Monitoring of radon anomalies in South-Eastern part of Romania for earthquake surveillance

South-Eastern part of Romania has a highest potential seismic risk in Europe due to the earthquake-prone Vrancea zone placed at conjunction of four tectonic blocks in the South-Eastern part of Carpathian Arc. This paper is an attempt to analyze the development of radon pre-earthquake anomaly in relation with moderate seismic events in Vrancea area through permanent monitoring with solid state nuclear track detectors CR-39 detectors. Radon in air above the ground was measured during 1?year period (November 2010?COctober 2011) in four selected test sites: Vrancioaia (VRI) and Plostina (PLOR) located in Vrancea zone, and Muntele Rosu-Cheia and Bucharest. During sampling period recorded earthquakes that occurred mostly in Vrancea epicentral region were minor-moderate of moment magnitudes in range of $ 2.0 \le M_{w} \le 4.9 $ . The average radon concentration in air above the ground measured with CR-39 detectors and 10?days period recorded simultaneously at all test sites, registered the following values: (1) in Vrancea area (similar in VRI and PLOR) was 1094.58? $ \pm $ ?150.3?Bq/m³; (2) at Muntele Rosu-Cheia seismic station measured in a mountain tunnel laboratory was 3695.91 ±?440?Bq/m³; (3) at Bucharest station was 380.53? $ \pm $ ?69.17?Bq/m³, and 10?days C_Rn fluctuations in the range of (88? $ \pm $ ?40 to 912 $ \pm $ ?130?Bq/m³). Clear radon anomalies, mostly at VRI and PLOR in Vrancea epicentral area as well as at Muntele Rosu-Cheia have been measured before seven minor earthquakes which were recorded in the range of moment magnitude $ 4 \le M_{w} \le 4.9 $ in Vrancea area. Temporal variation of radon in air near the ground have been examined in relation with meteorological parameters like as air temperature, relative humidity, air pressure and wind velocity. Permanent monitoring of radon concentration anomalies in seismic area Vrancea is an important issue as surveillance tool in the field of earthquake hazard for Romania.     

A boundary-driven reaction front

A model reaction scheme in which two species $A$ and $B$ react to form an inert product is considered, with the possible linear decay of $A$ to a further inert prduct also included. The reaction between $A$ and $B$ is maintained by the input of $A$ from the boundary which keeps $A$ at a constant concentration. The cases when $B$ is immobile or free to diffuse are treated. In the former case reaction fronts in $B$ are seen to develop. Large time asymptotic solutions are derived which show that these fronts propagate across the reactor at rates proportional to $t^{1/2}$ or $\log t$ ( $t$ is a dimensionless time) depending on whether the extra decay step is included. A similar situation is seen when $B$ can diffuse when the linear decay step is not present. However, when this extra step is included in the reaction scheme the reaction zone reaches only a finite distance fronm the boundary at large times.     

Effect of activation volume on the defect-induced anomalous electronic transport in Rb_{0.8}Fe_2Se_2

We adopted an absolute-reaction model which is considering the hole(defect)-induced charged frictionless transport to explain the unusual experiment: Two single crystalline samples of the same nominal composition Rb \(_{0.8}\) Fe \(_2\) Se \(_2\) were prepared using the self-flux technique via two different precursor routes. Although the difference in the final chemical composition falls within a narrow range, one was superconducting with a \(T_c \sim 31\) K, while the other behaves like a narrow gap semiconductor.     

Thermodynamic study of metal corrosion and inhibitor adsorption processes in copper/N-1-naphthylethylenediamine dihydrochloride monomethanolate/nitric acid system: part 2

N-1-Naphthylethylenediamine dihydrochloride monomethanolate (N-NEDHME) was tested as a corrosion inhibitor for copper in 2 M HNO₃ solution using the standard gravimetric technique at 303–343 K. N-NEDHME acts as an inhibitor for copper in an acidic medium. Inhibition efficiency increases with increase in concentration of N-NEDHME but decreases with a rise in temperature. Thermodynamic parameters such as adsorption heat ( $ \Updelta H_{\text{ads}}^\circ $ ), adsorption entropy ( $ \Updelta S_{\text{ads}}^\circ $ ) and adsorption free energy ( $ \Updelta G_{\text{ads}}^\circ $ ) were obtained from experimental data of the temperature studies of the inhibition process at five temperatures ranging from 303 to 343 K. Kinetic parameters activation such as $ E_{a} $ , $ \Updelta H_{\text{a}}^\circ $ , $ \Updelta S_{\text{a}}^\circ $ and pre-exponential factors have been calculated and are discussed. Adsorption of N-NEDHME on the copper surface in 2 M HNO₃ follows the Langmuir isotherm model.     

