The Unified Interaction Model (UNIM) is reformulated to include recent advances in the understanding of the role of spatial correlations leading to localized and delocalized recombination in LiF:Mg,Ti and to the correlation between the optical absorption bands and the glow peaks of composite peak 5. The reformulated UNIM is applied to the simulation of the linear/supralinear dose response and to calculations of the dose threshold, Dc, of supralinear behaviour and to the deviations from linearity in the dose range from 0.1 to 10 Gy.

Conventional spectral probes of quantum chaos require eigenvalues, and sometimes, eigenvectors of the quantum Hamiltonian. This involves computationally expensive diagonalization procedures. We test whether an unsupervised neural network can detect quantum chaos directly from the Hamiltonian matrix. We use a single-body Hamiltonian with an underlying random graph structure and random coupling constants, with a parameter that determines the randomness of the graph. The spectral analysis shows that increasing the amount of randomness in the underlying graph results in a transition from integrable spectral statistics to chaotic ones. We show that the same transition can be detected via unsupervised neural networks, or more specifically, self-organizing maps by feeding the Hamiltonian matrix directly into the neural network, without any diagonalization procedure.

The effect of natural rapid cooling and oven slow cooling on the precision of thermoluminescence measurements of LiF:Mg,Ti is investigated. Three separate series of measurements resulted in average precisions of 5.1 and 5.0%, respectively. However, the highest precision of 1.7% (1 SD) was achieved for an oven-cooled material.

The quantum phase transition observed experimentally in two-dimensional (2D) electron systems has been a subject of theoretical and experimental studies for almost 30 years. We suggest Gaussian approximation to the mean-field theory of the second-order phase transition to explain the experimental data. Our approach explains self-consistently the universal value of the critical exponent 3/2 (found after scaling measured resistivities on both sides of the transition as a function of temperature) as the result of the divergence of the correlation length when the electron density approaches the critical value. We also provide numerical evidence for the stretched exponential temperature dependence of the metallic phase's resistivities in a wide range of temperatures and show that it leads to correct qualitative results. Finally, we interpret the phase diagram on the density-temperature plane exhibiting the quantum critical point, quantum critical trajectory and two crossover lines. Our research presents a theoretical description of the seminal experimental results.

A seeming contradiction in the prediction of the spatially correlated trapping center/luminescent center model applied to LiF:Mg,Ti has been the linear/supralinear behavior of the dose response of glow peak 5a. In the TC/LC model, the localised electron-hole recombination, giving rise to glow peak 5a, is expected to result in an extended region of linear dose response. Deconvolution of the glow curves based on first order kinetic peak shapes results, however, in a dose response of peak 5a, which closely resembles the linear/supralinear dose response of peak 5. It is demonstrated herein that when general-order kinetics peak shapes are used for peak 5a, the analysis can result in a linear dose response of glow peak 5a up to dose levels as high as 30 Gy, well beyond the 1-Gy onset of supralinearity of peak 5. The extended linearity suggests a resolution of the contradiction.

The computerised deconvolution of thermoluminescence glow curves into component glow peaks is discussed in detail with special emphasis on advances of the subject post 2013. A plethora of computer codes have been developed using models based on first-order kinetics, second-orders kinetics, interactive traps and continuous distributions of activation energies. The glow curves of several materials are displayed and discussed along with new and improved dosimetric applications:precision effects of heating rate, heavy charged particles, mixed field α/ϒ dosimetry, fading and dose-response linearity. Finally recommendations are made for future efforts.

We solve analytically a three-dimensional Poisson equation for the potential produced by two coaxial metallic contacts at the edges of the Corbino disk. It is assumed that there is a finite tangential current, while the radial current is absent. This solution is compared with a solution of the two-dimensional problem for conducting Corbino disk. We calculate the magnetic dipole moment of Corbino disk and compare our results with the case of two-dimensional Coulomb distribution of the potential which is realized in Corbino disk in the presence of the radial current. We also discuss the application of torque magnetometry to study metal-insulator transition, in particular, in the quantum Hall regime.

