶瓷材料晶粒比较均匀,具有较高的力学性能,尤其是高的韦泊模数.添加于α-Si3N4中的β-Si3N4对陶瓷材料显微结构具有明显的调控作用.
N=4 Supersymmetric Yang-Mills Theory on a Kaehler Surface
Dijkgraaf, R; Schroers, B J
1998-01-01
We study N=4 supersymmetric Yang-Mills theory on a Kaehler manifold with $b_2^+ \\geq 3$. Adding suitable perturbations we show that the partition function of the N=4 theory is the sum of contributions from two branches: (i) instantons, (ii) a special class of Seiberg-Witten monopoles. We determine the partition function for the theories with gauge group SU(2) and SO(3), using S-duality. This leads us to a formula for the Euler characteristic of the moduli space of instantons.
Novel N4 Bacteriophages Prevail in the Cold Biosphere
Zhan, Yuanchao; Buchan, Alison
2015-01-01
Coliphage N4 is a lytic bacteriophage discovered nearly half a century ago, and it was considered to be a “genetic orphan” until very recently, when several additional N4-like phages were discovered to infect nonenteric bacterial hosts. Interest in this genus of phages is stimulated by their unique genetic features and propagation strategies. To better understand the ecology of N4-like phages, we investigated the diversity and geographic patterns of N4-like phages by examining 56 Chesapeake Bay viral communities, using a PCR-clone library approach targeting a diagnostic N4-like DNA polymerase gene. Many new lineages of N4-like phages were found in the bay, and their genotypes shift from the lower to the upper bay. Interestingly, signature sequences of N4-like phages were recovered only from winter month samples, when water temperatures were below 4°C. An analysis of existing metagenomic libraries from various aquatic environments supports the hypothesis that N4-like phages are most prolific in colder waters. In particular, a high number of N4-like phages were detected in Organic Lake, Antarctica, a cold and hypersaline system. The prevalence of N4-like phages in the cold biosphere suggests these viruses possess yet-to-be-determined mechanisms that facilitate lytic infections under cold conditions. PMID:26025897
Novel N4 Bacteriophages Prevail in the Cold Biosphere.
Zhan, Yuanchao; Buchan, Alison; Chen, Feng
2015-08-01
Coliphage N4 is a lytic bacteriophage discovered nearly half a century ago, and it was considered to be a "genetic orphan" until very recently, when several additional N4-like phages were discovered to infect nonenteric bacterial hosts. Interest in this genus of phages is stimulated by their unique genetic features and propagation strategies. To better understand the ecology of N4-like phages, we investigated the diversity and geographic patterns of N4-like phages by examining 56 Chesapeake Bay viral communities, using a PCR-clone library approach targeting a diagnostic N4-like DNA polymerase gene. Many new lineages of N4-like phages were found in the bay, and their genotypes shift from the lower to the upper bay. Interestingly, signature sequences of N4-like phages were recovered only from winter month samples, when water temperatures were below 4°C. An analysis of existing metagenomic libraries from various aquatic environments supports the hypothesis that N4-like phages are most prolific in colder waters. In particular, a high number of N4-like phages were detected in Organic Lake, Antarctica, a cold and hypersaline system. The prevalence of N4-like phages in the cold biosphere suggests these viruses possess yet-to-be-determined mechanisms that facilitate lytic infections under cold conditions. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Valner, René, 1972-
2001-01-01
Pärnu Linnavalitsuse ja Eesti Kunstiakadeemia korraldatud arhitektuuri ja kohamarketingi Riveside Workshop'ist 18.-28. VI 2001. a. Pärnus. Juhendajad: Viini arhitektuuribüroo Rataplan arhitektid Gerhard Huber ja Susanne Höhndorf, eesti arhitektid Siiri Vallner, Rene Valner ja Indrek Peil
Valner, René, 1972-
2001-01-01
Pärnu Linnavalitsuse ja Eesti Kunstiakadeemia korraldatud arhitektuuri ja kohamarketingi Riveside Workshop'ist 18.-28. VI 2001. a. Pärnus. Juhendajad: Viini arhitektuuribüroo Rataplan arhitektid Gerhard Huber ja Susanne Höhndorf, eesti arhitektid Siiri Vallner, Rene Valner ja Indrek Peil
Energy Technology Data Exchange (ETDEWEB)
Angelelli, G.; Stabile Ianora, A.A.; Scardapane, A.; Rotondo, A. [Bari Univ., Bari (Italy). Ist. di Radiologia
2000-02-01
anni) e di 20 soggetti sani (12 maschi, 8 femmine, eta' media: 58 anni). Lo studio TC e' stato eseguito con tecnica spirale trifasica; i dati acquisiti sono stati successivamente trasferiti su una stazione di lavoro ed analizzati con il software applicativo Multiplanar Reconstruction (MPR) che ha permesso ricostruzioni secondo piani assiale e coronale. Si sono considerati i parametri morfometrici (presenza di calcificazioni parenchimali e/o vascolari, dimensioni del rene nelle sezioni assiale e longitudinale, superficie renale in sezione longitudinale, rapporto cortico-midollare), densitometrici (densita' renale senza mdc, densita' della corticale e della midollare nella fase arteriosa, densita' nella fase tubulonefrografica) e funzionali (omogeneo incremento di densita' in fase tubulonefrografica e presenza della fase escretoria) e confrontato i valori ottenuti nei vari sottogruppi di pazienti diabetici e nel gruppo di controllo. Le dimensioni renali nella sezione assiale sono risultate significativamente inferiori (p<0,05) nei pazienti con durata minore del diabete presentavano reni significativamente piu' grandi nella sezione assiale rispetto agli altri gruppi; tali dimensioni si riducevano significativamente nel gruppo con durata piu' lunga della malattia. La valutazione delle dimensioni renali e soprattutto della riduzione della densita' della corticale renale nella fase arteriosa puo' essere utile come indice di nefropatia nei pazienti diabetici non insulino dipendenti. Ulteriori ricerche sono tuttavia necessarie per raggiungere validi protocolli utilizzabili nella pratica quotidiana.
Theoretical Hardness of Zr3N4 Films
Institute of Scientific and Technical Information of China (English)
GAO Fa-Ming
2011-01-01
The structures,energetics and properties for orthohombic Zr3N4 and cubic Zr3N4 are calculated by first-principles calculations.The agreement between the predicted properties with available experimental data is excellent.The cubic phase has a smaller volume (by 11.2％) and a slightly higher total energy (by 0.3eV/pair),in comparison to the orthohombic phase.We elucidate the effects of stress on hardness of Zr3N4 films.The results show that the hardness of c-Zr3N4 increases up to 23％ as the stress increases to 15 GPa.
Rodrigues, Vinola Z; Preema, C P; Naveen, S; Lokanath, N K; Suchetan, P A
2015-11-01
Crystal structures of two N-(ar-yl)aryl-sulfonamides, namely, 4-meth-oxy-N-(4-methyl-phen-yl)benzene-sulfonamide, C14H15NO3S, (I), and N-(4-fluoro-phen-yl)-4-meth-oxy-benzene-sulfonamide, C13H12FNO3S, (II), were determined and analyzed. In (I), the benzene-sulfonamide ring is disordered over two orientations, in a 0.516 (7):0.484 (7) ratio, which are inclined to each other at 28.0 (1)°. In (I), the major component of the sulfonyl benzene ring and the aniline ring form a dihedral angle of 63.36 (19)°, while in (II), the planes of the two benzene rings form a dihedral angle of 44.26 (13)°. In the crystal structure of (I), N-H⋯O hydrogen bonds form infinite C(4) chains extended in [010], and inter-molecular C-H⋯πar-yl inter-actions link these chains into layers parallel to the ab plane. The crystal structure of (II) features N-H⋯O hydrogen bonds forming infinite one dimensional C(4) chains along [001]. Further, a pair of C-H⋯O inter-molecular inter-actions consolidate the crystal packing of (II) into a three-dimensional supra-molecular architecture.
Mechanisms of deformation and fracture in high temperature low cycle fatigue of Rene 80 and IN 100
Romanoski, G. R., Jr.
1982-01-01
Specimens tested for the AGARD strain range partitioning program were investigated. Rene 80 and IN 100 were tested in air and in vacuum; at 871 C, 925 C, and 1000 C; and in the coated and uncoated condition. The specimens exhibited a multiplicity of high-temperature low-cycle fatigue damage. Observations of the various forms of damage were consistent with material and testing conditions and were generally in agreement with previous studies. In every case observations support a contention that failure occurs at a particular combination of crack length and maximum stress. A failure criterion which is applicable in the regime of testing studied is presented. The predictive capabilities of this criterion are straight forward.
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A special designed experiment was conducted for observing cr ack initiation and growth in P/M Rene95 superalloy under tension-tensi on loading by self-made SEM in-situ fatigue loading stag. Several alum ina inclusion particles exposed at the specimen surface were observed carefully. During fatigue test inclusions led to cracks initiation. Th e cracks can be formed by two mechanisms. Generally, the cracks nuclea ted at the interface between inclusion and matrix. Sometimes, cracks w ere also formed inside the inclusion. As the increase of cycles, some cracks at the interface between inclusion and matrix broadened and pro pagated along the direction about 45€?to the loading axis. On the oth er hand, the cracks inside the inclusion propagated in the inclusion a nd towards matrix.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The flow behavior of Rene 95 PM alloy was studied from 1050 to 1150℃with strain rate of 1€?10, 1€?10, 1€?10 and 1. At a given temperature and strain rate, flow curves exhibit a peak followed by flow softening up to a steady state. Moreover, at constant strain, flow stress increases with increasing strain rate and decreasing temperature. An equation relating hyperbolic sine of flow stress to hot working parameters, such as strain, strain rate and temperature, was established by using multiple nonlinear regression method. A very good agreement was found between predicted and experimental flow stress in all the strain range investigated. Application of the constitutive equation in predicting forming loads and flow behavior and temperature distribution in both upper and lower dies in an isothermal forging process of turbine disk of large dimension (about 630mm) by means of a finite element code was systematically analyzed.
Chachamics, Grigorios; Vera, Agustín Sabio
2011-01-01
Ratios of azimuthal angle correlations for Mueller-Navelet jets are compared in QCD and N = 4 SYM. Such observables are well suited to study the effects of Moebius invariance in the Regge limit. The role of the renormalization prescription and the size of conformal contributions is addressed, showing that the BLM procedure best reproduces the N = 4 SYM results.
Characterization of Si3N4 powders in aqueous dispersions
Directory of Open Access Journals (Sweden)
Castanho S. Mello
1998-01-01
Full Text Available alpha- Si3N4 can easily oxidize when exposed in air atmosphere or other oxidizing environment. The chemistry of Si3N4 particle surfaces can change by different synthesis routes and also by subsequent processing steps. To avoid this oxidation is a challenge when Si3N4 powder is shaped by slip casting process from aqueous suspension. This study shows the variations on Si3N4 powder surface after slip casting process using x-ray photoelectron spectroscopy (XPS and high resolution transmission electron microscopy (HTEM on the green compacts. The results show that the dispersant used during the preparation of the slurry can reduce the level of oxidation of the Si3N4 particles when processing in aqueous solutions.
Microstructure of Si3 N4/Si3 N4 joint brazed using Cu-Pd-Ti alloy filler
Institute of Scientific and Technical Information of China (English)
ZHANG Jie(张杰); N. Massaki; ZHOU Yu(周玉)
2004-01-01
Microstructure of the Si3 N4/Si3 N4 joint brazed using an active filler of Cu-Pd-Ti alloy was analyzed by means of EPMA and XRD. The results indicate that a perfect Si3 N4/Si3 N4 joint is obtained by using an active filler of Cu76.5Pd8.5Ti15 alloy with brazing temperature, pressure and holding time of 1 373 - 1 473 K, 2× 10-3 MPa and 1.8 ks, respectively. The filler alloy in the joint is a Cu-Pd solution containing reactant of TiN, PdTiSi and Pd2Si.The interface between the filler alloy and Si3 N4 ceramic is composed of TiN reactant.
Synthesis and characterization of C3N4 hard films
Institute of Scientific and Technical Information of China (English)
顾有松; 张永平; 常香荣; 田中卓; 陈难先; 时东霞; 张秀芳; 袁磊
2000-01-01
C3N4 films have been synthesized on both Si and R substrates by microwave plasma chemical vapor deposition (MPCVD) method. X-ray spectra were calculated for single phase α-C3N4 and p-C3N4 respectively. The experimental X-ray spectra of films deposited on both Si and R substrates showed all the strong peaks of α-C3N4 and β-C3N4 so the films are mixtures of α-C3N4 and β-C3N4. The N/C atomic ratio is in the range of 1.0-2.0. X-ray photoelectron spectroscopy (XPS) analysis indicated that the binding energy of C 1s and N 1s are 286.2 eV and 399.5 eV respectively, corresponding to polarized C-N bond. Fourier transform infrared absorption (FT-IR) and Raman spectra support the existence of C-N covalent bond in the films. Nano-indentation hardness tests showed that the bulk modulus of a film deposited on R is up to 349 GPa.
CO observation of the Galactic bubble N4
Li, Junyu; Liu, Yao; Wang, Yuan
2013-01-01
We presented a study on the Galactic bubble N4 using the 13.7 m millimeter telescope of Purple Mountain Observatory at the Qinghai Station. N4 is one of the science demonstration regions for the Milky Way Imaging Scroll Painting (WMISP). Simultaneous observations of $^{12}$CO (J = 1$-$0), $^{13}$CO (J = 1$-$0) and C$^{18}$O (J = 1$-$0) line emission towards N4 were carried out. We analyzed the spectral profile and the distribution of the molecular gas. Morphologically, the CO emissions correlate well with Spitzer IRAC 8.0 $\\mu$m emission. The channel map and velocity-position diagram shows that N4 is more likely an inclined expanding ring than a spherical bubble. We calculated the physical parameters of N4 including the mass, size, column density and optical depth. Some massive star candidates were discovered in the region of N4 using (J, J$-$H) color-magnitude diagram. We found an energy source candidate for the expansion of N4, a massive star with a mass of ${\\sim} 15\\,M_{\\odot}$ and an age of $\\sim$ 1 Myr....
N = (4,4 Supersymmetry and T-Duality
Directory of Open Access Journals (Sweden)
Malin Göteman
2012-10-01
Full Text Available A sigma model with four-dimensional target space parametrized by chiral and twisted chiral N =(2,2 superfields can be extended to N =(4,4 supersymmetry off-shell, but this is not true for a model of semichiral fields, where the N = (4,4 supersymmetry can only be realized on-shell. The two models can be related to each other by T-duality. In this paper we perform a duality transformation from a chiral and twisted chiral model with off-shell N = (4,4 supersymmetry to a semichiral model. We find that additional non-linear terms must be added to the original transformations to obtain a semichiral model with N =(4,4 supersymmetry, and that the algebra closes on-shell as a direct consequence of the T-duality.
Wang, Huimin; Li, Xingxing; Yang, Jinlong
2016-07-01
Water-splitting photocatalysts with good energy efficiency are highly desirable, among which metal-free graphitic carbon nitride (g-C3 N4 ) is considered to be very promising and has been intensively studied in recent years. However, its practical application is hindered by the relatively low efficiencies of visible-light absorption and electron-hole separation. Herein, based on first-principles calculations, it is predicted that, by forming nanocomposites with another carbon nitride (C2 N), the energy efficiency of g-C3 N4 can be significantly improved. On one hand, C2 N has a wide, strong optical absorption in the visible-light region, which acts as a photosensitizer and enhances the photoabsorption efficiency of the composite photocatalyst. On the other hand, C2 N forms a type II heterojunction with g-C3 N4 , which leads to efficient separation of photogenerated electron-hole pairs through the chemical potential difference between the two components. These results provide a potential route to achieve highly efficient metal-free photocatalysts for water splitting.
Thermal expansion of spinel-type Si3N4
DEFF Research Database (Denmark)
Paszkowics, W.; Minkikayev, R.; Piszora, P.
2004-01-01
The lattice parameter and thermal expansion coefficient (TEC) for the spinel-type Si3N4 phase prepared under high-pressure and high-temperature conditions are determined for 14 K......The lattice parameter and thermal expansion coefficient (TEC) for the spinel-type Si3N4 phase prepared under high-pressure and high-temperature conditions are determined for 14 K...
2005-01-01
Kuni 2. X Eesti Tarbekunsti- ja Disainimuuseumis avatud rahvusvahelisest köitekunstinäitusest "Scripta manent III. Maailma parim asi". Köitekunstist kõnelesid näituse korralduskomitee liikmed. Žürii koosseis. Kuldraamatud pälvisid Külli Grünbach-Sein, Kaire Olt ja Jaana Päeva. Näituse korralduskomitees ka Tulvi-Hanneli Turo ja Rene Haljasmäe TLÜARist
2005-01-01
Kuni 2. X Eesti Tarbekunsti- ja Disainimuuseumis avatud rahvusvahelisest köitekunstinäitusest "Scripta manent III. Maailma parim asi". Köitekunstist kõnelesid näituse korralduskomitee liikmed. Žürii koosseis. Kuldraamatud pälvisid Külli Grünbach-Sein, Kaire Olt ja Jaana Päeva. Näituse korralduskomitees ka Tulvi-Hanneli Turo ja Rene Haljasmäe TLÜARist
Täna ketšupivestern, homme kunstfilm! / Rene Vilbre
Vilbre, Renė, 1970-
2002-01-01
Seoses Theodor Lutsu sünniaastapäevaga Palamusel toimunud seitmendatel filmipäevadel leidis aset ka 5. lühifilmide avatud konkurss. Konkursi võidutöödest : Fraktsioon Õ mängufilmist "Tapja õllejogurti seiklused", Kullar Viimse dokumentaalfilmist "Kuhu lähed", Daniel Müntineni alias Dan Leadi animafilmist "Punapäine päikeseloojang" ning telerežii tudengi Heilika Võsu eksperimentaalfilmist "Hüsteerik"
Yanovska, Elina; Savchenko, Irina; Sternik, Dariusz; Kychkiruk, Olga; Ol'khovik, Lidiya; Buriachenko, Iana
2017-04-01
In situ immobilization of poly[ N-(4-carboxyphenyl)methacrylamide] has been performed on silica gel surface. Infrared (IR) and mass spectroscopies as well as thermogravimetry (TG) analysis have been used to elucidate the structure of immobilized polymer. An adsorption capacity of the synthesized composite towards Cu(II), Pb(II), Mn(II), Fe(III), Co(II), and Ni(II) ions has been estimated. Adsorption activity to microquantities of Pb(II), Cu(II), and Ni(II) in a neutral aqueous medium has been observed.
Theoretical Analysis of Structures of Ga4N4 Clusters
Institute of Scientific and Technical Information of China (English)
宋斌; 曹培林
2003-01-01
The structures and energies of a Ga4N4 cluster have been calculated using a full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO MD) method. We obtained twenty-four structures for a Ga4N4 cluster. The most stable structure we obtained is a Cs three-dimensional structure, the energy of which is lower than that of the C2v symmetry structure proposed by Kandalam et al. [J. Phys. Chem. B 106 (2002) 1945] The calculated results show that the isomer with an N3 subunit is preferred, supporting the previous result made by Kandalam et al.We found that the most stable structure of Ga4N4 clusters presented semiconductor-like properties through the calculation of the density of states.
N= 4 Supersymmetric Quantum Mechanical Model: Novel Symmetries
Krishna, S
2016-01-01
We discuss a set of novel discrete symmetry transformations of the N = 4 supersymmetric quantum mechanical model of a charged particle moving on a sphere in the background of Dirac magnetic monopole. The usual five continuous symmetries (and their conserved Noether charges) and two discrete symmetries together provide the physical realizations of the de Rham cohomological operators of differential geometry. We have also exploited the supervariable approach to derive the nilpotent N = 4 SUSY transformations and provided the geometrical interpretation in the language of translational generators along the Grassmannian directions onto (1, 4)-dimensional supermanifold.
Greskovich, C.; Yeh, H. C.
1983-01-01
The effects of small changes in the concentration of an oxygen content densification aid on the room temperature microhardness of hot isostatically pressed and sintered beta-Si3N4 ceramics are studied. The compositions studied were Si3N4 containing 7 wt. pct BeSiN2, a fixed nonoxide densification aid, and 1.9-3.7 wt. pct oxygen as a second, variable densification aid. A proportional relationship between high density and high oxygen content, regardless of heat treatment type, is noted.
[15]aneN4S: Synthesis, Thermodynamic Studies and Potential Applications in Chelation Therapy
Directory of Open Access Journals (Sweden)
Nuno Torres
2014-01-01
Full Text Available The purpose of this work was to synthesize and characterize the thiatetraaza macrocycle 1-thia-4,7,10,13-tetraazacyclopentadecane ([15]aneN4S. Its acid-base behaviour was studied by potentiometry at 25 °C and ionic strength 0.10 M in KNO3. The protonation sequence of this ligand was investigated by 1H-NMR titration that also allowed the determination of protonation constants in D2O. Binding studies of [15]aneN4S with Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ metal ions were further performed under the same experimental conditions. The results demonstrated that this compound has a higher selectivity and thermodynamic stability for Hg2+ and Cu2+, followed by Ni2+. The UV-visible-near IR spectroscopies and magnetic moment data for the Co(II and Ni(II complexes indicated a tetragonal distorted coordination geometry for both metal centres. The value of magnetic moment and the X-band EPR spectra of the Cu(II complex are consistent with a distorted square pyramidal geometry.
Phase structure of lattice N=4 super Yang-Mills
DEFF Research Database (Denmark)
Catterall, Simon; Damgaard, Poul H.; DeGrand, Thomas;
2012-01-01
We make a first study of the phase diagram of four-dimensional N = 4 super Yang-Mills theory regulated on a space-time lattice. The lattice formulation we employ is both gauge invariant and retains at all lattice spacings one exactly preserved supersymmetry charge. Our numerical results are consi...
S-duality in N=4 Yang-Mills theories
Girardello, L; Porrati, Massimo; Zaffaroni, A
1995-01-01
Evidence in favor of SL(2,Z) S-duality in N=4 supersymmetric Yang-Mills theories in four dimensions and with general compact, simple gauge groups is presented. (Contribution to the Proceedings of the Strings '95 conference, March 13-18, 1995, USC, and the Proceedings of the Trieste Conference on S-Duality and Mirror Symmetry June 5-9, 1995.)
Dijet Production in QCD and N=4 SYM
Chachamis, Grigorios; Vera, Agustín Sabio
2012-01-01
We investigate dijet production at large rapidity separation in QCD and N = 4 SYM, showing that both theories give similar predictions for observables only sensitive to conformal properties of the scattering such as ratios of azimuthal angle correlations. Renormalization prescriptions are important in this comparison.
Eigenvalue spectrum of lattice N=4 super Yang-Mills
Weir, D.; Catterall, S.; Mehta, D. B.
We present preliminary results for the eigenvalue spectrum of four-dimensional ${\\cal N}=4$ super Yang-Mills theory on the lattice. In particular, by studying the the spectral density a measurement of the anomalous dimension is made and found to be consistent with zero.
Syntheses of DNA Duplexes That Contain a N4C-alkyl-N4C Interstrand Cross-Link
Miller, Paul S.
2011-01-01
A simple procedure is described for preparing short DNA duplexes that contain a single N4C-alkyl-N4C interstrand cross-link. The synthesis is carried out on an automated DNA synthesizer using standard phosphoramidite chemistry. The cross-link is introduced during the synthesis of the duplex. The method can be used to prepare mg quantities of cross-linked duplexes suitable for physical studies and for the preparation of larger DNA molecules that can be used as substrates to study DNA repair in whole cell extracts and in living cells in culture. PMID:21400705
Directory of Open Access Journals (Sweden)
Mirabdullah Seyed Sadjadi
2008-08-01
Full Text Available The title complex, [Cd2(NO34(C24H16N6(CH4O2], displays a centrosymmetric dinuclear structure, in which the 2,3,5,6-tetra-2-pyridinylpyrazine (tppz ligand links two Cd ions separated by 7.323 (4 Å. Each CdII center is seven-coordinated by three N-atom donors of tppz in one plane, by two O atoms nearly normal to this plane, and by two O atoms 0.393 (3 and 0.488 (3 Å from that plane. The two CdII ions are above and below the plane of the pyrazine ring of the tppz ligand, oriented with respect to the pyridine rings at dihedral angles of 38.01 (3 and 31.90 (3°. The dihedral angle between the two pyridine rings is 41.11 (3°. In the crystal structure, intermolecular O—H...O hydrogen bonds link the molecules.
Directory of Open Access Journals (Sweden)
Anatolii Malivskyi
2015-12-01
Full Text Available Purpose. Based on the understanding of The New Time philosophy as a response to the challenges of the era in relation to the construction of an objective picture of the world and the self-creation of man, to analyze the main options for evaluating the ambivalence of the basic intention of the philosophy of Descartes in the research literature and to clarify the nature of ambiguity. To justify the dominant nature of anthropological intention in the text of the «Rules for Guiding the Mind in Searching for the Truth». Novelty. The nature of the ambivalence of the basic intention of the text of the "Rules" is clarified as a form of two basic existences, opposite to the New Time, namely the query on the objectivity of scientific knowledge and inquiry in anthropology as a cornerstone of philosophy. The author of the article proves the domination of anthropological component of the text «The Rules» in front of scientific knowledge. Conclusions. The main manifestations of ambivalence of basic directivity of philosophizing of Rene Descartes to construction of an objective picture of the world and self-creation of person were described. The determining influence on the process of the establishment of basic intention of the specificity of the experience of mathematical knowledge and Plato’s and Aristotle’s tradition of philosophizing for the first, and of personal tradition of Christianity in the second place was emphasized. In the reference to the text «The Rules» of Descartes the ambiguity of the basic direction was argued, the nature and domination of the anthropological intention were justified.
State-selective electron-capture measurements for N4+-H and N4+-H-2 collisions
Bliek, FW; Woestenenk, GR; Hoekstra, R; Morgenstern, R
1998-01-01
State-selective electron-capture cross-section measurements in the energy range between 1 and 4 keV/amu are reported for collisions between N4+ ions and atomic and molecular hydrogen. The cross sections are measured in a crossed-beam experiment by means of photon emission spectroscopy. The singlet a
Preface: Graphene and C3N4-based photocatalysts
Yu, Jiaguo; Jaroniec, Mietek
2015-12-01
In recent years, 2D layered materials including graphene and g-C3N4 have attracted more and more attention in the field of photocatalysis and have become the research hotspots due to their broad applications in energy and environment-related areas. A critical appraisal of recent developments related to these important materials was the main theme of the 1st International Workshop on Graphene and C3N4-based Photocatalysts (IWGCP) held at the Wuhan University of Technology, Wuhan, China on June 5-8, 2015. This workshop was jointly organized by Wuhan University of Technology, Jianghan University and Changsha University, China. More than 140 scientists from four continents (Asia, America, Australia and Europe) participated in this workshop, the agenda of which included 8 plenary lectures, 17 keynote lectures, 11 invited lectures, 6 oral presentations and 61 posters.
Integrability of Smooth Wilson Loops in N=4 Superspace
Beisert, Niklas; Plefka, Jan; Vergu, Cristian
2015-01-01
We perform a detailed study of the Yangian symmetry of smooth supersymmetric Maldacena-Wilson loops in planar N=4 super Yang-Mills theory. This hidden symmetry extends the global superconformal symmetry present for these observables. A gauge-covariant action of the Yangian generators on the Wilson line is established that generalizes previous constructions built upon path variations. Employing these generators the Yangian symmetry is proven for general paths in non-chiral N=4 superspace at the first perturbative order. The bi-local piece of the level-one generators requires the use of a regulator due to divergences in the coincidence limit. We perform regularization by point splitting in detail, thereby constructing additional local and boundary contributions as regularization for all level-one Yangian generators. Moreover, the Yangian algebra at level one is checked and compatibility with local kappa-symmetry is established. Finally, the consistency of the Yangian symmetry is shown to depend on two propertie...
The effect of microstructure, temperature, and hold-time on low-cycle fatigue of As HIP P/M Rene 95
Bashir, S.; Antolovich, S. D.
1984-01-01
The effects of microstructure, temperature, plastic strain range, and hold time on the low-cycle fatigue (LCF) life were studied for Rene 95, an important Ni base superalloy used in jet engine disks. It was shown that the life could be varied by approximately an order of magnitude at elevated temperatures by simple heat treatments. The life was largest for the microstructure that promoted the most homogeneous deformation mode. The results are explained using the concept of a synergistic interaction between the deformation mode and boundary oxidation.
The effect of microstructure, temperature, and hold-time on low-cycle fatigue of As HIP P/M Rene 95
Bashir, S.; Antolovich, S. D.
1984-01-01
The effects of microstructure, temperature, plastic strain range, and hold time on the low-cycle fatigue (LCF) life were studied for Rene 95, an important Ni base superalloy used in jet engine disks. It was shown that the life could be varied by approximately an order of magnitude at elevated temperatures by simple heat treatments. The life was largest for the microstructure that promoted the most homogeneous deformation mode. The results are explained using the concept of a synergistic interaction between the deformation mode and boundary oxidation.
Drag force in a charged N = 4 SYM plasma
Energy Technology Data Exchange (ETDEWEB)
Caceres, Elena [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico); Gueijosa, Alberto [Departamento de Fisica de Altas Energias, Instituto de Ciencias Nucleares, Universidad Autonoma de Mexico, Apdo. Postal 70-543, D.F. 04510 (Mexico)
2006-11-15
Following recent developments, we employ the AdS/CFT correspondence to determine the drag force exerted on an external quark that moves through an N = 4 super-Yang-Mills plasma with a non-zero R-charge density (or, equivalently, a non-zero chemical potential). We find that the drag force is larger than in the case where the plasma is neutral, but the dependence on the charge is non-monotonic.
Quark-anti-quark potential in N = 4 SYM
Gromov, Nikolay; Levkovich-Maslyuk, Fedor
2016-12-01
We construct a closed system of equations describing the quark-anti-quark potential at any coupling in planar N = 4 supersymmetric Yang-Mills theory. It is based on the Quantum Spectral Curve method supplemented with a novel type of asymptotics. We present a high precision numerical solution reproducing the classical and one-loop string predictions very accurately. We also analytically compute the first 7 nontrivial orders of the weak coupling expansion.
N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop
Bern, Z; Johansson, H
2011-01-01
We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of N >= 4 supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories.
Higher-Loop Integrability in N=4 Gauge Theory
Beisert, N
2004-01-01
The dilatation operator measures scaling dimensions of local operator in a conformal field theory. Algebraic methods of constructing the dilatation operator in four-dimensional N=4 gauge theory are reviewed. These led to the discovery of novel integrable spin chain models in the planar limit. Making use of Bethe ansaetze, a superficial discrepancy in the AdS/CFT correspondence was found, we discuss this issue and give a possible resolution.
N=2 vacua in electrically gauged N=4 supergravities
Energy Technology Data Exchange (ETDEWEB)
Horst, Christoph
2013-06-15
In this thesis we study N= 2 vacua in gauged N=4 supergravity theories in fourdimensional spacetime. Using the embedding tensor formalism that describes general consistent magnetic gaugings of an ungauged N=4 matter-coupled supergravity theory in a symplectic frame with SO(1,1) x SO(6,n) off-shell symmetry we formulate necessary conditions for partial supersymmetry breaking and find that the Killing spinor equations can be solved for the embedding tensor components. Subsequently, we show that the classification of theories that allow for vacua with partial supersymmetry amounts to solving a system of purely algebraic quadratic equations. Then, we restrict ourselves to the class of purely electric gaugings and explicitly construct a class of consistent super-Higgs mechanisms and study its properties. In particular, we find that the spectrum fills complete N=2 supermultiplets that are either massless or BPS. Furthermore, we demonstrate that (modulo an abelian Lie algebra) arbitrary unbroken gauge Lie algebras can be realized provided that the number of N=4 vector multiplets is sufficiently large. Finally, we compute the relevant terms of the effective action below the scale of partial supersymmetry breaking and argue that the special Kaehler manifold for the scalars of the N=2 vector multiplets has to be in the unique series of special Kaehler product manifolds.
N=4 superconformal Ward identities for correlation functions
Directory of Open Access Journals (Sweden)
A.V. Belitsky
2016-03-01
Full Text Available In this paper we study the four-point correlation function of the energy–momentum supermultiplet in theories with N=4 superconformal symmetry in four dimensions. We present a compact form of all component correlators as an invariant of a particular abelian subalgebra of the N=4 superconformal algebra. This invariant is unique up to a single function of the conformal cross-ratios which is fixed by comparison with the correlation function of the lowest half-BPS scalar operators. Our analysis is independent of the dynamics of a specific theory, in particular it is valid in N=4 super Yang–Mills theory for any value of the coupling constant. We discuss in great detail a subclass of component correlators, which is a crucial ingredient for the recent study of charge-flow correlations in conformal field theories. We compute the latter explicitly and elucidate the origin of the interesting relations among different types of flow correlations previously observed in arXiv:1309.1424.
New Results on N=4 SuperYang-Mills Theory
Baulieu, L; Baulieu, Laurent; Bossard, Guillaume
2005-01-01
The N=4 SuperYang--Mills theory is covariantly determined by a U(1) \\times SU(2) \\subset SL(2,R) \\times SU(2) internal symmetry and two scalar and one vector BRST topological symmetry operators. This determines an off-shell closed sector of N=4 SuperYang-Mills, with 6 generators, which is big enough to fully determine the theory, in a Lorentz covariant way. This reduced algebra derives from horizontality conditions in four dimensions. The horizontality conditions only depend on the geometry of the Yang-Mills fields. They also descend from a genuine horizontality condition in eight dimensions. In fact, the SL(2,R) symmetry is induced by a dimensional reduction from eight to seven dimensions, which establishes a ghost-antighost symmetry, while the SU(2) symmetry occurs by dimensional reduction from seven to four dimensions. When the four dimensional manifold is hyperKahler, one can perform a twist operation that defines the N=4 supersymmetry and its SL(2,H)\\sim SU(4) R-symmetry in flat space. (For defining a TQ...
Integrability in N=4 super Yang-Mills theory
Energy Technology Data Exchange (ETDEWEB)
Eden, B. [ITF and Spinoza Institute, University of Utrecht, Minnaertgebouw, Leuvenlaan 4, 3584 CE Utrecht (Netherlands)
2008-10-15
We use the Bethe ansatz to calculate the cusp anomalous dimension in planar N=4 super Yang-Mills theory as an exact function of the coupling constant. The calculation allows us to fix the remaining ambiguities in the integrable system describing the spectrum of operators/string energy levels in the AdS/CFT correspondence. The cusp anomalous dimension is not affected by finite size effects, which in general remain ill-understood. We suggest a method for computing the lowest example of an anomalous dimension modified by such corrections.
An N/4 fixed-point duality quantum search algorithm
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Here a fixed-point duality quantum search algorithm is proposed.This algorithm uses iteratively non-unitary operations and measurements to search an unsorted database.Once the marked item is found,the algorithm stops automatically.This algorithm uses a constant non-unitary operator,and requires N/4 steps on average(N is the number of data from the database) to locate the marked state.The implementation of this algorithm in a usual quantum computer is also demonstrated.
Non-unimodular reductions and N=4 gauged supergravities
Energy Technology Data Exchange (ETDEWEB)
Petropoulos, P.M. [Centre de Physique Theorique, Ecole Polytechnique, Palaiseau (France)
2008-08-05
We analyze the class of four-dimensional N=4 supergravities obtained by gauging the axionic shift and axionic rescaling symmetries. These theories are formulated with the machinery of embedding tensors and shown to be deducible from higher dimensions using a Scherk-Schwarz reduction with a twist by a non-compact symmetry. This allows to evade the usual unimodularity requirement and completes the dictionary between heterotic gaugings and fluxes, at least for the ''geometric sector''. (Abstract Copyright [2008], Wiley Periodicals, Inc.)
A Curious Truncation of N=4 Yang-Mills
Basu, A; Sethi, S; Basu, Anirban; Sethi, Savdeep
2004-01-01
The coupling constant dependence of correlation functions of BPS operators in N=4 Yang-Mills can be expressed in terms of integrated correlation functions. We approximate these integrated correlators by using a truncated OPE expansion. This leads to differential equations for the coupling dependence. When applied to a particular sixteen point correlator, the coupling dependence we find agrees with the corresponding amplitude computed via the AdS/CFT correspondence. We conjecture that this truncation becomes exact in the large N and large 't Hooft coupling limit.
A Note on Dual MHV Diagrams in N=4 SYM
Brandhuber, Andreas; Travaglini, Gabriele; Yang, Gang
2010-01-01
Recently a reformulation of the MHV diagram method in N=4 supersymmetric Yang-Mills theory in momentum twistor space was presented and was shown to be equivalent to the perturbative expansion of the expectation value of a supersymmetric Wilson loop in momentum twistor space. In this note we present related explicit Feynman rules in dual momentum space, which should have the interpretation of Wilson loop diagrams in dual momentum space. We show that these novel rules are completely equivalent to ordinary spacetime MHV rules and can be naturally viewed as their graph dual representation.
N=4 Multi-Particle Mechanics, WDVV Equation and Roots
Directory of Open Access Journals (Sweden)
Olaf Lechtenfeld
2011-03-01
Full Text Available We review the relation of N=4 superconformal multi-particle models on the real line to the WDVV equation and an associated linear equation for two prepotentials, F and U. The superspace treatment gives another variant of the integrability problem, which we also reformulate as a search for closed flat Yang-Mills connections. Three- and four-particle solutions are presented. The covector ansatz turns the WDVV equation into an algebraic condition, for which we give a formulation in terms of partial isometries. Three ideas for classifying WDVV solutions are developed: ortho-polytopes, hypergraphs, and matroids. Various examples and counterexamples are displayed.
Excited hexagon Wilson loops for strongly coupled N=4 SYM
Energy Technology Data Exchange (ETDEWEB)
Bartels, J.; Kotanski, J. [Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik; Schomerus, V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); British Columbia Univ., Vancouver, BC (Canada). Dept. of Physics and Astronomy
2010-10-15
This work is devoted to the six-gluon scattering amplitude in strongly coupled N=4 supersymmetric Yang-Mills theory. At weak coupling, an appropriate high energy limit of the so-called remainder function, i.e. of the deviation from the BDS formula, may be understood in terms of the lowest eigenvalue of the BFKL hamiltonian. According to Alday et al., amplitudes in the strongly coupled theory can be constructed through an auxiliary 1-dimensional quantum system. We argue that certain excitations of this quantum system determine the Regge limit of the remainder function at strong coupling and we compute its precise value. (orig.)
The Algebraic Curve of 1-loop Planar N=4 SYM
Schafer-Nameki, S
2004-01-01
The algebraic curve for the psu (2,2|4) quantum spin chain is determined from the thermodynamic limit of the algebraic Bethe ansatz. The Hamiltonian of this spin chain has been identified with the planar 1-loop dilatation operator of N=4 SYM. In the dual AdS_5 x S^5 string theory, various properties of the data defining the curve for the gauge theory are compared to the ones obtained from semiclassical spinning-string configurations, in particular for the case of strings on AdS_5 x S^1 and the su(2,2) spin chain agreement of the curves is shown.
Aspects of lattice N=4 supersymmetric Yang--Mills
Schaich, David
2015-01-01
Non-perturbative investigations of $\\mathcal N = 4$ supersymmetric Yang--Mills theory formulated on a space-time lattice have advanced rapidly in recent years. Large-scale numerical calculations are currently being carried out based on a construction that exactly preserves a single supersymmetry at non-zero lattice spacing. A recent development is the creation of an improved lattice action through a new procedure to regulate flat directions in a manner compatible with this supersymmetry, by modifying the moduli equations. In this proceedings I briefly summarize this new procedure and discuss the parameter space of the resulting improved action that is now being employed in numerical calculations.
Latest results from lattice N=4 supersymmetric Yang--Mills
Schaich, David; Damgaard, Poul H; Giedt, Joel
2016-01-01
We present some of the latest results from our numerical investigations of N=4 supersymmetric Yang--Mills theory formulated on a space-time lattice. Based on a construction that exactly preserves a single supersymmetry at non-zero lattice spacing, we recently developed an improved lattice action that is now being employed in large-scale calculations. Here we update our studies of the static potential using this new action, also applying tree-level lattice perturbation theory to improve the analysis of the potential itself. Considering relatively weak couplings, we obtain results for the Coulomb coefficient that are consistent with continuum perturbation theory.
Smooth Wilson loops in N=4 non-chiral superspace
Beisert, Niklas; Müller, Dennis; Plefka, Jan; Vergu, Cristian
2015-12-01
We consider a supersymmetric Wilson loop operator for 4d N = 4 super Yang-Mills theory which is the natural object dual to the AdS 5 × S 5 superstring in the AdS/CFT correspondence. It generalizes the traditional bosonic 1 /2 BPS Maldacena-Wilson loop operator and completes recent constructions in the literature to smooth (non-light-like) loops in the full N=4 non-chiral superspace. This Wilson loop operator enjoys global super-conformal and local kappa-symmetry of which a detailed discussion is given. Moreover, the finiteness of its vacuum expectation value is proven at leading order in perturbation theory. We determine the leading vacuum expectation value for general paths both at the component field level up to quartic order in anti-commuting coordinates and in the full non-chiral superspace in suitable gauges. Finally, we discuss loops built from quadric splines joined in such a way that the path derivatives are continuous at the intersection.
Integrability of smooth Wilson loops in N=4 superspace
Beisert, Niklas; Müller, Dennis; Plefka, Jan; Vergu, Cristian
2015-12-01
We perform a detailed study of the Yangian symmetry of smooth supersymmetric Maldacena-Wilson loops in planar N=4 super Yang-Mills theory. This hidden symmetry extends the global superconformal symmetry present for these observables. A gauge-covariant action of the Yangian generators on the Wilson line is established that generalizes previous constructions built upon path variations. Employing these generators the Yangian symmetry is proven for general paths in non-chiral N=4 superspace at the first perturbative order. The bi-local piece of the level-one generators requires the use of a regulator due to divergences in the coincidence limit. We perform regularization by point splitting in detail, thereby constructing additional local and boundary contributions as regularization for all level-one Yangian generators. Moreover, the Yangian algebra at level one is checked and compatibility with local kappa-symmetry is established. Finally, the consistency of the Yangian symmetry is shown to depend on two properties: the vanishing of the dual Coxeter number of the underlying superconformal algebra and the existence of a novel superspace "G-identity" for the gauge field theory. This tightly constrains the conformal gauge theories to which integrability can possibly apply.
Smooth Wilson Loops in N=4 Non-Chiral Superspace
Beisert, Niklas; Plefka, Jan; Vergu, Cristian
2015-01-01
We consider a supersymmetric Wilson loop operator for 4d N=4 super Yang-Mills theory which is the natural object dual to the AdS_5 x S^5 superstring in the AdS/CFT correspondence. It generalizes the traditional bosonic 1/2 BPS Maldacena-Wilson loop operator and completes recent constructions in the literature to smooth (non-light-like) loops in the full N=4 non-chiral superspace. This Wilson loop operator enjoys global superconformal and local kappa-symmetry of which a detailed discussion is given. Moreover, the finiteness of its vacuum expectation value is proven at leading order in perturbation theory. We determine the leading vacuum expectation value for general paths both at the component field level up to quartic order in anti-commuting coordinates and in the full non-chiral superspace in suitable gauges. Finally, we discuss loops built from quadric splines joined in such a way that the path derivatives are continuous at the intersection.
