Studies on the Microscopic Mechanism of the Thermodynamic Stability of Pesticide Microemulsion

The cryo-fracture electron microscope was used to study the micro-structure of pesticide mi-croemulsions. The hydromechanical radius (Rh) and the distribution (fRh) of pesticide microemulsions were determined by photo-correlation spectroscopy. This study showed that the Rh was significantly greater when the ratio of surfactants to water (w/w) decreased to 20/31 from 27/26, and a bicontinuous structure was formed when the ratio dropped to 15/36. These results explained the relationship between pesticide properties and the microscopic structure, and provided a good method for studying the microscopic structure of pesticide formulations.

Icosahedral quasicrystal structure of the Mg_(40)Zn_(55)Nd_(5) phase and its thermodynamic stability

The quasicrystal phase is beneficial to increasing the strength of magnesium alloys.However,its complicated structure and unclear phase relations impede the design of alloys with good mechanical properties.In this paper,the Mg_(40)Zn_(55)Nd_(5) icosahedral quasicrystal(I-phase)structure is discovered in an as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).A cloud-like morphology is observed with Mg_(41.6)Zn_(55.0)Nd_(3.4) composition.The selected area electronic diffrac-tion(SAED)analysis shows that the icosahedral quasicrystal structure has 5-fold,4-fold,3-fold,and 2-fold symmetry zone axes.The thermo-dynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry(DSC)in the annealed alloys.When an-nealed above 300℃,the Mg_(40)Zn_(55)Nd_(5) quasicrystal is found to decompose into a stable ternary phase Mg_(35)Zn_(60)Nd_(5),a binary phase MgZn,andα-Mg,suggesting that the quasicrystal is a metastable phase in the Mg-Zn-Nd system.

Thermodynamic stability of interacting fermions system with matrix eigenvalue method

A matrix eigenvalue method is applied to analyse the thermodynamic stability of two-component interacting fermions. The non-relativistic and ultra-relativistic d = 1, 2, 3 dimensions have been discussed in detail, respectively. The corresponding stability region has been given according to the two-body interaction strength and the particle number density ratio.

Thermodynamic Stability Research of Metal Complexes with a Tripodal Amide Ligand and Crystal Structure of its Cobalt(Ⅲ) Complex

A new Co（Ⅲ） complex with a tripodal amide ligand [CoL（N3）3] （L = N-acetyl- N＇,N＇-bis-[（2-pyridyl）methyl]-ethylenediamine） has been synthesized and characterized structurally by X-ray diffraction. It crystallizes in orthorhombic, space group Pnma with a = 9.2515（19）, b = 12.729（3）, c = 17.273（4） A, V = 2034.0（7） A3, C16H20CoN13O, Mr = 469.38, Dc = 1.533 g/cm3, μ（MoKα） = 0.884 mm^-1, F（000） = 968, Z = 4, the final R = 0.0392 and wR = 0.0818 for 2430 observed reflections. In the complex, the amide ligand L acts as a tridentate fashion and coordinates to the Co（Ⅲ） ion through three nitrogen atoms, while the other three positions of the Co（Ⅲ） center are occupied by three terminal azide anions. The complex is connected as a 1D chain structure by intermolecular hydrogen bonds between the uncoordinated amide groups. In order to investigate the coordination ability, thermodynamic stability of the ligand L with the first-series transition metal ions （Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ） and Zn（Ⅱ）） has been studied by potentiometric titration, and the results show that the order of their stability constants conforms to the Irving-Williams sequence.

Effects of Selective Biotinylation on the Thermodynamic Stability of Human Serum Albumin

