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During RNA-induced silencing complex (RISC) assembly the guide (or antisense) strand has to separate from its complementary passenger (or sense) strand to generate the active RISC complex. Although this process was found to be facilitated through sense strand cleavage, there is evidence for an alternate mechanism, in which the strands are dissociated without prior cleavage. Here we show that the potency of siRNA can be improved by modulating the internal thermodynamic stability profile with chemical modifications. Using a model siRNA targeting the firefly luciferase gene with subnanomolar IC50, we found that placement of thermally destabilizing modifications, such as non-canonical bases like 2,4-difluorotoluene or single base pair mismatches in the central region of the sense strand (9-12 nt), significantly improve the potency. For this particular siRNA, the strongest correlation between the decrease in thermal stability and the increase in potency was found at position 10. Controls with stabilized sugar-phosphate backbone indicate that enzymatic cleavage of the sense strand prior to strand dissociation is not required for silencing activity. Similar potency-enhancing effects were observed as this approach was applied to other functional siRNAs targeting a different site on the firefly luciferase transcript or endogenously expressed PTEN.

The K2O‐Al2O3‐SiO2 system is an important component of microcrystalline glass. The K2O‐Al2O3 and K2O‐SiO2 binary systems and the K2O‐Al2O3‐SiO2 ternary system were thermodynamically evaluated and optimized using the CALculation of PHAse Diagram (CALPHAD) method. The liquid phase is described by using the ionic two‐sublattice model, and the solid solutions involved in the ternary system are all described using the compound energy formalism (CEF) model. The new parameters obtained from the optimization are capable of describing the equilibrium phase relations of the ternary system and its subsystems, and the calculated thermodynamic properties of the ternary compounds are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Knowledge about the thermodynamic equilibria of the P2O5-Na2O and P2O5-MgO systems is very important for controlling the phosphorus content of steel materials in the process of steelmaking dephosphorization. The phase equilibrium and thermodynamic data of the P2O5-Na2O and P2O5-MgO systems were critically evaluated and re-assessed by the CALPHAD (CAlculation of PHAse Diagram) approach. The liquid phase was described by the ionic two-sublattice model for the first time with the formulas (Na+1)P(O−2, PO3−1, PO4−3, PO5/2)Q and (Mg+2)P(O−2, PO3−1, PO4−3, PO5/2)Q, respectively, and the selection of the species constituting the liquid phase was based on the structure of the phosphate melts. A new and improved self-consistent set of thermodynamic parameters for the P2O5-Na2O and P2O5-MgO systems was finally obtained, and the calculated phase diagram and thermodynamic properties exhibited excellent agreement with the experimental data. The difference in the phase composition of invariant reactions from the experimentally determined values reported in the literature is less than 0.9 mol.%. The present thermodynamic modeling contributes to constructing a multicomponent oxide thermodynamic database in the process of steelmaking dephosphorization. [ABSTRACT FROM AUTHOR]

The aim of the present study is the CALPHAD modeling of the systems CaO-SiO2-M2O (M=K,Na) based on a careful review of the available literature data – phase diagram and thermodynamics – as well as own experiments. The heat capacities (Cp) of three compounds, CaSiO3, K2Ca2Si2O7 and K8CaSi10O25 (determined using drop calorimetry), were included in the optimization of the ternary phase diagram CaO-SiO2-K2O.

It is necessary to strictly control the iron (Fe) impurity in Mg-Al alloys to guarantee good corrosion resistance and mechanical properties. In this work, the effects of alloying elements and temperatures on the solubilities of Fe in the Mg-Al-based alloy melts (Mg-rich liquid phases) at 963–1033 K were studied by combining the in situ sampling method for the high precision solution values and the multiple regression numerical analysis method for the feature analysis. The solubilities of Fe in Mg-xAl (x = 1 and 3 wt.%) alloy melts could be significantly reduced by adding the yttrium (Y) or manganese (Mn) elements. However, the solubilities of Fe in Mg alloy melts were not in a monotonous relationship with the contents of the alloying elements in the Mg alloys. For the addition of Mn or Y, the lowest solubilities of Fe presented in the Mg-rich liquid phases were for the Mg-xAl alloys with the addition of 2 wt.% Mn or 1 wt.% Y, respectively. Additionally, the Fe-containing precipitations in the related systems were analysed and the Fe was mainly combined with Mn or Y and precipitated, which contributed to the removal of Fe from the Mg melt. The present study provides fundamental thermodynamic information regarding Mg-Al-Fe based systems and the design principle for the removal of Fe in Mg alloys. [ABSTRACT FROM AUTHOR]

