Syntheses, Characterization, and Molecular Mechanics Calculations of Optically Active Silatrane Derivatives

A series of optically active silatrane derivatives, [Si{N(CHRCH(2)O)(CH(2)CH(2)O)(2)}X] (R = Me, i-Pr; X = Ph, OMe) has been synthesized by the reaction of optically active triethanolamine derivatives with XSi(OMe)(3), and characterized by (1)H NMR, (13)C NMR, (29)Si NMR, and mass spectroscopy, and the structures of six compounds have been determined by X-ray analysis. Molecular mechanics methods have also been employed to obtain the energy-minimized structures. The (29)Si NMR chemical shifts and the lengths of Si-N determined by X-ray analysis are sensitive to the bulkiness of the substituent (R). The Si-X bond lengths (X: trans position to nitrogen) do not appreciably differ from one another. The MM2 calculations indicated that the substituent exists in the equatorial position, and the results are in agreement with those of X-ray analysis and (1)H NMR spectroscopy. Crystallographic data: [R = H; X = OMe], C(7)H(15)NO(4)Si, orthorhombic, Pna2(1), a = 13.407(1) ?, b = 8.761(2) ?, c = 8.191(1) ?, Z = 4; [R = Me; X = OMe], C(8)H(17)NO(4)Si, orthorhombic, P2(1)2(1)2(1), a = 10.110(3) ?, b = 11.083(2) ?, c = 9.474(2) ?, Z = 4; [R = i-Pr; X = OMe], C(10)H(21)NO(4)Si, monoclinic, P2(1), a = 8.481(1) ?, b = 7.805(1) ?, c = 10.218(2) ?, beta = 111.31(1) degrees, Z = 2; [R = Me; X = Ph], C(13)H(19)NO(3)Si, orthorhombic, P2(1)2(1)2(1), a = 8.813(1) ?, b = 11.137(2) ?, c = 13.757(1) ?, Z = 4; [R = i-Pr; X = Ph], C(15)H(23)NO(3)Si, orthorhombic, P2(1)2(1)2(1), a = 8.365(1) ?, b = 13.538(2) ?, c = 13.841(2) ?, Z = 4.     

Poly(amide amine) dendrimer with naphthyl units as a fluorescent chemosensor for metal ions.

Poly(amide amine) dendrimer with naphthyl units (N8) as a fluorescent chemosensor for metal ions was synthesized. We investigated the metal ion recognition of N8. Large changes in the fluorescence spectra of N8 were observed upon the addition of cadmium and zinc ions.     

Dose equivalents inside the MIR Space Station measured by the combination of CR-39 plates and TLDs and their comparison with those on Space Shuttle STS-79, -84 and -91 missions

In 1997, four dosimeter packages, each of which contains two CR-39 plates and 18 TLDs (Mg2SiO4:Tb), were placed inside the MIR Space Station and flew on an orbit with an inclination angle of 51.6 degrees and an altitude of approximately 400 km for 40 days. We estimated the absorbed doses, dose equivalents and effective quality factors during the flight by combining CR-39 data and TLD data. We then compared these results to those obtained with the same analysis method from the dosimeter packages on board Space Shuttle missions STS-79, -84 and -91 that flew along the same orbit. Finally, the differences between our results and those obtained by another group using passive dosimeters on the MIR are discussed.     

Ecofriendly Route for the Synthesis of Highly Conductive Graphene Using Extremophiles for Green Electronics and Bioscience

Highly conductive biocompatible graphene is synthesized using ecofriendly reduction of graphene oxide (GO). Two strains of non‐pathogenic extremophilic bacteria are used for reducing GO under both aerobic and anaerobic conditions. Degree of reduction and quality of bacterially reduced graphene oxide (BRGO) are monitored using UV–vis spectroscopy, X‐ray photoelectron spectroscopy, and Raman spectroscopy. Structural morphology and variation in thickness are characterized using electron microscopy and atomic force microscopy, respectively. Electrical measurements by three‐probe method reveal that the conductivity has increased by 10⁴–10⁵ fold from GO to BRGO. Biocompatibility assay using mouse fibroblast cell line shows that BRGO is non‐cytotoxic and has a tendency to support as well as enhance the cell growth under laboratory conditions. Hereby, a cost effective, non‐toxic bulk reduction of GO to biocompatible graphene for green electronics and bioscience application is achieved using halophilic extremophiles for the first time.     