Thermal denaturation and stability of two commercially available preparations of Human Serum Albumin (HSA), differing in their advertised level of purity, were investigated by differential scanning calorimetry (DSC). These protein samples were 99% pure HSA (termed HSA99) and 96% pure HSA (termed HSA96). According to the supplier, the 3% difference in purity between HSA96 and HSA99 is primarily attributed to the presence of globulins and fatty acids. Our primary aim was to investigate the utility of DSC in discerning changes in HSA that occur when the protein is specifically adducted, and determine how adduct formation manifests itself in HSA denaturation curves, or thermograms, measured by DSC. Effects of site specific covalent attachment of biotin (the adduct) on the thermodynamic stability of HSA were investigated. Each of the HSA preparations was modified by biotinylation targeting a single site, or multiple sites on the protein structure. Thermograms of both modified and unmodified HSA samples successfully demonstrated the ability of DSC to clearly discern the two HSA preparations and the presence or absence of covalent modifications. DSC thermogram analysis also provided thermodynamic characterization of the different HSA samples of the study, which provided insight into how the two forms of HSA respond to covalent modification with biotin. Consistent with published studies [1] HSA96, the preparation with contaminants that contain globulins and fatty acids seems to be comprised of two forms, HSA96-L and HSA96-H, with HSA96-L more stable than HSA99. The effect of multisite biotinylation is to stabilize HSA96-L and destabilize HSA96-H. Thermodynamic analysis suggests that the binding of ligands comprising the fatty acid and globulin-like contaminant contributes approximately 6.7 kcal/mol to the stability HSA96-L.

Exploration of B-site alloying in partially reducing Pb toxicity and regulating thermodynamic stability and electronic properties of halide perovskites

Alloying strategies provide a high degree of freedom for reducing lead toxicity,improving thermodynamic stability, tuning the optoelectronic properties of ABX3 halide perovskites by varying the alloying element species and their contents.Given the key role of B-site cations in contributing band edge states and modulating structure factors in halide perovskites,the partial replacement of Pb2+with different B-site metal ions has been proposed.Although several experimental attempts have been made to date,the effect of B-site alloying on the stability and electronic properties of halide perovskites has not been fully explored.Herein,we take cubic CsPbBr3 perovskite as the prototype material and systematically explore the effects of B-site alloying on Pb-containing perovskites.According to the presence or absence of the corresponding perovskite phase,the ten alloying elements investigated are classified into three types(i.e.,Type Ⅰ:Sn Ge,Ca,Sr;Type Ⅱ:Cd,Mg,Mn;Type Ⅲ:Ba,Zn,Cu).Based on the first-principles calculations,we obtain the following conclusions.First,these B-site alloys will exist as disordered solid solutions rather than ordered structures at room temperature throughout the composition space.Second,the alloying of Sn and Ge enhances the thermodynamic stability of the cubic perovskite host,whereas the alloying of the other elements has no remarkable effect on the thermodynamic stability of the cubic perovskite host.Third,the underlying physical mechanism for bandgap tuning can be attributed to the atomic orbital energy mismatch or quantum confinement effect.Fourth,the alloying of different elements demonstrates the diversity in the regulation of crystal structure and electronic properties,indicating potential applications in photovoltaic s and self-trapped exciton-based light-emitting applications.Our work provides theoretical guidance for using alloying strategies to reduce lead toxicity,enhance stability,and optimize the electronic properties of halide perovskites to meet the needs of optoelectronic applications.

Energetics and thermodynamic stability of potential Fe (II) -hexa-aza-active sites for O_(2) reduction in PEM fuel cells

We present here a thermodynamic assessment of the stability behavior in acid environment at 298 and 353 K(80◦C)of two iron(II)hexa-aza-macrocyclic complexes and of an hexa-aza-iron-based site(Fe^(II)N_((4+2))/C)that should potentially be active for the oxygen reduction reaction in proton exchange membrane(PEM)fuel cells.The calculations of the equilibrium constant(K c)for the demetallation reaction indicate that the iron(II)-hexa-aza-macrocyclic complexes and Fe^(II)N_((4+2))/C are chemically stable in an acid medium at 298 and 353 K.Compared with two other potential model sites(Fe^(II)N_((4+2))/C and Fe II N(2+2)/C)that were thought to be present in the same Fe-based catalysts,K c of Fe^(II)N_((4+2))/C is two to three orders of magnitude smaller at 353 K,and three to four orders of magnitude smaller at 298 K,than K c for Fe^(II)N_((4+2))/C or Fe II N(2+2)/C,revealing the great chemical stability of Fe^(II)N_((4+2))/C.In this work,we discuss about a novel proposition that the two catalytic sites active in these Fe-based catalysts are Fe II N_(4)/C and Fe^(II)N_((4+2))/C.This proposition is in agreement with the durability behavior of these catalysts in PEM fuel cells and also with their known physico-chemical characterizations.The origin of the fast and slow decay behaviors of the different sites,which are active at the Fe–N–C-based cathode of PEM fuel cells,is also discussed.

