Icosahedral quasicrystals of intermetallic compounds are icosahedral twins of cubic crystals of three kinds, consisting of large (about 5000 atoms) icosahedral complexes in either a cubic body-centered or a cubic face-centered arrangement or smaller (about 1350 atoms) icosahedral complexes in the β-tungsten arrangement

PubMed Central

Pauling, Linus

1989-01-01

The twofold-axis electron-diffraction photographs of icosahedral quasicrystals are of three kinds, reflecting three different structures of the cubic crystals that by icosahedral twinning form the quasicrystals. The first kind, represented by Al13Cu4Fe3, contains two very large icosahedral complexes, each of about 4680 atoms, in the body-centered arrangement, with six smaller icosahedral complexes (104 atoms each) in the principal interstices. The second kind, represented by Al5Mn, contains four of the very large complexes in the face-centered arrangement (cubic close packing), with four of the smaller clusters in the interstices. The third kind, represented by Al6CuLi3, contains eight icosahedral complexes, each of about 1350 atoms, in the β-W arrangement. The supporting evidence for these cubic structures is discussed as well as other evidence showing that the simple quasicrystal theory, which states that quasicrystals do not involve any translational identity operations, has to be modified. Images PMID:16594078

Shear response of Σ3{112} twin boundaries in face-centered-cubic metals

NASA Astrophysics Data System (ADS)

Wang, J.; Misra, A.; Hirth, J. P.

2011-02-01

Molecular statics and dynamics simulations were used to study the mechanisms of sliding and migration of Σ3{112} incoherent twin boundaries (ITBs) under applied shear acting in the boundary in the face-centered-cubic (fcc) metals, Ag, Cu, Pd, and Al, of varying stacking fault energies. These studies revealed that (i) ITBs can dissociate into two phase boundaries (PBs), bounding the hexagonal 9R phase, that contain different arrays of partial dislocations; (ii) the separation distance between the two PBs scales inversely with increasing stacking fault energy; (iii) for fcc metals with low stacking fault energy, one of the two PBs migrates through the collective glide of partials, referred to as the phase-boundary-migration (PBM) mechanism; (iv) for metals with high stacking energy, ITBs experience a coupled motion (migration and sliding) through the glide of interface disconnections, referred to as the interface-disconnection-glide (IDG) mechanism.

Design of new face-centered cubic high entropy alloys by thermodynamic calculation

NASA Astrophysics Data System (ADS)

Choi, Won-Mi; Jung, Seungmun; Jo, Yong Hee; Lee, Sunghak; Lee, Byeong-Joo

2017-09-01

A new face-centered cubic (fcc) high entropy alloy system with non-equiatomic compositions has been designed by utilizing a CALculation of PHAse Diagram (CALPHAD) - type thermodynamic calculation technique. The new alloy system is based on the representative fcc high entropy alloy, the Cantor alloy which is an equiatomic Co- Cr-Fe-Mn-Ni five-component alloy, but fully or partly replace the cobalt by vanadium and is of non-equiatomic compositions. Alloy compositions expected to have an fcc single-phase structure between 700 °C and melting temperatures are proposed. All the proposed alloys are experimentally confirmed to have the fcc single-phase during materials processes (> 800 °C), through an X-ray diffraction analysis. It is shown that there are more chances to find fcc single-phase high entropy alloys if paying attention to non-equiatomic composition regions and that the CALPHAD thermodynamic calculation can be an efficient tool for it. An alloy design technique based on thermodynamic calculation is demonstrated and the applicability and limitation of the approach as a design tool for high entropy alloys is discussed.

Face Centered Cubic SnSe as a Z2 Trivial Dirac Nodal Line Material

NASA Astrophysics Data System (ADS)

Tateishi, Ikuma; Matsuura, Hiroyasu

2018-07-01

The presence of a Dirac nodal line in a time-reversal and inversion symmetric system is dictated by the Z2 index when spin-orbit interaction is absent. In a first principles calculation, we show that a Dirac nodal line can emerge in Z2 trivial material by calculating the band structure of SnSe in a face centered cubic lattice as an example. We qualitatively show that it becomes a topological crystalline insulator when spin-orbit interaction is taken into account. We clarify the origin of the Dirac nodal line by obtaining irreducible representations corresponding to bands and explain the triviality of the Z2 index. We construct an effective model representing the Dirac nodal line using the k · p method, and discuss the Berry phase and a surface state expected from the Dirac nodal line.

Formation of fivefold deformation twins in nanocrystalline face-centered-cubic copper based on molecular dynamics simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, A. J.; Wei, Y. G.

2006-07-24

Fivefold deformation twins were reported recently to be observed in the experiment of the nanocrystalline face-centered-cubic metals and alloys. However, they were not predicted previously based on the molecular dynamics (MD) simulations and the reason was thought to be a uniaxial tension considered in the simulations. In the present investigation, through introducing pretwins in grain regions, using the MD simulations, the authors predict out the fivefold deformation twins in the grain regions of the nanocrystal grain cell, which undergoes a uniaxial tension. It is shown in their simulation results that series of Shockley partial dislocations emitted from grain boundaries providemore » sequential twining mechanism, which results in fivefold deformation twins.« less

Single crystal plastic behavior of a single-phase, face-center-cubic-structured, equiatomic FeNiCrCo alloy

DOE PAGES

Wu, Zhenggang; Gao, Y. F.; Bei, Hongbin

2015-07-25

To understand the fundamental deformation mechanisms of compositionally complex alloys, single crystals of a multi-component equiatomic FeNiCoCr alloy with face-centered cubic (FCC) structure were grown for mechanical studies. Similarly to typical FCC pure metals, slip trace analyses indicate that dislocation slips take place on (1 1 1) planes along [11¯0] directions. The critical resolved shear stress (CRSS) obeys the Schmid law at both 77 and 293 K, and tension–compression asymmetry is not observed. Although this material slips in a normal FCC manner both at 293 and 77 K, compared to typical FCC metals the CRSS’s strong temperature dependence is abnormal.

Bismuth doping strategies in GeTe nanowires to promote high-temperature phase transition from rhombohedral to face-centered cubic structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jie; Huang, Rong; Wei, Fenfen

2014-11-17

The phase transition of Bi-doped (∼3 at. %) GeTe nanowires from a rhombohedral (R) to a face-centered cubic (C) structure was observed in in situ high-temperature X-ray diffraction. The promotion of high-temperature R-C phase transition by a doping approach was revealed. Ab initio energy calculations of doped GeTe at various Bi doping concentrations were performed to interpret the promoted temperature-induced phase transitions. Those results indicated that the total energy differences between R and C structures of doped GeTe decreased as Bi doping concentrations increased, which facilitated R-C phase transitions.

Stacking fault energy of face-centered cubic metals: thermodynamic and ab initio approaches

NASA Astrophysics Data System (ADS)

Li, Ruihuan; Lu, Song; Kim, Dongyoo; Schönecker, Stephan; Zhao, Jijun; Kwon, Se Kyun; Vitos, Levente

2016-10-01

The formation energy of the interface between face-centered cubic (fcc) and hexagonal close packed (hcp) structures is a key parameter in determining the stacking fault energy (SFE) of fcc metals and alloys using thermodynamic calculations. It is often assumed that the contribution of the planar fault energy to the SFE has the same order of magnitude as the bulk part, and thus the lack of precise information about it can become the limiting factor in thermodynamic predictions. Here, we differentiate between the interfacial energy for the coherent fcc(1 1 1)/hcp(0 0 0 1) interface and the ‘pseudo-interfacial energy’ that enters the thermodynamic expression for the SFE. Using first-principles calculations, we determine the coherent and pseudo-interfacial energies for six elemental metals (Al, Ni, Cu, Ag, Pt, and Au) and three paramagnetic Fe-Cr-Ni alloys. Our results show that the two interfacial energies significantly differ from each other. We observe a strong chemistry dependence for both interfacial energies. The calculated pseudo-interfacial energies for the Fe-Cr-Ni steels agree well with the available literature data. We discuss the effects of strain on the description of planar faults via thermodynamic and ab initio approaches.

Stacking fault energy of face-centered cubic metals: thermodynamic and ab initio approaches.

PubMed

Li, Ruihuan; Lu, Song; Kim, Dongyoo; Schönecker, Stephan; Zhao, Jijun; Kwon, Se Kyun; Vitos, Levente

2016-10-05

The formation energy of the interface between face-centered cubic (fcc) and hexagonal close packed (hcp) structures is a key parameter in determining the stacking fault energy (SFE) of fcc metals and alloys using thermodynamic calculations. It is often assumed that the contribution of the planar fault energy to the SFE has the same order of magnitude as the bulk part, and thus the lack of precise information about it can become the limiting factor in thermodynamic predictions. Here, we differentiate between the interfacial energy for the coherent fcc(1 1 1)/hcp(0 0 0 1) interface and the 'pseudo-interfacial energy' that enters the thermodynamic expression for the SFE. Using first-principles calculations, we determine the coherent and pseudo-interfacial energies for six elemental metals (Al, Ni, Cu, Ag, Pt, and Au) and three paramagnetic Fe-Cr-Ni alloys. Our results show that the two interfacial energies significantly differ from each other. We observe a strong chemistry dependence for both interfacial energies. The calculated pseudo-interfacial energies for the Fe-Cr-Ni steels agree well with the available literature data. We discuss the effects of strain on the description of planar faults via thermodynamic and ab initio approaches.

Multiple-photon excitation of nitrogen vacancy centers in diamond

NASA Astrophysics Data System (ADS)

Ji, Peng; Balili, R.; Beaumariage, J.; Mukherjee, S.; Snoke, D.; Dutt, M. V. Gurudev

2018-04-01

We report the observation of multiphoton photoluminescence excitation (PLE) below the resonant energies of nitrogen vacancy (NV) centers in diamond. The quadratic and cubic dependence of the integrated fluorescence intensity as a function of excitation power indicates a two-photon excitation pathway for the NV- charge state and a three-photon process involved for the neutral NV0 charge state, respectively. Comparing the total multiphoton energy with its single-photon equivalent, the PLE spectra follows the absorption spectrum of single photon excitation. We also observed that the efficiency of photoluminescence for different charge states, as well as the decay time constant, was dependent on the excitation wavelength and power.

Ion-beam-induced magnetic and structural phase transformation of Ni-stabilized face-centered-cubic Fe films on Cu(100)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gloss, Jonas; Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, 616 69 Brno; Shah Zaman, Sameena

2013-12-23

Metastable face-centered cubic (fcc) Fe/Cu(100) thin films are good candidates for ion-beam magnetic patterning due to their magnetic transformation upon ion-beam irradiation. However, pure fcc Fe films undergo spontaneous transformation when their thickness exceeds 10 ML. This limit can be extended to approximately 22 ML by deposition of Fe at increased CO background pressures. We show that much thicker films can be grown by alloying with Ni for stabilizing the fcc γ phase. The amount of Ni necessary to stabilize nonmagnetic, transformable fcc Fe films in dependence on the residual background pressure during the deposition is determined and a phasemore » diagram revealing the transformable region is presented.« less

Diophantine Approach to the Classification of Two-Dimensional Lattices: Surfaces of Face-Centered Cubic Materials.

PubMed

Jenkins, Stephen J

2018-04-03

The long-range periodic order of a crystalline surface is generally represented by means of a two-dimensional Bravais lattice, of which only five symmetrically distinct types are possible. Here, we explore the circumstances under which each type may or may not be found at the surfaces of face-centered cubic materials and provide means by which the type of lattice may be determined with reference only to the Miller indices of the surface; the approach achieves formal rigor by focusing on the number theory of integer variables rather than directly upon real geometry. We prove that the {100} and {111} surfaces are, respectively, the only exemplars of square and triangular lattices. For surfaces exhibiting a single mirror plane, we not only show that rectangular and rhombic lattices are the only two possibilities, but also capture their alternation in terms of the parity of the indices. In the case of chiral surfaces, oblique lattices predominate, but rectangular and rhombic cases are also possible and arise according to well-defined rules, here partially recounted.

Inverse opal with an ultraviolet photonic gap

NASA Astrophysics Data System (ADS)

Ni, Peigen; Cheng, Bingying; Zhang, Daozhong

2002-03-01

Photonic crystals composed of TiO2 and air voids fabricated by the template method exhibit an ultraviolet photonic stop band (˜380 nm) in the Γ-L direction. Scanning electron microscopy images show that the inverse opal possesses face-centered-cubic symmetry with a lattice constant of 240 nm. The transmission spectra show that the change in transmittance is one order of magnitude in the gap, which is in accord with the reflection spectrum.

Energy-landscape paving for prediction of face-centered-cubic hydrophobic-hydrophilic lattice model proteins

NASA Astrophysics Data System (ADS)

Liu, Jingfa; Song, Beibei; Liu, Zhaoxia; Huang, Weibo; Sun, Yuanyuan; Liu, Wenjie

2013-11-01

Protein structure prediction (PSP) is a classical NP-hard problem in computational biology. The energy-landscape paving (ELP) method is a class of heuristic global optimization algorithm, and has been successfully applied to solving many optimization problems with complex energy landscapes in the continuous space. By putting forward a new update mechanism of the histogram function in ELP and incorporating the generation of initial conformation based on the greedy strategy and the neighborhood search strategy based on pull moves into ELP, an improved energy-landscape paving (ELP+) method is put forward. Twelve general benchmark instances are first tested on both two-dimensional and three-dimensional (3D) face-centered-cubic (fcc) hydrophobic-hydrophilic (HP) lattice models. The lowest energies by ELP+ are as good as or better than those of other methods in the literature for all instances. Then, five sets of larger-scale instances, denoted by S, R, F90, F180, and CASP target instances on the 3D FCC HP lattice model are tested. The proposed algorithm finds lower energies than those by the five other methods in literature. Not unexpectedly, this is particularly pronounced for the longer sequences considered. Computational results show that ELP+ is an effective method for PSP on the fcc HP lattice model.

Site occupancy of interstitial deuterium atoms in face-centred cubic iron

PubMed Central

Machida, Akihiko; Saitoh, Hiroyuki; Sugimoto, Hidehiko; Hattori, Takanori; Sano-Furukawa, Asami; Endo, Naruki; Katayama, Yoshinori; Iizuka, Riko; Sato, Toyoto; Matsuo, Motoaki; Orimo, Shin-ichi; Aoki, Katsutoshi

2014-01-01

Hydrogen composition and occupation state provide basic information for understanding various properties of the metal–hydrogen system, ranging from microscopic properties such as hydrogen diffusion to macroscopic properties such as phase stability. Here the deuterization process of face-centred cubic Fe to form solid-solution face-centred cubic FeDx is investigated using in situ neutron diffraction at high temperature and pressure. In a completely deuterized specimen at 988 K and 6.3 GPa, deuterium atoms occupy octahedral and tetrahedral interstitial sites with an occupancy of 0.532(9) and 0.056(5), respectively, giving a deuterium composition x of 0.64(1). During deuterization, the metal lattice expands approximately linearly with deuterium composition at a rate of 2.21 Å3 per deuterium atom. The minor occupation of the tetrahedral site is thermally driven by the intersite movement of deuterium atoms along the ‹111› direction in the face-centred cubic metal lattice. PMID:25256789

BDA: A novel method for identifying defects in body-centered cubic crystals.

PubMed

Möller, Johannes J; Bitzek, Erik

2016-01-01

The accurate and fast identification of crystallographic defects plays a key role for the analysis of atomistic simulation output data. For face-centered cubic (fcc) metals, most existing structure analysis tools allow for the direct distinction of common defects, such as stacking faults or certain low-index surfaces. For body-centered cubic (bcc) metals, on the other hand, a robust way to identify such defects is currently not easily available. We therefore introduce a new method for analyzing atomistic configurations of bcc metals, the BCC Defect Analysis (BDA). It uses existing structure analysis algorithms and combines their results to uniquely distinguish between typical defects in bcc metals. In essence, the BDA method offers the following features:•Identification of typical defect structures in bcc metals.•Reduction of erroneously identified defects by iterative comparison to the defects in the atom's neighborhood.•Availability as ready-to-use Python script for the widespread visualization tool OVITO [http://ovito.org].

Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavrentiev, M. Yu., E-mail: Mikhail.Lavrentiev@ukaea.uk; Nguyen-Manh, D.; Dudarev, S. L.

A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rathermore » than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.« less

Cubic Unit Cell Construction Kit.

ERIC Educational Resources Information Center

Mattson, Bruce

2000-01-01

Presents instructions for building a simple interactive unit-cell construction kit that allows for the construction of simple, body-centered, and face-centered cubic lattices. The lit is built from inexpensive and readily available materials and can be built in any number of sizes. (WRM)

Use of the Primitive Unit Cell in Understanding Subtle Features of the Cubic Closest-Packed Structure

ERIC Educational Resources Information Center

Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.

2008-01-01

One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…

Symmetry and Structure of Cubic Semiconductor Surfaces.

PubMed

Jenkins, Stephen J

2017-11-07

A systematic stereographic approach to the description of surface symmetry and structure, applied previously to face-centered cubic, body-centered cubic, and hexagonal close-packed metals, is here extended to the surfaces of diamond-structure and zinc-blende-structure semiconductors. A variety of symmetry-structure combinations are categorized and the chiral properties of certain cases emphasized. A general condition for nonpolarity in the surfaces of zincblende materials is also noted.

Size-dependent plastic deformation of twinned nanopillars in body-centered cubic tungsten

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Startt, Jacob K.; Payne, Thomas G.; Deo, Chaitanya S.; McDowell, David L.

2017-05-01

Compared with face-centered cubic metals, twinned nanopillars in body-centered cubic (BCC) systems are much less explored partly due to the more complicated plastic deformation behavior and a lack of reliable interatomic potentials for the latter. In this paper, the fault energies predicted by two semi-empirical interatomic potentials in BCC tungsten (W) are first benchmarked against density functional theory calculations. Then, the more accurate potential is employed in large scale molecular dynamics simulations of tensile and compressive loading of twinned nanopillars in BCC W with different cross sectional shapes and sizes. A single crystal, a twinned crystal, and single crystalline nanopillars are also studied as references. Analyses of the stress-strain response and defect nucleation reveal a strong tension-compression asymmetry and a weak pillar size dependence in the yield strength. Under both tensile and compressive loading, plastic deformation in the twinned nanopillars is dominated by dislocation slip on {110} planes that are nucleated from the intersections between the twin boundary and the pillar surface. It is also found that the cross sectional shape of nanopillars affects the strength and the initial site of defect nucleation but not the overall stress-strain response and plastic deformation behavior.

Face-centred cubic to body-centred cubic phase transformation under [1 0 0] tensile loading

NASA Astrophysics Data System (ADS)

Xie, Hongxian; Yu, Jiayun; Yu, Tao; Yin, Fuxing

2018-06-01

Molecular dynamics simulation was used to verify a speculation of the existence of a certain face-centred cubic (FCC) to body-centred cubic (BCC) phase transformation pathway. Four FCC metals, Ni, Cu, Au and Ag, were stretched along the [1 0 0] direction at various strain rates and temperatures. Under high strain rate and low temperature, and beyond the elastic limit, the bifurcation of the FCC phase occurred with sudden contraction along one lateral direction and expansion along the other lateral direction. When the lattice constant along the expansion direction converged with that of the stretched direction, the FCC phase transformed into an unstressed BCC phase. By reducing the strain rate or increasing the temperature, dislocation or 'momentum-induced melting' mechanisms began to control the plastic deformation of the FCC metals, respectively.

Optical chirality of achiral three-dimensional photonic crystals

NASA Astrophysics Data System (ADS)

Romanov, Sergei G.

2017-04-01

Extrinsic optical chirality in a form of the asymmetric transmission of circularly polarized light at the oblique light incidence has been observed in three-dimensional opal photonic crystals assembled from monodisperse polymer spheres in the closely packed face-centered-cubic lattice. This effect has been assigned to the translation-rotation symmetry of the lattice. The cross-polarization conversion of the circularly polarized light and the related asymmetry of the transmission of the inverted circularly polarized light have been demonstrated.

Three-dimensional periodic dielectric structures having photonic Dirac points

DOEpatents

Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

2015-06-02

The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

Chemical Insights into the Design and Development of Face-Centered Cubic Ruthenium Catalysts for Fischer-Tropsch Synthesis.

PubMed

Li, Wei-Zhen; Liu, Jin-Xun; Gu, Jun; Zhou, Wu; Yao, Si-Yu; Si, Rui; Guo, Yu; Su, Hai-Yan; Yan, Chun-Hua; Li, Wei-Xue; Zhang, Ya-Wen; Ma, Ding

2017-02-15

Ruthenium is a promising low-temperature catalyst for Fischer-Tropsch synthesis (FTS). However, its scarcity and modest specific activity limit its widespread industrialization. We demonstrate here a strategy for tuning the crystal phase of catalysts to expose denser and active sites for a higher mass-specific activity. Density functional theory calculations show that upon CO dissociation there are a number of open facets with modest barrier available on the face-centered cubic (fcc) Ru but only a few step edges with a lower barrier on conventional hexagonal-closest packed (hcp) Ru. Guided by theoretical calculations, water-dispersible fcc Ru catalysts containing abundant open facets were synthesized and showed an unprecedented mass-specific activity in the aqueous-phase FTS, 37.8 mol CO ·mol Ru -1 ·h -1 at 433 K. The mass-specific activity of the fcc Ru catalysts with an average size of 6.8 nm is about three times larger than the previous best hcp catalyst with a smaller size of 1.9 nm and a higher specific surface area. The origin of the higher mass-specific activity of the fcc Ru catalysts is identified experimentally from the 2 orders of magnitude higher density of the active sites, despite its slightly higher apparent barrier. Experimental results are in excellent agreement with prediction of theory. The great influence of the crystal phases on site distribution and their intrinsic activities revealed here provides a rationale design of catalysts for higher mass-specific activity without decrease of the particle size.

Optical properties of three-dimensional P(St-MAA) photonic crystals on polyester fabrics

NASA Astrophysics Data System (ADS)

Liu, Guojin; Zhou, Lan; Wu, Yujiang; Wang, Cuicui; Fan, Qinguo; Shao, Jianzhong

2015-04-01

The three-dimensional (3D) photonic crystals with face-centered cubic (fcc) structure was fabricated on polyester fabrics, a kind of soft textile materials quite different from the conventional solid substrates, by gravitational sedimentation self-assembly of monodisperse P(St-MAA) colloidal microspheres. The optical properties of structural colors on polyester fabrics were investigated and the position of photonic band gap was characterized. The results showed that the color-tuning ways of the structural colors from photonic crystals were in accordance with Bragg's law and could be modulated by the size of P(St-MAA) colloidal microspheres and the viewing angles. The L∗a∗b∗ values of the structural colors generated from the assembled polyester fabrics were in agreement with their reflectance spectra. The photonic band gap position of photonic crystals on polyester fabrics could be consistently confirmed by reflectance and transmittance spectra.

Effectively infinite optical path-length created using a simple cubic photonic crystal for extreme light trapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frey, Brian J.; Kuang, Ping; Hsieh, Mei-Li

A 900 nm thick TiO 2 simple cubic photonic crystal with lattice constant 450 nm was fabricated and used to experimentally validate a newly-discovered mechanism for extreme light-bending. Absorption enhancement was observed extending 1–2 orders of magnitude over that of a reference TiO 2 film. Several enhancement peaks in the region from 600–950 nm were identified, which far exceed both the ergodic fundamental limit and the limit based on surface-gratings, with some peaks exceeding 100 times enhancement. These results are attributed to radically sharp refraction where the optical path length approaches infinity due to the Poynting vector lying nearly parallelmore » to the photonic crystal interface. The observed phenomena follow directly from the simple cubic symmetry of the photonic crystal, and can be achieved by integrating the light-trapping architecture into the absorbing volume. These results are not dependent on the material used, and can be applied to any future light trapping applications such as phosphor-converted white light generation, water-splitting, or thin-film solar cells, where increased response in areas of weak absorption is desired.« less

Effectively infinite optical path-length created using a simple cubic photonic crystal for extreme light trapping

DOE PAGES

Frey, Brian J.; Kuang, Ping; Hsieh, Mei-Li; ...

2017-06-23

A 900 nm thick TiO 2 simple cubic photonic crystal with lattice constant 450 nm was fabricated and used to experimentally validate a newly-discovered mechanism for extreme light-bending. Absorption enhancement was observed extending 1–2 orders of magnitude over that of a reference TiO 2 film. Several enhancement peaks in the region from 600–950 nm were identified, which far exceed both the ergodic fundamental limit and the limit based on surface-gratings, with some peaks exceeding 100 times enhancement. These results are attributed to radically sharp refraction where the optical path length approaches infinity due to the Poynting vector lying nearly parallelmore » to the photonic crystal interface. The observed phenomena follow directly from the simple cubic symmetry of the photonic crystal, and can be achieved by integrating the light-trapping architecture into the absorbing volume. These results are not dependent on the material used, and can be applied to any future light trapping applications such as phosphor-converted white light generation, water-splitting, or thin-film solar cells, where increased response in areas of weak absorption is desired.« less

ITMO Photonics: center of excellence

NASA Astrophysics Data System (ADS)

Voznesenskaya, Anna; Bougrov, Vladislav; Kozlov, Sergey; Vasilev, Vladimir

2016-09-01

ITMO University, the leading Russian center in photonics research and education, has the mission to train highlyqualified competitive professionals able to act in conditions of fast-changing world. This paradigm is implemented through creation of a strategic academic unit ITMO Photonics, the center of excellence concentrating organizational, scientific, educational, financial, laboratory and human resources. This Center has the following features: dissemination of breakthrough scientific results in photonics such as advanced photonic materials, ultrafast optical and quantum information, laser physics, engineering and technologies, into undergraduate and graduate educational programs through including special modules into the curricula and considerable student's research and internships; transformation of the educational process in accordance with the best international educational practices, presence in the global education market in the form of joint educational programs with leading universities, i.e. those being included in the network programs of international scientific cooperation, and international accreditation of educational programs; development of mechanisms for the commercialization of innovative products - results of scientific research; securing financial sustainability of research in the field of photonics of informationcommunication systems via funding increase and the diversification of funding sources. Along with focusing on the research promotion, the Center is involved in science popularization through such projects as career guidance for high school students; interaction between student's chapters of international optical societies; invited lectures of World-famous experts in photonics; short educational programs in optics, photonics and light engineering for international students; contests, Olympics and grants for talented young researchers; social events; interactive demonstrations.

Comparison of the magnetic properties of metastable hexagonal close-packed Ni nanoparticles with those of the stable face-centered cubic Ni nanoparticles.

PubMed

Jeon, Yoon Tae; Moon, Je Yong; Lee, Gang Ho; Park, Jeunghee; Chang, Yongmin

2006-01-26

We report the first magnetic study of pure and metastable hexagonal close-packed (hcp) Ni nanoparticles (sample 1). We also produced stable face-centered cubic (fcc) Ni nanoparticles, as mixtures with the hcp Ni nanoparticles (samples 2 and 3). We compared the magnetic properties of the hcp Ni nanoparticles with those of the fcc Ni nanoparticles by observing the evolution of magnetic properties from those of the hcp Ni nanoparticles to those of the fcc Ni nanoparticles as the number of fcc Ni nanoparticles increased from sample 1 to sample 3. The blocking temperature (T(B)) of the hcp Ni nanoparticles is approximately 12 K for particle diameters ranging between 8.5 and 18 nm, whereas those of the fcc Ni nanoparticles are 250 and 270 K for average particle diameters of 18 and 26 nm, respectively. The hcp Ni nanoparticles seem to be antiferromagnetic for T < T(B) and paramagnetic for T > T(B). This is very different from the fcc Ni nanoparticles, which are ferromagnetic for T < T(B) and superparamagnetic for T > T(B). This unusual magnetic state of the metastable hcp Ni nanoparticles is likely related to their increased bond distance (2.665 angstroms), compared to that (2.499 angstroms) of the stable fcc Ni nanoparticles.

Formation of met-cars and face-centered cubic structures. Thermodynamically or kinetically controlled

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, S.; Guo, B.C.; Deng, H.T.

1994-05-18

On the basis of a series of experimental studies from our laboratory, it is well established that metallocarbohedrenes, or Met-Cars for short, are a stable class of cluster materials. To account for their exceptional stability, we initially proposed a pentagonal dodecahedron structure. This cage-like structure is consistent with all the experimental findings. In general, there are two possible structures that can be developed in these metal-carbon systems, i.e., Met-Cars and cubes. Since only one structural pattern is generally observed for one particular cluster system, it has been suggested that their thermodynamical stabilities might be responsible for the selective formation ofmore » specific structures, e.g., Met-Cars or fcc structures. Herein, we present new experimental results on the system of Nb[sub m]C[sub n] under various conditions. It is shown that the experimental conditions are extremely critical for the formation of either Met-Cars or cubic structures, as predicted by Reddy and Khanma. Moreover, the new data show that the cubic structures do not develop on top of Met-Cars, but rather, they grow independently. The experiments were performed by using both time-of-flight and quadrupole mass spectrometer techniques coupled with a laser vaporization source. 23 refs., 1 fig.« less

Experimental evidence of body centered cubic iron in Earth's core

NASA Astrophysics Data System (ADS)

Hrubiak, R.; Meng, Y.; Shen, G.

2017-12-01

The Earth's core is mainly composed of iron. While seismic evidence has shown a liquid outer core and a solid inner core, the crystalline nature of the solid iron at the core condition remains debated, largely due to the difficulties in experimental determination of exact polymorphs at corresponding pressure-temperature conditions. We have examined crystal structures of iron up to 220 GPa and 6000 K with x-ray diffraction using a double-sided laser heating system at HPCAT, Advanced Photon Source. The iron sample is confined in a small chamber surrounded by single crystal MgO. The laser power can be modulated together with temperature measurements. The modulated heating of iron in an MgO single crystal matrix allows for microstructure analysis during heating and after the sample is quenched. We present experimental evidence of a body-centered-cubic (BCC) iron from about 100 GPa and 3000 K to at least 220 GPa and 4000 K. The observed BCC phase may be consistent with a theoretically predicted BCC phase that is dynamically stable in similar pressure-temperature conditions [1]. We will discuss the stability region of the BCC phase and the melting curve of iron and their implications in the nature of the Earth's inner core. References: A. B. Belonoshko et al., Nat. Geosci., 1-6 (2017).

Optical Characterization of Light-Bending Mechanisms in Photonic Crystals with Simple Cubic Symmetry

NASA Astrophysics Data System (ADS)

Frey, Brian James

For much of Earth's history, light was reputed to be an intangible, intractable, and transient quantity, but our understanding of light has since been revolutionized. The flow of electromagnetic energy through space can today be manipulated with a degree of precision and control once only dreamed of; rapidly developing technologies can create, guide, bend, and detect light to produce useful energy and information. One field where these technologies are most relevant is the field of light trapping, which concerns the harvesting of incident photons within a limited space by scattering, slowing, or otherwise prolonging and enhancing their interaction with matter. Over the past few decades, a class of materials, called photonic crystals (PCs), has emerged that is ideally suited for this task. This is because their wavelength-scale periodicity in one, two, or three dimensions can be designed to alter the dispersion relation and photonic density-of-states in a controllable manner. In this work, a TiO2 simple cubic PC with high dielectric contrast ( > 4:1) is fabricated with a lattice constant of 450 nm, and a newly discovered light-trapping mechanism is demonstrated, which bends light by 90 degrees and enhances optical absorption by one to two orders-of-magnitude over that in a reference film of the same thickness. It is shown that, for wavelengths from 450-950 nm, the achievable enhancement factor for this structure surpasses the theoretical limit of 4n2 derived under the assumption of ergodic system by multiple times. These results derive directly from the symmetry of the simple cubic lattice and are fundamental in nature, not depending on the material used or on the method of fabrication. The light trapping capability of these PCs has straight-forward applications that would be useful in a variety of areas where increased light-matter interaction is desirable, such as white-light generation, thin-film solar cells, photocatalytic pollutant degradation and hydrogen fuel

Deformation-induced structural transition in body-centred cubic molybdenum

PubMed Central

Wang, S. J.; Wang, H.; Du, K.; Zhang, W.; Sui, M. L.; Mao, S. X.

2014-01-01

Molybdenum is a refractory metal that is stable in a body-centred cubic structure at all temperatures before melting. Plastic deformation via structural transitions has never been reported for pure molybdenum, while transformation coupled with plasticity is well known for many alloys and ceramics. Here we demonstrate a structural transformation accompanied by shear deformation from an original <001>-oriented body-centred cubic structure to a <110>-oriented face-centred cubic lattice, captured at crack tips during the straining of molybdenum inside a transmission electron microscope at room temperature. The face-centred cubic domains then revert into <111>-oriented body-centred cubic domains, equivalent to a lattice rotation of 54.7°, and ~15.4% tensile strain is reached. The face-centred cubic structure appears to be a well-defined metastable state, as evidenced by scanning transmission electron microscopy and nanodiffraction, the Nishiyama–Wassermann and Kurdjumov–Sachs relationships between the face-centred cubic and body-centred cubic structures and molecular dynamics simulations. Our findings reveal a deformation mechanism for elemental metals under high-stress deformation conditions. PMID:24603655

A canonical stability-elasticity relationship verified for one million face-centred-cubic structures.

PubMed

Maisel, Sascha B; Höfler, Michaela; Müller, Stefan

2012-11-29

Any thermodynamically stable or metastable phase corresponds to a local minimum of a potentially very complicated energy landscape. But however complex the crystal might be, this energy landscape is of parabolic shape near its minima. Roughly speaking, the depth of this energy well with respect to some reference level determines the thermodynamic stability of the system, and the steepness of the parabola near its minimum determines the system's elastic properties. Although changing alloying elements and their concentrations in a given material to enhance certain properties dates back to the Bronze Age, the systematic search for desirable properties in metastable atomic configurations at a fixed stoichiometry is a very recent tool in materials design. Here we demonstrate, using first-principles studies of four binary alloy systems, that the elastic properties of face-centred-cubic intermetallic compounds obey certain rules. We reach two conclusions based on calculations on a huge subset of the face-centred-cubic configuration space. First, the stiffness and the heat of formation are negatively correlated with a nearly constant Spearman correlation for all concentrations. Second, the averaged stiffness of metastable configurations at a fixed concentration decays linearly with their distance to the ground-state line (the phase diagram of an alloy at zero Kelvin). We hope that our methods will help to simplify the quest for new materials with optimal properties from the vast configuration space available.

The Symmetry and Packing Fraction of the Body Centered Tetragonal Structure

ERIC Educational Resources Information Center

Dunlap, Richard A.

2012-01-01

It is shown that for different ratios of lattice parameters, "c/a," the body centered tetragonal structure may be view as body centered tetragonal, body centered cubic, face centered cubic or hexagonal. This illustrates that the apparent symmetry of a lattice depends on the choice of the conventional unit cell.

Inverse opal photonic crystals with photonic band gaps in the visible and near-infrared

NASA Astrophysics Data System (ADS)

Jarvis, Brandon C.; Gilleland, Cody L.; Renfro, Tim; Gutierrez, Jose; Parikh, Kunjal; Glosser, R.; Landon, Preston B.

2005-08-01

Colloidal silica spheres with 200nm, 250nm, and 290nm diameters were self-assembled with single crystal crystallites 4-5mm wide and 10-15mm long. Larger spheres with diameters between 1000-2300nm were self-assembled with single crystal crystallites up to 1.5mm wide and 2mm long. The silica opals self-assembled vertically along the [100] direction of the face centered cubic lattice resulting in self-templated opals. Inverse opal photonic crystals with a partial band gap possessing a maximum in the near infrared at 3.8μm were constructed from opal templates composed of 2300nm diameter spheres with chalcogenide Ge33As12Se55 (AMTIR-1), a transparent glass in the near infrared with high refractive index. Inverse gold and gold/ polypropylene composite photonic crystals were fabricated from synthetic opal templates composed of 200-290nm silica spheres. The reflectance spectra and electrical conductance of the resulting structures is presented. Gold was infiltrated into opal templates as gold chloride and heat converted to metallic gold. Opals partially infiltrated with gold were co-infiltrated with polypropylene plastic for mechanical support prior to removal of the silica template with hydrofluoric acid.

Emission properties of body-centered cubic elemental metal photocathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Tuo; Rickman, Benjamin L., E-mail: brickm2@uic.edu; Schroeder, W. Andreas

2015-04-07

A first principles analysis of photoemission is developed to explain the lower than expected rms transverse electron momentum measured using the solenoid scan technique for the body-centered cubic Group Vb (V, Nb, and Ta) and Group VIb (Cr, Mo, and W) metallic photocathodes. The density functional theory based analysis elucidates the fundamental role that the electronic band structure (and its dispersion) plays in determining the emission properties of solid-state photocathodes and includes evaluation of work function anisotropy using a thin-slab method.

National Technology Center and photonics

NASA Astrophysics Data System (ADS)

Vlannes, Nickolas P.

1992-05-01

A National Technology Center is proposed in order to meet the international challenges to the economy and security of the United States. This center would be tasked with the acquisition, analysis, assessment, and dissemination of worldwide scientific and technical information and data; technology transfer to the United States; and research and development in information and library sciences and technology. The National Technology Center would form a national network linking centers of excellence and expertise, and maintain a national technology library. With these functions, the National Technology Center has inherent requirements for technologies based on photonics, and will further motivate developments in this field.

Structural coloration of chitosan-cationized cotton fabric using photonic crystals

NASA Astrophysics Data System (ADS)

Yavuz, G.; Zille, A.; Seventekin, N.; Souto, A. P.

2017-10-01

In this work, poly (styrene-methyl methacrylate-acrylic acid) P(St-MMA-AA) composite nanospheres were deposited onto chitosan-cationized woven cotton fabrics followed by a second layer of chitosan. The deposited photonic crystals (PCs) on the fabrics were evaluated for coating efficiency and resistance, chemical analysis and color variation by optical and SEM microscopy, ATR-FTIR, diffuse reflectance spectroscopy and washing fastness. Chitosan deposition on cotton fabric provided cationic groups on the fiber surface promoting electrostatic interaction with photonic crystals. SEM images of the washed samples indicate that the PCs are firmly coated on the cotton surface only in the chitosan treated sample. The photonic nanospheres show an average diameter of 280 nm and display a face-centered cubic closepacking structure with an average thickness of 10 μm. A further chitosan post-treatment enhances color yield of the samples due to the chitosan transparent covering layer that induce bright reflections where the angles of incidence and reflection are the same. After washing, no photonic crystal can be detected on control fabric surface. However, the sample that received a chitosan post-treatment showed a good washing fastness maintaining a reasonable degree of iridescence. Chitosan fills the spaces between the polymer spheres in the matrix stabilizing the photonic structure. Sizeable variations in lattice spacing will allow color variations using more flexible non-close-packed photonic crystal arrays in chitosan hydrogels matrices.

Cyclic strain rate effects in fatigued face-centred and body-centred cubic metals

NASA Astrophysics Data System (ADS)

Mughrabi, Haël

2013-09-01

The present work deals mainly with the effect and the use of strain rate and temperature changes during cyclic deformation as a means to obtain valuable information on the thermally activated dislocation glide processes, based on the assessment of reversible changes of the thermal effective stress and of transient changes of the athermal stress. The importance of closed-loop testing in true plastic strain control with constant cyclic plastic strain rate throughout the cycle is explained and emphasized, especially with respect to the case of strain rate sensitive materials. Stress responses of face-centred cubic and body-centred cubic (bcc) metals to cyclic strain rate changes are presented to illustrate that the deformation modes of these two classes of materials differ characteristically at temperatures below that the so-called knee temperature of bcc metals. When such tests are performed in cyclic saturation, the temperature and strain rate dependence of bcc metals can be measured very accurately on one and the same specimen, permitting a thorough analysis of thermal activation.

Bragg reflection band width and optical rotatory dispersion of cubic blue-phase liquid crystals

NASA Astrophysics Data System (ADS)

Yoshida, Hiroyuki; Anucha, Konkanok; Ogawa, Yasuhiro; Kawata, Yuto; Ozaki, Masanori; Fukuda, Jun-ichi; Kikuchi, Hirotsugu

2016-10-01

The Bragg reflection band width and optical rotatory dispersion of liquid crystalline cholesteric blue phases (BPs) I and II are compared by numerical simulations. Attention is paid to the wavelength regions for which the reflection bands with lowest photon energies appear, i.e., the [110 ] direction for BP I and the [100 ] direction for BP II. Finite difference time domain and 4 ×4 matrix calculations performed on the theoretical director tensor distribution of BPs with the same material parameters show that BP II, which has simple cubic symmetry, has a wider photonic band gap than BP I, which has body centered cubic symmetry, possibly due to the fact that the density of the double-twist cylinders in BP II are twice that in BP I. The theoretical results on the Bragg reflection band width are supported by reflectance measurements performed on BPs I and II for light incident along the [110 ] and [100 ] directions, respectively.

Cross-slip in face-centered cubic metals: a general Escaig stress-dependent activation energy line tension model

NASA Astrophysics Data System (ADS)

Malka-Markovitz, Alon; Mordehai, Dan

2018-02-01

Cross-slip is a dislocation mechanism by which screw dislocations can change their glide plane. This thermally activated mechanism is an important mechanism in plasticity and understanding the energy barrier for cross-slip is essential to construct reliable cross-slip rules in dislocation models. In this work, we employ a line tension model for cross-slip of screw dislocations in face-centred cubic (FCC) metals in order to calculate the energy barrier under Escaig stresses. The analysis shows that the activation energy is proportional to the stacking fault energy, the unstressed dissociation width and a typical length for cross-slip along the dislocation line. Linearisation of the interaction forces between the partial dislocations yields that this typical length is related to the dislocation length that bows towards constriction during cross-slip. We show that the application of Escaig stresses on both the primary and the cross-slip planes varies the typical length for cross-slip and we propose a stress-dependent closed form expression for the activation energy for cross-slip in a large range of stresses. This analysis results in a stress-dependent activation volume, corresponding to the typical volume surrounding the stressed dislocation at constriction. The expression proposed here is shown to be in agreement with previous models, and to capture qualitatively the essentials found in atomistic simulations. The activation energy function can be easily implemented in dislocation dynamics simulations, owing to its simplicity and universality.

Photonic crystals: Theory and device applications

NASA Astrophysics Data System (ADS)

Fan, Shanhui

In this thesis, first-principle frequency-domain and time-domain methods are developed and applied to investigate various properties and device applications of photonic crystals. In Chapter 2, I discuss the two numerical methods used to investigate the properties of photonic crystals. The first solves Maxwell's equations in the frequency domain, while the second solves the equations in the time domain. The frequency-domain method yields the frequency, polarization, symmetry, and field distribution of every eigenmode of the system; the time-domain method allows one to determine the temporal behavior of the modes. In Chapter 3, a new class of three-dimensional photonic crystal structures is introduced that is amenable for fabrication at submicron-length scales. The structures give rise to a 3D photonic bandgap. They consist of a layered structure in which a series of cylindrical air holes are etched at normal incidence. The calculation demonstrates the existence of a gap as large as 14% of the mid-gap frequency using Si, SiO2, and air; and 23% using Si and air. In Chapter 4, the bandstructure and transmission properties of three-dimensional metallodielectric photonic crystals are presented. The metallodielectric crystals are modeled as perfect electrical conducting objects embedded in dielectric media. We investigate the face-centered-cubic (fcc) lattice, and the diamond lattice. Partial gaps are predicted in the fcc lattice, in excellent agreement with recent experiments. Complete gaps are found in a diamond lattice of isolated metal spheres. The gaps appear between the second and third bands, and their sizes can be larger than 60% when the radius of the spheres exceeds 21% of the cubic unit cell size. In Chapter 5, I investigate the properties of resonant modes which arise from the introduction of local defects in two-dimensional (2D) and 3D photonic crystals. The properties of these modes can be controlled by changing the nature and the size of the defects. The

The effect of center-of-mass motion on photon statistics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yang; Zhang, Jun; Wu, Shao-xiong

2015-10-15

We analyze the photon statistics of a weakly driven cavity quantum electrodynamics system and discuss the effects of photon blockade and photon-induced tunneling by effectively utilizing instead of avoiding the center-of-mass motion of a two-level atom trapped in the cavity. With the resonant interaction between atom, photon and phonon, it is shown that the bunching and anti-bunching of photons can occur with properly driving frequency. Our study shows the influence of the imperfect cooling of atom on the blockade and provides an attempt to take advantage of the center-of-mass motion.

Three-Dimensional Self-Assembled Photonic Crystal Waveguide

NASA Astrophysics Data System (ADS)

Baek, Kang-Hyun

Photonic crystals (PCs), two- or three-dimensionally periodic, artificial, and dielectric structures, have a specific forbidden band for electromagnetic waves, referred to as photonic bandgap (PBG). The PBG is analogous to the electronic bandgap in natural crystal structures with periodic atomic arrangement. A well-defined and embedded planar, line, or point defect within the PCs causes a break in its structural periodicity, and introduces a state in the PBG for light localization. It offers various applications in integrated optics and photonics including optical filters, sharp bending light guides and very low threshold lasers. Using nanofabrication processes, PCs of the 2-D slab-type and 3-D layer-by-layer structures have been investigated widely. Alternatively, simple and low-cost self-assembled PCs with full 3-D PBG, inverse opals, have been suggested. A template with face centered cubic closed packed structure, opal, may initially be built by self-assembly of colloidal spheres, and is selectively removed after infiltrating high refractive index materials into the interstitials of spheres. In this dissertation, the optical waveguides utilizing the 3-D self-assembled PCs are discussed. The waveguides were fabricated by microfabrication technology. For high-quality colloidal silica spheres and PCs, reliable synthesis, self-assembly, and characterization techniques were developed. Its theoretical and experimental demonstrations are provided and correlated. They suggest that the self-assembled PCs with PBG are feasible for the applications in integrated optics and photonics.

CENTER CONDITIONS AND CYCLICITY FOR A FAMILY OF CUBIC SYSTEMS: COMPUTER ALGEBRA APPROACH.

PubMed

Ferčec, Brigita; Mahdi, Adam

2013-01-01

Using methods of computational algebra we obtain an upper bound for the cyclicity of a family of cubic systems. We overcame the problem of nonradicality of the associated Bautin ideal by moving from the ring of polynomials to a coordinate ring. Finally, we determine the number of limit cycles bifurcating from each component of the center variety.

Photonic band gap templating using optical interference lithography

NASA Astrophysics Data System (ADS)

Chan, Timothy Y. M.; Toader, Ovidiu; John, Sajeev

2005-04-01

We describe the properties of three families of inversion-symmetric, large photonic band-gap (PBG) template architectures defined by iso-intensity surfaces in four beam laser interference patterns. These templates can be fabricated by optical interference (holographic) lithography in a suitable polymer photo-resist. PBG materials can be synthesized from these templates using two stages of infiltration and inversion, first with silica and second with silicon. By considering point and space group symmetries to produce laser interference patterns with the smallest possible irreducible Brillouin zones, we obtain laser beam intensities, directions, and polarizations which generate a diamond-like (fcc) crystal, a novel body-centered cubic (bcc) architecture, and a simple-cubic (sc) structure. We obtain laser beam parameters that maximize the intensity contrasts of the interference patterns. This optimizes the robustness of the holographic lithography to inhomogeneity in the polymer photo-resist. When the optimized iso-intensity surface defines a silicon to air boundary (dielectric contrast of 11.9 to 1), the fcc, bcc, and sc crystals have PBG to center frequency ratios of 25%, 21%, and 11%, respectively. A full PBG forms for the diamond-like crystal when the refractive index contrast exceeds 1.97 to 1. We illustrate a noninversion symmetric PBG architecture that interpolates between a simple fcc structure and a diamond network structure. This crystal exhibits two distinct and complete photonic band gaps. We also describe a generalized class of tetragonal photonic crystals that interpolate between and extrapolate beyond the diamond-like crystal and the optimized bcc crystal. We demonstrate the extent to which the resulting PBG materials are robust against perturbations to the laser beam amplitudes and polarizations, and template inhomogeneity. The body centered cubic structure exhibits the maximum robustness overall.

3D holographic polymer photonic crystal for superprism application

NASA Astrophysics Data System (ADS)

Chen, Jiaqi; Jiang, Wei; Chen, Xiaonan; Wang, Li; Zhang, Sasa; Chen, Ray T.

2007-02-01

Photonic crystal based superprism offers a new way to design new optical components for beam steering and DWDM application. 3D photonic crystals are especially attractive as they could offer more control of the light beam based on the needs. A polygonal prism based holographic fabrication method has been demonstrated for a three-dimensional face-centered-cubic (FCC)-type submicron polymer photonic crystal using SU8 as the photo-sensitive material. Therefore antivibration equipment and complicated optical alignment system are not needed and the requirement for the coherence of the laser source is relaxed compared with the traditional holographic setup. By changing the top-cut prism structure, the polarization of the laser beam, the exposure and development conditions we can achieve different kinds of triclinic or orthorhombic photonic crystals on demand. Special fabrication treatments have been introduced to ensure the survivability of the fabricated large area (cm2) nano-structures. Scanning electron microscopy and diffraction results proved the good uniformity of the fabricated structures. With the proper design of the refraction prism we have achieved a partial bandgap for S+C band (1460-1565nm) in the [111] direction. The transmission and reflection spectra obtained by Fourier transform infrared spectroscopy (FTIR) are in good agreement with simulated band structure. The superprism effects around 1550nm wavelength for the fabricated 3D polymer photonic crystal have been theoretically calculated and such effects can be used for beam steering purpose.

Dynamics of Single-Photon Emission from Electrically Pumped Color Centers

NASA Astrophysics Data System (ADS)

Khramtsov, Igor A.; Agio, Mario; Fedyanin, Dmitry Yu.

2017-08-01

Low-power, high-speed, and bright electrically driven true single-photon sources, which are able to operate at room temperature, are vital for the practical realization of quantum-communication networks and optical quantum computations. Color centers in semiconductors are currently the best candidates; however, in spite of their intensive study in the past decade, the behavior of color centers in electrically controlled systems is poorly understood. Here we present a physical model and establish a theoretical approach to address single-photon emission dynamics of electrically pumped color centers, which interprets experimental results. We support our analysis with self-consistent numerical simulations of a single-photon emitting diode based on a single nitrogen-vacancy center in diamond and predict the second-order autocorrelation function and other emission characteristics. Our theoretical findings demonstrate remarkable agreement with the experimental results and pave the way to the understanding of single-electron and single-photon processes in semiconductors.

Decomposition of algebraic sets and applications to weak centers of cubic systems

NASA Astrophysics Data System (ADS)

Chen, Xingwu; Zhang, Weinian

2009-10-01

There are many methods such as Gröbner basis, characteristic set and resultant, in computing an algebraic set of a system of multivariate polynomials. The common difficulties come from the complexity of computation, singularity of the corresponding matrices and some unnecessary factors in successive computation. In this paper, we decompose algebraic sets, stratum by stratum, into a union of constructible sets with Sylvester resultants, so as to simplify the procedure of elimination. Applying this decomposition to systems of multivariate polynomials resulted from period constants of reversible cubic differential systems which possess a quadratic isochronous center, we determine the order of weak centers and discuss the bifurcation of critical periods.

Two-dimensional photonic crystal slab nanocavities on bulk single-crystal diamond

NASA Astrophysics Data System (ADS)

Wan, Noel H.; Mouradian, Sara; Englund, Dirk

2018-04-01

Color centers in diamond are promising spin qubits for quantum computing and quantum networking. In photon-mediated entanglement distribution schemes, the efficiency of the optical interface ultimately determines the scalability of such systems. Nano-scale optical cavities coupled to emitters constitute a robust spin-photon interface that can increase spontaneous emission rates and photon extraction efficiencies. In this work, we introduce the fabrication of 2D photonic crystal slab nanocavities with high quality factors and cubic wavelength mode volumes—directly in bulk diamond. This planar platform offers scalability and considerably expands the toolkit for classical and quantum nanophotonics in diamond.

Lattice softening in body-centered-cubic lithium-magnesium alloys

NASA Astrophysics Data System (ADS)

Winter, I. S.; Tsuru, T.; Chrzan, D. C.

2017-08-01

A first-principles investigation of the influence of lattice softening on lithium-magnesium alloys near the body-centered-cubic (bcc)/hexagonal close-packed (hcp) transition composition is presented. Results show that lithium-magnesium alloys display a softening of the shear modulus C11-C12 , and an acoustic phonon branch between the Γ and N high symmetry points, as the composition approaches the stability limit for the bcc phase. This softening is accompanied by an increase in the size of the dislocation core region. Ideal tensile strength calculations predict that ordered phases of lithium-magnesium alloys are intrinsically brittle. Methods to make the alloys more ductile are discussed, and the propensity for these alloys to display gum-metal-like behavior is assessed.

Issues faced by community health centers.

PubMed

Grover, Jane

2009-05-01

Federally qualified health centers face numerous issues with regard to marketplace competition, staffing, and reimbursement streams that assure financial viability. Positioning the dental department of a health center to a high community profile strengthens the health center in professional educational development leading to a pipeline of workforce members, effective dental directors, and innovative fund-raising. A new dental team member developed by the American Dental Association can be utilized in health centers to make all traditional auxiliaries more productive.

Structural coloration of chitosan coated cellulose fabrics by electrostatic self-assembled poly (styrene-methyl methacrylate-acrylic acid) photonic crystals.

PubMed

Yavuz, Gönül; Zille, Andrea; Seventekin, Necdet; Souto, Antonio P

2018-08-01

The structural coloration of a chitosan-coated woven cotton fabric obtained by glutaraldehyde-stabilized deposition of electrostatic self-assembled monodisperse and spherically uniform (250 nm) poly (styrene-methyl methacrylate-acrylic acid) photonic crystal nanospheres (P(St-MMA-AA)) was investigated. Bright iridescent coatings displaying different colors in function of the viewing angle were obtained. The SEM, diffuse reflectance spectroscopy, TGA, DSC and FTIR analyses confirm the presence of structural color and the glutaraldehyde and chitosan ability to provide durable chemical bonding between cotton fabric and photonic crystal (PCs) coating with the highest degradation temperature and the lowest enthalpy. The coatings are characterized by a mixture of face-centered cubic and hexagonal close-packed arrays alternating random packing regions. For the first time a cost-efficient structural coloration with high washing and light fastness using self-assembled P(St-MMA-AA) photonic crystals was successfully developed onto woven cotton fabric using chitosan and/or glutaraldehyde as stabilizing agent opening new strategies for the development of dye-free coloration of textiles. Copyright © 2018 Elsevier Ltd. All rights reserved.

