Sauna,sweat and science II – do we sweat what we drink?

ABSTRACT

Inspired by a previous ‘Sauna, sweat and science’ study [Zech et al. Isot Environ Health Stud. 2015;51(3):439–447] and out of curiosity and enthusiasm for stable isotope and sauna research we aimed at answering the question ‘do we sweat (isotopically) what we drink’? We, therefore, pulse-labelled five test persons in a sauna experiment with beverages that were ²H-enriched at about +25,600?‰. Sweat samples were collected during six sauna rounds and the hydrogen isotope composition δ²H_sweat was determined using an isotope ratio mass spectrometer. Before pulse labelling, δ²H_sweat – reflecting by approximation body water – ranged from –32 to –22?‰. This is ～35?‰ enriched compared to usual mid-European drinking water and can be explained with hydrogen-bearing food as well as with the respiratory loss of ²H-depleted vapour. The absence of a clearly detectable ²H pulse in sweat after pulse labelling and δ²H_sweat results of ≤+250?‰ due to a fast ²H equilibration with body water are moreover a clearly negative answer to our research question also in a short-term consideration. Given that the recovery of the tracer based on an isotope mass balance calculation is clearly below 100?%, we finally answer the question ‘where did the rest of the tracer go?’     

Piezoelectric properties of non-uniform polymeric structures under static load

ABSTRACT

Piezo-electrical properties of structures containing ‘soft’ and ‘hard’ dielectric layers with charge stored on the interfaces are described in the paper. The piezo-activation process of structures containing layers with gas voids by partial discharges is described. The influence of the mechanical properties of the ‘soft’ layer on the piezoelectric parameter d₃₃ value and its dependence on the static pressure p are also discussed. It was found experimentally, that for the fibrous type of ‘soft’ dielectric layer, the dependence of the piezoelectric parameter d₃₃ (p) can be described by the function d₃₃ ÷ p^?n, where n ≤ 1.     

Spatial variability of 2H and 18O composition of meteoric freshwater lakes in Scotland

Coastal regions, and in particular islands where precipitation from clouds formed out at sea occurs for the first time, are prime candidates for regions where ²H and ¹⁸O composition of precipitation will deviate significantly from the global mean geographic and physiographic trends of vapour-transport patterns. The results reported here are the outcome of a study that aimed to test this hypothesis by ‘isotopographically’ mapping the characteristic δ²H and δ¹⁸O signatures of Scottish freshwaters. The resulting isotope abundance landscapes or ‘isoscapes’ will underpin studies aiming to authenticate origin of Scottish produce but may also offer a baseline against which environmental changes could be assessed. Between April 2011 and May 2012 freshwater samples were collected from 127 different freshwater lochs and reservoirs across Scotland, and analysis results were compared to precipitation data provided by the British Geological Survey. Here we present the results of the ²H and ¹⁸O analyses of these water samples as well as the first detailed Scotland freshwater isoscapes with a grid resolution of about 5 × 5 km (0.05 degrees).     

The use of fast field cycling to evaluate the time domain relaxation of starches from tropical fruit seeds

ABSTRACT

A proton NMR relaxation study of the molecular dynamics in flour samples of ‘Eugenia uniflora’ (‘Pitanga’), ’Citrus reticulate’ (‘Tangerine’), ‘Prunus persica’ (‘Peach’), ‘Vitis vinifera’ (‘Grape’), and ‘Cucumis melo’ (‘Honeydew melon’) seeds is presented. The spin–lattice relaxation time was obtained over a broad frequency range from 100?kHz to 100?MHz using both conventional and fast field-cycling NMR techniques. This relaxometry study made possible a comparison between the molecular dynamics behaviour of starch from different fruit seeds and from potatoes. I was possible to conclude that the spin–lattice dispersion presents slightly differences for all samples, in particular at low frequencies. All relaxation dispersions could be well interpreted in terms of power-law relaxation models and domains with different power-law relaxation exponents. For the Peach seeds flour the relaxation dispersion at low frequencies was very similar to that observed for potato’s starch incorporated with 5% organoclay Viscogel B8 nanoparticles.     

Relaxometric investigations addressing the determination of intracellular water lifetime: a novel tumour biomarker of general applicability

ABSTRACT

¹H Fast-Field Cycling NMR relaxometry is proposed as a powerful method to investigate tumour cell metabolism by measuring changes in cell water content and mobility across the cellular membrane. Measurements of intracellular water residence time in cultured cells were carried out by measuring T₁ at fixed field (0.2?T) after the addition of a paramagnetic Gd complex (Prohance) at different concentrations in the external medium. Investigations on tumour cells (mammary adenocarcinoma TS/A) grown in normo- or hypoxic conditions or suspended in ‘hypo-osmotic’ solutions allowed us to demonstrate that both hypoxic and hypo-osmotic conditions cause a marked increase in water mobility as assessed by the elongation of T₁. Conversely, the metabolic change caused by glutamine (an aminoacid essential for tumour growth) deprivation caused a water mobility decrease (shorter T₁). These findings suggest that T₁ measurements at low and variable magnetic field strengths, giving access to the assessment of intracellular water lifetime, can provide important information about tumour cell metabolism in real time and non-invasively.     

Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1 J (C,H) couplings and its dependence on solvent

The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of ¹ J(C, H) couplings has been studied from a theoretical point of view at the DFT-B3LYP level. The HN=CH₂, molecule was chosen as the primary model compound, in which both FC ¹ J(C, H) couplings were decomposed into bond contributions with the natural J coupling dissection approach (NJC). Differences between the ¹ J (C, H)^FC couplings for C——H bonds in synperiplanar and antiperiplanar orientations with respect to the nitrogen non-bonding electron pair closely follow the experimental trend. They are made up chiefly of three NJC contributions: ‘bond’, ‘direct lone pair’ and the ‘carbon-core orbitals’. The NHI influence on these terms was studied by applying the natural bond orbital (NBO) deletion procedure to the charge transfer interaction into the antiperiplanar (C——H) antibond (n(N)→(C——H)?) prior to the NJC dissection calculation. The dielectric solvation effect on both the total FC terms and the respective NJC contributions was estimated by carrying out the calculations using the polarization continuum model. Inhibition of the anomeric effect is evident when the solvent polarity is increased. NHI saturates rapidly with increasing solvent dielectric. Specific solute-solvent interaction effects on ¹ J(C, H) couplings were estimated by evaluating molecular complex models of the form CH₂=HN…S (S = H₂O and DMSO).     

Key properties of monohalogen substituted phenols: interpretation in terms of the electron localization function

This paper is an attempt to bridge the key properties of monohalogen substituted phenols with the electronic localization function, which has a vivid 3D topological pattern and the vector gradient field of which is determined by the electron transition current density. A primary goal is to interpret the ‘anomalous’ strength of the intramolecular hydrogen bond O—H···X formed in cis ortho-X substituted phenols, depending upon the halogen atom (X = F, Cl, and Br) in terms of the populations of the electronic localization function basins and a so-called core valence bifurcation index. A theoretical model is considered aiming to explain convincingly the cis-trans conversion in ortho-X phenols occurring in some solvents and resulting in the experimentally observed splitting of the ν_OH stretch and based on the Pauling model. Characteristic harmonic vibrational modes of all monohalogen substituted phenols are discussed thoroughly. The order of stability of monohalogen substituted phenols is established at a high level of computational performance, showing the ‘anomalous’ order of stability of fluorophenols, the result being that, in contrast to Cl and Br, the F atom favours the trans meta position over the cis ortho with formation of the intramolecular hydrogen bond.     

Critical angles and minimum yields for planar channeling

Abstract

Local regions on the surface of a sample of ZnO: Zn phosphor powder were deteriorated by low energy heavy ions to a depth of a few hundred Angstrom units. These regions behave as ‘thin films’ in which a negligible small amount of light is produced when an energetic projectile passes through it. The sample was then scanned across energetic ion beams. The scintillation response diminished when the beam impinged onto a film. The decrease, ΔL, in light intensity is the amount of light produced in a phosphor region whose thickness is equivalent to the film thickness. For ¹H and ⁴He the luminescent efficiency, ΔL/ΔE (the ratio of the light produced to the observed energy loss), is approximately independent of energy indicating that the scintillation response depends primarily on the inelastic projectile-electron collisions rather than the elastic projectile target atom encounters.

At a given velocity, a plot of ΔL versus the atomic number of the projectile exhibits oscillatory structure for which a tentative explanation is suggested.     

Magnetocaloric effect of the multiphase Gd4−xTbxCo3 system

ABSTRACT

Crystal structure, microstructural chemical analysis, magnetic properties and magnetocaloric effect for ‘as cast’ and annealed Gd_4?xTb_xCo₃ (x?=?0–4) were investigated. Only Gd₄Co₃ was homogeneous and crystallised in the hexagonal Ho₄Co₃-type of crystal structure. Samples substituted with terbium proved to be a mixture of (Gd,Tb)₁₂Co₇ and (Gd,Tb)Co₂ phases. With the increase of terbium content the entropy change increased and for the samples with x?=?3, 4 reached the highest values. Even ‘as-cast’ samples exhibit pronounced values of the magnetocaloric parameters.     