Korrosionshastigheder af rene zinkcoatings
DEFF Research Database (Denmark)
Bech-Nielsen, G.; Tang, Peter Torben; Ulrich, Dan
1991-01-01
Det har længe været den fremherskende opfattelse i galvanobranchen, at et zinkbad var et zinkbad og at der, tiltrods for de forskellige leverandørers gyldne løfter, ikke var den store forskel på de bade der kan købes på markedet idag. Det har ydermere været den almindelige opfattelse, at zinkbade......-bestandighed og udseende. Badenes alder har også vist sig at have endog meget stor betydning for kvaliteten af belægningerne....
DEFF Research Database (Denmark)
Pedersen, Jens Olaf Pepke
2011-01-01
Nedrustning. Bør vi ikke være mere bekymrede i dag, hvor færre våben bliver fordelt på flere og mere uforudsigelige lande? Her ser vi på, hvad der konkret skal til for at fremstille atombomber med henholdsvis plutonium og beriget uran.......Nedrustning. Bør vi ikke være mere bekymrede i dag, hvor færre våben bliver fordelt på flere og mere uforudsigelige lande? Her ser vi på, hvad der konkret skal til for at fremstille atombomber med henholdsvis plutonium og beriget uran....
Directory of Open Access Journals (Sweden)
Helmut Ritter
2014-10-01
Full Text Available The oxidative oligomerization of a chiral mandelamide derivative (N-(4-hydroxyphenylmandelamide, 1 was performed in the presence of horseradish peroxidase, laccase and N,N'-bis(salicylideneethylenediamine-iron(II to obtain chiral oligophenols 2. The low enantioselectivity of the enzymatic catalyzed asymmetric enantiomer-differentiating oligomerizations was investigated. In addition, the poor influence of cyclodextrin on the enantioselectivity of enzymatic catalyzed asymmetric enantiomer-differentiating oligomerizations was studied.
Effect of Auxiliary Gases on Combustion Synthesis of Si3N4
Institute of Scientific and Technical Information of China (English)
Weiping SHEN; Fei WANG; Zhuohui WU; Changchun GE
2005-01-01
This paper presents results of combustion synthesis (Self-Propagating High Temperature Synt hesis, SHS) of Si3N4under nitrogen with argon, hydrogen or ammonia. Higher percentages of α-Si3N4 content were obtained in large size cakes in SHS with hydrogen and ammonia than those with argon. Effect of the auxiliary gases for combustion synthesis of Si3N4 on α phase content, on phase transformation of α-Si3N4 toβ-Si3N4 in SHS Si3N4 and on oxygen content in SHS Si3N4 were investigated.
N=4 superconformal n-particle mechanics via superspace
Krivonos, Sergey; Polovnikov, Kirill
2008-01-01
We revisit the (untwisted) superfield approach to one-dimensional multi-particle systems with N=4 superconformal invariance. The requirement of a standard (flat) bosonic kinetic energy implies the existence of inertial (super-)coordinates, which is nontrivial beyond three particles. We formulate the corresponding integrability conditions, whose solution directly yields the superpotential, the two prepotentials and the bosonic potential. The structure equations for the two prepotentials, including the WDVV equation, follow automatically. The general solution for translation-invariant three-particle models is presented and illustrated with examples. For the four-particle case, we take advantage of known WDVV solutions to construct a D_3 and a B_3 model, thus overcoming a previously-found barrier regarding the bosonic potential. The general solution and classification remain a challenge.
On Form Factors in N=4 SYM Theory and Polytopes
Bork, L V
2014-01-01
In this paper we discuss different recursion relations (BCFW and all-line shift) for the form factors of the operators from the $\\mathcal{N}=4$ SYM stress-tensor current supermultiplet $T^{AB}$ in momentum twistor space. We show that cancelations of spurious poles and equivalence between different types of recursion relations can be naturally understood using geometrical interpretation of the form factors as special limit of the volumes of polytopes in $\\mathbb{C}\\mathbb{P}^4$ in close analogy with the amplitude case. We also show how different relations for the IR pole coefficients can be easily derived using momentum twistor representation. This opens an intriguing question - which of powerful on-shell methods and ideas can survive off-shell ?
Tessellating cushions: four-point functions in N=4 SYM
Eden, Burkhard
2016-01-01
We consider a class of planar tree-level four-point functions in N=4 SYM in a special kinematic regime: one BMN operator with two scalar excitations and three half-BPS operators are put onto a line in configuration space; additionally, for the half-BPS operators a co-moving frame is chosen in flavour space. In configuration space, the four-punctured sphere is naturally triangulated by tree-level planar diagrams. We demonstrate on a number of examples that each tile can be associated with a modified hexagon form-factor in such a way as to efficiently reproduce the tree-level four-point function. Our tessellation is not of the OPE type, fostering the hope of finding an independent, integrability-based approach to the computation of planar four-point functions.
The Coulomb Branch of 3d N= 4 Theories
Bullimore, Mathew; Dimofte, Tudor; Gaiotto, Davide
2017-09-01
We propose a construction for the quantum-corrected Coulomb branch of a general 3d gauge theory with N=4 supersymmetry, in terms of local coordinates associated with an abelianized theory. In a fixed complex structure, the holomorphic functions on the Coulomb branch are given by expectation values of chiral monopole operators. We construct the chiral ring of such operators, using equivariant integration over BPS moduli spaces. We also quantize the chiral ring, which corresponds to placing the 3d theory in a 2d Omega background. Then, by unifying all complex structures in a twistor space, we encode the full hyperkähler metric on the Coulomb branch. We verify our proposals in a multitude of examples, including SQCD and linear quiver gauge theories, whose Coulomb branches have alternative descriptions as solutions to Bogomolnyi and/or Nahm equations.
Compositional effects on Si3N4 fracture surfaces
Hench, L. L.; Ohuchi, F.; Vaidyanathan, P. N.; Dutta, S.
1983-01-01
Surface analysis techniques (X-ray, infrared reflection spectroscopy, Auger electron spectroscopy) applied to the same samples reveal that fracture surfaces of Si3N4 with Y2O3 densification aids possess a higher concentration of oxygen than the bulk. The oxide densification aids thus concentrate in the grain boundaries, and even low-temperature fracture is seen as occurring preferentially within the oxygen-enriched grain boundaries. It is found that increasing the concentrations of Y2O3 and Al2O3 increases the oxygen content of the fracture surface. A range of 13-15 percent Y2O3 + 6 percent Al2O3 gives an amorphous grain-boundary phase that is resistant to devitrification. Fracture occurs through the amorphous phase, and heat treatment at 1000 C has little effect on the amorphous phase.
The exact Schur index of $\\mathcal{N}=4$ SYM
Bourdier, Jun; Felix, Jan
2015-01-01
The Witten index counts the difference in the number of bosonic and fermionic states of a quantum mechanical system. The Schur index, which can be defined for theories with at least $\\mathcal{N}=2$ supersymmetry in four dimensions is a particular refinement of the index, dependent on one parameter $q$ serving as the fugacity for a particular set of charges which commute with the hamiltonian and some supersymmetry generators. This index has a known expression for all Lagrangian and some non-Lagrangian theories as a finite dimensional integral or a complicated infinite sum. In the case of $\\mathcal{N}=4$ SYM with gauge group $U(N)$ we rewrite this as the partition function of a gas of $N$ non interacting and translationally invariant fermions on a circle. This allows us to perform the integrals and write down explicit expressions for fixed $N$ as well as the exact all orders large $N$ expansion.
BPS domain walls in N=4 supergravity and dual flows
Cassani, Davide; Faedo, Anton F
2012-01-01
We establish the conditions for supersymmetric domain wall solutions to N=4 gauged supergravity in five dimensions. These read as BPS first-order equations for the warp factor and the scalar fields, driven by a superpotential and supplemented by a set of constraints that we specify in detail. Then we apply our results to certain consistent truncations of IIB supergravity, thus exploring their dual field theory renormalization group flows. We find a universal flow deforming superconformal theories on D3-branes at Calabi-Yau cones. Moreover, we obtain a superpotential for the solution corresponding to the baryonic branch of the Klebanov-Strassler theory, as well as the superpotential for the flow describing D3 and wrapped D5-branes on the resolved conifold.
N >= 4 Supergravity Amplitudes from Gauge Theory at Two Loops
Energy Technology Data Exchange (ETDEWEB)
Boucher-Veronneau, C.; Dixon, L.J.; /SLAC
2012-02-15
We present the full two-loop four-graviton amplitudes in N = 4, 5, 6 supergravity. These results were obtained using the double-copy structure of gravity, which follows from the recently conjectured color-kinematics duality in gauge theory. The two-loop four-gluon scattering amplitudes in N = 0, 1, 2 supersymmetric gauge theory are a second essential ingredient. The gravity amplitudes have the expected infrared behavior: the two-loop divergences are given in terms of the squares of the corresponding one-loop amplitudes. The finite remainders are presented in a compact form. The finite remainder for N = 8 supergravity is also presented, in a form that utilizes a pure function with a very simple symbol.
Institute of Scientific and Technical Information of China (English)
姚怀; 徐巧玉; 苌清华; 唐敬友
2008-01-01
以Y2O3-Al2O3-La2O3体系作烧结助剂,在5.4～5.7GPa、1620～1770K的高温高压条件下进行了α-Si3N4与γ-Si3N4、α-Si3N4粉体的烧结研究,并探讨了烧结温度及压力对烧结体性能的影响.实验结果表明:α-Si3N4、γ-Si3N4完全相变为βSi3N4;在相同的烧结条件下,α-Si3N4比γ-Si3N4、α-Si3N4混合粉体烧结试样的相对密度、维氏硬度高.α-Si3N4与γ-Si3N4、α-Si3N4混合粉体烧结试样的最高相对密度与维氏硬度分别为98.78%、21.87GPa和98.71%、21.76GPa.烧结体由相互交错的长柱状β-Si3N4晶粒组成,显微结构均匀.
Institute of Scientific and Technical Information of China (English)
席明哲; 高士友
2012-01-01
研究了激光快速成形(LRF)Rene 80高温合金厚壁件的凝固组织和裂纹的形成机理.结果表明,激光快速成形Rene 80高温合金的凝固组织为与沉积高度方向平行的定向凝固枝晶组织,由于凝固偏析,MC型碳化物和γ-γ′共晶组织分布于定向凝固组织的枝晶间区域.激光快速成形Rene 80高温合金厚壁件含有许多长度大于10 mm,扩展方向与沉积高度方向平行的宏观裂纹.分析表明,这些裂纹为液化裂纹,其形成原因为:激光快速成形时,紧邻激光熔池的热影响区(HAZ)内沿晶界分布的低熔点γ-γ′共晶组织发生熔化,形成热影响区内沿晶界扩展的晶界液相,在热影响区冷却过程中,由于热影响区内固相的收缩应力作用,沿晶界扩展的固-液界面被撕开,从而导致液化裂纹的产生.%The microstructures and mechanism, of cracks forming of a thick-wall part of Rene 80 superalloy fabricated by laser rapid forming (LRF) process are presented. Results show that the solidified microstructures of LRF Rene 80 high-temperature alloy consist of directionally solidified dendrites, which are parallel with the deposition direction. The MC type carbides and γ — γ' eutectic distribute in interdendritic region of the directionally solidified microstructure due to element segregation. The LRF Rene 80 high-temperature alloy thick-wall part contains many macro cracks, which have the length of more than 10 mm and expand along the direction parallel to the deposition direction. Analyses indicate that these macro cracks are liquated cracks. During LRF process, the γ—γ' eutectic with lower melting point particularly along the grain-boundary regions in heat-affected zone (HAZ) melt produced by laser melting pool and result in the formation of grain-boundary liquid. On the subsequent cooling process of the HAZ, the liquated cracks along the HAZ grain boundaries occurred by decohesion across the liquid-solid interface due to
Chiral three-nucleon force at N^4LO II: Intermediate-range contributions
Krebs, Hermann; Epelbaum, Evgeny
2013-01-01
We derive the subleading contributions to the two-pion-one-pion exchange and ring three-nucleon force topologies emerging at next-to-next-to-next-to-next-to-leading order in chiral effective field theory. The resulting expressions do not involve any unknown parameters. To study convergence of the chiral expansion we work out the most general operator structure of a local isospin-invariant three-nucleon force. Using the resulting operator basis with 22 independent structures, we compare the strength of the corresponding potentials in configuration space for individual topologies at various orders in the chiral expansion. As expected, the subleading contributions from the two-pion-one-pion-exchange and ring diagrams are large which can be understood in terms of intermediate excitation of the Delta(1232) isobar.
Institute of Scientific and Technical Information of China (English)
姚怀; 徐巧玉; 苌清华; 刘海洋
2008-01-01
以Y2O3-Al2O3-La2O3体系作烧结助剂,在5.4～5.7GPa、1620K～1770K的高温高压条件下进行了α-Si3N2与γ-Si3N4、α-Si3N4粉体的烧结研究.探讨了烧结温度及压力对烧结体性能的影响.实验测试结果表明:α-Si3N4、γ-Si3N4完全相变为β-Si3N4,相同的烧结条件下,α-Si3N4比γ-Si3N4、α-Si3N4混合粉体烧结试样的相对密度、维氏硬度高.α-Si3N4与γ-Si3N4、α-Si3N4混合粉体烧结试样的最高相对密度与维氏硬度分别为98.78%、21.87GPa和98.71%、21.76GPa.烧结体由相互交错的长柱状β-Si3N4晶粒组成,显微结构均匀.
Effect of the structure distortion on the high photocatalytic performance of C60/g-C3N4 composite
Ma, Xiaojuan; Li, Xinru; Li, Mengmeng; Ma, Xiangchao; Yu, Lin; Dai, Ying
2017-08-01
C60/g-C3N4 composite was reported experimentally to be of high photocatalytic activity in degrading organics. To investigate the underlying mechanism of high photocatalytic performance, the structural and electronic properties of g-C3N4 monolayers with adsorbing and removing fullerene C60 are studied by means of density functional theory calculations. After 25 possible configurations examination, it is found that C60 prefers to stay upon the ;junction nitrogen; with the carbon atom of fullerene being nearest to monolayers. Correspondingly, a type-I band alignment appears. Our results further demonstrate that the adsorption of C60 can lead to an irreversible structure distortion for g-C3N4 from flat to wrinkle, which plays a crucial role in improving photocatalytic performance other than the separation of carriers at interface due to the formation of type-II heterojunctions as previous report. Compared to flat one, the light absorption of wrinkled structure shows augmented, the valence band maximum shifts towards lower position along with a stronger photo-oxidation capability. Interestingly, the results indicate that the energy, light absorption and band edge all have a particular relationship with wrinkle degree. The work presented here can be helpful to understand the mechanism behind the better photocatalytic performance for C60 modified g-C3N4.
Si3N4陶瓷球加工工艺的研究%Study on processing technology of Si3N4 ceramics ball
Institute of Scientific and Technical Information of China (English)
王泉; 刘秀莲; 葛华伟
2012-01-01
According to the Si3N4 material performance, its certain characteristics are favorable for manufacturing rolling element, by researching Si3N4 ceramic ball test processing, the Si3N4 ceramic ball machining process was determined, ceramic ball meeting the G5 level requirements was developed.% 根据Si3N4的材料性能可知其某些特性对制造滚动体是有利的，通过对Si3N4陶瓷球试验加工工艺的研究，确定Si3N4陶瓷球加工工艺，研制出符合G5级要求的陶瓷球。
Interactions of the Infrared bubble N4 with the surroundings
Liu, Hong-Li; Wu, Yuefang; Yuan, Jing-Hua; Liu, Tie; Dubner, G; Paron, S; Ortega, M E; Molinari, Sergio; Huang, Maohai; Zavagno, Annie; Samal, Manash R; Huang, Ya-Fang; Zhang, Si-Ju
2016-01-01
The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with HII regions have been considered to be a good sample to investigate triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the HII region G11.898+0.747, analyzing its interaction with the surroundings and star formation histories therein, aiming at determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 $\\times10^{22}$ cm$^{-2}$, mean volume density of about 4.4 $\\times10^{4}$ cm$^{-3}$, and a mean mass of 320 $M_{\\odot}$. In addition, from PAH emission seen at 8 $\\mu$m, ...
Null Zig-Zag Wilson Loops in N=4 SYM
Xie, Zhifeng
2009-01-01
In planar ${\\cal N}=4$ supersymmetric Yang-Mills theory we have studied supersymmetric Wilson loops composed of a large number of light-like segments, i.e., null zig-zags. These contours oscillate around smooth underlying spacelike paths. At one-loop in perturbation theory we have compared the finite part of the expectation value of null zig-zags to the finite part of the expectation value of non-scalar-coupled Wilson loops whose contours are the underlying smooth spacelike paths. In arXiv:0710.1060 [hep-th] it was argued that these quantities are equal for the case of a rectangular Wilson loop. Here we present a modest extension of this result to zig-zags of circular shape and zig-zags following non-parallel, disconnected line segments and show analytically that the one-loop finite part is indeed that given by the smooth spacelike Wilson loop without coupling to scalars which the zig-zag contour approximates. We make some comments regarding the generalization to arbitrary shapes.
Null Zig-Zag Wilson Loops in {N}=4 Sym
Xie, Zhifeng
In planar {N}=4 supersymmetric Yang-Mills theory we have studied one kind of (locally) BPS Wilson loops composed of a large number of light-like segments, i.e. null zig-zags. These contours oscillate around smooth underlying spacelike paths. At one-loop in perturbation theory, we have compared the finite part of the expectation value of null zig-zags to the finite part of the expectation value of non-scalar-coupled Wilson loops whose contours are the underlying smooth spacelike paths. In arXiv:0710.1060 [hep-th] it was argued that these quantities are equal for the case of a rectangular Wilson loop. Here we present a modest extension of this result to zig-zags of circular shape and zig-zags following non-parallel, disconnected line segments and show analytically that the one-loop finite part is indeed that given by the smooth spacelike Wilson loop without coupling to scalars which the zig-zag contour approximates. We make some comments regarding the generalization to arbitrary shapes.
Analytic two-loop form factors in N=4 SYM
Brandhuber, Andreas; Yang, Gang
2012-01-01
We derive a compact expression for the three-point MHV form factors of half-BPS operators in N=4super Yang-Mills at two loops. The main tools of our calculation are generalised unitarity applied at the form factor level, and the compact expressions for supersymmetric tree-level form factors and amplitudes entering the cuts. We confirm that infrared divergences exponentiate as expected, and that collinear factorisation is entirely captured by an ABDK/BDS ansatz. Next, we construct the two-loop remainder function obtained by subtracting this ansatz from the full two-loop form factor and compute it numerically. Using symbology, combined with various physical constraints and symmetries, we find a unique solution for its symbol. With this input we construct a remarkably compact analytic expression for the remainder function, which contains only classical polylogarithms, and compare it to our numerical results. Furthermore, we make the surprising observation that our remainder is equal to the maximally transcendent...
Chiral 2D "Strange Metals" from N = 4 SYM
Berkooz, Micha; Zait, Amir
2014-01-01
Familiar field theories may contain closed subsectors made out of only fermions, which can be used to explore new and unusual phases of matter in lower dimensions. We focus on the fermionic su(1,1) sector in N=4 SYM and on its ground states, which are Fermi surface states/operators. By computing their spectrum to order $(g_{YM}^2 N)^2$, we argue that fluctuations around this fermi surface, within the sector and in the limit $k_F\\rightarrow\\infty$, are governed by a chiral 1+1 dimensional sector of the "strange metal" coset $SU(N)_N \\otimes SU(N)_N/SU(N)_{2N}$. On the gravity side, the conjectured dual configuration is an $S=0$ degeneration of a rotating black hole. On general grounds we expect that the near horizon excitations of $(S=0,\\Omega=1,J\\rightarrow\\infty)$ degenerations of black holes will be governed by a chiral sector of a 1+1 CFT.
Resummation and S-duality in N=4 SYM
Beem, Christopher; Sen, Ashoke; van Rees, Balt C
2013-01-01
We consider the problem of resumming the perturbative expansions for anomalous dimensions of low twist, non-BPS operators in four dimensional N=4 supersymmetric Yang-Mills theories. The requirement of S-duality invariance imposes considerable restrictions on any such resummation. We introduce several prescriptions that produce interpolating functions on the upper half plane that are compatible with a subgroup of the full duality group. These lead to predictions for the anomalous dimensions at all points in the fundamental domain of the complex gauge coupling, and in particular at the duality-invariant values \\tau=i and \\tau=exp(i\\pi/3). For low-rank gauge groups, the predictions are compatible with the bounds derived by conformal bootstrap methods for these anomalous dimensions; within numerical errors, they are in good agreement with the conjecture that said bounds are saturated at a duality-invariant point. We also find that the anomalous dimensions of the lowest twist operators lie within an extremely narr...
Bootstrap equations for $\\mathcal{N}=4$ SYM with defects
Liendo, Pedro
2016-01-01
This paper focuses on the analysis of $4d$ $\\mathcal{N}=4$ superconformal theories in the presence of a defect from the point of view of the conformal bootstrap. We will concentrate first on the case of codimension one, where the defect is a boundary that preserves half of the supersymmetry. After studying the constraints imposed by supersymmetry, we will write the Ward identities associated to two-point functions of $\\tfrac{1}{2}$-BPS operators and write their solution as a superconformal block expansion. Due to a surprising connection between spacetime and R-symmetry conformal blocks, our results not only apply to $4d$ $\\Nm=4$ superconformal theories with a boundary, but also to three more systems that have the same symmetry algebra: $4d$ $\\Nm=4$ superconformal theories with a line defect, $3d$ $\\Nm=4$ superconformal theories with no defect, and $OSP(4^*|4)$ superconformal quantum mechanics. The superconformal algebra implies that all these systems possess a closed subsector of operators in which the bootst...
Evaluation of the Properties of Si3N4/Si3N4 Joint Brazed Using a Filler Alloy Containing Pd
Institute of Scientific and Technical Information of China (English)
M. Naka; Jie ZHANG; Yu ZHOU
2003-01-01
Si3N4 ceramic was jointed to itself using a filler alloy of Cu76.5Pd8.5Ti15, and the mechanical properties of the jointwere measured and analyzed. By using a filler alloy of Cu76.5Pd8.5Ti15, the SisN4/SisN4 joints were obtained bybrazing at 1373～1473 K f
Si3N4陶瓷与Si3N4陶瓷及金属连接的研究进展%Progression of the Joining of Si3N4 Ceramic to Si3N4 Ceramic and to Metal
Institute of Scientific and Technical Information of China (English)
曹优明; 郑仕远
2002-01-01
对Si3N4陶瓷与Si3N4陶瓷、Si3N4陶瓷与金属的连接工艺进展进行了系统的介绍,重点评述了Si3N4直接钎焊法、Si3N4间接钎焊法、Si3N4陶瓷玻璃焊法的研究进展,并提出了今后研究的重点.
On the Constant Metric Dimension of Generalized Petersen Graphs P (n, 4)
Institute of Scientific and Technical Information of China (English)
Saba NAZ; Muhammad SALMAN; Usman ALI; Imran JAVAID; Syed Ahtsham-ul-Haq; BOKHARY
2014-01-01
In this paper, we consider the family of generalized Petersen graphs P (n, 4). We prove that the metric dimension of P (n, 4) is 3 when n≡0 (mod 4), and is 4 when n=4k+3 (k is even). For n ≡ 1, 2 (mod 4) and n = 4k+3 (k is odd), we prove that the metric dimension of P (n, 4) is bounded above by 4. This shows that each graph of the family of generalized Petersen graphs P (n, 4) has constant metric dimension.
Si3N4薄膜的成分与结构研究%Study on composition and structure of Si3N4 film
Institute of Scientific and Technical Information of China (English)
赵毅红; 陈荣发; 刘伯实
2004-01-01
通过PECVD方法,在Si基体表面制备了Si3N4薄膜,给出了XRD、TEM、AES、DPS的分析结果,表明Si3N4是非晶态结构,薄膜的主要成分是Si3N4,SEM分析结果显示Si3N4薄膜与基体材料的结合强度高,薄膜致密性好.
M-strings, elliptic genera and N = 4 string amplitudes
Energy Technology Data Exchange (ETDEWEB)
Hohenegger, S. [Department of Physics, CERN - Theory Division, Geneva (Switzerland); Iqbal, A. [Department of Physics, LUMS School of Science and Engineering, Lahore (Pakistan); Department of Mathematics, LUMS School of Science and Engineering, Lahore (Pakistan)
2014-03-06
We study mass-deformed N = 2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M-strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of C{sup 2} through a (singular) theta-transform. This form appears naturally as a specific class of one-loop scattering amplitudes in type II string theory on T{sup 2}, which we calculate explicitly. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Zhao, G. L.; Bachlechner, M. E.
1997-02-01
The electronic structure, charge distribution, and charge transfer in α- and β- Si3N4 and at the Si(111)/Si3N4(001) interface have been studied using a self-consistent first-principles LCAO method. The calculated charge transfer suggests that both in α- and β-phases, the ionic formula may be written as Si3+1.24N4-0.93. For the Si(111)/Si3N4(001) interface, the silicon atoms from the Si(111) side give some electrons to the N atoms of Si3N4 forming the Si-N bonds at the interface. One Si-N bond is associated with a charge transfer of about 0.31 electrons.
Improvement of g-C3N4 photocatalytic properties using the Hummers method.
Feng, Jing; Chen, Tingting; Liu, Shenna; Zhou, Qihang; Ren, Yueming; Lv, Yanzhuo; Fan, Zhuangjun
2016-10-01
In this study, graphitic C3N4 (g-C3N4) with high photocatalytic properties to methylene blue (MB) was synthesized by treating the bulk g-C3N4 using the Hummers method. The bulk g-C3N4 was obtained by calcining dicyandiamide. The g-C3N4 treated by the Hummers method (E-g-C3N4) was characterized and utilized for the photocatalytic removal of MB. The results showed that the Hummers treatment exfoliated the nanosheets bulk g-C3N4 into nanorods and improved the dispersion of E-g-C3N4 in an aqueous solution. It also distinctly enhanced the photocatalytic activity of g-C3N4 to MB, i.e., the removal efficiency increased from 38.45% for the bulk g-C3N4 to 96.61% for the E-g-C3N4.
Institute of Scientific and Technical Information of China (English)
ZHANG Jie; Naka Massaki; ZHOU Yu
2005-01-01
Si3N4 ceramic was jointed to Si3N4 ceramic using a filler alloy of Cu-Zn-Ti at 1 123-1 323 K for 0.3 -2.7 ks. Ti content in the Cu-Zn-Ti filler alloy was 15% (molar fraction). The effect of bonding parameters on the microstructure and mechanical properties of the Si3N4/Si3N4 joint were investigated. The results indicate that with increasing brazing temperature from 1 123K to 1 323 K and brazing time from 0.3 ks to 2.7 ks, the thickness of the interfacial reaction layer between the filler alloy and the Si3 N4 ceramic and the size and amount of the reactant products in the filler alloy increase, leading to an increase in shear strength of the joint from 163 MPa to 276 MPa. It is also found that the fracture behavior of the Si3 N4/Si3 N4 joint greatly depends on the microstructure of the joint.
Development of -N4-NIM for Molecular Imaging of Tumor Hypoxia
Directory of Open Access Journals (Sweden)
Mohammad S. Ali
2012-01-01
Full Text Available The nitro group of 2-nitroimidazole (NIM enters the tumor cells and is bioreductively activated and fixed in the hypoxia cells. 1,4,8,11-tetraazacyclotetradecane (N4 has shown to be a stable chelator for 99mTc. The present study was aimed to develop 99mTc-cyclam-2-nitroimidazole (99mTc-N4-NIM for tumor hypoxia imaging. N4-NIM precursor was synthesized by reacting N4-oxalate and 1,3-dibromopropane-NIM, yielded 14% (total synthesis. Cell uptake of 99mTc-N4-NIM and 99mTc-N4 was obtained in 13762 rat mammary tumor cells and mesothelioma cells in 6-well plates. Tissue distribution of 99mTc-N4-NIM was evaluated in breast-tumor-bearing rats at 0.5–4 hrs. Tumor oxygen tension was measured using an oxygen probe. Planar imaging was performed in the tumor-bearing rat and rabbit models. Radiochemical purity of 99mTc-N4-NIM was >96% by HPLC. Cell uptake of 99mTc-N4-NIM was higher than 99mTc-N4 in both cell lines. Biodistribution of 99mTc-N4-NIM showed increased tumor-to-blood and tumor-to-muscle count density ratios as a function of time. Oxygen tension in tumor tissue was 6–10 mmHg compared to 40–50 mmHg in normal muscle tissue. Planar imaging studies confirmed that the tumors could be visualized clearly with 99mTc-N4-NIM in animal models. Efficient synthesis of N4-NIM was achieved. 99mTc-N4-NIM is a novel hypoxic probe and may be useful in evaluating cancer therapy.
Si3N4-SiC材料的氧化性能研究%Study on Oxidation Performance of Si3N4-SiC
Institute of Scientific and Technical Information of China (English)
李杰
2009-01-01
通过对不同Si3N4含量、不同温度下Si3N4-SiC材料的氧化实验,分析氧化后的氧化增重率,得出Si3N4含量越高,材料氧化越严重;氧化温度越高,材料氧化越严重;且氧化增重率与氧化时间呈直线-抛物线规律.
Institute of Scientific and Technical Information of China (English)
姚怀; 徐巧玉; 唐敬友; 苌清华
2009-01-01
以Y2O3-Al2O3-La2O3体系作烧结助剂,在5.4～5.7 GPa、1 620～1 770 K的高温高压条件下进行了α-Si3N4与γ-Si3N4粉体的烧结,研究了烧结体的相对密度、韦氏硬度和物相组成.结果表明:α-Si3N4、γ-Si3N4在烧结后完全转变为β-Si3N4;在相同烧结条件下,γ-Si3N4烧结体的相对密度、维氏硬度比α-Si3N4的高γ-Si3N4与α-Si3N4烧结体的最高相对密度与维氏硬度分别为99.20%,23.42 GPa和98.78%,21.87 GPa;烧结体由相互交错的长柱状β-Si3N4晶粒组成,显微结构均匀.
Electronic structure and charge transfer in α- and β-Si3N4 and at the Si(111)/Si3N4(001) interface
Zhao, G. L.; Bachlechner, M. E.
1998-07-01
Using a self-consistent linear combination of atomic orbitals method based on density-functional theory in a local-density approximation, the electronic structure in the high-temperature ceramics α-Si3N4 and β-Si3N4 and at the Si(111)/Si3N4(001) interface have been calculated. The resulting charge transfer suggests that the ionic formula can be written as Si+1.243N-0.934. For the Si(111)/Si3N4(001) interface, the silicon atoms from the silicon side lose some electrons to the nitrogen atoms of the silicon nitride side forming Si-N bonds at the interface. The calculated electronic density of states spectrum of Si 2p core levels for this interface is in good agreement with x-ray photoemission spectroscopy experiments.
Research on Nano-Si3N4 Dispersion Technology%纳米Si3N4粉末分散工艺研究
Institute of Scientific and Technical Information of China (English)
田春艳; 刘宁
2006-01-01
研究了纳米Si3N4粉末的分散性能,得到了优化的分散工艺参数.实验结果表明,将纳米Si3N4进行超声分散,可以改善其分散状况;加入适量的表面活性剂能改善Si3N4的分散效果,阳离子型表面活性剂的分散效果优于非离子型表面活性剂;分散体系的pH值也影响纳米Si3N4粉的分散效果.
Nqrs Data for C6H16I2N4O8 [C6H14N4O2·2(HIO3)] (Subst. No. 0932)
Chihara, H.; Nakamura, N.
This document is part of Subvolume A `Substances Containing Ag … C10H15' of Volume 48 `Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III `Condensed Matter'. It contains an extract of Section `3.2 Data tables' of the Chapter `3 Nuclear quadrupole resonance data' providing the NQRS data for C6H16I2N4O8 [C6H14N4O2·2(HIO3)] (Subst. No. 0932)
Benbelaïd, R; Dot, D; Levy, G; Eid, N
2006-11-01
In addition to dental hospital clinical activity, dental students at Paris Rene Descartes University have the opportunity in their final year of study to practise clinically in a dental office, as associates. This paper outlines a pilot, experimental study designed to assess student reaction to this Vocational Clinical Activity (VCA) in order to identify relevant weaknesses of the undergraduate programme. Using questionnaires, data were collected for each of the following clinical or management skills: clinical difficulty, therapeutic decision-making, patient/practitioner relationship, time management, administrative matters and technical problems. Students were asked to rank each item in order of difficulty (1, high level to 6, low level). A high response rate was observed (90%) among the 50 undergraduate VCA students. The results pointed out three main difficulties encountered by undergraduate students during the VCA: time management (90% of the students), administrative matters (85% of the students) and clinical decision-making (80% of the students). These preliminary results need further investigation. However, they give us the incentive to carry on with this type of assessment and to extend it to young, qualified colleagues' perceptions and to other French Universities.
Fabrication of Si3N4 Nanocrystals and Nanowires Using PECVD
Directory of Open Access Journals (Sweden)
Jingwei Song
2010-01-01
Full Text Available Si3N4 nanowires and nanocrystals were prepared on Si substrates with or without Fe catalyst using silane (SiH4 and nitrogen (N2 as reactive gases through plasma-enhanced chemical vapor deposition (PECVD technology. With Fe catalyst, Si3N4 nanowires were developed, indicating that Fe catalyst played a role for Si3N4 molecules directionally depositing into strings. The density of the nanowires is closely related to the density of Fe catalyst. When the density of Fe ions on the substrate was decreased remarkably, a smooth superlong Si3N4 nanowire with 12 μm in length was fabricated. Having analyzed the growth mechanism, a growth model for Si3N4 nanowires was developed. The growth of Si3N4 nanocrystallines was attributed to be a vapor-solid (V-S deposition process.
INVESTIGATION OF MULTIPHASE-REINFORCED Si3N4 COMPOSITE MATERIAL
Institute of Scientific and Technical Information of China (English)
曾鸣; 丁博; 郭梦熊
1995-01-01
By means of whisker reinforce and paricle dispersion, the routes of property improvement on Si3N4 ceramic material have been studied. The mecihaniacl properties of Siw/Si3N4 and Siw/Si3N4TiC material was compared, which proved that multiphase reinforce had overlap effect. Microstructure of the material was investigated by means of SEM and the mechanisms of SiCw and TiCP reinforces had been disussed.
Terahertz generation from Si3N4 covered photoconductive dipole antenna
Institute of Scientific and Technical Information of China (English)
Wei Shi(施卫); Jingzhou Xu; X.-C.Zhang
2003-01-01
We observe enhanced terahertz (THz) radiation generated from a Si3N4 film-coated GaAs photoconductivedipole antenna. Compared to an uncoated antenna with identical electrode geometry and optical excitationpower, the Si3N4 film-coated antenna has a higher effective DC resistance and larger breakdown voltage.As a result, the peak amplitude of generated THz radiation is significantly enhanced due to the Si3N4film-coated layer.
Two Novel C3N4 Phases: Structural, Mechanical and Electronic Properties
Directory of Open Access Journals (Sweden)
Qingyang Fan
2016-05-01
Full Text Available We systematically studied the physical properties of a novel superhard (t-C3N4 and a novel hard (m-C3N4 C3N4 allotrope. Detailed theoretical studies of the structural properties, elastic properties, density of states, and mechanical properties of these two C3N4 phases were carried out using first-principles calculations. The calculated elastic constants and the hardness revealed that t-C3N4 is ultra-incompressible and superhard, with a high bulk modulus of 375 GPa and a high hardness of 80 GPa. m-C3N4 and t-C3N4 both exhibit large anisotropy with respect to Poisson’s ratio, shear modulus, and Young’s modulus. Moreover, m-C3N4 is a quasi-direct-bandgap semiconductor, with a band gap of 4.522 eV, and t-C3N4 is also a quasi-direct-band-gap semiconductor, with a band gap of 4.210 eV, with the HSE06 functional.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The sintering additives such as Al2O3 and/or Y2O3 were coated on the surfaces of Si3N4 particles via heterogeneousnucleation processing using a buffered pH solution as the precipitation reagent. They nucleated and grew only onthe surfaces of Si3N4 and did not form sol particles in solution by TEM observation. The isoelectric point (IEP) ofcoated Si3N4 was different from that of as-received Si3N4. The IEP of Al(OH)3-coated Si3N4 occurred at pH8.4,which is close to that of alumina. When Al(OH)3-coated Si3N4 particles were coated with Y(OH)3, the IEP of coatedSi3N4 powder shifted from pH8.4 to pH9.2, similar to that of yttria. In addition, the rheological data showed thatAl2O3 and/or Y2O3 coated Si3N4 suspension is nearly Newtonian and that added Si3N4 suspension shows a shearrate thinning behavior.
Pyrolysis Synthesized g-C3N4 for Photocatalytic Degradation of Methylene Blue
Directory of Open Access Journals (Sweden)
Gang Xin
2013-01-01
Full Text Available Graphitic carbon nitride (g-C3N4 was synthesized at 520°C by the pyrolysis of cyanamide, dicyandiamide, and melamine. The samples were characterized by X–ray diffraction (XRD, UV-visible diffuse reflectance spectra, Fourier transform infrared spectroscopy (FT-IR, and elemental analyzer. The photocatalytic activity of g-C3N4 was evaluated by the photodegrading experiments of methylene blue (MB. The results indicated that g-C3N4. A photocatalytic mechanism presumed the MB photodegradation over the C3N4 photocatalyst is attributed to photogenerated electron impelled multistep reduction of O2.
Institute of Scientific and Technical Information of China (English)
昝青峰; 黄勇; 汪长安; 余志勇; 崔学民
2001-01-01
本文采用流延法制备了Si3N4块体及Si3N4/BN层状材料.流延法已经在陶瓷的制备工艺中得到了广泛的应用,但是很少用于Si3N4体系,尤其是水基流延法.用流延法制备Si3N4/BN层状材料时,可以较为容易地控制坯片的厚度,得到性能稳定的层状材料.
The Impact of Si3N4 Content on the Si3N4-SiC Materials Corrosion%Si3N4含量对Si3N4-SiC材料腐蚀性能的影响
Institute of Scientific and Technical Information of China (English)
李杰
2009-01-01
利用Si3N4-SiC材料在冰晶石静态融盐电解质中的腐蚀实验研究材料的腐蚀性能,对腐蚀增重率进行记录分析,Si3N4的含量是影响材料腐蚀性能的重要因素,根据实验测定得出Si3N4的含量越高,Si3N4-SiC材料腐蚀程度越严重.
On superconformal Chern-Simons-matter theories in N=4 superspace
Kuzenko, Sergei M
2015-01-01
In three dimensions, every known N=4 supermultiplet has an off-shell completion. However, there is no off-shell N=4 formulation for the known extended superconformal Chern-Simons (CS) theories with eight and more supercharges. To achieve a better understanding of this issue, we provide N=4 superfield realisations for the equations of motion which correspond to various N=4 and N=6 superconformal CS theories, including the Gaiotto-Witten theory and the ABJM theory. These superfield realisations demonstrate that the superconformal CS theories with N>3 (except for the Gaiotto-Witten theory) require a reducible long N=4 vector multiplet, from which the standard left and right N=4 vector multiplets are obtained by constraining the field strength to be either self-dual or anti self-dual. Such a long multiplet naturally originates upon reduction of any off-shell N>4 vector multiplet to N=4 superspace. For the long N=4 vector multiplet we develop a prepotential formulation. It makes use of two prepotentials being subj...
Institute of Scientific and Technical Information of China (English)
古尚贤; 郭伟明; 伍尚华; 游洋; 蒋强国; 高棱
2015-01-01
以TiC和TiN粉为导电相,利用热压烧结制备了Si3N4-TiC和Si3N4-TiN复相导电陶瓷.比较了TiC和TiN对Si3N4陶瓷相组成、致密度、显微结构、力学性能、导电性能及电火花加工性能的影响.结果表明:高温下TiN与Si3N4具有良好稳定性,烧结后获得Si3N4-TiN复相导电陶瓷,然而高温下TiC却与Si3N4反应形成了TiC0.5N0.5和SiC,烧结后获得Si3 N4-TiC0.5N0.5-SiC复相导电陶瓷.虽然TiN和TiC的引入对Si3N4的硬度和断裂韧性的影响没有明显差别,然而TiC的引入可以更好的改善Si3N4的致密化、导电性能及电火花加工性能;与以TiN为导电相所制备的Si3N4基导电陶瓷相比,以TiC为导电相所制备的Si3N4基复相导电陶瓷电火花加工后表面的粗糙度值和材料去除率更低.
Directory of Open Access Journals (Sweden)
Jacqueline Zoe-Munn Chan
2014-10-01
Full Text Available Two bacteriophages, RPP1 and RLP1, infecting members of the marine Roseobacter clade were isolated from seawater. Their linear genomes are 74.7 and 74.6 kb and encode 91 and 92 coding DNA sequences, respectively. Around 30% of these are homologous to genes found in Enterobacter phage N4. Comparative genomics of these two new Roseobacter phages and twenty-three other sequenced N4-like phages (three infecting members of the Roseobacter lineage and twenty infecting other Gammaproteobacteria revealed that N4-like phages share a core genome of 14 genes responsible for control of gene expression, replication and virion proteins. Phylogenetic analysis of these genes placed the five N4-like roseophages (RN4 into a distinct subclade. Analysis of the RN4 phage genomes revealed they share a further 19 genes of which nine are found exclusively in RN4 phages and four appear to have been acquired from their bacterial hosts. Proteomic analysis of the RPP1 and RLP1 virions identified a second structural module present in the RN4 phages similar to that found in the Pseudomonas N4-like phage LIT1. Searches of various metagenomic databases, included the GOS database, using CDS sequences from RPP1 suggests these phages are widely distributed in marine environments in particular in the open ocean environment.
Pucher, Florian J; Marchuk, Alexey; Schmidt, Peter J; Wiechert, Detlef; Schnick, Wolfgang
2015-04-20
Nitridophosphates MP2 N4 :Eu(2+) (M=Ca, Sr, Ba) and BaSr2 P6 N12 :Eu(2+) have been synthesized at elevated pressures and 1100-1300 °C starting from the corresponding azides and P3 N5 with EuCl2 as dopant. Addition of NH4 Cl as mineralizer allowed for the growth of single crystals. This led to the successful structure elucidation of a highly condensed nitridophosphate from single-crystal X-ray diffraction data (CaP2 N4 :Eu(2+) (P63 , no. 173), a=16.847(2), c=7.8592(16) Å, V=1931.7(6) Å(3) , Z=24, 2033 observed reflections, 176 refined parameters, wR2 =0.096). Upon excitation by UV light, luminescence due to parity-allowed 4f(6) ((7) F)5d(1) →4f(7) ((8) S7/2 ) transition was observed in the orange (CaP2 N4 :Eu(2+) , λmax =575 nm), green (SrP2 N4 :Eu(2+) , λmax =529 nm), and blue regions of the visible spectrum (BaSr2 P6 N12 :Eu(2+) and BaP2 N4 :Eu(2+) , λmax =450 and 460 nm, respectively). Thus, the emission wavelength decreases with increasing ionic radius of the alkaline-earth ions. The corresponding full width at half maximum values (2240-2460 cm(-1) ) are comparable to those of other known Eu(2+) -doped (oxo)nitrides emitting in the same region of the visible spectrum. Following recently described quaternary Ba3 P5 N10 Br:Eu(2+) , this investigation represents the first report on the luminescence of Eu(2+) -doped ternary nitridophosphates. Similarly to nitridosilicates and related oxonitrides, Eu(2+) -doped nitridophosphates may have the potential to be further developed into efficient light-emitting diode phosphors.
