Galactose oxidase immobilized on silica in an analytical determination of galactose-containing carbohydrates.

Galactose oxidase from Fusarium graminearum IMV-1060 adsorbed on, and covalently bound to, silica carriers has been used for analytical determinations of D-galactose and galactose-containing sugars. Using a flowing oxygen electrode of the Clark-type, sensor system for enzymatic analysis of water solutions of galactose-containing carbohydrates was made. Measurements were taken both in the pulse and continuous modes of a substrate flowing through a column with an immobilized biocatalyst. The linear measurement ranges for galactose-containing carbohydrates concentrations were determined.     

Photochemistry of artificial photosynthetic reaction centers in liquid crystals probed by multifrequency EPR (9.5 and 95 GHz)

Photoinduced charge separation and recombination in a carotenoid-porphyrin-fullerene triad C-P-C(60)(1) have been followed by multifrequency time-resolved electron paramagnetic resonance (TREPR) at intermediate magnetic field and microwave frequency (X-band) and high field and frequency (W-band). The electron-transfer process has been characterized in the different phases of two uniaxial liquid crystals (E-7 and ZLI-1167). The triad undergoes photoinduced electron transfer, with the generation of a long-lived charge-separated state, and charge recombination to the triplet state, localized in the carotene moiety, mimicking different aspects of the photosynthetic electron-transfer process. Both the photoinduced spin-correlated radical pair and the spin-polarized recombination triplet are observed starting from the crystalline up to the isotropic phase of the liquid crystals. The W-band TREPR radical pair spectrum has allowed unambiguous assignment of the spin-correlated radical pair spectrum to the charge-separated state C(.+)-P-C(60)(.-). The magnetic interaction parameters have been evaluated by simulation of the spin-polarized radical pair spectrum and the spin-selective recombination rates have been derived from the time dependence of the spectrum. The weak exchange interaction parameter (J = +0.5 +/- 0.2 G) provides a direct measure of the dominant electronic coupling matrix element V between the C(.+)-P-C(60)(.-) radical pair state and the recombination triplet state (3)C-P-C(60). The kinetic parameters have been analyzed in terms of the effect of the liquid crystal medium on the electron-transfer process. Effects of orientation of the molecular triad in the liquid crystal are evidenced by simulations of the carotenoid triplet state EPR spectra at different orientations of the external magnetic field with respect to the director of the mesophase. The order parameter (S = 0.5 +/- 0.05) has been evaluated.     

Lossless Medical Image Compression by Using Difference Transform

This paper introduces a new method of compressing digital images by using the Difference Transform applied in medical imaging. The Difference Transform algorithm performs the decorrelation process of image data, and in this way improves the encoding process, achieving a file with a smaller size than the original. The proposed method proves to be competitive and in many cases better than the standards used for medical images such as TIFF or PNG. In addition, the Difference Transform can replace other transforms like Cosine or Wavelet.     

Shallow donor states induced by in-diffused Cu in ZnO: a combined HREELS and hybrid DFT study

A combined experimental and first principles study of Cu defects in bulk ZnO is presented. Cu particles are epitaxially deposited on the polar O-ZnO(0001) surface at room temperature. Upon heating, a broadening of the quasielastic peak in high resolution electron energy loss spectra is observed, corresponding to an electronic doping effect of Cu atoms in bulk ZnO with an ionization energy of 88 meV. Cu impurities in ZnO, although commonly acting as acceptors, are presently observed to induce shallow donor states. We assign these to interstitial Cu species on the basis of a hybrid density functional study.     

EPR-detected photoinduced electron transfer in three structurally related molecular triads

