Release of 3H and 14C during sampling and speciation in activated concrete

Journal of Radioanalytical and Nuclear Chemistry - Characterisation of contaminated and activated decommissioning waste require sampling of the studied material for the analysis of different...     

Solving monotone inclusions with linear multi-step methods

 In this paper a new class of proximal-like algorithms for solving monotone inclusions of the form T(x)∋0 is derived. It is obtained by applying linear multi-step methods (LMM) of numerical integration in order to solve the differential inclusion , which can be viewed as a generalization of the steepest decent method for a convex function. It is proved that under suitable conditions on the parameters of the LMM, the generated sequence converges weakly to a point in the solution set T ⁻¹ (0). The LMM is very similar to the classical proximal point algorithm in that both are based on approximately evaluating the resolvants of T. Consequently, LMM can be used to derive multi-step versions of many of the optimization methods based on the classical proximal point algorithm. The convergence analysis allows errors in the computation of the iterates, and two different error criteria are analyzed, namely, the classical scheme with summable errors, and a recently proposed more constructive criterion. Received: April 2001 / Accepted: November 2002 Published online: February 14, 2003 Key Words. proximal point algorithm – monotone operator – numerical integration – strong stability – relative error criterion Mathematics Subject Classification (1991): 20E28, 20G40, 20C20     

Metamorphic growth of tensile strained GaInP on GaAs substrate

Optical and structural properties of tensile strained graded Ga_xIn_1−xP buffers grown on GaAs substrate have been studied by photoluminescence, X-ray diffraction, atomic force microscopy, and scanning electron microscopy measurements. The Ga composition in the graded buffer layers was varied from x=0.51 (lattice matched to GaAs) to x=0.66 (1% lattice mismatch to GaAs). The optimal growth temperature for the graded buffer layer was found to be about 80–100 °C lower than that for the lattice matched GaInP growth. The photoluminescence intensity and surface smoothness of the Ga_0.66In_0.34P layer grown on top of the graded buffer were strongly enhanced by temperature optimization. The relaxation of tensile GaInP was found to be highly anisotropic. A 1.5 μm thick graded buffer led to a 92% average relaxation and a room temperature photoluminescence peak wavelength of 596 nm.     

Optical properties of thermally responsive amphiphilic gold nanoparticles protected with polymers

Amphiphilic thermally responsive gold nanoparticles have been prepared by protecting the particles with both polystyrene, PS, and poly(N-isopropylacrylamide), PNIPAM, chains. Particles form a monolayer on a water surface in a Langmuir trough, and according to in situ spectroscopic measurements, the surface plasmon resonance, SPR, band undergoes a blue-shift during the monolayer compression. The compression-induced blue-shift is related to a change in the conformation of tethered PNIPAM chains; the phenomenon is discussed on the basis of Mie-Drude theory. In contrast, a red-shift in the SPR of the multilayers of the same nanoparticles transferred at different temperatures has been observed with increasing the deposition cycle, attributed to the presence of a weak interparticle coupling in the multilayer.     

Fast gas chromatography/mass spectrometric assay for the validated quantitative determination of methadone and the primary metabolite EDDP in whole blood

A toxicological analysis was developed and validated for simultaneous screening and quantification of methadone (METH) and its primary metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP). The method employs microscale liquid-liquid extraction (microLLE) and direct injection of a separated aliquot of the organic layer into a gas chromatography/mass spectrometric (GC/MS) system without any other pre-treatment stages. A fast GC/MS runtime (total 5.8 min; METH, Rt = 3.55 min; EDDP, Rt = 3.40 min) combined with rapid sample preparation allowed cost-efficient and routinely applicable performance with a low amount of manual work. The validated parameters included: linearity (25-1000 ng mL(-1) both; R(METH)2 = 0.998 and R(EDDP)2 = 0.997), accuracy (Bias(METH): from -0.05 to 11.3%, Bias(EDDP): from 1.11 to 4.37%); intra and inter-assay precision (RSD(METH): from 2.4 to 3.9%, from 4.89 to 10.3%; RSD(EDDP): from 4.50 to 6.20%, from 4.57 to 15.2%), extraction efficiency (METH = 95.5%; EDDP = 90.6%), LOQ(Meth,EDDP) = 25 ng mL(-1). Samples were stable for at least 25 h and no selectivity problems or baseline interference were observed. The method should be applicable for identifying and quantitative confirmation of possible misuse and/or illegal use of METH in toxicological cases.     

Natural patterns of energy dispersal

Universal patterns such as power-law dependences, skewed distributions, tree-like structures, networks and spirals are associated with energy dispersal processes using the principle of least action. Also ubiquitous temporal courses such as sigmoid growth, bifurcations and chaos are ascribed to the decrease of free energy in the least time. Moreover, emergence of natural standards such as the common genetic code and chirality consensus of amino acids are understood to follow from the quest to maximize the dispersal of energy. Many mathematical functions that model natural patterns and processes are found as approximations of the evolutionary equation of motion that has been derived from statistical physics of open systems. The evolutionary processes can be described as flows of energy that run from high energy sources to low energy sinks in the least time. However, the equation of evolution cannot be solved in general because the flows of energy and their driving forces are inseparable. Since the energy of the system keeps changing, the paths of evolution cannot be integrated from a given initial state to a final state. Although evolutionary courses of these non-Hamiltonian systems with two or more alternative ways of dissipation cannot be predicted, the flows of energy will search and naturally select paths of least action, known as geodesics, to consume free energy in the least time. The scale-invariant natural patterns follow from this natural law that impinges on processes at all scales of space and time.     

Origin of hysteresis in a proximity josephson junction

We investigate hysteresis in the transport properties of superconductor-normal-metal-superconductor (S-N-S) junctions at low temperatures by measuring directly the electron temperature in the normal metal. Our results demonstrate unambiguously that the hysteresis results from an increase of the normal-metal electron temperature once the junction switches to the resistive state. In our geometry, the electron temperature increase is governed by the thermal resistance of the superconducting electrodes of the junction.     

Mesoscopic photon heat transistor

We show that the heat transport between two bodies, mediated by electromagnetic fluctuations, can be controlled with an intermediate quantum circuit--leading to the device concept of a mesoscopic photon heat transistor (MPHT). Our theoretical analysis is based on a novel Meir-Wingreen-Landauer-type of conductance formula, which gives the photonic heat current through an arbitrary circuit element coupled to two dissipative reservoirs at finite temperatures. As an illustration we present an exact solution for the case when the intermediate circuit can be described as an electromagnetic resonator. We discuss in detail how the MPHT can be implemented experimentally in terms of a flux-controlled SQUID circuit.     

An existence result for superparabolic functions

We study superparabolic functions related to nonlinear parabolic equations. They are defined by means of a parabolic comparison principle with respect to solutions. We show that every superparabolic function satisfies the equation with a positive Radon measure on the right-hand side, and conversely, for every finite positive Radon measure there exists a superparabolic function which is solution to the corresponding equation with measure data.