Relationship between surface free energy and development process (swelling and dissolution kinetics) of poly(4-hydroxystyrene) film in water and 2.38 wt% tetramethylammonium hydroxide aqueous solution

With the sharpening of optical images, the capability of resist materials has become a serious concern in lithography. The dissolution of a resist polymer is key to the realization of ultrafine patterning. However, the details of the dissolution of resist polymers remain unclarified. In this study, the relationships of surface free energy with swelling and dissolution kinetics were investigated using poly(4-hydroxystyrene) (PHS) film with triphenylsulfonium-nonaflate (TPS-nf). Developers were water and 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution. PHS and TPS-nf are a typical backbone polymer (a dissolution agent) and a typical acid generator of chemically amplified resists, respectively. The water intake and dissolution of PHS film with TPS-nf became fast with increasing UV exposure dose. It was found that the increase in the polar components (particularly, the hydrogen bonding component) and the decrease in the dispersion component of surface free energy underlie the fast water intake and dissolution.

ENSO predictability over the past 137 years based on a CESM ensemble prediction system

In this study, we conducted an ensemble retrospective prediction from 1881 to 2017 using the Community Earth System Model to evaluate El Niño–Southern Oscillation (ENSO) predictability and its variability on different timescales. To our knowledge, this is the first assessment of ENSO predictability using a long-term ensemble hindcast with a complicated coupled general circulation model (CGCM). Our results indicate that both the dispersion component (DC) and signal component (SC) contribute to the interannual variation of ENSO predictability (measured by relative entropy, RE). In detail, the SC is more important for ENSO events, whereas the DC is of comparable important for short lead times and in weak ENSO signal years. The SC dominates the seasonal variation of ENSO predictability, and an abrupt decrease in signal intensity results in the spring predictability barrier feature of ENSO. At the interdecadal scale, the SC controls the variability of ENSO predictability, while the magnitude of ENSO predictability is determined by the DC. The seasonal and interdecadal variations of ENSO predictability in the CGCM are generally consistent with results based on intermediate complexity and hybrid coupled models. However, the DC has a greater contribution in the CGCM than that in the intermediate complexity and hybrid coupled models.

Adhesion and Energy Characteristics of Rigid-Chain Polymer Surface: Polyamidoimides

The adhesion characteristics and surface energies of two series of polyamidoimides (PAI) with different molecular weights, monomer unit structures, hinge groups in the main chain of the macromolecules, and thermal prehistory were determined via delamination at 180° and test fluids contact angles. We found that PAI are high-energy polymers, the surface energy of which varies in the range from 32 to 45 mJ/m2. In contrast to flexible-chain polymers, the exponent in the McLeod equation is two, which is due to the flat parallel orientation of the macromolecular chains in the surface layers. The main contribution to the change in surface characteristics of these polymers is the change in the packing density of PAI macromolecules, which is reflected mainly in the change in the polymers’ dispersion component. We found that the adhesion properties of PAI with respect to high- and low-energy substrates are determined mainly by the macromolecules packing density in the surface layers with their conformation state unchanged.

Phosphorothioate Substitutions in RNA Structure Studied by Molecular Dynamics Simulations, QM/MM Calculations and NMR Experiments

Phosphorothioates (PTs) are important chemical modifications of the RNA backbone where a single non-bridging oxygen of the phosphate is replaced with a sulphur atom. PT can stabilize RNAs by protecting them from hydrolysis and is commonly used as tool to explore their function. It is, however, unclear what basic physical effects PT has on RNA stability and electronic structure. Here, we present Molecular Dynamics (MD) simulations, quantum mechanical (QM) calculations, and NMR spectroscopy measurements, exploring the effects of PT modifications in the structural context of the Neomycin-sensing riboswitch (NSR). The NSR is the smallest biologically functional riboswitch with a well-defined structure stabilized by a U-turn motif. Three of the signature interactions of the U-turn; an H-bond, an anion-π interaction and a potassium binding site; are formed by RNA phosphates, making the NSR an ideal model for studying how PT affects RNA structure and dynamics. By comparing with high-level QM calculations, we reveal the distinct physical properties of the individual interactions facilitated by the PT. The sulphur substitution, besides weakening the direct H-bond interaction, reduces the directionality of H-bonding while increasing its dispersion and induction components. It also reduces the induction and increases dispersion component of the anion-π stacking. The sulphur force-field parameters commonly employed in the literature do not reflect these distinctions, leading to unsatisfactory description of PT in simulations of the NSR. We show that it is not possible to accurately describe the PT interactions using one universal set of van der Waals sulphur parameters and provide suggestions for improving the force-field performance.

