Two-dimensional finite element simulations and experiments are presented to examine the ultrasonic wave propagation behavior in the corner section of CFRP (carbon fiber reinforced plastics) laminate ...structures. The numerical model consists of a right-angle corner section of CFRP laminate immersed in water and subjected to the ultrasonic wave incidence from its inner or outer side. The anisotropic stiffness constants of the unidirectional CFRP are identified experimentally and used to model the curved laminate structure. A commercial finite element analysis code is used to compute the reflection waveforms in the pulse-echo mode, and the effect of the laminate stacking sequence and the wave incidence direction is examined. It is shown that the reflection waveforms for the wave incidence from the outer side of the corner qualitatively resemble those for the plane laminate except that the echo signals of the former are substantially weaker. The numerical simulations are shown to well reproduce the qualitative features of experimental reflection measurements performed for the corner sections of 16-ply CFRP laminate. Experimental results indicate that the porosity content of the corner section can be estimated by the amplitude ratio of the surface and the back-wall echoes when a curvature-dependent calibration relation is properly used.
Schizophrenia is a known risk factor for coronavirus disease (COVID-19) infection and severity, and certain psychotropic drugs have been linked to increased mortality in infected patients with ...schizophrenia. However, little evidence exists regarding this risk. We retrospectively examined the association between mood stabilizers and the risk of pneumonia in patients with schizophrenia. This study included 99 patients with schizophrenia or schizoaffective disorder who were infected with COVID-19 in 2022 and met the inclusion criteria. After conducting propensity score matching to align patient backgrounds and concomitant medications, we assessed the impact of mood stabilizers, specifically sodium valproate, on the risk of pneumonia development. Univariate analysis revealed that patients with schizophrenia and COVID-19 who developed pneumonia were more likely to be older (64.5 14.2 vs. 57.4 11.5 years, p = 0.008) and using sodium valproate (44.4% vs. 16.7%, p = 0.004). Even after propensity score matching, patients who developed pneumonia were still more likely to be receiving sodium valproate than not (58.8% vs. 20.0%, p = 0.003). Sodium valproate use may be a risk factor for the development of pneumonia in patients with chronic schizophrenia who are infected with COVID-19 during long-term hospitalization.
Crack arresters were installed to suppress interfacial crack propagation between the skin and core of CFRP/foam core sandwich panels. The effect of the crack arrester on suppressing the propagation ...of a fatigue crack was investigated under mode I type loading using double cantilever beam specimens. Specimens were made from carbon/epoxy fabric prepreg and a polymethacrylimide foam core. The energy release rate, calculated by FE analysis, showed a considerable reduction at the crack tip as the tip approached the crack arrester. Fatigue crack propagation tests were carried out using sandwich panel specimens containing the crack arrester. The crack propagation rate, da/dN, decreased with decreasing distance from the crack tip to the arrester edge. Thus, the suppression effect of the crack arrester was demonstrated experimentally. This suppression effect correlated strongly with the decrease in the energy release rate due to the crack arrester when the thermal residual stress was taken into account.
The influence of porosity on the ultrasonic wave propagation in unidirectional carbon-fiber-reinforced composite laminates is investigated based on the two-dimensional finite element analysis and ...measurements. Random distributions of pores with different contents and size are considered in the analysis, together with the effects of viscoelastic plies and interlaminar resin-rich regions. The transient reflection waveforms are calculated from the frequency-domain finite-element solutions by the inverse Fourier transform. As the measures for porosity characterization, the ultrasonic wave velocity, attenuation coefficient, and interlaminar interface echo characteristics are examined for 24-ply unidirectional composite laminates. As a result, the wave velocity decreases with the porosity content in a manner insensitive to the pore size. On the other hand, the attenuation coefficient increases both with the porosity content and with the pore size. The time–frequency analysis of the reflection waveforms shows that the temporal decay rate of interlaminar interface echoes at the stop-band frequency is a good indicator of the porosity content. The measured porosity-content dependence of the wave velocity is better reproduced by the numerical simulations when the interlayer interfacial stiffnesses are adjusted according to the porosity content, indicating that not only the porosity features but also the interlaminar interfacial properties vary with curing conditions.
