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To obtain products by using additive manufacturing (AM) methods, it is necessary to take into account the features of the formed internal structure of the material. The internal structure depends on the 3D printing parameters. To predict it, it is effective to use computer modeling methods. For this purpose, using the example of aluminum bronze, the influence of the base structure and heat input during surfacing on the grain structure of the deposited layers was studied. To create numerical models, we used data obtained from electron backscatter diffraction (EBSD) analysis of samples. The heterogeneity of the formation of the structure in each selected zone is established, which indicates the heterogeneity of heat input in local areas of the material in one mode of surfacing. For typical cases of crystallization, modeling using the molecular dynamics (MD) method of crystallization processes with different heat inputs to the base with characteristics specified based on experimental data was carried out. It was established that the amount of heat input determines the degree of melting and the inherited defectiveness of growing crystals. The formation of misorientation boundaries and crystallization centers of new grains is determined by the conditions of joint growth of grains with given crystallographic parameters of the computational model. The grain structure obtained as a result of simulation is consistent with the experimentally observed structure of the samples.

Aim: Following the fourth to second digit ratios being used as a marker of sexual dimorphism and the embryogenetic hormonal origin in common with the permanent dentition, the aim of this study was to determine if a homologous ratio existed for the central and lateral incisors which correlated with the digit ratios. Materials and Methods: Bilateral linear lengths in millimeters of fourth and second digits (reversed for clearer analysis) were obtained using vernier calipers from standardized photocopies of the ventral palmar surfaces of 61 male and 51 female (n = 112) volunteer dental students, the ratios of which were correlated with the ratios of the linear measures (mm) of the inciso-cervical (IC) and mesiodistal (MD) measurements of their central to lateral incisors. Results: Dimorphic digit ratios were comparable with those of other investigators, with male digits and incisors significantly larger than females (p < .001). Although both male maxillary incisors, IC and MD, were significantly larger than females, the ratios unexpectedly were not, with only a limited number of low but significant correlations with the digit ratios. Conclusions: While there were only a limited number of significant sexually dimorphic correlations between the digit and incisor ratios for non-White participants, the results obtained suggest further investigation of possible relationships between the sexually dimorphic digit ratios and odontometric ratios other than central to lateral incisors. [ABSTRACT FROM AUTHOR]

When working out 3D building-up modes, it is necessary to predict the material properties of the resulting products. For this purpose, the crystallography of aluminum bronze grains after electron beam melting has been studied by EBSD analysis methods. To estimate the possibility of sample form changes by pressure treatment, we simulated structural changes by the method of molecular dynamics during deformation by compression of individual grains of established growth orientations. The analysis was carried out for free lateral faces and grain deformation in confined conditions. Simulation and experiments on single crystals with free lateral faces revealed the occurrence of stepwise deformation in different parts of the crystal and its division into deformation domains. Each domain is characterized by a shear along a certain slip system with the maximum Schmidt factor. Blocking the shear towards the lateral faces leads to selectivity of the shear along the slip systems that provide the required shape change. Based on the simulation results, the relationship between stress–strain curves and structural characteristics is traced. A higher degree of strain hardening and a higher density of defects were found upon deformation in confined conditions. The deformation of the columnar grains of the built material occurs agreed with the systems with the maximum Schmidt factor.

The importance of taking into account directional solidification of grains formed during 3D printing is determined by a substantial influence of their crystallographic orientation on the mechanical properties of a loaded material. This issue is studied in the present study using molecular dynamics simulations. The compression of an FCC single crystal of aluminum bronze was performed along the axis. A Ni single crystal, which is characterized by higher stacking fault energy (SFE) than aluminum bronze, was also considered. It was found that the first dislocations started to move earlier in the material with lower SFE, in which the slip of two Shockley partials was observed. In the case of the material with higher SFE, the slip of a full dislocation occurred via successive splitting of its segments into partial dislocations. Regardless of the SFE value, the deformation was primarily occurred by means of the formation of dislocation complexes involved stair-rod dislocations and partial dislocations on adjacent slip planes. Hardening and softening segments of the calculated stress–strain curve were shown to correspond to the periods of hindering of dislocations at dislocation pileups and dislocation movement between them. The simulation results well agree with the experimental findings.

