Contribution of multi-nuclear solid state NMR to the characterization of the <Emphasis Type="Italic">Thalassiosira pseudonana</Emphasis> diatom cell wall

A major issue in the study of biosilicification processes is the harsh chemical conditions required for silica dissolution, which often lead to denaturation of the associated bio-organic matter. In order to demonstrate the potential of solid state NMR for investigating silicified materials of natural origin, this technique was applied to isotopically enriched Thalassiosira pseudonana diatom cells. ²⁹Si, ¹H,³¹P, ¹³C and ¹⁵N solid state NMR studies were performed on whole cells, SDS-extracted and H₂O₂-cleaned silica shells. Cross-polarization techniques were useful for identifying the presence of mobile and rigid molecules, allowing loosely bound and silica-entrapped species to be discriminated. Successive cleaning procedures efficiently eliminated weakly associated organic matter. The H₂O₂-cleaned silica shell still contained carbohydrates (mainly chitin) and proteins as well as lipids. This suggests that the role of lipids in diatom shell formation may have been underestimated so far, demonstrating the potential of solid state NMR for studying composite biomaterials. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Hankel Operators on Bergman Spaces of Tube Domains over Symmetric Cones

We present here some criteria for Schatten-Von Neumann class membership for the small Hankel operator on Bergman space A ²(T _Ω), when T _Ω is the tube over the symmetric cone Ω. The author would like to thank professor Aline Bonami for helpful advices.     

Pd-catalyzed domino carbonylative-decarboxylative allylation: an easy and selective monoallylation of ketones

In the presence of an allyl alcohol, α-chloroacetophenones undergo an allyloxycarbonylation reaction followed by in situ decarboxylative allylation to selectively afford the corresponding monoallylated ketones via a Pd-catalyzed domino sequence. The scope of the reaction was extended to substituted α-chloroacetophenones as well as various allyl alcohols.     

Multifunctional nanoprobes for pathogen-selective capture and detection

The synthesis of magnetic and fluorescent particles is described. The particles are biofunctionalized by binding pathogen-specific proteins to the particles via interactions between His-tags of proteins and zinc of the quantum dots. Detection of Salmonella and Staphylococcus aureus (S. aureus) by these particles is demonstrated.     

Structural,electrical and optical properties of in-situ phosphorous-doped Ge layers

We have studied the impact of temperature and pressure on the structural and electronic properties of Ge:P layers grown with GeH₄+PH₃ on thick Ge buffers, themselves on Si(0 0 1). The maximum phosphorous atomic concentration [P] exponentially decreased as the growth temperature increased, irrespective of pressure (20 Torr, 100 Torr or 250 Torr). The highest values were however achieved at 100 Torr (3.6×10²⁰ cm^?3 at 400 °C, 2.5×10¹⁹ cm^?3 at 600 °C and 10¹⁹ cm^?3 at 750 °C). P atomic depth profiles, “box-like” at 400 °C, became trapezoidal at 600 °C and 750 °C, most likely because of surface segregation. The increase at 100 Torr of [P] with the PH₃ mass-flow, almost linear at 400 °C, saturated quite rapidly at much lower values at 600 °C and 750 °C. Adding PH₃ had however almost no impact on the Ge growth rate (be it at 400 °C or 750 °C). A growth temperature of 400 °C yielded Ge:P layers tensily-strained on the Ge buffers underneath, with a very high concentration of substitutional P atoms (5.4×10²⁰ cm^?3). Such layers were however rough and of rather low crystalline quality in X-ray Diffraction. Ge:P layers grown at 600 °C and 750 °C had the same lattice parameter and smooth surface morphology as the Ge:B buffers underneath, most likely because of lower P atomic concentrations (2.5×10¹⁹ cm^?3 and 10¹⁹ cm^?3, respectively). Four point probe measurements showed that almost all P atoms were electrically active at 600 °C and 750 °C (1/4th at 400 °C). Finally, room temperature photoluminescence measurements confirmed that high temperature Ge:P layers were of high optical quality, with a direct bandgap peak either slightly less intense (750 °C) or more intense (600 °C) than similar thickness intrinsic Ge layers. In contrast, highly phosphorous-doped Ge layers grown at 400 °C were of poor optical quality, in line with structural and electrical results.     

Optical switching and contrast enhancement in intense laser systems by cascaded optical parametric amplification

Optical parametric chirped-pulse amplification (OPCPA) can be used to improve the prepulse contrast in chirped-pulse amplification systems by amplifying the main pulse with a total saturated OPCPA gain, while not affecting the preceding prepulses of the seed oscillator mode-locked pulse train. We show that a simple modification of a multistage OPCPA system into a cascaded optical parametric amplifier (COPA) results in an optical switch and extreme contrast enhancement that can completely eliminate the preceding and trailing oscillator pulses. Instrument-limited measurement of a prepulse contrast ratio of 1.4 x 10(11) is demonstrated from COPA at a 30 mJ level.     

Synthesis, structural characterization, experimental, and computational spectrophotometric studies of 8-quinolinyloxymethyphosphonate compounds

The synthesis of diethyl-8-quinolinyloxymethylphosphonate 1 and 8-quinolinyloxymethylphosphonic acid hemihydroiodide 2 is reported along with their spectroscopic and analytical characteristics (NMR, infrared, mass spectra, and elemental analysis). The single-crystal X-ray structure of 2 is described. Solutions of the disodium phosphonate 3, from 2 and sodium hydroxide, were prepared and used in situ. The coordination complex between 1 and zinc chloride 4 is described according to its single-crystal X-ray structure. The spectrophotometric features (absorption and emission) of 1, 2, 3, and 4 are reported along with the fluorescence response and affinity of 3 to some metal cations. The origin of the fluorescence from compounds 1 and 4 is investigated using density functional theory and the oscillator strength for each transition is computed. Two deactivation pathways, one of which is only weakly emissive, are identified in 4. In contrast to 4, which is only moderately more emissive than 1 a strong zinc-activated fluorescence response is observed from aqueous solutions of 3.     

Decoration of TiO2 nanotube layers with WO3 nanocrystals for high-electrochromic activity

We report a simple approach to decorate ordered TiO₂ nanotube (TiNT) layers with tungsten trioxide nanocrystallites by the controlled hydrolysis of a WCl₆ precursor. These WO₃ nanocrystallites, when formed, are amorphous, but can be annealed to a monoclinic crystal structure. The WO₃ crystallites on the TiO₂ nanotube skeleton are electrochemically active, and hence ion insertion reactions are possible. As a result, the decorated nanotube layers show remarkable enhancement of the electrochromic properties. In particular, a significantly lower threshold voltage and an increased electrochromic contrast can be achieved compared with unloaded (neat) TiO₂ nanotube layers.     

A mode matching approach for modeling two dimensional porous grating with infinitely rigid or soft inclusions

This work investigates the acoustical properties of a multilayer porous material in which periodic inclusions are embedded. The material is assumed to be backed by a rigid wall. Most of the studies performed in this field used the multipole method and are limited to circular shape inclusions. Here, a mode matching approach, more convenient for a layered system, is adopted. The inclusions can be in the form of rigid scatterers of an arbitrary shape, in the form of an air-filled cavity or in the form of a porous medium with contrasting properties. The computational approach is validated on simple geometries against other numerical schemes and with experimental results obtained in an anechoic room on a rigid grating embedded in a porous material made of 2 mm glass beads. The method is used to study the acoustic absorption behavior of this class of materials in the low frequency range and at a range of angles of incidence.