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Arthur C Reber, Vikas Chauhan, Shiv N Khanna
The removal of a single ligand from the magnetic Ni9Te6(L)8 (L = P(CH3)3, CO) clusters is found to quench the magnetic moment. The reduction in magnetic moment is caused by a geometric deformation of the Ni9Te6 core that breaks the octahedral symmetry of the cluster. This effect is observed in both the CO and phosphine based ligands. The octahedral symmetry bare cluster is also found to have a large magnetic moment. These results highlight the dilemma faced by magnetic ligand protected clusters whose symmetry has been broken: whether to break the spin symmetry as in Hund's rules or to break the spatial symmetry as in the Jahn-Teller effect...
January 14, 2017: Journal of Chemical Physics
M C Kirkegaard, J Langford, J Steill, B Anderson, A Miskowiec
Uranyl fluoride (UO2F2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R3¯m symmetry. The formally closed-shell electron structure of anhydrous UO2F2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies...
January 14, 2017: Journal of Chemical Physics
R E Goetz, T A Isaev, B Nikoobakht, R Berger, C P Koch
Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem., Int. Ed. 51, 4755 (2012) and C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionization of the photoselected molecules...
January 14, 2017: Journal of Chemical Physics
J Rehacek, M Paúr, B Stoklasa, Z Hradil, L L Sánchez-Soto
We establish the conditions to attain the ultimate resolution predicted by quantum estimation theory for the case of two incoherent point sources using a linear imaging system. The solution is closely related to the spatial symmetries of the detection scheme. In particular, for real symmetric point spread functions, any complete set of projections with definite parity achieves the goal.
January 15, 2017: Optics Letters
Jan Kuhnert, Arash Rahimi-Iman, Wolfram Heimbrodt
Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K', respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS2) monolayers at temperatures of 2 K...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
S Iacovo, A Stesmans, M Houssa, V V Afanas'ev
A low-temperature (T  =  1.5-8 K) electron paramagnetic resonance study of p-type 2H-polytype natural MoS2 crystals reveals a previously unreported anisotropic signal of corresponding defect density (spin S  =  ½) ~5  ×  10(14) cm(-3). For the applied magnetic field B//c-axis, the response is comprised of a single central asymmetric Zeeman peak at zero-crossing g  =  2.102(1), amid a symmetrically positioned hyperfine doublet of splitting 6.6(2) G. Field angular observations reveal a two-branch g pattern, indicative of a defect of lower than axial symmetry, likely orthorhombic (C 2v)...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Qiang Cheng, Yinhan Zhang, Kunhua Zhang, Biao Jin, Changlian Zhang
We study the discrete symmetries satisfied by helical p-wave superconductors with the d-vectors [Formula: see text] or [Formula: see text] and the transformations brought by symmetry operations to ferromagnet and spin-singlet superconductors, which show intimate associations with the transport properties in heterojunctions, including helical superconductors. In particular, the partial symmetries of the Hamiltonian under spin-rotation and gauge-rotation operations are responsible for the novel invariances of the conductance in tunnel junctions and the new selection rules for the lowest current and peculiar phase diagrams in Josephson junctions, which were reported recently...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Shuhua Peng, Bat-El Shani Pinchasik, Hao Hao, Helmuth Möhwald, Xuehua Zhang
Constructing controllable liquid patterns with high resolution and accuracy is of great importance in droplet depositions for a range of applications, such as 3D printing of optical and electronic devices, bio-microarrays, and highly efficient chemical conversion in compartment. Simple surface chemical micropatterns are popularly used to regulate the shape of liquid droplets and the final structure of deposited materials from droplet evaporation. Understanding the morphological transition of liquid at a very small amount on a substrate is essential for the design and control of droplet deposition processes...
