2,153 research outputs found
The Role of Indexing in Subject Retrieval
On first reading the list of speakers proposed for this institute, I
became aware of being rather the "odd man out" for two reasons. Firstly, I
was asked to present a paper on PRECIS which is very much a verbal
indexing system-at a conference dominated by contributions on classification
schemes with a natural bias, as the centenary year approaches, toward the
Dewey Decimal Classification (DDC). Secondly, I feared (quite wrongly, as it
happens) that I might be at variance with one or two of my fellow speakers,
who would possibly like to assure us, in an age when we can no longer ignore
the computer, that traditional library schemes such as DDC and Library of
Congress Classification (LCC) are capable of maintaining their original
function of organizing collections of documents, and at the same time are also
well suited to the retrieval of relevant citations from machine-held files. In
this context, I am reminded of a review of a general collection of essays on
classification schemes which appeared in the Journal of Documentation in
1972. Norman Roberts, reviewing the papers which dealt specifically with the
well established schemes, deduced that "all the writers project their particular
schemes into the future with an optimism that springs, perhaps, as much from
a sense of emotional involvement as from concrete evidence." Since I do not
believe that these general schemes can play any significant part in the retrieval
of items from mechanized files, it appeared that I had been cast in the role of
devil's advocate.published or submitted for publicatio
Investigation of factors controlling the expression of molecules involved in neurite outgrowth
Nerve growth factor (NGF) induced morphological differentiation of the pheochromocytoma PC12 cell line is accompanied by cell surface modulation of the expression of specific cell surface recognition molecules. Changes in the relative expression of the Thy-1 glycoprotein, the neural cell adhesion molecule (N-CAM) and the LI antigen correlate with the onset of neuritic outgrowth indicating a role for these molecules in the neuritogenic process. NGF induced modulation of cell surface glycoprotein expression is, initially brought about by transcription dependent mechanisms, suggesting that the PC12 cell may be a suitable model for the investigation of primary signal transduction events. Studies utilising activators of adenylate cyclase and protein kinase C demonstrate that NGF induced differentiation events are mediated by a variety of independently acting transduction routes. Morphological and biochemical responses to NGF are sensitive to secondary cellular signals. Activators of adenylate cyclase acted synergistically with NGF to promote an accelerated phase of neuritic outgrowth while concomitantly causing differential modulation of NGF induced glycoprotein expression. Analysis of the morphological and biochemical status of PC12 cells grown on monolayer cultures of non-neuronal cells provided further evidence that responses to NGF are not immutable. While growth on myotubes and glioma cells provided permissible substrates for differentiation, PC12 cells grown on monolayers of skin fibroblasts failed to respond morphologically to NGF and in addition, NGF induced increases in the expression of neurofilament protein and the Thy-1 antigen were suppressed. The ability of primed PC12 cells to differentiate on fibroblast monolayers indicates that the inhibitory effects of fibroblast contact are directed at a component of primary, transcription dependent NGF-induced gene activation. Finally, the basic fibroblast growth factor (bFGF) was able to reproduce morphological and biochemical responses associated with NGF induced differentiation. A kinase inhibitor, K252a, was used to discriminate between responses induced by the two growth factors since its effects are specific for NGF
Electrical characterization of single-walled carbon nanotubes : leading toward electronic devices
This thesis presents research involving the electrical characterization of single-walled carbon nanotubes produced by the pulsed-laser vaporization technique. Carbon nanotubes were suspended in organic solvents and separated using ultrasonic excitation. The dispersed nanotubes were either physically deposited or spin-deposited onto electrode structures that were prefabricated using standard electron-beam lithography. Atomic force microscopy was used to locate and measure nanotubes that spanned across metal electrodes. Two-probe charge transport measurements were then made on these nanotube samples. The first sample exhibited current rectification, while many other carbon nanotubes were damaged by electrical breakdown. The effect of manipulating a nanotube at the electrode junction is also demonstrated. It was found that a potential barrier could be introduced, changing the I-V response of the nanotube device. Then, p-channel field-effect transistor behavior is shown for an individual single-walled carbon nanotube. Finally, an electrodeposition technique is presented for reducing the large contact resistance between a nanotube and the metal electrodes. This technique decreased the electrode-nanotube contact resistance by a factor of more than six, and maintained the semiconducting behavior of the nanotube. Energy band diagram models are used to try to explain some of the observed electronic properties
