Composite ion exchanger for removal of sodium-24 from mineralizates of biological materials in neutron activation analysis

A composite ion exchanger containing hydrated antimony pentoxide (HAP) in polystyrene-divinylbenzene matrix has been prepared. Its sorption properties with respect to Na, As, Au, Cd, Cu, Ga, Hg, In, K, La, Mn, Mo (Tc), Pd, Pt, Sb, W and Zn have been examined. Sodium is quantitatively retained on the sorbent from 8M HCl solution as well as from a mixture of conc. H₂SO₄+ conc. HNO₃+H₂O (1+1+2). As, W, Cd and Sb are partially retained, while the remaining elements are not retained and can be quantitatively eluted. The composite ion exchanger is stable to oxidizing acid media and it can be directly applied to separation of²⁴Na from mineralizates of neutron-irradiated biological materials.     

Preconcentration of some metals using metalfix chelamine resin prior to ICP-AES analysis

Preconcentration and separation of Ni, Pb and Cd have been investigated using the metalfix chelamine resin prior to inductively coupled plasma – atomic emission spectrometry (ICP-AES) under various experimental conditions. The recoveries of the analytes obtained with 95% confidence level were 92 ± 1% for Ni, 100 ± 4% for Pb and 93 ± 3% for Cd.     

Hydrogen and oxygen concentration analysis of porous silicon

Elastic recoil detection and Rutherford backscattering spectrometry combined with the nuclear reaction analysis method have been applied for the determination of oxygen, hydrogen and carbon concentration depth profiles of aged p⁺-type porous Si layers of different low and medium porosities. The plan view and cross-section scanning electron microscopy images have provided with information about both the diameter and silicon skeleton structure of the pores. The concentration depth profiles reveal the existence of a non-homogeneous subsurface porous film several hundred nanometers thick for all the studied samples. Differences in the atomic composition among low and medium porosity layers and the possible origin of various impurities are discussed. The maximum H content in PSi has been observed at the depth of 200–600 nm, while the highest oxygen concentration is typical of 200 nm thick subsurface layers. The highest obtained ratio of H/Si atomic concentrations reaches the value of 2 for the PSi samples with porosity P of 66%, comparing to N_H/N_Si = 0.27 in the case of P = 25% PSi.     

Examination of new chiral smectics with four aromatic rings

This paper presents the results of the study of four chiral mesogens with the acronym (4X₁X₂). The investigated compounds might be of interest for use as components of multicomponent mixtures useful in technical devices. The compounds have high chemical stability. Their mesomorphic properties were tested by means of polarizing optical microscopy and differential scanning calorimetry. The helical pitch of the prepared compounds and mixtures was estimated using the selective reflection method. Their phase smectic layer structure and usefulness for formulation of multicomponent antiferroelectric mixtures were then reported.     

Complements of Grassmann substructures in projective Grassmannians

We prove that a projective Grassmannian can be recovered from the complement of one of its Grassmann substructures. Even more, the underlying projective space with the interval of its distinguished subspaces can be recovered.     

Reversible photochromic effects in doped single crystals of bismuth germanium (Bi12GeO20) and bismuth silicon oxide (Bi12SiO20)

Absorption of Bi₁₂GeO₂₀ and Bi₁₂SiO₂₀ single crystals doped with Mn and Cr were investigated before and after illumination with visible light. Pronounced photochromic effects were found. The effects are explained in terms of light induced charge transfer Mn⁴⁺→Mn⁵⁺ and Cr³⁺→Cr²⁺.     

Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium

Neutron-rich isotopes of palladium were produced via the fission of²³⁸U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyväskylä. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For¹¹⁴Pd and¹¹⁶Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of¹¹⁸Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT _1/2=1.9±0.1 s andQ _β=4.0±0.2 MeV. The decay schemes of¹¹⁴Pd,¹¹⁶Pd and¹¹⁸Pd include — respectively — two, two and four 0⁺→1⁺ Gamow-Teller beta transitions with logft values between 4.1 and 5.1. The strength of these transitions is discussed in terms of the extreme single particle shell model with pairing and the spherical proton-neutron quasiparticle random phase approximation. The possible role of deformation is considered using a shell correction method. Predictions for the decay properties of the as yet unobserved¹²⁰Pd are given.     

Normal modes in the vicinity of the brillouin zone center of tightly bound units in Bi12GeO20 and Bi12SiO20

From Raman data and a group-theoretical analysis, we deduce that in Bi₁₂GeO₂₀ and Bi₁₂SiO₂₀ there are four weakly bound oxygen atoms and a tightly bound unit MO₄, where M = Ge or Si. Some normal modes of the tightly bound units are identified in Raman and in infrared reflection data. The kinds of interatomic binding forces in these crystals are determined. The results are compared with structure data determined by X-ray scattering.     

Consequences of the dynamical approach to the nuclear spin relaxation induced by molecular rotations in an external magnetic field

The evolution of two nuclear spins, interacting between themselves and with an external magnetic field, and situated on molecules of a fluid, is treated, under the assumption of the mixing property of molecular rotations, by the method of limit theorems for random differential equations. The limit diffusion behaviour of the system is derived and the results on relaxation times and (non-thermodynamical) equilibrium are obtained and discussed.