Small Positive Deviations Research Articles

Chemical bond features and microwave dielectric properties of olivine-type LiMSiO4 (M = Ho, In) ceramics

Orthorhombic olivine-structured LiMSiO4 (M = Ho, In) ceramics were synthesised using the solid-state reaction. Promising microwave dielectric properties of εr = 10.04, τf = 23.3 ppm/°C and a high-quality factor (Q × f) of 11,415 GHz for LiHoSiO4 were obtained at 1050 °C, and εr = 7.78, τf = −46.8 ppm/°C and Q × f = 23,390 GHz for LiInSiO4 were achieved at 1140 °C. According to the bond valence result, Ho3+ presented a slightly compressed state but Li+ and Si4+ exhibited a strong rattling state in LiHoSiO4, which led to higher εr than the εtheo. The integrated effect of rattling cations (Li+ and In3+) and a compressed cation (Si4+) in LiInSiO4 resulted in a small positive deviation Δεr. The larger packing fraction of LiInSiO4 contributed to a higher Q × f than LiHoSiO4. The Si–O bond in both ceramics played a leading role in influencing the Q × f according to the Phillips−Van Vechten−Levine chemical bond theory.

SURFACE TENSION AND DENSITY OF INDIUM–TIN MELTS AND THEIR DEPENDENCE ON COMPOSITION AND TEMPERATURE

The paper presents the results of measuring the surface tension (σ) and density (ρ) of indium-tin melts. The measurements of σ and ρ were carried out by different methods. The surface tension was measured by the sessile drop method and the maximum pressure in the droplet, while the density was measured by the areometer and sessile drop methods. High-purity metals In-00, tin – VHF were used for research. The maximum measurement error σ is 0.8%, and ρ is 0.2%. The dependence of σ of In–Sn melts on the composition is characterized by an extremum (flat minimum) in the region of equimolar composition. As the temperature increases, the depth of the minimum decreases, and its position shifts towards pure indium. Molar volumes have small positive deviations from additive values. As the temperature increases, the molar volumes approach additive values. The sessile drop method was used to measure the temperature dependences of σ and ρ of In–Sn solutions diluted with indium. It has been shown that indium additives lower the surface tension of tin. Given that the value of the surface tension of indium is higher than that of tin, this result indicates that the surface tension isotherms of the indium-tin system must pass through a minimum.

THERMODYNAMIC CALCULATIONS OF HIGH ENTROPY (FE-MN) BINARY ALLOY SYSTEM USING CALPHAD METHOD BASED ON THERMO-CALC PACKAGE AND PBINE,FEDATE DATABASES.

The thermodynamic analysis and calculations of the high entropy metastable binary alloy ironmanganese system have been carried out using the CALPHAD (Calculation of phase Diagram) method based on THERMO-CALC (thermodynamic calculations) package and FEDATE database. Thermodynamic analysis contain the assessment and calculation of phase diagram, Gibbs energy of mixing, excess Gibbs energies, thermodynamic molar activities, coefficient of activities, partial and integral values of enthalpy for Fe-Mn alloy system at three elevated temperatures 1200K, 1225K, and 1250K.The entropy of the said alloy system is calculated by showing linear accordance with temperature. The sudden increase is found in enthalpy curve due to overlapping of grain boundaries of the system. The high enthalpy shows increasing heat contents of the said alloy system with increasing temperature range. The alloy shows a positive deviation from Vegard’s law, Henry’s law and corresponding negative deviation from Raoults’s law ideal Gibbs curve. The obtained results show that the ferromagnetic states of Fe-Mn alloy is the most stable state FCC_A1#1. For Mn and Fe system, the phase equilibria show activity curve data for solid state and show ideal characteristics behaviors. Small positive deviation from Henry’s law was observed from the ideal curve. The alloy shows equilibrium and good stability.

Rhenium Distribution and Behavior in the Salinity Gradient of a Highly Stratified Estuary and Pristine Riverine Waters (The Krka River, Croatia).

