Study of TADF Emitters in OLEDs

Delayed fluorescence through thermally activated delayed fluorescence (TADF) has great potential for the creation of inexpensive and highly efficient white lighting applications, with superior colour rendering. Currently the highest external quantum efficiencies are achieved with small donor-acceptor-donor molecules utilising intramolecular charge transfer (ICT) states, and these molecules require a suitable host matrix to reside in. This thesis studies the effect of host material on the model molecule 2d, a proven efficient TADF emitter through diligent photophysical investigation. A combination of steady state and nanosecond time resolved spectroscopic studies confirm the importance of a high host triplet level to ensure that the ICT state is the lowest energy excited state to avoid high levels of quenching. More interestingly it is shown that the functional group combination of emitter and host is crucial in achieving efficient TADF in OLED devices. In particular combinations where both the host and dopant are carbazole-based should be avoided due to the formation of carbazole dimer. The effect of such dimerisation is to lower the host triplet level significantly, and further to deactivate the ability of the 2d dopant to produce the ICT state required for TADF by locking the 2d dopant in the ‘planar’ configuration. It is therefore clear that the chemical composition of the host is of critical importance for the design of future OLED devices. Experiment also suggests that there is a complex interplay between exciplex and ICT emission in 2d systems in the solid state, insofar as CT emission of any description has so far only been observed in conditions where exciplex can and does occur

Optimising medicines administration for patients with dysphagia in hospital:Medical or nursing responsibility?

Dysphagia is common—not only associated with stroke, dementia, Parkinson’s but also in many non-neurological medical problems—and is increasingly prevalent in ageing patients, where malnutrition is common and pneumonia is frequently the main cause of death. To improve the care of people with dysphagia (PWD) and minimise risk of aspiration and choking, the textures of food and drinks are frequently modified. Whilst medicines are usually concurrently prescribed for PWD, their texture is frequently not considered and therefore any minimisation of risk with respect to food and drink may be being negated when such medicines are administered. Furthermore, evidence is starting to emerge that mixing thickeners with medicines can, in certain circumstances, significantly affect drug bioavailability and therefore amending the texture of a medicine may not be straightforward. Research across a number of hospital trusts demonstrated that PWD are three times more likely to experience medication administration errors than those without dysphagia located on the same ward. Errors more commonly seen in PWD were missed doses, wrong formulation and wrong preparation through medicines alteration. Researchers also found that the same patient with dysphagia would be given their medicines in entirely different ways depending on the person administering the medicine. The alteration of medicines prior to administration has potential for patient harm, particularly if the medicine has been designed to release medicines at a pre-defined rate or within a pre-defined location. Alteration of medicines can have significant legal implications and these are frequently overlooked. Dispersing, crushing or mixing medicines can be part of, or misconstrued as, covert administration, thus introducing a further raft of legislation. Guidance within the UK recommends that following identification of dysphagia, the ongoing need for the medicine should be considered, as should the most appropriate route and formulation, with medicines alteration used as a last resort. The patient should be at the centre of any decision making. Evidence suggests that in the UK this guidance is not being followed. This article considers the clinical and legal issues surrounding administration of medicines to PWD from a UK perspective and debates whether medicines optimisation should be the primary responsibility of the prescriber when initiating therapy on the ward or the nurse who administers the medicine

Juvenile Victims of Property Crimes.

Property crime is the most frequent kind of criminal victimization and one with important economic and psychological consequences, although it has not received the same public attention as violent crime in recent years. Property crime victimization rates are much higher for juveniles than for adults, but very little attention has been paid to property crimes against juveniles or the particular features that characterize these crimes. This Bulletin tries to fill this gap by examining the characteristics of property crimes against juveniles. It uses crime information from the National Crime Victimization Survey (NCVS) for 1996–97 and the National Incident-Based Reporting System (NIBRS) for 1997

