Fluorescein Based Three-channel Probe for the Selective and Sensitive Detection of CO32− Ions in an Aqueous Environment and Real Water Samples

Journal of Fluorescence - We have constructed a novel fluorescein-based fluorescent chemosensor, FL-In, functionalised with an indole moiety and capable of sensing by both the optical...     

Wafer and epilayer improvement for integrated optics devices on InP: the ESPRIT project 2518

Ga _x In_1–x As _y P_1–y alloys lattice matched to InP substrates are currently used to fabricate optoelectronic and integrated optics devices. To achieve devices with high performances and high fabrication yield, the uniformity and reproducibility of the Ga _x In_1–x As _y P_1–y epitaxial layers (composition, thickness, doping, etc.) have become key parameters. These problems have been addressed in the frame of ESPRIT project 2518 and are presented in this paper. Several aspects have been considered starting from the optimization of InP substrates, the MOVPE growth of uniform GalnAsP layers, the material characterization to the validation of material uniformity on passive optical waveguides. Both scanning photoluminescence analysis and waveguide losses measurements performed on 2 inch wafers with a high lateral resolution have shown that high quality uniform GalnAsP layers can be obtained reproducibly on 2 InP substrates using a commercially available LP-MOCVD growth process. In particular, more than 60% of 36 mm long, 3m wide and 100m spaced rib waveguides exhibit losses below 0.8dBcm^–1.     

Corrosion prevention of mild steel in acidic medium by 2-Pyrrolidin-1-yl-1,3-thiazole-5-carboxylic acid: Theoretical and experimental approach

The inhibition efficiency of 2-Pyrrolidin-1-yl-1,3-thiazole-5-carboxylic acid (PTCA) against mild steel (MS) corrosion was investigated in acidic solution by using quantum chemical calculations based on Density Functional Theory (DFT) method and electrochemical measurements. The electrochemical impedance spectroscopy (EIS), potentiodynamic, potential zero charge (pzc) analysis and electrochemical noise (EN) measurements at various concentrations (from 0.1 to 10 mM) and immersion times were utilized in experimental part. The surface analysis was achieved scanning electron microscope (SEM) and contact angle measurements in the absence and presence of 10 mM PTCA. According to DFT results, PTCA exhibited 3.737 eV band gap and 8.130 Debye dipole moment which were a signal of potentially convenient corrosion inhibitor properties. PTCA has a remarkable corrosion inhibition capability to mild steel, which inhibited both anodic and cathodic corrosion rates, relying on it's physically adsorption on the metal solution interface and protection ability was increased with increasing PTCA concentration. The obtained adsorption equilibrium constant was 11.11 × 10³ M^-1 and calculated standard free energy of adsorption was ?33.03 kJ mol^?1. The determined activation energy values were 55.58 kJ mol^?1 and 96.86 kJ mol^?1 in 0.5 M HCl in the absence and presence of 10 mM PTCA, respectively. PTCA demonstrated a strong inhibition efficiency of 98.3%, after 168 h immersion, according to the EIS results. As a consequently, we recommend that PTCA is a convenient inhibitor in 0.1 M HCl for mild steel protection against corrosion.     

Entanglements in amorphous polymer networks

This paper consists of two parts. In the first part, the strain dependence of entanglements or constraints acting along the contour of a Gaussian chain is derived. The functional form of the elastic free energy resulting from constraints along the chain contour is identical to that obtained in the Flory constrained junction model. In the second part, the effective number of constraints acting along the contour of a chain is discussed. The choice of this number results from postulates imposed by various authors and cannot be derived by rigorous theory. The paper compares the predictions based on these assumptions with experimental data from model networks.     

Crystal structure and computational studies of (E)-1-(benzo[b]thiophen-3-yl)-N-(4-ethoxyphenyl)methanimine

Crystallography Reports - The title compound, C17H15NOS, crystallizes in the orthorhombic sp. gr. Pca21. Two molecules in the asymmetric unit have similar structure. Crystal structure contains weak...     

Adaptive image enhancement based on clustering of wavelet coefficients for infrared sea surveillance systems

Most of the techniques developed for infrared (IR) image enhancement (IE) depend heavily on the scene, environmental conditions, and the properties of the imaging system. So, with a set of predefined scenario properties, a content-based IR-IE technique can be developed for better situational awareness. This study proposes an adaptive IR-IE technique based on clustering of wavelet coefficients of an image for sea surveillance systems. Discrete wavelet transform (DWT) of an image is computed and feature vectors are constructed from subband images. Clustering operation is applied to group similar feature vectors that belong to different scene components such as target or background. Depending on the feature vectors, a weight is assigned to each cluster and these weights are used to compute gain matrices which are used to multiply wavelet coefficients for the enhancement of the original image. Enhancement results are presented and a comparison of the performance of the proposed algorithm is given through subjective tests with other well known frequency and histogram based enhancement techniques. The proposed algorithm outperforms previous ones in the truthfulness, detail visibility of the target, artificiality, and total quality criteria, while providing an acceptable computational load.     

Rubber elasticity in the range of small uniaxial tensions and compressions. Results for poly(dimethylsiloxane)

Results of uniaxial tension and compression experiments are reported on crosslinked polydimethylsiloxane (PDMS) networks in the unswollen state over the range 0.5 < α^?1 < 1.2 where α is the extension ratio. Curves representing the reduced force [f] = f(V⁰/V)^1/3(α – α^?2)^?1 plotted against α^?1 can be approximated by straight lines for 0.5 < α^?1 < 0.9, in agreement with the phenomenological Mooney equation. As α^?1 approaches 1, however, they tend to level off and continue into the α^?1 > 1 region with decreasing slope. These results are in agreement with the predictions of recent elasticity theories that incorporate the effect of junction-chain entanglements in the elastic free energy.     

Crystal and molecular structure of 1,4-diphenyl-2,3-dioxabicyclo[2,2,1] heptane,C17H16O2

The crystal structure of 1,4-diphenyl-2,3-dioxabicyclo [2,2,1] heptane has been determined from three-dimensional counter data and refined by full-matrix least-squares procedures. This endoperoxide compound crystallizes from ethanol in space groupP2₁/c with cell constantsa = 11.797(1),b = 9.051(8),c = 12.472(1) Å, = 93.78(1) °,Z = 4,D _x = 1.261, andD _m = 1.274 g cm^–3. The final residual for 2238 observed reflections is 0.063. The molecular structure possesses both an unusually long peroxide bond, 1.501(2) Å, and adjoining C-O bonds, 1.459(2) Å. This observation confirms a previously made conjecture that the forcedcis coplanarity of the C-O-O-C torsion angle would permit repulsive antisymmetric vicinal orbital interactions between the oxygen centers, destabilizing the peroxide bond relative to that normally encountered as the commonly observedgauche conformation.     

Vibrational Spectra and Structural-Dynamic Models of Phenyldichlorarsine and Phenyldichlorophosphine

Vibrational spectra of phenyldichlorarsine and phenyldichlorophosphine are analyzed for free molecules and in water solutions within the framework of the ab initio methods. Characteristic spectral parameters of compounds are determined for their subsequent use in ecological monitoring.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 58–61, March, 2005.     

A Ratiometric Fluorescent Probe for Gold and Mercury Ions

A fluorescent probe that displays a ratiometric fluorescence response towards gold and mercury ions has been devised. Emitting at a relatively longer wavelength, the conjugated form of the fluorescent dye transforms in the presence of the gold or mercury ions into a new dye, the molecular structure of which lacks the conjugation and consequently emits at a distinctly shorter wavelength.