Single-photon emission from a single nanoparticle consisting of a single conjugated polymer chain

Single-photon behavior in the emission from a single nanoparticle consisting of a single poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV, molecular weight: 2,600,000 amu) chain has been investigated. Photon correlation measurements of a number of single nanoparticles revealed that the probability of single-photon emission from the single nanoparticles clearly increases, compared with that of single chains embedded in host polymer matrices, poly(methyl methacrylate) (PMMA) and polystyrene (PS). The result suggested that even a single MEH-PPV chain with high molecular weight, which does not exhibit single-photon emission in PMMA and PS, is forced to exhibit single-photon emission by adopting “compact” chain conformation like nanoparticle. Efficient exciton migration and exciton annihilation processes in the compact chain conformation most probably result in the efficient single-photon emission from the single nanoparticle. The present results indicate that multi-quantum systems consisting of a large number of chromophores, such as the MEH-PPV, can be made to behave as single-photon sources by appropriately controlling their size.     

Characteristics of graphene-layer encapsulated nanoparticles fabricated using laser ablation method

Graphene layer-encapsulated Ni nanoparticles with diameters between 3 and 10 nm were fabricated by laser ablation techniques and deposited directly on the Si substrate at room temperature. It was found from the field-emission type scanning electron microscopy (FE–SEM) and transmission electron microscopy(TEM) analyses that any carbon nanotubes were not fabricated in the deposited nano-materials. High-resolution TEM observation showed the core-shell structure of Ni–C particles with crystalline nickel core surrounded by graphite-like layers. The X-ray diffraction(XRD) pattern also revealed that nanoparticles embedded in graphene capsules are crystalline nickel. With these Ni–C nanoparticles, we demonstrated the growth of vertically aligned carbon nanotubes with low spatial density on a silicon substrate by thermal CVD.     

Neutron production rate and plasma characteristics of spherically convergent beam fusion

Experimental and simulation results of a spherical glow discharge for a portable neutron source are presented. The experimental device is a 45‐cm‐diameter, 31‐cm‐high stainless‐steel cylindrical chamber, in which a spherical mesh‐type anode 30 cm in diameter is installed. The spherical grid cathode consists of 2.0‐mm‐diameter stainless‐steel wire, which is made into an open spherical grid of 5‐cm diameter. The system is maintained at a constant pressure of 1 to 15 mTorr by feeding hydrogen or deuterium gas. The basic characteristics of breakdown voltages versus pressure and electrostatic potential profiles were measured for hydrogen discharge. Using deuterium, a steady‐state neutron production of 10⁴ s^–1 was observed at a discharge of 40 kV, 2 mA. Motions of ions and electrons in the device were simulated by using a particle code, which is one‐dimensional in coordinate system and two‐dimensional in velocity space. It was confirmed by both the measurement and simulation that a virtual anode is formed in the central part inside the grid cathode. © 2001 Scripta Technica, Electr Eng Jpn, 135(2): 1–8, 2001     

New Candidates for Superconductors; A Series of Layered Oxysulfides (Cu2S2)(Sr n+1 M n O3n−1)

We have discovered three new layered transition-metal oxysulfides ; (Cu ₂ S ₂ )(Sr ₂ CuO ₂ ), (Cu ₂ S ₂ )(Sr ₂ NiO ₂ ) and (Cu ₂ S ₂ )(Sr ₃ Sc ₂ O ₅ ), whose compositions are generally formulated as (Cu ₂ S ₂ )(Sr _n+1 M _n O _3n–1 ). Their structures consist of alternate stackings of perovskite-based MO ₂ plane(s) and Cu ₂ S ₂ layers, showing great similarity to cuprate superconductors when the Cu ₂ S ₂ layer is considered as the blocking layer. The formation of these phases is limited by the ion size of M and elasticity of the Cu ₂ S ₂ layer. The newly found (Cu ₂ S ₂ )(Sr ₂ CuO ₂ ) posseses the horizontally extended tetragonal CuO ₂ plane, making itself a possible candidate for a new superconductor.     

Hydrothermal precipitation of hydroxyapatite on anodic titanium oxide films containing Ca and P

Highly-crystallized hydroxyapatite (HA) can be precipitated during heat treatment in high-pressure steam at 300 °C on an anodic titanium oxide film containing Ca and P (AOFCP), which has been electrochemically formed on a titanium substrate prior to the hydrothermal treatment. Factors affecting the precipitation, such as a percentage of distilled water in the autoclave and additives in the AOFCP, were evaluated by scanning electron microscopy. Ca²⁺ and PO^3– ₄ ions were leached from the AOFCP into a water layer covering the film surface, and nucleate HA heterogeneously on the porous TiO₂ matrix of the AOFCP which was made by the ion leaching. The morphology of the precipitated crystals was significantly affected by the water volume ratio because the concentrations of the Ca²⁺ and PO₄ ^3– ions varied depending on the thickness of the water layer. The amount of the precipitation decreased on the AOFCP which was formed in the solution containing a small amount of Mg²⁺ ions or formed on Ti-6Al-4V alloy instead of titanium.     

