Experimental demonstration of formation of iron-sulfide grains withFe-S coalescence technique and iron-sulfide grains in carbonaceouschondrite

The coalescence growth process of a joint cloud of fine smoke particles evaporated from Fe and those from S produces fine grains of pyrrhotite, in addition to stoichiometric troilite and marcasite. Pyrrhotite grains exhibited a typical DDSS (diffusion-dependence shell structure) shape produced by diffusion of iron atoms to the surface layer. Various superstructures of pyrrhotites were observed by changing the heater temperature. An outline of the experimental procedures of coalescence growth formation of iron sulfide and the main experimental results are described. Magnetic properties of some carbonaceous chondrites have been summarized and discussed in comparison with the characteristics of the coalescence product

Formation of micro-diamond by heat treatment of quenched carbonaceous composite (QCC)

In order to clarify the correlation between the structure and peak position in quenched carbonaceous composite (QCC), which shows an absorbance peak similar to the 217.5nm feature seen in the interstellar extinction curve, structural changes induced by heating were studied in situ using high resolution electron microscopy. As-prepared QCC particles composed of onion-like spherules changed into a structure with well ordered (002) fringes following heating in vacuum. In addition, formation of microdiamond of about 1 nm in diameter took place by heating at 100℃. The metamorphism is discussed based on a specific configuration of sp^3 hybridization existing on the surface of QCC particles

Heating experiments of carbon grains: Implication for the origin of interstellar dust

Amorphous carbonaceous grains produced in a methane gas atmosphere were analyzed by high resolution transmission electron microscope (HRTEM). Structural alteration of the amorphous carbonaceous grains was directly observed by in situ HRTEM observation. The specimen was heated to a maximum of 550℃. The HRTEM image of a prepared specimen showed the structure of the onion-like carbon. The onion-like structure distorted at 100℃, which suggested the evaporation of -OH groups included in the grains. Upon heating to 260℃, the centers of the onion-like grains formed holes of the order of 3 nm in size. On further heating to 550℃, the structure of the chained grains with a size of 10 nm changed to graphite sheets with a length of 50 nm by the surface melting coalescence among chained grains. The structural changes at the above temperatures have been observed only in amorphous carbonaceous grains produced in a methane gas atmosphere and have been attributed to the existence of hydrogen in the grains

Tetrataenite in chondrites and experimental demonstration on formation of tetrataenite fine grains

Tetrataenite (Fe_Ni_γ" phase) is a unique metallic mineral in meteorites. A magnetic granulometry analysis of chondrites on the basis of magnetic hysteresis parameters at various temperatures has shown that some LL chondrites contain very fine grains of tetrataenite metal, the grain sizes of which are 10nm or smaller in diameter. The coalescence growth process of a joint cloud of fine smoke particles evaporated from Fe and that from Ni produces fine grains of tetrataenite (FeNiγ"), in addition to those of ordered kamacite (Fe_3Ni), awaruite (FeNi_3) as well as disordered taenites. An outline of the experimental procedures of coalescence growth formation of tetrataenite and the other ordered crystal grains of Fe-Ni alloy and main results of the experiments is described

Experimental demonstration of formation of magnetite and wustitefine grains

Production method of magnetite and wustite grains have been introduced. Magnetite and wustite grains were produced in an Ar gas pressure range of 25 to 100 Torr and 17 to 20 Torr respectively by evaporating FeO powder from a tantalum boat. The growth of these grains has been discussed as the result of oxidation of Fe fine grains and coalescence growth among the oxidized grains

Electron microscopic and infrared spectral studies on the structure of alumina phases

Alumina produced by oxidation of aluminum in air was studied by infrared spectroscopy and electron microscopy. Infrared spectra of both alumina particles and alumina film oxidized in air showed an absorption peak at 10.8μm, though that of γ-Al_2O_3 particles showed a broad 13μm peak. On the basis of the infrared spectra and electron diffraction pattern, it was concluded that alumina produced by the oxidation of aluminum in air is η-Al_2O_3. The phase transition from η-phase to γ-phase and to α-phase took place at 900℃ and 1100℃, respectively. The relationships between infrared spectra and crystal structure of some alumina phases are discussed

Structural and infrared spectral changes of silicon oxide grains by heat treatments

In order to elucidate the relationship between crystallographic structures of amorphous silicon oxide grains and infrared (IR) spectra, ultrafine grains produced by the gas evaporation method have been studied on the basis of IR spectral measurements and electron microscopic (EM) observations. The shifts and disappearance in the IR absorption peaks of specimen heat-treated in air have been found. The spectral changes have been discussed in the relation with the polymorphism of silica

Prediction of pharmacological activities from chemical structures with graph convolutional neural networks

化合物の薬理作用を予測する技術を開発 --薬理作用ビッグデータを用いて--. 京都大学プレスリリース. 2021-01-13.Many therapeutic drugs are compounds that can be represented by simple chemical structures, which contain important determinants of affinity at the site of action. Recently, graph convolutional neural network (GCN) models have exhibited excellent results in classifying the activity of such compounds. For models that make quantitative predictions of activity, more complex information has been utilized, such as the three-dimensional structures of compounds and the amino acid sequences of their respective target proteins. As another approach, we hypothesized that if sufficient experimental data were available and there were enough nodes in hidden layers, a simple compound representation would quantitatively predict activity with satisfactory accuracy. In this study, we report that GCN models constructed solely from the two-dimensional structural information of compounds demonstrated a high degree of activity predictability against 127 diverse targets from the ChEMBL database. Using the information entropy as a metric, we also show that the structural diversity had less effect on the prediction performance. Finally, we report that virtual screening using the constructed model identified a new serotonin transporter inhibitor with activity comparable to that of a marketed drug in vitro and exhibited antidepressant effects in behavioural studies

Growth of Functional FeTi Clusters Covered with Carbon Layer

FeTi clusters with a diameter of less than 10 nm and covered with a graphitic layer have been preferentially produced in an H2 gas atmosphere at pressures of 10 and 26.6 kPa by the simultaneous evaporation of Fe and Ti wires from a concave carbon boat. To compare this result with cluster formation in an inert gas atmosphere, the result for an Ar gas pressure of 10 kPa is also discussed. The formation of disordered FeNi clusters predominately took place in an H2 gas atmosphere