Crystallography Reports最新文献

The scintillation properties of LiF crystals and the family of multicomponent compounds LiF–RF₃ (R = Y, Gd), activated by Ce³⁺ ions, proposed as materials sensitive to thermal neutrons and γ radiation, are compared. An abnormally large cross section of radiative capture of thermal neutrons in gadolinium and the calculated high values of the effective charge number Z of multicomponent compounds determine their efficiency as neutron and gamma scintillators in comparison with LiF. The absorption spectra of unirradiated and γ-irradiated LiF crystals activated by cerium ions are analyzed. The bands of induced color centers are identified. The conversion of the ion oxidation state, Ce⁴⁺ → Ce³⁺, related to effect of γ quanta on the crystals, is investigated. The light yield of all crystals studied was determined by comparing the positions of the maxima of total absorption peaks with the position of the maximum of the total absorption peak of a standard NaI(Tl) sample in the energy spectra from a ¹³⁷Cs γ source with an energy of 662 keV. The effect of increasing the light yield under γ irradiation of LiF crystals with Ce³⁺ ions was discovered and explained in terms of the participation of γ-induced color centers (F and F^- centers). The possibility of increasing additionally the light efficiency due to sensitized luminescence in LiGdF₄ : Ce³⁺ crystals was analyzed.

Low dimension Bi structures were obtained on Si(100) substrates by thermal evaporation in Ar at 10‒20 s deposition time. The sizes and distribution density of Bi nano- and microcrystals were determined by computer processing of electron SEM-images. The nanocrystal density was larger than the microcrystal density by a factor of 260. The decrease of the nanocrystal density by a factor of 2 with the increase of their sizes was observed with the increase up to 20 s deposition time. X-ray diffraction analysis has revealed oxide layers on Bi nanocrystals and the Si substrate surface. The decrease of Bi nanocrystals sizes and the increase of their density on the Si substrates as compared of deposition on glassy carbon substrates was established.

Metal–polymer composites have been obtained by matrix synthesis in pores of track membranes with different times of filling pores with permalloy. The geometric parameters of the resulting arrays of nanowires, which were the functional filling of composites, were determined using scanning electron microscopy. The microhardness of the nanocomposites was studied by the nanoindentation method. A relationship between the increase in the microhardness of the metal–polymer composite and the degree of filling the matrix is established. It is suggested that there is a relationship between the composite hardness and the number of intersections of nanowires in the matrix.

A subunit vaccine against African swine fever virus (ASFV) was computationally designed using immunoinformatics and molecular dynamics methods. The three–dimensional structure of the selected immunogenic CD2v protein of ASFV was modeled and its topology relative to the membrane was predicted. The B- and T-cell epitopes for the outer-membrane part of CD2v were predicted and their immunogenicity, allergenicity, and toxicity were evaluated. For the development of a subunit vaccine, the least variable site was identified based on the analysis of the conservancy of the predicted epitopes. For the selected outer-membrane region, its stability in an aqueous salt solution was evaluated by molecular dynamics methods, which demonstrated its structural stability. The immunomodulation study showed that the developed vaccine candidate can cause a persistent immune response and does not induce a cytokine storm.

Trifluoroacetamide CF₃C(O)NH₂, N,N'-bis(trifluoroacetyl)ethylenediamine CF₃C(O)NHCH₂CH₂HN(O)CCF₃, trifluoroacetyl-2-aminoethanol CF₃C(O)NHCH₂CH₂ОН, and 1,2-bis(trifluoroacetylaminoethoxy)ethane CF₃C(O)NHCH₂CH₂ОCH₂CH₂ОCH₂CH₂НN(O)CCF₃ were synthesized by the thermal decomposition (200–250°С, Ar) of the corresponding ammonium and aminium salts, such as ammonium trifluoroacetate CF₃C(O)O^{‒ +}NH₄, N,N'-ethylenediamine bis(trifluoroacetate) CF₃COO^{‒ +}NH₃CH₂CH₂H₃N^{+ ‒}OOCCF₃, 2-aminoethanol trifluoroacetate CF₃COO^{‒ +}NH₃CH₂CH₂ОН, and 1,2-bis(aminoethoxy)ethane bis(2-trifluoroacetate) CF₃COO^{‒ +}NH₃CH₂CH₂ОCH₂CH₂ОCH₂CH₂Н₃N^{+ ‒}OOCCF₃. The synthesized compounds were characterized by elemental analysis, powder X-ay diffraction, IR and NMR spectroscopy, mass spectrometry, thermogravimetry, optical and scanning electron microscopy. The molecular structure of ethylenediamine N,N'-bis(trifluoroacetate) was determined.

The EP741NP alloy samples destroyed during fatigue testing have been studied by transmission electron microscopy, energy-dispersive X-ray microanalysis, and electron diffraction. The composition and crystal structure of defects detected at the fatigue crack boundaries have been thoroughly examined. It has been shown that these defects have mainly the morphology of elongated flat “carpets” containing NiO, CTi_xNb(_{{1 - x}}), amorphous AlO_x, HfO₂, α-Al₂O₃, β-Al₂O₃, Al₂MgO₄, Co₇Mo₆, Co₃O₄, S₄Ti₃, NbO₂, TiO₂, and amorphous regions containing C, O, Ca, S, Na, and Cl. Assumptions concerning the source and time of formation of the investigated defects have been made.

Serial crystallography, which has been extensively developed in the past years, makes it possible to study dynamic processes occurring in protein molecules. The method is implemented at fourth-generation synchrotron sources or free electron lasers and it requires suspensions of microcrystals. It was demonstrated that small-angle X-ray scattering can be used to monitor the formation of such suspensions in crystallization conditions as exemplified by lysozyme.

The crystallization and absorption/fluorescent properties of linear conjugated molecules derived from 2,1,3-benzothiadiazole, specifically, 4,7-bis(2,5-dimethyl-[1,1'-biphenyl]-4-yl)benzothiadiazole (Ph-Xy-BTD) and 4,7-bis(4'-hexyl-2,5-dimethyl-[1,1'-biphenyl]-4-yl)benzothiadiazole (Hex-Ph-Xy-BTD), have been studied. The synthesis of a new derivative of Hex-Ph-Xy-BTD is described. It was found that the presence of terminal n-hexyl substituents in Hex-Ph-Xy-BTD reduces the melting temperature, increases solubility, and has a positive effect on crystallization as compared to Ph-Xy-BTD. Hex-Ph-Xy-BTD single crystals were grown from a hexane solution, and their structure was elucidated using single-crystal X-ray diffraction, confirming a monoclinic system (sp. gr. P2₁/c, Z = 4). Absorption and fluorescence spectra were obtained and analyzed for solutions in tetrahydrofuran, as well as for the Ph-Xy-BTD and Hex-Ph-Xy-BTD crystals, along with the study of the quantum yield and fluorescence lifetime.

A controlled modification of the parameters of the zinc oxide band structure has been demonstrated using the methods and approaches of nanostructure engineering by varying the duration of high-energy mechanical grinding. It has been shown that an increase in the dispersion time increases the monodispersity of ultrafine ZnO powder particles. A decrease in the zinc oxide band gap with increasing grinding duration is established based on spectrophotometric investigations. A nonmonotonic time dependence of the top of the valence band, as well as a high-energy shift of the valence and conduction bands for all dispersion durations, are demonstrated using experimental X-ray photoelectron spectroscopy data.