Values Of K1 Research Articles

The impact of clay fraction on the strength and stress ratio ( K 0 ) in Gulf of Mexico mudrocks and quartz silt mixtures: implications for borehole stability and fracture gradient

Mudrock strength parameters are required to improve the prediction of fracture gradient during drilling in poorly consolidated formations. Understanding the influence that mineral composition and consolidation stress have on the mechanical properties of mudrocks aids safe well design. Small changes in the mudrock clay content are shown to have significant effects on two important engineering parameters: the lateral stress ratio at rest, K 0 , and the critical state effective friction angle, ϕ ′ cs . A laboratory-testing programme using quartz silt and a Gulf of Mexico clay mixture investigates the effects of mudrock clay content on K 0 and ϕ ′ cs at two stress levels: 1 and 10 MPa. Values of K 0 and ϕ ′ cs were obtained by subjecting composition-controlled clay–silt specimens to a drained uniaxial vertical strain ( K 0 consolidation) phase, followed by an undrained compression triaxial shear phase. Triaxial tests illustrate consistent and systematic increases in K 0 and decreases in ϕ ′ cs , with increases in clay content at both stress levels. Stress dependence is observed through increases in K 0 and decreases in ϕ ′ cs with increases in stress level. Stress-dependent behaviour is shown to be more pronounced in mudrocks of high clay content. A predictive model is presented for K 0 in normally consolidated mudrocks, as a function of clay content and effective stress. The model is used to calculate the fracture gradient (least horizontal stress) profile at the International Ocean Drilling Program (IODP) Expedition 308 Site 1324. The estimated fracture gradient illustrates the effects of clay content and consolidation stress on safe mud weight design. Thematic collection: This article is part of the Geopressure collection available at: https://www.lyellcollection.org/cc/geopressure

Investigation on the Influencing Factors of K0 of Granular Materials Using Discrete Element Modelling

Earth pressure coefficient at rest K0 is commonly estimated by empirical equations, which to date has had insufficient accuracy and universality. For better prediction, the investigation on the factors influencing K0 is required. A series of discrete element method (DEM) simulations of oedometer tests are conducted to verify the key factors influencing K0 of granular materials. The influences of initial fabric anisotropy, particle shape, initial void ratio, inter-particle friction angle is investigated. The evolution of microstructure is monitored during the tests to reveal the relationship between the microstructure evolution and K0 values. The results show that the effect of fabric anisotropy exists but is limited. Particle shape, initial void ratio, and inter-particle friction angle all significantly affect the K0 values alone. According to the DEM results, an attempt is made to propose a more reasonable empirical equation in which K0 is a function of relative density, critical state friction angle, and “shape factor”. This new empirical equation has higher accuracy and can consider the effect of particle shape, inspiring the determination of K0 values in practical engineering.

Constitutive modeling of principal stress rotation associated with sand under simple shear loading

AbstractAn elasto‐plastic constitutive model is proposed to account for the effect of principal stress rotation that commonly occurs and significantly influences soil behavior. The model is based on a concept of adding plastic strain increments obtained from two mobilized planes: a plane of maximum shear stress which swings as the principal stress rotates, and a horizontal plane which is spatially fixed. Models based on the plane of maximum shear stress alone are particularly sensitive to horizontal effective stress ratioK0(=σ′x/σ′y), whereas the proposed model gives a similar skeleton behavior for soils at the same density and mean effective stress, regardless of the value ofK0, as observed in laboratory tests. The model is firstly calibrated by data from drained and undrained monotonic and cyclic Direct Simple Shear (DSS) tests onK0‐consolidated specimens of Nakdong River sand in loose and dense states. The capability of the proposed model in modeling of the conventional liquefaction effects: initial shear stress conditionα(=τ′xy/σ′y) withKαcorrections, and initial confining stress conditionσ´ywithKσcorrections, is also emphasized in this paper.

