7 research outputs found
Beyond problem identification: valuing methods in a ‘system usability practice’
Historically, usability evaluation methods (UEMs) have been evaluated on their
capability for problem identification. However, the relevance of this approach has been
questioned for applied usability work. To investigate alternative explanations of what is
important for method use a grounded theory of usability practitioners was developed (9
interviews from the website domain and 13 in the safety-critical domain). The analysis
proceeded in bottom-up and top-down stages. The bottom-up stages produced insight
from the data in an exploratory and inductive manner. This highlighted the importance
of contextual factors and the need for system descriptions: UEM adoption and
adaptation cannot be fully understood devoid of context. The top-down stages used
Distributed Cognition and Resilience Engineering conceptual frameworks as leverage
for exploring the data in a deductive manner. These were chosen for their functional
descriptions of systems. To illustrate the importance of context we describe three
models: 1) where previous research has highlighted the downstream utility of UEMs we
expand the metaphor to consider the landscape through which the stream flows, where
the landscape represents the project’s context; 2) where information propagation and
transformation in a project is influenced by social, information flow, artefact, physical
and evolutionary factors; and 3) where the functional couplings between parts of the
system of usability practice can be monitored and managed to positively resonate with
each other, thereby improving the performance of the system overall. The concept of
‘Positive Resonance’ is introduced to describe how practitioners adapt to the context to
maximise their impact under constrained resources. The functional couplings are
described in a functional resonance model of HCI practice. This model is validated by
interviewees and other practitioners outside of the study. This research shows that
problem identification is limited for valuing UEMs. Instead, functional couplings of
UEMs should be considered to improve system performance, which influence UEM
adoption and adaptation in practice
Prophylaxis of disease caused by bacterial pathogens of man
This thesis reports research undertaken which will lead to improved pretreatments
and therapies for disease caused by Clostridium perfringens, Francisella
tularensis, Yersinia pestis and Burkholderia pseudomallei.
C. perfringens is thought to be the most widely distributed bacterial pathogen and
is the most important Clostridial species associated with enteric disease in
domesticated animals. During warfare C. perfringens has been a significant
causes of mortality. Between 1 and 10% of wounded personnel developed gas
gangrene during the 1st and 2nd world wars. The ability of the bacterium to cause a
range of diseases is due largely to the differential production of toxins. The first
reported cloning and nucleotide sequencing of three of the four major toxins (α, β
and ε-toxins) is documented in this thesis. The regulation of expression of α-toxin
in C. perfringens has been investigated and methods for the expression of
recombinant proteins in E. coli have been devised This information has been used
to develop improved PCR-based diagnostic tests, and to investigate structure-function
relationships. A high resolution crystal structure of a-toxin (phospholipase
C) is reported. Using molecular and biophysical techniques, the functions of the
two domains of the protein have been determined. Residues that play roles in the
interaction of the toxin with host cell membranes have been identified using site-directed
mutagenesis. This work has also provided a major insight into the
structures and functions of related phospholipases C (the zincmetallophospholipases
C) from other bacterial pathogens. This pioneering work
with α-toxin is recognised by invitations to write reviews and book chapters on this
subject and on bacterial phospholipases C. C. perfringens β-toxin has been shown
to be related to pore forming toxins such as Staphylococcus aureus α-toxin. This
finding suggests, for the first time, the mode of action of β-toxin. The interaction of
C. perfringens ε-toxin with host cells has been investigated and progress made in
identifying the cell-surface receptor for the toxin. Genetically engineered toxoids
have been devised which induce high-level protection against α and ε-toxins.
These vaccines are currently being developed by industry for veterinary use.
Similar approaches have been used to devise a recombinant vaccine against
Clostridium botulinum toxin F. The wider applications of toxins as therapeutics
have also been investigated, and a novel cancer drug delivery system based on
targeted lysis of drug-containing liposomes by α-toxin has been devised and
patented.
F. tularensis is the etiological agent of tularemia, a disease of man that is found in
most countries in the Northern hemisphere and most frequently in Scandinavia, N.