Microstructure and mechanical properties of Ni-P-Si3N4 nanowire electroless composite coatings
Wang, Shilong; Huang, Xuefei; Gong, Mengxiao; Huang, Weigang
2015-12-01
In this paper, a new Ni-P-Si3N4 nanowire composite coating has been successfully prepared on AZ31 Mg substrate through electroless deposition technique. The effect of Si3N4 nanowire concentration in the plating bath on the surface morphology, hardness and wear behavior of the composite coatings have been investigated. The results show that when the concentrations of Si3N4 nanowire is 1.5 g/L, the morphology of composite coating appears the fine nodular structure. Moreover, the Si3N4 nanowire is uniformly dispersed in the coating at the 1.5 g/L concentrations of Si3N4 nanowire. But when the concentrations of Si3N4 nanowire in bath over 1.5 g/L, the coatings surface morphology become roughness and some pores appear on the coating surface because of the agglomeration of Si3N4 nanowire. As seen from the experiments results, the microhardness of the composite coating were significantly increased to about 790HV200 as plating, the friction coefficient and wear weight loss of the composite coating is both decreased to the 1/6 of conventional Ni-P electroless coating. These improvements have been attributed to the dispersion strengthening effect of Si3N4 nanowire.
Process control & monitoring for laser micromaching of Si3N4 ceramics
CSIR Research Space (South Africa)
Tshabalala, L
2012-09-01
Full Text Available Laser machining which is a non-contact process that offers the advantage of machining advanced ceramics. In laser machining Si3N4, surface temperature is increased and controlled to evaporate the YSiAlON glassy phase of the Si3N4. However...
Enhancement of photocatalytic and photoelectrocatalytic activity of Ag modified Mpg-C3N4 composites
He, Qiuchen; Zhou, Feng; Zhan, Su; Yang, Yifan; Liu, Yujun; Tian, Yu; Huang, Naibao
2017-01-01
In this study, mpg-C3N4/Ag composites of surface plasmon resonance structures were fabricated to improve the photocatalytic and photoelectrocatalytic activities of g-C3N4 via photo-assisted reduction method, which were characterized by XRD, EDS, XPS, FT-IR, FE-SEM, TEM, DRS and BET. The photocatalytic and photoelectrocatalytic activities were evaluated by the degradation of methylene blue (MB) and the oxygen reduction experiment under visible light. The results showed the photocatalytic and photoelectrocatalytic activities were dependent on the weight ratio of Ag and the optimum photocatalytic activity of mpg-C3N4/Ag at a weight ratio of 3% is almost 3 times as high as that of mpg-C3N4. Additionally, mpg-C3N4/Ag exhibited a significantly enhanced oxygen reduction performance under visible light. The limit current density was increased about 2 times by the modification of Ag nanoparticles, compared with that of pristine mpg-C3N4. Finally, based on the first principle, the enhancement mechanism of the photocatalytic and photoelectrocatalytic activities was discussed by the calculation on the band structure and density of states in the mpg-C3N4/Ag composites. The appropriate amount of Ag modification would cause the surface plasmon resonance effect, which improved the photocatalytic, photoelectrocatalytic, and oxygen reduction activities of mpg-C3N4.
Sintering and properties of Si3N4 with and without additives by HIP treatment
Kuratani, S.; Shimada, M.; Koizumi, M.
1986-01-01
Hot Isostatic Pressing (HIP) of Si3N4 powders with and without additives was performed using a glass container, and various kinds of pressureless-sintered Si3N4 were HIP'ed without a container. The effects of HIP treatment on density, microstructure, flexural strength, microhardness, and fracture toughness on Si3N4 ceramics were studied. Using a glass container it was difficult to reach theoretical density. The microhardness of HIP'ed Si3N4 without additives was low, and the fracture toughness of HIP'ed Si3N4 with and without additives was 22 to 25 W/m-K, and it decreased with increasing the amount of additives. The density and flexural strength, and hardness of pressureless-sintered Si3N4 which contained Al2O and Y2O3 as oxide additives were remarkably improved by HIP treatment using nitrogen as a pressure transmitting gas. It is very important to select the sintering conditions for fabricating the presintered body of Si3N4 in order to improve the mechanical properties of Si3N4 by HIP treatment.
High confinement, high yield Si3N4 waveguides for nonlinear optical applications
Epping, J.P.; Hoekman, M.; Mateman, R.; Leinse, A.; Heideman, R.G.; Rees, van A.; Slot, van der P.J.M.; Lee, C.J.; Boller, K-J.
2015-01-01
In this paper we present a novel fabrication technique for silicon nitride (Si3N4) waveguides with a thickness of up to 900 nm, which are suitable for nonlinear optical applications. The fabrication method is based on etching trenches in thermally oxidized silicon and filling the trenches with Si3N4
Effect of β-Si3N4 Content on Y2O3 -MgO-α-Si3N4 Properties%β-Si3N4含量对Y2O3-MgO-α-Si3N4陶瓷性能的影响
Institute of Scientific and Technical Information of China (English)
李荐; 李淳伟; 周宏明; 黄祖琼; 刘凡; 李艳芬; 杨俊; 杨亮
2011-01-01
利用扫描电子显微分析等手段,研究了棒状β-Si3N4含量对Y2O3-MgO-α-Si3N4陶瓷致密度、力学性能和显微结构的影响,确定了β-Si3N4和α-Si3N4的适宜配比.结果显示:随着β-Si3N4含量的增加,Y2O3-MgO-α-Si3N4陶瓷材料致密度和力学性能均先增加后降低,当β-Si3N4含量达到40％时,陶瓷致密度和力学性能同时达到最大,此时致密度为93％,横向断裂强度为583.4 MPa,断裂韧性为5.42 MPa·m1/2.%The influence of bar-shaped (3-Si3N4 content on the density, mechanical property and microstructure of Y2O3-MgO-a-Si3N4 was researched by using SME and other methods, and the most appropriate proportion of JJ-Si3N4 to ct-Si3N4 was determined. The results showed that with the increasing of the content of p-Si3N4 both of the density and mechanical property of Y2O3-MgO-a-Si3N4 ceramic material first increased, then decreased. When p-Si3N4 content achieved 40% , the density and mechanical property both reached to the maximum, with a density of 93% , transverse rupture strength of 583.4 Mpa and fracture toughness of 5.42 Mpa ? M1/2.
Effects of talc and clay addition on pressureless sintering of porous Si3N4 ceramics
Indian Academy of Sciences (India)
Yu Fangli; Yang Jianfeng; Xue Yaohui; Du Jun; Lu Yuan; Gao Jiqiang
2009-04-01
Porous Si3N4 ceramics were successfully synthesized using cheaper talc and clay as sintering additives by pressureless sintering technology and the microstructure and mechanical properties of the ceramics were also investigated. The results indicated that the ceramics consisted of elongated -Si3N4 and small Si2N2O grains. Fibrous -Si3N4 grains developed in the porous microstructure, and the grain morphology and size were affected by different sintering conditions. Adding 20% talc and clay sintered at 1700°C for 2 h, the porous Si3N4 ceramics were obtained with excellent properties. The final mechanical properties of the Si3N4 ceramics were as follows: porosity, 0 = 45.39%; density, ρ = 1.663.g.cm-3; flexural strength, b (average) = 131.59 MPa; Weibull modulus, = 16.20.
Effect of electrodeposition conditions on the properties of Cu-Si3N4 composite coatings
Eslami, Maryam; Saghafian, Hassan; Golestani-fard, Farhad; Robin, Alain
2014-05-01
Cu-Si3N4 composite coatings were obtained by co-electrodeposition under DC conditions from a copper sulphate bath containing suspended Si3N4 particles. The effect of some electroplating parameters such as surfactant (SDS) concentration, stirring rate, and particle concentration on microstructural and mechanical properties of the coatings was investigated. The incorporation of Si3N4 particles into the copper matrix resulted in the production of coatings with finer copper grains. The incorporation of Si3N4 particles also led to a change of the preferred growth orientation of copper grains from (2 0 0) to (2 2 0) crystal face. Cu-Si3N4 composite coatings presented lower friction coefficient and wear loss than pure copper deposit due to the increased hardness related to grain refinement strengthening and dispersion strengthening.
Effect of Rare Earths on Mechanical Properties and Microstructures of Si3N4-based Ceramics
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The effects of Y2O3, La2O3 and Nd2O3 on the mechanical properties and microstructures of Si3N4-based ceramics were studied. It shows that a significant improvement in mechanical properties can be obtained by adding rare earths oxides in Si3N4. The fracture toughness and the flexural strength of Si3N4 added with both Y2O3 and La2O3 are 7.8 MPa.m1/2 and 962 MPa, respectively. The main reason is that adding rare earths in Si3N4 can improve the microstructure of the material and increase the aspect ratio of β-Si3N4 grain.
Oxidation Behaviour of Si3N4 Materials in Air and Nitrogen Atmosphere
Institute of Scientific and Technical Information of China (English)
ZHANGQitu; LINGZhida
1999-01-01
Si3N4 powder and hot-pressed Si3N4 ceramics added with Al2O3 are used for investigate their oxidation behvior in air and nitrogen atmosphere(with oxygen partial pressure PO2=1-10Pa),The oxidation products of Si3N4 are examined by chemical analysi,X-ray diffraction (XRD) and XPS method,Also, thermodynamic calculation is made to analyze oxidation behavior of Si3N4.The results show that only passive oxidation will occur when Si3N4 is oxidized in air at high temperature,whereas in N2 at high temperature,the active oxidation is dominant in spite of the existence of a little passive oxidation.
Zhang, Ke; Du, Miao; Haoa, Lei; Meng, Jianping; Wang, Jining; Mi, Jing; Liu, Xiaopeng
2016-12-14
Highly corrosion resistant, layer-by-layer nanostructured Si3N4/Cr-CrNx/Si3N4 coatings were deposited on aluminum substrate by DC/RF magnetron sputtering. Corrosion resistance experiments were performed in 0.5, 1.0, 3.0, and 5.0 wt % NaCl salt spray at 35 °C for 168 h. Properties of the coatings were comprehensively investigated in terms of optical property, surface morphology, microstructure, elemental valence state, element distribution, and potentiodynamic polarization. UV-vis-near-IR spectrophotometer and FTIR measurements show that the change process in optical properties of Si3N4/Cr-CrNx/Si3N4/Al coatings can be divided into three stages: a rapid active degradation stage, a steady passivation stage, and a transpassivation degradation stage. With the increase in the concentration of NaCl salt spray, solar absorptance and thermal emittance experienced a slight degradation. SEM images reveal that there is an increase in surface defects, such as microcracks and holes and -cracks. XRD and TEM measurements indicate that the phase structure changed partially and the content of CrOx and Al2O3 has increased. Auger electron spectroscopy shows that the elements of Cr, N, and O have undergone a minor diffusion. Electrochemical polarization curves show that the as-deposited Si3N4/Cr-CrNx/Si3N4/Al coatings have excellent corrosion resistance of 3633.858 kΩ, while after corroding in 5.0 wt % NaCl salt spray for 168 h the corrosion resistance dropped to 13.759 kΩ. However, these coatings still have an outstanding performance of high solar absorptance of 0.924 and low thermal emittance of 0.090 after corroding in 3.0 wt % NaCl salt spray for 120 h. Thus, the Si3N4/Cr-CrNx/Si3N4/Al coating is a good choice for solar absorber coatings applied in the high-saline environment.
The Si/Si_3N4 Interface and Si/Si_3N4 Submicron Mesa: A Multi-million Atom Molecular Dynamics Study
Bachlechner, Martina E.; Omeltchenko, Andrey; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya; Ebbsjö, Ingvar; Madhukar, Anupam
1998-03-01
Using molecular dynamics simulations on parallel computers, the interface structure, stress distribution, crack propagation and fracture in a Si_3N4 film on Si substrate are studied. Bulk Si is described by Stillinger-Weber potential and Si_3N4 is represented by a combination of two- and three-body covalent interactions. At the interface, the charge transfer is taken from LCAO electronic structure calculations (G.-L. Zhao and M.E. Bachlechner, Europhys. Lett. 36, 287 (1997)). Results for structural correlations at the interface and 3D stress distribution for the submicron mesa are presented.
Institute of Scientific and Technical Information of China (English)
何钢; 石磊; 吕珺; 郑治祥
2001-01-01
利用反应烧结机制，在1 450 ℃制备了Si3N4结合SiC材料，研究表明，在引入微量纳米Si3N4粉后，材料的力学性能得到 明显提高，材料的组织也更加致密和均匀。通过X-ary、扫描电镜等技术手段分析表明，由 于纳米Si3N4粉的高表面能、高活性以及颗粒小等特点，加大了反应生成的Si3N4在 纳米Si3N4上沉积的几率，增大了氮化率，效果显著。%Si3N4 reaction bonded SiC with the addition of a small amount of nano-Si3N4 was produced at 1 450 ℃. The result showed that the mechanic properties of the material were greatly improved. The microstructu re of the material became more uniform. The mechanism of the strength improvemen t of the material was attributed to the addition. The nano-Si3N4 properties of high surface energy,high activity and small size particles increased the dep osit of Si3N4 reacted on the nano-Si3N4 and the nitriding rate of Si,th en improved the properties of the material.
Study to Material Al-Si3N4 Infiltration Technique%Al-Si3N4材料浸渗工艺研究
Institute of Scientific and Technical Information of China (English)
吴冉; 王雅红
2007-01-01
用β-Si3N4纳米颗粒浆料浸渍多孔聚合物材料,通过加热烧蚀掉聚合物,制备出三维空间连续网络结构预制块体,再通过无压浸渗将已熔炼好的铝液浸渗到预制体中,成功制备出陶瓷与金属相互贯穿的Si3N4/Al金属基复合材料.利用座滴定法测试了Al在Si3N4基片上的润湿角,探讨了其浸渗机理,分析了润湿角、浸渗力、浸渗温度和浸渗时间对Si3N4/Al金属基复合材料浸渗行为的影响.
Si3N4-SiCp Composites Reinforced by In Situ Co-Catalyzed Generated Si3N4 Nanofibers
Directory of Open Access Journals (Sweden)
Juntong Huang
2014-01-01
Full Text Available Si3N4-SiCp composites reinforced by in situ catalytic formed nanofibers were prepared at a relatively low sintering temperature. The effects of catalyst Co on the phase compositions, microstructures, and physicochemical-mechanical properties of samples sintered at 1350°C–1450°C were investigated. The results showed that the catalyst Co enhanced the nitridation of Si. With the increase of Co addition (from 0 wt% to 2.0 wt.%, the apparent porosity of as-prepared refractories was initially decreased and subsequently increased, while the bulk density and the bending strength exhibited an opposite trend. The Si3N4-SiCp composites sintered at 1400°C had the highest strength of 60.2 MPa when the Co content was 0.5 wt.%. The catalyst Co facilitated the sintering of Si3N4-SiCp composites as well as the formation of Si3N4 nanofibers which exhibited network connection and could improve their strength.
Fabrication and Properties of Porous Si_3N_4 Ceramic with High Porosity
Institute of Scientific and Technical Information of China (English)
Xiangming Li; Litong Zhang; Xiaowei Yin
2012-01-01
A novel process combining oxidation-bonding and sintering was developed to fabricate porous Si3N4 ceramic with high porosity. After sintering at 1800℃, the SiO2 in porous Si3N4 ceramic transforms into Si2N2O because of the reaction of SiO2 and Si3N4 . Due to the reaction of SiO2 and carbon, the porosity of porous Si3N4 ceramic increases obviously from 40.2% to 76.8% with the weight decreasing by 35.6%. As the porosity increases, the dielectric constant and loss of the porous Si3N4 ceramic decrease obviously from 3.08 to 1.61 and from 3.70×10(-3) to 0.74×10(-3) , but due to the production of Si2N2O whose mechanical properties are much higher than SiO2 and the increase of the bonding strength among Si3N4 particles, the flexural strength and the fracture toughness of the porous Si3N4 ceramic decrease from 55 to 39 MPa and from 0.7 to 0.5 MPa·m(1/2) , respectively, but its Vickers hardness increases from 1.2 to 1.3 GPa.
Pulse electrodeposition and corrosion properties of Ni–Si3N4 nanocomposite coatings
Indian Academy of Sciences (India)
S Kasturibai; G Paruthimal Kalaignan
2014-05-01
The development of modern technology requires metallic materials with better surface properties. In the present investigation; Si3N4-reinforced nickel nanocomposite coatings were deposited on a mild steel substrate using pulse current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of Ni and Ni–Si3N4 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of Si3N4 particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon nitride particles were obtained and the crystal grains on the surface of Ni–Si3N4 composite coating are compact. The crystallite structure was face centred cubic () for electrodeposited nickel and Ni–Si3N4 nanocomposite coatings. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si3N4 particle content. The corrosion potential (corr) in the case of Ni–Si3N4 nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating.
Hydrothermal synthesis of C3N4/BiOIO3 heterostructures with enhanced photocatalytic properties.
Wang, Wenjun; Cheng, Hefeng; Huang, Baibiao; Liu, Xiaolei; Qin, Xiaoyan; Zhang, Xiaoyang; Dai, Ying
2015-03-15
The C3N4/BiOIO3 composites with heterostructures have been fabricated by simply depositing BiOIO3 on the surface of C3N4 at hydrothermal conditions, using bismuth nitrate and potassium iodate as precursors. C3N4 is an excellent organic semiconductor, which can be excited by visible light. BiOIO3 is a layered bismuth-based compound that has an internal polar field. Coupling C3N4 with BiOIO3 can combine the advantages of the two compounds and obtain better photocatalytic properties. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transformation infrared spectra have been carried out to confirm the structures and morphologies of as-prepared products. The absorption properties have been characterized by diffuse reflectance spectra and the photocatalytic activities have been evaluated by photodegradation of methyl orange, Rhodamine B and 2,4-dichlorophenol. Compared with C3N4, all C3N4/BiOIO3 composites exhibit better visible-light-driven photocatalytic properties. It is a synergetic effect that enables the composites to harvest light and promote charge separation, which eventually leads to the enhancement of the photocatalytic efficiencies. Under UV-vis light irradiation, C3N4/BiOIO3 composites also exhibit better activities, and the charge transfer process is similar to a redox mediator-free Z-scheme system. Copyright © 2014 Elsevier Inc. All rights reserved.
Development of Si3N4/Al composite by pressureless melt infiltration
Institute of Scientific and Technical Information of China (English)
Akhtar Farid; GUO Shi-ju
2006-01-01
Pressureless infiltration process to synthesize Si3N4/Al composite was investigated. Al-2%Mg alloy was infiltrated into Si3N4 and Si3N4 containing 10% Al2O3 preforms in the atmosphere of nitrogen. It is possible to infiltrate Al-2%Mg alloy in Si3N4 and Si3N4 containing 10% Al2O3 preforms. The growth of the dense composite of useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. During infiltration Si3N4 reacted with aluminium to form Si and AlN,the growth of composite was found to proceed in two ways, depending on the Al2O3 content in the initial preform. Firstly, preform without Al2O3 content gives rise to AlN, Al3.27Si0.47 and Al type phases after infiltration. Secondly, perform with 10% Al2O3 content gives rise to AlN-Al2O3 solid solution phase (AlON), MgAl2O4, Al and Si type phases. AlON phase was only present in composite,containing 10% Al2O3 in the Si3N4 preforms before infiltration.
Effect of Si3N4 on Resistance of Magnesia Based Castable
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite (w(MgO)=95%) as starting material, 5iO2 micro-powder as binder, 0, 3%, 4% and 5% β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550℃ for 3h using Baosteel tundish slag and static crucible method. The result indicates that: introducing Si3N4 could obviously improve the slag resistance of MgO based castable, which increased with increasing Si3N4 Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable, the partial-pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere, Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.
26 CFR 1.103(n)-4T - Elective carryforward of unused private activity bond limit (temporary).
2010-04-01
... bond limit (temporary). 1.103(n)-4T Section 1.103(n)-4T Internal Revenue INTERNAL REVENUE SERVICE... Excluded from Gross Income § 1.103(n)-4T Elective carryforward of unused private activity bond limit... carryforward for any one or more projects described in A-5 of this § 1.103(n)-4T (carryforward projects). Q-2...
Thermal conductivity of pressureless sintered Si3N4 ceramics with Li-exchanged zeolite
Directory of Open Access Journals (Sweden)
SNEZANA BOSKOVIC
2004-09-01
Full Text Available The effects of temperature on the thermal conductivity of Si3N4 sintered with Li-exchanged zeolite were investigated. The highest conductivity was measured for the ceramics sintered with 10 % of additive. The complete a->b-Si3N4 transformation and maximum density (> 98 % TD were attained with the sample sintered at 1650 ºC. However, the results show that Al and O from the additive dissolve into the b-Si3N4 structure which act as phonon scattering sites resulting in a lowering of the conductivity and a weaker temperature dependance of the conductivity.
High confinement, high yield Si3N4 waveguides for nonlinear optical application
Epping, Jörn P; Mateman, Richard; Leinse, Arne; Heideman, René G; van Rees, Albert; van der Slot, Peter J M; Lee, Chris J; Boller, Klaus-J
2014-01-01
In this paper we present a novel fabrication technique for silicon nitride (Si3N4) waveguides with a thickness of up to 900 nm, which are suitable for nonlinear optical applications. The fabrication method is based on etching trenches in thermally oxidized silicon and filling the trenches with Si3N4. Using this technique no stress-induced cracks in the Si3N4 layer were observed resulting in a high yield of devices on the wafer. The propagation losses of the obtained waveguides were measured to be as low as 0.4 dB/cm at a wavelength of around 1550 nm.
Pyrolysis Synthesized g-C3N4 for Photocatalytic Degradation of Methylene Blue
2013-01-01
Graphitic carbon nitride (g-C3N4) was synthesized at 520°C by the pyrolysis of cyanamide, dicyandiamide, and melamine. The samples were characterized by X–ray diffraction (XRD), UV-visible diffuse reflectance spectra, Fourier transform infrared spectroscopy (FT-IR), and elemental analyzer. The photocatalytic activity of g-C3N4 was evaluated by the photodegrading experiments of methylene blue (MB). The results indicated that g-C3N4. A photocatalytic mechanism presumed the MB photodegradation o...
Structural and Biochemical Investigation of Bacteriophage N4-Encoded RNA Polymerases
Directory of Open Access Journals (Sweden)
Bryan R. Lenneman
2015-04-01
Full Text Available Bacteriophage N4 regulates the temporal expression of its genome through the activity of three distinct RNA polymerases (RNAP. Expression of the early genes is carried out by a phage-encoded, virion-encapsidated RNAP (vRNAP that is injected into the host at the onset of infection and transcribes the early genes. These encode the components of new transcriptional machinery (N4 RNAPII and cofactors responsible for the synthesis of middle RNAs. Both N4 RNAPs belong to the T7-like “single-subunit” family of polymerases. Herein, we describe their mechanisms of promoter recognition, regulation, and roles in the phage life cycle.
Selective Oxidation of Alcohols Using Photoactive VO@g‑C3N4
U.S. Environmental Protection Agency — A photoactive VO@g-C3N4 catalyst has been developed for the selective oxidation of alcohols to the corresponding aldehydes and ketones. The visible light mediated...
Complete low-energy effective action in N=4 SYM: a direct N=2 supergraph calculation
Energy Technology Data Exchange (ETDEWEB)
Buchbinder, I.L. E-mail: joseph@tspu.edu.ru; Ivanov, E.A. E-mail: eivanov@thsun1.jinr.ru; Petrov, A.Yu. E-mail: petrov@fma.if.usp.brpetrov@tspu.edu.ru
2003-03-10
Using the covariant N=2 harmonic supergraph techniques we calculate the one-loop low-energy effective action of N=4 super-Yang-Mills theory in Coulomb branch with gauge group SU(2) spontaneously broken down to U(1). The full dependence of the low-energy effective action on both the hypermultiplet and gauge fields is determined. The direct quantum calculation confirms the correctness of the exact N=4 SYM low-energy effective action derived in on the purely algebraic ground by invoking a hidden N=2 supersymmetry which completes the manifest N=2 one to N=4. Our results provide an exhaustive solution to the problem of finding out the exact completely N=4 supersymmetric low-energy effective action for the theory under consideration.
Conformal kernel for NLO BFKL equation in ${\\cal N}$=4 SYM
Energy Technology Data Exchange (ETDEWEB)
Balitsky, Ian; Chirilli, Giovanni
2009-01-01
Using the requirement of M\\"{o}bius invariance of ${\\cal N}$=4 SYM amplitudes in the Regge limit we restore the conformal NLO BFKL kernel out of the eigenvalues known from the forward NLO BFKL result.
Photocatalytic C−H Activation of Hydrocarbons over VO@g‑C3N4
U.S. Environmental Protection Agency — A highly selective and sustainable method has been developed for the oxidation of methyl arenes and their analogues. The VO@g-C3N4 catalyst is very efficient in the...
Temperature Influence on the Properties of Thin Si3N4 Films
Directory of Open Access Journals (Sweden)
V.S. Zakhvalinskii
2015-12-01
Full Text Available Applying Raman spectroscopy, small-angle x-ray scattering, and atomic force microscopy it were studied phase composition and surface morphology of nanoscale films Si3N4 (obtained by RF magnetron sputtering.
Institute of Scientific and Technical Information of China (English)
李杰
2009-01-01
利用Si3N4-SiC材料在冰晶石静态融盐电解质中的腐蚀实验研究材料的腐蚀性能,对腐蚀增重率进行记录分析,Si3N4的含量以及腐蚀时间都是影响Si3N4-SiC材料腐蚀性能的重要因素,腐蚀过程主要发生在25h前,并且随着Si3N4的含量增加,腐蚀程度越严重.
Elastic anisotropy and electronic properties of Si3N4 under pressures
Directory of Open Access Journals (Sweden)
Qingyang Fan
2016-08-01
Full Text Available First principles calculations are performed to systematically investigate the electronic structures, elastic, anisotropic and electronic properties of the monoclinic, tetragonal and orthorhombic structures of Si3N4 under pressure. Anisotropy studies show that three Si3N4 phases exhibit a large anisotropy. Furthermore, using the HSE06 hybrid functional, the monoclinic, tetragonal and orthorhombic phases are found to be wide band-gap semiconductors. The pressure induced band gap direct-indirect transition is found for monoclinic Si3N4. The elastic modulus, compressional and shear wave velocities as well as Debye temperatures as a function of pressure in three Si3N4 phases are also investigated in detail.
Parcels and Land Ownership, 1n4w-indian, Published in 2002, Duchesne County.
NSGIC GIS Inventory (aka Ramona) — This Parcels and Land Ownership dataset, was produced all or in part from Other information as of 2002. It is described as '1n4w-indian'. Data by this publisher are...
Pure and entangled N=4 linear supermultiplets and their one-dimensional sigma-models
Gonzales, Marcelo; Khodaee, Sadi; Toppan, Francesco
2012-01-01
"Pure" homogeneous linear supermultiplets (minimal and non-minimal) of the N=4-Extended one-dimensional Supersymmetry Algebra are classified. "Pure" means that they admit at least one graphical presentation (the corresponding graph/graphs are known as "Adinkras"). We further prove the existence of "entangled" linear supermultiplets which do not admit a graphical presentation, by constructing an explicit example of an entangled N=4 supermultiplet with field content (3,8,5). It interpolates between two inequivalent pure N=4 supermultiplets with the same field content. The one-dimensional N=4 sigma-model with a three-dimensional target based on the entangled supermultiplet is presented. The distinction between the notion of equivalence for pure supermultiplets and the notion of equivalence for their associated graphs (Adinkras) is discussed. Discrete properties such as chirality and coloring can discriminate different supermultiplets. The tools used in our classification have been previously introduced and discu...
Hecke Operator and S-Duality of N=4 ADE Gauge Theory on K3
Sasaki, T
2003-01-01
We determine ${\\cal N}=4$ partition functions on K3 for some ADE gauge groups, on the assumption that they are holomorphic. Our partition functions satisfy the gap condition and Montonen-Olive duality at the same time, like the SU(N) partition functions of Vafa and Witten. As a result, we reveal a close relation between Hecke operator and S-duality of ${\\cal N}=4 ADE$ gauge theory on K3.
Two-Loop Iteration of Five-Point N=4 Super-Yang-Mills Amplitudes
Bern, Z; Kosower, D A; Roiban, R; Smirnov, V A
2006-01-01
We confirm by explicit computation the conjectured all-orders iteration of planar maximally supersymmetric N=4 Yang-Mills theory in the nontrivial case of five-point two-loop amplitudes. We compute the required unitarity cuts of the integrand and evaluate the resulting integrals numerically using a Mellin--Barnes representation and the automated package of ref.~[1]. This confirmation of the iteration relation provides further evidence suggesting that N=4 gauge theory is solvable.
N=4 Super-Yang-Mills Theory, QCD and Collider Physics
Bern, Z; Kosower, D A
2004-01-01
We review how (dimensionally regulated) scattering amplitudes in N=4 super-Yang-Mills theory provide a useful testing ground for perturbative QCD calculations relevant to collider physics, as well as another avenue for investigating the AdS/CFT correspondence. We describe the iterative relation for two-loop scattering amplitudes in N=4 super-Yang-Mills theory found in C. Anastasiou et al., Phys. Rev. Lett. 91:251602 (2003), and discuss recent progress toward extending it to three loops.
Preparation of Si3N4–SiC composites by microwave route
Indian Academy of Sciences (India)
M Panneerselvam; K J Rao
2002-12-01
Si3N4–SiC composites have been microwave sintered using -Si3N4 and -SiC as starting materials. Si3N4 rich compositions (95 and 90 vol.% Si3N4) have been sintered above 96% of theoretical density without using any sintering additives in 40 min. A monotonic decrease in relative density is observed with increase in SiC proportion in the composite. Decrease in relative density has manifested in the reduction of fracture toughness and microhardness values of the composite with increase in SiC content although the good sintering of matrix Si3N4 limits the decrease of fracture toughness. Highest value of fracture toughness of 6.1 MPa m1/2 is observed in 10 vol.% SiC composite. Crack propagation appears to be transgranular in the Si3N4 matrix and the toughening of the composites is through crack deflection around hard SiC particles in addition to its debonding from the matrix.
Boron doped g-C3N4 with enhanced photocatalytic UO22+ reduction performance
Lu, Changhai; Chen, Rongyue; Wu, Xi; Fan, Meifeng; Liu, Yunhai; Le, Zhanggao; Jiang, Shujuan; Song, Shaoqing
2016-01-01
Tuning the band gap and absorption intensity of visible-light by element doping is an attractive strategy to enhance the photocatalytic activity of semiconductor materials. Here we doped boron into g-C3N4 to construct highly efficient photocatalysts (B-g-C3N4) for the photocatalytic reduction of UO22+. Characterization and photocatalysis tests showed the band gap of B-g-C3N4 was narrowed, and the absorption intensity of visible-light was enhanced with increasing the formed N-B-C (BCN) of B-g-C3N4, which is consistent with the trend of the photocatalytic performance of B-g-C3N4. The optimized B-g-C3N4 photocatalyst with BCN content of 1.01 at.% exhibited excellent removal efficiency of UO22+ and good photocatalytic stability. Therefore, these results may lead to a new strategy for exploring the advanced photocatalysts based on the carbon nanomaterials with abundant BCN for the photocatalytic reduction of U(VI) pollutant.
Donets, E. E.; Pashnev, A.; Juan Rosales, J.; Tsulaia, M. M.
2000-02-01
The multidimensional N=4 supersymmetric (SUSY) quantum mechanics (QM) is constructed using the superfield approach. As a result, the component form of the classical and quantum Lagrangian and Hamiltonian is obtained. In the SUSY QM considered, both classical and quantum N=4 algebras include central charges, and this opens various possibilities for partial supersymmetry breaking. It is shown that quantum-mechanical models with one-quarter, one-half, and three-quarters of unbroken (broken) supersymmetries can exist in the framework of the multidimensional N=4 SUSY QM, while the one-dimensional N=4 SUSY QM, constructed earlier, admits only one half or total supersymmetry breakdown. We illustrate the constructed general formalism, as well as all possible cases of partial SUSY breaking taking as an example a direct multidimensional generalization of the one-dimensional N=4 superconformal quantum-mechanical model. Some open questions and possible applications of the constructed multidimensional N=4 SUSY QM to the known exactly integrable systems and problems of quantum cosmology are briefly discussed.
Synthesis and photocatalytic performance of g-C3N4 nanosheets via liquid phase stripping
Miao, Jilin; Xu, Guangqing; Liu, Jiaqin; Lv, Jun; Wu, Yucheng
2017-02-01
Well dispersed g-C3N4 nanosheets were prepared by exfoliating the bulk g-C3N4 in concentrated sulfuric acid. Phase structures, morphologies and elemental compositions were characterized by X-ray diffractometer, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectrometer, respectively. Optical absorption and photoluminescence were also used to explain the optical performances of samples. NaI, BQ and IPA were used as the sacrificial agents for studying the surface reactions in the photocatalytic process. By the precipitation of g-C3N4 nanosheets in ethanol with different ratios between concentrated sulfuric acid and ethyl alcohol, well dispersed g-C3N4 nanosheets with high specific surface area can be obtained. The optimized g-C3N4 (1:10) nanosheets achieve the highest photocatalytic activities under UV light illumination, which can degrade 10 mg/L RhB about 98% in 60 min, which is 6 times that of bulk g-C3N4 under UV light.
Recent Progress in Photocatalysis of g-C3N4%g-C3N4光催化性能的研究进展
Institute of Scientific and Technical Information of China (English)
楚增勇; 原博; 颜廷楠
2014-01-01
利用光催化剂将太阳能转化为人类可以直接利用的能量，并用其解决地球资源的枯竭和生存环境的恶化是可再生清洁能源研究的一个方向。g-C3N4的独特结构赋予其良好的光催化性能，使之成为光催化领域的研究热点。目前在光催化领域， g-C3N4主要用于催化污染物分解、水解制氢制氧、有机合成及氧气还原。在实际应用中，为进一步提高 g-C3N4的光催化效果，科研工作者开发了多种改进方法，例如物理复合改性、化学掺杂改性、微观结构调整等。本文主要论述了 g-C3N4在光催化领域的应用以及光催化性能的改进方法，简要阐述了光催化和各种改进方法的机理，分析了目前g-C3N4在光催化领域面临的问题和挑战，展望了g-C3N4的应用前景。%Based on photocatalysts, solar energy can be converted into the energy that human can directly utilize, so as to solve the problems such as the depletion of the Earth’s resources and the deterioration of living environments. The unique structure of g-C3N4 gives it good photocatalytic performance. Its development and utilization have been a research hotspot recently. Generally, g-C3N4 can be used in the degradation of pollutions, hydrolysis to generate hy-drogen and oxygen, organic synthesis and oxygen reduction. However, in practical, its performance is not satisfactory. Researchers have tried many new methods to improve its photocatalysis, which include physical coupling modification, chemical bonding modification and microstructural modification. The review summarizes its photocatalysis and im-proving methods, briefly illustrates the catalysis mechanism, and presents detailed discussions and analysis on the ex-isting problems as well as potential applications.
Karakas, Asli; Ünver, Hüseyin
2010-05-01
( E)- N-(4-Nitrobenzylidene)-2,6-dimethylaniline ( 1) and ( E)- N-(4-nitrobenzylidene)-2,3-dimethylaniline ( 2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450 nm, showing good optical transparency to the visible light. To provide an insight into the microscopic third-order nonlinear optical (NLO) properties of the investigated molecules, both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities ( α) and second hyperpolarizabilities ( γ) at λ = 825-1125 nm and 1050-1600 nm wavelength areas have been computed using time-dependent Hartree-Fock (TDHF) method. According to the ab initio calculation results, the title molecules exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior.
Hydrophobic 'lock and key' recognition of N-4-nitrobenzoylamino acid by strychnine.
Białońska, Agata; Ciunik, Zbigniew
2006-12-01
During racemic resolution of N-4-nitrobenzoyl-DL-amino acids (alanine, serine and aspartic acid) by a fractional crystallization of strychninium salts, crystals of both diastereomeric salts were grown, and the crystal structures of strychninium N-4-nitrobenzoyl-L-alaninate methanol disolvate (1a), strychninium N-4-nitrobenzoyl-D-alaninate dihydrate (1b), strychninium N-4-nitrobenzoyl-D-serinate dihydrate (2a), strychninium N-4-nitrobenzoyl-L-serinate methanol solvate hydrate (2b), strychninium hydrogen N-4-nitrobenzoyl-L-aspartate 3.75 hydrate (3a) and strychninium hydrogen N-4-nitrobenzoyl-D-aspartate 2.25 hydrate (3b) were determined. The strychninium cations form corrugated layers, which are separated by hydrogen-bonded anions and solvent molecules. Common features of the corrugated layers are deep hydrophobic grooves at their surfaces, which are occupied by the 4-nitrobenzoyl groups of suitable anions. The hydrophobic ;lock and key' recognition of 4-nitrobenzoyl groups of amino acid derivatives in deep grooves of the strychnine self-assembly causes the resulting surface to have more hydrophilic properties, which are more appropriate for interactions in the hydrophilic environments from which strychninium salts were crystallized. In the crystal structure of (2a) and (3a), such hydrophobic ;lock and key' recognition is responsible for the lack of N-H+...O- hydrogen bonds that are usually formed between the protonated tertiary amine N atom of the strychninium cation and the deprotonated carboxyl group of the resolved acid. In the crystal structure of (2a) and (3a), the protonated amine N atom is a donor of hydrogen bonds, while the hydroxyl group of the serine derivative and water molecules are their acceptors. In light of the hydrophobic recognition, chiral discrimination depends on the nature of the hydrogen-bond networks, which involve anions, solvent molecules and the protonated amine N atom of strychninium cations.
The Human Pendrin Promoter Contains two N4 GAS Motifs with Different Functional Relevance
Directory of Open Access Journals (Sweden)
Simone Vanoni
2013-12-01
Full Text Available Background: Pendrin, an anion exchanger associated with the inner ear, thyroid and kidney, plays a significant role in respiratory tissues and diseases, where its expression is increased following IL-4 and IL-13 exposure. The mechanism leading to increased pendrin expression is in part due to binding of STAT6 to a consensus sequence (N4 GAS motif located in the pendrin promoter. As retrospective analyses of the 5' upstream sequence of the human pendrin promoter revealed an additional N4 GAS motif (1660 base pairs upstream of the one previously identified, we set out to define its contribution to IL-4 stimulated changes in pendrin promoter activity. Methods and Results: Electrophoretic mobility shift assays showed that STAT6 bound to oligonucleotides corresponding to both N4 GAS motifs in vitro, while dual luciferase promoter assays revealed that only one of the N4 GAS motifs was necessary for IL-4 -stimulated increases in pendrin promoter activity in living cells. We then examined the ability of STAT6 to bind each of the N4 GAS motifs in vivo with a site-specific ChIP assay, the results of which showed that STAT6 interacted with only the N4 GAS motif that was functionally implicated in increasing the activity of the pendrin promoter following IL-4 treatment. Conclusions: Of the two N4 GAS motifs located in the human pendrin promoter region analyzed in this study (nucleotides -3906 to +7, only the one located nearest to the first coding ATG participates in IL-4 stimulated increases in promoter activity.
African Journals Online (AJOL)
DR. AMINU
ABSTRACT. The manganese (II), cobalt (II), nickel (II) and copper (II) complexes of N, N' – ... temperature and coordinated water were determined ... indicating fairly stable complex compounds (Table 1). The complex compounds are insoluble [Table 2] in water and common organic solvents, but are readily soluble in ...
DEFF Research Database (Denmark)
Jørgensen, Thomas Ekman
2007-01-01
Kommentar til den diplomatiske krise mellem Italien og Kroatien i februar 2007 omkring erindringen af henholdsvis italienske og kroatiske krigsforbrydelser under anden verdenskrig. Krisen bruges som et eksempel på, at gamle medlemslande i EU stiller større krav om til erindringskulturen i ansøger...
A review on g-C3N4-based photocatalysts
Wen, Jiuqing; Xie, Jun; Chen, Xiaobo; Li, Xin
2017-01-01
As one of the most appealing and attractive technologies, heterogeneous photocatalysis has been utilized to directly harvest, convert and store renewable solar energy for producing sustainable and green solar fuels and a broad range of environmental applications. Due to their unique physicochemical, optical and electrical properties, a wide variety of g-C3N4-based photocatalysts have been designed to drive various reduction and oxidation reactions under light irradiation with suitable wavelengths. In this review, we have systematically summarized the photocatalytic fundamentals of g-C3N4-based photocatalysts, including fundamental mechanism of heterogeneous photocatalysis, advantages, challenges and the design considerations of g-C3N4-based photocatalysts. The versatile properties of g-C3N4-based photocatalysts are highlighted, including their crystal structural, surface phisicochemical, stability, optical, adsorption, electrochemical, photoelectrochemical and electronic properties. Various design strategies are also thoroughly reviewed, including band-gap engineering, defect control, dimensionality tuning, pore texture tailoring, surface sensitization, heterojunction construction, co-catalyst and nanocarbon loading. Many important applications are also addressed, such as photocatalytic water splitting (H2 evolution and overall water splitting), degradation of pollutants, carbon dioxide reduction, selective organic transformations and disinfection. Through reviewing the important state-of-the-art advances on this topic, it may provide new opportunities for designing and constructing highly effective g-C3N4-based photocatalysts for various applications in photocatalysis and other related fields, such as solar cell, photoelectrocatalysis, electrocatalysis, lithium battery, supercapacitor, fuel cell and separation and purification.
Investigation on The Properties of Fe-Si3N4 Bonded SiC Composite
Institute of Scientific and Technical Information of China (English)
ZHANG Yong; FENG Di; PENG Dayan
2005-01-01
The mechanical properties of pressureless sintering Fe-Si3N4 bonded SiC and Si3 N4 bonded SiC with same manufacture process have been compared in this paper.The oxidizing mechanism of Fe-Si3 N4 bonded SiC ceramic matrix composite has been investigated especially through TG-DSC (thermo gravimetric analysis-differential scanning calorimeter) experiment. During oxidation procedure the main reaction is the oxidation of SiC and Si3N4, SiO2 which form protecting film to prevent further oxidizing. And residual iron in the samples become Fe2 O3 and Fe3O4, the oxidation kinetics at 1100 ～ 1300℃ of re-Si3 N4 bonded SiC has been studied especially. The weight gain per unit area at initial stage changes according to beeline rule, in the middle according to conic, and in the last oxidation period follows parabola rule.
The crystal structures of four N-(4-halophenyl-4-oxo-4H-chromene-3-carboxamides
Directory of Open Access Journals (Sweden)
Ligia R. Gomes
2015-01-01
Full Text Available Four N-(4-halophenyl-4-oxo-4H-chromene-3-carboxamides (halo = F, Cl, Br and I, N-(4-fluorophenyl-4-oxo-4H-chromene-3-carboxamide, C16H10FNO3, N-(4-chlorophenyl-4-oxo-4H-chromene-3-carboxamide, C16H10ClNO3, N-(4-bromophenyl-4-oxo-4H-chromene-3-carboxamide, C16H10BrNO3, N-(4-iodophenyl-4-oxo-4H-chromene-3-carboxamide, C16H10INO3, have been structurally characterized. The molecules are essentially planar and each exhibits an anti conformation with respect to the C—N rotamer of the amide and a cis geometry with respect to the relative positions of the Carom—Carom bond of the chromone ring and the carbonyl group of the amide. The structures each exhibit an intramolecular hydrogen-bonding network comprising an N—H...O hydrogen bond between the amide N atom and the O atom of the carbonyl group of the pyrone ring, forming an S(6 ring, and a weak Carom—H...O interaction with the O atom of the carbonyl group of the amide as acceptor, which forms another S(6 ring. All four compounds have the same supramolecular structure, consisting of R22(13 rings that are propagated along the a-axis direction by unit translation. There is π–π stacking involving inversion-related molecules in each structure.
