Deviation Of Constants Research Articles

Metabolic disorders and androgen deficiency in the pathogenesis of urolithiasis

This review summarizes and critically analyzes current data on the pathogenesis of urolithiasis (urolithiasis, nephrolithiasis). Emphasis is placed on such issues as: mechanisms of urinary stone formation; risk factors for stone formation; the role of oxidative stress; the chemical composition of renal stones (and especially oxalates); the role of Randall’s plaques, osteopontin, uromodulin (Tamm–Horsfall protein), α-enolase; and the mechanism of stone formation in the collecting ducts. Insufficiently studied issues of microbiota influence — (a) kidney and urinary tract and (b) gastrointestinal tract are also considered. Attention is paid to new approaches to understanding the pathogenesis and treatment of urolithiasis, namely works on genetics, epigenetics, genetic engineering and proteomics. The imperfection of existing animal models of urolithiasis is shown. The issue of application of androgen replacement therapy in the treatment of patients suffering from urolithiasis is considered separately. The author considers the main theoretical result of his work to be the approval of the idea of urolithiasis as a systemic disease, in which any significant deviation of the internal environment constants violates the delicate balance that ensures the solubility of substances in primary urine and their excretion with secondary urine. The practical result is to confirm the applicability of androgen replacement therapy in the treatment of patients suffering from urolithiasis.

Reducing phase errors in multimode interference coupler by side grooves formed on its top surface.

The performance of multimode interference (MMI) couplers is limited by the presence of phase errors that represent the deviation of the propagation constants of the modes from the quadratic dependence on their order. In this work, we propose a simple and effective method for reducing the phase errors of spatial modes to a relatively high order by forming rectangular grooves near the side edges of the MMI coupler along its entire length. The influence of the groove dimensions and position on the propagation constants of higher-order modes is analyzed using the perturbation method and strict vector simulations for high- and medium-index contrast material platforms. Through numerical simulations, we demonstrate the effectiveness of the proposed method in improving the performance of air-cladded dual-mode (T E 0 and T E 1) MMI-based 50:50 and 100:0 splitters for 1.31µm wavelength made of medium- and high-contrast materials, T i O 2:S i O 2/S i O 2 and S i/S i O 2, respectively.

PHYSIOLOGICAL AND PATHOLOGICAL ASPECTS OF THE AGING PROCESS

Demographic changes in the world have begun to raise concerns among experts that health systems, pension funds, as well as health insurance companies and the public funding system will be affected in the long run, changes that will be severely affected by the rapid growth of population. The extent of older people's needs is growing and includes environmental, psychological, social, educational and financial functional confluences as well as physiological and structural problems. The elderly challenge the health care systems due to multiple levels of their needs. In general, medical problems are the result of poor nutrition, deviation of physiological constants, disorders in regulating the inflammatory reaction, walk disorder, immobility, confusion, syncope, sleep disorders. As a result, even the road to the pharmacy can be a torment. The physiological changes that occur as we age are undeniable. The most common visible changes are related to greying hair, changes in the perception of the sense organs, changes in the appearance of the skin, muscle tone, etc. Loss of vision may be a barometer of the onset of aging in somatically healthy patients

Exact quantum dynamics study of the H(2S)+SiH+(X1Σ+) reaction on a new potential energy surface of SiH * *Project supported by the National Natural Science Foundation of China (Grant Nos. 11674198 and 11804193), the Shandong Provincial Natural Science Foundation of China (Grant No. ZR2019PA012), and the First-class Discipline Construction Foundation of Shandong Agricultural University.

Based on a new global potential energy surface of , the exact quantum dynamical calculation for the H(2 S) + SiH+(X1Σ+) → H2 + Si+ reaction has been carried out by using the Chebyshev wave packet method. The initial state specified (ν i = 0, j i = 0) probabilities, integral cross sections (ICS) and thermal rate constants of the title reaction are calculated. All partial wave contributions up to J = 90 are calculated in exact quantum calculation including the full Coriolis coupling (CC) effect. The dynamical behaviors of probabilities, ICSs and rate constants are found to be in accord with an exothermic reaction without potential barrier. By comparing the probabilities of CC with the corresponding centrifugal sudden (CS) approximation ones, it can be concluded that neglecting CC effect will decrease the collision time, increase the amplitude of oscillation and lead to overestimation or underestimation of the reaction probability. For ICSs and rate constants, it is found that the deviation of CC and CS ICSs is small in the most of collision energy range except for the range of 0 eV–0.05 eV, while the deviation of both rate constants is considerable in the temperature range of 16 K–1000 K.