America, Japan and N. Russia. In this thesis the efficacy of antibiotics for the
prevention and treatment of experimental tularemia is documented. Two surface
antigens (lipopolysaccharide and FopA) have been evaluated as sub-unit
vaccines. Of these, lipopolysaccharide shows potential as a protective antigen.
However, because of the paucity of information available on this bacterium, a
wider approach to vaccine development, involving the determination of the
genome sequence of a fully virulent strain of F. tularensis has been undertaken. A
preliminary analysis of the genome sequence is reported here, which has allowed
the identification of targets for the development of a rationally attenuated mutant
for use as a live vaccine.
Y. pestis is generally recognised to have caused three major pandemics of
disease, and credible estimates indicate that together these resulted in 200
million deaths. WHO figures indicate that there is a continuing public health
problem from plague, especially in Africa, Asia and South America. In this thesis
existing vaccines and antibiotics have been evaluated for the prevention and
treatment of plague and found to have limitations. A number of approaches to the
development of an improved vaccine have been investigated including rationally
attenuated strains of the bacterium and isolated surface antigens. A sub-unit
vaccine against plague has been devised based on recombinant forms of the F1-
and V-antigens. This vaccine provides high level protection against both bubonic
and pneumonic plague. This recombinant sub-unit vaccine has been patented
and is currently in phase I clinical trials in man. This vaccine has been formulated
for single oral or intranasal delivery, using microencapsulated or Salmonella-based
delivery systems. Methods for enhancing the stability and efficacy of these
vaccines have been investigated. Reviews on plague and plague vaccines have
been written, confirming the status of the author as a world leader in this field. The
work to devise an improved vaccine has also provided insight into the molecular
basis of pathogencity of Y. pestis. A phoP / phoQ regulatory system has been
discovered in the bacterium, which plays a key role in survival of the bacterium
within macrophages. The V-antigen has been shown to be surface located to
play a key role in the translocation of effector proteins into host cells. The
biogenesis of the F1-capsular antigen has been investigated at a genetic and
biophysical level. In order to underpin future work with this pathogen, the genome
sequence is currently being determined. This work has already provided major
new insights into the evolution of this pathogen.
B. pseudomallei (formerly Pseudomonas pseudomallei) is found primarily in S. E.
Asia, N. Australia and other tropical areas of the world. Melioidosis has recently
appeared in temperate zones, including mainland France and the UK possible as
a consequence of increased international travel. Acute disease can be treated
with antibiotics but the bacterium can persist in the host and subsequent disease
episodes can occur. In this thesis ciprofloxacin and doxycyline have been are
evaluated and shown to have significant limitations for the treatment of
melioidodis. In the longer term there is a requirement for an effective vaccine
against melioidosis, and work is reported here to devise the genetic tools which
will be necessary for the genetic manipulation of the bacterium, with a view
towards the identification of virulence determinants
Proceedings of the First International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics
1st International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Kruger Park, 8-10 April 2002.This lecture is a principle-based review of a growing body
of fundamental work stimulated by multiple opportunities to
optimize geometric form (shape, structure, configuration,
rhythm, topology, architecture, geography) in systems for heat
and fluid flow. Currents flow against resistances, and by
generating entropy (irreversibility) they force the system global
performance to levels lower than the theoretical limit. The
system design is destined to remain imperfect because of
constraints (finite sizes, costs, times). Improvements can be
achieved by properly balancing the resistances, i.e., by spreading
the imperfections through the system. Optimal spreading means
to endow the system with geometric form. The system
construction springs out of the constrained maximization of
global performance. This 'constructal' design principle is
reviewed by highlighting applications from heat transfer
engineering. Several examples illustrate the optimized internal
structure of convection cooled packages of electronics. The
origin of optimal geometric features lies in the global effort to
use every volume element to the maximum, i.e., to pack the
element not only with the most heat generating components, but
also with the most flow, in such a way that every fluid packet is
effectively engaged in cooling. In flows that connect a point to
a volume or an area, the resulting structure is a tree with high conductivity
branches and low-conductivity interstices.tm201