Excess enthalpies of binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol,and heptane at T = 298.15 K and 313.15 K

Experimental excess molar enthalpies of the ternary systems {dibutyl ether (DBE) + 1-butanol + heptane} and the corresponding binary systems at T = 298.15 K and T = 313.15 K at atmospheric pressure are reported. A quasi-isothermal flow calorimeter has been used to make the measurements. All the binary and the ternary systems show endothermic character. The experimental data for the binary and ternary systems have been fitted using the Redlich–Kister equation, the NRTL and UNIQUAC models. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equations.     

The production of no carrier added arsenic radioisotopes in nuclear reactors

The comparative advantages and drawbacks of some reactor-produced arsenic radioisotopes having favourable characteristics for their use as tracers are discussed. The study comprises their preparation based on: (a) capture reactions on germanium; (b) threshold reactions on germanium, selenium and bromine; (c) secondary reactions on germanium, induced by recoil protons and tritons produced by the action of neutrons on lithium. The recommended options for the production of relatively short half-life radionuclides are ⁷⁷As by capture on germanium or ⁷⁶As via (n,α) reaction on bromine, while two different ways are applicable for the production of ⁷⁴As, longer-lived radioisotope.

     

<Emphasis Type="Italic">L</Emphasis><Superscript><Emphasis Type="Italic">p</Emphasis></Superscript>–dimension free boundedness for Riesz transforms associated to Hermite functions<Superscript>⋆</Superscript>

Riesz transforms associated to Hermite functions were introduced by S. Thangavelu, who proved that they are bounded operators on 1<p< . In this paper we give a different proof that allows us to show that the L^p–norms of these operators are bounded by a constant not depending on the dimension d. Moreover, we define Riesz transforms of higher order and free dimensional estimates of the L^p–bounds of these operators are obtained. In order to prove the mentioned results we give an extension of the Littlewood-Paley theory that we believe of independent interest.Mathematical Subject Classification (2000):42B20, 42B25, 42C10Partially supported by Instituto Argentino de Matemática CONICET, Convenio Universidad Autónoma de Madrid-Universidad Nacional del Litoral, UBACYT 2000-2002 and Ministerio de Ciencia y Tecnologí BFM2002-04013-C02-02