Coherent states for the hydrogen atom: discrete and continuous spectra

We construct the systems of generalised coherent states for the discrete and continuous spectra of the hydrogen atom. These systems are expressed in elementary functions and are invariant under the $SO(3, 2)$ (discrete spectrum) and $SO(4, 1)$ (continuous spectrum) subgroups of the dynamical symmetry group $SO(4, 2)$ of the hydrogen atom. Both systems of coherent states are particular cases of the kernel of integral operator which interwines irreducible representations of the $SO(4, 2)$ group.Comment: 15 pages, LATEX, minor sign corrections, to appear in J.Phys.

The past and future of enzyme measurements using surface enhanced Raman spectroscopy

The ability to accurately and sensitively measure the activity of specific enzymes is central to many aspects of modern chemistry and when combined with new nanoscience based approaches, offers significant opportunities for advancing other scientific disciplines. We review the development of surface enhanced resonance Raman scattering (SERRS) for the detection of enzymes, from the initial direct spectroscopy of enzymes, substrate/product and inhibitors adsorbed onto metallic colloids, to the current approach of measuring enzymatic activity by recording the SERRS spectra of a product which is only 'switched on' after enzyme activity. Developments focussed on improvements to modular masked SERRS substrates, which are unmasked by specific enzymes, are also reviewed. Finally, we set out the remaining grand challenges within the area of enzymatic analysis by SERRS which include single molecule detection, in vivo studies and increased multiplexing for screening of evolved enzyme libraries

Effect of the microalga Pavlova lutheri (Droop) Hibberd cultured with agricultural fertilizers on the growth and survival of larvae and postlarvae of the mussel Mytilus edulis (L.)

An evaluation was made of the growth and survival of Mytilus edulis larvae to metamorphosis, fed on Pavlova lutheri cultured with three nitrogen sources: two agricultural fertilizers (urea and ammonium sulphate) and laboratory-grade nitrate (medium f/2). In the larval stage, survival between trials was greater than 92.0%, whereas total survival was greater than 87.0% and there were no significant differences between the three treatments. Growth of larvae fed Pavlova lutheri cultured with ammonium sulphate and f/2 was the same during the first 20 days of larval development, except on days 6 and 10. Lesser growth occurred in the treatment with urea and there were significant differences relative to the other two treatments, except on day 20 when growth was the same as in the treatment with ammonium sulphate. Seed survival was better in the two treatments with agricultural fertilizers, with no differences between the two, than in the f/2 treatment, with significant differences relative to urea and ammonium sulphate. Better seed growth was obtained in the treatment with ammonium sulphate, whereas growth in the urea and f/2 treatments was similar and there were no significant differences between the two. The results indicate that urea and ammonium sulphate, especially the latter, can be considered good alternatives for use in the laboratory production of microalgae, reducing costs by 98.81% relative to f/2

Rapid and ultra-sensitive determination of enzyme activities using surface-enhanced resonance Raman scattering

Measurement of enzyme activity and selectivity at in vivo concentrations is highly desirable in a range of fields including diagnostics, functional proteomics and directed evolution. Here we demonstrate how surface-enhanced resonance Raman scattering (SERRS), measured using silver nanoparticles, can be used to detect the activity of hydrolases at ultra-low levels. This approach was made possible by designing 'masked' enzyme substrates that are initially completely undetected by SERRS. Turnover of the substrate by the enzyme leads to the release of a surface targeting dye, and intense SERRS signals proportional to enzyme activity are generated. The method was used to rapidly screen the relative activities and enantioselectivities of fourteen enzymes including examples of lipases, esterases and proteases. In the current format the sensitivity of the technique is sufficient to detect 500 enzyme molecules, which offers the potential to detect multiple enzyme activities simultaneously and at levels found within single cells

Sedimentological and geochemical evidence for multistage failure of volcanic island landslides: A case study from Icod landslide on north Tenerife, Canary Islands

Volcanic island landslides can pose a significant geohazard through landslide-generated tsunamis. However, a lack of direct observations means that factors influencing tsunamigenic potential of landslides remain poorly constrained. The study of distal turbidites generated from past landslides can provide useful insights into key aspects of the landslide dynamics and emplacement process, such as total event volume and whether landslides occurred as single or multiple events. The northern flank of Tenerife has undergone multiple landslide events, the most recent being the Icod landslide dated at ?165 ka. The Icod landslide generated a turbidite with a deposit volume of ?210 km3, covering 355,000 km2 of seafloor off northwest Africa. The Icod turbidite architecture displays a stacked sequence of seven normally graded sand and mud intervals (named subunits SBU1–7). Evidence from subunit bulk geochemistry, volume, basal grain size, volcanic glass composition and sand mineralogy, combined with petrophysical and geophysical data, suggests that the subunit facies represents multistage retrogressive failure of the Icod landslide. The basal subunits (SBU1–3) indicate that the first three stages of the landslide had a submarine component, whereas the upper subunits (SBU4–7) originated above sea level. The presence of thin, non-bioturbated, mud intervals between subunit sands suggests a likely time interval of at least several days between each stage of failure. These results have important implications for tsunamigenesis from such landslides, as multistage retrogressive failures, separated by several days and with both a submarine and subaerial component, will have markedly lower tsunamigenic potential than a single-block failure