Construction,Purification, and Characterization of Anti-BAFF scFv–Fc Fusion Antibody Expressed in CHO/dhfr<Superscript>−</Superscript> Cells

Elevated levels of B-cell-activating factor of the tumor necrosis factor family (BAFF) have been implicated in the pathogenesis of autoimmune diseases in human. In this study, we have constructed a vector for the expression of a novel compact antibody composed of anti-BAFF single-chain antibody fragment (scFv) and the Fc region (the hinge region, CH2, and CH3 domains) of human IgG1 in Chinese hamster ovary cells. The scFv–Fc fusion protein, showing spontaneous Fc fragment-mediated homodimerization via disulfide bridges, was affinity-purified on protein A Sepharose from culture supernatant. The scFv–Fc antibody was demonstrated to retain high binding affinity to antigen and prolonged clearance time in blood and to possess some human IgG crystallizable fragment effector functions such as protein A binding and antibody-dependent cellular cytotoxicity. These results suggest that this recombinant antibody may have therapeutic applications in the therapy of autoimmune disorders mediated by BAFF.     

Synthesis, structures and some reactions of Ru(CCCCFc)(PP)Cp (PP = dppm, dppe) and related compounds

The compounds Ru(CCCCFc)(PP)Cp [PP = dppe (1), dppm (2)], have been obtained from reactions between RuCl(PP)Cp and FcCCCCSiMe₃ in the presence of KF (1) or HCCCCFc and K[PF₆] (2), both with added dbu. The dppe complex reacts with Co₂(CO)₆(L₂) [L₂ = (CO)₂, dppm] to give 3, 4 in which the Co₂(CO)₄(L₂) group is attached to the outer CC triple bond. The PPh₃ analogue of 3 (5) has also been characterised. In contrast, tetracyanoethene reacts to give two isomeric complexes 6 and 7, in which the cyano-olefin has added to either CC triple bond. The reaction of RuCl(dppe)Cp with HCCCCFc, carried out in a thf/NEt₃ mixture in the presence of Na[BPh₄], gave [Ru{CCC(NEt₃)CHFc}(dppe)Cp]BPh₄ (8), probably formed by addition of the amine to an (unobserved) intermediate butatrienylidene [Ru(CCCCHFc)(dppe)Cp]⁺. The reaction of I₂ with 8 proceeds via an unusual migration of the alkynyl group to the Cp ring to give [RuI(dppe){η-C₅H₄CCC(NEt₃)CHFc}]I₃ (9). Single-crystal X-ray structural determinations of 1, 2 and 4-9 are reported.     

Amplitude noise suppression in high-repetition-rate pulse train generation from a frequency-modulated Er-Yb laser

A detailed experimental analysis of the amplitude noise in high-repetition-rate picosecond pulse trains generated by spectral filtering of a frequency-modulated Er-Yb:glass laser is reported. Two distinct sources of noise are identified, and stabilization techniques for noise suppression are proposed and experimentally demonstrated. Intensity noise suppression of ∼20 dB, corresponding to less than 2% residual amplitude fluctuations of the pulse train, has been achieved at repetition rates of 2.5 GHz and 5 GHz with pulse durations of ∼50 ps. Received: 28 July 1999 / Revised version: 13 September 1999 / Published online: 20 October 1999     

Surface Light Extraction Mapping from Photonic Quasicrystal on Current Two-Dimensional Array of 12-Fold Injected GaN-Based LEDs

A two-dimensional array of dodecagonal photonic quasicrystal （12PQC） is fabricated on the surface of current injected GaN-based LEDs to out-couple guided modes. The spatially-resolved surface light extraction mapping of 12PQC is observed and compared with that of triangular lattice photonic crystal （3PC） by microscopic electrical luminescence and scanning near-field microscopy. The higher enhancement factor of 12PQC is obtained to be larger than that of 3PC. It is shown that 12PQC is more favourable and efficient for light extraction of guided lights.     

Photon echo chirp transform using a stabilized frequency agile laser

We report on the demonstration of the chirp transform algorithm for the instantaneous optical frequency analysis of wide band radiofrequency signals. The process exploits photon echoes in an Er³⁺:YSO crystal at 1536 nm. The analysis covers a 1.6 GHz instantaneous bandwidth together with more than 24,000 independent channels. These performances require a frequency agile laser source that is phase-locked in order to take advantage of the tens of μs of coherence time offered by the crystal optical transition.     

