Time- and intensity-dependent broadband cavity-enhanced absorption spectroscopy with pulsed intra-cavity laser-induced plasmas

A pulsed laser-induced plasma (LIP) was generated in ambient air inside a high-finesse (F ≈ 5200) near-concentric optical cavity. The optical plasma emission was successfully trapped and sustained by the cavity, manifested by ring-down times in excess of 4 μs indicating effective mirror reflectivities of ∼0.9994. The light leaking from the cavity was used to measure broadband absorption spectra of gaseous azulene under ambient air conditions between 580 and 645 nm, employing (i) intensity-dependent cavity-enhanced, and (ii) time-dependent cavity-ring down methodologies. Minimum detectable absorption coefficients of 4.7 × 10−8 cm−1 and 7.4 × 10−8 cm−1 were achieved for the respective approaches. The two approaches were compared and implications of pulsed excitation for gated intensity-dependent measurements were discussed

Fluctuating magnetic moments in liquid metals

We re-analyze literature data on neutron scattering by liquid metals to show that non-magnetic liquid metals possess a magnetic moment that fluctuates on a picosecond time scale. This time scale follows the motion of the cage-diffusion process in which an ion rattles around in the cage formed by its neighbors. We find that these fluctuating magnetic moments are present in liquid Hg, Al, Ga and Pb, and possibly also in the alkali metals.Comment: 17 pages, 5 figures, submitted to PR

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

Abstract Much has been made of the capabilities of Field Programmable Gate Arrays (FPGA's

Using Online Role-playing Games for Entrepreneurship Training

This edited collection of chapters explores the application, potential and challenges of game-based learning and gamification across multiple disciplines and sectors, including psychology, education, business, history, languages and the ..

Tridentate Directing Groups Stabilize 6-Membered Palladacycles in Catalytic Alkene Hydrofunctionalization

Removable tridentate directing groups inspired by pincer ligands have been designed to stabilize otherwise kinetically and thermodynamically disfavored 6-membered alkyl palladacycle intermediates. This family of directing groups enables regioselective remote hydrocarbofunctionalization of several synthetically useful alkene-containing substrate classes, including 4-pentenoic acids, allylic alcohols, homoallyl amines, and bis-homoallylamines, under Pd­(II) catalysis. In conjunction with previous findings, we demonstrate regiodivergent hydrofunctionalization of 3-butenoic acid derivatives to afford either Markovnikov or anti-Markovnikov addition products depending on directing group choice. Preliminary mechanistic and computational data are presented to support the proposed catalytic cycle

A new model for magnetoreception

Certain migratory birds can sense the earth's magnetic field. The nature of this process is not yet properly understood. Here we offer a simple explanation according to which birds literally `see' the local magnetic field: Our model relates the well-established radical pair hypothesis to the phenomenon of Haidinger's brush, a capacity to see the polarisation of light. This new picture explains recent surprising experimental data indicating long lifetimes for the radical pair. Moreover there is a clear evolutionary path toward this field sensing mechanism: it is an enhancement of a weak effect that may be present in many species.Comment: 8 pages, 5 figures, version of final published pape

Reconnaissance Survey of the Irish Continental Shelf/Shelf Edge - Atlantic Irish Regional Survey (AIRS) 1996: A GLORIA Survey of the Irish Continental Margin