Thermodynamic Stability, Half-Metallic and Optical Properties of Sc_(2)CoSi [001] Film:a DFT Study

The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the ?lms thermodynamic stability of the [001] direction in four cases including:Sc-Sc, Sc-Co, Sc-Si and Co-Si terminations are studied using the ?rst principles calculations(FPLAPW) within the framework of the density functional theory(DFT). The band structure calculations represent the ferromagnetic halfmetallic properties with 100% spin polarization and 0.54 e V indirect gap in spin down for Sc2 CoSi bulk with optimized lattice parameters of 6.25 A?. The total magnetic moment obtained for this compound is-1.0 μB, which is in accordance with Slater-Pauling rule. The half-metallic(HM) behavior by 100% spin polarization at Fermi level is occurred in the Sc-Si termination with a 0.32 eV gap in down spin. The optical responses have been calculated for the bulk and ScSi termination by a red shift in these parameters and the metallic treatments have been increased. According to the thermodynamic phase diagrams, it is shown the Sc-Si and Sc-Sc terminations are more stable than other terminations.

Thermodynamic Stability of Ultrafine Monodispersed Colloidal Particles of Basic Yttrium Carbonate

A series of thermodynamic parameters in formation of ultrafine monodispersed colloidal particles of Y(OH)CO3 were measured, estimated and calculated. The thermodynamic stability of Y(OH)CO3 colloidal particles was studied and discussed by phenomenological model. It is suggested that ultrafine monodispersed colloidal particles of Y(OH)CO3 are stable only in a very narrow temporary supersaturation range ( 1<x<1 .08).

Predictive modeling of critical temperatures in magnesium compounds using transfer learning

This study presents a transfer learning approach for discovering potential Mg-based superconductors utilizing a comprehensive target dataset.Initially,a large source dataset(Bandgap dataset)comprising approximately∼75k compounds is utilized for pretraining,followed by fine-tuning with a smaller Critical Temperature(T_(c))dataset containing∼300 compounds.Comparatively,there is a significant improvement in the performance of the transfer learning model over the traditional deep learning(DL)model in predicting Tc.Subsequently,the transfer learning model is applied to predict the properties of approximately 150k compounds.Predictions are validated computationally using density functional theory(DFT)calculations based on lattice dynamics-related theory.Moreover,to demonstrate the extended predictive capability of the transfer learning model for new materials,a pool of virtual compounds derived from prototype crystal structures from the Materials Project(MP)database is generated.T_(c) predictions are obtained for∼3600 virtual compounds,which underwent screening for electroneutrality and thermodynamic stability.An Extra Trees-based model is trained to utilize E_(hull)values to obtain thermodynamically stable materials,employing a dataset containing Ehull values for approximately 150k materials for training.Materials with Ehull values exceeding 5 meV/atom were filtered out,resulting in a refined list of potential Mg-based superconductors.This study showcases the effectiveness of transfer learning in predicting superconducting properties and highlights its potential for accelerating the discovery of Mg-based materials in the field of superconductivity.

Synthesis and Characterization of <i>Citrus limonum</i>Essential Oil Based Nanoemulsion and Its Enhanced Antioxidant Activity with Stability for Transdermal Application

