Stable and controlled amphoteric doping by encapsulation of organic molecules inside carbon nanotubes

Single-walled carbon nanotubes (SWNTs) have strong potential for molecular electronics, owing to their unique structural and electronic properties. However, various outstanding issues still need to be resolved before SWNT-based devices can be made. In particular, large-scale, air-stable and controlled doping is highly desirable. Here we present a method for integrating organic molecules into SWNTs that promises to push the performance limit of these materials for molecular electronics. Reaction of SWNTs with molecules having large electron affinity and small ionization energy achieved p- and n-type doping, respectively. Optical characterization revealed that charge transfer between SWNTs and molecules starts at certain critical energies. X-ray diffraction experiments revealed that molecules are predominantly encapsulated inside SWNTs, resulting in an improved stability in air. The simplicity of the synthetic process offers a viable route for the large-scale production of SWNTs with controlled doping states.     

Flow and heat transfer on cryogenic flow boiling during tube quenching under upward and downward flow

The gravity effects on quenching of tube by cryogenic fluids for the development of cryogenic fluid management on orbit are studied. In this paper, the effects of the tube diameter, the flow directions, and the mass velocity on the tube quenching using liquid nitrogen are investigated systematically in the terrestrial conditions. The experiments are performed by the mass velocity between 100–600 kg/m²s in downward and upward flow directions by using three difference inner diameters of the transparent heated tube (7, 10, 13.6 mm) for measuring fluid behavior observations and heat transfer measurements simultaneously. The results indicate that the difference between the minimum heat fluxes under downward and upward flow conditions increased as the mass velocity increased. These characteristics of heat transfer were caused by filamentary flow pattern that was found in only downward flow and high mass velocity conditions.     

Query result caching for multiple event-driven continuous queries

With the increasing demands for advanced use of streaming data, efficient execution of continuous queries is an important research issue. This paper focuses on event-driven continuous queries that are activated by foreign events such as data arrival and the progression of time. Existing approaches to multiple continuous query optimization decide the optimal query plan by extracting common subexpressions from the given queries. Event-driven queries containing the common subexpressions may produce many common intermediate results when they are activated within a small interval, but may produce only disjoint data when activated at completely different timings.This paper proposes an efficient data stream processing scheme for multiple event-driven continuous queries. In the proposed approach, we introduce query result caching to achieve a flexible way to share common operators among queries activated by unpredictable events. When a query is activated, an intermediate result generated for the query is stored into the cache area if it is expected to be reused by other queries. When other queries including the same operator are activated, they reuse the cached result if the cache includes reusable data. Efficiency of the proposed scheme is validated by intensive experimental evaluations.     

Torsional Oscillator Experiments with High Stability and Reproducibility

We report experiments of the torsional oscillator to observe the superfluid transition in ⁴ He films in porous glass (the pore diameter is 1m). Stability and reproducibility of the oscillator, which quite often is problematic in previous experiments, is essential for a quantitative analysis of observations in different conditions. It follows that the friction of the superfluid films and the energy dissipation of the solid films are derived from comparisons of measurements for different film thickness.     

Quantifying variability of satellite data in the reflective band for long-term monitoring of the Earth's surface: inference from a multi-temporal relationship between remotely sensed pixels

Reliable long-term monitoring of the Earth's surface is urgently needed for a comprehensive understanding of our environment. However, remotely sensed data is generally affected by a number of temporal factors such as lifetime sensor degradation, Sun–target–satellite geometry and atmospheric conditions. The induced inconsistencies weaken the reliability of satellite-based change studies. A direct method is to remove the inconsistencies through converting the satellite digital number (DN) into a physical quantity using a physically or statistically based model. The associated errors in the conversion are generally hard to trace in the converted quantity, and this leaves questions unanswered. In this study, we propose an alternative approach to quantifying the influences on DN values, based on a multi-temporal relationship in the visible bands. First, we make use of the spectral dependency of aerosol optical thickness on wavelength to expand the validity of the multi-temporal relationship for reflective bands. As an inference of the relationship, a satellite DN value is determined analytically with the temporal influences in terms of a multiplicative and an additive component. In the case of the Landsat-5 Thematic Mapper (TM), we illustrate the variability in DN value in a spatio-temporal context. Lifetime sensor degradation (long-term effect) leads to an increase in the multiplicative effect and a minor change in the additive effect on the DN value. The combined Sun–target–satellite geometry and atmospheric variation induce periodic oscillations in both the multiplicative and additive effects on the DN value. The variation is generally larger for surfaces with a high reflectance than those with a low reflectance. The proposed approach combines sensor calibration and atmospheric correction into one equation, which offers the potential for tracing associated uncertainties propagated into a quantity converted or derived from satellite data, for long-term monitoring of changing surfaces.     

Influence of Aluminum Titanate Formation on Sintering of Bimodal Size-Distributed Alumina Powder Mixtures

The sintering behavior of green compacts, in which coarse alumina particles formed a skeletal structure and fine alumina and/or fine titania particles filled the voids of the skeletal structure, was investigated. Sinterability of the green compacts changed according to the titania content in the fine powder. The titania content of 33 mol% was the most effective for the densification. The volume expansion due to the aluminum titanate formation occurred in the voids of the skeletal structure, and the densification of the skeletal structure progressed more because the grain growth between the fine and coarse alumina particles did not proceed. As the titania content decreased, the densification did not progress more than that of the compact with 33 mol% titania content because the grain growth proceeded more. As the titania content increased, the expansion of the compacts was larger, and large grains were formed by the reaction between the titania and coarse alumina particles. Therefore, densification became difficult.     

