Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

Isolation of NO(3)(-)-N as 1-phenylazo-2-naphthol (Sudan-1) for measurement of delta(15)N

The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd.     

Combinatorics of reliability Monte Carlo

We study one class of unbiased Monte Carlo estimators for system reliability, avoiding the rare event difficulty. This class is closely related to the system combinatorics and contains unique “extreme” members, having the minimum and maximum relative error. Some known Monte Carlo heuristics for network reliability, including fully polynomial cases, are of this type. ©1999 John Wiley & Sons, Inc. Random Struct. Alg., 14: 329–343, 1999     

Observation of solitary elastic surface pulses

The formation of solitary elastic surface pulses from laser-generated pulselike initial conditions is reported. The nonlinearity of the medium is compensated by both normal dispersion and anomalous dispersion, which were realized by coating isotropic fused silica by a metal and titanium nitride film, respectively. As an anisotropic material, silicon covered with an oxide layer was studied. The experimental results agree with numerical simulations carried out with a nonlocal evolution equation, which describes nonlinear propagation of surface acoustic waves in a dispersive medium.     

A counterexample to the Bishop-Phelps Theorem in complex spaces

The Bishop-Phelps Theorem asserts that the set of functionals which attain the maximum value on a closed bounded convex subsetS of a real Banach spaceX is norm dense inX ^*. We show that this statement cannot be extended to general complex Banach spaces by constructing a closed bounded convex set with no support points.     

Analysis of Heterogeneous-Homogeneous Model of Oxidative Coupling of Methane Using Kinetic Scheme Reduction Procedure

Kinetics and Catalysis - The validity of using kinetic scheme reduction procedures to compare various kinetic models as well as the values of kinetic parameters of individual steps present in the...     

Parity-nonconservation effect in the helicities of conversion electrons accompanying the (5/2)− → (5/2)+ nuclear transition in the 229Pa nucleus

The ground state of the ²²⁹Pa nucleus is a 5/2^± doublet with a splitting energy of 220±50 eV. Such levels are peculiar to nuclei in the mass region around A=225 that are characterized by octupole deformations. A direct observation of P-odd effects in this system is of great interest because this can furnish information about the parity-nonconserving nucleon-nucleon potential. The transition between the two doublet states of opposite parities proceeds predominantly through internal conversion; therefore, P-odd mixing can be explored by studying the helicities of the conversion electron. It is shown that the helicities of the 6s _1/2, 6p _1/2, and 6p _3/2 conversion electrons are about 1%, which makes it possible to perform experiments aimed at determining the parameters of the effective parity-nonconserving nuclear potential.