Laser photolysis of photographic image dyes

Studies have been carried out investigating the photochemical and photophysical properties of pyrazolotriazole azomethine dyes. Such compounds can be used as magenta images in the subtractive colour photographic process. This work has been carried out both in dilute fluid solution and in high concentration, high viscosity systems designed to mimic the photographic product. Picosecond pump-probe laser flash photolysis studies have provided the first observation of photoinduced transient absorption changes attributable to the excited states of this class of dyes, and have allowed assignment of the excited singlet state lifetime as being in the range 1 to 3ps at room temperature, with little dependence upon solvent properties or the pattern of substituents on the dye skeleton. Using picosecond laser flash photolysis it has also been possible to observe evolution of the population along the ground state potential surface to the two isomeric forms, the rate of this process showing some solvent dependence. Nanosecond and picosecond laser flash photolysis studies have been used to investigate the process of syn-anti and anti-syn isomerisation about the azomethine linkage. The syn-anti photoisomerisation occurs on picosecond timescales, the anti isomer so produced relaxing thermally back to the syn form on timescales ranging from microseconds to milliseconds. The rate constant for this process is a complex function of solvent properties as well as being dependent upon steric factors within the molecule, and the reasons for this are discussed. Triplet energy sensitisation studies have demonstrated that a pathway exists for this isomerisation process via the triplet manifold, and has allowed determination of minimum isomerisation quantum yields from the triplet state. Such studies have also allowed estimation of limits for the molar decadic absorption coefficients of the anti isomer. The photographic product dyes have been demonstrated to be efficient quenchers of singlet molecular oxygen, the quenching mechanism being predominantly physical in nature. The quantum yields of singlet oxygen production are too small to be measured using time resolved techniques. These factors are used to explain in part the resistance of such compounds to oxidative photodegradation. Steady state irradiation of azomethine dyes in systems designed to simulate the photographic product by a high intensity source of known spectral profile has allowed determination of the quantum yields of photodegradation, which in combination with the results obtained in fluid solution provide a basis for explaining the behaviour of image dyes in the photographic product environment

Luminosity function of faint Galactic sources in the Chandra bulge field

We study the statistical properties of faint X-ray sources detected in the Chandra Bulge Field. The unprecedented sensitivity of the Chandra observations allows us to probe the population of faint Galactic X-ray sources down to luminosities L(2-10 keV)~1e30 erg/sec at the Galactic Center distance. We show that the luminosity function of these CBF sources agrees well with the luminosity function of sources in the Solar vicinity (Sazonov et al. 2006). The cumulative luminosity density of sources detected in the CBF in the luminosity range 1e30-1e32 erg/sec per unit stellar mass is L(2-10 keV)/M*=(1.7+/-0.3)e27 erg/sec/Msun. Taking into account sources in the luminosity range 1e32-1e34 erg/sec from Sazonov et al. (2006), the cumulative luminosity density in the broad luminosity range 1e30-1e34 erg/sec becomes L(2-10 keV)/M*=(2.4+/-0.4)e27 erg/sec/Msun. The majority of sources with the faintest luminosities should be active binary stars with hot coronae based on the available luminosity function of X-ray sources in the Solar environment.Comment: 5 pages, 4 figures, Accepted for publication in MNRA

Activation energies of photoinduced unimolecular, bimolecular and termolecular processes on silica gel surfaces

This article was published in the journal, Photochemical and Photobiological Sciences [© Royal Society of Chemistry and Owner Societies]. The definitive version is available at: http://dx.doi.org/10.1039/c0pp00256aActivation energies for energy and electron transfer have been measured in various systems on silica gel. In the case of ion-electron recombination, a facile technique involving fluorescence recovery is described which complements diffuse reflectance spectroscopy in the study of these systems. In bimolecular anthracene/azulene systems, activation energies have been shown to be independent of pre-treatment temperature in the range 25–210 °C, demonstrating that physisorbed water plays little role in determining diffusion rates on silica gel. In a ternary anthracene/azulene/perylene system, we have for the first time presented comparative activation energies for the diffusion of azulene and its radical cation, and have shown a greater activation energy for diffusion of the latter species

