Intermediates in the transformation of 1,2-dialkylpyrimidinium iodides in the Kost-Sagitullin rearrangement

Intermediate recyclization products were obtained in a study of the Kost-Sagitullin rearrangement of a series of 1,2-dialkylpyrimidinium iodides. The initial attack of the nucleophile leads to the formation of products of the addition of the hydroxyl group, namely, the corresponding pseudo bases. Heating one of these intermediates in ethanol or in the presence of primary amines leads to rearrangement to give a pyridone derivative. Upon heating in chloroform, the pseudo bases readily lose a water molecule and are converted to anhydro bases, namely, derivatives of 1-alkyl-1,2-dihydro-2-methylidenepyrimidine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 894–900, May, 2006.     

Efficient generation of terahertz pulses in lithium niobate crystal with integrated matching prism

We present results of experimental studies of Cherenkov-type generation of a terahertz (THz)-pulse during propagation of a femtosecond laser pulse in LiNbO₃ crystal with a Si-prism output coupler. Application of the Si-prism allows reducing essentially the damping of THz radiation because of shortening of the path of THz pulse in the nonlinear crystal. Results of experimental studies agree sufficiently well with theoretical calculations.     

New measurements of high-momentum nucleons and short-range structures in nuclei

We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate.     

Analysis of generation of terahertz radiation by nonlinear mixing of laser frequencies in GaAs crystal

Generation of terahertz (THz) radiation by nonlinear mixing of laser frequencies in GaAs crystal is considered for the case of free and guided propagation of THz waves. In the first case the strong diffraction of the THz radiation leads to the deviation from the known square-law growth of the generator power with increasing crystal length, In the second case the spatial divergence of the exciting laser beam results in the appearance of a maximum in the generated power dependence on the radius of the nonlinear waveguide. According to estimations, the optimal radius of the laser beam is 18 μm for the waveguide length of 6 mm and the maximal generated THz power is ～27 W at the laser beam power of 10 kW.     

Synthesis and some chemical transformations of novel functionalized 2-imino-2,5-dihydrofurans

Hitherto unknown functionalized 2-imino-3-(N-cyclohexylcarbamoyl)-2,5-dihydrofurans were synthesized by the reactions of tertiary α-hydroxy ketones with N-cyclohexyl(cyano-acetamide). Several reactions of thus synthesized compounds at the imino group were carried out.     

13C NMR spectra of 4-hydroxymethylpyrazoles and their chemical behavior at heating

It was established that in the ¹³C NMR spectra of 4-hydroxymethylpyrazoles the carbon atom of hydroxymethyl group of 1,3,5-trimethyl-4-hydroxymethylpyrazole is deshielded by 6.28–6.78 ppm compared to 1-methyl-4-hydroxymethyl-, 1,3-dimethyl-4-hydroxymethyl- and 1,5-dimethyl-4-hydroxymethylpyrazoles. It is assumed that this difference is related to their dissimilar behavior at heating.     

Determination of the pion charge form factor at Q2=1.60 and 2.45 (GeV/c)2

The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.     

Measurement of the charged pion electromagnetic form factor

Separated longitudinal and transverse structure functions for the reaction 1H(e,e(')pi(+))n were measured in the momentum transfer region Q2 = 0.6--1.6 (GeV/c)(2) at a value of the invariant mass W = 1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parametrization fitted to very low Q2 elastic data.     

On the possibility of application of SFCO sensors for investigation of vibration and acoustic signals from biological objects

The possibility of application of the vibrational and acoustic SFCO sensors for investigation of biomedical signals is discussed. The applicability of such sensors to register the muscle activity of vocalization apparatus of larynx and the prospect of their use for the research of the cardiovascular system are demonstrated. The physical principles and advantages of the SFCO sensors in biomedical investigations are also discussed.