The Al-Ca-Ni ternary system has been experimentally investigated and thermodynamically assessed to contribute to the development of a novel Al-base amorphous alloy. A new approach in alloy preparation was used due to the special properties of calcium. With selected equilibrated alloys, the isothermal sections of the Al-Ca-Ni system at 873 and 673 K were obtained by means of scanning electron microscopy, electron probe micro-analysis (EPMA) and powder X-ray diffractometry (XRD). Phase transformation temperatures were measured by differential scanning calorimetry (DSC) analysis. The liquidus projection of this ternary system was determined by identification of primary crystallization phases in as-cast samples and from the liquidus temperatures obtained from DSC analysis. A new ternary compound AlCaNi (referred to as τ here after) has been confirmed to exist in both the 873 and 673 K isothermal sections on the basis of EPMA and XRD analysis. All sample compositions are Al-rich: A1-A4 samples > 72.64 at.% Al, B1-B10, C1-C11 > 45 at.% Al, with only C12 at 36.8 at.% Al. Based on the available data of the binary systems Al-Ni, Al-Ca, Ca-Ni and the ternary system Al-Ca-Ni from the literature and present work, thermodynamic modelling of the Al-Ca-Ni ternary system was performed using the calculation of phase diagram method coupled with first-principle calculations. A set of consistent thermodynamic parameters for the Al-Ca-Ni ternary system was obtained with good agreement with the experimental results in the Al-rich region. The calculated data in the Al-poor region are a very plausible prediction, but not validated. [ABSTRACT FROM AUTHOR]

An overview about one thermodynamic database of multi-component Mg alloys is given in this work. This thermodynamic database includes thermodynamic descriptions for 145 binary systems and 48 ternary systems in 23-component (Mg–Ag–Al–Ca–Ce–Cu–Fe–Gd–K–La–Li–Mn–Na–Nd–Ni–Pr–Si–Sn–Sr–Th–Y–Zn–Zr) system. First, the major computational and experimental tools to establish the thermodynamic database of Mg alloys are briefly described. Subsequently, among the investigated binary and ternary systems, representative binary and ternary systems are shown to demonstrate the major feature of the database. Finally, application of the thermodynamic database to solidification simulation and selection of heat treatment schedule is described. [ABSTRACT FROM AUTHOR]

The isothermal sections of Mg-Zn-RE(Nd,Gd) ternary system at 553 K were measured with the help of diffusion triple technique. The results show that they were at metastable equilibrium instead of the final equilibrium state. Three ternary phases T1, T3 and T4 in Mg-Zn-Nd system have been detected. Specially, T3 was found out to be an independent ternary phase instead of a binary phase MgNd with very large solubility of Zn. Twelve tri-phases that reached local equilibriums have been identified in Mg-Zn-Nd system at 553 K. Two ternary compounds, W and I, have been found. The binary phases, MgGd and MgGd, have a solution of 3.0 at.% and 4.3 at.% Zn, respectively. The phase T-MgRE type found in Mg-Zn-Nd agrees with the calculated result from First-principle. [ABSTRACT FROM AUTHOR]

The Al-Ba was thermodynamically optimized with the help of CALPHAD method. The solution phases such as liquid, fcc and bcc phases were modeled as substitutional solution phases. The excess Gibbs energies of these phases were treated with Redlich-Kister polynomial functions. A set of self-consistent thermodynamic parameters for describing various phases in the Al-Ba system was obtained, which can well reproduce the corresponding experimental data. The Al-Ba-Ni ternary system were also extrapolated based on the present binary system. [ABSTRACT FROM AUTHOR]

Abstract: The phase diagrams of the M2O–SiO2 (M=K, Na) binary systems were assessed using the Calculation of Phase Diagram (CALPHAD) technique. The thermochemical and phase equilibrium information taken from the literature for these two binary systems have been evaluated, and a series of thermodynamic parameters was obtained to describe each phase in these systems. The liquid phase was described by the ionic two-sublattice model with the formula (M=K, Na). The heat capacities of solid phases were taken into consideration in this optimization process, a brief review of which is given in this work. The calculated phase equilibria were found to be in agreement with available experimental data. [Copyright &y& Elsevier]

