118,222 research outputs found
The Role of PSL(2, 7) in M‐theory: M2‐Branes, Englert Equation and the Septuples
No full textReconsidering the M2-brane solutions of (Formula presented.) supergravity with a transverse Englert flux introduced by one of us in 2016, we present a new purely group theoretical algorithm to solve Englert equation based on a specific embedding of the PSL(2, 7) group into (Formula presented.). The aforementioned embedding is singled out by the identification of PSL(2, 7) with the automorphism group of the Fano plane. Relying on the revealed intrinsic PSL(2, 7) symmetry of Englert equation and on the new algorithm we present an exhaustive classification of Englert fluxes. The residual supersymmetries of the corresponding M2-brane solutions associated with the first of the 8 classes into which we have partitioned Englert fluxes are exhaustively analyzed and we show that all residual (Formula presented.) supersymmetries with (Formula presented.) are available. Our constructions correspond to a particular case in the category of M2-brane solutions with transverse self-dual fluxes
1,10-Phenanthroline-5,6-dione Complexes of Middle Transition Elements: Mono- and Dinuclear Derivatives
No full textThe synthesis and the characterization of several mono- and dinuclear middle transition metal derivatives of 1,10-phenanthroline-
5,6-dione, 1, are presented. The reaction of 1 with CrCl2(THF)2 gives CrCl2(O,O0-C12H6N2O2)(THF)2, 2, while the halides of iron(II),
cobalt(II) and nickel(II) afford adducts of general formula MX2(N,N0-C12H6N2O2), M = Fe, 4, Co, 5, X = Cl; M = Ni, 6, X = Br. DFT
calculations on CrCl2(L)(THF)2 with L = O,O0-C12H6N2O2 or O,O0-C14H8O2 allowed a direct comparison of the coordination properties
of 9,10-phenanthrenequinone and 1,10-phenanthroline-5,6-dione to be made. Dinuclear compounds of general formula
CrCl2(THF)2(O,O0-C12H6N2O2-N,N0)MXnLm, M = Zr, 7, X = Cl, n = 4, m = 0; M = Cr, 8, X = Cl, n = 2, L = THF, m = 2;
M = Fe, 9, Co, 10, X = Cl, n = 2, m = 0; M=Ni, 11, X = Br, n = 2, m = 0, are prepared from 2 and the corresponding metal halide,
while VCp2(O,O0-C12H6N2O2-N,N0)FeCl2, 12, is synthesized by reacting 4 with VCp2. The electronic properties of the different complexes
are investigated by magnetic moment measurements and EPR spectroscopy
Self-consistent assessment of Englert-Schwinger model on atomic properties
No full textOur manuscript investigates a self-consistent solution of the statistical atom model proposed by Berthold-Georg Englert and Julian Schwinger (the ES model) and benchmarks it against atomic Kohn-Sham and two orbital-free models of the Thomas-Fermi-Dirac (TFD)-λvW family. Results show that the ES model generally offers the same accuracy as the well-known TFD-15vW model; however, the ES model corrects the failure in the Pauli potential near-nucleus region. We also point to the inability of describing low-Z atoms as the foremost concern in improving the present model.Peer reviewe
SYNTHESIS, REACTIVITY, AND CRYSTAL AND MOLECULAR-STRUCTURES OF NB(L)(ETA-6-C6H5-NXN)2B(C6H5-NXN)2, A CLASS OF MONONUCLEAR METAL-COMPOUNDS CONTAINING THE 12-ELECTRON-DONOR TETRAARYLBORATO LIGAND
No full textThe one-electron oxidation of Nb(mes)2 (mes = 1,3,5-trimethylbenzene) with ferrocenium tetraarylborate, produces the 16-electron [Nb(mes)2]+ cation, which adds disubstituted symmetrical alkynes to give the ionic compounds [Nb(mes)2)(alkyne)][Y] (alkyne = MeC2Me, Y = BPh4 (1a), Y = B(p-FC6H4)4 (1b), Y = B[3,5-(CF3)2C6H3]4 (1c); alkyne = PhC2Ph, Y = Bph4 (2a), Y = B(p-FC6H4)4 (2b)). 2b crystallizes in space group C2/c (No. 15) with four formula units in cells of dimensions a = 17.640(3) angstrom, b = 16.8386(8) angstrom, c = 19.616(2) angstrom, and beta = 97.230(9)degrees; the [Nb(mes)2(PhC2Ph)]+ cation contains bent eta6-mesitylene ligands, a coordination position being occupied by PhC2Ph as a formal two-electron donor. The alkyne in 1a-c is displaced by CO at room temperature and at atmospheric pressure to give the carbonyl derivatives [Nb-(mes)2CO][Y] (3a-c). Thermal treatment of 1a,b and 2a in toluene gave mesitylene displacement and formation of the neutral covalent compounds containing the uninegative tetraarylborato ligand of formula [Nb(RC2R)(eta6-C6H4X)2B(C6H4X)2] (R = Me, X = H (4a), X = p-F (4b); R = Ph, X = H (5a)). 4a crystallizes in space group P42(1)mBAR (No. 113), with two formula units in cells of dimensions a = 9.734(1) angstrom and c = 11.6333(9) angstrom; 4b crystallizes in space group P2(1)2(1)2, (No. 19) with eight formula units in cells of dimensions a = 11.776(3) angstrom, b = 15.666(3) angstrom, and c = 28.042(5) angstrom. 4a,b both contain the novel bonding arrangement of the tetraarylborato ligand with two interannularly niobium-bridged aryl rings. This new type of bonding is not restricted to the methyl-substituted (4a) or phenyl-substituted (4b) acetylenic derivatives: CO is also compatible with the new bonding arrangement. Alkyne displacement by CO gives the neutral covalent complex [Nb(CO)(eta6-C6H4X)2B(C6H4X)2] (X = H (6a), p-F (6b)). An X-ray diffractometric experiment on 6a has confirmed the novel bonding arrangement of the tetraarylborato ligand for this compound, which crystallizes in space group P2(1)2(1)2, (No. 19) with four formula units in cells of dimensions a = 10.495(2) A, b = 14.586(1) angstrom, and c = 17.174(3) angstrom
