Generating observation guided ensembles for data assimilation with denoising diffusion probabilistic model

This paper presents an ensemble data assimilation method using the pseudo ensembles generated by denoising diffusion probabilistic model. Since the model is trained against noisy and sparse observation data, this model can produce divergent ensembles close to observations. Thanks to the variance in generated ensembles, our proposed method displays better performance than the well-established ensemble data assimilation method when the simulation model is imperfect

Continuous data assimilation of large eddy simulation by lattice Boltzmann method and local ensemble transform Kalman filter (LBM-LETKF)

We investigate the applicability of the data assimilation (DA) to large eddy simulations (LESs) based on the lattice Boltzmann method (LBM). We carry out the observing system simulation experiment of a two-dimensional (2D) forced isotropic turbulence, and examine the DA accuracy of the nudging and the local ensemble transform Kalman filter (LETKF) with spatially sparse and noisy observation data of flow fields. The advantage of the LETKF is that it does not require computing spatial interpolation and/or an inverse problem between the macroscopic variables (the density and the pressure) and the velocity distribution function of the LBM, while the nudging introduces additional models for them. The numerical experiments with $256\times256$ grids and $10\%$ observation noise in the velocity showed that the root mean square error of the velocity in the LETKF with $8\times 8$ observation points ($\sim 0.1\%$ of the total grids) and 64 ensemble members becomes smaller than the observation noise, while the nudging requires an order of magnitude larger number of observation points to achieve the same accuracy. Another advantage of the LETKF is that it well keeps the amplitude of the energy spectrum, while only the phase error becomes larger with more sparse observation. We also see that a lack of observation data in the LETKF produces a spurious energy injection in high wavenumber regimes, leading to numerical instability. Such numerical instability is known as the catastrophic filter divergence problem, which can be suppressed by increasing the number of ensemble members. From these results, it was shown that the LETKF enables robust and accurate DA for the 2D LBM with sparse and noisy observation data.Comment: 27 pages, 14 figure

Generation of Embryonic Stem Cell Lines from Immature Rabbit Ovarian Follicles

In mammalian ovaries, many immature follicles remain after the dominant follicles undergo ovulation. Here we report the successful production of rabbit embryonic stem cells (ESCs) from oocytes produced by in vitro culture of immature follicles and subsequent in vitro maturation treatment. In total, we obtained 53 blastocysts from oocytes that received intracytoplasmic sperm injection followed by in vitro culture. Although only weak expression of POU5f1 was observed in the inner cell masses of in-vitro-cultured follicle-derived embryos, repeated careful cloning enabled establishment of 3 stable ESC lines. These ESC lines displayed the morphological characteristics of primed pluripotent stem cells. The ESC lines also expressed the pluripotent markers Nanog, POU5f1, and Sox2. Further, these ESCs could be differentiated into each of the 3 different germ layers both in vitro and in vivo. These results demonstrate that immature follicles from rabbits can be used to generate ESCs. Moreover, the use of rabbit oocytes as a cell source provides an experimental system that closely matches human reproductive and stem cell physiology.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140197/1/scd.2012.0300.pd

Development of static magnetic refrigeration system using multiple high-temperature superconducting coils

It is expected to build a sustainable social system that uses “hydrogen” as a fuel to generate electricity without emitting CO2. To realize this, technology for storing a large amount of hydrogen is indispensable, and storage as liquid hydrogen is ideal. However, the efficiency of the cooling device in the temperature range around 20 K required for long-term storage with liquid hydrogen is low, and the equipment is huge and expensive, so it has not been established as a widely used technology. Magnetic refrigeration is expected to be a highly efficient refrigerator in the temperature range of around 20 K because it can realize an ideal refrigeration cycle. However, in magnetic refrigeration, it is necessary to give a magnetic field change to the magneto caloric material (MCM). Further, in order to perform cooling with a large capacity and extremely low temperature by magnetic refrigeration, the magnetic field strength of a permanent magnet is insufficient, and it is indispensable to use a superconducting coil capable of generating a strong magnetic field with low power consumption. This study aims to develop a static magnetic refrigeration system using multiple high-temperature superconducting coils. By utilizing the energy storage characteristics of the superconducting coil, we are considering a magnetic refrigeration system that can repeatedly generate magnetic field changes to save energy without the need for large amounts of energy to be taken in and out of the outside. We report on the technical feasibility of a static magnetic refrigeration system using HTS coils. The power consumption including the AC loss of two superconducting coils, which is the basic configuration of the static magnetic refrigeration system, is calculated, and the efficiency is estimated as a ratio to the assumed refrigeration capacity of the MCM

Feasibility Study of High-Efficiency Cooling of High-Temperature Superconducting Coils by Magnetic Refrigeration

