985 resultados para U-series disequilibrium


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The Humphreys Quadrangle is a portion of the easternmost Ventura Basin underlain by a thick series of Tertiary sedimentary rocks. On these rocks a great variety of geomorphic forms have been molded by the processes of running water typical of a semi-arid climate and by several types of mass movement. Among the different categories of mass movement present, a new type, the siltflow, was observed.

The geomorphic forms of special interest present in the quadrangle are rock cones, open canyonheads, asymmetric canyons, and stream terraces and straths. The author urges the adoption of the definition of strath as that part of an old dissected valley floor, including the floors of tributary valleys, which was not part of the floodplain of the main valley stream.

An old erosion surface, the Puckett Mesa Surface, is present in the Humphreys Quadrangle which is correlative with certain of the older stream terraces. By correlating the variation of gradient and of fill of the stream terraces with post –Wisconsin climatic fluctuations the age of the Puckett Mesa Surface is set at approximately 6000 B.C. This correlation sets the probable age of the older Rancho La Brea deposits at 6000 to 8000 B. C. and the probable age of the Carpenteria brea deposits at 1000 to 1 B. C.

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Consider the Royden compactification R* of a Riemannian n-manifold R, Γ = R*\R its Royden boundary, Δ its harmonic boundary and the elliptic differential equation Δu = Pu, P ≥ 0 on R. A regular Borel measure mP can be constructed on Γ with support equal to the closure of ΔP = {q ϵ Δ : q has a neighborhood U in R* with UʃᴖRP ˂ ∞ }. Every enegy-finite solution to u (i.e. E(u) = D(u) + ʃRu2P ˂ ∞, where D(u) is the Dirichlet integral of u) can be represented by u(z) = ʃΓu(q)K(z,q)dmP(q) where K(z,q) is a continuous function on Rx Γ . A P~E-function is a nonnegative solution which is the infimum of a downward directed family of energy-finite solutions. A nonzero P~E-function is called P~E-minimal if it is a constant multiple of every nonzero P~E-function dominated by it. THEOREM. There exists a P~E-minimal function if and only if there exists a point in q ϵ Γ such that mP(q) > 0. THEOREM. For q ϵ ΔP , mP(q) > 0 if and only if m0(q) > 0 .

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The effectiveness of 17 α-hydroxy-20 β-dihydroprogesterone (17 α-20 β Pg) or of a trout hypophyseal gonadotrophic extract on the in vitro intrafollicular maturation of trout oocytes can be modulated by steroids which do not have a direct maturing effect; the effectiveness of the gonadotrophic extract is lowered by oestradiol and oestrone and increased by testosterone. As these steroids have no significant effect on maturation induced by 17 α-20 β Pg, the site of their activity is probably in the follicular envelopes. Corticosteroids, and Cortisol and cortisone in particular increase the effectiveness of the gonadotrophic extract, but increase the effectiveness of 17 α-20 β Pg even more strongly, suggesting that this 'progestagen' has a direct effect on oocyte sensitivity.

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We quantitatively study the domain inversion in a RuO2:LiNbO3 crystal wafer by the digital holographic interferometry. The crystal wafer is placed into one arm of a Mach-Zehnder-type interferometer to record a series of holograms. Making use of the angular spectrum backward propagation algorithm, we reconstruct the optical wave field in the crystal plane. The extracted phase difference from the reconstructed optical wave field is a well linear function of the applied external voltage. We deduce that the linear electro-optic coefficient of the detected RuO2:LiNbO3 crystal sample is 9.1x10(-12) m/V. An unexpected phase contrast at the antiparallel domain wall is observed and the influence of the applied external voltage on it is studied in detail. Also the built-in internal field is quantitatively measured as 0.72 kV/mm. (c) 2006 American Institute of Physics.