The abundance and distribution of dissolved Re (DRe) were determined in the freshwater part of the Krka River (Croatia), which drains a karst landscape, and in the salinity gradient of its highly stratified estuary. Due to the low DRe concentration, a batch procedure consisting of a pre-concentration step using an anion exchange resin (Dowex) and analysis of DRe in 8M HNO3 eluate using high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS) was applied. Due to potentially inconsistent recoveries, which ranged from 60 to 87%, quantification was performed using the isotope dilution technique (ID). DRe concentrations in the Krka River increased downstream, from 6.2pM at the spring site to 11.9pM upstream of the estuary region. Weathering of the surrounding carbonate lithology is assumed to be the source of the natural Re. Two specific anomalies were registered: a strong increase in DRe concentration due to anthropogenic input near the town of Knin (27.5pM) and a decrease at a downstream site caused by subsurface input of freshwater from the Zrmanja River, resulting in a relatively low DRe concentration (8.5pM). In the estuarine region, a near-conservative behavior of DRe was found in the salinity gradient of the upper surface layer, with DRe concentrations ranging from 18 to 38pM. Anthropogenic input was suspected within the estuarine segment near the urban area, causing a small positive deviation from the conservative line. In the bottom seawater layer, a minor decrease in DRe concentration in the most upstream estuarine regions was apparent, implying weak scavenging of Re.

Extended galactic rotational velocity profiles in f(R) gravity background

An attempt has been made to explore the geometric effects of f(R) action on the galactic dynamics under the weak field approximation. The rotational velocity is calculated beyond the Einstein’s geometric theory of gravity. It is inspired by the cosmological geometric relation obtained in the power-law f(R) gravity model in vacuum. We analyse the action with a small positive deviation from the Einstein–Hilbert gravity action (taking R as f(R)propto R^{1+delta }) at the galactic scales for the explanation of the flatness paradox associated with the clustered galactic dark matter. We obtain the contribution of a dynamical f(R) cosmological background geometry on accelerating the test mass. Furthermore, the integrated effective acceleration of the test mass due to a massive spherically symmetric source in f(R) background is calculated via the study of geodesics for the suitable spacetime metric and an equation for the effective rotational velocity has been developed. We test the viability of the proposed model by tracing the motion of a test mass far from the disk of galactic matter for smaller delta . The possible galactic rotational velocity curves in f(R) background are discussed for the formula obtained with delta<< 1. We also obtain constraints on delta O(10^{-6}) confirmed by observations.

Immiscible Anionic Gemini Surfactant-Perfluorinated Fatty Acid Langmuir Monolayer Films.

A new member of the N,N,N',N'-dialkyl-N,N'-diacetate ethylenediamine family of anionic gemini surfactants has been synthesized, and its miscibility with the model perfluorocarbon, perfluorotetradecanoic acid (PF), has been investigated in monolayer films at the air-water interface. Thermodynamics of mixing and the accompanying changes in the mixed film structure have been probed using a combination of compression isotherm measurements supported by Brewster angle microscope imaging and X-ray scattering measurements, and results have been compared with those collected for a previously studied, shorter tail chain variant of the surfactant. Thermodynamic measurements showed that the gemini surfactant and perfluorotetradecanoic acid were immiscible, with weak repulsive interactions, manifesting as small positive deviations from ideal mixing, observed between the two film components. Films were highly textured, with micrometer-scale, phase-separated domains readily detectable. Grazing incidence X-ray diffraction measurements showed that the gemini surfactant was disordered in the monolayers, whereas the perfluorocarbon formed discrete crystallites in the disordered matrix. Despite the small deviations from ideal mixing detected in the thermodynamic measurements, the X-ray measurements indicated that the presence of the gemini perturbs the PF crystal lattice from that of pure PF. Finally, X-ray reflectivity measurements showed that the addition of equimolar PF to the gemini monolayer induces a significant increase in the nominal head group thickness of the film, suggesting that interactions between the two surfactants can lead to structural rearrangements of gemini's head group near to the water surface.