Lemon oil (LO), also known as Citrus limonum is a highly volatile essential oil (EO) with potential therapeutic properties like anti-oxidative, anti-proliferative, anti-fungal and anti-cancerous. However, the efficacy of LO is limited due to its physiological factors such as high volatility, poor stability (particularly sensitive to sunlight) and quick degradability upon exposure. To overcome these challenges, we formulated lemon oil loaded nanoemulsion system (LO-NE) (oil-in-water), using aqueous titration method. The formulation comprised of lemon oil (LO), Tween 80 and ethanol as oil, surfactant and co-surfactant phases respectively. The existence zone of NE was established by constructing pseudo-ternary phase diagrams using different concentrations of LO, surfactant and co-surfactant (Smix). The quantitative estimation of LO was performed using a high throughput gas chromatography, revealing the presence of various compounds like Limonene, Alpha-Pinene and Linalyl acetate followed by the estimation of total phenolics and flavonoid content. The characterization of LO-NE indicated the particle size of 60 ± 2.5 nm along with the polydispersity index of 0.125 and zeta potential of −14.9 mV. The size range of the NE particles dispersed in the colloidal system was further verified by TEM micrograph which shows size range between 46.2 - 104.7 nm. All the anti-oxidant assays outcomes exhibited the higher activity of LO-NE in comparison to LO alone with lower IC50 values. The release kinetics statistical data showed that LO-NE had a sustained release and followed the Higuchi’s model in comparison to burst release of LO alone. Lastly, the stability analysis of the optimised formulation (LO-NE) and LO was estimated through antioxidant assay and subjecting them for thermodynamic stability after 6 months. The results attained, showed higher stability and anti-oxidant capability of LO-NE than LO alone. The study suggested that formulated nanoemulsion can be effectively used as a highly efficacious biologically active alternative nanoformulation against many transdermal disorders.

Thermodynamic Analysis of Chemical Vapor Deposition of BCl_3-NH_3-SiCl_4-H_2-Ar System

The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reactants, deposition temperature and total pressure) on the distribution regions of solid phase products were analyzed based on the diagrams. The results show that:(a) Solid phase products are mainly affected by deposition temperature. The area of BN+Si3N4 phase increases with the temperature rising from 650 to 900 ℃, and decreases with the temperature rising from 900 to 1 200 ℃;(b) When temperature and total pressure are constants, BN+Si3N4 phase exists at a high partial pressure of NH3;(c) The effect of total system pressure is correlated to deposition temperature. The temperature ranging from 700 to 900 ℃ under low total pressure is the optimum condition for the deposition.(d) Appropriate kinetic parameters can be determined based on the results of thermodynamic calculation. Si–B–N coating is obtained via low pressure chemical vapor deposition. The analysis by X-ray photoelectron spectroscopy indicates that B–N and Si–N are the main chemical bonds of the coating.

Oil maturity assessment using maturity indicators based on methylated dibenzothiophenes

Aromatic fractions of 140 oils and condensates that originated from different types of source rocks （marine shale,terrestrial shale and marine carbonate） were analyzed using gas chromatographymass spectrometry （GC-MS） to investigate the relative distributions of methylated dibenzothiophenes with respect to thermal maturity.The positions of methyl groups of trimethyldibenzothiophene isomers （TMDBTs） including those used in the definition of maturity indicator TMDBT index in previous studies were firmly identified by co-elution of internal standards in GC-MS analysis and by comparing with reported retention indices.A new maturity ratio related to dimethyldibenzothiophenes （DMDBTs） is proposed on the basis of the differences in thermodynamic stability among different DMDBT isomers.Another maturity index （TMDBT-I2） based on TMDBTs is also suggested on the basis of our empirical observations and presumed thermodynamic stability of TMDBT isomers.These two newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratio and TMDBT-I2 correlate well with MDR （4-/1-methyldibenzothiophene）and 2,4-/1,4-DMDBT ratios,suggesting their common chemical reaction mechanisms and similar behavior with increasing maturity.Therefore,they can be effectively applied for maturity assessments.Furthermore,the TMDBTs related maturity parameters are more reliable for over-mature oils and condensates due to the relatively higher concentrations of thermodynamically unstable TMDBT isomers,i.e.1,4,6-,1,4,8-and 3,4,6-TMDBT in this study than those of 1-methyldibenzothiophene （1-MDBT） or 1,4-DMDBT.In contrast with 4,6-/1,4-DMDBT,the newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratios for oils that originated from different types of source rocks have approximately same relationship with the oil maturity （Rc %）.This suggests that the lithology and organic facies may have relatively less influence on （2,6 ＋ 3,6）-/1,4-DMDBT ratio compared to 4,6-/1,4-DMDBT.The maturity parameters based on methylated dibenzothiophenes are particularly useful in the maturity assessments of post-and over-mature oils and condensates and can complement maturity indicators based on steranes and terpanes.