Impact of test environment on the fracture resistance of cortical bone

Water is a crucial component of bone, affecting the interplay of collagen and minerals and contributing to bone's high strength and ductility. Dehydration has been shown to significantly effect osseous mechanical properties; however, studies comparing the effects of various dehydrating environments on fracture toughness of bone are scarce. Accordingly, the crack resistance curve (R-curve) behavior of human and sheep cortical bone was characterized in a bio-bath, in ambient pressure air, and in scanning electron microscopes (SEMs) under three different environmental conditions (water vapor pressure, air pressure, and high-vacuum). The aim of this work was to better understand the impact of test environment on both intrinsic and extrinsic toughening and hence crack initiation toughness, K0 and crack growth resistance, dK/dΔa. Results show significantly lower K0 values for samples that were tested inside SEMs combined with pronounced extrinsic toughening through microcracking and crack path deflections out of the mode I plane. Importantly, all three SEM test environments gave similar results, and thus it does not matter which type of SEM is used. Ex situ testing of hydrated samples revealed similar K0 for both environments but elevated crack growth resistance for testing in ambient air relative to the bio-bath. Our data reveals the experimental difficulties to directly observe microscale crack propagation in cortical bone that resembles the in vivo situation. Ex situ testing immersed in Hanks' Balanced Salt Solution (HBSS) with subsequent crack path analysis, while tedious, is thought to presents the most realistic picture of the in vivo structure-fracture property relations in biological tissue.

A Method for Determining the Safe Thickness of Concrete Retaining Walls Based on Slab Structure Theory

The safe thickness of concrete retaining walls for curtain grouting on tunnel faces is an essential factor related to tunnel safety and grouting effects. In this research, the concrete retaining wall was simplified into a standard rectangular slab structure. The Rankine active earth pressure theory and the plastic hinge theory were used to analyze the lateral force of the concrete retaining wall. By deriving the safety-thickness equation of the concrete retaining wall, a quantitative criterion that can display the mechanism of the concrete retaining wall was obtained. The traditional empirical formula and Kalmykov formula had a particular connection with the method in this paper in determining the safe thickness of the concrete retaining wall. This was negatively related to the compressive (tensile) strength of the concrete and the groundwater level and positively associated with the buried depth of the tunnel. The conversion relationship between the traditional empirical formula and the theoretical formula was established, and the exact solution formula for the value of safety coefficient K0 was given. Finally, the rationality of the theoretical formula was verified by a field test, in novel work that provides a reference for similar projects.

A general mathematical model for the in vitro assembly dynamics of intermediate filament proteins

Intermediate filament (IF) proteins assemble into highly flexible filaments that organize into complex cytoplasmic networks: keratins in all types of epithelia, vimentin in endothelia, and desmin in muscle. Since IF elongation proceeds via end-to-end annealing of unit-length filaments and successively of progressively growing filaments, it is important to know how their remarkable flexibility, i.e., their persistence length lp, influences the assembly kinetics. In fact, their lp ranges between 0.3 μm (keratin K8/K18) and 1.0 μm (vimentin and desmin), and thus is orders of magnitude lower than that of microtubules and F-actin. Here, we present a unique mathematical model, which implements the semiflexible nature of the three IF types based on published semiflexible polymers theories and depends on a single free parameter k0. Calibrating this model to filament mean length dynamics of the three proteins, we demonstrate that the persistence length is indeed essential to accurately describe their assembly kinetics. Furthermore, we reveal that the difference in flexibility alone does not explain the significantly faster assembly rate of keratin filaments compared with that of vimentin. Likewise, desmin assembles approximately six times faster than vimentin, even though both their filaments exhibit the same lp value. These data strongly indicate that differences in their individual amino acid sequences significantly impact the assembly rates. Nevertheless, using a single k0 value for each of these three key representatives of the IF protein family, our advanced model does accurately describe the length distribution and mean length dynamics and provides effective filament assembly rates. It thus provides a tool for future investigations on the impact of posttranslational modifications or amino acid changes of IF proteins on assembly kinetics. This is an important issue, as the discovery of mutations in IF genes causing severe human disease, particularly for desmin and keratins, is steadily increasing.