Effects of global warming and solar geoengineering on precipitation seasonality

The effects of global warming and geoengineering on annual precipitation and its seasonality over different parts of the world are examined using the piControl, 4xCO2 and G1 simulations from eight global climate models participating in the Geoengineering Model Intercomparison Project. Specifically, we have used relative entropy, seasonality index, duration of the peak rainy season and timing of the peak rainy season to investigate changes in precipitation characteristics under 4xCO2 and G1 scenarios with reference to the piControl. In a 4xCO2 world, precipitation is projected to increase over many parts of the globe, along with an increase in both the relative entropy and seasonality index. Further, in a 4xCO2 world the increase in peak precipitation duration is found to be highest over the subpolar climatic region. However, over the tropical rain belt, the duration of the peak precipitation period is projected to decrease. Furthermore, there is a significant shift in the timing of the peak precipitation period by 15 days–2 months (forward) over many parts of the Northern Hemisphere except for over a few regions, such as North America and parts of Mediterranean countries, where a shift in the precipitation peak by 1–3 months (backward) is observed. However, solar geoengineering is found to significantly compensate many of the changes projected in a 4xCO2 scenario. Solar geoengineering nullifies the precipitation increase to a large extent. Relative entropy and the seasonality index are almost restored back to that in the control simulations, although with small positive and negative deviations over different parts of the globe, thus, significantly nullifying the impact of 4xCO2. However, over some regions, such as northern parts of South America, the Arabian Sea and Southern Africa, geoengineering does not significantly nullify changes in the seasonality index seen in 4xCO2. Finally, solar geoengineering significantly compensates the changes in timing of the peak and duration of the peak precipitation seen in 4xCO2.

Manipulation of profits in Italian publicly-funded healthcare trusts

ABSTRACTThis paper examines earnings management in state-funded Italian healthcare trusts. Italy is unique in requiring trusts to have balanced budgets by law. Small negative and positive deviations from a balanced budget had quite different consequences. The authors found no evidence of accounting manipulation when trusts posted small losses. However, trusts were found to manipulate discretionary accruals, provisions and non-operating expenses to reduce small positive deviations from zero-profit.

Climatic variability and thermal stress in Pakistan’s rice and wheat systems: A stochastic frontier and quantile regression analysis of economic efficiency

South Asia is the world’s most poverty-dense region, where climate change and climate variability are expected to result in increased heat stress and erratic precipitation patterns that affect agricultural productivity. Considerable evidence has been generated on the effects of these stresses on crop yield, though previous research has not yet examined their influence on the economic efficiency of cereal producers. Surveying 240 farmers across eight of Pakistan’s twelve agro-ecological zones, we examined the impact of temperature and precipitation anomalies – as indicators of climatic variability – and the number of days when temperature exceeds crop specific heat stress thresholds on the economic efficiency of rice and wheat production. To this end, we employed first-stage stochastic production frontier (SPF) models and second-stage ordinary least square (OLS) and quantile regression models. Both OLS and quantile regressions indicated that terminal heat >34 °C has a significant negative impact on wheat production economic efficiency. Small positive deviation (0.54 °C ± 0.16 SD) of the wheat season’s mean temperature from the medium-term historical mean also significantly and negatively affected economic efficiency across all regression models. Heat stress >35.5 °C during rice flowering in the monsoon also had a significant and negative impact. A slight positive deviation in temperature averaging 0.38 °C (±0.11 SD) above the medium-term mean also had significant negative effects across all regressions. Cumulative precipitation conversely had significant yet contrary effects, by offsetting farmers’ investment in supplementary irrigation and increasing economic efficiency. Our results highlight the fact that indicators of climatic variability and heat stress negatively affect the economic efficiency of both rice and wheat producing farmers. Farmers’ education and access to financial and extension services were however both positively associated with economic efficiency. Our findings point to the importance of developing interlinked agronomic, economic and socio-ecological policy strategies to adapt and increase the resilience of Pakistan’s cereal systems to climatic variability.

Vaporization and thermodynamics of forsterite-rich olivine and some implications for silicate atmospheres of hot rocky exoplanets

