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81.
Intensity-independent self-trapping of optical beams in photorefractive crystals was found recently. But we show that due to the existence of dark conductivity in some photorefractive materials or coherent and non-coherent background irradiance, the self-trapping of weak optical beams in photorefractive materials, such as SBN, becomes intensity dependent. The threshold condition of the applied external de electric field for self-trapping is determined as function of the material parameters as well as the initial transverse sizes and relative intensities of the beams. 相似文献
82.
《Electroanalysis》2005,17(21):1919-1923
We report a reference electrode for direct use in tetrahydrofuran (THF) at low temperatures. A reference solution containing equimolar amounts of ferrocene/ferrocenium hexafluorophosphate (Fc/Fc+) are prepared to give a 4 mM solution in THF that contains tetrabutylammonium hexafluorophosphate (TBAF) supporting electrolyte thus, minimizing liquid junction potentials. The reference solution is added to a sealed glass tube with a porous frit at one end, and a platinum wire is inserted into the tube. The reference electrode assembly is then inserted into a THF test solution. Potentiometric measurements show that the system responds in the expected Nernstian fashion over the concentration and temperature ranges, 4 mM to 40 μM and 20 °C to ?45 °C respectively. In addition, it is shown by steady–state cyclic voltammetry at a platinum microelectrode that the chemical reactivity of ferrocenium hexafluorophosphate (Fc+) otherwise seen in THF is suppressed by ion‐pairing with PF using tetrabutylammonium hexafluorophosphate (TBAF) as the supporting electrolyte. 相似文献
83.
Five new-type Fc receptor molecules were constructed based on streptococcal protein G (SpG) and staphylococcal protein A (SpA). These protein molecules contain one to six Fc binding domains to immunoglobulins which are structurally different from native SpG or SpA. Their expression levels reached 17-30% of the total bacterial proteins after heat induction in E. colt. Immunodiffusion and ELISA results showed that the engineered protein TG (184 amino acid residues) composed of three SpG C3 domain could bind more broadly and efficiently than the native SpG to the IgGs of human, goat, rabbit, etc. , and its optimal pH for binding became wider (pH5-8) compared with the SpG (pH5) ; and the protein TGA (357AA), fused by protein TG and the A, B, C domains of SpA, displayed both the binding pattern of SpG and SpA. 相似文献
84.
Transient mode locking of spiking solid-state lasers is studied with the help of two theoretical approaches. The first of them is an extension of the previous transient theory with single-mode rate equations to find the limited spike build-up time depending on the modulation index. The second is based on semiclassical multimode equations describing both spiking behaviour and formation of the picosecond pulse from the initial noise. The derivation of the equations as well as a comparison of results from both approaches are given. The obtained numerical results agree with experimental data. It is shown that the pulsewidth in a spiking laser can approach the small value predicted by the steady-state theory. This minimal pulsewidth can be reached at a smaller modulation index than predicted by the standard transient mode locking theory. The minimal modulation index for generation of good picosecond pulses free of noise is found to be 0.6 in our case. Losses connected with amplitude modulation have a negligible effect on spike build-up time and pulse duration. 相似文献
85.
Malovichko G. I. Grachev V. G. Kokanyan E. P. Schirmer O. F. Betzler K. Gather B. Jermann F. Klauer S. Schlarb U. Wöhlecke M. 《Applied Physics A: Materials Science & Processing》1993,56(2):103-108
The growth of LiNbO3 single crystals from a melt with the Li/Nb ratio of 0.946, to which 6 wt.% K2O has been added, leads to stoichiometric specimens, essentially free of potassium, with (50±0.15) mol% Li2O in the crystal. This is established by studying the composition dependence of the following properties: linewidths of the electron paramagnetic resonance (EPR) of Fe3+, energy of the fundamental absorption edge, Raman linewidths of phonon modes, and dispersion of the optical birefringence. Comparison of the results with relevant calibration scales leads to the above composition. In all cases the Li2O content was found to be closer to 50% than that of a LiNbO3 crystal vapor-phase equilibrated to 49.9mol% Li2O. The photorefractive effect at light intensities I107 W/m2 is suppressed in this stoichiometric material. The features of the ternary system K2O-Li2O-Nb2O5, which are possibly responsible for the unexpected growth of stoichiometric LiNbO3 from the indicated melts, are discussed. 相似文献
86.
