Comparison of phase characteristics and residual stresses in ti-6al-4v alloy manufactured by laser powder bed fusion (L-pbf) and electron beam powder bed fusion (eb-pbf) techniques

Ti-6Al-4V alloy fabricated by laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF) techniques have been studied for applications ranging from medicine to aviation. The fabrication technique is often selected based on the part size and fabrication speed, while less attention is paid to the differences in the physicochemical properties. Especially, the relationship between the evolution of α, α’, and β phases in as-grown parts and the fabrication techniques is unclear. This work systematically and quantitatively investigates how L-PBF and EB-PBF and their process parameters affect the phase evolution of Ti-6Al-4V and residual stresses in the final parts. This is the first report demonstrating the correlations among measured parameters, indicating the lattice strain reduces, and c/a increases, shifting from an α’ to α+β or α structure as the crystallite size of the α or α’ phase increases. The experimental results combined with heat-transfer simulation indicate the cooling rate near the β transus temperature dictates the resulting phase characteristics, whereas the residual stress depends on the cooling rate immediately below the solidification temperature. This study provides new insights into the previously unknown differences in the α, α’, and β phase evolution between L-PBF and EB-PBF and their process parameters.Takase A., Ishimoto T., Morita N., et al. Comparison of phase characteristics and residual stresses in ti-6al-4v alloy manufactured by laser powder bed fusion (L-pbf) and electron beam powder bed fusion (eb-pbf) techniques. Crystals, 11, 7, 796. https://doi.org/10.3390/cryst11070796

Barium appendicitis

We have presented a case of barium appendicitis, which is a rare complication of barium enema studies. Barium sulfate is used widely for gastrointestinal radiographic studies and is associated with few complications. Clinicians need to be fully aware of this complication

Epidermal γδ T cells sense precancerous cellular dysregulation and initiate immune responses

Hyperplasia associated with a loss of tissue homeostasis can induce DNA replication stress, leading to precancerous dysregulation. Epidermal γδ T cells reside in the primary barrier that protects against diverse environmental insults; however, the functions of these T cells in tissue surveillance are not completely understood. In mice with inducible Notch1 inactivation in keratinocytes that causes epidermal hyperplasia, epidermal γδ T cells sensed stressed keratinocytes and migrated into the cutaneous draining lymph nodes. Simultaneous induction of β-galactosidase (β-Gal) as a putative antigen expressed in the process of precancerous dysregulation and Notch1 ablation in the epidermis resulted in elevated β-Gal-specific IgG2a production. Epidermal γδ T cells were found to have the capacity to express chemokine (C-C motif) receptor 7 and migrate into the lymph nodes. Cutaneous draining lymph node cells in Notch1-inactivated mice expressed high levels of IFN-γ upon anti-CD3 plus anti-CD28 stimulation. Furthermore, induced expression of β-Gal in mice that lacked epidermal γδ T cells failed to induce anti-β-Gal IgG. These results suggest that epidermal γδ T cells play an essential role in the initiation process of epidermal antigen-specific humoral immune responses and demonstrate the importance of epidermal γδ T cells in sensing precancerous dysregulation and activating adaptive immunit

Fabrication of Ti-Alloy powder/solid composite with uniaxial anisotropy by introducing unidirectional honeycomb structure via electron beam powder bed fusion

In this study, a Ti–6Al–4V alloy composite with uniaxial anisotropy and a hierarchical structure is fabricated using electron beam powder bed fusion, one of the additive manufacturing techniques that enable arbitrary fabrication, and subsequent heat treatment. The uniaxial anisotropic deformation behavior and mechanical properties such as Young’s modulus are obtained by introducing a unidirectional honeycomb structure. The main feature of this structure is that the unmelted powder retained in the pores of the honeycomb structure. After appropriate heat treatment at 1020◦C, necks are formed between the powder particles and between the powder particles and the honeycomb wall, enabling a stress transmission through the necks when the composite is loaded. This means that the powder part has been mechanically functionalized by the neck formation. As a result, a plateau region appears in the stress–strain curve. The stress transfer among the powder particles leads to the cooperative deformation of the composites, contributing to the excellent energy absorption capacity. Therefore, it is expected that the composite can be applied to bone plates on uniaxially oriented microstructures such as long bones owing to its excellent energy absorption capacity and low elasticity to unidirectionally suppress stress shielding.Ikeo N., Matsumi T., Ishimoto T., et al. Fabrication of Ti-Alloy powder/solid composite with uniaxial anisotropy by introducing unidirectional honeycomb structure via electron beam powder bed fusion. Crystals, 11, 9, 1074. https://doi.org/10.3390/cryst11091074