We describe an experimental and theoretical study of olivine [Mg2SiO4 (Fo)–Fe2SiO4 (Fa)] vaporization. The vaporization behavior and thermodynamic properties of a fosterite-rich olivine (Fo95Fa5) have been explored by high-temperature Knudsen effusion mass spectrometry (KEMS) from 1750 to 2250K. The gases observed (in order of decreasing partial pressure) are Fe, SiO, Mg, O2 and O. We measured the solidus temperature (∼2050K), partial pressures of individual gases, the total vapor pressure, and thermodynamic activities and partial molar enthalpies of MgO, ‘FeO’, and SiO2 for the Fo95Fa5 olivine. The results are compared to other measurements and models of the olivine system. Our experimental data show olivine vaporizes incongruently. We discuss this system both as a psuedo-binary of Fo-Fa and a psuedo-ternary of MgO–‘FeO’–SiO2. Iron/magnesium molar ratios in the sample before (∼0.05) and after (∼0.04) vaporization are consistent with the small positive deviations from ideality of fayalite (γ ∼ 1.17) in olivine of the composition studied (e.g., Nafziger and Muan, 1967). Our data for olivine+melt confirm prior theoretical models predicting fractional vaporization of Fe relative to Mg from molten silicates (Fegley and Cameron, 1987; Schaefer and Fegley, 2009; Ito et al., 2015). If loss of silicate atmospheres occurs from hot rocky exoplanets with magma oceans the residual planet may be enriched in magnesium relative to iron.

GIS-mapping spatial distribution of soil salinity for Eco-restoring the Yellow River Delta in combination with Electromagnetic Induction

Soil salinization is one of serious ecological problems around the world, which seriously restricts the stability of ecosystem and the economic development of agriculture. Mapping and monitoring spatial distribution of soil salinity is important for management of ecology and agriculture. This study was carried out to explore the spatial distribution of soil salinity in the Yellow River Delta using the portable device EM38-MK2 with geostatistical analysis. Apparent soil electrical conductivities were measured under four kinds of measurement modes (0.5H, 0.5V, 1.0H and 1.0V, respectively). The results revealed that electrical conductivity of 1:5 soil to water extract (ECe) varied from 0.965 to 1.872dSm−1 for all sampled soil profiles, and the salinity of topsoil was the highest, which indicated that soil soluble salts accumulated to the surface. The salinity in the top layer showed strong spatial variability while salinities of other layers were moderate. Soil salinity displayed a significant zonal distribution, gradually decreasing with the increase of distance to the coastline. The regions with high ECa values were located in the north and the east of the study area, whereas regions with low ECa values were located in the south and the west parts. The correlation coefficient showed that salinities of adjacent two soil layers reached a significant level of 0.01, and gradually decreased with increasing soil depth. The linear interpretation models with ECa as independent variables and ECe as dependent variables for each depth were with R2 between 0.828 and 0.919. The interpretation models, taking ECa and ECe of 0- 15cm depth as independent variables, and ECe of each layer in 15–100cm depth as dependent variables, were with higher R2 between 0.930 and 0.953. The mean error (ME) showed that there was small positive deviation in 40–100cm whereas a high positive deviation in the topsoil (0–40cm). The scatter plots also indicated that the models had better accuracy of salinity estimation in the top soil layers (0–80cm). The results provides solid basis for eco-restoring in the Yellow River delta.

Theoretical assessment on mixing properties of liquid Tl–Na alloys

Thermodynamic and structural properties of mixing of molten Tl–Na alloys at 673 K have been investigated using quasi-chemical model. To understand the mixing behaviour in more detail, emphasis is placed on the role of interaction energy term, and viscosity and surface tension of the alloys have also been analysed under statistical considerations. Our study shows negative deviation from the Raoultian behaviour in the properties of Tl–Na alloy thereby indicating hetero-coordination in the Tl–Na melt at 673 K in the full range of concentration. Theoretically, computed thermodynamic data at 673 K agree very well with the corresponding experimental data. The viscosities of the alloys computed from Kaptay equation show small negative deviation and those computed from Singh and Sommer’s formulation show small positive deviation from ideal values while the Budai-Benko-Kaptay equation predicts noticeable negative deviation in Na-rich end and positive deviation in Tl-rich end of the composition. The calculations of surface tension reveal that results obtained from layered structure approach and compound formation model are in good agreement in the Na-rich side and in reasonable agreement in Tl-rich side of the composition, while those computed from Butler equation show noticeable deviations in the intermediate compositions. Both the viscosity and surface tension of liquid Tl–Na alloys increase with addition of Tl-component, viscosity having approximately linear variation with concentration. The study shows that there is non-linear variation in surface composition with bulk concentration and for most of the compositions the surface of the alloy is enriched with Na-atoms which segregate to the surface.

