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Lie symmetry

Christiane Binot, Jean-François Sadoc, Claude-Henri Chouard
Liquid crystals (LC) are an intermediate state between an ordered crystalline solid and a more disordered liquid. LCs (or mesophases) are ubiquitous in living systems, optimizing multiple biological functions that could not operate in purely solid or liquid environments as both mobility and organization are needed. One of us recently suggested that there is an information vector, shared by neurodegenerative and infectious pathologies, to be found within lipid rafts in an ordered liquid (Lo) form mediated by cholesterol...
July 2018: Heliyon
Joseph P Heindel, Elizabeth S Knodel, Daniel P Schofield
We have demonstrated the application of many-body expansions to calculations of the anharmonic, local-mode, OH-stretching vibrational frequencies of water clusters. We focused on five low-lying isomers of the water hexamer and the DD*(20,1) isomer of (H2 O)21 . Our approach provides accurate OH-stretching vibrational frequencies when treating one- and two-body interactions with the CCSD(T)-F12 level of theory and the three- and four-body interactions with the DF-MP2-F12 level. Additionally, we have investigated the physical origin of the large contribution that two- and three-body interactions make to the shifts of vibrational frequencies using symmetry-adapted perturbation theory (SAPT)...
August 8, 2018: Journal of Physical Chemistry. A
M E Sasin, A G Smolin, K-H Gericke, E Tokunaga, O S Vasyutinskii
This paper presents the detailed study of two-photon excited fluorescence in indole dissolved in propylene glycol produced by two-photon absorption from the molecular ground state to several high lying excited states. The experimental method involved excitation with linearly and circularly polarized femtosecond pulses and time-resolved detection of the polarized fluorescence decay. The fluorescence intensity, anisotropy, excited state lifetime, and rotation diffusion time as function of the excitation light wavelength in the spectral range 385-510 nm were determined in experiment...
August 1, 2018: Physical Chemistry Chemical Physics: PCCP
Joy Christian
The exceptional Lie group E 8 plays a prominent role in both mathematics and theoretical physics. It is the largest symmetry group associated with the most general possible normed division algebra, namely, that of the non-associative real octonions, which-thanks to their non-associativity-form the only possible closed set of spinors (or rotors) that can parallelize the 7-sphere. By contrast, here we show how a similar 7-sphere also arises naturally from the algebraic interplay of the graded Euclidean primitives, such as points, lines, planes and volumes, which characterize the three-dimensional conformal geometry of the ambient physical space, set within its eight-dimensional Clifford-algebraic representation...
May 2018: Royal Society Open Science
Christopher P Gordon, Satoru Shirase, Keishi Yamamoto, Richard A Andersen, Odile Eisenstein, Christophe Copéret
d0 metal-alkyl complexes (M = Ti, Zr, and Hf) show specific activity and selectivity in olefin polymerization and oligomerization depending on their ligand set and charge. Here, we show by a combined experimental and computational study that the 13 C NMR chemical shift tensors of the α-carbon of metal alkyls that undergo olefin insertion signal the presence of partial alkylidene character in the metal-carbon bond, which facilitates this reaction. The alkylidene character is traced back to the π-donating interaction of a filled orbital on the alkyl group with an empty low-lying metal d-orbital of appropriate symmetry...
June 26, 2018: Proceedings of the National Academy of Sciences of the United States of America
Davide Delmonte, Claudia Gori, Erica Lambruschi, Luciana Mantovani, Francesco Mezzadri, Danilo Bersani, Pier Paolo Lottici, Edmondo Gilioli, Massimo Solzi, Mario Tribaudino
We report a detailed study on the magnetic properties of the pyroxene series M2M1Si2 O6 , with M2  =  Ca and M1  =  Mg, where magnesium and then calcium are progressively substituted by cobalt. For cobalt site occupancy larger than 0.7 at the M1 site, a collinear antiferromagnetic phase is detected for T  <  T N1   =  12 K with a monodimensional character (i.e. M1 site intra-chain order parallel to c axis). Moreover the magnetization easy axis has been estimated to lie roughly along the [1 0 1] direction...
July 18, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Nadir Ghichi, Ali Benboudiaf, Yacine DJebli, Chawki Bensouici, Hocine Merazig
The whole mol-ecule of the title Schiff base compound, C34 H28 N2 O4 , is generated by mirror symmetry, with the mirror bis-ecting the central benzene ring. It was synthesized via the condensation reaction of 1,2-di-amine-benzene with 4-benz-yloxy-2-hy-droxy-benzaldehyde. The mol-ecule is V-shaped and there are two intra-molecular O-H⋯N hydrogen bonds present forming S (6) ring motifs. The configuration about the C=N imine bonds is E . The central benzene ring makes dihedral angles of 41.9 (2) and 43.6 (2)° with the phenol ring and the outer benz-yloxy ring, respectively...
