Two-phase steam-water flow through Y-junctions

An investigation has been made of steam-water flow in a vertical coplanar Y-junctions which are used, for example, in the condensate carrying pipework downstream of direct contact heat exchangers. The steam-water flow is stratified in the sloping limbs approaching the junction and this paper examines problems associated with the flooding of the junction. It is shown that at low water flowrates water falls freely through the junction, but as the water flowrate increases a condition is reached when the water starts to pile at the junction and the junction is said to be flooded. Further increase in the water flowrate causes the water level to rise within the sloping limbs approaching the junction. A simple analytical model is developed which describes reasonably well the flow phenomena observed.     

Rational Design of a Facially Coordinating P,N,N Ligand for Manganese-Catalysed Enantioselective Hydrogenation of Cyclic Ketones

DFT calculations on the full catalytic cycle for manganese catalysed enantioselective hydrogenation of a selection of ketones have been carried out at the PBE0-D3_PCM//RI-BP86_PCM level. Mn complexes of an enantiomerically pure chiral P,N,N ligand have been found to be most reactive when adopting a facial coordination mode. The use of a new ligand with an ortho-substituted dimethylamino-pyridine motif has been calculated to completely transform the levels of enantioselectivity possible for the hydrogenation of cyclic ketones relative to the first-generation Mn catalysts. In silico evaluation of substrates has been used to identify those likely to be reduced with high enantiomer ratios (er), and others that would exhibit less selectivity; good agreements were then found in experiments. Various cyclic ketones and some acetophenone derivatives were hydrogenated with er's up to 99 : 1.     

trans–cis and trans–cis–trans Microstructure Evolution of Azobenzene Liquid‐Crystal Polymer Networks

The photomechanics of azobenzene LCNs is modeled using a nonlinear continuum mechanics approach that couples photoisomerization of liquid crystal domain structures with light absorption and deformation of a glassy polymer network. The effects during UV‐stimulated trans–cis photomechanical deformation versus blue‐green light (trans–cis–trans) photomechanical deformation are simulated. Different bending deformation is predicted by assuming liquid‐crystal order/disorder behavior during trans–cis photoisomerization in comparison to light‐polarization‐driven reorientation of the trans phase during potential trans‐cis‐trans photoisomerization. Light‐controlled deformation mechanisms offer support for improved control of photo‐responsive morphing structures with a single blue‐green polarized light source.

     

Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb

We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.     

Iron-57 Mössbauer spectroscopy studies of meteorites recovered from Roosevelt County,USA

Some H5 ordinary chondrite meteorites recovered from the desert region of Roosevelt County in New Mexico, USA and¹⁴C dated to determine the terrestrial age have been examined by⁵⁷Fe Mössbauer spectroscopy. The preliminary results suggest the increasing oxidation of Fe⁰ in the iron-nickel alloy phase and of Fe²⁺ in the iron-sulphide and -silicate phases as a result of terrestrial weathering over ca. 38 000 years and which induces the formation of macroscopic iron oxide/oxyhydroxide phases.