We theoretically and experimentally investigated fundamental characteristics of an integrated optic pressure sensor using intermodal interference between the lowest-order TM-like and TE-like modes. The sensor consists of a rectangular diaphragm and a straight single-mode waveguide along an edge of the diaphragm. Its operation is based on a difference of phase retardations produced in the two guided modes through the photoelastic effect. The sensor was fabricated by bonding two glass substrates together: a Corning 0211 glass 300 μMm thick to form a waveguide and a thick substrate with a 10 mm × 10 mm square hole to define the diaphragm. The fabricated sensor was successfully tested using a He-Ne laser at 633 nm. The halfwave pressure was measured to be 77 kPa which is almost double the theoretical estimate. 相似文献
A theoretical model is proposed to explain the tokamak energy confinement time. With no adjustable numerical coefficients, the model predicts experimentally observed values to within a level of uncertainty consistent with the intrinsic spread of the experimental data and the necessity of calculating the confinement time without precise knowledge of the temperature profile. 相似文献
The borylation of arenes leads to the formation of synthetically versatile products from unactivated arene reagents. We report that Ir(I) precursors in conjunction with bipyridine ligands catalyze in high yields the borylation of arenes under mild conditions. These reactions encompase arenes bearing both electron-withdrawing and electron-donating substituents. The temperatures required for the transformation are much lower than those previously reported for direct arene borylation. The combination of [Ir(COE)2Cl]2 and (4,4-di-t-butyl)bipyridine even allows for reaction at room temperature. The same catalyst system at 100 degrees C provides remarkably high turnover numbers for a hydrocarbon functionalization process. Mechanistic studies show that the reactions involve uncommon, Ir(II) tris-boryl complexes. An example of this type of complex ligated by di-t-butylbipyridine was isolated and structurally characterized. It reacted rapidly at room temperature to produce aryl boronate esters in high yields. 相似文献
In order to reveal mechanisms for the electrospinning of proteins, this study focuses on the polymer chain conformation, which is considered to be a critical factor for successful electrospinning. Poly(gamma-benzyl-L-glutamate) (PBLG) is employed and the relationships between the chain conformations of the pre-spun PBLG molecules and the morphologies of the post-spun PBLG fibers are investigated. By combining viscosity measurements, and circular dichroism and FT-IR spectroscopies, chain conformations of the pre- and post-spun PBLG are characterized. The chain conformations of the pre-spun PBLG changes from an alpha-helix to a random coil upon changing the solvent ratios of dichloromethane (CH(2)Cl(2)) and trifluoroacetic acid (CF(3)COOH) from 100:0 to 0:100. In an alpha-helix conformation, the morphology of PBLG fibers is relatively thick, while that of the random coil is thin and homogenous. The mean fiber diameters decrease when the chain conformations change from an alpha-helix to a random coil. FT-IR spectroscopy and wide-angle X-ray diffraction measurements reveal that electrospinning predominantly induces an alpha-helical conformation in post-spun PBLG fibers, and more highly crystallized fibers are generated as the alpha-helical content in the pre-spun solution increases. 相似文献
The chemistry of phosphoserine [Ser(P)] containing peptides and polypeptides was extensively investigated to explore a new biomineralization material science. The selective cleavage of the O,O′‐diphenyl phospho‐protecting groups of Ser(PO3Ph2) was examined using hydrogenolysis catalysts. Among the catalysts examined, only PtO2 in 50% trifluoroacetic acid (TFA)/AcOH successfully cleaved the protecting group of Ser(PO3Ph2) to give Ser(P). Based on these characteristic new findings, Ser(P)‐containing dipeptides such as Gly‐Ser(P), Ala‐Ser(P), Ser‐Ser(P), Asp‐Ser(P), Glu‐Ser(P), and Lys‐Ser(P), and tetrapeptide [Asp‐Ser(P)]2 were synthesized by a facile method. When we used the Ser(PO3Ph2) residues at the C terminals, the amino functional groups of amino acids and peptides can be coupled by the unsymmetric mixed anhydride using isobutyl chloroformate but cannot be by the symmetric anhydride method using dicyclohexylcarbodiimide. Neither unsymmetric mixed anhydride nor symmetric anhydride can be coupled with p‐nitrophenol at their C terminals. High‐molecular‐weight sequential polypeptides containing Ser(P) such as poly[Ser(P)‐Xaa] (Xaa: Gly, Ala, Ser, Lys, Asp, Glu) and poly[Gly‐Ser(P)‐Gly] were first synthesized by the polycondensation of the di‐ and tripeptide p‐nitrophenyl active esters, followed by the quantitative elimination of the diphenyl protecting groups by PtO2 in TFA/AcOH. The new strategy to synthesize Ser(P)‐containing peptides and model proteins may help the development of hybrid formulations of marine and biomimetic protein minerals.
Natural protein fibers, such as silk, having high‐performance characteristics have been important materials in biopolymer research. This article reports the development of a silk‐like extensible poly(α,L ‐amino acid) fiber inspired by self‐assembly of polypeptides in living systems. Electrostatic interaction was employed as the driving force for building the fiber, and we succeeded in spinning the fiber from an aqueous solution interface between poly(α,L ‐lysine) (PLL) and poly(α,L ‐glutamic acid) (PLG). When the PLL/PLG fiber was formed, the conformations of PLL and PLG were changed from random to β‐structures. A remarkable feature of the PLL/PLG fiber is the high extensibility. Mechanical stretching of the PLL/PLG fiber resulted in a change from an extensible fiber to a rigid and strong fiber. These features depend on the molecular conformation and the deviation in the amino acid composition of the PLL/PLG fibers. This concept and the poly(α,L ‐amino acid) fibers themselves allow the production of new protein fibers and aid the development of the science of protein folding as well as giving insight into the noncovalent interactions involved in self‐assembly.
SEM micrograph showing that the surface of the stretched fiber is smooth. 相似文献
We determined the Pockels constant of water in the electric double layer (EDL) at the GaN electrode interface. For a positive
(negative) bias, the difference transmittance showed a blue (red) shift in the interference fringes in the visible. This was
caused by a negative (positive) refractive index change both in the EDL of water and in the space charge layer (SCL) of the
GaN. The latter was associated with the blue shift in the absorption edge in the UV due to the band population effect in the
GaN. The voltage drops took place within the interfacial layer at a ratio of about 3: 1 for the SCL vs EDL at the modulation
frequency of f = 20 Hz, estimated from the frequency dependence of the impedance. The Pockels constant of water in the EDL was determined
to be r13 = 0:63 × 100 pm/V for the GaN electrodes. This is three times smaller than that at the surface of the indium tin oxide (ITO)
electrode. 相似文献
Summary: A wide‐gap (up to 30 mm) radio frequency (RF) glow discharge was realized at atmospheric pressure, using soft X‐ray photo‐emission, pre‐ionization. The RF glow plasma was excited with an automated matching system, at industrial frequencies (13.56 and 27.12 MHz), in helium or helium‐diluted oxygen. Antibacterial effects were examined using spore‐forming bacteria: Bacillus atrophaeus, Bacillus subtilis, Geobacillus stearothermophilus, Bacillus pumilis, and selected species of bacteria, a mold, and a yeast‐like fungus: Pseudomonas aeroginosa, Salmonella enteritidis, Enterobactor aerogenes, Lactobacillus plantarum, Staphylococcus aureus, Candida albicans, and Aspergillus niger.
Experimental comparison of disinfection time using dry‐heat treatment and plasma treatment at 90 °C. 相似文献
