Theoretical study on reaction scheme of silver(I) containing 5-substituted uracils bridge formation

We present a reaction scheme of silver containing 5-substituted uracils (N) bridge formation with two silver ions to a silver-mediated base pair [N-Ag(2)-N] by using the conductor-like polarizable continuum model (CPCM)-B3LYP/aug-cc-pVDZ level of theory. The whole reaction scheme is divided into the following three steps: (1) silver ion binding and deprotonation, (2) silver ion transfer, and (3) dimer formation and structural fluctuation. With a new pK(a) computing scheme proposed in our previous studies, it is found that a silver coordination decreases the pK(a) of N by 2.5-3.0 pK(a) units, which is an important clue for silver-ion selectivity by N. Judging from the calculation, we revealed that the silver ion transfer reaction and the dimerization reaction occur spontaneously. Moreover, both reactions are independent of the C5 ligand in N so that the deprotonation reaction, which is the first step of this scheme, plays a key role in forming the [N-Ag(2)-N] pairing.     

Exploring the thermochromism of sulfite-embedded polyoxometalate capsules

The Dawson-type polyanion [α-Mo(18)O(54)(SO(3))(2)](4-), with two SO(3)(2-) templates embedded inside a polyoxomolybdate(vi) cage, exhibits thermochromism over an exceptionally wide temperature range (～500 K). The temperature dependence of the cluster structure, established from X-ray crystallography, IR and Raman spectroscopy and DFT calculations, is related to a decreasing HOMO-LUMO gap in the near UV with increasing temperature. We postulate this is due to geometrical changes that affect both the occupied and unoccupied frontier molecular orbitals of this cluster anion.     

FEM calculation and the effects of hydrogen diffusion in fabrication processes of long-period fiber gratings

The wavelength shift of a long-period fiber grating (LPG) related to re-distribution of hydrogen molecules was studied by the finite-element method (FEM) calculation and by the experiment. The FEM calculation was performed solving a diffusion equation of hydrogen in glass fiber, and the wavelength of an LPG was calculated. In the experiment, the hydrogen-loaded fiber was out-diffused before laser exposure, and the resonance wavelengths of LPGs fabricated by exposure were measured. The wavelength depended on the duration of out-diffusion, and the variation was up to 114 nm. The FEM calculation considering the hydrogen re-distribution by out-diffusion agreed with the experiment. After the laser exposure, the wavelength of an LPG shifted towards the long wavelength without any exposure. The FEM calculation assuming hydrogen depletion in the core and its recovery agreed with the measured wavelength shift. Extension of the FEM to fibers with more complicated structures has been discussed.     

Separation of V(V)-4-(2-pyridylazo)resorcinolato complex from a large excess reagent using an ODS cartridge for high-performance liquid chromatography.

A selective off-line preconcentration technique for the V(V) complex with 4-(2-pyridylazo)resorcinol has been developed and successfully applied to the determination of V(V) in an air-borne sample. The target complex was separated from excess reagent using an ODS cartridge and water as the eluent. The complex was then concentrated on another ODS cartridge using tetrabutylammonium bromide and eluted with methanol; the eluate was applied to a one-drop concentration/HPLC. A detection limit as low as (6.05 +/- 0.82)x 10(-11) M (5 ppt) was achieved.     

Die Löslichkeit von aromatischen Verbindungen mit polaren Gruppen in Wasser

Zusammenfassung Die Löslichkeiten folgender Verbindungen wurden in Wasser bei 5°-Intervallen von 0° bis 40° bestimmt; Anilin, Mtrobenzol, Chlorbenzol,-Oxynaphthalin und-Nitronaphthalin. Aus diesen Ergebnissen wurden die thermodynamischen Parameter für den Lösungsprozeß der reinen flüssigen Verbindungen in Wasser berechnet. Das Resultat wurde mit Hilfe des Begriffs der Eisberge erklärt.Beim Benzol, Anilin und Chlorbenzol waren die Lösungswärmen negativ bei niedrigeren Temperaturen und wurden mit steigender Temperatur positiver. Dagegen traten beim Nitrobenzol,-Oxynaphthalin und-Nitronaphthalin stets die positiven Lösungswärmen auf. Dies sollte auf die großen intermolekularen Kräfte in der reinen Flüssigkeit zurückzuführen sein.     

Synthesis and characterization of poly[4-(4-hydroxyphenoxy) benzoic acid]

Poly[4-(4-hydroxyphenoxy) benzoic acid] was prepared by the bulk polycondensation of 4-(4-acetoxyphenoxy) benzoic acid. Polycondensation was conducted at 350°C for 3 h under a reduced pressure of 0.1 mmHg and gave a polymer with X?n of 255. The polymer was characterized by elemental analysis, IR spectroscopy, differential scanning calorimetry, and wide-angle X-ray measurement. The crystal/nematic and nematic/isotropic phase transition temperatures of polymer, which depend on the molecular weight, were observed at about 300°C and 410°C, respectively. The polymers with low molecular weights showed nematic textures above 300°C. This nematic/isotropic phase transition temperature is lower than that of poly (4-hydroxybenzoic acid). This thermal behavior of polymer comes from ether units, which increase the flexibility (the rotation or torsion of skeletal bonds) of the polymer chain. © 1994 John Wiley & Sons, Inc.     

Classical and quantum mechanical aspects of time-dependent Hartree-Fock trajectories

In terms of a quantum mechanical representation based on Slater determinants, classical and quantum mechanical aspects of TDHF trajectories are investigated. The invariant integration measure of the determinantal representation is obtained in a general closed form. Phase space structures of the TDHF equation and its solutions are discussed on this basis. The formal classical structures provide a way of finding a semiclassical expression for the quantum mechanical propagator, into which the superposition principle among TDHF trajectories is incorporated. General properties of the semiclassical propagator such as the time translation/reversal symmetry, unitarity, etc., are studied. Two simple hamiltonian systems are employed as examples which exhibit analytical solutions for the propagator. To illustrate the effects of superposition of TDHF paths, a system of interacting two-level nuclei is numerically studied and a comparison with the exact result is made.     

Partial molar enthalphy of formation of solid solution in transition metal sulfides by a combustion calorimetry

The combustion calorimetry on the NbS system has been carried out under an oxygen atmosphere at 453°C using a Calvet-type twin calorimeter. The partial molar enthalphies of the formation of solid solution for both 2S-NbS_x and 3S-NbS_x phase on the NbS system has been determined.     

Compound-forming effect for the electrical resistivity of liquid IVB-Te alloys

The resistivity isotherm of liquid IVb(Sn,Pb)-Te alloys has a remarkable maximum and temperature coefficient of resistivity has large negative value around the equiatomic composition, suggesting that a kind of compound formation exists at this composition. The excess resistivities are interpreted in terms of resonance scattering by the compound of MTe(M=Sn, Pb) with a finite life time.