Model Evaluasi Kinerja Tanggung Jawab Sosial Lingkungan Perusahaan di Kota Bogor

Corporate Social Responsibility (CSR) is a critical partnership potential in regional development. This potential is currently not too significant in its role and contribution to growth in Bogor, considering that the number is still limited. The TJSLP Secretariat encourages the participation of all parties through the preparation of a mechanism for submitting community TJSLP to the company. The purpose of this research is to develop a model for evaluating CSRs performance, which can be used as a basis for making decisions for the recommendations of the Bogor City government to corporate partners who have CSR programs. The evaluation model uses the PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluation) method to see the feasibility of the proposal with several criteria, namely the suitability of the program with the RPJMD (K1), activity category (K2), and activity costs (K3). The research resulted in a weighted value of K1=0.50, K2=0.33, K3=0.17. That look the ranking of the most appropriate in terms of the policy is Proposal B (religious), G (health), C (spiritual), H (health), A ( health), K (sports), J (education), D (economy), E (economy), I (environment), F (background). The results of sensitivity analysis, Spearman's Rho correlation coefficient of 0.97, between the results of the PROMETHEE ranking before and after the change in the weight of the criteria indicate high consistency, which is far from subjectivity. This TJSLP performance evaluation model is helpful for the TJSLP secretariat to evaluate the implementation of the CSR program in Bogor City.

On some uncertainties related to static liquefaction triggering assessments

Static liquefaction has been identified as the cause of several recent tailings storage facility (TSF) failures. Partially based on the investigations carried out, significant advances on the analysis of static liquefaction triggering (SLT) have been made. These include applications of critical-state-based models in a stress–deformation framework to identify if in situ conditions are approaching a level where SLT could occur. However, several important uncertainties remain. In this work, three of these uncertainties (geostatic stress ratio K0, intermediate principal stress ratio and principal stress angle from vertical) were investigated, along with their effects (both independently and in conjunction) on the identification of SLT and slope failure. These uncertainties were examined through a series of numerical analyses of an idealised TSF. Various values of K0 were used to examine their effect on SLT, while different approaches were taken to assess the potential effects of the intermediate principal stress ratio and the principal stress angle from vertical on instability. This work revealed that the current state of knowledge in these areas is such that significant uncertainty seems unavoidable in attempting to identify exactly when a particular slope may undergo SLT. Experimental and in situ test programmes that may be useful in reducing this uncertainty are outlined.

Kinetic Study on High-Temperature H2S Removal over Mn-Based Regenerable Sorbent Using Deactivation Model.

The kinetics of high-temperature H2S removal over Mn/Al sorbents prepared by co-precipitation method was investigated in a fixed-bed reactor using a deactivation model. The initial sorption rate constant (k0), deactivation rate constant (kd), apparent activation energy (Ea), and deactivation energy (Ed) were obtained. The k0 and kd values of Mn/Al sorbents are much higher than those of pure Mn2O3. This indicates that Mn/Al sorbents have higher reactivity on the removal of H2S and less diffusion resistance caused by the formation of the sulfided product. The Ea and Ed values for the sorbent with the Mn content (wt %) of 35.4% are 38.18 and 31.05 kJ/mol, respectively. The deactivation model gives excellent predictions for the H2S breakthrough curves in the sulfidation–regeneration process.

Análisis del espesor coroideo en pacientes con queratocono

Objective. To determine and compare choroidal thickness (CT) in keratoconus (KC) patients using Enhanced Depth Imaging (EDI) OCT. Methods. A comparative cross-sectional study including 26 patients with KC and 26 healthy controls assessed with Pentacam and EDI-OCT. CT was measured manually with the Caliper function at thirteen locations at 500 µm regular intervals. Results. The average CT in T6 was 253.96 ± 88.95 μm in the KC group, and of 309.39 ± 94.11 μm in the control group (p <0.041). No significant differences in mean CT were observed in the rest of the points, including the subfoveal CT (M), 351.48 ± 106.3 vs 365.35 ± 114.6 μm, (p = 0.66). No correlation was observed between the mean subfoveal CT (M), the mean CT in the KC group, and the values of K1 (p = 0.977 and p = 0.498 respectively), K2 (p = 0.450 and p = 0.656), corneal asphericity (Q ) (p = 0.986 and p = 0.902), minimal pachymetry (Pachy) (p = 0.408 and p = 0.688), keratoconus index (KI) (p = 0.601 and p = 0.217), vertical asymmetry index (VAT) (p = 0.296 and p = 0.523), staging of KC (TKC) (p = 0.549 and p = 0.08) and corneal apex morphology. Conclusion. Significant lower CT was found in the KC group in T6 (3000 μm temporal to the fovea). No significant difference of CT values in KC patients and healthy subjects was found in the other twelve measurement locations.We found no association between the refractive and keratometric indexes obtained by corneal topography and subfoveal CT.

