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Zorawar Wadiasingh, Alice K Harding, Christo Venter, Markus Böttcher, Matthew G Baring
Multiwavelength followup of unidentified Fermi sources has vastly expanded the number of known galactic-field "black widow" and "redback" millisecond pulsar binaries. Focusing on their rotation-powered state, we interpret the radio to X-ray phenomenology in a consistent framework. We advocate the existence of two distinct modes differing in their intrabinary shock orientation, distinguished by the phase-centering of the double-peaked X-ray orbital modulation originating from mildly-relativistic Doppler boosting...
April 20, 2017: Astrophysical Journal
Morgan P Kelley, Gauthier J-P Deblonde, Jing Su, Corwin H Booth, Rebecca J Abergel, Enrique R Batista, Ping Yang
The hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) is a promising agent for biological decorporation of radionuclides, and allows spectroscopic detection of many lanthanide (Ln) and actinide (An) species via sensitized luminescence. Despite the manifest uses of this ligand, the structural and thermodynamic properties of its complexes across the An series remain understudied. Theoretical investigations of the binding of An(III) and An(IV) ions, from actinium to einsteinium, by the 3,4,3-LI(1,2-HOPO) ligand, as well as experimental extended X-ray absorption fine structure (EXAFS) studies on the trivalent americium, curium, and californium complexes were employed to address the resulting structures, thermodynamic parameters, redox properties, and corresponding electronic configurations...
April 6, 2018: Inorganic Chemistry
Jessica A Clayton, Katharina Keller, Mian Qi, Julia Wegner, Vanessa Koch, Henrik Hintz, Adelheid Godt, Songi Han, Gunnar Jeschke, Mark S Sherwin, Maxim Yulikov
The magnetic properties of paramagnetic species with spin S > 1/2 are parameterized by the familiar g tensor as well as "zero-field splitting" (ZFS) terms that break the degeneracy between spin states even in the absence of a magnetic field. In this work, we determine the mean values and distributions of the ZFS parameters D and E for six Gd(iii) complexes (S = 7/2) and critically discuss the accuracy of such determination. EPR spectra of the Gd(iii) complexes were recorded in glassy frozen solutions at 10 K or below at Q-band (∼34 GHz), W-band (∼94 GHz) and G-band (240 GHz) frequencies, and simulated with two widely used models for the form of the distributions of the ZFS parameters D and E...
April 4, 2018: Physical Chemistry Chemical Physics: PCCP
Sahar Izadi Vishkayi, Meysam Bagheri Tagani
Experimental observation of borophene nanoribbons (BNRs) motivated us to carry out a comprehensive investigation on BNRs, decomposed from a χ3 sheet, using density functional theory. Our results show that the stability and also the electrical and magnetic properties of the ribbons are strongly dependent on the edge configurations. We have studied two categories of ribbon: XBNRs and YBNRs. The first one is a nonmagnetic metal with armchair shaped edges, while YBNRs can be magnetic or nonmagnetic depending on the edge shape...
April 4, 2018: Physical Chemistry Chemical Physics: PCCP
Guangqian Ding, Cong Wang, Guoying Gao, Kailun Yao, Chaochao Dun, Chunbao Feng, Dengfeng Li, Gang Zhang
High band degeneracy and glassy phonon transport are two remarkable features of highly efficient thermoelectric (TE) materials. The former promotes the power factor, while the latter aims to break the lower limit of lattice thermal conductivity through phonon scattering. Herein, we use the unique possibility offered by a two-dimensional superlattice-monolayer structure (SLM) to engineer the band degeneracy, charge density and phonon spectrum to maximize the thermoelectric figure of merit (ZT). First-principles calculations with Boltzmann transport equations reveal that the conduction bands of ZrSe2/HfSe2 SLM possess a highly degenerate level which gives a high n-type power factor; at the same time, the stair-like density of states yields a high Seebeck coefficient...
April 4, 2018: Nanoscale
Andrew Miskowiec
The DFT+U approach, where U is the Hubbard-like on-site Coulomb interaction, has successfully been used to improve the description of transition metal oxides and other highly correlated systems, including actinides. The secret of the DFT+U approach is the breaking of d or f shell orbital degeneracy and adding an additional energetic penalty to non-integer occupation of orbitals. A prototypical test case, UO2, benefits from the +U approach whereby the bare LDA method predicts UO2 to be a ferromagnetic metal, whereas LDA+U correctly predicts UO2 to be insulating...
