1,720,955 research outputs found
Brain Glucose: Development and Characterisation of a Microelectrochemical Composite Biosensor for Chronic Real-time Monitoring in Freely Moving Rats
No full textThe aim of this project was to characterise a first-generation polymer enzyme
composite (PEC) biosensor for monitoring brain extracellular glucose. The brain is
heavily dependent on glucose as its primary energy source and dysregulation of
metabolism is linked to several neurological disorders including neurogenerative diseases
such as Alzheimer’s. Therefore, quantification and an improved understanding of glucose
changes and their relationship to other metabolites in the brain, are important research
goals. This project involved applying the composite biosensor design that has previously
been used to monitor other neurochemicals such as D-serine, choline, glutamate and
lactate to the existing glucose biosensor design that was previously developed by Lowry
et al. The core components of different crosslinking/stabilising agents, layering strategies
and drying times for the PEC biosensor design have already been optimised in the
previously developed devices. When the composite design was applied for the detection
of glucose the chosen sensor design was:
PtD(PoPD)(Sty)(GOx/GA)15
Where a PtD electrode (Platinum disc) was modified with PoPD (poly-ophenylenediamine),
an interference rejection layer, Sty (Styrene) an immobiliser, GOx
(glucose oxidase) the enzyme and finally GA (glutaraldehyde) a cross-linking agent.
Firstly, a literature review of neurochemical glucose biosensors was conducted to
compare and contrast the new glucose biosensor’s response characteristics (e.g.
sensitivity, Vmax and Km) with devices already reported. An in vitro characterisation of the
composite glucose biosensor was performed to determine the sensitivity of the device.
The sensor was exposed to a range of pH and temperatures that it may encounter in the
brain. Oxygen dependence studies were performed to ensure the low O2 concentration in
the brain would not hinder the biosensor’s performance. Biocompatibility tests were
conducted as exposure to brain tissue can lead to a decrease in sensitivity due to electrode
poisons, surfactants and surface modifying agents. A range of different stability
experiments were performed to determine the effect repeat calibrations had on the
sensitivity of the biosensor along with shelf-life experiments to assess the longevity of
the device. Finally, interference rejection was tested for common endogenous
electroactive interferents to ensure they had minimal effect on the glucose signal
recorded.
In summary, the polymer enzyme composite biosensor achieved an excellent
sensitivity of 32.42 ± 0.90 nA.cm-2.μM-1. It had a shelf-life of several weeks and no loss
of sensitivity was observed after repeat calibrations or exposure to ex vivo rodent brain
tissue (14 days). The sensor performed adequately under all physiologically relevant pH
and temperature ranges. The addition of a poly-ortho-phenylenediamine (PoPD) layer
provided the sensor with interference rejection properties which resulted in a reliable,
interference-free detection of glucose. Preliminary in vivo studies were performed in
freely moving rats where the sensor demonstrated reliable signals in response to neuronal
activation (tail pinch), and expected signals were observed when interference testing for
ascorbic acid and oxygen was performed. Future work will involve extending the vivo
characterisation of the biosensor
Brain Glucose: Development and Characterisation of a Microelectrochemical Composite Biosensor for Chronic Real-time Monitoring in Freely Moving Rats
No full textThe aim of this project was to characterise a first-generation polymer enzyme
composite (PEC) biosensor for monitoring brain extracellular glucose. The brain is
heavily dependent on glucose as its primary energy source and dysregulation of
metabolism is linked to several neurological disorders including neurogenerative diseases
such as Alzheimer’s. Therefore, quantification and an improved understanding of glucose
changes and their relationship to other metabolites in the brain, are important research
goals. This project involved applying the composite biosensor design that has previously
been used to monitor other neurochemicals such as D-serine, choline, glutamate and
lactate to the existing glucose biosensor design that was previously developed by Lowry
et al. The core components of different crosslinking/stabilising agents, layering strategies
and drying times for the PEC biosensor design have already been optimised in the
previously developed devices. When the composite design was applied for the detection
of glucose the chosen sensor design was:
PtD(PoPD)(Sty)(GOx/GA)15
Where a PtD electrode (Platinum disc) was modified with PoPD (poly-ophenylenediamine),
an interference rejection layer, Sty (Styrene) an immobiliser, GOx
(glucose oxidase) the enzyme and finally GA (glutaraldehyde) a cross-linking agent.
Firstly, a literature review of neurochemical glucose biosensors was conducted to
compare and contrast the new glucose biosensor’s response characteristics (e.g.
sensitivity, Vmax and Km) with devices already reported. An in vitro characterisation of the
composite glucose biosensor was performed to determine the sensitivity of the device.
