Theoretical rotational-vibrational and rotational-vibrational-electronic spectroscopy of triatomic molecules

The major part of this work is construction of 54 room-temperature infrared absorption line lists for isotopologues of carbon dioxide. In accurate nuclear motion calculations an exact nuclear kinetic energy operator is used in the Born-Oppenheimer approximation and three ab initio and semi-empirical potential energy surfaces for generation of rotational-vibrational wavefunctions and energy levels. Transition intensities are calculated with two different high quality ab initio dipole moment surfaces. The generated line lists are comprehensively compared to state-of-the-art measurements, spectroscopic databases and other theoretical studies. As a result, uncertainties in calculated transition intensities in several vibrational CO2 bands are shown below 1%, which is sufficient for use in remote sensing measurements of carbon dioxide in the Earth’s atmosphere. Results of the present calculations set a new state-of-the-art and have been included in the 2016 release of the HITRAN database. A theoretical procedure for estimating reliability of computed transition intensities is presented and applied to CO 2 line lists. As a result, each transition intensity received a reliability factor, a particularly useful descriptor for detecting resonance interactions between rotational-vibrational energy levels, as well as a good measure quantifying the strength of such interactions. The theoretical procedure used for CO 2 is extended to electronic transitions in the Born-Oppenheimer approximation. In this extended framework rotational- vibrational-electronic line lists for SO2 and CaOCa molecules are generated. For this purpose appropriate ab initio potential energy surfaces and a transition dipole moment surface are generated. Absolute transition intensities are then calculated both in the Franck-Condon approximation and with a full transition dipole moment surface. Resulting line lists are compared with available experimental and theoretical data. The unprecedented accuracy of the model used in these calculations and the rotational resolution of transition lines renders the present approach as promising for future uses in atmospheric science. Finally a theoretical framework for fully non-adiabatically coupled Hamiltonian is derived and discussed. A proposition for computer implementation of this theoretical scheme is also given

Investigation of the machining process of spheroidal cast iron using cubic boron nitride (CBN) tools

This paper presents the experimental results of the turning of spheroidal iron (EN-GJS-500-7 grade) using L-CBN tools. The cutting process can be classified as a High Performance Cutting (HPC) due to a relatively high material removal rate of about 190 cm3/min. The investigations performed include fundamental process quantities and machined surface characteristics, i.e. componential cutting forces, specific cutting energy, average and maximum values of cutting temperature as well as temperature distribution in the cutting zone, tool wear progress visualized by appropriate wear curves and 2D/3D surface roughness parameters

Modelling of non-metallic particles motion process in foundry alloys

The behaviour of non-metallic particles in the selected composites was analysed, in the current study. The calculations of particles floating in liquids differing in viscosity were performed. Simulations based on the Stokes equation were made for spherical SiC particles and additionally the particle size influence on Reynolds number was analysed.The movement of the particles in the liquid metal matrix is strictly connected with the agglomerate formation problem.Some of collisions between non-metallic particles lead to a permanent connection between them. Creation of the two spherical particles and a metallic phase system generates the adhesion force. It was found that the adhesion force mainly depends on the surface tension of the liquid alloy and radius of non-metallic particles

Modeling of MnS precipitation during the crystallization of grain oriented silicon steel

The process of manganese sulfide formation in the course of grain-oriented silicon steel solidification process is described in the paper. Fine dispersive MnS inclusions are grain growth inhibitors and apart from AlN inclusions they contribute to the formation of a privileged texture, i.e. Goss texture. A computer simulation of a high-silicon steel ingot solidification with the use of author’s software has been performed. Ueshima model was adapted for simulating the 3 % Si steel ingot solidification. The calculations accounted for the back diffusion effect according to Wołczyński equation. The computer simulation results are presented in the form of plots representing the process of steel components segregation in a solidifying ingot and curves illustrating the inclusion separation process

Modelling of the crystallization front – particles interactions in ZnAl/(SiC)p composites

The presented work focuses on solid particle interactions with the moving crystallization front during a solidification of the metal matrix composite. The current analyses were made for silicon carbide particles and ZnAl alloy with different additions of aluminium. It was found, that the chemical composition of the metal matrix influences the behaviour of SiC particles. At the same time calculations of the forces acting on a single particle near the crystallization front were performed. For each alloy type the critical conditions that determine whether particle will be absorbed or pushed, were specified

Scanning Tunneling Microscope Operating as a Spin-diode

We theoretically investigate spin-polarized transport in a system composed of a ferromagnetic Scanning Tunneling Microscope (STM) tip coupled to an adsorbed atom (adatom) on a host surface. Electrons can tunnel directly from the tip to the surface or via the adatom. Since the tip is ferromagnetic and the host surface (metal or semiconductor) is non-magnetic we obtain a spin-diode effect when the adatom is in the regime of single occupancy. This effect leads to an unpolarized current for direct bias (V > 0) and polarized current for reverse (V < 0) bias voltages, if the tip is nearby the adatom. Within the nonequilibrium Keldysh technique we analyze the interplay between the lateral displacement of the tip and the intra adatom Coulomb interaction on the spindiode effect. As the tip moves away from the adatom the spin-diode effect vanishes and the currents become polarized for both V > 0 and V < 0. We also find an imbalance between the up and down spin populations in the adatom, which can be tuned by the tip position and the bias. Finally, due to the presence of the adsorbate on the surface, we observe spin-resolved Friedel oscillations in the current, which reflects the oscillations in the calculated LDOS of the subsystem surface+adatom.Comment: 11 pages, 4 figures. Submitte

Structural basis for small molecule targeting of the programmed death ligand 1 (PD-L1)

Targeting the PD-1/PD-L1 immunologic checkpoint with monoclonal antibodies has provided unprecedented results in cancer treatment in the recent years. Development of chemical inhibitors for this pathway lags the antibody development because of insufficient structural information. The first nonpeptidic chemical inhibitors that target the PD-1/PD-L1 interaction have only been recently disclosed by Bristol-Myers Squibb. Here, we show that these small-molecule compounds bind directly to PD-L1 and that they potently block PD-1 binding. Structural studies reveal a dimeric protein complex with a single small molecule which stabilizes the dimer thus occluding the PD-1 interaction surface of PD-L1s. The small-molecule interaction "hot spots" on PD-L1 surfaces suggest approaches for the PD-1/PD-L1 antagonist drug discovery