3d puzzle in cube pattern for anisotropic/isotropic mechanical control of structure fabricated bymetal additivemanufacturing

Metal additive manufacturing is a powerful tool for providing the desired functional performance through a three-dimensional (3D) structural design. Among the material functions, anisotropic mechanical properties are indispensable for enabling the capabilities of structural materials for living tissues. For biomedical materials to replace bone function, it is necessary to provide an anisotropic mechanical property that mimics that of bones. For desired control of the mechanical performance of the materials, we propose a novel 3D puzzle structure with cube-shaped parts comprising 27 (3 × 3 × 3) unit compartments. We designed and fabricated a Co–Cr–Mo composite structure through spatial control of the positional arrangement of powder/solid parts using the laser powder bed fusion (L-PBF) method. The mechanical function of the fabricated structure can be predicted using the rule of mixtures based on the arrangement pattern of each part. The solid parts in the cubic structure were obtained by melting and solidifying the metal powder with a laser, while the powder parts were obtained through the remaining nonmelted powders inside the structure. This is the first report to achieve an innovative material design that can provide an anisotropic Young’s modulus by arranging the powder and solid parts using additive manufacturing technology.Ikeo N., Fukuda H., Matsugaki A., et al. 3d puzzle in cube pattern for anisotropic/isotropic mechanical control of structure fabricated bymetal additivemanufacturing. Crystals, 11, 8, 959. https://doi.org/10.3390/cryst11080959

The Effect of Cranial Change on Oropharyngeal Airway and Breathing During Sleep

Mandibular micrognathia is one of the characteristics of obstructive sleep apnea syndrome. The purpose of this study was to assess the effects of bimaxillary surgery without maxillary advancement on the upper airway using computational fluid dynamics (CFD) results of comparing pre- and post-operative finite element model. Seven female patients with jaw deformity, who underwent two-jaw surgery (Le Fort1 osteotomy and bilateral sagittal split ramus osteotomy; BSSRO) were enrolled. Maxillary was moved for correcting occlusal plane and mandibular was moved to advancement. Pharyngeal airway space and breathing during sleep were evaluated, comparing the periods of 2 days before and 6 months after the operation. The cross-sectional area of the level of the hard palate (HP) and the level of the tip of the uvula (TU), and airway volume of total, HP-TU, and TP- the level of the base of the epiglottis (BE) were increased. AI and AHI in 2 days before and 6 months after were decreased. As the result of nasal ventilation condition, velocity of HP and TU in 2 days before and 6 months after were decreased. We think that it was revealed that movement of the maxilla without advancement did not affect to the morphology and function of airway

Immunological Changes in Mesothelioma Patients and Their Experimental Detection

It is common knowledge that asbestos exposure causes asbestos-related diseases such as asbestosis, lung cancer and malignant mesothelioma (MM) not only in people who have handled asbestos in the work environment, but also in residents living near factories that handle asbestos. These facts have been an enormous medical and social problem in Japan since the summer of 2005. We focused on the immunological effects of asbestos and silica on the human immune system. In this brief review, we present immunological changes in patients with MM and outline their experimental detection. For example, there is over-expression of bcl-2 in CD4+ peripheral T-cells, high plasma concentrations of interleukin (IL)-10 and transforming growth factor (TGF)-ß, and multiple over-representation of T cell receptor (TcR)-Vß in peripheral CD3+ T-cells found in MM patients. We also detail an experimental long-term exposure T-cell model. Analysis of the immunological effects of asbestos may help our understanding of the biological effects of asbestos