A new method for calculating internal conversion rate constants (
k&cmb.b.line;
IC
), including anharmonic effects and using the Lagrangian multiplier technique, is proposed. The deuteration effect ...on
k&cmb.b.line;
IC
is investigated for naphthalene, anthracene, free-base porphyrin (
H
2
P
) and tetraphenylporphyrin (
H
2
TPP
). The results show that anharmonic effects are important when calculating
k&cmb.b.line;
IC
for transitions between electronic states that are energetically separated (Δ
E
) by more than 20 000-25 000 cm
−1
. Anharmonic effects are also important when Δ
E
< 20 000-25 000 cm
−1
and when the accepting modes are X-H stretching vibrations with a frequency larger than 2000 cm
−1
. The calculations show that there is mixing between the S
1
and S
2
states of naphthalene induced by non-adiabatic interactions. The non-adiabatic interaction matrix element between the S
1
and S
2
states is 250 cm
−1
and 50 cm
−1
for the normal and fully deuterated naphthalene structure and this difference significantly affects the estimated fluorescence quantum yield. Besides aromatic hydrocarbons
H
2
P
and
H
2
TPP
, the
k&cmb.b.line;
IC
rate constant is also calculated for pyrometene (PM567) and tetraoxa8circulene (4B) with a detailed analysis of the effect of the vibrational anharmonicity.
A new method for calculating internal conversion rate constants (
k
IC
), including anharmonic effects and using the Lagrangian multiplier technique, is proposed.
Based on the analysis of previous studies on the formation of electromagnetic fields in the optical range as a result of the interaction of hard radiation with matter, it is proposed to use a ...semiclassical approach to simulate Cherenkov detectors. The description of geometric structures and the working substance of the detectors is carried out using the capabilities of the GEANT package. The components of electromagnetic fields in the optical range are calculated in the space-time representation using the model of linear current.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Ultra-fine grain size in Mg-1Ca alloy increases its biodegradation time from days to months.•Continuous nanoprecipitation of Mg2Ca improves the corrosion resistance of the UFG alloy.•EIS inductive ...loop with negative time constant describes this increase in corrosion resistance.•Ultra-fine grained Mg-1Ca alloy is promising for biodegradable implant applications.
Biodegradation studies of Mg-1Ca alloy with different microstructures in Ringer’s solution reveal corrosion mechanism based on the balance between the anodic dissolution of the secondary phase and hydroxide precipitation, controlled by the secondary phase size and distribution uniformity. Alloy with ultrafine-grain structure shows at least 5-fold improvement in corrosion resistance compared to the coarse-grained alloy due to the separation of the particles of the secondary phase and its continuous intragranular nano-precipitation. This promotes an unusual low-frequency impedance behaviour described by an inductive loop with the negative time constant, which leads to the increased impedance modulus signifying the improved corrosion resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The semi-classical approach to the calculating electromagnetic fields formed by interaction between hard radiation and matter is used to consider the passage of high-energy positrons through a gas ...medium. Results from calculating changes in electromagnetic fields in the optical range for air when high-energy positrons pass through it are presented.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Structure and phase composition of five binary Al–Zn and Al–Mg alloys were studied before and after high pressure torsion (HPT) with a shear strain 300. The grain size of (Al) solid solution and ...crystals of reinforcing second phases decreases drastically after HPT reaching nanometer range. As a result of HPT, the Zn-rich (Al) supersaturated solid solution decomposes completely and reaches the equilibrium state corresponding to room temperature. The decomposition is less pronounced for Al–Mg alloys. We conclude that the severe plastic deformation of supersaturated solid solutions can be considered as a balance between deformation-induced disordering and deformation-accelerated diffusion towards the equilibrium state.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We study one-dimensional flows of an ideal (inviscid and non-heat-conducting) perfect gas with an adiabatic exponent γ behind a shock wave moving toward the center (ν = 3) or axis (ν = 2) of symmetry ...in a cold gas at rest. Flows with a reflected shock wave and flows terminating with simultaneous arrival of a shock wave and a piston, which has compressed the gas into a point or line, to the center of symmetry are admitted.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Simultaneous increase of the ductility and strength of bulk ultra‐fine‐grained (UFG) Cu is achieved by introducing large amounts of deformation twins and high‐angle grain boundaries via cryodrawing ...and cryorolling (red plots and image). Bulk UFG materials usually have high strength but disappointingly low ductility. Most previous attempts to enhance the ductility of single‐phased UFG materials sacrificed their yield strength. This work provides a new approach for increasing ductility without sacrificing strength.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Calculations are made for the angular distributions of changes in the energy of an electromagnetic field in the optical range formed by the interaction between high-energy electrons and a gas medium. ...The calculated values of the angular distributions are consistent with ones observed experimentally.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The electronic structure, absorption and emission spectra, aromaticity and photophysical behavior of the recently synthesized tetrasilatetrathia8circulene and tetragermatetrathia8circulene compounds ...have been studied computationally. Both compounds demonstrate a specific bifacial aromaticity, which is unusual for hetero8circulenes; the inner eight-membered core sustains an expected strong paratropic magnetically-induced ring current, while the outer perimeter contains saturated Si(Et)2 and Ge(Et)2 moieties which break the conjugation between the thiophene rings. The overall magnetically-induced ring current for both studied circulenes is close to zero because of the strong local diatropic currents in each thiophene ring that compensate the paratropic counterpart. The electronic absorption and emission spectra of tetrasilatetrathia8circulene and tetragermatetrathia8circulene demonstrate a clear visible vibronic progression. The 0-0 band is the most active one in the absorption spectra, while in the fluorescence spectra the 0-1 band composed of several normal vibrations is more intense compared with the 0-0 band in excellent agreement with experiment. Accounting for spin-orbit coupling effects, an analysis of the photophysical constants for the two compounds demonstrates: (1) a clear manifestation of the internal heavy atom effect on the inter-system crossing efficiency; (2) one to two order domination of non-radiative rates over the fluorescence rate; and (3) that the S1-S0 internal conversion is extremely slow and can not compete with the fluorescence, while the S1-Tn inter-system crossing is a main deactivation channel of the S1 excited state. These results provide new insight into the electronic structure and photophysics of tetrasilatetrathia8circulene and tetragermatetrathia8circulene as novel standalone representatives of hetero8circulenes - tetraannelated derivatives of tetrathienylene.
Magnetically induced ring currents are calculated from the magnetic shielding tensor by employing the Ampère-Maxwell law. The feasibility of the method is demonstrated by integrating the
zz
component ...of the shielding tensor along the symmetry axis of highly symmetric ring-shaped aromatic, antiaromatic and nonaromatic molecules. The calculated ring-current strengths agree perfectly with the ones obtained by integrating the current-density flux passing through a plane cutting half the molecular ring. The method can be used in combination with all electronic structure codes capable of calculating nuclear magnetic resonance (NMR) shielding tensors in general points in space. We also show that nucleus independent chemical shifts (NICS) along the symmetry axis are related to the spatial derivative of the strength of the global ring-current along the
z
axis.
We present a method based on Ampère-Maxwell's integral law for calculating strengths of magnetically induced ring currents.
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