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Giuseppe Zanotti, Francesca Vallese, Alberto Ferrari, Ilaria Menozzi, Tadeo E Saldaño, Paola Berto, Sebastian Fernandez-Alberti, Rodolfo Berni
The molecular symmetry of multimeric proteins is generally determined by using X-ray diffraction techniques, so that the basic question as to whether this symmetry is perfectly preserved for the same protein in solution remains open. In this work, human transthyretin (TTR), a homotetrameric plasma transport protein with two binding sites for the thyroid hormone thyroxine (T4), is considered as a case study. Based on the crystal structure of the TTR tetramer, a hypothetical D2 symmetry is inferred for the protein in solution, whose functional behavior reveals the presence of two markedly different Kd values for the two T4 binding sites...
2017: PloS One
Yannick Lefier, Roland Salut, Miguel Angel Suarez, Thierry Grosjean
As any physical particle or object, light undergoing a circular trajectory features a constant extrinsic angular momentum. Within strong curvatures, this angular momentum can match the spin momentum of a photon, thus providing the opportunity of a strong spin-orbit interaction. Using this effect, we demonstrate tunable symmetry breaking in the coupling of light into a curved nanoscale plasmonic waveguide. The helicity of the impinging optical wave controls the power distribution between the two counter-propagating subwavelength guided modes, including unidirectional waveguiding...
December 14, 2017: Nano Letters
Vladimir V Konotop, Dmitry A Zezyulin
We consider optical media, which feature antilinear symmetries. We show that (i) spectral singularities of such media (if any) are always self-dual, i.e., correspond to coherent perfect absorber lasers; (ii) under the change of a system parameter, the self-dual spectral singularity may split into a pair of isolated complex conjugate eigenvalues, which corresponds to an unconventional and overlooked, in the most of the previous studies, scenario of the phase transition (known as parity-time [PT]-symmetry breaking in systems obeying PT symmetry); (iii) if the antilinear symmetry is local, i...
December 15, 2017: Optics Letters
Giang-Nam Nguyen, Kevin Heggarty, Julien Le Meur, Andreas Bacher, Patrick Meyrueis
When building spot array binary Fourier diffractive optical elements (DOEs) having feature sizes on the order of the wavelength, we noticed remarkable variations in the experimental diffraction efficiency compared to the simulation results. Even with the use of high-cost electron beam lithography and rigorous Fourier modal method simulations, there appear to be no publications, to the best of our knowledge, showing close agreement in diffraction efficiency between the simulation and experimental results. In this Letter, we show that the diffraction symmetry of binary Fourier DOEs can be an efficient and consistent metric for evaluating the limit of the thin-element approximation and the effects of fabrication errors...
December 15, 2017: Optics Letters
Tao Wang, Xiaoning Pan, Zhanghang Zhu, Xiaoling Ji, Ke Cheng
The behavior of light waves on scattering from an ellipsoidal quasi-homogeneous particle with arbitrary orientation is discussed within the accuracy of the first-order Born approximation. It is shown that the orientation of a particle plays an important role for the spectral density and for the spectral degree of coherence of the scattered field. Numerical result shows that, when the ellipsoidal particle features rotational symmetry, the profile of the far zone distribution is governed by the polar angle of a particle's orientation, while the orientation of the far zone distribution is governed by the azimuthal angle of a particle's orientation...
December 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Simon J Woodings, Jochem W H Wolthaus, Bram van Asselen, J H Wilfred de Vries, Jan G M Kok, Jan J W Lagendijk, Bas W Raaymakers
Accurate small-field dosimetry is critical for a magnetic resonance linac (MRI-linac). The PTW 60019 microDiamond is close to an ideal detector for small field dosimetry due to its small physical size, high signal-to-noise ratio and approximate water equivalence. It is important to fully characterise the performance of the detector in a 1.5 T magnetic field prior to its use for MRI-linac commissioning and quality assurance. Standard techniques of detector testing have been implemented, or adapted where necessary to suit the capabilities of the MRI-linac...
December 14, 2017: Physics in Medicine and Biology
Aivaras Dirvanauskas, Rita Galavotti, Alessandro Lunghi, Alessio Nicolini, Fabrizio Roncaglia, Federico Totti, Andrea Cornia
The structure of pentachromium(ii) extended metal atom chain [Cr5(tpda)4Cl2] (2), which behaves as a single molecule magnet at low temperature, was investigated by Density Functional Theory (DFT) calculations and spectroscopic studies without the constraints of a crystal lattice (H2tpda = N2,N6-bis(pyridin-2-yl)pyridine-2,6-diamine). DFT studies both in the gas phase and including CH2Cl2 solvent effects indicate that an unsymmetric structure (C4 point group), with pairs of formally quadruply-bonded metal ions and one terminal metal center, is slightly more stable (2...