Observed tidal evolution of Kleopatra’s outer satellite

Aims. The orbit of the outer satellite Alexhelios of (216) Kleopatra is already constrained by adaptive-optics astrometry obtained with the VLT/SPHERE instrument. However, there is also a preceding occultation event in 1980 attributed to this satellite. Here, we try to link all observations, spanning 1980–2018, because the nominal orbit exhibits an unexplained shift by + 60° in the true longitude. Methods. Using both a periodogram analysis and an ℓ = 10 multipole model suitable for the motion of mutually interacting moons about the irregular body, we confirmed that it is not possible to adjust the respective osculating period P2. Instead, we were forced to use a model with tidal dissipation (and increasing orbital periods) to explain the shift. We also analysed light curves spanning 1977–2021, and searched for the expected spin deceleration of Kleopatra. Results. According to our best-fit model, the observed period rate is Ṗ2 = (1.8 ± 0.1) × 10−8 d d−1 and the corresponding time-lag Δt2 = 42 s of tides, for the assumed value of the Love number k2 = 0.3. This is the first detection of tidal evolution for moons orbiting 100 km asteroids. The corresponding dissipation factor Q is comparable with that of other terrestrial bodies, albeit at a higher loading frequency 2|ω − n|. We also predict a secular evolution of the inner moon, Ṗ1 = 5.0 × 10−8, as well as a spin deceleration of Kleopatra, Ṗ0 = 1.9 × 10−12. In alternative models, with moons captured in the 3:2 mean-motion resonance or more massive moons, the respective values of Δt2 are a factor of between two and three lower. Future astrometric observations using direct imaging or occultations should allow us to distinguish between these models, which is important for our understanding of the internal structure and mechanical properties of (216) Kleopatra.

Determination of Stability Constant of The Complexes of Metal Ion Fe(III), Mn(II) And Cr(III) With Some Substituted 2-Oxo-2H-Chromene-3-Carbohydrazide Derivatives at 0.1 M Ionic Strength at 42oC

Proton ligand and metal ligand stability constant are measured for Fe(III) and 1, 2-dihydroxy benzene and 1, 5-disulphonic acid complexes . Determination of stability constant of substituted of pyrazoles with rare earth metals form complexes are reported . Effect of temperature on formation constants of 2 acetylpyridine(N benzoyl)glycine hydrazone with lanthanide(III) ions at different ionic strengths are reported. Irving and Rossotti, Herson and Gilbert , Wilkins and Lewis and Rossotti and Rossotti have determined stability constant by Bjerrum-Calvin titration technique . Kabadi , Jahagirdar and Narwade have determined pK values of salicylaldehyde, salicylic acid and sulphonic acid respectively by similar procedure. The metal ligand stability constant of some β-diketones are reported . Stability constants have investigated for some substituted pyrazolines, isoxalline and diketone . The method most frequently applied for study of complex equilibria is pH-metric titration technique . Stepwise formation of mononuclear binary complexes is described by set of equilibrium constants. For pH-metric measurements an electrode must be selected. According to Bjerrum, Martell and Calvin , the formation of complex MLN is stepwise process and one has to deal with a series of equilibria of the type: Irving and Rossotti, Herson and Gilbert , Wilkins and Lewis and Rossotti and Rossotti have determined stability constant by Calvin-Bjerrum titration technique . The value of nA,n, pK, log K1 and log K2 are evaluated by Irving and Rossotti's equation. The stability constant and thermodynamic parameters of complexes containing lighter lanthanides , copper(II) , calcium and magnesium are reported. It is also important in environmental studies , medicinal and industrial chemistry . Effects of transition metal on stability constant of complexes have studied by pH metric method . Bendi , Janrao and Ramteke have studied stability constant of ligands with lanthanide metals complexes.The present work involves pH metric study of substituted 2-oxo-2H-chromene-3-carbohydrazide derivatives with metal ions Fe(III), Mn(II), Cr(III) and Ti(III) at temperature42oC. The Bjerrum-Calvin titration technique as modified by Irving and Rossotti has been employed in the present study. The following three sets of titrations are carried out in sequence.

