Synthesis of seven-membered carbocyclic rings via a microwave-assisted tandem oxyanionic 5-exo dig cyclization-claisen rearrangement process

Appropriately substituted 1-alkenyl-4-pentyn-1-ol systems, readily prepared from simple starting materials, serve as useful precursors to a number of substituted cyclohept-4-enone derivatives via a microwave-assisted tandem oxyanionic 5-exo cyclization/Claisen rearrangement sequence. The reactions involving terminally substituted 4-pentyn-1-ols were found to be highly stereoselective, with the alpha and beta groups in the final product showing a strong preference for the trans orientation.     

Focus in production: tonal shape, intensity and word order

The effect of word order and prosodic focus on the tonal shape and intensity in the production of prosody was studied. The results show that the production of focus in Finnish follows a global pattern with regard to tonal features. The relative pitch height difference between contrasted words is the most important pitch-related factor in signaling narrow prosodic focus. Narrow focus is not localized to prosodically emphasized words only but relates to the utterance as a whole. It was also found that syntactic structure with respect to both intensity and tonal structure modulated relative prosodic prominence of individual words.     

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.     

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.     

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.     

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.     

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.     

Tandem anionic 5-Exo dig cyclization/Claisen rearrangement as an efficient route to fused polycyclic ring systems

The scope and limitations of a tandem 5-exo dig cyclization/Claisen rearrangement sequence involving appropriately substituted 4-alkyn-1-ols as an efficient "one-pot" route to fused tricyclic ring systems is described. The reaction rates were found to be strongly dependent on the nature of the terminal substitutent of the triple bond. In some cases the entire sequence was found to proceed in good yield at temperatures as low as 115 degrees C.     

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).