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Search Results: 1 - 10 of 3711 matches for " Jerry Nathan Reider "
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Intense Visible Photoluminescence from C46H22N8O4KM (M = Co, Fe, Pb) Derivatives Thin Films  [PDF]
María Elena Sánchez, Juan Carlos Alonso, Jerry Nathan Reider
Advances in Materials Physics and Chemistry (AMPC) , 2011, DOI: 10.4236/ampc.2011.13010
Abstract: Strong visible photoluminescence (PL) at room temperature is obtained from thermal-evaporated thin solid films of Metallophthalocyanine (M = Co, Fe, Pb) and double potassium salt from 1,8 dihydroxyan-thraquinone. The PL of all the investigated samples is observed with the naked eye in a bright background. The deconvolution of the normalized PL spectra shows that each PL spectrum is composed of four emission bands which peak at approximately the same energies of 2.1, 2.2 and 2.4 eV and whose intensities and widths depend upon the structure of the complexes. FTIR and ellipsometry are employed to investigate the structural differences among the films. The optical absorption of the films is also investigated to evaluate the changes in the electronic structure of these metal organic compounds, with respect to other metalphtalocya-nines thin films. Our results suggest that the visible PL comes from radiative transitions between energy lev-els associated to the double potassium salt coordination to the metallic ion in the phthalocyanine.
RUNOFF ESTIMATES INTO THE WEIJA RESERVOIR AND ITS IMPLICATIONS FOR WATER SUPPLY TO THE ACCRA AREA, GHANA
Jerry Samuel Kuma,Donald Nathan Ashley
Journal of Urban and Environmental Engineering , 2008,
Abstract: Accra has a population of about 2.3 million and is supplied with water from both the Kpong and Weija Water Works. Water from the Weija treatment plant is taken from the Weija Reservoir which is fed by Rivers in the Densu River Basin (DRB) that flow into the Reservoir at Weija. With increasing annual population growth of Accra at 4.4% and inadequate water supply to it, this study has examined the hydrological data available on the Weija Reservoir from 1980 to 2007 in an attempt to estimate runoff into the Reservoir with the view of determining whether water is available to meet its present and future demands. Results show that even though water abstraction from the Reservoir has increased almost four times since 1980, to more than 67 million m3/year in 2007, and a maximum runoff of 7.97 ± 0.21 × 10-2 km3/year was estimated in 2005, this value is less than the true runoff into the Reservoir. It was also observed that potential evapotranspiration has increased by 0.14% while precipitation has decreased by 0.93% in the DRB, indicating that runoff from the Basin into the Reservoir is probably decreasing, albeit slowly. Additionally, fishing and waste disposal methods are poor; land use practices and other anthropogenic activities in the DRB pose a threat to the sustainability of the Reservoir. Serious educational programmes and enforcement measures need to be urgently adopted to safeguard continuous water flow into the Reservoir. Proper hydrological data collection and data management practices are recommended for the Reservoir and Densu River Basin if detailed planning of the water resources of the Reservoir are to be achieved.
Configuration of points and strings
Igor Reider
Mathematics , 2006, DOI: 10.1016/j.geomphys.2010.09.012
Abstract: Let $X$ be a smooth projective variety of dimension $n\geq 2$. It is shown that a finite configuration of points on $X$ subject to certain geometric conditions possesses rich inner structure. On the mathematical level this inner structure is a variation of Hodge-like structure. As a consequence one can attach to such point configurations: (i) Lie algebras and their representations (ii) Fano toric variety whose hyperplane sections are Calabi-Yau varieties. These features lead to a picture which is very suggestive of quantum gravity according to string theory.
Nonabelian Jacobian of smooth projective surfaces and representation theory
Igor Reider
Mathematics , 2011,
Abstract: The paper studies representation theoretic aspects of a nonabelian version of the Jacobian for a smooth complex projective surface $X$ introduced in [R1]. The sheaf of reductive Lie algebras $\bf\calG$ associated to the nonabelian Jacobian is determined and its Lie algebraic properties are explicitly related to the geometry of configurations of points on $X$. In particular, it is shown that the subsheaf of centers of $\bf\calG$ determines a distinguished decomposition of configurations into the disjoint union of subconfigurations. Furthermore, it is shown how to use $sl_2$-subalgebras associated to certain nilpotent elements of $\bf\calG$ to write equations defining con?figurations of $X$ in appropriate projective spaces. The same nilpotent elements are used to establish a relation of the nonabelian Jacobian with such fundamental objects in the representation theory as nilpotent orbits, Springer resolution and Springer fibres of simple Lie algebras of type $A_n$, for appropriate values of $n$. This leads to a construction of distinguished collections of objects in the category of representations of symmetric groups as well as in the category of perverse sheaves on the appropriate Hilbert schemes of points of $X$. Hence two ways of categorifying the second Chern class of vector bundles of rank 2 on smooth projective surfaces. We also give a `loop' version of the above construction by relating the nonabelian Jacobian to the Infinite Grassmannians of simple Lie groups of type $SL_n(\bf C)$, for appropriate values of n. This gives, via the geometric version of the Satake isomorphism, a distinguished collection of irreducible representations of the Langlands dual groups thus indicating a relation of the nonabelian Jacobian to the Langlands duality for smooth projective surfaces.