An experimental investigation into the possibility of dose-rate effects and wall scatter in the thermoluminescent response of LiF:Mg,Ti (TLD-100) was carried out. The investigation was motivated by theoretical simulations predicting the possible presence of dose-rate effects coupled with the lack of detailed experimental studies. The dose rate was varied by changing the source to sample distance, by the use of attenuators, sources of 137Cs of various activities, filtration and the construction of identical geometrical irradiators of Teflon and stainless steel. Four levels of dose in the linear dose response region were studied at 10-2 Gy, 1.5 × 10-2 Gy, 0.1 Gy and 0.5 Gy to avoid complications in interpretation due to supralinearity above 1 Gy. At the dose of 1.5 × 10-2 Gy, the dose rate was varied by five orders of magnitude from 4.9 × 10-3 Gy s-1 to 4.9 × 10-8 Gy s-1. At the other levels of dose, a one to two orders of magnitude in dose rate was achieved. Within the measurement uncertainty of 5-10%, no dose-rate effects were observed in any of the experimental measurements and no changes in the shape of the glow curve were observed. The maximum wall scatter effect (Teflon to stainless steel) was measured at ~8% within the experimental uncertainty and well below expectations. The results are encouraging with respect to the accurate and reproducible use of LiF:Mg,Ti under various experimental conditions of irradiation.

Self-organizing neural networks are used to analyze uncorrelated white noises of different distribution types (normal, triangular, and uniform). The artificially generated noises are analyzed by clustering the measured time signal sequence samples without its preprocessing. Using this approach, we analyze, for the first time, the current noise produced by a sliding "Wigner-crystal"-like structure in the insulating phase of a 2D electron system in silicon. The possibilities of using the method for analyzing and comparing experimental data obtained by observing various effects in solid-state physics and simulated numerical data using theoretical models are discussed.

Using a density functional theory approach with the B3LYP and PBE0 functionals and the 6-G31(d,p) basic set, we simulate the partial vibrational spectra of isolated H2O and C-60 molecules, of a periodic H2O structure (ice XI) and of a single H2O molecule encaged in a buckyball (H2O@C-60). A very significant result of the H2O@C-60 calculation is that the C-atoms of the hosting fullerene lattice (which for pure C-60 are subjected to a vibrational frequency spectrum that terminates at similar to 1600 cm(-1)) were found to participate in the high frequency modes at similar to 3800 cm(-1) of the H2O guest, indicating a coupling between the modes of the two sub systems. The effect of temperature between 5 and 300 K on the atomic kinetic energies, Ke(X) (X = C,O,H) were also deduced. The calculated Ke(C) in C-60 using B3LYP was found to be in better agreement with experiment than that of PBE0. Surprisingly, the zero point Ke(H) in the hydrogen bonds (HBs) free H2O@C-60, as well as its T-dependence, were found to be nearly the same as those of the HBs containing condensed bulks of H2O, namely ice and liquid water. This result is at variance with that of other H2O confining systems measured using deep inelastic neutron scattering, where anomalous Ke(H) values were generically observed. An attempt to understand this behavior is made in view of the observed coupling between the caged H2O modes and those of the C-60 host.

The cooling rate to room temperature following the 400°C pre-irradiation anneal is known to affect the thermoluminescent properties of LiF:Mg,Ti (TLD-100) as a result of migration and clustering of defects during the cooling down process. In this investigation the dose response over an extended dose range from 0.01 to 7000 Gy in both naturally cooled and the much slower furnace-cooled samples has been measured. Glow curve deconvolution based on first-order kinetics is employed to extract the dose response of the various glow peaks. Of especial interest is the behaviour of glow peaks 4, 5a and 5 as a function of dose. The idea is to modify the supralinear dose response of peak 5 from 1 to 30 Gy to a linear behaviour. This dose range is important for clinical therapy and a linear dose response is of substantial advantage leading to both improved accuracy and precision.

Sand spots, attached to a copper ball surface by means of polyvinyl acetate adhesive and distributed over the surface with areal density that ranges between one spot per 1.18 cm(2) (for low-density spots) and one spot per 0.51 cm(2) (for high-density spots), serve as a temporary heat transfer enhancer during the quenching in liquid nitrogen. Highest heat flux densities, achieved during quenching, lie in the range 10.8 to 20.2 W/cm(2), depending on the sand layer structure. Application of the temporary enhancer increases an amount of heat, evacuated by highly effective nucleate and transition boiling, by factor of 4.5 as compared with the bare sample. The process of sand layer preparation, data acquisition peculiarities, relationship between heat exchange efficiency and the spots areal density, along with sand grit size are discussed in this paper.

We perform numerical studies of strongly interacting electrons on a two-dimensional lattice in the Hartree-Fock approximation. The results clearly show significant ordering of the positions of the electrons with decreasing temperature signaling the formation of a two-dimensional Wigner crystal. The degree of order as a function of temperature is in a good qualitative agreement with experimental results for the threshold voltage at which the depinning of the crystal occurs. In the limit of very strong electron-electron interactions, the ordering of the electrons becomes almost perfect.