Preparation and degradation of chitosan-poly(p-dioxanone)/silk fibroin porous conduits

Chitosan-poly(p-dioxanone) (CH-PDO) copolymers with various poly(p-dioxanone) (PDO) percentages changing from around 20 to 70 wt% were synthesized. The selected CH-PDO with the PDO content of around 45 wt% was blended with prescribed amounts of silk fibroin (SF) to build porous conduits that are potentially suitable for the applications in long-gap nerve repair. Some conduits were further crosslinked using genipin to ensure their required compressive strength and proper degradation rate. By optimizing processing conditions, crosslinked CH-PDO/SF conduits had an average porosity of around 70% in their porous wall, and the pore-size in the conduit wall presented a radial change within a region varying from around 10 to ca.100 μm. After being exposed to PBS degradation system for various periods up to 10 weeks, the weight loss of crosslinked conduits was less than 8 wt% and the pH of degradation media showed a small positive deviation from their initial pH of 7.4. After 10-week implantation in rabbits, most optimally crosslinked CH-PDO/SF conduits were able to maintain regularly tubal shape with a small decrease in their length and diameter and their in vivo degradation rate was predominately controlled by crosslinking and synergetically regulated by the content of SF and PDO in the conduits; and in addition, they showed well-defined ability to retain the compressive strength at a retention rate higher than 70% in comparison to their original strength in wet state. These results suggest that these newly developed CH-PDO/silk fibroin conduits have promising potential for long-gap nerve repair.

Tsunami: Market Tightness and Asset Price Volatility

This paper considers an asset market subject to search frictions, where there are adjustment costs to the entry rate of buyers. An implication is that even in asset markets where the search frictions are very small, asset prices respond to changes in liquidity. Another implication is that asset liquidity is a state variable, the dynamics of which are analysed. I demonstrate that transition paths of liquidity to its (stable) steady state can exhibit dramatic divergence before convergence following small positive deviations in the measure of buyers in the market. Thus, adjustment costs of entry are a potential source of volatility by generating large waves of liquidity, or “tsunami”, in asset markets. I quantitatively assess the ability of the mechanism to generate asset market booms and busts via the implied price movements.

Quantitative Membrane Bending Energies at Extreme Curvatures from Molecular Dynamics Simulations

At mesoscopic length scales and small curvatures, Helfrich's well established continuum model [1] provides accurate membrane bending and stretching energies. For the small nanometer scales and extreme curvatures relevant for fundamental biological processes like synaptic fusion and tubulation, however, its validity is unclear. To test whether or not the bending energy remains a harmonic function of curvature, described by a simple bending modulus, we developed and applied a new type of collective umbrella sampling molecular dynamics (MD) simulations. Most MD simulations computing bending moduli are limited to thermally accessible energies (a few kBT) and curvatures. In this limited regime, the harmonic approximation has been repeatedly confirmed. Very few simulation strategies exist to compute bending energies at higher curvatures, due to the inherent difficulty of controlling membrane structures. These simulation studies have generally verified the harmonic bending approximation but were limited by the requirements of a soft coarse grained lipid model[2], and unavoidable coupling between bending and stretching[3]. To overcome these limitations, we have developed a novel approach to control membrane curvature thereby accessing the regime of <10nm curvature radii and ∼50 kBT energies. Our preliminary results show that at high curvatures, moduli have a small positive deviation from the harmonic approximation, that would not be discernible in the flat/thermal regime. As expected, we observe that increasing temperature decreases the elastic moduli and that ethanol and cholesterol act to soften and stiffen membranes, respectively. [1] W. Helfrich, Naturforsch [C] 28, p693 (1973). [2] V.A. Harmandris and M. Deserno, JCP 125, p204905 (2006). [3] W.K. den Otter and W.J. Briels, JCP 118, p4712 (2003).

Volumetric Properties for Binary Mixtures of Nonane + Decane at Temperatures from T=283.15 to 353.15 K and at p=0.7 atm

Densities of the binary mixture of nonane with decane were measured at temperatures from 283.15 to 353.15 K at atmospheric pressure (0.7 atm). Measurements have been made over the full range of compositions and for the pure compounds by using a vibrating-tube densimeter (VTD). Excess molar volumes have been obtained from these experimental results and were fitted to a Redlich–Kister type expansion. The excess molar volumes exhibit small positive and small negative deviations from ideal behavior in the temperature interval studied. Partial molar volumes and partial molar volumes at infinite dilution have been determined for each component.