January 12, 2017: Journal of Physical Chemistry Letters
Feng Shao, Benjamin Cahier, Eric Rivière, Régis Guillot, Nathalie Guihéry, Victoria E Campbell, Talal Mallah
This paper describes the correlation between Ising-type magnetic anisotropy and structure in trigonal bipyramidal Co(II) complexes. Three sulfur-containing trigonal bipyramidal Co(II) complexes were synthesized and characterized. It was shown that we can engineer the magnitude of the Ising anisotropy using ligand field theory arguments in conjunction with structural parameters. To prepare this series of compounds, we used, on the one hand, a tetradentate ligand containing three sulfur atoms and one amine (NS3(tBu)) and on the other hand three different axial ligands, namely, Cl(-), Br(-), and NCS(-)...
January 12, 2017: Inorganic Chemistry
Peter Spenst, Ryan M Young, Brian T Phelan, Michel Keller, Jakub Dostál, Tobias Brixner, Michael R Wasielewski, Frank Würthner
A series of semi-rigid perylene bisimide (PBI) macrocycles with varied ring size containing two to nine PBI chromophores were synthesized in a one-pot reaction and their photophysical properties were characterized by fluorescence, steady-state and transient absorption spectroscopy as well as femtosecond stimulated Raman spectroscopy. These macrocycles show solvent-dependent conformational equilibria and excited-state properties. In dichloromethane the macrocycles prevail in wide-stretched conformations and exhibit upon photoexcitation symmetry-breaking charge separation followed by charge recombination to triplet states, which photosensitize singlet oxygen formation...
January 12, 2017: Journal of the American Chemical Society
Hung Tan Pham, Devashis Majumdar, Jerzy Leszczynski, Minh Tho Nguyen
Geometries and electronic properties related to the ground state stabilities of several Si12M2 clusters (M: second-row (Nb and Mo) and third-row (Ta and W) transition metals, and their mixed bimetallic clusters M2: NbMo and TaW) were explored using density functional theory (DFT) computations. The computed results show that two different structural motifs emerge as the global energy minima of such clusters. They are basically singlet tubular structures in either a C2v prism ((1)A1) or a C6v antiprism ((1)A1) form...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
Mai Fujimoto, Migiwa Kanou, Kouichi Hosomi, Mitsutaka Takada
OBJECTIVE: The aim of this study was to examine the associations between angiotensin receptor blockers (ARBs) and the risk of 10 major cancers by employing different pharmacoepidemiological assessments. MATERIALS AND METHODS: Data from the first quarter of 2004 through 2012 were downloaded from the US Food and Drug Administration Adverse Event Reporting System (FAERS). The reporting odds ratio (ROR) and information component (IC) were used to detect the signals...
January 12, 2017: International Journal of Clinical Pharmacology and Therapeutics
Josephine Merker, Matthias Hartmann, Florian Kreuzpointner, Ansgar Schwirtz, Johannes-Peter Haas
OBJECTIVES: Postural control (PC) is fundamental for human movements. Different factors, such as injuries or diseases, can adversely affect PC. The purpose of this study was to evaluate PC in juvenile idiopathic arthritis (JIA) patients with different disease activity levels in comparison to healthy peers. METHODS: JIA patients with active and inactive lower limb joints (n=36 each group) were examined. Both groups have been on medication and have had physiotherapy for at least 5 years...
January 5, 2017: Clinical and Experimental Rheumatology
Alessio D'Errico, Maria Maffei, Bruno Piccirillo, Corrado de Lisio, Filippo Cardano, Lorenzo Marrucci
Optical singularities manifesting at the center of vector vortex beams are unstable, since their topological charge is higher than the lowest value permitted by Maxwell's equations. Inspired by conceptually similar phenomena occurring in the polarization pattern characterizing the skylight, we show how perturbations that break the symmetry of radially symmetric vector beams lead to the formation of a pair of fundamental and stable singularities, i.e. points of circular polarization. We prepare a superposition of a radial (or azimuthal) vector beam and a uniformly linearly polarized Gaussian beam; by varying the amplitudes of the two fields, we control the formation of pairs of these singular points and their spatial separation...
