209 research outputs found
Exactly Solvable BCS-BEC crossover Hamiltonians
We demonstrate a novel approach that allows the determination of very general
classes of exactly solvable Hamiltonians via Bethe ansatz methods. This
approach combines aspects of both the co-ordinate Bethe ansatz and algebraic
Bethe ansatz. The eigenfunctions are formulated as factorisable operators
acting on a suitable reference state. Yet, we require no prior knowledge of
transfer matrices or conserved operators. By taking a variational form for the
Hamiltonian and eigenstates we obtain general exact solvability conditions. The
procedure is conducted in the framework of Hamiltonians describing the
crossover between the low-temperature phenomena of superconductivity, in the
Bardeen-Cooper-Schrieffer (BCS) theory, and Bose-Einstein condensation (BEC).Comment: 6 Pages, To appear in Proceedings of The XXIXth International
Colloquium on Group-Theoretical Methods in Physics at Chern Institute of
Mathematic
Studying the effects of in-vehicle information systems on driver visual behaviour – implications for design
In-vehicle information systems (IVIS) are a common feature in modern vehicles. The interaction of drivers with IVIS when driving must be considered to minimise distraction whilst maintaining the benefits provided. This research investigates the glance behaviours of drivers, assessed from video data, when using two functions – a personal navigation device (study 1) and a green driving advisory device (study 2). The main focus was to establish the number of glances of 2 seconds or more to the IVIS and relate this to driver safety (as stipulated in new guidelines for use of IVIS proposed by NHTSA). In study 1, the percentage of eyes- off-road time for drivers was much greater in the experimental (with device) condition compared to the baseline condition (14.3% compared to 6.7%) but, whilst glances to the personal navigation device accounted for the majority of the increase, there were very few which exceeded 2 seconds. Drivers in study 2 spent on average 4.3% of their time looking at the system, at an average of 0.43 seconds per glance; no glances exceeded 2 seconds. The research showed that ordinary use of IVIS (excluding manual interaction) does not lead to driver visual distraction and therefore the impact on safety is minimal. The results of the study have important design implications for future in-vehicle information systems
Decision-analytic cost-effectiveness model to compare prostate cryotherapy to androgen deprivation therapy for treatment of radiation recurrent prostate cancer
Objective: To determine the cost-effectiveness of salvage cryotherapy (SC) in men with radiation recurrent prostate cancer (RRPC).
Design: Cost-utility analysis using decision analytic modelling by a Markov model.
Setting and methods: Compared SC and androgen deprivation therapy (ADT) in a cohort of patients with RRPC (biopsy proven local recurrence, no evidence of metastatic disease). A literature review captured published data to inform the decision model, and resource use data were from the Scottish Prostate Cryotherapy Service. The model was run in monthly cycles for RRPC men, mean age of 70 years. The model was run over the patient lifetime, to assess changes in patient health states and the associated quality of life, survival and cost impacts. Results are reported in terms of the discounted incremental costs and discounted incremental quality-adjusted life years (QALYs) gained between the 2 alternative interventions. Probabilistic sensitivity analysis used a 10 000 iteration Monte Carlo simulation.
Results: SC has a high upfront treatment cost, but delays the ongoing monthly cost of ADT. SC is the dominant strategy over the patient lifetime; it is more effective with an incremental 0.56 QALY gain (95% CI 0.28 to 0.87), and less costly with a reduced lifetime cost of £29 719 (€37 619) (95% CI −51 985 to −9243). For a ceiling ratio of £30 000, SC has a 100% probability to be cost-effective. The cost neutral point was at 3.5 years, when the upfront cost of SC (plus any subsequent cumulative cost of side effects and ADT) equates the cumulative cost in the ADT arm. Limitations of our model may arise from its insensitivity to parameter or structural uncertainty.