Interfacial Bonding Strength of TiN Film Coated on Si3N4 Ceramic Substrate
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The fraction of TiN/Si3N4 in the cross section was observed with scanning electric microscope (SEM), and residual stresses of TiN coated on the surface of Si3N4 ceramic were measured with X-ray diffraction (XRD).The hardness of TiN film was measured, and bonding strength of TiN film coated on Si3N4 substrate was measured by scratching method. The formed mechanism of residual stress and the failure mechanism of the bonding interface in the film were analyzed, and the adhesion mechanism of TiN film was investigated preliminarily. The results show that residual stresses of TiN film are all behaved as compressive stress, and TiN film is represented smoothly with brittle fracture, which is closely bonded with Si3N4 substrate. TiN film has high hardness and bonding strength of about 500 MPa, which could satisfy usage requests of the surface of cutting Si3N4 ceramic.
Ti-decorated graphitic-C3N4 monolayer: A promising material for hydrogen storage
Zhang, Weibin; Zhang, Zhijun; Zhang, Fuchun; Yang, Woochul
2016-11-01
Ti-decorated graphitic carbon nitride (g-C3N4) monolayer as a promising material system for high-capacity hydrogen storage is proposed through density functional theory calculations. The stability and hydrogen adsorption of Ti-decorated g-C3N4 is analyzed by computing the adsorption energy, the charge population, and electronic density of states. The most stable decoration site of Ti atom is the triangular N hole in g-C3N4 with an adsorption energy of -7.58 eV. The large diffusion energy barrier of the adsorbed Ti atom of ∼6.00 eV prohibits the cluster formation of Ti atoms. The electric field induced by electron redistribution of Ti-adsorbed porous g-C3N4 significantly enhanced hydrogen adsorption up to five H2 molecules at each Ti atom with an average adsorption energy of -0.30 eV/H2. The corresponding hydrogen capacity reaches up to 9.70 wt% at 0 K. In addition, the hydrogen capacity is predicted to be 6.30 wt% at 233 K and all adsorbed H2 are released at 393 K according to molecular dynamics simulation. Thus, the Ti-decorated g-C3N4 monolayer is suggested to be a promising material for hydrogen storage suggested by the DOE for commercial applications.
Research on C3N4 Superhard Compound Thin Film and Its Application
Institute of Scientific and Technical Information of China (English)
Wu Da-wei; Peng Li-li; Lu Ning; Peng You-gui
2003-01-01
By combination of DC reactive magnetron sputtering with multiple arcplating, the alternating C3 N4/TiN compound film is deposited onto HSS. The core level binding energy and the contents of carbon and nitrogen are characterized by X-ray photoelectron spectrum. X-ray diffraction(XRD) shows that compound thin film contains hard crystalline phases of α-C3N4 and β-C3N4. The Knoop microhardness in the load range of 50.5-54.1 GPa is measured. According to acoustic emission scratch test, the critical load values for the coatings on HSS substrates are in the range of 40-80 N. The metal coated with C3N4/TiN compound films has a great improvement in the resistance against corrosion. Many tests show that such a coating has a very high wearability. Compared with the uncoated and TiN coated tools, the C3N4/TiN coated tools have a much longer cutting life.
One-Loop Gauge Theory Amplitudes in N=4 Super Yang-Mills from MHV Vertices
Brandhuber, A; Travaglini, G; Brandhuber, Andreas; Spence, Bill; Travaglini, Gabriele
2004-01-01
We propose a new, twistor string theory inspired formalism to calculate loop amplitudes in N=4 super Yang-Mills theory. In this approach, maximal helicity violating (MHV) tree amplitudes of N=4 super Yang-Mills are used as vertices, using an off-shell prescription introduced by Cachazo, Svrcek and Witten, and combined into effective diagrams that incorporate large numbers of conventional Feynman diagrams. As an example, we apply this formalism to the particular class of MHV one-loop scattering amplitudes with an arbitrary number of external legs in N=4 super Yang-Mills. Remarkably, our approach naturally leads to a representation of the amplitudes as dispersion integrals, which we evaluate exactly. Our results for the MHV amplitudes are in precise agreement with the expressions for this class of amplitudes obtained previously by Bern, Dixon, Dunbar and Kosower using the cut-constructibility approach.
The Preparation of Cu-g-C3N4/AC Catalyst for Acetylene Hydrochlorination
Directory of Open Access Journals (Sweden)
Wenli Zhao
2016-12-01
Full Text Available A novel catalyst based on g-C3N4/activated carbon was prepared by adding CuCl2. The catalytic performance of the as-prepared catalyst was investigated in the acetylene hydrochlorination reaction. X-ray photoelectron spectroscopy, temperature programmed desorption, low temperature N2 adsorption/desorption (Brunauer–Emmett–Teller, and thermal gravity analysis showed that Cu-g-C3N4/AC significantly enhanced the catalytic performance of the original catalyst by increasing the relative pyrrolic N content. Cu-g-C3N4/AC also affected the adsorption of hydrogen chloride and acetylene, as well as inhibited the coke deposition during acetylene hydrochlorination.
Production and some properties of Si3N4 reinforced aluminium alloy composites
Directory of Open Access Journals (Sweden)
Pardeep Sharma
2015-09-01
Full Text Available The present research work focuses on the production of aluminium (AA6082-T6 matrix composites reinforced with various weight percentage of silicon nitride particles by conventional stir casting route. The percentage of reinforcement is varied from 0 wt.% to 12 wt.% in a stage of 3%. The microstructures and mechanical properties of the fabricated aluminium matrix composites are investigated. The scanning electron microstructure images reveal the presence of Si3N4 particles in the aluminium matrix. The distribution of Si3N4 particles has also been recognized with X-ray diffraction technique. The mechanical properties such as ultimate tensile strength and hardness have improved at the cost of reduction in ductility with increase in weight percentage of silicon nitride particulates in the aluminium metal matrix. The density and porosity of the composites also show an increasing trend with increase in volume fraction of Si3N4 particles in the aluminium matrix.
Growth of Co Nanoclusters on Si3N4 Surface Formed on Si(111)
Institute of Scientific and Technical Information of China (English)
刘熙; 贾金锋; 王俊忠; 薛其坤
2003-01-01
We have grown high density Co dusters with a narrow-sized distribution on the Si3N4(0001)-(8 × 8) surface. In the submonolayer regime, Co clusters tend to keep a certain size (～ 1.45 nm in diameter) irrespective of coverage.With increasing coverage above 0.92 ML, two new clusters with certain but larger sizes are formed. This novel growth behaviour can be explained by the quantum size effect [Phys. Rev. Lett. 90 (2003) 185506]. It is found that the Co cluster size distribution can be improved by post annealing. Even at high temperature (700℃ ), no reaction of Co with Si3N4 is observed, indicating that Si3N4(0001)-(8 × 8) is a promising substrate for growth of magnetic nanostructures.
Preparation of Si3N4 Form Diatomite via a Carbothermal Reduction-Nitridation Process
Ma, Bin; Huang, Zhaohui; Mei, Lefu; Fang, Minghao; Liu, Yangai; Wu, Xiaowen; Hu, Xiaozhi
2016-05-01
Si3N4 was produced using diatomite and sucrose as silicon and carbon sources, respectively. The effect of the C/SiO2 molar ratio, heating temperature and soaking time on the morphology and phase compositions of the final products was investigated by scanning electron microscopy, x-ray diffraction analysis and energy dispersive spectroscopy. The phase equilibrium relationships of the system at different heating temperatures were also investigated based on the thermodynamic analysis. The results indicate that the phase compositions depended on the C/SiO2 molar ratio, heating temperature and soaking time. Fabrication of Si3N4 from the precursor via carbothermal reduction nitridation was achieved at 1550°C for 1-8 h using a C/SiO2 molar ratio of 3.0. The as-prepared Si3N4 contained a low amount of Fe3Si (<1 wt.%).
Institute of Scientific and Technical Information of China (English)
陈祥生; 金宜芬; 等
1990-01-01
利用光散射和电子显微镜技术，对β－Si3N4的结构和形貌进行了研究和观察。结果指出：β－Si3N4的Raman光谱由188、210、230、480、624、865、930、936、1047cm－1峰组成，其中480cm－1附近的宽峰可归结为a－Si的Si－Si键振动。β－Si3N4呈透明片状堆积。
Investigation of the chemical interaction in the TiC-Si3N4 system
Directory of Open Access Journals (Sweden)
Izhevskyi V.A.
1999-01-01
Full Text Available Chemical interaction in the TiCSi3N4 system was investigated. Thermodynamic calculations and kinetic analysis were carried out for a number of powder mixtures with various TiC:Si3N4 molar ratios in the temperature range 1300-1750 °C. Stability regions of the TiC-Si3N4 composites were defined. It was shown that the main reaction products are silicon carbide and titanium carbonitride. The overall chemical interaction is described in terms of chemical reaction between titanium carbide and silicon nitride, and the diffusion of carbon and nitrogen through the coherent reaction products layer after completion of the initial direct interaction of the components.
Theoretical study of gallium nitride molecules, GaN2 and GaN4.
Tzeli, Demeter; Theodorakopoulos, Giannoula; Petsalakis, Ioannis D
2008-09-18
The electronic and geometric structures of gallium dinitride GaN 2, and gallium tetranitride molecules, GaN 4, were systematically studied by employing density functional theory and perturbation theory (MP2, MP4) in conjunction with the aug-cc-pVTZ basis set. In addition, for the ground-state of GaN 4( (2)B 1) a density functional theory study was carried out combining different functionals with different basis sets. A total of 7 minima have been identified for GaN 2, while 37 structures were identified for GaN 4 corresponding to minima, transition states, and saddle points. We report geometries and dissociation energies for all the above structures as well as potential energy profiles, potential energy surfaces and bonding mechanisms for some low-lying electronic states of GaN 4. The dissociation energy of the ground-state GaN 2 ( X (2)Pi) is 1.1 kcal/mol with respect to Ga( (2)P) + N 2( X (1)Sigma g (+)). The ground-state and the first two excited minima of GaN 4 are of (2)B 1( C 2 v ), (2)A 1( C 2 v , five member ring), and (4)Sigma g (-)( D infinityh ) symmetry, respectively. The dissociation energy ( D e) of the ground-state of GaN 4, X (2)B 1, with respect to Ga( (2)P) + 2 N 2( X (1)Sigma g (+)), is 2.4 kcal/mol, whereas the D e of (4)Sigma g (-) with respect to Ga( (4)P) + 2 N 2( X (1)Sigma g (+)) is 17.6 kcal/mol.
n4Studies: Sample Size Calculation for an Epidemiological Study on a Smart Device
Directory of Open Access Journals (Sweden)
Chetta Ngamjarus
2016-05-01
Full Text Available Objective: This study was to develop a sample size application (called “n4Studies” for free use on iPhone and Android devices and to compare sample size functions between n4Studies with other applications and software. Methods: Objective-C programming language was used to create the application for the iPhone OS (operating system while javaScript, jquery mobile, PhoneGap and jstat were used to develop it for Android phones. Other sample size applications were searched from the Apple app and Google play stores. The applications’ characteristics and sample size functions were collected. Spearman’s rank correlation was used to investigate the relationship between number of sample size functions and price. Results: “n4Studies” provides several functions for sample size and power calculations for various epidemiological study designs. It can be downloaded from the Apple App and Google play store. Comparing n4Studies with other applications, it covers several more types of epidemiological study designs, gives similar results for estimation of infinite/finite population mean and infinite/finite proportion from GRANMO, for comparing two independent means from BioStats, for comparing two independent proportions from EpiCal application. When using the same parameters, n4Studies gives similar results to STATA, epicalc package in R, PS, G*Power, and OpenEpi. Conclusion: “n4Studies” can be an alternative tool for calculating the sample size. It may be useful to students, lecturers and researchers in conducting their research projects.
A R^4 non-renormalisation theorem in N=4 supergravity
Tourkine, Piotr
2012-01-01
We consider the four-graviton amplitudes in CHL constructions providing four-dimensional N=4 models with various numbers of vector multiplets. We show that in these models the two-loop amplitude factorizes a d^2R^4. This implies a non-renormalisation theorem for the R^4 term, which forbids the appearance of a three-loop ultraviolet divergence in four dimensions in the four-graviton amplitude. We connect the special nature of the R^4 term to the U(1) anomaly of pure N=4 supergravity.
Twisted N=4 Super Yang-Mills Theory in Omega-background
Ito, Katsushi; Sasaki, Shin
2013-01-01
We study the twisted N=4 super Yang-Mills theories in the Omega-background with the constant R-symmetry Wilson line gauge field. Based on the classification of topological twists of N=4 supersymmetry (the half, the Vafa-Witten and the Marcus twists), we construct the deformed off-shell supersymmetry associated with the scalar supercharges for these twists. We find that the Omega-deformed action is written in the exact form with respect to the scalar supercharges as in the undeformed case.
Molecular Model Design and Quantum Chemistry Calculation of Cluster B4N4
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The B4N4 configurations were designed by using the molecular figure software. The full geometry optimization and harmonic vibration frequency analysis were performed at the 6-31G(d) level using density functional theory B3LYP method, which indicates that the five isomers are stationary points on the potential energy surface of B4N4 molecules. The geometry structure, frontier molecular orbital (FMO) and mulliken population have been analyzed. The bonding properties and hybrid type were also discussed in detail, showing the addition of hydro- gen atoms to boron or nitrogen atom would increase the stabilities of the BN clusters.
All Tree-Level MHV Form Factors in $\\mathcal{N}=4$ SYM from Twistor Space
Koster, Laura; Staudacher, Matthias; Wilhelm, Matthias
2016-01-01
We incorporate all gauge-invariant local composite operators into the twistor-space formulation of N=4 SYM theory, detailing and expanding on ideas we presented recently in arXiv:1603.04471. The vertices for these operators contain infinitely many terms and we show how they can be constructed by taking suitable derivatives of a light-like Wilson loop in twistor space and shrinking it down to a point. In particular, these vertices directly yield the tree-level MHV super form factors of all composite operators in N=4 SYM theory.
Introduction of atomic H into Si3N4/SiO2/Si stacks
Institute of Scientific and Technical Information of China (English)
JIN Hao; WEBER K.J.; LI Weitang; BLAKERS A.W.
2006-01-01
Atomic H generated by a plasma NH3 source at 400 ℃ was demonstrated to passivate dehydrogenated Si3N4/SiO2/Si stacks effectively by bonding with defectsin the Si3N4 film and at the Si-SiO2 interface. A subsequent anneal in N2 after atomic H reintroduction was demonstrated to further improve passivation of the Si-SiO2 interface. Isothermal and isochronal anneals in N2 were carried out in order to determine the optimized annealing conditions.
Institute of Scientific and Technical Information of China (English)
潘伟
2013-01-01
本文简要介绍了Si3N4薄膜的制备方法，详细介绍了低压化学气相淀积(Low Pressure Chemical Vapor Deposition)LPCVD制备氮化硅的工艺。并对工艺的结果进行了适当的分析，为LPCVD制备高质量的Si3N4薄膜奠定了基础。
The N=4 string is the same as the N=2 string
Siegel, Warren
1992-01-01
We redo the quantization of the N=4 string, taking into account the reducibility of the constraints. The result is equivalent to the N=2 string, with critical dimension D=4 and signature (++--). The N=4 formulation has several advantages: the sigma-model field equations are implied classically, rather than by quantum/beta-function calculations; self-duality/chirality is one of the super-Virasoro constraints; SO(2,2) covariance is manifest. This reveals that the theory includes fermions, and is apparently spacetime supersymmetric.
The operator product expansion between the 16 lowest higher spin currents in the N=4 superspace
Ahn, Changhyun; Kim, Man Hea
2016-07-01
Some of the operator product expansions (OPEs) between the lowest 16 higher spin currents of spins (1, 3/2, 3/2, 3/2, 3/2, 2, 2, 2, 2, 2, 2, 5/2, 5/2, 5/2, 5/2, 3) in an extension of the large N=4 linear superconformal algebra were constructed in N=4 superconformal coset SU(5)/SU(3) theory previously. In this paper, by rewriting these OPEs in the N=4 superspace developed by Schoutens (and other groups), the remaining undetermined OPEs in which the corresponding singular terms possess the composite fields with spins s =7/2, 4, 9/2, 5 are completely determined. Furthermore, by introducing arbitrary coefficients in front of the composite fields on the right-hand sides of the above complete 136 OPEs, reexpressing them in the N=2 superspace, and using the N=2 OPEs Mathematica package by Krivonos and Thielemans, the complete structures of the above OPEs with fixed coefficient functions are obtained with the help of various Jacobi identities. We then obtain ten N=2 super OPEs between the four N=2 higher spin currents denoted by (1, 3/2, 3/2, 2), (3/2, 2, 2, 5/2), (3/2, 2, 2, 5/2), and (2, 5/2, 5/2, 3) (corresponding 136 OPEs in the component approach) in the N=4 superconformal coset SU(N+2)/SU(N) theory. Finally, we describe them as one single N=4 super OPE between the above 16 higher spin currents in the N=4 superspace. The fusion rule for this OPE contains the next 16 higher spin currents of spins of (2, 5/2, 5/2, 5/2, 5/2, 3, 3, 3, 3, 3, 3, 7/2, 7/2, 7/2, 7/2, 4) in addition to the quadratic N=4 lowest higher spin multiplet and the large N=4 linear superconformal family of the identity operator. The various structure constants (fixed coefficient functions) appearing on the right-hand side of this OPE depend on N and the level k of the bosonic spin-1 affine Kac-Moody current. For convenience, the above 136 OPEs in the component approach for generic ( N, k) with simplified notation are given.
Integrable amplitude deformations for N =4 super Yang-Mills and ABJM theory
Bargheer, Till; Huang, Yu-Tin; Loebbert, Florian; Yamazaki, Masahito
2015-01-01
We study Yangian-invariant deformations of scattering amplitudes in 4d N =4 super Yang-Mills theory and 3d N =6 Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In particular, we obtain the deformed Graßmannian integral for 4d N =4 supersymmetric Yang-Mills theory, both in momentum and momentum-twistor space. For 3d ABJM theory, we initiate the study of deformed scattering amplitudes. We investigate general deformations of on-shell diagrams, and find the deformed Graßmannian integral for this theory. We furthermore introduce the algebraic R-matrix construction of deformed Yangian invariants for ABJM theory.
Yeap, Guan-Yeow; Al-Taifi, Elham A.; Ong, Chin-Hin; Kamil Mahmood, Wan Ahmad; Takeuchi, Daisuke; Ito, Masato M.
2012-06-01
A new series of non-symmetric liquid crystal dimers N-(4-(n-(4-(benzothiazol-2-yl)phenoxy)alkyloxy)benzylidene)-4-chloroaniline containing benzothiazole and benzylideneimine units connected by a flexible alkyl spacer, -(CH2) n -, with n ranging from 4 to 12 in even parity have been prepared. All five members of this homologous series exhibit an enantiotropic nematic phase. The compounds with greater n of 8-12 exhibit both nematic and smectic phases upon cooling. A notable feature among this series is that for the member with n = 10, the smectic-nematic transition is also present. The nematic-isotropic transition temperatures and associated entropy changes with respect to all compounds in this series exhibit a dramatic dependence on the length of the flexible spacer. A comparison of the transitional properties of this series with those of α-(4-benzylidenechloroaniline-4‧-oxy)-ω-[4-(thiophene-2-carboxyl)benzylideneaniline-4‧-oxy]alkanes reveals that replacing benzothiazole moiety at one side of the flexible alkyl spacer reduces the nematic-isotropic transition temperature.
Dekkers, Petrus J; Tuinman, Ilse L; Marijnissen, Jan C M; Friedlander, Sheldon K; Scarlett, B
2002-04-15
The gas to particle synthesis route is a relatively clean and efficient manner for the production of high-quality ceramic powders. These powders can be subsequently sintered in any wanted shape. The modeling of these production systems is difficult because several mechanisms occur in parallel. From theoretical considerations it can be determined, however, that coagulation and sintering are dominant mechanisms as far as shape and size of the particles are considered. In part I of this article an extensive theoretical analysis was given on the self-preserving size distribution theory for power law particles. In this second part, cumulative particle size distributions of silicon and silicon nitride agglomerates, produced in a laser reactor, were determined from TEM pictures and compared to the distributions calculated from this self-preserving theory for power law particles. The calculated distributions were in fair agreement with the measured results, especially at the high end of the distributions. Calculated and measured particle growth rates were also in fair agreement. Using the self-preserving theory an analysis was made on the distribution of annealed silicon agglomerates, of interest in applications to nanoparticle technology.
N=4 super-Yang-Mills in LHC superspace. Part I: Classical and quantum theory
Chicherin, Dmitry
2017-02-10
We present a formulation of the maximally supersymmetric N=4 gauge theory in Lorentz harmonic chiral (LHC) superspace. It is closely related to the twistor formulation of the theory but employs the simpler notion of Lorentz harmonic variables. They parametrize a two-sphere and allow us to handle efficiently infinite towers of higher-spin auxiliary fields defined on ordinary space-time. In this approach the chiral half of N=4 supersymmetry is manifest. The other half is realized non-linearly and the algebra closes on shell. We give a straightforward derivation of the Feynman rules in coordinate space. We show that the LHC formulation of the N=4 super-Yang-Mills theory is remarkably similar to the harmonic superspace formulation of the N=2 gauge and hypermultiplet matter theories. In the twin paper \\cite{twin} we apply the LHC formalism to the study of the non-chiral multipoint correlation functions of the N=4 stress-tensor supermultiplet.
An Approach to ${\\cal N}=4$ ADE Gauge Theory on K3
Jinzenji, M; Jinzenji, Masao; Sasaki, Toru
2002-01-01
We propose a recipe for determination of the partition function of ${\\cal N}=4$ $ADE$ gauge theory on $K3$ by generalizing our previous results of the SU(N) case. The resulting partition function satisfies Montonen-Olive duality for $ADE $ gauge group.
2PI Effective Action and Evolution Equations of N = 4 super Yang-Mills
Smolic, Jelena
2011-01-01
We employ nPI effective action techniques to study N = 4 super Yang-Mills, and write down the 2PI effective action of the theory. We also supply the evolution equations of two-point correlators within the theory.
Mapping the G-structures and supersymmetric vacua of five-dimensional N=4 supergravity
Energy Technology Data Exchange (ETDEWEB)
Liu, James T; Mahato, Manavendra; Vaman, Diana [Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States)
2007-03-07
We classify the supersymmetric vacua of N=4, d=5 supergravity in terms of G-structures. We identify three classes of solutions: with R{sup 3}, SU(2) and Id structure. Using the Killing spinor equations, we fully characterize the first two classes and partially solve the latter. With the N=4 graviton multiplet decomposed in terms of N=2 multiplets: the graviton, vector and gravitino multiplets, we obtain new supersymmetric solutions corresponding to turning on fields in the gravitino multiplet. These vacua are described in terms of an SO(5) vector sigma model coupled with gravity, in three or four dimensions. A new feature of these N=4 vacua, which is not seen from an N=2 point of view, is the possibility for preserving more exotic fractions of supersymmetry. We give a few concrete examples of these new supersymmetric (albeit singular) solutions. Additionally, we show how by truncating the N=4, d=5 set of fields to minimal supergravity coupled with one vector multiplet we recover the known two-charge solutions.
Photocatalytic C–H Activation of Hydrocarbons over VO@g-C3N4
A highly selective and sustainable method has been developed for the oxidation of methyl arenes and their analogues. The VO@g-C3N4 catalyst is very efficient in the C–H activation and oxygen insertion reaction resulting in formation of the corresponding carbonyl compounds a...
N = 4 super-Yang-Mills in LHC superspace part I: classical and quantum theory
Chicherin, Dmitry; Sokatchev, Emery
2017-02-01
We present a formulation of the maximally supersymmetric N = 4 gauge theory in Lorentz harmonic chiral (LHC) superspace. It is closely related to the twistor formulation of the theory but employs the simpler notion of Lorentz harmonic variables. They parametrize a two-sphere and allow us to handle efficiently infinite towers of higher-spin auxiliary fields defined on ordinary space-time. In this approach the chiral half of N =4 supersymmetry is manifest. The other half is realized non-linearly and the algebra closes on shell. We give a straightforward derivation of the Feynman rules in coordinate space. We show that the LHC formulation of the N = 4 super-Yang-Mills theory is remarkably similar to the harmonic superspace formulation of the N = 2 gauge and hypermultiplet matter theories. In the twin paper arXiv:1601.06804 we apply the LHC formalism to the study of the non-chiral multipoint correlation functions of the N = 4 stress-tensor supermultiplet.
Investigation based on nano-electromechanical system double Si3N4 resonant beam pressure sensor.
Yang, Chuan; Guo, Can; Yuan, Xiaowei
2011-12-01
This paper presents a type of NEMS (Nano-Electromechanical System) double Si3N4 resonant beams pressure sensor. The mathematical models are established in allusion to the Si3N4 resonant beams and pressure sensitive diaphragm. The distribution state of stress has been analyzed theoretically based on the mathematical model of pressure sensitive diaphragm; from the analysis result, the position of the Si3N4 resonant beams above the pressure sensitive diaphragm was optimized and then the dominance observed after the double resonant beams are adopted is illustrated. From the analysis result, the position of the Si3N4 resonant beams above the pressure sensitive diaphragm is optimized, illustrating advantages in the adoption of double resonant beams. The capability of the optimized sensor was generally analyzed using the ANSYS software of finite element analysis. The range of measured pressure is 0-400 Kpa, the coefficient of linearity correlation is 0.99346, and the sensitivity of the sensor is 498.24 Hz/Kpa, higher than the traditional sensors. Finally the processing techniques of the sensor chip have been designed with sample being successfully processed.
Photocatalytic oxidation of aqueous ammonia using atomic single layer graphitic-C3N4.
Wang, Hua; Su, Yan; Zhao, Huanxin; Yu, Hongtao; Chen, Shuo; Zhang, Yaobin; Quan, Xie
2014-10-21
Direct utilization of solar energy for photocatalytic removal of ammonia from water is a topic of strong interest. However, most of the photocatalysts with effective performance are solely metal-based semiconductors. Here, we report for the first time that a new type of atomic single layer graphitic-C(3)N(4) (SL g-C(3)N(4)), a metal-free photocatalyst, has an excellent photocatalytic activity for total ammonia nitrogen (TAN) removal from water. The results demonstrated that over 80% of TAN (initial concentration 1.50 mg · L(-1)) could be removed in 6 h under Xe lamp irradiation (195 mW · cm(-2)). Furthermore, the SL g-C(3)N(4) exhibited a higher photocatalytic activity in alkaline solution than that in neutral or acidic solutions. The investigation suggested that both photogenerated holes and hydroxyl radicals were involved the TAN photocatalytic oxidation process and that the major oxidation product was NO3(-)-N. In addition, SL g-C(3)N(4) exhibited good photocatalytic stability in aqueous solution. This work highlights the appealing application of an inexpensive metal-free photocatalyst in aqueous ammonia treatment.
Photocatalytic oxidation of aromatic amines using MnO2@g-C3N4
U.S. Environmental Protection Agency — An efficient and direct oxidation of aromatic amines to aromatic azo-compounds has been achieved using a MnO2@g-C3N4 catalyst under visible light as a source of...
2PI effective action and evolution equations of N=4 super Yang-Mills
Energy Technology Data Exchange (ETDEWEB)
Smolic, Jelena; Smolic, Milena [University of Amsterdam, Institute for Theoretical Physics, Amsterdam (Netherlands)
2012-08-15
We employ nPI effective action techniques to study N=4 super Yang-Mills, and write down the 2PI effective action of the theory to two-loop order in the symmetric phase. We also supply the evolution equations of two-point correlators within the theory. (orig.)
N=4 super-Yang-Mills in LHC superspace. Part I: Classical and quantum theory
Chicherin, Dmitry
2016-01-01
We present a formulation of the maximally supersymmetric N=4 gauge theory in Lorentz harmonic chiral (LHC) superspace. It is closely related to the twistor formulation of the theory but employs the simpler notion of Lorentz harmonic variables. They parametrize a two-sphere and allow us to handle efficiently infinite towers of higher-spin auxiliary fields defined on ordinary space-time. In this approach the chiral half of N=4 supersymmetry is manifest. The other half is realized non-linearly and the algebra closes on shell. We give a straightforward derivation of the Feynman rules in coordinate space. We show that the LHC formulation of the N=4 super-Yang-Mills theory is remarkably similar to the harmonic superspace formulation of the N=2 gauge and hypermultiplet matter theories. In the twin paper \\cite{twin} we apply the LHC formalism to the study of the non-chiral multipoint correlation functions of the N=4 stress-tensor supermultiplet.
Bifunctional Ag/C3N4.5 composite nanobelts for photocatalysis and antibacterium
Lei, Renbo; Jian, Jikang; Zhang, Zhihua; Song, Bo; Wu, Rong
2016-09-01
Multiple functions can be achieved in carbon nitride-based composite nanomaterials by tuning their components and structures. Here, we report on a large-scale synthesis of novel bifunctional Ag/C3N4.5 composite nanobelts (CNBs) with efficient photocatalytic and antibacterial activity. The Ag/C3N4.5 CNBs were synthesized in high yield by a two-step route including a homogeneous precipitation process and a subsequent calcination treatment. The structural, morphological, compositional, and spectroscopic characterizations revealed that the Ag/C3N4.5 CNBs are composed of N-deficient melem ultrathin nanobelts and crystalline Ag nanoparticles attached to the surface of the nanobelts with good contact. The band gap of the Ag/C3N4.5 CNBs is determined to be about 3.04 eV. The efficient photocatalytic and antibacterial activities of the composite nanomaterials are verified by testing the degradation of Rhodamine B (RhB) and the inhibition zone to bacterium E. coli. The work provides a facile route to bifunctional carbon nitride-based composites with potential applications in the fields of the environment and biology.
Eigenvalue spectrum of lattice $\\mathcal{N}=4$ super Yang-Mills
Weir, David J; Mehta, Dhagash
2013-01-01
We present preliminary results for the eigenvalue spectrum of four-dimensional ${\\cal N}=4$ super Yang-Mills theory on the lattice. In particular, by studying the the spectral density a measurement of the anomalous dimension is made and found to be consistent with zero.
Photocatalytic C−H Activation of Hydrocarbons over VO@g‑C3N4
A highly selective and sustainable method has beendeveloped for the oxidation of methyl arenes and their analogues.The VO@g-C3N4 catalyst is very efficient in the C−H activation andoxygen insertion reaction resulting in formation of the correspondingcarbonyl compounds and phenols...
Lable-free Enzyme Sensing with a Si3N4 Grated Waveguide Optical Cavity
Pham, S.V.; Dijkstra, M.; Hollink, A.J.F.; Kauppinen, L.J.; Ridder, de R.M.; Hoekstra, H.J.W.M.
2011-01-01
We report the label-free, sensitive detection of PepN enzyme using a Si3N4 grated waveguide optical cavity covered with an immobilized, selective (antibody) receptor layer. The receptor-enzyme reaction was monitored in real-time.
Koten, G. van; Steenwinkel, P.; James, S.L.; Gossage, R.A.; Grove, D.M.; Kooijman, H.; Smeets, W.J.J.; Spek, A.L.
1998-01-01
New air-stable ruthenium(II) complexes that contain the aryldiamine ligand [C6H3(CH2NMe2)2-2,6]- (NCN) are described. These complexes are [RuCl{2-C,N-C6H3(CH2NMe2)2-2,6}(6-C10H14)] (2; C10H14 = p-cymene = C6H4Me-iPr-4), [Ru{2-C,N-C6H3(CH2NMe2)2-2,6}(5-C5H5)(PPh3)] (5), and their isomeric forms [RuCl
Influence of Deposition Temperature on the Structure Of Si3N4 Thin Film Prepared By MWECR-PECVD
Institute of Scientific and Technical Information of China (English)
肖化; 陈俊芳; 张镇西
2004-01-01
The Si3N4 thin film is prepared by MWECR-PECVD at different deposition temperature and the structure of the Si3N4 thin film is investigated. The results indicate that the structure of the Si3N4 thin film prepared at low deposition temperature is in the amorphous phase. However, when the deposition temperature increases to 280℃, the Si3N4 thin film changes to crystalline -Si3N4 . With a further increase of the deposition temperature, the grain of the Si3N4 thin film becomes more fine, uniform and flat. XRD analysis shows that the structure of the Si3N4 thin film prepared at 280℃ is of a crystalline structure.
Li, Houfen; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhang, Yaobin
2016-01-27
Z-scheme photocatalytic system shows superiority in degradation of refractory pollutants and water splitting due to the high redox capacities caused by its unique charge transfer behaviors. As a key component of Z-scheme system, the electron mediator plays an important role in charge carrier migration. According to the energy band theory, we believe the interfacial energy band bendings facilitate the electron transfer via Z-scheme mechanism when the Fermi level of electron mediator is between the Fermi levels of Photosystem II (PS II) and Photosystem I (PS I), whereas charge transfer is inhibited in other cases as energy band barriers would form at the semiconductor-metal interfaces. Here, this inference was verified by the increased hydroxyl radical generation and improved photocurrent on WO3-Cu-gC3N4 (with the desired Fermi level structure), which were not observed on either WO3-Ag-gC3N4 or WO3-Au-gC3N4. Finally, photocatalytic degradation rate of 4-nonylphenol on WO3-Cu-gC3N4 was proved to be as high as 11.6 times than that of WO3-gC3N4, further demonstrating the necessity of a suitable electron mediator in Z-scheme system. This study provides scientific basis for rational construction of Z-scheme photocatalytic system.
Energy Technology Data Exchange (ETDEWEB)
Mancini, Marcello; Liuzzi, Raffaele [CNR, Napoli (Italy). Istituto di biostrutture e bioimmagini; Daniele, Stefania; Raffio, Teresa; Salvatore, Marco [Napoli Univ., Napoli (Italy). Dipartimento di diagnostica per immagini; Sabbatini, Massimo; Cianciaruso, Bruno [Napoli Univ., Napoli (Italy). Istituto di nefrologia medica; Ferrara, Liberato Aldo [Napoli Univ., Napoli (Italy). Dipartimento di medicina clinica e sperimentale
2005-04-01
Purpose: Aim of the presents study was to evaluate the repeatability and reproducibility of the Doppler Resistive Index (R.I.) and the Ultrasound renal volume measurement in renal transplants. Materials and methods: Twenty -six consecutive patients (18 men, 8 women) mean age of 42,8{+-}12,4 years (M{+-}SD)(range 22-65 years) were studied twice by each of two trained sonographers using a color Doppler ultrasound scanner. Twelve of them had a normal allograft function (defined as stable serum creatinine levels {<=}123,76 {mu}mol/L), whilst the remaining 14 had decreased allograft function (serum creatinine 132.6-265.2 {mu}mol/L). Results were given as mean of 6 measurements performed at upper, middle and lower pole of the kidney. Intra- and interobserver variability was assessed by the repeatability coefficient and coefficient of variation (CV). Results: Regarding Resistive Index measurement, repeatability coefficient was between 0.04 and 0.06 and the coefficient of variation was <5%. The analysis of the Student's test did not show any significant difference between the measurements (t=0.15; p=0.87 n.s.). A good reproducibility was also detected in US measurements of renal length and volume. Conclusions: These results suggest that Color Doppler Resistive Index measurements of renal allograft and Ultrasound renal volume measurements are repeatable and reproducible. [Italian] Scopo: Valutare la ripetibilit� e la riproducibilit� delle misurazioni ecografiche dell'Indice di Resistenza (I.R.) e del volume del rene trapiantato. Materiale e metodi: Ventisei pazienti (18 uomini, 8 donne) con et� media di 42,8{+-}12,4 anni (M{+-}SD)(range 22-65 anni) sono stati studiati consecutivamente due volte con eco-color-Doppler da due ecografisti esperti. Dodici pazienti avevano funzione renale normale (livello serico di creatina stabilmente {<=}123,76 {mu}mol/L, i rimanenti 14 avevano una lieve e stabile disfunzione del rene trapiantato (creatina serica 132.6-265.2 {mu
Institute of Scientific and Technical Information of China (English)
吴斌; 邹家生; 陈铮; 赵其章; 眭润舟; 楼宏青
2001-01-01
采用成分不同的Cu-Ni-Ti钎料进行了Si3N4/Si3N4的连接。结果表明：钎料成分、钎焊工艺 参数对连接强度均有重要影响。采用(Cu85Ni15)80Ti20钎料在1 373K×10 min条件下，Si3N4/Si3N4连接 强度达到最大值289 MPa。通过对Si3N4/Si3N4连接界面的微观分析，发现Si向钎料层扩散，钎料中的 Cu在接头中央富集，而Ti、Ni向Si3N4富集。相对Ni而言，Ti的富集区更靠近Si3N4陶瓷。%Si3N4/Si3N4 is bonded by using Cu-Ni-Ti Fill metal with different composition . The effects of the braze metal composition, and the procedure variables such as the brazing temperature and the brazing time on joining strength are investigated. The results show that at the temperature of 1 373 K for 10 min utes, the brazing alloy composition corresponding to the highest strength value (289 MPa) is (Cu85Ni15)80 Ti20. The analysis of the distribution of elements in Si3Na/Si3N4 joint shows that Si diffuses towards braze layer while Ti and Ni towards Si3N4. In the center part of the joint is mainly Cu element and the intensive area of Ti is closer to Si3N4 ceramics.
Decreased bacteria activity on Si3N4 surfaces compared with PEEK or titanium
Directory of Open Access Journals (Sweden)
Puckett S
2012-09-01
Full Text Available Deborah Gorth,1 Sabrina Puckett,1 Batur Ercan,1 Thomas J Webster,1 Mohamed Rahaman,2 B Sonny Bal31School of Engineering and Department of Orthopaedics, Brown University, Providence, RI, 2Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO, 3Department of Orthopaedic Surgery, School of Medicine, University of Missouri, Columbia, MO, USAAbstract: A significant need exists for orthopedic implants that can intrinsically resist bacterial colonization. In this study, three biomaterials that are used in spinal implants – titanium (Ti, poly-ether-ether-ketone (PEEK, and silicon nitride (Si3N4 – were tested to understand their respective susceptibility to bacterial infection with Staphylococcus epidermidis, Staphlococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus. Specifically, the surface chemistry, wettability, and nanostructured topography of respective biomaterials, and the effects on bacterial biofilm formation, colonization, and growth were investigated. Ti and PEEK were received with as-machined surfaces; both materials are hydrophobic, with net negative surface charges. Two surface finishes of Si3N4 were examined: as-fired and polished. In contrast to Ti and PEEK, the surface of Si3N4 is hydrophilic, with a net positive charge. A decreased biofilm formation was found, as well as fewer live bacteria on both the as-fired and polished Si3N4. These differences may reflect differential surface chemistry and surface nanostructure properties between the biomaterials tested. Because protein adsorption on material surfaces affects bacterial adhesion, the adsorption of fibronectin, vitronectin, and laminin on Ti, PEEK, and Si3N4 were also examined. Significantly greater amounts of these proteins adhered to Si3N4 than to Ti or PEEK. The findings of this study suggest that surface properties of biomaterials lead to differential adsorption of physiologic proteins, and that this
Ni-Sn-Ti合金钎料对Si3N4陶瓷的润湿性研究%Study on Wettability of Ni-Sn-Ti Solder Alloy on Si3N4 Ceramics
Institute of Scientific and Technical Information of China (English)
苏光; 程芳
2011-01-01
Si3N4/Si3N4 is bonded by a series of Ni-20Sn-xTi filler alloys. The results show that Ni-20Sn-10Ti alloy has good wettability on Si3N4 and can improve the bonding strength of welded joint.%采用一系列Ni-20Sn-xTi合金钎料进行了Si3N4/Si3N4真空钎焊连接研究.结果表明:Ni-20Sn-10Ti合金钎料对Si3N4陶瓷具有最好的润湿性,同时能够有效地提高接头的连接强度.
Topics In N = 4 Yang-mills And The Self-dual String
Basu, A
2005-01-01
We analyze some systematics of the coupling constant dependence of correlators in N = 4 Yang- Mills, which is the world-volume theory on D3-branes. We use the fact that the operator Ot that generates infinitesimal changes of the coupling constant in this theory sits in the same supermultiplet as the superconformal currents. We show how superconformal current Ward identities determine a class of terms in the operator product expansion of Ot with any other operator. In certain cases, this leads to constraints on the coupling dependence of correlation functions in N = 4 Yang-Mills. As an application, we demonstrate the exact non-renormalization of two and certain three-point correlation functions of BPS operators. We next approximate these integrated correlators by using a truncated OPE expansion. This leads to differential equations for the coupling dependence. When applied to a particular sixteen point correlator, the coupling dependence we find agrees with the corresponding amplitude computed via the Ad...
One-Loop Self-Dual and N=4 Super Yang-Mills
Bern, Z; Dunbar, D C; Kosower, D A
1997-01-01
We conjecture a simple relationship between the one-loop maximally helicity violating gluon amplitudes of ordinary QCD (all helicities identical) and those of N=4 supersymmetric Yang-Mills (all but two helicities identical). Because the amplitudes in self-dual Yang Mills have been shown to be the same as the maximally helicity violating ones in QCD, this conjecture implies that they are also related to the maximally helicity violating ones of N=4 supersymmetric Yang-Mills. We have an explicit proof of the relation up to the six-point amplitude; for amplitudes with more external legs, it remains a conjecture. A similar conjecture relates amplitudes in self-dual gravity to maximally helicity violating N=8 supergravity amplitudes.
On non-minimal N = 4 supermultiplets in 1D and their associated {sigma}-models
Energy Technology Data Exchange (ETDEWEB)
Gonzales, Marcelo; Khodaee, Sadi; Toppan, Francesco, E-mail: marcbino@cbpf.b, E-mail: khodaee@cbpf.b, E-mail: toppan@cbpf.b
2010-10-15
We construct the non-minimal linear representations of the N = 4 Extended Supersymmetry in one-dimension. They act on 8 bosonic and 8 fermionic fields. Inequivalent representations are specified by the mass-dimension of the fields and the connectivity of the associated graphs. The oxidation to minimal N = 5 linear representations is given. Two types of N = 4 {sigma}-models based on non-minimal representations are obtained: the resulting off-shell actions are either manifestly invariant or depend on a constrained pre potential. The connectivity properties of the graphs play a decisive role in discriminating inequivalent actions. These results find application in partial breaking of supersymmetric theories. (author)
NLL resummation for the static potential in N=4 SYM theory
Energy Technology Data Exchange (ETDEWEB)
Stahlhofen, Maximilian [Wien Univ. (Austria). Fakultaet fuer Physik
2012-09-15
We determine the complete NLL running of the static potential associated with the locally 1/2 BPS Wilson loop in N=4 supersymmetric Yang-Mills theory. We present results for the SU(N{sub c}) singlet as well as for the adjoint configuration and arbitrary N{sub c} at weak coupling. In order to derive the respective anomalous dimensions we perform a two-loop calculation in the N=4 supersymmetric version of the effective field theory pNRQCD. In addition we confirm the recently obtained fixed-order result for the singlet static potential generated exclusively by ladder diagrams to the third order in the t'Hooft coupling. We also give an explicit expression for the logarithmic contribution of all non-ladder diagrams at this order.
pH controlled dispersion and slip casting of Si3N4 in aqueous media
Indian Academy of Sciences (India)
R Ramachandra Rao; H N Roopa; T S Kannan
2001-02-01
The dispersion characteristics of commercial Si3N4 powder in aqueous media (deionized water) was studied as a function of pH in the range 2–11. The slip was characterized for its dispersion quality by various experimental techniques like particle size analysis, sedimentation phenomena, viscosity and flow behaviour and zeta potential analysis. The optimum dispersion was found to be in the pH region 9–11 wherein the slurry displayed minimum sedimentation height, minimum viscosity, near Newtonian flow behaviour and maximum zeta potential. The slip is highly agglomerated in the pH range 2–8 as manifested by higher sedimentation height, higher viscosity, lower zeta potential and thixotropic non-Newtonian flow behaviour. The 72 wt% (44 vol.%) Si3N4 slips made at pH = 10 resulted in green bodies having 53–59% of theoretical density after casting into plaster molds.
