1,589 research outputs found
Enantioselective Organocatalytic α-Fluorination of Aldehydes
The first direct enantioselective catalytic α-fluorination of aldehydes has been accomplished. The use of enamine catalysis has provided a new organocatalytic strategy for the enantioselective fluorination of aldehydes to generate α-fluoro aldehydes, an important chiral synthon for medicinal agent synthesis. The use of imidazolidinone 1 as the asymmetric catalyst has been found to mediate the fluorination of a large variety of aldehyde substrates with N-fluorobenzenesulfonimide serving as the electrophilic source of fluorine. A diverse spectrum of aldehyde substrates can also be accommodated in this new organocatalytic transformation. While catalyst quantities of 20 mol % were generally employed in this study, successful halogenation can be accomplished using catalyst loadings as low as 2.5 mol %
Importance measures for non-coherent-system analysis
Component importance analysis is a key part of the
system reliability quantification process. It enables the weakest
areas of a system to be identified and indicates modifications,
which will improve the system reliability. Although a wide range of
importance measures have been developed, the majority of these
measures are strictly for coherent system analysis. Non-coherent
systems can occur and accurate importance analysis is essential.
This paper extends four commonly used measures of importance,
using the noncoherent extension of Birnbaum’s measure of
component reliability importance. Since both component failure
and repair can contribute to system failure in a noncoherent
system, both of these influences need to be considered. This paper
highlights that it is crucial to choose appropriate measures to
analyze component importance. First the aims of the analysis
must be outlined and then the roles that component failures and
repairs can play in system state deterioration can be considered.
For example, the failure/repair of components in safety systems
can play only a passive role in system failure, since it is usually
inactive, hence measures that consider initiator importance are
not appropriate to analyze the importance of these components.
Measures of importance must be chosen carefully to ensure
analysis is meaningful and useful conclusions can be drawn
Birnbaum’s measure of component importance for noncoherent systems
Importance analysis of noncoherent systems is limited,
and is generally inaccurate because all measures of importance
that have been developed are strictly for coherent analysis.
This paper considers the probabilistic measure of component
importance developed by Birnbaum (1969). An extension of this
measure is proposed which enables noncoherent importance analysis.
As a result of the proposed extension the average number
of system failures in a given interval for noncoherent systems
can be calculated more efficiently. Furthermore, because Birnbaum’s
measure of component importance is central to many
other measures of importance; its extension should make the
derivation of other measures possible
Calculating the failure intensity of a non-coherent fault tree using the BDD technique.
This paper considers a technique for calculating the unconditional failure intensity of
any given non-coherent fault tree. Conventional Fault Tree Analysis (FTA)
techniques involve the evaluation of lengthy series expansions and approximations are
unavoidable even for moderate sized fault trees. The Binary Decision Diagram (BDD)
technique overcomes some of the shortfalls of conventional FTA techniques enabling
efficient and exact quantitative analysis of both coherent and non-coherent fault trees
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Using Voice Recognition Software to improve communicative writing and social participation in an individual with severe acquired dysgraphia: an experimental single case therapy study
Background
Two previous single-case studies have reported that voice recognition software (VRS) can be a powerful tool for circumventing impaired writing in aphasia (Bruce et al, 2003; Estes & Bloom, 2011). However, these studies report mixed results regarding transfer of skills to functional tasks, such as emailing.
Method
A single-case therapy study was conducted with “Stephen”, a 63 -year old man with fluent aphasia and severe acquired dysgraphia and dyslexia limiting his social participation and ability to return to work. Treatment consisted of 16 one-hour sessions. Stephen was trained to use Dragon NaturallySpeakingRTM VRS to assist writing and Read+WriteGoldRTM text-to-speech software to assist reading, and to develop computer skills required to use email. Outcome measures evaluated writing efficiency and communicative effectiveness, the functional impact of the intervention, and changes in participation.
Results
Training produced significant gains in the efficiency and communicative effectiveness of Stephen’s writing, despite his underlying writing impairment remaining unchanged. Gains generalised to everyday functional communication, leading to increased social participation with Stephen undertaking a wider range of social activities and increasing his social network following treatment. Gains were maintained at follow-up assessment.
Discussion
Results indicate that a relatively short training period with assistive technologies achieved extensive generalisation to independent, functional communicative writing. Indeed, for this case, VRS training may have exceeded the degree of improvement in functional text writing that could have been achieved through impairment therapy, since gains were not limited to treated vocabulary. Some challenges were encountered in training Stephen to use VRS but, through adaptations to the training process, were largely overcome. Importantly, regaining independent writing skills resulted in profound and life-changing improvements to social participation. This may have resulted in Stephen reconnecting with important aspects of his pre-stroke identity, and improving his self-esteem.
Conclusion
This case adds to a small evidence base indicating that training in the use of VRS, in combination with text-to-speech software, may be an effective way to address writing impairments in chronic aphasia for individuals with relatively well-preserved spoken output. Not only can these technologies improve the efficiency and communicative effectiveness of writing, they can also lead to significant gains in functional communication and social participation. Further research is needed trialing this approach with a larger group of people with aphasia
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