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https://www.readbyqxmd.com/read/28445071/polymorphic-assembly-from-beveled-gold-triangular-nanoprisms
#1
Juyeong Kim, Xiaohui Song, Fei Ji, Binbin Luo, Nicole F Ice, Qipeng Liu, Qiao Zhang, Qian Chen
The shape anisotropy of nanoparticle building blocks is of critical importance in determining their packing symmetry and assembly directionality. While there has been extensive research on the effect of their overall geometric shapes, the importance of nanometer morphology details is not well-recognized or understood. Here we draw on shape-anisotropic gold triangular nanoprism building blocks synthesized based on a method we recently developed; besides the "large-scale" triangular prism shape (79.8 nm in side length and 22...
April 26, 2017: Nano Letters
https://www.readbyqxmd.com/read/28415377/delay-induced-depinning-of-localized-structures-in-a-spatially-inhomogeneous-swift-hohenberg-model
#2
Felix Tabbert, Christian Schelte, Mustapha Tlidi, Svetlana V Gurevich
We report on the dynamics of localized structures in an inhomogeneous Swift-Hohenberg model describing pattern formation in the transverse plane of an optical cavity. This real order parameter equation is valid close to the second-order critical point associated with bistability. The optical cavity is illuminated by an inhomogeneous spatial Gaussian pumping beam and subjected to time-delayed feedback. The Gaussian injection beam breaks the translational symmetry of the system by exerting an attracting force on the localized structure...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28415291/experimental-demonstration-of-low-laser-plasma-instabilities-in-gas-filled-spherical-hohlraums-at-laser-injection-angle-designed-for-ignition-target
#3
Ke Lan, Zhichao Li, Xufei Xie, Yao-Hua Chen, Chunyang Zheng, Chuanlei Zhai, Liang Hao, Dong Yang, Wen Yi Huo, Guoli Ren, Xiaoshi Peng, Tao Xu, Yulong Li, Sanwei Li, Zhiwen Yang, Liang Guo, Lifei Hou, Yonggang Liu, Huiyue Wei, Xiangming Liu, Weiyi Cha, Xiaohua Jiang, Yu Mei, Yukun Li, Keli Deng, Zheng Yuan, Xiayu Zhan, Haijun Zhang, Baibin Jiang, Wei Zhang, Xuewei Deng, Jie Liu, Kai Du, Yongkun Ding, Xiaofeng Wei, Wanguo Zheng, Xiaodong Chen, E M Campbell, Xian-Tu He
Octahedral spherical hohlraums with a single laser ring at an injection angle of 55^{∘} are attractive concepts for laser indirect drive due to the potential for achieving the x-ray drive symmetry required for high convergence implosions. Laser-plasma instabilities, however, are a concern given the long laser propagation path in such hohlraums. Significant stimulated Raman scattering has been observed in cylindrical hohlraums with similar laser propagation paths during the ignition campaign on the National Ignition Facility (NIF)...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28411214/achiral-symmetry-breaking-and-positive-gaussian-modulus-lead-to-scalloped-colloidal-membranes
#4
Thomas Gibaud, C Nadir Kaplan, Prerna Sharma, Mark J Zakhary, Andrew Ward, Rudolf Oldenbourg, Robert B Meyer, Randall D Kamien, Thomas R Powers, Zvonimir Dogic
In the presence of a nonadsorbing polymer, monodisperse rod-like particles assemble into colloidal membranes, which are one-rod-length-thick liquid-like monolayers of aligned rods. Unlike 3D edgeless bilayer vesicles, colloidal monolayer membranes form open structures with an exposed edge, thus presenting an opportunity to study elasticity of fluid sheets. Membranes assembled from single-component chiral rods form flat disks with uniform edge twist. In comparison, membranes composed of a mixture of rods with opposite chiralities can have the edge twist of either handedness...
