The use of radioanalytical techniques to study intermediate energy,relativistic, and ultra-relativistic nuclear collisions

The use of radioanalytical techniques to study heavy ion induced nuclear reactions offers some distinct advantages over conventional physical techniques. Among these are (a) unit Z and A resultion in detecting the reaction products (b) high sensitivity for low probability events (c) lack of low energy thresholds or cutoffs in measuring reactcion product energy spectcra (d) economical use of accelerator time and (e) simple, portable experimental apparatus allowing broad survey measurements of reaction mechanisms at a variety of nuclear particle accelerators. We describe examples of these advantages from our research in nuclear chemistry.     

Dynamic capacity and mass transfer for removal of Na+ by a composite hydrated antimony pentoxide-organic ion exchanger

The removal of Na⁺ by a composite hydrated antimony pentoxide-sulfonated phenol-formaldehyde ion exchanger (C-HAP) from 4M HCl was studied using the breakthrough technique. The dynamic removal capacity for Na⁺ from 4M HCl is 12.3 mg Na⁺/g and 9.87 mg Na⁺/g at 0.2 ml/min and 0.8 ml/min, respectively. Height equivalent to a theoretical plate varies almost linearly with flow rate indicating particle diffusion control.     

Rotordynamical simulations of a fibre refiner during production

A key component in panel board production is the refiner, whose task is to break raw cellulose wood chips into slender fibres, done by a relative angular motion between stator and rotor. The main problem in predicting the dynamics of these machines is to model the complicated fibre breaking process, since the refining process leads to a three-phase flow (solid wood, water and steam) between the stator and rotor. By modelling the rotor as a rigid body, the process can only contribute by a resulting force and a resulting moment. Through this approach and axial force measurements, it has been shown that the refining process can be treated as a time dependent stiffness matrix and external load. The objective for this paper is to predict and explain dynamical characteristics of fibre refiners during production in such a way that the results can be used already at early stages of the product development process. Two different pressure distribution cases are studied, i.e. one axisymmetric with only radial variations and one non-axisymmetric. It is found that the axisymmetric case only excited forward modes, while the non-axisymmetric case excited all modes. The time dependent stiffness matrix resulted in unstable domains, but also in stable domains with intermittent high amplitudes.     

Investigation of proton-proton short-range correlations via the 12C(e,e'pp) reaction

We investigated simultaneously the 12C(e,e'p) and 12C(e,e'pp) reactions at Q2=2 (GeV/c)2, xB=1.2, and in an (e, e'p) missing-momentum range from 300 to 600 MeV/c. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For (9.5+/-2)% of the 12C(e,e'p) events, a recoiling partner proton was observed back-to-back to the 12C(e,e'p) missing-momentum vector, an experimental signature of correlations.     

Uncertainty analysis of correlated stability constants

Every attempt of using a computer to model reality has two main uncertainties: the conceptual uncertainty and the data uncertainty. The conceptual uncertainty deals with the choice of model selected for the simulation and the data uncertainty is about the precision and accuracy of the input data. They are often determined experimentally and may thus be encumbered by a number of uncertainties. Normally when treating uncertainties in input data these data are treated as independent variables. However, since many of these parameters are determined together they are actually correlated. This paper focuses on chemical stability constants, a most important parameter for chemical calculations based on speciation. Commonly in the literature they are at best given with an uncertainty interval. We propose to also give the covariance matrix thus giving the opportunity to really assess correlations. In addition we discuss the effect of these correlations on speciations.     

Optimum group selection in multi-radionuclide determinations

A possible way to quantify inter-isotope and inter-element interferences in high resolution gamma-ray spectroscopy is described and possible future developments outlined. The use of a version of simulated annealing and the Metropolis algorithm in finding optimum element groupings is described and some results from tests of this procedure are given.     

Semicarbazide-functionalized Si(111) surfaces for the site-specific immobilization of peptides

The covalent attachment of semicarbazide-functionalized layers to hydrogen-terminated Si(111) surfaces is reported. The surface modification, based on the photoinduced hydrosilylation of a Si(111) surface with protected semicarbazide-functionalized alkenes, was investigated by means of X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM). The removal of the protecting group yielded a semicarbazide-terminated monolayer which was reacted with peptides bearing a glyoxylyl group for site-specific alpha-oxo semicarbazone ligation.     

Compton scattering from the deuteron and extracted neutron polarizabilities

Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45 degrees, 125 degrees, and 135 degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N)+beta(N)=17.4+/-3.7 and alpha(N)-beta(N)=6.4+/-2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p)-beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n)=8.8+/-2.4(total)+/-3.0(model) and beta(n)=6.5-/+2.4(total)-/+3.0(model), respectively.     

Quasielastic 3He(e,e'p)2H reaction at Q2 = 1.5 GeV2 for recoil momenta up to 1 GeV/c

We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.     

Was natural β radioactivity of carbon-14 the origin of optical one-handedness in life?

¹⁴C labelled solid D- and L-leucine decomposes with significantly different rates by auto-radiolysis. The -decarboxylation ratio (10³xCO₂%)_D/(10³xCO₂%)_L was found to be (2.3±0.2)/(1.2±0.2)= 1.9±0.5 for samples kept in evacuated tubes at room temperature for 1 year /sp. activity: 0.9 MBq g^–1; -dose: 224 Gy/. EPR indicates a 10% higher radical concentration in the stored solid D-leucine samples than in L-leucine. The relevance of these results to the question of origin of optical onehandedness in life, is discussed.