Learner-Centered Teaching Style: Comparing Face-to-Face and Online Adult Educators' Commitment Levels

ERIC Educational Resources Information Center

Edwards, Shanda E.

2013-01-01

For at least 50 years, prominent adult learning theorists have recommended that adult educators commit to a learner-centered teaching approach. Extensive teaching styles research has been conducted on face-to-face and online adult educators, albeit separately, to examine their commitment levels to the learner-centered style. In addition, there has…

Texture evolution and mechanical behaviour of irradiated face-centred cubic metals

NASA Astrophysics Data System (ADS)

Chen, L. R.; Xiao, X. Z.; Yu, L.; Chu, H. J.; Duan, H. L.

2018-02-01

A physically based theoretical model is proposed to investigate the mechanical behaviour and crystallographic texture evolution of irradiated face-centred cubic metals. This model is capable of capturing the main features of irradiated polycrystalline materials including irradiation hardening, post-yield softening and plasticity localization. Numerical results show a good agreement with experimental data for both unirradiated and irradiated stress-strain relationships. The study of crystallographic texture reveals that the initial randomly distributed texture of unirradiated metals under tensile loading can evolve into a mixture of [111] and [100] textures. Regarding the irradiated case, crystallographic texture develops in a different way, and an extra part of [110] texture evolves into [100] and [111] textures. Thus, [100] and [111] textures become dominant more quickly compared with those of the unirradiated case for the reason that [100] and [111]-oriented crystals have higher strength, and their plastic deformation behaviours are more active than other oriented crystals. It can be concluded that irradiation-induced defects can affect both the mechanical behaviour and texture evolution of metals, both of which are closely related to irradiation hardening.

Full Vector Wave Calculation of Photonic Band Structures in Face-Centered Cubic Dielectric Media

DTIC Science & Technology

1990-01-01

refractive index ratios90 0(;o8 070 2 were painstakingly machined out of low-loss dk’-tric materials. This very time comsuming approach was necessary to...find that the X-gap goes to zero for f=0.66. This is very close to the experimental value of 0.68. The physical origin of this behavior has been fully

Group Theoretical Route to Deterministic Weyl Points in Chiral Photonic Lattices.

PubMed

Saba, Matthias; Hamm, Joachim M; Baumberg, Jeremy J; Hess, Ortwin

2017-12-01

Topological phases derived from point degeneracies in photonic band structures show intriguing and unique behavior. Previously identified band degeneracies are based on accidental degeneracies and subject to engineering on a case-by-case basis. Here we show that deterministic pseudo Weyl points with nontrivial topology and hyperconic dispersion exist at the Brillouin zone center of chiral cubic symmetries. This conceivably allows realization of topologically protected frequency isolated surface bands in 3D and n=0 properties as demonstrated for a nanoplasmonic system and a photonic crystal.

Group Theoretical Route to Deterministic Weyl Points in Chiral Photonic Lattices

NASA Astrophysics Data System (ADS)

Saba, Matthias; Hamm, Joachim M.; Baumberg, Jeremy J.; Hess, Ortwin

2017-12-01

Topological phases derived from point degeneracies in photonic band structures show intriguing and unique behavior. Previously identified band degeneracies are based on accidental degeneracies and subject to engineering on a case-by-case basis. Here we show that deterministic pseudo Weyl points with nontrivial topology and hyperconic dispersion exist at the Brillouin zone center of chiral cubic symmetries. This conceivably allows realization of topologically protected frequency isolated surface bands in 3D and n =0 properties as demonstrated for a nanoplasmonic system and a photonic crystal.

Theoretical study of the crystal-field energy levels and two-photon absorption intensities of Tb3+ in cubic host lattices.

PubMed

Duan, Chang-Kui; Tanner, Peter A

2011-03-17

Published two photon excitation (TPE) intensities for the cubic elpasolite systems Cs(2)NaTbX(6) (X = Cl, F) have been simulated by a calculation of two photon absorption (TPA) intensities which takes into account electric dipole transitions involving the detailed crystal-field structure of 4f(7)5d intermediate states, as well as the interactions of the 4f(7) core with the d-electron. The intensity calculation employed parameters from an energy level calculation which not only presented an accurate fit, but also yielded parameters consistent with those from other lanthanide ions. The calculated intensities were used to confirm or adjust the previous assignments of energy levels, resulting in some minor revisions. Generally, the TPA intensity simulations were in better agreement with experimental data for the fluoride, rather than the chloride, system and possible reasons for this are given.

Micro-pixelation and color mixing in biological photonic structures (presentation video)

NASA Astrophysics Data System (ADS)

Bartl, Michael H.; Nagi, Ramneet K.

2014-03-01

The world of insects displays myriad hues of coloration effects produced by elaborate nano-scale architectures built into wings and exoskeleton. For example, we have recently found many weevils possess photonic architectures with cubic lattices. In this talk, we will present high-resolution three-dimensional reconstructions of weevil photonic structures with diamond and gyroid lattices. Moreover, by reconstructing entire scales we found arrays of single-crystalline domains, each oriented such that only selected crystal faces are visible to an observer. This pixel-like arrangement is key to the angle-independent coloration typical of weevils—a strategy that could enable a new generation of coating technologies.

Bond-order potential for magnetic body-centered-cubic iron and its transferability

NASA Astrophysics Data System (ADS)

Lin, Yi-Shen; Mrovec, M.; Vitek, V.

2016-06-01

We derived and thoroughly tested a bond-order potential (BOP) for body-centered-cubic (bcc) magnetic iron that can be employed in atomistic calculations of a broad variety of crystal defects that control structural, mechanical, and thermodynamic properties of this technologically important metal. The constructed BOP reflects correctly the mixed nearly free electron and covalent bonding arising from the partially filled d band as well as the ferromagnetism that is actually responsible for the stability of the bcc structure of iron at low temperatures. The covalent part of the cohesive energy is determined within the tight-binding bond model with the Green's function of the Schrödinger equation determined using the method of continued fractions terminated at a sufficient level of the moments of the density of states. This makes the BOP an O (N ) method usable for very large numbers of particles. Only d d bonds are included explicitly, but the effect of s electrons on the covalent energy is included via their screening of the corresponding d d bonds. The magnetic part of the cohesive energy is included using the Stoner model of itinerant magnetism. The repulsive part of the cohesive energy is represented, as in any tight-binding scheme, by an empirical formula. Its functional form is physically justified by studies of the repulsion in face-centered-cubic (fcc) solid argon under very high pressure where the repulsion originates from overlapping s and p closed-shell electrons just as it does from closed-shell s electrons in transition metals squeezed into the ion core under the influence of the large covalent d bonding. Testing of the transferability of the developed BOP to environments significantly different from those of the ideal bcc lattice was carried out by studying crystal structures and magnetic states alternative to the ferromagnetic bcc lattice, vacancies, divacancies, self-interstitial atoms (SIAs), paths continuously transforming the bcc structure to

Insights on activation enthalpy for non-Schmid slip in body-centered cubic metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hale, Lucas M.; Lim, Hojun; Zimmerman, Jonathan A.

2014-12-18

We use insights gained from atomistic simulation to develop an activation enthalpy model for dislocation slip in body-centered cubic iron. Furthermore, using a classical potential that predicts dislocation core stabilities consistent with ab initio predictions, we quantify the non-Schmid stress-dependent effects of slip. The kink-pair activation enthalpy is evaluated and a model is identified as a function of the general stress state. Thus, our model enlarges the applicability of the classic Kocks activation enthalpy model to materials with non-Schmid behavior.

Exploitation of 3D face-centered cubic mesoporous silica as a carrier for a poorly water soluble drug: influence of pore size on release rate.

PubMed

Zhu, Wenquan; Wan, Long; Zhang, Chen; Gao, Yikun; Zheng, Xin; Jiang, Tongying; Wang, Siling

2014-01-01

The purposes of the present work were to explore the potential application of 3D face-centered cubic mesoporous silica (FMS) with pore size of 16.0nm as a delivery system for poorly soluble drugs and investigate the effect of pore size on the dissolution rate. FMS with different pore sizes (16.0, 6.9 and 3.7nm) was successfully synthesized by using Pluronic block co-polymer F127 as a template and adjusting the reaction temperatures. Celecoxib (CEL), which is a BCS class II drug, was used as a model drug and loaded into FMS with different pore sizes by the solvent deposition method at a drug-silica ratio of 1:4. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) was used to systematically investigate the drug loading process. The results obtained showed that CEL was in a non-crystalline state after incorporation of CEL into the pores of FMS-15 with pore size of 16.0nm. In vitro dissolution was carried out to demonstrate the effects of FMS with different pore sizes on the release of CEL. The results obtained indicated that the dissolution rate of CEL from FMS-15 was significantly enhanced compared with pure CEL. This could be explained by supposing that CEL encountered less diffusion resistance and its crystallinity decreased due to the large pore size of 16.0nm and the nanopore channels of FMS-15. Moreover, drug loading and pore size both play an important role in enhancing the dissolution properties for the poorly water-soluble drugs. As the pore size between 3.7 and 16.0nm increased, the dissolution rate of CEL from FMS gradually increased. © 2013.

Rotation-limited growth of three-dimensional body-centered-cubic crystals

NASA Astrophysics Data System (ADS)

Tarp, Jens M.; Mathiesen, Joachim

2015-07-01

According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered-cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe, as a function of the quenching depth, a crossover between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescence through rotation and alignment of the lattices of neighboring grains. We show that the grain rotation per volume change of a grain follows a power law with an exponent of -1.25 . The scaling exponent is consistent with theoretical considerations based on the conservation of dislocations.

Bright nanowire single photon source based on SiV centers in diamond

DOE PAGES

Marseglia, L.; Saha, K.; Ajoy, A.; ...

2018-01-01

The practical implementation of quantum technologies such as quantum commu- nication and quantum cryptography relies on the development of indistinguishable, robust, and bright single photon sources that works at room temperature. The silicon- vacancy (SiV -) center in diamond has emerged as a possible candidate for a single photon source with all these characteristics. Unfortunately, due to the high refraction index mismatch between diamond and air, color centers in diamond show low photon out-coupling. This drawback can be overcome by fabrication of photonic structures that improve the in-coupling of excitation laser to the diamond defect as well as the out-couplingmore » emission from the color centers. An additional shortcoming is due to the random localization of native defects in the diamond sample. Here we demonstrate deterministic implantation of Si ions with high conversion effciency to single SiV -, targeted to fabricated nanowires. The co-localization of single SiV - defects with the nanostructures yields a ten times higher light coupling effciency as compared to single SiV - in the bulk. This result, with its intrinsic scalability, enables a new class of devices for integrated photonics and quantum information processing.« less

Monolithic photonic crystals created by partial coalescence of core-shell particles.

PubMed

Lee, Joon-Seok; Lim, Che Ho; Yang, Seung-Man; Kim, Shin-Hyun

2014-03-11

Colloidal crystals and their derivatives have been intensively studied and developed during the past two decades due to their unique photonic band gap properties. However, complex fabrication procedures and low mechanical stability severely limit their practical uses. Here, we report stable photonic structures created by using colloidal building blocks composed of an inorganic core and an organic shell. The core-shell particles are convectively assembled into an opal structure, which is then subjected to thermal annealing. During the heat treatment, the inorganic cores, which are insensitive to heat, retain their regular arrangement in a face-centered cubic lattice, while the organic shells are partially fused with their neighbors; this forms a monolithic structure with high mechanical stability. The interparticle distance and therefore stop band position are precisely controlled by the annealing time; the distance decreases and the stop band blue shifts during the annealing. The composite films can be further treated to give a high contrast in the refractive index. The inorganic cores are selectively removed from the composite by wet etching, thereby providing an organic film containing regular arrays of air cavities. The high refractive index contrast of the porous structure gives rise to pronounced structural colors and high reflectivity at the stop band position.

Dislocation nucleation from symmetric tilt grain boundaries in body-centered cubic vanadium

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Su, Yanqing

2018-05-01

We perform molecular dynamics (MD) simulations with two interatomic potentials to study dislocation nucleation from six symmetric tilt grain boundaries (GB) using bicrystal models in body-centered cubic vanadium. The influences of the misorientation angle are explored in the context of activated slip systems, critical resolved shear stress (CRSS), and GB energy. It is found that for four GBs, the activated slip systems are not those with the highest Schmid factor, i.e., the Schmid law breaks down. For all misorientation angles, the bicrystal is associated with a lower CRSS than their single crystalline counterparts. Moreover, the GB energy decreases in compressive loading at the yield point with respect to the undeformed configuration, in contrast to tensile loading.

Anti-iridescent colloidal photonic nanostructure from thermal gradients and polymeric brush effects

NASA Astrophysics Data System (ADS)

Lee, Seung Yeol; Kim, Hyoungsoo; Kim, Shin-Hyun; Stone, Howard

2017-11-01

Colloidal nanostructures induced by self-assembly are important in reflective displays, plasmonic or photonic sensors, and color pigments. During the evaporation of droplets of colloidal suspension, due to the non-uniform evaporation rate along the droplet interface, a radially outward flow is created and it carries colloidal particles to the pinned contact line of the droplet. We document that the packing at the contact line is a face-center-cubic (fcc) colloidal nanostructure in a ring shape. The fcc structure of the colloidal nanoparticles exhibits angle-dependent color. In particular, we introduce a novel method to suppress the familiar coffee-ring effect and modify colloidal nanostructures to exhibit angle-independent optical properties. A suspension of polyethylene oxide (PEO)-coated silica nanoparticles dispersed in ethanol-water mixture is prepared. The droplet containing the nanoparticles dries on a heated substrate, which creates a thermal gradient along the interface of the droplet. This thermal gradient induces thermal-Marangoni stresses that suppress the coffee-ring effects. PEO adsorbed on the surface of silica nanoparticles produces an additional interaction between colloidal nanoparticles, which makes the final structure disordered. The disordered photonic nanostructures in our experiments exhibit angle-independent structural color. This technique can be applied to printing or optical filtering systems.

Enhancing the brightness of electrically driven single-photon sources using color centers in silicon carbide

NASA Astrophysics Data System (ADS)

Khramtsov, Igor A.; Vyshnevyy, Andrey A.; Fedyanin, Dmitry Yu.

2018-03-01

Practical applications of quantum information technologies exploiting the quantum nature of light require efficient and bright true single-photon sources which operate under ambient conditions. Currently, point defects in the crystal lattice of diamond known as color centers have taken the lead in the race for the most promising quantum system for practical non-classical light sources. This work is focused on a different quantum optoelectronic material, namely a color center in silicon carbide, and reveals the physics behind the process of single-photon emission from color centers in SiC under electrical pumping. We show that color centers in silicon carbide can be far superior to any other quantum light emitter under electrical control at room temperature. Using a comprehensive theoretical approach and rigorous numerical simulations, we demonstrate that at room temperature, the photon emission rate from a p-i-n silicon carbide single-photon emitting diode can exceed 5 Gcounts/s, which is higher than what can be achieved with electrically driven color centers in diamond or epitaxial quantum dots. These findings lay the foundation for the development of practical photonic quantum devices which can be produced in a well-developed CMOS compatible process flow.

Nonlinear Frequency Conversion in III-V Semiconductor Photonic Crystals

DTIC Science & Technology

2012-03-01

nanocavities, by localizing light into sub-cubic optical wavelength volumes with long photon storage times, can greatly enhance the efficiency of...dissertation shows how optical nanocavities, by localizing light into sub-cubic optical wavelength volumes with long photon storage times, can greatly...8.2.3 Lithographic localization of molecules to cavity region . . . . . 86 8.2.4 Low temperature spectroscopy of DNQDI . . . . . . . . . . . 89 8.2.5

Tunable photonic crystals with partial bandgaps from blue phase colloidal crystals and dielectric-doped blue phases.

PubMed

Stimulak, Mitja; Ravnik, Miha

2014-09-07

Blue phase colloidal crystals and dielectric nanoparticle/polymer doped blue phases are demonstrated to combine multiple components with different symmetries in one photonic material, creating a photonic crystal with variable and micro-controllable photonic band structure. In this composite photonic material, one contribution to the band structure is determined by the 3D periodic birefringent orientational profile of the blue phases, whereas the second contribution emerges from the regular array of the colloidal particles or from the dielectric/nanoparticle-doped defect network. Using the planewave expansion method, optical photonic bands of the blue phase I and II colloidal crystals and related nanoparticle/polymer doped blue phases are calculated, and then compared to blue phases with no particles and to face-centred-cubic and body-centred-cubic colloidal crystals in isotropic background. We find opening of local band gaps at particular points of Brillouin zone for blue phase colloidal crystals, where there were none in blue phases without particles or dopants. Particle size and filling fraction of the blue phase defect network are demonstrated as parameters that can directly tune the optical bands and local band gaps. In the blue phase I colloidal crystal with an additionally doped defect network, interestingly, we find an indirect total band gap (with the exception of one point) at the entire edge of SC irreducible zone. Finally, this work demonstrates the role of combining multiple - by symmetry - differently organised components in one photonic crystal material, which offers a novel approach towards tunable soft matter photonic materials.

Large-area photonic crystals

NASA Astrophysics Data System (ADS)

Ruhl, Tilmann; Spahn, Peter; Hellmann, Gotz P.; Winkler, Holger

2004-09-01

Materials with a periodically modulated refractive index, with periods on the scale of light wavelengths, are currently attracting much attention because of their unique optical properties which are caused by Bragg scattering of the visible light. In nature, 3d structures of this kind are found in the form of opals in which monodisperse silica spheres with submicron diameters form a face-centered-cubic (fcc) lattice. Artificial opals, with the same colloidal-crystalline fcc structure, have meanwhile been prepared by crystallizing spherical colloidal particles via sedimentation or drying of dispersions. In this report, colloidal crystalline films are introduced that were produced by a novel technique based on shear flow in the melts of specially designed submicroscopic silica-polymer core-shell hybrid spheres: when the melt of these spheres flows between the plates of a press, the spheres crystallize along the plates, layer by layer, and the silica cores assume the hexagonal order corresponding to the (111) plane of the fcc lattice. This process is fast and yields large-area films, thin or thick. To enhance the refractive index contrast in these films, the colloidal crystalline structure was inverted by etching out the silica cores with hydrofluoric acid. This type of an inverse opal, in which the fcc lattice is formed by mesopores, is referred to as a polymer-air photonic crystal.

Polymer Stabilization of Liquid-Crystal Blue Phase II toward Photonic Crystals.

PubMed

Jo, Seong-Yong; Jeon, Sung-Wook; Kim, Byeong-Cheon; Bae, Jae-Hyun; Araoka, Fumito; Choi, Suk-Won

2017-03-15

The temperature ranges where a pure simple-cubic blue phase (BPII) emerges are quite narrow compared to the body-centered-cubic BP (BPI) such that the polymer stabilization of BPII is much more difficult. Hence, a polymer-stabilized BPII possessing a wide temperature range has been scarcely reported. Here, we fabricate a polymer-stabilized BPII over a temperature range of 50 °C including room temperature. The fabricated polymer-stabilized BPII is confirmed via polarized optical microscopy, Bragg reflection, and Kossel diagram observations. Furthermore, we demonstrate reflective BP liquid-crystal devices utilizing the reflectance-voltage performance as a potential application of the polymer-stabilized BPII. Our work demonstrates the possibility of practical application of the polymer-stabilized BPII to photonic crystals.

Plastic fluctuations in empty crystals formed by cubic wireframe particles

NASA Astrophysics Data System (ADS)

McBride, John M.; Avendaño, Carlos

2018-05-01

We present a computer simulation study of the phase behavior of colloidal hard cubic frames, i.e., particles with nonconvex cubic wireframe geometry interacting purely by excluded volume. Despite the propensity of cubic wireframe particles to form cubic phases akin to their convex counterparts, these particles exhibit unusual plastic fluctuations in which a random and dynamic fraction of particles rotate around their lattice positions in the crystal lattice while the remainder of the particles remains fully ordered. We argue that this unexpected effect stems from the nonconvex geometry of the particles in which the faces of a particle can be penetrated by the vertices of the nearest neighbors even at high number densities.

Computational prediction of body-centered cubic carbon in an all- s p 3 six-member ring configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhen -Zhen; Lian, Chao -Sheng; Xu, Jing

2015-06-11

Recent shock compression experiments produced clear evidence of a new carbon phase, but a full structural identification has remained elusive. Here we establish by ab initio calculations a body-centered cubic carbon phase in Ia3¯d(O 10 h) symmetry, which contains twelve atoms in its primitive cell, thus termed BC12, and comprises all-sp 3 six-membered rings. This structural configuration places BC12 carbon in the same bonding type as cubic diamond, and its stability is verified by phonon mode analysis. Simulated x-ray diffraction patterns provide an excellent match to the previously unexplained distinct diffraction peak found in shock compression experiments. Electronic band andmore » density of states calculations reveal that BC12 is a semiconductor with a direct band gap of ~2.97eV. Lastly, these results provide a solid foundation for further exploration of this new carbon allotrope.« less

On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector.

PubMed

Aray, Yosslen; Paredes, Ricardo; Álvarez, Luis Javier; Martiz, Alejandro

2017-06-14

The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges. On the contrary, for the transition metals, there are low-valued localized electrons detector isocontours defining a zone of highly delocalized electrons that extends throughout the material. We have found that the best conductors are those in which the electron density at this low-value zone is the lowest.

Cubic GaN quantum dots embedded in zinc-blende AlN microdisks

NASA Astrophysics Data System (ADS)

Bürger, M.; Kemper, R. M.; Bader, C. A.; Ruth, M.; Declair, S.; Meier, C.; Förstner, J.; As, D. J.

2013-09-01

Microresonators containing quantum dots find application in devices like single photon emitters for quantum information technology as well as low threshold laser devices. We demonstrate the fabrication of 60 nm thin zinc-blende AlN microdisks including cubic GaN quantum dots using dry chemical etching techniques. Scanning electron microscopy analysis reveals the morphology with smooth surfaces of the microdisks. Micro-photoluminescence measurements exhibit optically active quantum dots. Furthermore this is the first report of resonator modes in the emission spectrum of a cubic AlN microdisk.

On the mechanical stability of the body-centered cubic phase and the emergence of a metastable cI16 phase in classical hard sphere solids

NASA Astrophysics Data System (ADS)

Warshavsky, Vadim B.; Ford, David M.; Monson, Peter A.

2018-01-01

The stability of the body-centered cubic (bcc) solid phase of classical hard spheres is of intrinsic interest and is also relevant to the development of perturbation theories for bcc solids of other model systems. Using canonical ensemble Monte Carlo, we simulated systems initialized in a perfect bcc lattice at various densities in the solid region. We observed that the systems rapidly evolved into one of four structures that then persisted for the duration of the simulation. Remarkably, one of these structures was identified as cI16, a cubic crystalline structure with 16 particles in the unit cell, which has recently been observed experimentally in lithium and sodium solids at high pressures. The other three structures do not exhibit crystalline order but are characterized by common patterns in the radial distribution function and bond-orientational order parameter distribution; we refer to them as bcc-di, with i ranging from 1 to 3. We found similar outcomes when employing any of the three single occupancy cell (SOC) restrictions commonly used in the literature. We also ran long constant-pressure simulations with box shape fluctuations initiated from bcc and cI16 initial configurations. At lower pressures, all the systems evolved to defective face-centered cubic (fcc) or hexagonal close-packed (hcp) structures. At higher pressures, most of the systems initiated as bcc evolved to cI16 with some evolving to defective fcc/hcp. High pressure systems initiated from cI16 remained in that structure. We computed the chemical potential of cI16 using the Einstein crystal reference method and found that it is higher than that of fcc by ˜0.5kT-2.5kT over the pressure range studied, with the difference increasing with pressure. We find that the undistorted bcc solid, even with constant-volume and SOC restrictions applied, is so mechanically unstable that it is unsuitable for consideration as a metastable phase or as a reference system for studying bcc phases of other systems

Robust Eye Center Localization through Face Alignment and Invariant Isocentric Patterns

PubMed Central

Teng, Dongdong; Chen, Dihu; Tan, Hongzhou

2015-01-01

The localization of eye centers is a very useful cue for numerous applications like face recognition, facial expression recognition, and the early screening of neurological pathologies. Several methods relying on available light for accurate eye-center localization have been exploited. However, despite the considerable improvements that eye-center localization systems have undergone in recent years, only few of these developments deal with the challenges posed by the profile (non-frontal face). In this paper, we first use the explicit shape regression method to obtain the rough location of the eye centers. Because this method extracts global information from the human face, it is robust against any changes in the eye region. We exploit this robustness and utilize it as a constraint. To locate the eye centers accurately, we employ isophote curvature features, the accuracy of which has been demonstrated in a previous study. By applying these features, we obtain a series of eye-center locations which are candidates for the actual position of the eye-center. Among these locations, the estimated locations which minimize the reconstruction error between the two methods mentioned above are taken as the closest approximation for the eye centers locations. Therefore, we combine explicit shape regression and isophote curvature feature analysis to achieve robustness and accuracy, respectively. In practical experiments, we use BioID and FERET datasets to test our approach to obtaining an accurate eye-center location while retaining robustness against changes in scale and pose. In addition, we apply our method to non-frontal faces to test its robustness and accuracy, which are essential in gaze estimation but have seldom been mentioned in previous works. Through extensive experimentation, we show that the proposed method can achieve a significant improvement in accuracy and robustness over state-of-the-art techniques, with our method ranking second in terms of accuracy

Silver chlorobromide nanocubes with significantly improved uniformity: synthesis and assembly into photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zheng; Okasinski, John S.; Gosztola, David J.

2015-01-01

Silver chlorobromide (AgClxBr1-x, 0 < x < 1) nanocubes with a highly uniform size, morphology, and crystallinity have been successfully synthesized through a co-precipitation of Ag+ ions with both Cl- and Br- ions in ethylene glycol containing polyvinyl pyrrolidone at mild temperatures. Compositions of the synthesized nanocubes can be easily tuned by controlling the molar ratio of Cl- to Br- ions in the reaction solutions. The size of the nanocubes is determined by varying a number of parameters including the molar ratio of Cl- to Br- ions, injection rate of Ag+ ions, and reaction temperature. The real-time formation of colloidalmore » AgClxBr1-x nanocubes has been monitored, for the first time, by in situ highenergy synchrotron X-ray diffraction. The time-resolved results reveal that a fast injection rate of Ag+ ions is critical for the formation of AgClxBr1-x nanocubes with a highly pure face-centered cubic crystalline phase. The improved uniformity of the AgClxBr1-x nanocubes is beneficial for assembling them into order superlattices (e.g., photonic crystals) even by simply applying centrifugation forces. The stop band of the resulting photonic crystals can be easily tuned from the ultraviolet to the infrared region by using AgClxBr1-x nanocubes with different sizes. The variation of the dielectric constant of AgClxBr1-x associated with the change of the relative concentration of halide ions provides an additional knob to tune the optical properties of photonic crystals.« less

Applying Learner-Centered Principles and Strategies: From Face to Face Instruction to a Hybrid Course Learning Format

ERIC Educational Resources Information Center

McDonough, Darlene

2012-01-01

This paper discusses the transition from traditional face to face instruction to a hybrid format using the newly drafted 8 Standards of the Educational Leadership Constituents Council (2010) as guidelines for the curriculum, the 14 Learner Centered Principles (1997) from the American Psychological Association as elements for instructional…

Stabilizing the body centered cubic crystal in titanium alloys by a nano-scale concentration modulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, H. L.; Shah, S. A. A.; Hao, Y. L.

It is well-known that the body centered cubic (bcc) crystal in titanium alloys reaches its stability limit as the electron-to-atom (e/a) ratio of the alloy drops down to ~4.24. This critical value, however, is much higher than that of a multifunctional bcc type alloy (e/a = 4.15). Here we demonstrate that a nano-scale concentration modulation created by spinodal decomposition is what stabilizes the bcc crystal of the alloy. Aided by such a nano-scale concentration heterogeneity, unexpected properties from its chemically homogeneous counterpart are obtained. This provides a new strategy to design functional titanium alloys by tuning the spinodal decomposition.

Center-of-Mass Tomography and Wigner Function for Multimode Photon States

NASA Astrophysics Data System (ADS)

Dudinets, Ivan V.; Man'ko, Vladimir I.

2018-06-01

Tomographic probability representation of multimode electromagnetic field states in the scheme of center-of-mass tomography is reviewed. Both connection of the field state Wigner function and observable Weyl symbols with the center-of-mass tomograms as well as connection of the Grönewold kernel with the center-of-mass tomographic kernel determining the noncommutative product of the tomograms are obtained. The dual center-of-mass tomogram of the photon states are constructed and the dual tomographic kernel is obtained. The models of other generalized center-of-mass tomographies are discussed. Example of two-mode even and odd Schrödinger cat states is presented in details.

Ground-state ordering of the J1-J2 model on the simple cubic and body-centered cubic lattices

NASA Astrophysics Data System (ADS)

Farnell, D. J. J.; Götze, O.; Richter, J.

2016-06-01

The J1-J2 Heisenberg model is a "canonical" model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the coupled cluster method (CCM) to study the spin-half J1-J2 model with antiferromagnetic nearest-neighbor bonds J1>0 and next-nearest-neighbor bonds J2>0 for the simple cubic (sc) and body-centered cubic (bcc) lattices. In particular, we wish to study the ground-state ordering of these systems as a function of the frustration parameter p =z2J2/z1J1 , where z1 (z2) is the number of nearest (next-nearest) neighbors. We wish to determine the positions of the phase transitions using the CCM and we aim to resolve the nature of the phase transition points. We consider the ground-state energy, order parameters, spin-spin correlation functions, as well as the spin stiffness in order to determine the ground-state phase diagrams of these models. We find a direct first-order phase transition at a value of p =0.528 from a state of nearest-neighbor Néel order to next-nearest-neighbor Néel order for the bcc lattice. For the sc lattice the situation is more subtle. CCM results for the energy, the order parameter, the spin-spin correlation functions, and the spin stiffness indicate that there is no direct first-order transition between ground-state phases with magnetic long-range order, rather it is more likely that two phases with antiferromagnetic long range are separated by a narrow region of a spin-liquid-like quantum phase around p =0.55 . Thus the strong frustration present in the J1-J2 Heisenberg model on the sc lattice may open a window for an unconventional quantum ground state in this three-dimensional spin model.

Application of Mahler measure theory to the face-centred cubic lattice Green function at the origin and its associated logarithmic integral

NASA Astrophysics Data System (ADS)

Joyce, G. S.

2012-07-01

The mathematical properties of the face-centred cubic lattice Green function \\begin{equation*} \\fl G(w) \\equiv {1\\over {\\pi ^3}}\\int _{0}^{\\pi }\\int _{0}^{\\pi }\\int _{0}^{\\pi } {{d\\theta _1\\,d\\theta _2\\,d\\theta _3}\\over {w-c(\\theta _1)\\,c(\\theta _2)- c(\\theta _2)\\,c(\\theta _3)-c(\\theta _3)\\,c(\\theta _1)}} \\end{equation*} and the associated logarithmic integral \\begin{eqnarray*} \\fl S(w) \\equiv {1\\over {\\pi ^3}}\\int _{0}^{\\pi }\\int _{0}^{\\pi }\\int _{0}^{\\pi } \\ln [ w-c(\\theta _1)\\,c(\\theta _2)-c(\\theta _2)\\,c(\\theta _3)\

Roadmap on silicon photonics

NASA Astrophysics Data System (ADS)

Thomson, David; Zilkie, Aaron; Bowers, John E.; Komljenovic, Tin; Reed, Graham T.; Vivien, Laurent; Marris-Morini, Delphine; Cassan, Eric; Virot, Léopold; Fédéli, Jean-Marc; Hartmann, Jean-Michel; Schmid, Jens H.; Xu, Dan-Xia; Boeuf, Frédéric; O'Brien, Peter; Mashanovich, Goran Z.; Nedeljkovic, M.

2016-07-01

Silicon photonics research can be dated back to the 1980s. However, the previous decade has witnessed an explosive growth in the field. Silicon photonics is a disruptive technology that is poised to revolutionize a number of application areas, for example, data centers, high-performance computing and sensing. The key driving force behind silicon photonics is the ability to use CMOS-like fabrication resulting in high-volume production at low cost. This is a key enabling factor for bringing photonics to a range of technology areas where the costs of implementation using traditional photonic elements such as those used for the telecommunications industry would be prohibitive. Silicon does however have a number of shortcomings as a photonic material. In its basic form it is not an ideal material in which to produce light sources, optical modulators or photodetectors for example. A wealth of research effort from both academia and industry in recent years has fueled the demonstration of multiple solutions to these and other problems, and as time progresses new approaches are increasingly being conceived. It is clear that silicon photonics has a bright future. However, with a growing number of approaches available, what will the silicon photonic integrated circuit of the future look like? This roadmap on silicon photonics delves into the different technology and application areas of the field giving an insight into the state-of-the-art as well as current and future challenges faced by researchers worldwide. Contributions authored by experts from both industry and academia provide an overview and outlook for the silicon waveguide platform, optical sources, optical modulators, photodetectors, integration approaches, packaging, applications of silicon photonics and approaches required to satisfy applications at mid-infrared wavelengths. Advances in science and technology required to meet challenges faced by the field in each of these areas are also addressed together with

Ultra-high-Q three-dimensional photonic crystal nano-resonators.

PubMed

Tang, Lingling; Yoshie, Tomoyuki

2007-12-10

Two nano-resonator modes are designed in a woodpile three-dimensional photonic crystal by the modulation of unit cell size along a low-loss optical waveguide. One is a dipole mode with 2.88 cubic half-wavelengths mode volume. The other is a quadrupole mode with 8.3 cubic half-wavelengths mode volume. Light is three-dimensionally confined by a complete photonic band gap so that, in the analyzed range, the quality factor exponentially increases as the increase in the number of unit cells used for confinement of light.

Face-Centred Cubic Iron: Ab Initio Calculations of Sound Velocities in the Lunar Core

NASA Astrophysics Data System (ADS)

Wood, M. C.; Wood, I. G.; Vočadlo, L.

2017-12-01

Studies, such as the reanalysis of the Apollo lunar seismograms [1], have shown that the Moon has undergone differentiation and possesses a small core. The composition of the lunar core is not well constrained, and many compositional models have been suggested including combinations of iron, nickel, and light elements such as sulphur and carbon [e.g. 1, 2, 3, 4], and other more exotic compositions [5]. Additional constraints are crucial to our understanding of the Moon, including its formation, the dynamics of its interior, and a lunar dynamo. We use ab initio molecular dynamics simulations to calculate elastic constants of face-centred cubic (fcc) iron and iron alloys and hence sound velocities at lunar core conditions, at 5-6 GPa and 1,300-1,900 K [3]. The results from these simulations will then be compared with the data from the Apollo seismograms and experimental data to help form a description of the lunar interior. [1] Weber et al. (2011) Science 331, 309-312. [2] Dasgupta et al. (2009) Geochim. Cosmochim. Acta 73, 6678-6692. [3] Antonangeli et al. (2015) Proc. Natl. Acad. Sci. U.S.A. 112, 3916-3919. [4] Righter et al. (2017) Earth Planet. Sci. Lett. 463, 323-332. [5] Wieczorek & Zuber (2002) Lunar Planet. Sci. 33, abstract 1384.

Photonics classes in high school

NASA Astrophysics Data System (ADS)

John, Pearl V.; Shanks, Richard A.

2002-05-01

In continuing the development of a three-year high school photonics program, the Columbia Area Career Center (Missouri, USA) faces the challenges associated with introducing a new subject area to career technical education in the public school system. The program was established to address the severe lack of Laser Electro-Optical Technicians (LEOTs) in the local manufacturing industry. Its goals are to increase student awareness of the expanding job opportunities available in photonics and optics, teach skills needed for the field, and foster close ties with industry and post-secondary institutions. This paper examines the success of the program to date and outlines the problems associated with teaching an advanced curriculum at the high school level.

Dark photons from the center of the Earth: Smoking-gun signals of dark matter

NASA Astrophysics Data System (ADS)

Feng, Jonathan L.; Smolinsky, Jordan; Tanedo, Philip

2016-01-01

Dark matter may be charged under dark electromagnetism with a dark photon that kinetically mixes with the Standard Model photon. In this framework, dark matter will collect at the center of the Earth and annihilate into dark photons, which may reach the surface of the Earth and decay into observable particles. We determine the resulting signal rates, including Sommerfeld enhancements, which play an important role in bringing the Earth's dark matter population to their maximal, equilibrium value. For dark matter masses mX˜100 GeV - 10 TeV , dark photon masses mA'˜MeV -GeV , and kinetic mixing parameters ɛ ˜1 0-9- 1 0-7 , the resulting electrons, muons, photons, and hadrons that point back to the center of the Earth are a smoking-gun signal of dark matter that may be detected by a variety of experiments, including neutrino telescopes, such as IceCube, and space-based cosmic ray detectors, such as Fermi-LAT and AMS. We determine the signal rates and characteristics and show that large and striking signals—such as parallel muon tracks—are possible in regions of the (mA',ɛ ) plane that are not probed by direct detection, accelerator experiments, or astrophysical observations.

Tapered fiber coupling of single photons emitted by a deterministically positioned single nitrogen vacancy center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liebermeister, Lars, E-mail: lars.liebermeister@physik.uni-muenchen.de; Petersen, Fabian; Münchow, Asmus v.

2014-01-20

A diamond nano-crystal hosting a single nitrogen vacancy (NV) center is optically selected with a confocal scanning microscope and positioned deterministically onto the subwavelength-diameter waist of a tapered optical fiber (TOF) with the help of an atomic force microscope. Based on this nano-manipulation technique, we experimentally demonstrate the evanescent coupling of single fluorescence photons emitted by a single NV-center to the guided mode of the TOF. By comparing photon count rates of the fiber-guided and the free-space modes and with the help of numerical finite-difference time domain simulations, we determine a lower and upper bound for the coupling efficiency ofmore » (9.5 ± 0.6)% and (10.4 ± 0.7)%, respectively. Our results are a promising starting point for future integration of single photon sources into photonic quantum networks and applications in quantum information science.« less

Detail of windows at center of west elevation; camera facing ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of windows at center of west elevation; camera facing east. - Mare Island Naval Shipyard, WAVES Officers Quarters, Cedar Avenue, west side between Tisdale Avenue & Eighth Street, Vallejo, Solano County, CA

Plasma facing materials performance under ITER-relevant mitigated disruption photonic heat loads

NASA Astrophysics Data System (ADS)

Klimov, N. S.; Putrik, A. B.; Linke, J.; Pitts, R. A.; Zhitlukhin, A. M.; Kuprianov, I. B.; Spitsyn, A. V.; Ogorodnikova, O. V.; Podkovyrov, V. L.; Muzichenko, A. D.; Ivanov, B. V.; Sergeecheva, Ya. V.; Lesina, I. G.; Kovalenko, D. V.; Barsuk, V. A.; Danilina, N. A.; Bazylev, B. N.; Giniyatulin, R. N.

2015-08-01

PFMs (Plasma-facing materials: ITER grade stainless steel, beryllium, and ferritic-martensitic steels) as well as deposited erosion products of PFCs (Be-like, tungsten, and carbon based) were tested in QSPA under photonic heat loads relevant to those expected from photon radiation during disruptions mitigated by massive gas injection in ITER. Repeated pulses slightly above the melting threshold on the bulk materials eventually lead to a regular, "corrugated" surface, with hills and valleys spaced by 0.2-2 mm. The results indicate that hill growth (growth rate of ∼1 μm per pulse) and sample thinning in the valleys is a result of melt-layer redistribution. The measurements on the 316L(N)-IG indicate that the amount of tritium absorbed by the sample from the gas phase significantly increases with pulse number as well as the modified layer thickness. Repeated pulses significantly below the melting threshold on the deposited erosion products lead to a decrease of hydrogen isotopes trapped during the deposition of the eroded material.

4. View of center tower at Clover Island, facing northeast. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. View of center tower at Clover Island, facing northeast. Pasco-Kennewick automobile bridge in background, lower right. - Pasco-Kennewick Transmission Line, Columbia River Crossing Towers, Columbia Drive & Gum Street, Kennewick, Benton County, WA

Three-Dimensional Random Voronoi Tessellations: From Cubic Crystal Lattices to Poisson Point Processes

NASA Astrophysics Data System (ADS)

Lucarini, Valerio

2009-01-01

We perturb the simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC) structures with a spatial Gaussian noise whose adimensional strength is controlled by the parameter α and analyze the statistical properties of the cells of the resulting Voronoi tessellations using an ensemble approach. We concentrate on topological properties of the cells, such as the number of faces, and on metric properties of the cells, such as the area, volume and the isoperimetric quotient. The topological properties of the Voronoi tessellations of the SC and FCC crystals are unstable with respect to the introduction of noise, because the corresponding polyhedra are geometrically degenerate, whereas the tessellation of the BCC crystal is topologically stable even against noise of small but finite intensity. Whereas the average volume of the cells is the intensity parameter of the system and does not depend on the noise, the average area of the cells has a rather interesting behavior with respect to noise intensity. For weak noise, the mean area of the Voronoi tessellations corresponding to perturbed BCC and FCC perturbed increases quadratically with the noise intensity. In the case of perturbed SCC crystals, there is an optimal amount of noise that minimizes the mean area of the cells. Already for a moderate amount of noise ( α>0.5), the statistical properties of the three perturbed tessellations are indistinguishable, and for intense noise ( α>2), results converge to those of the Poisson-Voronoi tessellation. Notably, 2-parameter gamma distributions constitute an excellent model for the empirical pdf of all considered topological and metric properties. By analyzing jointly the statistical properties of the area and of the volume of the cells, we discover that also the cells shape, measured by the isoperimetric quotient, fluctuates. The Voronoi tessellations of the BCC and of the FCC structures result to be local maxima for the isoperimetric quotient among space

On the Cubic Lattice Green Functions

NASA Astrophysics Data System (ADS)

Joyce, G. S.

1994-05-01

Wheatstone Physics Laboratory, King's College, University of London, Strand, London WC2R 2LS, U.K. It is proved that K (k+) = [(4-eta )1/2 - (1 - eta )1/2]K(k-), where eta is a complex variable which lies in a certain region R2 of the eta plane, and K (k±) are complete elliptic integrals of the first kind with moduli k± which are given by k±2equiv k±2(eta ) = 1/2 ± 1/4eta (4 - eta )1/2 - 1/4(2-eta )(1-eta )1/2. This basic result is then used to express the face-centred cubic and simple cubic lattice Green functions at the origin in terms of the square of a complete elliptic integral of the first kind. Several new identities involving the Heun function F(a, b; α , β , γ , δ ; eta ) are also derived. Next it is shown that the three cubic lattice Green functions all have parametric representations which involve the Green function for the two-dimensional honeycomb lattice. Finally, the results are applied to a variety of problems in lattice statistics. In particular, a new simplified formula for the generating function of staircase polygons on a four-dimensional hypercubic lattice is derived.

The role of grain boundaries in hydrogen diffusion in metals at 25 C

NASA Technical Reports Server (NTRS)

Danford, M. D.

1993-01-01

The effect of grain size on hydrogen diffusion at 25 C was examined for 4340 steel (body-centered cubic) and for Inconel 718 (face-centered cubic). It was found that the effect of grain size is important for body-centered cubic structures, but plays a much less important role in face centered cubic structures. Accurate measurements of hydrogen desorption coefficients during hydrogen desorption show that these are not greatly different for both types of structures.

Single-crystalline cubic structured InP nanosprings

NASA Astrophysics Data System (ADS)

Shen, G. Z.; Bando, Y.; Zhi, C. Y.; Yuan, X. L.; Sekiguchi, T.; Golberg, D.

2006-06-01

Cubic structured nanosprings, InP nanosprings, have been synthesized via a simple thermochemical process using InP and ZnS as the source materials. Each InP nanospring is formed by rolling up a single InP nanobelt with the growth direction along the ⟨111⟩ orientation. The formation of these novel nanostructures is mainly attributed to the minimization of the electrostatic energy due to the polar charges on the ±(002) side surfaces of cubic InP. Cathodoluminescence properties were also studied, which reveal that the InP nanosprings have three emission bands centered at ˜736, ˜920, and ˜980nm.

Polarization-free integrated gallium-nitride photonics

PubMed Central

Bayram, C.; Liu, R.

2017-01-01

Gallium Nitride (GaN) materials are the backbone of emerging solid state lighting. To date, GaN research has been primarily focused on hexagonal phase devices due to the natural crystallization. This approach limits the output power and efficiency of LEDs, particularly in the green spectrum. However, GaN can also be engineered to be in cubic phase. Cubic GaN has a lower bandgap (~200 meV) than hexagonal GaN that enables green LEDs much easily. Besides, cubic GaN has more isotropic properties (smaller effective masses, higher carrier mobility, higher doping efficiency, and higher optical gain than hexagonal GaN), and cleavage planes. Due to phase instability, however, cubic phase materials and devices have remained mostly unexplored. Here we review a new method of cubic phase GaN generation: Hexagonal-to-cubic phase transition, based on novel nano-patterning. We report a new crystallographic modelling of this hexagonal-to-cubic phase transition and systematically study the effects of nano-patterning on the GaN phase transition via transmission electron microscopy and electron backscatter diffraction experiments. In summary, silicon-integrated cubic phase GaN light emitters offer a unique opportunity for exploration in next generation photonics. PMID:29307953

Repeat-until-success cubic phase gate for universal continuous-variable quantum computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, Kevin; Pooser, Raphael; Siopsis, George

2015-03-24

We report that to achieve universal quantum computation using continuous variables, one needs to jump out of the set of Gaussian operations and have a non-Gaussian element, such as the cubic phase gate. However, such a gate is currently very difficult to implement in practice. Here we introduce an experimentally viable “repeat-until-success” approach to generating the cubic phase gate, which is achieved using sequential photon subtractions and Gaussian operations. Ultimately, we find that our scheme offers benefits in terms of the expected time until success, as well as the fact that we do not require any complex off-line resource state,more » although we require a primitive quantum memory.« less

Melting curves and entropy of fusion of body-centered cubic tungsten under pressure

NASA Astrophysics Data System (ADS)

Liu, Chun-Mei; Chen, Xiang-Rong; Xu, Chao; Cai, Ling-Cang; Jing, Fu-Qian

2012-07-01

The melting curves and entropy of fusion of body-centered cubic (bcc) tungsten (W) under pressure are investigated via molecular dynamics (MD) simulations with extended Finnis-Sinclair (EFS) potential. The zero pressure melting point obtained is better than other theoretical results by MD simulations with the embedded-atom-method (EAM), Finnis-Sinclair (FS) and modified EAM potentials, and by ab initio MD simulations. Our radial distribution function and running coordination number analyses indicate that apart from the expected increase in disorder, the main change on going from solid to liquid is thus a slight decrease in coordination number. Our entropy of fusion of W during melting, ΔS, at zero pressure, 7.619 J/mol.K, is in good agreement with the experimental and other theoretical data. We found that, with the increasing pressure, the entropy of fusion ΔS decreases fast first and then oscillates with pressure; when the pressure is higher than 100 GPa, the entropy of fusion ΔS is about 6.575 ± 0.086 J/mol.K, which shows less pressure effect.

Collaborative Center in Polymer Photonics

DTIC Science & Technology

2009-02-28

the inorganic residue in the thermogravimetric analysis TGA of the samples, Figure 6. It can be noticed that only approximately 1/3 of the...photonics, nanoparticles , structure, organic-inorganic hybrids, nanocomposites, photonic band gap, plasma-enhanced chemical vapor deposition, discotic liquid...the surface structure of nanoparticles made us focus our study on the morphological and thermodynamic properties of metallic nanoparticles . We cannot

Getting off the Bain path: Are there any metastable states of cubic elements?

NASA Astrophysics Data System (ADS)

Mehl, Michael J.; Boyer, Larry L.

2003-03-01

Body-centered and face-centered cubic crystals can be considered as special cases of a body-centered tetragonal crystal with c/a = 1 and 2, respectively. First-principles calculations along this Bain path show that elements with an fcc (bcc) ground state are elastically unstable with respect to a tetragonal distortion in the bcc (fcc) phase. Starting with a normally fcc element and calculating E(c/a) for c/a < 1 we find a local minimum near c/a = 2/3, while for a bcc element we find a local minimum at some c/a > 2. It is tempting to conclude that these bct minima, which are required by continuity, are metastable, but calculations by several authors show that, at least for Al, Cu, and Pd, the bct structures are unstable with respect to an orthorhombic distortion. We use a simple "magic strain" construction(L. L. Boyer, Acta Cryst. A) 45, FC29 (1989).(M. J. Mehl and L. L. Boyer, Phys. Rev. B) 43, 9498 (1991). to study the stability of these bct states, and present examples which suggest that no fcc or bcc element has a metastable bct state.

On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits.

PubMed

Elshaari, Ali W; Zadeh, Iman Esmaeil; Fognini, Andreas; Reimer, Michael E; Dalacu, Dan; Poole, Philip J; Zwiller, Val; Jöns, Klaus D

2017-08-30

Quantum light plays a pivotal role in modern science and future photonic applications. Since the advent of integrated quantum nanophotonics different material platforms based on III-V nanostructures-, colour centers-, and nonlinear waveguides as on-chip light sources have been investigated. Each platform has unique advantages and limitations; however, all implementations face major challenges with filtering of individual quantum states, scalable integration, deterministic multiplexing of selected quantum emitters, and on-chip excitation suppression. Here we overcome all of these challenges with a hybrid and scalable approach, where single III-V quantum emitters are positioned and deterministically integrated in a complementary metal-oxide-semiconductor-compatible photonic circuit. We demonstrate reconfigurable on-chip single-photon filtering and wavelength division multiplexing with a foot print one million times smaller than similar table-top approaches, while offering excitation suppression of more than 95 dB and efficient routing of single photons over a bandwidth of 40 nm. Our work marks an important step to harvest quantum optical technologies' full potential.Combining different integration platforms on the same chip is currently one of the main challenges for quantum technologies. Here, Elshaari et al. show III-V Quantum Dots embedded in nanowires operating in a CMOS compatible circuit, with controlled on-chip filtering and tunable routing.

Hybrid photonic crystal cavity and waveguide for coupling to diamond NV-centers.

PubMed

Barclay, Paul E; Fu, Kai-Mei; Santori, Charles; Beausoleil, Raymond G

2009-06-08

A design for an ultra-high Q photonic crystal nanocavity engineered to interact with nitrogen-vacancy (NV) centers located near the surface of a single crystal diamond sample is presented. The structure is based upon a nanowire photonic crystal geometry, and consists of a patterned high refractive index thin film, such as gallium phosphide (GaP), supported by a diamond substrate. The nanocavity supports a mode with quality factor Q > 1.5 x 10(6) and mode volume V < 0.52(lambda/nGaP)(3), and promises to allow Purcell enhanced collection of spontaneous emission from an NV located more than 50 nm below the diamond surface. The nanowire photonic crystal waveguide can be used to efficiently couple light into and out of the cavity, or as an efficient broadband collector of NV phonon sideband emission. The proposed structures can be fabricated using existing materials and processing techniques.

On-demand transfer of trapped photons on a chip.

PubMed

Konoike, Ryotaro; Nakagawa, Haruyuki; Nakadai, Masahiro; Asano, Takashi; Tanaka, Yoshinori; Noda, Susumu

2016-05-01

Photonic crystal nanocavities, which have modal volumes of the order of a cubic wavelength in the material, are of great interest as flexible platforms for manipulating photons. Recent developments in ultra-high quality factor nanocavities with long photon lifetimes have encouraged us to develop an ultra-compact and flexible photon manipulation technology where photons are trapped in networks of such nanocavities. The most fundamental requirement is the on-demand transfer of photons to and from the trapped states of arbitrary nanocavities. We experimentally demonstrate photon transfer between two nearly resonant nanocavities at arbitrary positions on a chip, triggered by the irradiation of a third nonresonant nanocavity using an optical control pulse. We obtain a high transfer efficiency of ~90% with a photon lifetime of ~200 ps.

Cesium hafnium chloride: A high light yield, non-hygroscopic cubic crystal scintillator for gamma spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burger, Arnold, E-mail: aburger@fisk.edu; Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235; Rowe, Emmanuel

We report on the scintillation properties of Cs{sub 2}HfCl{sub 6} (cesium hafnium chloride or CHC) as an example of a little-known class of non-hygroscopic compounds having the generic cubic crystal structure of K{sub 2}PtCl{sub 6}. The crystals are easily growable from the melt using the Bridgman method with minimal precursor treatments or purification. CHC scintillation is centered at 400 nm, with a principal decay time of 4.37 μs and a light yield of up to 54 000 photons/MeV when measured using a silicon CCD photodetector. The light yield is the highest ever reported for an undoped crystal, and CHC also exhibits excellent lightmore » yield nonproportionality. These desirable properties allowed us to build and test CHC gamma-ray spectrometers providing energy resolution of 3.3% at 662 keV.« less

Phase transitions in the antiferromagnetic Ising model on a body-centered cubic lattice with interactions between next-to-nearest neighbors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murtazaev, A. K.; Ramazanov, M. K., E-mail: sheikh77@mail.ru; Kassan-Ogly, F. A.

2015-01-15

Phase transitions in the antiferromagnetic Ising model on a body-centered cubic lattice are studied on the basis of the replica algorithm by the Monte Carlo method and histogram analysis taking into account the interaction of next-to-nearest neighbors. The phase diagram of the dependence of the critical temperature on the intensity of interaction of the next-to-nearest neighbors is constructed. It is found that a second-order phase transition is realized in this model in the investigated interval of the intensities of interaction of next-to-nearest neighbors.

Excited-state lifetime measurement of silicon vacancy centers in diamond by single-photon frequency upconversion

NASA Astrophysics Data System (ADS)

Rong, Youying; Ma, Jianhui; Chen, Lingxiao; Liu, Yan; Siyushev, Petr; Wu, Botao; Pan, Haifeng; Jelezko, Fedor; Wu, E.; Zeng, Heping

2018-05-01

We report a method with high time resolution to measure the excited-state lifetime of silicon vacancy centers in bulk diamond avoiding timing jitter from the single-photon detectors. Frequency upconversion of the fluorescence emitted from silicon vacancy centers was achieved from 738 nm to 436 nm via sum frequency generation with a short pump pulse. The excited-state lifetime can be obtained by measuring the intensity of upconverted light while the pump delay changes. As a probe, a pump laser with pulse duration of 11 ps provided a high temporal resolution of the measurement. The lifetime extracted from the pump–probe curve was 0.755 ns, which was comparable to the timing jitter of the single-photon detectors.