April 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28394313/structure-of-the-mycobacterial-esx-5-type-vii-secretion-system-membrane-complex-by-single-particle-analysis
#5
Katherine S H Beckham, Luciano Ciccarelli, Catalin M Bunduc, Haydyn D T Mertens, Roy Ummels, Wolfgang Lugmayr, Julia Mayr, Mandy Rettel, Mikhail M Savitski, Dmitri I Svergun, Wilbert Bitter, Matthias Wilmanns, Thomas C Marlovits, Annabel H A Parret, Edith N G Houben
Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids(1). To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also known as ESX) secretion systems(2). In Mycobacterium tuberculosis, these ESX systems are essential for growth and full virulence and therefore represent an attractive target for anti-tuberculosis drugs(3). However, the molecular details underlying type VII secretion are largely unknown, due to a lack of structural information...
April 10, 2017: Nature Microbiology
https://www.readbyqxmd.com/read/28390355/optimizing-the-formation-of-solid-solutions-with-components-of-different-shapes
#6
Fernando A Escobedo
A key challenge to engineer ordered solids from the co-assembly of two differently shaped building blocks is to predict the key particle characteristics that lead to maximal mutual ordered-phase compatibility (MaxOC). While both entropy disparity, as captured by the relative size of the components, and energetic inter-species selectivity affect MaxOC, it is the former whose effect is less intuitive and the main focus of this work. Such MaxOC predictive rules are formulated and validated by using Monte Carlo simulation results for hard-core mixtures of octahedra and spheres and of other previously studied mixtures...
April 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28388187/bilayer-graphene-as-a-platform-for-bosonic-symmetry-protected-topological-states
#7
Zhen Bi, Ruixing Zhang, Yi-Zhuang You, Andrea Young, Leon Balents, Chao-Xing Liu, Cenke Xu
Bosonic symmetry protected topological (BSPT) states, the bosonic analogue of topological insulators, have attracted enormous theoretical interest in the last few years. Although BSPT states have been classified by various approaches, there is so far no successful experimental realization of any BSPT state in two or higher dimensions. In this paper, we propose that a two-dimensional BSPT state with U(1)×U(1) symmetry can be realized in bilayer graphene in a magnetic field. Here the two U(1) symmetries represent total spin S^{z} and total charge conservation, respectively...
March 24, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28347722/testosterone-the-progesterone-estradiol-ratio-and-female-ratings-of-masculine-facial-fluctuating-asymmetry-for-a-long-term-relationship
#8
Leonor Hernández-López, Dafne M García-Granados, Roberto Chavira-Ramírez, Ricardo Mondragón-Ceballos
Idiosyncratic variation within the normal range of androgens levels in women account for significant variations in personality and behavior. We studied if testosterone introduces significant biases in women's perception of fluctuating symmetry of male faces suitability for a long-term relationship. Participants were 145 female college students asked to rate in a two-choice forced paradigm the attractiveness, suitability as a long-term partner, and economic success, fatherliness and fidelity of an asymmetric and a symmetric male face...
March 24, 2017: Physiology & Behavior
https://www.readbyqxmd.com/read/28342572/exploring-the-atomic-structure-of-1-8nm-monolayer-protected-gold-clusters-with-aberration-corrected-stem
#9
Jian Liu, Nan Jian, Isabel Ornelas, Alexander J Pattison, Tanja Lahtinen, Kirsi Salorinne, Hannu Häkkinen, Richard E Palmer
Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au144(SCH2CH2Ph)60 provided by two different research groups...
November 22, 2016: Ultramicroscopy
https://www.readbyqxmd.com/read/28334152/repeated-and-diverse-losses-of-corolla-bilateral-symmetry-in-the-lamiaceae
#10
Jinshun Zhong, Jill C Preston, Lena C Hileman, Elizabeth A Kellogg
Background and Aims: Independent evolution of derived complex characters provides a unique opportunity to assess whether and how similar genetic changes correlate with morphological convergence. Bilaterally symmetrical corollas have evolved multiple times independently from radially symmetrical ancestors and likely represent adaptations to attract specific pollinators. On the other hand, losses of bilateral corolla symmetry have occurred sporadically in various groups, due to either modification of bilaterally symmetrical corollas in late development or early establishment of radial symmetry...