Coupling Analysis, Simulation, and Experimentation in Natural and Engineered Biological Systems at the Molecular Scale
Cellular functions are controlled by genetic regulatory networks called gene circuits. Recently, there has been much interest in how gene circuits deal with or even exploit stochastic fluctuations in molecular species within the cellular environment. Through a coupling of analysis and simulation with experimentation, this dissertation work furthers the understanding of gene circuit noise behavior and makes significant contributions to the analytical and experimental tools that are currently available for the study and design of natural and synthetic gene circuits. In this study, models are developed for unregulated and autoregulated gene circuits. Results from the analysis are compared to computer simulations and experimental results. Exact stochastic simulations show that the derived analytical expressions are valid even for populations as low as 10 molecules, despite linear approximations made by the analysis. The experimental portion of this work presents a novel method for acquiring in vivo measurements of real-time gene expression. The techniques developed here are used to report the very first measurements of frequency content in gene circuit noise and verify theoretical predictions that negatively autoregulated gene circuits shift their noise spectra up to higher frequency. Through measured shifts in noise spectra, these frequency measurements can also reveal subtle and condition-dependent regulatory pathways. Measured noise spectra may also permit in vivo estimation of gene circuit kinetic rate parameters
Expertise and Dynamics within Crowdsourced Musical Knowledge Curation: A Case Study of the Genius Platform
Many platforms collect crowdsourced information primarily from volunteers. As
this type of knowledge curation has become widespread, contribution formats
vary substantially and are driven by diverse processes across differing
platforms. Thus, models for one platform are not necessarily applicable to
others. Here, we study the temporal dynamics of Genius, a platform primarily
designed for user-contributed annotations of song lyrics. A unique aspect of
Genius is that the annotations are extremely local -- an annotated lyric may
just be a few lines of a song -- but also highly related, e.g., by song, album,
artist, or genre. We analyze several dynamical processes associated with lyric
annotations and their edits, which differ substantially from models for other
platforms. For example, expertise on song annotations follows a ``U shape''
where experts are both early and late contributors with non-experts
contributing intermediately; we develop a user utility model that captures such
behavior. We also find several contribution traits appearing early in a user's
lifespan of contributions that distinguish (eventual) experts from non-experts.
Combining our findings, we develop a model for early prediction of user
expertise.Comment: 9 pages. 10 figure
Using VALiD to understand value from the stakeholder perspective
A āvalue agendaā has arisen in the UKās cultural development in recent years. In the construction sector, a desire to
make worthwhile building investments that are socially beneficial as well as commercially successful has become
commonplace. This value agenda has become embodied in government policy which has, in turn, shaped the
investment strategies of public bodies. Construction projects are becoming concerned with engaging directly with
stakeholders to understand and reflect their attitudes, opinions and values in the final solution. In the private sector,
the value agenda has stimulated business and societal debate to the stage where fulfilment of stakeholdersā
expectations is seen as a precursor to commercial success. It is increasingly held that people seek to use buildings
and facilities that reflect their values and which, therefore, they feel at ease with.
In response to the above, VALiD (Value in Design) has been developed as a flexible framework that helps
construction project teams explore and understand stakeholdersā values as a precursor to delivering value. Within
this framework, VALiD defines value as the relationship of stakeholder benefits sought, sacrifices accepted, and
resources expended. It is defined individually for every stakeholder in recognition that each has different underlying
values and, therefore, a different perception of value.