Influence of Low-Pressure RF Plasma Treatment on Aramid Yarns Properties

The aim of the study was to modify the surface free energy (SFE) of meta- (mAr) and para-aramid (pAr) yarns by their activation in low-pressure air radio frequency (RF) (40 kHz) plasma and assessment of its impact on the properties of the yarns. After 10 and 90 min of activation, the SFE value increased, respectively, by 14% and 37% for mAr, and by 10% and 37% for pAr. The value of the polar component increased, respectively by 22% and 57% for mAr and 20% and 62% for pAr. The value of the dispersion component for mAr and pAr increased respectively by 9% and 25%. The weight loss decreased from 49% to 46% for mAr and 62% to 50% for pAr after 90 min of activation. After 90 min, the specific strength for mAr did not change and for pAr it decreased by 40%. For both yarns, the 10 min activation in plasma is sufficient to prepare their surface for planned nanomodification.

The assessment of power influence of discharge flow from surges under conditions of hydrologically hazardous natural phenomena

Introduction. The analysis of studies on waves of translation and their dynamic effects on water infrastructure facilities indicates the incompleteness of accounting the dispersion component of wave motions in discharge flows. Existing analysis methods for the surge parameters with the dependence of the propagation velocity and wave pressure on the wavelength should be only considered as a rough approximation of the role of dispersion processes accompanying the surge propagation in river flows. The purpose of the research is to increase the accuracy of reliability analyses for equipment and auxiliary mechanisms of hydraulic structures and water facilities in the context of the growth of hydrologically hazardous natural phenomena in the form of surges. Materials and methods. The article used an analytical method for calculating the wave motion parameters. It is based on determining the conditions for synchronism of jumps and discontinuities in the parameters of the medium state when passing through front surfaces. An option was suggested for using the frontal characteristics method for integrating equations of unsteady currents in open flows. The paper presented a scheme for solving the differential equations of unsteady motions and continuity of flows in river streams with surges in the presence of resistance forces. Results. Analytical design relations were obtained for the velocity and power effects of surges with dispersion dependence on wavelength. An analysis of the obtained solutions is carried out by illustrating the dynamic effects of wave dispersion on water infrastructure facilities. Conclusions. The suggested method of the more accurate analysis for the force impact of the discharge flow from surges on the structural elements of hydro-economic and water-transport facilities can be used to determine the reliability of hydraulic structures and water-transport facilities. The obtained analysis relations for determining the kinematic and dynamic characteristics of the dispersion of the surges are advisably recommended to supplement the existing regulatory documents on hydraulic engineering.

How the oxazole fragment influences the conformation of the tetraoxazocane ring in a cyclohexanespiro-3′-(1,2,4,5,7-tetraoxazocane): single-crystal X-ray and theoretical study

Single crystals of (2S,5R)-2-isopropyl-5-methyl-7-(5-methylisoxazol-3-yl)cyclohexanespiro-3′-(1,2,4,5,7-tetraoxazocane), C16H26N2O5, have been studied via X-ray diffraction. The tetraoxazocane ring adopts a boat–chair conformation in the crystalline state, which is due to intramolecular interactions. Conformational analysis of the tetraoxazocane fragment performed at the B3LYP/6-31G(d,2p) level of theory showed that there are three minima on the potential energy surface, one of which corresponds to the conformation realized in the solid state, but not to a global minimum. Analysis of the geometry and the topological parameters of the electron density at the (3,−1) bond critical points (BCPs), and the charge transfer in the tetraoxazocane ring indicated that there are stereoelectronic effects in the O—C—O and N—C—O fragments. There is a two-cross hyperconjugation in the N—C—O fragment between the lone electron pair of the N atom (lpN) and the antibonding orbital of a C—O bond (σ*C—O) and vice versa between lpO and σ*C—N. The oxazole substituent has a considerable effect on the geometry and the topological parameters of the electron density at the (3,−1) BCPs of the tetraoxazocane ring. The crystal structure is stabilized via intermolecular C—H...N and C—H...O hydrogen bonds, which is unambiguously confirmed with PIXEL calculations, a quantum theory of atoms in molecules (QTAIM) topological analysis of the electron density at the (3,−1) BCPs and a Hirshfeld analysis of the electrostatic potential. The molecules form zigzag chains in the crystal due to intermolecular C—H...N interactions being electrostatic in origin. The molecules are further stacked due to C—H...O hydrogen bonds. The dispersion component in the total stabilization energy of the crystal lattice is 68.09%.

