Photopolyaddition of dithiols to bis(alkoxyallene)s

Polyadditions of 1,4-benzenedithiol (BDT) to bis(alkoxyallene)s, such as 1,4-bis(allenyloxy)xylene (3) and 1,4-bis(allenyloxy) benzene (4) , were carried out in benzene at 25°C by irradiation with a high pressure mercury lamp. Thiol groups were added to the terminal double bonds of the allenyloxy groups selectively to afford polymers containing reactive carbon–carbon double bonds in the main chain, similar to the radical polyadditions using azobis(isobutyronitrile) (AIBN). The molecular weight of the polymer obtained from BDT and 3 was 10 times higher than that of the polymer produced in the radical polyaddition with AIBN; whereas the molecular weight of the polymer from BDT and 4 was similar to that in the radical polyaddition, probably because of poor solubility of 4 and the polymer toward benzene. The geometrical structure of carbon–carbon double bonds in the polymer isomerized from an E to Z structure with reaction time by virtue of both the addition elimination of thiyl radical to the double bonds and the UV irradiation. © 1996 John Wiley & Sons, Inc.     

在粗糙表面上用液晶空间光调制器进行振动测量

为实现在一段时间内连续实时观测振动物体的全息干涉图形,采用覆盖铝箔的喇叭作为振动物体,利用铝箔原有未经特殊处理表面反射的漫反射光成像,并用光寻址液晶空间光调制器(Liquid crystal-sparial lightmodulator,LC-SLM)作为全息记录载体,来实现振动测量。实验中采用时间平均干涉测量法,得到了不同振动频率下物体的干涉图形。同时在连续改变振动物体的振动频率时,可以清晰地观察到物体振动全息干涉图形的变化过程,即近实时的全息干涉图形。     

Universal generation of higher-order multiringed Laguerre-Gaussian beams by using a spatial light modulator

Laguerre-Gaussian (LG) beams of various higher-order radial modes are generated by using a reflective phase-only liquid crystal on silicon (LCOS) spatial light modulator (SLM). Because of the LCOS SLM's phase-modulation characteristic of a wide spatial bandwidth, a phase modulation scheme effectively generates higher-order LG beams of up to the fifth-order radial mode. We also perform correlation analyses between the observed and the theoretical two-dimensional mode profiles to universally obtain correlation coefficients of more than 0.946, which suggest mode generations of high quality.     

Unequally spaced multiple mid-infrared wavelength generation using an engineered quasi-phase-matching device

We propose a novel quasi-phase-matched (QPM) device that can generate unequally spaced multiple wavelengths. Unequally spaced multiple QPM peaks can be obtained by employing the optimized phase modulation of a periodic domain structure. We fabricated a LiNbO3 waveguide device for 3.2-3.4 microm band difference frequency generation based on the design. Using the multiple mid-infrared outputs, we demonstrate the detection of multiple hydrocarbon gases, namely, methane, ethylene, and ethane.     

Structure and mechanical properties of nylon 6.12 prepared by temperature slope crystallization. I. Crystallization of oriented spherulitic textures

Oriented spherulitic textures of a rod-shaped nylon 6.12 sample were crystallized by the temperature slope method. Crystallization conditions were compared by changing temperatures and growth rates. Three types of textures (negative spherulites, positive spherulites, and spherulitic aggregates) were observed by this method. The negative textures appeared when the growth rate was less than 0.1 mm/h. Crystalline orientation and mechanical properties of the textures were investigated by x-ray diffraction and micro-hardness measurements, respectively. The hydrogen-bonded (010) planes were perpendicular to the growth direction in the negative spherulite, while they were parallel to the growth direction in the positive spherulite. In the spherulitic aggregates, the b axis was parallel to the growth direction, while the (010) planes formed roughly an angle of 45° with the growth direction. Due to the orientation of the hydrogen-boned planes, the negative texture exhibited an anisotropy, with hardness values of 106 MPa and 137 Mpa when measured perpendicular or parallel to the growth direction, respectively.     

