Landau parameters for nuclear matter using the Skyrme interaction

Landau parameters for nuclear matter are calculated for several Skyrme interactions. Resulting values of G_o and G′_o are in disgreement with empirical values and lead to instability against spin collapse in several cases. A suitable generalization of the interaction is suggested to overcome these difficulties.     

A microbiological six-plate method for the identification of certain antibiotic groups in incurred kidney and muscle samples

A microbiological method was developed for group level identification of antibiotics in incurred kidney and muscle samples from cattle and pigs. The method was composed of six test bacterium-plate growth medium combinations and the result was recorded as a profile of growth inhibition zones. The sample profiles were compared to two sets of references: one constructed with standard antibiotic solution profiles, and the other with these combined with profiles of microbiologically and chemically identified residues from incurred samples. The algorithm employed in profile comparison located the minimal sum of absolute pairwise differences over the tests, with the addition of a number of experimentally observed intra-test criteria. Chemical identification and quantitation of incurred residues was based on liquid chromatography. The method identified penicillin G as a penicillinase sensitive penicillin, enrofloxacin and ciprofloxacin belonging to fluoroquinolone group, and oxytetracycline belonging to tetracycline group. Each of these residues was microbiologically identified below the Maximum Residue Limit (MRL) for kidney tissue. Combining sample profiles with the standard reference data set did not enhance the resolution. Microbiological and chemical identification test results were in good agreement. The results of this study show that a microbiological identification method is a useful tool in preliminary characterisation of antibiotic residues in animal tissues.     

A calculation of some parameters in Migdal's theory of nuclei

Some of the parameters in Migdal's theory of nuclei have been calculated. We used principally Landau's phenomenological approach to obtain the quasi-particle interaction. The energy was calculated by Brueckner's theory. We have used effective interactions which in infinite nuclear matter give the same potential energies in (¹S₀+¹D₂ and (³S₁+³D₁) states as the Hamada-Johnston potential. Other contributions to the binding energy were neglected. The nuclear compressibility K was calculated both from the energy-versus-density curve and from the calculated parameters of Migdal's theory. The results were not in conflict with each other. The values of K obtained were 100–150 MeV, which agrees reasonably well with other calculations in infinite nuclear matter, but they are only about of the values bsed by Migdal and collaborators. We obtained 0.7 for the effective mass and 22–25 MeV for the symmetry energy. The latter result agrees reasonably well with empirical values. An attempt to use the Green function approach in the calculations of the parameters was not successful because of poor convergence, if any.     

Thermogravimetric Analysis of γ-Aminopropyl-trimethoxysilane Adsorbed on Silica Support

When ethylene-vinyl acetate copolymer, EVA, is heated, a two-stage thermal degradation occurs following its melting. The vinyl acetate content of the copolymer was determined to be 43.8% by using TA 2950 and TA 2050 thermogravimetric instruments. TG/FTIR was used to detect the evolved gas. Acetic acid and trans-1-R-4-R'-cyclohexane were the main products evolved from EVA in the first and second stage, respectively. The apparent activation energies were determined for both stages by differential methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pauli principle sum rule and consistency relations for phenomenologically adjusted fermi liquid parameters

The sum rules for the Landau parameters which follow from the Pauli principle and the consistency relations between those parameters and the compressibility of nuclear matter and the symmetry energy are badly violated by the phenomenologically adjusted parameters used up to now. Here we show that all these relations can be nicely fulfilled if the one-pion-exchange and one-rho-exchange contributions are explicitly added to the l = 0 part (zero range) of the original Landau-Migdal interaction. It is important, however, to choose the particle-hole spectrum and the particle-hole interaction consistently.     

On Brueckner's approximation for the magnetic susceptibility of liquid He

The expansion parameters in Brueckner's approximation for the magnetic susceptibility of liquid ³He should be the densities of spin up and spin down particles. The corrected expansion is equivalent to that obtained by Bertsch within the framework of Landau's theory.     

Calculation of Landau's fermi-liquid parameters in pure neutron matter

The Landau parameters F₀, F₁, G₀ and G₁ have been calculated in pure neutron matter including the interaction induced by exchange of density-density and spin-density excitations at densities up to k_F = 2.5 fm^?1. The main effect of the induced interaction is to make the matter more incompressible.     

Investment timing and optimal capacity choice for small hydropower projects

This paper presents a method for assessing small hydropower projects that are subject to uncertain electricity prices. We present a real options-based method with continuous scaling, and we find that there is a unique price limit for initiating the project. If the current electricity price is below this limit it is never optimal to invest, but above this limit investment is made according to the function for optimal size. The connection between the real option and the physical properties of a small hydropower plant is dealt with using a spreadsheet model that performs a technical simulation of the production in a plant, based on all the important choices for such a plant. The main results of the spreadsheet are simulated production size and the investment costs, which are in turn used for finding the value of the real option and the price limit. The method is illustrated on three different Norwegian small hydropower projects.     

Calculation of spin-dependent parameters in the Landau-Migdal theory of nuclei

Contributions to the spin-dependent parameter G'₀, the coefficient of σ₁·σ₂τ₁·τ₂δ(r₁?r₂) in the Fermi-liquid interaction, and to the tensor invariants, are related back to elementary-particle exchange. Once finite-range pion-nucleon interactions are used, almost all of G'₀ comes from theρ-exchange nucleon-nucleon potential. Using modern parameterizations of the strength in the ρ-channel, we find G'₀ to be in the region of 1.5 to 2.4 which agrees well with an empirical determination.