Coherent scattering phenomena in apertureless scanning near-field fluorescence microscopy

We study near-field fluorescence images of samples composed of aggregates of 100 nm dye-doped latex spheres. These images have been performed by a reflection Apertureless Scanning Near-field Optical Microscope (A-SNOM). We show that the near-field distribution in fluorescence A-SNOM images arises from coherent scattering phenomena between all spheres. This is a consequence of the coherent nature of the fluorescence emission of each single sphere. The results shown here are significant for all fluorescent samples characterised by a nonnegligible topography.     

Passive mode locking with slow saturable absorbers

We give a comprehensive overview on passive mode locking of solid-state lasers with slow saturable absorbers, based on analytical and numerical calculations. For picosecond lasers, we present a simple equation to estimate the obtained pulse duration and compare the results to those for mode locking with fast saturable absorbers. We also discuss how much shorter the pulse duration can be compared to the absorber recovery time and present a simple rule. The effect of self-phase modulation is found to be qualitatively different compared to the case of a fast saturable absorber, and the effect of phase changes in the absorber is also discussed. Finally, we discuss various issues concerning soliton mode-locked lasers. Received: 20 July 2001 / Revised version: 28 September 2001 / Published online: 7 November 2001     

Linear hydrodynamics and viscoelasticity of nematic elastomers

We develop a continuum theory of linear viscoelastic response in oriented monodomain nematic elastomers. The expression for the dissipation function is analogous to the Leslie-Ericksen version of anisotropic nematic viscosity; we propose the relations between the anisotropic rubber moduli and new viscous coefficients. A new dimensionless number is introduced, which describes the relative magnitude of viscous and rubber-elastic torques. In an elastic medium with an independently mobile internal degree of freedom, the nematic director with its own relaxation dynamics, the model shows a dramatic decrease in the dynamic modulus in certain deformation geometries. The degree to which the storage modulus does not altogether drop to zero is shown to be both dependent on frequency and to be proportional to the semi-softness, the non-ideality of a nematic network. We consider the most interesting geometry for the implementation of the theory, calculating the dynamic response to an imposed simple shear and making predictions for effective moduli and (exceptionally high) loss factors. Received 16 October 2000 and Received in final form 10 December 2000     

ODMR and EPR investigations of Fe centers in KTaO3

The analysis of EPR spectra obtained from iron doped KTaO₃ crystals in the as-grown state revealed three dominant iron centers: Fe³⁺-O_I, axial Fe-centers with spinS = 3/2 and rhombic Fe³⁺. By comparison with data from literature possible assignments for the center withS = 3/2 are discussed. For the rhombic species the temperature dependence of the main parameters of the Spin- Hamiltonian was measured. The result makes it most plausible that only one rhombic iron center exists in KTaO₃, in contrast with literature. The understanding of the EPR spectra allows us to assign transitions, observed at very low magnetic fields by optically detected magnetic resonance (ODMR), to this rhombic Fe center. On this basis, the magnetic circular dichroism (MCD) of this defect could be identified using the method of tagged-MCD. This spectrum is compared to the tagged-MCD of Fe³⁺-O₁ and of axial Fe⁴⁺ centers, which may be generated metastably by optical charge transfer. Considerably different structures in the MCD spectra of both Fe³⁺ centers indicate different local surroundings and electronic states.Dedicated to O. F. Schirmer on the occasion of his 60th birthday     

A continuous-mode model of the mode locking in a pump-modulated laser

The active mode-locking process of the multimode laser with an external pump modulation is theoretically investigated in the frequency domain within the framework of the continuous-mode approximation. Intermode interaction and mode-coupling effects, including both AM and FM modulations, are naturally considered in a hierarchical equation of the mode components derived from the multimode Maxwell-Bloch equations. It is reduced to a continuous-mode equation that can be solved analytically in a stationary case, and used to discuss the spectral line shape and the phase dynamics of mode-components as a function of modulation amplitude and detuning of the modulation frequency. We predict a novel oscillation existing below the threshold of the ordinary complete mode-locking: The intensity of the total electric field yields a stable pulse train but its phase varies irregularly in time. This semi-locked state is characterized by a nonlinear chirping, an asymmetric spectrum, and drifting phases of the field mode-components.