The Atlantic Irish Regional Survey (AIRS96) sidescan sonar survey was carried out in August 1996. Covering an area of 200,000 sq.km it represented the largest reconnaissance seabed survey of the Irish Continental Shelf region. It covered both margins, together with much of the basin floor, of the Irish sector of the Rockall Trough and extended into the northern part of the Porcupine Seabight. The objectives of this project were two fold: 1. Strategic: •to undertake, for the first time a preliminary reconnaissance survey of the Irish Continental Shelf/Shelf Edge, •to establish a strategic database on Shelf/Slope Edge conditions, •to provide training and experience to Irish researchers in state of the art marine surveying equipment (GLORIA) and data processing. 2. Scientific: •to document slope stability and mass wasting features on the margins of the Rockall Trough, •to map, where possible, occurrences of deep water carbonate mounds, •to investigate the sediment erosional, transport and depositional mechanisms that have shaped the present morphology of the region. The survey revealed a range of sedimentary features across the steep (i.e. >6º slope) margins and the basin floor in the Rockall Trough. Four classes of sedimentary feature are recognised: (1) mass failure, (2) canyon systems, (3) sediment fans, and (4) sediment drifts. The western margin is characterised by large-scale downslope mass movement features. The western and central parts of the basin floor in the Rockall Trough contain the Feni Sediment Ridge, a large Miocene-Recent contourite sediment accumulation draped by large sediment waves trending sub-parallel to the dominant modern current pattern. A large-scale downslope mass failure feature is recognised across 14,000 sq.km of the northeastern margin of the Rockall Trough. Smaller slides and slumps occur along the eastern margin in association with more prevalent canyon, channel and fan systems. A cluster of carbonate mounds was imaged in the northern part of the Porcupine Seabight. These represent part of one of the most extensive suites of deep-water carbonate mounds in the Atlantic Margin and are currently the subject of a number of new EU-funded research projects. Strong northward-directed bottom currents along the eastern margin are suggested to erode, circulate and re-deposit sediment on the basin floor and on the western margin of the Rockall Trough. The main terrigenous sedimentary input was from the Irish Mainland Shelf. A broad interplay of alongslope and downslope sediment transport processes shaped the morphology of the Rockall Trough, while tectonically-driven basin subsidence, Quaternary glaciations and glacio-eustatic sea-level fluctuations also influenced the overall sedimentation pattern in the Rockall Trough.Funder: Marine Institut

Hydrogen-Bonded Homoleptic Fluoride–Diarylurea Complexes::Structure, Reactivity, and Coordinating Power

Hydrogen-bonding with fluoride is a key interaction encountered when analyzing the mode of action of 5'-fluoro-5'-deoxyadenosine synthase, the only known enzyme capable of catalyzing the formation of a C-F bond from F-. Further understanding of the effect of hydrogen-bonding on the structure and reactivity of complexed fluoride is therefore important for catalysis and numerous other applications, such as anion supramolecular chemistry. Herein we disclose a detailed study examining the structure of 18 novel urea-fluoride complexes in the solid state, by X-ray and neutron diffraction, and in solution phase and explore the reactivity of these complexes as a fluoride source in SN2 chemistry. Experimental data show that the structure, coordination strength and reactivity of the urea-fluoride complexes are tunable by modifying substituents on the urea receptor. Hammett analysis of aryl groups on the urea indicates that fluoride bind-ing is dependent on [sigma]p and [sigma]m parameters with stronger binding being observed for electron-deficient urea ligands. For the first time, defined urea-fluoride complexes are used as fluoride-binding reagents for the nucleophilic substitution of a model alkyl bromide. The reaction is slower in comparison with known alcohol-fluoride complexes, but SN2 is largely favored over E2, at a ratio surpassing all hydrogen-bonded complexes documented in the literature for the model alkyl bromide employed. Increased second-order rate constants at higher dilution support the hypothesis that the reactive species is a 1:1 urea-fluoride complex of type [UF]- (U = urea) resulting from partial dissociation of the parent compound [U2F]- . The dissociation processes can be quantified through a combination of UV and NMR assays, including DOSY and HOESY analyses that illuminate the complexation state and H-bonding in solution

An approach to evaluating the user experience of serious games

The use of serious games to support learning continues to expand across a range of educational and training settings. Hence, a need exists to understand more fully how users experience such games. This study seeks to describe and assess an approach to the evaluation of user-experience applied within the context of a specific serious game developed to address the training needs of people working in social enterprises. Drawing on an extensive literature review, the development of a survey instrument to capture the multi-dimensional nature of user-experience is explained as is the evaluation process employed. Findings from surveys of individuals working in social enterprises are analysed and discussed. The results demonstrate the value of the proposed method of user-experience evaluation. Recommendations for practice and further research are outlined, identifying in particular the importance of qualitative insights in the evaluation process and the need for greater understanding of the inter-relationships between the various dimensions and attributes of user-experience in serious games