Neutron in-beam Mössbauer spectroscopy of iron disulfide at 298 and 78 K

Emission Mössbauer spectra of ⁵⁷Fe arising from the ⁵⁶Fe(n, γ)⁵⁷Fe reaction in two crystal forms of iron disulfide were measured at room temperature and liquid nitrogen temperature. Both forms exhibited two doublets assignable to the parent material and the new species produced by the nuclear reaction. At low temperature three doublets explained the spectra obtained. Production of thermally unstable species after the neutron capture reaction was suggested.     

An analog experiment of magma fragmentation: behavior of rapidly decompressed starch sirup

Paper reports a result of analog experiments regarding the simulation of magma fragmentation. We filled a starch sirup foam, as an analog material, in a 117–240 mm long and a 50 mm diameter high pressure chamber and exposed it to a rapid decompression. The foam was prepared by mixing starch sirups of dynamic viscosities ranging from 5 to 10¹² Pa· s at temperatures ranging from 293 to 343 K with nitrogen at 2.5 MPa gauge pressure. In ejecting high-pressure foams into a low-pressure chamber, diagnostics of foam’s fragmentation process were pressure measurment and high-speed video recording. Prior to decompression experiments, we examined visco-elastic properties of foam specimens by using a rheometer. The foam deformation under decompression was found to be axial–symmetrical, and strongly coupled with bubble growth and coalescence. These effects contributed even more efficiently to fragmentation processes than previous laboratory experiments using other analog materials. Fragment shapes varied widely depending on the temperature and water concentration of starch sirup foams, which proved that fragmentation process was governed by not only ductile deformation but also brittle failure, and determined by the degree of visco-elasticities of starch sirup foams.      

An accurate quantitative analysis of polymorphic content by chemometric X-ray powder diffraction.

Data from X-ray powder diffraction (XRD) were subjected to a partial least-squares regression analysis (PLS) to build a calibration model for predicting the polymorphic content of carbamazepine (CBZ). The effectiveness of the PLS method in the construction of calibration models was analyzed by a scientific approach based on a regulation vector. CBZ forms I and III were characterized by differential scanning calorimetry (DSC) and XRD. Powder mixtures of forms I and III at various ratios (0-100% w/w; form III) were subjected to XRD. Five diffraction peaks were used for the peak-area method to compare with PLS. The results obtained by PLS had a better predictive accuracy compared to those of the peak-area method. The XRD-PLS method was established as a non-destructive, non-contact way to avoid the particle orientation effect based on statistical theory.     

Effects of chamber temperature and pressure on the characteristics of high speed diesel jets

This study is an investigation into the effects of temperature and pressure within a test chamber on the dynamic characteristics of injected supersonic diesel fuel jets. These jets were generated by the impact of a projectile driven by a horizontal single stage powder gun. A high speed video camera and a shadowgraph optical system were used to capture their dynamic characteristics. The test chamber had controlled air conditions of temperature and pressure up to 150 °C and 8.2 bar, respectively. It was found experimentally that, at the highest temperature, a maximum jet velocity of around 1,500 m/s was obtained. At this temperature, a narrow pointed jet appeared while at the highest pressure, a thick, blunt headed jet was obtained. Strong shock waves were generated in both cases at the jet head. For analytical prediction, equations of jet tip velocity and penetration from the work of Dent and of Hiroyasu were employed to describe the dynamic characteristics of the experiments at a standard condition of 1 bar, 30 °C. These analytical predictions show reasonable agreement to the experimental results, the experimental trend differing in slope because of the effect of the pressure, density fluctuation of the injection and the shock wave phenomena occurring during the jet generation process.     

Solid-State Hydrogen-Bond Alterations in a [Co2Fe2] Complex with Bifunctional Hydrogen-Bonding Donors

A hydrogen-bonding donor–acceptor system, [Co₂Fe₂(bpy*)₄(CN)₆(tp*)₂](PF₆)₂⋅2ABA⋅4BN⋅2PE ( 1 s_olv ), was prepared by co-crystallization of an external stimuli-responsive cyanide-bridged tetranuclear [Co₂Fe₂] complex and bifunctional hydrogen-bonding donors, p-aminobenzoic acid. Compound 1 s_olv exhibited a gradual electron-transfer-coupled spin transition (ETCST), and the removal of solvent molecules led to an abrupt thermal ETCST behavior with increased transition temperature. X-ray structural analysis revealed that the modification of ETCST was caused by a significant alteration of a hydrogen-bonding mode between the tetranuclear [Co₂Fe₂]²⁺ cations and ABA molecules. Variable temperature IR measurements indicated that the desolvated form, 1 d_esolv , showed dynamic alteration of hydrogen-bonding interactions coupled with thermal ETCST behavior. These results suggested that the tetranuclear [Co₂Fe₂] complex shows solid-state modulations of hydrogen-bond strengths by external stimuli.     

Numerical simulation of shock wave interaction with a water column

The paper describes a scheme which is based on the CIP scheme and modified to properly describe a gas/liquid interface without smearing the density jump across the interface. This was achieved by calculating the density separately for each phase. The density at each grid point was determined by using a density function in a similar fashion as CIP. As a result a sharp density gradient was obtainable throughout the flow field and the scheme could handle properly gas/liquid interfaces having a large density ratio. Shock wave interaction with a cylindrical water column was simulated. The numerical results were compared with appropriate interferograms. Good agreement was found between the two. The results obtained for the cylindrical water column were compared with a similar solid cylinder case. The comparison reveled that even 40 s after shock impingement some differences were found between a liquid column and the solid cylinder. Received 11 July 2000 / Accepted 28 March 2001     

Synthesis and absolute configuration of a new 3,4-dihydro-beta-carboline-type alkaloid, 3,4-dehydro-5(S)-5-carboxystrictosidine,isolated from Peruvian Uña de Gato (Uncaria tomentosa)

The structure including the absolute configuration of a new glucoalkaloid, 3,4-dehydro-5(S)-5-carboxystrictosidine, isolated from Peruvian U?a de Gato (Cat's Claw, original plant: Uncaria tomentosa), was confirmed by synthesis starting from secologanin and L-tryptophan.