Study of Inverse Ni-based Photonic Crystal using the Microradian X-ray Diffraction

NASA Astrophysics Data System (ADS)

Vasilieva, A. V.; Grigoryeva, N. A.; Mistonov, A. A.; Sapoletova, N. A.; Napolskii, K. S.; Eliseev, A. A.; Lukashin, A. V.; Tretyakov, Yu D.; Petukhov, A. V.; Byelov, D.; Chernyshov, D.; Okorokov, A. I.; Bouwman, W. G.; Grigoriev, S. V.

2010-10-01

Inverse photonic nickel-based crystal films formed by electrocrystallization of metal inside the voids of polymer artificial opal have been studied using the microradian X-ray diffraction. Analysis of the diffraction images agrees with an face-centred cubic (FCC) structure with the lattice constant a0 = 650 ± 10 nm and indicates two types of stacking sequences coexisting in the crystal (twins of ABCABC... and ACBACB... ordering motifs), the ratio between them being 4:5 The transverse structural correlation length Ltran is 2.4 ± 0.1 μm, which corresponds to a sample thickness of 6 layers. The in-plane structural correlation length Llong is 3.4 ± 0.2 μm, and the structure mosaic is of order of 10°.

Deformation Twins in Nanocrystalline Body-Centered Cubic Mo as Predicted by Molecular Dynamics Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Tonks; Bulent biner; Yongfeng Zhang

2012-10-01

This work studies deformation twins in nanocrystalline body-centered cubic Mo, including the nucleation and growth mechanisms as well as their effects on ductility, through molecular dynamics simulations. The deformation processes of nanocrystalline Mo are simulated using a columnar grain model with three different orientations. The deformation mechanisms identified, including dislocation slip, grain-boundary-mediated plasticity, deformation twins and martensitic transformation, are in agreement with previous studies. In (1 1 0) columnar grains, the deformation is dominated by twinning, which nucleates primarily from the grain boundaries by successive emission of twinning partials and thickens by jog nucleation in the grain interiors. Upon arrestmore » by a grain boundary, the twin may either produce continuous plastic strain across the grain boundary by activating compatible twinning/slip systems or result in intergranular failure in the absence of compatible twinning/slip systems in the neighboring grain. Multiple twinning systems can be activated in the same grain, and the competition between them favors those capable of producing continuous deformation across the grain boundary.« less

Surprising stability of neutral interstitial hydrogen in diamond and cubic BN

DOE PAGES

Lyons, J. L.; Van de Walle, C. G.

2016-01-21

We report that in virtually all semiconductors and insulators, hydrogen interstitials (H i) act as negative-U centers, implying that hydrogen is never stable in the neutral charge state. Using hybrid density functional calculations, we find a different behavior for H i in diamond and cubic BN. In diamond, H i is a very strong positive-U center, and the H 0 icharge state is stable over a Fermi-level range of more than 2 eV. In cubic BN, a III-V compound similar to diamond, we also find positive-U behavior, though over a much smaller Fermi-level range. Finally, these results highlight the uniquemore » behavior of Hi in these covalent wide-band-gap semiconductors.« less

Optical properties of opal photonic crystals

NASA Astrophysics Data System (ADS)

Eradat-Oskouei, Nayer

2001-10-01

Photonic crystals (PC) are a class of artificial structures with a periodic dielectric function in one, two, or three dimensions, in which the propagation of electromagnetic waves within a certain frequency band is forbidden. This forbidden frequency band has been dubbed photonic band gap (PBG). The position, width, depth, and shape of the PBG strongly depend on the periodicity, symmetry properties, dielectric constant contrast, and internal lattice structure of the unit cell. There is a common belief that PCs will perform many functions with light that ordinary crystals do with electrons. At the same time, PCs are of great promise to become a laboratory for testing fundamental processes involving interactions of radiation with matter in novel conditions. We have studied the optical properties of opal PCs that are infiltrated with metals, laser dyes, π-conjugated polymers, and J-aggregates. Opals are self-assembled structures of silica (SiO2) spheres mostly packed in a face centered cubic (fcc) lattice. Our research is summarized in the following six chapters. Chapter 1 is a review on the concepts related to PBG and PC, eigenvalue problem of electromagnetism, material systems that exhibit PBG. Chapter 2 covers all the fabrication and measurement techniques including angle resolved reflectivity, transmission, photoluminescence, photo-induced absorption, and coherent backscattering. Chapter 3 focuses on the relationship between a polaritonic gap and a photonic stop-band when they resonantly coexist in the same structure. Infiltration of opal with polarizable molecules combines the polaritonic and Bragg diffractive effects. The experimental results on reflectivity and its dependence on the impinging angle and concentration of the polarizable medium are in agreement with the theoretical calculations. In Chapter 4, the optical studies of three-dimensional metallic mesh composites are reported. Photonic and electronic properties of these PCs strongly depend on their

Photonic Component Qualification and Implementation Activities at NASA Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

Ott, Melanie N.; Jin, Xiaodan Linda; Chuska, Richard F.; LaRocca, Frank V.; MacMurphy, Shawn L.; Matuszeski, Adam J.; Zellar, Ronald S.; Friedberg, Patricia R.; Malenab, Mary C.

2006-01-01

The photonics group in Code 562 at NASA Goddard Space Flight Center supports a variety of space flight programs at NASA including the: International Space Station (ISS), Shuttle Return to Flight Mission, Lunar Reconnaissance Orbiter (LRO), Express Logistics Carrier, and the NASA Electronic Parts and Packaging Program (NEPP). Through research, development, and testing of the photonic systems to support these missions much information has been gathered on practical implementations for space environments. Presented here are the highlights and lessons learned as a result of striving to satisfy the project requirements for high performance and reliable commercial optical fiber components for space flight systems. The approach of how to qualify optical fiber components for harsh environmental conditions, the physics of failure and development lessons learned will be discussed.

Studies on photonic crystal composites: Fabrication and applications

NASA Astrophysics Data System (ADS)

Ying, Yurong

There is considerable interest in developing three-dimensional ordered dielectric structures because of their unique optical property, the photonic band gap. A material containing this photonic band gap can be used to control the propagation of electromagnetic waves. This characteristic can be utilized in fabricating a number of diffractive optical devices. A crystalline colloidal array (CCA) is one such three-dimensional ordered dielectric structure, formed through the self-assembly of monodispersed, surface-charged colloidal particles when they are dispersed in a polar liquid medium. Previous work has demonstrated that monodispersed, negatively charged polystyrene spheres can self-assemble into a face-centered cubic (fcc) structure when they are dispersed in a polar medium. This fee lattice can be locked in a hydrogel-based polymeric network and then encapsulated into a water-free elastomer network. These photonic crystal hydrogel films exhibit a solvatochromic effect. A method has been developed for creating patterns in photonic crystal hydrogel films based on this solvatochromic effect via a direct photopolymerization process. The multicolor pattern generation induced by this method resulted in macro- and micropatterns with a large color contrast, i.e. the difference between the patterned area and the background is greater than 150 nm. Unfortunately, CCA systems often exhibit intrinsic and extrinsic defects. To reduce the extrinsic defects incurred during the film fabrication process, a modified lithographic technique was developed to fabricate a high quality, large area, ca. 1 cm2 and a robust, water-free photonic band gap composite film having a thickness of 35 mum. The optical properties of these composite films change in response to their mechanical deformation. These robust films can change shape and recover after stretching or compression without destroying the order of the crystal. These thin films have a high sensitivity to a pressure variation when

Optical Anisotropy of Photonic Crystals of Cubic Symmetry Induced by Multiple Diffraction of Light

NASA Astrophysics Data System (ADS)

Ukleev, T. A.; Shevchenko, N. N.; Iurasova, D. I.; Sel'kin, A. V.

2018-05-01

The optical spectra of Bragg reflection from opal-like photonic crystals under conditions of the resonant enhancement of the multiple diffraction of light have been studied experimentally and theoretically using the photonic crystal structures prepared of monodisperse polystyrene globules. It is shown that the reflection signal registered in mutually orthogonal configurations of the polarizer and analyzer is related to the intrinsic optical anisotropy of the crystals and is a specific manifestation of the multiple Bragg diffraction in three-dimensional photonic crystals.

New edge-centered photonic square lattices with flat bands

NASA Astrophysics Data System (ADS)

Zhang, Da; Zhang, Yiqi; Zhong, Hua; Li, Changbiao; Zhang, Zhaoyang; Zhang, Yanpeng; Belić, Milivoj R.

2017-07-01

We report a new class of edge-centered photonic square lattices with multiple flat bands, and consider in detail two examples: the Lieb-5 and Lieb-7 lattices. In these lattices, there are 5 and 7 sites in the unit cell and in general, the number is restricted to odd integers. The number of flat bands m in the new Lieb lattices is related to the number of sites N in the unit cell by a simple formula m =(N - 1) / 2. The flat bands reported here are independent of the pseudomagnetic field. The properties of lattices with even and odd number of flat bands are different. We consider the localization of light in such Lieb lattices. If the input beam excites the flat-band mode, it will not diffract during propagation, owing to the strong mode localization. In the Lieb-7 lattice, the beam will also oscillate during propagation and still not diffract. The period of oscillation is determined by the energy difference between the two flat bands. This study provides a new platform for investigating light trapping, photonic topological insulators, and pseudospin-mediated vortex generation.

Singular orientations and faceted motion of dislocations in body-centered cubic crystals.

PubMed

Kang, Keonwook; Bulatov, Vasily V; Cai, Wei

2012-09-18

Dislocation mobility is a fundamental material property that controls strength and ductility of crystals. An important measure of dislocation mobility is its Peierls stress, i.e., the minimal stress required to move a dislocation at zero temperature. Here we report that, in the body-centered cubic metal tantalum, the Peierls stress as a function of dislocation orientation exhibits fine structure with several singular orientations of high Peierls stress-stress spikes-surrounded by vicinal plateau regions. While the classical Peierls-Nabarro model captures the high Peierls stress of singular orientations, an extension that allows dislocations to bend is necessary to account for the plateau regions. Our results clarify the notion of dislocation kinks as meaningful only for orientations within the plateau regions vicinal to the Peierls stress spikes. These observations lead us to propose a Read-Shockley type classification of dislocation orientations into three distinct classes-special, vicinal, and general-with respect to their Peierls stress and motion mechanisms. We predict that dislocation loops expanding under stress at sufficiently low temperatures, should develop well defined facets corresponding to two special orientations of highest Peierls stress, the screw and the M111 orientations, both moving by kink mechanism. We propose that both the screw and the M111 dislocations are jointly responsible for the yield behavior of BCC metals at low temperatures.

126. MOTOR CONTROL CENTER 1 (MCC1), FACING NORTH IN ROW ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

126. MOTOR CONTROL CENTER 1 (MCC-1), FACING NORTH IN ROW OF ELECTRICAL CABINETS JUST SOUTH OF TRANSFORMER SUBSTATION CABINETS IN TRANSFORMER ROOM (112), LSB (BLDG. 770) - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

Estimating the board foot to cubic foot ratio

Treesearch

Steve P. Verrill; Victoria L. Herian; Henry N. Spelter

2004-01-01

Certain issues in recent softwood lumber trade negotiations have centered on the method for converting estimates of timber volumes reported in cubic meters to board feet. Such conversions depend on many factors; three of the most important of these are log length, diameter, and taper. Average log diameters vary by region and have declined in the western United States...

Formation of prismatic loops from C15 Laves phase interstitial clusters in body-centered cubic iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yongfeng; Bai, Xian-Ming; Tonks, Michael R.

2015-03-01

This Letter reports the transition of C15 phase self-interstitial clusters to loops in body-centered-cubic Iron. Molecular dynamics simulations are performed to evaluate the relative stabilities of difference interstitial cluster configurations including C15 phase structure and <100> and <111>/2 loops. Within a certain size range, C15 cluster are found more stable than loops, and the relative stabilities are reversed beyond that range. In accordance to the crossover in relative stabilities, C15 clusters may grow by absorbing individual interstitials at small sizes and transitions into loops eventually. The transition takes place by nucleation and reaction of <111>/2 loop segments. These observations explainmore » the absence of C15 phase interstitial clusters predicted by density-functional-theory calculations in previous experimental observations. More importantly, the current results provide a new formation mechanism of <100> loops which requires no interaction of loops.« less

Energy gap formation mechanism through the interference phenomena of electrons in face-centered cubic elements and compounds with the emphasis on half-Heusler and Heusler compounds

NASA Astrophysics Data System (ADS)

Mizutani, U.; Sato, H.

2018-05-01

Many face-centred cubic elements and compounds with the number of atoms per unit cell N equal to 8, 12 and 16 are known to be stabilised by forming either a band gap or a pseudogap at the Fermi level. They are conveniently expressed as cF8, cF12 and cF16, respectively, in the Pearson symbol. From the cF8 family, we worked on three tetravalent elements C (diamond), Si and Ge, SZn-type AsGa compound and NaCl-type compounds like BiLu, AsSc, etc. From the cF12 family, more than 80 compounds were selected, with a particular emphasis on ABC- and half-Heusler-type ternary equiatomic compounds. Among cF16 compounds, both the Heusler compounds ABC2 and Zintl compounds were studied. We revealed that, regardless of whether or not the transition metal (TM) and/or rare-earth (RE) elements are involved as constituent elements, the energy gap formation mechanism for cF8, cF12 and cF16 compounds can be universally discussed in terms of interference phenomenon of itinerant electrons with set of reciprocal lattice planes with ? = 8, 11 and 12, where ? refers to square of the critical reciprocal of lattice vector of an fcc lattice. The number of itinerant electrons per unit cell, e/uc, for all these band gap/pseudogap-bearing compounds is found to fall on a universal line called "3/2-power law" when plotted against ? on a logarithmic scale. This proves the validity of the fulfilment of the interference condition ? in conformity with other pseudogap compounds with different crystal symmetries and different sizes of the unit cell reported in literature.

Interpretation of small-angle diffraction experiments on opal-like photonic crystals

NASA Astrophysics Data System (ADS)

Marlow, F.; Muldarisnur, M.; Sharifi, P.; Zabel, H.

2011-08-01

Comprehensive structural information on artificial opals involving the deviations from the strongly dominating face-centered cubic structure is still missing. Recent structure investigations with neutrons and synchrotron sources have shown a high degree of order but also a number of unexpected scattering features. Here, we point out that the exclusion of the allowed 002-type diffraction peaks by a small atomic form factor is not obvious and that surface scattering has to be included as a possible source for the diffraction peaks. Our neutron diffraction data indicate that surface scattering is the main reason for the smallest-angle peaks in the diffraction patterns.

Calculations of and evidence for chain packing stress in inverse lyotropic bicontinuous cubic phases.

PubMed

Shearman, Gemma C; Khoo, Bee J; Motherwell, Mary-Lynn; Brakke, Kenneth A; Ces, Oscar; Conn, Charlotte E; Seddon, John M; Templer, Richard H

2007-06-19

Inverse bicontinuous cubic lyotropic phases are a complex solution to the dilemma faced by all self-assembled water-amphiphile systems: how to satisfy the incompatible requirements for uniform interfacial curvature and uniform molecular packing. The solution reached in this case is for the water-amphiphile interfaces to deform hyperbolically onto triply periodic minimal surfaces. We have previously suggested that although the molecular packing in these structures is rather uniform the relative phase behavior of the gyroid, double diamond, and primitive inverse bicontinuous cubic phases can be understood in terms of subtle differences in packing frustration. In this work, we have calculated the packing frustration for these cubics under the constraint that their interfaces have constant mean curvature. We find that the relative packing stress does indeed differ between phases. The gyroid cubic has the least packing stress, and at low water volume fraction, the primitive cubic has the greatest packing stress. However, at very high water volume fraction, the double diamond cubic becomes the structure with the greatest packing stress. We have tested the model in two ways. For a system with a double diamond cubic phase in excess water, the addition of a hydrophobe may release packing frustration and preferentially stabilize the primitive cubic, since this has previously been shown to have lower curvature elastic energy. We have confirmed this prediction by adding the long chain alkane tricosane to 1-monoolein in excess water. The model also predicts that if one were able to hydrate the double diamond cubic to high water volume fractions, one should destabilize the phase with respect to the primitive cubic. We have found that such highly swollen metastable bicontinuous cubic phases can be formed within onion vesicles. Data from monoelaidin in excess water display a well-defined transition, with the primitive cubic appearing above a water volume fraction of 0.75. Both of

Large-area metallic photonic lattices for military applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting Shan

2007-11-01

In this project we developed photonic crystal modeling capability and fabrication technology that is scaleable to large area. An intelligent optimization code was developed to find the optimal structure for the desired spectral response. In terms of fabrication, an exhaustive survey of fabrication techniques that would meet the large area requirement was reduced to Deep X-ray Lithography (DXRL) and nano-imprint. Using DXRL, we fabricated a gold logpile photonic crystal in the <100> plane. For the nano-imprint technique, we fabricated a cubic array of gold squares. These two examples also represent two classes of metallic photonic crystal topologies, the connected networkmore » and cermet arrangement.« less

Hybrid quantum gates between flying photon and diamond nitrogen-vacancy centers assisted by optical microcavities

PubMed Central

Wei, Hai-Rui; Lu Long, Gui

2015-01-01

Hybrid quantum gates hold great promise for quantum information processing since they preserve the advantages of different quantum systems. Here we present compact quantum circuits to deterministically implement controlled-NOT, Toffoli, and Fredkin gates between a flying photon qubit and diamond nitrogen-vacancy (NV) centers assisted by microcavities. The target qubits of these universal quantum gates are encoded on the spins of the electrons associated with the diamond NV centers and they have long coherence time for storing information, and the control qubit is encoded on the polarizations of the flying photon and can be easily manipulated. Our quantum circuits are compact, economic, and simple. Moreover, they do not require additional qubits. The complexity of our schemes for universal three-qubit gates is much reduced, compared to the synthesis with two-qubit entangling gates. These schemes have high fidelities and efficiencies, and they are feasible in experiment. PMID:26271899

Characterization of photonic colloidal crystals in real and reciprocal space

NASA Astrophysics Data System (ADS)

Thijssen, J. H. J.

2007-05-01

In this thesis, we present experimental work on the characterization of photonic colloidal crystals in real and reciprocal space. Photonic crystals are structures in which the refractive index varies periodically in space on the length scale of the wavelength of light. Self-assembly of colloidal particles is a promising route towards three-dimensional (3-D) photonic crystals. However, fabrication of photonic band-gap materials remains challenging, so calculations that predict their optical properties are indispensable. Our photonic band-structure calculations on binary Laves phases have led to a proposed route towards photonic colloidal crystals with a band gap in the visible region. Furthermore, contrary to results in literature, we found that there is no photonic band gap for inverse BCT crystals. Finally, optical spectra of colloidal crystals were analyzed using band-structure calculations. Self-assembled photonic crystals are fabricated in multiple steps. Each of these steps can significantly affect the 3-D structure of the resulting crystal. X-rays are an excellent probe of the internal structure of photonic crystals, even if the refractive-index contrast is large. In Chapter 3, we demonstrate that an angular resolution of 0.002 mrad is achievable at a third-generation synchrotron using compound refractive optics. As a result, the position and the width of Bragg reflections in 2D diffraction patterns can be resolved, even for lattice spacings larger than a micrometer (corresponding to approximately 0.1 mrad). X-ray diffraction patterns and electron-microscopy images are used in Chapter 4 to determine the orientation of hexagonal layers in convective-assembly colloidal crystals. Quantitative analysis revealed that, in our samples, the layers were not exactly hexagonal and the stacking sequence was that of face-centered cubic (FCC) crystals, though stacking faults may have been present. In Chapter 5, binary colloidal crystals of organic spheres (polystyrene

Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.

PubMed

Nakatani, Tomotaka; Yoshiasa, Akira; Nakatsuka, Akihiko; Hiratoko, Tatsuya; Mashimo, Tsutomu; Okube, Maki; Sasaki, Satoshi

2016-02-01

A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.

Signature of dislocations and stacking faults of face-centred cubic nanocrystals in coherent X-ray diffraction patterns: a numerical study.

PubMed

Dupraz, Maxime; Beutier, Guillaume; Rodney, David; Mordehai, Dan; Verdier, Marc

2015-06-01

Crystal defects induce strong distortions in diffraction patterns. A single defect alone can yield strong and fine features that are observed in high-resolution diffraction experiments such as coherent X-ray diffraction. The case of face-centred cubic nanocrystals is studied numerically and the signatures of typical defects close to Bragg positions are identified. Crystals of a few tens of nanometres are modelled with realistic atomic potentials and 'relaxed' after introduction of well defined defects such as pure screw or edge dislocations, or Frank or prismatic loops. Diffraction patterns calculated in the kinematic approximation reveal various signatures of the defects depending on the Miller indices. They are strongly modified by the dissociation of the dislocations. Selection rules on the Miller indices are provided, to observe the maximum effect of given crystal defects in the initial and relaxed configurations. The effect of several physical and geometrical parameters such as stacking fault energy, crystal shape and defect position are discussed. The method is illustrated on a complex structure resulting from the simulated nanoindentation of a gold nanocrystal.

Invariant Deformation Element Model Interpretation to the Crystallography of Diffusional Body-Centered-Cube to Face-Centered-Cube Phase Transformations

NASA Astrophysics Data System (ADS)

Liu, Hongwei; Liu, Jiangwen; Su, Guangcai; Li, Weizhou; Zeng, Jianmin; Hu, Zhiliu

2012-10-01

The crystallography of body-centered-cube to face-centered cube (bcc-to-fcc) diffusion phase transformations in a duplex stainless steel and a Cu-Zn alloy, including long axis, orientation relationship (OR), habit plane (HP), and dislocation spacing, is successfully interpreted with one-step rotation from the Bain lattice relationship by applying a simplified invariant line (IL) analysis. It is proposed that the dislocation slipping direction in the matrix plays an important role in controlling the crystallography of precipitation.

Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

NASA Technical Reports Server (NTRS)

Tatarenko, Valentine A.; Tsysman, Constantin L.; Oltarzhevskaya, Yelena T.

1995-01-01

The calculations in a majority of previous works for the fulleride (AqC-60) crystals were performed within the framework of the rigid-lattice model, neglecting the distortion relaxation of the host fullerene (C-60) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distortion field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. The given paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of static concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method(*). In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the static inherent reorientation and/or displacements of the solvent molecules from the 'average-lattice' sites' as well as on the lattice parameter a of a elastically-anysotropic 'cubic' C-60 crystal are taken into account.

Nanoscale characterization of local structures and defects in photonic crystals using synchrotron-based transmission soft X-ray microscopy

PubMed Central

Nho, Hyun Woo; Kalegowda, Yogesh; Shin, Hyun-Joon; Yoon, Tae Hyun

2016-01-01

For the structural characterization of the polystyrene (PS)-based photonic crystals (PCs), fast and direct imaging capabilities of full field transmission X-ray microscopy (TXM) were demonstrated at soft X-ray energy. PS-based PCs were prepared on an O2-plasma treated Si3N4 window and their local structures and defects were investigated using this label-free TXM technique with an image acquisition speed of ~10 sec/frame and marginal radiation damage. Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components. Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated. This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties. PMID:27087141

Pressures We Face in Running Counseling Centers on College and University Campuses

ERIC Educational Resources Information Center

Meilman, Philip W.

2016-01-01

In this article, Georgetown University Counseling and Psychiatric Service director Philip Meilman discusses two distinct emerging pressures faced by directors of college and university counseling centers. The first of these is the pressure to provide more of, and an increasing range of, counseling and psychiatric services. The second is related:…

Application of quantum-dot multi-wavelength lasers and silicon photonic ring resonators to data-center optical interconnects

NASA Astrophysics Data System (ADS)

Beckett, Douglas J. S.; Hickey, Ryan; Logan, Dylan F.; Knights, Andrew P.; Chen, Rong; Cao, Bin; Wheeldon, Jeffery F.

2018-02-01

Quantum dot comb sources integrated with silicon photonic ring-resonator filters and modulators enable the realization of optical sub-components and modules for both inter- and intra-data-center applications. Low-noise, multi-wavelength, single-chip, laser sources, PAM4 modulation and direct detection allow a practical, scalable, architecture for applications beyond 400 Gb/s. Multi-wavelength, single-chip light sources are essential for reducing power dissipation, space and cost, while silicon photonic ring resonators offer high-performance with space and power efficiency.

Body centered cubic magnesium niobium hydride with facile room temperature absorption and four weight percent reversible capacity.

PubMed

Tan, XueHai; Wang, Liya; Holt, Chris M B; Zahiri, Beniamin; Eikerling, Michael H; Mitlin, David

2012-08-21

We have synthesized a new metastable metal hydride with promising hydrogen storage properties. Body centered cubic (bcc) magnesium niobium hydride (Mg(0.75)Nb(0.25))H(2) possesses 4.5 wt% hydrogen gravimetric density, with 4 wt% being reversible. Volumetric hydrogen absorption measurements yield an enthalpy of hydride formation of -53 kJ mol(-1) H(2), which indicates a significant thermodynamic destabilization relative to the baseline -77 kJ mol(-1) H(2) for rutile MgH(2). The hydrogenation cycling kinetics are remarkable. At room temperature and 1 bar hydrogen it takes 30 minutes to absorb a 1.5 μm thick film at sorption cycle 1, and 1 minute at cycle 5. Reversible desorption is achieved in about 60 minutes at 175 °C. Using ab initio calculations we have examined the thermodynamic stability of metallic alloys with hexagonal close packed (hcp) versus bcc crystal structure. Moreover we have analyzed the formation energies of the alloy hydrides that are bcc, rutile or fluorite.

Universal photonic quantum gates assisted by ancilla diamond nitrogen-vacancy centers coupled to resonators

NASA Astrophysics Data System (ADS)

Wei, Hai-Rui; Long, Gui Lu

2015-03-01

We propose two compact, economic, and scalable schemes for implementing optical controlled-phase-flip and controlled-controlled-phase-flip gates by using the input-output process of a single-sided cavity strongly coupled to a single nitrogen-vacancy-center defect in diamond. Additional photonic qubits, necessary for procedures based on the parity-check measurement or controlled-path and merging gates, are not employed in our schemes. In the controlled-path gate, the paths of the target photon are conditionally controlled by the control photon, and these two paths can be merged back into one by using a merging gate. Only one half-wave plate is employed in our scheme for the controlled-phase-flip gate. Compared with the conventional synthesis procedures for constructing a controlled-controlled-phase-flip gate, the cost of which is two controlled-path gates and two merging gates, or six controlled-not gates, our scheme is more compact and simpler. Our schemes could be performed with a high fidelity and high efficiency with current achievable experimental techniques.

Signature of dislocations and stacking faults of face-centred cubic nanocrystals in coherent X-ray diffraction patterns: a numerical study1

PubMed Central

Dupraz, Maxime; Beutier, Guillaume; Rodney, David; Mordehai, Dan; Verdier, Marc

2015-01-01

Crystal defects induce strong distortions in diffraction patterns. A single defect alone can yield strong and fine features that are observed in high-resolution diffraction experiments such as coherent X-ray diffraction. The case of face-centred cubic nanocrystals is studied numerically and the signatures of typical defects close to Bragg positions are identified. Crystals of a few tens of nanometres are modelled with realistic atomic potentials and ‘relaxed’ after introduction of well defined defects such as pure screw or edge dislocations, or Frank or prismatic loops. Diffraction patterns calculated in the kinematic approximation reveal various signatures of the defects depending on the Miller indices. They are strongly modified by the dissociation of the dislocations. Selection rules on the Miller indices are provided, to observe the maximum effect of given crystal defects in the initial and relaxed configurations. The effect of several physical and geometrical parameters such as stacking fault energy, crystal shape and defect position are discussed. The method is illustrated on a complex structure resulting from the simulated nanoindentation of a gold nanocrystal. PMID:26089755

Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatarenko, V.A.; Tsysman, C.L.; Oltarzhevskaya, Y.T.

1994-12-31

The calculations in a majority of previous works for the fulleride (AqC{sub 60}) crystals were performed within the framework of the rigid-lattice model, neglecting the distoration relaxation of the host fullerene (C{sub 60}) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distoration field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. This paper seeks to find a functional relationmore » between the amplitudes of the doping-induced structure-distortion waves and of statistic concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method. In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the statistic inherent reorientation and/or displacements of the solvent molecules from the average-lattice sites as well as on the lattice parameter a of the elastically-anysotropic cubic C{sub 60} crystal are taken into account.« less

Dosimetry quality audit of high energy photon beams in greek radiotherapy centers.

PubMed

Hourdakis, Constantine J; Boziari, A

2008-04-01

Dosimetry quality audits and intercomparisons in radiotherapy centers is a useful tool in order to enhance the confidence for an accurate therapy and to explore and dissolve discrepancies in dose delivery. This is the first national comprehensive study that has been carried out in Greece. During 2002--2006 the Greek Atomic Energy Commission performed a dosimetry quality audit of high energy external photon beams in all (23) Greek radiotherapy centers, where 31 linacs and 13 Co-60 teletherapy units were assessed in terms of their mechanical performance characteristics and relative and absolute dosimetry. The quality audit in dosimetry of external photon beams took place by means of on-site visits, where certain parameters of the photon beams were measured, calculated and assessed according to a specific protocol and the IAEA TRS 398 dosimetry code of practice. In each radiotherapy unit (Linac or Co-60), certain functional parameters were measured and the results were compared to tolerance values and limits. Doses in water under reference and non reference conditions were measured and compared to the stated values. Also, the treatment planning systems (TPS) were evaluated with respect to irradiation time calculations. The results of the mechanical tests, dosimetry measurements and TPS evaluation have been presented in this work and discussed in detail. This study showed that Co-60 units had worse performance mechanical characteristics than linacs. 28% of all irradiation units (23% of linacs and 42% of Co-60 units) exceeded the acceptance limit at least in one mechanical parameter. Dosimetry accuracy was much worse in Co60 units than in linacs. 61% of the Co60 units exhibited deviations outside +/-3% and 31% outside +/-5%. The relevant percentages for the linacs were 24% and 7% respectively. The results were grouped for each hospital and the sources of errors (functional and human) have been investigated and discussed in details. This quality audit proved to be a

Scalable fabrication of coupled NV center - photonic crystal cavity systems by self-aligned N ion implantation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schröder, T.; Walsh, M.; Zheng, J.

2017-04-06

Towards building large-scale integrated photonic systems for quantum information processing, spatial and spectral alignment of single quantum systems to photonic nanocavities is required. In this paper, we demonstrate spatially targeted implantation of nitrogen vacancy (NV) centers into the mode maximum of 2-d diamond photonic crystal cavities with quality factors up to 8000, achieving an average of 1.1 ± 0.2 NVs per cavity. Nearly all NV-cavity systems have significant emission intensity enhancement, reaching a cavity-fed spectrally selective intensity enhancement, F int, of up to 93. Although spatial NV-cavity overlap is nearly guaranteed within about 40 nm, spectral tuning of the NV’smore » zero-phonon-line (ZPL) is still necessary after fabrication. To demonstrate spectral control, we temperature tune a cavity into an NV ZPL, yielding F ZPL int~5 at cryogenic temperatures.« less

Face, Body, and Center of Gravity Mediate Person Detection in Natural Scenes

ERIC Educational Resources Information Center

Bindemann, Markus; Scheepers, Christoph; Ferguson, Heather J.; Burton, A. Mike

2010-01-01

Person detection is an important prerequisite of social interaction, but is not well understood. Following suggestions that people in the visual field can capture a viewer's attention, this study examines the role of the face and the body for person detection in natural scenes. We observed that viewers tend first to look at the center of a scene,…

Where do the 3.5 keV photons come from? A morphological study of the Galactic Center and of Perseus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlson, Eric; Jeltema, Tesla; Profumo, Stefano, E-mail: erccarls@ucsc.edu, E-mail: tesla@ucsc.edu, E-mail: profumo@ucsc.edu

We test the origin of the 3.5 keV line photons by analyzing the morphology of the emission at that energy from the Galactic Center and from the Perseus cluster of galaxies. We employ a variety of different templates to model the continuum emission and analyze the resulting radial and azimuthal distribution of the residual emission. We then perform a pixel-by-pixel binned likelihood analysis including line emission templates and dark matter templates and assess the correlation of the 3.5 keV emission with these templates. We conclude that the radial and azimuthal distribution of the residual emission is incompatible with a darkmore » matter origin for both the Galactic center and Perseus; the Galactic center 3.5 keV line photons trace the morphology of lines at comparable energy, while the Perseus 3.5 keV photons are highly correlated with the cluster's cool core, and exhibit a morphology incompatible with dark matter decay. The template analysis additionally allows us to set the most stringent constraints to date on lines in the 3.5 keV range from dark matter decay.« less

Drude weight and optical conductivity of a two-dimensional heavy-hole gas with k-cubic spin-orbit interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mawrie, Alestin; Ghosh, Tarun Kanti

We present a detailed theoretical study on zero-frequency Drude weight and optical conductivity of a two-dimensional heavy-hole gas (2DHG) with k-cubic Rashba and Dresselhaus spin-orbit interactions. The presence of k-cubic spin-orbit couplings strongly modifies the Drude weight in comparison to the electron gas with k-linear spin-orbit couplings. For large hole density and strong k-cubic spin-orbit couplings, the density dependence of Drude weight deviates from the linear behavior. We establish a relation between optical conductivity and the Berry connection. Unlike two-dimensional electron gas with k-linear spin-orbit couplings, we explicitly show that the optical conductivity does not vanish even for equal strengthmore » of the two spin-orbit couplings. We attribute this fact to the non-zero Berry phase for equal strength of k-cubic spin-orbit couplings. The least photon energy needed to set in the optical transition in hole gas is one order of magnitude smaller than that of electron gas. Types of two van Hove singularities appear in the optical spectrum are also discussed.« less

Photonic crystal surface-emitting lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chua, Song Liang; Lu, Ling; Soljacic, Marin

2015-06-23

A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-planemore » feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.« less

Using Latex Balls and Acrylic Resin Plates to Investigate the Stacking Arrangement and Packing Efficiency of Metal Crystals

ERIC Educational Resources Information Center

Ohashi, Atsushi

2015-01-01

A high-school third-year or undergraduate first-semester general chemistry laboratory experiment introducing simple-cubic, face-centered cubic, body-centered cubic, and hexagonal closest packing unit cells is presented. Latex balls and acrylic resin plates are employed to make each atomic arrangement. The volume of the vacant space in each cell is…

Packing of nonoverlapping cubic particles: Computational algorithms and microstructural characteristics

NASA Astrophysics Data System (ADS)

Malmir, Hessam; Sahimi, Muhammad; Tabar, M. Reza Rahimi

2016-12-01

Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO2 sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir et al., Sci. Rep. 6, 35024 (2016), 10.1038/srep35024]. A modification of the random sequential addition (RSA) algorithm has been developed to generate such packings, and a variety of microstructural descriptors, including the radial distribution function, the face-normal correlation function, two-point probability and cluster functions, the lineal-path function, the pore-size distribution function, and surface-surface and surface-void correlation functions, have been computed, along with the specific surface and mean chord length of the packings. The results indicate the existence of both spatial and orientational long-range order as the the packing density increases. The maximum packing fraction achievable with the RSA method is about 0.57, which represents the limit for a structure similar to liquid crystals.

Blended Outreach: Face-to-Face and Remote Programs

ERIC Educational Resources Information Center

Poeppelmeyer, Diana

2011-01-01

The Texas School for the Deaf (TSD) has two missions. One is to provide educational services to deaf and hard of hearing students and their families on the Austin campus--this is the traditional, face-to-face, center-based service model. The other is to serve as a resource center for the state, providing information, referral, programs, and…

A topological coordinate system for the diamond cubic grid.

PubMed

Čomić, Lidija; Nagy, Benedek

2016-09-01

Topological coordinate systems are used to address all cells of abstract cell complexes. In this paper, a topological coordinate system for cells in the diamond cubic grid is presented and some of its properties are detailed. Four dependent coordinates are used to address the voxels (triakis truncated tetrahedra), their faces (hexagons and triangles), their edges and the points at their corners. Boundary and co-boundary relations, as well as adjacency relations between the cells, can easily be captured by the coordinate values. Thus, this coordinate system is apt for implementation in various applications, such as visualizations, morphological and topological operations and shape analysis.

Einsteinian cubic gravity

NASA Astrophysics Data System (ADS)

Bueno, Pablo; Cano, Pablo A.

2016-11-01

We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a D -dimensional cubic theory of gravity which satisfies the following properties: (1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; (2) it is defined in the same way in general dimensions; (3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones. We show that, up to cubic order, there exists only one additional theory satisfying requirements (1) and (2). Interestingly, this theory is, along with Einstein gravity, the only one which also satisfies (3).

General hyperconcentration of photonic polarization-time-bin hyperentanglement assisted by nitrogen-vacancy centers coupled to resonators

NASA Astrophysics Data System (ADS)

Du, Fang-Fang; Deng, Fu-Guo; Long, Gui-Lu

2016-11-01

Entanglement concentration protocol (ECP) is used to extract the maximally entangled states from less entangled pure states. Here we present a general hyperconcentration protocol for two-photon systems in partially hyperentangled Bell states that decay with the interrelation between the time-bin and the polarization degrees of freedom (DOFs), resorting to an input-output process with respect to diamond nitrogen-vacancy centers coupled to resonators. We show that the resource can be utilized sufficiently and the success probability is largely improved by iteration of the hyper-ECP process. Besides, our hyper-ECP can be directly extended to concentrate nonlocal partially hyperentangled N-photon Greenberger-Horne-Zeilinger states, and the success probability remains unchanged with the growth of the number of photons. Moreover, the time-bin entanglement is a useful DOF and it only requires one path for transmission, which means it not only economizes on a large amount of quantum resources but also relaxes from the path-length dispersion in long-distance quantum communication.

General hyperconcentration of photonic polarization-time-bin hyperentanglement assisted by nitrogen-vacancy centers coupled to resonators

PubMed Central

Du, Fang-Fang; Deng, Fu-Guo; Long, Gui-Lu

2016-01-01

Entanglement concentration protocol (ECP) is used to extract the maximally entangled states from less entangled pure states. Here we present a general hyperconcentration protocol for two-photon systems in partially hyperentangled Bell states that decay with the interrelation between the time-bin and the polarization degrees of freedom (DOFs), resorting to an input-output process with respect to diamond nitrogen-vacancy centers coupled to resonators. We show that the resource can be utilized sufficiently and the success probability is largely improved by iteration of the hyper-ECP process. Besides, our hyper-ECP can be directly extended to concentrate nonlocal partially hyperentangled N-photon Greenberger-Horne-Zeilinger states, and the success probability remains unchanged with the growth of the number of photons. Moreover, the time-bin entanglement is a useful DOF and it only requires one path for transmission, which means it not only economizes on a large amount of quantum resources but also relaxes from the path-length dispersion in long-distance quantum communication. PMID:27804973

Photonic band gap properties of one-dimensional Thue-Morse all-dielectric photonic quasicrystal

NASA Astrophysics Data System (ADS)

Yue, Chenxi; Tan, Wei; Liu, Jianjun

2018-05-01

In this paper, the photonic band gap (PBG) properties of one-dimensional (1D) Thue-Morse photonic quasicrystal (PQC) S4 structure are theoretically investigated by using transfer matrix method in Bragg condition. The effects of the center wavelength, relative permittivity and incident angle on PBG properties are elaborately analyzed. Numerical results reveal that, in the case of normal incidence, the symmetry and periodicity properties of the photonic band structure are presented. As the center wavelength increases, the PBG center frequency and PBG width decrease while the photonic band structure is always symmetrical about the central frequency and the photonic band structure repeats periodically in the expanding observation frequency range. With the decrease of relative permittivity contrast, the PBG width and the relative PBG width gradually decreases until PBG disappears while the symmetry of the photonic band structure always exists. In the case of oblique incidence, as the incident angle increases, multiple narrow PBGs gradually merge into a wide PBG for the TE mode while for the TM mode, the number of PBG continuously decreases and eventually disappears, i.e., multiple narrow PBGs become a wide passband for the TM mode. The research results will provide a reference for the choice of the material, the incident angle for the PBG properties and its applications of 1D Thue-Morse PQC.

Cubic nitride templates

DOEpatents

Burrell, Anthony K; McCleskey, Thomas Mark; Jia, Quanxi; Mueller, Alexander H; Luo, Hongmei

2013-04-30

A polymer-assisted deposition process for deposition of epitaxial cubic metal nitride films and the like is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures under a suitable atmosphere to yield metal nitride films and the like. Such films can be used as templates for the development of high quality cubic GaN based electronic devices.

Cubic martensite in high carbon steel

NASA Astrophysics Data System (ADS)

Chen, Yulin; Xiao, Wenlong; Jiao, Kun; Ping, Dehai; Xu, Huibin; Zhao, Xinqing; Wang, Yunzhi

2018-05-01

A distinguished structural characteristic of martensite in Fe-C steels is its tetragonality originating from carbon atoms occupying only one set of the three available octahedral interstitial sites in the body-centered-cubic (bcc) Fe lattice. Such a body-centered-tetragonal (bct) structure is believed to be thermodynamically stable because of elastic interactions between the interstitial carbon atoms. For such phase stability, however, there has been a lack of direct experimental evidence despite extensive studies of phase transformations in steels over one century. In this Rapid Communication, we report that the martensite formed in a high carbon Fe-8Ni-1.26C (wt%) steel at room temperature induced by applied stress/strain has actually a bcc rather than a bct crystal structure. This finding not only challenges the existing theories on the stability of bcc vs bct martensite in high carbon steels, but also provides insights into the mechanism for martensitic transformation in ferrous alloys.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, Amit; Budai, John D.; Kroeger, Donald M.; Norton, David P.; Specht, Eliot D.; Christen, David K.

1998-01-01

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, Amit; Budai, John D.; Kroeger, Donald M.; Norton, David P.; Specht, Eliot D.; Christen, David K.

1999-01-01

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon.

Solving Cubic Equations by Polynomial Decomposition

ERIC Educational Resources Information Center

Kulkarni, Raghavendra G.

2011-01-01

Several mathematicians struggled to solve cubic equations, and in 1515 Scipione del Ferro reportedly solved the cubic while participating in a local mathematical contest, but did not bother to publish his method. Then it was Cardano (1539) who first published the solution to the general cubic equation in his book "The Great Art, or, The Rules of…

Multicolor photonic crystal laser array

DOEpatents

Wright, Jeremy B; Brener, Igal; Subramania, Ganapathi S; Wang, George T; Li, Qiming

2015-04-28

A multicolor photonic crystal laser array comprises pixels of monolithically grown gain sections each with a different emission center wavelength. As an example, two-dimensional surface-emitting photonic crystal lasers comprising broad gain-bandwidth III-nitride multiple quantum well axial heterostructures were fabricated using a novel top-down nanowire fabrication method. Single-mode lasing was obtained in the blue-violet spectral region with 60 nm of tuning (or 16% of the nominal center wavelength) that was determined purely by the photonic crystal geometry. This approach can be extended to cover the entire visible spectrum.

Using the Plan View to Teach Basic Crystallography in General Chemistry

ERIC Educational Resources Information Center

Cushman, Cody V.; Linford, Matthew R.

2015-01-01

The plan view is used in crystallography and materials science to show the positions of atoms in crystal structures. However, it is not widely used in teaching general chemistry. In this contribution, we introduce the plan view, and show these views for the simple cubic, body-centered cubic, face-centered cubic, hexagonal close packed, CsCl, NaCl,…

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

1998-04-21

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

1998-04-14

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

1999-04-27

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

Fiber-coupled superconducting nanowire single-photon detectors integrated with a bandpass filter on the fiber end-face

NASA Astrophysics Data System (ADS)

Zhang, W. J.; Yang, X. Y.; Li, H.; You, L. X.; Lv, C. L.; Zhang, L.; Zhang, C. J.; Liu, X. Y.; Wang, Z.; Xie, X. M.

2018-07-01

Superconducting nanowire single-photon detectors (SNSPDs) with both high system detection efficiency (SDE) and low dark count rate (DCR) play significant roles in quantum information processes and various applications. The background dark counts of SNSPDs originate from the room temperature blackbody radiation coupled to the device via a fiber. Therefore, a bandpass filter (BPF) operated at low temperature with minimal insert loss is necessary to suppress the background DCR. Herein, a low-loss BPF integrated on a single-mode fiber end-face was designed, fabricated and verified for the low temperature implement. The fiber end-face BPF was featured with a typical passband width about 40 nm in the 1550 nm telecom band and a peak transmittance of over 0.98. SNSPD with high SDE fabricated on a distributed Bragg reflector was coupled to the BPF. The device with such a BPF showed an SDE of 80% at a DCR of 0.5 Hz, measured at 2.1 K. Compared the same device without a BPF, the DCR was reduced by over 13 dB with an SDE decrease of <3%.

Light-Driven Reversible Transformation between Self-Organized Simple Cubic Lattice and Helical Superstructure Enabled by a Molecular Switch Functionalized Nanocage.

PubMed

Zhou, Kang; Bisoyi, Hari Krishna; Jin, Jian-Qiu; Yuan, Cong-Long; Liu, Zhen; Shen, Dong; Lu, Yan-Qing; Zheng, Zhi-Gang; Zhang, Weian; Li, Quan

2018-04-23

Self-organized stimuli-responsive smart materials with adjustable attributes are highly desirable for a plethora of device applications. Simple cubic lattice is quite uncommon in soft condensed matter due to its lower packing factor. Achieving a stable simple cubic soft lattice and endowing such a lattice with dynamic reconstruction capability solely by a facile light irradiation are of paramount significance for both fundamental studies and engineering explorations. Herein, an elegant stable self-organized simple cubic soft lattice, i.e., blue phase II, in a chiral liquid crystal (LC) system is disclosed, which is stable down to room temperature and exhibits both reversible lattice deformation and transformation to a helical superstructure, i.e., cholesteric LC, by light stimulation. Such an amazing trait is attained by doping a judiciously designed achiral photoresponsive molecular switch functionalized polyhedral oligomeric silsesquioxane nanocage into a chiral LC host. An unprecedented reversible collapse and reconstruction of such a high symmetric simple cubic blue phase II driven by light has been achieved. Furthermore, a well-defined conglomerate micropattern composed of simple cubic soft lattice and helical superstructure, which is challenging to fabricate in organic and inorganic crystalline materials, is produced using photomasking technology. Moreover, the promising photonic application based on such a micropattern is demonstrated. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Origin of coloration in beetle scales: An optical and structural investigation

NASA Astrophysics Data System (ADS)

Nagi, Ramneet Kaur

In this thesis the origin of angle-independent yellowish-green coloration of the exoskeleton of a beetle was studied. The beetle chosen was a weevil with the Latin name Eupholus chevrolati. The origin of this weevil's coloration was investigated by optical and structural characterization techniques, including optical microscopy, scanning electron microscopy imaging and focused ion beam milling, combined with three-dimensional modeling and photonic band structure calculations. Furthermore, using color theory the pixel-like coloring of the weevil's exoskeleton was investigated and an interesting additive color mixing scheme was discovered. For optical studies, a microreflectance microscopy/spectroscopy set-up was optimized. This set-up allowed not only for imaging of individual colored exoskeleton domains with sizes ˜2-10 μm, but also for obtaining reflection spectra of these micrometer-sized domains. Spectra were analyzed in terms of reflection intensity and wavelength position and shape of the reflection features. To find the origin of these colored exoskeleton spots, a combination of focused ion beam milling and scanning electron microscopy imaging was employed. A three-dimensional photonic crystal in the form of a face-centered cubic lattice of ABC-stacked air cylinders in a biopolymeric cuticle matrix was discovered. Our photonic band structure calculations revealed the existence of different sets of stop-gaps for the lattice constant of 360, 380 and 400 nm in the main lattice directions, Gamma-L, Gamma-X, Gamma-U, Gamma-W and Gamma-K. In addition, scanning electron microscopy images were compared to the specific directional-cuts through the constructed face-centered cubic lattice-based model and the optical micrographs of individual domains to determine the photonic structure corresponding to the different lattice directions. The three-dimensional model revealed stop-gaps in the Gamma-L, Gamma-W and Gamma-K directions. Finally, the coloration of the weevil as

Experimental instruction in photonics for high school students: approaches to managing problems faced

NASA Astrophysics Data System (ADS)

Choong, Zhengyang

2017-08-01

Student research projects are increasingly common at the K-12 level. However, students often face difficulties in the course of their school research projects such as setting realistic timelines and expectations, handling problems stemming from a lack of self-confidence, as well as being sufficiently disciplined for sustained communication and experimentation. In this work, we explore manifestations of these problems in the context of a photonics project, characterising the spectrum of the breakdown flash from Silicon Avalanche Photodiodes. We report on the process of planning and building the setup, data collection, analysis and troubleshooting, as well as the technical and human problems at each step. Approaches that were found to be helpful in managing the aforementioned problems are discussed, including an attention to detail during experimental work, as well as communicating in a forthcoming manner. Œe former allowed for clearer planning and the setting of quantifiable proximal goals; the latter helped in motivating discipline, and also helped in the understanding of research as an iterative learning process without a clear definition of success or failure.

Rheology of Ultraswollen Bicontinuous Lipidic Cubic Phases.

PubMed

Speziale, Chiara; Ghanbari, Reza; Mezzenga, Raffaele

2018-05-01

Rheological studies of liquid crystalline systems based on monopalmitolein and 5 or 8% of 1,2 distearoylphosphatidylglycerol are reported. Such cubic phases have been shown to possess unusually large water channels because of their ability of accommodating up to 80 wt % of water, a feature that renders these systems suitable for crystallizing membrane proteins with large extracellular domains. Their mechanical properties are supposed to be substantially different from those of traditional cubic phases. Rheological measurements were carried out on cubic phases of both Pn3 m and Ia3 d symmetries. It was verified that these ultraswollen cubic phases are less rigid than the normal cubic phases, with the Pn3 m being softer that the Ia3 d ones. Furthermore, for the Pn3 m case, the longest relaxation time is shown to decrease logarithmically with increasing surface area per unit volume, proving the critical role of the density of interfaces in establishing the macroscopic viscoelastic properties of the bicontinuous cubic phases.

Out of Field Doses in Clinical Photon and Proton Beam

NASA Astrophysics Data System (ADS)

Kubančák, Ján

2010-01-01

Out-of-field doses in homogenous cubical polymethylmethacrylate (PMMA) phantom were studied in this work. Measurements were performed in clinical 171 MeV proton and megavoltae photon beam. As detectors, CaSO:Dy thermoluminescent detectors were used. According to expectancy, results showed that out-of-field doses are substantially lower for clinical proton beam in comparison with clinical proton beam.

Terre des Lasers: the new Aquitaine outreach and communication center in photonics

NASA Astrophysics Data System (ADS)

Prulhiere, Jean Paul; Sarger, Laurent

2009-06-01

The competitive cluster "Route des Lasers" has been labeled by the French Government in July 2005. In this context, it has launched in September 2005, in cooperation with Commissariat à l'Energie Atomique (CEA) and Regional Council a project involving scientific exhibitions, called "Terre des Lasers ®", in order to create an exhibition and an area of communication and science discovery or a very large target (public, school, industry) in the fields of optics, lasers, optronics and imaging. This initiative is part of the strategy of the "Route des Lasers" center which aims to promote technologies developed in the areas of photonics, targeting in particular children and teenagers and their awareness for this particular industrial and scientific topic.

How Cubic Can Ice Be?

DOE PAGES

Amaya, Andrew J.; Pathak, Harshad; Modak, Viraj P.; ...

2017-06-28

Using an X-ray laser, we investigated the crystal structure of ice formed by homogeneous ice nucleation in deeply supercooled water nanodrops (r ≈ 10 nm) at ~225 K. The nanodrops were formed by condensation of vapor in a supersonic nozzle, and the ice was probed within 100 μs of freezing using femtosecond wide-angle X-ray scattering at the Linac Coherent Light Source free-electron X-ray laser. The X-ray diffraction spectra indicate that this ice has a metastable, predominantly cubic structure; the shape of the first ice diffraction peak suggests stacking-disordered ice with a cubicity value, χ, in the range of 0.78 ±more » 0.05. The cubicity value determined here is higher than those determined in experiments with micron-sized drops but comparable to those found in molecular dynamics simulations. Lastly, the high cubicity is most likely caused by the extremely low freezing temperatures and by the rapid freezing, which occurs on a ~1 μs time scale in single nanodroplets.« less

Neuroimaging, Genetics, and Clinical Data Sharing in Python Using the CubicWeb Framework

PubMed Central

Grigis, Antoine; Goyard, David; Cherbonnier, Robin; Gareau, Thomas; Papadopoulos Orfanos, Dimitri; Chauvat, Nicolas; Di Mascio, Adrien; Schumann, Gunter; Spooren, Will; Murphy, Declan; Frouin, Vincent

2017-01-01

In neurosciences or psychiatry, the emergence of large multi-center population imaging studies raises numerous technological challenges. From distributed data collection, across different institutions and countries, to final data publication service, one must handle the massive, heterogeneous, and complex data from genetics, imaging, demographics, or clinical scores. These data must be both efficiently obtained and downloadable. We present a Python solution, based on the CubicWeb open-source semantic framework, aimed at building population imaging study repositories. In addition, we focus on the tools developed around this framework to overcome the challenges associated with data sharing and collaborative requirements. We describe a set of three highly adaptive web services that transform the CubicWeb framework into a (1) multi-center upload platform, (2) collaborative quality assessment platform, and (3) publication platform endowed with massive-download capabilities. Two major European projects, IMAGEN and EU-AIMS, are currently supported by the described framework. We also present a Python package that enables end users to remotely query neuroimaging, genetics, and clinical data from scripts. PMID:28360851

Neuroimaging, Genetics, and Clinical Data Sharing in Python Using the CubicWeb Framework.

PubMed

Grigis, Antoine; Goyard, David; Cherbonnier, Robin; Gareau, Thomas; Papadopoulos Orfanos, Dimitri; Chauvat, Nicolas; Di Mascio, Adrien; Schumann, Gunter; Spooren, Will; Murphy, Declan; Frouin, Vincent

2017-01-01

In neurosciences or psychiatry, the emergence of large multi-center population imaging studies raises numerous technological challenges. From distributed data collection, across different institutions and countries, to final data publication service, one must handle the massive, heterogeneous, and complex data from genetics, imaging, demographics, or clinical scores. These data must be both efficiently obtained and downloadable. We present a Python solution, based on the CubicWeb open-source semantic framework, aimed at building population imaging study repositories. In addition, we focus on the tools developed around this framework to overcome the challenges associated with data sharing and collaborative requirements. We describe a set of three highly adaptive web services that transform the CubicWeb framework into a (1) multi-center upload platform, (2) collaborative quality assessment platform, and (3) publication platform endowed with massive-download capabilities. Two major European projects, IMAGEN and EU-AIMS, are currently supported by the described framework. We also present a Python package that enables end users to remotely query neuroimaging, genetics, and clinical data from scripts.