Photorefractive effect in the relaxor ferroelectric material 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3

The photorefractive effect in a nominally undoped 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 single crystal is measured. We report what is, to our knowledge, the first observation of the photorefractive effect in Pb-based relaxor ferroelectric crystals. The crystal is grown by the flux solution method. Then it is cut into a 2 mm x 4 mm x 8 mm piece and electrically poled along the [111] direction. The coupling constant of the two-wave mixing is 17 cm(-1), and the normalized time constant under 1-W/cm(2) illumination is 12 s at a wave-length of 476 nm. The effective trap density is calculated as 5 x 10(16) cm(-3) from the Debye screening length under the assumption of Kukhtarev's band-transport model. The dominant carrier is identified to be holes from the direction of two-wave mixing energy transfer.     

M?ssbauer spectroscopic study on valence-detrapping and trapping of mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes

Magnetorheological (MR) fluids are new iron-based materials, whose applications include brakes, dampers, clutches, shock absorbers systems and polishing of optical surfaces (lens and mirrors). They are dependent on the size and shape of particles as the magnetic properties. Interested in the possibility of using iron-rich powders, commonly used in nondestructive testing, ranging in size from a few μm to about 200?μm and lower cost than those commercially used for MR fluids, a study of the structural and magnetic properties of iron-rich metallic particles by X-ray diffraction (XRD) and M?ssbauer spectroscopy (MS) at room temperature has been done. Powders, as received, were separated into particle sizes smaller than 20?μm (sample A) and in the range of 20–38?μm (sample B) because these are the sizes generally required for applications in MR fluids. The particles whose sizes exceed the above values were ground in a high energy planetary mill for 3?h, using different values of rotational speed/time: 200?rpm for one hour, a pause of 10?s, 140?rpm for one hour, pause 10?s and then 175?rpm during the last hour. These powders were sieved to obtain particles smaller than 20?μm (sample C). According XRD results, in all samples, only α-Fe (lattice parameter a = 2,867(2) ?) and Fe₂O₃ (lattice parameter a = 5,037(1) ? and c = 13,755(8) ?) were present. The M?ssbauer spectra were fitted with two sextets. The hyperfine parameters values allowed us to assign the highest relative area spectrum (sextet) corresponding to α-Fe and the second one to Fe₂O₃ in accord to the XRD results. Thus, the preparation method using mechanical milling for diminishing the size of the metallic particles allowed us to get particles with size and magnetic properties that could lead to potentially MR fluids applications.     

Application of Protonic Acid-Doped Silica Gels to Electric Double-Layer Capacitors

Silica gels doped with several protonic acids such as HClO₄, H₂SO₄ and H₃PO₄ have been prepared by the sol-gel method and totally solid electric double-layer capacitors have been successfully fabricated using the highly proton-conductive silica gels as an electrolyte and activated carbon powder (ACP) hybridized with the silica gels as a polarizable electrode. It was found that the addition of HClO₄, which had the highest value of acid dissociation constant among these three acids, most effectively increased the proton conductivity of the resultant acid-doped silica gels. Tablets of the HClO₄-doped silica gels exhibited conductivities as high as 10^–5–10^–2 S cm^–1 at room temperature in dry N₂ atmosphere. One of the capacitors fabricated using the protonic acid-doped silica gels had a capacitance of 44 F/(gram of total ACP in the capacitor), which was comparable to those of conventional capacitors using liquid electrolytes.     

Preconcentration Systems Using Polyurethane Foam/Me-BDBD for Determination of Copper in Food Samples

A new reagent, 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD), was synthesised and used in on-line and off-line systems for copper preconcentration by solid-phase extraction. Spectrophotometry and Flame Atomic Absorption Spectrometry (FAAS) were the detection techniques. Polyurethane foam loaded with Me-BDBD packed in a minicolumn was used as sorbent in both systems. The spectral characteristics of Me-BDBD were investigated. The optimum pH values for maximum sorption of the metal are between 7.0 and 8.5. Copper was desorbed with 0.05 and 0.50 mol L⁻¹ hydrochloric acid solutions, for on-line and off-line systems, respectively. The effects of several foreign substances on the adsorption of copper are reported. The enrichment factors obtained were 7 (on-line) and 26 (off-line) for the systems. The proposed procedures allowed the determination of copper with detection limits of 3.4 and 1.4 μg L⁻¹ (0.85 and 0.35 μg per gram of sample) for on-line and off-line systems, respectively. The precision of the procedures was also calculated: 3.2 (on-line) and 1.9% (off-line). The validation of the procedures was carried out by analysis of certified reference material. The copper contents in corn and rice flour and black tea samples were determined by applying the proposed procedures.