Development of High-Speed and Large-Scale Culture Technology of Marine Algae Using Seawater With High Concentrations of Dissolved Carbon Dioxide

The effective use of marine biomass has recently been identified as a feasible method of renewable energy production. Therefore, to facilitate the effective use of algae biomass, it is essential to develop techniques for the mass production of algal cultures. It is also important to develop artificial culture techniques that are not affected by natural phenomena such as weather. This study utilized a newly developed culture technology that uses seawater with high concentrations of dissolved CO₂ (CO₂ seawater). The experiments in this study were conducted to test the effects of CO₂ seawater on algal growth. In addition to experimental conditions that were previously investigated in industrial algae farming scenarios, it is also necessary to consider the effects of new parameters associated with increased CO₂ concentrations. The following four conditions were experimentally investigated: (1) the tolerance of algae to changes in pH, (2) the effect of CO₂ seawater on long-term culture growth, (3) the effect of continuous culture experiments, and (4) the effect of water flow rate on cultured algae. The results in terms of having excelled especially indicate that a 1-month long-term algae culture period in seawater with CO₂ concentration of 1.0% led to growth that was approximately 4.5 times faster than growth in seawater without the CO₂ additive. Furthermore, the results also provided useful information regarding the proper flow rate needed to enhance algal growth.     

Synthesis and Chemical Characterization of Hydrocarbons with a 6,9,11-, 3,6,9,11-, or 1,3,6,9-Polyene System,Pheromone Candidates in Lepidoptera

Lepidopteran Type II sex pheromones are mainly composed of 6,9-dienes, 3,6,9-trienes, and their epoxy derivatives, which are biosynthesized from linoleic and linolenic acids by the species in some families of higher Lepidoptera. To investigate further structural modifications on this theme, we synthesized polyunsaturated hydrocarbons with a C(17)-C(21) chain, which included an extra double bond. Using the Wittig reaction, (Z,Z,E)-6,9,11-trienes and (Z,Z,Z,E)-3,6,9,11-tetraenes were synthesized from (E)-2-alkenals with appropriate carbon chains, and (Z,Z,Z)-1,3,6,9-tetraenes were synthesized from 3-hexyn-1,6-diol. The gas chromatography-mass spectrometry (GC-MS) analysis of each synthetic polyene, whose chemical structure was confirmed by (1)H NMR and (13)C NMR, revealed some characteristic fragment ions reflecting the positions of the double bonds, i.e., m/z 79, 110, 163, and M-85 of the 6,9,11-trienes, m/z 79, 108, and M-82 of the 3,6,9,11-tetraenes, and m/z 79, 91, 106, and M-54 of the 1,3,6,9-tetraenes. Because the determination of the unsaturated positions is difficult to accomplish by chemical derivatization with a limited amount of natural pheromones, these diagnostic ions found in authentic samples would help identify the hydrocarbons in a pheromone extract. Furthermore, we carried out field screening tests of these polyenes in forests in Japan, and documented the attraction of four geometrid species in Tokyo and one noctuid species in the Iriomote Islands.     

Studies on comonomer compositional distribution and its effect on some physical properties of bacterial poly(3‐hydroxybutyric acid‐co‐3‐hydroxypropionic acid)

Comonomer compositional distribution of bacterially synthesized poly(3‐hydroxybutyric acid‐co‐3‐hydroxypropionic acid) [P(3HB‐co‐3HP)] was investigated via solvent/non‐solvent fractionation techniques. The result indicates the presence of extremely broad comonomer compositional distribution in the original bacterial product. Furthermore, utilizing compositionally fractionated bacterial copolyesters with much narrower comonomer compositional distributions, the 3HP comonomer content‐dependence of their thermal and crystallization behavior was studied by means of differential scanning calorimeter (DSC) and polarized optical microscopy and the results compared with those of unfractionated copolyesters. It was revealed that the physical features of the fractionated copolyester P(3HB‐co‐3HP)s strongly depends on the 3HP comonomer content. In addition, to clarify the effect of the compositional distribution on the properties of the unfractionated copolyester, the miscibility between bacterial poly(3‐hydroxybutyric acid) [P(3HB)] and two fractionated P(3HB‐co‐3HP) samples with 11.3 and 14.9% 3HP was investigated for blends obtained by solvent casting techniques. The evidence of thermal analysis and spherulitic growth rates imply miscibility of the P(3HB)/3HB‐rich P(3HB‐co‐3HP) binary blends. © 1999 Society of Chemical Industry     

Fabrication and mechanical characterization of continuous carbon fiber-reinforced thermoplastic using a preform by three-dimensional printing and via hot-press molding

A new 3D printer equipped novel nozzle structure for continuous carbon fiber-reinforced thermoplastics (C-CFRTP) was developed and the suitable printing conditions were studied. C-CFRTP filament and additional matrix resin were supplied independently using each extruder, which is useful for variety printing and precise form control in 3D printing. To measure the mechanical properties, specimens for tensile strength testing were fabricated using C-CFRTP filament (Vf:50%) without additional matrix resin. The experimental results indicate that the tensile strength and Young’s modulus were approximately 700 MPa and 53 GPa, respectively. The recrystallization effect through annealing after 3D printing yielded no drastic improvement. The mechanical properties were considerably improved by a hot-press treatment after 3D printing. The tensile strength and Young’s modulus increased to approximately 1400 MPa and approximately 90 GPa, respectively. These results suggest that one of the useful applications of C-CFRTP 3D printing technology is preforming of small parts in industrial products.