High pressure/temperature equation of state of gold silver alloys

NASA Astrophysics Data System (ADS)

Jenei, Zsolt; Lipp, Magnus J.; Klepeis, Jae-Hyun P.; Cynn, Hyunchae; Evans, William J.; Park, Changyong

2012-02-01

Gold-silver alloys crystallize in face centered cubic structures, like their constituent pure elements [McKeehan -- Phys.Rev. 20, 424 (1922)]. The cell parameter of the alloys does not scale linearly with the ratio of Ag/Au. In this work we investigate the high-pressure/temperature behavior of gold-silver alloys with different Au/Ag ratios. Powder x-ray diffraction experiments performed at HPCAT/Advanced Photon Source confirm the stability of the alloy's fcc structure to pressures/temperatures exceeding 100 GPa/1000 K. We will present isothermal EOS of the alloys from ambient temperature up to 1000 K, discuss the thermal expansion and its variation with pressure.

The electric field of a uniformly charged cubic shell

NASA Astrophysics Data System (ADS)

McCreery, Kaitlin; Greenside, Henry

2018-01-01

As an integrative and insightful example for undergraduates learning about electrostatics, we discuss how to use symmetry, Coulomb's law, superposition, Gauss's law, and visualization to understand the electric field E (x ,y ,z ) produced by a uniformly charged cubic shell. We first discuss how to deduce qualitatively, using freshman-level physics, the perhaps surprising fact that the interior electric field is nonzero and has a complex structure, pointing inwards from the middle of each face of the shell and pointing outwards towards each edge and corner. We then discuss how to understand the quantitative features of the electric field by plotting an analytical expression for E along symmetry lines and on symmetry surfaces of the shell.

Theoretical Investigation of Stabilizing Mechanism by Boron in Body-Centered Cubic Iron Through (Fe,Cr)23(C,B)6 Precipitates

NASA Astrophysics Data System (ADS)

Sahara, Ryoji; Matsunaga, Tetsuya; Hongo, Hiromichi; Tabuchi, Masaaki

2016-05-01

Small amounts of boron improve the mechanical properties in high-chromium ferritic heat-resistant steels. In this work, the stabilizing mechanism by boron in body-centered cubic iron (bcc Fe) through (Fe,Cr)23(C,B)6 precipitates was investigated by first-principles calculations. Formation energy analysis of (Fe,Cr)23(C,B)6 reveals that the compounds become more stable to elemental solids as the boron concentration increases. Furthermore, the interface energy of bcc Fe(110) || Fe23(C,B)6(111) also decreases with boron concentration in the compounds. The decreased interface energy caused by boron addition is explained by the balance between the change in the phase stability of the precipitates and the change in the misfit parameter for the bcc Fe matrix and the precipitates. These results show that boron stabilizes the microstructure of heat-resistant steels, which is important for understanding the origins of the creep strength in ferritic steels.

Gunshot wounds to the face: level I urban trauma center: a 10-year level I urban trauma center experience.

PubMed

Pereira, Clifford; Boyd, J Brian; Dickenson, Brian; Putnam, Brant

2012-04-01

Gunshot wounds (GSWs) to the face are an infrequent occurrence outside of a war zone. However, when they occur, they constitute a significant reconstructive challenge. We present our 10-year experience at an urban level I trauma center to define the patterns of injury, assess the morbidity and mortality, and estimate the cost to the health care system. A retrospective review was performed on all patients admitted to Harbor-UCLA Medical Center with GSWs to the head and neck region between January 1997 and January 2007. Those who had sustained GSWs to the face requiring operative intervention were closely reviewed. Between 1997 and 2007, a total of 702 patients were admitted to the Harbor UCLA Emergency Department having sustained GSWs to the head and neck region, of which 501 patients survived. Of the survivors, 28 patients (26 male, 2 female) sustained GSWs to their face requiring operative intervention. The mean age of these patients was 28 (±8.3) years. They generally presented within a few hours of the injury, but 1 individual arrived over 24 hours later. Low-velocity single gunshots (from handguns) were predominantly involved, with facial fractures occurring in all cases. Fractures were of a localized shattering type without the major displacement of bony complexes seen in motor vehicle accidents. Most required wound debridement and fracture fixation. A few patients (14.2%) underwent free tissue transfer for reconstruction (3 fibular flaps, 1 TRAM). Tracheostomy was performed in 35.7% of patients. Mean length of hospital stay was 8.3 (±7.1) days, with 50% of cases requiring admission to the intensive care unit. Mean length of intensive care unit stay was 5.2 (±5.7) days. The average cost per patient exceeded $100,000.

Optomechanics of two- and three-dimensional soft photonic crystals

NASA Astrophysics Data System (ADS)

Krishnan, Dwarak

Soft photonic crystals are a class of periodic dielectric structures that undergo highly nonlinear deformation due to strain or other external stimulus such as temperature, pH etc. This can in turn dramatically affect optical properties such as light transmittance. Moreover certain classes of lithographically fabricated structures undergo some structural distortion due to the effects of processing, eventually affecting the optical properties of the final photonic crystal. In this work, we study the deformation mechanics of soft photonic crystal structures using realistic physics-based models and leverage that understanding to explain the optomechanics of actual 2-D and 3-D soft photonic crystals undergoing similar symmetry breaking nonlinear deformations. We first study the optomechanics of two classes of 3-D soft photonic crystals: (1) hydrogel and (2) elastomer based material systems. The hydrogel based inverse face-centered-cubic structure undergoes swelling with change in pH of the surrounding fluid. The inverse structure is a network of bulky domains with thin ligament-like connections, and it undergoes a pattern transformation from FCC to L11 as a result of swelling. A continuum scale poroelasticity based coupled fluid-diffusion FEM model is developed to accurately predict this mechanical behavior. Light transmittance simulation results qualitatively explain the experimentally observed trends in the optical behavior with pH change. The elastomer based, lithographically fabricated material experiences shrinkage induced distortion upon processing. This behavior is modeled using FEM with the material represented by a neo-Hookean constitutive law. The light transmittance calculations for normal incidence are carried out using the transfer matrix method and a good comparison is obtained for the positions of first and second order reflectance peaks. A unit cell based approach is taken to compute the photonic bandstructure to estimate light propagation through the

Implementation of single-photon quantum routing and decoupling using a nitrogen-vacancy center and a whispering-gallery-mode resonator-waveguide system.

PubMed

Cao, Cong; Duan, Yu-Wen; Chen, Xi; Zhang, Ru; Wang, Tie-Jun; Wang, Chuan

2017-07-24

Quantum router is a key element needed for the construction of future complex quantum networks. However, quantum routing with photons, and its inverse, quantum decoupling, are difficult to implement as photons do not interact, or interact very weakly in nonlinear media. In this paper, we investigate the possibility of implementing photonic quantum routing based on effects in cavity quantum electrodynamics, and present a scheme for single-photon quantum routing controlled by the other photon using a hybrid system consisting of a single nitrogen-vacancy (NV) center coupled with a whispering-gallery-mode resonator-waveguide structure. Different from the cases in which classical information is used to control the path of quantum signals, both the control and signal photons are quantum in our implementation. Compared with the probabilistic quantum routing protocols based on linear optics, our scheme is deterministic and also scalable to multiple photons. We also present a scheme for single-photon quantum decoupling from an initial state with polarization and spatial-mode encoding, which can implement an inverse operation to the quantum routing. We discuss the feasibility of our schemes by considering current or near-future techniques, and show that both the schemes can operate effectively in the bad-cavity regime. We believe that the schemes could be key building blocks for future complex quantum networks and large-scale quantum information processing.

Establishment of a Photon Data Section of the BNL National Nuclear Data Center: A preliminary proposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, A.L.; Pearlstein, S.

1992-05-01

It is proposed to establish a Photon Data Section (PDS) of the BNL National Nuclear Data Center (NNDC). This would be a total program encompassing both photon-atom and photon-nucleus interactions. By utilizing the existing NNDC data base management expertise and on-line access capabilities, the implementation of photon interaction data activities within the existing NNDC nuclear structure and nuclear-reaction activities can reestablish a viable photon interaction data program at minimum cost. By taking advantage of the on-line capabilities, the x-ray users' community will have access to a dynamic, state-of-the-art data base of interaction information. The proposed information base would include datamore » that presently are scattered throughout the literature usually in tabulated form. It is expected that the data bases would include at least the most precise data available in photoelectric cross sections, atomic form factors and incoherent scattering functions, anomalous scattering factors, oscillator strengths and oscillator densities, fluorescence yields, Auger electron yields, etc. It could also include information not presently available in tabulations or in existing data bases such as EXAFS (extended x-ray absorption fine structure) reference spectra, chemical bonding induced shifts in the photoelectric absorption edge, matrix corrections, x-ray Raman, and x-ray resonant Raman cross sections. The data base will also include the best estimates of the accuracy of the interaction data as it exists in the data base. It is proposed that the PDS would support computer programs written for calculating scattering cross sections for given solid angles, sample geometries, and polarization of incident x-rays, for calculating Compton profiles, and for analyzing data as in EXAFS and x-ray fluorescence.« less

Establishment of a Photon Data Section of the BNL National Nuclear Data Center: A preliminary proposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, A.L.; Pearlstein, S.

1992-05-01

It is proposed to establish a Photon Data Section (PDS) of the BNL National Nuclear Data Center (NNDC). This would be a total program encompassing both photon-atom and photon-nucleus interactions. By utilizing the existing NNDC data base management expertise and on-line access capabilities, the implementation of photon interaction data activities within the existing NNDC nuclear structure and nuclear-reaction activities can reestablish a viable photon interaction data program at minimum cost. By taking advantage of the on-line capabilities, the x-ray users` community will have access to a dynamic, state-of-the-art data base of interaction information. The proposed information base would include datamore » that presently are scattered throughout the literature usually in tabulated form. It is expected that the data bases would include at least the most precise data available in photoelectric cross sections, atomic form factors and incoherent scattering functions, anomalous scattering factors, oscillator strengths and oscillator densities, fluorescence yields, Auger electron yields, etc. It could also include information not presently available in tabulations or in existing data bases such as EXAFS (extended x-ray absorption fine structure) reference spectra, chemical bonding induced shifts in the photoelectric absorption edge, matrix corrections, x-ray Raman, and x-ray resonant Raman cross sections. The data base will also include the best estimates of the accuracy of the interaction data as it exists in the data base. It is proposed that the PDS would support computer programs written for calculating scattering cross sections for given solid angles, sample geometries, and polarization of incident x-rays, for calculating Compton profiles, and for analyzing data as in EXAFS and x-ray fluorescence.« less

Electrostatic swelling of bicontinuous cubic lipid phases.

PubMed

Tyler, Arwen I I; Barriga, Hanna M G; Parsons, Edward S; McCarthy, Nicola L C; Ces, Oscar; Law, Robert V; Seddon, John M; Brooks, Nicholas J

2015-04-28

Lipid bicontinuous cubic phases have attracted enormous interest as bio-compatible scaffolds for use in a wide range of applications including membrane protein crystallisation, drug delivery and biosensing. One of the major bottlenecks that has hindered exploitation of these structures is an inability to create targeted highly swollen bicontinuous cubic structures with large and tunable pore sizes. In contrast, cubic structures found in vivo have periodicities approaching the micron scale. We have been able to engineer and control highly swollen bicontinuous cubic phases of spacegroup Im3m containing only lipids by (a) increasing the bilayer stiffness by adding cholesterol and (b) inducing electrostatic repulsion across the water channels by addition of anionic lipids to monoolein. By controlling the composition of the ternary mixtures we have been able to achieve lattice parameters up to 470 Å, which is 5 times that observed in pure monoolein and nearly twice the size of any lipidic cubic phase reported previously. These lattice parameters significantly exceed the predicted maximum swelling for bicontinuous cubic lipid structures, which suggest that thermal fluctuations should destroy such phases for lattice parameters larger than 300 Å.

Three-dimensional function photonic crystals

NASA Astrophysics Data System (ADS)

Zhang, Hai-Feng

2017-11-01

In this paper, the properties of the photonic band gaps (PBGs) of three-dimensional (3D) function photonic crystals (PCs) are theoretically investigated by a modified plane wave expansion (PWE) method, whose equations for computations are deduced. The configuration of 3D function PCs is the dielectric spheres inserted in the air background with simple-cubic (SC) lattices whose dielectric constants are the functions of space coordinates, which can be realized by the electro-optical or optical Kerr effect in the practice. The influences of the parameter for 3D function PCs on the PBGs also are discussed. The calculated results show that the bandwidths and number of PBGs can be tuned with different distributions of function dielectrics. Compared with the conventional 3D dielectric PCs with SC lattices, the larger and more PBGs can be obtained in the 3D function PCs. Those results provide a new way to design the novel practical devices.

Northeastern forest survey revised cubic-foot volume equations

Treesearch

Charles T. Scott

1981-01-01

Cubic-foot volume equations are presented for the 17 species groups used in the forest survey of the 14 northeastern states. The previous cubic- foot volume equations were simple linear in form; the revised cubic-foot volume equations are nonlinear.

Composition design for Laves phase-related body-centered cubic-V solid solution alloys with large hydrogen storage capacities.

PubMed

Wang, H B; Wang, Q; Dong, C; Yuan, L; Xu, F; Sun, L X

2008-03-19

This paper analyzes the characteristics of alloy compositions with large hydrogen storage capacities in Laves phase-related body-centered cubic (bcc) solid solution alloy systems using the cluster line approach. Since a dense-packed icosahedral cluster A(6)B(7) characterizes the local structure of AB(2) Laves phases, in an A-B-C ternary system, such as Ti-Cr (Mn, Fe)-V, where A-B forms AB(2) Laves phases while A-C and B-C tend to form solid solutions, a cluster line A(6)B(7)-C is constructed by linking A(6)B(7) to C. The alloy compositions with large hydrogen storage capacities are generally located near this line and are approximately expressed with the cluster-plus-glue-atom model. The cluster line alloys (Ti(6)Cr(7))(100-x)V(x) (x = 2.5-70 at.%) exhibit different structures and hence different hydrogen storage capacities with increasing V content. The alloys (Ti(6)Cr(7))(95)V(5) and Ti(30)Cr(40)V(30) with bcc solid solution structure satisfy the cluster-plus-glue-atom model.

The properties of the extraordinary mode and surface plasmon modes in the three-dimensional magnetized plasma photonic crystals based on the magneto-optical Voigt effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hai-Feng, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn; Nanjing Artillery Academy, Nanjing 211132; Liu, Shao-Bin, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn

2014-06-15

In this paper, the properties of the extraordinary mode and surface plasmon modes in the three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) with face-centered-cubic lattices that are composed of the core tellurium (Te) spheres with surrounded by the homogeneous magnetized plasma shells inserted in the air, are theoretically investigated in detail by the plane wave expansion method, as the magneto-optical Voigt effects of magnetized plasma are considered (the incidence electromagnetic wave vector is perpendicular to the external magnetic field at any time). The optical switching or wavelength division multiplexer can be realized by the proposed 3D MPPCs. Our analyses demonstratemore » that the complete photonic band gaps (PBGs) and two flatbands regions for the extraordinary mode can be observed obviously. PBGs can be tuned by the radius of core Te sphere, the plasma density and the external magnetic field. The flatbands regions are determined by the existence of surface plasmon modes. Numerical simulations also show that if the thickness of magnetized plasma shell is larger than a threshold value, the band structures of the extraordinary mode will be similar to those obtained from the same structure containing the pure magnetized plasma spheres. In this case, the band structures also will not be affected by the inserted core spheres. It is also provided that the upper edges of two flatbands regions will not depend on the topology of lattice. However, the frequencies of lower edges of two flatbands regions will be convergent to the different constants for different lattices, as the thickness of magnetized plasma shell is close to zero.« less

Generalized Vaidya spacetime for cubic gravity

NASA Astrophysics Data System (ADS)

Ruan, Shan-Ming

2016-03-01

We present a kind of generalized Vaidya solution of a new cubic gravity in five dimensions whose field equations in spherically symmetric spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its spherically symmetric apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally, we present the first law and second law hold in this gravity. Although all the results are analogous to those in Lovelock gravity, we in fact introduce the contribution of a new cubic term in five dimensions where the cubic Lovelock term is just zero.

Improved reference standards for femtosecond three-photon excitation of fluorescence in the wavelength range 950 - 1750 nm

NASA Astrophysics Data System (ADS)

Rebane, Aleksander; Mikhaylov, Alexander

2018-02-01

Fluorescence excited by instantaneous three-photon absorption (3PA) in organic fluorophores is gaining importance as a versatile modality for deep-tissue microscopy and imaging. However, due to technical difficulty of quantifying the higher-order nonlinear absorption cross-section, reliable 3PA cross section values, σ3PA, covering a broad spectral range have been so far not available. This lack of experimental data hinders us from gaining quantitative understanding of relevant structure-property relationships as well as impedes progress towards developing 3-photon fluorophores optimized for various applications. We report on measurement of the absolute 3PA cross section spectra in the 950 - 1750 nm range in a series of common organic fluorophores in various solvents: (a) Rhodamine 6G in deuterated methanol, (b) Coumarin 153 in DMSO and toluene, (c) Prodan in DMSO and toluene, (d) Fluorescein in pH11 buffer, (e) AF455 in toluene, (f) BDPAS in deuterated methylene chloride. In these experiments, we employ femtosecond wavelength-tunable optical parametric amplifier to excite fluorescence signal that has cubic dependence on the incident photon flux. Absolute values of σ3PA are determined using two complementary methods: (i) calibrating the fluorescence signal relative to one-photon (linear) excitation combined with accurate measurement of the pulse temporal- and spatial profile to determine the excitation photon flux and (ii) calibration of the cubic fluorescence signal relative to quadratic florescence excited in fluorophores with known two-photon absorption cross section. Depending on the method utilized, the peak σ3PA values have estimated accuracy 50% and vary in the range, σ3PA = 10-81 - 10-79 cm6 s2 photon-2 , depending on the system studied, with AF455 showing the most enhanced 3PA efficiency. The 3PA spectral shapes have estimated accuracy of 20% and show some unexpected deviations from corresponding one-photon spectral profiles.

Bifurcation of small limit cycles in cubic integrable systems using higher-order analysis

NASA Astrophysics Data System (ADS)

Tian, Yun; Yu, Pei

2018-05-01

In this paper, we present a method of higher-order analysis on bifurcation of small limit cycles around an elementary center of integrable systems under perturbations. This method is equivalent to higher-order Melinikov function approach used for studying bifurcation of limit cycles around a center but simpler. Attention is focused on planar cubic polynomial systems and particularly it is shown that the system studied by Żoła¸dek (1995) [24] can indeed have eleven limit cycles under perturbations at least up to 7th order. Moreover, the pattern of numbers of limit cycles produced near the center is discussed up to 39th-order perturbations, and no more than eleven limit cycles are found.

Influences of the third and fourth nearest neighbouring interactions on the surface anisotropy of face-centred-cubic metals

NASA Astrophysics Data System (ADS)

Luo, Yongkun; Qin, Rongshan

2014-06-01

The structure and the anisotropic properties of the surfaces of face-centred-cubic (FCC) metals have been studied using the broken-bond model while considering the third and fourth nearest neighbouring (3rd and 4th NN) interactions. The pair potential expressions are obtained using the Rose-Vinet universal potential equation. The model is suitable for calculation of the property of a surface with arbitrary crystallographic orientations and can provide absolute unrelaxed surface energy values using three input parameters, namely the lattice constant, bulk modulus and cohesive energy. These parameters are available for the majority of FCC metals. The numerical results for 7 FCC metals have been obtained and compared with these obtained from ab initio calculations and experimental measurements. Good agreement is observed between the two. Taking into account up to the 4th NN interactions, the overall surface energy anisotropy for FCC metals was found to be between 12% to 16%, and the ratio between the surface energies at (100) and (111) planes was found to be 1.05. These values are less than those reported by conventional calculations but more similar to experimental measurements. It is found that the strength of 3rd and 4th NN interactions differs from one element to another, the Ni and Cu interactions being the most significant while the Au, Pt and Pb interactions are the least significant. This suggests that the polar diagrams of the surface energy of Ni and Cu are different from those of Au, Pt and Pb by showing cusps of the unconventional {110} and high-index {210}, {311} and possibly {135} poles. This provides explanations to the recent experimental observations of the {110}, {210}, {311} and {135} facets in equilibrated Ni and Cu crystallines.

Bond-Energy and Surface-Energy Calculations in Metals

ERIC Educational Resources Information Center

Eberhart, James G.; Horner, Steve

2010-01-01

A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is…

Photonic Quantum Networks formed from NV(-) centers.

PubMed

Nemoto, Kae; Trupke, Michael; Devitt, Simon J; Scharfenberger, Burkhard; Buczak, Kathrin; Schmiedmayer, Jörg; Munro, William J

2016-05-24

In this article we present a simple repeater scheme based on the negatively-charged nitrogen vacancy centre in diamond. Each repeater node is built from modules comprising an optical cavity containing a single NV(-), with one nuclear spin from (15)N as quantum memory. The module uses only deterministic processes and interactions to achieve high fidelity operations (>99%), and modules are connected by optical fiber. In the repeater node architecture, the processes between modules by photons can be in principle deterministic, however current limitations on optical components lead the processes to be probabilistic but heralded. Our resource-modest repeater architecture contains two modules at each node, and the repeater nodes are then connected by entangled photon pairs. We discuss the performance of such a quantum repeater network with modest resources and then incorporate more resource-intense strategies step by step. Our architecture should allow large-scale quantum information networks with existing or near future technology.

Photonic Quantum Networks formed from NV− centers

PubMed Central

Nemoto, Kae; Trupke, Michael; Devitt, Simon J.; Scharfenberger, Burkhard; Buczak, Kathrin; Schmiedmayer, Jörg; Munro, William J.

2016-01-01

In this article we present a simple repeater scheme based on the negatively-charged nitrogen vacancy centre in diamond. Each repeater node is built from modules comprising an optical cavity containing a single NV−, with one nuclear spin from 15N as quantum memory. The module uses only deterministic processes and interactions to achieve high fidelity operations (>99%), and modules are connected by optical fiber. In the repeater node architecture, the processes between modules by photons can be in principle deterministic, however current limitations on optical components lead the processes to be probabilistic but heralded. Our resource-modest repeater architecture contains two modules at each node, and the repeater nodes are then connected by entangled photon pairs. We discuss the performance of such a quantum repeater network with modest resources and then incorporate more resource-intense strategies step by step. Our architecture should allow large-scale quantum information networks with existing or near future technology. PMID:27215433

Single photon quantum cryptography.

PubMed

Beveratos, Alexios; Brouri, Rosa; Gacoin, Thierry; Villing, André; Poizat, Jean-Philippe; Grangier, Philippe

2002-10-28

We report the full implementation of a quantum cryptography protocol using a stream of single photon pulses generated by a stable and efficient source operating at room temperature. The single photon pulses are emitted on demand by a single nitrogen-vacancy color center in a diamond nanocrystal. The quantum bit error rate is less that 4.6% and the secure bit rate is 7700 bits/s. The overall performances of our system reaches a domain where single photons have a measurable advantage over an equivalent system based on attenuated light pulses.

Strong confinement of optical fields using localized surface phonon polaritons in cubic boron nitride.

PubMed

Chatzakis, Ioannis; Krishna, Athith; Culbertson, James; Sharac, Nicholas; Giles, Alexander J; Spencer, Michael G; Caldwell, Joshua D

2018-05-01

Phonon polaritons (PhPs) are long-lived electromagnetic modes that originate from the coupling of infrared (IR) photons with the bound ionic lattice of a polar crystal. Cubic-boron nitride (cBN) is such a polar, semiconductor material which, due to the light atomic masses, can support high-frequency optical phonons. Here we report on random arrays of cBN nanostructures fabricated via an unpatterned reactive ion etching process. Fourier-transform infrared reflection spectra suggest the presence of localized surface PhPs within the reststrahlen band, with quality factors in excess of 38 observed. These can provide the basis of next-generation IR optical components such as antennas for communication, improved chemical spectroscopies, and enhanced emitters, sources, and detectors.

High pressure/temperature equation of state of gold-silver alloys

NASA Astrophysics Data System (ADS)

Evans, W. J.; Jenei, Zs.; Sinogeikin, S. V.; Yang, W.; Shebanova, O.

2010-03-01

It has been reported previously (McKeehan Phys.Rev. 20 p424) that gold-silver alloys crystallize in face centered cubic structures, like their constituant pure elements and the cell parameter of the alloy has a linear relationship with the ratios of Ag/Au in the alloy. We investigate the high-pressure/temperature behavior of gold-silver alloys with different Au/Ag ratios. Powder x-ray diffraction experiments performed at HPCAT/Advanced Photon Source confirm the stability of the alloy's fcc structure to pressures/temperatures exceeding 100 GPa/1000 K. We will present isothermal EOS of the alloys from ambient temperature up to 1000 K, discuss the thermal expansion and its variation with pressure.

Low pressure growth of cubic boron nitride films

NASA Technical Reports Server (NTRS)

Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

1997-01-01

A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.

III-nitrides on oxygen- and zinc-face ZnO substrates

NASA Astrophysics Data System (ADS)

Namkoong, Gon; Burnham, Shawn; Lee, Kyoung-Keun; Trybus, Elaissa; Doolittle, W. Alan; Losurdo, Maria; Capezzuto, Pio; Bruno, Giovanni; Nemeth, Bill; Nause, Jeff

2005-10-01

The characteristics of III-nitrides grown on zinc- and oxygen-face ZnO by plasma-assisted molecular beam epitaxy were investigated. The reflection high-energy electron diffraction pattern indicates formation of a cubic phase at the interface between III-nitride and both Zn- and O-face ZnO. The polarity indicates that Zn-face ZnO leads to a single polarity, while O-face ZnO forms mixed polarity of III-nitrides. Furthermore, by using a vicinal ZnO substrate, the terrace-step growth of GaN was realized with a reduction by two orders of magnitude in the dislocation-related etch pit density to ˜108cm-2, while a dislocation density of ˜1010cm-2 was obtained on the on-axis ZnO substrates.

The competitive growth of cubic domains in Ti(1-x)AlxN films studied by diffraction anomalous near-edge structure spectroscopy.

PubMed

Pinot, Y; Tuilier, M-H; Pac, M-J; Rousselot, C; Thiaudière, D

2015-11-01

Titanium and aluminium nitride films deposited by magnetron sputtering generally grow as columnar domains made of oriented nanocrystallites with cubic or hexagonal symmetry depending on Al content, which are embedded in more disordered grain boundaries. The substitution of Al atoms for Ti in the cubic lattice of the films improves their resistance to wear and oxidation, allowing their use as protective coatings. Ti K-edge X-ray absorption spectroscopy, which probes both crystallized and more disordered grain boundaries, and X-ray diffraction anomalous fine structure, which is sensitive to short- and long-range order within a given crystallized domain, are carried out on a set of Ti(1-x)AlxN films deposited by magnetron sputtering on Si substrates. Attention is paid to the shape of the pre-edge region, which is sensitive to the symmetry of the site occupied by Ti atoms, either octahedral in face-centred-cubic Ti-rich (TiN, Ti0.54Al0.46N) samples or tetrahedral in hexagonal-close-packed Al-rich (Ti0.32Al0.68N) films. In order to obain information on the titanium environment in the well crystallized areas, subtraction of the smooth part of the energy-dependent structure factor for the Bragg reflections is applied to the pre-edge region of the diffraction anomalous data in order to restore their spectroscopic appearance. A flat pre-edge is related to the typical octahedral environment of Ti atoms for cubic reflections. The difference observed between pre-edge spectra associated with face-centred-cubic 200 and 111 Bragg reflections of Ti0.54Al0.46N is assigned to Ti enrichment of 111 large well ordered domains compared with the more disordered 200 ones. The sharp peak observed in the spectrum recorded from the hexagonal 002 peak of Ti0.32Al0.68N can be regarded as a standard for the pure tetrahedral Ti environment in hexagonal-close-packed nitride.

Cubic polynomial maps with periodic critical orbit, Part II

NASA Astrophysics Data System (ADS)

Bonifant, Araceli; Kiwi, Jan; Milnor, John

The parameter space S_p for monic centered cubic polynomial maps with a marked critical point of period p is a smooth affine algebraic curve whose genus increases rapidly with p . Each S_p consists of a compact connectedness locus together with finitely many escape regions, each of which is biholomorphic to a punctured disk and is characterized by an essentially unique Puiseux series. This note will describe the topology of S_p , and of its smooth compactification, in terms of these escape regions. In particular, it computes the Euler characteristic. It concludes with a discussion of the real sub-locus of S_p .

Nuclear Photonics

NASA Astrophysics Data System (ADS)

Nedorezov, V. G.; Savel'ev-Trofimov, A. B.

2017-12-01

A review of works performed at the Institute for Nuclear Research of the Russian Academy of Sciences and at the International Laser Center of the Moscow State University in the context of the new research area called "nuclear photonics" is presented. Nuclear photonics is based on creation of the new-generation gamma-ray sources which make it possible to solve a number of fundamental and applied problems, including research of low-energy photonuclear reactions, namely, investigation of collective excitations of nuclei near the threshold (pygmy resonances); nuclear safety assurance; production of low-energy positron beams; and phase-contrast X-ray imaging.

CUBIC pathology: three-dimensional imaging for pathological diagnosis.

PubMed

Nojima, Satoshi; Susaki, Etsuo A; Yoshida, Kyotaro; Takemoto, Hiroyoshi; Tsujimura, Naoto; Iijima, Shohei; Takachi, Ko; Nakahara, Yujiro; Tahara, Shinichiro; Ohshima, Kenji; Kurashige, Masako; Hori, Yumiko; Wada, Naoki; Ikeda, Jun-Ichiro; Kumanogoh, Atsushi; Morii, Eiichi; Ueda, Hiroki R

2017-08-24

The examination of hematoxylin and eosin (H&E)-stained tissues on glass slides by conventional light microscopy is the foundation for histopathological diagnosis. However, this conventional method has some limitations in x-y axes due to its relatively narrow range of observation area and in z-axis due to its two-dimensionality. In this study, we applied a CUBIC pipeline, which is the most powerful tissue-clearing and three-dimensional (3D)-imaging technique, to clinical pathology. CUBIC was applicable to 3D imaging of both normal and abnormal patient-derived, human lung and lymph node tissues. Notably, the combination of deparaffinization and CUBIC enabled 3D imaging of specimens derived from paraffin-embedded tissue blocks, allowing quantitative evaluation of nuclear and structural atypia of an archival malignant lymphoma tissue. Furthermore, to examine whether CUBIC can be applied to practical use in pathological diagnosis, we performed a histopathological screening of a lymph node metastasis based on CUBIC, which successfully improved the sensitivity in detecting minor metastatic carcinoma nodules in lymph nodes. Collectively, our results indicate that CUBIC significantly contributes to retrospective and prospective clinicopathological diagnosis, which might lead to the establishment of a novel field of medical science based on 3D histopathology.

Thermoelectric properties of p-type cubic and rhombohedral GeTe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, Guangzong; Sun, Jifeng; Li, Yuwei

Here, we investigate the electronic and thermoelectric properties of GeTe in both cubic and rhombohedral phases. We find that cubic GeTe has an electronic structure with a narrow band gap that is unfavorable at high temperature, where the cubic phase is normally stable. However, cubic GeTe has electronic features that may lead to p-type performance superior to the normal rhombohedral phase at lower temperature. This is explained in part by the combination of light and heavy band character that is very effective in obtaining high thermopower and conductivity. In addition, the valence band edge carrier pockets in cubic GeTe possessmore » the largest anisotropy among cubic IV-VI analogs. These effects are stronger than the effect of band convergence in the rhombohedral structure. The results suggest further study of stabilized cubic GeTe as a thermoelectric.« less

Thermoelectric properties of p-type cubic and rhombohedral GeTe

DOE PAGES

Xing, Guangzong; Sun, Jifeng; Li, Yuwei; ...

2018-05-21

Here, we investigate the electronic and thermoelectric properties of GeTe in both cubic and rhombohedral phases. We find that cubic GeTe has an electronic structure with a narrow band gap that is unfavorable at high temperature, where the cubic phase is normally stable. However, cubic GeTe has electronic features that may lead to p-type performance superior to the normal rhombohedral phase at lower temperature. This is explained in part by the combination of light and heavy band character that is very effective in obtaining high thermopower and conductivity. In addition, the valence band edge carrier pockets in cubic GeTe possessmore » the largest anisotropy among cubic IV-VI analogs. These effects are stronger than the effect of band convergence in the rhombohedral structure. The results suggest further study of stabilized cubic GeTe as a thermoelectric.« less

Ultraviolet Raman Wide-Field Hyperspectral Imaging Spectrometer for Standoff Trace Explosive Detection.

PubMed

Hufziger, Kyle T; Bykov, Sergei V; Asher, Sanford A

2017-02-01

We constructed the first deep ultraviolet (UV) Raman standoff wide-field imaging spectrometer. Our novel deep UV imaging spectrometer utilizes a photonic crystal to select Raman spectral regions for detection. The photonic crystal is composed of highly charged, monodisperse 35.5 ± 2.9 nm silica nanoparticles that self-assemble in solution to produce a face centered cubic crystalline colloidal array that Bragg diffracts a narrow ∼1.0 nm full width at half-maximum (FWHM) UV spectral region. We utilize this photonic crystal to select and image two different spectral regions containing resonance Raman bands of pentaerythritol tetranitrate (PETN) and NH 4 NO 3 (AN). These two deep UV Raman spectral regions diffracted were selected by angle tuning the photonic crystal. We utilized this imaging spectrometer to measure 229 nm excited UV Raman images containing ∼10-1000 µg/cm 2 samples of solid PETN and AN on aluminum surfaces at 2.3 m standoff distances. We estimate detection limits of ∼1 µg/cm 2 for PETN and AN films under these experimental conditions.

Monotonicity preserving splines using rational cubic Timmer interpolation

NASA Astrophysics Data System (ADS)

Zakaria, Wan Zafira Ezza Wan; Alimin, Nur Safiyah; Ali, Jamaludin Md

2017-08-01

In scientific application and Computer Aided Design (CAD), users usually need to generate a spline passing through a given set of data, which preserves certain shape properties of the data such as positivity, monotonicity or convexity. The required curve has to be a smooth shape-preserving interpolant. In this paper a rational cubic spline in Timmer representation is developed to generate interpolant that preserves monotonicity with visually pleasing curve. To control the shape of the interpolant three parameters are introduced. The shape parameters in the description of the rational cubic interpolant are subjected to monotonicity constrained. The necessary and sufficient conditions of the rational cubic interpolant are derived and visually the proposed rational cubic Timmer interpolant gives very pleasing results.

The stability of a crystal with diamond structure for patchy particles with tetrahedral symmetry.

PubMed

Noya, Eva G; Vega, Carlos; Doye, Jonathan P K; Louis, Ard A

2010-06-21

The phase diagram of model anisotropic particles with four attractive patches in a tetrahedral arrangement has been computed at two different values of the range of the potential, with the aim of investigating the conditions under which a diamond crystal can be formed. We find that the diamond phase is never stable for our longer-ranged potential. At low temperatures and pressures, the fluid freezes into a body-centered-cubic solid that can be viewed as two interpenetrating diamond lattices with a weak interaction between the two sublattices. Upon compression, an orientationally ordered face-centered-cubic crystal becomes more stable than the body-centered-cubic crystal, and at higher temperatures, a plastic face-centered-cubic phase is stabilized by the increased entropy due to orientational disorder. A similar phase diagram is found for the shorter-ranged potential, but at low temperatures and pressures, we also find a region over which the diamond phase is thermodynamically favored over the body-centered-cubic phase. The higher vibrational entropy of the diamond structure with respect to the body-centered-cubic solid explains why it is stable even though the enthalpy of the latter phase is lower. Some preliminary studies on the growth of the diamond structure starting from a crystal seed were performed. Even though the diamond phase is never thermodynamically stable for the longer-ranged model, direct coexistence simulations of the interface between the fluid and the body-centered-cubic crystal and between the fluid and the diamond crystal show that at sufficiently low pressures, it is quite probable that in both cases the solid grows into a diamond crystal, albeit involving some defects. These results highlight the importance of kinetic effects in the formation of diamond crystals in systems of patchy particles.

Introduction: Photons and ground-based

NASA Astrophysics Data System (ADS)

Spann, James; Moore, Thomas

2017-02-01

A Conference on Measurement Techniques for Solar and Space Physics was held on 20-24 April 2015 in Boulder, Colorado, at the National Center for Atmospheric Research Center Green Campus. The present volume collects together the conference papers for photons and ground-based categories.

Phase composition and microstructure of WC-Co alloys obtained by selective laser melting

NASA Astrophysics Data System (ADS)

Khmyrov, Roman S.; Shevchukov, Alexandr P.; Gusarov, Andrey V.; Tarasova, Tatyana V.

2018-03-01

Phase composition and microstructure of initial WC, BK8 (powder alloy 92 wt.% WC-8 wt.% Co), Co powders, ball-milled powders with four different compositions (1) 25 wt.% WC-75 wt.% Co, (2) 30 wt.% BK8-70 wt.% Co, (3) 50 wt.% WC-50 wt.% Co, (4) 94 wt.% WC-6 wt.% Co, and bulk alloys obtained by selective laser melting (SLM) from as-milled powders in as-melted state and after heat treatment were investigated by scanning electron microscopy and X-ray diffraction analysis. Initial and ball-milled powders consist of WC, hexagonal α-Co and face-centered cubic β-Co. The SLM leads to the formation of major new phases W3Co3C, W4Co2C and face-centered cubic β-Co-based solid solution. During the heat treatment, there occurs partial decomposition of the face-centered cubic β-Co-based solid solution with the formation of W2C and hexagonal α-Co solid solution. The microstructure of obtained bulk samples, in general, corresponds to the observed phase composition.

Plasmon polaritons in cubic lattices of spherical metallic nanoparticles

NASA Astrophysics Data System (ADS)

Lamowski, Simon; Mann, Charlie-Ray; Hellbach, Felicitas; Mariani, Eros; Weick, Guillaume; Pauly, Fabian

2018-03-01

We theoretically investigate plasmon polaritons in cubic lattices of spherical metallic nanoparticles. The nanoparticles, each supporting triply-degenerate localized surface plasmons, couple through the Coulomb dipole-dipole interaction, giving rise to collective plasmons that extend over the whole metamaterial. The latter hybridize with photons forming plasmon polaritons, which are the hybrid light-matter eigenmodes of the system. We derive general analytical expressions to evaluate both plasmon and plasmon-polariton dispersions and the corresponding eigenstates. These are obtained within a Hamiltonian formalism, which takes into account retardation effects in the dipolar interaction between the nanoparticles and considers the dielectric properties of the nanoparticles as well as their surrounding. Within this model we predict polaritonic splittings in the near-infrared to the visible range of the electromagnetic spectrum that depend on polarization, lattice symmetry, and wave-vector direction. Finally, we show that the predictions of our model are in excellent quantitative agreement with conventional finite-difference frequency-domain simulations, but with the advantages of analytical insight and significantly reduced computational cost.

Looking northwest, Face B Array to left, Face C (rear) ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Looking northwest, Face B Array to left, Face C (rear) center, Power Plant (Building 5761), to right - Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Techinical Equipment Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

Σ 3 (111 ) grain boundary of body-centered cubic Ti-Mo and Ti-V alloys: First-principles and model calculations

NASA Astrophysics Data System (ADS)

Yan, Jia-Yi; Ehteshami, Hossein; Korzhavyi, Pavel A.; Borgenstam, Annika

2017-07-01

The energetics and atomic structures of Σ 3 [1 1 ¯0 ] (111 ) grain boundary (GB) of body-centered cubic (bcc) Ti-Mo and Ti-V alloys are investigated using density-functional-theory calculations and virtual crystal approximation. The electron density in bcc structure and the atomic displacements and excess energy of the GB are correlated to bcc-ω phase stability. Model calculations based on pairwise interplanar interactions successfully reproduce the chemical part of GB energy. The chemical GB energy can be expressed as a sum of excess pairwise interactions between bcc (111) layers, which are obtained from Gaussian elimination of the total energies of a number of periodic structures. The energy associated with the relaxation near the GB is solved by numerical minimization using the derivatives of the excess interactions. Anharmonic interlayer interactions are necessary for obtaining accurate relaxation energy and excess GB volume from model calculations. The effect of GB on vibrational spectrum is also investigated. Segregation energies of B and Y to a substitutional site on the GB plane are calculated. Preliminary results suggest that Y tends to segregate, while B tends to antisegregate.

Direction-aware Slope Limiter for 3D Cubic Grids with Adaptive Mesh Refinement

DOE PAGES

Velechovsky, Jan; Francois, Marianne M.; Masser, Thomas

2018-06-07

In the context of finite volume methods for hyperbolic systems of conservation laws, slope limiters are an effective way to suppress creation of unphysical local extrema and/or oscillations near discontinuities. We investigate properties of these limiters as applied to piecewise linear reconstructions of conservative fluid quantities in three-dimensional simulations. In particular, we are interested in linear reconstructions on Cartesian adaptively refined meshes, where a reconstructed fluid quantity at a face center depends on more than a single gradient component of the quantity. We design a new slope limiter, which combines the robustness of a minmod limiter with the accuracy ofmore » a van Leer limiter. The limiter is called Direction-Aware Limiter (DAL), because the combination is based on a principal flow direction. In particular, DAL is useful in situations where the Barth–Jespersen limiter for general meshes fails to maintain global linear functions, such as on cubic computational meshes with stencils including only faceneighboring cells. Here, we verify the new slope limiter on a suite of standard hydrodynamic test problems on Cartesian adaptively refined meshes. Lastly, we demonstrate reduced mesh imprinting; for radially symmetric problems such as the Sedov blast wave or the Noh implosion test cases, the results with DAL show better preservation of radial symmetry compared to the other standard methods on Cartesian meshes.« less

Direction-aware Slope Limiter for 3D Cubic Grids with Adaptive Mesh Refinement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velechovsky, Jan; Francois, Marianne M.; Masser, Thomas

In the context of finite volume methods for hyperbolic systems of conservation laws, slope limiters are an effective way to suppress creation of unphysical local extrema and/or oscillations near discontinuities. We investigate properties of these limiters as applied to piecewise linear reconstructions of conservative fluid quantities in three-dimensional simulations. In particular, we are interested in linear reconstructions on Cartesian adaptively refined meshes, where a reconstructed fluid quantity at a face center depends on more than a single gradient component of the quantity. We design a new slope limiter, which combines the robustness of a minmod limiter with the accuracy ofmore » a van Leer limiter. The limiter is called Direction-Aware Limiter (DAL), because the combination is based on a principal flow direction. In particular, DAL is useful in situations where the Barth–Jespersen limiter for general meshes fails to maintain global linear functions, such as on cubic computational meshes with stencils including only faceneighboring cells. Here, we verify the new slope limiter on a suite of standard hydrodynamic test problems on Cartesian adaptively refined meshes. Lastly, we demonstrate reduced mesh imprinting; for radially symmetric problems such as the Sedov blast wave or the Noh implosion test cases, the results with DAL show better preservation of radial symmetry compared to the other standard methods on Cartesian meshes.« less

Stability of the bcc phase of 4He close to the melting curve: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Belonoshko, A. B.; Koči, L.; Rosengren, A.

2012-01-01

We have investigated whether the Aziz [J. Chem. Phys.JCPSA60021-960610.1063/1.438007 70, 4330 (1979)] model for 4He renders the body-centered cubic phase more stable than the face-centered cubic phase in the proximity of the melting curve. Using molecular dynamics, we have simulated these solid phases in equilibrium with the liquid at a number of densities. In contrast to previous free energy molecular dynamics calculations, the model stabilizes the body-centered cubic phase. The stability field is just 5∘ wide below the melting curve at pressures around 140 Kbar and about 70∘ wide at pressures around 750 Kbar. Considering that the body-centered cubic phase is dynamically unstable at low temperature, this result bears striking similarities to transition metal phase diagrams.

Optical enhancement of Au doped ZrO2 thin films by sol-gel dip coating method

NASA Astrophysics Data System (ADS)

John Berlin, I.; Joy, K.

2015-01-01

Homogeneous and transparent Au doped ZrO2 thin films were prepared by sol-gel dip coating method. The films have mixed phase of tetragonal, monoclinic and face centered cubic with crack free surface. Due to the increase in Au doping concentration many-body interaction occurs between free carriers and ionized impurities causing decrease in optical band gap from 5.72 to 5.40 eV. Localized surface plasmon resonance peak of the Au doped films appeared at 610 nm. Conversion of photons to surface plasmons allows the sub-wavelength manipulation of electromagnetic radiation. Hence the prepared Au doped ZrO2 thin films can be applied in nanoscale photonic devices such as lenses, switches, waveguides etc. Moreover the photoluminescence (PL) intensity of Au doped ZrO2 thin films decrease due to decrease in the radiative recombination, life time of the excitons and suppression of grain growth of ZrO2 with increasing Au dopant.

Emerging technologies in Si active photonics

NASA Astrophysics Data System (ADS)

Wang, Xiaoxin; Liu, Jifeng

2018-06-01

Silicon photonics for synergistic electronic–photonic integration has achieved remarkable progress in the past two decades. Active photonic devices, including lasers, modulators, and photodetectors, are the key challenges for Si photonics to meet the requirement of high bandwidth and low power consumption in photonic datalinks. Here we review recent efforts and progress in high-performance active photonic devices on Si, focusing on emerging technologies beyond conventional foundry-ready Si photonics devices. For emerging laser sources, we will discuss recent progress towards efficient monolithic Ge lasers, mid-infrared GeSn lasers, and high-performance InAs quantum dot lasers on Si for data center applications in the near future. We will then review novel modulator materials and devices beyond the free carrier plasma dispersion effect in Si, including GeSi and graphene electro-absorption modulators and plasmonic-organic electro-optical modulators, to achieve ultralow power and high speed modulation. Finally, we discuss emerging photodetectors beyond epitaxial Ge p–i–n photodiodes, including GeSn mid-infrared photodetectors, all-Si plasmonic Schottky infrared photodetectors, and Si quanta image sensors for non-avalanche, low noise single photon detection and photon counting. These emerging technologies, though still under development, could make a significant impact on the future of large-scale electronicSilicon photonics for synergistic electronic-photonic integration has achieved remarkable progress in the past two decades. Active photonic devices, including lasers, modulators, and photodetectors, are the key challenges for Si photonics to meet the requirement of high bandwidth and low power consumption in photonic datalinks. Here we review recent efforts and progress in high-performance active photonic devices on Si, focusing on emerging technologies beyond conventional foundry-ready Si photonics devices. For emerging laser sources, we will discuss recent

Weak lensing probe of cubic Galileon model

NASA Astrophysics Data System (ADS)

Dinda, Bikash R.

2018-06-01

The cubic Galileon model containing the lowest non-trivial order action of the full Galileon action can produce the stable late-time cosmic acceleration. This model can have a significant role in the growth of structures. The signatures of the cubic Galileon model in the structure formation can be probed by the weak lensing statistics. Weak lensing convergence statistics is one of the strongest probes to the structure formation and hence it can probe the dark energy or modified theories of gravity models. In this work, we investigate the detectability of the cubic Galileon model from the ΛCDM model or from the canonical quintessence model through the convergence power spectrum and bi-spectrum.

Molecular dynamic simulation for nanometric cutting of single-crystal face-centered cubic metals.

PubMed

Huang, Yanhua; Zong, Wenjun

2014-01-01

In this work, molecular dynamics simulations are performed to investigate the influence of material properties on the nanometric cutting of single crystal copper and aluminum with a diamond cutting tool. The atomic interactions in the two metallic materials are modeled by two sets of embedded atom method (EAM) potential parameters. Simulation results show that although the plastic deformation of the two materials is achieved by dislocation activities, the deformation behavior and related physical phenomena, such as the machining forces, machined surface quality, and chip morphology, are significantly different for different materials. Furthermore, the influence of material properties on the nanometric cutting has a strong dependence on the operating temperature.

Dislocation structures of Σ3 {112} twin boundaries in face centered cubic metals

NASA Astrophysics Data System (ADS)

Wang, J.; Anderoglu, O.; Hirth, J. P.; Misra, A.; Zhang, X.

2009-07-01

High resolution transmission electron microscopy of nanotwinned Cu films revealed Σ3 {112} incoherent twin boundaries (ITBs), with a repeatable pattern involving units of three {111} atomic planes. Topological analysis shows that Σ3 {112} ITBs adopt two types of atomic structure with differing arrangements of Shockley partial dislocations. Atomistic simulations were performed for Cu and Al. These studies revealed the structure of the two types of ITBs, the formation mechanism and stability of the associated 9R phase, and the influence of stacking fault energies on them. The results suggest that Σ3 {112} ITBs may migrate through the collective glide of partial dislocations.

Exploring relationship between face-to-face interaction and team performance using wearable sensor badges.

PubMed

Watanabe, Jun-ichiro; Ishibashi, Nozomu; Yano, Kazuo

2014-01-01

Quantitative analyses of human-generated data collected in various fields have uncovered many patterns of complex human behaviors. However, thus far the quantitative evaluation of the relationship between the physical behaviors of employees and their performance has been inadequate. Here, we present findings demonstrating the significant relationship between the physical behaviors of employees and their performance via experiments we conducted in inbound call centers while the employees wore sensor badges. There were two main findings. First, we found that face-to-face interaction among telecommunicators and the frequency of their bodily movements caused by the face-to-face interaction had a significant correlation with the entire call center performance, which we measured as "Calls per Hour." Second, our trial to activate face-to-face interaction on the basis of data collected by the wearable sensor badges the employees wore significantly increased their performance. These results demonstrate quantitatively that human-human interaction in the physical world plays an important role in team performance.

Exploring Relationship between Face-to-Face Interaction and Team Performance Using Wearable Sensor Badges

PubMed Central

Watanabe, Jun-ichiro; Ishibashi, Nozomu; Yano, Kazuo

2014-01-01

Quantitative analyses of human-generated data collected in various fields have uncovered many patterns of complex human behaviors. However, thus far the quantitative evaluation of the relationship between the physical behaviors of employees and their performance has been inadequate. Here, we present findings demonstrating the significant relationship between the physical behaviors of employees and their performance via experiments we conducted in inbound call centers while the employees wore sensor badges. There were two main findings. First, we found that face-to-face interaction among telecommunicators and the frequency of their bodily movements caused by the face-to-face interaction had a significant correlation with the entire call center performance, which we measured as “Calls per Hour.” Second, our trial to activate face-to-face interaction on the basis of data collected by the wearable sensor badges the employees wore significantly increased their performance. These results demonstrate quantitatively that human-human interaction in the physical world plays an important role in team performance. PMID:25501748

Photonic crystal surface-emitting lasers enabled by an accidental Dirac point

DOEpatents

Chua, Song Liang; Lu, Ling; Soljacic, Marin

2014-12-02

A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

Lattice matched crystalline substrates for cubic nitride semiconductor growth

DOEpatents

Norman, Andrew G; Ptak, Aaron J; McMahon, William E

2015-02-24

Disclosed embodiments include methods of fabricating a semiconductor layer or device and devices fabricated thereby. The methods include, but are not limited to, providing a substrate having a cubic crystalline surface with a known lattice parameter and growing a cubic crystalline group III-nitride alloy layer on the cubic crystalline substrate by coincident site lattice matched epitaxy. The cubic crystalline group III-nitride alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter of the substrate (a). The group III-nitride alloy may be a cubic crystalline In.sub.xGa.sub.yAl.sub.1-x-yN alloy. The lattice parameter of the In.sub.xGa.sub.yAl.sub.1-x-yN or other group III-nitride alloy may be related to the substrate lattice parameter by (a')= 2(a) or (a')=(a)/ 2. The semiconductor alloy may be prepared to have a selected band gap.

Surfactant-Enabled Epitaxy of Smooth, Cubic Oxides on Gallium Nitride

NASA Astrophysics Data System (ADS)

Paisley, Elizabeth Aldret

Epitaxial integration of polar oxides with polar semiconductors presents the possibility of tunable 2D charge carriers at polar interfaces and integration of non-linear dielectric properties if defect densities are low and interfaces are smooth. Achieving this in materials with highly dissimilar structure and symmetry remains a serious challenge and requires a dramatically improved understanding of chemically and structurally dissimilar interfaces and their synthesis. Current efforts to achieve such devices are impeded by the fact that many polar oxides have a close-packed cubic substructure that requires the oxide to grow along the {111} direction, which is compatible with hexagonal (0002) GaN. Since the {111} direction is not the lowest energy face for these oxides, conventional methods used to synthesize these oxides usually allow the interface to compensate by forming facets resulting in defects, detrimental to the sustaining interface conductivity. This thesis demonstrates a new methodology developed to allow in situ stabilization of desired crystallographic habits where water vapor is utilized during growth to hydroxylate the oxide (111) surfaces, changing the equilibrium habit from cubic to octahedral, eliminating the (100)-faceting tendency. Bulk thermodynamic calculations show that a hydroxide termination can stabilize the (111)-face. Further, Ca(OH)2 (the structure likely to represent such termination) provides a low-energy surface with six-fold symmetry and atomic registry matching {111}-CaO and GaN. Additionally, the relative free energies of formation for CaO and Ca(OH)2 provide an adequate processing window to avoid competition between oxide and hydroxide deposition. This approach is demonstrated for three model systems of rocksalt oxides grown along a polar direction on GaN: MgO, CaO, and lattice-matched compositions: Mg0.52Ca0.48O. MBE growth of smooth (111) CaO is demonstrated using RHEED intensity vs. time oscillations that show layer

Atomistic simulation of cubic and tetragonal phases of U-Mo alloy: Structure and thermodynamic properties

NASA Astrophysics Data System (ADS)

Starikov, S. V.; Kolotova, L. N.; Kuksin, A. Yu.; Smirnova, D. E.; Tseplyaev, V. I.