May 1, 2018: Acta Crystallographica. Section E, Crystallographic Communications
Sandra Fusco, Angela Tuzi, Roberto Centore, Antonio Carella
Mol-ecules of the title compound, C24 H8 F4 N2 O8 , have C i point-group symmetry in the crystal, as they lie on crystallographic inversion centres ( Z ' = 1/2). The di-fluoro-phenyl ring is disordered over two orientations; the final refined occupancy factors of the two components of disorder are 0.947 (4) and 0.053 (4). In the crystal, some Car -H⋯F inter-actions are present, which involve the most acidic H atom of the mol-ecule.
February 1, 2018: Acta Crystallographica. Section E, Crystallographic Communications
Raphael F Ribeiro, Joel Yuen-Zhou
Explorations of the consequences of the Jahn-Teller (JT) effect remain active in solid-state and chemical physics. In this topical review we revisit the class of JT models which exhibit continuous vibronic symmetries. A treatment of these systems is given in terms of their algebraic properties. In particular, the compact symmetric spaces corresponding to JT models carrying a vibronic Lie group action are identified, and their invariants used to reduce their adiabatic potential energy surfaces into orbit spaces of the corresponding Lie groups...
August 22, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Duo Lin, Tianxun Gong, Zi-Yao Hong, Sufang Qiu, Jianji Pan, Chinh-Yu Tseng, Shangyuan Feng, Rong Chen, Kien Voon Kong
By taking advantage of the spectral properties of metal carbonyls, we have designed a surface-enhanced Raman spectroscopy (SERS) ratiometric assay for measuring cell-free circulating DNA (cfDNA) from Epstein-Barr virus in blood for nasopharyngeal carcinoma (NPC). This assay consists of a rhenium carbonyl (Re-CO) to serve as a DNA probe, an osmium carbonyl (Os-CO) embedded within the SERS-active substrate as an internal reference, and a streptavidin layer on the surface of the substrate. Hybridization of cfDNA with biotinylated-capture sequence leads to immobilization of cfDNA on the substrate...
June 19, 2018: Analytical Chemistry
Vivek Kumar, Manfred Reehuis, Andreas Hoser, Peter Adler, Claudia Felser
We have investigated the crystal and magnetic structure of Mn2 PtPd alloy using powder x-ray and neutron diffraction experiments. This compound is believed to belong to the Heusler family having crystal symmetry I4/mmm (TiAl3 -type). However, in this work we found that the Pd and Pt atoms are disordered and thus Mn2 PtPd crystallizes in the L10 structure having P4/mmm symmetry (CuAu-I type) like MnPt and MnPd binary alloys. The lattice constants are a  =  2.86 Å and c  =  3.62 Å at room temperature...
July 4, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Heli K Hyytiäinen, Sari H Mölsä, Jouni J T Junnila, Outi M Laitinen-Vapaavuori, Anna K Hielm-Björkman
This study aimed at developing a quantitative testing battery for dogs' stifle functionality, as, unlike in human medicine, currently none is available in the veterinary field. Forty-three dogs with surgically treated unilateral cranial cruciate ligament rupture and 21 dogs with no known musculoskeletal problems were included. Eight previously studied tests: compensation in sitting and lying positions, symmetry of thrust in hindlimbs when rising from lying and sitting, static weight bearing, stifle flexion and extension and muscle mass symmetry, were summed into the Finnish Canine Stifle Index (FCSI)...
May 19, 2018: Veterinary Record
François Gay-Balmaz, Darryl D Holm
Inspired by spatiotemporal observations from satellites of the trajectories of objects drifting near the surface of the ocean in the National Oceanic and Atmospheric Administration's "Global Drifter Program", this paper develops data-driven stochastic models of geophysical fluid dynamics (GFD) with non-stationary spatial correlations representing the dynamical behaviour of oceanic currents. Three models are considered. Model 1 from Holm (Proc R Soc A 471:20140963, 2015) is reviewed, in which the spatial correlations are time independent...
