Effect of organosilane agents on the vulcanizate structure and physical properties of silica-filled solution styrene butadiene rubber compounds

Physical properties of rubber compounds are affected by the filler-rubber interaction, filler dispersion in the rubber matrix, and crosslink structure formed during vulcanization. Organosilane agents are essentially used in silica-rubber compounds to inhibit the formation of silica agglomerates and increase the formation of silica-rubber networks. Generally, organosilane agents have an alkoxysilyl alkyl sulfide structure and are classified into silane coupling and covering agents depending upon the presence of sulfur. Coupling agents have a sulfur moiety and serve as a sulfur donor during the vulcanization process, thus increasing the formation of filler-rubber and chemical crosslink networks. On the other hand, covering agents promote the hydrophobation of silica surfaces, decreasing the adsorption loss of vulcanization additives, which increases the formation of chemical crosslink networks. This implies that organosilane agents can affect the vulcanizate structure, which causes a variation in the properties of silica compounds. Therefore, in this study, the effect of coupling (bis(3-triethoxysilylpropyl)disulfide (TESPD) and bis(3-triethoxysilylpropyl)tetrasulfide (TESPT)) agents and a covering (triethoxy(octyl)silane) agent on the vulcanizate structure and properties of silica compounds was investigated and compared. In the comparative study of coupling and covering agents, the influence of sulfur donors on the formation of vulcanizate structures was investigated. In the case of the coupling agents, the effect of sulfur rank on the vulcanizate structure and properties of silica-rubber compounds was quantitatively analyzed through various characterization techniques.     

Comparison of the effects of particle shape on thin FeSiCr electromagnetic wave absorber

The raw materials of FeSiCr were processed in the ball mill for 30 h and the shape of the FeSiCr particles was changed from sphere to flake type, which was observed using a scanning electron microscope. And FeSiCr composite microwave absorbers were mixed with silicone for mobile phones and the effects of the thickness of the samples on the absorption were measured using a network analyzer in order to investigate the relationship between the microwave absorption and the material constants. The flake-type FeSiCr-rubber composite showed high reflection loss, which was due to the high complex permittivity and permeability. Also, the matching frequency shifted toward lower frequency range with microwave absorber thickness, and the maximum reflection loss of −8.7 dB was observed in 1.85 GHz for a 1.6 mm thickness.     

Performance of the far‐IR beamline of the 6 MeV tabletop synchrotron light source

The performance of the far‐infrared (FIR) beamline of the 6 MeV tabletop synchrotron light source MIRRORCLE‐6FIR dedicated to far‐infrared spectroscopy is presented. MIRRORCLE‐6FIR is equipped with a perfectly circular optical system (PhSR) placed around the 1 m‐long circumference electron orbit. To illustrate the facility of this light source, the FIR output as well as its spectra were measured. The optimum optical system was designed by using the ray‐tracing simulation code ZEMAX. The measured FIR intensity with the PhSR in place is about five times higher than that without the PhSR, which is in good agreement with the simulation results. The MIRRORCLE‐6FIR spectral flux is compared with a standard thermal source and is found to be 1000 times greater than that from a typical thermal source at ～15 cm^?1. It is also observed that the MIRRORCLE‐6FIR radiation has a highly coherent nature. The broadband infrared allows the facility to reach the spectral range from 10 cm^?1 to 100 cm^?1. MIRRORCLE‐6FIR, owing to a large beam current, the PhSR mirror system, a large dynamic aperture and small ring energy, can deliver a bright flux of photons in the FIR/THz region useful for broadband spectroscopy.     

Analytic calculation of the lineshapes in polarization spectroscopy of rubidium

This paper reports on analytic calculations of the lineshapes for polarization spectroscopy of rubidium atoms. Under the use of a weak circularly polarized pump beam, the time-dependent population of each magnetic sublevel was obtained analytically from the rate equations up to the lowest order of the pump beam intensity, and the associated circular birefringence experienced by a counterpropagating probe beam was calculated. In particular, analytic forms of the polarization spectroscopy spectra were obtained for ⁸⁷Rb and ⁸⁵Rb atoms using the mean transit time crossing the pump beam, and the analytic results were compared with the numerical data, experimental results and Nakayama model’s results, showing a good agreement one another.     