Dynamics of iodine anions in KI and LiI aqueous solutions studied by <Superscript>127</Superscript>I nuclear resonant quasi-elastic scattering

The dynamics of iodine ions in potassium iodide (KI) and lithium iodide (LiI) aqueous solutions have been studied through ¹²⁷I nuclear resonant quasi-elastic scattering (NRQES). A newly developed Si (12 2 2) double crystal monochromator for ¹²⁷I 57.6 keV excitation is used. Broadening due to a diffusive motion is measured in the energy spectra of the NRQES from the solutions.     

Self-assembly of parallel atomic wires and periodic clusters of silicon on a vicinal Si111 surface

Silicon self-assembly at step edges in the initial stage of homoepitaxial growth on a vicinal Si(111) surface is studied by scanning tunneling microscopy. The resulting atomic structures change dramatically from a parallel array of 0.7 nm wide wires to one-dimensionally aligned periodic clusters of diameter approximately 2 nm and periodicity 2.7 nm in the very narrow range of growth temperatures between 400 and 300 degrees C. These nanostructures are expected to play important roles in future developments of silicon quantum computers. Mechanisms leading to such distinct structures are discussed.     

Synthesis and redox behavior of ene-diyne scaffolds that bear ferrocenes at the periphery

The ene-diyne systems 1 and 2 possessing ferrocenyl groups at the periphery were prepared by the simple one-pot Sonogashira-Hagihara coupling reaction of ethynylferrocene with 9-dibromomethylene-9H-fluorene (4) and 9,10-bis(dibromomethylene)-9,10-dihydroanthracene (5). The novel ferrocene-substituted ene-diyne compounds exhibited amphoteric redox behavior with a reversible one-stage electrochemical oxidation upon cyclic voltammetry.     

Reliability Analysis of a One-Unit System with Unrepairable Spare Units and its Optimization Applications

It is assumed that a unit is either in operation or is in repair. When the main unit is under repair, spare units which cannot be repaired are used. In this system the following quantities are of interest: (i) The time distribution and the mean time to first-system failure, given that the n spare units are provided at time 0. (ii) The probability that the number of the failed spare units are equal to exactly n during the interval (0, t], and its expected number during the interval (0, t]. These quantities are derived by solving the renewal-type equations.Two optimization problems are discussed using the results obtained, viz.: (i) The expected cost of two systems, one with both a main unit and spare units and the other with only spare units is considered. (ii) A preventive maintenance policy of the main unit is considered in order to minimize the expected cost rate. Some policies of the two problems are discussed under suitable conditions. Numerical examples are also presented.     

Mechanical anisotropy of regenerated cellulose films in relation to orientations of crystalline and noncrystalline phases

The mechanical anisotropy of regenerated cellulose films is investigated, first, on the basis of the theory of infinitesimal elasticity. Fairly good agreement of calculated with observed results is obtained on the basis of orthogonal anisotropy with respect to the machine direction and the transverse and thickness directions of the films. The shear modulus G₂₃ along the film plane and the Poisson ratio v₃₂ are 1.5 times; 10² kg/mm² and about 0.4, respectively, in the standard dry state. Second, the mechanical anisotropy in three different dry states is analyzed in terms of the degree of biaxial orientation of two kinds of structural units, cellulose II crystallites and noncrystalline chain segments, and their mechanical anisotropy. The calculation for averaging the mechanical anisotropies of these structural units on the basis of the homogeneous strain hypothesis gives results much higher than the experimental data, whereas the calculation on the basis on the homogeneous stress hypothesis gives results rather lower than experiment. As a modification of the two extreme calculations, a different averaging gives considerably better agreement between the calculated and observed results. The mechanical anisotropy in the wet state is further analyzed primarily in terms of the degree of biaxial orientation of noncrystalline chains by a modification of Krigbaum treatment, based on application of the kinetic theory of entropy elasticity for semicrystalline polymers, to anisotropic systems. The calculation gives results, however, much lower than those obtained experimentally, unless the ratio of the end-to-end distance of the noncrystalline chain to its fully stretched length is taken as unusually large. This may be due to underestimation of the contribution of the crystalline phase to terms of the same type as appear in the Krigbaum treatment.