The sensor was exposed to a range of pH and temperatures that it may encounter in the
brain. Oxygen dependence studies were performed to ensure the low O2 concentration in
the brain would not hinder the biosensor’s performance. Biocompatibility tests were
conducted as exposure to brain tissue can lead to a decrease in sensitivity due to electrode
poisons, surfactants and surface modifying agents. A range of different stability
experiments were performed to determine the effect repeat calibrations had on the
sensitivity of the biosensor along with shelf-life experiments to assess the longevity of
the device. Finally, interference rejection was tested for common endogenous
electroactive interferents to ensure they had minimal effect on the glucose signal
recorded.
In summary, the polymer enzyme composite biosensor achieved an excellent
sensitivity of 32.42 ± 0.90 nA.cm-2.μM-1. It had a shelf-life of several weeks and no loss
of sensitivity was observed after repeat calibrations or exposure to ex vivo rodent brain
tissue (14 days). The sensor performed adequately under all physiologically relevant pH
and temperature ranges. The addition of a poly-ortho-phenylenediamine (PoPD) layer
provided the sensor with interference rejection properties which resulted in a reliable,
interference-free detection of glucose. Preliminary in vivo studies were performed in
freely moving rats where the sensor demonstrated reliable signals in response to neuronal
activation (tail pinch), and expected signals were observed when interference testing for
ascorbic acid and oxygen was performed. Future work will involve extending the vivo
characterisation of the biosensor
Brain Glucose: Development and Characterisation of a Microelectrochemical Composite Biosensor for Chronic Real-time Monitoring in Freely Moving Rats
No full textThe aim of this project was to characterise a first-generation polymer enzyme
composite (PEC) biosensor for monitoring brain extracellular glucose. The brain is
heavily dependent on glucose as its primary energy source and dysregulation of
metabolism is linked to several neurological disorders including neurogenerative diseases
such as Alzheimer’s. Therefore, quantification and an improved understanding of glucose
changes and their relationship to other metabolites in the brain, are important research
goals. This project involved applying the composite biosensor design that has previously
been used to monitor other neurochemicals such as D-serine, choline, glutamate and
lactate to the existing glucose biosensor design that was previously developed by Lowry
et al. The core components of different crosslinking/stabilising agents, layering strategies
and drying times for the PEC biosensor design have already been optimised in the
previously developed devices. When the composite design was applied for the detection
of glucose the chosen sensor design was:
PtD(PoPD)(Sty)(GOx/GA)15
Where a PtD electrode (Platinum disc) was modified with PoPD (poly-ophenylenediamine),
an interference rejection layer, Sty (Styrene) an immobiliser, GOx
(glucose oxidase) the enzyme and finally GA (glutaraldehyde) a cross-linking agent.
Firstly, a literature review of neurochemical glucose biosensors was conducted to
compare and contrast the new glucose biosensor’s response characteristics (e.g.
sensitivity, Vmax and Km) with devices already reported. An in vitro characterisation of the
composite glucose biosensor was performed to determine the sensitivity of the device.
The sensor was exposed to a range of pH and temperatures that it may encounter in the
brain. Oxygen dependence studies were performed to ensure the low O2 concentration in
the brain would not hinder the biosensor’s performance. Biocompatibility tests were
conducted as exposure to brain tissue can lead to a decrease in sensitivity due to electrode
poisons, surfactants and surface modifying agents. A range of different stability
experiments were performed to determine the effect repeat calibrations had on the
sensitivity of the biosensor along with shelf-life experiments to assess the longevity of
the device. Finally, interference rejection was tested for common endogenous
electroactive interferents to ensure they had minimal effect on the glucose signal
recorded.
In summary, the polymer enzyme composite biosensor achieved an excellent
sensitivity of 32.42 ± 0.90 nA.cm-2.μM-1. It had a shelf-life of several weeks and no loss
of sensitivity was observed after repeat calibrations or exposure to ex vivo rodent brain
tissue (14 days). The sensor performed adequately under all physiologically relevant pH
and temperature ranges. The addition of a poly-ortho-phenylenediamine (PoPD) layer
provided the sensor with interference rejection properties which resulted in a reliable,
interference-free detection of glucose. Preliminary in vivo studies were performed in
freely moving rats where the sensor demonstrated reliable signals in response to neuronal
activation (tail pinch), and expected signals were observed when interference testing for
ascorbic acid and oxygen was performed. Future work will involve extending the vivo
characterisation of the biosensor
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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