Reflection characteristics of a copper metal-organic chemical-vapor-deposited thin film for vertical micromirror applications

We introduce Cu metal-organic chemical-vapor deposition as a potential means of conformal metal coating of the sidewalls of micromachined vertical mirrors. The optimal process temperature was experimentally found to be 215 degrees C, which gives high step coverage of better than 90%, and the surface roughness was less than 27 nm. The roughness, measured with an atomic force microscope, will induce a scattering loss less than 0.12 dB, which is small enough for vertical micromirror application. The experimental reflectances of Cu thin film were measured with a distributed-feedback laser (1550 nm) and found to be greater than 0.9 for incidence angles of 22.5 degrees and 45 degrees , and these reflectances were in good agreement with theoretical values.     

Time-delayed spatial patterns in a two-dimensional array of coupled oscillators

We investigated the effect of time delays on phase configurations in a set of two-dimensional coupled phase oscillators. Each oscillator is allowed to interact with its neighbors located within a finite radius, which serves as a control parameter in this study. It is found that distance-dependent time delays induce various patterns including traveling rolls, squarelike and rhombuslike patterns, spirals, and targets. We analyzed the stability boundaries of the emerging patterns and briefly pointed out the possible empirical implications of such time-delayed patterns.     

Enantioselective synthesis of bicyclo[3.1.0]hexane carbocyclic nucleosides via a lipase-catalyzed asymmetric acetylation. Characterization of an unusual acetal byproduct

The bicyclo[3.1.0]hexane scaffold can lock the conformation of a carbocyclic nucleoside into one of the two antipodal (north or south) conformations typical of conventional nucleosides that normally exist in a rapid, two-state equilibrium in solution. In a recent brief communication, we reported a practical method to access the requisite bicyclo[3.1.0]hexane pseudosugar for the north antipode via an intramolecular olefin-ketocarbene cycloaddition. The most attractive features of this synthesis was that a relatively complex synthon was obtained from simple and inexpensive starting materials and that the resulting racemic mixtures of purine nucleosides could be successfully resolved by adenosine deaminase (ADA) hydrolysis. In this work, we describe the development of a more general, lipase-catalyzed double-acetylation reaction, which could successfully resolve an earlier precursor, 4-(tert-butyldiphenylsilamethoxy)-1-(hydroxymethyl)bicyclo[3.1.0]hexan-2-ol [(+/-)-7], into enantiomerically pure (+)-diacetate 8 and (-)-monoacetate 9. The former diacetate was converted to the conformationally locked (north)-carbocyclic guanosine (+)-17 identical to the one obtained previously by ADA resolution. The present method represents a more general and efficient process applicable to the synthesis of all classes of (north) bicyclo[3.1.0]hexane nucleosides, including pyrimidine analogues. During the lipase-catalyzed resolution, we were able to demonstrate the presence of an unusual acetal-forming reaction that consumed small amounts of the unreactive monoacetate (-)-9. This side reaction was also enzyme-catalyzed and was triggered by the byproduct acetaldehyde generated during the reaction.     

Modes of binding interaction between viologen guests and the cucurbit[7]uril host

[structure: see text] Host-guest interactions between cucurbit[7]uril (CB7) and a series of dialkyl-4,4'-bipyridinium (viologen) dicationic guests were investigated by NMR spectroscopy. CB7 includes the aromatic nucleus of short chain viologens, but the mode of interaction is different with longer chain viologens due to the favorable hydrophobic interactions between the terminal alkyl substituents and the inner cavity of the host. A new pseudorotaxane was designed and synthesized on the basis of viologen-CB7 binding interactions.