► We examine mechanical properties of Al alloys produced by several casting processes. ► The mechanical properties obtained are different depending on the casting process. ► The mechanical properties ...are related to the lattice mis-orientation angle. ► The tensile strengths are evaluated by Hall–Petch relations. ► The fatigue properties are explained by power law dependence.
The mechanical properties of an Al–Si–Cu alloy (ADC12), produced using various casting technologies, have been examined experimentally. Four different casting processes were employed, including gravity casting (GC), cold-chamber die-casting (CD), twin rolled continuous casting (TRC) and the Ohno continuous casting process (OCC). Although these produced the same Al–Si–Cu aluminum alloy, different mechanical properties were obtained, in particular microstructural characteristics and dislocation density. The microstructure of GC and CD samples was formed mainly with coarse α-Al phase and needle-shaped Si and Fe based eutectic structures. In contrast, a fine round α-Al phase and tiny eutectic structures were observed for the TRC and OCC samples. Such a change of microstructure was caused by the different casting process parameters, namely injection speed, casting pressure and cooling rate. High internal stress as well as high dislocation density was detected for GC and TRC, caused by the high shrinkage force and high applied rolling force, respectively. Because of the different material properties, the tensile and fatigue strength were altered. A clear Hall–Petch relation with σ0.2=kyd−0.5+B was obtained, and the fatigue properties were evaluated with the power law dependence σa=σfNf−b. The mechanical properties obtained were also analyzed in relation to the crystal orientation and lattice mis-orientation angle.
The effects of microstructural characteristics on the mechanical properties of an aluminum alloy (ADC12: Al–Si11.3–Cu1.9–Zn0.8–Fe0.8–Mg0.2–Mn0.2) produced by various casting technologies are studied ...experimentally and numerically. Six different casting processes are employed: gravity casting, cold-chamber die-casting, hot-chamber die-casting, squeeze casting, twin-rolled continuous casting and heated-mold continuous casting. Microstructural characteristics, dislocation density and defect density vary depending on the casting method, owing to differences in solidification rate, casting pressure and injection speed. The material characteristics of the samples affect their mechanical properties. Multiple regression analysis is carried out to find equations to predict tensile strength using five independent factors: secondary dendrite arm spacing, microporosity rate, diameter of eutectic structures, aspect ratio of eutectic structures and dislocation density. All these factors influence the tensile properties, although to different degrees. The estimated values of tensile strength are in good agreement with experimental results.
Silver bromide, which is an indirect transition-type semiconductor, has been used as a photographic film and a charged particle tracking detector since the 19th century because it is sensitive to ...absorption of light or energy loss by charged particles. At cryogenic temperatures, it is known that the luminescence occurs in silver bromide with high quantum efficiency via impurities such as iodide ions. It was studied only by photo-excitation and tribo-excitation in the previous studies, and in this paper, for the first time, we observed the luminescence produced by charged-particle excitation by using a fine-grained nuclear emulsion consisting of 40 nm silver iodobromide crystals. The ratios of the contribution to luminescence among the electron–hole pairs expected by the energy deposition of charged particles were (5.7 ± 0.8)% with 5.48 MeV α-rays and (22.5 ± 3.5)% with 10 to 60 keV γ-rays at 88 K. The luminescence wavelength produced by α-rays had a peak at 540 nm and was shorter than that produced by photo-excitation having a peak at 575 nm.
Titanium is used as a metal for biocompatible materials such as dental implants or restorations because of its excellent chemical stability. However, the corrosion of Ti in the prophylactic ...fluoride-containing environment can become problematic. To clarify the effects of fluoride concentration and pH on the corrosion behavior of Ti, we conducted anodic polarization and immersion tests in NaF solution of various concentrations and pH values. The concentrations of dissolved Ti in the test solutions were analyzed by inductively coupled plasma mass spectroscopy. There were obvious limits of fluoride concentration and the pH value at which the corrosion behavior of Ti changed. The corrosion of Ti in the solution containing fluoride depended on the concentration of hydrofluoric acid (HF). When the HF concentration in the solution was higher than about 30 ppm, the passivation film of the Ti was destroyed. The results of this study revealed a relation between the fluoride concentrations and pH values at which Ti corrosion occurred and provided data on such corrosion in environments where the fluoride concentration and pH value are known.
We describe a successful surgical technique of abdominal trachelectomy and re‐vaginoplasty for cervico‐vaginal stenosis following unsuccessful uterovaginal anastomosis and vaginoplasty in a patient ...with congenital cervical and vaginal aplasia. After the surgical procedure, cervico‐vaginal stenosis was resolved and periodic menstruation without dysmenorrhoea resumed. While long‐term follow‐up is essential to ensure successful pregnancy and delivery, we conclude that this novel surgical procedure is a promising alternative for improvement of the quality of life and normal sexual function, and for preservation of fertility in patients with cervical and vaginal aplasia.