Development of control system for waste pyrolysis unit of agricultural complex with the application of fuzzy logic

The object of research is the control system for the pyrolysis reactor of agricultural waste (plant biomass). The subject of research is the stability and the value of the calorific value of synthesis gas formed by pyrolysis of plant biomass. The biggest problem of the technological object (the pyrolysis reactor of agricultural waste) is the high sensitivity of the heating value of synthesis gas to disturbances in the composition of plant biomass. This sensitivity is expressed as a square law of the amount of oxidant required to achieve a high calorific value. Another problem is the deviation of certain time constants of the control object, caused by changes in the chemical composition of the plant biomass. The built control system provides a high calorific value of the generated syngas by determining the composition of the waste, pyrolysis by determining the composition of the generated syngas in a separate isoenthalpic device, and stabilizes it. Information on the composition of raw materials allows to calculate the optimal parameters for the pyrolysis process, and, accordingly, update the controller's task. This information also makes it possible to compensate for changes in the time constants of the control object caused by changes in the chemical composition of raw materials, which made it possible to achieve a high robustness of the system. Compensation for these changes was carried out by training a regression polynomial. The training was carried out on test sets of time constant deviations. The resulting polynomials were used for convolution with membership functions of a fuzzy controller. Such a convolution made it possible to obtain the following membership functions that ensure compliance with the control quality parameters close to those obtained without deviations in the time constants. Simulation of the constructed control system showed a significantly reduced sensitivity of the calorific value to the composition of raw materials, and also revealed a low sensitivity of the control quality from the deviations of the time constants of the control object caused by disturbances in the chemical composition of the waste. The method by which the control system for the pyrolysis reactor was built differs from the existing ones in that the use of information on the composition of the pyrolyzed substance is used to accurately calculate the optimal values of the pyrolysis parameters, as well as to mutate the membership functions of the fuzzy controller. The method can be used in other similar systems designed for the pyrolysis of organic substances in order to expand their scope. In particular, for the integration of such systems into technological objects, they are more sensitive to deviations in the calorific value of the gas used as fuel.

Low-temperature properties of nematic liquid crystal materials for display

ABSTRACT The orientation of Nematic liquid crystal (NLC) and order degree of LC molecules are easily affected by ambient temperature, so it is of great significance to explore the low-temperature properties of NLC materials to improve the low-temperature performance of LC devices. The dielectric and elastic constant of the NLC material 1M10500-000 under the high and low-temperature conditions were obtained by the dual-cell capacitance method, linear fitting method and numerical fitting, and were compared. The dynamic response of the NLC at different temperatures was tested, and the rotational viscosity was calculated. The experimental results show that the dielectric constant is still proportional to the order parameter at low temperature. The elastic constants k 11 and k 33 and the square of order parameter no longer conform to the proportional relationship at low temperature, and the lower the temperature, the greater the deviation of elastic constants from the proportional relationship. As the temperature decreases, the ratio of k 33/k 11 changes from 2.62 to 2.71, and the rotational viscosity coefficient changes from 5.66 mPa.s to 177.64 mPa.s. Finally, the transient hysteresis phenomenon at low temperature was proposed and explained by the residual direct current voltage.

Selectivity evaluation of core-shell silica columns for reversed-phase liquid chromatography using the solvation parameter model

For the selectivity evaluation of core-shell silica, siloxane-bonded reversed-phase columns by the solvation parameter model a minimal set of thirty-five calibration compounds were identified for applications with mobile phases containing from 20-70 % (v/v) methanol- or acetonitrile-water. The Kennard-Stone uniform mapping algorithm was employed to select the calibration compounds from a larger database of compounds with known retention properties used previously for column selectivity evaluation. The number and identity of the calibration compounds was optimized by considering the statistical quality of the calibration models, the absolute value for the standard deviation of the individual system constants, and the closeness of the estimated system constants for the calibration models to the values for the full data set on seven core-shell columns with different morphology for mobile phases containing 50 % (v/v) methanol- or acetonitrile-water. The predictive capability of the calibration models was evaluated for an external test set for 50 % (v/v) methanol-water for the same columns with a typical root mean square error of prediction (log k) of 0.028 for the thirty-five calibration compounds (n = 35) models. For all columns and mobile phase compositions the calibration models with n = 35 had a range for the coefficient of determination from 0.999 to 0.970 with < 5 % smaller than 0.99 (84 models) and a standard error of the estimate from 0.011 to 0.057 with 75 % < 0.030. System constants determined at 10 % (v/v) increments of organic solvent were utilized for the construction of system maps and correlation diagrams on Kinetex columns with octadecylsiloxane-bonded (C18 and EVO C18), diisobutyloctadecylsiloxane-bonded (XB-C18) octylsiloxane-bonded (C8), biphenylsiloxane-bonded (Biphenyl), phenylhexylsiloxane-bonded (Phenyl-Hexyl) and pentafluorophenylpropylsiloxane-bonded (F5) silica stationary phases for 20-70 % (v/v) methanol- and acetonitrile-water mobile phases. System maps for the Kinetex Phenyl-Hexyl column and correlation diagrams for columns of similar selectivity (Kinetex C8 and Phenyl-Hexyl) and dissimilar selectivity (Kinetex EVO C18 and Biphenyl) is used to illustrate the general approach to selectivity evaluation.