Nilay Bereli Gizem Ertürk M.Aşkın Tümer Rıdvan Say Adil Denizli 《Biomedical chromatography : BMC》2013,27(5):599-607
Antibodies are used in many applications, especially as diagnostic and therapeutic agents. Among the various techniques used for the purification of antibodies, immunoaffinity chromatography is by far the most common. For this purpose, oriented immobilization of antibodies is an important step for the efficiency of purification step. In this study, Fc fragment‐imprinted poly(hydroxyethyl methacrylate) cryogel (MIP) was prepared for the oriented immobilization of anti‐hIgG for IgG purification from human plasma. Non‐imprinted poly(hydroxyethyl methacrylate) cryogel (NIP) was also prepared for random immobilization of anti‐hIgG to compare the adsorption capacities of oriented (MIP/anti‐hIgG) and random (NIP/anti‐hIgG) cryogel columns. The amount of immobilized anti‐hIgG was 19.8 mg/g for the NIP column and 23.7 mg/g for the MIP column. Although the amount of immobilized anti‐hIgG was almost the same for the NIP and MIP columns, IgG adsorption capacity was found to be three times higher than the NIP/anti‐hIgG column (29.7 mg/g) for the MIP/anti‐hIgG column (86.9 mg/g). Higher IgG adsorption capacity was observed from human plasma (up to 106.4 mg/g) with the MIP/anti‐hIgG cryogel column. Adsorbed IgG was eluted using 1.0 m NaCl with a purity of 96.7%. The results obtained here are very encouraging and showed the usability of MIP/anti‐hIgG cryogel prepared via imprinting of Fc fragments as an alternative to conventional immunoaffinity techniques for IgG purification. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
87.
Many materials are good candidates for diode-pumped ultra-short-pulse lasers: several transition-metal-ion-doped crystals
can or could support extremely short fs pulses. This goal, so far, has only been reached by Cr3+:LiSAF, but there are good chances for other crystals like Cr4+:YAG having its bandwidth within the third communication window, and the high-yield Cr2+:ZnSe with its impressive bandwidth in the near IR. Rare-earth-ion-doped media deliver only sub-ps pulses but allow unprecedented
and scalable high average powers, like a SESAM mode-locked Yb:YAG thin-disk laser described recently. In all ranges of pulse
durations there are fascinating applications ready for widespread employment as soon as compact, reliable and moderately priced
ultra-short-pulse systems will be available for the non-laser-skilled user. The highest impact in the near future is attributed
to microstructuring of materials and processing of biological samples, including dental enamel, by ps and sub-ps pulses, and
optical coherence tomography needing pulses in the 10-fs regime at very modest average powers.
Received: 29 June 2000 / Published online: 6 December 2000 相似文献
88.
Light distributions near resonant metal nanoparticles are recorded by a scattering-type scanning near-field optical microscope
(s-SNOM), for the first time with a sub-particle-size resolution (<10 nm) and with simultaneous amplitude and phase contrast.
The images depict the optical oscillation patterns of single plasmon particles. Examples are presented of particles excited
in dominantly dipolar and quadrupolar modes, and also of closely spaced particles sustaining a gap mode. The gap mode can
provide enhanced optical fields in nanometric spots for non-linear and single-molecule spectroscopy applications.
Received: 20 June 2001 / Revised version: 3 August 2001 / Published online: 19 September 2001 相似文献
89.
A reagentless signal-on electrochemiluminescence (ECL) biosensor for DNA hybridization detection was developed based on the quenching effect of ferrocene (Fc) on intrinsic cathodic ECL at thin oxide covered glassy carbon (C/CxO1−x) electrodes. To construct the DNA biosensor, molecular beacon (MB) modified with ferrocene (3′-Fc) was attached to a C/CxO1−x electrode via the covalent bound between labeled amino (5′-NH2) and surface functional groups. It was found that the immobilization of the probe on the electrode surface mainly depended on the fraction of surface carbonyl moiety. When a complementary target DNA (cDNA) was present, the stem-loop of MB on the electrode was converted into a linear double-helix configuration due to hybridization, resulting in the moving away of Fc from the electrode surface, and the restoring of the cathodic ECL signal. The restoration of the ECL intensity was linearly changed with the logarithm of cDNA concentration in the range of 1.0 × 10−11 to 7.0 × 10−8 M, and the detection limit was ca. 5.0 pM (S/N = 3). Additionally, single-base mismatched DNA can be effectively discriminated from the cDNA. The great advantage of the biosensor lies in its simplicity and cost-effective with ECL generated from the electrode itself, and no adscititious luminophore is required. 相似文献
90.
Toward passive mode locking by nonlinear polarization evolution in a cascaded Raman fiber ring laser
We demonstrate a cascaded Raman fiber ring laser delivering a pulsed fourth-order Stokes component. Periodic emission of subnanosecond pulses is achieved from the interplay between nonlinear polarization evolution and Raman cascade process. 相似文献