A parameter reduced adaptive quasi-linear viscoelastic model for soft biological tissue in uniaxial tension

Mechanical characterisation of soft viscous materials is essential for many applications including aerospace industries, material models for surgical simulation, and tissue mimicking materials for anatomical models. Constitutive material models are, therefore, necessary to describe soft biological tissues in physiologically relevant strain ranges. Hereby, the adaptive quasi-linear viscoelastic (AQLV) model enables accurate modelling of the strain-dependent non-linear viscoelastic behaviour of soft tissues with a high flexibility. However, the higher flexibility produces a large number of model parameters.In this study, porcine muscle and liver tissue samples were modelled in the framework of the originally published AQLV (3-layers of Maxwell elements) model using four incremental ramp-hold experiments in uniaxial tension. AQLV model parameters were reduced by decreasing model layers (M) as well as the number of experimental ramp-hold steps (N).Leave One out cross validation tests show that the original AQLV model (3M4N) with 19 parameters, accurately describes porcine muscle tissue with an average R2 of 0.90 and porcine liver tissue, R2 of 0.86. Reducing the number of layers (N) in the model produced acceptable model fits for 1-layer (R2 of 0.83) and 2-layer models (R2 of 0.89) for porcine muscle tissue and 1-layer (R2 of 0.84) and 2-layer model (R2 of 0.85) for porcine liver tissue. Additionally, a 2 step (2N) ramp-hold experiment was performed on additional samples of porcine muscle tissue only to further reduce model parameters. Calibrated spring constant values for 2N ramp-hold tests parameters k1 and k2 had a 16.8% and 38.0% deviation from those calibrated for a 4 step (4N) ramp hold experiment. This enables further reduction of material parameters by means of step reduction, effectively reducing the number of parameters required to calibrate the AQLV model from 19 for a 3M4N model to 8 for a 2M2N model, with the added advantage of reducing the time per experiment by 50%.This study proposes a ’reduced-parameter’ AQLV model (2M2N) for the modelling of soft biological tissues at finite strain ranges. Sequentially, the comparison of model parameters of soft tissues is easier and the experimental burden is reduced.

Evaluation of using electric arc furnace slag as an adsorbent for dyes removal

ABSTRACT The adsorption of two common textile dyes – orange G and methyl violet – onto an electric arc furnace slag was studied. Batch study shows that adsorption of orange G and methyl violet were dependent highly on pH value. Removal of orange G decreased with the increase of initial pH with optimum pH observed at 3. Moreover, the total removal percentage was low and did not exceed 45% at optimum pH. However, the removal of methyl violet increased with initial pH, and maximum removal (about 94%) was observed at pH 11. Based on the obtained data, methyl violet dye was chosen to study the effect of agitation speed, initial dye concentration, adsorbent dosage and adsorbent particle size on adsorption capacity. For the adsorbent under investigation, equilibrium adsorption capacity qe (mg/g) for orange G and methyl violet dyes were 17.4 mg/g and 3.29 mg/g, respectively. Also, batch studies show that the adsorption rate for methyl violet was rapid at the beginning and slowed down till equilibrium.In contrast, the orange G adsorption rate was slow until it approached equilibrium. The Pseudo-Second order model well represented the kinetics studies data. The value of K2 increased with adsorbent dosage while the K2 value decreased with an increase in initial dye concentration and adsorbent particle size. Equilibrium data were evaluated using Langmuir and Freundlich isotherm models and it was found that the Langmuir isotherm model best fitted to the experiments data.

