Synthesis and Evaluation of Some Schiff Base Surfactants for Treating Crude Oil Emulsions

Water soluble nonionic surfactants based on Schiff base monomers were prepared by their etherification with β,^` β- dichlorodiethylether and PEG 400 in presence of NaOH. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The prepared nonionic surfactants were evaluated as demulsifiers for synthetic water in crude-oil emulsions that were pronounced at different ratios of crude oil: water at 45°C and 60°C. The experimental results showed that the dehydration rate of the prepared demulsifiers reached 90% and 100% at some concentrations.     

Competitive amperometric immunosensor based on covalent linking of a protein conjugate to dendrimer-functionalised nanogold substrate for the determination of 2,4,6-trinitrotoluene

A new amperometric immunosensor for 2,4,6-trinitrotoluene based on the working principle of competitive enzyme-linked immunosorbent assay was developed and characterised. An electrodeposited nanogold substrate was functionalised by deposition of self-assembled monolayers of 2-aminoethanethiol as linkers for the subsequent immobilisation of polyamidoaminic dendrimers. Our approach makes use of those dendrimers to anchor a trinitrobenzene-ovalbumin conjugate on the electrode surface. The immunosensor was tested and validated for the determination of 2,4,6-trinitrotoluene showing high selectivity with respect to other nitroaromatic compounds, a limit of detection of 4.8 ng/mL and a limit of quantitation of 6 ng/mL. The immunosensor was tested for the quantification of the analyte in spiked soils and in a real sample of post-blast soil, evidencing a good recovery rate (113 %).

Synthesis of Unsymmetrical Ureas and S‐Thiocarbamates under Catalyst‐free Conditions in a [BMIM]BF4 Ionic Liquid

Unsymmetrical ureas and S‐thiocarbamates were prepared in good to excellent yields by direct condensation of phenylurea with amines and thiols in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM]BF₄) without the addition of any additives. The [BMIM]BF₄ ionic liquid is a mild medium and can be recycled and reused several times.     

The interaction of iron and metal‐free meso‐tetra (4‐sulfonatophenyl) porphines with CVD graphene: a comparative Raman spectroscopy study

In this work, a non‐covalent interaction of iron and metal‐free meso‐tetra (4‐sulfonatophenyl) porphines (FeTPPS and TPPS, respectively) with high‐quality single‐layer graphene is studied by Raman spectroscopy. Such a kind of graphene functionalization is promising for a development of novel optoelectronic devices and sensors. Our results show that the central metal atom of porphyrin macrocycle, iron particularly, plays an important role in the integrity of FeTPPS on graphene surface; however, the predicted Raman enhancement is not significant. The interaction of metal‐free TPPS with graphene leads to the deprotonation of TPPS molecules and higher Raman enhancement values. Moreover, initially deprotonated TPPS solutions after the adsorption onto the graphene surface demonstrate the appearance of new Raman bands and significantly enhanced Raman signals. We propose that a strong interaction between deprotonated TPPS and graphene is realized through pyrrole and desulfonated phenyl rings of closely located planar TPPS molecules on the graphene surface. The results show that both the protonation of porphyrin macrocycle and the existence of central metal atom are crucial for a formation of nanocomposites with defined electronic properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of Pyrido[2′,3′: 3,4]pyrazolo[1,5‐a]pyrimidine,Pyrido[2′,3′:3,4]pyrazolo[5,1‐c][1,2,4]triazine,and Pyrazolyl Oxadiazolylthieno[2,3‐b]pyridine Derivatives

6‐(2‐Thienyl)‐4‐(trifluoromethyl)‐1H‐pyrazolo[3,4‐b]pyridine‐3‐amine reacted with different active methylene compounds to afford pyridopyrazolopyrimidine derivatives. On the other hand, it reacted with some halo compounds to give the imidazo[1′,2′:1,5]pyrazolo[3,4‐b]pyridine derivatives. Also, it diazotized to give the corresponding diazonium chloride that is coupled with several active methylene compounds to give the corresponding triazine derivatives. Furthermore, compound 3‐amino‐6‐(2(thienyl)‐4‐(trifluoromethyl)thieno[2,3‐b]pyridine‐2‐carbohydrazide reacted with some β‐dicarbonyl compounds and some sulfur‐containing compounds to afford the corresponding pyrazolyl oxadiazolylthieno[2,3‐b]pyridine derivatives.     

Discrete nonlinear Schrödinger equation and polygonal solitons with applications to collapsed proteins

We introduce a novel generalization of the discrete nonlinear Schr?dinger equation. It supports solitons that we utilize to model chiral polymers in the collapsed phase and, in particular, proteins in their native state. As an example we consider the villin headpiece HP35, an archetypal protein for testing both experimental and theoretical approaches to protein folding. We use its backbone as a template to explicitly construct a two-soliton configuration. Each of the two solitons describe well over 7.000 supersecondary structures of folded proteins in the Protein Data Bank with sub-angstrom accuracy suggesting that these solitons are common in nature.     

Long‐Lived Circularly Polarized Phosphorescence in Helicene‐NHC Rhenium(I) Complexes: The Influence of Helicene,Halogen, and Stereochemistry on Emission Properties

The first enantiopure chiral‐at‐rhenium complexes of the form fac‐ReX(CO)₃(:C^N) have been prepared, where :C^N is a helicene‐N‐heterocyclic carbene (NHC) ligand and X=Cl or I. These have complexes show strong changes in the emission characteristics, notably strongly enhanced phosphorescence lifetimes (reaching 0.7 ms) and increased circularly polarized emission (CPL) activity, as compared to their parent chiral models lacking the helicene unit. The halogen along with its position within the dissymmetric stereochemical environment strongly affect the photophysics of the complexes, particularly the phosphorescence quantum yield and lifetime. These results give fresh insight into fine tuning of photophysical and chiroptical properties of Re‐NHC systems.     

Algebraic signatures of convex and non-convex codes

A convex code is a binary code generated by the pattern of intersections of a collection of open convex sets in some Euclidean space. Convex codes are relevant to neuroscience as they arise from the activity of neurons that have convex receptive fields. In this paper, we develop algebraic methods to determine if a code is convex. Specifically, we use the neural ideal of a code, which is a generalization of the Stanley–Reisner ideal. Using the neural ideal together with its standard generating set, the canonical form, we provide algebraic signatures of certain families of codes that are non-convex. We connect these signatures to the precise conditions on the arrangement of sets that prevent the codes from being convex. Finally, we also provide algebraic signatures for some families of codes that are convex, including the class of intersection-complete codes. These results allow us to detect convexity and non-convexity in a variety of situations, and point to some interesting open questions.     

Geodesic motion in the 5D magnetized Schwarzschild-like solutions

Geodesics for a 5D magnetized Schwarzschild-like solution are analyzed by reducing the problem to the motion of a test particle in an effective potential. In absence of magnetic field comparison is established with Schwarzschild's geometry. Embedding diagrams are constructed in order to visualize the geometry of the metric. The study performed here is also valid, when the electromagnetic interactions are neglected, for the low energy superstring theory and the Brans-Dicke theory.