Lamellar/Disorder Phase Transition in a Mixture of Water/2,6-Dimethylpyridine/Antagonistic Salt

The effects of adding an antagonistic salt, sodium tetraphenylborate ( \(\hbox {NaBPh}_4\) ), to a binary mixture of deuterated water and 2,6-dimethylpyridine were investigated by visual inspection, optical microscopy, and small-angle neutron scattering. With increasing salt concentration, the two-phase region shrinks. When the concentration of \(\hbox {NaBPh}_4\) is \(85\hbox { mmol}{\cdot} \hbox {L}^{-1}\) , a temperature-induced lamellar/disorder phase transition is observed at 338 K. These trends are similar to those observed for a mixture of water/3-methylpyridine/ \(\hbox {NaBPh}_4\) (Sadakane et al., Phys. Rev. Lett. 103, 167803 (2009)).     

Amino acid hydration in aqueous ammoniu chloride and sodium chloride solutions

Partial volumes $\bar V^0$ of amino acids in aqueous NH₄Cl and NaCl solutions are discussed. The salts have different effects on water structure. The contributions of the charged NH ₃ ⁺ and COO^? groups of amino acids are found. Structural characteristics of hydrated complexes are calculated: partial volumes of water inside and outside the hydration sphere and hydration numbers. The same value of $\bar V^0$ (NH ₃ ⁺ , COO^?) is achieved at a higher NH₄Cl concentration. The two salt systems with the same $\bar V^0$ (NH ₃ ⁺ , COO^?) have similar values of the partial volumes of water and hydration numbers.     

Free ions Pr IV (4\text{ f }^{2}) and Tm IV (4\text{ f }^{12}): intermediate versus LS coupling scheme

The intermediate and LS-coupling schemes for the free lanthanide ions $\text{ Pr }^{3+}$ Pr 3 + and $\text{ Tm }^{3+}$ Tm 3 + have been compared by the matrix elements of the tensor operator ${{\varvec{U}}}^{({\varvec{k}})}, \text{ k } = 2, 4, 6$ U ( k ) , k = 2 , 4 , 6 . The necessary eigenvectors and eigenvalues have been computed with the aid of four parameters, $\text{ F }_{2}, \text{ F }_{4}, \text{ F }_{6}$ F 2 , F 4 , F 6 , and $\zeta _{4\mathrm{f}}$ ζ 4 f , known from free-ion spectra of the same ions. It has been found that both coupling types for each ion lead to close values of ${\vert }{{\varvec{U}}}^{({\varvec{k}})}{\vert }^{2}$ | U ( k ) | 2 only for transitions from the ground level to certain lower-lying energy levels within the $4\text{ f }^\mathrm{N}$ 4 f N configuration.     

Spin correlation in Pr IV and Tm IV free ions

The coefficients \(c_{k}\) (k = 2, 4, 6) that pertain to spin-correlated matrix elements of the tensor operator \({{\varvec{U}}}^{{\varvec{(k)}}}\) have been evaluated by means of the differences \({{\varvec{U}}}^{{\varvec{(k)}}}\) (intermediate) \(-\) \({{\varvec{U}}}^{{\varvec{(k)}}}\) (LS) and the reduced matrix elements of the operator \({{\varvec{V}}}^{{\varvec{(1k)}}}\) . Only spin-allowed transitions have been considered from each ground level to the excited energy levels within the \(4\hbox {f}^{2}\) and \(4\hbox {f}^{12}\) configurations of the free ions Pr (3+) and Tm (3+), respectively. The values of the coefficients \(c_{k}\) thus found correspond in most cases by sign and order of magnitude to those determined in other sources as corrections to lanthanide (3+) crystal-field parameters.     

