Tokyo Institute of Technology

About: Tokyo Institute of Technology is a education organization based out in Tokyo, Tôkyô, Japan. It is known for research contribution in the topics: Thin film & Catalysis. The organization has 46775 authors who have published 101656 publications receiving 2357893 citations. The organization is also known as: Tokyo Tech & Tokodai.

A Pseudomonas thrives in high concentrations of toluene

Abstract: TOLUENE, like many organic sovents, is highly biotoxic and kills most microorganisms at low concentrations (0.1% v/v). It is often used therefore to sterilize microbial cultures and lyse bacterial cells in the assay of bacterial enzymes1–3. The physiological basis of such solvent toxicity, however, remains poorly characterized. Although some microorganisms, including Pseudomonas4–6 , Achromobacter4 and Nocardia7 , can assimilate toluene, their toler-ance for the solvent is less than 0.3% (v/v). We report here the discovery of a variant strain of Pseudomonas putida which is capable of growing in media culture containing more than 50% (v/v) toluene or high concentrations of cyclohexane, xylene, styrene and heptanol. By studying this unusually tolerant strain we show that the relative toxicities of different solvents are determined by their polarities.

Direct importance estimation for covariate shift adaptation

Abstract: A situation where training and test samples follow different input distributions is called covariate shift. Under covariate shift, standard learning methods such as maximum likelihood estimation are no longer consistent—weighted variants according to the ratio of test and training input densities are consistent. Therefore, accurately estimating the density ratio, called the importance, is one of the key issues in covariate shift adaptation. A naive approach to this task is to first estimate training and test input densities separately and then estimate the importance by taking the ratio of the estimated densities. However, this naive approach tends to perform poorly since density estimation is a hard task particularly in high dimensional cases. In this paper, we propose a direct importance estimation method that does not involve density estimation. Our method is equipped with a natural cross validation procedure and hence tuning parameters such as the kernel width can be objectively optimized. Furthermore, we give rigorous mathematical proofs for the convergence of the proposed algorithm. Simulations illustrate the usefulness of our approach.

Robust speed identification for speed sensorless vector control of induction motors

Abstract: This paper describes a new approach to estimating induction motor speed from measured terminal voltages and currents for speed-sensorless vector control. The proposed approach is based on observing the instantaneous reactive power of the motor. The estimated speed is used as feedback in an indirect vector control system. The described technique is very simple and robust to variations of motor parameters. The new approach is not dependent upon the knowledge of the value of the stator resistance, nor is it affected by stator resistance thermal variations. Furthermore, pure integration of sensed variables, in principle, is not required at all. Therefore, this new method can achieve much wider bandwidth speed control than previous tacholess drives. The effectiveness is verified by simulation and experiment. >

Evidence from fluid inclusions for microbial methanogenesis in the early Archaean era

Abstract: Methanogenic microbes may be one of the most primitive organisms, although it is uncertain when methanogens first appeared on Earth. During the Archaean era (before 2.5 Gyr ago), methanogens may have been important in regulating climate, because they could have provided sufficient amounts of the greenhouse gas methane to mitigate a severely frozen condition that could have resulted from lower solar luminosity during these times. Nevertheless, no direct geological evidence has hitherto been available in support of the existence of methanogens in the Archaean period, although circumstantial evidence is available in the form of approximately 2.8-Gyr-old carbon-isotope-depleted kerogen. Here we report crushing extraction and carbon isotope analysis of methane-bearing fluid inclusions in approximately 3.5-Gyr-old hydrothermal precipitates from Pilbara craton, Australia. Our results indicate that the extracted fluids contain microbial methane with carbon isotopic compositions of less than -56 per thousand included within original precipitates. This provides the oldest evidence of methanogen (> 3.46 Gyr ago), pre-dating previous geochemical evidence by about 700 million years.

Thermodynamic properties of a spin-1/2 spin-liquid state in a κ -type organic salt

Abstract: Spins in a two-dimensional triangular lattice are geometrically frustrated and cannot form an ordered ground state. Instead, a spin-liquid state is expected, and now thermodynamic measurements suggest that a spin liquid exists down to the lowest temperatures. In two-dimensional triangular lattices, geometric frustration prohibits the formation of ordering even at the lowest temperatures, and therefore a liquid-like ground state is expected. The spin-liquid problem has been one of the central topics of condensed-matter science for more than 30 yr in relation to the resonating-valence-bond model1. One of the characteristic features proposed is the existence of a linear temperature-dependent contribution to the heat capacity, as the degeneracy of the energy states should give rise to gapless excitations. Here, we show thermodynamic evidence for the realization of a spin-liquid ground state through a single-crystal calorimetric study of the dimer-based organic charge-transfer salt κ-(BEDT-TTF)2Cu2(CN)3, with a triangular lattice structure down to 75 mK. In addition, we report an unexpected hump structure in the heat capacity around 6 K, which may indicate a crossover into the quantum spin liquid.