Thermal properties of hydrazine in nitric acid solution

Since some combustible, oxidative and reductive chemicals are used in the extracting process in the nuclear reprocessing plant the process has potential hazards of a fire and explosion due to the undesired reaction. In this study to obtain a better understanding of the thermal properties of hydrazine in nitric acid solution which is used for preventing the oxidation of extracted plutonium, thermal analysis was carried out for the mixtures in various conditions. From the results of DSC it was revealed that the vessel material has an influence on the thermal decomposition of hydrazine. It was also found that hydrazine reacted with nitric acid in an autocatalytic manner, and concentration of nitric acid has a strong influence on the thermal hazard of hydrazine and nitric acid mixtures.     

An integrated microfluidic system for long-term perfusion culture and on-line monitoring of intestinal tissue models

Conventional cell-based assays in life science and medical applications can be difficult to maintain functionally over long periods. Microfluidics is an emerging technology with potential to provide integrated environments for cell maintenance, continuous perfusion, and monitoring. In this study, we developed an integrated microfluidic device with on-chip pumping and detection functionalities. The microfluidic structure in the device is divided into two independent channels separated by a semipermeable membrane on which cells are inoculated and cultured. Perfusion and fluorescence measurements of culture media for each channel can be conducted by the on-chip pumping system and optical fiber detection system. Performance of the device was examined through long-term culture and monitoring of polarized transport activity of intestinal tissue models (Caco-2 cells). The cells could be cultured for more than two weeks, and monolayer transport of rhodamine 123 was successfully monitored by on-line fluorescent measurement. This device may have applications in toxicity testing and drug screening.     

Reinvestigation on the buildup mechanism of alternate multilayers consisting of poly(L-glutamic acid) and poly(L-, D-, and DL-lysines)

The buildup mechanism of polypeptide multilayers prepared by the layer-by-layer deposition of a polyanion (poly(L-glutamic acid) (PGA)) and polycations (poly(L-lysine) (PLL), poly(D-lysine) (PDL), and copoly(DL-lysine)(PDLL)) was reinvestigated by using in situ ATR-IR spectroscopy. A difference spectral technique applied to analyze the spectra indicated that the deposition of both the PGA and PLL (PDL) layers accompanies the formation of secondary structures consisting mainly of the antiparallel pleated sheet (the beta-sheet) structure, and that the formation of the beta-sheet structure cannot always be explained in terms of polyanion/polycation complex formation or charge compensation between the polyanion and polycations, although it has been considered as a major process in the multilayer buildup process. Instead, the present paper proposes the following mechanism. During the deposition of the polyelectrolyte, a small amount of the beta-sheet structures are produced at the interface as a result of charge compensation between a polyelectrolyte and an oppositely charged polyelectrolyte in the multilayer. The beta-sheets act as nuclei from which further propagation of the structure takes place at the solution/multilayer interfaces. The driving force of the buildup process in the new mechanism is a kinetically favorable insolubilization of each polyelectrolyte in solution at the interfaces.     

Structural order in perfluoropentacene thin films and heterostructures with pentacene

Synchrotron x-ray diffraction reciprocal space mapping was performed on perfluoropentacene (PFP) thin films on SiO2 in order to determine the crystal structure of a novel, substrate-induced thin film phase to be monoclinic with unit cell parameters of a = 15.76 +/- 0.02 A, b = 4.51 +/- 0.02 A, c = 11.48 +/- 0.02 A, and beta = 90.4 +/- 0.1 degrees . Moreover, layered and co-deposited heterostructures of PFP and pentacene (P) were investigated by specular and grazing-incidence x-ray diffraction, atomic force microscopy, and Fourier-transform infrared spectroscopy. For a ca. three-monolayers-thick PFP film grown on a P underlayer, slightly increased lattice spacing was found. In contrast, co-deposited P/PFP films form a new mixed-crystal structure with no detectable degree of phase separation. These results highlight the structural complexity of these technically relevant molecular heterojunctions for use in organic electronics.     