Comparison of ordered mesoporous materials sorption properties towards amino acids

The adsorption of amino acids such as l-phenylalanine and l-histidine was carried out on a series of mesoporous carbons obtained with the use ordered silicas KIT-6, SBA-16, SBA-15 as templates and furfuryl alcohol as carbon precursor. Small angle XRD analysis confirmed the ordered mesoporous structures of all materials obtained. They were also characterised by well-developed surface areas and high pore volumes. Adsorption behaviour of amino acids on ordered mesoporous carbons was investigated in potassium phosphate buffer solutions with adjustable l-phenylalanine and l-histidine concentration, ion strength, and pH. The highest sorption capacity towards the amino acids were observed at pH close to the isoelectric point of l-phenylalanine (pI = 5.48) and l-histidine (pI = 7.59). Electrostatic, hydrophobic and steric interactions had very strong effect on the adsorption of amino acids on mesoporous carbons. The amount of l-phenylalanine and l-histidine adsorbed decreased in the following sequence: C_KIT-6 > C_SBA-16 > C_SBA-15 that was strongly related to their structure, surface areas and average pore diameters.     

Study of Malachite Green Fading in Water–Ethanol–Ethylene Glycol Ternary Mixtures

The rate constant of malachite green (MG⁺) alkaline fading was measured in water–ethanol–ethylene glycol ternary mixtures. This reaction was studied under pseudo-first-order conditions at 283–303 K. In each series of experiments, the concentration of ethanol was kept constant and the concentration of ethylene glycol was changed. It was shown that due to hydrogen bonding and hydrophobic interaction between MG⁺ and alcohol molecules the observed reaction rate constant, $ k_{\text{obs}} $ , increased in the water–ethanol–ethylene glycol ternary mixtures. The fundamental rate constants of MG⁺ fading in these solutions ( $ k_{1} $ , $ k_{ - 1} $ and $ k_{2} $ ) were obtained by the SESMORTAC model. Analysis of $ k_{1} $ and $ k_{2} $ values in solutions containing constant ethanol concentrations show that in low concentrations of ethylene glycol, hydrogen bonding formed between ethanol and ethylene glycol molecules and in high concentrations of ethylene glycol, ethanol as a solvent for ethylene glycol affected the reaction rate.     

Volumetric Properties of l-Alanine and l-Serine in Aqueous N,N-Dimethylformamide Solutions at 298.15 K

The densities of l-alanine and l-serine in aqueous solutions of N,N-dimethylformamide (DMF) have been measured at 298.15 K with an Anton Paar Model 55 densimeter. Apparent molar volumes $ (V_{\phi } ) $ ( V ? ) , standard partial molar volumes $ (V_{\phi }^{0} ) $ ( V ? 0 ) , standard partial molar volumes of transfer $ (\Updelta_{\text{tr}} V_{\phi }^{0} ) $ ( Δ tr V ? 0 ) and hydration numbers have been determined for the amino acids. The $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 values of l-serine are positive which suggest that hydrophilic–hydrophilic interactions between l-serine and DMF are predominant. The –CH₃ group of l-alanine has much more influence on the volumetric properties and the $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 have smaller negative values. The results have been interpreted in terms of the cosphere overlap model.     

Two-dimensional high-performance liquid chromatographic determination of day–night variation of d-alanine in mammals and factors controlling the circadian changes

d-Alanine (d-Ala) is one of the naturally occurring d-amino acids in mammals, and its amount is known to have characteristic circadian changes. It is a candidate for a novel physiologically active substance and/or a biomarker, and the regulation mechanisms of the intrinsic amounts of d-Ala are expected to be clarified. In the present study, the effects of the possible factors controlling the d-Ala amounts, e.g., diet, d-amino acid oxidase (DAO) and intestinal bacteria, on the day–night changes in the intrinsic d-Ala amounts have been investigated using a highly sensitive and selective two-dimensional high-performance liquid chromatographic system combining a reversed-phase column and an enantioselective column. The circadian rhythm was not changed under fasting conditions. In the mice lacking d-amino acid oxidase activity (ddY/DAO^- mice), clear day–night changes were still observed, suggesting that the factors controlling the d-Ala rhythm were not their food and DAO activity. On the other hand, in the germ-free mice, quite low amounts of d-Ala were detected compared with those in the control mice, indicating that the main origin of d-Ala in the mice is intestinal bacteria. Because the d-Ala amounts in the digesta containing intestinal bacteria did not show the day–night changes, the controlling factor of the circadian changes of the d-Ala amount was suggested to be the intestinal absorption.     

