Micro-/Nano-Structuring in Stainless Steels by Metal Forming and Materials Processing

Austenitic stainless steel type AISI304 sheets and plates as well as fine-grained type AISI316 (FGSS316) substrates and wires were employed as a work material in the intense rolling, the piercing and the plasma nitriding. AISI304 sheet after intense rolling had textured microstructure in the rolling direction. Crystallographic state changed itself to have distorted polycrystalline state along the shearing plane by piercing, with the strain induced phase transformation. FGSS316 substrates were plasma nitrided at 623 K for 14.4 ks to have two-phase fine nanostructure with the average grain size of 100 nm as a surface layer with the thickness of 30 μm. FGSS316 wires were also plasma nitrided at the same conditions to form the nitrided surface down to the depth of 30 μm. This nitrided wire was further uniaxially loaded in tensile to attain more homogeneously nitrided surface nano-structure and to form the austenitic and martensitic fiber structure aligned in the tensile direction. Each crystallographic structure intrinsic to metals and metallic alloys was tailored to have preferable micro−/nano-structured cells by metal forming and nitrogen supersaturation. The crystallographic change by metal forming in a priori and posterior to nitriding was discussed to find out a new way for materials design

Integrated Manufacturing of Fine-Grained Stainless Steels for Industries and Medicals

Austenitic stainless steels have been widely utilized in industries, infrastructures, housing structures, kitchen components, and medical tools. Higher hardness and strength as well as more improvement of wear and corrosion toughness are often required in the industrial and medical applications. Fine-grained stainless steel (FGSS) provides a solution to increase the strength without loss of ductility and toughness. Deeper research and development in manufacturing of FGSS is required to make full use of its properties toward its applications in industries and medicals. First, its mechanical properties and microstructure is introduced as a basic knowledge of FGSS with comparison to the normal stainless steels. Mechanical and laser machinability of FGSS is stated and discussed to finish the products in seconds. Its performance in metal forming and diffusion bonding is explained to explore its applications in third. Its surface treatment and tooling is discussed to describe the grain-size effect on the low temperature plasma nitriding and to demonstrate its effectiveness in die-making in forth. Finally, every aspect in manufacturing of FGSS sheets and solids is summarized as a conclusion

Shock vaporization/devolatilization of evaporitic minerals, halite and gypsum, in an open system investigated by a two-stage light gas gun

Dry lakebeds might constitute large volatile reservoirs on Mars. Hypervelocity impacts onto ancient dry lakebeds would have affected the volatile distribution on Mars. We developed a new experimental method to investigate the response of evaporitic minerals (halite and gypsum) to impact shocks in an open system. This technique does not result in chemical contamination from the operation of the gas gun. The technique is termed the two-valve method and the gun system is located in the Planetary Exploration Research Center, Chiba Institute of Technology, Japan. We detected the vaporization of halite at 31 GPa and devolatilization from gypsum at 11 GPa, suggesting that impact-induced volatile release from dry lakebeds has periodically occurred throughout Martian history. The vaporization of halite deposits might have enhanced the production of perchlorates, which are found globally on Mars. The water loss from gypsum possibly explains the coexisting types of Ca-sulfates found in Gale Crater.Comment: 17 pages, 4 figures, 1 supporting information, accepted for publication in Geophysical Research Letter

Study of hadron interactions in a lead-emulsion target

Topological and kinematical characteristics of hadron interactions have been studied using a lead-emulsion target exposed to 2, 4 and 10 GeV/c hadron beams. A total length of 60 m $\pi^-$ tracks was followed using a high speed automated emulsion scanning system. A total of 318 hadron interaction vertices and their secondary charged particle tracks were reconstructed. Measurement results of interaction lengths, charged particle multiplicity, emission angles and momenta of secondary charged particles are compared with a Monte Carlo simulation and appear to be consistent. Nuclear fragments emitted from interaction vertices were also detected by a newly developed emulsion scanning system with wide-angle acceptance. Their emission angle distributions are in good agreement with the simulated distributions. Probabilities of an event being associated with at least one fragment track are found to be greater than 50% for beam momentum $P > 4$ GeV/c and are well reproduced by the simulation. These experimental results validate estimation of the background due to hadron interactions in the sample of $\tau$ decay candidates in the OPERA $\nu_{\mu} \to \nu_{\tau}$ oscillation experiment.Comment: 14 pages, 11 figure

Nitrogen Supersaturation of AISI316 Base Stainless Steels at 673 K and 623 K for Hardening and Microstructure Control

