Numerical model for cough-generated droplet dispersion on moving escalator with multiple passengers.

To investigate the motion of virus-laden droplets between moving passengers in line, we performed numerical simulations of the distribution of airborne droplets within a geometrically detailed model similar to an actual escalator. The left and right sides and the ceiling of the escalator model were surrounded by walls, assuming a subway used by many people every day with concern to virus-laden droplets. Steps and handrails were incorporated in the model to faithfully compute the escalator-specific flow field. The ascending and descending movements of the escalator were performed with 10 or 5 passengers standing at different boarding intervals. To resolve the unsteady airflow that is excited by a moving boundary consisting of passengers, steps, and handrails, the moving computational domain method based on the moving-grid finite-volume method was applied. On the basis of the consideration that the droplets were small enough, droplet dispersion was computed by solving the equation of virus-laden droplet motion using a pre-computed velocity field, in which the flow rate of a cough, diameter distribution, and evaporation of droplets are incorporated. The simulation resolved the detailed motion of droplets in flow, and therefore, we were able to evaluate the risk of viral adhesion to following passengers. As a result, we found that the ascending escalator had a higher risk of being exposed to virus-laden droplets than the descending escalator. We also reported that the chance of viral droplet adhesion decreases as the distance from the infected person increases, emphasizing the importance of social distancing.

Quantifying the COVID19 infection risk due to droplet/aerosol inhalation.

The dose-response model has been widely used for quantifying the risk of infection of airborne diseases like COVID-19. The model has been used in the room-average analysis of infection risk and analysis using passive scalars as a proxy for aerosol transport. However, it has not been employed for risk estimation in numerical simulations of droplet dispersion. In this work, we develop a framework for the evaluation of the probability of infection in droplet dispersion simulations using the dose-response model. We introduce a version of the model that can incorporate the higher transmissibility of variant strains of SARS-CoV2 and the effect of vaccination in evaluating the probability of infection. Numerical simulations of droplet dispersion during speech are carried out to investigate the infection risk over space and time using the model. The advantage of droplet dispersion simulations for risk evaluation is demonstrated through the analysis of the effect of ambient wind, humidity on infection risk, and through a comparison with risk evaluation based on passive scalars as a proxy for aerosol transport.

Computational investigation of prolonged airborne dispersion of novel coronavirus-laden droplets.

We have performed highly accurate numerical simulations to investigate prolonged dispersion of novel coronavirus-laden droplets in classroom air. Approximately 10,900 virus-laden droplets were released into the air by a teacher coughing and tracked for 90 min by numerical simulations. The teacher was standing in front of multiple students in a classroom. To estimate viral transmission to the students, we considered the features of the novel coronavirus, such as the virus half-life. The simulation results revealed that there was a high risk of prolonged airborne transmission of virus-laden droplets when the outlet flow of the classroom ventilation was low (i.e., 4.3 and 8.6 cm/s). The rates of remaining airborne virus-laden droplets produced by the teacher coughing were 40% and 15% after 45 and 90 min, respectively. The results revealed that students can avoid exposure to the virus-laden droplets by keeping a large distance from the teacher (5.5 m), which is more than two times farther than the currently suggested social distancing rules. The results of this study provide guidelines to set a new protection plan in the classroom to prevent airborne transmission of virus-laden droplets to students.

A rare case of peliosis hepatis in a patient with chronic renal failure and renal cell carcinoma.

Peliosis hepatis (PH) is a rare disease characterized by the presence of sinusoidal dilation and blood-filled cysts throughout the hepatic parenchyma. We report a case of PH in a 49-year-old woman with chronic renal failure (CRF) on hemodialysis and with renal cell carcinoma (RCC). Dynamic contrast-enhanced computed tomography (CT) showed a 35-mm-diameter, hypervascular tumor in the liver and RCC in the right renal cyst. Ultrasound and superparamagnetic iron oxide-enhanced magnetic resonance imaging were also performed; however, the liver tumor could not be distinguished from the metastasis of RCC. Therefore, echo-guided biopsy of the liver tumor using an 18-G Majima needle was performed. Histological evaluation of the specimen showed irregular sinusoidal dilatation and blood-filled cavities without malignant cells. She was ultimately diagnosed with PH. Subsequently, she underwent total right nephrectomy for RCC and was diagnosed with RCC stage 1 (pT1N0M0). A follow-up CT performed 4 months after nephrectomy showed no growth of PH. Although the development of PH in patients with CRF or RCC who do not undergo renal transplantation is extremely rare, it should be considered in the differential diagnosis to distinguish PH from the metastasis of RCC.

A case of pancreatic pseudocysts accompanied by infection, pseudoaneurysm ruptures, and pseudocystocolonic fistulae.