Grassmannians for scattering amplitudes in 4d $\\mathcal{N}=4$ SYM and 3d ABJM
Elvang, Henriette; Keeler, Cynthia; Lam, Thomas; Olson, Timothy M; Roland, Samuel B; Speyer, David E
2014-01-01
Scattering amplitudes in 4d $\\mathcal{N}=4$ super Yang-Mills theory (SYM) can be described by Grassmannian contour integrals whose form depends on whether the external data is encoded in momentum space, twistor space, or momentum twistor space. After a pedagogical review, we present a new, streamlined proof of the equivalence of the three integral formulations. A similar strategy allows us to derive a new Grassmannian integral for 3d $\\mathcal{N}=6$ ABJM theory amplitudes in momentum twistor space: it is a contour integral in an orthogonal Grassmannian with the novel property that the internal metric depends on the external data. The result can be viewed as a central step towards developing an amplituhedron formulation for ABJM amplitudes. Various properties of Grassmannian integrals are examined, including boundary properties, pole structure, and a homological interpretation of the global residue theorems for $\\mathcal{N}=4$ SYM.
Effects of organic additives on microstructure and mechanical properties of porous Si3N4 ceramics
Indian Academy of Sciences (India)
Yu Fangli; Wang Huanrui; Yang Jianfeng; Gao Jiqiang
2010-06-01
Green bodies of porous Si3N4 ceramics were shaped by extrusion technique using different organic additives as binder during extrusion molding. Different porosity, microstructures and mechanical properties after the extrusion, drying, debinding and sintering stages were investigated. The solid slurry content of 70–75% and extrusion pressure of 0.5–1.0 MPa had played a decisive role in the smooth realization of extrusion molding. The porous Si3N4 ceramics were obtained with excellent properties using 4% hydroxypropyl methyl cellulose (HPMC) as binder and polyethylene glycol (PEG) of molecular weight, 1000, as plasticizer with a density of 1.91 g cm-3, porosity of 41.70%, three-point bending strength of 166.53 ± 20 MPa, fracture toughness of 2.45 ± 0.2 MPa m1/2 and Weibull modulus (m) of 20.75.
Exact momentum fluctuations of an accelerated quark in N=4 super Yang-Mills
Fiol, Bartomeu; Torrents, Genis
2013-01-01
In this work we consider a heavy quark moving with constant proper acceleration in the vacuum of any four dimensional conformal field theory. We argue that the two-point function of its momentum fluctuations is exactly captured by the Bremsstrahlung function that gives the total radiated power. For the particular case of N=4 SU(N) SYM this function is exactly known, so in this case we obtain an explicit expression for the momentum diffusion coefficient, and check that various limits of this result are reproduced by probe computations in AdS_5. Finally, we evaluate this transport coefficient for a heavy quark accelerated in the vacuum of N=4 SU(3) SYM, and comment on possible lessons of our results for the study of heavy quarks traversing the super Yang-Mills plasma.
Hyperkähler Singularities in Superstrings Compactification and 2d N = 4 Conformal Field Theory
Belhaj, A
2001-01-01
We study the singularities of the Higgs branch of supersymmetric U(1)^r gaugetheories with eight supercharges. We derive new solutions for the moduli spaceof vacua preserving manifestly the eight supercharges by using a geometricrealization of the SU(2)_R symmetry and a separation procedure of the gauge andSU(2)_R charges, which allow us to put the hypermultiplet vacua in a formdepending on a parameter $\\gamma$. For $\\gamma=1$, we obtain new models whichflow in the infrared to 2d N=(4,4) conformal models and we show that theclassical moduli spaces are given by intersecting cotangent weighted complexprojective spaces containing the small instanton singularity, discussed in[17], as a leading special case. We also make comments regarding the d$2d N=4conformal Liouville description of the Higgs branch throat by following theanalysis of [18]. Other features are also discussed.
One-Loop Partition Functions in Deformed $\\mathcal{N}=4$ SYM Theory
Fokken, Jan
2014-01-01
We study the thermodynamic behaviour of the real $\\beta$- and $\\gamma_i$-deformation of $\\mathcal{N}=4$ Super Yang-Mills theory on $\\mathbb{R}\\times S^3$ in the planar limit. These theories were shown to be the most general asymptotically integrable supersymmetric and non-supersymmetric field-theory deformations of $\\mathcal{N}=4$ Super Yang-Mills theory, respectively. We calculate the first loop correction to their partition functions using an extension of the dilatation-operator and P\\'{o}lya-counting approach. In particular, we account for the one-loop finite-size effects which occur for operators of length one and two. Remarkably, we find that the $\\mathcal{O}(\\lambda)$ correction to the Hagedorn temperature is independent of the deformation parameters, although the partition function depends on them in a non-trivial way.
Four-point correlation function of stress-energy tensors in N=4 superconformal theories
Korchemsky, G P
2015-01-01
We derive the explicit expression for the four-point correlation function of stress-energy tensors in four-dimensional N=4 superconformal theory. We show that it has a remarkably simple and suggestive form allowing us to predict a large class of four-point correlation functions involving the stress-energy tensor and other conserved currents. We then apply the obtained results on the correlation functions to computing the energy-energy correlations, which measure the flow of energy in the final states created from the vacuum by a source. We demonstrate that they are given by a universal function independent of the choice of the source. Our analysis relies only on N=4 superconformal symmetry and does not use the dynamics of the theory.
N=4 Super-Yang-Mills on Conic Space as Hologram of STU Topological Black Hole
Huang, Xing
2014-01-01
We construct four-dimensional N=4 super-Yang-Mills theories on a conic sphere with various background R-symmetry gauge fields. We study free energy and supersymmetric Renyi entropy using heat kernel method as well as localization technique. We find that the universal contribution to the partition function in the free field limit is the same as that in the strong coupling limit, which implies that it may be protected by supersymmetry. Based on the fact that, the conic sphere can be conformally mapped to $S^1\\times H^3$ and the R-symmetry background fields can be supported by the R-charges of black hole, we propose that the holographic dual of these theories are five-dimensional, supersymmetric STU topological black holes. We demonstrate perfect agreement between N=4 super-Yang-Mills theories in the planar limit and the STU topological black holes.
Transport properties of N=4 supersymmetric Yang-Mills theory at finite coupling
Benincasa, P; Benincasa, Paolo; Buchel, Alex
2006-01-01
Gauge theory-string theory duality describes strongly coupled N=4 supersymmetric SU(n) Yang-Mills theory at finite temperature in terms of near extremal black 3-brane geometry in type IIB string theory. We use this correspondence to compute the leading correction in inverse 't Hooft coupling to the shear diffusion constant, bulk viscosity and the speed of sound in the large-n N=4 supersymmetric Yang-Mills theory plasma. The transport coefficients are extracted from the dispersion relation for the shear and the sound wave lowest quasinormal modes in the leading order alpha'-corrected black D3 brane geometry. We find the shear viscosity extracted from the shear diffusion constant to agree with result of [hep-th/0406264]; also, the leading correction to bulk viscosity and the speed of sound vanishes. Our computation provides a highly nontrivial consistency check on the hydrodynamic description of the alpha'-corrected nonextremal black branes in string theory.
Twist-2 at seven loops in planar N=4 SYM theory: Full result and analytic properties
Marboe, Christian
2016-01-01
The anomalous dimension of twist-2 operators of arbitrary spin in planar N=4 SYM theory is found at seven loops by using the quantum spectral curve to compute values at fixed spin, and reconstructing the general result using the LLL-algorithm together with modular arithmetic. The result of the analytic continuation to negative spin is presented, and its relation with the recently computed correction to the BFKL and double-logarithmic equation is discussed.
Superspace Formulation of N=4 Super Yang-Mills Theory with a Central Charge
Saito, J
2005-01-01
A superspace formulation using superconnections and supercurvatures is specifically constructed for N=4 extended super Yang-Mills theory with a central charge in four dimensions, first proposed by Sohnius, Stelle and West long ago. We find that the constraints, almost uniquely derived from the possible spin structure of the multiplet, can be algebraically solved which results in an off-shell supersymmetric formulation of the theory on the superspace.
Crystalline and liquid Si3 N4 characterization by ﬁrst-principles molecular dynamics simulations
Directory of Open Access Journals (Sweden)
Castellani Niccoló
2011-05-01
Full Text Available Silicon nitride (Si3 N4 has a wide range of engineering applications where its mechanical and electronic properties can be eﬀectively exploited. In particular, in the microelectronics ﬁeld, the amorphous silicon nitride ﬁlms are widely used as charge storage layer in metal-alumina-nitrideoxide nonvolatile memory devices. Atomic structure of amorphous silicon nitride is characterized by an high concentration of traps that control the electric behavior of the ﬁnal device by the trappingde-trapping mechanism of the electrical charge occurring in its traps. In order to have a deep understanding of the material properties and, in particular, the nature of the electrical active traps a detailed numerical characterization of the crystalline and liquid phases is mandatory. For these reasons ﬁrst-principles molecular dynamics simulations are extensively employed to simulate the crystalline Si3 N4 in its crystalline and liquid phases. Good agreement with experimental results is obtained in terms of density and formation entalpy. Detailed characterization of c-Si3 N4 electronic properties is performed in terms of band structure and band gap. Then constant temperature and constant volume ﬁrst-principles molecular dynamics is used to disorder a stoichiometric sample of Si3 N4 . Extensive molecular dynamics simulations are performed to obtain a reliable liquid sample whose atomic structure does not depend on the starting atomic conﬁguration. Detailed characterization of the atomic structure is achieved in terms of radial distribution functions and total structure factor.
N=4, d=3 Born-Infeld theory in component approach
Kozyrev, Nikolay
2016-01-01
Using the formalism of nonlinear realizations we construct the component on-shell action of the N=4,d=3 Born-Infeld theory, which is the action of N=2, d=3 vector supermultiplet, fixed by invariance with respect to the additional spontaneously broken N=2, d=3 supersymmetry. Our construction shows that dealing with the systems with partial breaking of supersymmetry with vector fields in the multiplet, it is preferrable to use their formulation in terms of fermionic superfields only.
Thermo-Oxidative Degradation Of SiC/Si3N4 Composites
Baaklini, George Y.; Batt, Ramakrishna T.; Rokhlin, Stanislav I.
1995-01-01
Experimental study conducted on thermo-oxidative degradation of composite-material specimens made of silicon carbide fibers in matrices of reaction-bonded silicon nitride. In SiC/Si3N4 composites of study, interphase is 3-micrometers-thick carbon-rich coat on surface of each SiC fiber. Thermo-oxidative degradation of these composites involves diffusion of oxygen through pores of composites to interphases damaged by oxidation. Nondestructive tests reveal critical exposure times.
Twist-2 at seven loops in planar N=4 SYM theory: full result and analytic properties
Energy Technology Data Exchange (ETDEWEB)
Marboe, Christian [School of Mathematics, Trinity College Dublin,College Green, Dublin 2 (Ireland); Institut für Mathematik und Institut für Physik, Humboldt-Universität zu Berlin,IRIS Adlershof, Zum Großen Windkanal 6, 12489 Berlin (Germany); Velizhanin, Vitaly [Theoretical Physics Division, NRC “Kurchatov Institute”,Petersburg Nuclear Physics Institute, Orlova Roscha,Gatchina, 188300 St. Petersburg (Russian Federation); Institut für Mathematik und Institut für Physik, Humboldt-Universität zu Berlin,IRIS Adlershof, Zum Großen Windkanal 6, 12489 Berlin (Germany)
2016-11-04
The anomalous dimension of twist-2 operators of arbitrary spin in planar N=4 SYM theory is found at seven loops by using the quantum spectral curve to compute values at fixed spin, and reconstructing the general result using the LLL-algorithm together with modular arithmetic. The result of the analytic continuation to negative spin is presented, and its relation with the recently computed correction to the BFKL and double-logarithmic equation is discussed.
Statistical mechanics for dilatations in N=4 super Yang--Mills theory
Sochichiu, C
2006-01-01
Matrix model describing the anomalous dimensions of composite operators in $\\mathcal{N}=4$ super Yang--Mills up to one-loop level theory is considered at finite temperature. We compute the thermal effective action for this model, which we define as the log of the partition function restricted to the states of given length and spin. The result is obtained in the limits of high and low temperature.
Infrared Safe Observables in ${\\cal N}=4$ Super Yang-Mills Theory
Bork, L V; Vartanov, G S; Zhiboedov, A V
2009-01-01
The infrared structure of MHV gluon amplitudes in ${\\cal N}=4$ super Yang-Mills theory is considered in the next-to-leading order of PT. Explicit cancelation of the infrared divergencies in properly defined cross-sections is demonstrated. The remaining finite parts for some inclusive differential cross-sections are calculated analytically. In general, contrary to the virtual corrections, they do not reveal any simple structure.
Application of Silicon Nitride (Si3N4) Ceramics in Ball Bearing
2016-01-01
This paper is discus about silicon nitride ceramics in application to ball bearing. Silicon nitride (Si3N4) have advance properties such as consistent at temperature operation up to 1000°C, greater thermal shock resistance, lower density and low thermal expansion. This properties gives some benefit for ball bearing material such as higher running speed, reduce vibration of the shaft, will improve the life time and maintenance cost, lower heat generated, less energy consumption, lower wear ...
Coupling of Yang-Mills to N = 4, d = 4 supergravity
Bergshoeff, E.; Koh, I.G.; Sezgin, E.
1985-01-01
We couple N = 4, d = 4 supersymmetric Yang-Mills theory to supergravity. The scalars of the theory parametrize the coset (SO(n,6)/[SO(n)Ã—SO(6)])Ã—(SU(1,1)/U(1)). Keeping the composite local SO(n)Ã—SO(6)Ã—U(1) invariance intact, we gauge an (n + 6) parameter subgroup of SO(n,6) which is either (i) S
Wilson loops in 3d $\\mathcal{N}=4$ SQCD from Fermi gas
Okuyama, Kazumi
2016-01-01
We study 1/2 BPS Wilson loops in 3d $\\mathcal{N}=4$ $U(N)$ Yang-Mills theory with one adjoint and $N_f$ fundamental hypermultiplets from the Fermi gas approach. By numerical fitting, we find the first few worldsheet instanton corrections to the Wilson loops with winding numbers 1, 2 and 3. We verify that our Fermi gas results are consistent with the matrix model results in the planar limit.
Demystifying the twistor construction of composite operators in N=4 super-Yang-Mills theory
Chicherin, Dmitry
2016-01-01
We explain some details of the construction of composite operators in N=4 SYM that we have elaborated earlier in the context of Lorentz harmonic chiral (LHC) superspace. We give a step-by-step elementary derivation and show that the result coincides with the recent hypothesis put forward in arXiv:1603.04471 within the twistor approach. We provide the appropriate LHC-to-twistors dictionary.
Phase Transition of γ-Si3N4 Under High Pressure and High Temperature%高温高压下γ-Si3N4的相变
Institute of Scientific and Technical Information of China (English)
姚怀; 徐巧玉; 朱广林
2013-01-01
为了研究γ-Si3N4在高温高压下的相变,在压力为5.2、5.4及5.7 GPa,温度为1 300～1 450 K,保温时间为15min条件下,以Y2O3、Al2O3和La2O3为烧结助剂,制备了γ-Si3N4烧结体.用X射线衍射和扫描电子显微镜对烧结样品进行了分析和观察.结果表明:γ-Si3N4首先转变为α-Si3N4,再由α-Si3N4转变为β-Si3N4; β-Si3N4烧结体主要由长柱状的晶粒组成,晶粒相互连接,呈交叉分布,显微结构较为均匀,结构致密.拟合了三相相界方程,得到了n γ+α、α、α+β、β-Si3N4相界方程,并讨论了相关的相变机制.%In order to investigate the phase transition of γ-Si3N4 under high pressure and high temperature, γ-Si3N4 was sintered with Y2O3, A12O3 and La2O3 as additives at 5.2, 5.4 and 5.7 GPa and 1300-1450 K for 15min, respectively. The sintered samples were analyzed by X-ray diffraction and scanning electron microscopy. The results show that the γ-Si3N4 powder is firstly transformed into α-Si3N4, and then α-Si3N4 is transformed into β-Si3N4. When the γ-Si3N4 powder was completely transformed into β-Si3N4, the sintered samples were mainly composed of the elongated rod crystals with the interconnected and cross distribution, and had the more uniformity and compact microstructure. The rough boundary equations of γ, γ+α, α,α+β and β could be used to fit the experimental data, respectively. In addition, the related mechanism of phase transformation was also discussed.
Si3N4/环氧树脂导热复合材料制备和性能研究%Preparation and performance of Si3N4/EP-828 thermal conductivity composites
Institute of Scientific and Technical Information of China (English)
王明明; 张小耕
2010-01-01
采用硅烷偶联剂KH-550对氮化硅(β-Si3N4)进行表面处理,浇注制备氮化硅/环氧树脂(Si3N4/EP-828)复合材料,研究了Si3N4粒径、用量和表面改性对复合材料导热性能和力学性能的影响.结果表明,Si3N4/EP-828的导热性能随Si3N4用量的增加而提高,当Si3N4体积分数为30%时,热导率为0.83W/mK,为纯环氧树脂4倍多;力学性能则随Si3N4用量的增加先增大后降低.表面改性有助于进一步提高复合材料的导热性能和力学性能.初步分析表明,Si3N4/EP-828热导率与Si3N4形成的导热网链和Si-O-Si键导热骨架有关.
Directory of Open Access Journals (Sweden)
Grete Damberg
2010-01-01
Full Text Available Det har i de senere år skjedd store forandringer på folketrygdens område. Det har blitt lagt mer og mer vekt på viktigheten av å kunne være i aktivitet hvis det ikke er medisinske hindringer for dette. I endringene som er foretatt, er det fokus på den enkeltes muligheter til å være i arbeid mer enn på eventuelle begrensninger. Dette kommer fram gjennom endringer på sykefraværsområdet med innføring av aktivitetsplikt for den sykmeldte og gjennom ny sykefraværsmodell med fokus på oppfølging, involvering av arbeidsgiver, behandler og NAV. Arbeidsplassen er hovedarena for sykefraværsoppfølging, og arbeidsgiver og arbeidstaker er hovedaktører. Dette er en videreføring av føringene i Intensjonsavtalen om et inkluderende arbeidsliv. Også på området for rehabiliteringspenger, yrkesrettet attføring og uføreytelser legges det vekt på at den enkelte skal forsøke seg i arbeid hvis det medisinsk sett er mulig. I 2010 skjer det en større endring ved at rehabiliteringspenger, yrkesrettet attføring og tidsbegrenset uførestønad fjernes og erstattes med arbeidsavklaringspenger, en ytelse hvor det også legges vekt på aktivitet. Samtidig innføres arbeidsevnevurdering med full tyngde som arbeidsmetode internt i NAV. På yrkesskadeområdet har det skjedd få endringer, men organiseringen av yrkesskadeordningen i Norge er under utredning. Samhandling med og kompetansetilbud til sykmeldere er gjennomført i de siste årene. Det er også utviklet statistikk over sykmeldinger skrevet ut av fastleger, et verktøy som kan benyttes i dialog med den enkelte fastlege. Fortsatt er mange sykmeldt eller på varige ytelser. Årsakene til dette er sammensatte. Det er behov for videre forskning på folketrygdens områder. Damberg G. "From inactivity to action" - a review of development and changes in the national insurance scheme in recent years. Nor J Epidemiol 2009; 19 (2: 139-146. ENGLISH SUMMARYRecent years have seen major changes within
Energy Technology Data Exchange (ETDEWEB)
Villagra, Evelyn [Facultad de Quimica y Biologia, Departamento de Quimica de los Materiales, Universidad de Santiago de Chile (USACH), Casilla 40, Correo 33, Santiago (Chile); Bedioui, Fethi [Laboratoire de Pharmacologie Chimique et Genetique, UMR CNRS 8151/U INSERM 640, Ecole Nationale Superieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75231 Paris cedex 05 (France); Nyokong, Tebello [Department of Chemistry, Rhodes University, Grahamstown (South Africa); Canales, J. Carlos; Sancy, Mamie; Paez, Maritza A.; Costamagna, Juan [Facultad de Quimica y Biologia, Departamento de Quimica de los Materiales, Universidad de Santiago de Chile (USACH), Casilla 40, Correo 33, Santiago (Chile); Zagal, Jose H. [Facultad de Quimica y Biologia, Departamento de Quimica de los Materiales, Universidad de Santiago de Chile (USACH), Casilla 40, Correo 33, Santiago (Chile)], E-mail: jzagal@lauca.usach.cl
2008-05-30
Graphite electrodes modified with four different cobalt N4 macrocyclics, namely Co tetrapentapyridinophthalocyanine, (CoTPenPyrPc), Co tetrapyridinoporphyrazine (CoTPyPz), Co octa(hydroxyethylthio)phthalocyanine (CoOEHTPc) and Co tetranitrophthalocyanine (CoTNPc) exhibit catalytic activity for the oxidation of glucose in alkaline media. The purpose of this work is to establish correlations between the catalytic activity of these complexes and their redox potential. The activity of the different modified electrodes was tested by linear voltammetry under hydrodynamic conditions using the rotating disk technique. Tafel plots constructed from mass-transport corrected currents give slopes ranging from 0.080 to 0.160 V/decade for the different catalysts which suggests that a first one-electron step is rate controlling with the symmetry of the energy barrier depending on the nature of the ligand of the Co complex. A plot of log I versus the Co(II)/(I) formal potential gives a volcano curve that also includes catalysts studied previously. This illustrates the concept that the formal potential of the catalyst needs to be tuned to a certain value for achieving maximum activity. A theoretical interpretation of these results is given in terms of Langmuir isotherms for the adsorption of glucose on the Co sites of the surface-confined metal complexes.
Phases of $\\mathcal{N}=4$ SYM, S-duality and Nilpotent Cones
Balasubramanian, Aswin
2016-01-01
In this note, I describe the space of vacua $\\mathcal{V}$ of four dimensional $\\mathcal{N}=4$ SYM on $\\mathbb{R}^4$ with gauge group a compact simple Lie Group $G$ as a stratified space. On each stratum, the low energy effective field theory is different. This language allows one to make precise the idea of moving in the space of vacua $\\mathcal{V}$. A particular subset of the strata of $\\mathcal{N}=4$ SYM can be efficiently described using the theory of sheets in a Lie algebra. For these strata, I study the conjectural action of S-duality. I also indicate some benefits of using such a language for the study of the available space of vacua $\\overline{\\mathcal{V}}$ on the boundary of GL twisted $\\mathcal{N}=4$ SYM on a half-space $\\mathbb{R}^3 \\times \\mathbb{R}^+$. As an application of boundary symmetry breaking, I indicate how a) the Local Nilpotent Cone arises as part of the available symmetry breaking choices on the boundary of the four dimensional theory and b) the Global Nilpotent Cone arises in the theor...
Phases of N=4 SYM, S-duality and nilpotent cones
Energy Technology Data Exchange (ETDEWEB)
Balasubramanian, Aswin [DESY Theory, Hamburg (Germany); Hamburg Univ. (Germany). Dept. of Mathematics
2016-10-15
In this note, I describe the space of vacua V of four dimensional N=4 SYM on R{sup 4} with gauge group a compact simple Lie Group G as a stratified space. On each stratum, the low energy effective field theory is different. This language allows one to make precise the idea of moving in the space of vacua V. A particular subset of the strata of N=4 SYM can be efficiently described using the theory of sheets in a Lie algebra. For these strata, I study the conjectural action of S-duality. I also indicate some benefits of using such a language for the study of the available space of vacua V on the boundary of GL twisted N=4 SYM on a half-space R{sup 3} x R{sup +}. As an application of boundary symmetry breaking, I indicate how a) the Local Nilpotent Cone arises as part of the available symmetry breaking choices on the boundary of the four dimensional theory and b) the Global Nilpotent Cone arises in the theory reduced down to two dimensions on a Riemann Surface C. These geometries play a critical role in the Local and Global Geometric Langlands Program(s).
Twisted compactifications of 3d N = 4 theories and conformal blocks
Gaiotto, Davide
2016-01-01
Three-dimensional N = 4 supersymmetric quantum field theories admit two topological twists, the Rozansky-Witten twist and its mirror. Either twist can be used to define a supersymmetric compactification on a Riemann surface and a corre- sponding space of supersymmetric ground states. These spaces of ground states can play an interesting role in the Geometric Langlands program. We propose a description of these spaces as conformal blocks for certain non-unitary Vertex Operator Algebras and test our conjecture in some important examples. The two VOAs can be constructed respectively from a UV Lagrangian description of the N = 4 theory or of its mirror. We further conjecture that the VOAs associated to an N = 4 SQFT inherit properties of the theory which only emerge in the IR, such as enhanced global symmetries. Thus knowledge of the VOAs should allow one to compute the spaces of supersymmetric ground states for a theory coupled to supersymmetric background connections for the full symmetry group of the IR SCFT. ...
Glauber - Gribov approach for DIS on nuclei in N=4 SYM
Levin, E; Kopeliovich, B Z; Scmidt, Ivan
2009-01-01
In this paper the Glauber-Gribov approach for deep-inelastic scattering (DIS) with nuclei is developed in N=4 SYM. It is shown that the amplitude displays the same general properties, such as geometrical scaling, as is the case in the high density QCD approach. We found that the quantum effects leading to the graviton reggeization, give rise to an imaginary part of the nucleon amplitude, which makes the DIS in N=4 SYM almost identical to the one expected in high density QCD. We concluded that the impact parameter dependence of the nucleon amplitude is very essential for N=4 SYM, and the entire kinematic region can be divided into three regions which are discussed in the paper. We revisited the dipole description for DIS and proposed a new renormalized Lagrangian for the shock wave formalism which reproduces the Glauber-Gribov approach in a certain kinematic region. However the saturation momentum turns out to be independent of energy, as it has been discussed by Albacete, Kovchegov and Taliotis. We discuss th...
The low-energy N=4 SYM effective action in diverse harmonic superspaces
Buchbinder, I L; Samsonov, I B
2016-01-01
We review various superspace approaches to the description of the low-energy effective action in N=4 super Yang-Mills (SYM) theory. We consider the four-derivative part of the low-energy effective action in the Coulomb branch. The typical components of this effective action are the gauge field F^4/X^4 and the scalar field Wess-Zumino terms. We construct N=4 supersymmetric completions of these terms in the framework of different harmonic superspaces supporting N=2,3,4 supersymmetries. These approaches are complementary to each other in the sense that they make manifest different subgroups of the total SU(4) R-symmetry group. We show that the effective action acquires an extremely simple form in those superspaces which manifest the non-anomalous maximal subgroups of SU(4). The common characteristic feature of our construction is that we restore the superfield effective actions exclusively by employing the N=4 supersymmetry and/or superconformal PSU(2,2|4) symmetry.
Energy Technology Data Exchange (ETDEWEB)
Pitchaimari, G.; Vijayakumar, C.T., E-mail: ctvijay22@yahoo.com
2014-01-10
Graphical abstract: - Highlights: • UV cure materials are more thermally stable than the thermally cured materials. • Cyanate ester functionalization offers better thermal stability. • The Ea values for Poly NVPs are low compared to other materials investigated. • The UV cured materials showed higher Ea values than the thermally cured materials. - Abstract: The results of the studies concerning the thermal and photo initiated copolymerization of N-(4-acryloyloxy phenyl) maleimide (AX), N-(4-methacryloyloxy phenyl) maleimide (MAX) and N-(4-cyanato phenyl) maleimide (CNX) with N-vinyl-2-pyrrolidone (NVP) were presented. The structures of all the copolymers prepared were confirmed by FTIR studies. The thermogravimetric studies of both the thermal and UV cured materials indicated that the UV cured materials were comparatively thermally more stable than the thermally polymerized materials during thermal degradation. Of all the materials investigated, liquid composition having NVP and CNX cured by UV irradiation showed better thermal stability. The degradation kinetic studies using Flynn–Wall–Ozawa, Vyazovkin and Friedman methods showed that the activation energies (Ea) for the thermal degradation of polymeric materials cured by UV irradiation were slightly higher than the Ea values calculated for the thermally polymerized materials.
The Operator Product Expansion between the 16 Lowest Higher Spin Currents in the N=4 Superspace
Ahn, Changhyun
2015-01-01
Some of the operator product expansions (OPEs) between the lowest 16 higher spin currents of spins (1, 3/2, 3/2, 3/2, 3/2, 2, 2, 2, 2, 2, 2, 5/2, 5/2, 5/2, 5/2, 3) in an extension of the large N=4 linear superconformal algebra were constructed in the N=4 superconformal coset SU(5)/SU(3) theory previously. In this paper, by rewriting the above OPEs in the N=4 superspace developed by Schoutens (and other groups), the remaining undetermined OPEs where the corresponding singular terms possess the composite fields with spins s =7/2, 4, 9/2, 5 are completely determined. Furthermore, by introducing the arbitrary coefficients in front of the composite fields in the right hand sides of the above complete 136 OPEs, reexpressing them in the N=2 superspace and using the N=2 OPEs mathematica package by Krivonos and Thielemans, the complete structures of the above OPEs with fixed coefficient functions are obtained with the help of various Jacobi identities. Then one obtains ten N=2 super OPEs between the four N=2 higher sp...
Pressureless infiltration of Si3N4 preforms with an Al-2wt %Mg alloy
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infiltrate the Al-2wt%Mg alloy in silicon nitride preforms. The growth of the composite with useful thickness wasfacilitated by the presence of magnesium powder at the interface and by flowing nitrogen. The microstructure of the Si3N4-Al composite has been characterized using scanning electron microscope.During the infiltration of Si3N4 preforms, Si3N4 reacted with aluminium to form silicon and AlN. Thesilicon produced during the growth consumed in the formation of MgSiAlO, MgSiAlN and Al3.27Si0.47 type phases. The growth of the composite was found to proceed in two ways, depending on the oxide content in the initial preforms. First, less oxide content preforms gave rise to MgAlSiO and MgAlSiN type phases after infiltration. Second, more oxide content preforms gave rise to AlN-Al2O3 solid solution phase(AlON). The AlON phase was only present in the composite, containing 10% aluminium in the silicon nitride preforms before infiltration.
The low-energy N = 4 SYM effective action in diverse harmonic superspaces
Buchbinder, I. L.; Ivanov, E. A.; Samsonov, I. B.
2017-05-01
We review various superspace approaches to the description of the low-energy effective action in N = 4 super Yang-Mills (SYM) theory. We consider the four-derivative part of the low-energy effective action in the Coulomb branch. The typical components of this effective action are the gauge field F 4/ X 4 and the scalar field Wess-Zumino terms. We construct N = 4 supersymmetric completions of these terms in the framework of different harmonic superspaces supporting N = 2,3,4 supersymmetries. These approaches are complementary to each other in the sense that they make manifest different subgroups of the total SU(4) R-symmetry group. We show that the effective action acquires an extremely simple form in those superspaces which manifest the non-anomalous maximal subgroups of SU(4). The common characteristic feature of our construction is that we restore the superfield effective actions exclusively by employing the N = 4 supersymmetry and/or superconformal PSU(2, 2| 4) symmetry.
High efficiency photocatalysis for pollutant degradation with MoS2/C3N4 heterostructures.
Li, Qian; Zhang, Ning; Yang, Yong; Wang, Guozhong; Ng, Dickon H L
2014-07-29
Porous graphitic carbon nitride was synthesized by controllable thermal polymerization of urea in air. Their textural, electrical, and optical properties were tuned by varying the heating rate. The presence of proper residual oxygen in carbon nitride matrix had enhanced light absorption and inhibited the recombination of charge carriers. Furthermore, the MoS2 nanosheets were coupled into the carbon nitride to form MoS2/C3N4 heterostructures via a facile ultrasonic chemical method. The optimized MoS2/C3N4 heterostructure with 0.05 wt % MoS2 showed a reaction rate constant as high as 0.301 min(-1), which was 3.6 times that of bare carbon nitride. As analyzed by SEM, TEM, UV-vis absorption, PL and photoelectrochemical measurements, intimate contact interface, extended light response range, enhanced separation speed of charge carriers, and high photocurrent density upon MoS2 coupling led to the photocatalytic promotion of the MoS2/C3N4 heterostructures. In this architecture, MoS2 served as electron trapper to extend the lifetime of separated electron-hole pairs. Meanwhile, the accumulated holes on the surface of carbon nitride oxidized the organic dye directly, which was a predominant process in the photodegradation of organic pollutants in water treatment. The promotional mechanisms and principles reported here would have great significance in heterogeneous photocatalysis.
OSp(N|4) group and their contractions to P(3,1)xGauge
Ayala, M; Ayala, Mauricio; Haase, Richard
2001-01-01
Starting from SO(n,m) groups, we are in search of groups that: (1.) in a simple way, include N supersymmetric generators(see \\cite{Nahm}) (2.) contain as subgroup: the de Sitter group SO(4,1) or the Anti-de Sitter group SO(3,2) (3.) permit nontrivial gauge symmetry groups. The smallest groups satisfyng above conditions are the OSp(N|4) groups, which contain Sp(4)xSO(N) ($Sp(4)\\sim SO(3,2)$) or OSp(1|4)xSO(N-1). Because of this, it is possible to generate P(3,1)xG using groups contraction mechanism, which may be: $SO(3,2)\\to P(3,1)$ o $OSp(N|4)\\to ^SP(3,1|N)$ where P(3,1) is the Poincar\\'e group and G is a gauge group, say SO(N) or SO(N-1). This group contraction mechanism and its consequences upon different groups representations including SO(3,2) or SO(4,1), is clarified and extended to OSp(N|4) representations (see \\cite{Nicolai}), contracted to its N-extensi\\'on SuperPoincar\\'e group $\\ ^SP(3,1|N)$.
Characterization of rare-earth doped Si 3 N4 /SiC micro/nanocomposites
Directory of Open Access Journals (Sweden)
Peter Tatarko
2010-03-01
Full Text Available Influence of various rare-earth oxide additives (La2O3, Nd2O3, Sm2O3, Y2O3, Yb2O3 and Lu2O3 on the mechanical properties of hot-pressed silicon nitride and silicon nitride/silicon carbide micro/nano-composites has been investigated. The bimodal character of microstructures was observed in all studied materials where elongated β-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements. The fracture toughness of composites was always lower than that of monoliths due to their finer Si3N4/SiC microstructures. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements either in monoliths or composites. On the other hand, the positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element. Significantly improved creep resistance was observed in case either of composite materials or materials with smaller radius of RE3+.
Microstructure of reactive sintered Al bonded Si3N4-SiC ceramics
Institute of Scientific and Technical Information of China (English)
CUI Chong; WANG Yuan-ting; JIANG Jin-guo; CHEN Guang; SUN Qiang-jin
2006-01-01
Aluminium nitride-silicon nitride-silicon carbide (AlN-Si3N4-SiC) composite ceramics were prepared to increase the bending strength and improve the phase structure of Si3N4-based ceramics. The ceramics were made by reactive sintering in N2 atmosphere at 1 360 ℃, using Al as sintering additive. The phase composing of ceramics was identified with an X-ray diffractometer and the microstructure of the materials was studied by scanning electron microscopy. The results indicate that the phase structure is affected remarkably and the interface modality is changed. The interface between Si3N4 and SiC becomes blurry and that between SiC and AlN matches more better at the same time. But the liquid-phase appears during the reactive sintering along with the addition of Al by which the melting point of Si is decreased. The appearance of liquid Si decreases the bending strength of the ceramics. Lower temperature nitrification technic was introduced to avoid the appearance of liquid-phase Si. The optimum addition of Al was investigated by XRD and SEM analysis in order to obtain the maximal bending strength of materials.
Reactive diffusion bonding of Si3N4 to MA6000
Kaysser, W. A.; Frisch, A.; Zhang, W.; Petzow, G.
The procedure for joining Si3N4 to the MA6000 superalloy by diffusion bonding during HIP is described. Due to the large thermal mismatch between both components, it was necessary to introduce multiphase interlayers to allow relaxation of thermal stresses. Calculations of the stress development and the results of experiments showed that stress relaxation by thin soft interlayers in Si3N4/MA6000 is very limited: during bonding of Si3N4 to metals suitable as interlayers, brittle reaction products often form at the metal/ceramic interfaces. Experiments were then performed with iron-based alloys with small thermal expansion coefficients at low temperatures, combined with V, Nb, and Hf-based layers, and the reactions at the layer interfaces and the fracture surfaces were investigated by SEM, EDX, and WDX. It was found that, in systems with low deformability of the stiff reaction layers, stress relaxation by controlled microcrack formation reduced the interfacial damage and improved the mechanical stability of the joints.
Pressureless sintered beta prime-Si3N4 solid solution: Fabrication, microstructure, and strength
Dutta, S.
1977-01-01
Si3N4, AlN, and Al2O3 were used as basic constituents in a study of the pressureless sintering of beta prime-Si3N4 solid solution as a function of temperature. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 MPa were achieved at moderate temperature (1000 C), but decreased to 228 MPa at 1380 C. This substantial strength loss was attributed to a glassy grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.
Pressureless sintered beta-prime-Si3N4 solid solution - Fabrication, microstructure, and strength
Dutta, S.
1977-01-01
Pressureless sintering of beta-prime-Si3N4 solid solution was studied as a function of temperature using Si3N4, A1N, and Al2O3 as basic constituents. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta-prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 M Pa were achieved at moderate temperature (1000 C), but decreased to 228 M Pa at 1380 C. This substantial strength loss was attributed to a 'glassy' grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.
Li, Wenbo; Huang, Xiaoli; Bao, Kuo; Zhao, Zhonglong; Huang, Yanping; Wang, Lu; Wu, Gang; Zhou, Bo; Duan, Defang; Li, Fangfei; Zhou, Qiang; Liu, Bingbing; Cui, Tian
2017-02-01
The high-pressure behaviors of nitrogen-rich 1H-tetrazole (CH2N4) have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman scattering up to 75 GPa. A first crystalline-to-crystalline phase transition is observed and identified above ~3 GPa with a large volume collapse (∼18% at 4.4 GPa) from phase I to phase II. The new phase II forms a dimer-like structure, belonging to P1 space group. Then, a crystalline-to-amorphous phase transition takes place over a large pressure range of 13.8 to 50 GPa, which is accompanied by an interphase region approaching paracrystalline state. When decompression from 75 GPa to ambient conditions, the final product keeps an irreversible amorphous state. Our ultraviolet (UV) absorption spectrum suggests the final product exhibits an increase in molecular conjugation.
Li, Xiangming; Gao, Mingjun
2016-07-01
A Si3N4 ceramic with gradient distribution of pyrolytic carbon (Gradient-PyC-Si3N4) was fabricated by a combined technique of precursor infiltration pyrolysis and directional oxidation. An electromagnetic wave could enter Gradient-PyC-Si3N4 with little reflection because of a weak impedance mismatch at its surface, and the electromagnetic wave entering Gradient-PyC-Si3N4 could propagate forward along the PyC changing belt and simultaneously be absorbed by PyC with little reflection. The electromagnetic reflectivity of the Gradient-PyC-Si3N4 with an absence of PyC could reach a low level of -12.1 dB, which means that about 94% of the incident energy is absorbed and so makes the Gradient-PyC-Si3N4 a promising electromagnetic absorbing material for covert action.
Directory of Open Access Journals (Sweden)
S. Ganesh Babu
2015-10-01
Full Text Available Herein, Cu2O spheres were prepared and encapsulated with reduced graphene oxide (rGO. The Cu2O–rGO–C3N4 composite covered the whole solar spectrum with significant absorption intensity. rGO wrapped Cu2O loading caused a red shift in the absorption with respect to considering the absorption of bare C3N4. The photoluminescence study confirms that rGO exploited as an electron transport layer at the interface of Cu2O and C3N4 heterojunction. Utmost, ∼2 fold synergistic effect was achieved with Cu2O–rGO–C3N4 for the photocatalytic reduction of 4-nitrophenol to 4-aminophenol in comparison with Cu2O–rGO and C3N4. The Cu2O–rGO–C3N4 photocatalyst was reused for four times without loss in its activity.
Omidvar, Akbar
2017-08-01
Electrical charging of Co/N4 cluster embedded in graphene (Co/N4/G) is proposed as an approach for electrocatalytically switchable hydrogen adsorption. Using density functional theory, we found that the H2 molecule is weakly adsorbed on the uncharged Co/N4/G cluster. Our results show that the adsorption energy of hydrogen molecule on Co/N4/G cluster is significantly increased by introducing extra positive charges into the cluster. Once the charges are removed, H2 molecule spontaneously desorb from the Co/N4/G absorbent. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Our study indicates that the Co/N4/G nanomaterial is excellent absorbent for controllable and reversible adsorption and release of H2.
Institute of Scientific and Technical Information of China (English)
BAI Ling; GE Changchun; SHEN Weiping; MAO Xiaodong; ZHANG Ke
2008-01-01
TiC/Si3N4 composites were prepared using the β-Si3N4 powder synthesized by self-propagating high-temperature synthesis (SHS) and 35 wt.% TiC by spark plasma sintering. Y2O3 and A12O3 were added as sintering additives. The almost full sintered density and the highest fracture toughness (8.48 MPa·m1/2) values of Si3N4-based ceramics could be achieved at 1550℃. No interfacial interactions were noticeable between TiC and Si3N4. The toughening mechanisms in TiC/Si3N4 composites were attributed to crack deflection, microcrack toughening, and crack impedance by the periodic compressive stress in the Si3N4 matrix. However, increasing microcracks easily led to excessive connection of microcracks, which would not be beneficial to the strength.
Effect of nano-Si3N4 surface treatment on the tribological performance of epoxy composite
Directory of Open Access Journals (Sweden)
2010-03-01
Full Text Available To overcome the disadvantages generated by the loose nano-partilce agglomerates dispersed in polymer composites, a chemical grafting method was applied to modify nano-Si3N4 by covalently bonding glycidyl methacrylate (GMA onto the particles. The tribological behavior of the epoxy composite filled with nano-Si3N4 or GMA treated Si3N4 (Si3N4-g-PGMA was studied using a ring-on-block wear tester under dry sliding, and the worn surface of the filled epoxy composite and the surface roughness of the composites after the sliding wear test were investigated by SEM (scanning electron microscopy and AFM (atomic force microscopy, respectively. In comparison to the composites filled with untreated nano-Si3N4 particles, the composites with the grafted Sinano-3N4 exhibit improved sliding wear resistance and reduced friction coefficient owing to the chemical bonding at the filler/matrix interface.
