Two-photon four-level hologram recording in poly-(alkyl-α-cyanoacrylates)

We have investigated the suitability of poly-(alkyl--cyanoacrylates) (p-(alkyl-CAc)) for two-photon four-level holographic recording. It is shown that these materials follow indeed a two-photon four-level mechanism with the second absorption step in the near infrared. Light induces the polymerization of residual monomer in the matrix. The reaction is associated with positive density changes. The sensitivity ofp-(alkyl-CAc) depends strongly on composition and age of the sample. Maximum sensitivities achieved are comparable to the so far best-known two-photon four-level ir-sensitive systems.     

Two-photon absorption in quadrupolar pi-conjugated molecules: influence of the nature of the conjugated bridge and the donor-acceptor separation

Quadrupolar-type substitution of pi-conjugated chromophores with donor and acceptor groups has been shown to increase their two-photon absorption (TPA) response by up to two orders of magnitude. Here, we apply highly correlated quantum-chemical calculations to evaluate the impact of the nature of conjugated bridge and the charge-transfer distance on that enhancement. We compare chromophores with phenylenevinylene-, thienylenevinylene-, polyene-, and indenofluorene-type backbones substituted by dimethylamino and cyano groups. In all compounds, we find a strongly TPA-active A(g) state (either 2A(g) or 3A(g)) in the low-energy region, as well as a higher lying TPA-active state (mA(g)) at close to twice the energy of the lowest lying one-photon allowed state; the smaller energy detuning in the mA(g) states results in very large TPA cross sections delta. We also investigate the influence of the degree of ground-state polarization on TPA. Independent of the nature of the backbone and the donor-acceptor separation, delta displays the same qualitative evolution with a maximum before the cyanine-like limit; the highest TPA cross sections are calculated for distirylbenzene- and polyene-based systems.     

X-ray structure and variable temperature NMR spectra of [meso-triarylcorrolato]copper(III)

The diamagnetic square planar d(8) complexes [meso-arylcorrolato]copper(III) become paramagnetic upon warming, indicative of the equilibrium between the [corrolato]copper(III) and the [corrolato](+)* copper(II) forms of the complex. [meso-Triphenylcorrolato]copper(III) was structurally characterized and found to be saddled.     

Separation and detection of oxidation products of fluorodeoxyglucose and glucose by high-performance liquid chromatography-electrospray ionisation mass spectrometry

2-Deoxy-2-[18F]fluoro-D-glucose ([18F] FDG), the most popular positron emitting radiopharmaceutical, may oxidise by autoradiolysis in aqueous solution. The aim of this work was to use LC-MS for determination of the oxidation products of fluorodeoxyglucose and glucose (Glc) obtained by oxidation with Fenton's reagent. Asahipak NH2P-50 polyamide silica column and acetonitrile-0.025% aqueous ammonium formate (80:20 (v/v)) eluent were utilised with an Agilent 1100 HPLC-MS instrument. Ten major oxidation products of FDG and Glc were separated and identified by mass spectrometry: 2-fluorogluconic acid, 2-fluoroglucuronic acid, 2-oxoerythronic acid, arabinose, arabonic acid, araburonic acid, erythrose, erythrulose, gluconic acid, and glucuronic acid. The most intensive electrospray ionisation signals were found in the negative ion spectra and were due to HCOO- adducts, the other acids being in their lactone forms.     

Filter Diagonalization with Finite Fourier Transform Eigenfunctions

Below, we briefly report on the progress in the development of the Filter Diagonalization technique when filtering is carried out with the aid of Finite Fourier Transform (FFT) eigenfunctions. During recent years interest in these functions, also known as ‘prolates’, or ‘slepians’, has increased among scientists doing research in the field of signal processing. The main explanation to this follows from the set of very special extremal and orthogonality properties exibited by the FFT eigenfunctions. Recent results of Walter and Shen on sampling with prolate spheroidal functions will necessary produce a new wave of interest. In the presented, Filter diagonalization machinery, we show that the sampling formula of Walter and Shen simplifies essentially the computation of matrix elements as certain 2D–integrals involving FFT eigenfunctions.     

J and term dependences in the isotope shift of Eu I

High-resolution laser atomic beam spectroscopy has been applied to studyJ and term dependences in the isotope shift of the levels 4f ⁷5d6s a ¹⁰ D _J ,a ⁸ D _J of Eu I. A parametric analysis of the isotope shift has been performed. TheJ dependence is interpreted through two term-dependent parametersz _5d , and the term dependence through one parameterΔT:z _5d (a ¹⁰ D)=44.1 (2.6) MHz,z _5d (a ⁸ D)=55.9 (2.3) MHz,ΔT=408.5 (3.2) MHz. Ab initio Hartree-Fock and Dirac-Fock calculations have been made to interpret these parameters. Within the accuracy of the calculations the parameters can be attributed to field shift effects.     