A comparative electron paramagnetic resonance (EPR) study has been performed on a series of structurally related molecular triads which undergo photoinduced electron transfer and differ one from the other in terms of the acceptor or donor moieties. The molecular triads, C-P-C₆₀, TTF-P-C₆₀ and C-P-P_F, share the same free-base, tetraarylporphyrin (P) as the primary electron donor, which after light excitation initiates the electron transfer process, but differ either in terms of the electron acceptor (fullerene derivative, C₆₀, versus fluorinated free-base porphyrin, P_F), or in terms of the final electron donor (carotenoid polyene, C, versus tetrathiafulvalene, TTF). All these molecular triads can be considered artificial photosynthetic reaction centers in their ability to mimic several key properties of the reaction center primary photochemistry. Photoinduced charge separation and recombination have been followed by time-resolved EPR in a glass of 2-methyltetrahydrofuran and in the nematic phase of the uniaxial liquid crystal E-7. All the triads undergo photoinduced electron transfer, with the generation of charge-separated states in both the low-dielectric environment of the 2-methyl-tetrahydrofuran glass and in anisotropic E-7 medium. Different photochemical pathways have been recognized depending on the specific donor and acceptor moieties constituting the molecular triads. In the presence of the tetrathiafulvalene electron donor singlet- and triplet-initiated electron transfer routes are concurrently active. Recombination to the low-lying carotenoid triplet state occurs in the carotene-based triads, while singlet recombination is the only active route for the TTF-P-C₆₀ triad, where a low-lying triplet state is lacking. Long-lived charge separation has been observed in the case of TTF-P-C₆₀: about 8 μs for the singlet-born radical pair in the glassy isotropic matrix and about 7 μs for the triplet-born radical pair in the nematic phase of E-7. For all the molecular triads, a weak exchange interaction (J?1 G) between the electrons in the final spin-correlated radical pair has been evaluated by simulation of the EPR spectra, providing evidence for superexchange electronic interactions mediated by the tetraarylporphyrin bridge.     

Passively Q-switched Tm:YLF laser

Stable passive Q-switching of a Tm: LiYF4 laser is obtained using polycrystalline Cr2+: ZnS as a saturable absorber. The achieved maximum pulse energy of 0.9 mJ and peak power of 65 kW for a pulse duration of ～14 ns represent substantial improvement and highest values for a passively Q-switched diode-pumped Tm laser operating at ～1.9 μm.     

Line Intensity of R(0) and R(3) of the CH4 2ν3 Band from Diode Laser Spectroscopy

We have determined the spectroscopic parameters that are necessary to describe accurately the R(0) line profile of the CH₄ 2ν₃ band from about 1 Torr to a few hundred Torr of pure CH₄. The intensities determined at each pressure are in overall agreement to better than 0.7%. The R(3) manifold of the same band has also been investigated. Relative positions and absolute intensities of the three transitions composing the triplet have been determined. The intensity distribution inside the triplet is in fair agreement with recent theoretical predictions.     

Succession of one-soliton pulses in the zero-dispersion region of silica optical fibres: The role of the phase difference between the adjacent pulses

Some features of the propagation of one-soliton successions in the third order dispersion region are presented for the case where the phase difference between adjacent pulses is rads. We show that this considerably improves the stability of the pulses in the zero-dispersion region. Walk-off can be diminished by increasing the number of pulses in the succession. These features may help optimize the bandwidth of non-linear fibre communication links.     

Measurement and interpretation of the 1-0 band of 14N16O at 1900 cm−1

The wavenumbers of the vibration rotation band lines of ¹⁴N¹⁶O are reported for the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ subbands of the 1-0 transition in the infrared. The full set of spectroscopic constants for this band has been determined by direct approach using the analysis of Zare, Schmeltekopf, Harrop, and Albritton. In addition to the band origin ν₀ and the B, D, H constants for the lower and upper vibrational levels, the following spin-orbit coupling constants have been derived: $\text{A}\text{?}{}_0\text{= 123.02772 ± 0.00011}$ and $\text{A}\text{?}{}_1\text{= 122.78248 ± 0.00011}$ (in cm^?1). Apparent centrifugal corrections to these constants have been determined and the values obtained for them are $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>0</mtext>}}\text{= (0.347573 ± 0.00051) × 10}{}^{\mathrm{?3}}$ and $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>1</mtext>}}\text{= (0.337135 ± 0.00050) × 10}{}^{\mathrm{?3}}\text{cm}{}^{\mathrm{?1}}$. Λ-Type doubling constants evaluated by using both grating and tunable laser data are also reported.     

Calculation of collisional and radiative transition probabilities between excited argon levels

Average radiative transition probabilities for argon atoms have been calculated for transitions between 24 levels in two groups characterized by the atomic core terms ²P_1/2 and ²P_3/2 by using the method of Bates and Damgaard. The results are compared with data in the NBS tables (Wiese et al.) and with those of Katsonis and Drawin. We find satisfactory agreement for the order of magnitude, even for transitions between lower lying levels. Parameters, which appear in Drawin's semiempirical cross-section expressions for electronic excitation of optically allowed and parity-forbidden transitions, are determined with the multipole expansion method proposed by Sobel'man for transitions between the specified levels. Most of these are easily obtained, but the method must be improved for transitions between levels having the same azimuthal quantum number because the summation over the constituent terms does not converge.