2018-02-01

We studied structure and thermodynamic properties of cubic and tetragonal phases of pure uranium and U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. The main attention was paid to the metastable γ0 -phase that is formed in U-Mo alloys at low temperature. Structure of γ0 -phase is similar to body-centered tetragonal (bct) lattice with displacement of a central atom in the basic cell along [ 001 ] direction. Such displacements have opposite orientations for part of the neighbouring basic cells. In this case, such ordering of the displacements can be designated as antiferro-displacement. Formation of such complex structure may be interpreted through forming of short U-U bonds. At heating, the tetragonal structure transforms into cubic γs -phase, still showing ordering of central atom displacements. With rise in temperature, γs -phase transforms to γ-phase with a quasi body-centered cubic (q-bcc) lattice. The local positions of uranium atoms in γ-phase correspond to γs -phase, however, orientations of the central atom displacements become disordered. Transition from γ0 to γ can be considered as antiferro-to paraelastic transition of order-disorder type. This approach to the structure description of uranium alloy allows to explain a number of unusual features found in the experiments: anisotropy of lattice at low temperature; remarkably high self-diffusion mobility in γ-phase; decreasing of electrical resistivity at heating for some alloys. In addition, important part of this work is the development of new interatomic potential for U-Mo system made with taking into account details of studied structures.

CubiCal: Suite for fast radio interferometric calibration

NASA Astrophysics Data System (ADS)

Kenyon, J. S.; Smirnov, O. M.; Grobler, T. L.; Perkins, S. J.

2018-05-01

CubiCal implements several accelerated gain solvers which exploit complex optimization for fast radio interferometric gain calibration. The code can be used for both direction-independent and direction-dependent self-calibration. CubiCal is implemented in Python and Cython, and multiprocessing is fully supported.

Subalgebras of BCK/BCI-Algebras Based on Cubic Soft Sets

PubMed Central

Muhiuddin, G.; Jun, Young Bae

2014-01-01

Operations of cubic soft sets including “AND” operation and “OR” operation based on P-orders and R-orders are introduced and some related properties are investigated. An example is presented to show that the R-union of two internal cubic soft sets might not be internal. A sufficient condition is provided, which ensure that the R-union of two internal cubic soft sets is also internal. Moreover, some properties of cubic soft subalgebras of BCK/BCI-algebras based on a given parameter are discussed. PMID:24895652

Comparing the results of an analytical model of the no-vent fill process with no-vent fill test results for a 4.96 cubic meters (175 cubic feet) tank

NASA Technical Reports Server (NTRS)

Taylor, William J.; Chato, David J.

1993-01-01

The NASA Lewis Research Center (NASA/LeRC) have been investigating a no-vent fill method for refilling cryogenic storage tanks in low gravity. Analytical modeling based on analyzing the heat transfer of a droplet has successfully represented the process in 0.034 m and 0.142 cubic m commercial dewars using liquid nitrogen and hydrogen. Recently a large tank (4.96 cubic m) was tested with hydrogen. This lightweight tank is representative of spacecraft construction. This paper presents efforts to model the large tank test data. The droplet heat transfer model is found to over predict the tank pressure level when compared to the large tank data. A new model based on equilibrium thermodynamics has been formulated. This new model is compared to the published large scale tank's test results as well as some additional test runs with the same equipment. The results are shown to match the test results within the measurement uncertainty of the test data except for the initial transient wall cooldown where it is conservative (i.e., overpredicts the initial pressure spike found in this time frame).

Superhard BC(3) in cubic diamond structure.

PubMed

Zhang, Miao; Liu, Hanyu; Li, Quan; Gao, Bo; Wang, Yanchao; Li, Hongdong; Chen, Changfeng; Ma, Yanming

2015-01-09

We solve the crystal structure of recently synthesized cubic BC(3) using an unbiased swarm structure search, which identifies a highly symmetric BC(3) phase in the cubic diamond structure (d-BC(3)) that contains a distinct B-B bonding network along the body diagonals of a large 64-atom unit cell. Simulated x-ray diffraction and Raman peaks of d-BC(3) are in excellent agreement with experimental data. Calculated stress-strain relations of d-BC(3) demonstrate its intrinsic superhard nature and reveal intriguing sequential bond-breaking modes that produce superior ductility and extended elasticity, which are unique among superhard solids. The present results establish the first boron carbide in the cubic diamond structure with remarkable properties, and these new findings also provide insights for exploring other covalent solids with complex bonding configurations.

Strength and texture of Pt compressed to 63 GPa

NASA Astrophysics Data System (ADS)

Dorfman, Susannah M.; Shieh, Sean R.; Duffy, Thomas S.

2015-02-01

Angle- and energy-dispersive X-ray diffraction experiments in a radial geometry were performed in the diamond anvil cell on polycrystalline platinum samples at pressures up to 63 GPa. Observed yield strength and texture depend on grain size. For samples with 70-300-nm particle size, the yield strength is 5-6 GPa at ˜60 GPa. Coarse-grained (˜2-μm particles) Pt has a much lower yield strength of 1-1.5 GPa at ˜60 GPa. Face-centered cubic metals Pt and Au have lower strength to shear modulus ratio than body-centered cubic or hexagonal close-packed metals. While a 300-nm particle sample exhibits the <110> texture expected of face-centered-cubic metals under compression, smaller and larger particles show a weak mixed <110> and <100> texture under compression. Differences in texture development may also occur due to deviations from uniaxial stress under compression in the diamond anvil cell.

Research and education at the NASA Fisk University Center for Photonic Materials and Devices

NASA Astrophysics Data System (ADS)

Silberman, Enrique

1996-07-01

In 1992, NASA awarded Fisk University a 5 year grant to establish a center for research and education on photonic materials are synthesized, characterized and, in some cases, developed into devices with applications in the fields of radiation detectors and nonlinear optical crystals, glasses and nanomaterials. The educational components include participation in the research by 3 types of students majoring in Physics, Chemistry and Biology: 1) Fisk undergraduates participating during the academic year. 2) Fisk graduates performing their Maser Thesis research. 3) Fisk and other HBCU's and Minority Institutions' undergraduates attending a 10 week summer workshop with a very rigorous program of study, research and progress reporting. Funds are available for supporting participating students. Prerequisite, schedules of activities, evaluation procedures and typical examples of the outcome are presented.

Planar Cubics Through a Point in a Direction

NASA Technical Reports Server (NTRS)

Chou, J. J.; Blake, M. W.

1993-01-01

It is shown that the planar cubics through three points and the associated tangent directions can be found by solving a cubic equation and a 2 x 2 system of linear equations. The result is combined with a previous published scheme to produce a better curve-fitting method.

Use of Pom Pons to Illustrate Cubic Crystal Structures.

ERIC Educational Resources Information Center

Cady, Susan G.

1997-01-01

Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)

Suppressing spectral diffusion of emitted photons with optical pulses

DOE PAGES

Fotso, H. F.; Feiguin, A. E.; Awschalom, D. D.; ...

2016-01-22

In many quantum architectures the solid-state qubits, such as quantum dots or color centers, are interfaced via emitted photons. However, the frequency of photons emitted by solid-state systems exhibits slow uncontrollable fluctuations over time (spectral diffusion), creating a serious problem for implementation of the photon-mediated protocols. Here we show that a sequence of optical pulses applied to the solid-state emitter can stabilize the emission line at the desired frequency. We demonstrate efficiency, robustness, and feasibility of the method analytically and numerically. Taking nitrogen-vacancy center in diamond as an example, we show that only several pulses, with the width of 1more » ns, separated by few ns (which is not difficult to achieve) can suppress spectral diffusion. As a result, our method provides a simple and robust way to greatly improve the efficiency of photon-mediated entanglement and/or coupling to photonic cavities for solid-state qubits.« less

Photonic technology revolution influence on the defence area

NASA Astrophysics Data System (ADS)

Galas, Jacek; Litwin, Dariusz; Błocki, Narcyz; Daszkiewicz, Marek

2017-10-01

Revolutionary progress in the photonic technology provides the ability to develop military systems of new properties not possible to obtain with the use of classical technologies. In recent years, this progress has resulted in developing advanced, complex, multifunctional and relatively cheap Photonic Integrated Circuits (PIC) or Hybrid Photonics Circuits (HPC) built of a collection of standardized optical, optoelectronic and photonic components. This idea is similar to the technology of Electronic Integrated Circuits, which has revolutionized the microelectronic market. The novel approach to photonic technology is now revolutionizing the photonics' market. It simplifies the photonics technology and enables creation of technological centers for designing, development and production of advanced optical and photonic systems in the EU and other countries. This paper presents some selected photonic technologies and their impact on such defense systems like radars, radiolocation, telecommunication, and radio-communication systems.

Phonons and superconductivity in fcc and dhcp lanthanum

NASA Astrophysics Data System (ADS)

Baǧcı, S.; Tütüncü, H. M.; Duman, S.; Srivastava, G. P.

2010-04-01

We have investigated the structural and electronic properties of lanthanum in the face-centered-cubic (fcc) and double hexagonal-close-packed (dhcp) phases using a generalized gradient approximation of the density functional theory and the ab initio pseudopotential method. It is found that double hexagonal-close-packed is the more stable phase for lanthanum. Differences in the density of states at the Fermi level between these two phases are pointed out and discussed in detail. Using the calculated lattice constant and electronic band structure for both phases, a linear response approach based on the density functional theory has been applied to study phonon modes, polarization characteristics of phonon modes, and electron-phonon interaction. Our phonon results show a softening behavior of the transverse acoustic branch along the Γ-L direction and the Γ-M direction for face-centered-cubic and double hexagonal-close-packed phases, respectively. Thus, the transverse-phonon linewidth shows a maximum at the zone boundary M(L) for the double hexagonal-close-packed phase (face-centered-cubic phase), where the transverse-phonon branch exhibits a dip. The electron-phonon coupling parameter λ is found to be 0.97 (1.06) for the double hexagonal-close-packed phase (face-centered-cubic phase), and the superconducting critical temperature is estimated to be 4.87 (dhcp) and 5.88 K (fcc), in good agreement with experimental values of around 5.0 (dhcp) and 6.0 K (fcc). A few superconducting parameters for the double hexagonal-close-packed phase have been calculated and compared with available theoretical and experimental results. Furthermore, the calculated superconducting parameters for both phases are compared between each other in detail.

Aberrated surface soliton formation in a nonlinear 1D and 2D photonic crystal

PubMed Central

Lysak, Tatiana M.; Trykin, Evgenii M.

2018-01-01

We discuss a novel type of surface soliton—aberrated surface soliton—appearance in a nonlinear one dimensional photonic crystal and a possibility of this surface soliton formation in two dimensional photonic crystal. An aberrated surface soliton possesses a nonlinear distribution of the wavefront. We show that, in one dimensional photonic crystal, the surface soliton is formed at the photonic crystal boundary with the ambient medium. Essentially, that it occupies several layers at the photonic crystal boundary and penetrates into the ambient medium at a distance also equal to several layers, so that one can infer about light energy localization at the lateral surface of the photonic crystal. In the one dimensional case, the surface soliton is formed from an earlier formed soliton that falls along the photonic crystal layers at an angle which differs slightly from the normal to the photonic crystal face. In the two dimensional case, the soliton can appear if an incident Gaussian beam falls on the photonic crystal face. The influence of laser radiation parameters, optical properties of photonic crystal layers and ambient medium on the one dimensional surface soliton formation is investigated. We also discuss the influence of two dimensional photonic crystal configuration on light energy localization near the photonic crystal surface. It is important that aberrated surface solitons can be created at relatively low laser pulse intensity and for close values of alternating layers dielectric permittivity which allows their experimental observation. PMID:29558497

High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt

NASA Astrophysics Data System (ADS)

Ueland, B. G.; Saunders, S. M.; Bud'Ko, S. L.; Schmiedeshoff, G. M.; Canfield, P. C.; Kreyssig, A.; Goldman, A. I.

YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below T* = 0 . 7 K, fragile antiferromagnetic order below TN = 0 . 4 K, a Kondo temperature of TK ~ 1 K, and crystalline-electric-field splitting (CEF) on the order of E /kB = 1 - 10 K. Its lattice is face-centered cubic at ambient temperature, but certain data, particularly those from studies aimed at determining the CEF level scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-energy x-ray diffraction experiments which show that, within our experimental resolution of ~ 6 - 10 ×10-5 Å, no structural phase transition occurs between 1 . 5 and 50 K. Despite this result, we demonstrate that the compound's thermal expansion may be modeled using CEF level schemes appropriate for Yb3+ residing on a site with either cubic or less than cubic point symmetry. Work at the Ames Laboratory was supported by the US DOE, BES, DMSE, under Contract No. DE-AC02-07CH11358. Work at Occidental College was supported by the NSF under DMR-1408598. This research used resources at the Advanced Photon Source a US DOE, Office of Science, User Facility.

Superhard BC 3 in cubic diamond structure

DOE PAGES

Zhang, Miao; Liu, Hanyu; Li, Quan; ...

2015-01-06

We solve the crystal structure of recently synthesized cubic BC 3 using an unbiased swarm structure search, which identifies a highly symmetric BC 3 phase in the cubic diamond structure (d–BC3) that contains a distinct B-B bonding network along the body diagonals of a large 64-atom unit cell. Simulated x-ray diffraction and Raman peaks of d–BC 3 are in excellent agreement with experimental data. Calculated stress-strain relations of d–BC 3 demonstrate its intrinsic superhard nature and reveal intriguing sequential bond-breaking modes that produce superior ductility and extended elasticity, which are unique among superhard solids. Here, the present results establish themore » first boron carbide in the cubic diamond structure with remarkable properties, and these new findings also provide insights for exploring other covalent solids with complex bonding configurations.« less

Nonlocal dark solitons under competing cubic-quintic nonlinearities.

PubMed

Chen, L; Wang, Q; Shen, M; Zhao, H; Lin, Y-Y; Jeng, C-C; Lee, R-K; Krolikowski, W

2013-01-01

We investigate properties of dark solitons under competing nonlocal cubic-local quintic nonlinearities. Analytical results, based on a variational approach and confirmed by direct numerical simulations, reveal the existence of a unique dark soliton solutions with their width being independent of the degree of nonlocality, due to the competing cubic-quintic nonlinearities.

The effect of face patch microstimulation on perception of faces and objects.

PubMed

Moeller, Sebastian; Crapse, Trinity; Chang, Le; Tsao, Doris Y

2017-05-01

What is the range of stimuli encoded by face-selective regions of the brain? We asked how electrical microstimulation of face patches in macaque inferotemporal cortex affects perception of faces and objects. We found that microstimulation strongly distorted face percepts and that this effect depended on precise targeting to the center of face patches. While microstimulation had no effect on the percept of many non-face objects, it did affect the percept of some, including non-face objects whose shape is consistent with a face (for example, apples) as well as somewhat facelike abstract images (for example, cartoon houses). Microstimulation even perturbed the percept of certain objects that did not activate the stimulated face patch at all. Overall, these results indicate that representation of facial identity is localized to face patches, but activity in these patches can also affect perception of face-compatible non-face objects, including objects normally represented in other parts of inferotemporal cortex.

Transdermal delivery of paeonol using cubic gel and microemulsion gel

PubMed Central

Luo, Maofu; Shen, Qi; Chen, Jinjin

2011-01-01

Background The aim of this study was to develop new systems for transdermal delivery of paeonol, in particular microemulsion gel and cubic gel formulations. Methods Various microemulsion vehicles were prepared using isopropyl myristate as an oil phase, polyoxyethylated castor oil (Cremophor® EL) as a surfactant, and polyethylene glycol 400 as a cosurfactant. In the optimum microemulsion gel formulation, carbomer 940 was selected as the gel matrix, and consisted of 1% paeonol, 4% isopropyl myristate, 28% Cremophor EL/polyethylene glycol 400 (1:1), and 67% water. The cubic gel was prepared containing 3% paeonol, 30% water, and 67% glyceryl monooleate. Results A skin permeability test using excised rat skins indicated that both the cubic gel and microemulsion gel formulations had higher permeability than did the paeonol solution. An in vivo pharmacokinetic study done in rats showed that the relative bioavailability of the cubic gel and microemulsion gel was enhanced by about 1.51-fold and 1.28-fold, respectively, compared with orally administered paeonol suspension. Conclusion Both the cubic gel and microemulsion gel formulations are promising delivery systems to enhance the skin permeability of paeonol, in particular the cubic gel. PMID:21904450

Bi-cubic interpolation for shift-free pan-sharpening

NASA Astrophysics Data System (ADS)

Aiazzi, Bruno; Baronti, Stefano; Selva, Massimo; Alparone, Luciano

2013-12-01

Most of pan-sharpening techniques require the re-sampling of the multi-spectral (MS) image for matching the size of the panchromatic (Pan) image, before the geometric details of Pan are injected into the MS image. This operation is usually performed in a separable fashion by means of symmetric digital low-pass filtering kernels with odd lengths that utilize piecewise local polynomials, typically implementing linear or cubic interpolation functions. Conversely, constant, i.e. nearest-neighbour, and quadratic kernels, implementing zero and two degree polynomials, respectively, introduce shifts in the magnified images, that are sub-pixel in the case of interpolation by an even factor, as it is the most usual case. However, in standard satellite systems, the point spread functions (PSF) of the MS and Pan instruments are centered in the middle of each pixel. Hence, commercial MS and Pan data products, whose scale ratio is an even number, are relatively shifted by an odd number of half pixels. Filters of even lengths may be exploited to compensate the half-pixel shifts between the MS and Pan sampling grids. In this paper, it is shown that separable polynomial interpolations of odd degrees are feasible with linear-phase kernels of even lengths. The major benefit is that bi-cubic interpolation, which is known to represent the best trade-off between performances and computational complexity, can be applied to commercial MS + Pan datasets, without the need of performing a further half-pixel registration after interpolation, to align the expanded MS with the Pan image.

Cubic liquid crystalline nanoparticles: optimization and evaluation for ocular delivery of tropicamide.

PubMed

Verma, Purnima; Ahuja, Munish

2016-10-01

The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC 0→1440 min ) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.

Design Study of an MBA Lattice for the Advanced Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Decker, Glenn

2014-11-02

Recent interest in ultra-low-emittance designs for storage-ring-based synchrotron light sources has spurred a focused design effort on a multi-bend achromat (MBA) storage ring replacement for the Advanced Photon Source (APS). The APS is relatively large (1104 m circumference) and, as such, an upgrade to a fourth-generation storage ring holds the potential for a two to three order of magnitude enhancement of X-ray brightness due to the approximate inverse cubic scaling of emittance with the number of dipole bend magnets.

High Efficiency Photonic Switch for Data Centers

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaComb, Lloyd J.; Bablumyan, Arkady; Ordyan, Armen

2016-12-06

The worldwide demand for instant access to information is driving internet growth rates above 50% annually. This rapid growth is straining the resources and architectures of existing data centers, metro networks and high performance computer centers. If the current business as usual model continues, data centers alone will require 400TWhr of electricity by 2020. In order to meet the challenges of a faster and more cost effective data centers, metro networks and supercomputing facilities, we have demonstrated a new type of optical switch that will support transmissions speeds up to 1Tb/s, and requires significantly less energy per bit than

The thermal expansion of gold: point defect concentrations and pre-melting in a face-centred cubic metal.

PubMed

Pamato, Martha G; Wood, Ian G; Dobson, David P; Hunt, Simon A; Vočadlo, Lidunka

2018-04-01

On the basis of ab initio computer simulations, pre-melting phenomena have been suggested to occur in the elastic properties of hexagonal close-packed iron under the conditions of the Earth's inner core just before melting. The extent to which these pre-melting effects might also occur in the physical properties of face-centred cubic metals has been investigated here under more experimentally accessible conditions for gold, allowing for comparison with future computer simulations of this material. The thermal expansion of gold has been determined by X-ray powder diffraction from 40 K up to the melting point (1337 K). For the entire temperature range investigated, the unit-cell volume can be represented in the following way: a second-order Grüneisen approximation to the zero-pressure volumetric equation of state, with the internal energy calculated via a Debye model, is used to represent the thermal expansion of the 'perfect crystal'. Gold shows a nonlinear increase in thermal expansion that departs from this Grüneisen-Debye model prior to melting, which is probably a result of the generation of point defects over a large range of temperatures, beginning at T / T m > 0.75 (a similar homologous T to where softening has been observed in the elastic moduli of Au). Therefore, the thermodynamic theory of point defects was used to include the additional volume of the vacancies at high temperatures ('real crystal'), resulting in the following fitted parameters: Q = ( V 0 K 0 )/γ = 4.04 (1) × 10 -18  J, V 0 = 67.1671 (3) Å 3 , b = ( K 0 ' - 1)/2 = 3.84 (9), θ D = 182 (2) K, ( v f /Ω)exp( s f / k B ) = 1.8 (23) and h f = 0.9 (2) eV, where V 0 is the unit-cell volume at 0 K, K 0 and K 0 ' are the isothermal incompressibility and its first derivative with respect to pressure (evaluated at zero pressure), γ is a Grüneisen parameter, θ D is the Debye temperature, v f , h f and s f are the vacancy formation volume, enthalpy and entropy

Looking at faces from different angles: Europeans fixate different features in Asian and Caucasian faces.

PubMed

Brielmann, Aenne A; Bülthoff, Isabelle; Armann, Regine

2014-07-01

Race categorization of faces is a fast and automatic process and is known to affect further face processing profoundly and at earliest stages. Whether processing of own- and other-race faces might rely on different facial cues, as indicated by diverging viewing behavior, is much under debate. We therefore aimed to investigate two open questions in our study: (1) Do observers consider information from distinct facial features informative for race categorization or do they prefer to gain global face information by fixating the geometrical center of the face? (2) Does the fixation pattern, or, if facial features are considered relevant, do these features differ between own- and other-race faces? We used eye tracking to test where European observers look when viewing Asian and Caucasian faces in a race categorization task. Importantly, in order to disentangle centrally located fixations from those towards individual facial features, we presented faces in frontal, half-profile and profile views. We found that observers showed no general bias towards looking at the geometrical center of faces, but rather directed their first fixations towards distinct facial features, regardless of face race. However, participants looked at the eyes more often in Caucasian faces than in Asian faces, and there were significantly more fixations to the nose for Asian compared to Caucasian faces. Thus, observers rely on information from distinct facial features rather than facial information gained by centrally fixating the face. To what extent specific features are looked at is determined by the face's race. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Purely cubic action for string field theory

NASA Technical Reports Server (NTRS)

Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.

1986-01-01

It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.

Professional development in optics and photonics education

NASA Astrophysics Data System (ADS)

Donnelly, Judith F.; Hanes, Fenna; Massa, Nicholas J.; Washburn, Barbara R.

2002-05-01

In recent years, several New England projects have promoted professional development and curriculum design in optics and photonics. Funded in part by the Advanced Technological Education (ATE) program of the National Science Foundation (NSF), these projects have prepared middle and high school teachers, college faculty and career counselors from more than 100 New England institutions to introduce fiber optics, telecommunications and photonics technology education. Four of these projects will be discussed here: (1) The New England Board of Higher Education's (NEBHE) Fiber Optics Technology Education Project, (FOTEP) was designed to teach fiber optics theory and to provide laboratory experiences at the secondary and postsecondary levels. (2) Springfield Technical Community College's Northeast Center for Telecommunications Technologies (NCTT) is developing curricula and instructional materials in lightwave, networking and wireless telecommunications technologies. (3) The Harvard-Smithsonian Center for Astrophysics project ComTech developed a 12-week, hands-on curriculum and teaching strategies for middle and high school science and technology teachers in telecommunications and focused on optical communication (fiber optics). (4) NEBHE's project PHOTON is preparing middle, secondary and postsecondary instructors to introduce theory and laboratory experiences in photonics, including geometric and wave optics as well as principles of lasers and photonics applications.

Polytype transition of N-face GaN:Mg from wurtzite to zinc-blende

NASA Astrophysics Data System (ADS)

Monroy, E.; Hermann, M.; Sarigiannidou, E.; Andreev, T.; Holliger, P.; Monnoye, S.; Mank, H.; Daudin, B.; Eickhoff, M.

2004-10-01

We have investigated the polytype conversion of a GaN film from N-face wurtzite (2H) to zinc-blende (3C) structure due to Mg doping during growth by plasma-assisted molecular-beam epitaxy. Structural analysis by high-resolution transmission electron microscopy and high-resolution x-ray diffraction measurement revealed alignment of the cubic phase with the [111] axis perpendicular to the substrate surface. The optical characteristics of GaN:Mg layers are shown to be very sensitive to the presence of the cubic polytype. For low Mg doping, photoluminescence is dominated by a phonon-replicated donor-acceptor pair at ˜3.25eV, related to the shallow Mg acceptor level, accompanied by a narrow excitonic emission. For high Mg doping, the photoluminescence spectra are also dominated by a line around 3.25eV, but this emission displays the behavior of excitonic luminescence from cubic GaN. A cubic-related donor-acceptor transition at ˜3.16eV is also observed, together with a broad blue band around 2.9eV, previously reported in heavily Mg-doped 3C-GaN(001).

Accelerated formation of cubic phases in phosphatidylethanolamine dispersions.

PubMed Central

Tenchov, B; Koynova, R; Rapp, G

1998-01-01

By means of x-ray diffraction we show that several sodium salts and the disaccharides sucrose and trehalose strongly accelerate the formation of cubic phases in phosphatidylethanolamine (PE) dispersions upon temperature cycling through the lamellar liquid crystalline-inverted hexagonal (Lalpha-HII) phase transition. Ethylene glycol does not have such an effect. The degree of acceleration increases with the solute concentration. Such an acceleration has been observed for dielaidoyl PE (DEPE), dihexadecyl PE, and dipalmitoyl PE. It was investigated in detail for DEPE dispersions. For DEPE (10 wt% of lipid) aqueous dispersions at 1 M solute concentration, 10-50 temperature cycles typically result in complete conversion of the Lalpha phase into cubic phase. Most efficient is temperature cycling executed by laser flash T-jumps. In that case the conversion completes within 10-15 cycles. However, the cubic phases produced by laser T-jumps are less ordered in comparison to the rather regular cubic structures produced by linear, uniform temperature cycling at 10 degrees C/min. Temperature cycles at scan rates of 1-3 degrees C/min also induce the rapid formation of cubic phases. All solutes used induce the formation of Im3m (Q229) cubic phase in 10 wt% DEPE dispersions. The initial Im3m phases appearing during the first temperature cycles have larger lattice parameters that relax to smaller values with continuation of the cycling after the disappearance of the Lalpha phase. A cooperative Im3m --> Pn3m transition takes place at approximately 85 degrees C and transforms the Im3m phase into a mixture of coexisting Pn3m (Q224) and Im3m phases. The Im3m/Pn3m lattice parameter ratio is 1. 28, as could be expected from a representation of the Im3m and Pn3m phases with the primitive and diamond infinite periodic minimal surfaces, respectively. At higher DEPE contents ( approximately 30 wt%), cubic phase formation is hindered after 20-30 temperature cycles. The conversion does not go

The So-Called Face

NASA Image and Video Library

2002-05-21

The so-called Face on Mars can be seen slightly above center and to the right in this NASA Mars Odyssey image. This 3-km long knob was first imaged by NASA Viking spacecraft in the 1970 and to some resembled a face carved into the rocks of Mars.

Silicon photonics cloud (SiCloud)

NASA Astrophysics Data System (ADS)

DeVore, Peter T. S.; Jiang, Yunshan; Lynch, Michael; Miyatake, Taira; Carmona, Christopher; Chan, Andrew C.; Muniam, Kuhan; Jalali, Bahram

2015-02-01

We present SiCloud (Silicon Photonics Cloud), the first free, instructional web-based research and education tool for silicon photonics. SiCloud's vision is to provide a host of instructional and research web-based tools. Such interactive learning tools enhance traditional teaching methods by extending access to a very large audience, resulting in very high impact. Interactive tools engage the brain in a way different from merely reading, and so enhance and reinforce the learning experience. Understanding silicon photonics is challenging as the topic involves a wide range of disciplines, including material science, semiconductor physics, electronics and waveguide optics. This web-based calculator is an interactive analysis tool for optical properties of silicon and related material (SiO2, Si3N4, Al2O3, etc.). It is designed to be a one stop resource for students, researchers and design engineers. The first and most basic aspect of Silicon Photonics is the Material Parameters, which provides the foundation for the Device, Sub-System and System levels. SiCloud includes the common dielectrics and semiconductors for waveguide core, cladding, and photodetection, as well as metals for electrical contacts. SiCloud is a work in progress and its capability is being expanded. SiCloud is being developed at UCLA with funding from the National Science Foundation's Center for Integrated Access Networks (CIAN) Engineering Research Center.

Photon-momentum transfer in molecular photoionization

NASA Astrophysics Data System (ADS)

Chelkowski, Szczepan; Bandrauk, André D.

2018-05-01

In most models and theoretical calculations describing multiphoton ionization by infrared light, the dipole approximation is used. This is equivalent to setting the very small photon momentum to zero. Using numerical solutions of the (nondipole) three-dimensional time-dependent Schrödinger equation for one electron in a H2+ molecular ion we investigate the effect the photon-momentum transfer to the photoelectron in an H2+ ion in various regimes. We find that the photon-momentum transfer in a molecule is very different from the transfer in atoms due to two-center interference effects. The photon-momentum transfer is very sensitive to the symmetry of the initial electronic state and is strongly dependent on the internuclear distance and on the ellipticity of the laser.

Eliminating cubic terms in the pseudopotential lattice Boltzmann model for multiphase flow

NASA Astrophysics Data System (ADS)

Huang, Rongzong; Wu, Huiying; Adams, Nikolaus A.

2018-05-01

It is well recognized that there exist additional cubic terms of velocity in the lattice Boltzmann (LB) model based on the standard lattice. In this work, elimination of these cubic terms in the pseudopotential LB model for multiphase flow is investigated, where the force term and density gradient are considered. By retaining high-order (≥3 ) Hermite terms in the equilibrium distribution function and the discrete force term, as well as introducing correction terms in the LB equation, the additional cubic terms of velocity are entirely eliminated. With this technique, the computational simplicity of the pseudopotential LB model is well maintained. Numerical tests, including stationary and moving flat and circular interface problems, are carried out to show the effects of such cubic terms on the simulation of multiphase flow. It is found that the elimination of additional cubic terms is beneficial to reduce the numerical error, especially when the velocity is relatively large. Numerical results also suggest that these cubic terms mainly take effect in the interfacial region and that the density-gradient-related cubic terms are more important than the other cubic terms for multiphase flow.

Performance analysis of communication links based on VCSEL and silicon photonics technology for high-capacity data-intensive scenario.

PubMed

Boletti, A; Boffi, P; Martelli, P; Ferrario, M; Martinelli, M

2015-01-26

To face the increased demand for bandwidth, cost-effectiveness and simplicity of future Ethernet data communications, a comparison between two different solutions based on directly-modulated VCSEL sources and Silicon Photonics technologies is carried out. Also by exploiting 4-PAM modulation, the transmission of 50-Gb/s and beyond capacity per channel is analyzed by means of BER performance. Applications for optical backplane, very short reach and in case of client-optics networks and intra and inter massive data centers communications (up to 10 km) are taken into account. A comparative analysis based on the power consumption is also proposed.

Photonic crystal microprisms obtained by carving artificial opals

NASA Astrophysics Data System (ADS)

Fenollosa, R.; Ibisate, M.; Rubio, S.; López, C.; Meseguer, F.; Sánchez-Dehesa, J.

2003-01-01

A method for fabrication of photonic crystal prisms is demonstrated. The procedure is based on micromanipulation techniques, here applied to artificial opals. By means of a microgrinder an opal prism comprising a single crystal (several tens of microns in size) has been carved with three different faces: (111), (110), and (100). The faces were morphologically characterized by scanning electron microscopy and their optical reflectance spectra measured and compared with the theoretical band structure.

Silicon photonics for high-performance interconnection networks

NASA Astrophysics Data System (ADS)

Biberman, Aleksandr

2011-12-01

We assert in the course of this work that silicon photonics has the potential to be a key disruptive technology in computing and communication industries. The enduring pursuit of performance gains in computing, combined with stringent power constraints, has fostered the ever-growing computational parallelism associated with chip multiprocessors, memory systems, high-performance computing systems, and data centers. Sustaining these parallelism growths introduces unique challenges for on- and off-chip communications, shifting the focus toward novel and fundamentally different communication approaches. This work showcases that chip-scale photonic interconnection networks, enabled by high-performance silicon photonic devices, enable unprecedented bandwidth scalability with reduced power consumption. We demonstrate that the silicon photonic platforms have already produced all the high-performance photonic devices required to realize these types of networks. Through extensive empirical characterization in much of this work, we demonstrate such feasibility of waveguides, modulators, switches, and photodetectors. We also demonstrate systems that simultaneously combine many functionalities to achieve more complex building blocks. Furthermore, we leverage the unique properties of available silicon photonic materials to create novel silicon photonic devices, subsystems, network topologies, and architectures to enable unprecedented performance of these photonic interconnection networks and computing systems. We show that the advantages of photonic interconnection networks extend far beyond the chip, offering advanced communication environments for memory systems, high-performance computing systems, and data centers. Furthermore, we explore the immense potential of all-optical functionalities implemented using parametric processing in the silicon platform, demonstrating unique methods that have the ability to revolutionize computation and communication. Silicon photonics

Colossal photon bunching in quasiparticle-mediated nanodiamond cathodoluminescence

NASA Astrophysics Data System (ADS)

Feldman, Matthew A.; Dumitrescu, Eugene F.; Bridges, Denzel; Chisholm, Matthew F.; Davidson, Roderick B.; Evans, Philip G.; Hachtel, Jordan A.; Hu, Anming; Pooser, Raphael C.; Haglund, Richard F.; Lawrie, Benjamin J.

2018-02-01

Nanoscale control over the second-order photon correlation function g(2 )(τ ) is critical to emerging research in nonlinear nanophotonics and integrated quantum information science. Here we report on quasiparticle control of photon bunching with g(2 )(0 ) >45 in the cathodoluminescence of nanodiamond nitrogen vacancy (NV0) centers excited by a converged electron beam in an aberration-corrected scanning transmission electron microscope. Plasmon-mediated NV0 cathodoluminescence exhibits a 16-fold increase in luminescence intensity correlated with a threefold reduction in photon bunching compared with that of uncoupled NV0 centers. This effect is ascribed to the excitation of single temporally uncorrelated NV0 centers by single surface plasmon polaritons. Spectrally resolved Hanbury Brown-Twiss interferometry is employed to demonstrate that the bunching is mediated by the NV0 phonon sidebands, while no observable bunching is detected at the zero-phonon line. The data are consistent with fast phonon-mediated recombination dynamics, a conclusion substantiated by agreement between Bayesian regression and Monte Carlo models of superthermal NV0 luminescence.

Multiphoton-Excited Fluorescence of Silicon-Vacancy Color Centers in Diamond

NASA Astrophysics Data System (ADS)

Higbie, J. M.; Perreault, J. D.; Acosta, V. M.; Belthangady, C.; Lebel, P.; Kim, M. H.; Nguyen, K.; Demas, V.; Bajaj, V.; Santori, C.

2017-05-01

Silicon-vacancy color centers in nanodiamonds are promising as fluorescent labels for biological applications, with a narrow, nonbleaching emission line at 738 nm. Two-photon excitation of this fluorescence offers the possibility of low-background detection at significant tissue depth with high three-dimensional spatial resolution. We measure the two-photon fluorescence cross section of a negatively charged silicon vacancy (Si -V- ) in ion-implanted bulk diamond to be 0.74 (19 )×10-50 cm4 s /photon at an excitation wavelength of 1040 nm. Compared to the diamond nitrogen-vacancy center, the expected detection threshold of a two-photon excited Si -V center is more than an order of magnitude lower, largely due to its much narrower linewidth. We also present measurements of two- and three-photon excitation spectra, finding an increase in the two-photon cross section with decreasing wavelength, and we discuss the physical interpretation of the spectra in the context of existing models of the Si -V energy-level structure.

Two-Photon Fluorescence Correlation Spectroscopy

NASA Technical Reports Server (NTRS)

Zimmerli, Gregory A.; Fischer, David G.

2002-01-01

We will describe a two-photon microscope currently under development at the NASA Glenn Research Center. It is composed of a Coherent Mira 900 tunable, pulsed Titanium:Sapphire laser system, an Olympus Fluoview 300 confocal scanning head, and a Leica DM IRE inverted microscope. It will be used in conjunction with a technique known as fluorescence correlation spectroscopy (FCS) to study intracellular protein dynamics. We will briefly explain the advantages of the two-photon system over a conventional confocal microscope, and provide some preliminary experimental results.

Three-photon excitation of 2,5-bis(4-biphenyl)oxazole: steady-state and time-resolved intensities and anisotropies

NASA Astrophysics Data System (ADS)

Gryczynski, Ignacy; Malak, Henryk; Hell, Stefan W.; Lakowicz, Joseph R.

1996-10-01

Three-photon excitation of 2,5-bis(4-biphenyl) oxazole (BBO) was observed when it was excited with the fundamental output of a femtosecond Ti:sapphire laser above 820 nm. The emission spectrum of BBO was identical for one-, two-, and three-photon excitation at 320, 640, and 960 nm, respectively. In toluene and triacetin, the emission intensity of BBO depended on the square of the laser power for wavelengths below 820 nm and displayed a sharp transition to a cubic dependence at longer wavelengths. The spatial distribution of the emission of BBO with three- photon excitation was more strongly localized than for two- photon excitation of a coumarin fluorophore at the same wavelength. The same single exponential intensity decay was observed for one-, two-, and three-photon excitation. However, the frequency domain anisotropy decay with three- photon excitation at 960 nm revealed a larger time-zero anisotropy, larger differential polarized phase angle, and larger modulated anisotropy than is possible for two-photon excitation with colinear oscillators. In triacetin, the anisotropy is not constant for three-photon excitation at different wavelengths. Surprisingly, the fluorescence intensities for three-photon excitation were only about 100- fold less than for two-photon excitation. The increasing availability of Ti:sapphire lasers suggests that multiphoton excitation can become a common tool in fluorescence spectroscopy.

Survey of Portions of the Chromium-Cobalt-Nickel-Molybdenum Quaternary System at 1,200 Degrees C

NASA Technical Reports Server (NTRS)

Rideout, Sheldon Paul; Beck, Paul A

1953-01-01

A survey was made of portions of the chromium-cobalt-nickel-molybdenum quaternary system at 1,200 degrees c by means of microscopic and x-ray diffraction studies. Since the face-centered cubic (alpha) solid solutions form the matrix of almost all practically useful high-temperature alloys, the solid solubility limits of the quaternary alpha phase were determined up to 20 percent molybdenum. The component cobalt-nickel-molybdenum, chromium-cobalt-molybdenum, and chromium-nickel-molybdenum ternary systems were also studied. The survey of these systems was confined to the determination of the boundaries of the face-centered cubic (alpha) solid solutions and of the phases coexisting with alpha at 1,200 degrees c.

Photogrammetric Network for Evaluation of Human Faces for Face Reconstruction Purpose

NASA Astrophysics Data System (ADS)

Schrott, P.; Detrekői, Á.; Fekete, K.

2012-08-01

Facial reconstruction is the process of reconstructing the geometry of faces of persons from skeletal remains. A research group (BME Cooperation Research Center for Biomechanics) was formed representing several organisations to combine knowledgebases of different disciplines like anthropology, medical, mechanical, archaeological sciences etc. to computerize the face reconstruction process based on a large dataset of 3D face and skull models gathered from living persons: cranial data from CT scans and face models from photogrammetric evaluations. The BUTE Dept. of Photogrammetry and Geoinformatics works on the method and technology of the 3D data acquisition for the face models. In this paper we will present the research and results of the photogrammetric network design, the modelling to deal with visibility constraints, and the investigation of the developed basic photogrammetric configuration to specify the result characteristics to be expected using the device built for the photogrammetric face measurements.

Experimental Comparison of Face-Milled and Face-Hobbed Spiral Bevel Gears

NASA Technical Reports Server (NTRS)

Handschuh, Robert F.; Nanlawala, Michael; Hawkins, John M.; Mahan, Danny

2001-01-01

An experimental comparison of face-milled and face-hobbed spiral bevel gears was accomplished. The two differently manufactured spiral bevel gear types were tested in a closed-loop facility at NASA Glenn Research Center. Strain, vibration, and noise testing were completed at various levels of rotational speed and load. Tests were conducted from static (slow-roll) to 12600 rpm and up to 269 N-m (2380 in.-lb) pinion speed and load conditions. The tests indicated that the maximum stress recorded at the root locations had nearly the same values, however the stress distribution was different from the toe to the heel. Also, the alternating stress measured was higher for the face-milled pinion than that attained for the face-hobbed pinion (larger minimum stress). The noise and vibration results indicated that the levels measured for the face-hobbed components were less than those attained for the face-milled gears tested.

Accidental degeneracy in photonic bands and topological phase transitions in two-dimensional core-shell dielectric photonic crystals.

PubMed

Xu, Lin; Wang, Hai-Xiao; Xu, Ya-Dong; Chen, Huan-Yang; Jiang, Jian-Hua

2016-08-08

A simple core-shell two-dimensional photonic crystal is studied where the triangular lattice symmetry and the C₆ point group symmetry give rich physics in accidental touching points of photonic bands. We systematically evaluate different types of accidental nodal points at the Brillouin zone center for transverse-magnetic harmonic modes when the geometry and permittivity of the core-shell material are continuously tuned. The accidental nodal points can have different dispersions and topological properties (i.e., Berry phases). These accidental nodal points can be the critical states lying between a topological phase and a normal phase of the photonic crystal. They are thus very important for the study of topological photonic states. We show that, without breaking time-reversal symmetry, by tuning the geometry of the core-shell material, a phase transition into the photonic quantum spin Hall insulator can be achieved. Here the "spin" is defined as the orbital angular momentum of a photon. We study the topological phase transition as well as the properties of the edge and bulk states and their application potentials in optics.

Structural stability and energetics of grain boundary triple junctions in face centered cubic materials

NASA Astrophysics Data System (ADS)

Adlakha, I.; Solanki, K. N.

2015-03-01

We present a systematic study to elucidate the role of triple junctions (TJs) and their constituent grain boundaries on the structural stability of nanocrystalline materials. Using atomistic simulations along with the nudge elastic band calculations, we explored the atomic structural and thermodynamic properties of TJs in three different fcc materials. We found that the magnitude of excess energy at a TJ was directly related to the atomic density of the metal. Further, the vacancy binding and migration energetics in the vicinity of the TJ were examined as they play a crucial role in the structural stability of NC materials. The resolved line tension which takes into account the stress buildup at the TJ was found to be a good measure in predicting the vacancy binding tendency near the TJ. The activation energy for vacancy migration along the TJ was directly correlated with the measured excess energy. Finally, we show that the resistance for vacancy diffusion increased for TJs with larger excess stored energy and the defect mobility at some TJs is slower than their constituent GBs. Hence, our results have general implications on the diffusional process in NC materials and provide new insight into stabilizing NC materials with tailored TJs.

BF into cubic meters

Treesearch

Henry Spelter

2002-01-01

Noted forest products industry researcher and writer says the conversion factor traditionally used to convert logs measured in board feet to cubic meters has risen. In the U.S., most timber is measured in terms of board feet. The log scales currently in use to estimate lumber recovery from roundwood, however, were created in the 19th century according to sawmill...

Distorted asymmetric cubic nanostructure of soluble fullerene crystals in efficient polymer:fullerene solar cells.

PubMed

Kim, Youngkyoo; Nelson, Jenny; Zhang, Tong; Cook, Steffan; Durrant, James R; Kim, Hwajeong; Park, Jiho; Shin, Minjung; Nam, Sungho; Heeney, Martin; McCulloch, Iain; Ha, Chang-Sik; Bradley, Donal D C

2009-09-22

We found that 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C(61) (PCBM) molecules make a distorted asymmetric body-centered cubic crystal nanostructure in the bulk heterojunction films of reigoregular poly(3-hexylthiophene) and PCBM. The wider angle of distortion in the PCBM nanocrystals was approximately 96 degrees , which can be assigned to the influence of the attached side group to the fullerene ball of PCBM to bestow solubility. Atom concentration analysis showed that after thermal annealing the PCBM nanocrystals do preferentially distribute above the layer of P3HT nanocrystals inside devices.

A fast, parallel algorithm for distant-dependent calculation of crystal properties

NASA Astrophysics Data System (ADS)

Stein, Matthew

2017-12-01

A fast, parallel algorithm for distant-dependent calculation and simulation of crystal properties is presented along with speedup results and methods of application. An illustrative example is used to compute the Lennard-Jones lattice constants up to 32 significant figures for 4 ≤ p ≤ 30 in the simple cubic, face-centered cubic, body-centered cubic, hexagonal-close-pack, and diamond lattices. In most cases, the known precision of these constants is more than doubled, and in some cases, corrected from previously published figures. The tools and strategies to make this computation possible are detailed along with application to other potentials, including those that model defects.

SU-F-T-661: Dependence of Gold Nano Particles Cluster Morphology On Dose Enhancement of Photon Radiation Therapy Apply for Radiation Biology Effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahn, S; Chung, K; Han, Y

Purpose: Injected gold nano particles (GNPs) to a body for dose enhancement are known to form in the tumorcell cluster morphology. We investigated the dependence of dose enhancement on the morphology characteristic with an approximated morphology model by using Monte Carlo simulations. Methods: For MC simulation, TOPAS version 2.0P-03 was used. GNP cluster morphology was approximated as a body center cubic(BCC) model by placing 8 GNPs at the corner and one at the center of cube with length from 2.59 µm to 0.25 µm located in a 4 µm length water filled cube phantom. 4 µm length square shaped beamsmore » of poly-energetic 50, 260 kVp photons were irradiated to the water filled cube phantom with 100 nm diameter GNPs in it. Dose enhancement ratio(DER) was computed as a function of distance from the surface of the GNP at the cube center for 18 cubes geometries. For scoring particles, 10 nm width of concentric shell shaped detector was constructed up to 100 nm from the center. Total dose in a sphere of 100 nm radius of detector were normalized to 2.59 µm length cube morphology. To verified biological effect of BCC model applied to cell survival curve fitting. Results: DER increase as the distance of the GNPs reduces. DER was largest for 0.25 µm length cube. Dependence of GNP distance DER increment was 1.73, 1.60 for 50 kVp, 260 kVp photons, respectively. Also, Using BCC model applied to cell survival curve was well prediction. Conclusion: DER with GNPs was larger when they are closely packed in the phantom. Therefore, better therapeutic effects can be expected with close-packed GNPs. This research was supported by the NRF funded by the Ministry of Science, ICT & Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081].« less

Optical Fiber Assemblies for Space Flight from the NASA Goddard Space Flight Center, Photonics Group

NASA Technical Reports Server (NTRS)

Ott, Melanie N.; Thoma, William Joe; LaRocca, Frank; Chuska, Richard; Switzer, Robert; Day, Lance

2009-01-01

The Photonics Group at NASA Goddard Space Flight Center in the Electrical Engineering Division of the Advanced Engineering and Technologies Directorate has been involved in the design, development, characterization, qualification, manufacturing, integration and anomaly analysis of optical fiber subsystems for over a decade. The group supports a variety of instrumentation across NASA and outside entities that build flight systems. Among the projects currently supported are: The Lunar Reconnaissance Orbiter, the Mars Science Laboratory, the James Webb Space Telescope, the Express Logistics Carrier for the International Space Station and the NASA Electronic Parts. and Packaging Program. A collection of the most pertinent information gathered during project support over the past year in regards to space flight performance of optical fiber components is presented here. The objective is to provide guidance for future space flight designs of instrumentation and communication systems.

Integrated nonlinear optical imaging microscope for on-axis crystal detection and centering at a synchrotron beamline

PubMed Central

Madden, Jeremy T.; Toth, Scott J.; Dettmar, Christopher M.; Newman, Justin A.; Oglesbee, Robert A.; Hedderich, Hartmut G.; Everly, R. Michael; Becker, Michael; Ronau, Judith A.; Buchanan, Susan K.; Cherezov, Vadim; Morrow, Marie E.; Xu, Shenglan; Ferguson, Dale; Makarov, Oleg; Das, Chittaranjan; Fischetti, Robert; Simpson, Garth J.

2013-01-01

Nonlinear optical (NLO) instrumentation has been integrated with synchrotron X-ray diffraction (XRD) for combined single-platform analysis, initially targeting applications for automated crystal centering. Second-harmonic-generation microscopy and two-photon-excited ultraviolet fluorescence microscopy were evaluated for crystal detection and assessed by X-ray raster scanning. Two optical designs were constructed and characterized; one positioned downstream of the sample and one integrated into the upstream optical path of the diffractometer. Both instruments enabled protein crystal identification with integration times between 80 and 150 µs per pixel, representing a ∼103–104-fold reduction in the per-pixel exposure time relative to X-ray raster scanning. Quantitative centering and analysis of phenylalanine hydroxylase from Chromobacterium violaceum cPAH, Trichinella spiralis deubiquitinating enzyme TsUCH37, human κ-opioid receptor complex kOR-T4L produced in lipidic cubic phase (LCP), intimin prepared in LCP, and α-cellulose samples were performed by collecting multiple NLO images. The crystalline samples were characterized by single-crystal diffraction patterns, while α-cellulose was characterized by fiber diffraction. Good agreement was observed between the sample positions identified by NLO and XRD raster measurements for all samples studied. PMID:23765294

Pattern formation in three-dimensional reaction-diffusion systems

NASA Astrophysics Data System (ADS)

Callahan, T. K.; Knobloch, E.

1999-08-01

Existing group theoretic analysis of pattern formation in three dimensions [T.K. Callahan, E. Knobloch, Symmetry-breaking bifurcations on cubic lattices, Nonlinearity 10 (1997) 1179-1216] is used to make specific predictions about the formation of three-dimensional patterns in two models of the Turing instability, the Brusselator model and the Lengyel-Epstein model. Spatially periodic patterns having the periodicity of the simple cubic (SC), face-centered cubic (FCC) or body-centered cubic (BCC) lattices are considered. An efficient center manifold reduction is described and used to identify parameter regimes permitting stable lamellæ, SC, FCC, double-diamond, hexagonal prism, BCC and BCCI states. Both models possess a special wavenumber k* at which the normal form coefficients take on fixed model-independent ratios and both are described by identical bifurcation diagrams. This property is generic for two-species chemical reaction-diffusion models with a single activator and inhibitor.

Temperature and pressure tuneable swollen bicontinuous cubic phases approaching nature's length scales.

PubMed

Barriga, H M G; Tyler, A I I; McCarthy, N L C; Parsons, E S; Ces, O; Law, R V; Seddon, J M; Brooks, N J

2015-01-21

Bicontinuous cubic structures offer enormous potential in applications ranging from protein crystallisation to drug delivery systems and have been observed in cellular membrane structures. One of the current bottlenecks in understanding and exploiting these structures is that cubic scaffolds produced in vitro are considerably smaller in size than those observed in biological systems, differing by almost an order of magnitude in some cases. We have addressed this technological bottleneck and developed a methodology capable of manufacturing highly swollen bicontinuous cubic membranes with length scales approaching those seen in vivo. Crucially, these cubic systems do not require the presence of proteins. We have generated highly swollen Im3m symmetry bicontinuous cubic phases with lattice parameters of up to 480 Å, composed of ternary mixtures of monoolein, cholesterol and negatively charged lipid (DOPS or DOPG) and we have been able to tune their lattice parameters. The swollen cubic phases are highly sensitive to both temperature and pressure; these structural changes are likely to be controlled by a fine balance between lipid headgroup repulsions and lateral pressure in the hydrocarbon chain region.

The diagonalization of cubic matrices

NASA Astrophysics Data System (ADS)

Cocolicchio, D.; Viggiano, M.

2000-08-01

This paper is devoted to analysing the problem of the diagonalization of cubic matrices. We extend the familiar algebraic approach which is based on the Cardano formulae. We rewrite the complex roots of the associated resolvent secular equation in terms of transcendental functions and we derive the diagonalizing matrix.

A structural analysis of small vapor-deposited 'multiply twinned' gold particles

NASA Technical Reports Server (NTRS)

Yang, C. Y.; Heinemann, K.; Yacaman, M. J.; Poppa, H.

1979-01-01

High resolution selected zone dark field, Bragg reflection imaging and weak beam dark field techniques of transmission electron microscopy were used to determine the structure of small gold particles vapor deposited on NaCl substrates. Attention was focused on the analysis of those particles in the 50-150 A range that have pentagonal or hexagonal bright field profiles. These particles have been previously described as multiply twinned crystallites composed of face-centered cubic tetrahedra. The experimental evidence of the present studies can be interpreted on the assumption that the particle structure is a regular icosahedron or decahedron for the hexagonal or the pentagonal particles respectively. The icosahedron is a multiply twinned rhombohedral crystal and the decahedron is a multiply twinned body-centered orthorhombic crystal, each of which constitutes a slight distortion from the face-centered cubic structure.

Effects of the proposed Prosperity Reservoir on ground water and water quality in lower Center Creek basin, Missouri

USGS Publications Warehouse

Berkas, Wayne R.; Barks, James H.

1980-01-01

Effects of the proposed Prosperity Reservoir on ground water and water quality in lower Center Creek basin depend partly on the effectiveness of Grove Creek as a hydrologic boundary between the reservoir site and the Oronogo-Duenweg mining belt. Results of two dye traces indicate that Grove Creek probably is not an effective boundary. Therefore, higher water levels near the reservoir may cause more ground water to move into the mining belt and cause a greater discharge of zinc-laden mine water into Center Creek.Ground-water-level measurements and seepage runs on Center Creek indicate a relationship between ground-water levels, mine-water discharge and seepage, and base flow in Center Creek. From March to October 1979, ground-water levels generally decreased from 5 to 20 feet at higher elevations (recharge areas) and from 1 to 3 feet near Center Creek (discharge area); total mine water discharged to the surface before entering Center Creek decreased from 5.4 to 2.2 cubic feet per second; mine-water seepage directly to Center Creek decreased from an estimated 1.9 to 1.1 cubic feet per second; and the discharge of Center Creek near Carterville decreased from 184 to 42 cubic feet per second.Fertilizer industry wastes discharged into Grove Creek resulted in significant increases of nitrogen and phosphorus in lower Center Creek.

Optical soliton solutions of the cubic-quintic non-linear Schrödinger's equation including an anti-cubic term

NASA Astrophysics Data System (ADS)

Kaplan, Melike; Hosseini, Kamyar; Samadani, Farzan; Raza, Nauman

2018-07-01

A wide range of problems in different fields of the applied sciences especially non-linear optics is described by non-linear Schrödinger's equations (NLSEs). In the present paper, a specific type of NLSEs known as the cubic-quintic non-linear Schrödinger's equation including an anti-cubic term has been studied. The generalized Kudryashov method along with symbolic computation package has been exerted to carry out this objective. As a consequence, a series of optical soliton solutions have formally been retrieved. It is corroborated that the generalized form of Kudryashov method is a direct, effectual, and reliable technique to deal with various types of non-linear Schrödinger's equations.