March 1, 2017: Annals of Botany
https://www.readbyqxmd.com/read/28318225/in-plane-anisotropies-of-polarized-raman-response-and-electrical-conductivity-in-layered-tin-selenide
#11
Xiaolong Xu, Qingjun Song, Haifeng Wang, Pan Li, Kun Zhang, Yilun Wang, Kai Yuan, Zichen Yang, Yu Ye, Lun Dai
The group IV-VI compound tin selenide (SnSe) has recently attracted particular interest due to its unexpectedly low thermal conductivity and high power factor and shows great promise for thermoelectric applications. With an orthorhombic lattice structure, SnSe displays intriguing anisotropic properties due to the low symmetry of the puckered in-plane lattice structure. When thermoelectric materials, such as SnSe, have decreased dimensionality, their thermoelectric conversion efficiency may be improved due to increased power factor and decreased thermal conductivity...
March 28, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28306294/nonlinear-zel-dovich-effect-parametric-amplification-from-medium-rotation
#12
Daniele Faccio, Ewan M Wright
The interaction of light with rotating media has attracted recent interest for both fundamental and applied studies including rotational Doppler shift measurements. It is also possible to obtain amplification through the scattering of light with orbital angular momentum from a rotating and absorbing cylinder, as proposed by Zel'dovich more than forty years ago. This amplification mechanism has never been observed experimentally yet has connections to other fields such as Penrose superradiance in rotating black holes...
March 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28248487/practical-stereochemistry
#13
Richard M Kellogg
The relationship between fundamental and applied is often uneasy, particularly in modern political climates. A familiar political view, aimed negatively at the scientific community, is that the former is a waste of money whereas the latter gives value for investment. The answer that fundamental is required as the basis for practical suffers from the fact that the timelines between fundamental and practical are often long and the routes contorted and unexpected. This has been my experience. In this Account, examples are given from the research in which I have been involved wherein quite fundamental considerations have led to various applications...
March 1, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28240902/organic-cation-rotation-and-immobilization-in-pure-and-mixed-methylammonium-lead-halide-perovskites
#14
Oleg Selig, Aditya Sadhanala, Christian Müller, Robert Lovrincic, Zhuoying Chen, Yves L A Rezus, Jarvist M Frost, Thomas L C Jansen, Artem A Bakulin
Three-dimensional lead-halide perovskites have attracted a lot of attention due to their ability to combine solution processing with outstanding optoelectronic properties. Despite their soft ionic nature these materials demonstrate a surprisingly low level of electronic disorder resulting in sharp band edges and narrow distributions of the electronic energies. Understanding how structural and dynamic disorder impacts the optoelectronic properties of these perovskites is important for many applications. Here we combine ultrafast two-dimensional vibrational spectroscopy and molecular dynamics simulations to study the dynamics of the organic methylammonium (MA) cation orientation in a range of pure and mixed trihalide perovskite materials...
March 9, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28211709/pt-symmetric-real-dirac-fermions-and-semimetals
#15
Y X Zhao, Y Lu
Recently, Weyl fermions have attracted increasing interest in condensed matter physics due to their rich phenomenology originated from their nontrivial monopole charges. Here, we present a theory of real Dirac points that can be understood as real monopoles in momentum space, serving as a real generalization of Weyl fermions with the reality being endowed by the PT symmetry. The real counterparts of topological features of Weyl semimetals, such as Nielsen-Ninomiya no-go theorem, 2D subtopological insulators, and Fermi arcs, are studied in the PT symmetric Dirac semimetals and the underlying reality-dependent topological structures are discussed...
