Persistent Homology Analysis of the Microstructure of Laser-Powder-Bed-Fused Al-12Si Alloy.

The laser powder bed fusion (L-PBF) process provides the cellular microstructure (primary α phase surrounded by a eutectic Si network) inside hypo-eutectic Al-Si alloys. The microstructure changes to the particle-dispersed microstructure with heat treatments at around 500 °C. The microstructural change leads to a significant reduction in the tensile strength. However, the microstructural descriptors representing the cellular and particle-dispersed microstructures have not been established, resulting in difficulty in terms of discussion regarding the structure-property relationship. In this study, an attempt was made to analyze the microstructure in L-PBF-built and subsequently heat-treated Al-12Si (mass%) alloys using the persistent homology, which can analyze the spatial distributions and connections of secondary phases. The zero-dimensional persistent homology revealed that the spacing between adjacent Si particles was independent of Si particle size in the as-built alloy, whereas fewer Si particles existed near large Si particles in the heat-treated alloy. Furthermore, the first principal component of a one-dimensional persistent homology diagram would represent the microstructural characteristics from cellular to particle-dispersed morphology. These microstructural descriptors were strongly correlated with the tensile and yield strengths. This study provides a new insight into the microstructural indices describing unique microstructures in L-PBF-built alloys.

Impact of the COVID-19 pandemic on the hospitalizations, time course, presenting symptoms, and mid-term outcomes in patients with myocardial infarctions in a Japanese multi-center registry.

To investigate the impact of the coronavirus disease 2019 (COVID-19) pandemic on myocardial infarctions (MIs), consecutive MI patients were retrospectively reviewed in a multi-center registry. The patient characteristics and 180-day mortality for both ST-segment elevation myocardial infarctions (STEMIs) and non-STEMIs (NSTEMIs) in the after-pandemic period (7 April 2020-6 April 2021) were compared to the pre-pandemic period (7 April 2019-6 April 2020). Inpatients with MIs, STEMIs, and NSTEMIs decreased by 9.5%, 12.5%, and 4.1% in the after-pandemic period. The type of the presenting symptoms (as classified as typical symptoms, atypical symptoms, and out-of-hospital cardiac arrests [OHCAs]) did not differ between the two time periods for both STEMIs and NSTEMIs, while the rate of OHCAs was numerically higher in the after-pandemic period for the STEMIs (12.1% vs. 8.0%, p = 0.30). The symptom-to-admission time (STAT) did not differ between the two time periods for both STEMIs and NSTEMIs, but the door-to-balloon time (DTBT) for STEMIs was significantly longer in the after-pandemic period (83.0 [67.0-100.7] min vs. 70.0 [59.0-88.7] min, p = 0.004). The 180-day mortality did not significantly differ between the two time periods for both STEMIs (15.9% vs. 11.4%, p = 0.14) and NSTEMIs (9.9% vs. 8.0%, p = 0.59). In conclusion, hospitalizations for MIs decreased after the COVID-19 pandemic. Although the DTBTs were significantly longer in the after-pandemic period, the mid-term outcomes for MIs were preserved.

Bradyarrhythmia Suspected to be Associated with Sleep Apnea Syndrome.

Sleep apnea syndrome (SAS) is a condition in which apnea and hypoventilation at night cause hypoxemia and impaired wakefulness during the day, resulting in a general malaise and dozing. Sleep apnea has been implicated in the development of hypertension, ischemic heart disease, arrhythmia, heart failure, and cerebrovascular disease.1) Approximately 50% of patients with sleep-disordered breathing have an arrhythmia. In severe cases with an apnea-hypopnea index (AHI) of 30 or more, the frequency of arrhythmias during sleep is two to four times that of individuals without SAS. Bradyarrhythmias such as sinus bradycardia, sinus arrest, and atrioventricular block occurs at night in about 5%-10% of patients with sleep-disordered breathing.2)During nocturnal sleep, vagal excitation causes excessive muscle relaxation of the upper airway, leading to periodic airway diameter reduction, which increases snoring and obstructive apnea. As a result, hypoxemia is likely, further increasing vagal tone and leading to bradycardia. An increase in ventilation rate and volume quickly compensates for the decrease in arterial partial pressure of oxygen during apnea, which leads to new bradycardia due to a decrease in the partial pressure of oxygen in arterial blood, which suppresses vagal tone and respiration.3)We experienced a case of a 44-year-old patient with bradyarrhythmia that might be associated with SAS. After continuous positive airway pressure treatment, AHI decreased, and very long cardiac arrests resolved.

Diagnostic Utility of Cardiac Magnetic Resonance in Recurrent "Third Time" Myocarditis Without Electrocardiographic Changes.

A few studies have reported on recurrent myocarditis occurring more than twice in one patient. In this study, we present a recurrent "third time" acute myocarditis in a young female Japanese patient with a history of a definitive diagnosis of lymphocytic myocarditis by endomyocardial biopsy, cardiac magnetic resonance imaging (CMR), and catheter examination twice in the past. Although chest pain and an increase in the cardiac enzymes were observed the third time, no significant changes were noted in the 12-lead electrocardiogram (ECG), and a definitive diagnosis could be achieved by CMR. This case suggested that in patients with a history of myocarditis, if there is chest pain and elevated cardiac enzymes even without any changes in the 12-lead ECG, acute myocarditis should be considered, and CMR is useful for the differentiation.Only four case reports including this present case were found through the previous literatures. More than two recurrent episodes of myocarditis have been extremely rare, but all cases have typical chest symptoms and a troponin level increase, leading to a relatively benign prognosis.

[A Case of Synchronous Multiple Colon Carcinoma-A Case Report].

A 67-year-old woman with anemia was referred to us for further study. A colonoscopy exhibited multiple tumors(tub1)in the transverse and sigmoid colon(two regions)and rectum. Contrast-enhanced CT revealed no apparent distant and lymph node metastases. Thus, subtotal colectomy with D3 lymph node dissection was performed. Pathologically, the tumor was diagnosed as pStage Ⅱand pStage 0. After surgery, the patient had no recurrence for 8 months. We herein report a rare case of four synchronous colorectal carcinomas that were successfully treated.