Synthesis and Application of Novel Triazine-Based Charring-Foaming Agents in Intumescent Flame Retardant Polypropylene

Three novel triazine-based charring-foaming agents (M2-CFA, M4-CFA, and M6-CFA) were synthesized successfully with only water as the solvent and were characterized by FT-IR and thermal gravimetric analysis (TGA). These three charring-foaming agents and the byproduct 944-by were employed to study the effectiveness of the novel intumescent flame retardant dopant on the fire retardancy of polypropylene(PP) investigated through UL-94 and limiting oxygen index (LOI) tests. TGA results showed that the M4-CFA presented good char formation ability (char residue: 26.8% at 700 °C). It was found that the sample with a 2/1 mass ratio of APP to M4-CFA exhibited the best flame retardancy among all the PP composites: 35.5% LOI and a V-0 rating of UL-94. Additionally, the microstructure and morphology of char residues were further studied by XRD, Raman spectroscopy and SEM. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

High volumetric hydrogen density phases of magnesium borohydride at high-pressure:A first-principles study

The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg（BH4）2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. It is found that the ambient pressure phases of meta-stable I41/amd and unstable P-3ml proposed recently are extra stable and cannot decompose under high pressure. Enthalpy calculation indicates that the ground state of F222 structure proposed by Zhou et al. [2009 Phys. Rev. B 79 212102] will transfer to I41/amd at 0.7 GPa, and then to a P-3ml structure at 6.3 GPa. The experimental P6122 structure （a-phase） transfers to I41/amd at 1.2 GPa. Furthermore, both I41/arnd and P-3ml can exist as high volumetric hydrogen density phases at low pressure. Their theoretical volumetric hydrogen densities reach 146.351 g H2/L and 134.028 g H2/L at ambient pressure, respectively. The calculated phonon dispersion curve shows that the I41/amd phase is dynamically stable in a pressure range from 0 to 4 CPa and the P-3ral phase is stable at pressures higher than 1 GPa. So the I41/arnd phase may be synthesized under high pressure and retained to ambient pressure. Energy band structures show that they are both always ionic crystalline and insulating with a band-gap of about 5 eV in this pressure range. In addition, they each have an anisotropic compressibility. The c axis of these structures is easy to compress. Especially, the c axis and volume of P-3ml phase are extraordinarily compressible, showing that compression along the e axis can increase the volumetric hydrogen content for both I41/amd and P-3ml structures.

Band gap narrowing of TiO_2 by compensated codoping for enhanced photocatalytic activity

In this study, we have performed first-principles screened exchanged hybrid density function theory with the HSE06 function calculations of the C-Mo, C-W, N-Nb and N-Ta codoped anatase TiO2 systems to investigate the effect of codoping on the electronic structure of TiO2. The calculated results demonstrate that （W（s）＋C（s）） codoped TiO2 narrows the band gap significantly, and have little influence on the position of conduction band edges, therefore, enhances the efficiency of the photocatalytic hydrogen generation from water and the photodegradation of organic pollutants. Moreover, the proper oxygen pressure and temperature are two key factors during synthesis which should be carefully under control so that the desired （W（s）＋C（s）） codoped TiO2 can be obtained.

Thermal expansion in dysprosium tungstate Dy_(10)W_2O_(21)

The complex oxide Dy_(10)W_2O_(21) was synthesized by a solid-state reactionand isolated in cubic symmetry by an X-ray diffractometry (XRD) method. Differential scanningcalorimetry (DSC) measurements show that the compound is thermodynamically stable. The intrinsicthermal expansion coefficients were determined by extra-power powder X-ray diffractometry from roomtemperature to 1000 deg C: linear coefficient alpha-bar = 1.07 X 10^(-5) deg C^(-1) and bulkcoefficient beta-bar = 3.20 X 10^(-5) deg C^(-1). Dilatometry was used to measure the extrinsicthermal expansion coefficient (9.2 X 10^(-6) deg C^(-1)).