Atmospheric pressure electrospray ionization mass spectra of glucose and 2-fluorodeoxyglucose for quantitative analysis of 2-fluorodeoxyglucose by high-performance liquid chromatography

2-Fluoro-2-deoxy-D-glucose (FDG) labeled by fluorine-18 is the most widely used radiopharmaceutical for positron emission tomography (PET). For high-performance liquid chromatography (HPLC)/MS assay and quality control, the mass spectra of FDG and glucose (Glc) in organic + water solutions were studied by flow injection analysis (FIA) and in a chromatographic eluate. In acetonitrile (MeCN) + 0.025% ammonium formate (NH(4)HCO(2)) solvent (80 : 20), electrospray ionisation (ESI) of glucose-FDG provides M.NH(4)(+) and 2M.Na(+) (M = Glc or FDG) as the most intense positive ions. Formation of the latter ions and also of M.MeCN.Na(+) and 2MeCN. Na(+) is typical of the presence of NaCl in the ESI inlet. The positive ions include heavier ions corresponding to the impurities separated by HPLC and also to the cross-ring fragmentation of complexes (2FDG. aMeCNX)L, where a = 0 or 1, L is either Na(+) or NH(4)(+) and X is a fragmented pyranose or anhydropyranose residue. The second most abundant Glc negative ion is m/z = 359 which was interpreted as (2GlcH(+))(). The negative-ion spectrum of FDG has dominating lines due to FDG.HCO(2)() ions at m/z 227 and also (2FDGH(+))() at m/z 363. The m/z 363 signal is suppressed in the presence of NaCl at a molar ratio of 4 : 1 to NH(4)HCO(2), while the ions at m/z 217 and 219, i.e. FDG.Cl(), become three times more intense than FDG.HCO(2)(). The latter ion appears to be most suitable as an analytical signal for chemical analysis of FDG at m/z 226 and 227. Limits of FDG quantitation (LOQ) of 19 ng and 21 ng were found for the 200(+) and 227() ion signals, respectively, and are wholly adequate for verification of total FDG content in radiopharmaceuticals.     

Analysis of functional groups on the surface of plasma-treated carbon nanofibers

Plasma chemically modified carbon nanofibers were characterized by X-ray photoelectron spectroscopy with regard to the content of carbon, oxygen, and nitrogen and the contribution of carboxylic groups or ester, carbonyl and hydroxylic groups or ether on the surface. Unfortunately, X-ray photoelectron spectroscopy only provides an average value of the first 10 to 15 molecular layers. For comparison, depth profiles were measured and wet chemical methods were applied to estimate the thickness of the functionalized layer and the distribution of oxygen-containing functional groups within the near-surface layers. The results indicate that the fiber surface is covered by a monomolecular oxygen-containing layer and that plasma treatment allows a complete oxygen functionalization of the uppermost surface layer. The best conditions for plasma treatment found within the set of parameters applied to generate complete functionalization are: plasma gas O(2)/Ar ratio 1:1, gas pressure 1-1.5 hPa, plasma power 80 W, treatment time >or= 5 min. Additionally, three quick and easy methods are presented to estimate the efficiency of plasma treatment with regard to surface functionalization: pyrolysis, contact angle measurements, and light permeability measurements of aqueous carbon nanofiber suspensions.     

Comparison of electric light scattering and birefringence for polydisperse suspensions

Summary A review is made of the existing theoretical expressions, describing the change of the scattered light intensity and the birefringence by application of an electrical field to a colloid solution.Furthermore, the geometrical functions for disc-shaped particles are calculated in this article for the case of electric light scattering and are. presented graphically. In addition, expressions are derived for the average value of the electrical polarizability () for the case of polydisperse solutions.

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Zusammenfassung Es wird ein überblick über die existierenden theoretischen Beziehungen gegeben, die die Änderung der Intensität des Streulichtes und der Doppelbrechung von Kolloidsuspensionen im elektrischen Feld beschreiben.Weiterhin sind die geometrischen Funktionen für scheibchenförmige Teilchen in dieser Arbeit für den Fall der elektrooptischen Lichtstreuung berechnet und grafisch dargestellt. Außerdem werden Beziehungen für den Mittelwert der elektrischen Polarisierbarkeit () für den Fall polydisperser Suspensionen abgeleitet.

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With 1 figure and 1 table     

Synthesis,vibrational, and conformational properties of novel polyazadioxime chain molecules

Novel large polyazadioxime molecules 4,5,8,9-tetraaza-3,6,7,10-tetramethyl -3,5,7,9-dodecatetraene-2, 11-dione-2, 11-dioxime (H₂doxN₄) and 4,5,8,9,12, 13-hexaaza-3,6,7,10,11,14-hexamethyl-3, 5,7,9,11,13-hexadecahexane-2,15-dione-2, 15-dioxime (H₂doxN₆) were synthesized. The molecular geometries of these molecules as well as smaller dioxime molecules, H₂dox and H₂doxN₂ were optimized by using modified intermediate neglect of differential overlap (MNDO) calculations. The optimized conformations for all the molecules under study are close to the all-E, all-s trans conformation of C_2h symmetry group. However, the energy barriers of internal rotation around the N-N single bonds were found to be low. Therefore some distortions of the polyazabackbone through internal rotation the N-N bonds have been evidenced. By infrared and Raman spectroscopies in the solid state as well as in solution. From the MNDO calculations and vibrational spectroscopy, the polyaza chain molecules under study appear as a poorly conjugated system and can be represented as a sequence of single and double bond alternation.