April 3, 2018: Physical Chemistry Chemical Physics: PCCP
Gabriela I Depetri, Felipe A C Pereira, Boris Marin, Murilo S Baptista, J C Sartorelli
The dynamics of a parametric simple pendulum submitted to an arbitrary angle of excitation ϕ was investigated experimentally by simulations and analytically. Analytical calculations for the loci of saddle-node bifurcations corresponding to the creation of resonant orbits were performed by applying Melnikov's method. However, this powerful perturbative method cannot be used to predict the existence of odd resonances for a vertical excitation within first order corrections. Yet, we showed that period-3 resonances indeed exist in such a configuration...
March 2018: Chaos
Dhanushika Ratnayake, Morgan Newman, Michael Lardelli
OBJECTIVE: Repeat expansion of polyglutamine tracks leads to a group of inherited human neurodegenerative disorders. Studying such repetitive sequences is required to gain insight into the pathophysiology of these diseases. PCR-based manipulation of repetitive sequences, however, is challenging due to the absence of unique primer binding sites or the generation of non-specific products. RESULTS: We have utilised the degeneracy of the genetic code to generate a polyglutamine sequence with low repeat similarity...
March 27, 2018: BMC Research Notes
Wei-Tao Lu, Yun-Fang Li, Hong-Yu Tian
We study the spin- and valley-dependent energy band and transport property of silicene under a periodic potential, where both spin and valley degeneracies are lifted. It is found that the Dirac point, miniband, band gap, anisotropic velocity, and conductance strongly depend on the spin and valley indices. The extra Dirac points appear as the voltage potential increases, the critical values of which are different for electron with different spins and valleys. Interestingly, the velocity is greatly suppressed due to the electric field and exchange field, other than the gapless graphene...
March 23, 2018: Nanoscale Research Letters
HyunGi Cho, Suyong Yeon, Hyunga Choi, Nakju Doh
In a group of general geometric primitives, plane-based features are widely used for indoor localization because of their robustness against noises. However, a lack of linearly independent planes may lead to a non-trivial estimation. This in return can cause a degenerate state from which all states cannot be estimated. To solve this problem, this paper first proposed a degeneracy detection method. A compensation method that could fix orientations by projecting an inertial measurement unit's (IMU) information was then explained...
March 22, 2018: Sensors
C F Clauser, N R Arista
We present a study of the stopping power of plasmas using two main approaches: the collisional (scattering theory) and the dielectric formalisms. In the former case, we use a semiclassical method based on quantum scattering theory. In the latter case, we use the full description given by the extension of the Lindhard dielectric function for plasmas of all degeneracies. We compare these two theories and show that the dielectric formalism has limitations when it is used for slow heavy ions or atoms in dense plasmas...
February 2018: Physical Review. E
Shenglong Xu, Congjun Wu
Crystal structures and the Bloch theorem play a fundamental role in condensed matter physics. We extend the static crystal to the dynamic "space-time" crystal characterized by the general intertwined space-time periodicities in D+1 dimensions, which include both the static crystal and the Floquet crystal as special cases. A new group structure dubbed a "space-time" group is constructed to describe the discrete symmetries of a space-time crystal. Compared to space and magnetic groups, the space-time group is augmented by "time-screw" rotations and "time-glide" reflections involving fractional translations along the time direction...
March 2, 2018: Physical Review Letters
Chang-Hwan Yi, Julius Kullig, Jan Wiersig
One of the interesting features of open quantum and wave systems is the non-Hermitian degeneracy called an exceptional point, where not only energy levels but also the corresponding eigenstates coalesce. We demonstrate that such a degeneracy can appear in optical microdisk cavities by deforming the boundary extremely weakly. This surprising finding is explained by a semiclassical theory of dynamical tunneling. It is shown that the exceptional points come in nearly degenerated pairs, originating from the different symmetry classes of modes...
March 2, 2018: Physical Review Letters
Dmitry S Novikov, Jelle Veraart, Ileana O Jelescu, Els Fieremans
We develop a general analytical and numerical framework for estimating intra- and extra-neurite water fractions and diffusion coefficients, as well as neurite orientational dispersion, in each imaging voxel. By employing a set of rotational invariants and their expansion in the powers of diffusion weighting, we analytically uncover the nontrivial topology of the parameter estimation landscape, showing that multiple branches of parameters describe the measurement almost equally well, with only one of them corresponding to the biophysical reality...