On Closing the Circle

Ghirardi sought to “close the circle”—to find a place for human experience of measurement outcomes within quantum mechanics. I argue that Ghirardi’s spontaneous collapse approach succeeds at this task, and in fact does so even without the postulation of a particular account of “primitive ontology”, such as a mass density distribution or a discrete “flashes”. Nevertheless, I suggest that there is a remaining ontological problem facing spontaneous collapse theories concerning the use of classical concepts like “particle” in quantum mechanical explanation at the micro-level. Neither the mass density nor the flash ontology is any help with this problem

A 1D fluid model of the Centaurus A jet

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Final published version available at: https://doi.org/10.1093/mnras/stz348.We implement a steady, one-dimensional flow model for the X-ray jet of Centaurus A in which entrainment of stellar mass loss is the primary cause of dissipation. Using over 260 ks of new and archival Chandra/ACIS data, we have constrained the temperature, density and pressure distributions of gas in the central regions of the host galaxy of Centaurus A, and so the pressure throughout the length of its jet. The model is constrained by the observed profiles of pressure and jet width, and conserves matter and energy, enabling us to estimate jet velocities, and hence all the other flow properties. Invoking realistic stellar populations within the jet, we find that the increase in its momentum flux exceeds the net pressure force on the jet unless only about one half of the total stellar mass loss is entrained. For self-consistent models, the bulk speed only falls modestly, from ~0.67c to ~0.52c over the range of 0.25-5.94 kpc from the nucleus. The sonic Mach number varies between ~5.3 and 3.6 over this range.Peer reviewe

Probing the interplay between factors determining reaction rates on silica gel using termolecular systems

This article was published in the journal, Photochemical and Photobiological Sciences [© Royal Society of Chemistry and Owner Societies]. The definitive version is available at: http://dx.doi.org/10.1039/c2pp25171jIn this study we have compared energy and electron transfer reactions in termolecular systems using a nanosecond diffuse reflectance laser flash photolysis technique. We have previously investigated these processes on silica gel surfaces for bimolecular systems and electron transfer in termolecular systems. The latter systems involved electron transfer between three arene molecules with azulene acting as a molecular shuttle. In this study we present an alternative electron transfer system using trans β-carotene as an electron donor in order to effectively immobilise all species except the shuttle, providing the first unambiguous evidence for radical ion mobility. In the energy transfer system we use naphthalene, a structural isomer of azulene, as the shuttle, facilitating energy transfer from a selectively excited benzophenone sensitiser to 9-cyanoanthracene. Bimolecular rate constants for all of these processes have been measured and new insights into the factors determining the rates of these reactions on silica gel have been obtained

Piloting the Global Subsidy: The Impact of Subsidized Artemisinin-Based Combination Therapies Distributed through Private Drug Shops in Rural Tanzania

BACKGROUND: WHO estimates that only 3% of fever patients use recommended artemisinin-based combination therapies (ACTs), partly reflecting their high prices in the retail sector from where many patients seek treatment. To overcome this challenge, a global ACT subsidy has been proposed. We tested this proposal through a pilot program in rural Tanzania. METHODS/PRINCIPAL FINDINGS: Three districts were assigned to serve either as a control or to receive the subsidy plus a package of supporting interventions. From October 2007, ACTs were sold at a 90% subsidy through the normal private supply chain to intervention district drug shops. Data were collected at baseline and during intervention using interviews with drug shop customers, retail audits, mystery shoppers, and audits of public and NGO facilities. The proportion of consumers in the intervention districts purchasing ACTs rose from 1% at baseline to 44.2% one year later (p<0.001), and was significantly higher among consumers purchasing for children under 5 than for adults (p = 0.005). No change in ACT usage was observed in the control district. Consumers paid a mean price of $0.58 for ACTs, which did not differ significantly from the price paid for sulphadoxine-pyrimethamine, the most common alternative. Drug shops in population centers were significantly more likely to stock ACTs than those in more remote areas (p<0.001). CONCLUSIONS: A subsidy introduced at the top of the private sector supply chain can significantly increase usage of ACTs and reduce their retail price to the level of common monotherapies. Additional interventions may be needed to ensure access to ACTs in remote areas and for poorer individuals who appear to seek treatment at drug shops less frequently. TRIAL REGISTRATION: Controlled-Trials.com ISRCTN39125414