Exploiting thermodynamic data to optimize the enantioseparation of underivatized amino acids in ligand exchange capillary electrophoresis

Stereoselective amino acid analysis has increasingly moved into the scope of interest of the scientific community. In this work, we report a study on the chiral separation of underivatized d,l-His by ligand exchange capillary electrophoresis (LECE), utilizing accurate ex ante calculations. This has been obtained by the addition to the background electrolytes (BGE) of NaClO₄ which renders the separations “all in solution processes”, allowing to accurately calculate in advance the concentrations of the species present in solution and to optimize the system performances. To this aim, the formation of ternary complexes of Cu²⁺ ion and l-lysine (l-Lys) or l-ornithine (l-Orn) with l- and d-histidine (His), and histamine (Hm) have been studied by potentiometry and calorimetry at 25 °C and with 0.1 mol dm^?3 (KNO₃) in aqueous solution. The ternary species [Cu(L)(l-His)H]⁺ and [Cu(L)(d-His)H]⁺ (where L?=?l-Lys or l-Orn) show a slight but still detectable stereoselectivity, and the determination of ΔH° and ΔS° values allowed the understanding of the factors which determine this phenomenon. The stereoselectivity showed by the protonated ternary species has been exploited to chirally separate d,l-His in LECE, by using the binary complexes of copper(II) with l-Lys or l-Orn as background electrolytes added with the appropriate amounts of NaClO₄.

Asymptotics (p\rightarrow \infty ) of L_p-norms of hypergeometric orthogonal polynomials

The determination of the weighted $L_p$ norms of the real orthogonal polynomials of hypergeometric type $\left\{ y_n(x)\right\} $ is not only a very important problem per se in the theory of special functions, but also because of their recent entropic characterization and applications in quantum chemistry, quantum physics and information theory. Indeed, they essentially describe the $p$ th-order Rényi and Tsallis entropies of the numerous quantum systems whose wavefunctions are controlled by these polynomials. Moreover, for different values of $p$ , up to a constant factor, these norms characterize various fundamental and experimentally accessible quantities of many-electron systems. As well, the $L_p$ norms have been used to develop and interpret all energy components in the density-functional theory of the ground-state of atoms and molecules. The asymptotics of these quantities when $n \rightarrow \infty $ and $p>0$ have been recently calculated for Hermite polynomials, although not yet for Laguerre and Jacobi polynomials. Here, we determine the asymptotics ( $p\rightarrow \infty $ , $n$ fixed) of the weighted $L_p$ norms for general orthogonal polynomials in terms of the weight function and the coefficients of the second-order hypergeometric differential equation that they satisfy, and we apply it to the three classical families of real orthogonal polynomials. Moreover we analyse and discuss the monotonicity of this asymptotics, and we carry out a detailed numerical study of it.     

A theoretical and experimental investigation of the formation of S 2 - from CS2 by electron impact

Theoretical and experimental investigation of the formation of S ₂ ^- from CS₂ by electron impact has been carried out. Molecular orbital calculations show that some of the low lying states of CS ₂ ^- have lower potential energy in the bent geometries suggesting a transformation in the geometric structure of the precursor molecular ion, leading to the formation of S ₂ ^- . In contrast to the formation of S ₂ ^- and S ₂ ^- , the kinetic energy associated with S ₂ ^- is small and disproportionate to the increase in electron energy, indicating the formation of S ₂ ^- in vibrationally excited states due to the mechanism of its formation.     

Weak harmonic confinement of the quintet solution of a Moshinsky atom with 4 electrons

Bruch, in early work, treated a spatially free Moshinsky atom with four parallel-spin electrons interacting harmonically. Here we add a harmonic external potential, having an unrelated spring constant $k$ , and use the variational method, with a one-parameter trial wave function, to examine the quintet ground state energy and electron density, particularly in the weak confinement limit $k\rightarrow 0$ . The results are compared with Bruch’s and modest contact is made with the early work of Post.     

A note on Li–Yorke chaos in a coupled lattice system related with Belusov–Zhabotinskii reaction