Computational prediction of a new class of tri-coordinate cyclic heavier carbene analogues RM(μ-R)2AlR2 (M = Ge,Sn, Pb)

Design of stable heavier carbene analogues M(II) (M = Ge, Sn, Pb) with structural motifs different from the traditional di-coordinate analogues is extremely of interest and challengeable. In this paper, we computationally designed a novel class of tri-coordinate cyclic heavier analogues of carbenes covering a number of substituents, i.e., RM(μ-R)₂AlR₂ (M = Ge, Sn, Pb) 1, in which two sets of inter-molecular donor–acceptor interactions were formed between the di-coordinate carbene MR₂ and the AlR₃ moiety. The M-centre was found to undergo both the nucleophilic and insertion reactions, indicative of the ‘carbene’ character. We also designed c-1 starting from the known di-coordinate cyclic MR₂ and AlR₃ under 16 kinds of substituents [NR′₂, OR′, PR′₂, SR′(R′ = H, Me, iPr, Ph)]; c-1 also has favourable thermodynamic stability. After the only known cyclic tri-coordinate M(II) [M₂,R₄] inter-molecularly formed between two di-coordinate MR₂, the presently designed new tri-coordinate cyclic heavier carbene analogues should expand the higher coordinate M(II) family and await future laboratory synthesis.     

Molecular dynamics calculation of the dielectric constant

Molecular dynamics (MD) simulations of an isolated dipolar system (made of Stockmayer molecules) has been performed. A two dimensional system has been adopted, using a ‘2-D electrostatics’ dipolar interaction.

The isolated system was a disc in vacuo. The autocorrelation function (ACF) of the moment of the disc was extracted from our runs, together with the ACF of the moment of a small inner disc (‘microscopic’ or ‘multimolecular’ ACF). Comparison of these two ACF has allowed us to compute the response function of the annulus between the two discs. The behaviour of the latter was that predicted by the theory of Fatuzzo and Mason. It is thus shown, for the first time, that one can obtain, by numerical simulation of a few hundred molecules, reliable values of the complex permittivity of highly polar fluids, despite the long range character of the dipolar interaction.

Its behaviour is surprisingly realistic when compared with that of real 3-D polar liquids.

Monomolecular ACF have also been extracted from the MD runs. They recall that of the Itinerant Oscillator model, the long time behaviour of <u(0). u(t)> being diffusive, but shorter-lived than that of the multimolecular ACF. Compared to the free rotation, the monomolecular orientational correlation time dt (u(0). u(t)> cannot be explained quantitatively using the theory of dielectric friction derived from the Onsager reaction field. Finally a comparison between this monomolecular correlation time and the multimolecular one is made: Models linking the ratio of these two times to the Kirkwood g _K factor are examined.     

Quantum effects in rutherford back-scattering and emission of electrons near a crystal axis

Abstract

By increasing the strength of the interaction potential for a reasonable range of values, we show that the angular pattern of the electron intensity, about a crystallographic axis, changes from one dominated by Bragg peaks to an essentially structureless curve. This retains a significant dependence on h, and by that token cannot be identified with the ‘classical envelope’.     

Proton spin relaxation in 2-chloroacrylontirile by double resonance

Nuclear magnetic double resonance experiments were performed on the strongly coupled two-proton system (AB) in 2-chloroacrylontirile to study the spin relaxation processes. The single resonance parameters of the AB spectrum are (operating frequency 100 MHz): |vA - vB|=9.85±0.1 Hz and J _AB=2.8±0.1 Hz. Frequency-sweep double resonance spectra were obtained by irradiating each of the four transitions at different strengths of irradiation in the range 0.015 Hz to 2.35 Hz. These spectra were analysed by using the ‘Bloch approximation’ in the rotating frame for the ‘high’ irradiation strengths and the ‘simple line’ approximation for the ‘low’ irradiation strengths. The analysis showed that the proton relaxation in this molecule can be described by interaction with isotropic random fields of nearly equal strengths at the two nuclei with no appreciable correlation between them. Internal dipole-dipole interaction is not a significant mechanism (at room temperature). It is shown that for analysing ‘low’ irradiation spectra the choice of certain functions of intensity changes would lead to a marked distinction between the different relaxation mechanisms.     

A novel determination of activation quantities and reaction order(s) for the hydrothermal destruction and its applications

Abstract

A novel determination method of activation quantities and reaction order(s) of hydro-thermal reactions was developed in order to achieve economically, easily and speedily research and development of new hydrothermal plants. This method is called the NIT method (abbreviation of ‘Nonisothemal method’) in the case of a batch reactor and the F-NIT method (abbreviation of ‘nonisothermal method for flow reactor’) in the case of a plugged flow reactor. The main merit of the NIT method (or the F-NIT method) is to give access to the determination of activation quantities and/or reaction orders by measuring the changes in amount of chemical species under nonisothermal conditions.

After summary of the recently published NIT method, the newly F-NIT method is described briefly. Then the two types of hydrothermal fluids (hydrothermal steam and supercritical/subcritical water) are applied to the destruction of phenol under nonisothermal conditions. The activation quantities can be obtained at once by use of these methods and are compared with the reported values in the scWO.     