The effect of temperature on the mean kinetic energy of Oxygen, Ke(O), in silica hydrogel (constituting of water confined in a silica Xerogel matrix) was computed between 5 and 325 K. The results are higher by up to 40% than those deduced from a recent deep inelastic neutron scattering (DINS) measurement. Note that when the mean kinetic energy of Hydrogen Ke(H) was computed using the same method a good agreement was obtained with the DINS measurement. This seems to indicate that the measured Ke(O) values are strongly underestimated due to the DINS method of analysis of the n-scattering intensities as discussed in the text.

We study a system which can be realized in a dirty, gapless superconductor in which time-reversal symmetry for orbital motion is broken, but spin-rotation symmetry is intact. We present a phase diagram in a phase-space of spin Hall conductance and energy of quasiparticles Δ. It exhibits a direct transition between two insulating phases with quantized Hall conductances of zero and two for the conserved quasiparticles when Δ = 0. The ener-gy of the quasiparticles acts as a relevant symmetry-breaking field at the critical point, which splits the direct transition into two conventional plateau transitions. We use updated correct values of the critical exponents to define these two critical lines as ϵ∼±Δ6/7.

The possibility of using a frost layer, created on the surface of a sample that undergoes cryogenic treatment, as a heat transfer enhancer was recently studied. This layer grows on the preliminary cooled sample surface as a result of its contact with moist air flow prior to its immersion into liquid nitrogen. A significant increase in the outflow heat flux (up to 12.8 times), or, alternatively, a cooling time shortening, in comparison with the bare sample was found. A detailed description of the frost layer development along with the influence of the thickness of the layer on the efficiency of the cooling process, as well as environmental parameters that affect the thickness itself is presented in the paper.

We generalize the seminal Julliere formula for the tunnel magnetoresistance (TMR) of a spin valve to include the spin memory loss of an electron in course of travel between the electrodes. This generalized version applies locally and for arbitrary mechanism of the spin dephasing. On the basis of the generalized formula we demonstrate that the distribution of TMR along the surface of magnetized electrodes is very broad and includes the sign reversals. (C) 2015 Elsevier B.V. All rights reserved.

Motivated by recent experiments, where the tunnel magnetoresitance (TMR) of a spin valve was measured locally, we theoretically study the distribution of TMR along the surface of magnetized electrodes. We show that, even in the absence of interfacial effects (like hybridization due to donor and acceptor molecules), this distribution is very broad, and the portion of area with negative TMR is appreciable even if on average the TMR is positive. The origin of the local sign reversal is quantum interference of subsequent spin-rotation amplitudes in the course of incoherent transport of carriers between the source and the drain. We find the distribution of local TMR exactly by drawing upon formal similarity between evolution of spinors in time and of the reflection coefficient along a 1D chain in the Anderson model. The results obtained are confirmed by the numerical simulations.

In some industrial activities, the use of permanent heat transfer enhancements such as metal coating, pins, and grooves in cryogenic treatment is quite problematic. Such permanent heat transfer enhancers were replaced with temporary enhancers made of different crystalline materials, here focusing on NaCl, MgSO4·7H2O, CaCl2·2H2O, and C6H5Na3O7·2H2O, which were used during quenching of the sample in the cryogenic liquid, i.e., nitrogen. The time required for sample cooling until the liquid nitrogen saturation temperature is reached decreases significantly when a crystalline coating is applied. The dependence of the cooling time on temporary coating creation parameters such as solution concentration, initial temperature of the sample, and solution spreading time is discussed.

Enhanced boiling conditions during quenching by use of frost as a temporary heat transfer enhancer were determined experimentally. The frost coating was obtained by the application of air moisture on the previously cooled surface of a product.We found that heat transfer intensity can be adjusted by the change in coating structure characteristics. These characteristics, on the other hand, depend on frost formation parameters such as a temperature of the preliminarily cooled sample, an air temperature, a relative humidity, an air movement velocity and a frost formation time range. During the subsequent sample quenching in liquid nitrogen, a heat exchange enhancement was 10.2-12.4 when cooling down to the nitrogen's saturation temperature. By limiting the cooling temperature within the range of 90 K-110 K, the additional heat exchange enhancement increased 1.4-1.5 times. (C) 2012 Elsevier Ltd. All rights reserved.