Crystal Structure of (E)-1-(((3-nitrophenyl)imino)methyl)naphthalen-2-ol

Crystallography Reports - Formation of the title Schiff base compound (E)-1-(((3-nitrophenyl)imino)methyl)naphthalen-2-ol, C17H12N2O3 (1) was achieved by the condensation of...     

Fourier transform ion cyclotron resonance mass spectrometry in the speciation of high molecular weight sulfur heterocycles in vacuum gas oils of different boiling ranges

The analysis of sulfur aromatics in vacuum gas oils (VGO) distilled from an Iranian light crude oil is discussed. The VGOs were fractionated into three boiling ranges, 390–460, 460–520, and 520–550 °C, and were analyzed using liquid chromatographic separation on a Pd(II)-bonded stationary phase followed by identification with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It was possible to detect a large number of thiophenes, including a substantial number of isomers, in the three VGO fractions. Separation on the palladium phase and inclusion of sulfur-selective derivatization makes electrospray ionization of these nonpolar compounds possible. An elemental composition can be assigned to a large number of S₁ compounds without ambiguity in the presence of abundant hydrocarbons. With an increase in boiling temperature, an increase in the size of the aromatic system and the number of side chain carbon atoms was observed. In addition, the masses of higher magnitude shifted toward larger aromatic systems with an increase in boiling range. A comparison of FT-ICR MS and comprehensive gas chromatography is also given. This work is dedicated to Prof. B. Krebs on the occasion of his 70th birthday.     

Synthesis, spectroscopic characterization and X-ray structure determination of tetrabutylammonium trans-diamminetetranitrocobaltate(III)

The cobalt(III) complex salt [(C₄H₉)₄N][trans-Co(NH₃)₂(NO₂)₄] has been synthesized in high yield by reacting equimolar quantities of [(C₄H₉)₄N]Br and K[trans-Co(NH₃)₂(NO₂)₄] in aqueous medium at room temperature. The product thus formed has been re-crystallised from acetone-water mixture, in the monoclinic space group P 2₁/n, with cell dimensions a=11.651(3) ?, b=19.005(4) ?, c=11.733(5) ?, β=90.28(3)°. The X-ray structure determination revealed the presence of discrete ions, [(C₄H₉)₄N]⁺ and [trans-Co(NH₃)₂(NO₂)₄]⁻. The central metal ion cobalt(III) in the anion is found in octahedral environment, in trans geometry, while the organic counterion is a quaternary alkylammonium cation. The crystal lattice is stabilized by electrostatic interactions between the cations and anions.Supplementary material Crystallographic data (excluding structure factors) for the structure(s) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC 291300. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (44) 1223 336-033; e-mail: deposit@ccdc.cam.ac.uk.     

On the converse of a theorem of Schur

A well known theorem of Schur states that for any group G, if G/Z(G) is finite, then G′ is finite. We give a very short and elementary proof of a further generalization of the converse of Schur’s theorem proved by Niroomand [5] and Sury [7] and also improve the bound for the order of G/Z(G) obtained by Niroomand and Sury.     

Dissolution arrest and stability of particle-covered bubbles

Experiments show that bubbles covered with monodisperse polystyrene particles, with particle to bubble radius ratios of about 0.1, evolve to form faceted polyhedral shapes that are stable to dissolution in air-saturated water. We perform Surface Evolver simulations and find that the faceted particle-covered bubble represents a local minimum of energy. At the faceted state, the Laplace overpressure vanishes, which together with the positive slope of the bubble pressure-volume curve, ensures phase stability. The repulsive interactions between the particles cause a reduction of the curvature of the gas-liquid interface, which is the mechanism that arrests dissolution and stabilizes the bubbles.     

Biosensors based on screen-printing technology,and their applications in environmental and food analysis

This review summarizes scientific research activity on biosensors, especially screen-printed, electrode-based biosensors. The basic configurations of biosensors based on screen-printing technology are discussed and different procedures for immobilization of the biorecognition component are reviewed. Theoretical aspects are exemplified by practical environmental and food-analysis applications of screen-printed, electrode-based biosensors.     

Interaction of different metal ions with carboxylic acid group: a quantitative study

