Noise Stability of SIS Receivers

There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability.     

Demetallation of α,β,γ,δ-tetrakis(p-sulfophenyl) porphiniron(III) in mineral acid–alcohol–water media

Demetallation rates of α,β,γ,δ-tetrakis(p-sulfophenyl)porphiniron(III) in hydrochloric acid–ethanol–water, perchloric acid–ethanol–water, and sulfuric acid–alcohol–water media were determined. For a given acidity value H₀ the order of the rates for the three acids was HCl > H₂SO₄ > HClO₄. This is also the order for complex formation between acid anion and iron(III). Consequently ligands as well as protons are involved in the breaking of bonds between the metal and the porphyrin leading to the formation of the activated complex. The log k values for HCl and HClO₄ media were not linearly related to the Hammett acidity function as they were for sulfuric acid–ethanol–water media. The average ΔH? and ΔS?values for the HCl media were 18.4 ± 1.4 kcal/mol and ? 19 ± 3 cal K mol, respectively, in very close agreement with those for H₂SO₄ media despite the difference in H ₀ dependence. For H₂SO₄–alcohol–water media the order of the rates was butanol > propanol > ethanol with little difference between isomeric alcohols.     

On Green's function for the reduced wave equation in a spherical annular domain with Dirichlet's boundary conditions

Summary In this study Green's function for the reduced wave equation (Helmholtz equation) in a spherical annular domain with Dirichlet's boundary conditions is derived. The convergence of the series solution representing Green's function is then established. Finally it is shown that Green's function for the Dirichlet problem reduces to Green's function for the exterior of a sphere as given by Franz and Etiènne, when the outer radius is moved towards infinity, and when a special position of the coordinate system is chosen.     

On Green's functions for the reduced wave equation in a circular annular domain with dirichlet, Neumann and radiation type boundary conditions

Summary In this paper Green's functions for the reduced wave equation (Helmholtz equation) in a circular annular domain with the Dirichlet, the radiation, and Neumann boundary conditions are derived. The convergence of the series representing Green's functions is then established. Finally it is shown that these functions reduce to Green's function for the exterior of a circle as given by Franz and Etiènne when the outer radius is moved towards infinity.     

Circle and sphere theorems for the biharmonic equation (interior and exterior problems)

Zusammenfassung In dieser Arbeit werden Kreis- und Kugelsätze hergeleitet, von denen der erste im Zusammenhang mit den Verschiebungsfeldern einer eingespannten Platte unter reiner Biegung interessiert. Mit Hilfe des biharmonischen Feldes im unbeschränkten Bereich werden Lösungen angegeben, wobei das Endergebnis für den beschränkten Bereich innerhalb des Kreises bzw. der Kugel die gleichen Singularitäten aufweist wie dasjenige für den unbeschränkten Bereich.