RIPless compressed sensing from anisotropic measurements

Compressed sensing is the art of reconstructing a sparse vector from its inner products with respect to a small set of randomly chosen measurement vectors. It is usually assumed that the ensemble of measurement vectors is in isotropic position in the sense that the associated covariance matrix is proportional to the identity matrix. In this paper, we establish bounds on the number of required measurements in the anisotropic case, where the ensemble of measurement vectors possesses a non-trivial covariance matrix. Essentially, we find that the required sampling rate grows proportionally to the condition number of the covariance matrix. In contrast to other recent contributions to this problem, our arguments do not rely on any restricted isometry properties (RIP's), but rather on ideas from convex geometry which have been systematically studied in the theory of low-rank matrix recovery. This allows for a simple argument and slightly improved bounds, but may lead to a worse dependency on noise (which we do not consider in the present paper).Comment: 19 pages. To appear in Linear Algebra and its Applications, Special Issue on Sparse Approximate Solution of Linear System

P-adic interpolation of metaplectic forms of cohomological type

Let G be a reductive algebraic group over a number field k. It is shown how Emerton's methods may be applied to the problem of p-adically interpolating the metaplectic forms on G, i.e. the automorphic forms on metaplectic covers of G, as long as the metaplectic covers involved split at the infinite places of k.Comment: 37 page

Characteristics of Crimes Against Juveniles

Until recently, it has been difficult to obtain a national statistical picture of juvenile crime victimization. The Uniform Crime Reporting (UCR) system, which has served as the Nation’s primary source of information about crime since 1929, has never collected information or reported crimes by age of victim, with the exception of homicides. The National Crime Victimization Survey (NCVS), the victim self-report survey conducted by the U.S. Department of Commerce, Bureau of the Census on behalf of the U.S. Department of Justice, Bureau of Justice Statistics for the past 20 years, has collected data only on crimes occurring to persons 12 years of age or older. Consequently, even such a basic fact as the percentage of all violent crimes that are committed against juveniles (youth ages 17 and younger) has been unavailable. The Federal Bureau of Investigation’s (FBI’s) developing National IncidentBased Reporting System (NIBRS), however, does provide detailed statistical information about juvenile victims of reported crimes. As more jurisdictions begin to participate in NIBRS, the outlines of a national picture of juvenile crime victims are beginning to emerge. Even though NIBRS is far from a comprehensive national data system, the fact that only partial data were available previously makes it particularly useful to see what information about juvenile victims can be gleaned from this system. An analysis of 1997 NIBRS data from jurisdictions in 12 States reveals some key findings

The Liberian Truth and Reconciliation Commission: reconciling or re-dividing Liberia?

After 14 years of civil war and violence followed by the momentous and rather unusual elections of 2005, in which a woman defeated a footballer for the presidency, Liberia has seen over six years of state reconstruction and relative peace. Two recent announcements have, however, served as a warning to the extent of progress. The most recent is President Ellen Johnson-Sirleaf’s declaration that she will, despite previous statements to the contrary, stand for re-election in 2011 due to shortcomings in progress. The announcement preceding Johnson-Sirleaf’s was made in the form of the report of the Liberian Truth and Reconciliation Commission (TRC). It recommended that Johnson-Sirleaf, and indeed many others accused of involvement in the war, should be barred from public office for the next 30 years, and still more should stand trial on charges of war crimes. Four important questions arise. First, what was the mandate and findings of the TRC? Second, how has Liberia and the wider international community reacted to the final report? Third, has the TRC fulfilled its mandate and contributed to a process of reconciliation? Finally, and in a much broader sense, where does the TRC stand relative to the much wider liberal peace model

Individual and Collective Behavior of Small Vibrating Motors Interacting Through a Resonant Plate

We report on experiments of many small motors -- cell phone vibrators -- glued to and interacting through a resonant plate. We find that individual motors interacting with the plate demonstrate hysteresis in their steady-state frequency due to interactions with plate resonances. For multiple motors running simultaneously, the degree of synchronization between motors increases when the motors' frequencies are near a resonance of the plate, and the frequency at which the motors synchronize shows a history dependence.Comment: 7 pages, 8 figure