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A small investigation of the ecology of the river Lambourn was carried out during 1967-70. During this period it became clear that detailed and reliable information could only be obtained by a much larger investigation. The present study was planned to meet the minimum requirements. No pumping is expected during this period and, since the pumping carried out during the pilot scheme was on a small scale, it is reasonable to assume that the river is still relatively unaffected by pumping.The present investigation has two main objectives both of which depend on obtaining a detailed picture of the ecology of the river at the present time. First, it will provide basic information on the state of the river prior to the development of the pumping scheme which will be available for comparison at any later date. Secondly, it may be possible to use some of the data to predict the ecological changes which may occur if the flow of the river is altered by the pumping scheme. This report is part of a series of fives studies on the River Lambourn which were undertaken between 1970 and 1979. [PDF contains 83 pages]

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Few detailed studies have been made on the ecology of the chalk streams. A complex community of plants and animals is present and much more information is required to achieve an understanding of the requirements and interactions of all the species. It is important that the rivers affected by this scheme should be studied and kept under continued observation so that any effects produced by the scheme can be detected. This need has been recognised by the Thames Conservancy and the Water Resources Board who jointly sponsored this investigation on one of the chalk streams involved in the scheme. The present investigation has two main objectives both of which depend on obtaining a detailed picture of the ecology of the river at the present time. First, it will provide basic information on the state of the river prior to the development of the pumping scheme which will be available for comparison at any later date. Secondly, it may be possible to use some of the data to predict the ecological changes which may occur if the flow of the river is altered by the pumping scheme. The study covers suspended solids, invertebrates, fish.This report is part of a series of fives studies on the River Lambourn which were undertaken between 1970 and 1979. [PDF contains 24 pages]

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This work is concerned with estimating the upper envelopes S* of the absolute values of the partial sums of rearranged trigonometric sums. A.M. Garsia [Annals of Math. 79 (1964), 634-9] gave an estimate for the L2 norms of the S*, averaged over all rearrangements of the original (finite) sum. This estimate enabled him to prove that the Fourier series of any function in L2 can be rearranged so that it converges a.e. The main result of this thesis is a similar estimate of the Lq norms of the S*, for all even integers q. This holds for finite linear combinations of functions which satisfy a condition which is a generalization of orthonormality in the L2 case. This estimate for finite sums is extended to Fourier series of Lq functions; it is shown that there are functions to which the Men’shov-Paley Theorem does not apply, but whose Fourier series can nevertheless be rearranged so that the S* of the rearranged series is in Lq.

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High-resolution, natural-abundance 13C spectra have been obtained from a wide variety of organic compounds; 13C chemical shifts and coupling constants have been correlated with other molecular properties.

Geminal and vicinal, carbon-proton couplings in benzene and the five- and six-membered aromatic heterocycles have been related to the corresponding proton-proton couplings in substituted ethylenes. The carbon-proton coupling constants in benzene are JCCH = + 1.0, JCCCH = +7.4 and JCCCH = -1.1 Hz. Extended Hückel wavefunctions are uniformly poor in explaining the long-range, carbon-proton couplings in aromatic systems.

Couplings between carbon and elements other than hydrogen have been observed in proton decoupled 13C spectra. All of the carbons in fluorobenzene and 1-fluoronaphthalene, but only six of the carbons in 2-fluoronaphthalene are coupled to the fluorine. One-bond, carbon-phosphorus coupling in trialkylphosphines is negative, while one-bond, carbon-phosphorus coupling in tetra-alkylphosphonium ions is positive. Atoms which do not use hybrid orbitals to form bonds to carbon (F, P(III), Se, Te) may have negative, one-bond coupling constants because of the failure of the average energy approximation. One-bond couplings between carbon and carbon, silicon, tin, lead and mercury appear to be explainable in terms of an effective nuclear charge and the s-bond order of the metal. Couplings between carbon and nitrogen and phosphorus (IV) have significant negative contributions to the Fermi contact coupling expression, though, within one series, correlations with s-bond order may be valid. Carbon-carbon coupling in cyclopropane derivatives (10-15 Hz) is consistent with a high degree of p character in the interior orbitals. Some two- and three-bond carbon-carbon coupling constants have also been observed.

Substituent effects of hydroxyl groups on the 13C chemical shifts of continuous-chain alkanes depend both on steric and electronic factors. The hydroxyl substituent effects in the long-chain, primary alcohols are α = -48.3, β = -10.2, and γ = +6.0 ppm. The upfield γ effect is attributed to steric crowding in the gauche conformations. Additivity of the hydroxyl and carbonyl and alkyl substituent effects in alkyl-substituted cyclohexanols and cyclohexanones has been demonstrated.

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The problem considered is that of minimizing the drag of a symmetric plate in infinite cavity flow under the constraints of fixed arclength and fixed chord. The flow is assumed to be steady, irrotational, and incompressible. The effects of gravity and viscosity are ignored.