As a high-efficiency cooling technology for high-temperature superconducting coils, we have begun research and development to examine the feasibility of a cooling assist technology that maintains a cryogenic state by combining the magnetic force generated by the superconducting coil with magnetic refrigeration technology. Magnetic refrigeration requires the magneto caloric material to change the magnetic field. In many cases, the magnetic field change is obtained by moving the magnetic source, but moving the superconducting coil is not a good idea. Although it is possible to generate a change in the magnetic field by turning on and off the power supply of the high-temperature superconducting coil, it is unlikely to be established as a system that assists cooling of the superconducting coil because the coil generates heat due to AC loss. Therefore, it was considered that the magnetic field change can be obtained if the magnetic force generated from the superconducting coil can be controlled by the magnetic shield. As a verification of the principle, it was clarified experimentally that a magnetic field change can be obtained by repeatedly inserting and removing the magnetic shield into and from the gap between the magnetic field generation source and the magneto caloric material, and the temperature change can be extracted by the magneto caloric effect. In the experiment, the temperature change obtained when a magnetic shield was inserted into the air gap was measured by a simple test device using an iron-based magneto caloric material having high magneto caloric effect performance at room temperature and a permanent magnet. The principle verification confirmation test was performed using several types of magnetic shielding materials such as Permalloy bulks and the electrical steel sheets. In addition, numerical analysis is performed on the magnetic shielding effect, and the shielding effect is improved by increasing the thickness of the shielding material and the possibility of using high temperature superconductors as magnetic shielding materials were also analyzed. In this study, we report the possibility of cooling the high-temperature superconducting coil with high efficiency by combining the magnetic field created by the superconducting coil and magnetic refrigeration

Isolation and Structural Determination of the First 8-epi-type Tetrodotoxin Analogs from the Newt, Cynops ensicauda popei, and Comparison of Tetrodotoxin Analogs Profiles of This Newt and the Puffer Fish, Fugu poecilonotus

Identification of new tetrodotoxin (TTX) analogs from TTX-possessing animals might provide insight into its biosynthesis and metabolism. In this study, four new analogs, 8-epi-5,6,11-trideoxyTTX, 4,9-anhydro-8-epi-5,6,11-trideoxyTTX, 1-hydroxy-8-epi-5,6,11-trideoxyTTX, and 1-hydroxy-4,4a-anhydro-8-epi-5,6,11-trideoxyTTX, were isolated from the newt, Cynops ensicauda popei, and their structures were determined using spectroscopic methods. These are the first 8-epi-type analogs of TTX that have been found in a natural source. Furthermore, we examined the composition of the TTX analogs in this newt and in the ovary of the puffer fish, Fugu poecilonotus, using LC/MS. The results indicate that TTX and 11-deoxyTTX were present in both sources. However, 6-epiTTX and 8-epi-type analogs were detected only in the newt, while 5,6,11-trideoxyTTX was a specific and major analog in the puffer fish. Such considerable differences among analog compositions might reflect differences in the biosynthesis or metabolism of TTX between these animals

TRANSPORT AND TRANSFORMATION OF CHEMICAL COMPONENTS IN THE GROUNDWATER FLOW SYSTEM OF JAKARTA METROPOLITAN AREA

ABSTRACT The aim of this study is to examine the transport and transformation of chemical components within the groundwater flow in Jakarta area, and to evaluate the effects of accelerated urbanization on it. The collected data showed that the current hydraulic potential in the Jakarta metropolitan area is below sea level because of prior excess abstraction of groundwater. The distribution of Cl- and Mn2- concentration in groundwater suggests that the decline in hydraulic potential has caused the intrusion of seawater to shallow groundwater and the movement of shallow groundwater into deep groundwater. It implies an accumulation of contaminants in deep aquifers. On the other hands, the presentation of NO3--N in groundwater is suggested to be attenuated by the processes of denitrification and dilution in the coastal area

Measurement of Decay Time Constant of Shielding Current in ITER-TF Joint Samples

Joint sample tests have been carried out as a qualification test for ITER Toroidal Field (TF) coils. The joint sample comprises two short TF conductors that have "twin-box" joint terminals at both ends. The lower joint is a testing part that is a full size joint of the TF coils. Hall probes are attached on the lower joint box at around the center of the external field coil of the test facility. The magnetic field induced by shielding currents in the joint can be estimated from the difference between the measured magnetic field strength and the magnetic field generated by the external field coil. The magnetic field by the shielding currents during shut-off of the external field coil from -1.0 T is evaluated for six samples. The decay time constants of the shielding currents are gradually elongated with decrease of the shielding currents in all the samples. In comparison with simulation results, it is considered that the main shielding current flows in superconducting cables in the two conductors with crossing the jointed plane and that the joint resistance is decreased at low total current