Conclusions: The platform for SC versus ADT cost-effective analysis can be employed to evaluate other treatment modalities or strategies in RRPC. SC is the dominant strategy, costing less over a patient's lifetime with improvements in QALYs
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I. Enantioselective Acylation of Silyl Ketene Acetals through Fluoride Anion-Binding Catalysis II. Development of a Practical Method for the Synthesis of Highly Enantioenriched Trans-1,2-Amino Alcohols
A highly enantioselective acylation of silyl ketene acetals with acyl fluorides was developed to generate useful α,α-disubstituted butyrolactone products in high yield and excellent enantioselectivities. This transformation is promoted by an arylpyrrolidino thiourea catalyst and 4-pyrrolidinopyridine and represents the first example of enantioselective thiourea anion-binding catalysis with fluoride. Mechanistic investigations revealed both catalysts to be necessary for reaction to occur, suggesting the thiourea aids in the generation of the key N-acylpyridinium/fluoride ion pair. The outstanding hydrogen-bond-accepting ability of fluoride is likely important in this regard. In addition, a strong dependence on both the N-acylpyridinium counteranion and the substituents on the silicon group of the silyl ketene acetal were observed, highlighting the importance of the silicon-fluoride interaction. A cyclic oligomeric (salen)Co–OTf complex was used to catalyze a highly enantioselective addition of phenyl carbamate to meso-epoxides to afford protected trans-1,2-amino alcohols. The use of an oligomeric (salen)Co–OTf complex as the catalyst and aryl carbamates as nucleophiles was crucial to the development of this reaction protocol. This method is amenable to large-scale synthesis due to the low catalyst loadings and high concentration used, its operational simplicity, and the use of inexpensive, commercially-available starting materials. To demonstrate the synthetic utility of this protocol, optically pure trans-2-aminocyclohexanol hydrochloride and trans-2-aminocyclopentanol hydrochloride were prepared on a multigram scale using only 0.5 and 1 mol% catalyst loading, respectively.Chemistry and Chemical Biolog
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Enantioselective Acylation of Silyl Ketene Acetals through Fluoride Anion-Binding Catalysis
A highly-enantioselective acylation of silyl ketene acetals with acyl fluorides has been developed to generate useful , -disubstituted butyrolactone products. This reaction is promoted by a new thiourea catalyst and 4-pyrrolidinopyridine and represents the first example of enantioselective thiourea anion-binding catalysis with fluoride.Chemistry and Chemical Biolog
Investigating what level of visual information inspires trust in a user of a highly automated vehicle
The aim of this research is to investigate whether visual feedback alone can affect a driver’s trust in an autonomous vehicle, and in particular, what level of feedback (no feedback vs. moderate feedback vs. high feedback) will evoke the appropriate level of trust. Before conducting the experiment, the Human Machine Interfaces (HMI) were piloted with two sets of six participants (before and after iterations), to ensure the meaning of the displays can be understood by all. A static driving simulator experiment was conducted with a sample of 30 participants (between 18 and 55). Participants completed two pre-study questionnaires to evaluate previous driving experience, and attitude to trust in automation. During the study, participants completed a trust questionnaire after each simulated scenario to assess their trust level in the autonomous vehicle and HMI displays, and on intention to use and acceptance. The participants were shown 10 different driving scenarios that lasted approximately 2 minutes each. Results indicated that the ‘high visual feedback’ group recorded the highest trust ratings, with this difference significantly higher than for the ‘no visual feedback’ group (U = .000; p = <0.001 < α) and the ‘moderate visual feedback’ group (U = .000; p = <0.001 < α). There is an upward inclination of trust in all groups due to familiarity to both the interfaces and driving simulator over time. Participants’ trust level was also influenced by the driving scenario, with trust reducing in all displays during safety verses non-safety-critical situations
Distraction effects of navigation and green-driving systems – results from field operational tests (FOTs) in the UK
Navigation systems and green-driving advisory systems are now a common feature in modern vehicles. The interaction of drivers with such systems when driving must be considered to minimise distraction whilst maintaining the benefits provided. This research investigates the glance behaviours of drivers, assessed from video data, when using a navigation device (study 1) and a green-driving advisory device (study 2). The main research question addressed was ‘Does the device cause visual distraction that might be detrimental to safety?’ The main focus was to establish the number of glances of 2 s or more to the systems and relate this to driver safety (as stipulated in new guidelines for use of in-vehicle systems proposed by the National Highway Traffic Safety Administration (NHTSA) in the US)
Usability of TeleFOT Nomadic and Aftermarket Devices [D1.8]
This deliverable reports on the Usability activities undertaken in TeleFOT mainly within WPs
4.8 and 4.10. These planned to support the Sub-Project 4 of TeleFOT in Evaluation and
Assessment of nomadic devices within the national Field Operational Tests (FOTs). The key
objective of WP4.8 in this regard is to provide measurable data that allows comparing
usability and user experience of different driver assistance services whilst the key objective
of WP4.10 is to identify and define the target and actual technical performance metrics for
the Nomadic Devices (NDs) used.
Two approaches are described in this Deliverable which have been utilised within TeleFOT
for evaluating the usability of the nomadic and aftermarket devices tested within the
TeleFOT FOTs. The first approach describes the feedback received from the TeleFOT
participants with regard to their user experiences with the devices tested during the FOTs.
To complement this information, each test site was asked to supply usability information
specifically related to the time taken and the number of user interactions (aka button
presses) to access certain functions within their ND. These included time and interactions to
access the main menu and primary function, or adjust the volume, as well as to start up and
shut down. The participants’ opinions on the design of the device, user interface, initial
reactions and benefits to the NDs were then recorded as were ‘Other Issues’ which related
to participants’ perceived usefulness, reliability and ease to interpret the information
offered by the ND. This method allowed in-depth information to be captured surrounding
issues which may have influenced the use of the ND during the FOT and/or common issues
which arose.
The second approach involved expert evaluations undertaken by HMI analysts working at
the test-sites on a number of devices that were tested within TeleFOT. Not all of the devices
that were tested within TeleFOT were subjected to expert evaluations. However, the
procedure for such evaluations is described along with the results
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