To examine the configuration of CFRP face plates/foamed plastic core sandwich panel joints, a tapered end-closure-type joint is selected and studied. In this type of joint, the sandwich panel is ...tapered to form a solid laminate comprising two face plates near the joint, and the two panels to be joined are mechanically fastened at the solid laminate with a splice plate. This type of joint may be suitable for aircraft panels because a flat surface can be obtained at the joint, which is advantageous from an aerodynamic viewpoint. However, in a previous study on such a joint, it was found that a delamination crack initiated from the tapered core end and propagated through the interface between the two face plates as an initial failure mode at a much lower tensile load than the final failure load in a tensile strength test. In this study, the angle of the tapered panel was focused on and the effect of changing the taper angle on suppressing the initial failure was investigated through experiments and numerical analysis. It was found that a smaller taper angle is more effective for suppressing the initial failure.
A 25-year-old woman delivered her first-born child weighing 3400 g by full-term normal delivery. Bloody stool developed 3 days after delivery. Colonoscopic examination revealed two linear ulcers ...parallel to the anal column on the posterior side of the rectal ampulla about 5 cm from the anal ring. Coagulated blood was detected at the ulcer bottom, suggesting the site of hemorrhage. Bowel rest in the absence of oral intake resulted in the disappearance of bloody stool. Three days later colonoscopic examination revealed improvement in the ulcer. There was no sign of constipation. A lateral pelvic radiograph showed that the apex of the coccyx was flexed anteriorly. The parturient canal may have physically pressed the rectum against the apex of the coccyx during delivery, causing mucosal injury. Only a few studies have reported the complication of a rectal ulcer due to injury during delivery. Furthermore, none of the previous studies has reported a rectal ulcer caused by deformity of the coccyx.
An 85-year-old woman with pneumonia had a fresh tracheostomy for prolonged orotracheal intubation. On the 14th day after the tracheostomy, difficulty occurred when attempting to change to a fresh ...tracheostomy tube, creating a false passage and loss of the airway. After several unsuccessful attempts at changing the tracheal tube for about 5 minutes, we inserted a tracheostomy tube under the guidance of a curved metallic detector which was inserted in the inner space of the tracheostomy tube. The tracheostomy tube could then be reinserted easily and safely. It is suggested that the curved metallic detector may be of benefit when a tracheostomy tube needs to be changed before maturation of the tracheal cutaneous tract.
We describe 2 siblings with multiple gastrointestinal stromal tumors (GISTs) and cutaneous hyperpigmentation. Both had a point mutation of the c-kit gene. The patients were sisters who had exhibited ...cutaneous hyperpigmentation since their late teens, but the diagnosis of multiple gastrointestinal submucosal tumors was not made until they were 41 and 45 years old. Histologic examination showed that these tumors were GISTs expressing CD34 and Kit protein. Both patients died of GISTs. Single-strand conformation polymorphism analysis showed a mutation of c-kit in tumor DNA extracted from paraffin-embedded specimens. Direct sequencing analysis showed that the point mutation occurred at codon 559 of exon 11(Val→Ala). The same single-point mutation was detected in DNA extracted from peripheral leukocytes obtained from the younger sister and her 2 children (who had similar general hyperpigmentation) as well as in DNA from a skin biopsy specimen taken from the older sister. The germline mutation at codon 559 of the c-kit gene found in the present familial GISTs differed from that in a previously reported case of familial GISTs. We propose that GISTs caused by a germline mutation of the c-kit gene should be referred to as GIST—cutaneous hyperpigmentation disease.
For the configuration of the CFRP face plates/foamed plastic core sandwich panel joint, a tapered end-closure type joint is selected and studied. In this type of joint, the sandwich panel is tapered ...to form the solid laminate of two face plates near the joint portion and two panels to be joined are mechanically fastened at the solid laminate portions with a splice plate. This type of joint could be suitable for the aircraft panel joint configuration, because a flat surface can be obtained at the joint portion, which is advantageous in an aerodynamic point of view. However, in a previous study, it was reported on the results of tensile strength test that the delamination crack initiating from tapered core end and propagating through the interface between two face plates was observed as an initial failure mode at much lower tensile load compared to the final failure load. In this study, the angle of tapered panel portion is focused on and the initial failure suppression effect caused by the change of taper angle is investigated through experiment and numerical analysis. And it is found that the smaller taper angle is preferred to suppress the initial failure.
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