Matrix Exponential via Clifford Algebras

Abstract

Expanded version of a talk presented at the Special Session on ‘Octonions and Clifford Algebras’, 1997 Spring Western Sectional 921st Meeting of the American Mathematical Society, Oregon State University, Corvallis, OR, 19–20 April 1997.

We use isomorphism ? between matrix algebras and simple orthogonal Clifford algebras C (Q) to compute matrix exponential e^A of a real, complex, and quaternionic matrix A. The isomorphic image p = ?(A) in C (Q), where the quadratic form Q has a suitable signature (p, q), is exponentiated modulo a minimal polynomial of p using Clifford exponential. Elements of C (Q) are treated as symbolic multivariate polynomials in Grassmann monomials. Computations in C (Q) are performed with a Maple package ‘CLIFFORD’. Three examples of matrix exponentiation are given.     

Solubility and precipitation of metal impurities in alkali halide crystals: Dielectric,mössbauer and optical measurements

Abstract

The thermodynamical equilibrium concentration of divalent impurity-vacancy dipoles in solution in different alkali halides is studied by means of ionic thermoconductivity. The activation energy of the ‘associated impurity solubility’ is of the order of 0.10 ÷ 2 eV.

Mössbauer effect measurements performed on NaCl⁵⁷ CoCl₂, with different Co concentrations outlined that the precipitation phenomenon of divalent impunties is quite complex. The details of Mossbauer spectra are discussed. Moreover ‘charge transfer’ bands induced in optical absorption spectrum by cobalt are examined from the point of view of solution-precipitation reaction.     

On the microstructure of the charge density wave observed in La1− x Ca x MnO3

We have used low temperature (90?K) transmission electron microscopy to investigate the ‘charge ordering’ modulation in the mixed valent manganite, La_{1? x} Ca _x MnO₃. It has been stated that Mn³⁺ and Mn⁴⁺ ions order at low temperature to produce a structural modulation composed of supercells whose size is an integer multiple of the unmodulated unit cell. Here, we use convergent beam electron diffraction to show that the periodicity of the modulation need not be an integer multiple of the undistorted cell, even on the smallest scales. We therefore suggest that this modulation is a charge density wave with a uniform periodicity. We show that the modulation wavevector lies close to the a* axis of the crystal but need not be exactly collinear. A typical grain of size 0.5?µm in La_0.48Ca_0.52MnO₃ had a wavevector which varied on a scale of tens of nanometres with an average of ?q??=?0.450a * and a standard deviation Δq?=?0.004?a* in its magnitude and Δθ?=?0.56° in its direction at 90?K. The magnitude of the wavevector in this composition fell by 20% as the temperature was increased from 90?K to room temperature. This change occurred by nucleation and growth. Although weak, the modulation was still present at room temperature, some 30?K above the ‘charge ordering temperature’.     

The dissipative modulated structures in a distribution of interacting vacancies in the elastically anisotropic body-centred cubic crystals under an isothermal irradiation

ABSTRACT

Dissipative mechanism of formation of a modulated structure of vacancies in a body-centred cubic (b.c.c.) crystal is considered as its intrinsic property under an isothermal irradiation irrespectively of elastic-anisotropy factor sign. Conditions of self-organisation of a precursor of formation of a ‘superlattice’ of nanovoids, namely, the modulated structure in a spatial distribution of the diffusing vacancies generated by irradiation, because of the instability of their homogeneous distribution as a result of interaction between them in a b.c.c. host crystal under irradiation, are analysed. As shown for the first time, the ‘cohesive’ and ‘elastic’ couplings between interacting (and diffusing) vacancies have a crucial role in a pattern-selection process accordingly with different (positive or negative) elastic-anisotropy factors.     

Density functionals for nondynamical correlation constructed from an upper bound to the exact exchange energy density

ABSTRACT

Hyper-generalised-gradient approximations (hGGAs) for the exact exchange-correlation functional are increasingly popular in density functional theory. HGGAs model nondynamical correlation using a flexible local combination of exact (Hartree–Fock, HF) exchange and approximate exchange. We present a simplified ‘Rung 3.5’ upper bound to the HF exchange energy density, the essential ingredient of hGGAs. We also present a nonempirical generalised gradient approximation for this upper bound. Both upper bounds go to zero in the high-density and density tail limits, facilitating the construction of hGGAs that recover HF exchange in these limits. The ‘Rung 3.5’ construction enables facile evaluation of analytic derivatives and calculations in periodic boundary conditions. Extensive numerical tests show that the upper bounds capture the critical difference between HF and approximate exchange, showing these ingredients' promise for building simple hGGAs. The tests also indicate a need for more sophisticated semi-local upper bounds.