Selection of calibration compounds for selectivity evaluation of siloxane-bonded silica columns for reversed-phase liquid chromatography by the solvation parameter model

For the faster evaluation of selectivity in reversed-phase liquid chromatography of siloxane-bonded silica columns using the solvation parameter model a minimal set of calibration compounds is described suitable for mobile phase composition from 20-70% (v/v) methanol-, acetonitrile-, or tetrahydrofuran-water. The Kennard-Stone uniform mapping algorithm is used to select the calibration compounds from a larger database of compounds with known retention properties used earlier for column selectivity evaluation. Thirty-five compounds are shown to be necessary to minimize the standard deviation of the system constants and to minimize the difference between the system constants determined by conventional calibration and the values obtained for the reduced calibration compounds. The models for SunFire C18 with methanol-, acetonitrile- and tetrahydrofuran-water mobile phase compositions and XBridge Shield RP18, XBridge C8, XBridge Phenyl and Discovery HS F5 with methanol- and acetonitrile-water mobile phase compositions had an average coefficient of determination of 0.996 (standard deviation = 0.003, n = 11) and average standard error of the estimate 0.025 (standard deviation = 0.005, n = 11) for the reduced calibration compounds. Some octadecylsiloxane-bonded silica stationary phases with a high bonding density and methanol-water mobile phase compositions containing ≤ 30% (v/v) methanol exhibit extreme retention factors (log k > 2.5) for the low-polarity, two-ring aromatic compounds in the thirty-five compound calibration set. Alternative calibration compounds with more favorable retention properties are suggested as replacements in these cases. The predictive capability of the calibration models is validated using external test sets characterized by the average error, average absolute error and root mean square error of prediction. For the thirty-five calibration compounds sets the average absolute error 0.026 (standard deviation = 0.009, n = 11) and root mean square error of prediction 0.032 (standard deviation = 0.010, n = 11) confirm the suitability of the calibration models for column selectivity evaluation. System maps for XBridge Shield RP18 for 20-70% (v/v) methanol-water and Synergi Hydro-RP and 50% (v/v) methanol-water at temperatures from 25-65 °C together with a correlation diagram for XBridge Shield RP18 and SunFire C18 are presented as representative applications of the reduced calibration compounds for column selectivity evaluation.

Selection of calibration compounds for selectivity evaluation of wall-coated, open-tubular columns for gas chromatography by the solvation parameter model.

To facilitate faster selectivity evaluation of wall-coated, open-tubular columns using the solvation parameter model a reduced set of calibration compounds is identified and validated for the temperature ranges 60-140 °C and 160-260 °C. The Kennard-Stone uniform mapping algorithm is used to identify the calibration compounds from a larger database of compounds with known retention properties previously adopted for column selectivity evaluation. Thirty-five compounds for each temperature range are required to minimize the standard deviation of the system constants used for selectivity evaluation and to minimize differences between system constants determined by conventional calibration and the reduced calibration compounds. The models for the reduced calibration compounds on ten siloxane-based and poly(ethylene glycol) stationary phases have a coefficient of determination of 0.984 to 0.998 and standard error of the estimate of 0.012 to 0.30. The predictive capability of models is evaluated for the reduced sets of calibration compounds using external test sets with ranking of the calibration models by changes in the average error, average absolute error and root mean square error of prediction for the test sets. For the selected thirty-five reduced calibration compounds the range for the average absolute error was 0.014 to 0.033 and 0.016 to 0.040 for the root mean square error of prediction for the independent test sets.

