Detection of explosives on skin using ambient ionization mass spectrometry

Single nanogram amounts of the explosives TNT, RDX, HMX, PETN and their mixtures were detected and identified in a few seconds on the surface of human skin without any sample preparation by desorption electrospray ionization (DESI) using a spray solution of methanol-water doped with sodium chloride to form the chloride adducts with RDX, HMX, and PETN while TNT was examined as the radical anion and tandem mass spectrometry was used to confirm the identifications.     

A consistent approach to variable bubble-point systems

Here, it is shown that the “traditional approach” to variable bubble-point problems, using black-oil models, is not consistent, because it violates the “bubble-point conservation law.” In order to have a consistent approach, it is necessary to incorporate shocks—discussed in previous papers—in which the bubble-point is discontinuous. A “consistent approach” is applied to specific examples, and results compared with those of the “traditional” one. The conclusion that the “traditional approach” generally yields large errors for the production rates and other parameters of interest in the oil industry, is reached. © 1997 John Wiley & Sons, Inc.     

Triphenylphosphine oxide–3‐chlorobenzoic acid (1/1)

In the title compound, C₁₈H₁₅OP·C₇H₅ClO₂, the tri­phenyl­phosphine oxide molecule forms a single directed hydrogen bond with the 3‐chloro­benzoic acid molecule, with an O⃛O=P distance of 2.607 (2) Å. The C—Cl and C=O bonds adopt a cisoid conformation in the 3‐chloro­benzoic acid molecule.     

Mixed Convection in a Ventilated Cavity Filled with a Triangular Porous Layer

Accurate prediction of the macroscopic flow parameters needed to describe flow in porous media relies on a good knowledge of flow field distribution at a much smaller scale—in the pore spaces. The extent of the inertial effect in the pore spaces cannot be underestimated yet is often ignored in large-scale simulations of fluid flow. We present a multiscale method for solving Oseen’s approximation of incompressible flow in the pore spaces amid non-periodic grain patterns. The method is based on the multiscale finite element method [MsFEM Hou and Wu in J Comput Phys 134:169–189, 1997)] and is built in the vein of Crouzeix and Raviart elements (Crouzeix and Raviart in Math Model Numer Anal 7:33–75, 1973). Simulations of inertial flow in highly non-periodic settings are conducted and presented. Convergence studies in terms of numerical errors relative to the reference solution are given to demonstrate the accuracy of our method. The weakly enforced continuity across coarse element edges is shown to maintain accurate solutions in the vicinity of the grains without the need for any oversampling methods. The penalisation method is employed to allow a complicated grain pattern to be modelled using a simple Cartesian mesh. This work is a stepping stone towards solving the more complicated Navier–Stokes equations with a nonlinear inertial term.     

Synthesis of 2,2'-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) in aqueous medium at room temperature

The reaction of dimedone with various aromatic aldehydes produces 2,2'-arylmethylene bis (3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) in excellent yields. The reactions occur in water as solvent at room temperature and avoiding the addition of any catalyst. The workup procedure is very simple and the products do not required further purification.     

Synthesis of pseudo-C-nucleosides from β-formyl-α,β-unsaturated ester bearing a β-furanosidic moiety

Abstract  

Pseudo-C-nucleosides have potential biological activity, and an efficient synthesis of new pseudo-C-nucleosides has been developed via the reaction of a β-formyl-α,β-unsaturated ester bearing a β-sugar moiety with hydrazines in neutral and acidic conditions. The preparation of the β-formyl-α,β-unsaturated ester was accomplished by oxidation of the secondary hydroxyl group of 3-O-benzyl-1,2-O-isopropylidene-α-d-glucofuranose, followed by elongation of its carbon chain with (ethoxycarbonylmethylene)triphenylphosphorane and oxidation of the hydroxymethyl group.     

Precipitate flotation-separation, speciation and hydride generation atomic absorption spectrometric determination of selenium(IV) in food stuffs

A method for flotation and determination of selenium(IV) in foodstuffs using p-chlorophenylthiosemicarbazide (HCPT) was investigated. At pH  2, selenium(IV) forms a 1:1 reddish-brown precipitate with HCPT easily floated using oleic acid (HOL) surfactant. The separated complex was dissolved in 4 M HCl and diluted in 10-ml double-distilled water (DDW). Selenium(IV) content in the eluate was determined by hydride generation atomic absorption spectrometry (HG-AAS) at 196.4 nm using sodium borohydride. The HCPT–Se(IV) complexes formed in absence and presence of oleic acid were characterized by elemental analysis, mass and infrared spectral studies. The mode of chelation between Se(IV) and HCPT is proposed to be through S and N coordination. Interferences, on the flotation process, from various foreign ions were avoided by adding excess HCPT. The proposed flotation methodology was successfully applied to the analysis of selenium in real foodstuffs and natural water spiked with known amounts of Se(IV) with a preconcentration factor of 100 and a detection limit of 20 pg. Application was also extended to separate Se(IV) successfully from Se(VI) in their synthetic mixtures. The separation mechanism is proposed to be due to hydrogen bond formation between the COOH group of HOL and –NH of the HCPT–Se(IV) complex.