2018: Journal of Nonlinear Science
Mieke Wesdorp, Pia A M de Koning Gans, Margit Schraders, Jaap Oostrik, Martijn A Huynen, Hanka Venselaar, Andy J Beynon, Judith van Gaalen, Vitória Piai, Nicol Voermans, Michelle M van Rossum, Bas P Hartel, Stefan H Lelieveld, Laurens Wiel, Berit Verbist, Liselotte J Rotteveel, Marieke F van Dooren, Peter Lichtner, Henricus P M Kunst, Ilse Feenstra, Ronald J C Admiraal, Helger G Yntema, Lies H Hoefsloot, Ronald J E Pennings, Hannie Kremer
Unraveling the causes and pathomechanisms of progressive disorders is essential for the development of therapeutic strategies. Here, we identified heterozygous pathogenic missense variants of LMX1A in two families of Dutch origin with progressive nonsyndromic hearing impairment (HI), using whole exome sequencing. One variant, c.721G > C (p.Val241Leu), occurred de novo and is predicted to affect the homeodomain of LMX1A, which is essential for DNA binding. The second variant, c.290G > C (p.Cys97Ser), predicted to affect a zinc-binding residue of the second LIM domain that is involved in protein-protein interactions...
May 12, 2018: Human Genetics
Xinqiang Ji, Zhiwei Sun, Wenze Ouyang, Shenghua Xu
The dynamic process of homogenous nucleation in charged colloids is investigated by brute-force molecular dynamics simulation. To check if the liquid-solid transition will pass through metastable bcc, simulations are performed at the state points that definitely lie in the phase region of thermodynamically stable fcc. The simulation results confirm that, in all of these cases, the preordered precursors, acting as the seeds of nucleation, always have predominant bcc symmetry consistent with Ostwald's step rule and the Alexander-McTague mechanism...
May 7, 2018: Journal of Chemical Physics
Kiran Kumar, Shin M Woo, Thomas Siu, Wilian A Cortopassi, Fernanda Duarte, Robert S Paton
We have studied the cation-π interactions of neutral aromatic ligands with the cationic amino acid residues arginine, histidine and lysine using ab initio calculations, symmetry adapted perturbation theory (SAPT), and a systematic meta-analysis of all available Protein Data Bank (PDB) X-ray structures. Quantum chemical potential energy surfaces (PES) for these interactions were obtained at the DLPNO-CCSD(T) level of theory and compared against the empirical distribution of 2012 unique protein-ligand cation-π interactions found in X-ray crystal structures...
March 14, 2018: Chemical Science
Levi Gonçalves Dos Santos, Klaus Franzreb, Fernando R Ornellas
A high level theoretical investigation of the low-lying electronic states of the diatomic dications SrO2+ and SrH2+ is presented for the first time along with experimental results of their mass spectra where they were detected. A global and reliable picture of the potential energy curves of the electronic states and the associated spectroscopic parameters provide quantitative results attesting to the thermodynamic stability of both species. Inclusion of spin-orbit interactions does not significantly change the energetic characterization...
March 28, 2018: Journal of Chemical Physics
J Nieves, R Pavao, L Tolos
We have reviewed the renormalization procedure used in the unitarized coupled-channel model of Romanets et al. (Phys Rev D 85:114032, 2012), and its impact in the [Formula: see text], [Formula: see text], and [Formula: see text] sector, where five [Formula: see text] states have been recently observed by the LHCb Collaboration. The meson-baryon interactions used in the model are consistent with both chiral and heavy-quark spin symmetries, and lead to a successful description of the observed lowest-lying odd parity resonances [Formula: see text] and [Formula: see text], and [Formula: see text] and [Formula: see text] resonances...
2018: European Physical Journal. C, Particles and Fields
Jamie L Manson, Jamie Brambleby, Paul A Goddard, Peter M Spurgeon, Jacqueline A Villa, Junjie Liu, Saman Ghannadzadeh, Francesca Foronda, John Singleton, Tom Lancaster, Stewart J Clark, Iorwerth O Thomas, Fan Xiao, Robert C Williams, Francis L Pratt, Stephen J Blundell, Craig V Topping, Christopher Baines, Charles Campana, Bruce Noll
Strong hydrogen bonds such as F···H···F offer new strategies to fabricate molecular architectures exhibiting novel structures and properties. Along these lines and, to potentially realize hydrogen-bond mediated superexchange interactions in a frustrated material, we synthesized [H2 F]2 [Ni3 F6 (Fpy)12 ][SbF6 ]2 (Fpy = 3-fluoropyridine). It was found that positionally-disordered H2 F+ ions link neutral NiF2 (Fpy)4 moieties into a kagome lattice with perfect 3-fold rotational symmetry. Detailed magnetic investigations combined with density-functional theory (DFT) revealed weak antiferromagnetic interactions (J ~ 0...
March 16, 2018: Scientific Reports
Nicolas Algarra, Panagiotis G Karagiannopoulos, Arnaud Lazarus, Damien Vandembroucq, Evelyne Kolb
We study the quasistatic penetration of a flexible beam into a two-dimensional dense granular medium lying on a horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading and unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single nondimensional parameter L/L_{c}, which is the ratio of the length of the flexible beam L to L_{c}, a bending elastogranular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium...
February 2018: Physical Review. E
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