Real-time monitoring of all-optical poling by two-beam second-harmonic generation

We demonstrate a simple method for monitoring all-optical poling in real time. The poling pattern created by the writing beam at the fundamental frequency and the seed beam at the second-harmonic frequency is reconstructed by two-beam second-harmonic generation because of the writing beam and an additional probe beam at the fundamental frequency. When the probe beam is sufficiently weak, it does not distort the poling process. The method provides a significantly stronger signal than monitoring based on a probe beam alone.     

Advantages of polarized two-beam second-harmonic generation in precise characterization of thin films

Polarized second-harmonic generation using two fundamental beams, instead of one, offers significant advantages for characterizing nonlinear optical thin films. The technique is more precise and allows the internal consistency of the results to be verified. The superiority of the two-beam arrangement over the traditional single-beam arrangement is demonstrated by determining the susceptibility tensors of Langmuir-Blodgett films. We show that, for a well-understood reference sample, the results obtained using two fundamental beams agree qualitatively with those obtained with a single fundamental beam, but are more precise. In a more complicated situation, however, the single-beam technique appears to work well but yields results that are, in fact, incorrect. The two-beam technique, instead, yields clearly inconsistent results, thereby highlighting systematic errors in the experimental arrangement or in the theoretical model used to interpret the results.     

Quantum circuits for general multiqubit gates

We consider a generic elementary gate sequence which is needed to implement a general quantum gate acting on n qubits-a unitary transformation with 4(n) degrees of freedom. For synthesizing the gate sequence, a method based on the so-called cosine-sine matrix decomposition is presented. The result is optimal in the number of elementary one-qubit gates, 4(n), and scales more favorably than the previously reported decompositions requiring 4(n)-2(n+1) controlled NOT gates.     

CP asymmetry in B-->phiK(S) decays in left-right models and its implications for Bs decays

In left-right models the gluonic penguin contribution to b-->ss;s transition is enhanced by m(t)/m(b) due to the presence of (V+A) currents and by large values of loop functions. Together those effects may overcome the suppression due to the small left-right mixing angle xi less, similar 0.013. Two independent new phases in the B-->phiK(S) decay amplitude appearing in a large class of left-right models can modify the time-dependent CP asymmetry in this decay mode by O(1) and explain the recent BABAR and Belle CP asymmetry measurements in this channel. This scenario implies observable deviations from the standard model also in B(s) decays which could be measured at Tevatron and LHC.     

Nonlinear optical technique for precise retardation measurements

We present a highly sensitive nonlinear optical technique to measure optical retardation. The technique is based on second-harmonic generation from thin films using two beams at the fundamental frequency. The sensitive polarization dependence of the process allows measuring optical retardation very precisely. The technique relies on fundamental symmetry principles and does therefore not require complicated experimental arrangement or data analysis. The technique was demonstrated by determining the retardation of a nominal half-wave plate to a precision and repeatability better than lambda/10(4).     

Determination of second-order susceptibility components of thin films by two-beam second-harmonic generation

We measure the susceptibility components of a poled polymer film by second-harmonic generation with two beams at the fundamental frequency. The technique allows the consistency of experimental data and the validity of the theoretical model used to analyze the results to be addressed. Our results are in agreement with the expected values, provided that the linear optical properties of the sample are properly included.     

Thin trading and estimation of systematic risk: An application of an error-correction model

Financial economics literature indicates that estimates for securities' systematic risk, i.e. the beta coefficients, are highly affected by infrequent trading. This is an especially serious problem in small security markets. In this study, the applicability of an error-correction model is investigated for modeling the risk behavior of thinly traded securities. The empirical results from a small stock market, i.e. the Helsinki Stock Exchange, indicate the estimated error-correction term to be highly dependent on the underlying trading frequency of the stock, while the direct effect is dependent merely on the market value of the firm. The model thus appears to produce useful information about the risk characteristics of thinly traded stocks.     

Negative gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles at 0.02 Tesla

Gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles were evaluated in vitro and in rabbits at 0.02 Tesla. Test tubes containing 0.01–1.0 mg particles/ml were imaged in an oil or water bath in order to demonstrate the concentration-dependent signal void and image distortion in vitro at several pulse sequences. The lowest concentration of particles tested clearly decreased the signal intensity. Image distortion was observed when the concentration exceeded 0.07 mg/ml and was more pronounced on the T₂-weighted images. The in vitro T₂ relaxation time decreased from 122 ms to 56 ms with an increase in the particle concentration from 0.01 to 0.06 mg/ml. A loss of the GI-tract signal was observed in rabbits after the administration of 1 mg particles/kg, given as a 0.03 mg/ml suspension. At a dose of 20 mg/kg (0.6 mg/ml suspension) significant image distortion was observed.     

Synthesis and Luminescence of Novel EuIII Complexing Agents and Labels with 4-(Phenylethynyl)pyridine Subunits

The synthesis of novel 4-(phenylethynyl)pyridine subunits containing H₂O-soluble complexing agents and their luminescence with Eu^III ions are reported. Ligands with high luminescence intensities as well as quantum yields were obtained. Also the prepared labeling reagents as antibody conjugates gave the highest quantum and luminescence yields reported for H₂O-soluble Eu^III labels.