February 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28191927/foldectures-3d-molecular-architectures-from-self-assembly-of-peptide-foldamers
#16
Sung Hyun Yoo, Hee-Seung Lee
The wide range of fascinating supramolecular architectures found in nature, from DNA double helices to giant protein shells, inspires researchers to mimic the diverse shapes and functions of natural systems. Thus, a variety of artificial molecular platforms have been developed by assembling DNA-, peptide-, and protein-based building blocks for medicinal and biological applications. There has also been a significant interest in the research of non-natural oligomers (i.e., foldamers) that fold into well-defined secondary structures analogous to those found in proteins, because the assemblies of foldamers are expected not only to form biomimetic supramolecular architectures that resemble those of nature but also to display unique functions and unprecedented topologies at the same time due to their different folding propensities from those of natural building blocks...
February 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28185393/kibble-zurek-scaling-during-defect-formation-in-a-nematic-liquid-crystal
#17
Nicholas Fowler, Dr Ingo Dierking
Symmetry-breaking phase transitions are often accompanied by the formation of topological defects, as in cosmological theories of the early universe, superfluids, liquid crystals or solid-state systems. This scenario is described by the Kibble-Zurek mechanism, which predicts corresponding scaling laws for the defect density ρ. One such scaling law suggests a relation ρ≈τQ(-1/2) with τQ the change of rate of a control parameter. In contrast to the scaling of the defect density during annihilation with ρ≈t(-1) , which is governed by the attraction of defects of the same strength but opposite sign, the defect formation process, which depends on the rate of change of a physical quantity initiating the transition, has only rarely been investigated...
February 10, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28185330/smectic-layer-origami-via-preprogrammed-photoalignment
#18
Ling-Ling Ma, Ming-Jie Tang, Wei Hu, Ze-Qun Cui, Shi-Jun Ge, Peng Chen, Lu-Jian Chen, Hao Qian, Li-Feng Chi, Yan-Qing Lu
Hierarchical architecture is of vital importance in soft materials. Focal conic domains (FCDs) of smectic liquid crystals, characterized by an ordered lamellar structure, attract intensive attention. Simultaneously tailoring the geometry and clustering characteristics of FCDs remains a challenge. Here, the 3D smectic layer origami via a 2D preprogrammed photoalignment film is accomplished. Full control of hierarchical superstructures is demonstrated, including the domain size, shape, and orientation, and the lattice symmetry of fragmented toric FCDs...
April 2017: Advanced Materials
https://www.readbyqxmd.com/read/28182489/do-capuchin-monkeys-sapajus-apella-prefer-symmetrical-face-shapes
#19
Annika Paukner, Lauren J Wooddell, Carmen E Lefevre, Eric Lonsdorf, Elizabeth Lonsdorf
In humans, facial symmetry has been linked to an individual's genetic quality, and facial symmetry has a small yet significant effect on ratings of facial attractiveness. The same evolutionary processes underlying these phenomena may also convey a selective advantage to symmetrical individuals of other primate species, yet to date, few studies have examined sensitivity to facial symmetry in nonhuman primates. Here we presented images of symmetrical and asymmetrical human and monkey faces to tufted capuchin monkeys (Sapajus apella) and hypothesized that capuchins would visually prefer symmetrical faces of opposite-sex conspecifics...
February 2017: Journal of Comparative Psychology
https://www.readbyqxmd.com/read/28157123/a-three-dimensional-zn-ii-coordination-polymer-constructed-from-1-1-biphenyl-2-2-4-4-tetracarboxylate-and-1-4-bis-1h-imidazol-1-yl-benzene-ligands-exhibiting-photoluminescence
#20
Feng Su, Liping Lu, Chengyong Zhou, Xiaoxia Wang, Long Sun, Chun Han
Ligands based on polycarboxylic acids are excellent building blocks for the construction of coordination polymers; they may bind to a variety of metal ions and form clusters, as well as extended chain or network structures. Among these building blocks, biphenyltetracarboxylic acids (H4bpta) with C2 symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three-dimensional coordination polymer poly[(μ5-1,1'-biphenyl-2,2',4,4'-tetracarboxylato)bis[μ2-1,4-bis(1H-imidazol-1-yl)benzene]dizinc(II)], [Zn2(C16H6O8)(C12H10N4)]n, was synthesized solvothermally and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy...
February 1, 2017: Acta Crystallographica. Section C, Structural Chemistry
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