To obtain products by using additive manufacturing (AM) methods, it is necessary to take into account the features of the formed internal structure of the material. The internal structure depends on the 3D printing parameters. To predict it, it is effective to use computer modeling methods. For this purpose, using the example of aluminum bronze, the influence of the base structure and heat input during surfacing on the grain structure of the deposited layers was studied. To create numerical models, we used data obtained from electron backscatter diffraction (EBSD) analysis of samples. The heterogeneity of the formation of the structure in each selected zone is established, which indicates the heterogeneity of heat input in local areas of the material in one mode of surfacing. For typical cases of crystallization, modeling using the molecular dynamics (MD) method of crystallization processes with different heat inputs to the base with characteristics specified based on experimental data was carried out. It was established that the amount of heat input determines the degree of melting and the inherited defectiveness of growing crystals. The formation of misorientation boundaries and crystallization centers of new grains is determined by the conditions of joint growth of grains with given crystallographic parameters of the computational model. The grain structure obtained as a result of simulation is consistent with the experimentally observed structure of the samples. [ABSTRACT FROM AUTHOR]

Обґрунтовано доцільність використання методу мурашиної колонії та його модифікацій як способу вирішення складних комбінаторних задач оптимізації в економічних і технічних галузях. Досліджено біологічне підґрунтя, переваги, недоліки та можливі напрями використання цього методу. Визначено основні особливості, закладений математичний апарат і механізм функціонування методу мурашиної колонії. Проаналізовано відмінності між різновидами методу мурашиної колонії в розрізі критеріїв ефективності розв'язку задач. Запропоновано перспективні шляхи покращення цього методу.

When working out 3D building-up modes, it is necessary to predict the material properties of the resulting products. For this purpose, the crystallography of aluminum bronze grains after electron beam melting has been studied by EBSD analysis methods. To estimate the possibility of sample form changes by pressure treatment, we simulated structural changes by the method of molecular dynamics during deformation by compression of individual grains of established growth orientations. The analysis was carried out for free lateral faces and grain deformation in confined conditions. Simulation and experiments on single crystals with free lateral faces revealed the occurrence of stepwise deformation in different parts of the crystal and its division into deformation domains. Each domain is characterized by a shear along a certain slip system with the maximum Schmidt factor. Blocking the shear towards the lateral faces leads to selectivity of the shear along the slip systems that provide the required shape change. Based on the simulation results, the relationship between stress–strain curves and structural characteristics is traced. A higher degree of strain hardening and a higher density of defects were found upon deformation in confined conditions. The deformation of the columnar grains of the built material occurs agreed with the systems with the maximum Schmidt factor. [ABSTRACT FROM AUTHOR]

Objective: To develop a mouse orthodontic organ culture model and examine early-induced changes in osteoblast differentiation markers within the periodontal ligament (PDL) and alveolar bone. Methods: Mandibles from 4- to 12-week-old transgenic mice were dissected and hemisected. A conventional superelastic orthodontic spring (25 grams) was bonded to the incisor and first molar on one side of the mandible; the other side served as a control. Dissected mandibles were cultured for 6 hours and then were histologically analyzed for proliferation (BrdU immunostaining) and fluorescent protein expression. Additionally, an in vivo model using the same methods was applied to 3.6 Col1-GFP transgenic mice. Results: In vitro, after 6 hours of orthodontic loading, a significant increase was noted in 3.6Col 1-GFP- and BSP-GFP-positive cells within the tension side of the PDL compared with unloaded controls. On the compression side, a significant decrease in positive cells in 3.6 Col1-GFP mice was observed in the PDL compared with unloaded controls. In vivo, the same tendencies were found. Conclusion: This novel in vitro mandibular tooth movement organ culture model coupled with transgenic mouse technology provides a powerful tool for delineating initial cellular and molecular events of orthodontic tooth movement. [ABSTRACT FROM AUTHOR]

The importance of taking into account directional solidification of grains formed during 3D printing is determined by a substantial influence of their crystallographic orientation on the mechanical properties of a loaded material. This issue is studied in the present study using molecular dynamics simulations. The compression of an FCC single crystal of aluminum bronze was performed along the <111> axis. A Ni single crystal, which is characterized by higher stacking fault energy (SFE) than aluminum bronze, was also considered. It was found that the first dislocations started to move earlier in the material with lower SFE, in which the slip of two Shockley partials was observed. In the case of the material with higher SFE, the slip of a full dislocation occurred via successive splitting of its segments into partial dislocations. Regardless of the SFE value, the deformation was primarily occurred by means of the formation of dislocation complexes involved stair-rod dislocations and partial dislocations on adjacent slip planes. Hardening and softening segments of the calculated stress–strain curve were shown to correspond to the periods of hindering of dislocations at dislocation pileups and dislocation movement between them. The simulation results well agree with the experimental findings. [ABSTRACT FROM AUTHOR]