Behavior of isobaric heat capacity of R32 in the gas phase

The specific isobaric heat capacity was measured for R 32 (difluoromethane) in the gas phase. Twenty-one measurements for R 32 were obtained at temperatures from 282 to 319 K and at pressures from 1.0 to 2.4 MPa, which are very close to the saturation curve. The expanded uncertainty (k = 2) of the temperature measurements is estimated to be less than 23 mK, and that of the pressure measurements is less than 15 kPa. The expanded uncertainty for c_p is estimated to range from 15 to 47 J kg^?1 K^?1. The measurements were compared with available equations of state. Based on the measurements, heat capacity curves of the ideal gas and saturated vapor of R 32 were specified. These data will be very useful for improving available models, especially for correcting behavior in the gas phase, so as to represent reliable thermodynamic properties of R 32 and refrigerant mixtures with R32 that are used for refrigeration and air conditioning systems.     

Ammonia accumulation in culture broth by the novel nitrogen-fixing bacterium, Lysobacter sp. E4

This is the first report that Lysobacter fixes nitrogen under free-living conditions, as shown by its ability to grow on nitrogen-free medium and accumulate relatively high amounts of ammonia in the culture broth. Growth of the E4 Lysobacter strain, isolated in a screen for nitrogen-fixing and ammonia-producing bacteria, resulted in higher ammonia accumulation (0.53 mM ammonium ion concentration) in media containing glucose rather than other tested carbon sources. The optimum glucose concentration was 0.30% at an initial medium pH of 7.0 and incubation temperature of 30 °C. From time-course experiments, when the glucose in the culture was exhausted, ammonia began to be accumulated, and maximum ammonia accumulation (∼ 1.60 mM) was reached after 8 days of incubation. Ammonia accumulation by this strain required molybdenum, manganese, and iron.     

A prediction model of IASCC initiation stress for bolts in PWR core internals

A model of IASCC initiation stress for bolts of core internals in pressurized water reactors was developed considering differences in material property changes due to irradiation and material conditions. Assuming that IASCC initiation was controlled by grain boundary composition and yield strength, these values for each specimen of post-irradiation IASCC initiation tests were calculated by physical kinetic models considering dose rate, temperature, material composition and surface hardening. Then, correlations of grain boundary composition and yield strength with IASCC initiation stress were determined. The model predicted that the IASCC initiation stress became lower with dose and was lower for higher temperature, lower flux and higher surface hardening level.     

Synthesis of chiral side-chain liquid crystalline polyacetylenes bearing succinic acid spacer

A chiral acetylene monomer having a cholesteryl group (PSCh) and novel three types of chiral acetylene monomers having a o-substituted tyrosine methyl ester (PSMY-Rs: –COC₆H₅=PSMY-Bz; –COC₆H₄CN=PSMY-BzCN; –COC₁₂H₉=PSMY-PhBz) as a pendant group were synthesized from 4-oxo-4-(prop-2-ynyloxy)butanoic acid (PS), and polymerized with the rhodium-catalyzed system. Structures and properties of the monomers and the resulting polymers were characterized and evaluated by NMR, IR, GPC, and DSC. In addition, these optical properties were investigated by polarimetric detector and circular dichroism (CD) analyses.     

Antitermite Activities of Coumarin Derivatives and Scopoletin from <Emphasis Type="Italic">Protium javanicum</Emphasis> Burm. f.

The antitermite (termiticidal and antifeedant) activity of Protium javanicum Burm. f. extract was investigated. The ethyl acetate fraction was active. Scopoletin (1), quercetin, and stigmasterol were isolated by bioassay-guided fractionation. Scopoletin had the highest activity among the three compounds. In order to investigate the structure-activity relationship (SAR) of the methoxy and hydroxy groups at the C-6 and C-7 positions of the coumarin skeleton, we synthesized several coumarin derivatives whose chemical structures are similar to scopoletin. Scopoletin exhibited the strongest termiticidal activity among the 10 compounds tested, followed by 6-methoxycoumarin (3), 6-hydroxycoumarin (7), and umbelliferone (8). All compounds except coumarin (9) showed antifeedant activity.     

Change of chemical states of niobium in the oxide layer of zirconium–niobium alloys with oxide growth

The change of chemical states of niobium with oxide growth was examined in the oxide layers of Zr–2.5Nb around the first kinetic transition by the conversion electron yield – X-ray absorption near-edge structure measurements. The detailed depth profiles of niobium chemical states were obtained in both the pre- and the post-transition oxide layers of Zr–2.5Nb formed in water at 663 K for 40–280 d. The depth profiling revealed that the inner oxide layer remained protective to oxidizing species even though in the post-transition region and this excellent stability of barrierness would be attributed the suppression of hydrogen pickup.     

Convenient Synthesis of Mesoporous Aluminosilicates by Using Pre-heated Sodium Aluminosilicate Gel

Hydrothermally stable Al-MCM-48 with variety of Si/Al ratios and Al-MCM-41 with tunable pore sizes were successfully obtained from pre-heated aluminosilicate gel precursor. They showed the higher acid strength and hydrothermal stability comparing with conventional ones. Thus, this synthetic strategy offers a straightforward and convenient access to mesoporous aluminosilicates with zeolite-like acidity and stability.     

Nb2O5 hollow nanospheres as anode material for enhanced performance in lithium ion batteries

Nb₂O₅ hollow nanospheres of average diameter ca. ～29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb₂O₅ hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g^?1 after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g^?1. The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb₂O₅ shell domain that facilitates fast lithium intercalation/deintercalation kinetics.     

Accuracy bounds and optimal computation of robot localization

We present an optimal method for estimating the current location of a mobile robot by matching an image of the scene taken by the robot with a model of the known environment. We first derive a theoretical accuracy bound and then give a computational scheme that can attain that bound, which can be viewed as describing the probability distribution of the current location. Using real images, we demonstrate that our method is superior to the naive least-squares method. We also confirm the theoretical predictions of our theory by applying the bootstrap procedure. Received: 17 March 1998 / Accepted: 7 April 2001