An optimized method for the synthesis of amino-functionalized phosphatidylcholine

Phosphatidylcholine analogues were synthesised as affinity ligands for the capture of membrane proteins. Several protecting group strategies were investigated to synthesize the amino-functionalized phosphatidylcholine: 11-aminoundecyl 2-(trimethylammonio)ethyl phosphate (4). The acid-mediated deprotection of the Boc group generated a mixture of the target products which could only be purified by HPLC. However, an alternative strategy, using the hydrazine-labile phthalimide group route, followed by a gel filtration step proved straightforward to afford the desired amino-functionalized phosphatidylcholine product in high yield and purity.     

Observation of the Fermi-edge singularity in n-doped single asymmetric quantum wells: the influence of residual acceptors

The investigation of the evolution of the photoluminescence spectra, in single asymmetric quantum wells (SAQWs), from a typical emission spectrum to a Fermi-edge singularity, is carried out as a function of both the optical excitation intensity and the temperature. The three samples used here are n-doped, low carrier density (below 5×10¹¹ cm⁻²), GaAs/Al_0.35Ga_0.65As SAQWs grown by molecular beam epitaxy. The strong collective recombination of electrons with different k states up to the Fermi wave vector as well as the optical signature of the Fermi-edge singularity is observed in two samples containing residual acceptors inside the GaAs SAQW. In contrast, a third sample containing no experimental evidence of residual acceptors in the GaAs SAQW shows no optical signature of the Fermi-edge singularity.     

An overview on flow methods for the chemiluminescence determination of phosphorus

A review on the flow analysis of phosphorus with chemiluminescence detection is presented. A brief discussion of the chemiluminescence principles and applications is given. Particular emphasis is devoted to coupling different flow techniques (flow injection, sequential injection, multicommutation, multisyringe flow injection, multi-pumping) to chemiluminescence detection. Enzymatic and non-enzymatic methods, mostly applied to environmental samples, are summarized and compared in terms of application range, detection limits, flow configuration, repeatability and sampling rate.     

Determination of sulfate in natural and residual waters by turbidimetric flow-injection analysis

A turbidimetric flow-injection system was developed for the determination of sulfate in natural and residual water samples, with no previous treatment, using spectrophotometric detection. The precipitating agent, 7.0% (w/v) barium chloride solution prepared in 0.10% (w/v) polyvinyl alcohol, was added by using the merging-zones approach. A 100 mg/L sulfate solution in 0.07M nitric acid was mixed with the sample before it entered the injection loop to improve the detection limit, provide in-line pH adjustment, and prevent the interference of some anionic species. The relative standard deviations of the results were between 1.4 and 3.0% and were in agreement with results obtained by the reference method. Samples within a linear concentration range of 10-120 mg SO4(2-)/L can be analyzed at a rate of 40/h. The detection limit is 5 mg SO4(2-)/L.     

Synthesis and non-isothermal kinetic study of the thermal decomposition of gadolinium(III) complexes

Summary Pyrrolidinedithiocarbamate (Pyr), piperidinedithiocarbamate (Pip), morpholinedithiocarbamate (Mor) and diethanolaminedithiocarbamate (DEDC) ammonium salts; pyrrolidinedithiocarbamic acid-pyrrolidineammonium salt (HPyrPyr), piperidinedithiocarbamic acid-piperidineammonium salt (HPipPip), morpholinedithiocarbamic acid-morpholineammonium salt (HMorMor), hexamethylenedithiocarbamic acid-hexamethyleneammonium salt (HHexHex), diethanolaminedithiocarbamic acid-diethanolamineammonium salt (HDEADEDC) were synthesized, characterized by IR and elemental analysis and their thermal behaviours were investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC).     

SnCl<Subscript>2</Subscript>-catalyzed synthesis of carbamates from renewable origin alcohols

Effects of structure and reactivity of renewable origin alcohols in the conversion and selectivity of the SnCl₂-catalyzed reactions in the presence and absence of urea were assessed. Convenient simple and suitable method for the synthesis of carbamates from renewable origin alcohols and urea in one-step are provided. We have assessed the activity of SnCl₂ catalyst, a commercially affordable Lewis acid, in reactions of urea alcoholysis with different natural origin alcohols (geranyl, neryl, bornyl, cinnamyl, α-terpinyl and benzyl alcohols), aiming to synthesize carbamates, which are biologically active compounds, building blocks in organic synthesis and raw material to synthesize polyurethanes. The low cost of urea, the water tolerant catalyst and phosgene free reaction are positive aspects of this carbamates synthesis process. The different reaction pathways were assessed. A mechanism was proposed based on FT-IR experiments and experimental data.     

A family of fundamental solutions of elliptic partial differential operators with quaternion constant coefficients

The purpose of this paper is to construct a family of fundamental solutions for elliptic partial differential operators with quaternion constant coefficients. The elements of such family are expressed by means of functions, which depend jointly real analytically on the coefficients of the operators and on the spatial variable. We show some regularity properties in the frame of Schauder spaces for the corresponding single layer potentials. Ultimately, we exploit our construction by showing a real analyticity result for perturbations of the layer potentials corresponding to complex elliptic partial differential operators of order two. Copyright © 2012 John Wiley & Sons, Ltd.     

Partially carboxymethylated cotton dust waste for sorption of textile wastewater coloured with the cationic dye Basic Blue 41 as a model: synthesis,regeneration and biodegradability

The removal of residual dyes in coloured textile wastewaters is mandatory, and a significant portion of the dyes used are cationic. Textile factories mainly process cotton yarns, and 8 % of this virgin feedstock is lost as cotton dust waste (CDW). Using factorial experimental design, this dust was derivatised with monochloroacetic acid (MCAA) to produce a partially carboxymethylated cellulose (CM^?-CDW) with NaOH, MCAA and isopropanol for the retention of Basic Blue 41 dye (BB 41) (column and batch), and biodegradability was investigated. The dye retention efficiency was examined with additional experiments varying the initial concentration, contact time and addition of salts. Heteronuclear multiple bonding correlation-nuclear magnetic resonance confirmed the covalent insertion of CM^? groups in the cellulosic fibres. The selected matrix provided a dye sorption of 58.33 (column) and 64.50 mg/g (batch). The Langmuir isotherm was a good fit to the sorption data. The efficiency of uptake of BB 41 was predominantly dictated by the concentration of alkali in the matrix synthesis. Biodegradability by cellulases was similar when using uncharged and dye-charged matrices. The latter were fully regenerated by washing in dilute acid. Retention was proportional to the initial dye concentration and the contact time required to reach equilibrium, which was longer for higher dye concentrations. The addition of 10 mmol/l NaCl decreased BB 41 retention by 50 %. Therefore, CM^?-CDW proved effective for the removal of the cationic dye BB 41 and thus represents an important alternative in the treatment of coloured textile effluents.     

Al-K-Auger energy spectra: Probing the electron dynamics in ion-solid interactions

K-Auger electron emission has been investigated for incident electrons and for different types of heavy ions interacting with mono-crystalline aluminum (100) targets at specific kinetic energies of 3 to 5 MeV/u. In an effort to gain a profound knowledge about the ionization and vacancy-decay dynamics for the K-shell in Al, spectra have been measured with different energy resolutions and angular distributions have been taken as well. Here we concentrate on the energy spectra — we identify the measured peak structures and we investigate different line intensities and mean target charge-states quantitatively, in comparison with theoretical results.