Leptin, an adipocytokine encoded by an obesity gene and expressed in adipose tissue, affects feeding behavior, thermogenesis, and neuroendocrine status via leptin receptors distributed in the brain, ...especially in the hypothalamus. Leptin may also modulate the synaptic plasticity and behavioral performance related to learning and memory since: leptin receptors are found in the hippocampus, and both leptin and its receptor share structural and functional similarities with the interleukin-6 family of cytokines that modulate long-term potentiation (LTP) in the hippocampus. We therefore examined the effect of leptin on (1) behavioral performance in emotional and spatial learning tasks, (2) LTP at Schaffer collateral-CA1 synapses, (3) presynaptic and postsynaptic activities in hippocampal CA1 neurons, (4) the intracellular Ca
2+ concentration (Ca
2+
i) in CA1 neurons, and (5) the activity of Ca
2+/calmodulin protein kinase II (CaMK II) in the hippocampal CA1 tissue that exhibits LTP. Intravenous injection of 5 and/or 50
μg/kg, but not of 500
μg/kg leptin, facilitated behavioral performance in passive avoidance and Morris water-maze tasks. Bath application of 10
−12
M leptin in slice experiments enhanced LTP and increased the presynaptic transmitter release, whereas 10
−10
M leptin suppressed LTP and reduced the postsynaptic receptor sensitivity to
N-methyl-
d-aspartic acid. The increase in the Ca
2+
i induced by 10
−10
M leptin was two times greater than that induced by 10
−12
M leptin. In addition, the facilitation (10
−12
M) and suppression (10
−10
M) of LTP by leptin was closely associated with an increase and decrease in Ca
2+-independent activity of CaMK II. Our results show that leptin not only affects hypothalamic functions (such as feeding, thermogenesis, and neuroendocrine status), but also modulates higher nervous functions, such as the behavioral performance related to learning and memory and hippocampal synaptic plasticity.
Abstract The risk factors for recurrence of head and neck cancer are classified as being of high or intermediate risk. Those of intermediate risk include multiple positive nodes without extracapsular ...nodal spread, perineural/vascular invasion, pT3/T4 primary tumours, and positive level IV/V nodes. However, little evidence is available to validate these intermediate risk factors. We analyzed perineural/vascular invasion in 89 patients who underwent radical surgery for oral tongue squamous cell carcinoma, whose records were reviewed retrospectively. Perineural invasion was found in 27.0% of cases and vascular invasion in 23.6%; both had a strong relationship with histopathological nodal status ( P = 0.005). The 5-year disease-specific survival (DSS) and overall survival rates of patients with perineural invasion were significantly lower than those of patients without perineural invasion ( P < 0.001 and P = 0.002, respectively). The 5-year DSS of UICC stage I and II cases with perineural/vascular invasion was significantly lower than those without ( P < 0.001 and P = 0.008, respectively). Perineural invasion and vascular invasion are risk factors for regional metastasis and a poor prognosis. We recommend elective neck dissection when perineural/vascular invasion is found in clinical stage I and II cases. The accumulation of further evidence to consider intermediate risks is required.
Aims The plasma level of interleukin-6 (IL-6) has been reported to be associated with left ventricular (LV) remodelling after myocardial infarction (MI). The present study was designed to examine ...whether anti-IL-6 receptor antibody (MR16-1) prevents the development of LV remodelling after MI. Methods and results Balb/c male mice were subjected to MI by ligating the left anterior descending coronary artery. The mice were then treated with an intraperitoneal injection of MR16-1 (500 µg/body) or control IgG. MR16-1 decreased the myocardial myeloperoxidase activity and monocyte chemoattractant protein-1 concentration in the infarct region, concomitant with decreases in neutrophil and macrophage infiltration 3 days after ligation, while infarct size was comparable between the control IgG- and MR16-1-treated mice. At 7 days after ligation, MR16-1 significantly suppressed matrix metalloproteinase-2 activity in the infarct region. Furthermore, the MR16-1-treated mice demonstrated a reduction in LV dilatation and an improvement in LV contractile function compared with the control IgG-treated mice at 7 and 28 days after surgery, leading to an improvement in survival rate (80.6 vs. 59.5%, P < 0.05) at 28 days after surgery. The beneficial effects of MR16-1 were accompanied by histological suppression of cardiomyocyte hypertrophy and interstitial fibrosis in the non-infarct region. Conclusion Administration of MR16-1 after MI suppressed myocardial inflammation, resulting in the amelioration of LV remodelling. Neutralization of the IL-6 receptor is a potentially useful strategy for protecting hearts from LV remodelling after MI.
Abstract Local recurrence of oral squamous cell carcinoma (OSCC) after primary surgery has been considered to be a poor prognostic entity in terms of survival rate. The purpose of this study is to ...evaluate the incidence of local recurrence and to identify significant risk factors for the local recurrence in OSCC. The authors retrospectively reviewed records for 187 patients who underwent radical surgery for OSCC. The local recurrence rate was 16.0% (30/187 patients) in this study. The survival rate of patients with local recurrence was 33.3%, which was significantly lower than that (94.3%) of patients without local recurrence. Pattern of invasion (POI), neoadjuvant chemotherapy (NAC), and the status of the surgical margin were identified as factors influencing local recurrence. In particular, NAC and the status of the surgical margin were independent risk factors by multivariate analysis. The deep margin was resected at a close site in many NAC-treated patients, suggesting that NAC may lead to local recurrence and poor outcomes. No efficacy of NAC was observed, suggesting that the standard treatment of oral cancers is surgery alone.
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