The effect of metal artifact reduction algorithms on CT image quality was considered. The mean signal intensities and noise levels were compared for objects with different X-ray densities and spatial ...positions using phantom modeling. It was shown that, despite an improvement in the visual characteristics of the images, their quantitative characteristics may deteriorate: the change in the mean density reached in some cases 15%; the increase in noise, 30%.
The processes in a flat palladium target irradiated with an intense picosecond laser pulse are studied. In the experiment, the parameters of the irradiating pulse, as well as the depth of the spall ...cavity formed as a result of the complex flow of compression and expansion waves through the substance are determined. The interaction dynamics of these waves are modeled using a new equation of state for palladium over a wide range of densities and pressures. Based on the results of the experiment and numerical simulation, the maximum tensile stress in the spall plane at a high tensile rate is estimated.
An economics-mathematical model for performing analytical calculations of the present value of separative work for uranium isotopes in a separation plant currently being designed using gas centrifuge ...technology is examined. Analytical expressions are obtained for the present value of the separative work, the internal rate of return, and the payback period of the separation plant as a function of its main engineering and economics parameters – productivity (capacity), capital investment, and operating expenses. Calculations of these criteria for investment efficiency are presented for a wide range of initial data. It is shown that the calculation of the present value of separative work must be performed in a complex with other investment efficiency criteria in order to determine their optimal combination.
This paper focuses on the energetics of photoinduced charge separation reactions between closely spaced molecules of chlorophyll (Chl) and pheophytin (Pheo). The reaction centers of photosystems PSI ...and PSII include three pairs of spectrally similar porphyrin cofactors, whose structure allows the implementation of alternative mechanisms of primary charge separation. A continuum model for the formation of ion-radical pairs in a dielectric environment based on partial charges calculated
ab initio
is considered. The model describes the experimental variation of the midpoint redox potentials of Chl and Pheo in solutions with different permittivities. Within this model, the formation energy of primary ion-radical pairs is estimated for the alternative mechanisms of charge separation in PSI and PSII discussed in the literature. In the considered approximation in PSII, the primary charge separation between the monomer of Chl (Chl
D1
) and Pheo (Pheo
D1
) is the only energetically allowed mechanism. The absence of Pheo in the same position in the reaction center of PSI denies the possibility of the Chl monomer in this complex acting as the primary electron donor. Stabilization of the primary ion-radical pair in PSI can occur due to the delocalization of the electron density along the dimer of a special pair of Chl molecules (Р
700
) and the heterodimer of Chl molecules forming the primary acceptor
A
0
.
The pigment-protein complex of photosystem 2 (PS 2) catalyzes the light-driven oxidation of water molecule and the reduction of plastoquinone. In this work, we studied the effect of the disaccharide ...trehalose, which is unique in its physicochemical properties, on isolated PS 2 complex. It was found that trehalose significantly stimulated the steady-state rate of oxygen evolution. The study of single flash-induced fluorescence decay kinetics demonstrated that trehalose did not affect the rate of Q
A
−
oxidation, although it led to an increase in the relative fractions of PS 2 reaction centers capable of Q
A
−
oxidation. Trehalose also prevented PS 2 complexes from being inactivated on prolonged storage. We propose that in the presence of trehalose, which affects the extent of hydration, the protein can preferentially exist in a more optimal conformation for effective functioning.
This article presents the results of studying the causes of the thermal instability of blast furnace smelting in nonstationary fuel-and-commodity and gas dynamic conditions when using PCI in air ...blasting and when injecting pulverized coal together with natural gas. The study results have allowed developing a decision support system for controlling the thermal state of blast furnace smelting in an adviser mode for process teams of blast furnace shops.
A new approach to selecting the optimal batch composition and properties in briquetting is proposed. To that end, the influence of the batch composition and properties on briquet production and ...applicability is analyzed. On that basis, four basic aspects of the stepwise optimization of batch composition and properties are considered. For each aspect, the conditions on the batch are formulated. Optimization criteria are developed and used to select the best batch composition.
Chemical shifts of the
K
α1
and
K
β1
lines of X-ray-emission spectra of niobium in oxides (Nb
2
O
5
)
n
,
n
= 1–4, relative to metal Nb have been calculated. Stoichiometric clusters (Nb2O5)n the ...electronic structure of which was calculated using accurate relativistic pseudopotentials and two-component version of the density functional theory are considered as prototypes for modeling different crystal forms of niobium(V) oxide. The chemical shifts were calculated using the method based on using the property of approximate proportionality of valence spinors in the core region of the heavy atom 11. Corrections to values of chemical shifts have been determined with allowance for deviations from the abovementioned proportionality. Rapid convergence of results with respect to the size of the niobium oxide cluster has been demonstrated.