Cubication of Conservative Nonlinear Oscillators

ERIC Educational Resources Information Center

Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada

2009-01-01

A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…

Influence of Two-Photon Absorption Anisotropy on Terahertz Emission Through Optical Rectification in Zinc-Blende Crystals

NASA Astrophysics Data System (ADS)

Sanjuan, Federico; Gaborit, Gwenaël; Coutaz, Jean-Louis

2018-04-01

We report for the first time on the observation of an angular anisotropy of the THz signal generated by optical rectification in a < 111 > ZnTe crystal. This cubic (zinc-blende) crystal in the < 111 > orientation exhibits both transverse isotropy for optical effects involving the linear χ (1) and nonlinear χ (2) susceptibilities. Thus, the observed anisotropy can only be related to χ (3) effect, namely two-photon absorption, which leads to the photo-generation of free carriers that absorb the generated THz signal. Two-photon absorption in zinc-blende crystals is known to be due to a spin-orbit interaction between the valence and higher-conduction bands. We perform a couple of measurements that confirm our hypothesis, as well as we fit the recorded data with a simple model. This two-photon absorption effect makes difficult an efficient generation, through optical rectification in < 111 > zinc-blende crystals, of THz beams of any given polarization state by only monitoring the laser pump polarization.

Subwavelength photonic crystal waveguide with trapezoidal shaped dielectric pillars in optical systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xiaochuan; Chen, Ray T.

2017-02-07

A method for reducing loss in a subwavelength photonic crystal waveguide bend is disclosed. The method comprising: forming the subwavelength photonic crystal waveguide bend with a series of trapezoidal shaped dielectric pillars centered about a bend radius; wherein each of the trapezoidal shaped dielectric pillars comprise a top width, a bottom width, and a trapezoid height; wherein the length of the bottom width is greater than the length of the top width; and wherein the bottom width is closer to the center of the bend radius of the subwavelength photonic crystal waveguide bend than the top width. Other embodiments aremore » described and claimed.« less

Negative thermal expansion materials related to cubic zirconium tungstate

NASA Astrophysics Data System (ADS)

Lind, Cora

2001-12-01

A non-hydrolytic sol-gel method for the preparation of ZrW2O 8 was developed. A new trigonal polymorph was discovered, which is structurally related to trigonal ZrMO2O8 and MnRe2O 8 as evidenced by powder x-ray diffraction and EXAFS studies. Seeding of the starting mixtures with cubic ZrW2O8 promoted crystallization of the cubic phase instead of trigonal material. Dehydration of ZrW2O7(OH)2·2H 2O gave cubic ZrW2O8 at 650°C, and a modification of this route led to the discovery of the new NTE materials cubic ZrMo 2O8 and HfMo2O8. These compounds crystallize in the same temperature range as the more stable trigonal AMo2O 8 polymorphs. To facilitate preparation of phase pure cubic molybdates, the influence of precursor chemistry on the crystallization behavior was investigated. The synthesis was extended to the solid solution system ZrxHf 1-xMoyW2-yO8 (0 ≤ x ≤ 1, 0 ≤ y ≤ 2). All compounds showed negative thermal expansion between 77 and 573 K. High-pressure in situ diffraction experiments were conducted on several AM2O8 polymorphs. With the exception of monoclinic ZrMo2O8, all materials underwent at least one pressure induced phase transition. Quasi-hydrostatic experiments on cubic AMo 2O8 led to a reversible transition to a new high-pressure structure, while low-pressure amorphization was observed under non-hydrostatic conditions. Isothermal kinetic studies of the cubic to trigonal transformation for ZrMo2O8 were carried out on four samples. Apparent activation energies of 170--290 kJ/mol were obtained using an Avrami model in combination with an Arrhenius analysis. This corresponds to 5% conversion levels after one year at temperatures between 220 and 315°C. Ex situ studies showed that the conversion at lower temperatures was considerably slower than what would be expected from extrapolation of the kinetic data. Drop solution calorimetry was carried out on several polymorphs of ZrMo 2O8, HfMo2O8 and ZrW2O 8. Only monoclinic ZrMo2O8 was enthalpically

Modeling and Optimization of Optical Half Adder in Two Dimensional Photonic Crystals

NASA Astrophysics Data System (ADS)

Sonth, Mahesh V.; Soma, Savita; Gowre, Sanjaykumar C.; Biradar, Nagashettappa

2018-05-01

The output of photonic integrated devices is enhanced using crystal waveguides and cavities but optimization of these devices is a topic of research. In this paper, optimization of the optical half adder in two-dimensional (2-D) linear photonic crystals using four symmetric T-shaped waveguides with 180° phase shift inputs is proposed. The input section of a T-waveguide acts as a beam splitter, and the output section acts as a power combiner. The constructive and destructive interference phenomenon will provide an output optical power. Output port Cout will receive in-phase power through the 180° phase shifter cavity designed near the junction. The optical half adder is modeled in a 2-D photonic crystal using the finite difference time domain method (FDTD). It consists of a cubic lattice with an array of 39 × 43 silicon rods of radius r 0.12 μm and 0.6 μm lattice constant a. The extinction ratio r e of 11.67 dB and 12.51 dB are achieved at output ports using the RSoft FullWAVE-6.1 software package.

Transformation of topologically close-packed β-W to body-centered cubic α-W: Comparison of experiments and computations.

PubMed

Barmak, Katayun; Liu, Jiaxing; Harlan, Liam; Xiao, Penghao; Duncan, Juliana; Henkelman, Graeme

2017-10-21

The enthalpy and activation energy for the transformation of the metastable form of tungsten, β-W, which has the topologically close-packed A15 structure (space group Pm3¯n), to equilibrium α-W, which is body-centered cubic (A2, space group Im3¯m), was measured using differential scanning calorimetry. The β-W films were 1 μm-thick and were prepared by sputter deposition in argon with a small amount of nitrogen. The transformation enthalpy was measured as -8.3 ± 0.4 kJ/mol (-86 ± 4 meV/atom) and the transformation activation energy as 2.2 ± 0.1 eV. The measured enthalpy was found to agree well with the difference in energies of α and β tungsten computed using density functional theory, which gave a value of -82 meV/atom for the transformation enthalpy. A calculated concerted transformation mechanism with a barrier of 0.4 eV/atom, in which all the atoms in an A15 unit cell transform into A2, was found to be inconsistent with the experimentally measured activation energy for any critical nucleus larger than two A2 unit cells. Larger calculations of eight A15 unit cells spontaneously relax to a mechanism in which part of the supercell first transforms from A15 to A2, creating a phase boundary, before the remaining A15 transforms into the A2 phase. Both calculations indicate that a nucleation and growth mechanism is favored over a concerted transformation. More consistent with the experimental activation energy was that of a calculated local transformation mechanism at the A15-A2 phase boundary, computed as 1.7 eV using molecular dynamics simulations. This calculated phase transformation mechanism involves collective rearrangements of W atoms in the disordered interface separating the A15 and A2 phases.

Protective Face Mask

NASA Technical Reports Server (NTRS)

1981-01-01

Mask to protect the physically impaired from injuries to the face and head has been developed by Langley Research Center. It is made of composite materials, usually graphite or boron fibers woven into a matrix. Weighs less than three ounces.

Predicted cubic-foot yields of sawmill products for black cherry trees

Treesearch

Leland F. Hanks

1980-01-01

Equations and tables for estimating the cubic-foot volumes of lumber, sawdust, and sawmill residue for black cherry trees are presented. Also included are cubic-foot and board-foot predictions for the sawlog portion of the trees.

Face Patch Resting State Networks Link Face Processing to Social Cognition

PubMed Central

Schwiedrzik, Caspar M.; Zarco, Wilbert; Everling, Stefan; Freiwald, Winrich A.

2015-01-01

Faces transmit a wealth of social information. How this information is exchanged between face-processing centers and brain areas supporting social cognition remains largely unclear. Here we identify these routes using resting state functional magnetic resonance imaging in macaque monkeys. We find that face areas functionally connect to specific regions within frontal, temporal, and parietal cortices, as well as subcortical structures supporting emotive, mnemonic, and cognitive functions. This establishes the existence of an extended face-recognition system in the macaque. Furthermore, the face patch resting state networks and the default mode network in monkeys show a pattern of overlap akin to that between the social brain and the default mode network in humans: this overlap specifically includes the posterior superior temporal sulcus, medial parietal, and dorsomedial prefrontal cortex, areas supporting high-level social cognition in humans. Together, these results reveal the embedding of face areas into larger brain networks and suggest that the resting state networks of the face patch system offer a new, easily accessible venue into the functional organization of the social brain and into the evolution of possibly uniquely human social skills. PMID:26348613

Preparing technicians for photonics industries and organizations

NASA Astrophysics Data System (ADS)

Souders, John; Hull, Dan

2012-10-01

U.S. photonics organizations need about 800 new photonics technicians each year. Thirty-one community and technical colleges have approximately 700 students enrolled in photonics related programs; about 275 of them complete their coursework and enter the workforce each year. A disparity exists between the demand and supply of qualified photonics technicians in the U.S. OP-TEC, the National Center for Optics and Photonics Education is a consortium of seven colleges, under the leadership of the University of Central Florida, and sponsored by NSF. OP-TEC's mission is to increase the quantity and quality of photonics technicians prepared at two-year colleges. OP-TEC maintains the National Photonics Skill Standards for Technicians, provides curriculum models, teaching materials, faculty training/professional development and planning services to strengthen existing college photonics programs and to attract and support new ones. OP-TEC is converting its text materials to E-Books to support students in technical programs. Through OP-TEC's recruitment efforts 84 additional colleges are interested in initiating new photonics programs. The OP-TEC Photonics College Network (OPCN) consists of 28 colleges that are currently providing photonics education. This fall OPCN will lead an additional national effort to further educate employed photonics technicians through on-line courses, complemented by lab experiences at nearby colleges. OP-TEC is expanding its outreach to photonics employers and colleges by regionalizing its approach to offering its services. OP-TEC is also planning to develop new curricula and instructional materials for AAS programs to prepare Precision Optics Technicians. This paper will detail OP-TEC's work with particular emphases on its materials and services.

The compressibility of cubic white and orthorhombic, rhombohedral, and simple cubic black phosphorus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Simon M; Zaug, Joseph

2010-03-10

The effect of pressure on the crystal structure of white phosphorus has been studied up to 22.4 GPa. The ?alpha phase was found to transform into the alpha' phase at 0.87 +- 0.04 GPa with a volume change of 0.1 +- 0.3 cc/mol. A fit of a second order Birch- Murnaghan equation to the data gave Vo = 16.94 ? 0.08 cc/mol and Ko = 6.7 +- 0.5 GPa for the alpha phase and Vo = 16.4 +- 0.1 cc/mol and Ko = 9.1 +- 0.3 GPa for the alpha' phase. The alpha' phase was found to transform to themore » A17 phase of black phosphorus at 2.68 +- 0.34 GPa and then with increasing pressure to the A7 and then simple cubic phase of black phosphorus. A fit of a second order Birch-Murnaghan equation to our data combined with previous measurements gave Vo = 11.43 +- 0.05 cc/mol and Ko = 34.7 +- 0.5 GPa for the A17 phase, Vo = 9.62 +- 0.01 cc/mol and Ko = 65.0 +- 0.6 GPa for the A7 phase and , Vo = 9.23 +- 0.01 cc/mol and Ko = 72.5 +- 0.3 GPa for the simple cubic phase.« less

Advanced Face Gear Surface Durability Evaluations

NASA Technical Reports Server (NTRS)

Lewicki, David G.; Heath, Gregory F.

2016-01-01

The surface durability life of helical face gears and isotropic super-finished (ISF) face gears was investigated. Experimental fatigue tests were performed at the NASA Glenn Research Center. Endurance tests were performed on 10 sets of helical face gears in mesh with tapered involute helical pinions, and 10 sets of ISF-enhanced straight face gears in mesh with tapered involute spur pinions. The results were compared to previous tests on straight face gears. The life of the ISF configuration was slightly less than that of previous tests on straight face gears. The life of the ISF configuration was slightly greater than that of the helical configuration.

Cubic-foot tree volume equations and tables for western juniper.

Treesearch

Judith M. Chittester; Colin D. MacLean

1984-01-01

This note presents cubic-foot volume equations and tables for western juniper (Juniperus occidentalis Hook. ). Total cubicfoot volume (ground to tip, excluding all branches (CVTS)) is expressed as a function of diameter at breast height (DBH) and total height. Utilizable cubic-foot volume (top of 12-inch stump to a 4-inch top, excluding all...

Aspects on mediated glucose oxidation at a supported cubic phase.

PubMed

Aghbolagh, Mahdi Shahmohammadi; Khani Meynaq, Mohammad Yaser; Shimizu, Kenichi; Lindholm-Sethson, Britta

2017-12-01

A supported liquid crystalline cubic phase housing glucose oxidase on an electrode surface has been suggested as bio-anode in a biofuel. The purpose of this investigation is to clarify some aspect on the mediated enzymatic oxidation of glucose in such a bio-anode where the mediator ferrocene-carboxylic acid and glucose were dissolved in the solution. The enzyme glucose oxidase was housed in the water channels of the mono-olein cubic phase. The system was investigated with cyclic voltammetry at different scan rates and the temperature was varied between 15°C and 30°C. The diffusion coefficient of the mediator and also the film resistance was estimated showing a large decrease in the mass-transport properties as the temperature was decreased. The current from mediated oxidation of glucose at the electrode surface increased with decreasing film thickness. The transport of the mediator in the cubic phase was the rate-limiting step in the overall reaction, where the oxidation of glucose took place at the outer surface of the cubic phase. Copyright © 2017 Elsevier B.V. All rights reserved.

A Unit Cell Laboratory Experiment: Marbles, Magnets, and Stacking Arrangements

ERIC Educational Resources Information Center

Collins, David C.

2011-01-01

An undergraduate first-semester general chemistry laboratory experiment introducing face-centered, body-centered, and simple cubic unit cells is presented. Emphasis is placed on the stacking arrangement of solid spheres used to produce a particular unit cell. Marbles and spherical magnets are employed to prepare each stacking arrangement. Packing…

Extending a Property of Cubic Polynomials to Higher-Degree Polynomials

ERIC Educational Resources Information Center

Miller, David A.; Moseley, James

2012-01-01

In this paper, the authors examine a property that holds for all cubic polynomials given two zeros. This property is discovered after reviewing a variety of ways to determine the equation of a cubic polynomial given specific conditions through algebra and calculus. At the end of the article, they will connect the property to a very famous method…

Cubic Polynomials with Real or Complex Coefficients: The Full Picture

ERIC Educational Resources Information Center

Bardell, Nicholas S.

2016-01-01

The cubic polynomial with real coefficients has a rich and interesting history primarily associated with the endeavours of great mathematicians like del Ferro, Tartaglia, Cardano or Vieta who sought a solution for the roots (Katz, 1998; see Chapter 12.3: The Solution of the Cubic Equation). Suffice it to say that since the times of renaissance…

In situ nanomechanical testing of twinned metals in a transmission electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Nan; Wang, Jiangwei; Mao, Scott

This paper focuses on in situ transmission electron microscope (TEM) characterization to explore twins in face-centered-cubic and body-centered-cubic monolithic metals, and their impact on the overall mechanical performance. Taking advantage of simultaneous nanomechanical deformation and nanoscale imaging using versatile in situ TEM tools, direct correlation of these unique microscopic defects with macroscopic mechanical performance becomes possible. This article summarizes recent evidence to support the mechanisms related to strengthening and plasticity in metals, including nanotwinned Cu, Ni, Al, Au, and others in bulk, thin film, and nanowire forms.

In situ nanomechanical testing of twinned metals in a transmission electron microscope

DOE PAGES

Li, Nan; Wang, Jiangwei; Mao, Scott; ...

2016-04-01

This paper focuses on in situ transmission electron microscope (TEM) characterization to explore twins in face-centered-cubic and body-centered-cubic monolithic metals, and their impact on the overall mechanical performance. Taking advantage of simultaneous nanomechanical deformation and nanoscale imaging using versatile in situ TEM tools, direct correlation of these unique microscopic defects with macroscopic mechanical performance becomes possible. This article summarizes recent evidence to support the mechanisms related to strengthening and plasticity in metals, including nanotwinned Cu, Ni, Al, Au, and others in bulk, thin film, and nanowire forms.

Preferences for Online and/or Face-to-Face Counseling among University Students in Malaysia

PubMed Central

Wong, Kah P.; Bonn, Gregory; Tam, Cai L.; Wong, Chee P.

2018-01-01

Increasingly, online counseling is considered to be a cost-effective and highly accessible method of providing basic counseling and mental health services. To examine the potential of online delivery as a way of increasing overall usage of services, this study looked at students’ attitudes toward and likelihood of using both online and/or face-to-face counseling. A survey was conducted with 409 students from six universities in Malaysia participating. Approximately 35% of participants reported that they would be likely to utilize online counseling services but would be unlikely to participate in face-to-face counseling. Based on these results, it is suggested that offering online counseling, in addition to face-to-face services, could be an effective way for many university counseling centers to increase the utilization of their services and thus better serve their communities. PMID:29445352

Preferences for Online and/or Face-to-Face Counseling among University Students in Malaysia.

PubMed

Wong, Kah P; Bonn, Gregory; Tam, Cai L; Wong, Chee P

2018-01-01

Increasingly, online counseling is considered to be a cost-effective and highly accessible method of providing basic counseling and mental health services. To examine the potential of online delivery as a way of increasing overall usage of services, this study looked at students' attitudes toward and likelihood of using both online and/or face-to-face counseling. A survey was conducted with 409 students from six universities in Malaysia participating. Approximately 35% of participants reported that they would be likely to utilize online counseling services but would be unlikely to participate in face-to-face counseling. Based on these results, it is suggested that offering online counseling, in addition to face-to-face services, could be an effective way for many university counseling centers to increase the utilization of their services and thus better serve their communities.

Absence of metastable states in strained monoatomic cubic crystals.

NASA Astrophysics Data System (ADS)

Aguayo, Aarón; Mehl, Michael L.; de Coss, Romeo

2005-03-01

The Bain path distortion of a metal with an fcc (bcc) ground state toward the bcc (fcc) structure initially requires an increase in energy, but at some point along the Bain path the energy will again decrease until a local minimum is reached. We have studied the tetragonal distortion (Bain path) of monoatomic cubic crystals, using a combination of parametrized tight-binding and first-principles linearized augmented plane wave calculations. We show that this local minimum is unstable with respect to an elastic distortion, except in the rare case that the minimum is at the bcc (fcc) point on the Bain path. This shows that body-centered-tetragonal phases of these materials, which have been seen in epitaxially grown thin films, must be stabilized by the substrate and cannot be freestanding films. This work was partially supported by Consejo Nacional de Ciencia y Tecnolog'ia (CONACYT, M'exico) under Grant No. 43830-F.

High reflected cubic cavity as long path absorption cell for infrared gas sensing

NASA Astrophysics Data System (ADS)

Yu, Jia; Gao, Qiang; Zhang, Zhiguo

2014-10-01

One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

Technical Assessment: Integrated Photonics

DTIC Science & Technology

2015-10-01

in global internet protocol traffic as a function of time by local access technology. Photonics continues to play a critical role in enabling this...communication networks. This has enabled services like the internet , high performance computing, and power-efficient large-scale data centers. The...signal processing, quantum information science, and optics for free space applications. However major obstacles challenge the implementation of

Discovery of a diamond-based photonic crystal structure in beetle scales.

PubMed

Galusha, Jeremy W; Richey, Lauren R; Gardner, John S; Cha, Jennifer N; Bartl, Michael H

2008-05-01

We investigated the photonic crystal structure inside iridescent scales of the weevil Lamprocyphus augustus. By combining a high-resolution structure analysis technique based on sequential focused ion beam milling and scanning electron microscopy imaging with theoretical modeling and photonic band-structure calculations, we discovered a natural three-dimensional photonic structure with a diamond-based crystal lattice operating at visible wavelengths. Moreover, we found that within individual scales, the diamond-based structure is assembled in the form of differently oriented single-crystalline micrometer-sized pixels with only selected lattice planes facing the scales' top surface. A comparison of results obtained from optical microreflectance measurements with photonic band-structure calculations reveals that it is this sophisticated microassembly of the diamond-based crystal lattice that lends Lamprocyphus augustus its macroscopically near angle-independent green coloration.

Cubic nonlinearity in shear wave beams with different polarizations

PubMed Central

Wochner, Mark S.; Hamilton, Mark F.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.

2008-01-01

A coupled pair of nonlinear parabolic equations is derived for the two components of the particle motion perpendicular to the axis of a shear wave beam in an isotropic elastic medium. The equations account for both quadratic and cubic nonlinearity. The present paper investigates, analytically and numerically, effects of cubic nonlinearity in shear wave beams for several polarizations: linear, elliptical, circular, and azimuthal. Comparisons are made with effects of quadratic nonlinearity in compressional wave beams. PMID:18529167

Change of Energy of the Cubic Subnanocluster of Iron Under Influence of Interstitial and Substitutional Atoms.

PubMed

Nedolya, Anatoliy V; Bondarenko, Natalya V

2016-12-01

Energy change of an iron face-centred cubic subnanocluster was evaluated using molecular mechanics method depending on the position of a carbon interstitial atom and substitutional atoms of nickel. Calculations of all possible positions of impurity atoms show that the energy change of the system are discrete and at certain positions of the atoms are close to continuous.In terms of energy, when all impurity atoms are on the same edge of an atomic cluster, their positions are more advantageous. The presence of nickel atoms on the edge of a cubic cluster resulted in decrease of potential barrier for a carbon atom and decrease in energy in the whole cluster. A similar drift of a carbon atom from central octahedral interstitial site to the surface in the direction <011> occurred under the influence of surface factors.Such configuration corresponds to decreasing symmetry and increasing the number of possible energy states of a subnanocluster, and it corresponds to the condition of spontaneous crystallization process in an isolated system.Taking into account accidental positions of the nickel atom in the iron cluster, such behaviour of the carbon atom can explain the mechanism of growth of a new phase and formation of new clusters in the presence of other kind of atoms because of surface influence.

A programmable Si-photonic node for SDN-enabled Bloom filter forwarding in disaggregated data centers

NASA Astrophysics Data System (ADS)

Moralis-Pegios, M.; Terzenidis, N.; Vagionas, C.; Pitris, S.; Chatzianagnostou, E.; Brimont, A.; Zanzi, A.; Sanchis, P.; Marti, J.; Kraft, J.; Rochracher, K.; Dorrestein, S.; Bogdan, M.; Tekin, T.; Syrivelis, D.; Tassiulas, L.; Miliou, A.; Pleros, N.; Vyrsokinos, K.

2017-02-01

Programmable switching nodes supporting Software-Defined Networking (SDN) over optical interconnecting technologies arise as a key enabling technology for future disaggregated Data Center (DC) environments. The SDNenabling roadmap of intra-DC optical solutions is already a reality for rack-to-rack interconnects, with recent research reporting on interesting applications of programmable silicon photonic switching fabrics addressing board-to-board and even on-board applications. In this perspective, simplified information addressing schemes like Bloom filter (BF)-based labels emerge as a highly promising solution for ensuring rapid switch reconfiguration, following quickly the changes enforced in network size, network topology or even in content location. The benefits of BF-based forwarding have been so far successfully demonstrated in the Information-Centric Network (ICN) paradigm, while theoretical studies have also revealed the energy consumption and speed advantages when applied in DCs. In this paper we present for the first time a programmable 4x4 Silicon Photonic switch that supports SDN through the use of BF-labeled router ports. Our scheme significantly simplifies packet forwarding as it negates the need for large forwarding tables, allowing for its remote control through modifications in the assigned BF labels. We demonstrate 1x4 switch operation controlling the Si-Pho switch by a Stratix V FPGA module, which is responsible for processing the packet ID and correlating its destination with the appropriate BF-labeled outgoing port. DAC- and amplifier-less control of the carrier-injection Si-Pho switches is demonstrated, revealing successful switching of 10Gb/s data packets with BF-based forwarding information changes taking place at a time-scale that equals the duration of four consecutive packets.

Controlling gain one photon at a time

PubMed Central

Schwartz, Gregory W; Rieke, Fred

2013-01-01

Adaptation is a salient property of sensory processing. All adaptational or gain control mechanisms face the challenge of obtaining a reliable estimate of the property of the input to be adapted to and obtaining this estimate sufficiently rapidly to be useful. Here, we explore how the primate retina balances the need to change gain rapidly and reliably when photons arrive rarely at individual rod photoreceptors. We find that the weakest backgrounds that decrease the gain of the retinal output signals are similar to those that increase human behavioral threshold, and identify a novel site of gain control in the retinal circuitry. Thus, surprisingly, the gain of retinal signals begins to decrease essentially as soon as background lights are detectable; under these conditions, gain control does not rely on a highly averaged estimate of the photon count, but instead signals from individual photon absorptions trigger changes in gain. DOI: http://dx.doi.org/10.7554/eLife.00467.001 PMID:23682314

Super-hard cubic BN layer formation by nitrogen ion implantation

NASA Astrophysics Data System (ADS)

Komarov, F. F.; Pilko, V. V.; Yakushev, V. A.; Tishkov, V. S.

1994-11-01

Microcrystalline and amorphous boron thin films were implanted with nitrogen ions at energies from 25 to 125 keV and with doses from 2 × 10 17 to 1 × 10 18 at.cm 2 at temperatures below 200°C. The structure of boron nitride phases after ion implantation, formation of phases and phase transformations were investigated by TEM and TED methods. The cubic boron nitride phase is revealed. The microhardness of the formed films was satisfactorily explained in terms of chemical compound formation by polyenergetic ion implantation. The influence of the copper impurity on the formation of the cubic boron nitride phase is demonstrated. It has also been shown that low concentrations of copper promote cubic BN boundary formation.

Three-body spectrum in a finite volume: The role of cubic symmetry

DOE PAGES

Doring, M.; Hammer, H. -W.; Mai, M.; ...

2018-06-15

The three-particle quantization condition is partially diagonalized in the center-of-mass frame by using cubic symmetry on the lattice. To this end, instead of spherical harmonics, the kernel of the Bethe-Salpeter equation for particle-dimer scattering is expanded in the basis functions of different irreducible representations of the octahedral group. Such a projection is of particular importance for the three-body problem in the finite volume due to the occurrence of three-body singularities above breakup. Additionally, we study the numerical solution and properties of such a projected quantization condition in a simple model. It is shown that, for large volumes, these solutions allowmore » for an instructive interpretation of the energy eigenvalues in terms of bound and scattering states.« less

Three-body spectrum in a finite volume: The role of cubic symmetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doring, M.; Hammer, H. -W.; Mai, M.

The three-particle quantization condition is partially diagonalized in the center-of-mass frame by using cubic symmetry on the lattice. To this end, instead of spherical harmonics, the kernel of the Bethe-Salpeter equation for particle-dimer scattering is expanded in the basis functions of different irreducible representations of the octahedral group. Such a projection is of particular importance for the three-body problem in the finite volume due to the occurrence of three-body singularities above breakup. Additionally, we study the numerical solution and properties of such a projected quantization condition in a simple model. It is shown that, for large volumes, these solutions allowmore » for an instructive interpretation of the energy eigenvalues in terms of bound and scattering states.« less

Synthesis of nanowires and nanoparticles of cubic aluminium nitride

NASA Astrophysics Data System (ADS)

Balasubramanian, C.; Godbole, V. P.; Rohatgi, V. K.; Das, A. K.; Bhoraskar, S. V.

2004-03-01

Nanostructures of cubic aluminium nitride were synthesized by DC arc-plasma-induced melting of aluminium in a nitrogen-argon ambient. The material flux ejected from the molten aluminium surface was found to react with nitrogen under highly non-equilibrium conditions and subsequently condense on a water-cooled surface to yield a mixture of nanowires and nanoparticles of crystalline cubic aluminium nitride. Both x-ray diffraction and electron diffraction measurements revealed that the as-synthesized nitrides adopted the cubic phase. Fourier transform infrared spectroscopy was used to understand the bonding configuration. Microstructural features of the synthesized material were best studied by transmission electron microscopy. From these analyses cubic aluminium nitride was found to be the dominating phase for both nanowires and nanoparticles synthesized at low currents. The typical particle size distribution was found to range over 15-80 nm, whereas the wires varied from 30 to 100 nm in diameter and 500 to 700 nm in length, depending upon the process parameters such as arc current and the nitrogen pressure. The reaction products inside the plasma zone were also obtained theoretically by minimization of free energy and the favourable zone temperature necessary for the formation of aluminium nitride was found to be {\\sim } 6000 K. Results are discussed in view of the highly non-equilibrium conditions that prevail during the arc-plasma synthesis.

Frequency Control of Single Quantum Emitters in Integrated Photonic Circuits

NASA Astrophysics Data System (ADS)

Schmidgall, Emma R.; Chakravarthi, Srivatsa; Gould, Michael; Christen, Ian R.; Hestroffer, Karine; Hatami, Fariba; Fu, Kai-Mei C.

2018-02-01

Generating entangled graph states of qubits requires high entanglement rates, with efficient detection of multiple indistinguishable photons from separate qubits. Integrating defect-based qubits into photonic devices results in an enhanced photon collection efficiency, however, typically at the cost of a reduced defect emission energy homogeneity. Here, we demonstrate that the reduction in defect homogeneity in an integrated device can be partially offset by electric field tuning. Using photonic device-coupled implanted nitrogen vacancy (NV) centers in a GaP-on-diamond platform, we demonstrate large field-dependent tuning ranges and partial stabilization of defect emission energies. These results address some of the challenges of chip-scale entanglement generation.

Frequency Control of Single Quantum Emitters in Integrated Photonic Circuits.

PubMed

Schmidgall, Emma R; Chakravarthi, Srivatsa; Gould, Michael; Christen, Ian R; Hestroffer, Karine; Hatami, Fariba; Fu, Kai-Mei C

2018-02-14

Generating entangled graph states of qubits requires high entanglement rates with efficient detection of multiple indistinguishable photons from separate qubits. Integrating defect-based qubits into photonic devices results in an enhanced photon collection efficiency, however, typically at the cost of a reduced defect emission energy homogeneity. Here, we demonstrate that the reduction in defect homogeneity in an integrated device can be partially offset by electric field tuning. Using photonic device-coupled implanted nitrogen vacancy (NV) centers in a GaP-on-diamond platform, we demonstrate large field-dependent tuning ranges and partial stabilization of defect emission energies. These results address some of the challenges of chip-scale entanglement generation.

Dirac directional emission in anisotropic zero refractive index photonic crystals.

PubMed

He, Xin-Tao; Zhong, Yao-Nan; Zhou, You; Zhong, Zhi-Chao; Dong, Jian-Wen

2015-08-14

A certain class of photonic crystals with conical dispersion is known to behave as isotropic zero-refractive-index medium. However, the discrete building blocks in such photonic crystals are limited to construct multidirectional devices, even for high-symmetric photonic crystals. Here, we show multidirectional emission from low-symmetric photonic crystals with semi-Dirac dispersion at the zone center. We demonstrate that such low-symmetric photonic crystal can be considered as an effective anisotropic zero-refractive-index medium, as long as there is only one propagation mode near Dirac frequency. Four kinds of Dirac multidirectional emitters are achieved with the channel numbers of five, seven, eleven, and thirteen, respectively. Spatial power combination for such kind of Dirac directional emitter is also verified even when multiple sources are randomly placed in the anisotropic zero-refractive-index photonic crystal.

Dirac directional emission in anisotropic zero refractive index photonic crystals

PubMed Central

He, Xin-Tao; Zhong, Yao-Nan; Zhou, You; Zhong, Zhi-Chao; Dong, Jian-Wen

2015-01-01

A certain class of photonic crystals with conical dispersion is known to behave as isotropic zero-refractive-index medium. However, the discrete building blocks in such photonic crystals are limited to construct multidirectional devices, even for high-symmetric photonic crystals. Here, we show multidirectional emission from low-symmetric photonic crystals with semi-Dirac dispersion at the zone center. We demonstrate that such low-symmetric photonic crystal can be considered as an effective anisotropic zero-refractive-index medium, as long as there is only one propagation mode near Dirac frequency. Four kinds of Dirac multidirectional emitters are achieved with the channel numbers of five, seven, eleven, and thirteen, respectively. Spatial power combination for such kind of Dirac directional emitter is also verified even when multiple sources are randomly placed in the anisotropic zero-refractive-index photonic crystal. PMID:26271208

Single-chip photonic transceiver based on bulk-silicon, as a chip-level photonic I/O platform for optical interconnects.

PubMed

Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Kim, In Gyoo; Oh, Jin Hyuk; Kim, Sun Ae; Park, Jaegyu; Kim, Sanggi

2015-06-10

When silicon photonic integrated circuits (PICs), defined for transmitting and receiving optical data, are successfully monolithic-integrated into major silicon electronic chips as chip-level optical I/Os (inputs/outputs), it will bring innovative changes in data computing and communications. Here, we propose new photonic integration scheme, a single-chip optical transceiver based on a monolithic-integrated vertical photonic I/O device set including light source on bulk-silicon. This scheme can solve the major issues which impede practical implementation of silicon-based chip-level optical interconnects. We demonstrated a prototype of a single-chip photonic transceiver with monolithic-integrated vertical-illumination type Ge-on-Si photodetectors and VCSELs-on-Si on the same bulk-silicon substrate operating up to 50 Gb/s and 20 Gb/s, respectively. The prototype realized 20 Gb/s low-power chip-level optical interconnects for λ ~ 850 nm between fabricated chips. This approach can have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, hybrid memory cube, and LAN, SAN, data center and network applications.

Intrinsic behavior of face-centered-cubic supra-crystals of nanocrystals self-organized on mesoscopic scale

NASA Astrophysics Data System (ADS)

Pileni, M. P.

2005-12-01

We describe intrinsic behavior due to the high ordering of nanocrystals at the mesoscopic scale. The first example shows well-defined columns in the formation of cobalt nanocrystals when an applied magnetic field is applied during the evaporation process. Collective breathing properties between nanocrystals are demonstrated. In both cases, these features are observed when the nanocrystals are highly ordered in fcc supra-crystals.

Simulation for F.C.C. deformation texture by modified pencil glide theory[Face Centered Cubic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masui, H.

1999-11-26

Inspired by the pencil glide theory for b.c.c. metal, modified pencil glide theory for f.c.c. metal was proposed, dividing the 12 glide systems of f.c.c. metal into three groups individually composed of eight {l{underscore}brace}111{r{underscore}brace}{l{underscore}angle}110{r{underscore}angle} glide systems around the principal axes X[100], Y[010] and Z[001]. These assumptions yielded two mathematical solutions {Omega}(3) and {Omega}(1). In {Omega}(3), from the three groups with four complete conjugated glide systems composed of, respectively, two glide systems of common {l{underscore}angle}110{r{underscore}angle} direction, only one group with the maximum plastic work may operate if the requirements are satisfied, otherwise glide systems in {Omega}(1) where one of the fourmore » conjugated glide systems is zero are activated. The model considering the 12 glide systems of f.c.c. as a whole explained many experimentally stable orientations in axisymmetric and rolling deformation. The differences between the two pencil glide theories for b.c.c. and f.c.c. are also discussed with data.« less

Atomistic Simulations of Surface Cross-Slip Nucleation in Face-Centered Cubic Nickel and Copper (Postprint)

DTIC Science & Technology

2013-02-15

molecular dynamics code, LAMMPS [9], developed at Sandia National Laboratory. The simulation cell is a rectangular parallelepiped, with the z-axis...with assigned energies within LAMMPs of greater than 4.42 eV (Ni) or 3.52 eV (Cu) (the energy of atoms in the stacking fault region), the partial...molecular dynamics code LAMMPS , which was developed at Sandia National Laboratory by Dr. Steve Plimpton and co-workers. This work was supported by the

Process for producing wurtzitic or cubic boron nitride

DOEpatents

Holt, J.B.; Kingman, D.D.; Bianchini, G.M.

1992-04-28

Disclosed is a process for producing wurtzitic or cubic boron nitride comprising the steps of: [A] preparing an intimate mixture of powdered boron oxide, a powdered metal selected from the group consisting of magnesium or aluminum, and a powdered metal azide; [B] igniting the mixture and bringing it to a temperature at which self-sustaining combustion occurs; [C] shocking the mixture at the end of the combustion thereof with a high pressure wave, thereby forming as a reaction product, wurtzitic or cubic boron nitride and occluded metal oxide; and, optionally [D] removing the occluded metal oxide from the reaction product. Also disclosed are reaction products made by the process described.

Process for producing wurtzitic or cubic boron nitride

DOEpatents

Holt, J. Birch; Kingman, deceased, Donald D.; Bianchini, Gregory M.

1992-01-01

Disclosed is a process for producing wurtzitic or cubic boron nitride comprising the steps of: [A] preparing an intimate mixture of powdered boron oxide, a powdered metal selected from the group consisting of magnesium or aluminum, and a powdered metal azide; [B] igniting the mixture and bringing it to a temperature at which self-sustaining combustion occurs; [C] shocking the mixture at the end of the combustion thereof with a high pressure wave, thereby forming as a reaction product, wurtzitic or cubic boron nitride and occluded metal oxide; and, optionally [D] removing the occluded metal oxide from the reaction product. Also disclosed are reaction products made by the process described.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filippov, A. V., E-mail: fav@triniti.ru

The interaction of two charged point macroparticles located in Wigner–Seitz cells of simple cubic (SC), body-centered cubic (BCC), or face-centered cubic (FCC) lattices in an equilibrium plasma has been studied within the Debye approximation or, more specifically, based on the linearized Poisson–Boltzmann model. The shape of the outer boundary is shown to exert a strong influence on the pattern of electrostatic interaction between the two macroparticles, which transforms from repulsion at small interparticle distances to attraction as the interparticle distance approaches half the length of the computational cell. The macroparticle pair interaction potential in an equilibrium plasma is shown tomore » be nevertheless the Debye one and purely repulsive for likely charged macroparticles.« less

Linear complexions: Confined chemical and structural states at dislocations

NASA Astrophysics Data System (ADS)

Kuzmina, M.; Herbig, M.; Ponge, D.; Sandlöbes, S.; Raabe, D.

2015-09-01

For 5000 years, metals have been mankind’s most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe-9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states.

The Many Faces of Patient-Centered Simulation: Implications for Researchers.

PubMed

Arnold, Jennifer L; McKenzie, Frederic Rick D; Miller, Jane Lindsay; Mancini, Mary E

2018-06-01

Patient-centered simulation for nonhealthcare providers is an emerging and innovative application for healthcare simulation. Currently, no consensus exists on what patient-centered simulation encompasses and outcomes research in this area is limited. Conceptually, patient-centered simulation aligns with the principles of patient- and family-centered care bringing this educational tool directly to patients and caregivers with the potential to improve patient care and outcomes. This descriptive article is a summary of findings presented at the 2nd International Meeting for Simulation in Healthcare Research Summit. Experts in the field delineated a categorization for better describing patient-centered simulation and reviewed the literature to identify a research agenda. Three types of patient-centered simulation patient-directed, patient-driven, and patient-specific are presented with research priorities identified for each. Patient-centered simulation has been shown to be an effective educational tool and has the potential to directly improve patient care outcomes. Presenting a typology for patient-centered simulation provides direction for future research.

X-ray detection with zinc-blende (cubic) GaN Schottky diodes

NASA Astrophysics Data System (ADS)

Gohil, T.; Whale, J.; Lioliou, G.; Novikov, S. V.; Foxon, C. T.; Kent, A. J.; Barnett, A. M.

2016-07-01

The room temperature X-ray responses as functions of time of two n type cubic GaN Schottky diodes (200 μm and 400 μm diameters) are reported. The current densities as functions of time for both diodes showed fast turn-on transients and increases in current density when illuminated with X-ray photons of energy up to 35 keV. The diodes were also electrically characterized: capacitance, implied depletion width and dark current measurements as functions of applied bias at room temperature are presented. At -5 V reverse bias, the capacitances of the diodes were measured to be (84.05 ± 0.01) pF and (121.67 ± 0.02) pF, respectively. At -5 V reverse bias, the dark current densities of the diodes were measured to be (347.2 ± 0.4) mA cm-2 and (189.0 ± 0.2) mA cm-2, respectively. The Schottky barrier heights of the devices (0.52 ± 0.07) eV and (0.63 ± 0.09) eV, respectively, were extracted from the forward dark current characteristics.

Wiring up pre-characterized single-photon emitters by laser lithography

NASA Astrophysics Data System (ADS)

Shi, Q.; Sontheimer, B.; Nikolay, N.; Schell, A. W.; Fischer, J.; Naber, A.; Benson, O.; Wegener, M.

2016-08-01

Future quantum optical chips will likely be hybrid in nature and include many single-photon emitters, waveguides, filters, as well as single-photon detectors. Here, we introduce a scalable optical localization-selection-lithography procedure for wiring up a large number of single-photon emitters via polymeric photonic wire bonds in three dimensions. First, we localize and characterize nitrogen vacancies in nanodiamonds inside a solid photoresist exhibiting low background fluorescence. Next, without intermediate steps and using the same optical instrument, we perform aligned three-dimensional laser lithography. As a proof of concept, we design, fabricate, and characterize three-dimensional functional waveguide elements on an optical chip. Each element consists of one single-photon emitter centered in a crossed-arc waveguide configuration, allowing for integrated optical excitation and efficient background suppression at the same time.

Real-Time Fluorescence Detection in Aqueous Systems by Combined and Enhanced Photonic and Surface Effects in Patterned Hollow Sphere Colloidal Photonic Crystals.

PubMed

Zhong, Kuo; Wang, Ling; Li, Jiaqi; Van Cleuvenbergen, Stijn; Bartic, Carmen; Song, Kai; Clays, Koen

2017-05-16

Hollow sphere colloidal photonic crystals (HSCPCs) exhibit the ability to maintain a high refractive index contrast after infiltration of water, leading to extremely high-quality photonic band gap effects, even in an aqueous (physiological) environment. Superhydrophilic pinning centers in a superhydrophobic environment can be used to strongly confine and concentrate water-soluble analytes. We report a strategy to realize real-time ultrasensitive fluorescence detection in patterned HSCPCs based on strongly enhanced fluorescence due to the photonic band-edge effect combined with wettability differentiation in the superhydrophobic/superhydrophilic pattern. The orthogonal nature of the two strategies allows for a multiplicative effect, resulting in an increase of two orders of magnitude in fluorescence.

Two-photon interference of temporally separated photons.

PubMed

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2016-10-06

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms.

Two-photon interference of temporally separated photons

PubMed Central

Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

2016-01-01

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms. PMID:27708380

Two-Photon Excitation of Launched Cold Atoms in Flight

NASA Astrophysics Data System (ADS)

Goodsell, Anne; Gonzalez, Rene; Alejandro, Eduardo; Erwin, Emma

2017-04-01

We demonstrate two-photon bi-chromatic excitation of cold rubidium atoms in flight, using the pathway 5S1 / 2 -> 5P3 / 2 -> 5D5 / 2 with two resonant photons. In our experiment, atoms are laser-cooled in a magneto-optical trap and launched upward in discrete clouds with a controllable vertical speed of 7.1 +/-0.6 m/s and a velocity spread that is less than 10% of the launch speed. Outside the cooling beams, as high as 14 mm above the original center of the trap, the launched cold atoms are illuminated simultaneously by spatially-localized horizontal excitation beams at 780 nm (5S1 / 2 -> 5P3 / 2) and 776 nm (5P3 / 2 -> 5D5 / 2). We monitor transmission of the 780-nm beam over a range of intensities of 780-nm and 776-nm light. As the center of the moving cloud passes the excitation beams, we observe as much as 97.9 +/-1.2% transmission when the rate of two-photon absorption is high and the 5S1 / 2 and 5P3 / 2 states are depopulated, compared to 87.6 +/-0.9% transmission if only the 780-nm beam is present. This demonstrates two-photon excitation of a launched cold-atom source with controllable launch velocity and narrow velocity spread, as a foundation for three-photon excitation to Rydberg states. Research supported by Middlebury College Bicentennial Fund, Palen Fund, and Gladstone Award.

[An Improved Cubic Spline Interpolation Method for Removing Electrocardiogram Baseline Drift].

PubMed

Wang, Xiangkui; Tang, Wenpu; Zhang, Lai; Wu, Minghu

2016-04-01

The selection of fiducial points has an important effect on electrocardiogram(ECG)denoise with cubic spline interpolation.An improved cubic spline interpolation algorithm for suppressing ECG baseline drift is presented in this paper.Firstly the first order derivative of original ECG signal is calculated,and the maximum and minimum points of each beat are obtained,which are treated as the position of fiducial points.And then the original ECG is fed into a high pass filter with 1.5Hz cutoff frequency.The difference between the original and the filtered ECG at the fiducial points is taken as the amplitude of the fiducial points.Then cubic spline interpolation curve fitting is used to the fiducial points,and the fitting curve is the baseline drift curve.For the two simulated case test,the correlation coefficients between the fitting curve by the presented algorithm and the simulated curve were increased by 0.242and0.13 compared with that from traditional cubic spline interpolation algorithm.And for the case of clinical baseline drift data,the average correlation coefficient from the presented algorithm achieved 0.972.

Why Do Membranes of Some Unhealthy Cells Adopt a Cubic Architecture?

DOE PAGES

Xiao, Qi; Wang, Zhichun; Williams, Dewight; ...

2016-12-05

Nonlamellar lipid arrangements, including cubosomes, appear in unhealthy cells, e.g., when they are subject to stress, starvation, or viral infection. The bioactivity of cubosomes—nanoscale particles exhibiting bicontinuous cubic structures—versus more common vesicles is an unexplored area due to lack of suitable model systems. Here, glycodendrimercubosomes (GDCs)—sugar-presenting cubosomes assembled from Janus glycodendrimers by simple injection into buffer—are proposed as mimics of biological cubic membranes. The bicontinuous cubic GDC architecture has been demonstrated by electron tomography. The stability of these GDCs in buffer enabled studies on lectin-dependent agglutination, revealing significant differences compared with the vesicular glycodendrimersome (GDS) counterpart. In particular, GDCs showedmore » an increased activity toward concanavalin A, as well as an increased sensitivity and selectivity toward two variants of banana lectins, a wild-type and a genetically modified variant, which is not exhibited by GDSs. These results suggest that cells may adapt under unhealthy conditions by undergoing a transformation from lamellar to cubic membranes as a method of defense.« less

Why Do Membranes of Some Unhealthy Cells Adopt a Cubic Architecture?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Qi; Wang, Zhichun; Williams, Dewight

Nonlamellar lipid arrangements, including cubosomes, appear in unhealthy cells, e.g., when they are subject to stress, starvation, or viral infection. The bioactivity of cubosomes—nanoscale particles exhibiting bicontinuous cubic structures—versus more common vesicles is an unexplored area due to lack of suitable model systems. Here, glycodendrimercubosomes (GDCs)—sugar-presenting cubosomes assembled from Janus glycodendrimers by simple injection into buffer—are proposed as mimics of biological cubic membranes. The bicontinuous cubic GDC architecture has been demonstrated by electron tomography. The stability of these GDCs in buffer enabled studies on lectin-dependent agglutination, revealing significant differences compared with the vesicular glycodendrimersome (GDS) counterpart. In particular, GDCs showedmore » an increased activity toward concanavalin A, as well as an increased sensitivity and selectivity toward two variants of banana lectins, a wild-type and a genetically modified variant, which is not exhibited by GDSs. These results suggest that cells may adapt under unhealthy conditions by undergoing a transformation from lamellar to cubic membranes as a method of defense.« less

Call for Papers: Photonics in Switching

NASA Astrophysics Data System (ADS)

Wosinska, Lena; Glick, Madeleine

2006-04-01

center">Call for Papers: Photonics in Switching

center">Guest Editors:

center"> Lena Wosinska, Royal Institute of Technology (KTH) / ICT Sweden Madeleine Glick, Intel Research, Cambridge, UK

Scope of Submission

• WDM node architectures
• Novel device technologies enabling photonics in switching, such as optical switch fabrics, optical memory, and wavelength conversion
• Routing protocols
• WDM switching and routing
• Quality of service
• Performance measurement and evaluation
• Next-generation optical networks: architecture, signaling, and control
• Traffic measurement and field trials
• Optical burst and packet switching
• OBS/OPS node architectures
• Burst/Packet scheduling and routing algorithms
• Contention resolution/avoidance strategies
• Services and applications for OBS/OPS (e.g., grid networks, storage-area networks, etc.)
• Burst assembly and ingress traffic shaping

• FAmily CEntered (FACE) advance care planning: Study design and methods for a patient-centered communication and decision-making intervention for patients with HIV/AIDS and their surrogate decision-makers.

  PubMed

  Kimmel, Allison L; Wang, Jichuan; Scott, Rachel K; Briggs, Linda; Lyon, Maureen E

  2015-07-01

  Although the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) has become a chronic illness, disease-specific advance care planning has not yet been evaluated for the palliative care needs of adults with HIV/AIDS. This prospective, longitudinal, randomized, two-arm controlled clinical trial aims to test the efficacy of FAmily CEntered advance care planning among adults living with AIDS and/or HIV with co-morbidities on congruence in treatment preferences, healthcare utilization, and quality of life. The FAmily CEntered intervention arm is two face-to-face sessions with a trained, certified facilitator: Session 1) Disease-Specific Advance Care Planning Respecting Choices Interview; Session 2) Completion of advance directive. The Healthy Living Control arm is: Session 1) Developmental/Relationship History; Session 2) Nutrition. Follow-up data will be collected at 3, 6, 12, and 18 months post-intervention. A total of 288 patient/surrogate dyads will be enrolled from five hospital-based, out-patient clinics in Washington, District of Columbia. Participants will be HIV positive and ≥ 21 years of age; surrogates will be ≥ 18 years of age. Exclusion criteria are homicidality, suicidality, psychosis, and impaired cognitive functioning. We hypothesize that this intervention will enhance patient-centered communication with a surrogate decision-maker about end of life treatment preferences over time, enhance patient quality of life and decrease health care utilization. We further hypothesize that this intervention will decrease health disparities for Blacks in completion of advance directives. If proposed aims are achieved, the benefits of palliative care, particularly increased treatment preferences about end-of-life care and enhanced quality of life, will be extended to people living with AIDS. Copyright © 2015 Elsevier Inc. All rights reserved.

• Optical analysis of the fine crystalline structure of artificial opal films.

  PubMed

  Lozano, G; Dorado, L A; Schinca, D; Depine, R A; Míguez, H

  2009-11-17

  Herein, we present a detailed analysis of the structure of artificial opal films. We demonstrate that, rather than the generally assumed face centered cubic lattice of spheres, opal films are better approximated by rhombohedral assemblies of distorted colloids. Detailed analysis of the optical response in a very wide spectral range (0.4 < or = a/lambda < or = 2, where a is the conventional lattice constant), as well as at perpendicular and off-normal directions, unambiguously shows that the interparticle distance coincides very approximately with the expected diameter only along directions contained in the same close-packed plane but differs significantly in directions oblique to the [111] one. A full description of the real and reciprocal lattices of actual opal films is provided, as well as of the photonic band structure of the proposed arrangement. The implications of this distortion in the optical response of the lattice are discussed.

EDITORIAL: TaCoNa-Photonics 2008 TaCoNa-Photonics 2008

NASA Astrophysics Data System (ADS)

Chigrin, Dmitry N.; Busch, Kurt; Lavrinenko, Andrei V.

2009-11-01

intensify theoretical discussions and to put them on `solid' ground it was decided to invite world-leading experts in experimental photonics for plenary talks. Over three days, the workshop has brought together more than 70 specialists in theoretical and computational nano-photonics. The workshop took place in the historical `Physikzentrum Bad Honnef', whose unique atmosphere supported a multitude of highly interesting debates and discussions that often lasted until midnight and beyond. Different theoretical and numerical aspects of light generation, control and detection in general inhomogeneous media, photonic crystals, plasmonic structures, metamaterials and integrated optical systems were covered in 15 invited talks and 52 contributed oral and posters presentations. The plenary talks were given by Professor M Wegener (metamaterials) and Professor W Barnes (plasmonics). This special section is a cross-sectional selection of papers which were submitted by the authors of invited and contributed oral presentations. It also includes two papers of the winners of the Best Poster Awards. We hope that these papers will enhance the interest of the scientific community regarding nano-photonics in general and regarding the TaCoNa-Photonics workshop series in particular. It is our distinct pleasure to acknowledge the generous financial support of our sponsors: Karlsruhe School of Optics & Photonics (KSOP) (Germany), U.S. Army International Technology Center-Atlantic, Research Division (USA), and the Office of Naval Research Global (USA). Without the organizational assistance from the International Department of the Universität Karlsruhe GmbH (Germany) this event would simply have been impossible.

Comparing face-to-face, synchronous, and asynchronous learning: postgraduate dental resident preferences.

PubMed

Kunin, Marc; Julliard, Kell N; Rodriguez, Tobias E

2014-06-01

The Department of Dental Medicine of Lutheran Medical Center has developed an asynchronous online curriculum consisting of prerecorded PowerPoint presentations with audio explanations. The focus of this study was to evaluate if the new asynchronous format satisfied the educational needs of the residents compared to traditional lecture (face-to-face) and synchronous (distance learning) formats. Lectures were delivered to 219 dental residents employing face-to-face and synchronous formats, as well as the new asynchronous format; 169 (77 percent) participated in the study. Outcomes were assessed with pretests, posttests, and individual lecture surveys. Results found the residents preferred face-to-face and asynchronous formats to the synchronous format in terms of effectiveness and clarity of presentations. This preference was directly related to the residents' perception of how well the technology worked in each format. The residents also rated the quality of student-instructor and student-student interactions in the synchronous and asynchronous formats significantly higher after taking the lecture series than they did before taking it. However, they rated the face-to-face format as significantly more conducive to student-instructor and student-student interaction. While the study found technology had a major impact on the efficacy of this curricular model, the results suggest that the asynchronous format can be an effective way to teach a postgraduate course.

Center for space microelectronics technology

NASA Technical Reports Server (NTRS)

1993-01-01

The 1992 Technical Report of the Jet Propulsion Laboratory Center for Space Microelectronics Technology summarizes the technical accomplishments, publications, presentations, and patents of the center during the past year. The report lists 187 publications, 253 presentations, and 111 new technology reports and patents in the areas of solid-state devices, photonics, advanced computing, and custom microcircuits.