Outflowing gas in a compact ionization cone in the Seyfert 2 galaxy ESO 153-G20

ABSTRACT We present two-dimensional ionized gas and stellar kinematics in the inner 1.4 × 1.9 kpc2 of the Seyfert 2 galaxy ESO 153-G20 obtained with the Gemini-South/Gemini multi-object spectrograph integral field unit (GMOS-IFU) at a spatial resolution of ~250 pc and spectral resolution of 36 km s−1. Strong [O iii], Hα, [N ii] and [S ii] emission lines are detected over the entire field of view. The stellar kinematics trace circular rotation with a projected velocity amplitude of ±96 km s−1, a kinematic major axis in position angle of 11°, and an average velocity dispersion of 123 km s−1. To analyse the gas kinematics, we used aperture spectra, position–velocity diagrams and single/double Gaussian fits to the emission lines. All lines show two clear kinematic components: a rotating component that follows the stellar kinematics, and a larger-dispersion component, close to the systemic velocity (from which most of the [O iii] emission comes), mainly detected to the south-west. We interpret this second component as gas outflowing at ∼400 km s−1 in a compact (300 pc) ionization cone with a half-opening angle ≤40°. The counter-cone is probably obscured behind a dust lane. We estimate a mass outflow rate of 1.1 M$\odot$ yr−1, 200 times larger than the estimated accretion rate on to the supermassive black hole, and a kinetic to radiative power ratio of 1.7 × 10−3. Bar-induced perturbations probably explain the remaining disturbances observed in the velocity field of the rotating gas component.

Regularities of formation of adhesive contact “sol-silicate paint - substrate”

Introduction. The use as a binder in the manufacture of silicate paints polysilicate solutions obtained by mixing liquid glass and silica sol is considered. To regulate the rheological properties of the paint, improve the filling and prevent the pigment part from sagging, it has been proposed to introduce glycerin into the binder composition. The results of studying the interfacial interaction between the paint and the substrate are given. Materials and methods. In developing the formulation of silicate paints based on polysilicate solutions, MK-2 microcalcite, marshalite, diatomite and talc of MT-GSM grade were used as a filler, and titanium dioxide as a pigment. Polysilicate solutions were obtained by reacting stabilized solutions of colloidal silica (sols) with aqueous solutions of alkali silicates (liquid glasses). Nanosil 20 and Nanosil 30 silicic acid sol were used, produced by the Promsteklocentr PC. Used potassium liquid glass with module M = 3.29. A thermodynamic method was used to assess the interfacial interaction. Results. Shown that the introduction of glycerol into the formulation of a sol of silicate paint promotes a decrease in the interfacial surface tension and a better wetting of the surface of the mortar substrate. An increase in wetting coefficient is observed. Coatings based on sol silicate paints with the addition of glycerin are characterized by increased crack resistance. An increase in tensile strength, maximum tensile properties, and decrease in the elastic modulus of paint membranes based on the composition with glycerol has been established. The values of the free surface energy of the coating based on the sol of silicate paint and the ratio of the polar to the dispersion component of the free energy of the surface are given. Coatings based on sol of silicate paint with the addition of glycerin are characterized by a large value of the free energy of the surface. In the process of moistening a decrease in the free surface energy is observed due to a decrease in the dispersion component. Conclusions. Studies have shown that the introduction of an additive of glycerin in the formulation of a silicate paint sol contributes to an increase in the performance properties of coatings based on it.

EVALUATION OF THE MECHANICAL PROPERTIES OF DIFFUSION LAYER IN THE PROCESS OF MICROARC STEEL VANADATION

Traditional processes of thermochemical treatment of steel have a longer duration, so there are proposed the new methods of intensification of diffusion saturation with high-energy impacts on the material surface. In the process of micro-arc alloying the steel product is immersed in a container filled with powder of coal, and is heated by passing electric current. In a powder environment, microdischarges are formed, which are concentrated around the product and create an area of gas discharge with the formation of a carbonaceous gas environment, which enables carburizing of steel. The application of coating containing diffusant allows forming coating of a carbide type due to simultaneous carbon diffusion into alloying elements. The influence of micro-arc surface alloying of steel with vanadium on mechanical properties of diffusion coatings is studied, and the primary mechanism of steel hardening at microarc alloying is revealed. Cylindrical samples of 20 steel were used; the source diffusant was a powder of ferrovanadium. Current density on the sample surface was 0.3 A/cm2, total duration of the process was 3 min. The mechanical properties of coatings were evaluated by means of indentation using pyramidal indenter, at loads of 2.5 mN, 20 mN and 100mN. The diffusion layer with thickness of 170 – 180 μm consists of a base with hardness of 8 – 9 GPa, containing mild etching inclusions of up to 5 μm with microhardness of 21 – 25 GPa. The base of the layer represents an α-solid solution of vanadium in iron, and inclusions are carbides of VC0.863 type. By atomic force microscopy it was established, that the surface relief is defined by single, relatively large carbide particles with a size of up to 3 μm, and by plural nano-sized carbide particles, which act as the strengthening phase, providing high microhardness of the coating. By method of indentation of the hardened layer cross section using different loads hardening effect of the carbide particles is proven. Estimation of possible mechanisms of hardening have shown that the greatest contribution to diffusion layer hardening is made by dispersion component significantly increasing the yield stress of α-solid solution of iron in comparison with the initial state, which is 38 times greater than the contribution of solid-solution hardening.