Research and development of liquid hydrogen (LH2) temperature monitoring system for marine applications

Monitoring the temperature in liquid hydrogen (LH₂) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.     

Optical manipulation of multiple stable states in photorefractive four-wave mixing

Abstract

We propose an approach to manipulate the convergence in multiple solutions of phase conjugate reflectivity in photorefractive four-wave mixing. Although a method forcibly adding a π-phase shift to an incident beam has been already proposed to control the reflectivity, some restrictions have been required in the boundary conditions for the successful operation. Here, we control the reflectivity with the boundary conditions in which the phase shift operation is ineffective by itself. In our method, the phase shift operation is combined with the procedure of turning an incident beam on and off. With a numerical analysis of four-wave mixing, we show that our new approach brings drastic change in the spatial distribution of the index grating and leads the phase conjugate reflectivity which was not manipulated previously.     

Preparation and characterization of nanoporous films derived from alicyclic copolyimides having pendent poly(propyleneglycol) groups

Nanoporous films were prepared with alicyclic copolyimides (coPIs) having polypropylene glycol (PPG) side chains by way of spontaneous phase separation in the film forming process and the subsequent thermal degradation of PPG moieties. PIs having various content (6.5, 11.9, 26.3, 52.7 wt%) and different length (M_w = 1.2 × 10³ and 2.4 × 10³) of PPG side chains were examined in order to clarify the relationship between chemical structure and pore characteristics. Nanopores were formed by heating the coPI films at 200 °C for 9 h under slightly reduced pressure. The size and the number of the pores observed by SEM varied depending on the content and molecular weight of PPG moieties. In many cases, the pore size was larger than those of the reported values for related aromatic copolyimide films. The dielectric constant of the nanoporous films ranged from 2.52 to 3.38.     

Calculations of heats of formation for nitroaromatics with PM3 and MM2

Abstract

We have attempted to calculate heats of formation (Δ H _f °) for various aromatic nitro compounds with the semi-empirical molecular orbital theory and the molecular mechanics. As the results we may say that PM3, a semi-empirical MO method, and MM2, molecular mechanics, can estimate Δ H _f ° of energetic materials with accuracy enough to use Δ H_f° for energy hazards prediction. In case of aromatic polynitro compounds, both methods may be able to calculate accurate Δ H_f°.     

Contribution of amino acid substitutions at two different interior positions to the conformational stability of human lysozyme

To elucidate correlative relationships between structural changeand thermodynamic stability in proteins, a series of mutanthuman lysozymes modified at two buried positions (Ile56 andIle59) were examined. Their thermodynamic parameters of denaturationand crystal structures were studied by calorimetry and X-raycrystallography. The mutants at positions 56 and 59 exhibiteddifferent responses to a series of amino acid substitutions.The changes in stability due to substitutions showed a linearcorrelation with changes in hydrophobicity of substituted residues,having different slopes at each mutation site. However, thestability of each mutant was found to be represented by a uniqueequation involving physical properties calculated from mutantstructures. By fitting present and previous stability data formutant human lysozymes substituted at various positions to theequation, the magnitudes of the hydrophobicity of a carbon atomand the hydrophobicity of nitrogen and neutral oxygen atomswere found to be 0.178 and –0.013 kJ/mol.Ų, respectively.It was also found that the contribution of a hydrogen bond witha length of 3.0 Å to protein stability was 5.1 kJ/moland the entropy loss of newly introduction of a water moleculeswas 7.8 kJ/mol.     

Evaluation and Optimization of Preparative Variables for Controlled-Release Floatable Microspheres Prepared by Poor Solvent Addition Method

The aim of this study was to evaluate and optimize preparative parameters for floatable theophylline microspheres prepared by the emulsion–solvent evaporation method. A three-factor three-level Box–Behnken design was employed using amount of poor solvent, temperature-increase rate and drug loading as independent factors, and percentage floating at 3 h and time required for 50% drug release as dependent variables. Simultaneous optimization of the parameters for maximum buoyancy and desirable drug release was conducted using a partitioned artificial neural network. A microsphere using 27.6% of drug loading, 0.29°C/min of temperature-increase rate, and 1.7 mL of poor solvent was identified for maximizing buoyancy and sustaining drug release.     

Improvement of fracture properties of hydroxyapatite particle filled poly(l-lactide)/poly(ε-caprolactone) biocomposites using lysine tri-isocyanate

Effects of LTI addition on the mode I fracture energy of HA/PLLA/PCL were examined and the micro-structural modification due to LTI addition was investigated. Both the mode I energy release rate, G _in, and averaged fracture energy, E _f, are improved dramatically due to LTI addition. The reason is considered to be the improvements of the interfacial structure connecting HA particles with PLLA/PCL matrix and the miscibility between PLLA and PCL. These changes of blend morphology and interfacial structure reduce the stress concentration and lead to the ductile deformation and resulted in the increase of those fracture properties.