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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,729 records · Page 96
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DOE OSTI2015

More on rotations as spin matrix polynomials

Any nonsingular function of spin j matrices always reduces to a matrix polynomial of order 2j. The challenge is to find a convenient form for the coefficients of the matrix polynomial. The theory of biorthogonal systems is a useful framework to meet this challenge. Central factorial numbers play a key role in the theoretical development. Explicit polynomial coefficients for rotations expressed either as exponentials or as rational Cayley transforms are considered here. Structural features of the results are discussed and compared, and large j limits of the coefficients are examined.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions

We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

A simple method for understanding the triangular growth patterns of transition metal dichalcogenide sheets

Triangular nanoflake growth patterns have been commonly observed in synthesis of transition metal dichalcogenide sheets and their hybrid structures. Triangular nanoflakes not only show exceptional properties, but also can serve as building blocks for two or three dimensional structures. In this study, taking the MoS{sub 2} system as a test case, we propose a Matrix method to understand the mechanism of such unique growth pattern. Nanoflakes with different edge types are mathematically described with configuration matrices, and the total formation energy is calculated as the sum of the edge formation energies and the chemical potentials of sulfur and molybdenum. Based on energetics, we find that three triangular patterns with the different edge configurations are energetically more favorable in different ranges of the chemical potential of sulfur, which are in good agreement with experimental observations. Our algorithm has high efficiency and can deal with nanoflakes in microns which are beyond the ability of ab-initio method. This study not only elucidates the mechanism of triangular nanoflake growth patterns in experiment, but also provides a clue to control the geometric configurations in synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Polarization-dependent diffraction in all-dielectric, twisted-band structures

We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Curved noncommutative tori as Leibniz quantum compact metric spaces

We prove that curved noncommutative tori are Leibniz quantum compact metric spaces and that they form a continuous family over the group of invertible matrices with entries in the image of the quantum tori for the conjugation by modular conjugation operator in the regular representation, when this group is endowed with a natural length function.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Transparent bulk-size nanocomposites with high inorganic loading

With relatively high nanoparticle loading in polymer matrices, hybrid nanocomposites made by colloidal dispersion routes suffer from severe inhomogeneous agglomeration, a phenomenon that deteriorates light transmission even when the refractive indices of the inorganic and organic phases are closely matched. The dispersion of particles in a matrix is of paramount importance to obtain composites of high optical quality. Here, we describe an innovative, yet straightforward method to fabricate monolithic transparent hybrid nanocomposites with very high particle loading and high refractive index mismatch tolerance between the inorganic and organic constituents. We demonstrate 77% transmission at 800 nm in a 2 mm-thick acrylate polymer nanocomposite containing 61 vol. % CaF{sub 2} nanoparticles. Modeling shows that similar performance could easily be obtained with various inorganic phases relevant to a number of photonic applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Optimization of micropillar sequences for fluid flow sculpting

Inertial fluid flow deformation around pillars in a microchannel is a new method for controlling fluid flow. Sequences of pillars have been shown to produce a rich phase space with a wide variety of flow transformations. Previous work has successfully demonstrated manual design of pillar sequences to achieve desired transformations of the flow cross section, with experimental validation. However, such a method is not ideal for seeking out complex sculpted shapes as the search space quickly becomes too large for efficient manual discovery. We explore fast, automated optimization methods to solve this problem. We formulate the inertial flow physics in microchannels with different micropillar configurations as a set of state transition matrix operations. These state transition matrices are constructed from experimentally validated streamtraces for a fixed channel length per pillar. This facilitates modeling the effect of a sequence of micropillars as nested matrix-matrix products, which have very efficient numerical implementations. With this new forward model, arbitrary micropillar sequences can be rapidly simulated with various inlet configurations, allowing optimization routines quick access to a large search space. We integrate this framework with the genetic algorithm and showcase its applicability by designing micropillar sequences for various useful transformations. We computationally discover micropillar sequences for complex transformations that are substantially shorter than manually designed sequences. We also determine sequences for novel transformations that were difficult to manually design. Finally, we experimentally validate these computational designs by fabricating devices and comparing predictions with the results from confocal microscopy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Solution of second order supersymmetrical intertwining relations in Minkowski plane

Supersymmetrical (SUSY) intertwining relations are generalized to the case of quantum Hamiltonians in Minkowski space. For intertwining operators (supercharges) of second order in derivatives, the intertwined Hamiltonians correspond to completely integrable systems with the symmetry operators of fourth order in momenta. In terms of components, the intertwining relations correspond to the system of nonlinear differential equations which are solvable with the simplest—constant—ansatzes for the “metric” matrix in second order part of the supercharges. The corresponding potentials are built explicitly both for diagonalizable and nondiagonalizable form of “metric” matrices, and their properties are discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Effect of laser UV radiation on the eye scleral tissue in patients with open-angle glaucoma

