Experimental and Theoretical Study of High Temperature-Stability and Low-Chirp 1.55 µm Semiconductor Laser with an External Fiber Grating

An experimental and theoretical study of the effect of temperature on the static and dynamic characteristics of packaged external fiber grating semiconductor lasers (FGL) is reported on. Operating in single frequency mode, the laser exhibits high output power (> 8 mW), high temperature stability of operating frequency (-3.4 GHz/K), and low static chirp (-60 MHz/mA). The observed hysteresis in wavelength versus temperature dependence is explained in the frame of a time-domain FGL model accounting for asymmetric nonlinear gain. The laser has low dynamic chirp (~16 MHz/mA) under 2.5 GB/s direct modulation, which is the key factor determining low penalty transmission over 312 km of SSM fiber. Dense WDM transmission performed at 2.6 Gbit/s over 117 km of SSM fiber shows that an FGL-based transmitter is a factor of 7 more tolerant to temperature variations than externally modulated DFB lasers.     

Temperature-dependent structure of methyltributylammonium bis(trifluoromethylsulfonyl)amide: X ray scattering and simulations

We report the combined results of computational and x ray scattering studies of amorphous methyltributylammonium bis(trifluoromethylsulfonyl)amide as a function of temperature. These studies included the temperature range for the normal isotropic liquid, a deeply supercooled liquid and the glass. The low q peaks in the range from 0.3 to 1.5 A(-1) in the structure function of this liquid can be properly accounted for by correlations between first and second nearest neighbors. The lowest q peak can be assigned to real space correlations between ions of the same charge, while the second peak arises mostly from nearest neighbors of opposite charge. Peaks at larger q values are mostly intramolecular in nature. While our simulated structure functions provide an excellent match to our experimental results and our experimental findings agree with previous studies reported for this liquid, the prior interpretation of the experimental data in terms of an interdigitated smectic A phase is not supported by our simulations. In this work, we introduce a set of general theoretical partitions of real and reciprocal space correlations that allow for unambiguous analysis of all intra- and interionic contributions to the structure function and coherent scattering intensity. We find that the intermolecular contributions to the x ray scattering intensity are dominated by the anions and cross terms between cations and anions for this ionic liquid.     

Synthesis of hexacyclo[7.4.0.02,8.03,7.06,11]Tridecane-10,13-dione(“homosecohexaprismane-10,13-dione”)

HEXACYCLO[7.4.0.0^2,8.0^3,7.0^6,11]tridecane-10,13-dione (“homosecohexaprismane-10,13-dione”, 8) has been prepared via a six-step sequence that results in homologation of two of the cyclopentane rings in pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]-undecane-8,11-dione, 1. The structure of 8 has been established unequivocally via single crystal X-ray structural analysis.     

Photo-physical aspects of BODIPY-coumarin conjugated sensor and detection of Al3+ in MCF-7 cell

ABSTRACT

BODIPY azine bearing chemosensor R1 has been synthesised for selective detection of Al³⁺with visual colour change from red-purple to purple and photo-physical studies were explained through Förster Resonance Energy Transfer (FRET) mechanism. Chemosensor showed good sensing capability with high binding constant and lower Limit of Detection (LOD) towards Al³⁺. Cell viability and fluorescence microscopic experiments illustrated about the cytocompatibily of the sensor in presence of Al³⁺ in living cells (MCF-7).     

"Click chemistry" inspired synthesis of pseudo-oligosaccharides and amino acid glycoconjugates

[reaction: see text] Various pseudo-oligosacchardies and amino acid glycoconjugates were synthesized via an intermolecular 1,3-dipolar cycloaddition ("click") reaction using easily accessible carbohydrate and amino acid derived azides and alkynes as building blocks. It is pertinent to mention that the conjugation reaction is highly regioselective and high yielding and can be carried out under mild reaction conditions.     

Propargyl glycosides as stable glycosyl donors: anomeric activation and glycoside syntheses

The advantages of stable glycosyl donors for saccharide coupling are many, and we describe herein the utility of propargyl glycosides for anomeric activation and glycoside synthesis exploiting the alkynophilicity of AuCl3. Various aglycones were reacted with propargyl glycosides, resulting in the formation of an alpha,beta-mixture of glycosides and disaccharides in good yields.     

Dilute solution properties of methyl methacrylate—acrylonitrile copolymer (MA2)

This article deals with studies of the dilute solution properties of methyl methacrylate-acrylonitrile (MMA-AN) copolymer of 0.415 mole fraction (mf) of acrylonitrile composition. Mark—Houwink parameters for this copolymer have been evaluated in acetonitrile (MeCN), 2-butanone (MEK), dimethyl formamide (DMF), and γ-butyrolactone (γ-BL). The Mark-Houwink exponent a in all four solvents at all temperatures is larger than the corresponding values of the parent homopolymers. The solvent power is in the order of DMF < γ–BL < MEK < MeCN; [η] decreases with an increase in temperature, which is behavior characteristic of polymers in good solvent. The unperturbed dimensions (K₀) values, obtained by the Stockmayer–Fixman method, are lower than those for the parent homopolymers and depend on solvent as well as temperature. The solute—solvent interaction parameter X₁ values are close to 0.5; X₁ is independent of temperature. The excess interaction parameter X_ABvalues are negative. The results for this copolymer system in regard to low second virial coefficient A₂, large X₁, and high a values suggest that the large extension of these copolymer chains is due to the unusual short-range interactions.