December 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Francesco Basso Basset, Sergio Bietti, Marcus Reindl, Luca Esposito, Alexey Fedorov, Daniel Huber, Armando Rastelli, Emiliano Bonera, Rinaldo Trotta, Stefano Sanguinetti
Several semiconductor quantum dot techniques have been investigated for the generation of entangled photon pairs. Among the other techniques, droplet epitaxy enables the control of the shape, size, density, and emission wavelength of the quantum emitters. However, the fraction of the entanglement-ready quantum dots that can be fabricated with this method is still limited to around 5%, and matching the energy of the entangled photons to atomic transitions-a promising route towards quantum networking-remains an outstanding challenge...
December 14, 2017: Nano Letters
Anna C Severin, Brendan J Burkett, Mark R McKean, Aaron N Wiegand, Mark G L Sayers
Background: The presence of pain during movement typically results in changes in technique. However, the physical properties of water, such as flotation, means that water-based exercise may not only reduce compensatory movement patterns but also allow pain sufferers to complete exercises that they are unable to perform on land. The purpose of this study was to assess bilateral kinematics during double-leg squats and single-leg squats on land and in water in individuals with unilateral anterior knee pain...
2017: BMC Sports Science, Medicine and Rehabilitation
Konstantinos N Blazakis, Maria Kosma, George Kostelenos, Luciana Baldoni, Marina Bufacchi, Panagiotis Kalaitzis
Background: The morphological analysis of olive leaves, fruits and endocarps may represent an efficient tool for the characterization and discrimination of cultivars and the establishment of relationships among them. In recent years, much attention has been focused on the application of molecular markers, due to their high diagnostic efficiency and independence from environmental and phenological variables. Results: In this study, we present a semi-automatic methodology of detecting various morphological parameters...
2017: Plant Methods
Karini B Dos Santos, Paulo C Barauce Bento, Gleber Pereira, Carl Payton, André L F Rodacki
The aims of this study were to investigate whether land-based and tethered swimming strength tests can explain swimming performance in 200-meter front crawl and, whether these tests were able to identify bilateral symmetry in force production. In the first session, eighteen swimmers completed a maximum effort 200 m front crawl swim (swimming performance) and 15 seconds maximal effort tethered front crawl swim. In the second session, participants performed the upper extremity isometric strength test. Peak force production of tethered swimming and isometric strength tests were significantly correlated for the strongest and weakest sides (r = 0...
December 2017: Journal of Sports Science & Medicine
Baichuan Duan, Xi-Ping Dong, Luis Porras, Kelly Vargas, John A Cunningham, Philip C J Donoghue
Early Cambrian Pseudooides prima has been described from embryonic and post-embryonic stages of development, exhibiting long germ-band development. There has been some debate about the pattern of segmentation, but this interpretation, as among the earliest records of ecdysozoans, has been generally accepted. Here, we show that the 'germ band' of P. prima embryos separates along its mid axis during development, with the transverse furrows between the 'somites' unfolding into the polar aperture of the ten-sided theca of Hexaconularia sichuanensis, conventionally interpreted as a scyphozoan cnidarian; co-occurring post-embryonic remains of ecdysozoans are unrelated...
December 20, 2017: Proceedings. Biological Sciences
Damien Morger, Franziska Zosel, Martin Bühlmann, Sara Züger, Maximilian Mittelviefhaus, Benjamin Schuler, Jeremy Luban, Markus G Grütter
Rhesus TRIM5α (rhTRIM5α) potently restricts replication of human immunodeficiency virus type 1 (HIV-1). Restriction is mediated through direct binding of the C-terminal B30.2 domain of TRIM5α to the assembled HIV-1 capsid core. This host-pathogen interaction involves multiple capsid molecules within the hexagonal HIV-1 capsid lattice. However, the molecular details of this interaction and the precise site at which the B30.2 domain binds remains largely unknown. The human orthologue of TRIM5α (hsTRIM5α) fails to block infection by HIV-1 both in vivo and in vitro This is thought to be due to differences in binding to the capsid lattice...