Uncovering treatment burden as a key concept for stroke care: a systematic review of qualitative research

&lt;b&gt;Background&lt;/b&gt; Patients with chronic disease may experience complicated management plans requiring significant personal investment. This has been termed ‘treatment burden’ and has been associated with unfavourable outcomes. The aim of this systematic review is to examine the qualitative literature on treatment burden in stroke from the patient perspective.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Methods and findings&lt;/b&gt; The search strategy centred on: stroke, treatment burden, patient experience, and qualitative methods. We searched: Scopus, CINAHL, Embase, Medline, and PsycINFO. We tracked references, footnotes, and citations. Restrictions included: English language, date of publication January 2000 until February 2013. Two reviewers independently carried out the following: paper screening, data extraction, and data analysis. Data were analysed using framework synthesis, as informed by Normalization Process Theory. Sixty-nine papers were included. Treatment burden includes: (1) making sense of stroke management and planning care, (2) interacting with others, (3) enacting management strategies, and (4) reflecting on management. Health care is fragmented, with poor communication between patient and health care providers. Patients report inadequate information provision. Inpatient care is unsatisfactory, with a perceived lack of empathy from professionals and a shortage of stimulating activities on the ward. Discharge services are poorly coordinated, and accessing health and social care in the community is difficult. The study has potential limitations because it was restricted to studies published in English only and data from low-income countries were scarce.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Conclusions&lt;/b&gt; Stroke management is extremely demanding for patients, and treatment burden is influenced by micro and macro organisation of health services. Knowledge deficits mean patients are ill equipped to organise their care and develop coping strategies, making adherence less likely. There is a need to transform the approach to care provision so that services are configured to prioritise patient needs rather than those of health care systems

A core outcome set for aphasia treatment research: the ROMA consensus statement

Background: A core outcome set (COS; an agreed, minimum set of outcomes) was needed to address the heterogeneous measurement of outcomes in aphasia treatment research and to facilitate the production of transparent, meaningful and efficient outcome data. Objective: The Research Outcome Measurement in Aphasia (ROMA) consensus statement provides evidence-based recommendations for the measurement of outcomes for adults with post-stroke aphasia within phase I-IV aphasia treatment studies. Methods: This statement was informed by a four-year program of research which comprised investigation of stakeholder-important outcomes using consensus processes, a scoping review of aphasia outcome measurement instruments, and an international consensus meeting. This paper provides an overview of this process and presents the results and recommendations arising from the international consensus meeting. Results: Five essential outcome constructs were identified: Language, communication, patient-reported satisfaction with treatment and impact of treatment, emotional wellbeing, and quality of life. Consensus was reached for the following measurement instruments: Language: The Western Aphasia Battery Revised (WAB-R) (74% consensus); emotional well-being: General Health Questionnaire (GHQ)-12 (83% consensus); quality of life: Stroke and Aphasia Quality of Life Scale (SAQOL-39) (96% consensus). Consensus was unable to be reached for measures of communication (where multiple measures exist) or patient-reported satisfaction with treatment or impact of treatment (where no measures exist). Discussion: Harmonisation of the ROMA COS with other core outcome initiatives in stroke rehabilitation is discussed. Ongoing research and consensus processes are outlined. Conclusion: The WAB-R, GHQ, and SAQOL-39 are recommended to be routinely included within phase I-IV aphasia treatment studies. This consensus statement has been endorsed by the Collaboration of Aphasia Trialists, the British Aphasiology Society, the German Society for Aphasia Research and Therapy, and the Royal College of Speech Language Therapists