Abstract: Phase equilibria in the ternary Al–Cu–Y system have been analyzed by coupling the CALPHAD method and first-principles calculations, and a complete thermodynamic description was obtained. The thermodynamic descriptions of its three constituent binary systems were taken from the literature. Most of the binary intermetallic phases, except Al3Y, Al2Y, and Cu2Y, were treated to have zero solubility in the ternary system. Based on experimental data, eight stable ternary intermetallic phases were taken into consideration in the present work. Among them, three phases were treated as line compounds with large homogeneity ranges for Al and Cu. The others were treated as stoichiometric compounds. The calculated phase equilibria were in agreement with available experimental data. [Copyright &y& Elsevier]

Knowledge about the thermodynamic equilibria of the Al 2 O 3 –TiO 2 –CaO system is important for the design of refractory and ceramic materials. The Al 2 O 3 –TiO 2 , Al 2 O 3 –CaO and CaO–TiO 2 binary systems were reoptimized and the Al 2 O 3 –TiO 2 –CaO ternary system was assessed by CALPHAD (CAlculation of PHAse Diagram) approach due to the reliability of phase diagram and thermodynamic property data. The liquid phase was described by the ionic two-sublattice model with the formula (Al+3,Ti+2,Ti+3,Ca+2) P (O−2,AlO 1.5 ,Va,O,TiO 2) Q. A set of self-consistent thermodynamic parameters for the Al 2 O 3 –TiO 2 –CaO ternary system was finally obtained, reproducing well the phase diagram and thermodynamic properties, predicting the Ca 4 Ti 3 O 10 primary crystallization field. The present thermodynamic description is of interest for the design of refractory and ceramic materials as well as the development of thermodynamic databases for multicomponent aluminosilicate system. [ABSTRACT FROM AUTHOR]

The Bi-Te phase diagram was determined by equilibrium alloy method, combined with electron probe microanalysis (EPMA), X-ray diffraction (XRD) and thermal analysis (DSC). The experimental result shows that there is a β-phase with a large composition range at low temperature, while Bi 2 Te and Bi 4 Te 3 are relatively stable in the solid-liquid region. A consistent phase diagram that covers the experimental findings has been achieved. Based on the new experimental phase diagram, coupling with the reported thermodynamic data, the thermodynamic optimization of the Bi-Te binary system was carried out with the help of CALPHAD approach. A group of reasonable thermodynamic parameters was obtained. [ABSTRACT FROM AUTHOR]

Abstract Thermodynamic optimization of the Ni-Al-Nd ternary system and Al-Nd binary systems have been conducted in the present work. A self-consistent set of thermodynamic parameters for the Al-Nd binary system and Ni-Al-Nd ternary system have been optimized using CALPHAD method. Isothermal sections at 600 and 700 °C as well as the liquidus projection have been reproduced. Isopleths with 93 at% Al, 9 at% Ni and 3 at% Nd, have been calculated also. The calculated thermodynamic and phase equilibria data for both the binary and the ternary systems agree fairly well with the experimental data. This work can be used as multi-component thermodynamic database for Ni-based alloys. [ABSTRACT FROM AUTHOR]

Detailed thermodynamic and kinetic descriptions of the Ti–Zn system are of especial significance for designing novel titanium alloys. However, there are still inconsistencies between the literature data and the existing phase diagram of the Ti–Zn system. Besides, little report about the kinetics of the Ti–Zn system is available. In the present work, the Ti–Zn system has been revisited via experimental, ab initio and CALPHAD (CALculation of PHAse Diagrams)-type investigations with a thermodynamic database being in good agreement with experimental information. A Ti/Zn diffusion couple and a Zn-rich equilibrated alloy were employed to contribute to the knowledge of the phase equilibria at 500 °C and 600 °C. The formation enthalpies of the intermetallic Ti–Zn compounds were computed via ab initio calculations, while those of body-centered cubic (bcc) and hexagonal-close packed (hcp) phases were obtained with the special quasirandom structure (SQS) method. In addition, another diffusion couple of bcc Ti/Ti-3at.% Zn was assembled and annealed at 900 °C and 1100 °C respectively for 72h to extract interdiffusion coefficients. Based on the newly developed thermodynamic description in this work and our experimental results, the atomic mobility parameters of the bcc phase for the Ti–Zn system were assessed. [Display omitted] • A diffusion path was (αZn) → Ti 3 Zn 22 → TiZn 3 → (αTi) at 500 °C. • An equilibrated alloy was located in the (Zn) + TiZn 3 region at around 600 °C. • Ti–Zn system were computed via ab initio calculations with the SQS method. • An up-to-date and reliable Ti–Zn phase diagram has been constructed. • A set of self-consistent thermodynamic parameters for the Ti–Zn system and atomic mobility of its bcc phase were assessed. [ABSTRACT FROM AUTHOR]