The high-density plasma nitriding at 673 K and 623 K was employed to make 10% of nitrogen supersaturation on AISI316 base austenitic stainless steels. The processing parameters and nitrogen-hydrogen gas flow ratio were optimized to increase the yield of N2+ ion and NH-radical for efficient nitriding. The nitrided AISI316 specimens were prepared for multidimensional analysis to describe the fundamental features of low-temperature plasma nitriding. First, macroscopic evaluation revealed that nitrogen supersaturation induced the γ-lattice expansion and the higher nitrogen content than 4% of mass in depth. The mesoscopic analysis describes the holding temperature and initial grain-size effects on the microstructure changes. Plastic straining, grain-size refinement, and nitrogen zone-boundary diffusion processes advance with nitrogen supersaturation to drive the inner nitriding behavior. The microscopic analysis explains the microstructure refinement, the two-phase structuring, and the microstructure modification. Through this multi-dimensional analysis, the essential characteristics of the low-temperature plasma nitriding of 316 austenitic stainless steels were precisely understood to extend the engineering treatise on the bulk nitrogen stainless steels for surface modification and treatment of stainless steels by nitriding. This plasma nitriding was applied to strengthen and harden the AISI316 wire surfaces toward its application on surgery wires

ヒトウニョウビョウセイ ジンフゼン デ イジ トウセキチュウ ニ キュウセイ ハッショウ 1ガタ トウニョウビョウ オ ハッショウ シタ コウキ コウレイシャ ノ 1レイ

We herein presented a case of a ７５-year-old man who was referred to our hospital for hyperglycemia in a drowsy state following a convulsive seizure after receiving hemodialysis at another clinic. He had been receiving maintenance hemodialysis for non-diabetic renal failure from the age of ７３ years. He was diagnosed with diabetic ketosis because his blood glucose level was ７０７mg/dl, HbA１c ８．３％, glycoalbumin ４０．５％, serum osmolality ３２３mosm/kg, and ３-hydroxybutyric acid ５．８ mmol/l. Continuous intravenous insulin infusion therapy was immediately initiated and was changed to intensive insulin therapy on the ７th day after his admission. He did not have metabolic acidosis or serious dehydration associated with the acute metabolic derangement observed on arrival because fluid corrections for acid-base and electrolyte imbalances in the blood had been achieved by hemodialysis prior to his referral to our hospital. ΔCPR at six minutes in the glucagon loading test was hardly affected, indicating that his endogenous insulin secretory capacity was markedly reduced. The GAD antibody was negative. He had the haplotype of HLA DR４, which is considered to reflect disease susceptibility for type１diabetes in Japanese individuals. Acuteonset type １ diabetes mellitus was diagnosed based on the diagnostic criteria for acute-onset type１ diabetes mellitus （２０１２） by the Committee of the Japan Diabetes Society. At the time of his discharge, ８ units of insulin lispro were being administered prior to each meal in addition to ２ units of insulin glargine before sleeping. He was transferred to a local clinic on the ２３rd day after his admission. Although glycoalbumin had been measured every six months in the present case, it was not useful for detecting new onset diabetes. Therefore, blood glucose measurements before dialysis need to be regularly performed, even in dialysis patients with non-diabetic renal failure, in order to detect the new onset of diabetes at an early stage

A fluorenylidene-acridane that becomes dark in color upon grinding – ground state mechanochromism by conformational change

UTokyo FOCUS Articles掲載「力を加えると大きく色が変わる分子を発見 電気の流れやすさも変化」https://www.u-tokyo.ac.jp/focus/ja/articles/z0508_00130.htmlUTokyo FOCUS Articles "New molecule responds to mechanical pressure with drastic color change : Mechanical stimulus also enhances electron mobility" https://www.u-tokyo.ac.jp/focus/en/articles/z0508_00129.htm

Enriched Expression of Serotonin 1B and 2A Receptor Genes in Macaque Visual Cortex and their Bidirectional Modulatory Effects on Neuronal Responses

To study the molecular mechanism how cortical areas are specialized in adult primates, we searched for area-specific genes in macaque monkeys and found striking enrichment of serotonin (5-hydroxytryptamine, 5-HT) 1B receptor mRNA, and to a lesser extent, of 5-HT2A receptor mRNA, in the primary visual area (V1). In situ hybridization analyses revealed that both mRNA species were highly concentrated in the geniculorecipient layers IVA and IVC, where they were coexpressed in the same neurons. Monocular inactivation by tetrodotoxin injection resulted in a strong and rapid (<3 h) downregulation of these mRNAs, suggesting the retinal activity dependency of their expression. Consistent with the high expression level in V1, clear modulatory effects of 5-HT1B and 5-HT2A receptor agonists on the responses of V1 neurons were observed in in vivo electrophysiological experiments. The modulatory effect of the 5-HT1B agonist was dependent on the firing rate of the recorded neurons: The effect tended to be facilitative for neurons with a high firing rate, and suppressive for those with a low firing rate. The 5-HT2A agonist showed opposite effects. These results suggest that this serotonergic system controls the visual response in V1 for optimization of information processing toward the incoming visual inputs