Overcoming the boundary effects in surface spline interpolation

Surface spline interpolation when the domain is all of R^d isknown to converge much faster to the data function f than inthe case when the domain is the unit ball. This difference isunderstood to be due to boundary effects which, as will be shown,also affect the size of the surface spline's coefficients. Wepropose a modified form of surface spline interpolation which,to a great extent, overcomes these boundary effects. This modifiedsurface spline interpolant uses only the values of f at thegiven interpolation points.     

On the field dependence of the interface energy in AF/FM bilayers

In the investigations of antiferromagnetic (AF)/ferromagnetic (FM) bilayer samples, often distinct experimental techniques yield different values for the measured exchange anisotropy field (H_E). We propose that the observed discrepancy may be accounted in part by the dependence of the unidirectional anisotropy with the value of the externally applied cooling field (h). Using a simple microscopic model for representing the AF/FM interface, which incorporates the effect of interface roughness, we show that the interface energy between the AF and FM layer indeed varies with h, as recently observed in anisotropic magnetoresistance measurements, lending support to our proposal.     

Influence of gamma-radiation on the behavior of humic acids from peat and tropical soil

HA samples obtained from sedimentary soil and peat in aqueous media were irradiated with -rays, in the dose range from 10 to 100 kGy, with the aim to study the chemical differences in the material before and after irradiation. The materials were analyzed by elemental analysis, UV/Vis spectroscopy (E₄/E₆ ratio), functional groups content, gel permeation chromatography (GPC) and IR spectroscopy. Gas chromatography was utilized to analyze the generated gases. Humic acids from peat and from soil are quite different. After irradiation an increasing in the average molecular weight was observed which depends on the material characteristics. There was observed also a release of CO₂ upon irradiation. By infrared spectroscopy, with the help of computer simulations, the characteristic bands of ester C=O and C–O stretchings reinforces the contribution of carboxylic groups in the condensation process.     

Kinetic study of the reaction between hydroxylated polybutadienes and isocyanates. 1. Reaction with tolylene diisocyanate (TDI)

A comparative kinetic study of the reaction of three different hydroxylated liquid polybutadienes (M _n ? 3000) — R - 45M, R-45HT, and H-034—and tolylene diisocyanate (TDI), was carried out in toluene solution. An analytical method was used to follow the kinetics of the reactions at four different temperatures. The reactions presented an apparent second-order rate law. In the second-order plots, a discontinuity was observed. The R-45M polybutadiene was about twice more reactive than R-45HT and H-034; these latter two polybutadienes presented similar reactivities.     

Calibration of the LNMRI Secondary Standard Ionization Chamber for 131I capsules used in nuclear medicine

The radionuclide ¹³¹I has been increasingly used in nuclear medicine therapy procedures. Nowadays, the ¹³¹I source administered to the patient is manufactured in two different geometries: solution and capsules. The purpose of this study is the accurate measurement of the activity present in a ¹³¹I capsule without destroys it. The methodology to determine the capsules activity is to obtain the calibration factor of an IG12 secondary standard activity measurement system based on the IG12 well-type ionization chamber set up at Brazilian national metrology laboratory for ionizing radiation (LNMRI) of institute of radiation protection and dosimetry (IRD).The result obtained, 6.4670?±?0.0381?×?10^?18?A?Bq^?1, is quite similar to the calibration factor of the ¹³¹I solution contained in the standard ampoule geometry, 6.4515?±?0.0368?×?10^?18?A?Bq^?1. After obtaining the calibration factor it was used to measure ¹³¹I therapy capsules in order to check the performance of radionuclide calibrators of some Brazilian nuclear medicine centers.