The use of VALiD to define project objectives and assess value delivery performance is described. The paper
presents a summary of construction organisationsā response to this treatment of value, including the status of its
development through continuing industry and academic research in the UK
Solving design problems to add value
Value management is well established in construction to structure early project briefing and to
agree satisficing project values and objectives among project stakeholders. Current practice
concentrates on the consideration of value during project definition. This paper proposes
Integral Value Engineering as a design management practice that considers value in design
throughout project resolution and delivery.
An expansion of value management principles is proposed to include the adoption of a
problem-solving approach and value-adding tools. These can help assemble value-adding
frameworks in which design activity is more explicitly focused on project values. The use of
problem solving frameworks to relate design method and outcome to project values is
described and the notion of documenting these relationships to create a value-adding audit
trail introduced. Integral Value Engineering is defined as the consideration of value when
solving design problems, irrespective of the project stage in which they occur or their
technical nature.
The adaptability of the problem solving approach is discussed, together with its ability to
accommodate the extensive variability in problem scope and concurrency in construction
projects. The role of individual design engineers as practitioners of Integral Value
Engineering is also described; this focuses on collaborative forums to incorporate the
expertise of specialised suppliers. A web-based Value-Adding Toolbox is described to
disseminate value-adding tool descriptions, methods and examples within a single
organisation or managed value chain.
The paper concludes that, for integral value engineering to be effective, suitable metrics must
be identified to monitor the extent to which technical design solutions satisfy overall project
values. This would allow responsive mechanisms to be defined so that design development
can be managed throughout project duration to ensure that the satisficing values initially
defined by value management at project outset will be delivered
Integral value engineering in design
Construction industry clients demand certainty in project cost, quality and time. The
inability of traditionally composed design teams to consistently deliver this suggests
that their expertise is sometimes inadequate. As clients become more dynamic in the
next millennium, they are likely to demand greater certainty when construction
projects are implemented to support frequent revisions in their short term function. By
establishing a collaborative working framework it is proposed that supply chains can
be better managed to identify and design out potential problems using integrated,
collaborative design processes. This proposal is being investigated by the Integrated
Collaborative Design (ICD) research project, a collaboration of AMEC Construction,
Loughborough University and eleven supply organisations, supported by the EPSRC
and DETR through the IDAC Link programme.
Focusing on one component of the ICD project, this paper reviews existing, reactive,
value engineering methods and by identifying their inadequacies establishes the need
for an integrated approach. A value management context is described which integrates
value engineering into continuous design processes. The paper discusses the
opportunities for utilising supplier design expertise by modelling design process
information flows. It also identifies potential cultural barriers to the use of design
processes incorporating integral value engineering techniques and describes the
linkage to other ICD components that are addressing these issues
Construction value management revisited: the designer's role
Value management is well established in construction. The method provides a
structured, documentable consideration of project stakeholders to ensure that projects
are required, framed to satisfy values and sufficiently supported by all stakeholders to
ensure successful completion. A variety of construction-specific value management
methods exist and many UK design management contractors offer the practice to
clients as a structured method of considering the role of each project in adding value
to clientsā business activities.
Value management in construction has grown from the manufacturing sector, but
historical review suggests it was extrapolated verbatim, with limited revision for
construction application. The soundness of this foundation is examined. The paper
reviews the extent to which designers are currently provided with mechanisms to
consider stakeholder values during the project stages when most design output is
produced. Integral Value Engineering is proposed to continuously relate ongoing
design activity to the project values current at the time of each design taskās
completion.
The paper describes a toolbox of value-adding tools that provide project designers
with methods of structuring design activity to relate technical design solutions to
stakeholder values. Development of the toolbox as a web-based resource is reviewed,
and its supporting role confirmed by validation exercises. The paper concludes by
establishing the need for all designers in the supply chain to be provided with methods
of structuring their problem solving processes to address value delivery, and the
suitability of the value-adding toolbox to them. Future work must develop means of
actively maintaining a shared understanding of values throughout project progression,
providing a framework and objective for ongoing design activity
- ā¦