Optical coherence tomography using a frequency-tunable optical source

We have developed a simple, wide-optical-bandwidth, high-resolution system for performing rapid optical frequency domain reflectometry measurements and applied it to multidimensional tomographic imaging. The source is a grating-tuned external cavity semiconductor laser with a tuning capability of 25 nm in 100 ms. We discuss system performance and show a two-dimensional optical coherence tomography image of a thin glass sandwich structure as a preliminary demonstration of the systems depth and resolution capabilities.     

BaIr0,67Be0,33O3: Eine stabilisierte kubische Form von BaIrO3

Inhaltsübersicht. Es ist gelungen, ein durch BeO stabilisiertes Bariumoxoiridat der Zusammensetzung BaIr_0,67Be_0,33O₃ in der Kristallform eines kubischen Perowskits mit kleiner Elementarzelle erstmals darzustellen. Raumgruppe O¹_h–Pm3m, a = 4,1009 Å, Z = 1. Ir⁵⁺ und Be² + besetzen die Oktaederposition des Perowskits statistisch. BaIr_0,67Be_0,33O₃: A Stabilized Cubic Form of BaIrO₃ For the first time it was possible to prepare a new barium-oxoiridate of the formula BaIr_0,67Be_0,33O₃, stabilized by BeO. It crystallizes in a small cubic unit cell of the perovskite type. Space group O¹_h–Pm3m; a = 4.1009 Å; Z = 1. Ir⁵⁺ and Be²⁺ occupy the octahedra positions of the perovskite structure statistically.     

Self-assembled diisocyanide monolayer films on gold and palladium

Self-assembled monolayers (SAMs) of the aromatic diisocyanides, 1,4-phenylenediisocyanide, 2,3,5,6-tetramethyl-1,4-phenylenediisocyanide, 4,4'-biphenyldiisocyanide, 3,3',5,5'-tetramethyl-4,4'-biphenyldiisocyanide, and 4,4' '-p-terphenyldiisocyanide, were prepared on gold and palladium surfaces. The SAMs were characterized by ellipsometry, polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and grazing-angle attenuated total reflectance infrared spectroscopy (GATR). Based on the position of the metal-coordinated isocyanide stretching band, the SAMs on gold were found to bind in the terminal (eta(1)) geometry, while the SAMs on palladium prefer a different geometry which is possibly a triply bridging (mu(3)-eta(1)) geometry. A side-reaction of the unbound isocyanide in the SAM was identified as oxidation to an isocyanate group.     

Detection of vacancy clustering by combined PAC and lattice location measurements

The formation of impurity-vacancy agglomerates starting with the trapping of monovacancies was studied using a combination of three complementary techniques applied to the system InCu: Perturbed -angular correlation, ion channeling and channeling of conversion electrons. This results in an almost complete picture of the first stage of vacancy agglomeration at In impurities in Cu.This work was supported by the Bundesminister für Forschung und Technologie.     

The electric field gradient for Gd in gadolinium metal

We have examined the temperture dependence of the efg for GdGd above the Curie point. Using anI =10⁺ isomer in¹⁴⁴Gd as a probe nucleus, we find a weakT ^3/2 dependence withB=(1.5±0.4) 10^–5 K^–3/2. The absolute value of the efg at 332 K was measured by Coulomb excitation of 2⁺ states in^{156, 158, 160}Gd, yielding |eq(332 K)|=(3.43±0.14) 10¹⁷ V/cm². A possible small deviation from theT ^3/2 temperature dependence of the efg for ferromagnetic Gd is discussed.     

Molecular recognition and self-assembled polymer films for vapor phase detection of explosives

Selective and sensitive polymer films for detecting explosives were studied and fabricated onto surface acoustic wave (SAW) devices. Polymers and molecular host species were self-assembled on functionalized silicon oxide surfaces through a catalytic hydrosilylation reaction. The covalently attached thin polymer films are stable, continuous and uniform with film thickness ranging from 15 to 30 nm. The microsensors coated with the polymer films show high sensitivity towards 2,4-dinitrotoluene (DNT) and o-nitrotoluene, an explosive simulant. Sensor responses to possible common interferents in land mine detection were studied and the sensor sensitivities to them were found to be much lower than that to DNT and explosives simulants. Response patterns for interferants and o-nitrotoluene were constructed and the sensors coated with functionalized cyclodextrins were able to detect 2,4-DNT and 2,4,6-trinitrotoluene (TNT) under ambient laboratory conditions.     

Automated synthesis of a protected N-linked glycoprotein core pentasaccharide

[structure: see text] Described is the first automated solid-phase synthesis of the core N-linked pentasaccharide, common to all N-linked glycoproteins via stepwise assembly from mono- and disaccharide building blocks. The challenging beta-mannosidic linkage was incorporated by the inclusion of a disaccharide trichloroacetimidate. This automated synthesis provides rapid access to an oligosaccharide common to an entire class of glycoconjugates.     

High-resolution spectra of the 1(1,1) ← 0(0,0) rotational transition of water in argon and krypton matrices

The high-resolution spectra of H₂¹⁶O, H₂¹⁸O, HD¹⁶O, HD¹⁸O, D₂¹⁶O, and D₂¹⁸O isolated in argon and krypton matrices are reported in the 10–60 cm^?1 region. The high resolution is obtained by observing very dilute mixtures of water in the rare gases. No discrete absorbances attributable to pure argon or krypton are found in this region. In all cases the relative gas—matrix shifts of the isotopimers are consistent with the rotation—translation coupling model. The linewidths are found to correlate with rotation—translation coupling. The integrated intensity of the 1(1,1) — 0(0,0) transition of HDO exhibits a temperature dependence which does not deviate significantly from that expected from a Boltzmann distribution in rigid rotor energy levels.