This paper is concerned with the following system which comes from a lattice dynamical system stated by Kaneko in (Phys Rev Lett 65:1391–1394, 1990) and is related to the Belusov–Zhabotinskii reaction: $$\begin{aligned} x_{n}^{m+1}=(1-\varepsilon )f(x_{n}^{m})+\frac{1}{2}\varepsilon \left[ f(x_{n-1}^{m})+f(x_{n+1}^{m})\right] , \end{aligned}$$ x n m + 1 = ( 1 ? ε ) f ( x n m ) + 1 2 ε [ f ( x n ? 1 m ) + f ( x n + 1 m ) ] , where $m$ m is discrete time index, $n$ n is lattice side index with system size $L$ L (i.e., $n=1, 2, \ldots , L$ n = 1 , 2 , … , L ), $\varepsilon $ ε is coupling constant, and $f(x)$ f ( x ) is the unimodal map on $I$ I (i.e., $f(0)=f(1)=0$ f ( 0 ) = f ( 1 ) = 0 and $f$ f has unique critical point $c$ c with $0<c<1$ 0 < c < 1 and $f(c)=1$ f ( c ) = 1 ). It is proved that for coupling constant $\varepsilon =1$ ε = 1 , this CML (Coupled Map Lattice) system is chaotic in the sense of Li–Yorke for each unimodal selfmap on the interval $I=[0, 1]$ I = [ 0 , 1 ] .     

Clar and Fries numbers for benzenoids

A Kekulé structure of a benzenoid or a fullerene $\Gamma $ Γ is a set of edges $K$ K such that each vertex of $\Gamma $ Γ is incident with exactly one edge in $K$ K . The set of faces in $\Gamma $ Γ that have exactly three edges in $K$ K are called the benzene faces of $K$ K . The Fries number of $\Gamma $ Γ is the maximum number of benzene faces over all possible Kekulé structures for $\Gamma $ Γ . The Clar number is the maximum number of independent benzene faces over all possible Kekulé structures for $\Gamma $ Γ . It is often assumed, but never proved, that some set of independent benzene faces giving the Clar number is a subset of a set of benzene faces giving the Fries number. In Hartung (The Clar structure of fullerenes, Ph.D. Dissertation. Syracuse University, 2012) it is shown that this assumption is false for a large class of fullerenes. In this paper, we prove that this assumption is valid for a large a class of benzenoids.     

A new chiral electrochemical sensor for the enantioselective recognition of penicillamine enantiomers

A new chiral electrochemical sensor has been successfully prepared through chemical linking l-methotrexate (l-Mtx) onto the gold electrode surface. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the enantioselective interaction between l-Mtx and Pen enantiomers. The results showed that the l-Mtx-modified gold electrode can selectively recognize penicillamine (Pen) enantiomers using Zn(II) as central ion, and larger response signal was observed from d-Pen owing to the selective formation of Zn complexes. The interaction time between the modified electrode and Pen enantiomers containing Zn(II) was considered. And the electrochemical response of the modified electrode to a series of different concentration of Pen in the presence of Zn(II) was also monitored. In addition, the enantiomeric composition of d- and l-Pen enantiomer mixtures was monitored by measuring the current responses of the sample.     

Solvation Thermodynamics of a Series of Homologous α-Amino Acids in Non-aqueous Binary Mixtures of Protic Ethylene Glycol and Dipolar Aprotic Acetonitrile

Standard transfer Gibbs energies $ \left( {\Updelta G_{t}^{0} (i)} \right) $ ( Δ G t 0 ( i ) ) and entropies $ \left( {\Updelta S_{t}^{0} (i)} \right) $ ( Δ S t 0 ( i ) ) of transfer of the homologous α-amino acids: glycine, dl-alanine, dl-α-amino butyric acid and dl-nor-valine (nor-val) from protic ethylene glycol (EG) to proton/cation-phobic dipolar aprotic acetonitrile (ACN) mixed solvents with 0, 20, 40, 60, 80 and 100 wt% ACN compositions have been determined at 25 °C. For this purpose solubilities of the α-amino acids were measured by “formol titrimetry” at 15, 20, 25, 30 and 35 °C. The chemical components of these Gibbs energies $ \left( {\Updelta G_{t,\rm{ch}}^{0} (i)} \right) $ ( Δ G t , ch 0 ( i ) ) and entropies $ \left( {{\rm T}\Updelta S_{t,\rm{ch}}^{0} (i)} \right) $ ( T Δ S t , ch 0 ( i ) ) of the homologous α-amino acids have been computed by subtracting the cavity effects and dipole–dipole interaction effects. The chemical contributions of transfer energetics of these homologous α-amino acids are determined by different types of interactions. The decreased acidity, basicity, H-bonding capacity, solvophilic solvation and solvophobic solvation and increased dispersion and soft–soft interaction of ethylene glycol and acetonitrile mixtures, as compared to EG, are the guiding factors. The characteristics of the solvation thermodynamics of α-amino acids in protic EG and proton/cation-philic dipolar aprotic DMF mixed solvent systems studied earlier are also discussed here for comparison.