January 12, 2017: Scientific Reports
Jorg Bunemann, Florian Gebhard
Coulomb matrix elements are needed in all studies in solid-state theory that are based on Hubbard-type multi-orbital models. Due to symmetries, the matrix elements are not independent. We determine a set of independent Coulomb parameters for a $d$-shell and an $f$-shell and all point groups with up to $16$ elements ($O_h$, $O$, $T_d$, $T_h$, $D_{6h}$, and $D_{4h}$). Furthermore, we express all other matrix elements as a function of the independent Coulomb parameters. Apart from the solution of the general point-group problem we investigate in detail the spherical approximation and first-order corrections to the spherical approximation...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Guo-Yu Yang, Jia-Jia Wang, Qi Wei, Bai-Feng Yang
Two new copper borates with 3D supramolecular framework with mesoscale cavities have been made under solvothermal conditions, showing novel cubic supramolecular cages assembled by [(µ4-O)Cu4@B20O32(OH)8] ({Cu4@B20}) clusters with different point-group symmetry.
January 12, 2017: Chemistry: a European Journal
Joshua B Gross, Andrew Gangidine, Amanda K Powers
Craniofacial asymmetry is a convergent trait widely distributed across animals that colonize the extreme cave environment. Although craniofacial asymmetry can be discerned easily, other complex phenotypes (such as sensory organ position and numerical variation) are challenging to score and compare. Certain bones of the craniofacial complex demonstrate substantial asymmetry, and co-localize to regions harboring dramatically expanded numbers of mechanosensory neuromasts. To determine if a relationship exists between this expansion and bone fragmentation in cavefish, we developed a quantitative measure of positional symmetry across the left-right axis...
November 2016: Symmetry
Jacqueline Ann Palmer, Ryan Zarzycki, Susanne M Morton, Trisha M Kesar, Stuart A Binder-Macleod
Imbalance of corticomotor excitability between the paretic and nonparetic limbs has been associated with the extent of upper extremity motor recovery post-stroke, is greatly influenced by specific testing conditions such as the presence or absence of volitional muscle activation, and may vary across muscle groups. However, despite its clinical importance, post-stroke corticomotor drive to lower extremity muscles has not been thoroughly investigated. Additionally, while conventional gait rehabilitation strategies for stroke survivors focus on paretic limb foot drop and dorsiflexion impairments, most contemporary literature has indicated that paretic limb propulsion and plantarflexion impairments are the most significant limiters to post-stroke walking function...
January 11, 2017: Journal of Neurophysiology
Alexander A Tulub, Vassily E Stefanov
Despite the fact that DNA molecule is studied up and down, we know very little about the role of DNA triplets in coding amino acids and stop-codons. The paper aims to fill this gap through attracting spintronic ideas and carrying out QM/MM computations on a full-turn DNA fragment. The computations reveal two hidden symmetries: the spin splitting (the Rashba effect), confined within each triplet, and the quantum "phase" link between the triplet nature (in total, 64 triplets) and the corresponding amino acid and three stop-codons...
January 7, 2017: Journal of Theoretical Biology
Jelena Savić, Vladimir Dobričić, Katarina Nikolic, Sote Vladimirov, Sanda Dilber, Jasmina Brborić
Prediction of gastrointestinal absorption of thirteen newly synthesized β-hydroxy-β-arylalkanoic acids (HAA) and ibuprofen was performed using PAMPA test. The highest values of PAMPA parameters (%T and Papp) were calculated for 1C, 1B and 2C and these parameters were significantly lower in comparison to ibuprofen. QSPR analysis was performed in order to identify molecular descriptors with the highest influence on %T and -logPapp and to create models which could be used for the design of novel HAA with improved gastrointestinal absorption...
January 7, 2017: European Journal of Pharmaceutical Sciences
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