Fermion masses for the Englert solution on the round seven-sphere
No full textUsing a mass formula for Englert-type solutions on arbitrary coset spaces, we have found that if the coset is the round S7, no massless fermions exist. For this purpose we develop a method to decompose SO(8) representations with respect to spin(7), which enables us to compute the eigenvalues of the spin(7)-invariant differential operators in the mass matrix by using algebraic identities satisfied by them
Celebrations of National Anniversaries by Polish Political Emigration in Great Britain in the Light of Occasional Prints of Juliusz L. Englert
No full textNiniejszy artykuł zawiera prezentację wyników badań nad pracami Juliusza L. Englerta jako kronikarza emigracji, grafika i współautora programów obchodów rocznic narodowych. Podstawę źródłową tych rozważań stanowi szeroki dorobek publikacyjny Englerta, dostępny głównie w archiwach i bibliotekach polskich w Wielkiej Brytanii. Prace kronikarza są doskonałym materiałem poglądowym na temat genezy, okoliczności i przebiegu obchodów ważnych dla polskiego uchodźstwa wydarzeń z historii Polski.This article is a presentation of the results of research on the works of Juliusz L. Englert as a chronicler of the emigration, graphic artist and co-author of the programmes celebrating national historical anniversaries. The study is based on Englert’s extensive publishing output, available mainly in Polish archives and libraries in Great Britain. Englert’s works are excellent demonstrative material for a thorough analysis of the genesis, circumstances and course of the celebrations of events from Polish history important for the Polish people in exile
Synthesis, reactivity and structures of mono- and dihaloacetato complexes of copper(I) and copper(II)
No full textThe reactions of copper(I) oxide with the carboxylic acids CH3nXnCOOH (X/Cl, Br, n/1, 2; X/I, n/1) and dioxygen give
the corresponding haloacetates of copper(II) Cu(CH3nXnCOO)2 or Cu(CH3nXnCOO)2L, L/RCOOH, H2O. Lewis base
adducts of general formula Cu2(CH3nXnCOO)4L2 (X/Cl, n/1, L/THF; X/Cl, n/2, L/CH3CN; X/Br, n/1, L/py)
have been obtained and structurally characterized. They are dinuclear compounds showing the typical paddle-wheel dinuclear
structure, i.e., with four bridging haloacetato groups and two axial ligands. Monohaloacetato complexes of copper(I) have been
prepared by reacting Cu2O with CH2ClCOOH or by haloacetato exchange from Cu(CF3COO) in excellent (X/Cl, Br) or low (X/
I) yields. The copper(I) derivatives Cu(CH2XCOO) reversibly bind carbon monoxide both in the solid state and in toluene, the
carbonyl derivative Cu(CH2ClCOO)(CO) being quantitatively obtained by carbonylation of Cu(CH2ClCOO) in the solid state
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
[NB(B(ETA-6-C6H5)2(C6H5)2)(ETA-2-H3CC2CH3)] - THE 1ST COMPOUND WITH BENT TETRAPHENYLBORATE AS 12-ELECTRON DONOR LIGAND
No full textThe "counterion" BPh4- functions a sandwich ligand in the niobium(I) complex 1. This is confirmed by the X-ray structure analysis of 1a. The BPh4- complexes 1 are the first in which two of the four phenyl rings of the tetraphenylborate bind to one metal center. Such complexes could be important as model compounds for catalytic processes
REDOX REACTIONS OF VANADIUM(0) AND NIOBIUM(0) BIS(MESITYLENE) (MES) DERIVATIVES WITH METAL-CARBONYL HALIDES OF GROUP-7 - THE CRYSTAL AND MOLECULAR-STRUCTURE OF [MES(CO)(2)NB(MU-I)(2)RE(CO)(3)], A METAL-METAL BONDED HETEROBIMETALLIC COMPLEX
No full textRedox reactions of [M(eta(6)-1,3,5-Me(3)C(6)H(3))(2)], [Mmes(2)], (M = V or Nb) with [MX(CO)(5)] (M = Mn, X = Cl, Br, or I; M = Re, X = Br or I) leading to oxidation of the organometallic of Group 5 have been investigated. The crystal structure of [mes(CO)(2)Nb(mu-I)(2)Re(CO)(3)] 1b, has been solved by X-ray diffraction methods; the organometallic derivative can best be described as containing rhenium(0) and niobium(II) centres of d(7) and d(3) configurations, respectively, with a Nb-Re distance (average) of 2.921(4) Angstrom
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