Pancreatic pseudocysts (PPs) can be accompanied by infection, pseudoaneurysm ruptures, and fistulae to other organs, which can be fatal without appropriate treatment. Herein, we present the case of an 82-year-old man with PPs accompanied by infection, pseudoaneurysm rupture, and pseudocystocolonic fistula that were managed via multidisciplinary treatment. Computed tomography (CT) revealed two inflamed PPs, one each in the pancreatic head and tail. He was, therefore, diagnosed with infectious PPs. The pancreatic head PP shrunk on endoscopic nasopancreatic drainage (ENPD), but the pancreatic tail PP did not. Endoscopic ultrasound (EUS)-guided transluminal drainage was performed to treat the pancreatic tail PP; his symptoms improved. However, he vomited blood at 14 day post-drainage. Angiography revealed pseudoaneurysm rupture in a left gastric artery branch. After successful angioembolization, he developed hematochezia 2 days later. We suspected re-bleeding of the pseudoaneurysm. The bleeding stopped spontaneously, but CT and radiography revealed the presence of a pseudocystocolonic fistula. Careful follow-up was performed, and he has not had any symptoms at 9 month post-discharge. We managed PP-related complications via ENPD, EUS-guided transluminal drainage, angioembolization, and careful follow-up. Infection, pseudoaneurysm rupture, and pseudocystocolonic fistula are rare, but can occur simultaneously. Therefore, clinicians should consider these complications when treating patients with PPs.

[Use of dexmedetomidine hydrochloride as a sedative during local therapy for hepatocellular carcinoma].

Sedation using dexmedetomidine hydrochloride (DEX) was administered to patients with hepatocellular carcinoma (HCC) prior to local therapy. Case 1 was a 58-year-old man undergoing radiofrequency ablation in combination with transcatheter arterial chemoembolization for HCC in S3. In accordance with the package insert, the initial loading dose was set at 6 µg/kg/hour. Although a favorable sedative effect was achieved, his blood pressure and pulse rate decreased. Case 2 was a 79-year-old woman undergoing percutaneous ethanol injection therapy for HCC in S6. Half the initial loading dose indicated in the package insert (3 µg/kg/hour) was administered, but the sedative effect was appreciable. No marked blood pressure or pulse rate decreases were observed. We believe that the use of DEX as a sedative agent in local therapy for HCC can be expected to increase. However, the optimal dose setting for DEX requires further examination.

[A case report: an ileus caused by cecal volvulus and intersigmoidal hernia due to mesenterium commune].

A 33-year old woman was referred to our hospital because of gradually progressing abdominal pain and abdominal distension. A computed tomography demonstrated that distended cecum was located in the left retroperitoneal space. Barium enema revealed that the descending colon was positioned at the right side of the abdomen and transverse colon became severely tapered. Ceacal volvulus in addition to the internal herniation into the left retroperitoneal space was clinically diagnosed. The patient received an emergent operation. Operative findings showed that mesenterium commune, no fixation of the colon to the retroperitonium, and the internal herniation of terminal ileum to transverse colon into the sigmoid mesentery. Moreover, the cecal volvulus was diagnosed at the left retroperitoneal space. The mesenterium commune with internal herniation and cecal volvulus is extremely rare but one of important causes of acute abdomen.

Pure gastric yolk sac tumor that was diagnosed after curative resection: case report and review of literature.

We recently experienced an 87-yr-old man with gastric yolk sac tumor. Preoperative diagnosis was poorly differentiated adenocarcinoma in the cardia of stomach without apparent metastasis. A total gastrectomy was performed. The precise histological examination after surgery revealed the tumor was composed of pure gastric yolk sac tumor without adenocarcinomatous components. The surgical margin and the resected lymph nodes were histologically negative for the tumor and a curative resection was performed. Five months after the operation, enlargement of the intraabdominal lymph nodes occurred with elevation of serum alpha fetoprotein (AFP), and the patient died 2 mo later. Gastric yolk sac tumors are very rare, and only six cases of gastric yolk sac tumors have been previously reported in the literature. Five out of six cases are accompanied by components of adenocarcinoma, and our present case is the second report of pure gastric yolk sac tumor to the best of our knowledge.

[A case of effective weekly paclitaxel administration for primary lesion of schirrous gastric cancer].

We report a case of advanced schirrous gastric cancer with carcinomatous peritonitis. Chemotherapy with TS-1 was applied during the first 4 weeks, but the tumor did not respond to this therapy. Next, paclitaxel (TXL) was administered at a weekly dose of 90 mg/body/day for 3 weeks followed by a week interval of rest. Remarkable mass reduction of primary tumor was observed after 3 courses of treatment, and the symptom derived from primary tumor was relieved without significant side effects. The clinical course for schirrous gastric cancer with carcinomatous peritonitis is still miserable for patients, although many attempts have been made to improve its prognosis. A weekly paclitaxel regimen appears to be one of the promising treatment for schirrous gastric cancer.

CH/π Attraction: The Origin of Enantioselectivity in Transfer Hydrogenation of Aromatic Carbonyl Compounds Catalyzed by Chiral η6 -Arene-Ruthenium(II) Complexes.

The through-space CH/π attraction between the η6 -arene ligand on Ru and the carbonyl aryl substituent (see transition states in picture) plays a key role in the enantioselective transfer hydrogenation of aromatic carbonyl compounds with 2-propanol or formic acid, catalyzed by chiral η6 -arene-RuII complexes.