Generalization techniques of neural networks for fluid flow estimation

We demonstrate several techniques to encourage practical uses of neural networks for fluid flow estimation. In the present paper, three perspectives which are remaining challenges for applications of machine learning to fluid dynamics are considered: 1. interpretability of machine-learned results, 2. bulking out of training data, and 3. generalizability of neural networks. For the interpretability, we first demonstrate two methods to observe the internal procedure of neural networks, i.e., visualization of hidden layers and application of gradient-weighted class activation mapping (Grad-CAM), applied to canonical fluid flow estimation problems -- $(1)$ drag coefficient estimation of a cylinder wake and $(2)$ velocity estimation from particle images. It is exemplified that both approaches can successfully tell us evidences of the great capability of machine learning-based estimations. We then utilize some techniques to bulk out training data for super-resolution analysis and temporal prediction for cylinder wake and NOAA sea surface temperature data to demonstrate that sufficient training of neural networks with limited amount of training data can be achieved for fluid flow problems. The generalizability of machine learning model is also discussed by accounting for the perspectives of inter/extrapolation of training data, considering super-resolution of wakes behind two parallel cylinders. We find that various flow patterns generated by complex interaction between two cylinders can be reconstructed well, even for the test configurations regarding the distance factor. The present paper can be a significant step toward practical uses of neural networks for both laminar and turbulent flow problems.Comment: 24 pages, 24 figure

VLBI Monitoring Observations of Water Masers Around the Semi-Regular Variable Star R Crateris

We monitored water-vapor masers around the semi-regular variable star R Crateris with the Japanese VLBI Network (J-Net) at the 22 GHz band during four epochs with intervals of one month. The relative proper motions and Doppler-velocity drifts of twelve maser features were measured. Most of them existed for longer than 80 days. The 3-D kinematics of the features indicates a bipolar expanding flow. The major axis of the asymmetric flow was estimated to be at P.A. = 136 degrees. The existence of a bipolar outflow suggests that a Mira variable star had already formed a bipolar outflow. The water masers are in a region of apparent minimum radii of 1.3 x 10^12 m and maximum radii of 2.6 x 10^12 m, between which the expansion velocity ranges from 4.3 to 7.4 km/s. These values suggest that the water masers are radially accelerated, but still gravitationally bound, in the water-maser region. The most positive and negative velocity-drifting features were found relatively close to the systemic velocity of the star. We found that the blue-shifted features are apparently accelerated and the red-shifted apparently decelerated. The acceleration of only the blue-shifted features seems to be consistent with that of the expanding flow from the star.Comment: 15 pages, 5 figures, Accepted for publication in PASJ (2001), preprint can be obtained via WWW on http://www.nro.nao.ac.jp/library/report/list.htm

Evaluation of Blood Supply with Indocyanine Green Fluorescence in Resection for Concurrent Gastric and Pancreatic Cancer: A Case Report

We present a rare case of concurrent resection of pancreatic and gastric cancer in which indocyanine green (ICG) fluorescence was used to evaluate the remnant stomach. An 80-year-old man was referred with a tumor in the distal pancreas. Computed tomography showed a 25-mm mass in the pancreatic tail; endoscopic ultrasound-guided fine-needle aspiration revealed adenocarcinoma. Upper gastrointestinal endoscopy and subsequent upper gastrointestinal series revealed advanced gastric cancer in the mid-stomach. Concurrent resection of the pancreatic and gastric tumors was performed. After distal pancreatectomy and distal gastrectomy, ICG evaluation of the stomach showed fluorescence extending only 3 cm distal from the cardia. To avoid ischemic change at the remnant stomach, total gastrectomy was performed. Since remnant gastric necrosis and anastomotic leak following ischemia can lead to fatal outcomes, the use of ICG to evaluate blood supply at anastomotic sites can help determine the extent of safe resection in such cases

The Structure of the Mammalian 20S Proteasome at 2.75 Å Resolution

AbstractThe 20S proteasome is the catalytic portion of the 26S proteasome. Constitutively expressed mammalian 20S proteasomes have three active subunits, β1, β2, and β5, which are replaced in the immunoproteasome by interferon-γ-inducible subunits β1i, β2i, and β5i, respectively. Here we determined the crystal structure of the bovine 20S proteasome at 2.75 Å resolution. The structures of α2, β1, β5, β6, and β7 subunits of the bovine enzyme were different from the yeast enzyme but enabled the bovine proteasome to accommodate either the constitutive or the inducible subunits. A novel N-terminal nucleophile hydrolase activity was proposed for the β7 subunit. We also determined the site of the nuclear localization signals in the molecule. A model of the immunoproteasome was predicted from this constitutive structure

Pressure effects on an organic radical ferromagnet: 2,5-difluorophenyl-a-nitronyl nitroxide

Raising a transition temperature (Tc) in organic radical ferromagnets is a desire for material scientists. We investigated the pressure effects on an organic radical ferromagnet 2,5-difluorophenyl-α-nitronyl nitroxide (2,5-DFPNN), which has a ferromagnetic transition at 0.45 K. The hydrostatic pressure effects were investigated through measurements of ac magnetic susceptibility (χ) up to P=1.7GPa, heat capacity (Cp) up to P=1.5GPa, and powder x-ray diffraction up to P=4.7GPa. Furthermore, ac magnetic susceptibility under nonhydrostatic pressure was also measured in the pressure region up to 10.0 GPa. As for 2,5-DFPNN, we observed the pressure-induced enhancement of Tc as dTc/dP=7.9×10−2K/GPa [Tc(P=1.5GPa)=0.57K], while other prototypes, the β phase of p-NPNN and p−Cl−C6H4−CH=N−TEMPO show the negative pressure effects. The results for the Cp and the crystal structural analysis suggest that the magnetic dimension of the short-range order developing above Tc transforms from one dimension (a axis) to two dimensions (ac plane) under high pressure. This increase of the magnetic dimension probably promotes to increase Tc. The ferromagnetic signal of χ, however, decreases with increasing pressure, and finally disappears for P>~5.0GPa. The decrease seems to originate from the decrease of the ferromagnetic interaction along the b axis. Similar instability of organic ferromagnetic long range order against pressure has been observed for the β phase of p-NPNN and p−Cl−C6H4−CH=N−TEMPO