First-principle calculations of the fundamental properties of CuBrxI1−x ternary alloy

Ab initio full-potential linearised augmented plane wave (FP-LAPW) method within density functional theory is applied to study the effect of composition on the structural, electronic and thermodynamic properties of CuBrxI1−x ternary alloy. The structural properties at equilibrium are investigated by using the new form of generalised gradient approximations that are based on the optimisation of total energy. For band structure calculations, both Engel–Vosko and modified Becke–Johnson of the exchange-correlation energy and potential, respectively, are used. Deviation of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence are observed. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing ∆Hm as well as the phase diagram by calculating the critical temperatures. A numerical first-principle calculations of the elastic constants as function of pressure is used to calculate C11, C12 and C44.

Pressure induced lattice anomalies in pnictides

Hydrostatic pressure Raman and synchrotron XRD measurements at room temperature have been carried out on a series of NdFeAsO1−xFy (Nd1111) oxypnictides in order to investigate pressure-induced lattice modifications. The synchrotron XRD data indicate that there is an increased deviation of the lattice constants from smooth pressure dependence in the superconducting compound, in close agreement with the results from SmFeAsO1−xFx (Sm1111), although the effect is less pronounced in Nd1111. As in Sm1111 the hydrostatic pressure Raman measurements show that the A1g mode of the rare earth atom deviates from the linear pressure dependence. Anomalous pressure dependence and a hysteresis is observed in the phonon width of the phonon modes. The calculated Grüneisen parameter for the Nd phonon is very similar to the corresponding value for SmFeAsO1−xFx compound and it does not vary with substitution. For the As mode it has a lower value indicating a stiffer phonon with the increased ion size. In connection with the XRD measurements the Raman data show a sudden increase of the pressure-induced lattice anomalies close to doping where the compounds become superconducting.

Environmental variation of constants in screened modified theories of gravity

Models of modified gravity, whereby local tests of gravity are evaded thanks to a screening mechanism of the chameleon or Damour-Polyakov types, lead to a spatial variation of the particle masses and the fine structure constant. This is triggered by the environmental dependence of the value of the scalar field whose presence modifies gravity. In dense media, the field settles at a density dependent value while in sparse environments it takes the background cosmological value. We estimate that the maximal deviation of constants from their present values is constrained by local tests of gravity, and must be less than $1{0}^{\ensuremath{-}6}$.

Theoretical Investigations of the Physical Properties of Cd1−xCaxO Ternary Alloys

The structural, electronic and thermodynamic properties of Cd1−xCaxO ternary alloys are calculated using the first principles calculations performed within the framework of density functional theory. The exchange correlation potential for structural properties is calculated by the standard generalized gradient approximation (GGA) of Perdew et al., while for the electronic properties, the modified Becke-Johnson (MBJ) scheme is also applied. A deviation of the lattice constants from Vegard's law and bulk modulus from linear concentration dependence (LCD) are observed for the alloys. In addition, the thermodynamic stability of the alloys is investigated by calculating the critical temperatures of alloys.

Structural, electronic and thermodynamic properties of SrxCd1−xO: A first-principles study

First principles calculations have been performed within the framework of density functional theory to investigate the structural, electronic and thermodynamic properties of SrxCd1−xO ternary alloys. The exchange-correlation potential for structural properties was calculated by the standard local density approximation (LDA) and GGA (PBE), a more accurate nonempirical density functional generalized gradient approximation (GGA), as proposed by Wu and Cohen [Physical Review B 73 (2006) 235116], while for electronic properties, the Engel and Vosko GGA (EVGGA) and the modified Becke–Johnson (MBJ) of the exchange-correlation energy and potential, respectively, are used. Deviation of the lattice constants from Vegard's law and bulk modulus from linear concentration dependence (LCD) were observed for the ternary alloys. The MBJ band gaps values agree well with the available experimental results. In addition the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.

Analysis of the composition of (Al,Ga)As alloys by secondary ion mass spectroscopy and X-ray diffractometry

Calibration lines for the layer-by-layer analysis of the concentration of matrix elements in AlxGa1 − xAs layers are obtained using a TOF.SIMS-5 secondary-ion mass spectrometer. The alloy concentration for the set of test samples was independently measured by high-resolution X-ray diffractometry allowing for deviation of the lattice constants and elastic moduli from Vegard’s law. It is shown that when using Cs+ sputtering ions and a Bi+ beam in secondary-ion mass spectrometry, the dependence of the intensity ratio Y(CsAl+)/Y(CsAs+) on x(AlAs) is close to linear for positive ions; and when detecting negative ions, the dependence Y(Al2As−)/Y(As−) on x is close to linear. These data allow us to normalize the profiles of layer-by-layer analysis in the AlxGa1 − xAs/GaAs system. In addition, a simple variant for the introduction of corrections to the deviation from Vegard’s law in the X-ray data is suggested.