Using complex variables, expressions for the drag, arclength, and chord, are derived in terms of two hodograph variables, Γ (the logarithm of the speed) and β (the flow angle), and two real parameters, a magnification factor and a parameter which determines how much of the plate is a free-streamline.

Two methods are employed for optimization:

(1) The parameter method. Γ and β are expanded in finite orthogonal series of N terms. Optimization is performed with respect to the N coefficients in these series and the magnification and free-streamline parameters. This method is carried out for the case N = 1 and minimum drag profiles and drag coefficients are found for all values of the ratio of arclength to chord.

(2) The variational method. A variational calculus method for minimizing integral functionals of a function and its finite Hilbert transform is introduced, This method is applied to functionals of quadratic form and a necessary condition for the existence of a minimum solution is derived. The variational method is applied to the minimum drag problem and a nonlinear integral equation is derived but not solved.

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Accurate, analytical series expressions for the far-field diffraction of it Gaussian beam normally incident on a circular and central obscured aperture are derived with the help of the integration of parts method. With this expression, the far-field intensity distribution pattern can be obtained and the divergence angle is deduced too. Using the first five items of the series, the accuracy can satisfy most laser application fields. Compared with the conventional numerical integral method, the series representation is very convenient for understanding the physical meanings. (C) 2007 Elsevier GmbH. All rights reserved.

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Part I.

The stoichiometry and kinetics of the reaction between Co(CN5H3- and HgX2 (X = CN, OH) have been investigated. The products of the reaction are two new complexes, [(NC)5Co-HgX]3- and [(NC)5Co-Hg-Co(CN)5]6-, whose spectra are reported. The kinetic measurements produced a value for the forward rate constant of the reaction Co(CN)5H3- + OH- k1/k-1 Co(CN)54- +H2O, k1 = (9.7 ± 0.8) x 10-2 M-1 sec-1 at 24°C, and an equilibrium constant for the reaction K = 10-6 M-1.

Part II.

Unusually large and sharp "adsorption waves" appear in cyclic voltammograms of Co(CN)53- and several cobalt(III) pentacyano complexes at stationary mercury electrodes. The nature of the adsorbed species and the reasons for the absence of the adsorption waves in polarograms taken with a d.m.e. have been examined. The data are compatible with the adsorption, in all cases, of a coordinatively unsaturated cobalt(II) complex, Co(CN)42-, by means of a cobalt-mercury bond. When the resulting adsorbed complex is reduced, a series of subsequent chemical and electrode reactions is initiated in which three faradays of charge are consumed for each mole of adsorbed complex. The adsorption of the anionic complex strongly retards the reduction of other negatively charged complexes.

Part III.

A number of formal redox potentials for RuIII (NH3)5L + e = RuII (NH3)5L and RuIII(NH3)4L2 + e = RuII (NH3)4L2 (where L is various ligands) has been measured by cyclic voltammetry, potentiometry, and polarography and are discussed in terms of the properties of the ligands, such as π-accepting capability. Reduction of coordinated pyrazine in the complexes, Ru(NH3)5 Pz2+, cis- and trans-Ru(NH3)4Pz22+, on a mercury electrode has been observed. The behavior of this reduction in various acidity of the solution as well as the reoxidation of the reduction products are discussed.

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[ES]La adaptación de la Universidad Española al Espacio Europeo de Educación Superior (EEES) ha supuesto un cambio en los estudios universitarios que se advierte en su estructura (títulos de grado de cuatro años,) y que debe manifestarse también en las metodologías utilizadas. En los estudios de Magisterio la nueva ordenación de las enseñanzas ha supuesto la unificación de las anteriores especialidades en dos títulos de grado: Maestro de Educación Infantil y Maestro de Educación Primaria. En estos nuevos títulos las Prácticas de Enseñanza continúan teniendo un importante papel y constituyen un momento privilegiado de integración entre la teoría y la realidad de las aulas. El Practicum es el conjunto de actividades en las que diversas instituciones colaboran con la Escuela Universitaria de Magisterio, a fin de poner al alumnado en contacto con el mundo profesional. Supone la inmersión de los estudiantes en centros educativos con la finalidad de conocerlos directamente, integrar conocimientos teórico-prácticos, y adquirir competencias profesionales en todos los ámbitos de actuación.