Study of steam, helium and supercritical CO2 turbine power generations in prototype fusion power reactor

Power generation systems such as steam turbine cycle, helium turbine cycle and supercritical CO₂ (S-CO₂) turbine cycle are examined for the prototype nuclear fusion reactor. Their achievable cycle thermal efficiencies are revealed to be 40%, 34% and 42% levels for the heat source outlet coolant temperature of 480 °C, respectively, if no other restriction is imposed. In the current technology, however, low temperature divertor heat source is included. In this actual case, the steam turbine system and the S-CO₂ turbine system were compared in the light of cycle efficiency and plant cost. The values of cycle efficiency were 37.7% and 36.4% for the steam cycle and S-CO₂ cycle, respectively. The construction cost was estimated by means of component volume. The volume became 16,590 m³ and 7240 m³ for the steam turbine system and S-CO₂ turbine system, respectively. In addition, separation of permeated tritium from the coolant is much easier in S-CO₂ than in H₂O. Therefore, the S-CO₂ turbine system is recommended to the fusion reactor system than the steam turbine system.     

Overview of R&D activities on tritium processing and handling technology in JAEA

In JAEA, the tritium processing and handling technologies have been studied at TPL (Tritium Process Laboratory). The main R&D activities are: the tritium processing technology for the blanket recovery systems; the basic tritium behavior in confinement materials; and detritiation and decontamination. The R&D activities on tritium processing and handling technologies for a demonstration reactor (DEMO) are also planned to be carried out in the broader approach (BA) program by JAEA with Japanese universities. The ceramic proton conductor has been studied as a possible tritium processing method for the blanket system. The BIXS method has also been studied as a monitoring of tritium in the blanket system. The hydrogen transfer behavior from water to metal has been studied as a function of temperature. As for the behavior of high concentration tritium water, it was observed that the formation of the oxidized layer was prevented by the presence of tritium in water (0.23 GBq/cc). A new hydrophobic catalyst has been developed for the conversion of tritium to water. The catalyst could convert tritium to water at room temperature. A new Nafion membrane has also been developed by gamma ray irradiation to get the strong durability for tritium.     

A measurement‐based performance evaluation method for IP networks and its implementation

In recent years, IP networks have become increasingly complex and the range of network applications has widened. As a result, the need for experimental evaluation of application performance has increased. We introduce a measurement‐based performance evaluation method that combines a function to generate various patterns of application traffic with one to measure end‐to‐end network performance at the application level. For our method, we also propose traffic models of various applications that can represent the characteristics of these applications, for example, the burstiness of traffic. This method has already been implemented as a benchmarking tool on UNIX operating systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Triphenyltin chloride induces glucose intolerance by the suppression of insulin release from hamster pancreatic beta-cells

An increased activity of phospholipase A2 has been observed in the plasma of patients with uremia. This enzyme converts phosphatidylcholine to lysophosphatidylcholine (LPC), an inhibitor of platelet aggregation. We measured the levels of plasma phospholipids including LPC, and platelet aggregation in 7 patients with uremia. Platelet response to agonists was defective, mainly with collagen (p < 0.001). The patients' levels of LPC in plasma were similar to those of controls (109.7 +/- 41.6 vs. 80.4 +/- 16.8 nmol/ml) and did not correlate with the platelet response to adenosine diphosphate (r = -0.51). The amount of phosphatidylcholine was increased with respect to normal plasma (1,041.0 +/- 201.8 vs. 760.8 +/- 142.7 nmol/ml, p < 0.01), while the levels of other phospholipids were normal. These results do not suggest a participation of plasma LPC in the genesis of the platelet defect observed in patients with uremia.     

A learning method of immune multi-agent neural networks

Many different learning algorithms for neural networks have been developed, with advantages offered in terms of network structure, initial values of some parameters, learning speed, and learning accuracy. If we train the networks only on good examples, without noise and shortage, the neural network can be trained to classify, with reasonable accuracy, target patterns or random patterns, but not both. To solve this problem, we propose a learning method of immune multi-agent neural networks (IMANNs), which have agents of macrophages, B-cells and T-cells. Each agent employs a different type of neural network. Because the agents work cooperatively and competitively, IMANNs can automatically classify the training dataset into some subclasses. In this paper, two types of IMANNs are described and their classification capabilities are compared. In order to verify the effectiveness of our proposed method, we used two datasets: the dataset of the MONKs problem (as a traditional classification problem) and a dataset from a medical diagnosis problem (hepatobiliary disorders).