We report the results of an experimental study of the effect of short-pulse laser UV radiation on the eye scleral tissue. As samples, we used isolated flaps of the eye scleral tissue from the patients with open-angle glaucoma of the second and third stages. The impact was implemented using the radiation of an excimer XeCl laser with a wavelength of 308 nm and a laser with a wavelength tunable within from 210 to 355 nm. Depending on the problem to be solved, the energy density on the surface of the irradiated tissue varied from a fraction of mJ cm{sup –2} to 15 J cm{sup –2}. For the first time we studied the optical properties of the intraocular fluid in the UV and blue spectral range. The study of the ablation process under the action of radiation with a wavelength of 308 nm showed that the rate of material evaporation can vary within 24 % – 30 % at an energy density above 7 J cm{sup –2}, depending on the glaucoma stage and the individual features of a patient. The excitation – emission matrices of laser-induced fluorescence (LIF) of the eye scleral tissue were studied experimentally using a laser with a wavelength tuned in the range 210 – 355 nm. We found the differences in the LIF spectra caused by the excitation wavelength and the open-angle glaucoma stage. (laser medicine)

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Problems of development of tunable hybrid bismuth – erbium fibrelasers

Experimental data and experience in the development of tunable fibre lasers based on active bismuth centres in silica glasses with different compositions and luminescence bands in the range 1200–1800 nm are considered. It is shown that continuous-wave narrow-band laser radiation with a milliwatt power (1–10 mW) covering this wavelength range can be obtained using hybrid fibre schemes and, probably, co-doping of matrices with bismuth and erbium. Continuously tunable bismuth fibre lasers with partially overlapping spectral ranges of 1270–1370, 1360–1540, and 1600–1800 nm are studied. Hybrid schemes of fibre lasers emitting in the spectral range from 1500 to 1600 nm, which includes the erbium luminescence band, are proposed. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Inverse problem of polarimetry for media with orthogonal eigenpolarisations

We consider the problem of the ambiguity of the inverse problem of polarimetry for a homogeneous anisotropic medium characterised by orthogonal eigenpolarisations generated by non-commutativity of Jones and Mueller matrices of elementary types of anisotropy. The differences between two variants of the orthogonality conditions for the eigenpolarisations of an arbitrary anisotropic medium, the existence of which is due to this ambiguity, are investigated. The results obtained can be used to analyse the adequacy of the solution of the inverse problem of this class and in the problems of the synthesis of polarisation elements with given characteristics. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Self-affine polytopes. Applications to functional equations and matrix theory

A special kind of functional equation with compression of the argument--the affine self-similarity equation--is studied. The earlier known one-dimensional self-similarity equations are generalized to the multidimensional case of functions of several variables. A criterion for the existence and uniqueness of an L{sub p}-solution is established. Description of such equations involves classification of finite-dimensional convex self-affine compact sets. In this work properties of such objects are thoroughly analysed; in particular, a counterexample to the well-known conjecture about the structure of such bodies, which was put forward in 1991, is given. Applications of the results obtained include some facts about the convergence of products of stochastic matrices; also, criteria for the convergence of some subdivision algorithms are suggested. Bibliography: 39 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2013

A family of Nikishin systems with periodic recurrence coefficients

Suppose we have a Nikishin system of p measures with the kth generating measure of the Nikishin system supported on an interval {Delta}{sub k} subset of R with {Delta}{sub k} Intersection {Delta}{sub k+1} = Empty-Set for all k. It is well known that the corresponding staircase sequence of multiple orthogonal polynomials satisfies a (p+2)-term recurrence relation whose recurrence coefficients, under appropriate assumptions on the generating measures, have periodic limits of period p. (The limit values depend only on the positions of the intervals {Delta}{sub k}.) Taking these periodic limit values as the coefficients of a new (p+2)-term recurrence relation, we construct a canonical sequence of monic polynomials {l_brace}P{sub n}{r_brace}{sub n=0}{sup {infinity}}, the so-called Chebyshev-Nikishin polynomials. We show that the polynomials P{sub n} themselves form a sequence of multiple orthogonal polynomials with respect to some Nikishin system of measures, with the kth generating measure being absolutely continuous on {Delta}{sub k}. In this way we generalize a result of the third author and Rocha [22] for the case p=2. The proof uses the connection with block Toeplitz matrices, and with a certain Riemann surface of genus zero. We also obtain strong asymptotics and an exact Widom-type formula for functions of the second kind of the Nikishin system for {l_brace}P{sub n}{r_brace}{sub n=0}{sup {infinity}}. Bibliography: 27 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2011

Enhanced Sensitivity for Selected Reaction Monitoring–Mass Spectrometry-based Targeted Proteomics using a Dual-Stage Electrodynamic Ion Funnel Interface