Effects of extrusion deformation on mechanical properties of sub-micron Si_3N_(4p)/2024 composite
Institute of Scientific and Technical Information of China (English)
XIU Zi-yang; CHEN Guo-qin; LIU Yan-mei; YANG Wen-shu; WU Gao-hui
2009-01-01
Si_3N_(4p)/2024Al composite was fabricated by squeeze casting method and treated by extrusion deformation. Microstructure analyses indicate that Si_3N_4 particles in the composite are in cylindrical polyhedron shape. Extrusion deformation is beneficial to uniform distribution of Si_3N_4 particles and improves the relative density of Si_3N_(4p)/2024Al composite. Tensile strength of Si_3N_(4p)/2024Al composite increases by 76.6% after T6 treatment, and after extrusion and T6 treatment it is by 57.6% more than T6 treatment only. Elastic modulus of Si_3N_(4p)/2024Al composite increases a little after T6 treatment but increases by 33.5% after extrusion deformation.
Institute of Scientific and Technical Information of China (English)
薛海涛(编译); 王晓阳(校)
2013-01-01
氮化硅-氮化钛陶瓷的氧化行为是建立在对其微观结构的观察，对这种氧化模型现象进行了描述，并对其氧化动力学模型进行研究。当温度＜1000℃，只有TiN相被氧化。此氧化过程是由氧气通过TiO2扩散来控制的，由氧化动力学抛物线方程来描述。超过1000℃的过程是非常复杂的，那是因为同时发生Si3 N4和TiN相的两种氧化反应。三种氧化模型都被清晰的扩散机理所控制，是接连发生的。第1步，Si3 N4和TiN相被独立的氧化，它们分别被氧化为SiO2和TiO2相。 Si3 N4的氧化是由氧通过SiO2扩散控制的，而TiN的氧化由钛通过TiO2扩散所控制。第2步，TiN的氧化被氧通过TiO2扩散控制，而通过SiO2被氧化形成Si3 N4。第3步，TiN和Si3 N4的氧化由氧通过二氧化硅层扩散控制。动力学方程可以由这三种氧化模型的任意一种决定。
Mechanical properties of microwave sintered Si3N4-based ceramics
Directory of Open Access Journals (Sweden)
Getman O.I.
2002-01-01
Full Text Available The mechanical properties and microstructure formation processes in Si3N4+3% AI2O3+5% Y2O3(Yb2O3 ceramic compacts sintered under microwave heating (MWH and under traditional heating (TH were investigated. The initial ceramic materials were powder blends of silicon nitride with oxides. The mean powder particle sizes were 0.5-1.0 mim. The content of alfa-phase in the Si3N4 powder was more than 95 %. The samples were sintered at 1800BC in nitrogen at normal pressure, the heating rate in all experiments was 60BC/min. The Vickers hardness (HV, fracture toughness (K1C and bending strength (on were determined. The microstructures of fracture surfaces of samples were studied by SEM. Quantitative microstructure analysis was carried out. It was shown that the values of HV and Kic of ceramic samples sintered under MWH at 1800BC rose steadily with the sintering time. This caused an increase in density, which reached maximum as fast as after 30 min of the MWH sintering; the mass loss at that time amounted to 3-4 %. The porosity of sintered samples with an addition of yttria was less than 1 %, that of ytterbia was greater, 2.4 %. For similar values of relative density, the hardness and fracture toughness of ceramic samples produced under MWH were higher as compared with those of samples sintered under TH. The microstructure of samples had the form of elongated grains in a matrix of polyhedral grains of the beta-Si3N4 phase. Measurements showed the mean size of grains in samples produced by MWH to be greater that in samples produced by TH. A larger number of elongated grains were formed. It was concluded that for sintering under MWH of Si3N4-based ceramics the growth of elongated beta-Si3N4 grains and formation of a "reinforced" microstructure were promoted and thereby improved the mechanical properties of such ceramics.
Development and Application of Al2O3 - Si3N4 Refractories Used in Blast Furnace
Institute of Scientific and Technical Information of China (English)
LI Xianming; LI Yong; KANG Huarong; DONG Shengying; XUE Wendong; SONG Wen
2008-01-01
Newly developed Al2O3-Si3N4 composite refracto-ries used for blast furnace is introduced in this work.Al2O3-Si3N4 composite refractories attacked by alkali vapor and blast Jhrnace slag was investigated. High per-formance Al2O3 -Si3N4 composite refractories was pro-duced and used at both 2 560 m3 blast furnaces of Tan-gsteel and No. 5 blast furnace of Shaosteel.
Directory of Open Access Journals (Sweden)
Vasilii GRAUR
2015-12-01
Full Text Available The paper presents the synthesis of the ligand 1-(2-hydroxyphenylethanone N(4-allyl-3-thiosemicarbazone (H2L and six coordination compounds of copper, nickel and cobalt with this ligand. The structure of thiosemicarbazone H2L was studied using 1H and 13С NMR spectroscopy. The synthesized coordination compounds were studied using elemental analysis, gravimetric analysis of water content, molar conductivity, and magnetochemistry. For H2L the antitumor activity towards human leukemia HL-60 cells and cervical cancer HeLa cells was determined. It was established that the substitution of hydrogen atom with methyl group in the azomethinic fragment leads to the growth of antitumor activity.SINTEZA ŞI ACTIVITATEA ANTITUMORALĂ A COMPUŞILOR COMPLECŞI AI CUPRULUI, NICHELULUI ŞI COBALTULUI CU N(4-ALIL-3-TIOSEMICARBAZONA 1-(2-HIDROXIFENILETANONEILucrarea conţine descrierea sintezei N(4-alil-3-tiosemicarbazonei 1-(2-hidroxifeniletanonei (H2L şi a şase compuşi coordinativi ai cuprului, nichelului şi cobaltului cu acest ligand. Structura tiosemicarbazonei H2L a fost stabilită în baza datelor spectroscopiei RMN 1H şi 13C. Compuşi coordinativi au fost studiaţi cu ajutorul analizei elementale, analizei gravimetrice a conţinutului de apă, conductivitaţii molare şi magnetochimiei. Pentru H2L a fost determinată activitatea antitumorală faţă de celulele leucemiei umane HL-60 şi ale cancerului cervical HeLa. S-a stabilit că înlocuirea atomului de hidrogen cu o grupare metil în fragmentul azomethinic conduce la creşterea activitaţii antitumorale.
Energy Technology Data Exchange (ETDEWEB)
Lambert, C.; Lecointre, C.; Nicolas, M.; Feuermann, M.
1993-12-01
This report presents some aspects of the acoustical situation in the workrooms of the electricity building of the nuclear plant N4 of Chooz. It enables us to draw up a diagnosis of the present situation. This diagnosis will contribute to the choice of the technical solutions, at the conception of this type of building. A particular study is devoted to the kitchen of the building. This study shows the impact of a RRI (intermediary refrigeration circuit), which is responsible for a high noise level in this room. The fixation type of the pipe appears to be the cause of the annoyance. This study justifies the need for the uncoupling between this pipe type and the building structures, at the conception time. Noise levels measured in the different rooms are essentially induced by the ventilation networks. This levels are generally too high, compared with the objectives. This leads us to consider that the installation rules about the ventilation network are still to define. (authors). 7 figs., 2 annexes.
Directory of Open Access Journals (Sweden)
Harsha Varthan Shanmugakumar
2016-09-01
Full Text Available The mechanical and electronic properties of β-Si3N4, TiC-Si3N4 and TiN-Si3N4 ceramics are investigated using density functional theory implemented with GGA/PBE functional. The pristine β-Si3N4 exhibits fracture for a strain of 10%. However, TiC-Si3N4 and TiN-Si3N4 ceramics exhibits fracture for a strain of 20%. The Young’s modulus, shear modulus and bulk modulus of the pristine β-Si3N4, TiC-Si3N4 and TiN-Si3N4 ceramics are reported. TiN-Si3N4 ceramic is found to be the least compressible and hard. The band gap is found to decrease for TiC-Si3N4 and TiN-Si3N4 ceramics compared with the pristine β-Si3N4. The density of states spectrum shows more peak maxima for TiC-Si3N4 and TiN-Si3N4 ceramics rather than β-Si3N4. The finding of the present work gives a clear insight on the mechanical and electronic properties of β-Si3N4, TiC-Si3N4 and TiN-Si3N4 ceramics at the atomistic level.
Indian Academy of Sciences (India)
Yu Fangli; Wang Huanrui; Bai Yu; Yang Jianfeng
2010-10-01
Porous silicon nitride (Si3N4) ceramics were fabricated by compression molding and slip casting methods using petroleum coke as pore forming agent, and Y2O3–Al2O3 as sintering additives. Microstructure, mechanical properties and gas permeability of porous Si3N4 ceramics were investigated. The mechanical properties and microstructure of porous Si3N4 ceramics prepared by compression molding were better than those which were prepared by slip casting method, whereas slip casting method is suitable for the preparation of porous Si3N4 ceramics with higher porosity and excellent gas permeability.
Institute of Scientific and Technical Information of China (English)
王华彬; 韩杰才; 杜善义
2000-01-01
主要研究了氮气压力对自蔓延高温合成Si3N4的影响,并通过放气法详细地研究了β-Si3N4的生长机理.结果表明:随着氮气压的增加和燃烧温度的提高,促进了Si的蒸发,从而致使产物中Si3N4的α/β相的比例增加.通过放气法实验,观察到了棒状Si3N4(β相)以气-液-固(VLS)机制生长的中间形态.X射线能谱分析表明β-Si3N4以气-液-固(VLS)机制生长所需的液相依赖于反应物中的含氧杂质,而不是金属杂质.由于在生长过程中,β-Si3N4顶端的液相中的氧得不到补偿,致使Si3N4长成短棒状.溶解-析出机制是燃烧合成Si3N4过程中α相转变为β相的主要机制.
Preparation of WO3/g-C3N4 composites and their application in oxidative desulfurization
Zhao, Rongxiang; Li, Xiuping; Su, Jianxun; Gao, Xiaohan
2017-01-01
WO3/graphitic carbon nitride (g-C3N4) composites were successfully synthesized through direct calcining of a mixture of WO3 and g-C3N4 at 400 °C for 2 h. The WO3 was prepared by calcination of phosphotungstic acid at 550 °C for 4 h, and the g-C3N4 was obtained by calcination of melamine at 520 °C for 4 h. The WO3/g-C3N4 composites were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and Brunner-Emmett-Teller analysis (BET). The WO3/g-C3N4 composites exhibited stronger XRD peaks of WO3 and g-C3N4 than the WO3 and pure g-C3N4. In addition, two WO3 peaks at 25.7° and 26.6° emerged for the 36% -WO3/g-C3N4 composite. This finding indicated that WO3 was highly dispersed on the surface of the g-C3N4 nanosheets and interacted with the nanosheets, which resulted in the appearance of (012) and (022) planes of WO3. The WO3/g-C3N4 composite also exhibited a larger specific surface area and higher degree of crystallization than WO3 or pure g-C3N4, which resulted in high catalytic activity of the catalyst. Desulfurization experiments demonstrated that the desulfurization rate of dibenzothiophene (DBT) in model oil reached 91.2% under optimal conditions. Moreover, the activity of the catalyst was not significantly decreased after five recycles.
Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction
Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.
2017-02-01
TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.
Sosinski, J; Chapin, C; Thakar, J H; Houghton, P J
1991-01-01
The effect of extracellular pH (pH(e)) on the accumulation and cytotoxicity of the diarylsulfonylurea antitumor agent N-(4-methylphenylsulfonyl)-N'-(4-chlorophenyl)urea (MPCU) has been examined. In a human colon adenocarcinoma cell line, GC3/C1, the initial rate of uptake of [3H]MPCU (2.4 microM) was increased by 4.5-fold as pH(e) was reduced from 7.4 to 6.5. Steady state levels of MPCU were inversely proportional to pH(e) and were 5-fold greater at pH 6.0 compared to 7.4. Similar results were obtained using Rh30 cells derived from an alveolar rhabdomyosarcoma. MPCU rapidly re-equilibrated after achieving steady state when pH(e) was altered, indicating that MPCU was not tightly bound within cells. In both cell lines, the uncoupling agent, carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), significantly reduced (GC3/C1) or completely inhibited (Rh30) accumulation of MPCU at each pH(e) examined. Sodium azide had the same effect on the accumulation of MPCU as FCCP. The effects of FCCP and azide appeared to be due to collapse of the pH differential across the mitochondrial inner membrane rather than the gradient across the plasma membrane. As extracellular pH (pH(e)) decreased, intracellular pH(pH(i)) also decreased in GC3/C1 cells, such that the greatest pH differential (pH(i) - pH(e)) was 0.2 units at pH(e) 6.0. Neither FCCP nor azide significantly altered this pH gradient, indicating a minor role, if any, for the plasma membrane pH gradient in accumulation of MPCU in GC3/C1 cells. The effect of pH(e) (7.4 to 6.0) on cytotoxicity of MPCU was determined after exposure of cells for 4 hr to various concentrations of MPCU in the presence of 10% fetal bovine serum. Decreasing the pH(e) from 7.4 to 6.0 increased the potency of MPCU by 4.7- and 4.5-fold in Rh30 and GC3/C1 cells, respectively. In cells exposed to drug/pH(e) combinations that resulted in 50% reduction in colony forming potential, the steady state levels of [3H]MPCU were similar (range 8.8 +/- 0.9 to 10
用Al作中间层的Si3N4陶瓷的扩散焊接%Diffusion Joining of Si3N4 Joints With Al Interlayers
Institute of Scientific and Technical Information of China (English)
阎俊霞; 王立君
2002-01-01
在温度为600℃、压强为30 MPa和保温2 h的条件下,成功地实现了Si3N4/Al/Si3N4试样的真空扩散连接.用SEM和EPMA方法进行的连接机理分析表明,Si3N4和Al的连接是通过有限的原子相互扩散实现的.用SEM和EDXA方法研究了Si3N4/Al界面的断口.结果表明,Si3N4/Al界面的断裂模式属于界面脆性剥离.
Photoelectrochemical Conversion from Graphitic C3N4 Quantum Dot Decorated Semiconductor Nanowires.
An, Tiance; Tang, Jing; Zhang, Yueyu; Quan, Yingzhou; Gong, Xingao; Al-Enizi, Abdullah M; Elzatahry, Ahmed A; Zhang, Lijuan; Zheng, Gengfeng
2016-05-25
Despite the recent progress of developing graphitic carbon nitride (g-C3N4) as a metal-free photocatalyst, the synthesis of nanostructured g-C3N4 has still remained a complicated and time-consuming approach from its bulk powder, which substantially limits its photoelectrochemical (PEC) applications as well as the potential to form composites with other semiconductors. Different from the labor-intensive methods used before, such as exfoliation or assistant templates, herein, we developed a facile method to synthesize graphitic C3N4 quantum dots (g-CNQDs) directly grown on TiO2 nanowire arrays via a one-step quasi-chemical vapor deposition (CVD) process in a homemade system. The as-synthesized g-CNQDs uniformly covered over the surface of TiO2 nanowires and exhibited attractive photoluminescence (PL) properties. In addition, compared to pristine TiO2, the heterojunction of g-CNQD-decorated TiO2 nanowires showed a substantially enhanced PEC photocurrent density of 3.40 mA/cm(2) at 0 V of applied potential vs Ag/AgCl under simulated solar light (300 mW/cm(2)) and excellent stability with ∼82% of the photocurrent retained after over 10 h of continuous testing, attributed to the quantum and sensitization effects of g-CNQDs. Density functional theory calculations were further carried out to illustrate the synergistic effect of TiO2 and g-CNQD. Our method suggests that a variety of g-CNQD-based composites with other semiconductor nanowires can be synthesized for energy applications.
N=4 Supersymmetric Yang-Mills Theory on Orbifold-$T^4/{\\bf Z}_2$
Jinzenji, M; Jinzenji, Masao; Sasaki, Toru
2001-01-01
We derive the partition function of N=4 supersymmetric Yang-Mills theory on orbifold-$T^4/{\\bf Z}_2$. In classical geometry, K3 surface is constructed from the orbifold-$T^4/{\\bf Z}_2$. Along the same way as the orbifold construction, we construct the partition function of K3 surface from orbifold-$T^4/{\\bf Z}_2$. The partition function is given by the product of the contribution of the untwisted sector of $T^4/{\\bf Z}_2$, and that of the twisted sector of $T^4/{\\bf Z}_2$ i.e., ${\\cal O}(-2)$ curve blow-up formula.
N-(4,6-Dimethylpyrimidin-2-yl-1,3-benzothiazol-2-amine
Directory of Open Access Journals (Sweden)
Shaaban K. Mohamed
2011-11-01
Full Text Available In the title compound, C13H12N4S, an amino N atom is connected to a 1,3-benzothiazole fused-ring system and a dimethyl-substituted pyrimidine ring, these components being aligned [interplanar dihedral angle = 1.9 (1°]. The secondary amino N atom forms an intermolecular N—H...N hydrogen bond to an N atom of the fused ring of an adjacent molecule, generating a centrosymmetric cyclic hydrogen-bonded dimer [graph set R22(8].
Cut-and-join operators and N=4 super Yang-Mills
Energy Technology Data Exchange (ETDEWEB)
Brown, T.W. [DESY, Hamburg (Germany). Theory Group
2010-02-15
We show which multi-trace structures are compatible with the symmetrisation of local operators in N=4 super Yang-Mills when they are organised into representations of the global symmetry group. Cut-and-join operators give the non-planar expansion of correlation functions of these operators in the free theory. Using these techniques we find the 1/N corrections to the quarter-BPS operators which remain protected at weak coupling. We also present a new way of counting these chiral ring operators using the Weyl group S{sub N}. (orig.)
On symmetries of N=(4,4) sigma models on T^4
Volpato, Roberto
2014-01-01
Motivated by an analogous result for K3 models, we classify all groups of symmetries of non-linear sigma models on a torus T^4 that preserve the N=(4,4) superconformal algebra. The resulting symmetry groups are isomorphic to certain subgroups of the Weyl group of E8, that plays a role similar to the Conway group for the case of K3 models. Our analysis heavily relies on the triality automorphism of the T-duality group SO(4,4,Z). As a byproduct of our results, we discover new explicit descriptions of K3 models as asymmetric orbifolds of torus CFTs.
An all order identity between ABJM and N=4 SYM four-point amplitudes
Bianchi, Marco S; Penati, Silvia
2011-01-01
We derive an exact algebraic identity between the two-loop four-point amplitude in ABJM theory and the corresponding one-loop amplitude in N=4 SYM theory. This identity generalizes previous partial results to an exact relation valid at all orders in the IR regulator. Moreover, it allows to conjecture an exact iterative expression for the complete three dimensional amplitude in terms of the BDS ansatz for the four dimensional one, indicating that the strict relation between the two amplitudes experimented at two loops might propagate to all orders. In particular, an almost complete expression for the ABJM amplitude at four loops is derived.
Dynamic study in partial transient liquid phase bonding of Si3N4
Institute of Scientific and Technical Information of China (English)
邹家生; 初雅杰; 许志荣; 陈光
2004-01-01
Dynamics in partial transient liquid phase bonding (PTLP bonding) of Si3N4 ceramic with Ti/Cu/Ti multi-interlayer was systematically studied through micro-analysis of joint interfaces. The results show that growth of reaction layer and isothermal solidification procession do at the same time. Growth of reaction layer and moving of isothermal solidification interface obey the parabolic law governed by the diffusion of participating elements during the PTLP bonding. Coordination of the above two dynamics process is done through time and temperature. When reaction layer thickness is suitable and isothermal solidification process is finished, the high bonding strength at room temperature and high temperature are obtained.
A note on dual MHV diagrams in mathcal{N} = 4 SYM
Brandhuber, Andreas; Spence, Bill; Travaglini, Gabriele; Yang, Gang
2010-12-01
Recently a reformulation of the MHV diagram method in mathcal{N} = 4 supersymmetric Yang-Mills theory in momentum twistor space was presented and was shown to be equivalent to the perturbative expansion of the expectation value of a supersymmetric Wilson loop in momentum twistor space. In this note we present related explicit Feynman rules in dual momentum space, which should have the interpretation of Wilson loop diagrams in dual momentum space. We show that these novel rules are completely equivalent to ordinary spacetime MHV rules and can be naturally viewed as their graph dual representation.
Dyon spectrum in generic N = 4 supersymmetric Z{sub N} orbifolds
Energy Technology Data Exchange (ETDEWEB)
David, Justin R.; Jatkar, Dileep P.; Sen, Ashoke [Harish-Chandra Research Institute, Chhatnag Road, Jhusi, Allahabad 211019 (India)
2007-01-15
We find the exact spectrum of a class of quarter BPS dyons in a generic N = 4 supersymmetric Z{sub N} orbifold of type IIA string theory on K3 x T{sup 2} or T{sup 6}. We also find the asymptotic expansion of the statistical entropy to first non-leading order in inverse power of charges and show that it agrees with the entropy of a black hole carrying same set of charges after taking into account the effect of the four derivative Gauss-Bonnet term in the effective action of the theory.
α'-expansion of antisymmetric Wilson loops in N =4 SYM from Fermi gas
Horikoshi, Masaatsu; Okuyama, Kazumi
2016-11-01
We study the large 't Hooft coupling expansion of 1/2 BPS Wilson loops in the antisymmetric representation in N =4 super Yang-Mills (SYM) theory at the leading order in the 1/N expansion. Via AdS/CFT correspondence, this expansion corresponds to the α expansion in bulk type IIB string theory. We show that this expansion can be systematically computed by using the low temperature expansion of the Fermi distribution function, known as the Sommerfeld expansion in statistical mechanics. We check numerically that our expansion agrees with the exact result of antisymmetric Wilson loops recently found by Fiol and Torrents.
The Bethe roots of Regge cuts in strongly coupled N=4 SYM theory
Energy Technology Data Exchange (ETDEWEB)
Bartels, J. [II. Institute for Theoretical Physics, Hamburg University,Luruper Chaussee 149, 22671 Hamburg (Germany); Schomerus, V. [DESY Hamburg, Theory Group,Notkestraße 85, 22607 Hamburg (Germany); Sprenger, M. [DESY Hamburg, Theory Group,Notkestraße 85, 22607 Hamburg (Germany); Institute for Theoretical Physics, ETH Zürich,Wolfgang-Pauli-Strasse 27, 8093 Zürich (Switzerland)
2015-07-20
We describe a general algorithm for the computation of the remainder function for n-gluon scattering in multi-Regge kinematics for strongly coupled planar N=4 super Yang-Mills theory. This regime is accessible through the infrared physics of an auxiliary quantum integrable system describing strings in AdS{sub 5}×S{sup 5}. Explicit formulas are presented for n=6 and n=7 external gluons. Our results are consistent with expectations from perturbative gauge theory. This paper comprises the technical details for the results announced in http://dx.doi.org/10.1007/JHEP10(2014)067.
BPS Equations in Omega-deformed N=4 Super Yang-Mills Theory
Ito, Katsushi; Nakajima, Hiroaki; Sasaki, Shin
2015-01-01
We study supersymmetry of N=4 super Yang-Mills theory in four dimensions deformed in the Omega-background. We take the Nekrasov-Shatashvili limit of the background so that two-dimensional super Poincare symmetry is recovered. We compute the deformed central charge of the superalgebra and study the 1/2 and 1/4 BPS states. We obtain the Omega-deformed 1/2 and 1/4 BPS dyon equations from the deformed supersymmetry transformation and the Bogomol'nyi completion of the energy.
On a CFT limit of planar $\\gamma_i$-deformed $\\mathcal{N}=4$ SYM theory
Sieg, Christoph
2016-01-01
We show that an integrable four-dimensional non-unitary field theory that was recently proposed as a certain limit of the $\\gamma_i$-deformed $\\mathcal{N}=4$ SYM theory is incomplete and not conformal -- not even in the planar limit. We complete this theory by double-trace couplings and find conformal one-loop fix-points when admitting respective complex coupling constants. These couplings must not be neglected in the planar limit, as they can contribute to planar multi-point functions. Based on our results for certain two-loop planar anomalous dimensions, we propose tests of integrability.
Composite Operators in the Twistor Formulation of $\\mathcal{N}=4$ SYM Theory
Koster, Laura; Staudacher, Matthias; Wilhelm, Matthias
2016-01-01
We incorporate gauge-invariant local composite operators into the twistor-space formulation of $\\mathcal{N}=4$ Super Yang-Mills theory. In this formulation, the interactions of the elementary fields are reorganized into infinitely many interaction vertices and we argue that the same applies to composite operators. To test our definition of the local composite operators in twistor space, we compute several corresponding form factors, thereby also initiating the study of form factors using the position twistor-space framework. Throughout this letter, we use the composite operator built from two identical complex scalars as a pedagogical example; we treat the general case in a follow-up paper.
Gluon scattering in N=4 super-Yang-Mills theory fromweak to strong coupling
Energy Technology Data Exchange (ETDEWEB)
Dixon, Lance J.; /SLAC
2008-03-25
I describe some recent developments in the understanding of gluon scattering amplitudes in N = 4 super-Yang-Mills theory in the large-N{sub c} limit. These amplitudes can be computed to high orders in the weak coupling expansion, and also now at strong coupling using the AdS/CFT correspondence. They hold the promise of being solvable to all orders in the gauge coupling, with the help of techniques based on integrability. They are intimately related to expectation values for polygonal Wilson loops composed of light-like segments.
Refined counting of necklaces in one-loop N=4 SYM
Suzuki, Ryo
2017-06-01
We compute the grand partition function of N=4 SYM at one-loop in the SU(2) sector with general chemical potentials, extending the results of Pólya's theorem. We make use of finite group theory, applicable to all orders of perturbative 1 /N c expansion. We show that only the planar terms contribute to the grand partition function, which is therefore equal to the grand partition function of an ensemble of {XXX}_{1/2} spin chains. We discuss how Hagedorn temperature changes on the complex plane of chemical potentials.
Real space renormalization group for twisted lattice N=4 super Yang-Mills
Catterall, Simon
2014-01-01
A necessary ingredient for our previous results on the form of the long distance effective action of the twisted lattice N=4 super Yang-Mills theory is the existence of a real space renormalization group which preserves the lattice structure, both the symmetries and the geometric interpretation of the fields. In this brief article we provide an explicit example of such a blocking scheme and illustrate its practicality in the context of a small scale Monte Carlo renormalization group calculation. We also discuss the implications of this result, and the possible ways in which to use it in order to obtain further information about the long distance theory.
Plane wave matrix theory vs. N=4 D=4 super Yang-Mills
Energy Technology Data Exchange (ETDEWEB)
Kim, N. [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, 14476 Golm (Germany)
2004-06-01
A mass deformed, supersymmetric, Yang-Mills quantum mechanics has been introduced recently as the matrix model of M-theory on plane-wave backgrounds. Here we point out that the massive matrix model can be obtained as a dimensional reduction of N=4, D=4 Super Yang-Mills theory on S{sup 3}. The hamiltonian of the matrix model can be matched with the dilatation operator of the conformal field theory, and we discuss how they behave in the perturbative computations. (Abstract Copyright [2004], Wiley Periodicals, Inc.)
Development of Sintered Si3N4 for High Performance Thermomechanical Applications.
1984-01-01
material had unexcelled creep and oxidation characteristics relative to any sintered Si3 N4 reported to date . The absolute strength of the material at room...experi- ments conducted on Lots A-L0 and A-18. The oxygen content is listed for each compostion , since it was previously established, with SN502 powder...Silicon Nitride, ibid 10 1169-74 (1975). 15. M. Mitomo, "Pressure Sintering of Si 3N411, ibid 11, 1103-07 (1976). 16. C. Greskovich and 3.A. Palm
Poly[μ-aqua-μ-(N,4-di-chloro-2-methyl-benzene-sulfonamidato)-potassium].
Spandana, H S; Foro, Sabine; Gowda, B Thimme
2013-01-01
In the title compound, [K(C7H6Cl2NO2S)(H2O)] n , the K(+) cation is hepta-coordinated by two water O atoms, a sulfonyl O atom from each of four different N,4-dichloro-2-methyl-benzene-sulfonamidate anions and a Cl atom of one of the anions. Further, K-O-K bridges form extensive polymeric chains along the b axis. In the crystal structure, the anions are linked into layers parallel to (100) by O-H⋯Cl and O-H⋯N hydrogen bonds.
Visible Light-Driven Photocatalytic Performance of N-Doped ZnO/g-C3N4 Nanocomposites
Kong, Ji-Zhou; Zhai, Hai-Fa; Zhang, Wei; Wang, Shan-Shan; Zhao, Xi-Rui; Li, Min; Li, Hui; Li, Ai-Dong; Wu, Di
2017-09-01
N-doped ZnO/g-C3N4 composites have been successfully prepared via a facile and cost-effective sol-gel method. The nanocomposites were systematically characterized by XRD, FE-SEM, HRTEM, FT-IR, XPS, and UV-vis DRS. The results indicated that compared with the pure N-doped ZnO, the absorption edge of binary N-doped ZnO/g-C3N4 shifted to a lower energy with increasing the visible-light absorption and improving the charge separation efficiency, which would enhance its photocatalytic activity. Compared with the pure g-C3N4, ZnO, N-doped ZnO and the composite ZnO/g-C3N4, the as-prepared N-doped ZnO/g-C3N4 exhibits a greatly enhanced photocatalytic degradation of methylene blue and phenol under visible-light irradiation. Meanwhile, N-doped ZnO/g-C3N4 possesses a high stability. Finally, a proposed mechanism for N-doped ZnO/g-C3N4 is also discussed. The improved photocatalysis can be attributed to the synergistic effect between N-doped ZnO and g-C3N4, including the energy band structure and enhanced charge separation efficiency.
Visible Light-Driven Photocatalytic Performance of N-Doped ZnO/g-C3N4 Nanocomposites.
Kong, Ji-Zhou; Zhai, Hai-Fa; Zhang, Wei; Wang, Shan-Shan; Zhao, Xi-Rui; Li, Min; Li, Hui; Li, Ai-Dong; Wu, Di
2017-09-06
N-doped ZnO/g-C3N4 composites have been successfully prepared via a facile and cost-effective sol-gel method. The nanocomposites were systematically characterized by XRD, FE-SEM, HRTEM, FT-IR, XPS, and UV-vis DRS. The results indicated that compared with the pure N-doped ZnO, the absorption edge of binary N-doped ZnO/g-C3N4 shifted to a lower energy with increasing the visible-light absorption and improving the charge separation efficiency, which would enhance its photocatalytic activity. Compared with the pure g-C3N4, ZnO, N-doped ZnO and the composite ZnO/g-C3N4, the as-prepared N-doped ZnO/g-C3N4 exhibits a greatly enhanced photocatalytic degradation of methylene blue and phenol under visible-light irradiation. Meanwhile, N-doped ZnO/g-C3N4 possesses a high stability. Finally, a proposed mechanism for N-doped ZnO/g-C3N4 is also discussed. The improved photocatalysis can be attributed to the synergistic effect between N-doped ZnO and g-C3N4, including the energy band structure and enhanced charge separation efficiency.
The Influences of Process Parameters on the Continumous Production of Si3N4 Powder by rentitridation
Institute of Scientific and Technical Information of China (English)
LIUJian－hua; ZHANGGui－cai; 等
1995-01-01
In this paper,the influcnce of chief process parameters on the ontinuous production of Si3N4 powder by renitridation has been studied,The sutiable process parameters have been found,and high quality Si3N4 powder has been developed.
Novel β-C3N4/CuO nanoflakes: facile synthesis and unique photocatalytic performance
Zou, Lan-Rong; Huang, Gui-Fang; Li, Dong-Feng; Tian, Qing-Nan; Yang, Ke; Si, Yuan; Chang, Shengli; Zhang, Xue-Ao; Huang, Wei-Qing
2017-09-01
For the first time, novel β-C3N4/CuO composites with superior photocatalytic activity are successfully fabricated via a facile reflux method followed by a thermal process. The morphologies, particle size and microstructure of the synthesized β-C3N4/CuO composites largely depended upon copper chloride and the volume ratio of V water:V ethanol in the mixed precursors. The fabricated β-C3N4/CuO nanoflakes exhibited obviously enhanced visible light photocatalytic activity for the degradation of methylene blue (MB) with an ∼3.4 and 1.9 fold increase in efficiency over that of pure g-C3N4 and commercial P25, respectively. The β-C3N4/CuO composite photocatalyst also showed photocatalytic activity for the degradation of methyl orange (MO). Moreover, the β-C3N4/CuO nanoflakes showed almost no loss of photocatalytic activity after three recycles of the degradation of the MB. A multiple synergetic mechanism in β-C3N4/CuO nanoflakes, which is featured by the highly reactive {0 0 2} facets, exposed many active sites of nanoflakes and the efficient charge separation are proposed to account for the distinguished photocatalytic activity. This work provides a facile and cost-effective strategy for designing novel β-C3N4/CuO photocatalysts for application in environmental purification.
Directory of Open Access Journals (Sweden)
S. Naveen
2017-03-01
Full Text Available The syntheses and crystal structures of the isomeric 4-bromo-N-[(2-nitrophenylsulfonyl]benzamide, (I, and 4-bromo-N-[(4-nitrophenylsulfonyl]benzamide, (II, are described (molecular formula = C13H9BrN2O5S in each case. The asymmetric unit of (I contains two independent molecules [(IA and (IB], while that of (II contains one molecule. The benzoic acid aromatic ring of molecule (IA is disordered due to rotation about the Car—C(=O bond over two orientations in a 0.525 (9:0.475 (9 ratio. The dihedral angle between the benzene rings is 85.9 (3° in (IA and 65.22 (19° in (IB, while in (II, the corresponding value is 56.7 (7°. In the crystals of (I and (II, N—H...O, C—H...O and C—H...π interactions generate three-dimensional networks.
Si3N4超微粉体及其制备%Preparation of silicon nitride ultrafine-powder
Institute of Scientific and Technical Information of China (English)
王锐; 高峰; 李道火
2006-01-01
Si3N4陶瓷因其优异的力学性能和化学稳定性而在工业生产中广泛使用.Si3N4粉体的合成是制备Si3N4陶瓷的基础.本文在介绍Si3N4陶瓷性能、用途的基础上,详细论述了硅粉直接氮化法、SiO2还原氮化法、热分解法、气相法等Si3N4超微粉体制备技术,并对这4种工艺的优缺点进行对比.
On Connected m-HPK(n1,n2,n3,n4[Kt]-Residual Graphs
Directory of Open Access Journals (Sweden)
Huiming Duan
2013-01-01
Full Text Available We define m-HPK(n1,n2,n3,n4[Kt]-residual graphs in which HPK is a hyperplane complete graph. We extend P. Erdös, F. Harary, and M. Klawe's definition of plane complete residual graph to hyperplane and obtain the hyperplane complete residual graph. Further, we obtain the minimum order of HPK(n1,n2,n3,n4[Kt]-residual graphs and m-HPK(n1,n2,n3,n4[Kt]-residual graphs. In addition, we obtain a unique minimal HPK(n1,n2,n3,n4[Kt]-residual graphs and a unique minimal m-HPK(n1,n2,n3,n4[Kt]-residual graphs.
Isolation and molecular characterisation of Achromobacter phage phiAxp-3, an N4-like bacteriophage
Ma, Yanyan; Li, Erna; Qi, Zhizhen; Li, Huan; Wei, Xiao; Lin, Weishi; Zhao, Ruixiang; Jiang, Aimin; Yang, Huiying; Yin, Zhe; Yuan, Jing; Zhao, Xiangna
2016-01-01
Achromobacter xylosoxidans, an opportunistic pathogen, is responsible for various nosocomial and community-acquired infections. We isolated phiAxp-3, an N4-like bacteriophage that infects A. xylosoxidans, from hospital waste and studied its genomic and biological properties. Transmission electron microscopy revealed that, with a 67-nm diameter icosahedral head and a 20-nm non-contractile tail, phiAxp-3 has features characteristic of Podoviridae bacteriophages (order Caudovirales). With a burst size of 9000 plaque-forming units and a latent period of 80 min, phiAxp-3 had a host range limited to only four A. xylosoxidans strains of the 35 strains that were tested. The 72,825 bp phiAxp-3 DNA genome, with 416-bp terminal redundant ends, contains 80 predicted open reading frames, none of which are related to virulence or drug resistance. Genome sequence comparisons place phiAxp-3 more closely with JWAlpha and JWDelta Achromobacter phages than with other N4 viruses. Using proteomics, we identified 25 viral proteins from purified phiAxp-3 particles. Notably, investigation of the phage phiAxp-3 receptor on the surface of the host cell revealed that lipopolysaccharide serves as the receptor for the adsorption of phage phiAxp-3. Our findings advance current knowledge about A. xylosoxidans phages in an age where alternative therapies to combat antibiotic-resistant bacteria are urgently needed. PMID:27094846
Chiral low-energy physics from squashed branes in deformed ${\\cal N}=4$ SYM
Steinacker, Harold C
2015-01-01
We discuss the low-energy physics which arises on stacks of squashed brane solutions of $SU(N)$ ${\\cal N}=4$ SYM, deformed by a cubic soft SUSY breaking potential. A brane configuration is found which leads to a low-energy physics similar to the standard model in the broken phase, assuming suitable VEV's of the scalar zero modes. Due to the triple self-intersection of the branes, the matter content includes that of the MSSM with precisely 3 generations and right-handed neutrinos. No exotic quantum numbers arise, however there are extra chiral superfields with the quantum numbers of the Higgs doublets, the $W,Z$, $e_R$ and $u_R$, whose fate depends on the details of the rich Higgs sector. The chiral low-energy sector is complemented by a heavy mirror sector with the opposite chiralities, as well as super-massive Kaluza-Klein towers completing the ${\\cal N}=4$ multiplets. The sectors are protected by two gauged global $U(1)$ symmetries.
Konishi form factor at three loops in N =4 supersymmetric Yang-Mills theory
Ahmed, Taushif; Banerjee, Pulak; Dhani, Prasanna K.; Rana, Narayan; Ravindran, V.; Seth, Satyajit
2017-04-01
We present the first results on the third order corrections to on-shell form factor (FF) of the Konishi operator in N =4 supersymmetric Yang-Mills theory using Feynman diagrammatic approach in modified dimensional reduction (D R ¯ ) scheme. We show that it satisfies the KG equation in D R ¯ scheme while the result obtained in four dimensional helicity (FDH) scheme needs to be suitably modified not only to satisfy the KG equation but also to get the correct ultraviolet (UV) anomalous dimensions. We find that the cusp, soft and collinear anomalous dimensions obtained to third order are same as those of the FF of the half-BPS operator confirming the universality of the infrared (IR) structures of on-shell form factors. In addition, the highest transcendental terms of the FF of the Konishi operator are identical to those of half-BPS operator indicating the probable existence of deeper structure of the on-shell FF. We also confirm the UV anomalous dimensions of the Konishi operator up to third order providing a consistency check on the both UV and universal IR structures in N =4 .
Carbonaceous thin film coating with Fe-N4 site for enhancement of dioxovanadium ion reduction
Maruyama, Jun; Hasegawa, Takahiro; Iwasaki, Satoshi; Fukuhara, Tomoko; Orikasa, Yuki; Uchimoto, Yoshiharu
2016-08-01
It has been found that carbonaceous materials containing a transition metal coordinated by 4 nitrogens in the square-planar configuration (metal-N4 site) on the surface possessed a catalytic activity for various electrochemical reactions related to energy conversion and storage; i.e., oxygen reduction, hydrogen evolution, and quite recently, the electrode reactions in vanadium redox flow batteries (VRFB). The catalyst for the VRFB positive electrode discharge reaction, i.e., the dioxovanadium ion reduction, was formed by coating the surface of cup-stack carbon nanotubes with a carbonaceous thin film with the Fe-N4 site generated by the sublimation, deposition, and pyrolysis of iron phthalocyanine. In this study, the influence of the physical properties of the catalyst on the electrochemical reactions was investigated to optimize the coating. With an increase in the coating, the specific surface area increased, whereas the pore size decreased. The surface Fe concentration was increased in spite of the Fe aggregation inside the carbon matrix. The catalytic activity enhancement was achieved due to the increase in the specific surface area and the surface Fe concentration, but was lowered due to the decrease in the pore size, which was disadvantageous for the penetration of the electrolyte and the mass transfer.
Supersymmetric Lifshitz-like backgrounds from N=4 SYM with heavy quark density
Energy Technology Data Exchange (ETDEWEB)
Faedo, Anton F.; Fraser, Benjo; Kumar, S. Prem [Department of Physics, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom)
2014-02-17
We examine a class of gravity backgrounds obtained by considering the backreaction of a spatially uniform density of mutually BPS Wilson lines or heavy quarks in N=4 SUSY Yang-Mills theory. The configurations preserve eight supercharges and an SO(5) subgroup of the SO(6) R-symmetry. They are obtained by considering the (1/4)-BPS geometries associated to smeared string/D3-brane (F1-D3) intersections. We argue that for the (partially) localized intersection, the geometry exhibits a flow from AdS{sub 5}×S{sup 5} in the UV to a novel IR scaling solution displaying anisotropic Lifshitz-like scaling with dynamical critical exponent z=7, hyperscaling violation and a logarithmic running dilaton. We also obtain a two-parameter family of smeared (1/4)-BPS solutions on the Coulomb branch of N=4 SYM exhibiting Lifshitz scaling and hyperscaling violation. For a certain parametric range these yield IR geometries which are conformal to AdS{sub 2}×ℝ{sup 3}, and which have been argued to be relevant for fermionic physics.
Construction of Infrared Finite Observables in N=4 Super Yang-Mills Theory
Bork, L V; Vartanov, G S; Zhiboedov, A V
2009-01-01
In this paper we give all the details of the calculation that we presented in our previous paper ArXiv:0908.0387 where the infrared structure of the MHV gluon amplitudes in the planar limit for ${\\cal N}=4$ super Yang-Mills theory was considered in the next-to-leading order of perturbation theory. Explicit cancellation of the infrared divergencies in properly defined inclusive cross-sections is demonstrated first in a toy model example of "conformal QED" and then in the real ${\\cal N}=4$ SYM theory. We give the full-length details both for the calculation of the real emission and for the diagrams with splitting in initial and final states. The finite parts for some inclusive differential cross-sections are presented in an analytical form. In general, contrary to the virtual corrections, they do not reveal any simple structure. An example of the finite part containing just the log functions is presented. The dependence of inclusive cross-section on the external scale related to the definition of asymptotic sta...
Biosensors based on Si3N4 asymmetric Mach-Zehnder interferometers
Chalyan, Tatevik; Pasquardini, Laura; Falke, Floris; Zanetti, Manuela; Guider, Romain; Gandolfi, Davide; Schreuder, Eric; Pederzolli, Cecilia; Heideman, René G.; Pavesi, Lorenzo
2016-04-01
In this work, we present a study on photonic biosensors based on Si3N4 asymmetric Mach-Zehnder Interferometers (aMZI) for Aflatoxin M1 (AFM1) detection. AFM1 is an hepatotoxic and a carcinogenic toxin present in milk. The biosensor is based on an array of four Si3N4 aMZI that are optimized for 850nm wavelength. We measure the bulk Sensitivity (S) and the Limit of Detection (LOD) of our devices. In the array, three devices are exposed and have very similar sensitivities. The fourth aMZI, which is covered by SiO2, is used as an internal reference for laser (a VCSEL) and temperature fluctuations. We measured a phase sensitivity of 14300+/-400 rad/RIU. To characterize the LOD of the sensors, we measure the uncertainty of the experimental readout system. From the measurements on three aMZI, we observe the same value of LOD, which is ≍ 4.5×10-7 RIU. After the sensor characterization on homogeneous sensing, we test the surface sensing performances by flowing specific Aflatoxin M1 and non-specific Ochratoxin in 50 mM MES pH 6.6 buffer on the top of the sensors functionalized with Antigen-Recognising Fragments (Fab'). The difference between specific and non-specific signals shows the specificity of our sensors. A moderate regeneration of the sensors is obtained by using glycine solution.
