Detection of illicit material using neutron activation: weakness and solutions

Poisoning the illicit materials by a neutron absorber leads to false detection when the detection is relied on combined thermal neutron activation and fast neutron activation to identify the elements of interest. The use of adjacent transmission thermal neutron detector for verifying the presence of neutron poisons and to trigger an alarm was investigated experimentally and using MCNP calculations. The illicit material of high hydrogen content will affect the detector response in the presence or absence of poisons.     

Suspension bead array branch migration displacement assay for rapid STR analysis

STR analysis is commonly used in forensic and genetic studies. STRs are currently discriminated based on size, primarily by gel- and column-based approaches. Hybridization-based approaches have the potential to allow high-throughput analysis of STRs; however, development of such approaches has been limited by the difficulty in discriminating between STRs of similar length. We have recently described several innovations to enable STR analysis using an array-based hybridization approach for high- throughput STR analysis. Here we extend that approach by incorporating the array into microspheres and adding a discriminatory branch migration displacement step. This microsphere-based platform uses Luminex xMAP technology and improves the sensitivity, selectivity, and speed of the assay. We demonstrate the feasibility, speed, and reliability of the assay for STR detection by correctly analyzing two STR loci in 20 forensic DNA samples of known STR type. The multiplex, bead-based approach provides a high-throughput and more portable STR analysis.     

β-Tetra-brominated meso-tetraphenylporphyrin: A conformational study and application to the Mn-porphyrin catalyzed epoxidation of olefins with tetrabutylammonium oxone

X-ray crystallographic studies have shown that the free base β-tetra-brominated meso-tetraphenylporphyrin (H₂TPPBr₄) has a slightly ruffled structure with the dihedral angles of 70.1–79.2° between the phenyl groups and the porphyrin mean plane. The N(pyrrole)–N(pyrrolenine) distance is very similar to that of the standard planar porphyrins. The decreased N–H bond length of H₂TPPBr₄ with respect to that of meso-tetraphenylporphyrin (H₂TPP) seems to be due to the weaker intramolecular hydrogen bond of the former relative to the latter caused by the electron-withdrawing effects of the β-bromine substituents. The large red shifts of the Soret and Q(0,0) bands of H₂TPPBr₄ in comparison with those of H₂TPP, in spite of the nearly planar porphyrin core of the compound, also may be explained on the basis of the electron-withdrawing effects of the bromine atoms. Oxidation of styrene, the para-substituted derivatives and cyclooctene with tetrabutylammonium oxone in the presence of catalytic amounts of β-tetra-brominated meso-tetraphenylporphyrinatomanganese(III) acetate immediately gives the epoxide as the sole product. Terminal double bonds and unconjugated ones are less reactive than the conjugated double bonds and show lower selectivities. Catalytic activity of the electron-deficient Mn(H₂TPPBr₄)OAc dramatically depends on the Co-catalytic activity of the nitrogen donors as the axial base. The best axial bases are the nitrogenous donors with mixed σ- and π-donor ability to the metal centre.     

Construction of 1,3-disubstituted 4-oxo-1,4-dihydroquinolines as a potential antibacterial agents

Research on Chemical Intermediates - A novel series of 1,3-disubstituted 4-oxo-1,4-dihydroquinolines as antimicrobial agents were designed and synthesized. Their structures have been confirmed...     

聚乙烯基吡啶高氯酸盐作为高效固体酸催化剂在无溶剂条件下催化醛化学选择性制备二乙酸盐(英文)

Poly(4-vinylpyridinium) perchlorate has been used as a supported,recyclable,environmentally-benign catalyst for the formation of acylals from aliphatic and aromatic aldehydes in good to excellent yields under solvent-free conditions.Notably,the reaction conditions were tolerant of ketones.This methodology offers several distinct advantages,including its operational simplicity and high product yield,as well as being green in terms of avoiding the use of toxic catalysts and solvents.Furthermore,the catalyst can be recovered and reused several times without any loss in its activity.     

Simulation of conjugate radiation–forced convection heat transfer in a porous medium using the lattice Boltzmann method

In this paper, a lattice Boltzmann method is employed to simulate the conjugate radiation–forced convection heat transfer in a porous medium. The absorbing, emitting, and scattering phenomena are fully included in the model. The effects of different parameters of a silicon carbide porous medium including porosity, pore size, conduction–radiation ratio, extinction coefficient and kinematic viscosity ratio on the temperature and velocity distributions are investigated. The convergence times of modified and regular LBMs for this problem are 15 s and 94 s, respectively, indicating a considerable reduction in the solution time through using the modified LBM. Further, the thermal plume formed behind the porous cylinder elongates as the porosity and pore size increase. This result reveals that the thermal penetration of the porous cylinder increases with increasing the porosity and pore size. Finally, the mean temperature at the channel output increases by about 22% as the extinction coefficient of fluid increases in the range of 0–0.03.

     

From the Boltzmann equation to the Stokes‐Fourier system in a bounded domain

We prove that the renormalized solutions of the Boltzmann equation considered in a bounded domain with different types of (kinetic) boundary conditions converge to the Stokes‐Fourier system with different types of (fluid) boundary conditions when the main free path goes to zero. This extends the work of F. Golse and D. Levermore [9] to the case of a bounded domain. © 2003 Wiley Periodicals, Inc.