Selected reaction monitoring-mass spectrometry (SRM-MS) is playing an increasing role in quantitative proteomics and biomarker discovery studies as a method for high throughput candidate quantification and verification. While SRM-MS offers advantages in sensitivity and quantification compared to other MS-based techniques, current SRM technologies are still challenged by detection and quantification of low-abundance proteins (e.g., present at ~10 ng/mL or lower levels in blood plasma). Here we report enhanced detection sensitivity and reproducibility for SRM-based targeted proteomics by coupling a dual electrodynamic ion funnel interface to a commercial triple quadrupole mass spectrometer. Due to the increased efficiency in ion transmission, significant enhancements in overall signal intensities and improved limits of detection were observed with the new interface compared to the original (capillary/skimmer) interface for SRM measurements of tryptic peptides from proteins spiked into non-depleted mouse plasma over a range of concentrations. Overall, average SRM peak intensities were increased by ~70-fold. The average level of detection for peptides also improved by ~14-fold, with notably improved reproducibility of peptide measurements as indicated by the reduced coefficients of variance. The ability to detect proteins ranging from 40 to 80 ng/mL within mouse plasma was demonstrated for all spiked proteins without the application of front-end immunoaffinity depletion and fractionation. This significant improvement in detection sensitivity for low-abundance proteins in complex matrices is expected to enhance a broad range of SRM-MS applications in addition to targeted protein and metabolite validation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

POLARIZED LINE FORMATION WITH J-STATE INTERFERENCE IN THE PRESENCE OF MAGNETIC FIELDS. I. PARTIAL FREQUENCY REDISTRIBUTION IN THE COLLISIONLESS REGIME

Quantum interference phenomena play a fundamental role in astrophysical spectra that are formed by coherent scattering processes. Here we derive a partial frequency redistribution (PRD) matrix that includes J-state interference in the presence of magnetic fields of arbitrary strength. The paper focuses on PRD in the collisionless regime, which in the traditional PRD terminology is referred to as Hummer's type-II scattering. By limiting the treatment to the linear Zeeman regime, for which the Zeeman splitting is much smaller than the fine-structure splitting, it is possible to formulate analytical expressions for the PRD matrices. In the special case of non-magnetic scattering we recover the redistribution matrix derived from an independent quantum electrodynamic formulation based on the metalevel theory.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

PROBING PRIMORDIAL NON-GAUSSIANITY WITH WEAK-LENSING MINKOWSKI FUNCTIONALS

We study the cosmological information contained in the Minkowski functionals (MFs) of weak gravitational lensing convergence maps. We show that the MFs provide strong constraints on the local-type primordial non-Gaussianity parameter f {sub NL}. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing to generate 100 independent convergence maps of a 25 deg{sup 2} field of view for f {sub NL} = -100, 0 and 100. We perform a Fisher analysis to study the degeneracy among other cosmological parameters such as the dark energy equation of state parameter w and the fluctuation amplitude {sigma}{sub 8}. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For upcoming wide-field observations such as those from the Subaru Hyper Suprime-Cam survey with a proposed survey area of 1500 deg{sup 2}, the primordial non-Gaussianity can be constrained with a level of f {sub NL} {approx} 80 and w {approx} 0.036 by weak-lensing MFs. If simply scaled by the effective survey area, a 20,000 deg{sup 2} lensing survey using the Large Synoptic Survey Telescope will yield constraints of f {sub NL} {approx} 25 and w {approx} 0.013. We show that these constraints can be further improved by a tomographic method using source galaxies in multiple redshift bins.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Structural engineering of epitaxial, self-assembled ferromagnetic cobalt/yttria-stabilized zirconia nanocomposites for ultrahigh-density storage media

We report on a low-cost, innovative approach for synthesizing prepatterned, magnetic nanostructures, the shapes and dimensions of which can be easily tuned to meet requirements for next-generation data storage technology. The magnetic nanostructures consist of self-assembled Co nanodots and nanowires embedded in yttria-stabilized zirconia (YSZ) matrices. The controllable size and aspect ratio of the nanostructures allows the selection of morphologies ranging from nanodots to nanowires. Co nanowires show strong shape anisotropy and large remanence at 300 K. In contrast, Co nanodots display minimal effects of magnetocrystalline anisotropy and superparamagnetic relaxation above the blocking temperature. These prepatterned magnetic nanostructures are very promising candidates for data storage technology with an ultrahigh density of 1 terabit in{sup -2} or higher.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Charting an Inflationary Landscape with Random Matrix Theory

We construct a class of random potentials for N >> 1 scalar fields using non-equilibrium random matrix theory, and then characterize multifield inflation in this setting. By stipulating that the Hessian matrices in adjacent coordinate patches are related by Dyson Brownian motion, we define the potential in the vicinity of a trajectory. This method remains computationally efficient at large N, permitting us to study much larger systems than has been possible with other constructions. We illustrate the utility of our approach with a numerical study of inflation in systems with up to 100 coupled scalar fields. A significant finding is that eigenvalue repulsion sharply reduces the duration of inflation near a critical point of the potential: even if the curvature of the potential is fine-tuned to be small at the critical point, small cross-couplings in the Hessian cause the curvature to grow in the neighborhood of the critical point.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