Stress relaxation and bonding in Si3N4/MA6000 joints by reactive interlayers
Frisch, A.; Kaysser, W. A.; Zhang, W.; Petzow, G.
Diffusion bonding of Si3N4 to the new generation of ODS-superalloys, such as MA6000, may yield strongly joined metal-ceramic systems for high-temperature applications. Si3N4 has been diffusion bonded to MA6000 during HIP at 100 MPa at 1100-1300 C. Stresses caused by the large thermal mismatch were reduced by multiphase interlayers. To promote the chemical adhesion, reactive and adhesive interlayers were used at the metal-ceramic interface which, in the absence of such layers, fail at low stresses. It has been shown that, during reactive bonding, brittle phases are frequently formed at the interfaces which may lead to a failure of the joint. The reduce of thermal stresses by thin soft interlayers is very limited but can be obtained by a microcrack-induced stress relaxation mechanism. During adhesive diffusion bonding, the mechanical strength of the bond is limited by the stress state and the strength of the ceramic component.
Transport properties of N = 4 supersymmetric Yang-Mills theory at finite coupling
Energy Technology Data Exchange (ETDEWEB)
Benincasa, Paolo [Department of Applied Mathematics, University of Western Ontario, Middlesex College, London, ON, N6A 5B7 (Canada); Buchel, Alex [Department of Applied Mathematics, University of Western Ontario, Middlesex College, London, ON, N6A 5B7 (Canada); Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, ON, N2L 2Y5 (Canada)
2006-01-15
Gauge theory-string theory duality describes strongly coupled N = 4 supersymmetric SU(n{sub c}) Yang-Mills theory at finite temperature in terms of near extremal black 3-brane geometry in type IIB string theory. We use this correspondence to compute the leading correction in the inverse 't Hooft coupling to the shear diffusion constant, bulk viscosity and the speed of sound in the large-n{sub c} N = 4 supersymmetric Yang-Mills theory plasma. The transport coefficients are extracted from the dispersion relation of the shear and the sound wave lowest quasinormal modes in the leading order {alpha}'-corrected black D3 brane geometry. We find the shear viscosity extracted from the shear diffusion constant to agree with result of [hep-th/0406264]; also, the leading correction to bulk viscosity and the speed of sound vanishes. Our computation provides a highly nontrivial consistency check on the hydrodynamic description of the {alpha}'-corrected nonextremal black branes in string theory.
Transport properties of Script N = 4 supersymmetric Yang-Mills theory at finite coupling
Benincasa, Paolo; Buchel, Alex
2006-01-01
Gauge theory-string theory duality describes strongly coupled Script N = 4 supersymmetric SU(nc) Yang-Mills theory at finite temperature in terms of near extremal black 3-brane geometry in type IIB string theory. We use this correspondence to compute the leading correction in the inverse 't Hooft coupling to the shear diffusion constant, bulk viscosity and the speed of sound in the large-nc Script N = 4 supersymmetric Yang-Mills theory plasma. The transport coefficients are extracted from the dispersion relation of the shear and the sound wave lowest quasinormal modes in the leading order α'-corrected black D3 brane geometry. We find the shear viscosity extracted from the shear diffusion constant to agree with result of [hep-th/0406264]; also, the leading correction to bulk viscosity and the speed of sound vanishes. Our computation provides a highly nontrivial consistency check on the hydrodynamic description of the α'-corrected nonextremal black branes in string theory.
The shape of emergent quantum geometry from an N=4 SYM minisuperspace approximation
Berenstein, David
2010-01-01
We study numerically various wave functions in a gauged matrix quantum mechanics of six commuting hermitian $N\\times N$ matrices. Our simulations span ranges of $N$ up to 10000. This system is a truncated and quenched version of N=4 SYM that serves as a minisuperspace approximation to the full ${\\cal N}=4$ SYM system. This setup encodes aspects of the geometry of the AdS dual in terms of joint eigenvalue distributions for the matrices in the large $N$ limit. We analyze the problem of determining geometric measurements from these fluctuating distributions at finite $N$ and how fast they approach to the large N limit. We treat this eigenvalue geometry information as a proxy for geometric calculations in quantum gravity in a description where gravity is an emergent phenomenon. Our results show that care is needed in choosing the observables that measure the geometry: different choices of observables give different answers, have different size fluctuations at finite $N$ and they converge at different rates to the...
Directory of Open Access Journals (Sweden)
Lan Ching Sim
2017-01-01
Full Text Available The visible-light-driven photocatalytic degradation of Bisphenol A (BPA was investigated using the binary composite of alkaline treated g-C3N4 (HT-g-C3N4 deposited over commercial TiO2 (Evonik Degussa GmbH, Essen, Germany. The existence and contribution of both TiO2 and g-C3N4/HT-g-C3N4 in the composite was confirmed through various analytical techniques including powder X-ray diffraction (XRD, high-resolution transmission electron microscopy (HRTEM, field emission scanning electron microscopy (FESEM, Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS, ultraviolet-visible diffuse reflectance spectra (UV-vis-DRS, and photoluminescence (PL analysis. The results showed that the titania in the binary composite exhibited both pure rutile and anatase phases. The morphological analysis indicated that the spongy “morel-like” structure of g-C3N4 turned to nanotube form after alkaline hydrothermal treatment and thereby decreased the specific surface area of HT-g-C3N4. The low surface area of HT-g-C3N4 dominates its promising optical property and effective charge transfer, resulting in a deprived degradation efficiency of BPA two times lower than pure g-C3N4. The binary composite of HT-g-C3N4/TiO2 exhibited excellent degradation efficiency of BPA with 2.16 times higher than the pure HT-g-C3N4. The enhanced photocatalytic activity was mainly due to the promising optical band gap structure with heterojunction interface, favorable specific surface area, and good charge separation.
Institute of Scientific and Technical Information of China (English)
修子扬; 陈国钦; 武高辉; 杨文澍; 刘艳梅
2011-01-01
采用压力浸渗法制备Si3N4体积分数分别为45％、50％和55％的颗粒增强铝基复合材料(Si3N4/Al).研究Si3N4体积分数和T6热处理对Si3N4/Al复合材料微观组织和力学性能的影响.结果表明:Si3N4颗粒分散均匀,Si3N4/Al复合材料浸渗良好,没有明显的孔洞和铸造缺陷；在Si3N4颗粒附近的铝基体中,可以观察到高密度位错；Si3N4/Al复合材料的弯曲强度随着Si3N4体积分数的增大而降低；T6热处理能提高复合材料的强度；复合材料的弹性模量随着Si3N4体积分数的增加而线性增加；在低Si3N4体积分数时,可以观察到更多的撕裂棱和韧窝；T6热处理对断口形貌的影响较小.%Si3N4 particles reinforced aluminium matrix composites (Si3N4/Al) with different particle volume fractions (45％,50％,and 55％) were fabricated by pressure infiltration method.The effects of Si3N4 volume fraction and T6 treatment on mierostructure and mechanical properties of Si3N4/Al composite were investigated.The results show that Si3N4/Al composites are well infiltrated with good particles dispersion and no apparent porosity or significant casting defects are observed.High density of dislocations in Al matrix around Si3N4 particles is observed.The bending strength of Si3N4/Al composites decreases with an increase in Si3N4 volume fraction,and can be greatly improved by T6 treatment.Elastic modulus of composites increases linearly with Si3N4 volume fraction.At a lower Si3N4 volume fraction,more tearing ridge and dimples with elongation are observed.T6 heat treatment shows minor effect on the fracture surface of composite.
Study on the Preparation, Properties and Mechnism of β-Si3N4 Crystal Seeds%β-Si3N4晶种的制备、性能与机理研究
Institute of Scientific and Technical Information of China (English)
于方丽; 白宇; 杜军; 于平平; 王俭志; 杨建锋
2011-01-01
In the paper, the choice and optimization of the additions of β-Si3N4 powder, the species of sintering additives and sintering temperature were effective for the grain size and morphology of (J-Si3N4 seeds, and reaction mechanism was also discussed. P-Si3N4 with completeness of phase transformation and rod-liked morphology was developed by means of heating the initial ot-Si3N4 powder with certain additives of β-Si3N4 powder, MgO, Y2O3 and SiO2 and rinsing out the glass phase. The influences of p-Si3N4 contents and sintering additive species on phase transformation, grain morphology and size distribution were investigated. The results showed that rod-like p-Si3N4 grains with good aspect ratio and well distribution were sythesised by controlling β-Si3N4 powder with 10 wt% and MgO with 5 wt% additive contents under 1750 ℃ for 1.5 h, the average aspect ratio was close to 7.0.%本论文通过对β-Si3N4粉末的加入量、烧结助剂的种类及煅烧温度等参数的合理选择及优化,达到对β-Si3N4晶粒尺寸和形貌的有效控制,并探讨分析β -Si3N4晶种的反应机理.以MgO、Y2O3及SiO2为助烧剂,加入一定量的β-Si3N4粉末,通过对原始α-Si3N4粉末进行热处理,经去除掉玻璃相等漂洗工艺后,制备出相变充分、具有柱状形貌β-Si3N4晶种.重点研究了β-Si3N4粉末加入量及助烧剂种类对Si3N4相变、晶体形貌及晶粒尺寸分布的影响.研究结果表明:β-Si3N4粉末添加量10 wt％、MgO添加量5wt％时,在1750℃下热处理1.5h能得到具有比较理想长径比、缺陷少且晶粒尺寸与长径比分布较均匀β-Si3N4品种,平均长径比接近于7.0.
Institute of Scientific and Technical Information of China (English)
宋振兴; 姚素薇; 王宏智; 张卫国
2007-01-01
采用电沉积方法,在Ni-W-P合金中复合Si3N4微粒,获得(Ni-W-P)-Si3N4复合镀层.研究了镀液中Si3N4质量浓度、电流密度以及搅拌速度等工艺条件对复合镀层中Si3N4质量分数的影响.X-射线衍射、扫描电子显微镜测试结果表明:Si3N4微粒在镀层中均匀分布,与Ni-W-P合金各自在特定的角度出现衍射特征峰,彼此之间互不干扰.随着镀层中Si3N4质量分数的增加,镀层的性能均按照一定的规律发生变化.当Si3N4的质量分数为最大值10.3%时,镀层性能在各组实验比较中均最优,耐磨性能最好.
Institute of Scientific and Technical Information of China (English)
邓振华; 易耀勇; 房卫萍; 卢斌
2013-01-01
Si3N4 ceramic was brazed with Cu-Ni-Ti amorphous filler metal. The interfacial microstructure was observed by SEM and EDS. The results show that the interfacial microstructure is composed of two parts. The interaction layer I and II is made up of TiN and Ti-Si compound, respectively. The maximum bonding strength is 284.6 MPa with the brazing process of 1100℃ for 10 min. Under the same brazing condition, the bonding strength brazed with amorphous filler metal increases compared with the crystalline.%采用Cu-Ni-Ti非晶钎料钎焊Si3N4陶瓷,利用SEM、EDS等分析手段研究了其钎焊界面的微观结构.结果表明:反应层由两部分组成,其中紧靠Si3N4陶瓷的反应层Ⅰ由TiN化合物组成,Ti-Si化合物构成了反应层Ⅱ.在1100℃×10 min下钎焊时,其接头强度有最大值284.6 MPa.在相同的钎焊工艺条件下,非晶钎料接头强度高于同成分晶态钎料.
Si3N4陶瓷球批量加工缺陷原因分析%Analysis on Cause for Defects of Si3N4 Ceramic Balls in Batch Manufacture
Institute of Scientific and Technical Information of China (English)
陈志军; 张永乾
2005-01-01
Si3N4陶瓷球的各类加工缺陷是影响其疲劳寿命的主要原因之一,减少Si3N4陶瓷球批量化生产中加工缺陷是降低其生产成本的重要方法.对Si3N4陶瓷球批量化生产各加工工序中出现的缺陷及其产生原因进行归纳分析,并提出解决办法.
Inhibitory effects of N-(4-hydrophenyl) retinamide on liver cancer and malignant melanoma cells
Institute of Scientific and Technical Information of China (English)
Xing-Zhong Wu; Li Zhang; Bi-Zhi Shi; Ping Hu
2005-01-01
AIM: To investigate the effect of N-(4-hydrophenyl) retinamide (4-HPR), the derivative of retinoic acid, on inhibition of migration, invasion, cell growth, and induction of apoptosis in hepatocellular carcinoma cells (HCCs) and malignant melanoma cells.METHODS: 4-HPR was chemically synthesized. Cellular migration and invasion were assayed by Borden chamber experiment. Cell growth was assayed by MTT chromometry.Apoptosis effect was measured using Hoechst 32258 staining and flow cytometry. Gene transfection was performed with lipofectamine.RESULTS: We observed that the migration of HCC and melanoma cells was significantly suppressed by 4-HPR and the migration cells were reduced to 58±5.03 (control 201±27.2, P＜0.05, n = 4) in SMMC 7721-k3 HCC, and to 254±25.04 (control 302±30.1, P＜0.05, n = 4) in melanoma cells after 6-h incubation with 4-HPR. The invasion through reconstituted basement membrane was also significantly reduced by 4-HPR treatment to 11.2±3.3 in SMMC 7721-k3 HCC (control 27±13.1), and to 24.3±3.2 in melanoma cells (control 67.5±10.1, P＜0.05, n = 3). Cell growth, especially in melanoma cells, was also significantly inhibited.Furthermore, 3 μmol/L of 4-HPR induced apoptosis in B16 melanoma cells (37.11±0.94%) more significantly than all-trans retinoic acid (P＜0.05), but it failed to induce apoptosis in SMMC 7721-k3 HCC. The mechanism for 4-HPR-induced apoptosis was not clear, but we observed that 4-HPR could regulate p27kip1, and overexpression of cerebroside sulfotransferase (CST) diminished the apoptosis induced by 4-HPR in melanoma cells.CONCLUSION: 4-HPR is a potent inhibitor of HCC migration and inducer of melanoma cell apoptosis. CST and p27kip1 expression might be associated with 4-HPR-induced apoptosis.
Hydrothermal synthesis of In2S3/g-C3N4 heterojunctions with enhanced photocatalytic activity.
Xing, Chaosheng; Wu, Zhudong; Jiang, Deli; Chen, Min
2014-11-01
Graphitic carbon nitride (g-C3N4) was hybridized by In2S3 to form a novel In2S3/g-C3N4 heterojunction photocatalyst via a hydrothermal method. TEM and HRTEM results reveal that In2S3 nanoparticles and g-C3N4 closely contact with each other to form an intimate interface. The as-obtained In2S3/g-C3N4 heterojunctions exhibit higher photocatalytic activity than those of pure g-C3N4 and In2S3 for the photodegradation of rhodamine B (RhB) under visible light irradiation. The enhanced photocatalytic performance of In2S3/g-C3N4 heterojunctions could be attributed to its wide absorption in the visible region and efficient electron-hole separation. On the basis of radical scavenger experiments, superoxide radicals and holes are suggested to play a critical role in RhB degradation over In2S3/g-C3N4 heterojunctions.
Development of Tyrosine-Based Radiotracer Tc99m-N4-Tyrosine for Breast Cancer Imaging
Directory of Open Access Journals (Sweden)
Fan-Lin Kong
2012-01-01
Full Text Available The purpose of this study was to develop an efficient way to synthesize Tc99m-O-[3-(1,4,8,11-tetraazabicyclohexadecane-propyl]-tyrosine (Tc99m-N4-Tyrosine, a novel amino acid-based radiotracer, and evaluate its potential in breast cancer gamma imaging. Precursor N4-Tyrosine was synthesized using a 5-step procedure, and its total synthesis yield was 38%. It was successfully labeled with Tc99m with high radiochemical purity (>95%. Cellular uptake of Tc99m-N4-Tyrosine was much higher than that of Tc99m-N4 and the clinical gold standard 18F-2-deoxy-2-fluoro-glucose (18F-FDG in rat breast tumor cells in vitro. Tissue uptake and dosimetry estimation in normal rats revealed that Tc99m-N4-Tyrosine could be safely administered to humans. Evaluation in breast tumor-bearing rats showed that although Tc99m-N4-Tyrosine appeared to be inferior to 18F-FDG in distinguishing breast tumor tissue from chemical-induced inflammatory tissue, it had high tumor-to-muscle uptake ratios and could detect breast tumors clearly by planar scintigraphic imaging. Tc99m-N4-Tyrosine could thus be a useful radiotracer for use in breast tumor diagnostic imaging.
Fabrication and photoelectrochemical properties of silicon nanowires/g-C3N4 core/shell arrays
Chen, Zhen; Ma, Ge; Chen, Zhihong; Zhang, Yongguang; Zhang, Zhe; Gao, Jinwei; Meng, Qingguo; Yuan, Mingzhe; Wang, Xin; Liu, Jun-ming; Zhou, Guofu
2017-02-01
A photoelectrochemical (PEC) cell made of metal-free carbon nitride (g-C3N4) @siliconnanowire(Si NW) arrays (denoted as Si NWs/g-C3N4) is presented in this work. The as-prepared photoelectrodes with different mass contents of g-C3N4 have been synthesized via a metal-catalyzed electroless etching (MCEE), liquid atomic layer deposition (LALD) and annealing methods. The amount of g-C3N4 on the Si NW arrays can be controlled by tuning the concentration of the cyanamide solution used in the LALD procedure. The dense and vertically aligned Si NWs/g-C3N4 core/shell nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In comparison with FTO/g-C3N4 and Si NW samples, the Si NWs/g-C3N4 samples showed significantly enhanced photocurrents over the entire potential sweep range. Electrochemical impedance spectroscopy (EIS) was conducted to investigate the properties of the charge transfer process, and the results indicated that the enhanced PEC performance may be due to the increased photo-generated interfacial charge transfer between the Si NWs and g-C3N4. The photocurrent density reached 45 μA/cm2 under 100 mW/cm2 (AM 1.5 G) illumination at 0 V (vs. Pt) in neutral Na2SO4 solution (pH ∼ 7.62). Finally, a systematical PEC mechanism of the Si NWs/g-C3N4 was proposed.
Correlation functions in the Coulomb branch of N=4 SYM from AdS/CFT correspondence
Rashkov, R C
2000-01-01
In the present paper we study $S(N)\\to S(U(N/2)\\times U(N/2))$ symmetry breaking in ${\\mathcal N}=4$ SYM via AdS/CFT correspondence. We consider two stacks of N/2 parallel D3 branes separated by a distance $2\\vec d$. In this case there is mixing between the different l-wave dilatonic KK modes. We calculate certain two point correlation functions in the dual gauge theory. Due to mode mixing, the diagonal correlation functions have 1/N conformal-like correction as well as deformation terms. The off-diagonal correlators are also nonvanishing and their leading order is 1/N. We discuss briefly the spectrum of the glueball exitations.
Chiral primaries in the Leigh-Strassler deformed N=4 SYM -- a perturbative study
Madhu, K; Madhu, Kallingalthodi; Govindarajan, Suresh
2007-01-01
We look for chiral primaries in the general Leigh-Strassler deformed N=4 super Yang-Mills theory by systematically computing the planar one-loop anomalous dimension for single trace operators up to dimension six. The operators are organised into representations of the trihedral group, \\Delta(27), which is a symmetry of the Lagrangian. We find an interesting relationship between the U(1)_R-charge of chiral primaries and the representation of \\Delta(27) to which the operator belongs. Up to scaling dimension \\Delta_0=6 (and conjecturally to all dimensions) the following holds: The planar one-loop anomalous dimension vanishes only for operators that are in the singlet or three dimensional representations of \\Delta(27). For other operators, the vanishing of the one-loop anomalous dimension occurs only in a sub-locus in the space of couplings.
Phase transitions of an anisotropic N=4 super Yang-Mills plasma via holography
Banks, Elliot
2016-01-01
Black hole solutions of type IIB supergravity were previously found that are dual to N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial deformation. In the zero temperature limit, these black holes approach a Liftshitz like scaling solution in the IR. It was recently shown that these black holes are unstable, and at low temperatures there is a new class of black hole solutions that are thermodynamically preferred. We extend this analysis, by considering consistent truncations of the Kaluza-Klein reduction of IIB supergravity on a five-sphere that preserves multiple scalar and $U(1)$ gauge fields. We show that the previously constructed black holes become unstable at low temperatures, and construct new classes of exotic black hole solutions. We study the DC thermo-electric conductivity of these $U(1)$ charged black holes, and find a diverging DC conductivity at zero temperature due to the divergence of the gauge field coupling.
Grassmannian Integral for General Gauge Invariant Off-shell Amplitudes in N=4 SYM
Bork, L V
2016-01-01
In this paper we consider tree-level gauge invariant off-shell amplitudes (Wilson line form factors) in $\\mathcal{N}=4$ SYM with arbitrary number of off-shell gluons or equivalently Wilson line operator insertions. We make a conjecture for the Grassmannian integral representation for such objects and verify our conjecture on several examples. It is remarkable that in our formulation one can consider situation when on-shell particles are not present at all, i.e. we have Grassmannian integral representation for purely off-shell object. In addition we show that off-shell amplitude with arbitrary number of off-shell gluons could be also obtained using quantum inverse scattering method for auxiliary $\\mathfrak{gl}(4|4)$ super spin chain.
Dyson-Schwinger equations and {N}=4 SYM in Landau gauge
Maas, Axel; Zitz, Stefan
2016-03-01
{N}=4 Super Yang-Mills theory is a highly constrained theory, and therefore a valuable tool to test the understanding of less constrained Yang-Mills theories. Our aim is to use it to test our understanding of both the Landau gauge beyond perturbation theory and the truncations of Dyson-Schwinger equations in ordinary Yang-Mills theories. We derive the corresponding equations within the usual one-loop truncation for the propagators after imposing the Landau gauge. We find a conformal solution in this approximation, which surprisingly resembles many aspects of ordinary Yang-Mills theories. We furthermore discuss which role the Gribov-Singer ambiguity in this context could play, should it exist in this theory.
Three-Point Functions of Twist-Two Operators in N=4 SYM at One Loop
Plefka, Jan
2012-01-01
We calculate three-point functions of two protected operators and one twist-two operator with arbitrary even spin j in N=4 SYM theory to one-loop order. In order to carry out the calculations we project the indices of the spin j operator to the light-cone and evaluate the correlator in a soft-limit where the momentum coming in at the spin j operator becomes zero. This limit largely simplifies the perturbative calculation, since all three-point diagrams effectively reduce to two-point diagrams and the dependence on the one-loop mixing matrix drops out completely. The results of our direct calculation are in agreement with the structure constants obtained by F.A. Dolan and H. Osborn from the operator product expansion of four-point functions of half-BPS operators.
On super form factors of half-BPS operators in N=4 super Yang-Mills
Penante, Brenda; Travaglini, Gabriele; Wen, Congkao
2014-01-01
We compute form factors of half-BPS operators in N=4 super Yang-Mills dual to massive Kaluza-Klein modes in supergravity. These are appropriate supersymmetrisations T_k of the scalar operators Tr(\\phi^k) for any k, which for k=2 give the chiral part of the stress-tensor multiplet operator. Using harmonic superspace, we derive simple Ward identities for these form factors, which we then compute perturbatively at tree level and one loop. We propose a novel on-shell recursion relation which links form factors with different numbers of fields. Using this, we conjecture a general formula for the n-point MHV form factors of T_k for arbitrary k and n. Finally, we use supersymmetric generalised unitarity to derive compact expressions for all one-loop MHV form factors of T_k in terms of one-loop triangles and finite two-mass easy box functions.
Directory of Open Access Journals (Sweden)
Joel T. Mague
2014-09-01
Full Text Available In the title molecule, C15H20N4OS2, the acetamido fragment is nearly coplanar with the pyridyl ring [C—N—C—C torsion angle = −4.1 (2°], while the cyclohexylsulfanyl portion protrudes from this plane [N—C—C—S torsion angle = −40.8 (6°]. In the crystal, alternating pairwise N—H...O and N—H...N hydrogen bonds across inversion centres form chains along [101], which are associated into stepped layers via offset π–π stacking between pyridyl rings [centroid–centroid distance = 3.566 (1 Å]. The cyclohexyl group and the two atoms of the S—C bond attached to it are disordered over two sets of sites with site-occupancy factors of 0.8845 (18 and 0.1155 (18.
Dyson-Schwinger equations and N = 4 SYM in Landau gauge
Energy Technology Data Exchange (ETDEWEB)
Maas, Axel; Zitz, Stefan [University of Graz, Institute of Physics, NAWI Graz, Graz (Austria)
2016-03-15
N = 4 Super Yang-Mills theory is a highly constrained theory, and therefore a valuable tool to test the understanding of less constrained Yang-Mills theories. Our aim is to use it to test our understanding of both the Landau gauge beyond perturbation theory and the truncations of Dyson-Schwinger equations in ordinary Yang-Mills theories. We derive the corresponding equations within the usual one-loop truncation for the propagators after imposing the Landau gauge. We find a conformal solution in this approximation, which surprisingly resembles many aspects of ordinary Yang-Mills theories. We furthermore discuss which role the Gribov-Singer ambiguity in this context could play, should it exist in this theory. (orig.)
Dyson-Schwinger equations and ${\\cal N}=4$ SYM in Landau gauge
Maas, Axel
2015-01-01
${\\cal N}=4$ Super Yang-Mills theory is a highly constrained theory, and therefore a valuable tool to test the understanding of less constrained Yang-Mills theories. Our aim is to use it to test our understanding of both the Landau gauge beyond perturbation theory as well as truncations of Dyson-Schwinger equations in ordinary Yang-Mills theories. We derive the corresponding equations within the usual one-loop truncation for the propagators after imposing the Landau gauge. We find a conformal solution in this approximation, which surprisingly resembles many aspects of ordinary Yang-Mills theories. We furthermore identify which role the Gribov-Singer ambiguity in this context could play, should it exist in this theory.
Resolved gravity duals of ${\\cal N}=4$ quiver field theories in 2+1 dimensions
Cottrell, William
2016-01-01
We generalize the construction by Aharony, Hashimoto, Hirano, and Ouyang of ${\\cal N}=4$ quiver gauge theory with gauge group $U(N+M) \\times U(N)$, $k$ fundamentals charged under $U(N)$ and bi-fundamentals, to the case with gauge group $\\prod_{i=1}^{\\hat k} U(N_i)$ with $k_i$ fundamentals charged under $U(N_i)$. This construction is facilitated by considering the resolved $ALE_{\\hat k} \\times TN_{k}$ background in M-theory including non-trivial fluxes through the resolved 4-cycles in the geometry. We also describe the M-theory lift of the IIA Page charge quantization condition. Finally, we clarify the role of string corrections in various regimes of parameter space.
Resolved gravity duals of N=4 quiver field theories in 2 + 1 dimensions
Cottrell, William; Hashimoto, Akikazu
2016-10-01
We generalize the construction by Aharony, Hashimoto, Hirano, and Ouyang of N=4 quiver gauge theory with gauge group U( N + M) × U( N), k fundamentals charged under U( N ) and bi-fundamentals, to the case with gauge group {{prod}_{i=1}^{widehat{k}}U({N}_i)} with k i fundamentals charged under U( N i ). This construction is facilitated by considering the resolved AL{E}_{widehat{k}}× T{N}_k background in M-theory including non-trivial fluxes through the resolved 4-cycles in the geometry. We also describe the M-theory lift of the IIA Page charge quantization condition. Finally, we clarify the role of string corrections in various regimes of parameter space.
BFKL Pomeron and Bern-Dixon-Smirnov amplitudes in N=4 SUSY
Energy Technology Data Exchange (ETDEWEB)
Lipatov, L.N. [Petersburg Nuclear Physics Institute (Russian Federation)]|[Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2008-10-15
We review the theoretical approaches for investigations of the high energy hadron-hadron scattering in the Regge kinematics. It is demonstrated, that the gluon in QCD is reggeized and the Pomeron is a composite state of the reggeized gluons. Remarkable properties of the BFKL equation for the Pomeron wave function in QCD and supersymmetric gauge theories are outlined. Due to the AdS/CFT correspondence the BFKL Pomeron is equivalent to the reggeized graviton in the extended N=4 SUSY. The properties of the maximal transcendentality and integrability are realized in this model. The BDS multi-gluon scattering amplitudes are investigated in the Regge limit. They do not contain the Mandelstam cuts and are not valid beyond one loop. It is shown, that the hamiltonian for these composite states coincides with the hamiltonian of an integrable open Heisenberg spin chain. (orig.)
Generating all tree amplitudes in {N} = 4{{SYM}} by Inverse Soft Limit
Nandan, Dhritiman; Wen, Congkao
2012-08-01
The idea of adding particles to construct amplitudes has been utilized in various ways in exploring the structure of scattering amplitudes. This idea is often called Inverse Soft Limit, namely it is the reverse mechanism of taking particles to be soft. We apply the Inverse Soft Limit to the tree-level amplitudes in {N} = 4 super Yang-Mills theory, which allows us to generate full tree-level superamplitudes by adding "soft" particles in a certain way. With the help from Britto-Cachazo-Feng-Witten recursion relations, a systematic and concrete way of adding particles is determined recursively. The amplitudes constructed solely by adding particles not only have manifest Yangian symmetry, but also make the soft limit transparent. The method of generating amplitudes by Inverse Soft Limit can also be generalized for constructing form factors.
Coulomb branches for rank 2 gauge groups in 3d N=4 gauge theories
Hanany, Amihay
2016-01-01
The Coulomb branch of 3-dimensional N=4 gauge theories is the space of bare and dressed BPS monopole operators. We utilise the conformal dimension to define a fan which, upon intersection with the weight lattice of a GNO-dual group, gives rise to a collection of semi-groups. It turns out that the unique Hilbert bases of these semi-groups are a sufficient, finite set of monopole operators which generate the entire chiral ring. Moreover, the knowledge of the properties of the minimal generators is enough to compute the Hilbert series explicitly. The techniques of this paper allow an efficient evaluation of the Hilbert series for general rank gauge groups. As an application, we provide various examples for all rank two gauge groups to demonstrate the novel interpretation.
Nakajima, Hiraku
2015-01-01
Consider the $3$-dimensional $\\mathcal N=4$ supersymmetric gauge theory associated with a compact Lie group $G$ and its quaternionic representation $\\mathbf M$. Physicists study its Coulomb branch, which is a noncompact hyper-K\\"ahler manifold, such as instanton moduli spaces on $\\mathbb R^4$, $SU(2)$-monopole moduli spaces on $\\mathbb R^3$, etc. In this paper and its sequel, we propose a mathematical definition of the coordinate ring of the Coulomb branch, using the vanishing cycle cohomology group of a certain moduli space for a gauged $\\sigma$-model on the $2$-sphere associated with $(G,\\mathbf M)$. In this first part, we check that the cohomology group has the correct graded dimensions expected from the monopole formula proposed by Cremonesi, Hanany and Zaffaroni arXiv:1309.2657. A ring structure (on the cohomology of a modified moduli space) will be introduced in the sequel of this paper.
Large N Free Energy of 3d N=4 SCFTs and AdS/CFT
Assel, Benjamin; Yamazaki, Masahito
2012-01-01
We provide a non-trivial check of the AdS_4/CFT_3 correspondence recently proposed in arXiv:1106.4253 by verifying the GKPW relation in the large N limit. The CFT free energy is obtained from the previous works (arXiv:1105.2551, arXiv:1105.4390) on the S^3 partition function for 3-dimensional N=4 SCFT T[SU(N)]. This is matched with the computation of the type IIB action on the corresponding gravity background. We unexpectedly find that the leading behavior of the free energy at large N is 1/2 N^2 ln N. We also extend our results to richer theories and argue that 1/2 N^2 ln N is the maximal free energy at large N in this class of gauge theories.
New integrable non-gauge 4D CFTs from strongly deformed planar N=4 SYM
Gurdogan, Omer
2015-01-01
We consider the $\\gamma$-deformed $\\mathcal{N}=4$ SYM in the double scaling limit of large imaginary twist and small coupling, which discards the gauge fields and retains only certain Yukawa and scalar interactions with three arbitrary couplings. In the 't Hooft limit, these 4D theories are conformal and integrable, with the whole arsenal of AdS/CFT integrability applicable. In particular, for one non-zero coupling, we obtain a QFT of two complex scalars with a chiral, quartic interaction. The BMN vacuum anomalous dimension is dominated in each order by a single "wheel" graph, in principle computable by integrability. Thus we also provide an explicit conjecture for the periods of double-wheel graphs with an arbitrary number of spokes.
Phase transitions of an anisotropic N=4 super Yang-Mills plasma via holography
Banks, Elliot
2016-07-01
Black hole solutions of type IIB supergravity were previously found that are dual to N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial deformation. In the zero temperature limit, these black holes approach a Liftshitz like scaling solution in the IR. It was recently shown that these black holes are unstable, and at low temperatures there is a new class of black hole solutions that are thermodynamically preferred. We extend this analysis, by considering consistent truncations of the Kaluza-Klein reduction of IIB supergravity on a five-sphere that preserves multiple scalar and U(1) gauge fields. We show that the previously constructed black holes become unstable at low temperatures, and construct new classes of exotic black hole solutions. We study the DC thermo-electric conductivity of these U(1) charged black holes, and find a diverging DC conductivity at zero temperature due to the divergence of the gauge field coupling.
Fabrication and characterization of SiO2(f)/Si3N4 composites
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A silicon dioxide fiber-reinforced silicon nitride matrix (SiO2/Si3N4) composite used for radomes was prepared by chemical vapor infiltration (CVI) process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra (EDS) result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction (XRD) results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope (SEM). As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.
Three-dimensional N=4 linear quivers and non-Abelian T-duals
Energy Technology Data Exchange (ETDEWEB)
Lozano, Yolanda [Department of Physics, University of Oviedo,Avda. Calvo Sotelo 18, Oviedo, 33007 (Spain); Macpherson, Niall T. [Dipartimento di Fisica, Università di Milano-Bicocca and INFN, sezione di Milano-Bicocca,Milano, I-20126 (Italy); Montero, Jesús [Department of Physics, University of Oviedo,Avda. Calvo Sotelo 18, Oviedo, 33007 (Spain); Núñez, Carlos [Department of Physics, Swansea University,Swansea, SA2 8PP United Kingdom (United Kingdom)
2016-11-22
In this paper we construct a new Type IIB background with an AdS{sub 4} factor that preserves N=4 Supersymmetry. This solution is obtained using a non-Abelian T-duality transformation on the Type IIA reduction of the AdS{sub 4}×S{sup 7} background. We interpret our configuration as a patch of a more general background with localised sources, dual to the renormalisation fixed point of a T{sub ρ}{sup ρ̂}(SU(N)) quiver field theory. This relates explicitly the AdS{sub 4} geometry to a D3-D5-NS5 brane intersection, illuminating what seems to be a more general phenomenon, relating AdS{sub p+1} backgrounds generated by non-Abelian T-duality to Dp-D(p+2)-NS5 branes intersections.
Structure constants of planar N =4 Yang Mills at one loop
Alday, L F; Gava, E; Narain, K S; Alday, Luis F.; David, Justin R.; Gava, Edi
2005-01-01
We study structure constants of gauge invariant operators in planar N=4 Yang-Mills at one loop with the motivation of determining features of the string dual of weak coupling Yang-Mills. We derive a simple renormalization group invariant formula characterizing the corrections to structure constants of any primary operator in the planar limit. Applying this to the scalar SO(6) sector we find that the one loop corrections to structure constants of gauge invariant operators is determined by the one loop anomalous dimension Hamiltonian in this sector. We then evaluate the one loop corrections to structure constants for scalars with arbitrary number of derivatives in a given holomorphic direction. We find that the corrections can be characterized by suitable derivatives on the four point tree function of a massless scalar with quartic coupling. We show that individual diagrams violating conformal invariance can be combined together to restore it using a linear inhomogeneous partial differential equation satisfied ...
Spinning squashed extra dimensions and chiral gauge theory from N=4 SYM
Directory of Open Access Journals (Sweden)
Harold C. Steinacker
2015-07-01
Full Text Available New solutions of SU(N N=4 SYM on R4 interpreted as spinning self-intersecting extra dimensions are discussed. Remarkably, these backgrounds lead to a low-energy sector with 3 generations of chiral fermions coupled to scalar and gauge fields, with standard Lorentz-invariant kinematics. This sector arises from zero modes localized on the rotation axes, which are oblivious to the background rotation. The remaining modes are not described by a Lorentz-invariant field theory and are mostly “heavy”, but there is one sextet of tachyonic excitations. Assuming that the latter get stabilized, e.g. by quantum effects, we argue that different rotation frequencies would induce a VEV for some of the low-energy scalar fields. We discuss configurations which may lead to a low-energy physics not far from the broken phase of the standard model.
Molecular dynamics simulations of the mechanical strength of Si/ Si3 N4 interfaces
Bachlechner, Martina E.; Zhang, Jennifer; Wang, Ye; Schiffbauer, Jarrod; Knudsen, Steven R.; Korakakis, Dimitris
2005-09-01
Molecular dynamics simulations are performed on parallel computers to investigate the crystalline Si(111)/Si3N4(0001) interface that is modeled as an eight-component system. The average total energy per particle and the average kinetic energy per particle of the subsystems are monitored during the preparation of the system. The Young’s modulus of the interface is compared with that of the silicon part alone and that of the silicon-nitride film, respectively. The results for one extended simulation feature a crack in the silicon-nitride film and dislocated atoms in silicon below the crack. Simulations at rates of strain ranging from 0.00125to0.05ps-1 show that for lower strain rates, the systems stretched faster reach their ultimate strength at a higher strain value than those that were stretched more slowly. At the highest strain rates, however, the failure mechanisms change qualitatively indicative of a more ductile behavior.
Central extended D=2 N=4 SU(2) Liouville self interacting model and explicit hyperkahler metric
Hssaini, M; Maroufi, B; Sedra, M B
2000-01-01
Methods developed in the context of 2d conformal field theories and integrable models are used, in the harmonic superspace language, to solve the system of non linear harmonic differential equations that appear in the central extension of D=2 N=4 SU(2) Liouville self interacting model and compute the explicit form of the associated hyperkahler metric. Among the results obtained, we derive new general solutions for the auxiliary fields and the Lagrange field and present explicitly the associated purely bosonic dependent action in the central extension case. We derive also the explicit form of the associated hyperkahler metric as well as the induced non trivial scalar potential shown to depend on the square term. This provides then a way to make a comparison with the standard result in which the term proportional to is known to correspond to the BPS mass.
High-reflectivity $Si\\_3N\\_4$ photonic-crystal membranes for optomechanics
Chen, X; Makles, K; Caër, C; Chua, S; Braive, R; Robert-Philip, I; Briant, T; Cohadon, P -F; Heidmann, A; Jacqmin, T; Deléglise, S
2016-01-01
Nanomechanical resonators strongly coupled to the electromagnetic field are a promising resource for quantum-limited mass and force sensors, and as transducers for coupling otherwise incompatible quantum systems such as microwave and optical photons. In particular, suspended nanomem-branes obtained by chemical release of a high-tensile stress layer are an advantageous platform for such transducers, combining an extremely high mechanical quality factor and a low mass. We demonstrate the successful implementation of a photonic-crystal reflector on a high-tensile stress $Si\\_3N\\_4$ nanomembrane, enabling its direct coupling to a high-finesse optical cavity. This approach is particularly well suited for hybrid opto-electro-mechanical transducers, where the membrane motion is simultaneously coupled to an optical and a microwave cavity. We provide an illustration of the physical process underlying the high reflectivity by measuring the photonic crystal band diagram. Moreover, we introduce a clear theoretical descri...
External beam IBA set-up with large-area thin Si3N4 window
Palonen, V.; Mizohata, K.; Nissinen, T.; Räisänen, J.
2016-08-01
A compact external beam setup has been constructed for Particle Induced X-ray Emission (PIXE) and Nuclear Reaction (NRA) analyses. The key issue in the design has been to obtain a wide beam spot size with maximized beam current utilizing a thin Si3N4 exit window. The employed specific exit window support enables use of foils with thickness of 100 nm for a beam spot size of 4 mm in diameter. The durable thin foil and the large beam spot size will be especially important for the complementary external beam NRA measurements. The path between the exit foil and sample is filled with flowing helium to minimize radiation hazard as well as energy loss and straggling, and to cool the samples. For sample-independent beam current monitoring and irradiation fluence measurement, indirect charge integration, based on secondary electron current measurement from a beam profilometer, is utilized.
Three-dimensional N=4 Linear Quivers and non-Abelian T-duals
Lozano, Yolanda; Montero, Jesus; Nunez, Carlos
2016-01-01
In this paper we construct a new Type IIB background with an $AdS_4$ factor that preserves ${\\cal N}=4$ Supersymmetry. This solution is obtained using a non-Abelian T-duality transformation on the Type IIA reduction of the $AdS_4\\times S^7$ background. We interpret our configuration as a patch of a more general background with localised sources, dual to the renormalisation fixed point of a $T_{\\rho}^{\\hat{\\rho}} (SU(N))$ quiver field theory. This relates explicitly the $AdS_4$ geometry to a D3-D5-NS5 brane intersection, illuminating what seems to be a more general phenomenon, relating $AdS_{p+1}$ backgrounds generated by non-Abelian T-duality to Dp-D(p+2)-NS5 branes intersections.
Three-point functions in ${\\cal N}=4$ SYM: the hexagon proposal at three loops
Eden, Burkhard
2015-01-01
Basso, Komatsu and Vieira recently proposed an all-loop framework for the computation of three-point functions of single-trace operators of ${\\cal N}=4$ super-Yang-Mills, the "hexagon program". This proposal results in several remarkable predictions, including the three-point function of two protected operators with an unprotected one in the $SU(2)$ and $SL(2)$ sectors. Such predictions consist of an "asymptotic" part---similar in spirit to the asymptotic Bethe Ansatz of Beisert and Staudacher for two-point functions---as well as additional finite-size "wrapping" L\\"uscher-like corrections. The focus of this paper is on such wrapping corrections, which we compute at three-loops in the $SL(2)$ sector. The resulting structure constants perfectly match the ones obtained in the literature from four-point correlators of protected operators.
Perturbative and instanton corrections to the OPE of CPOs in N=4 $SYM_{4}$
Arutyunov, G E; Petkou, Anastasios C
2001-01-01
We study perturbative and instanton corrections to the Operator Product Expansion of the lowest weight Chiral Primary Operators of N=4 SYM_4. We confirm the recently observed non-renormalization of various operators (notably of the double-trace operator with dimension 4 in the 20 irrep of SU(4)), that appear to be unprotected by unitarity restrictions. We demonstrate the splitting of the free-field theory stress tensor and R-symmetry current in supermultiplets acquiring different anomalous dimensions in perturbation theory and argue that certain double-trace operators also undergo a perturbative splitting into operators dual to string and two-particle gravity states respectively. The instanton contributions affect only those double-trace operators that acquire finite anomalous dimensions at strong coupling. For the leading operators of this kind, we show that the ratio of their anomalous dimensions at strong coupling to the anomalous dimensions due to instantons is the same number.