Endocyclic extension of porphyrin pi-system by interior functionalization of N-confused porphyrins

Internally alkynylated or cyanated N-confused porphyrins have been prepared, and these have been characterized by NMR, UV/Vis/NIR absorption, and X-ray analysis. The desired porphyrins have been synthesized by interconversion between an N-confused porphyrin and an N-fused porphyrin. In the case of terminal alkyne derivatives, intramolecular addition of a pyrrolic NH moiety to the triple bond occurred at ambient temperature to give etheno-bridged N-confused porphyrins. Significant bathochromic shifts in the absorbances of these compounds may be reasonably explained in terms of an increase in their HOMO energy levels due to effective overlap of the porphyrin pi-orbital and the bridged alkene pi-orbital. The corresponding rhodium(I) complexes have also been prepared, and these have been characterized by NMR and X-ray analysis.     

Development of multiple prompt gamma-ray analysis

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇔ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system [M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L = p-tert-butylcalix[4]arene-tetrakis (N, N-dimethylthioacetamide); aq = aqueous phase, nb = nitrobenzene phase] were evaluated. Furthermore, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Cs⁺<Rb⁺<K⁺<Li⁺<Na⁺.     

Reduction of Compton background from hydrogen in prompt gamma-ray analysis by multiple photon detection

Low-energy photons produced by the Compton scattering from hydrogen increase the background in the lower-energy region of the gamma-ray spectrum. This results in an increase in the detection limit for trace elements. In multiple photon detection prompt gamma-ray analysis (MPGA), only those elements that simultaneously emit two or more prompt gamma-rays, which have cascade relation and are emitted within a short interval, can be measured. Therefore, the influence of hydrogen can be reduced. In this study, standard polymer and food samples are measured. The hydrogen background is reduced in MPGA.     

Sound velocity dispersion in room temperature ionic liquids studied using the transient grating method

Sound velocity is determined by the transient grating method in a range from 10(6) to 10(10) Hz in three room temperature ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, and N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide. In all room temperature ionic liquids studied, the sound velocity increased with increasing frequency. The cause of this change is posited to be structural relaxation in the room temperature ionic liquids. Frequency dependence of the sound velocity is not reproduced by a simple Debye relaxation model. The sound velocity dispersion relation in 1-butyl-3-methylimidazolium hexafluorophosphate matches a Cole-Davidson function with parameters determined by a dielectric relaxation [C. Daguenet et al., J. Phys. Chem. B 110, 12682 (2006)], indicating that structural and reorientational relaxations are strongly coupled. Conversely, the sound velocity dispersions of the other two ionic liquids measured do not match those measured for dielectric relaxation, implying that structural relaxation is much faster than the reorientational relaxation. This difference is discussed in relation to the motilities of anions and cations.     

Synthesis of Pt/Ru bimetallic nanoparticles in high-temperature and high-pressure fluids

A high-temperature and high-pressure flow-reactor system was applied to the synthesis of monometallic ruthenium (Ru) nanoparticles and platinum/ruthenium (Pt/Ru) bimetallic nanoparticles using the thermal reduction of ruthenium ion (Ru(III)) and the mixture of platinum (Pt(IV)) and ruthenium ions in water and ethanol mixture in the presence of poly(N-vinyl-2-pyrrolidone). Monometallic Ru nanoparticles with an average diameter of ca. 2 nm were synthesized above 200 degrees C at 30 MPa. The monometallic Ru nanoparticles tended to make large aggregates in colloidal dispersions. By the reduction of the mixture solution of Pt(IV) and Ru(III) in water and ethanol above 200 degrees C at 30 MPa, Pt/Ru bimetallic nanoparticles with an average diameter of ca. 2.5 nm were synthesized with relatively small size distribution. The EXAFS spectra for the Pt/Ru bimetallic particles indicated that the particle possesses metallic bonds between Pt and Ru atoms in contrast to the case of the nanoparticles produced by thermal reduction under ambient pressure at 100 degrees C [M. Harada, N. Toshima, K. Yoshida, S. Isoda, J. Colloid Interface Sci. 283 (2005) 64], and that the Pt/Ru bimetallic particle has a Pt-core/Ru-shell structure.