Zeeman coherence in saturated absorption

By modulating the saturating beam polarization, it is possible to extract from the probe beam a signal which depends only on the Zeeman coherence Δm = 2 (transverse alignment), and to study velocity changing collisions which do not destroy the alignment. This type of collisions appears to be of small importance in neon, so that width of the saturated absorption curve from alignment is narrower than that from populations.     

Mean lifetimes of excited levels of Ar II. I. Time correlation measurements

Mean Lifetimes of excited levels of Ar II have been measured using the method of time-correlated photons in cascade. The following results were obtained: for 4p⁴S^°_{$\text{3}\text{2}$}, τ = 7·2±0·3ns; for 4p′²F^°_{$\text{7}\text{2}$}, τ = 8·8±0·2 ns; for 4p′²F^°_{$\text{5}\text{2}$}, τ = 8·0±0·2 ns. These results are compared with experimental and theoretical values.     

Spectrofluorimetric determination of formaldehyde in maple syrup

A quick and simple method was developed for determination of formaldehyde in maple syrup. In this method, formaldehyde reacts with Fluoral P to form a complex which is chemically extracted by isobutanol and determined by spectrofluorimetry. Performance, as gauged by the limits of detection (0.16 mg/kg) and quantitation (0.21 mg/kg), recovery (>79%), and variability (1.9-16.1%, depending on fortification level and class of syrup) were superior to the current official AOAC standard method.     

Nonequilibrium molecular dynamics simulation for studying the effect of pressure difference and periodic boundary conditions on water transport through a CNT membrane

A NEMD simulation system is constructed to simulate at two-dimensional (2D) periodic boundary conditions (PBCs) and to create two different pressures on two sides of the carbon nanotube (CNT) membrane. The simulation results show that water permeation through the same CNT membrane driven by different pressure differences exhibit similar transport phenomenon including unusually fast water permeation and a periodic (non-parabolic) radial velocity distribution unlike the parabolic form characteristic of continuum flow in the CNT membrane. A three-dimensional (3D) PBC system is also constructed to simulate water permeation through the same CNT membrane at the same pressure differences, to show the effect of PBC and simulation methodologies on transport phenomenon. The two systems both show that the forward/backward water flux increases/decreases with increasing the pressure difference from 1.0 MPa to 8.0 MPa. However, the net flux is higher for the 3D PBC system, especially at higher pressure difference is high. In general, the NEMD simulation method using the 2D PBC system is shown to be a feasible and valuable tool for studying pressure-driven permeation processes such as nanofiltration through these studies with model CNT membrane.     

Lubricated compression and X-ray microtomography to analyse the rheology of a fibre-reinforced mortar

In this work, the microstructure and the rheology of a glass-fibre-reinforced fresh mortar were studied. Various fibre contents and aspect ratios and two types of fibrous reinforcement, i.e. slender fibre bundles and fibres, were tested. The microstructure was analysed by using X-ray microtomography. It is shown that the non-deformed mortar is a porous granular suspension, the porous microstructure of which is not influenced by the presence of fibres, which in turn display a 2D planar random fibre orientation. The rheology was investigated by subjecting samples to constant axial strain rate and lubricated compression. The roles of the actual strain, the mortar resting time, the fibre content and aspect ratio on recorded stress levels are emphasised. Besides, for the investigated strain rate and material parameters, the mortar flow is quasi-incompressible and does not affect significantly the porous microstructure nor the fibrous one. Lastly, the stress increase which is induced by the addition of fibre bundles is similar to that predicted by Newtonian models of semi-dilute fibre suspensions.     

Synthesis and Properties of Higher Nuclearity Polyazanes

Polyazanes (i.e., higher nuclearity homologues of hydrazines) with increasing numbers of bound nitrogen atoms (from 3 to 5), including the first pentazane ever described, were prepared by the addition of lower-order polyazanes to diazo reagents. A structure was obtained. It was shown that the polynitrogen chains adopt a helical conformation. DFT modeling shows that the arrangement persists in solution. Although the polyazanes are all reducing agents, they become less so as the number of nitrogens increases.     

Determination of the neuropeptides arginine vasotocin and isotocin in brains of three-spined sticklebacks (Gasterosteus aculeatus) by off-line solid phase extraction-liquid chromatography-electrospray tandem mass spectrometry

A method based on solid phase extraction (SPE) followed by liquid chromatography-electrospray ionisation tandem mass spectrometry for the determination of the nonapeptides arginine vasotocin (AVT) and isotocin (IT) in brains of three-spined sticklebacks (Gasterosteus aculeatus) is described. Separation and detection were optimized using synthetic standards. Limits of detection (LOD) for standard solutions were 160 pg mL(-1) for AVT and 250 pg mL(-1) for IT. The SPE procedure hardly affected the LODs for standard solutions. Mainly because of ion suppression, LODs for AVT and IT in brains were approximately 5 and 25 pg mg(-1), respectively. The concentrations determined in the brain of several fishes ranged from 10 to 500 pg mg(-1) for AVT and from 400 to 4000 pg mg(-1) for IT.