December 13, 2017: Journal of Virology
Josep M Ribó, David Hochberg, Joaquim Crusats, Zoubir El-Hachemi, Albert Moyano
Recent reports on both theoretical simulations and on the physical chemistry basis of spontaneous mirror symmetry breaking (SMSB), that is, asymmetric synthesis in the absence of any chiral polarizations other than those arising from the chiral recognition between enantiomers, strongly suggest that the same nonlinear dynamics acting during the crucial stages of abiotic chemical evolution leading to the formation and selection of instructed polymers and replicators, would have led to the homochirality of instructed polymers...
December 2017: Journal of the Royal Society, Interface
Everton H Souza, Fernanda V D Souza, Mônica L Rossi, Renan M Packer, Maria Amelia V Cruz-Barros, Adriana P Martinelli
Pollen morphology characterization is important in taxonomy, conservation and plant breeding, and pollen viability studies can support breeding programs. This study investigated pollen morphology and male fertility in 18 species of Bromeliaceae with ornamental potential. For morphological characterization, pollen grains were acetolyzed and characterization of exine was done using scanning and transmission electron microscopy. Pollen viability was investigated by in vitro germination and histochemical tests...
December 7, 2017: Anais da Academia Brasileira de Ciências
Zhiwei Ding, Jiawei Zhou, Bai Song, Vazrik Chiloyan, Mingda Li, Te-Huan Liu, Gang Chen
In the hydrodynamic regime, phonons drift with a nonzero collective velocity under a temperature gradient, reminiscent of viscous gas and fluid flow. The study of hydrodynamic phonon transport has spanned over half a century but has been mostly limited to cryogenic temperatures (~1 K) and more recently to low-dimensional materials. Here, we identify graphite as a three-dimensional material that supports phonon hydrodynamics at significantly higher temperatures (~100 K) based on first-principles calculations...
December 13, 2017: Nano Letters
Juergen Weizenecker
Calculating the dynamic properties of magnetization of single-domain particles is of great importance for the tomographic imaging modality known as magnetic particle imaging (MPI). Although the assumption of instantaneous thermodynamic equilibrium (Langevin function) after application of time-dependent magnetic fields is sufficient for understanding the fundamental behavior, it is essential to consider the finite response times of magnetic particles for optimizing or analyzing various aspects, e.g., interpreting spectra, optimizing MPI sequences, developing new contrasts, and evaluating simplified models...
December 13, 2017: Physics in Medicine and Biology
Nathan Dostart, Yangyang Liu, Miloš A Popović
A numerical method of solving for the elastic wave eigenmodes in acoustic waveguides of arbitrary cross-section is presented. Operating under the assumptions of linear, isotropic materials, it utilizes a finite-difference method on a staggered grid to solve for the acoustic eigenmodes (field and frequency) of the vector-field elastic wave equation with a given propagation constant. Free, fixed, symmetry, and anti-symmetry boundary conditions are implemented, enabling efficient simulation of acoustic structures with geometrical symmetries and terminations...
December 13, 2017: Scientific Reports
Jakub Kollar, Vladimir Frecer
During the last decades, the application of hybrid quantum mechanical/molecular mechanical (QM/MM) methods has been extended to the field of drug design. In principle, the approximate QM/MM approach offers a more complete description of drug-receptor non-covalent interactions. This is especially true when charge or proton transfer, chelation of metal ions or strong polarization of ligand and protein or surface chemical groups are involved. The aim of this work was to assess the accuracy of calculated non-covalent ligand-protein interaction energies ([Formula: see text]) obtained by the hybrid QM/MM approach employed in QSite/Jaguar of Schrödinger's Small-Molecule Drug Discovery Suite on a set of small-molecule model systems when compared to rigorous QM calculations...
December 12, 2017: Journal of Molecular Modeling
Mei-Ming Xie, Kang-Lai Tang, Chen-Song Yuan
Stage IIIc Kienböck's disease is a clinical challenge to treat collapse of the lunate bone. A new reconstructive surgery was described in one patient using 3D printing lunate prosthesis. The prosthesis shape was designed by tomographic image processing and segmentation using technology compared with the intact side matched by mirror symmetry and 3D post-processing technologies. The patient recovered nearly full range of motion of the wrist after 12 months. The visual analog scale scores and Cooney scores were 2 points and 91 points...
December 12, 2017: Archives of Orthopaedic and Trauma Surgery
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