Structural, electronic, thermodynamic and optical properties of alkaline earth oxides MgO, SrO and their alloys

The structural, electronic, optical and thermodynamic properties of Mg1−xSrxO ternary alloys in NaCl structures at various Sr concentrations are presented. The calculations were performed using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the local density approximation (LDA) and two developed refinements, namely the generalized gradient approximation (GGA) of Perdew et al (1996 Phys. Rev. Lett. 77 3865) for the structural properties and Engel and Vosko (1993 Phys. Rev. B 47 13164) for the band structure calculations. Deviation of the lattice constants from Vegard's law and the bulk modulus from the linear concentration dependence (LCD) were observed for the alloys. The microscopic origins of the gap bowing were explained by using the approach of Bernard and Zunger (1986 Phys. Rev. Lett. 34 5982). The refractive index and optical dielectric constant for the alloys of interest were calculated by using different models. In addition, the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.

Ab initio structural parameters and transition pressures of GaN x As1− x dilute alloys

The results are presented of an ab initio total energy study of the high-pressure phases of GaN x As1− x dilute alloys calculated within the full-potential linearized augmented plane wave method in the generalized gradient approximation. Three candidate structures, namely zinc-blende, rocksalt and CsCl, have been considered. In each case, the structural parameters and transition pressures of dilute alloys of interest are calculated. In agreement with earlier calculations of Stenuit and Fahy [Phys. Rev. B 76 (2007) 035201], the deviation of the lattice constants from Vegard's law for zinc-blende GaN x As1− x alloys is found to be negligible.

Measurement of Elastic Constants of Nanohoneycomb Structures

Five engineering constants of transversely isotropic nanohoneycomb material are obtained, using one tensile test, two bending tests, and two indentation tests. The advantage is that all these tests can be carried out using only simple beam shape specimens. In all but the tensile test, a desired material constant is to be extracted from mixed materials constants. A disadvantage is that the deviation of the desired material constants are increased by the deviation of other related material constants. This is the first attempt to measure mechanical properties of microscopic specimens of brittle transversely isotropic material. It is intended to lay the foundation for easy and simple measurement of complex material constants of microscopic specimens.

FP-LAPW investigations of SrS1−xSex, SrS1−xTex and SrSe1−xTex ternary alloys

The ab initio full potential linearized augmented plane wave (FP-LAPW) methodwithin density functional theory (DFT) was applied to study the effect ofcomposition on the structural, electronic, optical and thermodynamic properties ofSrS1−xSex,SrS1−xTex and SrSe1−xTex ternary alloys. For exchange–correlation energy and corresponding potential, thegeneralized gradient approximation (GGA) by Perdew–Burke–Ernzerhof (PBE) andEngel–Vosko (EVGGA) have been used. Deviation of the lattice constants from Vegard’slaw and the bulk modulus from linear concentration dependence (LCD) were observed forthe three alloys. The microscopic origins of the gap bowing were explained by using theapproach of Zunger and co-workers. The refractive index and optical dielectric constant forthe alloys of interest are calculated by using different models. In addition thethermodynamic stability of the alloys was investigated by calculating the criticaltemperatures of alloys.

Interactions of Fluorinated Gases with Ionic Liquids: Solubility of CF4, C2F6, and C3F8 in Trihexyltetradecylphosphonium Bis(trifluoromethylsulfonyl)amide

The interactions between ionic liquids and totally fluorinated alkanes are investigated by associating gas solubility measurements with molecular simulation calculations. Experimental values for the solubility of perfluoromethane, perfluoroethane, and perfluoropropane in one ionic liquidtrihexyltetradecylphophonium bis(trifluoromethylsulfonyl)amide [P 6,6,6,14][Ntf 2]are reported between 303 and 343 K and close to atmospheric pressure. All mole fraction solubilities decrease with increasing temperature. From the variation of Henry's law constants with temperature, the thermodynamic functions of solvation were calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry's law constants from appropriate smoothing equations, is always better than +/-3%. By the analysis of the differences between the solute-solvent radial distribution functions of perfluoromethane and perfluoropropane obtained by molecular simulation, it was possible to explain why solubility increases with the size of the perfluoroalkane. The trend of solubility is explained on the basis of the location of the solute with respect to the solvent ions as well as on the differences in the solute-solvent energies of interaction.