Electronic and thermoelectric properties of alkali metal-based perovskites CsYbF3 and RbYbF3

The electronic and thermoelectric properties of alkali metal-based fluorides CsYbF3 and RbYbF3 are studied by using Wien2k and BoltzTraP codes.The structural and thermodynamic stability of these materials are confirmed by tolerance factor(0.94 and 0.99 for RbYbF3 and CsYbF3)and negative formation energy.The optimized lattice constants and bulk moduli are consistent with the results reported in the literature.The reported band gap for RbYbF3 is 0.86 eV which decreases to 0.83 eV by the replacement of Cs with Rb.The electrical and thermal conductivities along with Seebeck coefficients decrease with temperature rising from 0 K to 800 K.The large values of thermoelectric parameters for positive chemical potentials show that the character is dominated by electrons.The studied materials have figures of merit 0.82 and 0.81 at room temperature respectively,for RbYbF3 and CsYbF3 and increase with temperature rising.Therefore,the materials under study may have potential application values in thermoelectric generators and refrigerators.

Comprehensive investigation on the structural,electronic and mechanical properties of T-Mg_(32)(Al,Zn)_(49)phases in Al-Mg-Zn alloys

In the development process of crossover aluminum alloys,T-Mg_(32)(Al,Zn)_(49)phases play a significant role in the precipitation strengthening effect.However,comprehensive understandings of the structural characteristics,interactions among alloying elements,mechanical property dependence on composition variation,effects of doping and defects etc.are still inadequate.A combination of density functional theory(DFT)calculations and special quasi-random structures(SQSs)was applied to investigate the formation energies,lattice parameters,electronic structures and mechanical properties of the disordered T-phases,as well as the effects of possible defects and alloying elements.The formation energy and lattice constant of the T-phase gradually vary from 0 to-0.12 eV/atom and from 1.460 to 1.405 nm,respectively,with increasing Zn contents.Zn-3d orbitals exhibit stronger hybridization with Al-3s than Mg-3s orbitals,and this is further enhanced by increasing Zn contents,leading to improved covalency and mechanical properties of the T-phase.The T-phases show good ductility according to the Poisson's ratio ν,Cauchy's pressure and G/B.The A site is more favorable to remain vacant in Al-rich and Zn-poor environments,which is consistent with the previous experimental observations.For alloying elements,Zn atoms tends to occupy Al atoms at the B,C and F sites and Mg atoms at the G sites.Both Cu and Ag elements can decrease the formation energy of T-phases and possibly produce a greater number of T-phases during the precipitation process.The effect of Ag is more significant relative to Cu due to the deeper orbital hybridization.The computational results show good agreement with previous experimental data and provide new insights into the compositional design of new Al-Mg-Zn alloys.

Molecular levers enable anomalously enhanced strength and toughness of cellulose nanocrystal at cryogenic temperature

The quest for widespread applications especially in extreme environments accentuates the necessity to design materials with robust mechanical and thermodynamic stabilities.Almost all existing materials yield temperature-variant mechanical properties,essentially determined by their different atomic bonding regimes.In general,weak non-covalent interactions are considered to diminish the structural anti-destabilization of covalent crystals despite the toughening effect.Whereas,starting from multiscale theoretical modeling,we herein reveal an anomalous stabilizing effect in cellulose nanocrystals(CNCs)by the cooperation between the non-covalent hydrogen bonds and covalent glucosidic skeleton,namely molecular levers(MLs).It is surprising to find that the hydrogen bonds in MLs behave like covalent bindings under cryogenic conditions,which provide anomalously enhanced strength and toughness for CNCs.Thermodynamic analyses demonstrate that the unique dynamical mechanical behaviors from ambient to deep cryogenic temperatures are synergetic results of the intrinsic temperature dependence veiled in MLs and the overall thermo-induced CNC destabilization/amorphization.As the consequence,the variation trend of mechanical strength exhibits a bilinear temperature dependence with~77 K as the turning point.Our underlying investigations not only establish the bottom–up interrelations from the hydrogen bonding thermodynamics to the crystal-scale mechanical properties,but also facilitate the potential application of cellulose-based materials at extremely low temperatures such as those in outer space.