MODIFIKASI KOEFISIEN DIAGRAM TEGANGAN BETON SERAT PADA BERBAGAI SUHU

Fiber concrete is a building material that has been widely introduced in Indonesia. The advantages of fiber concrete are that it can increase the tensile strength of concrete, besides fiber concrete can increase ductility compared to concrete without fibers. In this study, steel wire fibers were used. The weakness of this fiber concrete is against high temperatures. Experiments were carried out with reinforcing fiber concrete at temperatures of 332°C, 621.4°C, and 957.4°C. Fiber concrete that is burned at high temperatures has a significant decrease in strength when it is burned reaching a temperature of 957.4°C. On the stress curve, fiber concrete that is burned at a temperature of 621.4°C has a stress drop of up to 67%. The stress-strain behavior of steel-wire fiber concrete is very ductile when compared to fiber-free concrete. In the concrete stress diagram, the ß1 and k3 coefficients in fiberless concrete and fiber concrete are not the same. Based on the calculations carried out, the value of k3 in fiber concrete at various temperatures is taken as 0.92fc’, while the value of ß1 in fiber concrete at various temperatures is 0.75.

The Kinetics Investigation of CO2 Absorption into TEA and DEEA Amine Solutions Containing Carbonic Anhydrase

Tertiary amines have been used as alternative absorbents for traditional primary and secondary amines in the process of carbon capture. However, the carbon dioxide (CO2) absorption rates in these kinds of amine are relatively slow, which implies greater investment and construction costs and limits the large-scale application of carbon capture. Carbonic anhydrase (CA) is considered to be an ideal homogeneous catalyst for accelerating the rate of CO2 into aqueous amine solution. In this work, CO2 absorption combining CA with two single aqueous tertiary amines, namely triethanolamine (TEA) and 2-(diethylamino)ethanol (DEEA), was studied by use of the stopped-flow apparatus over temperature ranging from 293 to 313 K. The concentrations of selected aqueous amine solution and CA used in the experiment were ranging among 0.1–0.5 kmol/m3 and 0–50 g/m3 , respectively. Compared to the solution without the addition of CA, the pseudo first-order reaction rate in the presence of CA (k0,withCA) is significantly increased. The values of k0,withCA have been calculated by a new kinetics model. The results of experimental and calculated k0,amine and k0,withCA in CO2-amine-H2O solutions were also investigated,respectively.

Isoflurane as an Accurate Negative Mode Calibrant for Ion Mobility Spectrometry.

The search for suitable ion mobility spectrometry (IMS) calibrant compounds is ongoing and necessitates the use of highly accurate reduced ion mobility (K0) values across a range of instrumental conditions. Such values will be used in calibrating devices to shift the ion mobility scales and alarm windows for chemicals of interest to their proper locations based on the instrumental conditions present during calibration and sampling. Many positive ion mode calibrants have been investigated, whereas investigations for a negative ion detection mode calibrant have been more limited. Isoflurane (IsoF) is a strong candidate as a negative ion mode calibrant. This report documents the accurately measured K0 values for IsoF product ions as a function of multiple instrumental parameters. K0 values were measured in two instrumentation modes as a function of drift gas temperature, water concentration, and dopant concentration. This report culminates with our evaluation of the suitability of IsoF as a negative ion mode calibrant for IMS applications.

Laser‐Induced Graphene on Paper toward Efficient Fabrication of Flexible, Planar Electrodes for Electrochemical Sensing