The binding strength of the carboxylic acid group (-COOH) with different divalent metal ions displays considerable variation in arachidic acid (AA) thin films. It is considered that in AA thin films the metal ions straddle the hydrophilic regions of the stacked bilayers of AA molecules via formation of carboxylates. In this study first the uptake of different divalent cations in films of AA is estimated by atomic absorption spectroscopy (AAS). Through the amount of cation uptake, it is found that the strength of binding of different cations varies as Ca2+>Co2+>Pb2+>Cd2+. Variation in the binding strength of different ions is also manifested in experiments where AA thin films are exposed to metal ion mixtures. The higher binding strength of AA with certain metal ions when exposed individually, as well as the preference over the other metal ions when exposed to mixtures, reveal some interesting deviation from the expected behavior based on considerations of ionic radii. For example, Pb2+ is always found to bind to AA much more strongly than Cd2+ even though the latter has smaller ionic radius, indicating that other factors also play an important role in governing the binding strength trends apart from the effects of ionic radii. Then, to get a more meaningful knowledge regarding the binding capability, first-principles calculations based on density functional theory have been applied to study the interaction of different cations with the simplest carboxylic acid, acetic acid, that can result in formation of metal diacetates. Their electronic and molecular structures, cohesive energies, and stiffness of the local potential energy well at the cation (M) site are determined and attempts are made to understand the diversity in geometry and the properties of binding of different metal ions with -COOH group. We find that the calculated M-O bond energies depend sensitively on the chemistry of M atom and follow the experimentally observed trends quite accurately. The trends in M-O bond energies and hence the total M-acetate binding energy trends can actually be related to their molecular structures that fall into different categories: Ca and Cd have tetrahedral coordination; Fe, Ni, and Co exhibit planar 4-fold coordination; and Pb is off-centered from the planar structure (forming pyramidal structure) due to its stereochemically active lone pair of electrons.     

Controlled assembly of Ag nanoparticles and carbon nanotube hybrid structures for biosensing

Here we report a chemical-free, simple, and novel method in which a part from a silver-based anode is controllably used in a straightforward manner to produce silver nanoparticles (Ag NPs) in order to fabricate a controlled assembly of Ag NPs and single walled carbon nanotube (SWCNT) hybrid structures. The attachment and distribution of Ag NPs along SWCNTs have been investigated and characterized by field emission scanning electron microscopy (FESEM). We have achieved the decoration of SWCNTs with different densities of Ag NPs by changing the deposition time, the applied voltage, and the location of carbon nanotubes with respect to the anode. At low voltage, single silver nanoparticle is successfully attached at the open ends of SWCNTs whereas at high voltage, intermediate and full coverage densities of Ag NPs are observed. As voltage is further increased, fractals of Ag NPs along SWCNTs are observed. In addition, a device based on a Ag NPs-SWNT hybrid structure is used for the label-free detection of ssDNA molecules immobilized on it. We believe that the proposed method can be used to decorate and/or assemble metal nanoparticles or fractal patterns along SWCNTs with different novel metals such as gold, silver, and copper and can be exploited in various sensitive applications for fundamental research and nanotechnology.     

Purification of ß-glucosidases from <Emphasis Type="Italic">Pichia etchellsii</Emphasis> Using CIM Monolith Columns

β-Glucosidases (EC 3.2.1.21) are industrially important glycosyl hydrolases used for cellulose saccharification as well as for synthesis of glyco-conjugates. Crystal structure of only one β-glucosidase of family 3 of the glycosyl hydrolase families is available due to difficulty in purification of these closely related enzymes from a given source. Multiple steps used during purification result in low yield, making it difficult to study their properties. Conditions for purification of two closely related β-glucosidases (BGL I and BGL II) of family 3 from Pichia etchellsii were investigated in this study. Two weak anion exchange columns convective interaction media-diethyl amino ethyl (CIM-DEAE) and CIM-ethylenediamine (CIM-EDA) were used for this purpose. The results obtained at 0.34 ml disk (CIM-DEAE) level were scaled up to 8 ml CIM-DEAE tube column wherein BGL I and BGL II were separated from the major contaminants in the cell-free extract. The recovered enzymes were completely resolved in the second step using CIM-EDA. A final specific activity of 9,180 IU/mg and 2,345.3 IU/mg was achieved for BGL I and BGL II respectively with an overall yield of 33%. The system should be applicable to resolution of other closely related enzymes from this family.     

Detecting the impact area of BP deepwater horizon oil discharge: an analysis by time varying coefficient logistic models and boosted trees

The Deepwater Horizon oil discharge in the Gulf of Mexico is considered to be one of the worst environmental disasters to date. The spread of the oil spill and its consequences thereof had various environmental impacts. The National Oceanic and Atmospheric Administration (NOAA) in conjunction with the Environmental Protection Agency (EPA), the US Fish and Wildlife Service, and the American Statistical Association (ASA) have made available a few datasets containing information of the oil spill. In this paper, we analyzed four of these datasets in order to explore the use of applied statistics and machine learning methods to understand the spread of the oil spill. In particular, we analysed the “gliders, floats, boats” and “birds” data. The former contains various measurements on sea water such as salinity, temperature, spacial locations, depth and time. The latter contains information on the living conditions of birds, such as living status, oil conditions, locations and time. A varying-coefficients logistic regression was fitted to the birds data. The result indicated that the oil was spreading more quickly along the East–West direction. Analysis via boosted trees and logistic regression showed similar results based on the information provided by the above data.