Transverse load sensing by use of pi-phase-shifted fiber Bragg gratings

The birefringence of a pi -phase-shifted fiber Bragg grating can be determined with high accuracy by measurement of the polarization-induced spectral splitting of its narrow central transmission window. The use of this feature for sensing of a load applied in the direction transverse to the optical fiber is demonstrated. A distributed force resolution of 1.4x10(-3) N/mm was obtained, which corresponds to a difference in the principal strains of the fiber core of 0.5mu? . We also show that the transverse load response of the sensor is insensitive to temperature.     

Reactions des derives du phosphore trivalent avec les composes a halogene positif—II : Phosphites d'alcoyle et α-cyano α-haloesters: Synthese et reactivite de cetenimines n-phosphoryles

Trialkylphosphites P(OR)₃ react with substituted α-cyano α-haloesters by initial attack of the phosphorous compound at the halogen atom to give N-phosphorylated ketenimines or a mixture of ketenimines and vinylphosphates when R = Me ou Et The reaction occurs via an intermediate ion pair. Nucleophiles (water, methanol, amines, carbanions) react with ketenimines in two ways: a phosphoryl displacement and an addition of the nucleophilic reagent. In the latter, ketenimines yield phosphoramides which, according to the nature of the substituants attached to the initial esters, can be converted into heterocycles (Δ₂ pyrrolines, pyrrolidines, furans).     

Detection of paraoxon by immobilized organophosphorus hydrolase in a Langmuir–Blodgett film

Langmuir–Blodgett (LB) film deposition technique was employed for the immobilization of organophosphorus hydrolase (OPH). OPH enzyme was covalently bonded to a fluorescent probe, fluorescein isothiocyanate (FITC), and used as a biological recognition element. Under optimal experimental conditions, OPH monolayers were deposited onto the surface of silanized quartz slides as LB film and utilized as a bioassay for the detection of paraoxon. Two different methods were employed for detection of paraoxon: the fluorescence quenching of the fluorescence probe (FITC) covalently bonded to OPH and the UV–vis absorption spectrum of the paraoxon hydrolysis product. The UV–vis absorption measurement demonstrated a linear relationship between the absorbance at 400 nm and the concentration of paraoxon solutions over the range of 1.0 × 10⁻⁷–1.0 × 10⁻⁵ M (0.27–27 ppm). By observing the FITC fluorescence quenching, the concentration of paraoxon can be detected as low as 10⁻⁹ M (S/N = 3). The research described herein showed that the LB film bioassay had high sensitivity, rapid response time and good reproducibility.     

The interaction between OPH and paraoxon at the air-water interface studied by AFM and epifluorescence microscopies

The paraoxon hydrolysis reaction catalyzed by organophosphorus hydrolase (OPH) monolayer at the air-water interface was studied. OPH-paraoxon interactions, occurring at the two-dimensional interface, by close-packed, highly orientated OPH monolayer, were investigated by several different surface chemistry techniques; e.g. surface pressure area isotherms, atomic force microscopy (AFM), and in situ epifluorescence microscopy. The characterization of OPH Langmuir and Langmuir-Blodgett films prepared in both the presence and absence of paraoxon, demonstrated significantly distinctive feature when compared with one another. Continuous growth of the OPH aggregates is a distinct phenomenon associated with hydrolysis, in addition to the pH changes in the local environment of the enzyme macromolecules.     

THE EFFECT OF COORDINATING LIGANDS ON THE TRIPLET STATE OF CHLOROPHYLL

Under laser excitation at 457.9 and 514.5 nm, a frozen solution of chlorophyll a in n -octane displays fluorescence peak maxima at 2K that may be assigned to two distinct monomeric chlorophyll species. Using zero-field fluorescence-detected magnetic resonance the triplet state properties of the two chlorophyll species have been assigned to the monoligated and biligated chlorophyll monomer in which water serves as the ligand coordinated to the magnesium metal center. These triplet state properties for chlorophyll in solution are then utilized in interpreting triplet state results for in vivo chlorophylls associated with the light harvesting chlorophyll protein complex. It is shown that the triplet state data are consistent with attachment of the chlorophyll molecule to the protein site with a single ligand coordinated to the chlorophyll metal center.     

Total synthesis of lipoxin B: assignment of stereochemistry

Four isomers of lipoxin B were synthesized using carbohydrate precursors. An authentic sample of lipoxin B (from human leukocytes) was found to be a mixture of all-trans isomers 1a and 1c.     

Hydrogen bonded H3O, H2O, HF, F in fluoride metalates (Al, Cr, Fe, Zr, Ta) templated with tren (tris-(2-aminoethyl)amine)

The environment of H₃O⁺, H₂O, HF and F⁻ species (non-bonded to metals) is considered in fluoride metalates which crystallise from the (Al(OH)₃, Cr(OH)₃, FeF₃, ZrF₄, Ta₂O₅)-tren-HF_aq·-ethanol systems (microwave heating at 190 °C during 1 h). The presence of (H₃O)(H₂O)₆⁺ clusters or H₃O⁺ cations, of isolated or associated H₂O molecules, of (HF₂)⁻ and F⁻ anions is evidenced. The thermal stability of the solids depends strongly on the nature of the hydrogen-bonded species associated with the preceding cations or anions and on the formation of water ribbons or layers.     

Mössbauer investigation of hexagonal tungsten bronze type FeIII fluorides: (H2O)0.33 FeF3 and anhydrous FeF3

The new HTB (Hexagonal Tungsten Bronze) phases of FeF₃ and (H₂O)_0.33 FeF₃ have been characterized by ⁵⁷Fe Mössbauer spectroscopy; they have saturation hyperfine fields of (577 ±3) and (560±3) kOe and magnetic ordering temperatures (97±2) and (128.7 ± 0.5) K, respectively. The magnetic ordering temperature and the electric hyperfine interactions on iron are sensitive to the presence of zeolitic water in the system. Hydrolysed samples have also been investigated.     

Serum albumin in 2D: A Langmuir monolayer approach

Understanding of protein interaction at the molecular level raises certain difficulties which is the reason a model membrane system such as the Langmuir monolayer technique was developed. Ubiquitous proteins such as serum albumin comprise 50% of human blood plasma protein content and are involved in many biological functions. The important nature of this class of protein demands that it be studied in detail while modifying the experimental conditions in two dimensions to observe it in all types of environments. While different from bulk colloidal solution work, the two dimensional approach allows for the observation of the interaction between molecules and subphase at the air–water interface. Compiled in this review are studies which highlight the characterization of this protein using various surroundings and also observing the types of interactions it would have when at the biomembrane interface. Free-energy changes between molecules, packing status of the bulk analyte at the interface as well as phase transitions as the monolayer forms a more organized or aggregated state are just some of the characteristics which are observed through the Langmuir technique. This unique methodology demonstrates the chemical behavior and physical behavior of this protein at the phase boundary throughout the compression of the monolayer.