AbstractLaser irradiation to induce networks of graphene‐based structures toward cost‐effective, flexible device fabrication is a highly pursued area, with applications in various polymeric substrates. This work reports the application of this approach toward commonly available, eco‐friendly, low‐cost substrates, namely, chromatographic and office papers. Through an appropriate chemical treatment with sodium tetraborate as a fire‐retardant agent, photothermal conversion to porous laser‐induced graphene (LIG) on paper is achieved. Raman peaks are identified, with I2D/IG and ID/IG peak ratios of 0.616 ± 0.095 and 1.281 ± 0.173, showing the formation of multilayered graphenic material, exhibiting sheet resistances as low as 56.0 Ω sq–1. Coplanar, LIG‐based, three‐electrode systems (working, counter and reference electrodes) are produced and characterized, showing high current Faradaic oxidation and reduction peaks, translating in high electrochemical active area, doubling the geometric area. Good electron transfer kinetics performed exclusively with on‐chip measurements are reached, with k0 values as high as 7.15 × 10–4 cm s–1. Proof‐of‐concept, amperometric, enzymatic glucose biosensors are developed, exhibiting good analytical performance in physiologically relevant glucose levels, with results pointing to the applicability of paper‐based LIG toward efficient, disposable electrochemical sensor development, increasing their sustainability and accessibility, while simplifying their production and reducing their cost.

Matching of models of Titan with tidal Love numbers

The restrictions on the heat flux, the structure of the water-ice shell, and the composition of the Titan ocean, which are necessary to match the calculated (model) and experimental Love numbers, are considered. Estimates are obtained for model Love numbers and maximum surface heat fluxes for the L/LL chondrite composition of the rock-iron component of Titan, taking into account the radiogenic and tidal energy, as well as the energy of ice crystallization in the ocean due to satellite cooling. The values of the tidal Love numbers k2 of Titan were calculated for various models of the water-ice shell of the satellite, including the outer ice crust (ice Ih ± CO2 clathrates) and the internal ocean of various compositions (pure or sea water, ammonia + dissolved salts solution, aqueous solutions of ammonia and methanol). Titan models with an outer ice crust (ice Ih + 5% CO2 clathrates) and with an internal ocean of low salinity based on ammonia (5% NH3) aqueous solution better than other tested models satisfy the k2 experimental values.

Thermostructural and Elastic Properties of PbTe and Pb0.884Cd0.116Te: A Combined Low-Temperature and High-Pressure X-ray Diffraction Study of Cd-Substitution Effects

Rocksalt-type (Pb,Cd)Te belongs to IV–VI semiconductors exhibiting thermoelectric properties. With the aim of understanding of the influence of Cd substitution in PbTe on thermostructural and elastic properties, we studied PbTe and Pb0.884Cd0.116Te (i) at low temperatures (15 to 300 K) and (ii) at high pressures within the stability range of NaCl-type PbTe (up to 4.5 GPa). For crystal structure studies, powder and single crystal X-ray diffraction methods were used. Modeling of the data included the second-order Grüneisen approximation of the unit-cell-volume variation, V(T), the Debye expression describing the mean square atomic displacements (MSDs), <u2>(T), and Birch–Murnaghan equation of state (BMEOS). The fitting of the temperature-dependent diffraction data provided model variations of lattice parameter, the thermal expansion coefficient, and MSDs with temperature. A comparison of the MSD runs simulated for the PbTe and mixed (Pb,Cd)Te crystal leads to the confirmation of recent findings that the cation displacements are little affected by Cd substitution at the Pb site; whereas the Te displacements are markedly higher for the mixed crystal. Moreover, information about static disorder caused by Cd substitution is obtained. The calculations provided two independent ways to determine the values of the overall Debye temperature, θD. The resulting values differ only marginally, by no more than 1 K for PbTe and 7 K for Pb0.884Cd0.116Te crystals. The θD values for the cationic and anionic sublattices were determined. The Grüneisen parameter is found to be nearly independent of temperature. The variations of unit-cell size with rising pressure (the NaCl structure of Pb0.884Cd0.116Te sample was conserved), modeled with the BMEOS, provided the dependencies of the bulk modulus, K, on pressure for both crystals. The K0 value is 45.6(2.5) GPa for PbTe, whereas that for Pb0.884Cd0.116Te is significantly reduced, 33.5(2.8) GPa, showing that the lattice with fractional Cd substitution is less stiff than that of pure PbTe. The obtained experimental values of θD and K0 for Pb0.884Cd0.116Te are in line with the trends described in recently reported theoretical study for (Pb,Cd)Te mixed crystals.