Data reduction using cubic rational B-splines

NASA Technical Reports Server (NTRS)

Chou, Jin J.; Piegl, Les A.

1992-01-01

A geometric method is proposed for fitting rational cubic B-spline curves to data that represent smooth curves including intersection or silhouette lines. The algorithm is based on the convex hull and the variation diminishing properties of Bezier/B-spline curves. The algorithm has the following structure: it tries to fit one Bezier segment to the entire data set and if it is impossible it subdivides the data set and reconsiders the subset. After accepting the subset the algorithm tries to find the longest run of points within a tolerance and then approximates this set with a Bezier cubic segment. The algorithm uses this procedure repeatedly to the rest of the data points until all points are fitted. It is concluded that the algorithm delivers fitting curves which approximate the data with high accuracy even in cases with large tolerances.

Phase stability and magnetic behavior of FeCrCoNiGe high-entropy alloy

NASA Astrophysics Data System (ADS)

Huang, Shuo; Vida, Ádám; Molnár, Dávid; Kádas, Krisztina; Varga, Lajos Károly; Holmström, Erik; Vitos, Levente

2015-12-01

We report an alternative FeCrCoNiGe magnetic material based on FeCrCoNi high-entropy alloy with Curie point far below the room temperature. Investigations are done using first-principles calculations and key experimental measurements. Results show that the equimolar FeCrCoNiGe system is decomposed into a mixture of face-centered cubic and body-centered cubic solid solution phases. The increased stability of the ferromagnetic order in the as-cast FeCrCoNiGe composite, with measured Curie temperature of 640 K, is explained using the exchange interactions.

The diagram of phase-field crystal structures: an influence of model parameters in a two-mode approximation

NASA Astrophysics Data System (ADS)

Ankudinov, V.; Galenko, P. K.

2017-04-01

Effect of phase-field crystal model (PFC-model) parameters on the structure diagram is analyzed. The PFC-model is taken in a two-mode approximation and the construction of structure diagram follows from the free energy minimization and Maxwell thermodynamic rule. The diagram of structure’s coexistence for three dimensional crystal structures [Body-Centered-Cubic (BCC), Face-Centered-Cubic (FCC) and homogeneous structures] are constructed. An influence of the model parameters, including the stability parameters, are discussed. A question about the structure diagram construction using the two-mode PFC-model with the application to real materials is established.

Mechanism of slip and twinning

NASA Technical Reports Server (NTRS)

Rastani, Mansur

1992-01-01

The objectives are to: (1) demonstrate the mechanisms of deformation in body centered cubic (BCC), face centered cubic (FCC), and hexagonal close-packed (HCP)-structure metals and alloys and in some ceramics as well; (2) examine the deformed microstructures (slip lines and twin boundaries) in different grains of metallic and ceramic specimens; and (3) study visually the deformed macrostructure (slip and twin bands) of metals and alloys. Some of the topics covered include: deformation behavior of materials, mechanisms of plastic deformation, slip bands, twin bands, ductile failure, intergranular fracture, shear failure, slip planes, crystal deformation, and dislocations in ceramics.

Interplay between quantum confinement and surface effects in thickness selective stability of thin Ag and Eu films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xiaojie; Wang, Cai -Zhuang

Using first-principles calculations, we show that both face-centered cubic (fcc) Ag (1 1 0) ultrathin films and body-centered cubic (bcc) Eu(1 1 0) ultrathin films exhibit thickness selective stability. Furthermore, the origin of such thickness selection is different. While the thickness selective stability in fcc Ag(1 1 0) films is mainly due to the well-known quantum well states ascribed to the quantum confinement effects in free-electron-like metal films, the thickness selection in bcc Eu(1 1 0) films is more complex and also strongly correlated with the occupation of the surface and surface resonance states.

Interplay between quantum confinement and surface effects in thickness selective stability of thin Ag and Eu films

DOE PAGES

Liu, Xiaojie; Wang, Cai -Zhuang

2017-04-03

Using first-principles calculations, we show that both face-centered cubic (fcc) Ag (1 1 0) ultrathin films and body-centered cubic (bcc) Eu(1 1 0) ultrathin films exhibit thickness selective stability. Furthermore, the origin of such thickness selection is different. While the thickness selective stability in fcc Ag(1 1 0) films is mainly due to the well-known quantum well states ascribed to the quantum confinement effects in free-electron-like metal films, the thickness selection in bcc Eu(1 1 0) films is more complex and also strongly correlated with the occupation of the surface and surface resonance states.

On the phase evolution of AlCoCrCuFeMnSix high entropy alloys prepared by mechanical alloying and arc melting route

NASA Astrophysics Data System (ADS)

Kumar, Anil; Chopkar, Manoj

2018-05-01

Effect of Si addition on phase formation of AlCoCrCuFeMnSix (x=0, 0.3, 0.6 and 0.9) high entropy alloy have been investigated in this work. The alloys are prepared by mechanical alloying and vacuum arc melting technique. The X-ray diffraction results reveals the formation of mixture of face centered and body centered cubic solid solution phases in milled powders. The addition of Si favours body centered cubic structure formation during milling process. Whereas, after melting the milled powders, body centered phases formed during milling is partial transformed into sigma phases. XRD results were also correlated with the SEM elemental mapping of as casted samples. Addition of Si favours σ phase formation in the as cast samples.

Surface plasmon induced direct detection of long wavelength photons.

PubMed

Tong, Jinchao; Zhou, Wei; Qu, Yue; Xu, Zhengji; Huang, Zhiming; Zhang, Dao Hua

2017-11-21

Millimeter and terahertz wave photodetectors have long been of great interest due to a wide range of applications, but they still face challenges in detection performance. Here, we propose a new strategy for the direct detection of millimeter and terahertz wave photons based on localized surface-plasmon-polariton (SPP)-induced non-equilibrium electrons in antenna-assisted subwavelength ohmic metal-semiconductor-metal (OMSM) structures. The subwavelength OMSM structure is used to convert the absorbed photons into localized SPPs, which then induce non-equilibrium electrons in the structure, while the antenna increases the number of photons coupled into the OMSM structure. When the structure is biased and illuminated, the unidirectional flow of the SPP-induced non-equilibrium electrons forms a photocurrent. The energy of the detected photons is determined by the structure rather than the band gap of the semiconductor. The detection scheme is confirmed by simulation and experimental results from the devices, made of gold and InSb, and a room temperature noise equivalent power (NEP) of 1.5 × 10 -13 W Hz -1/2 is achieved.

Multimetallic nanoparticle catalysts with enhanced electrooxidation

DOEpatents

Sun, Shouheng; Zhang, Sen; Zhu, Huiyuan; Guo, Shaojun

2015-07-28

A new structure-control strategy to optimize nanoparticle catalysis is provided. The presence of Au in FePtAu facilitates FePt structure transformation from chemically disordered face centered cubic (fcc) structure to chemically ordered face centered tetragonal (fct) structure, and further promotes formic acid oxidation reaction (FAOR). The fct-FePtAu nanoparticles show high CO poisoning resistance, achieve mass activity as high as about 2810 mA/mg Pt, and retain greater than 90% activity after a 13 hour stability test.

A Retrospective Look at Replacing Face-to-Face Embryology Instruction with Online Lectures in a Human Anatomy Course

ERIC Educational Resources Information Center

Beale, Elmus G.; Tarwater, Patrick M.; Lee, Vaughan H.

2014-01-01

Embryology is integrated into the Clinically Oriented Anatomy course at the Texas Tech University Health Sciences Center School of Medicine. Before 2008, the same instructor presented embryology in 13 face-to-face lectures distributed by organ systems throughout the course. For the 2008 and 2009 offerings of the course, a hybrid embryology…

Cubic and Hexagonal Liquid Crystals as Drug Delivery Systems

PubMed Central

Chen, Yulin; Ma, Ping; Gui, Shuangying

2014-01-01

Lipids have been widely used as main constituents in various drug delivery systems, such as liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-based lyotropic liquid crystals. Among them, lipid-based lyotropic liquid crystals have highly ordered, thermodynamically stable internal nanostructure, thereby offering the potential as a sustained drug release matrix. The intricate nanostructures of the cubic phase and hexagonal phase have been shown to provide diffusion controlled release of active pharmaceutical ingredients with a wide range of molecular weights and polarities. In addition, the biodegradable and biocompatible nature of lipids demonstrates the minimum toxicity and thus they are used for various routes of administration. Therefore, the research on lipid-based lyotropic liquid crystalline phases has attracted a lot of attention in recent years. This review will provide an overview of the lipids used to prepare cubic phase and hexagonal phase at physiological temperature, as well as the influencing factors on the phase transition of liquid crystals. In particular, the most current research progresses on cubic and hexagonal phases as drug delivery systems will be discussed. PMID:24995330

Moral dilemmas faced by hospitals in time of war: the Rambam Medical Center during the second Lebanon war.

PubMed

Bar-El, Yaron; Reisner, Shimon; Beyar, Rafael

2014-02-01

Rambam Medical Center, the only tertiary care center and largest hospital in northern Israel, was subjected to continuous rocket attacks in 2006. This extreme situation posed serious and unprecedented ethical dilemmas to the hospital management. An ambiguous situation arose that required routine patient care in a tertiary modern hospital together with implementation of emergency measures while under direct fire. The physicians responsible for hospital management at that time share some of the moral dilemmas faced, the policy they chose to follow, and offer a retrospective critical reflection in this paper. The hospital's first priority was defined as delivery of emergency surgical and medical services to the wounded from the battlefields and home front, while concomitantly providing the civilian population with all elective medical and surgical services. The need for acute medical service was even more apparent as the situation of conflict led to closure of many ambulatory clinics, while urgent or planned medical care such as open heart surgery and chemotherapy continued. The hospital management took actions to minimize risks to patients, staff, and visitors during the ongoing attacks. Wards were relocated to unused underground spaces and corridors. However due to the shortage of shielded spaces, not all wards and patients could be relocated to safer areas. Modern warfare will most likely continue to involve civilian populations and institutes, blurring the division between peaceful high-tech medicine and the rough battlefront. Hospitals in high war-risk areas must be prepared to function and deliver treatment while under fire or facing similar threats.

Single-chip photonic transceiver based on bulk-silicon, as a chip-level photonic I/O platform for optical interconnects

PubMed Central

Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Gyoo Kim, In; Hyuk Oh, Jin; Ae Kim, Sun; Park, Jaegyu; Kim, Sanggi

2015-01-01

When silicon photonic integrated circuits (PICs), defined for transmitting and receiving optical data, are successfully monolithic-integrated into major silicon electronic chips as chip-level optical I/Os (inputs/outputs), it will bring innovative changes in data computing and communications. Here, we propose new photonic integration scheme, a single-chip optical transceiver based on a monolithic-integrated vertical photonic I/O device set including light source on bulk-silicon. This scheme can solve the major issues which impede practical implementation of silicon-based chip-level optical interconnects. We demonstrated a prototype of a single-chip photonic transceiver with monolithic-integrated vertical-illumination type Ge-on-Si photodetectors and VCSELs-on-Si on the same bulk-silicon substrate operating up to 50 Gb/s and 20 Gb/s, respectively. The prototype realized 20 Gb/s low-power chip-level optical interconnects for λ ~ 850 nm between fabricated chips. This approach can have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, hybrid memory cube, and LAN, SAN, data center and network applications. PMID:26061463

Photon-counting intensified random-access charge injection device

NASA Astrophysics Data System (ADS)

Norton, Timothy J.; Morrissey, Patrick F.; Haas, Patrick; Payne, Leslie J.; Carbone, Joseph; Kimble, Randy A.

1999-11-01

At NASA GSFC we are developing a high resolution solar-blind photon counting detector system for UV space based astronomy. The detector comprises a high gain MCP intensifier fiber- optically coupled to a charge injection device (CID). The detector system utilizes an FPGA based centroiding system to locate the center of photon events from the intensifier to high accuracy. The photon event addresses are passed via a PCI interface with a GPS derived time stamp inserted per frame to an integrating memory. Here we present imaging performance data which show resolution of MCP tube pore structure at an MCP pore diameter of 8 micrometer. This data validates the ICID concept for intensified photon counting readout. We also discuss correction techniques used in the removal of fixed pattern noise effects inherent in the centroiding algorithms used and present data which shows the local dynamic range of the device. Progress towards development of a true random access CID (RACID 810) is also discussed and astronomical data taken with the ICID detector system demonstrating the photon event time-tagging mode of the system is also presented.

Photons, photon jets, and dark photons at 750 GeV and beyond.

PubMed

Dasgupta, Basudeb; Kopp, Joachim; Schwaller, Pedro

2016-01-01

In new physics searches involving photons at the LHC, one challenge is to distinguish scenarios with isolated photons from models leading to "photon jets". For instance, in the context of the 750 GeV diphoton excess, it was pointed out that a true diphoton resonance [Formula: see text] can be mimicked by a process of the form [Formula: see text], where S is a new scalar with a mass of 750 GeV and a is a light pseudoscalar decaying to two collinear photons. Photon jets can be distinguished from isolated photons by exploiting the fact that a large fraction of photons convert to an [Formula: see text] pair inside the inner detector. In this note, we quantify this discrimination power, and we study how the sensitivity of future searches differs for photon jets compared to isolated photons. We also investigate how our results depend on the lifetime of the particle(s) decaying to the photon jet. Finally, we discuss the extension to [Formula: see text], where there are no photons at all but the dark photon [Formula: see text] decays to [Formula: see text] pairs. Our results will be useful in future studies of the putative 750 GeV signal, but also more generally in any new physics search involving hard photons.

Electron microscopic and optical studies of prism faces of synthetic quartz

NASA Technical Reports Server (NTRS)

Buzek, B. C.; Vagh, A. S.

1977-01-01

Application of electron and optical microscopic techniques to the study of growth spirals on quartz crystal faces is described. Attention is centered on the centers of the spirals and on screw ledges; overhanging kinks are revealed on one side of the spiral centers. The possibility that these special features may have developed after growth of the crystals went to completion is explored. The conjecture is raised that such structures might result from adsorption of growth-inhibiting impurities at the center of the growth spiral on the quartz habit faces.

Proceedings of RIKEN BNL Research Center Workshop: Thermal Photons and Dileptons in Heavy-Ion Collisions. Volume 119

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, G.; Rapp, R.; Ruan, L.

The RIKEN BNL Research Center (RBRC) was established in April 1997 at Brookhaven National Laboratory. It is funded by the ''Rikagaku Kenkyusho'' (RIKEN, The Institute of Physical and Chemical Research) of Japan and the U. S. Department of Energy’s Office of Science. The RBRC is dedicated to the study of strong interactions, including spin physics, lattice QCD, and RHIC physics through the nurturing of a new generation of young physicists. The RBRC has theory, lattice gauge computing and experimental components. It is presently exploring the possibility of an astrophysics component being added to the program. The primary theme for thismore » workshop related to sharing the latest experimental and theoretical developments in area of low transverse momentum (p T) dielectron and photons. All the presentations given at the workshop are included in this proceedings, primarily as PowerPoint presentations.« less

Anharmonic phonon decay in cubic GaN

NASA Astrophysics Data System (ADS)

Cuscó, R.; Domènech-Amador, N.; Novikov, S.; Foxon, C. T.; Artús, L.

2015-08-01

We present a Raman-scattering study of optical phonons in zinc-blende (cubic) GaN for temperatures ranging from 80 to 750 K. The experiments were performed on high-quality, cubic GaN films grown by molecular-beam epitaxy on GaAs (001) substrates. The observed temperature dependence of the optical phonon frequencies and linewidths is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional-theory calculations. The longitudinal-optical (LO) mode relaxation is found to occur via asymmetric decay into acoustic phonons, with an appreciable contribution of higher-order processes. The transverse-optical mode linewidth shows a weak temperature dependence and its frequency downshift is primarily determined by the lattice thermal expansion. The LO phonon lifetime is derived from the observed Raman linewidth and an excellent agreement with previous theoretical predictions is found.

Self-Assembled Cubic Liquid Crystalline Nanoparticles for Transdermal Delivery of Paeonol

PubMed Central

Li, Jian-Chun; Zhu, Na; Zhu, Jin-Xiu; Zhang, Wen-Jing; Zhang, Hong-Min; Wang, Qing-Qing; Wu, Xiao-Xiang; Wang, Xiu; Zhang, Jin; Hao, Ji-Fu

2015-01-01

Background The aim of this study was to optimize the preparation method for self-assembled glyceryl monoolein-based cubosomes containing paeonol and to characterize the properties of this transdermal delivery system to improve the drug penetration ability in the skin. Material/Methods In this study, the cubic liquid crystalline nanoparticles loaded with paeonol were prepared by fragmentation of glyceryl monoolein (GMO)/poloxamer 407 bulk cubic gel by high-pressure homogenization. We evaluated the Zeta potential of these promising skin-targeting drug-delivery systems using the Malvern Zeta sizer examination, and various microscopies and differential scanning calorimetry were also used for property investigation. Stimulating studies were evaluated based on the skin irritation reaction score standard and the skin stimulus intensity evaluation standard for paeonol cubosomes when compared with commercial paeonol ointment. In vitro tests were performed on excised rat skins in an improved Franz diffusion apparatus. The amount of paeonol over time in the in vitro penetration and retention experiments both was determined quantitatively by HPLC. Results Stimulating studies were compared with the commercial ointment which indicated that the paeonol cubic liquid crystalline nanoparticles could reduce the irritation in the skin stimulating test. Thus, based on the attractive characteristics of the cubic crystal system of paeonol, we will further exploit the cosmetic features in the future studies. Conclusions The transdermal delivery system of paeonol with low-irritation based on the self-assembled cubic liquid crystalline nanoparticles prepared in this study might be a promising system of good tropical preparation for skin application. PMID:26517086

The time-dependence of the defective nature of ice Ic (cubic ice) and its implications for atmospheric science

NASA Astrophysics Data System (ADS)

Sippel, Christian; Koza, Michael M.; Hansen, Thomas C.; Kuhs, Werner F.

2010-05-01

flat low-indexed crystal faces. [1] T Kobayashi & T Kuroda (1987) Snow Crystals. In: Morphology of Crystals (ed. I Sunagawa), Terra Scientific Publishing, Tokyo, pp.649-743. [2] RS Gao & 19 other authors (2004) Evidence that nitric acid increases relative humidity in low-temperature cirrus clouds. Science 303, 516-520. [3] T Peter, C Marcolli, P Spichtinger, T Corti, MC Baker & T Koop (2006) When dry air is too humid. Science 314, 1399-1402. [4] JE Shilling, MA Tolbert, OB Toon, EJ Jensen, BJ Murray & AK Bertram (2006) Measurements of the vapor pressure of cubic ice and their implications for atmospheric ice clouds. Geophys.Res.Lett. 33, 026671. [5] TC Hansen, MM Koza & WF Kuhs (2008) Formation and annealing of cubic ice: I Modelling of stacking faults. J.Phys.Cond.Matt. 20, 285104. [6] TC Hansen, MM Koza, P Lindner & WF Kuhs (2008) Formation and annealing of cubic ice: II. Kinetic study. J.Phys.Cond.Matt. 20, 285105. [7] WF Kuhs, G Genov, DK Staykova & AN Salamatin, T Hansen (2004) Ice perfection and the onset of anomalous preservation of gas hydrates. Phys.Chem.Chem.Phys. 6, 4917-4920. [8] BJ Murray, DA Knopf & AK Bertram (2005) The formation of cubic ice under conditions relevant to Earth's atmosphere. Nature 434, 292-205.

Microwave Photonics: current challenges towards widespread application.

PubMed

Capmany, José; Li, Guifang; Lim, Christina; Yao, Jianping

2013-09-23

Microwave Photonics, a symbiotic field of research that brings together the worlds of optics and radio frequency is currently facing several challenges in its transition from a niche to a truly widespread technology essential to support the ever-increasing values for speed, bandwidth, processing capability and dynamic range that will be required in next generation hybrid access networks. We outline these challenges, which are the subject of the contributions to this focus issue.

Interaction of anions with lipid cubic phase membranes, an electrochemical impedance study.

PubMed

Meynaq, Mohammad Yaser Khani; Lindholm-Sethson, Britta; Tesfalidet, Solomon

2018-05-29

Electrochemical impedance spectroscopy is useful to monitor anionic interactions with a Lipid Cubic Phase, as previously demonstrated for cationic interaction (Khani Meynaq et al., 2016). It was expected that the smaller hydrophilic anions, acetate and chloride, would interact differently than the large tryptophan anion with its hydrophobic tail. The impedance measurements enabled estimation of resistances and capacitances of a freestanding lipid cubic phase membrane at exposure to 4 and 40 mM solutions of NaCl, NaOAc and NaTrp. Small-angle X-ray scattering was used for cubic phase identification and to track structural changes within the cubic phase when exposed to the different electrolytes. The membrane resistance increases at exposure to the electrolytes in the order Cl -  < OAc -  < Trp - . The membrane resistance decreases with time at exposure to the hydrophilic anions and increases with time at Trp - exposure. The membrane capacitances were lower for NaTrp compared to NaCl and NaOAc at the corresponding concentrations which is consistent with the results from SAXRD. It is concluded that Trp - ions do not enter the aqueous channels of the cubic phase but are strongly adsorbed to the membrane/electrolyte interface leading to large alteration of the lipid phase structure and a high membrane resistance. Copyright © 2018 Elsevier Inc. All rights reserved.

Effective optical path length for tandem diffuse cubic cavities as gas absorption cell

NASA Astrophysics Data System (ADS)

Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.

2014-12-01

Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap < 0.01, which coincided well with theoretical analysis. The simulating EOPL was smaller than experimental results at fap > 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.

Precise control of coupling strength in photonic molecules over a wide range using nanoelectromechanical systems

PubMed Central

Du, Han; Zhang, Xingwang; Chen, Guoqiang; Deng, Jie; Chau, Fook Siong; Zhou, Guangya

2016-01-01

Photonic molecules have a range of promising applications including quantum information processing, where precise control of coupling strength is critical. Here, by laterally shifting the center-to-center offset of coupled photonic crystal nanobeam cavities, we demonstrate a method to precisely and dynamically control the coupling strength of photonic molecules through integrated nanoelectromechanical systems with a precision of a few GHz over a range of several THz without modifying the nature of their constituent resonators. Furthermore, the coupling strength can be tuned continuously from negative (strong coupling regime) to zero (weak coupling regime) and further to positive (strong coupling regime) and vice versa. Our work opens a door to the optimization of the coupling strength of photonic molecules in situ for the study of cavity quantum electrodynamics and the development of efficient quantum information devices. PMID:27097883

Three-photon N00N states generated by photon subtraction from double photon pairs.

PubMed

Kim, Heonoh; Park, Hee Su; Choi, Sang-Kyung

2009-10-26

We describe an experimental demonstration of a novel three-photon N00N state generation scheme using a single source of photons based on spontaneous parametric down-conversion (SPDC). The three-photon entangled state is generated when a photon is subtracted from a double pair of photons and detected by a heralding counter. Interference fringes measured with an emulated three-photon detector reveal the three-photon de Broglie wavelength and exhibit visibility > 70% without background subtraction.

High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt

DOE PAGES

Ueland, B. G.; Saunders, S. M.; Bud'ko, S. L.; ...

2015-11-30

In this study, YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of T*=0.7K, fragile antiferromagnetic order below T N = 0.4K, a Kondo temperature of T K ≈ 1K, and crystalline-electric-field splitting on the order of E/k B = 1 – 10K. Whereas the compound has a face-centered-cubic lattice at ambient temperature, certain experimental data, particularly those from studies aimed at determining its crystalline-electric-field scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-resolution, high-energy x-ray diffraction experiments which show that, within our experimental resolution of ≈ 6 – 10more » × 10 –5 Å, no structural phase transition occurs between T = 1.5 and 50 K. In combination with results from dilatometry measurements, we further show that the compound's thermal expansion has a minimum at ≈ 18 K and a region of negative thermal expansion for 9 ≲ T ≲ 18 K. Despite diffraction patterns taken at 1.6 K which indicate that the lattice is face-centered cubic and that the Yb resides on a crystallographic site with cubic point symmetry, we demonstrate that the linear thermal expansion may be modeled using crystalline-electric-field level schemes appropriate for Yb 3+ residing on a site with either cubic or less than cubic point symmetry.« less

Photon structure studied at an electron ion collider

DOE PAGES

Chu, X.; Aschenauer, E. C.; Lee, J. H.; ...

2017-10-30

We report that a future electron ion collider (EIC) will be able to provide collisions of polarized electrons with protons and heavy ions over a wide range of center-of-mass energies (20 GeV to 140 GeV) at an instantaneous luminosity of 10 33 - 10 34cm -2s -1. One of its promising physics programs is the study of the partonic structure of quasireal photons. Measuring dijets in quasireal photoproduction events, one can effectively access the underlying parton dynamics of the photons. In this paper, we discuss the feasibility of tagging resolved photon processes and measuring the dijet cross section as a function of jet transverse momentum in the range of 0.01 < xmore » $$rec\\atop{γ}$$ < 1 at an EIC. Finally, it will be shown that both unpolarized and polarized parton distributions in the photon can be extracted, and that the flavor of the parton can be tagged at an EIC.« less

Photon correlation in single-photon frequency upconversion.

PubMed

Gu, Xiaorong; Huang, Kun; Pan, Haifeng; Wu, E; Zeng, Heping

2012-01-30

We experimentally investigated the intensity cross-correlation between the upconverted photons and the unconverted photons in the single-photon frequency upconversion process with multi-longitudinal mode pump and signal sources. In theoretical analysis, with this multi-longitudinal mode of both signal and pump sources system, the properties of the signal photons could also be maintained as in the single-mode frequency upconversion system. Experimentally, based on the conversion efficiency of 80.5%, the joint probability of simultaneously detecting at upconverted and unconverted photons showed an anti-correlation as a function of conversion efficiency which indicated the upconverted photons were one-to-one from the signal photons. While due to the coherent state of the signal photons, the intensity cross-correlation function g(2)(0) was shown to be equal to unity at any conversion efficiency, agreeing with the theoretical prediction. This study will benefit the high-speed wavelength-tunable quantum state translation or photonic quantum interface together with the mature frequency tuning or longitudinal mode selection techniques.

Deterministic photon-emitter coupling in chiral photonic circuits.

PubMed

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Deterministic photon-emitter coupling in chiral photonic circuits

NASA Astrophysics Data System (ADS)

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Remote online ergonomic assessment in the office environment as compared to face-to-face ergonomic assessment.

PubMed

Eyal, Levy; Ribak, Joseph; Badihi, Yehuda

2012-01-01

remote online ergonomic assessment in the office environment as compared to face-to-face ergonomic assessment and examination of the applicability of remote online ergonomic assessment to office workers. 40 employees from a large Israeli hi-tech company were ergonomically assessed per the University of California computer usage checklist, according to the two assessment types (face-to-face and remote). An additional Ergonomist "assessor 2" examined the credibility of the process. Research hypothesis 1 was verified: 21 out of 22 questions (95.45%) from the checklist indicated compatibility between "assessor 1" to the "Gold Standard" at an 80% level. Research hypothesis 2: examining the credibility between the assessors with regard to remote assessment. This hypothesis was partially verified, the correlation between the assessors was measured at 0.54. Research hypothesis 3: examining the extent of deviation of natural posture between distal body parts assessment (distant from the center of the body) and proximal body parts (close to the center of the body). This hypothesis was clearly verified. It has been proven that there is statistical significance between the results. The current research has proved that there is an additional method to assess musculoskeletal disorders risk factors remotely online at office environment.

Single photon source with individualized single photon certifications

NASA Astrophysics Data System (ADS)

Migdall, Alan L.; Branning, David A.; Castelletto, Stefania; Ware, M.

2002-12-01

As currently implemented, single-photon sources cannot be made to produce single photons with high probability, while simultaneously suppressing the probability of yielding two or more photons. Because of this, single photon sources cannot really produce single photons on demand. We describe a multiplexed system that allows the probabilities of producing one and more photons to be adjusted independently, enabling a much better approximation of a source of single photons on demand. The scheme uses a heralded photon source based on parametric downconversion, but by effectively breaking the trigger detector area into multiple regions, we are able to extract more information about a heralded photon than is possible with a conventional arrangement. This scheme allows photons to be produced along with a quantitative 'certification' that they are single photons. Some of the single-photon certifications can be significantly better than what is possible with conventional downconversion sources, as well as being better than faint laser sources. With such a source of more tightly certified single photons, it should be possible to improve the maximum secure bit rate possible over a quantum cryptographic link. We present an analysis of the relative merits of this method over the conventional arrangement.

Ethical Issues in Pediatric Face Transplantation: Should We Perform Face Transplantation in Children?

PubMed

Marchac, Alexandre; Kuschner, Tomasine; Paris, John; Picard, Arnaud; Vazquez, Marie Paule; Lantieri, Laurent

2016-08-01

In 2005, face transplantation ceased to be fiction and became a scientific reality. Today, 10 teams from six different countries have performed 32 face transplantations. Immunosuppressive treatments are similar to other solid organ transplants, and patients have experienced a significant functional improvement. The authors are logically considering expanding face transplantation to children; however, children are not simply small adults. The authors searched for pediatric patients in need of restoration of fundamental functions of the face, such as orbicularis oris or oculi muscle closure by, first, selecting cases from a pediatric plastic surgery reference center and, second, analyzing the feasibility of face transplantation in those patients. The authors then identified the specific problems that they would encounter during a pediatric face transplant. The authors identified three potential candidates for pediatric face transplantation. Children's youth imposes additional ethical and psychological considerations, such as the balance of risk to benefit when it is quality of life, not life itself, that is at stake; the process of informed consent; the selection process; and the protection of privacy against media exposure. The question becomes not whether children should be included as candidates for face transplantation but whether any ethical barriers should preclude children as candidates for a full face transplant. After careful consideration of the physical, psychological, and ethical aspects of such a procedure, the authors found no such barrier that would either disqualify such vulnerable subjects as profoundly disfigured children or conflict with their best interests.

Broadband photon-photon interactions mediated by cold atoms in a photonic crystal fiber

PubMed Central

Litinskaya, Marina; Tignone, Edoardo; Pupillo, Guido

2016-01-01

We demonstrate theoretically that photon-photon attraction can be engineered in the continuum of scattering states for pairs of photons propagating in a hollow-core photonic crystal fiber filled with cold atoms. The atoms are regularly spaced in an optical lattice configuration and the photons are resonantly tuned to an internal atomic transition. We show that the hard-core repulsion resulting from saturation of the atomic transitions induces bunching in the photonic component of the collective atom-photon modes (polaritons). Bunching is obtained in a frequency range as large as tens of GHz, and can be controlled by the inter-atomic separation. We provide a fully analytical explanation for this phenomenon by proving that correlations result from a mismatch of the quantization volumes for atomic excitations and photons in the continuum. Even stronger correlations can be observed for in-gap two-polariton bound states. Our theoretical results use parameters relevant for current experiments and suggest a simple and feasible way to induce interactions between photons. PMID:27170160

Overview of surface-water resources at the U.S. Coast Guard Support Center Kodiak, Alaska, 1987-89

USGS Publications Warehouse

Solin, G.L.

1996-01-01

Hydrologic data at a U.S. Coast Guard Support Center on Kodiak Island, Alaska, were collected from 1987 though 1989 to determine hydrologic conditions and if contamination of soils, ground water, or surface water has occurred. This report summarizes the surface-water-discharge data collected during the study and estimates peak, average, and low-flow values for Buskin River near its mouth. Water-discharge measurements were made at least once at 48 sites on streams in or near the Center. Discharges were measured in the Buskin River near its mouth five times during 1987-89 and ranged from 27 to 367 cubic feet per second. Tributaries of Buskin River below Buskin Lake that had discharges greater than 1 cubic foot per second include Bear Creek, Alder Creek, Magazine Creek, Devils Creek and an outlet from Lake Louise. Streams having flows generally greater than 0.1 cubic foot per second but less than 1 cubic foot per second include an unnamed tributary to Buskin River, an unnamed tributary to Lake Catherine and a drainage channel at Kodiak airport. Most other streams flowing into Buskin River, and all streams on Nyman Peninsula, usually had little or no flow except during periods of rainfall or snowmelt. During a low-flow period in February 1989, discharge measurements in Buskin River and its tributaries indicate that three reaches of Buskin River below Buskin Lake lost water to the ground-water system, whereas two reaches gained water; the net gain in streamflow attributed to ground-water inflow at a location near the mouth was estimated to be 2.2 cubic feet per second. The 100-year peak flow for Buskin River near its mouth was estimated to be 4,460 cubic feet per second. Average discharge was estimated to be 125 cubic feet per second and the 7-day 10-year low flow was estimated to be 5.8 cubic feet per second.

Coupled multi-group neutron photon transport for the simulation of high-resolution gamma-ray spectroscopy applications

NASA Astrophysics Data System (ADS)

Burns, Kimberly Ann

cross-section libraries and the methods used to produce neutron-induced photons were unsuitable for high-resolution gamma-ray spectroscopy applications. Central to this work was the development of a method for generating multigroup neutron-photon cross-sections in a way that separates the discrete and continuum photon emissions so the neutron-induced photon signatures were preserved. The RADSAT-NG cross-section library was developed as a specialized multigroup neutron-photon cross-section set for the simulation of high-resolution gamma-ray spectroscopy applications. The methodology and cross sections were tested using code-to-code comparison with MCNP5 [2] and NJOY [3]. A simple benchmark geometry was used for all cases compared with MCNP. The geometry consists of a cubical sample with a 252Cf neutron source on one side and a HPGe gamma-ray spectrometer on the opposing side. Different materials were examined in the cubical sample: polyethylene (C2H4), P, N, O, and Fe. The cross sections for each of the materials were compared to cross sections collapsed using NJOY. Comparisons of the volume-averaged neutron flux within the sample, volume-averaged photon flux within the detector, and high-purity gamma-ray spectrometer response (only for polyethylene) were completed using RADSAT and MCNP. The code-to-code comparisons show promising results for the coupled Monte Carlo-deterministic method. The RADSAT-NG cross-section production method showed good agreement with NJOY for all materials considered although some additional work is needed in the resonance region and in the first and last energy bin. Some cross section discrepancies existed in the lowest and highest energy bin, but the overall shape and magnitude of the two methods agreed. For the volume-averaged photon flux within the detector, typically the five most intense lines agree to within approximately 5% of the MCNP calculated flux for all of materials considered. The agreement in the code-to-code comparisons cases

Quantum Computation Based on Photons with Three Degrees of Freedom

PubMed Central

Luo, Ming-Xing; Li, Hui-Ran; Lai, Hong; Wang, Xiaojun

2016-01-01

Quantum systems are important resources for quantum computer. Different from previous encoding forms using quantum systems with one degree of freedom (DoF) or two DoFs, we investigate the possibility of photon systems encoding with three DoFs consisting of the polarization DoF and two spatial DoFs. By exploring the optical circular birefringence induced by an NV center in a diamond embedded in the photonic crystal cavity, we propose several hybrid controlled-NOT (hybrid CNOT) gates operating on the two-photon or one-photon system. These hybrid CNOT gates show that three DoFs may be encoded as independent qubits without auxiliary DoFs. Our result provides a useful way to reduce quantum simulation resources by exploring complex quantum systems for quantum applications requiring large qubit systems. PMID:27174302

Quantum Computation Based on Photons with Three Degrees of Freedom.

PubMed

Luo, Ming-Xing; Li, Hui-Ran; Lai, Hong; Wang, Xiaojun

2016-05-13

Quantum systems are important resources for quantum computer. Different from previous encoding forms using quantum systems with one degree of freedom (DoF) or two DoFs, we investigate the possibility of photon systems encoding with three DoFs consisting of the polarization DoF and two spatial DoFs. By exploring the optical circular birefringence induced by an NV center in a diamond embedded in the photonic crystal cavity, we propose several hybrid controlled-NOT (hybrid CNOT) gates operating on the two-photon or one-photon system. These hybrid CNOT gates show that three DoFs may be encoded as independent qubits without auxiliary DoFs. Our result provides a useful way to reduce quantum simulation resources by exploring complex quantum systems for quantum applications requiring large qubit systems.

Airborne UV photon-counting radiometer

NASA Astrophysics Data System (ADS)

Bauer, Marc C.; Wilcher, George; Banks, Calvin R.; Wood, Ronald L.

2000-11-01

The radiometric measurements group at the Arnold Engineering Development Center (AEDC) has developed new solar-blind radiometers for the SENSOR TALON flight test. These radiometers will be flown in an instrument pod by the 46th Test Wing at Eglin AFB. The radiometers are required to fit into a single quadrant of a 22-in.-diam sphere turret of the instrument pod. Because of minimal space requirements and photon-counting sensitivity needs, the radiometric measurements group used image intensifiers instead of the standard photomultiplier tubes (PMTs). The new design concept improved the photon-counting sensitivity, dynamic range, and uniformity of the field of view as compared to standard PMTs. A custom data acquisition system was required to miniaturize the electronics and generate a pulse code-modulated (PCM) data stream to the standard tape recording system.

Load Deflection of Dow Corning SE 1700 Face Centered Tetragonal Direct Ink Write Materials: Effect of Thickness and Filament Spacing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Small, Ward; Pearson, Mark A.; Metz, Tom R.

Dow Corning SE 1700 (reinforced polydimethylsiloxane) porous structures were made by direct ink writing (DIW) in a face centered tetragonal (FCT) configuration. The filament diameter was 250 μm. Structures consisting of 4, 8, or 12 layers were fabricated with center-to-center filament spacing (“road width” (RW)) of 475, 500, 525, 550, or 575 μm. Three compressive load-unload cycles to 2000 kPa were performed on four separate areas of each sample; three samples of each thickness and filament spacing were tested. At a given strain during the third loading phase, stress varied inversely with porosity. At 10% strain, the stress was nearlymore » independent of the number of layers (i.e., thickness). At higher strains (20- 40%), the stress was highest for the 4-layer structure; the 8- and 12-layer structures were nearly equivalent suggesting that the load deflection is independent of number of layers above 8 layers. Intra-and inter-sample variability of the load deflection response was higher for thinner and less porous structures.« less

Enhanced-locality fiber-optic two-photon-fluorescence live-brain interrogation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fedotov, I. V.; Doronina-Amitonova, L. V.; Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125

2014-02-24

Two-photon excitation is shown to substantially enhance the locality of fiber-based optical interrogation of strongly scattering biotissues. In our experiments, a high-numerical-aperture, large-core-are fiber probe is used to deliver the 200-fs output of a 100-MHz mode-locked ytterbium fiber laser to samples of live mouse brain, induce two-photon fluorescence of nitrogen–vacancy centers in diamond markers in brain sample. Fiber probes with a high numerical aperture and a large core area are shown to enable locality enhancement in fiber-laser–fiber-probe two-photon brain excitation and interrogation without sacrificing the efficiency of fluorescence response collection.

Some Curious Properties and Loci Problems Associated with Cubics and Other Polynomials

ERIC Educational Resources Information Center

de Alwis, Amal

2012-01-01

The article begins with a well-known property regarding tangent lines to a cubic polynomial that has distinct, real zeros. We were then able to generalize this property to any polynomial with distinct, real zeros. We also considered a certain family of cubics with two fixed zeros and one variable zero, and explored the loci of centroids of…

Photonics industry in China: from current status and trends to the importance of innovation

NASA Astrophysics Data System (ADS)

Fan, Chongcheng

2011-12-01

Current status and trends in various sectors of photonics industry in Mainland China are reviewed, which includes optical fiber communication, optical preform, fiber and cable, photonic devices and chips, LED illumination and display, and photovoltaics. Then, from the challenges and risks they are facing, critical importance of innovation is discussed. In the evolving Innovation Economy, the core competence of a company, an industry or a country is its innovation power and the capability to grab (and manage) talented people.

Study on sensing property of one-dimensional ring mirror-defect photonic crystal

NASA Astrophysics Data System (ADS)

Chen, Ying; Luo, Pei; Cao, Huiying; Zhao, Zhiyong; Zhu, Qiguang

2018-02-01

Based on the photon localization and the photonic bandgap characteristics of photonic crystals (PCs), one-dimensional (1D) ring mirror-defect photonic crystal structure is proposed. Due to the introduction of mirror structure, a defect cavity is formed in the center of the photonic crystal, and then the resonant transmission peak can be obtained in the bandgap of transmission spectrum. The transfer matrix method is used to establish the relationship model between the resonant transmission peak and the structure parameters of the photonic crystals. Using the rectangular air gate photonic crystal structure, the dynamic monitoring of the detected gas sample parameters can be achieved from the shift of the resonant transmission peak. The simulation results show that the Q-value can attain to 1739.48 and the sensitivity can attain to 1642 nm ṡ RIU-1, which demonstrates the effectiveness of the sensing structure. The structure can provide certain theoretical reference for air pollution monitoring and gas component analysis.

Low-power chip-level optical interconnects based on bulk-silicon single-chip photonic transceivers

NASA Astrophysics Data System (ADS)

Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Kim, In Gyoo; Kim, Sun Ae; Oh, Jin Hyuk; Park, Jaegyu; Kim, Sanggi

2016-03-01

We present new scheme for chip-level photonic I/Os, based on monolithically integrated vertical photonic devices on bulk silicon, which increases the integration level of PICs to a complete photonic transceiver (TRx) including chip-level light source. A prototype of the single-chip photonic TRx based on a bulk silicon substrate demonstrated 20 Gb/s low power chip-level optical interconnects between fabricated chips, proving that this scheme can offer compact low-cost chip-level I/O solutions and have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, 3D-IC, and LAN/SAN/data-center and network applications.

Room temperature single photon source using fiber-integrated hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Vogl, Tobias; Lu, Yuerui; Lam, Ping Koy

2017-07-01

Single photons are a key resource for quantum optics and optical quantum information processing. The integration of scalable room temperature quantum emitters into photonic circuits remains to be a technical challenge. Here we utilize a defect center in hexagonal boron nitride (hBN) attached by Van der Waals force onto a multimode fiber as a single photon source. We perform an optical characterization of the source in terms of spectrum, state lifetime, power saturation and photostability. A special feature of our source is that it allows for easy switching between fiber-coupled and free space single photon generation modes. In order to prove the quantum nature of the emission we measure the second-order correlation function {{g}(2)}≤ft(τ \\right) . For both fiber-coupled and free space emission, the {{g}(2)}≤ft(τ \\right) dips below 0.5 indicating operation in the single photon regime. The results so far demonstrate the feasibility of 2D material single photon sources for scalable photonic quantum information processing.

Enhancing the microwave absorption properties of amorphous CoO nanosheet-coated Co (hexagonal and cubic phases) through interfacial polarizations.

PubMed

Deng, Jiushuai; Li, Shimei; Zhou, Yuanyuan; Liang, Luyang; Zhao, Biao; Zhang, Xi; Zhang, Rui

2018-01-01

Core-shell flower-like composites were successfully prepared by a simple polyol method. These composites were formed by coating dual-phased (face-centered cubic [fcc] and hexagonal close-packed [hcp]) Co with amorphous CoO nanosheets. The microwave absorption properties of the flower-like Co@CoO paraffin composites with various Co@CoO amounts were then investigated. Results showed that the paraffin-based composite containing 70wt% flower-like Co@CoO displayed excellent microwave absorption properties (R E =24.74dB·GHz/mm). The minimum reflection loss of -30.4dB was obtained at 16.1GHz with a small thickness of 1.5mm, and 1.5mm bandwidth reached 4.6GHz (13.4-18GHz) below -10dB (90% microwave absorption). The excellent microwave absorption properties of flower-like Co@CoO are attributed to the synergetic effect between magnetic loss and dielectric loss, and the magnetic loss makes a main contribution to absorption. The core-shell flower-like structures with dual Co phases also contributed to microwave absorption. The amorphous CoO nanosheets were able to generate multiple reflections and exhibit scattering. In addition, the novel absorption mechanism that enhanced interfacial polarization was proposed. This enhancement resulted from the presence of interfaces between the hcp and fcc phases and between the core-shell Co@CoO composites. Copyright © 2017 Elsevier Inc. All rights reserved.

Impact of medium-range order on the glass transition in liquid Ni-Si alloys

NASA Astrophysics Data System (ADS)

Lü, Y. J.; Entel, P.

2011-09-01

We study the thermophysical properties and structure of liquid Ni-Si alloys using molecular dynamics simulations. The liquid Ni-5% and 10%Si alloys crystallize to form the face-centered cubic (Ni) at 900 and 850 K, respectively, and the glass transitions take place in Ni-20% and 25%Si alloys at about 700 K. The temperature-dependent self-diffusion coefficients and viscosities exhibit more pronounced non-Arrhenius behavior with the increase of Si content before phase transitions, indicating the enhanced glass-forming ability. These appearances of thermodynamic properties and phase transitions are found to closely relate to the medium-range order clusters with the defective face-centered cubic structure characterized by both local translational and orientational order. This locally ordered structure tends to be destroyed by the addition of more Si atoms, resulting in a delay of nucleation and even glass transition instead.

X-Ray Diffraction (XRD) Characterization Methods for Sigma=3 Twin Defects in Cubic Semiconductor (100) Wafers

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Kim, Hyun Jung (Inventor); Skuza, Jonathan R. (Inventor); Lee, Kunik (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor)

2017-01-01

An X-ray defraction (XRD) characterization method for sigma=3 twin defects in cubic semiconductor (100) wafers includes a concentration measurement method and a wafer mapping method for any cubic tetrahedral semiconductor wafers including GaAs (100) wafers and Si (100) wafers. The methods use the cubic semiconductor's (004) pole figure in order to detect sigma=3/{111} twin defects. The XRD methods are applicable to any (100) wafers of tetrahedral cubic semiconductors in the diamond structure (Si, Ge, C) and cubic zinc-blend structure (InP, InGaAs, CdTe, ZnSe, and so on) with various growth methods such as Liquid Encapsulated Czochralski (LEC) growth, Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), Czochralski growth and Metal Organic Chemical Vapor Deposition (MOCVD) growth.

Does the Computer Make a Difference? Computerized versus Face-to-Face versus Self-Report Assessment of Alcohol, Drug and Tobacco Use.

ERIC Educational Resources Information Center

Skinner, Harvey A.; Allen, Barbara A.

1983-01-01

Compared histories of alcohol, drug, and tobacco use obtained by computerized interview, face-to-face interview, and self-report in clients (N=150) from an addiction treatment center. Multivariate analyses revealed no important differences. The computerized interview was rated less friendly but faster and more interesting. (Author/JAC)

Cubic ice and large humidity with respect to ice in cold cirrus clouds

NASA Astrophysics Data System (ADS)

Bogdan, A.; Loerting, T.

2009-04-01

Recently several studies have reported about the possible formation of cubic ice in upper-tropospheric cirrus ice clouds and its role in the observed elevated relative humidity with respect to hexagonal ice, RHi, within the clouds. Since cubic ice is metastable with respect to stable hexagonal ice, its vapour pressure is higher. A key issue in determining the ratio of vapour pressures of cubic ice Pc and hexagonal ice Ph is the enthalpy of transformation from cubic to hexagonal ice Hc→h. By dividing the two integrated forms of the Clausius-Clapeyron equation for cubic ice and hexagonal ice, one obtains the relationship (1): ln Pc-- ln P*c-=--(Hc→h--) Ph P*h R 1T-- 1T* (1) from which the importance of Hc→h is evident. In many literature studies the approximation (2) is used: ln Pc-= Hc-→h. Ph RT (2) Using this approximated form one can predict the ratio of vapour pressures by measuring Hc→h. Unfortunately, the measurement of Hc→h is difficult. First, the enthalpy difference is very small, and the transition takes place over a broad temperature range, e.g., between 230 K and 260 K in some of our calorimetry experiments. Second, cubic ice (by contrast to hexagonal ice) can not be produced as a pure crystal. It always contains hexagonal stacking faults, which are evidenced by the (111)-hexagonal Bragg peak in the powder diffractogram. If the number of hexagonal stacking faults in cubic ice is high, then one could even consider this material as hexagonal ice with cubic stacking faults. Using the largest literature value of the change of enthalpy of transformation from cubic to hexagonal ice, Hc→h ? 160 J/mol, Murphy and Koop (2005) calculated that Pc would be ~10% higher than that of hexagonal ice Phat 180 K - 190 K, which agrees with the measurements obtained later by Shilling et al. (2006). Based on this result Shilling et al. concluded that "the formation of cubic ice at T < 202 K may significantly contribute to the persistent in

Breakup of Kol'mogorov-Arnol'd-Moser tori of cubic irrational winding number

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, J.; Helleman, R.H.G.

1989-01-01

For the special case in which the irrational winding number is the root of a cubic equation, we present numerical evidence for the validity of some form of residue criterion (Greene, J. Math. Phys. 20, 1182 (1979)). This is a criterion for the breakup of Kol'mogorov-Arnol'd-Moser tori in two degrees of freedom. The cubic case is essential for future work on four-dimensional maps. While the residues do approach infinity (respectively, 0) after (respectively, before) the breaking point, it is numerically very difficult to estimate a critical residue value R/sub cr/ for this cubic case (0.15approx. ..infinity, with a ''new'' scalingmore » constant xiapprox. =0.72, where p/sub n//q/sub n/ is the nth rational approximant in the continued-fraction expansion of the cubic irrational. For a quadratic irrational this scaling reduces to the usual power-law scaling approx.delta/sup -//sup n/.« less

The Normals to a Parabola and the Real Roots of a Cubic

ERIC Educational Resources Information Center

Bains, Majinder S.; Thoo, J. B.

2007-01-01

The geometric problem of finding the number of normals to the parabola y = x[squared] through a given point is equivalent to the algebraic problem of finding the number of distinct real roots of a cubic equation. Apollonius solved the former problem, and Cardano gave a solution to the latter. The two problems are bridged by Neil's (semi-cubical)…

CubiCal - Fast radio interferometric calibration suite exploiting complex optimisation

NASA Astrophysics Data System (ADS)

Kenyon, J. S.; Smirnov, O. M.; Grobler, T. L.; Perkins, S. J.

2018-05-01

It has recently been shown that radio interferometric gain calibration can be expressed succinctly in the language of complex optimisation. In addition to providing an elegant framework for further development, it exposes properties of the calibration problem which can be exploited to accelerate traditional non-linear least squares solvers such as Gauss-Newton and Levenberg-Marquardt. We extend existing derivations to chains of Jones terms: products of several gains which model different aberrant effects. In doing so, we find that the useful properties found in the single term case still hold. We also develop several specialised solvers which deal with complex gains parameterised by real values. The newly developed solvers have been implemented in a Python package called CubiCal, which uses a combination of Cython, multiprocessing and shared memory to leverage the power of modern hardware. We apply CubiCal to both simulated and real data, and perform both direction-independent and direction-dependent self-calibration. Finally, we present the results of some rudimentary profiling to show that CubiCal is competitive with respect to existing calibration tools such as MeqTrees.

Inclusive photon production at forward rapidities in proton–proton collisions at $$\\mathbf {\\sqrt{s}}$$ = 0.9, 2.76 and 7 TeV

DOE PAGES

Abelev, B.; Adam, J.; Adamová, D.; ...

2015-04-09

The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities (2.3 < η < 3.9) in proton–proton collisions at three center-of-mass energies, √s = 0.9, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2 ± 0.3 % (stat) ± 8.8 % (sys) and 61.2more » ± 0.3 % (stat) ± 7.6 % (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. As a result, limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range.« less

Lattice Rotation Patterns and Strain Gradient Effects in Face-Centered-Cubic Single Crystals Under Spherical Indentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Y. F.; Larson, B. C.; Lee, J. H.

Strain gradient effects are commonly modeled as the origin of the size dependence of material strength, such as the dependence of indentation hardness on contact depth and spherical indenter radius. However, studies on the microstructural comparisons of experiments and theories are limited. First, we have extended a strain gradient Mises-plasticity model to its crystal plasticity version and implemented a finite element method to simulate the load-displacement response and the lattice rotation field of Cu single crystals under spherical indentation. The strain gradient simulations demonstrate that the forming of distinct sectors of positive and negative angles in the lattice rotation fieldmore » is governed primarily by the slip geometry and crystallographic orientations, depending only weakly on strain gradient effects, although hardness depends strongly on strain gradients. Second, the lattice rotation simulations are compared quantitatively with micron resolution, three-dimensional X-ray microscopy (3DXM) measurements of the lattice rotation fields under 100mN force, 100 mu m radius spherical indentations in < 111 >, < 110 >, and < 001 > oriented Cu single crystals. Third, noting the limitation of continuum strain gradient crystal plasticity models, two-dimensional discrete dislocation simulation results suggest that the hardness in the nanocontact regime is governed synergistically by a combination of strain gradients and source-limited plasticity. However, the lattice rotation field in the discrete dislocation simulations is found to be insensitive to these two factors but to depend critically on dislocation obstacle densities and strengths.« less

Vacancy-impurity centers in diamond: prospects for synthesis and applications

NASA Astrophysics Data System (ADS)

Ekimov, E. A.; Kondrin, M. V.

2017-06-01

The bright luminescence of impurity-vacancy complexes, combined with high chemical and radiation resistance, makes diamond an attractive platform for the production of single-photon emitters and luminescent biomarkers for applications in nanoelectronics and medicine. Two representatives of this kind of defects in diamond, silicon-vacancy (SiV) and germanium-vacancy (GeV) centers, are discussed in this review; their similarities and differences are demonstrated in terms of the more thoroughly studied nitrogen-vacancy (NV) complexes. The recent discovery of GeV luminescent centers opens a unique opportunity for the controlled synthesis of single-photon emitters in nanodiamonds. We demonstrate prospects for the high-pressure high-temperature (HPHT) technique to create single-photon emitters, not only as an auxiliary to chemical vapor deposition (CVD) and ion-implantation methods but also as a primary synthesis tool for producing color centers in nanodiamonds. Besides practical applications, comparative studies of these two complexes, which belong to the same structural class of defects, have a fundamental importance for deeper understanding of shelving levels, the electronic structure, and optical properties of these centers. In conclusion, we discuss several open problems regarding the structure, charge state, and practical application of these centers, which still require a solution.

Deterministic Generation of All-Photonic Quantum Repeaters from Solid-State Emitters

NASA Astrophysics Data System (ADS)

Buterakos, Donovan; Barnes, Edwin; Economou, Sophia E.