Nonabelian Jacobian of Smooth Projective Surfaces - A Survey
Igor Reider
Mathematics , 2011,
Abstract: The nonabelian Jacobian $\JA$ of a smooth projective surface $X$ is inspired by the classical theory of Jacobian of curves. It is built as a natural scheme interpolating between the Hilbert scheme $\XD$ of subschemes of length $d$ of $X$ and the stack ${\bf M}_X (2,L,d)$ of torsion free sheaves of rank 2 on $X$ having the determinant $\OO_X (L)$ and the second Chern class (= number) $d$. It relates to such influential ideas as variations of Hodge structures, period maps, nonabelian Hodge theory, Homological mirror symmetry, perverse sheave, geometric Langlands program. These relations manifest themselves by the appearance of the following structures on $\JA$: 1) a sheaf of reductive Lie algebras, 2) (singular) Fano toric varieties whose hyperplane sections are (singular) Calabi-Yau varieties, 3) trivalent graphs. This is an expository paper giving an account of most of the main properties of $\JA$ uncovered in [R1] and [R2].
Infinitesimal Torelli Theorem for regular surfaces with very ample canonical divisor
Igor Reider
Mathematics , 2014,
Abstract: The article proves the theorem in the title under the assumption that a surface contains no lines. The main novelty is a realization of the Kodaira-Spencer classes lying in the kernel of the cohomology cup-product controlling the derivative of the period map of weight 2 in the category of the coherent sheaves of a surface.
Determination of the Optical GAP in Thin Films of Amorphous Dilithium Phthalocyanine Using the Tauc and Cody Models
María Elena Sánchez-Vergara,Juan Carlos Alonso-Huitron,Arturo Rodriguez-Gómez,Jerry N. Reider-Burstin
Molecules , 2012, DOI: 10.3390/molecules170910000
Abstract: Semiconducting thin films were grown on quartz substrates and crystalline silicon wafers, using dilithium phthalocyanine and the organic ligands 2,6-dihydroxyanthraquinone and 2,6-diaminoanthraquinone as the starting compounds. The films, thus obtained, were characterized by Fourier Transform infrared (FTIR), fast atomic bombardment (FAB+) mass and ultraviolet-visible (UV-Vis) spectroscopies. The surface morphology of these films was analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). It was found that the temperature-dependent electric current in all cases showed a semiconductor behavior with conductivities on the order of 10?6·S cm?1, whereas the highest value corresponded to the thin film based upon the bidentate amine. The Tauc and Cody optical band gap values of thin films were calculated from the absorption coefficients and were found to be around 1.5 eV, with another strong band between 2.3 and 2.43 eV, arising from non-direct transitions. The curvature in the Tauc plot influencing the determination of the optical gap, the Tauc optical gap corresponding to the thicker film is smaller. The dependence of the Cody optical gap on the film thickness was negligible.
Workforce quality goals and the implications for education: The Oregon experience.
Nathan Sivers-Boyce,Tom Hibbard,Jerry Gray
Education Policy Analysis Archives , 2005,
Abstract: We review a plan that attracted the attention of public sector planners everywhere, Oregon's 1989 Oregon Shines: An Economic Strategy for the Pacific Century. In particular, we focus on Oregon's aspirations for world-class workforce quality; a status that the state's planners argued would contribute to a host of other outcomes that foster citizen well-being. The broader purpose of the paper is to emphasize the importance of timing. Planners must remain mindful of the long timeframe required for educational improvements to directly benefit the economy. We begin by reviewing the arguments that planners offered for the centrality of workforce quality. Second, we briefly review a few indicators of the state's commitment to achieving a world-class workforce and the consequences of this commitment to date. Third, we show that failure to dynamically model the linkages between actions and outcomes led to adoption of a workforce goal that was unattainable even if commitment had been Herculean. Finally, we consider other planning targets that might be improved by understanding why Oregon's workforce quality goals were unachievable.
Twisted Kodaira-Spencer classes and the geometry of surfaces of general type
Daniel Naie,Igor Reider
Mathematics , 2011,
Abstract: We study the cohomology groups $H^1(X,\Theta_X(-mK_X))$, for $m\geq1$, where $X$ is a smooth minimal complex surface of general type, $\Theta_X$ its holomorphic tangent bundle, and $K_X$ its canonical divisor. One of the main results is a precise vanishing criterion for $H^1(X,\Theta_X (-K_X))$. The proof is based on the geometric interpretation of non-zero cohomology classes of $H^1(X,\Theta_X (-K_X))$. This interpretation in turn uses higher rank vector bundles on $X$. We apply our methods to the long standing conjecture saying that the irregularity of surfaces in $\PP^4$ is at most 2. We show that if $X$ has prescribed Chern numbers, no irrational pencil, and is embedded in $\PP^4$ with a sufficiently large degree, then the irregularity of $X$ is at most 3.
Accuracy of Discrete-Velocity BGK Models for the Simulation of the Incompressible Navier-Stokes Equations
Marc B. Reider,James D. Sterling
Physics , 1993,
Abstract: Two discretizations of a 9-velocity Boltzmann equation with a BGK collision operator are studied. A Chapman-Enskog expansion of the PDE system predicts that the macroscopic behavior corresponds to the incompressible Navier-Stokes equations with additional terms of order Mach number squared. We introduce a fourth-order scheme and compare results with those of the commonly used lattice Boltzmann discretization and with finite-difference schemes applied to the incompressible Navier-Stokes equations in primitive-variable form. We numerically demonstrate convergence of the BGK schemes to the incompressible Navier-Stokes equations and quantify the errors associated with compressibility and discretization effects. When compressibility error is smaller than discretization error, convergence in both grid spacing and time step is shown to be second-order for the LB method and is confirmed to be fourth-order for the fourth-order BGK solver. However, when the compressibility error is simultaneously reduced as the grid is refined, the LB method behaves as a first-order scheme in time.
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