March 12, 2018: NeuroImage
Guo Zhang, Wang-Ding Yuan, Ferdinand S Vilim, Elena V Romanova, Ke Yu, Si-Yuan Yin, Zi-Wei Le, Ying-Yu Xue, Ting-Ting Chen, Guo-Kai Chen, Song-An Chen, Elizabeth C Cropper, Jonathan V Sweedler, Klaudiusz R Weiss, Jian Jing
When individual neurons in a circuit contain multiple neuropeptides, these peptides can target different sets of follower neurons. This endows the circuit with a certain degree of flexibility. Here we identified a novel family of peptides, the Aplysia SPTR-Gene Family-Derived peptides (apSPTR-GF-DPs). We demonstrated apSPTR-GF-DPs, particularly apSPTR-GF-DP2, are expressed in the Aplysia CNS using immunohistochemistry and MALDI-TOF MS. apSPTR-GF-DP2 is present in single projection neurons, e.g., in the cerebral-buccal interneuron-12 (CBI-12)...
March 15, 2018: ACS Chemical Neuroscience
Sushanta Kumar Pal, P Senthilkumaran
The dependence of fringe contrast on the state of polarization (SOP) can be altered when more than two beams interfere, and it is possible to achieve high contrast fringes. We use a six-pinhole interferometer, in which a judicious choice (but not unique) of SOPs for the interfering beams is made to realize the lattice of C points at intensity nulls. These dark C points occur due to overlapping of singularities. These are not simply a minor variation of bright C points, in which the intensity dims to zero, but are poorly understood, unusual objects in their own right...
March 15, 2018: Optics Letters
Vadim I Agol, Anatoly P Gmyl
Reproduction of RNA viruses is typically error-prone due to the infidelity of their replicative machinery and the usual lack of proofreading mechanisms. The error rates may be close to those that kill the virus. Consequently, populations of RNA viruses are represented by heterogeneous sets of genomes with various levels of fitness. This is especially consequential when viruses encounter various bottlenecks and new infections are initiated by a single or few deviating genomes. Nevertheless, RNA viruses are able to maintain their identity by conservation of major functional elements...
June 2018: Microbiology and Molecular Biology Reviews: MMBR
Juan Carlos Estrada Saldaña, Yann-Michel Niquet, Jean-Pierre Cleuziou, Eduardo J H Lee, Diana Car, Sébastien R Plissard, Erik P A M Bakkers, Silvano De Franceschi
We report an experimental study of one-dimensional (1D) electronic transport in an InSb semiconducting nanowire. A total of three bottom gates are used to locally deplete the nanowire, creating a ballistic quantum point contact with only a few conducting channels. In a magnetic field, the Zeeman splitting of the corresponding 1D sub-bands is revealed by the emergence of conductance plateaus at multiples of e2 /h, yet we find a quantized conductance pattern largely dependent on the configuration of voltages applied to the bottom gates...
March 7, 2018: Nano Letters
Wenlong Gao, Biao Yang, Ben Tremain, Hongchao Liu, Qinghua Guo, Lingbo Xia, Alastair P Hibbins, Shuang Zhang
Nodal line semimetals (NLS) are three-dimensional (3D) crystals that support band crossings in the form of one-dimensional rings in the Brillouin zone. In the presence of spin-orbit coupling or lowered crystal symmetry, NLS may transform into Dirac semimetals, Weyl semimetals, or 3D topological insulators. In the photonics context, despite the realization of topological phases, such as Chern insulators, topological insulators, Weyl, and Dirac degeneracies, no experimental demonstration of photonic nodal lines (NLs) has been reported so far...
March 5, 2018: Nature Communications
Małgorzata Sternik, Urszula D Wdowik
Dynamical properties of the two-dimensional Ti2 C and Ti2 N MXenes were investigated using density functional theory and discussed in connection with their structures and electronic properties. To elucidate the influence of magnetic interactions on the fundamental properties of these systems, the nonmagnetic, ferromagnetic and three distinct antiferromagnetic spin arrangements on titanium sublattice were considered. Each magnetic configuration was also studied at two directions of the spin magnetic moment with respect to the MXene layer...
March 5, 2018: Physical Chemistry Chemical Physics: PCCP
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