Improvement in Contact Strength of Si3N4/SiC Composite by Crack Healing
Directory of Open Access Journals (Sweden)
Koji Takahashi
2013-01-01
Full Text Available Ceramics have been used as bearing and cutting tool components, which are subjected to contact loading during their operation. The presence of surface cracks on these components decreases their contact strength. Thus, the reliability of ceramic components can be increased by improving their contact strength through crack healing. In the present study, the effects of crack healing on the contact strength of a silicon carbide-(SiC- reinforced silicon nitride (Si3N4 composite subjected to various machining processes were investigated. The contact strength of this composite was evaluated using a sphere indentation test in which acoustic emission was used. The results showed that the contact strength of the composite improved when it was subjected to crack healing in combination with rapping; this was true even when the composite had cracks due to a heavy machining process.
Graphene on β-Si3N4: An ideal system for graphene-based electronics
Directory of Open Access Journals (Sweden)
Ming Yang
2011-09-01
Full Text Available One of the most severe limits in future design of graphene-based electronic devices is that when supported on a substrate, the electron mobility of graphene is often reduced by an order of magnitude or more. In this paper, via theoretical calculations, we show that the non-polar β-Si3N4 (0001 surface may be an excellent support for both single-layer or bi-layer graphene to overcome this limit. Since the high-κ dielectric material is an indispensable component in integrated circuits, the silicon nitride supported graphene as discussed in this paper may provide an ideal platform for future graphene-based electronics.
Regge meets collinear in strongly-coupled $\\mathcal{N} = 4$ super Yang-Mills
Sprenger, Martin
2016-01-01
We revisit the calculation of the six-gluon remainder function in planar $\\mathcal{N} = 4$ super Yang-Mills theory from the strong coupling TBA in the multi-Regge limit and identify an infinite set of kinematically subleading terms. These new terms can be compared to the strong coupling limit of the finite-coupling expressions for the impact factor and the BFKL eigenvalue proposed by Basso et al. in arXiv:1407.3766, which were obtained from an analytic continuation of the Wilson loop OPE. After comparing the results order by order in those subleading terms, we show that it is possible to precisely map both formalisms onto each other. A similar calculation can be carried out for the seven-gluon amplitude, the result of which shows that the central emission vertex does not become trivial at strong coupling.
tert-Butyl N-{4-methyl-3-[4-(3-pyridylpyrimidin-2-yloxy]phenyl}carbamate
Directory of Open Access Journals (Sweden)
Shi-Gui Tang
2009-08-01
Full Text Available In the molecule of the title compound, C21H22N4O3, the pyrimidine ring is oriented at dihedral angles of 0.51 (3 and 50.76 (3° to the pyridine and benzene rings, respectively. In the crystal structure, intermolecular N—H...N hydrogen bonds link the molecules into centrosymmetric dimers, forming R22(24 ring motifs; the dimers are linked by intermolecular C—H...O hydrogen bonds into a two-dimensional network. π–π contacts between the benzene rings and between the pyrimidine and pyridine rings [centroid–centroid distances = 3.891 (1 and 3.646 (1 Å, respectively] may further stabilize the structure. Two weak C—H...π interactions are also present.
Coulomb branches for rank 2 gauge groups in 3dN=4 gauge theories
Energy Technology Data Exchange (ETDEWEB)
Hanany, Amihay [Theoretical Physics Group, Imperial College London,Prince Consort Road, London, SW7 2AZ (United Kingdom); Sperling, Marcus [Institut für Theoretische Physik, Leibniz Universität Hannover,Appelstraße 2, 30167 Hannover (Germany)
2016-08-02
The Coulomb branch of 3-dimensional N=4 gauge theories is the space of bare and dressed BPS monopole operators. We utilise the conformal dimension to define a fan which, upon intersection with the weight lattice of a GNO-dual group, gives rise to a collection of semi-groups. It turns out that the unique Hilbert bases of these semi-groups are a sufficient, finite set of monopole operators which generate the entire chiral ring. Moreover, the knowledge of the properties of the minimal generators is enough to compute the Hilbert series explicitly. The techniques of this paper allow an efficient evaluation of the Hilbert series for general rank gauge groups. As an application, we provide various examples for all rank two gauge groups to demonstrate the novel interpretation.
Spin-Orbit Coupling Effects in AumPtn Clusters (m + n = 4).
Moreno, Norberto; Ferraro, Franklin; Flórez, Elizabeth; Hadad, C Z; Restrepo, Albeiro
2016-03-17
A study of AumPtn(m + n = 4) clusters with and without spin-orbit (SO) coupling using scalar relativistic (SR) and two component methods with the ZORA Hamiltonian was carried out. We employed the PW91 functional in conjunction with the all-electron TZ2P basis set. This paper offers a detailed analysis of the SO effects on the cluster geometries, on the LUMO-HOMO gap, on the charge distribution, and on the relative energies for each relativistic method. In general, SO coupling led to an energetic rearrangement of the species, to changes in geometries and structural preferences, to changes in the structural identity of the global minimum for the Au3Pt, AuPt3 and Pt4 cases, and to a reduction of relative energies among the clusters, an effect that appears stronger as the amount of Pt increases.
A note on perturbative aspects of Leigh-Strassler deformed N=4 SYM theory
Madhu, Kallingalthodi
2007-01-01
We carry out a perturbative study of the Leigh-Strassler deformed N=4 SYM theory in order to verify that the trihedral Delta(27) symmetry holds in the quantum theory. We show that the Delta(27) symmetry is preserved to two loops (at finite N) by explicitly computing the superpotential. The perturbative superpotential is not holomorphic in the couplings due to finite contributions. However, there exist coupling constant redefinitions that restore holomorphy. Interestingly, the same redefinitions appear (in the work of Jack, Jones and North[hep-ph/9603386]) if one requires the three-loop anomalous dimension to vanish in a theory where the one-loop anomalous dimension vanishes. However, the two field redefinitions seem to differ by a factor of two.
Three-dimensional {N}=4 linear quivers and non-Abelian T-duals
Lozano, Yolanda; Macpherson, Niall T.; Montero, Jesús; Núñez, Carlos
2016-11-01
In this paper we construct a new Type IIB background with an AdS 4 factor that preserves {N}=4 Supersymmetry. This solution is obtained using a non-Abelian T-duality transformation on the Type IIA reduction of the AdS 4 × S 7 background. We interpret our configuration as a patch of a more general background with localised sources, dual to the renormalisation fixed point of a {T}_{ρ}^{widehat{ρ}}(SU(N)) quiver field theory. This relates explicitly the AdS 4 geometry to a D3-D5-NS5 brane intersection, illuminating what seems to be a more general phenomenon, relating AdS p+1 backgrounds generated by non-Abelian T-duality to Dp- D( p + 2)-NS5 branes intersections.
Numerical study of the chaotic N=4 problem in a background potential
Ryu, Taeho; Perna, Rosalba
2016-01-01
We perform a large suite of $N=4$ numerical scattering experiments between two identical binaries consisting of identical point particles in a (continuous) background potential. For investigative purposes, albeit without loss of generality, we assume that the potential corresponds to a uniform (natal or star-forming) gas medium. We explore a range of constant gas densities, from $n=10~ {\\rm cm}^{-3}$ to $10^{5}~ {\\rm cm}^{-3}$. These densities are relevant for various astrophysical environments, including molecular clouds (i.e., star-forming regions) and denser, fragmented cores within these clouds. Our primary goal is to characterize the effects of the background potential on the subsequent stellar dynamics. We consider the outcome probabilities as well as the properties of any binaries formed during the binary-binary encounters, such as the distributions of binary binding energies and eccentricities. We also present the final velocity distributions of the ejected single stars. The background potential has t...
BPS Wilson loops in N=4 SYM: Examples on hyperbolic submanifolds of space-time
Branding, Volker
2009-01-01
In this paper we present a family of supersymmetric Wilson loops of N=4 supersymmetric Yang-Mills theory in Minkowski space. Our examples focus on curves restricted to hyperbolic submanifolds, H_3 and H_2, of space-time. Generically they preserve two supercharges, but in special cases more, including a case which has not been discussed before, of the hyperbolic line, conformal to the straight line and circle, which is half-BPS. We discuss some general properties of these Wilson loops and their string duals and study special examples in more detail. Generically the string duals propagate on a complexification of AdS_5 x S^5 and in some specific examples the compact sphere is effectively replaced by a de-Sitter space.
Xu, Jingwen; Zhou, Xuemei; Li, Yuzhen; Gao, Zhi-Da; Song, Yan-Yan; Schmuki, Patrik
2016-01-01
In this work, we introduce a facile procedure to graft a thin graphitic C3N4 (g-C3N4) layer on aligned TiO2 nanotube arrays (TiNT) by one-step chemical vapor deposition (CVD) approach. This provides a platform to enhance the visible-light response of TiO2 nanotubes for antimicrobial applications. The formed g- C3N4/TiNT binary nanocomposite exhibits excellent bactericidal efficiency against E. coli as a visiblelight activated antibacterial coating.
原位增韧β-Si3N4/α-Sialon复相陶瓷%In-situ Toughening Multi-phase β-Si3N4/α-Sialon Ceramics
Institute of Scientific and Technical Information of China (English)
武安华; 葛昌纯
2002-01-01
通过XRD, SEM和力学性能测试研究了β-Si3N4/α-Sialon复相陶瓷热压烧结的致密化、相组成、力学性能和微观结构.结果表明,β-Si3N4/α-Sialon复相陶瓷综合了β-Si3N4和α-Sialon的力学性能,可通过改变起始粉末的组成,可以调整相组成及裁剪材料的力学性能.由于加入具有大的长径比的物相β-Si3N4,提高了材料的强度和韧性.
Olesk, Peeter, 1953-
2001-01-01
Tõnu Kaljuste juhatab Ljubljana Gallus Hallis Johannes Brahmsi "Saksa reekviemi". EMA kuratooriumi ja rahvusooperi Estonia nõukogu arutasid ühisistungil Eesti ooperikunsti, muusikateatri ja kõrgema muusikalise hariduse probleeme. 7. XII kell 19.00 saab "Klassikaraadiost" kuulata Milano La Scala hooaja avaetenduse otseülekannet. Antese väljaandel ilmus CD Rene Eespere kammerteostega. 29.XI ئ 2.XII viibis Eestis Sibeliuse akadeemia klassikalise kitarri õppejõud Jukka Savijoki. 23. ja 24. XI toimus Tartus kolme keskastme muusikakooli noorte pianistide konkurss. 8.XII toimub EMA kammersaalis suur jõulukontsert, kus esinevad parimad EMA üliõpilased. Kontserdiagentuuri Concerto Grosso sari "Advendiaeg poistekooridega" viib kontserte Eestimaa erinevatesse linnadesse. Plaadi "Kahest üks" esitluskontserdiga, kus tuleb esiettekandele Urmas Sisaski kantaat "Armastusesle", tähistab TTÜ Akadeemiline Naiskoor oma 50. aastapäeva . Eesti Naistelaulu Seltsi korraldusel toimus 2. XII Balti Misjonikeskuses Tallinna naiskooride advendikontsert. 28. XI toimus Estonia talveaias Tarmo Lepiku 55. sünniaastapäevale pühendatud mälestuskontsert. 17.XI toimus Põlva kultuuri ja huvikeskuses VII Lõuna-Eesti meestelaulu päev
Si3N4/钢的几种钎接工艺比较%Comparison on Some Group of Brazing Process of Si3N4 to Steel
Institute of Scientific and Technical Information of China (English)
王夏冰
2003-01-01
实验比较和分析了几种Si3N4/钢钎接工艺的特点.表明,含Ti活性钎料适用于Si3N4/钢的直接钎焊;合适的应力缓和层的选择以及套封结构的使用均能明显提高钎接接头强度.
High-Temperature Corrosion Resistance of Si3N4-SiC Composites%Si3N4结合SiC复合材料的抗高温腐蚀性
Institute of Scientific and Technical Information of China (English)
王晓利
2009-01-01
对Si3N4结合SiC复合陶瓷材料在高温条件下的抗氧化性和抗侵蚀性进行了研究,指出复合材料比单-SiC材料和Si3N4在空气条件下表现出良好的抗侵蚀性和抗氧化性.
Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya
2005-09-01
A hybrid atomistic-continuum simulation approach has been implemented to study strain relaxation in lattice-mismatched Si/Si3N4 nanopixels on a Si(111) substrate. We couple the molecular-dynamics (MD) and finite-element simulation approaches to provide an atomistic description near the interface and a continuum description deep into the substrate, increasing the accessible length scales and greatly reducing the computational cost. The results of the hybrid simulation are validated against full multimillion-atom MD simulations. We find that strain relaxation in Si/Si3N4 nanopixels may occur through the formation of a network of interfacial domain boundaries reminiscent of interfacial misfit dislocations. They result from the nucleation of domains of different interfacial bonding at the free edges and corners of the nanopixel, and subsequent to their creation they propagate inwards. We follow the motion of the domain boundaries and estimate a propagation speed of about ˜2.5×103m/s . The effects of temperature, nanopixel architecture, and film structure on strain relaxation are also investigated. We find: (i) elevated temperature increases the interfacial domain nucleation rates; (ii) a thin compliant Si layer between the film and the substrate plays a beneficial role in partially suppressing strain relaxation; and (iii) additional control over the interface morphology may be achieved by varying the film structure.
Junggeburth, Sebastian C; Oeckler, Oliver; Johrendt, Dirk; Schnick, Wolfgang
2008-12-15
The alkaline earth nitridogermanate nitrides AE(7)[GeN(4)]N(2) (AE = Ca, Sr) have been synthesized using a Na flux technique in sealed Ta tubes. According to single-crystal X-ray diffraction the isotypic compounds crystallize in space group Pbcn (No. 60) with Z = 4, (Sr(7)[GeN(4)]N(2): a = 1152.6(2), b = 658.66(13), c = 1383.6(3) pm, V = 1050.5(4) x 10(6) pm(3), R1 = 0.049; Ca(7)[GeN(4)]N(2): a = 1082.6(2), b = 619.40(12), c = 1312.1(3) pm, V = 879.8(3) x 10(6) pm(3), R1 = 0.016). Owing to the high N/Ge ratio, the compounds contain discrete N(3-) ions coordinated by six AE(2+) besides discrete [GeN(4)](8-) tetrahedrons. One of the AE(2+) ion is coordinated by only four N(3-) ions, which is rather an unusual low coordination number for Sr(2+). Together with the isolated [GeN(4)](8-) tetrahedrons, these Sr(2+) ions form chains of alternating cation centered edge sharing tetrahedrons. The electronic structure and chemical bonding in Sr(7)[GeN(4)]N(2) has been analyzed employing linear muffin-tin orbital (LMTO) band structure calculations.
Energy Technology Data Exchange (ETDEWEB)
Carvalho, L. Faria; Toppan, F., E-mail: leofc@cbpf.b, E-mail: toppan@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Kuznetsova, Z., E-mail: zhanna.kuznetsova@ufabc.edu.b [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil)
2009-07-01
We discuss four off-shell N = 4 D = 1 supersymmetry transformations, their associated one-dimensional -models and their mutual relations. They are given by I - the (4, 4){sub lin} linear 'root' supermultiplet (supersymmetric extension of R{sup 4}), II - the (3, 4, 1){sub lin} linear supermultiplet (supersymmetric extension of R3), III - the (3, 4, 1){sub nl} non-linear supermultiplet living on S{sup 3} and IV - the (2, 4, 2){sub nl} non-linear supermultiplet living on S{sup 2}. The I {yields} II map is the supersymmetric extension of the R4 {yields} R3 bilinear map, while the II {yields} IV map is the supersymmetric extension of the S{sup 3} {yields} S{sup 2} first Hopf fibration. The restrictions on the S{sup 3}, S{sup 2} spheres are expressed in terms of the stereo graphic projections. The non-linear supermultiplets, whose super transformations are local differential polynomials, are not equivalent to the linear supermultiplets with the same field content. The -models are determined in terms of an unconstrained pre potential of the target coordinates. The Uniformization Problem requires solving an inverse problem for the pre potential. The basic features of the supersymmetric extension of the second and third Hopf maps are briefly sketched. Finally, the Schur's lemma (i.e. the real, complex or quaternionic property) is extended to all minimal linear supermultiplets up to N {<=} 8. (author)
Institute of Scientific and Technical Information of China (English)
陈威; 高义民; 居发亮; 汪勇
2009-01-01
利用MMU-5G销-盘式端面磨损试验机考察了蒸馏水润滑条件下Si3N4-hBN(六方氮化硼)复合陶瓷与Si3N4陶瓷配副时的摩擦磨损性能,并分别采用扫描电子显微镜、激光扫描显微镜、X光电子能谱和X射线能谱分析了摩擦面的形貌和物质组成.结果表明:在滴定法水润滑条件下,Si3N4-hBN/Si3N4配副的摩擦因数随hBN含量的增加而显著降低,当hBN体积分数为20%时,摩擦因数降至0.01,Si3N4-hBN的磨损率接近0;在浸入法水润滑条件下,Si3N4-hBN/Si3N4配副的摩擦因数均降至0.01.在滴定法水润滑条件下,磨屑不易被水带走,当Si3N4-hBN与Si3N4配副摩擦时,由于Si3N4-hBN摩擦面上hBN偏聚区域发生脆性断裂和剥落而形成剥落坑,磨屑在剥落坑中堆积并氧化、水解,反应产物富集于剥落坑中,进而在摩擦表面形成含B2O3和SiO2的摩擦化学反应膜,从而保护了Si3N4-hBN和Si3N4摩擦面,使其变得光滑,为发生流体润滑提供了条件.
Kato, J; Miyake, A; Kato, Junji; Kawamoto, Noboru; Miyake, Akiko
2005-01-01
We propose N=4 twisted superspace formalism in four dimensions by introducing Dirac-Kahler twist. In addition to the BRST charge as a scalar counter part of twisted supercharge we find vector and tensor twisted supercharges. By introducing twisted chiral superfield we explicitly construct off-shell twisted N=4 SUSY invariant action. We can propose variety of supergauge invariant actions by introducing twisted vector superfield. We may, however, need to find further constraints to identify twisted N=4 super Yang-Mills action. We propose a superconnection formalism of twisted superspace where constraints play a crucial role. It turns out that N=4 superalgebra of Dirac-Kahler twist can be decomposed into N=2 sectors. We can then construct twisted N=2 super Yang-Mills actions by the superconnection formalism of twisted superspace in two and four dimensions.
Synthesis of dark orange montmorillonite/g-C3N4 composites and their applications in the environment
Li, Pengpeng; Huang, Liying; Li, Yeping; Xu, Yuanguo; Huang, Shuquan; Yuan, Ding; Xu, Hui; Li, Huaming
2017-08-01
Dark orange montmorillonite/g-C3N4 composites were prepared through a conventional calcination route. The obtained samples were analyzed by XRD, TEM, TG, XPS, FT-IR, DRS, Photocurrent-time and PL measurements. The photocatalytic performance of montmorillonite/g-C3N4 composites was assessed by the methylene blue (MB) degradation. Compared to pure g-C3N4, the obtained photocatalysts displayed outstanding photocatalytic activity. The improved photocatalytic activity was ascribed to the improved absorbance in the visible light range and favorable adsorptive capacity to MB dye. The electron spin resonance (ESR) analysis and trapping experiment showed that •O2- and h+ played a major role in the decomposition of MB. In addition, it was found that montmorillonite/g-C3N4 (0.5) composite had a new property, which showed that it can be applied as a sensor in the photoelectrochemical detection of trace amount of Cu2+.
Preparation of electrospun Ag/g-C3N4 loaded composite carbon nanofibers for catalytic applications
Yu, Bo; Liu, Yongkun; Jiang, Guohua; Liu, Depeng; Yu, Weijiang; Chen, Hua; Li, Lei; Huang, Qin
2017-01-01
In this paper, the electrospun Ag nanoparticles and g-C3N4 (Ag/g-C3N4) loaded composite carbon nanofibers were successfully prepared combing the electrospinning technology and carbonization treatment. The composition and microstructure of the resultant composite nanofibers were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM) and x-ray photoelectron spectrometry (XPS). Due to the synergistic effect between catalytic activity of Ag nanoparticles (NPs) and g-C3N4 and excellent adsorption capacity of carbon nanofibers, the resultant electrospun Ag/g-C3N4 loaded composite carbon nanofibers exhibited excellent conversion of 4-nitrophenol to 4-aminophenol and benzylamine to N-benzylbenzaldimine. The resultant hybrid carbon composite nanofibers offer the significant advantages, such as low dosage, high catalytic activity, easy recycling and excellent stability.
Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles
Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing
2015-09-01
Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.
Magnetic Fe@g‑C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes
U.S. Environmental Protection Agency — A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically...
N-(4-Methylsulfonamido-3-phenoxyphenyl-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximide
Directory of Open Access Journals (Sweden)
Vangala Ranga Reddy
2011-10-01
Full Text Available The title compound, N-(4-methylsulfonamido-3-phenoxyphenyl-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximide was synthesized in high yield by reaction of N-(4-amino-2-phenoxyphenylmethanesulfonamide and 9,10-dihydroanthracene-9,10-endo-α,β-succinic anhydride in glacial acetic acid. The structure of the compound was fully characterized by IR, 1H and 13C NMR, mass spectral analysis and elemental analysis.
MOHAN, T; THOMAS, CJ; RAO, MNS; ARAVAMUDAN, G; MEETSMA, A; VANDEGRAMPEL, JC
1994-01-01
Tetrasulfurtetranitride, S4N4 reacts with (2-pyridylamino)-diphenylphosphine in MeCN at room temperature to form the cyclotrithiazene (NC5H4NH)-Ph2PN-S3N3 (1) in good yield. By contrast, the cyclophosphathiazenes Ph2PS2N3(2) and 1,5(Ph2P)2S2N4 (3) are isolated from the same reaction mixture under re
Fabrication of AgFeO2/g-C3N4 nanocatalyst with enhanced and stable photocatalytic performance
Tang, Dandan; Zhang, Gaoke
2017-01-01
This work reported a novel AgFeO2/g-C3N4 composite with enhanced photocatalytic activity, which was fabricated by a simple precipitation method. The g-C3N4 sheets with thickness of 2•4 nm were successfully loaded on the surface of the AgFeO2 particles. As compared to pure AgFeO2 and pure g-C3N4, the as-prepared AgFeO2/g-C3N4 photocatalysts exhibited superior absorption in the visible-light region and displayed promising visible-light photocatalytic performance in the degradation of organic contaminations both in water and in air. About 94% of Acid red G (ARG) can be degraded by the optimized AgFeO2/g-C3N4 sample, which is ∱/47.5 and ∱/410.7 times higher than that by pure AgFeO2 and pure g-C3N4, respectively. Meanwhile, it can also effectively degrade ∱/487% of gaseous formaldehyde to CO2 within 9 h. The enhanced photocatalytic property and stability of the AgFeO2/g-C3N4 composite can be attributed to its specific nanostructure, effective electron-hole separation and the formation of Z-scheme heterostructure between AgFeO2 and g-C3N4. This work could provide new and helpful insights into the photocatalytic application of Ag-based delafossite materials.
The impact resistance of SiC and other mechanical properties of SiC and Si3N4
Bradt, R. C.
1984-01-01
Studies focused on the impact and mechanical behavior of SiC and Si3N4 at high temperatures are summarized. Instrumented Charpy impact testing is analyzed by a compliance method and related to strength; slow crack growth is related to processing, and creep is discussed. The transient nature of flaw populations during oxidation under load is emphasized for both SiC and Si3N4.
Magnetic Ordering in Cerium Monochalcogenides: A Test Case for Epsilon-Expansions with n=4
DEFF Research Database (Denmark)
Ott, H. R.; Kjems, Jørgen; Hulliger, F.
1979-01-01
CeSe and CeTe are found by neutron diffraction to be type-II antiferromagnets with the moment along the propagation vector. The phase transitions are continuous with the critical exponent for the magnetization β=0.36±0.02. This constitutes a violation of the ε-expansion predictions of Bak, Krinsky...
Synergistic effect of efficient adsorption g-C3N4/ZnO composite for photocatalytic property
Li, Xuefei; Li, Ming; Yang, Jinghai; Li, Xiuyan; Hu, Tingjing; Wang, Jingshu; Sui, Yingrui; Wu, Xingtong; Kong, Lingnan
2014-03-01
Novel g-C3N4/ZnO composite photocatalyst was synthesized from an oxygen-containing precursor by direct thermal decomposition urea in air without any other templates assistance. Different percentages of g-C3N4 were hybridized with ZnO via the monolayer-dispersed method. The prepared g-C3N4/ZnO composites were characterized by XRD, SEM, UV-vis diffuse reflectance spectra (DRS), FT-IR, TEM and XPS. The composites showed much higher efficiency for degradation of Rhodamine B (RhB) than ZnO under UV and visible light irradiation. Especially, the photocatalytic efficiency was the highest under UV light irradiation when the percentage of g-C3N4 was 6%. The improved photocatalytic activity may be due to synergistic effect of photon acquisition and direct contact between organic dyestuff and photocatalyst. Then, effective separation of photogenerated electron-hole pairs at the interface of g-C3N4 is an important factor for improvement of photocatalytic activity. This work indicates that g-C3N4 hybrid semiconductors photocatalyst is a promising material in pollutants degradation.
Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation
Yao, Guisheng; Li, Yong; Jiang, Peng; Jin, Xiuming; Long, Menglong; Qin, Haixia; Kumar, R. Vasant
2017-04-01
Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si3N4 and Si2N2O are formed as the nitridation products in the samples. Fibroid and short columnar Si3N4 are detected in the samples. The formation mechanisms of Si3N4 and Si2N2O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O2 in N2 atmosphere, forming a thin film of SiO2 on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO2 film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO2 film will crack, and N2 is infiltrated into the central section of the sample through cracks, generating Si2N2O and short columnar Si3N4 in situ. At the same time, metastable SiO(g) reacts with N2 and form fibroid Si3N4. In the regions where the oxygen partial pressure is high, Si3N4 is oxidized into Si2N2O.
Gao, Daqiang; Liu, Yonggang; Liu, Peitao; Si, Mingsu; Xue, Desheng
2016-10-01
Since the graphitic carbon nitride (g-C4N3), which can be seen as C-doped graphitic-C3N4 (g-C3N4), was reported to display ferromagnetic ground state and intrinsic half-metallicity (Du et al., PRL,108,197207,2012), it has attracted numerous research interest to tune the electronic structure and magnetic properties of g-C3N4 due to their potential applications in spintronic devices. In this paper, we reported the experimentally achieving of high temperature ferromagnetism in metal-free ultrathin g-C3N4 nanosheets by introducing of B atoms. Further, first-principles calculation results revealed that the current flow in such a system was fully spin-polarized and the magnetic moment was mainly attributed to the p orbital of N atoms in B doped g-C3N4 monolayer, giving the theoretic evidence of the ferromagnetism and half-metallicity. Our finding provided a new perspective for B doped g-C3N4 spintronic devices in future.
Shen, Yu; Guo, Xiaojuan; Bo, Xiangkun; Wang, Yongzheng; Guo, Xiangke; Xie, Mingjiang; Guo, Xuefeng
2017-02-01
In view of the fact that the photocatalytic activity of graphitic carbon nitride (g-C3N4) is greatly influenced by its electronic structure, herein, effect of templates induced surface species variation on the electronic structure and photocatalytic activity of the templated g-C3N4 was investigated. By mixing the precursor of cyanamide with different templates (SiO2, Al2O3 and template-free) in the preparation of graphitic carbon nitride (g-C3N4), carbon nitrides with different surface species were obtained. The obtained carbon nitride (g-C3N4-Si) templated by SiO2 nanoparticles exhibits enlarged band gap (3.26 eV) and enhanced photo-degradation ability towards Methyl Orange (MO) compared to that of bulk g-C3N4 (2.67 eV) synthesized from direct condensation/carbonization of melamine and Al2O3-templated g-C3N4-Al (2.76 eV). Detailed characterizations confirm that the introduction of templates in the synthesis process resulted in more non-graphitic species (sp3sbnd Csbnd Csbnd and sbnd NHx) on the surface of the derived carbon nitrides, exerting remarkable effect on the electronic structure and photocatalytic performance.
Institute of Scientific and Technical Information of China (English)
Xuetao Luo; Lifu Chen; Qianjun Huang; Litong Zhang
2004-01-01
Self-reinforced Si3N4 ceramics containing high oxynitride glass have been fabricated by the control of microstructure evolution and a-Si3N4 grain growth. The effects of the size distribution of the elongated a-Si3N4 grains, and the a-Si3N4 grain growth as well as the oxynitride glass chemical characteristic on the microstructure and mechanical properties were investigated. The experimental results show that the a-Si3N4 grains in high oxynitride glass grow to elongated rod-like crystals and form the stereo-network structure. Under the sintering conditions of 1800℃ and 60 min, a quite uniform microstructure with an average aspect ratio of 6.5temperature fracture toughness because of its high softening temperature and high viscosity. In the present material, the crack deflection and pullout of the elongated rod-like a-Si3N4 grains are the primary toughening mecl anisms.
Institute of Scientific and Technical Information of China (English)
李君; 陈斐; 张东明; 沈强; 张联盟
2008-01-01
利用流延成型使α-Si3N4晶须在基体中定向排列，并采用热压烧结技术制备了Si3N4陶瓷。用X射线衍射和扫描电镜对陶瓷的物相和显微结构进行了研究，讨论了流延成型对坯体中晶须的分布状态的影响和烧结条件对所得到的块体的显微结构的影响。结果表明：流延成型和热压烧结可以使晶须呈一维定向排布；随着烧结温度的升高，烧结样品的相对密度增大；添加10．6％（质量分数）α-Si3N4晶须在1500℃下烧结，Si3N4陶瓷的断裂韧性为9．24MPa·m1/2，Vickers硬度为15．74GPa。在1600℃ α-Si3N4转变成的长柱状β—Si3N4颗粒，大大提高了Si3N4陶瓷的力学性能，其断裂韧性和Vickers硬度分别为10．26MPa·m1/2和16．56GPa。
Cation-Cation Interactions in [(UO2)2(OH)n](4-n) Complexes
Energy Technology Data Exchange (ETDEWEB)
Odoh, Samuel O.; Govind, Niranjan; Schreckenbach, Georg; De Jong, Wibe A.
2013-10-07
The structures and bonding of gas-phase [(UO2)2(OH)n]4-n (n=2-6) complexes have been studied using density functional theory (DFT), MP2 and CCSD(T) methods with particular emphasis on ground state structures featuring cation-cation interactions (CCIs) between the uranyl groups. An interesting trend is observed in the stabilities of members of this series of complexes. The structures of [(UO2)2(OH)2]2+, [(UO2)2(OH)4] and [(UO2)2(OH)6]2- featuring CCIs are found at higher energies (by 3-20 kcal/mol) in comparison to their conventional μ2-dihydroxo structures. In contrast, the CCI structures of [(UO2)2(OH)3]+ and [(UO2)2(OH)5]- are respectively almost degenerate with and lower in energy than the structures with the μ2-dihydroxo format. The origin of this trend lies in the ‘symmetry’-based need to balance the coordination numbers and effective atomic charges of each uranium center. The calculated IR vibrational frequencies provide signature probes that can be used in differentiating the lowenergy structures and in experimentally confirming the existence of the structures featuring CCIs. Analysis of the bonding in the structures of [(UO2)2(OH)3]+ and [(UO2)2(OH)5]- shows that the CCIs and bridging hydroxo between the dioxo-uranium units are mainly electrostatic in nature.
Antagonistic Effects of Sodium Butyrate and N-(4-Hydroxyphenyl-retinamide on Prostate Cancer
Directory of Open Access Journals (Sweden)
Rainer Kuefer
2007-03-01
Full Text Available Butyrates and retinoids are promising antineoplastic agents. Here we analyzed effects of sodium butyrate and N-(4-hydroxyphenyl-retinamide (4-HPR on prostate cancer cells as monotherapy or in combination in vitro and in vivo. Sodium butyrate and 4-HPR induced concentration-dependent growth inhibition in prostate cancer cells in vitro. The isobologram analysis revealed that sodium butyrate and 4-HPR administered together antagonize effects of each other. For the in vivo studies, a water-soluble complex (4-HPR with a cyclodextrin was created. A single dose of sodium butyrate and 4-HPR showed a peak level in chicken plasma within 30 minutes. Both compounds induced inhibition of proliferation and apoptosis in xenografts of the chicken chorioallantoic membrane. Analysis of the cytotoxic effects of the drugs used in combination demonstrated an antagonistic effect on inhibition of proliferation and on induction of apoptosis. Prolonged jun N-terminal kinase phosphorylation induced by sodium butyrate and 4-HPR was strongly attenuated when both compounds were used in combination. Both compounds induced inhibition of NF-κ,B. This effect was strongly antagonized in LNCaP cells when the compounds were used in combination. These results indicate that combinational therapies have to be carefully investigated due to potential antagonistic effects in the clinical setting despite promising results of a monotherapy.
Copolymers of N-(4-bromophenyl-2-methacrylamide with 2-hydroxyethyl methacrylate
Directory of Open Access Journals (Sweden)
2007-09-01
Full Text Available The radical-initiated copolymerization of N-(4-bromophenyl-2-methacrylamide (BrPMAAm with 2-hydroxyethylmethacrylate (HEMA was carried out in 1,4-dioxane solution at 70°C using 2,2’-azobisisobutyronitrile (AIBN as an initiator with different monomer-to-monomer ratios in the feed. The copolymers were characterized by FTIR, 1H- and 13C-NMR spectral studies. Gel permeation chromatography was employed for estimating the weight average (Mw and number average (Mn molecular weights and polydispersity index (PDI of the copolymers. The copolymer composition was evaluated by nitrogen content (N for BrPMAAm-units in polymers, which allowed the determination of reactivity ratios. Monomer reactivity ratios for BrPMAAm (M1-HEMA (M2 pair were determined by the application of conventional linearization methods such as Fineman-Ross (F-R, Kelen-Tüdõs (KT and Extended Kelen-Tüdõs (EKT and a nonlinear error invariable model method using a computer program RREVM. The characterizations were done thermogravimetric analysis (TGA. The antimicrobial effects of polymers were also tested on various bacteria, and yeast.
Probing Wilson loops in N=4 Chern–Simons-matter theories at weak coupling
Directory of Open Access Journals (Sweden)
Luca Griguolo
2016-02-01
Full Text Available For three-dimensional N=4 super-Chern–Simons-matter theories associated to necklace quivers U(N0×U(N1×⋯U(N2r−1, we study at quantum level the two kinds of 1/2 BPS Wilson loop operators recently introduced in arXiv:1506.07614. We perform a two-loop evaluation and find the same result for the two kinds of operators, so moving to higher loops a possible quantum uplift of the classical degeneracy. We also compute the 1/4 BPS bosonic Wilson loop and discuss the quantum version of the cohomological equivalence between fermionic and bosonic Wilson loops. We compare the perturbative result with the Matrix Model prediction and find perfect matching, after identification and remotion of a suitable framing factor. Finally, we discuss the potential appearance of three-loop contributions that might break the classical degeneracy and briefly analyze possible implications on the BPS nature of these operators.
Konishi Form Factor at Three Loop in ${\\cal N}=4$ SYM
Ahmed, Taushif; Dhani, Prasanna K; Rana, Narayan; Ravindran, V; Seth, Satyajit
2016-01-01
We present the first results on the third order corrections to on-shell form factor (FF) of the Konishi operator in ${\\cal N}=4$ supersymmetric Yang-Mills theory using Feynman diagrammatic approach in modified dimensional reduction ($\\overline {DR}$) scheme. We show that it satisfies KG equation in $\\overline {DR}$ scheme while the result obtained in four dimensional helicity (FDH) scheme needs to be suitably modified not only to satisfy the KG equation but also to get the correct ultraviolet (UV) anomalous dimensions. We find that the cusp, soft and collinear anomalous dimensions obtained to third order are same as those of the FF of the half-BPS operator confirming the universality of the infrared (IR) structures of on-shell form factors. In addition, the highest transcendental terms of the FF of Konishi operator are identical to those of half-BPS operator indicating the probable existence of deeper structure of the on-shell FF. We also confirm the UV anomalous dimensions of Konishi operator up to third ord...
Half-BPS half-BPS twist two at four loops in N=4 SYM
Eden, Burkhard
2016-01-01
We consider a double OPE limit of the planar four-point function of stress tensor multiplets in N = 4 SYM theory. Loop integrands for this correlator have been constructed to very high order, but the corresponding integrals are explicitly known only up to three loops. Fortunately, the double coincidence limit of the four-loop integrals can be found by the method of expansion by regions, which reduces the problem of computing the four-point integrals to the evaluation of a large set of massless propagator integrals. These can in turn be evaluated by IBP reduction. The OPE limit of the stress tensor four-point function allows us to extract the (square of the) three-point couplings between two stress tensor multiplets and one twist two operator in the 20' of SU(4). The latest available IBP software accomplishes this task up to and including spin 8. With the data obtained we hope to further the development of the recent integrable systems picture for correlation functions.
Multi-Loop Positivity of the Planar ${\\cal N}=4$ SYM Six-Point Amplitude
Dixon, Lance J; McLeod, Andrew J; Trnka, Jaroslav
2016-01-01
We study the six-point NMHV ratio function in planar ${\\cal N}=4$ SYM theory in the context of positive geometry. The Amplituhedron construction of the integrand for the amplitudes provides a kinematical region in which the integrand was observed to be positive. It is natural to conjecture that this property survives integration, i.e. that the final result for the ratio function is also positive in this region. Establishing such a result would imply that preserving positivity is a surprising property of the Minkowski contour of integration and it might indicate some deeper underlying structure. We find that the ratio function is positive everywhere we have tested it, including analytic results for special kinematical regions at one and two loops, as well as robust numerical evidence through five loops. There is also evidence for not just positivity, but monotonicity in a "radial" direction. We also investigate positivity of the MHV six-gluon amplitude. While the remainder function ceases to be positive at fou...
On the cusp anomalous dimension in the ladder limit of $\\mathcal N=4$ SYM
Beccaria, Matteo; Macorini, Guido
2016-01-01
We analyze the cusp anomalous dimension in the (leading) ladder limit of $\\mathcal N=4$ SYM and present new results for its higher-order perturbative expansion. We study two different limits with respect to the cusp angle $\\phi$. The first is the light-like regime where $x = e^{i\\,\\phi}\\to 0$. This limit is characterised by a non-trivial expansion of the cusp anomaly as a sum of powers of $\\log x$, where the maximum exponent increases with the loop order. The coefficients of this expansion have remarkable transcendentality features and can be expressed by products of single zeta values. We show that the whole logarithmic expansion is fully captured by a solvable Woods-Saxon like one-dimensional potential. From the exact solution, we extract generating functions for the cusp anomaly as well as for the various specific transcendental structures appearing therein. The second limit that we discuss is the regime of small cusp angle. In this somewhat simpler case, we show how to organise the quantum mechanical pert...
Multi-loop positivity of the planar N = 4 SYM six-point amplitude
Dixon, Lance J.; von Hippel, Matt; McLeod, Andrew J.; Trnka, Jaroslav
2017-02-01
We study the six-point NMHV ratio function in planar N = 4 SYM theory in the context of positive geometry. The Amplituhedron construction of the integrand for the amplitudes provides a kinematical region in which the integrand was observed to be positive. It is natural to conjecture that this property survives integration, i.e. that the final result for the ratio function is also positive in this region. Establishing such a result would imply that preserving positivity is a surprising property of the Minkowski contour of integration and it might indicate some deeper underlying structure. We find that the ratio function is positive everywhere we have tested it, including analytic results for special kinematical regions at one and two loops, as well as robust numerical evidence through five loops. There is also evidence for not just positivity, but monotonicity in a "radial" direction. We also investigate positivity of the MHV six-gluon amplitude. While the remainder function ceases to be positive at four loops, the BDS-like normalized MHV amplitude appears to be positive through five loops.
Liu, Haitao; Fang, Minghao; Huang, Zhaohui; Huang, Juntong; Liu, Yan-gai; Wu, Xiaowen
2016-08-01
Herein, ultralong silicon nitride nanowires were synthesized via a chemical vapor deposition method by using the low-cost quartz and silicon powder as raw materials. Simple processes were used for the fabrication of disordered and ordered nanowire membranes of pure silicon nitride nanowires. The nanowires in the disordered nanopapers are intertwined with each other to form a paper-like structure which exhibit excellent flame retardancy and mechanical properties. Fourier-transform infrared spectroscopy and thermal gravity analysis were employed to characterize the refractory performance of the disordered nanopapers. Highly ordered nanowire membranes were also assembled through a three-phase assembly approach which make the Si3N4 nanowires have potential use in textured ceramics and semiconductor field. Moreover, the surface nanowires can also be modified to be hydrophobic; this characteristic make the as-prepared nanowires have the potential to be assembled by the more effective Langmuir-Blodgett method and also make the disordered nanopapers possess a super-hydrophobic surface.
Transverse Momentum Broadening of a Fast Quark in a $\\N=4$ Yang Mills Plasma
Casalderrey-Solana, J; Casalderrey-Solana, Jorge; Teaney, Derek
2007-01-01
We compute the momentum broadening of a heavy fundamental charge propagating through a $\\mathcal{N}=4$ Yang Mills plasma at large t' Hooft coupling. We do this by expressing the medium modification of the probe's density matrix in terms of a Wilson loop averaged over the plasma. We then use the AdS/CFT correspondence to evaluate this loop, by identifying the dual semi-classical string solution. The calculation introduces the type ``1'' and type ``2'' fields of the thermal field theory and associates the corresponding sources with the two boundaries of the AdS space containing a black hole. The transverse fluctuations of the endpoints of the string determine $\\kappa_T = \\sqrt{\\gamma \\lambda} T^3 \\pi$ -- the mean squared momentum transfer per unit time. ($\\gamma$ is the lorentz gamma factor of the quark.) The result reproduces previous results for the diffusion coefficient of a heavy quark. We compare our results with previous AdS/CFT calculations of $\\hat{q}$.
Transverse momentum broadening of a fast quark in a Script N = 4 Yang-Mills plasma
Casalderrey-Solana, Jorge; Teaney, Derek
2007-04-01
We compute the momentum broadening of a heavy fundamental charge propagating through a Script N = 4 Yang Mills plasma at large t' Hooft coupling. We do this by expressing the medium modification of the probe's density matrix in terms of a Wilson loop averaged over the plasma. We then use the AdS/CFT correspondence to evaluate this loop, by identifying the dual semi-classical string solution. The calculation introduces the type ``1'' and type ``2'' fields of the thermal field theory and associates the corresponding sources with the two boundaries of the AdS space containing a black hole. The transverse fluctuations of the endpoints of the string determine κT = (γλ)1/2T3π—the mean squared momentum transfer per unit time. (γ is the Lorentz gamma factor of the quark.) The result reproduces previous results for the diffusion coefficient of a heavy quark. We compare our results with previous AdS/CFT calculations of hat q.
Multiple zeta functions and double wrapping in planar N=4 SYM
Leurent, Sébastien
2013-01-01
Using the FiNLIE solution of the AdS/CFT Y-system, we compute the anomalous dimension of the Konishi operator in planar N=4 SYM up to eight loops, i.e. up to the leading double wrapping order. At this order a non reducible Euler-Zagier sum, zeta(1,2,8), appears for the first time. We find that at all orders in perturbation, every spectral-dependent quantity of the Y-system is expressed through multiple Hurwitz zeta functions, hence we provide a Mathematica package to manipulate these functions, including the particular case of Euler-Zagier sums. Furthermore, we conjecture that only Euler-Zagier sums can appear in the answer for the anomalous dimension at any order in perturbation theory. We also resum the leading transcendentality terms of the anomalous dimension at all orders, obtaining a simple result in terms of Bessel functions. Finally, we demonstrate that exact Bethe equations should be related to an absence of poles condition that becomes especially nontrivial at double wrapping.