2017-10-01

Quantum repeaters are nodes in a quantum communication network that allow reliable transmission of entanglement over large distances. It was recently shown that highly entangled photons in so-called graph states can be used for all-photonic quantum repeaters, which require substantially fewer resources compared to atomic-memory-based repeaters. However, standard approaches to building multiphoton entangled states through pairwise probabilistic entanglement generation severely limit the size of the state that can be created. Here, we present a protocol for the deterministic generation of large photonic repeater states using quantum emitters such as semiconductor quantum dots and defect centers in solids. We show that arbitrarily large repeater states can be generated using only one emitter coupled to a single qubit, potentially reducing the necessary number of photon sources by many orders of magnitude. Our protocol includes a built-in redundancy, which makes it resilient to photon loss.

Numerical simulation of a shear-thinning fluid through packed spheres

NASA Astrophysics Data System (ADS)

Liu, Hai Long; Moon, Jong Sin; Hwang, Wook Ryol

2012-12-01

Flow behaviors of a non-Newtonian fluid in spherical microstructures have been studied by a direct numerical simulation. A shear-thinning (power-law) fluid through both regular and randomly packed spheres has been numerically investigated in a representative unit cell with the tri-periodic boundary condition, employing a rigorous three-dimensional finite-element scheme combined with fictitious-domain mortar-element methods. The present scheme has been validated for the classical spherical packing problems with literatures. The flow mobility of regular packing structures, including simple cubic (SC), body-centered cubic (BCC), face-centered cubic (FCC), as well as randomly packed spheres, has been investigated quantitatively by considering the amount of shear-thinning, the pressure gradient and the porosity as parameters. Furthermore, the mechanism leading to the main flow path in a highly shear-thinning fluid through randomly packed spheres has been discussed.

Linear complexions: Confined chemical and structural states at dislocations.

PubMed

Kuzmina, M; Herbig, M; Ponge, D; Sandlöbes, S; Raabe, D

2015-09-04

For 5000 years, metals have been mankind's most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe-9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states. Copyright © 2015, American Association for the Advancement of Science.

Diamond-based single-photon emitters

NASA Astrophysics Data System (ADS)

Aharonovich, I.; Castelletto, S.; Simpson, D. A.; Su, C.-H.; Greentree, A. D.; Prawer, S.

2011-07-01

The exploitation of emerging quantum technologies requires efficient fabrication of key building blocks. Sources of single photons are extremely important across many applications as they can serve as vectors for quantum information—thereby allowing long-range (perhaps even global-scale) quantum states to be made and manipulated for tasks such as quantum communication or distributed quantum computation. At the single-emitter level, quantum sources also afford new possibilities in terms of nanoscopy and bio-marking. Color centers in diamond are prominent candidates to generate and manipulate quantum states of light, as they are a photostable solid-state source of single photons at room temperature. In this review, we discuss the state of the art of diamond-based single-photon emitters and highlight their fabrication methodologies. We present the experimental techniques used to characterize the quantum emitters and discuss their photophysical properties. We outline a number of applications including quantum key distribution, bio-marking and sub-diffraction imaging, where diamond-based single emitters are playing a crucial role. We conclude with a discussion of the main challenges and perspectives for employing diamond emitters in quantum information processing.

Design and performance of tapered cubic anvil used for achieving higher pressure and larger sample cell

NASA Astrophysics Data System (ADS)

Han, Qi-Gang; Yang, Wen-Ke; Zhu, Pin-Wen; Ban, Qing-Chu; Yan, Ni; Zhang, Qiang

2013-07-01

In order to increase the maximum cell pressure of the cubic high pressure apparatus, we have developed a new structure of tungsten carbide cubic anvil (tapered cubic anvil), based on the principle of massive support and lateral support. Our results indicated that the tapered cubic anvil has some advantages. First, tapered cubic anvil can push the transfer rate of pressure well into the range above 36.37% compare to the conventional anvil. Second, the rate of failure crack decreases about 11.20% after the modification of the conventional anvil. Third, the limit of static high-pressure in the sample cell can be extended to 13 GPa, which can increase the maximum cell pressure about 73.3% than that of the conventional anvil. Fourth, the volume of sample cell compressed by tapered cubic anvils can be achieved to 14.13 mm3 (3 mm diameter × 2 mm long), which is three and six orders of magnitude larger than that of double-stage apparatus and diamond anvil cell, respectively. This work represents a relatively simple method for achieving higher pressures and larger sample cell.

Collapse of ultrashort spatiotemporal pulses described by the cubic generalized Kadomtsev-Petviashvili equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leblond, Herve; Kremer, David; Mihalache, Dumitru

2010-03-15

By using a reductive perturbation method, we derive from Maxwell-Bloch equations a cubic generalized Kadomtsev-Petviashvili equation for ultrashort spatiotemporal optical pulse propagation in cubic (Kerr-like) media without the use of the slowly varying envelope approximation. We calculate the collapse threshold for the propagation of few-cycle spatiotemporal pulses described by the generic cubic generalized Kadomtsev-Petviashvili equation by a direct numerical method and compare it to analytic results based on a rigorous virial theorem. Besides, typical evolution of the spectrum (integrated over the transverse spatial coordinate) is given and a strongly asymmetric spectral broadening of ultrashort spatiotemporal pulses during collapse is evidenced.

Mass-induced instability of SAdS black hole in Einstein-Ricci cubic gravity

NASA Astrophysics Data System (ADS)

Myung, Yun Soo

2018-05-01

We perform the stability analysis of Schwarzschild-AdS (SAdS) black hole in the Einstein-Ricci cubic gravity. It shows that the Ricci tensor perturbations exhibit unstable modes for small black holes. We call this the mass-induced instability of SAdS black hole because the instability of small black holes arises from the massiveness in the linearized Einstein-Ricci cubic gravity, but not a feature of higher-order derivative theory giving ghost states. Also, we point out that the correlated stability conjecture holds for the SAdS black hole by computing the Wald entropy of SAdS black hole in Einstein-Ricci cubic gravity.

Spiraling elliptic Laguerre-Gaussian soliton in isotropic nonlocal competing cubic-quintic nonlinear media

NASA Astrophysics Data System (ADS)

Wang, Qing; Li, JingZhen; Xie, WeiXin

2018-06-01

This paper introduce a kind of spiraling elliptic Laguerre-Gaussian (SELG) soliton which has complicated structures in its profile and phase, and find that it can be formed in nonlocal cubic, quantic and competing cubic-quintic nonlinear media, respectively. The different-order SELG solitons with the same ellipticity have the same rotation period, cross-term phase coefficient, critical power and different critical orbital angular momentums (OAM). However, with the increase of ellipticity, the rotation period, cross-term phase coefficient, critical power and OAM are all increased. In particular, there are bistable SELG solitons stemmed by the competing effect between self-focusing cubic and self-defocusing quintic nonlinearities.

Two-photon absorption by spectrally shaped entangled photons

NASA Astrophysics Data System (ADS)

Oka, Hisaki

2018-03-01

We theoretically investigate two-photon excitation by spectrally shaped entangled photons with energy anticorrelation in terms of how the real excitation of an intermediate state affects two-photon absorption by entangled photons. Spectral holes are introduced in the entangled photons around the energy levels of an intermediate state so that two-step excitation via the real excitation of the intermediated state can be suppressed. Using a three-level atomic system as an example, we show that the spectral holes well suppress the real excitation of the intermediate state and recover two-photon absorption via a virtual state. Furthermore, for a short pulse close to a monocycle, we show that the excitation efficiency by the spectrally shaped entangled photons can be enhanced a thousand times as large as that by uncorrelated photons.

An analytical method for computing voxel S values for electrons and photons.

PubMed

Amato, Ernesto; Minutoli, Fabio; Pacilio, Massimiliano; Campenni, Alfredo; Baldari, Sergio

2012-11-01

The use of voxel S values (VSVs) is perhaps the most common approach to radiation dosimetry for nonuniform distributions of activity within organs or tumors. However, VSVs are currently available only for a limited number of voxel sizes and radionuclides. The objective of this study was to develop a general method to evaluate them for any spectrum of electrons and photons in any cubic voxel dimension of practical interest for clinical dosimetry in targeted radionuclide therapy. The authors developed a Monte Carlo simulation in Geant4 in order to evaluate the energy deposited per disintegration (E(dep)) in a voxelized region of soft tissue from monoenergetic electrons (10-2000 keV) or photons (10-1000 keV) homogeneously distributed in the central voxel, considering voxel dimensions ranging from 3 mm to 10 mm. E(dep) was represented as a function of a dimensionless quantity termed the "normalized radius," R(n) = R∕l, where l is the voxel size and R is the distance from the origin. The authors introduced two parametric functions in order to fit the electron and photon results, and they interpolated the parameters to derive VSVs for any energy and voxel side within the ranges mentioned above. In order to validate the results, the authors determined VSV for two radionuclides ((131)I and (89)Sr) and two voxel dimensions and they compared them with reference data. A validation study in a simple sphere model, accounting for tissue inhomogeneities, is presented. The E(dep)(R(n)) for both monoenergetic electrons and photons exhibit a smooth variation with energy and voxel size, implying that VSVs for monoenergetic electrons or photons may be derived by interpolation over the range of energies and dimensions considered. By integration, S values for continuous emission spectra from β(-) decay may be derived as well. The approach allows the determination of VSVs for monoenergetic (Auger or conversion) electrons and (x-ray or gamma-ray) photons by means of two functions whose

Use of Documentary and Face to Face Interaction in Working Toward School Improvement. Draft. Documentation and Technical Assistance in Urban Schools.

ERIC Educational Resources Information Center

Holmes, Manford

This paper compares the usefulness of documentary (written materials) versus face to face delivery of information in helping to bring about urban school improvement. The paper is based on the experiences of the Documentation and Technical Assistance Project (DTA) of the Center for New Schools (Chicago, Illinois), a program that aims to increase…

Nonlinear bias compensation of ZiYuan-3 satellite imagery with cubic splines

NASA Astrophysics Data System (ADS)

Cao, Jinshan; Fu, Jianhong; Yuan, Xiuxiao; Gong, Jianya

2017-11-01

Like many high-resolution satellites such as the ALOS, MOMS-2P, QuickBird, and ZiYuan1-02C satellites, the ZiYuan-3 satellite suffers from different levels of attitude oscillations. As a result of such oscillations, the rational polynomial coefficients (RPCs) obtained using a terrain-independent scenario often have nonlinear biases. In the sensor orientation of ZiYuan-3 imagery based on a rational function model (RFM), these nonlinear biases cannot be effectively compensated by an affine transformation. The sensor orientation accuracy is thereby worse than expected. In order to eliminate the influence of attitude oscillations on the RFM-based sensor orientation, a feasible nonlinear bias compensation approach for ZiYuan-3 imagery with cubic splines is proposed. In this approach, no actual ground control points (GCPs) are required to determine the cubic splines. First, the RPCs are calculated using a three-dimensional virtual control grid generated based on a physical sensor model. Second, one cubic spline is used to model the residual errors of the virtual control points in the row direction and another cubic spline is used to model the residual errors in the column direction. Then, the estimated cubic splines are used to compensate the nonlinear biases in the RPCs. Finally, the affine transformation parameters are used to compensate the residual biases in the RPCs. Three ZiYuan-3 images were tested. The experimental results showed that before the nonlinear bias compensation, the residual errors of the independent check points were nonlinearly biased. Even if the number of GCPs used to determine the affine transformation parameters was increased from 4 to 16, these nonlinear biases could not be effectively compensated. After the nonlinear bias compensation with the estimated cubic splines, the influence of the attitude oscillations could be eliminated. The RFM-based sensor orientation accuracies of the three ZiYuan-3 images reached 0.981 pixels, 0.890 pixels, and 1

Tuning single-photon sources for telecom multi-photon experiments.

PubMed

Greganti, Chiara; Schiansky, Peter; Calafell, Irati Alonso; Procopio, Lorenzo M; Rozema, Lee A; Walther, Philip

2018-02-05

Multi-photon state generation is of great interest for near-future quantum simulation and quantum computation experiments. To-date spontaneous parametric down-conversion is still the most promising process, even though two major impediments still exist: accidental photon noise (caused by the probabilistic non-linear process) and imperfect single-photon purity (arising from spectral entanglement between the photon pairs). In this work, we overcome both of these difficulties by (1) exploiting a passive temporal multiplexing scheme and (2) carefully optimizing the spectral properties of the down-converted photons using periodically-poled KTP crystals. We construct two down-conversion sources in the telecom wavelength regime, finding spectral purities of > 91%, while maintaining high four-photon count rates. We use single-photon grating spectrometers together with superconducting nanowire single-photon detectors to perform a detailed characterization of our multi-photon source. Our methods provide practical solutions to produce high-quality multi-photon states, which are in demand for many quantum photonics applications.

Enhanced solar-blind responsivity of photodetectors based on cubic MgZnO films via gallium doping.

PubMed

Xie, Xiuhua; Zhang, Zhenzhong; Li, Binghui; Wang, Shuangpeng; Jiang, Mingming; Shan, Chongxin; Zhao, Dongxu; Chen, Hongyu; Shen, Dezhen

2014-01-13

We report on gallium (Ga) doped cubic MgZnO films, which have been grown by metal organic chemical vapor deposition. It was demonstrated that Ga doping improves the n-type conduction of the cubic MgZnO films. A two-orders of magnitude enhancement in lateral n-type conduction have been achieved for the cubic MgZnO films. The responsivity of the cubic MgZnO-based photodetector has been also enhanced. Depletion region electric field intensity enhanced model was adopted to explain the improvement of quantum efficiency in Ga doped MgZnO-based detectors.

Single-Photon Emitters in Boron Nitride Nanococoons.

PubMed

Ziegler, Joshua; Blaikie, Andrew; Fathalizadeh, Aidin; Miller, David; Yasin, Fehmi S; Williams, Kerisha; Mohrhardt, Jordan; McMorran, Benjamin J; Zettl, Alex; Alemán, Benjamín

2018-04-11

Quantum emitters in two-dimensional hexagonal boron nitride (hBN) are attractive for a variety of quantum and photonic technologies because they combine ultra-bright, room-temperature single-photon emission with an atomically thin crystal. However, the emitter's prominence is hindered by large, strain-induced wavelength shifts. We report the discovery of a visible-wavelength, single-photon emitter (SPE) in a zero-dimensional boron nitride allotrope (the boron nitride nanococoon, BNNC) that retains the excellent optical characteristics of few-layer hBN while possessing an emission line variation that is lower by a factor of 5 than the hBN emitter. We determined the emission source to be the nanometer-size BNNC through the cross-correlation of optical confocal microscopy with high-resolution scanning and transmission electron microscopy. Altogether, this discovery enlivens color centers in BN materials and, because of the BN nanococoon's size, opens new and exciting opportunities in nanophotonics, quantum information, biological imaging, and nanoscale sensing.

Testing a generalized cubic Galileon gravity model with the Coma Cluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terukina, Ayumu; Yamamoto, Kazuhiro; Okabe, Nobuhiro

2015-10-01

We obtain a constraint on the parameters of a generalized cubic Galileon gravity model exhibiting the Vainshtein mechanism by using multi-wavelength observations of the Coma Cluster. The generalized cubic Galileon model is characterized by three parameters of the turning scale associated with the Vainshtein mechanism, and the amplitude of modifying a gravitational potential and a lensing potential. X-ray and Sunyaev-Zel'dovich (SZ) observations of the intra-cluster medium are sensitive to the gravitational potential, while the weak-lensing (WL) measurement is specified by the lensing potential. A joint fit of a complementary multi-wavelength dataset of X-ray, SZ and WL measurements enables us tomore » simultaneously constrain these three parameters of the generalized cubic Galileon model for the first time. We also find a degeneracy between the cluster mass parameters and the gravitational modification parameters, which is influential in the limit of the weak screening of the fifth force.« less

Aluminum nitride integrated photonics platform for the ultraviolet to visible spectrum.

PubMed

Lu, Tsung-Ju; Fanto, Michael; Choi, Hyeongrak; Thomas, Paul; Steidle, Jeffrey; Mouradian, Sara; Kong, Wei; Zhu, Di; Moon, Hyowon; Berggren, Karl; Kim, Jeehwan; Soltani, Mohammad; Preble, Stefan; Englund, Dirk

2018-04-30

We demonstrate a wide-bandgap semiconductor photonics platform based on nanocrystalline aluminum nitride (AlN) on sapphire. This photonics platform guides light at low loss from the ultraviolet (UV) to the visible spectrum. We measure ring resonators with intrinsic quality factor (Q) exceeding 170,000 at 638 nm and Q >20,000 down to 369.5 nm, which shows a promising path for low-loss integrated photonics in UV and visible spectrum. This platform opens up new possibilities in integrated quantum optics with trapped ions or atom-like color centers in solids, as well as classical applications including nonlinear optics and on-chip UV-spectroscopy.

Multi-Institution Research Centers: Planning and Management Challenges

ERIC Educational Resources Information Center

Spooner, Catherine; Lavey, Lisa; Mukuka, Chilandu; Eames-Brown, Rosslyn

2016-01-01

Funding multi-institution centers of research excellence (CREs) has become a common means of supporting collaborative partnerships to address specific research topics. However, there is little guidance for those planning or managing a multi-institution CRE, which faces specific challenges not faced by single-institution research centers. We…

Shadows, signals, and stability in Einsteinian cubic gravity

NASA Astrophysics Data System (ADS)

Hennigar, Robie A.; Jahani Poshteh, Mohammad Bagher; Mann, Robert B.

2018-03-01

We conduct a preliminary investigation into the phenomenological implications of Einsteinian cubic gravity (ECG), a four-dimensional theory of gravity cubic in curvature of interest for its unique formulation and properties. We find an analytic approximation for a spherically symmetric black hole solution to this theory using a continued fraction ansatz. This approximate solution is valid everywhere outside of the horizon and we use it to study the orbit of massive test bodies near a black hole, specifically computing the innermost stable circular orbit. We compute constraints on the ECG coupling parameter imposed by Shapiro time delay. We then compute the shadow of an ECG black hole and find it to be larger than its Einsteinian counterpart in general relativity for the same value of the mass. Applying our results to Sgr A*, we find that departures from general relativity are small but in principle distinguishable.

Analysis of pulsed-neutron powder diffraction patterns of the icosahedral quasicrystals Pd3Siu and AlCuLiMg (three alloys) as twinned cubic crystals with large units.

PubMed Central

Pauling, L

1991-01-01

The low-Q peaks on three pulsed-neutron powder patterns (total, U differential, and Pd differential) of the icosahedral quasicrystal Pd3SiU have been indexed on the basis of an assumed cubic structure of the crystals that by icosahedral twinning form the quasicrystal. The primitive unit cube is found to have edge length 56.20 A and to contain approximately 12,100 atoms. Similar analyses of pulsed-neutron patterns of Al55Cu10Li35, Al55Cu10Li30Mg5, and Al510Cu125Li235Mg130 give values of the cube edge length 58.3, 58.5, and 58.4 A, respectively, with approximately 11,650 atoms in the unit cube. It is suggested that the unit contains eight complexes in the beta-W positions, plus some small interstitial groups of atoms, with each complex consisting of a centered icosahedron of 13 clusters, each of 116 atoms with the icosahedral structure found in the body-centered cubic crystal Mg32(Al,Zn)49. PMID:11607201

Analysis of pulsed-neutron powder diffraction patterns of the icosahedral quasicrystals Pd3Siu and AlCuLiMg (three alloys) as twinned cubic crystals with large units.

PubMed

Pauling, L

1991-08-01

The low-Q peaks on three pulsed-neutron powder patterns (total, U differential, and Pd differential) of the icosahedral quasicrystal Pd3SiU have been indexed on the basis of an assumed cubic structure of the crystals that by icosahedral twinning form the quasicrystal. The primitive unit cube is found to have edge length 56.20 A and to contain approximately 12,100 atoms. Similar analyses of pulsed-neutron patterns of Al55Cu10Li35, Al55Cu10Li30Mg5, and Al510Cu125Li235Mg130 give values of the cube edge length 58.3, 58.5, and 58.4 A, respectively, with approximately 11,650 atoms in the unit cube. It is suggested that the unit contains eight complexes in the beta-W positions, plus some small interstitial groups of atoms, with each complex consisting of a centered icosahedron of 13 clusters, each of 116 atoms with the icosahedral structure found in the body-centered cubic crystal Mg32(Al,Zn)49.

Unusually large unit cell of lipid bicontinuous cubic phase: towards nature's length scales

NASA Astrophysics Data System (ADS)

Kim, Hojun; Leal, Cecilia

Lipid bicontinuous cubic phases are of great interest for drug delivery, protein crystallization, biosensing, and templates for directing hard material assembly. Structural modulations of lipid mesophases regarding phase identity and unit cell size are often necessary to augment loading and gain pore size control. One important example is the need for unit cells large enough to guide the crystallization of bigger proteins without distortion of the templating phase. In nature, bicontinuous cubic constructs achieve unit cell dimensions as high as 300 nm. However, the largest unit cell of lipid mesophases synthesized in the lab is an order of magnitude lower. In fact, it has been predicted theoretically that lipid bicontinuous cubic phases of unit cell dimensions exceeding 30 nm could not exist, as high membrane fluctuations would damp liquid crystalline order. Here we report non-equilibrium assembly methods of synthesizing metastable bicontinuous cubic phases with unit cell dimensions as high as 70 nm. The phases are stable for very long periods and become increasingly ordered as time goes by without changes to unit cell dimensions. We acknowledge the funding source as a NIH.

Exact optical solitons in (n + 1)-dimensions with anti-cubic nonlinearity

NASA Astrophysics Data System (ADS)

Younis, Muhammad; Shahid, Iram; Anbreen, Sumaira; Rizvi, Syed Tahir Raza

2018-02-01

The paper studies the propagation of optical solitons in (n + 1)-dimensions under anti-cubic law of nonlinearity. The bright, dark and singular optical solitons are extracted using the extended trial equation method. The constraint conditions, for the existence of these solitons, are also listed. Additionally, a couple of other solutions known as singular periodic and Jacobi elliptic solutions, fall out as a by-product of this scheme. The obtained results are new and reported first time in (n + 1)-dimensions with anti-cubic law of nonlinearity.

A review on single photon sources in silicon carbide.

PubMed

Lohrmann, A; Johnson, B C; McCallum, J C; Castelletto, S

2017-03-01

This paper summarizes key findings in single-photon generation from deep level defects in silicon carbide (SiC) and highlights the significance of these individually addressable centers for emerging quantum applications. Single photon emission from various defect centers in both bulk and nanostructured SiC are discussed as well as their formation and possible integration into optical and electrical devices. The related measurement protocols, the building blocks of quantum communication and computation network architectures in solid state systems, are also summarized. This includes experimental methodologies developed for spin control of different paramagnetic defects, including the measurement of spin coherence times. Well established doping, and micro- and nanofabrication procedures for SiC may allow the quantum properties of paramagnetic defects to be electrically and mechanically controlled efficiently. The integration of single defects into SiC devices is crucial for applications in quantum technologies and we will review progress in this direction.

Modeling of Photonic Band Gap Crystals and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Kady, Ihab Fathy

In this work, the authors have undertaken a theoretical approach to the complex problem of modeling the flow of electromagnetic waves in photonic crystals. The focus is to address the feasibility of using the exciting phenomena of photonic gaps (PBG) in actual applications. The authors start by providing analytical derivations of the computational electromagnetic methods used in their work. They also present a detailed explanation of the physics underlying each approach, as well as a comparative study of the strengths and weaknesses of each method. The Plane Wave expansion, Transfer Matrix, and Finite Difference time Domain Methods are addressed. Theymore » also introduce a new theoretical approach, the Modal Expansion Method. They then shift the attention to actual applications. They begin with a discussion of 2D photonic crystal wave guides. The structure addressed consists of a 2D hexagonal structure of air cylinders in a layered dielectric background. Comparison with the performance of a conventional guide is made, as well as suggestions for enhancing it. The studies provide an upper theoretical limit on the performance of such guides, as they assumed no crystal imperfections and non-absorbing media. Next, they study 3D metallic PBG materials at near infrared and optical wavelengths. The main objective is to study the importance of absorption in the metal and the suitability of observing photonic band gaps in such structures. They study simple cubic structures where the metallic scatters are either cubes or interconnected metallic rods. Several metals are studied (aluminum, gold, copper, and silver). The effect of topology is addressed and isolated metallic cubes are found to be less lossy than the connected rod structures. The results reveal that the best performance is obtained by choosing metals with a large negative real part of the dielectric function, together with a relatively small imaginary part. Finally, they point out a new direction in photonic

Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals

PubMed Central

Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

2016-01-01

Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals. PMID:26956377

Direct experimental observation of nonclassicality in ensembles of single-photon emitters

NASA Astrophysics Data System (ADS)

Moreva, E.; Traina, P.; Forneris, J.; Degiovanni, I. P.; Ditalia Tchernij, S.; Picollo, F.; Brida, G.; Olivero, P.; Genovese, M.

2017-11-01

In this work we experimentally demonstrate a recently proposed criterion addressed to detect nonclassical behavior in the fluorescence emission of ensembles of single-photon emitters. In particular, we apply the method to study clusters of nitrogen-vacancy centers in diamond characterized with single-photon-sensitive confocal microscopy. Theoretical considerations on the behavior of the parameter at any arbitrary order in the presence of Poissonian noise are presented and, finally, the opportunity of detecting manifold coincidences is discussed.

CMOS-compatible photonic devices for single-photon generation

NASA Astrophysics Data System (ADS)

Xiong, Chunle; Bell, Bryn; Eggleton, Benjamin J.

2016-09-01

Sources of single photons are one of the key building blocks for quantum photonic technologies such as quantum secure communication and powerful quantum computing. To bring the proof-of-principle demonstration of these technologies from the laboratory to the real world, complementary metal-oxide-semiconductor (CMOS)-compatible photonic chips are highly desirable for photon generation, manipulation, processing and even detection because of their compactness, scalability, robustness, and the potential for integration with electronics. In this paper, we review the development of photonic devices made from materials (e.g., silicon) and processes that are compatible with CMOS fabrication facilities for the generation of single photons.

Curvature and bottlenecks control molecular transport in inverse bicontinuous cubic phases

NASA Astrophysics Data System (ADS)

Assenza, Salvatore; Mezzenga, Raffaele

2018-02-01

We perform a simulation study of the diffusion of small solutes in the confined domains imposed by inverse bicontinuous cubic phases for the primitive, diamond, and gyroid symmetries common to many lipid/water mesophase systems employed in experiments. For large diffusing domains, the long-time diffusion coefficient shows universal features when the size of the confining domain is renormalized by the Gaussian curvature of the triply periodic minimal surface. When bottlenecks are widely present, they become the most relevant factor for transport, regardless of the connectivity of the cubic phase.

The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutherland, Kevin Jerome

Over the last ten years, photonic band gap (PBG) theory and technology have become an important area of research because of the numerous possible applications ranging from high-efficiency laser diodes to optical circuitry. This research concentrates on reducing the length scale in the fabrication of layered photonic band gap structures and developing procedures to improve processing consistency. Various procedures and materials have been used in the fabrication of layered PBG structures. This research focused on an economical micro transfer molding approach to create the final PBG structure. A poly dimethylsiloxane (PDMS) rubber mold was created from a silicon substrate. Itmore » was filled with epoxy and built layer-by-layer to create a 3-D epoxy structure. This structure was infiltrated with nanoparticle titania or a titania sol-gel, then fired to remove the polymer mold, leaving a monolithic ceramic inverse of the epoxy structure. The final result was a lattice of titania rolds that resembles a face-centered tetragonal structure. The original intent of this research was to miniaturize this process to a bar size small enough to create a photonic band gap for wavelengths of visible electro-magnetic radiation. The factor limiting progress was the absence of a silicon master mold of small enough dimensions. The Iowa State Microelectronics Research Center fabricated samples with periodicities of 2.5 and 1.0 microns with the existing technology, but a sample was needed on the order of 0.3 microns or less. A 0.4 micron sample was received from Sandia National Laboratory, which was made through an electron beam lithography process, but it contained several defects. The results of the work are primarily from the 2.5 and 1.0 micron samples. Most of the work focused on changing processing variables in order to optimize the infiltration procedure for the best results. Several critical parameters were identified, ranging from the ambient conditions to the specifics of the

INTERIOR VIEW OF BUILDING 593 FACING WEST. U.S. Naval ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

INTERIOR VIEW OF BUILDING 593 FACING WEST. - U.S. Naval Base, Pearl Harbor, Retail Warehouse, Fleet Landing Halawa, near Kamehameha Highway between Richardson Recreation Center & USS Arizona Memorial Visitor Center, Pearl City, Honolulu County, HI

Photonic band gap structure simulator

DOEpatents

Chen, Chiping; Shapiro, Michael A.; Smirnova, Evgenya I.; Temkin, Richard J.; Sirigiri, Jagadishwar R.

2006-10-03

A system and method for designing photonic band gap structures. The system and method provide a user with the capability to produce a model of a two-dimensional array of conductors corresponding to a unit cell. The model involves a linear equation. Boundary conditions representative of conditions at the boundary of the unit cell are applied to a solution of the Helmholtz equation defined for the unit cell. The linear equation can be approximated by a Hermitian matrix. An eigenvalue of the Helmholtz equation is calculated. One computation approach involves calculating finite differences. The model can include a symmetry element, such as a center of inversion, a rotation axis, and a mirror plane. A graphical user interface is provided for the user's convenience. A display is provided to display to a user the calculated eigenvalue, corresponding to a photonic energy level in the Brilloin zone of the unit cell.

Rapid Generation of Large Dimension Photon Sieve Designs

NASA Technical Reports Server (NTRS)

Hariharan, Shravan; Fitzpatrick, Sean; Kim, Hyun Jung; Julian, Matthew; Sun, Wenbo; Tedjojuwono, Ken; MacDonnell, David

2017-01-01

A photon sieve is a revolutionary optical instrument that provides high resolution imaging at a fraction of the weight of typical telescopes (areal density of 0.3 kg/m2 compared to 25 kg/m2 for the James Webb Space Telescope). The photon sieve is a variation of a Fresnel Zone Plate consisting of many small holes spread out in a ring-like pattern, which focuses light of a specific wavelength by diffraction. The team at NASA Langley Research Center has produced a variety of small photon sieves for testing. However, it is necessary to increase both the scale and rate of production, as a single sieve previously took multiple weeks to design and fabricate. This report details the different methods used in producing photon sieve designs in two file formats: CIF and DXF. The difference between these methods, and the two file formats were compared, to determine the most efficient design process. Finally, a step-by-step sieve design and fabrication process was described. The design files can be generated in both formats using an editing tool such as Microsoft Excel. However, an approach using a MATLAB program reduced the computing time of the designs and increased the ability of the user to generate large photon sieve designs. Although the CIF generation process was deemed the most efficient, the design techniques for both file types have been proven to generate complete photon sieves that can be used for scientific applications

Multi-photon absorption limits to heralded single photon sources

PubMed Central

Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; De Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

2013-01-01

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

Non-Poissonian photon statistics from macroscopic photon cutting materials.

PubMed

de Jong, Mathijs; Meijerink, Andries; Rabouw, Freddy T

2017-05-24

In optical materials energy is usually extracted only from the lowest excited state, resulting in fundamental energy-efficiency limits such as the Shockley-Queisser limit for single-junction solar cells. Photon-cutting materials provide a way around such limits by absorbing high-energy photons and 'cutting' them into multiple low-energy excitations that can subsequently be extracted. The occurrence of photon cutting or quantum cutting has been demonstrated in a variety of materials, including semiconductor quantum dots, lanthanides and organic dyes. Here we show that photon cutting results in bunched photon emission on the timescale of the excited-state lifetime, even when observing a macroscopic number of optical centres. Our theoretical derivation matches well with experimental data on NaLaF 4 :Pr 3+ , a material that can cut deep-ultraviolet photons into two visible photons. This signature of photon cutting can be used to identify and characterize new photon-cutting materials unambiguously.

High-entropy alloys in hexagonal close-packed structure

DOE PAGES

Gao, Michael C.; Zhang, B.; Guo, S. M.; ...

2015-08-28

The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Lastly, experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.

Antiswarming: Structure and dynamics of repulsive chemically active particles

NASA Astrophysics Data System (ADS)

Yan, Wen; Brady, John F.

2017-12-01

Chemically active Brownian particles with surface catalytic reactions may repel each other due to diffusiophoretic interactions in the reaction and product concentration fields. The system behavior can be described by a "chemical" coupling parameter Γc that compares the strength of diffusiophoretic repulsion to Brownian motion, and by a mapping to the classical electrostatic one component plasma (OCP) system. When confined to a constant-volume domain, body-centered cubic (bcc) crystals spontaneously form from random initial configurations when the repulsion is strong enough to overcome Brownian motion. Face-centered cubic (fcc) crystals may also be stable. The "melting point" of the "liquid-to-crystal transition" occurs at Γc≈140 for both bcc and fcc lattices.

MURI Center for Photonic Quantum Information Systems

DTIC Science & Technology

2009-10-16

conversion; solid- state quantum gates based on quantum dots in semiconductors and on NV centers in diamond; quantum memories using optical storage...of our high-speed quantum cryptography systems, and also by continuing to work on quantum information encoding into transverse spatial modes. 14...make use of cavity QED effects for quantum information processing, the quantum dot needs to be addressed coherently . We have probed the QD-cavity

Children Facing Divorce: A Treatment Program

ERIC Educational Resources Information Center

Magid, Kenneth M.

1977-01-01

The children facing divorce program began last year and was built on the talents of an interdisciplinary staff. Included are experts in client-centered counseling, sociometry and psychodrama, Gestalt and TA, behavior modification, and various eclectic approaches to family therapy. (Author)

Deterministically swapping frequency-bin entanglement from photon-photon to atom-photon hybrid systems

NASA Astrophysics Data System (ADS)

Ou, Bao-Quan; Liu, Chang; Sun, Yuan; Chen, Ping-Xing

2018-02-01

Inspired by the recent developments of the research on the atom-photon quantum interface and energy-time entanglement between single-photon pulses, we are motivated to study the deterministic protocol for the frequency-bin entanglement of the atom-photon hybrid system, which is analogous to the frequency-bin entanglement between single-photon pulses. We show that such entanglement arises naturally in considering the interaction between a frequency-bin entangled single-photon pulse pair and a single atom coupled to an optical cavity, via straightforward atom-photon phase gate operations. Its anticipated properties and preliminary examples of its potential application in quantum networking are also demonstrated. Moreover, we construct a specific quantum entanglement witness tool to detect such extended frequency-bin entanglement from a reasonably general set of separable states, and prove its capability theoretically. We focus on the energy-time considerations throughout the analysis.

Phase conversion from hexagonal CuS(y)Se(1-y) to cubic Cu(2-x)S(y)Se(1-y): composition variation, morphology evolution, optical tuning, and solar cell applications.

PubMed

Xu, Jun; Yang, Xia; Yang, Qingdan; Zhang, Wenjun; Lee, Chun-Sing

2014-09-24

In this work, we report a simple and low-temperature approach for the controllable synthesis of ternary Cu-S-Se alloys featuring tunable crystal structures, compositions, morphologies, and optical properties. Hexagonal CuS(y)Se(1-y) nanoplates and face centered cubic (fcc) Cu(2-x)S(y)Se(1-y) single-crystal-like stacked nanoplate assemblies are synthesized, and their phase conversion mechanism is well investigated. It is found that both copper content and chalcogen composition (S/Se atomic ratio) of the Cu-S-Se alloys are tunable during the phase conversion process. Formation of the unique single-crystal-like stacked nanoplate assemblies is resulted from oriented stacking coupled with the Ostwald ripening effect. Remarkably, optical tuning for continuous red shifts of both the band-gap absorption and the near-infrared localized surface plasmon resonance are achieved. Furthermore, the novel Cu-S-Se alloys are utilized for the first time as highly efficient counter electrodes (CEs) in quantum dot sensitized solar cells (QDSSCs), showing outstanding electrocatalytic activity for polysulfide electrolyte regeneration and yielding a 135% enhancement in power conversion efficiency (PCE) as compared to the noble metal Pt counter electrode.

Neuromorphic photonic networks using silicon photonic weight banks.

PubMed

Tait, Alexander N; de Lima, Thomas Ferreira; Zhou, Ellen; Wu, Allie X; Nahmias, Mitchell A; Shastri, Bhavin J; Prucnal, Paul R

2017-08-07

Photonic systems for high-performance information processing have attracted renewed interest. Neuromorphic silicon photonics has the potential to integrate processing functions that vastly exceed the capabilities of electronics. We report first observations of a recurrent silicon photonic neural network, in which connections are configured by microring weight banks. A mathematical isomorphism between the silicon photonic circuit and a continuous neural network model is demonstrated through dynamical bifurcation analysis. Exploiting this isomorphism, a simulated 24-node silicon photonic neural network is programmed using "neural compiler" to solve a differential system emulation task. A 294-fold acceleration against a conventional benchmark is predicted. We also propose and derive power consumption analysis for modulator-class neurons that, as opposed to laser-class neurons, are compatible with silicon photonic platforms. At increased scale, Neuromorphic silicon photonics could access new regimes of ultrafast information processing for radio, control, and scientific computing.

Comparison of Node-Centered and Cell-Centered Unstructured Finite-Volume Discretizations: Viscous Fluxes

NASA Technical Reports Server (NTRS)

Diskin, Boris; Thomas, James L.; Nielsen, Eric J.; Nishikawa, Hiroaki; White, Jeffery A.

2010-01-01

Discretization of the viscous terms in current finite-volume unstructured-grid schemes are compared using node-centered and cell-centered approaches in two dimensions. Accuracy and complexity are studied for four nominally second-order accurate schemes: a node-centered scheme and three cell-centered schemes - a node-averaging scheme and two schemes with nearest-neighbor and adaptive compact stencils for least-square face gradient reconstruction. The grids considered range from structured (regular) grids to irregular grids composed of arbitrary mixtures of triangles and quadrilaterals, including random perturbations of the grid points to bring out the worst possible behavior of the solution. Two classes of tests are considered. The first class of tests involves smooth manufactured solutions on both isotropic and highly anisotropic grids with discontinuous metrics, typical of those encountered in grid adaptation. The second class concerns solutions and grids varying strongly anisotropically over a curved body, typical of those encountered in high-Reynolds number turbulent flow simulations. Tests from the first class indicate the face least-square methods, the node-averaging method without clipping, and the node-centered method demonstrate second-order convergence of discretization errors with very similar accuracies per degree of freedom. The tests of the second class are more discriminating. The node-centered scheme is always second order with an accuracy and complexity in linearization comparable to the best of the cell-centered schemes. In comparison, the cell-centered node-averaging schemes may degenerate on mixed grids, have a higher complexity in linearization, and can fail to converge to the exact solution when clipping of the node-averaged values is used. The cell-centered schemes using least-square face gradient reconstruction have more compact stencils with a complexity similar to that of the node-centered scheme. For simulations on highly anisotropic

A SiPM-based isotropic-3D PET detector X'tal cube with a three-dimensional array of 1 mm(3) crystals.

PubMed

Yamaya, Taiga; Mitsuhashi, Takayuki; Matsumoto, Takahiro; Inadama, Naoko; Nishikido, Fumihiko; Yoshida, Eiji; Murayama, Hideo; Kawai, Hideyuki; Suga, Mikio; Watanabe, Mitsuo

2011-11-07

We are developing a novel, general purpose isotropic-3D PET detector X'tal cube which has high spatial resolution in all three dimensions. The research challenge for this detector is implementing effective detection of scintillation photons by covering six faces of a segmented crystal block with silicon photomultipliers (SiPMs). In this paper, we developed the second prototype of the X'tal cube for a proof-of-concept. We aimed at realizing an ultimate detector with 1.0 mm(3) cubic crystals, in contrast to our previous development using 3.0 mm(3) cubic crystals. The crystal block was composed of a 16 × 16 × 16 array of lutetium gadolinium oxyorthosilicate (LGSO) crystals 0.993 × 0.993 × 0.993 mm(3) in size. The crystals were optically glued together without inserting any reflector inside and 96 multi-pixel photon counters (MPPCs, S10931-50P, i.e. six faces each with a 4 × 4 array of MPPCs), each having a sensitive area of 3.0 × 3.0 mm(2), were optically coupled to the surfaces of the crystal block. Almost all 4096 crystals were identified through Anger-type calculation due to the finely adjusted reflector sheets inserted between the crystal block and light guides. The reflector sheets, which formed a belt of 0.5 mm width, were placed to cover half of the crystals of the second rows from the edges in order to improve identification performance of the crystals near the edges. Energy resolution of 12.7% was obtained at 511 keV with almost uniform light output for all crystal segments thanks to the effective detection of the scintillation photons.

Energy absorption ability of buckyball C720 at low impact speed: a numerical study based on molecular dynamics

PubMed Central

2013-01-01

The dynamic impact response of giant buckyball C720 is investigated by using molecular dynamics simulations. The non-recoverable deformation of C720 makes it an ideal candidate for high-performance energy absorption. Firstly, mechanical behaviors under dynamic impact and low-speed crushing are simulated and modeled, which clarifies the buckling-related energy absorption mechanism. One-dimensional C720 arrays (both vertical and horizontal alignments) are studied at various impact speeds, which show that the energy absorption ability is dominated by the impact energy per buckyball and less sensitive to the number and arrangement direction of buckyballs. Three-dimensional stacking of buckyballs in simple cubic, body-centered cubic, hexagonal, and face-centered cubic forms are investigated. Stacking form with higher occupation density yields higher energy absorption. The present study may shed lights on employing C720 assembly as an advanced energy absorption system against low-speed impacts. PMID:23360618

Modeling antigen-antibody nanoparticle bioconjugates and their polymorphs

NASA Astrophysics Data System (ADS)

Desgranges, Caroline; Delhommelle, Jerome

2018-03-01

The integration of nanomaterials with biomolecules has recently led to the development of new ways of designing biosensors, and through their assembly, to new hybrid structures for novel and exciting applications. In this work, we develop a coarse-grained model for nanoparticles grafted with antibody molecules and their binding with antigens. In particular, we isolate two possible states for antigen-antibody pairs during the binding process, termed as recognition and anchoring states. Using molecular simulation, we calculate the thermodynamic and structural features of three possible crystal structures or polymorphs, the body-centered cubic, simple cubic, and face-centered cubic phases, and of the melt. This leads us to determine the domain of stability of the three solid phases. In particular, the role played by the switching process between anchoring and recognition states during melting is identified, shedding light on the complex microscopic mechanisms in these systems.

Membrane protein crystallization in meso: lipid type-tailoring of the cubic phase.

PubMed Central

Cherezov, Vadim; Clogston, Jeffrey; Misquitta, Yohann; Abdel-Gawad, Wissam; Caffrey, Martin

2002-01-01

Hydrated monoolein forms the cubic-Pn3m mesophase that has been used for in meso crystallization of membrane proteins. The crystals have subsequently provided high-resolution structures by crystallographic means. It is possible that the hosting cubic phase created by monoolein alone, which itself is not a common membrane component, will limit the range of membrane proteins crystallizable by the in meso method. With a view to expanding the range of applicability of the method, we investigated by x-ray diffraction the degree to which the reference cubic-Pn3m phase formed by hydrated monoolein could be modified by other lipid types. These included phosphatidylcholine (PC), phosphatidylethanolamine, phosphatidylserine, cardiolipin, lyso-PC, a polyethylene glycol-lipid, 2-monoolein, oleamide, and cholesterol. The results show that all nine lipids were accommodated in the cubic phase to some extent without altering phase identity. The positional isomer, 2-monoolein, was tolerated to the highest level. The least well tolerated were the anionic lipids, followed by lyso-PC. The others were accommodated to the extent of 20-25 mol %. Beyond a certain concentration limit, the lipid additives either triggered one or a series of phase transitions or saturated the phase and separated out as crystals, as seen with oleamide and cholesterol. The series of phases observed and their order of appearance were consistent with expectations in terms of interfacial curvature changes. The changes in phase type and microstructure have been rationalized on the basis of lipid molecular shape, interfacial curvature, and chain packing energy. The data should prove useful in the rational design of cubic phase crystallization matrices with different lipid profiles that match the needs of a greater range of membrane proteins. PMID:12496106

Highly birefringent suspended-core photonic microcells for refractive-index sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057; Jin, Wa

2014-08-11

An in-line photonic microcell with a highly birefringent suspended microfiber core is fabricated by locally heating and pressurizing selected air-holes of an endless single mode photonic crystal fiber. The microfiber core has rhombus-like cross-sectional geometry and could achieve a high birefringence of up to 10{sup −2}. The microfiber core is fixed at the center of the microcell by thin struts attached to an outer jacket tube, which protects and isolates the microfiber from environmental contaminations. Highly sensitive and robust refractive index sensors based on such microcells are experimentally demonstrated.

Vibrational renormalisation of the electronic band gap in hexagonal and cubic ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engel, Edgar A., E-mail: eae32@cam.ac.uk; Needs, Richard J.; Monserrat, Bartomeu

2015-12-28

Electron-phonon coupling in hexagonal and cubic water ice is studied using first-principles quantum mechanical methods. We consider 29 distinct hexagonal and cubic ice proton-orderings with up to 192 molecules in the simulation cell to account for proton-disorder. We find quantum zero-point vibrational corrections to the minimum electronic band gaps ranging from −1.5 to −1.7 eV, which leads to improved agreement between calculated and experimental band gaps. Anharmonic nuclear vibrations play a negligible role in determining the gaps. Deuterated ice has a smaller band-gap correction at zero-temperature of −1.2 to −1.4 eV. Vibrations reduce the differences between the electronic band gapsmore » of different proton-orderings from around 0.17 eV to less than 0.05 eV, so that the electronic band gaps of hexagonal and cubic ice are almost independent of the proton-ordering when quantum nuclear vibrations are taken into account. The comparatively small reduction in the band gap over the temperature range 0 − 240 K of around 0.1 eV does not depend on the proton ordering, or whether the ice is protiated or deuterated, or hexagonal, or cubic. We explain this in terms of the atomistic origin of the strong electron-phonon coupling in ice.« less

Photonic and Phononic Entanglement with Hybrid Species Ion Chains

NASA Astrophysics Data System (ADS)

Crocker, Clayton; Lichtman, Martin; Sosnova, Ksenia; Nguyen, Tuan; Carter, Allison; Inlek, Volkan; Ruth, Hanna; Monroe, Christopher

2017-04-01

Trapped atomic ions represent a leading platform for quantum information networks due to their long coherence times and diverse set of entangling operations. External fields can drive strong local entangling interactions via phonons, and remote qubits can be entangled via emitted photons. Unfortunately, resonant light from the photonic entanglement process can disrupt nearby memory qubits. We resolve this crosstalk by introducing a separate atomic species to the trap for use as a photonic entanglement qubit. We report successful demonstration of both entangling gates between the mixed species qubit pair through their collective motion, and entanglement between our remote entanglement qubit and emitted visible photons. We additionally report our progress on a new trapping apparatus that was implemented to improve these operations to a level required for scaling up the system size. This work is supported by the ARO with funding from the IARPA LogiQ program, the AFOSR, the ARO MURI on Modular Quantum Circuits, the AFOSR MURI on Quantum Transduction, and the ARL Center for Distributed Quantum Information.

Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources.

PubMed

Ghorbani, Mahdi; Mehrpouyan, Mohammad; Davenport, David; Ahmadi Moghaddas, Toktam

2016-06-01

The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems.

Formation of hexagonal and cubic ice during low-temperature growth

PubMed Central

Thürmer, Konrad; Nie, Shu

2013-01-01

From our daily life we are familiar with hexagonal ice, but at very low temperature ice can exist in a different structure––that of cubic ice. Seeking to unravel the enigmatic relationship between these two low-pressure phases, we examined their formation on a Pt(111) substrate at low temperatures with scanning tunneling microscopy and atomic force microscopy. After completion of the one-molecule-thick wetting layer, 3D clusters of hexagonal ice grow via layer nucleation. The coalescence of these clusters creates a rich scenario of domain-boundary and screw-dislocation formation. We discovered that during subsequent growth, domain boundaries are replaced by growth spirals around screw dislocations, and that the nature of these spirals determines whether ice adopts the cubic or the hexagonal structure. Initially, most of these spirals are single, i.e., they host a screw dislocation with a Burgers vector connecting neighboring molecular planes, and produce cubic ice. Films thicker than ∼20 nm, however, are dominated by double spirals. Their abundance is surprising because they require a Burgers vector spanning two molecular-layer spacings, distorting the crystal lattice to a larger extent. We propose that these double spirals grow at the expense of the initially more common single spirals for an energetic reason: they produce hexagonal ice. PMID:23818592

Determination of the Interaction Position of Gamma Photons in Monolithic Scintillators Using Neural Network Fitting

NASA Astrophysics Data System (ADS)

Conde, P.; Iborra, A.; González, A. J.; Hernández, L.; Bellido, P.; Moliner, L.; Rigla, J. P.; Rodríguez-Álvarez, M. J.; Sánchez, F.; Seimetz, M.; Soriano, A.; Vidal, L. F.; Benlloch, J. M.

2016-02-01

In Positron Emission Tomography (PET) detectors based on monolithic scintillators, the photon interaction position needs to be estimated from the light distribution (LD) on the photodetector pixels. Due to the finite size of the scintillator volume, the symmetry of the LD is truncated everywhere except for the crystal center. This effect produces a poor estimation of the interaction positions towards the edges, an especially critical situation when linear algorithms, such as Center of Gravity (CoG), are used. When all the crystal faces are painted black, except the one in contact with the photodetector, the LD can be assumed to behave as the inverse square law, providing a simple theoretical model. Using this LD model, the interaction coordinates can be determined by means of fitting each event to a theoretical distribution. In that sense, the use of neural networks (NNs) has been shown to be an effective alternative to more traditional fitting techniques as nonlinear least squares (LS). The multilayer perceptron is one type of NN which can model non-linear functions well and can be trained to accurately generalize when presented with new data. In this work we have shown the capability of NNs to approximate the LD and provide the interaction coordinates of γ-photons with two different photodetector setups. One experimental setup was based on analog Silicon Photomultipliers (SiPMs) and a charge division diode network, whereas the second setup was based on digital SiPMs (dSiPMs). In both experiments NNs minimized border effects. Average spatial resolutions of 1.9 ±0.2 mm and 1.7 ±0.2 mm for the entire crystal surface were obtained for the analog and dSiPMs approaches, respectively.

Learned face-voice pairings facilitate visual search.

PubMed

Zweig, L Jacob; Suzuki, Satoru; Grabowecky, Marcia

2015-04-01

Voices provide a rich source of information that is important for identifying individuals and for social interaction. During search for a face in a crowd, voices often accompany visual information, and they facilitate localization of the sought-after individual. However, it is unclear whether this facilitation occurs primarily because the voice cues the location of the face or because it also increases the salience of the associated face. Here we demonstrate that a voice that provides no location information nonetheless facilitates visual search for an associated face. We trained novel face-voice associations and verified learning using a two-alternative forced choice task in which participants had to correctly match a presented voice to the associated face. Following training, participants searched for a previously learned target face among other faces while hearing one of the following sounds (localized at the center of the display): a congruent learned voice, an incongruent but familiar voice, an unlearned and unfamiliar voice, or a time-reversed voice. Only the congruent learned voice speeded visual search for the associated face. This result suggests that voices facilitate the visual detection of associated faces, potentially by increasing their visual salience, and that the underlying crossmodal associations can be established through brief training.

Proposed square spiral microfabrication architecture for large three-dimensional photonic band gap crystals.

PubMed

Toader, O; John, S

2001-05-11

We present a blueprint for a three-dimensional photonic band gap (PBG) material that is amenable to large-scale microfabrication on the optical scale using glancing angle deposition methods. The proposed chiral crystal consists of square spiral posts on a tetragonal lattice. In the case of silicon posts in air (direct structure), the full PBG can be as large as 15% of the gap center frequency, whereas for air posts in a silicon background (inverted structure) the maximum PBG is 24% of the center frequency. This PBG occurs between the fourth and fifth bands of the photon dispersion relation and is very robust to variations (disorder) in the geometrical parameters of the crystal.

Super-focusing of center-covered engineered microsphere.

PubMed

Wu, Mengxue; Chen, Rui; Soh, Jiahao; Shen, Yue; Jiao, Lishi; Wu, Jianfeng; Chen, Xudong; Ji, Rong; Hong, Minghui

2016-08-16

Engineered microsphere possesses the advantage of strong light manipulation at sub-wavelength scale and emerges as a promising candidate to shrink the focal spot size. Here we demonstrated a center-covered engineered microsphere which can adjust the transverse component of the incident beam and achieve a sharp photonic nanojet. Modification of the beam width and working distance of the photonic nanojet were achieved by tuning the cover ratio of the engineered microsphere, leading to a sharp spot size which exceeded the optical diffraction limit. At a wavelength of 633 nm, a focal spot of 245 nm (0.387 λ) was achieved experimentally under plane wave illumination. Strong localized field with Bessel-like distribution was demonstrated by employing the linearly polarized beam and a center-covered mask being engineered on the microsphere.

3. SIXTH FLOOR VIEW TO WEST, WITH FACE POWDER MAKING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. SIXTH FLOOR VIEW TO WEST, WITH FACE POWDER MAKING UNIT: CHARGE HOPPER (CENTER FOREGROUND), PERFUME MIXER (LEFT), AND DUST COLLECTOR (REAR CENTER) - Colgate & Company Jersey City Plant, G Block, 81-95 Greene Street, Jersey City, Hudson County, NJ

Comb-based radiofrequency photonic filters with rapid tunability and high selectivity

NASA Astrophysics Data System (ADS)

Supradeepa, V. R.; Long, Christopher M.; Wu, Rui; Ferdous, Fahmida; Hamidi, Ehsan; Leaird, Daniel E.; Weiner, Andrew M.

2012-03-01

Photonic technologies have received considerable attention regarding the enhancement of radiofrequency electrical systems, including high-frequency analogue signal transmission, control of phased arrays, analog-to-digital conversion and signal processing. Although the potential of radiofrequency photonics for the implementation of tunable electrical filters over broad radiofrequency bandwidths has been much discussed, the realization of programmable filters with highly selective filter lineshapes and rapid reconfigurability has faced significant challenges. A new approach for radiofrequency photonic filters based on frequency combs offers a potential route to simultaneous high stopband attenuation, fast tunability and bandwidth reconfiguration. In one configuration, tuning of the radiofrequency passband frequency is demonstrated with unprecedented (~40 ns) speed by controlling the optical delay between combs. In a second, fixed filter configuration, cascaded four-wave mixing simultaneously broadens and smoothes the comb spectra, resulting in Gaussian radiofrequency filter lineshapes exhibiting an extremely high (>60 dB) main lobe to sidelobe suppression ratio and (>70 dB) stopband attenuation.