Multiple-bipolar-tap tunable spectrum sliced microwave photonic filter

A spectrum sliced microwave photonic signal processor structure, which is all-fiber based and features simplicity, together with the ability to realize tunability, reconfigurability, bipolar taps, and multiple-tap rf filtering, is presented. It is based on thermally controlled optical slicing filters induced into two linearly chirped fiber Bragg gratings. Experimental results demonstrate the realization of versatile microwave photonic filters with frequency tunable, reconfiguration, and bipolar-tap generation capabilities.     

Imaging the neural circuitry and chemical control of aggressive motivation

Background  

With the advent of functional magnetic resonance imaging (fMRI) in awake animals it is possible to resolve patterns of neuronal activity across the entire brain with high spatial and temporal resolution. Synchronized changes in neuronal activity across multiple brain areas can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviors. To this end, fMRI in conscious rats combined with 3D computational analysis was used to identifying the putative distributed neural circuit involved in aggressive motivation and how this circuit is affected by drugs that block aggressive behavior.     

Asymptotic distribution of the increase of the largest canonical correlation when one of the vectors is augmented

Let r₁ > r₂ > … be the sample canonical correlations in a sample of size n from a multivariate normal population partitioned into two subvectors with population canonical correlations ₁ > ₂ > …. Let one of the subvectors be augmented by adding one or more variables to it. For the increase in the largest canonical correlation, Δr in the sample and Δ in the population, it is shown that √n(Δr − Δ) → ^DN(0, σ²) and a formula for σ² is derived.     

Equilibrium charge-state fractions for 2.7–31 keV deuterium atoms and ions in strontium vapor

Equilibrium charge-state fractions of 2.7–31 keV deuterium in strontium vapor are reported. The energy dependence of the D^- equilibrium yield is discussed. The results are compared with the D^- yield in cesium and magnesium vapors.     

Integral approximations for molecular orbital theory

The electron repulsion integrals arising in LCAO-MO theory are approximated by replacement of the product of two orbitals on different centers by linear combinations of one-center products. The approximation differs from those previously proposed in that the coefficients of the various terms are determined by requiring agreement for certain integrals, and in the emphasis of the role of symmetry in selecting the one-center products. For two-center integrals, the new approximation is significantly better than older approximate methods. Reasons are given for expecting this improvement to extend also to multi-center integrals.

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Zusammenfassung Es wird ein Verfahren zur näherungsweisen Berechnung von Elektronenwechselwirkungsintegralen der LCAO-MO-Theorie beschrieben, bei welchem das Produkt zweier Zustandsfunktionen an verschiedenen Zentren durch eine Linearkombination von Produkten am gleichen Zentrum ersetzt wird. Der Unterschied zu ähnlichen Ansätzen liegt in der Justierung der Koeffizienten. Für Zweizentrenintegrale liefert die hier vorgeschlagene Methode bedeutend bessere Ergebnisse als das Mulliken-Verfahren.

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Résumé Les intégrales de répulsion électroniques intervenant dans la théorie LCAO MO sont calculées d'une manière approchée en remplaçant le produit de deux orbitales sur des centres différents par des combinaisons linéaires de produits à un centre. Cette approximation diffère de celles proposées auparavant par la détermination des coefficients des différents termes au moyen de l'ajustement de certaines intégrales et par l'importance du rôle de la symétrie dans le choix des produits monocentriques. Cette nouvelle approximation est bien meilleure que les anciennes en ce qui concerne les intégrales bi-centriques. Nous donnons des raisons d'espérer que cette amélioration s'étendra aux intégrales polycentriques.

     

The spectrophotometric and titrimetric determination of gold with ferroin as reagent

A spectrophotometric and a photometric titration method in a two-phase system for the determination of gold with ferroin is reported. Both methods are rapid and reproducible with an accuracy of ±1%. In the spectrophotometric determination Co²⁺, Cu²⁺, Ni²⁺ , Fe³⁺, Zn²⁺, Mn²⁺ and Cr³⁺ do not interfere with the determination of gold and Pt⁴⁺, Pd²⁺, Hg²⁺, Ir⁴⁺ and Os⁴⁺ can be tolerated up to a ratio of 1:1. The titrations can also be carried out in the presence of a number of diverse ions, e.g. Ni²⁺, Cu²⁺, Co²⁺, Fe³⁺, Zn²⁺, Cr³⁺, Mn²⁺, without interference; the platinum metals and Hg²⁺ cause interference but, by the use of the spectrophotometric procedure, this can be reduced.     

Sequence distribution of partially hydrolyzed poly(vinyl acetate)

Copolymers of vinyl acetate and vinyl alcohol were studied by differential thermal analysis. The melting points of the copolymers are not a simple function of the composition, but depend on the method of preparation of the copolymers. Partial saponification of poly(vinyl acetate) with sodium hydroxide leads to high melting, ordered copolymers, while reacetylation of poly(vinyl alcohol) leads to low melting, random copolymers. Catalytic alcoholysis of PVAc yields copolymers intermediate in melting point and order. The results are treated by assuming that equal melting points indicate similar sequence length distributions of crystallizable units.     

A theoretical study of the electromagnetic properties of ferrocene and the ferrocenium ion

An iterative extended Hückel molecular orbital calculation was used to obtain wave functions for the ground state of ferrocene and several low lying states of the ferrocenium ion. Photoemission spectra in terms of relative ionization potentials and the electric field gradient at the iron nucleus were calculated for ferrocene andg values and the electric field gradient were calculated for the ferrocenium ion. These values are in good agreement with experiment. The nature of the molecular orbitals was compared with results of previous semi-empirical andab initio calculations.     

Structural considerations from dielectric measurements on the aliphatic alcohols

Precise static dielectric constants are reported for methanol, ethanol, andn-propanol at 10,25, and 40° C and at pressures up to 3 kbar. The measurements were carried out by a low-frequency bridge method using a threeterminal, all-glass cell. An uncertainty of 0.05% is claimed for the data. The results are compared to data from previous investigations, whith the agreement in the absolute magnitude poor but the agreement in the pressure coefficient reasonable in most cases. The data are analyzed in terms of the Kirkwood correlation factorg _K as obtained from the Fröhlich equation. In all cases, theg _K factor decreases with increased pressure. The problems involved in calculating this factor from the experimental data are discussed, and it is shown that the trends ing _K are very dependent upon the assumptions made in isolating the liquid dipole moment from its gas-phase value. This fact also indicates that an interpretation of theg _K values in terms of stepwise association of correlation dipoles is premature at this time.