On the Electronic Spectroscopy of Closed Shell Cations Derived From Resonance Stabilized Radicals: Insights From Theory and Franck-Condon Analysis

Context. Recent attention has been directed on closed-shell aromatic cations as potential carriers of the diffuse interstellar bands. The spectra of mass-selected, matrix-isolated benzylium, and tropylium cations were recently reported. The visible spectrum of benzylium exhibits a large Franck-Condon (FC) envelope, inconsistent with diffuse interstellar band carriers. Aims. We perform a computational analysis of the experimentally studied benzylium spectrum before extending the methods to a range of larger, closed-shell aromatic cations to determine the potential for this class of systems as diffuse interstellar band carriers. Methods. Density functional theory (DFT), time-dependant ((TD)DFT), and multi-configurational self-consistent field second-order perturbation theory (MRPT2) methods in concert with multidimensional FC analysis is used to model the benzylium spectrum. These methods are extended to larger closed-shell aromatic hydrocarbon cations derived from resonance-stabilized radicals, which are predicted to show strong S0 → Sn transitions in the visible region. The ionization energies of a range of these systems are also calculated by DFT. Results. The simulated benzylium spectrum was found to yield excellent agreement with the experimental spectrum showing an extended progression in a low frequency (510 cm-1) ring distortion mode. The FC progression was found to be significantly quenched in the larger species: 1-indanylium, 1-naphthylmethylium, and fluorenium. Excitation and ionization energies of the closed-shell cations were found to be consistent with diffuse interstellar band carriers, with the former lying in the visible range and the latter straddling the Lyman limit in the 13−14 eV range. Conclusions. Large closed-shell polycyclic aromatic hydrocarbon cations remain viable candidate carriers of the diffuse interstellar bands

May 11, 1846: To John. B. Cornell

Letter to John. B. Cornell from his friend W. P. Reid; detailing Reid\u27s life in Oberlin

Electrodeposition from supercritical fluids

Recent studies have shown that it is possible to electrodeposit a range of materials, such as Cu, Ag and Ge, from various supercritical fluids, including hydrofluorocarbons and mixtures of CO2 with suitable co-solvents. In this perspective we discuss the relatively new field of electrodeposition from supercritical fluids. The perspective focuses on some of the underlying physical chemistry and covers both practical and scientific aspects of electrodeposition from supercritical fluids. We also discuss possible applications for supercritical fluid electrodeposition and suggest some key developments that are required to take the field to the next stage

Coal-shale interface detection system

A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through

Casimir repulsion between metallic objects in vacuum

We give an example of a geometry in which two metallic objects in vacuum experience a repulsive Casimir force. The geometry consists of an elongated metal particle centered above a metal plate with a hole. We prove that this geometry has a repulsive regime using a symmetry argument and confirm it with numerical calculations for both perfect and realistic metals. The system does not support stable levitation, as the particle is unstable to displacements away from the symmetry axis.Comment: 4 pages, 4 figures; added references, replaced Fig.

What do you need? 2001-02: findings from a national survey of people living with HIV

Duration: October 2000 - June 2002 Despite the importance attached to the needs of people with HIV in defining policy, there is no consensus about how such needs should be identified and measured. This UK-wide study gives priority to individual understandings of need, describing them in a way that respects the subjectivity of people's lives. Using self-completion, freepost return questionnaires the survey assesses difficulties and needs in the following 18 key areas of life: housing; eating and drinking; sleeping; household chores and looking after yourself; mobility; money; managing anxiety and depression; problems with drugs and alcohol; relationships with regular partners; looking after children; friendships; sex; discrimination; self-confidence; knowledge of HIV treatments; ability to take treatments regularly; dealing with health professionals; and training and opportunities. For each category, questions addressed experience of problems, feelings about personal state and capacity to benefit from further support. Data was collected between July and October 2001. Questionnaires were distributed by 200 service providers including HIV outpatients and GUM clinics, AIDS service organisations, HIV newsletters and the 'HIV-positive' press. This study recruited 1,821 people with HIV from across the UK which represented about 8% of the entire population of people with diagnosed HIV at that time. The most frequently reported problems related to anxiety and depression (67%), sleep (59%), sex (51%), self-confidence (48%) and eating / appetite (42%). Among those on anti-HIV therapy, 32% reported problems taking treatments and 26% reported problems dealing with health professionals, whereas problems with knowledge of HIV treatments were reported by only 5%. These problem indicators are only half the story. Some respondents were happy with their current state despite reporting a problem, suggesting an acceptance of the problem and / or satisfactory management of it. Alternatively, some respondents were unhappy with their current state but did not report a problem, indicating the importance of goals, as well as problems, in defining needs. Needs are complex and dynamic. They are shaped by immediate circumstances and resources, but also depend on individual perceptions of the value and possibilities of life. If the perceived possibilities of life increase, so may personal needs. The relationship of illness and treatments to needs is therefore far from straightforward. The final report was called What do you need? Findings from a national survey of people living with HIV. Results were also written up in a Journal article called The needs of people with HIV in the UK: findings from a national survey (International Journal of STDs & AIDS 2004)

Violations of Bell Inequalities for Measurements with Macroscopic Uncertainties: What does it Mean to Violate Macroscopic Local Realism?

We suggest to test the premise of ``macroscopic local realism'' which is sufficient to derive Bell inequalities when measurements of photon number are only accurate to an uncertainty of order $n$ photons, where $n$ is macroscopic. Macroscopic local realism is only sufficient to imply, in the context of the original Einstein-Podolsky-Rosen argument, fuzzy ``elements of reality'' which have a macroscopic indeterminacy. We show therefore how the violation of local realism in the presence of macroscopic uncertainties implies the failure of ``macroscopic local realism''. Quantum states violating this macroscopic local realism are presented.Comment: 28 pages, 5 figures- new version is unchanged but tightened-20 pages, 5 figure

Flux calibration of the AAO/UKST SuperCOSMOS H-alpha Survey

The AAO/UKST SuperCOSMOS H$\alpha$ Survey (SHS) was, when completed in 2003, a powerful addition to extant wide-field surveys. The combination of areal coverage, spatial resolution and sensitivity in a narrow imaging band, still marks it out today as an excellent resource for the astronomical community. The 233 separate fields are available online in digital form, with each field covering 25 square degrees. The SHS has been the motivation for equivalent surveys in the north, and new digital H$\alpha$ surveys now beginning in the south such as VPHAS+. It has been the foundation of many important discovery projects with the Macquarie/AAO/Strasbourg H$\alpha$ planetary nebula project being a particularly successful example. However, the full potential of the SHS has been hampered by lack of a clear route to acceptable flux calibration from the base photographic data. We have determined the calibration factors for 170 individual SHS fields, and present a direct pathway to the measurement of integrated H$\alpha$ fluxes and surface brightnesses for resolved nebulae detected in the SHS. We also include a catalogue of integrated H$\alpha$ fluxes for $>$100 planetary and other nebulae measured from the SHS, and use these data to show that fluxes, accurate to $\pm$ 0.10 - 0.14 dex ($\sim$25-35 per cent), can be obtained from these fields. For the remaining 63 fields, a mean calibration factor of 12.0 counts pix$^{-1}$ R$^{-1}$ can be used, allowing the determination of reasonable integrated fluxes accurate to better than $\pm$0.2 dex ($\sim$50 per cent). We outline the procedures involved and the caveats that need to be appreciated in achieving such flux measurements. This paper forms a handy reference source that will significantly increase the scientific utility of the SHS.Comment: 14 pages, 12 figures, 2 tables (plus 7 pp. of supplementary online information). Version to appear in MNRA