Amplification of the generation of the sum-frequency signal in multilayer periodic structures at the edges of the Bragg band gap

A new property of a one-dimensional periodic structure — amplification of the sum-frequency signal arising under the simultaneous action of two laser pulses on this structure with radiation frequencies corresponding to the edges of the fixed Bragg band gap — is experimentally observed and described. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 718–721 (10 December 1999)     

Synthesis and Diels-Alder Reactions of a New Kind of Chiral Dienophiles: Cyclic Vinyl-p-tolylsulfilimines

A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group.     

Gas filter correlation instrument for air monitoring at submillimeter wavelengths

A gas filter correlation (GFC) instrument for air monitoring at submillimeter wavelengths has been developed. We used a high-power terahertz radiation source in combination with a specific gas filter cell to obtain a highly selective instrument to differentiate species present in an unknown mixture. This approach provides a new method for survey measurements in the spectrum from 100 to 1000 GHz, in which many molecular rotational lines appear. Basic operational considerations and preliminary experiments with hydrogen sulfide are described.     

Capillary electrophoresis separation of a mixture of chitin and chitosan oligosaccharides derivatized using a modified fluorophore conjugation procedure

A capillary electrophoresis (CE) method was developed for the simultaneous analysis of small chitin and chitosan oligosaccharides. For detection purposes, the oligomers were derivatized with 8-aminopyrene-1,3,6-trisulfonic acid (APTS), a well known fluorophore for oligosaccharides analysis. The detection was performed by laser-induced fluorescence (LIF) with an argon ion laser having an excitation wavelength of 488 nm and with emission monitored at 520 nm. Derivatization parameters such as reaction time and conditions were examined. Separation conditions were also varied by testing a range of buffer pHs and concentrations. The best conditions were found using an 80 mM borate buffer at pH 8.4. This CE-LIF optimized method was used for the analysis of an enzymatically produced oligo-chitosan sample composed of a complex mixture and having an average degree of polymerization of 3.7 monomer units and 80% deacetylation. The oligo-chitosan sample was treated with a chitin deacetylase-like enzyme, the products were derivatized with APTS, and then analyzed without purification. The goal was to determine whether the deacetylase-like enzyme could increase the extent of deacetylation of the oligo-chitosan sample.     

Zeros of the Whittaker function associated to Coulomb waves

The zeros in the complex z plane of the Whittaker function W_c/z,µ(z),closely related to spherical waves in the quantum-mechanicalCoulomb problem, are investigated for varying real values ofthe parameters c and µ     

Flashlamp-pumped Nd:KGW laser in MOPA configuration: comparative study of several rods

The laser performance of the Nd:KGW crystal has been studied in a master oscillator and power amplifier configuration (MOPA). Several crystals from two different producers were investigated for the oscillator and the amplifier. A maximum single-pass gain of 25 was observed in free-running and Q-switched mode. We obtained a maximum output amplified energy of 400 mJ at 30 Hz (with a pulse duration of 10 to 30 ns) with a divergence less than 3 mrad. We also studied the limitations of this configuration due to the very high gain of the Nd:KGW crystal. Received: 21 September 1998 / Revised version: 10 January 1999 / Published online: 19 May 1999     

Credibility premiums for the zero-inflated Poisson model and new hunger for bonus interpretation

The purpose of this paper is to explore and compare the credibility premiums in generalized zero-inflated count models for panel data. Predictive premiums based on quadratic loss and exponential loss are derived. It is shown that the credibility premiums of the zero-inflated model allow for more flexibility in the prediction. Indeed, the future premiums not only depend on the number of past claims, but also on the number of insured periods with at least one claim. The model also offers another way of analysing the hunger for bonus phenomenon. The accident distribution is obtained from the zero-inflated distribution used to model the claims distribution, which can in turn be used to evaluate the impact of various credibility premiums on the reported accident distribution. This way of analysing the claims data gives another point of view on the research conducted on the development of statistical models for predicting accidents. A numerical illustration supports this discussion.     

Molecular beam millimeter sidebands Fourier transform spectrometer (MB-MMSBFT)

The high resolution Fourier transform technique has been extensively applied in the centimeter range. In the past few years great progress have been made in observing molecular complexes. Most instruments operate between 2 and 26 GHz. So, very light interesting molecular species cannot be observed. The extension of the method towards the millimeter range suffers important technological shortcomings. A sidebands generation technic allowing the generation of very short pulses, all over the millimeter wave range, is described. For the first time, the experiment is performed in a resonant cavity and on a supersonic nozzle beam.     

A Tunable Difference Frequency Spectrometer for Quantitative Analysis of Heavy Molecules

A continuous-wave (cw) mid-infrared spectrometer based on laser difference frequency generation (DFG) in gallium selenide (GaSe) crystal was developed for quantitative analysis of heavy molecules. The spectrometer and its spectroscopic applications to study of molecular line parameters (such as line strength, pressure broadening coefficients) are presented. The first measurement, to our knowledge, of the self and air broadening coefficients for the ₇ 8 _2,7 8 _1,7 ethylene (C₂H₄) transition line at 958.1531 cm^–1 is reported.     

Microwave spectra of propyne and its [13C] isotopic species: Refined molecular structure of propyne

The ground state microwave spectrum of propyne is remeasured between 60 and 240 GHz with a molecular beam spectrometer. These high resolution measurements allows us to accurately determine the rotational constant and all the determinable quartic and sextic centrifugal distortion constants: B = 8 545 877.12 (12) kHz; D_J = 2.9423 (13) kHz; D_JK = 163.423 (20) kHz; H_J = 0.0097 (40) Hz; H_JK = 0.935 (136) Hz; and H_KJ = 5.23 (27) Hz (95% confidence limits are shown in parentheses). The spectra of the [¹³C]isotopic species are also reinvestigated between 30 and 240 GHz with a video spectrometer. With the accurate rotational constants we derive from those spectra a new r₈ structure is calculated for the CC bond lengths: $\text{r}{}_8\text{(}\text{CC}\text{) = 1.4586 (2)}\text{A}\text{?}$ and $\text{r}{}_8\text{(}\text{CC}\text{) = 1.2066 (2)}\text{A}\text{?}$.