Vapor–liquid equilibrium for the binary systems tetrahydrothiophene + toluene and tetrahydrothiophene + o-xylene at 368.15 K and 383.15 K

Isothermal vapor–liquid equilibrium (VLE) for tetrahydrothiophene + toluene and tetrahydrothiophene + o-xylene at 368.15 K and 383.15 K was measured with a recirculation still. Liquid- and vapor-phase compositions were determined with gas chromatography. All systems exhibit a small positive deviation from Raoult's law and show nearly ideal behavior. All VLE measurements passed the point test used. The experimental results were correlated with the Wilson model and compared with COSMO-SAC predictive models. COSMO-SAC predictions show a slight negative deviation from Raoult's law for all systems measured. Raoult's law can be used to describe all systems studied. The activity coefficients at infinite dilution are presented.

Prediction of Hildebrand solubility parameters of acrylate and methacrylate monomers and their mixtures by molecular simulation

AbstractHildebrand solubility parameters are predicted from molecular simulations using the transferable potentials for phase equilibrium‐united atom (TraPPE‐UA) and Dreiding force fields for the n‐alkyl acrylate and methacrylate esters (n ≤ 10), as well as the 2‐ethylhexyl acrylate, 2‐hydroxyethyl acrylate, isooctyl esters of acrylic acid, and the 2‐hydroxyethyl ester of methacrylic acid. The TraPPE‐UA force field yields very accurate solubility parameters (with a mean unsigned percent error of 2% or 0.2 Hildebrand units), whereas the Dreiding force field overpredicts the solubility parameter in every case examined. Correlations based on the normal boiling point or the refractive index do not yield satisfactory results for this monomer set with the former overestimating the magnitude and the latter yielding the incorrect sign for the decrease in the solubility parameter with chain length. Simulations with the TraPPE‐UA force field yield solubility parameters for binary mixtures of methyl methacrylate with 2‐ethylhexyl or isooctyl acrylate, which are very well described by a linear interpolation using the pure compound cohesive energies and molar volumes, whereas those for mixtures with 2‐hydroxyethyl acrylate or methacrylate small positive deviations due to structural microheterogeneity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermodynamic properties of aqueous solutions of pyridine and piperidine

This research was designed to examine the thermodynamic properties of aqueous solutions of pyridine and piperidine. The density, excess molar enthalpy of mixing, H E, and excess molar volume of mixing, v E of piperidine–water and pyridine–water mixtures were studied at three temperatures, ranging from 294 K to 315 K. The H E and v E are negative for both mixtures, minimizing at a water mole fraction of about 0.55. The minimum H E for piperidine–water mixtures is −2.23 kJ/mol which is compared with −1.63 kJ/mol for pyridine–water mixtures. The minimum v E are about −1.7 cm 3/mol and −0.7 cm 3/mol for piperidine–water and pyridine–water mixtures, respectively. The thermal expansion coefficients α T at 303 K, calculated from the density studies, exhibited significant positive deviations (about 20%) from ideality for piperidine–water mixtures. In contrast to this pyridine–water α T only exhibited small positive deviations from ideality of about 2%. The results predict decreases in the absolute magnitude of v E with an increase in temperature which are 5. × 10 −3 cm 3/K mol and 1. × 10 −3 cm 3/K mol, for piperidine–water and pyridine–water mixtures, respectively. The results for v E for piperidine–water mixtures agree with the very precise work of Afzal et al., J. Chem. Thermodyn. 40 (2008) 47–53. The data are interpreted in terms of the greater number of opportunities for hydrogen bonding interactions between the unlike molecules for the piperidine–water mixtures.

X-ray study of melts of the Ni-Mn system

Melts of the Ni-Mn system have been X-ray studied over a wide range of concentrations at temperatures about 50°C above the liquidus line. It has been found that the concentration dependences of the averaged parameters of the local structure of atoms and molar volume are characterized by small positive deviations from additivity.