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61.
Hiroshi Noguchi Tsuyoshi Michinobu Nozomu Fujii Masahiro Funahashi Masatoshi Tokita Junji Watanabe Kiyotaka Shigehara 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):5101-5114
Cyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (Mn) of ~ 104 and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10?4–10?5 cm2 V?1 s?1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008 相似文献
62.
Karataev P Aryshev A Boogert S Howell D Terunuma N Urakawa J 《Physical review letters》2011,107(17):174801
We represent the first experimental observation of the point spread function (PSF) of optical transition radiation (OTR) performed at KEK-Accelerator Test Facility extraction line. We have demonstrated that the PSF vertical polarization component has a central minimum with a two lobe distribution. However, the distribution width varied significantly with wavelength. We assume that we observed a severe effect from spherical or chromatic aberrations which are not taken into account in any existing theoretical model. We believe that the result of this work will encourage theoreticians to continue developing the theory as it is important for various transition radiation applications. Nonuniform distribution of the OTR PSF creates an opportunity for developing a submicrometer transverse beam size monitor. 相似文献
63.
Shogo Ura Kenji Kintaka Hideyuki Awazu Yasuhiro Awatsuji Junji Nishii 《Optical Review》2011,18(1):99-102
An interference exposure system using a phase-shifting mask was proposed for generating periodic sawtooth optical intensity
profile with chirp in period. Multiple space-harmonic waves are launched from the mask by diffraction, and the sawtooth optical
intensity is formed by interference based on Fourier synthesis after propagation through an air gap. The design concept merely
utilizing positive diffraction-order harmonics with tilt illumination of an exposure light and a design algorithm based on
time-reversed configuration for calculating required phase shift amount were proposed and discussed. A phase-shifting mask
for a blazed grating of very high chirp rate was designed to demonstrate its potential and feasibility. The grating period
changes from 2.2 to 3.1 μm gradually within 0.3 mm length. Sawtooth-like optical intensity profile was confirmed by theoretical
simulation as well as preliminary experimental results. 相似文献
64.
Conductive polymer three-dimensional microstructures were photofabricated utilizing the two-photon absorption of a sensitizer
dye. The resulting three-dimensional structures were excised from the transparent polymer sheet using a micro-manipulator.
The processing precisions for the vertical direction of the conductive polymer three-dimensional microstructure obtained in
the transparent polymer sheet were evaluated in the present study. As a result, for the configurations of the obtained polypyrrole
line deposition, the line height/line width ratios were around 5: 1; this ratio is higher than that of other UV resin works
(h: w 2:4–3: 1) and the cross section distortion is not negligible for maintaining the higher reproducibility of the photofabrication. 相似文献
65.
A substitution on 2,2-difluorovinylic carbon was investigated by using ab initio molecular orbital calculations. Three feasible mechanisms, which are the SN1-like, the SN2-type and the addition-elimination mechanisms, were ex- amined for a model borate, 2,2-difluoro-1-mesyloxyvinyl(trimethyl)borate. Four TSs were obtained depending on the position of Li+ around the vinylborate although activation energies in the gas phase are rather high (ca. 30–40 kcal mol−1) in comparison with that expected from the experimental conditions. It was confirmed at the SCRF-IPCM calculations that the solvent effect reduces the acti- vation energy of one SN2-type mechanism very much (4. l kcal mol−1 at the B3LYP/6-31+G*//RHF/6-31+G/s* level of theory) while those for the other mechanisms do not change very much. Therefore, the SN2-type mechanism is applicable to the substitution reaction observed for the vinylborate. 相似文献
66.
The Laser Undulator Compact X-ray source(LUCX) is a test bench for a compact high brightness X-ray generator,based on inverse Compton Scattering at KEK,which requires high intensity multi-bunch trains with low transverse emittance.A photocathode RF gun with emittance compensation solenoid is used as an electron source.Much endeavor has been made to increase the beam intensity in the multi-bunch trains.The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects,so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough.A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform.In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance.With the uniform driving laser and the unbalanced RF gun,the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm.mrad. 相似文献
67.
Xuexi Tie a Junji Cao b a National Center for Atmospheric Research Boulder CO USA b SKLLQG Institute of Earth Environment Chinese Academy of Sciences No. Fenghui South Road High-Tech Zone Xi’an China 《中国颗粒学报》2010,8(1)
PARTICUOLOGY regrets that the above paper was mistakenly classified as a ‘Review’ rather than an ‘Invited paper’ when originally published in volume 7, issue 6, 426–431. 相似文献
68.
Kento Okoshi Anubhav Saxena Masanobu Naito Goro Suzaki Masatoshi Tokita Junji Watanabe Michiya Fujiki 《Liquid crystals》2004,31(2):279-283
A smectic A-cholesteric phase transition for a rigid-rod helical polymer, poly[n-decyl-(S)-2-methylbutylsilane] (PD2MBS), with a narrow molecular weight distribution, has been observed for the first time. Polarizing optical microscopy showed that the fan-shaped texture of the smectic A phase turned into the characteristic planar texture of the cholesteric phase upon heating. The positive CD band, which corresponds to the reflection band of the cholesteric phase, gradually decreased in intensity within a range 30°C below the transition temperature on cooling, while the peak maximum shifted towards shorter wavelengths. It was concluded that the system has a very wide temperature region over which the cholesteric-smectic A phase transition occurs and in which the cholesteric pitch varies with temperature. 相似文献
69.
Phase transition of the layer structure of poly(p-benzenedithiol-co-p-diethylbenzene) obtained in solid state polymerization was studied by a thermal treatment or UV irradiation under a nitrogen atmosphere. The peak intensities in the X-ray diffraction diagram of polymers gradually decreased with the thermal treatment time above 55°C. Below 50°C the layer structure of polymers hardly changed. The apparent activation energy for the phase transition was about 15 Kcal/mol [63 KJ/mol] at the initial stage and gradually decreased to a few Kcal/mol [ca. 2 KJ/mol]. UV light from a high-pressure mercury lamp also gradually induced the phase transition from the layer structure to an amorphous one. The pristine polymer possesses phase transition points at 75, 95 and 130°C. The exothermic transition at 75°C can be understood as the thermal destruction of the semistable layer structure. The exothermic transition at 95°C may be correspond to the cis → trans thermal isomerization of the C?°C bond in the polymer main chain. The diffuse reflectance spectrum of the pristine polymer differed from that of the amorphous polymer obtained by the thermal treatment of the pristine polymer. SEM photographs of the pristine polymer showed a particular surface structure, i.e. entangled fibrous material. TEM photographs of the pristine polymer exhibited a bright valley-and-hill structure, whereas that of the amorphous polymer obtained by thermal treatment exhibited a plain surface. 相似文献
70.
Using elastic recoil detection analysis and low energy electron diffraction we have investigated the adsorption process of hydrogen on the
surface. We find that (1) room temperature adsorption of atomic hydrogen induces a structure transformation from the
to Si(111)-1 × 1-Ag(H) structures, (2) a saturation coverage of hydrogen is 1.5 monolayer, which almost coincides with the one on a clean 7 × 7 surface, and (3) thermal desorption of hydrogen from the ordered 1 × 1-Ag(H) surface results in the recovery of the original
surface. 相似文献