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Search Results: 1 - 10 of 14805 matches for " Ian Scott MacKenzie "
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A Note on the Validity of the Shannon Formulation for Fitts’ Index of Difficulty  [PDF]
Ian Scott MacKenzie
Open Journal of Applied Sciences (OJAppS) , 2013, DOI: 10.4236/ojapps.2013.36046
Abstract:

The three most common variations of Fitts’ index of difficulty are the Fitts formulation, the Welford formulation, and the Shannon formulation. A recent paper by Hoffmann [1] critiqued the three and concluded that the Fitts and Welford formulations are valid and that the Shannon formulation is invalid. In this paper, we challenge Hoffmann’s position regarding the Shannon formulation. It is argued that the issue of validity vs. invalidity is ill-conceived, given that Fitts’ law is a “model by analogy” with no basis in human motor control. The relevant questions are of utility: Does a model work? How well? Is it useful? Where alternative formulations exist, they may be critiqued and compared for strengths and weaknesses, but validity is an irrelevant construct. In a reanalysis of data from Fitts’ law experiments, models built using the Shannon formulation are (re)affirmed to be as good as, and generally better than, those built using the Fitts or Welford formulation.

Familial frontotemporal dementia with neuronal intranuclear inclusions is not a polyglutamine expansion disease
Ian R Mackenzie, Stefanie L Butland, Rebecca S Devon, Emily Dwosh, Howard Feldman, Caroline Lindholm, Scott J Neal, BF Francis Ouellette, Blair R Leavitt
BMC Neurology , 2006, DOI: 10.1186/1471-2377-6-32
Abstract: We studied DNA and post mortem brain tissue from 5 affected members of 4 different families with NII and one affected individual with familial FTLD-U without NII. Patient DNA was screened for CAA/CAG trinucleotide expansion in a set of candidate genes identified using a genome-wide computational approach. Genes containing CAA/CAG trinucleotide repeats encoding at least five glutamines were examined (n = 63), including the nine genes currently known to be associated with human disease. CAA/CAG tract sizes were compared with published normal values (where available) and with those of healthy controls (n = 94). High-resolution agarose gel electrophoresis was used to measure allele size (number of CAA/CAG repeats). For any alleles estimated to be equal to or larger than the maximum measured in the control population, the CAA/CAG tract length was confirmed by capillary electrophoresis. In addition, immunohistochemistry using a monoclonal antibody that recognizes proteins containing expanded polyglutamines (1C2) was performed on sections of post mortem brain tissue from subjects with NII.No significant polyglutamine-encoding repeat expansions were identified in the DNA from any of our FTLD-U patients. NII in the FTLD-U cases showed no 1C2 immunoreactivity.We find no evidence to suggest that autosomal dominant FTLD-U with NII is a polyglutamine expansion disease.Frontotemporal dementia (FTD, OMIM: 600274) is a neurodegenerative disease characterized by abnormalities in personality, behaviour and language with relative early preservation of episodic memory [1,2]. The pathology underlying clinical FTD is heterogeneous [3]. In some cases, post mortem examination discloses abnormal accumulations of the microtubule associated protein tau in neurons and/or glial cells. However, several recent studies have demonstrated that the most common pathology associated with clinical FTD is the presence of dystrophic neurites and neuronal cytoplasmic inclusions in the cerebral cortex and h
Brain-stem auditory evoked responses during microvascular decompression for trigeminal neuralgia: Predicting post-operative hearing loss
Ramnarayan Ramachandran,Mackenzie Ian
Neurology India , 2006,
Abstract: Context: The importance of brainstem auditory evoked potential monitoring in reducing hearing loss during microvascular decompression for trigeminal neuralgia is now accepted. However the extent of the changes in the pattern of these potentials and the safe limits to which these changes are relevant in reducing postoperative hearing loss have not been established. Aims: The aim of this study is to quantify these changes and relate these to the postoperative hearing loss. Settings and Design: This study was done at the Walton Centre for neurology and neurosurgery, Liverpool, United Kingdom. The study was designed to give a measure of the change in the wave pattern following microvascular decompression and relate it to postoperative hearing loss. Materials and Methods: Seventy-five patients undergoing microvascular decompression for trigeminal neuralgia had preoperative and postoperative hearing assessments and intraoperative brainstem auditory evoked potential monitoring. Statistical Analysis Used: Chi-square tests. Results: It was found that the wave V latency was increased by more than 0.9ms in nine patients, eight of whom suffered significant postoperative hearing loss as demonstrated by audiometry. It was also seen that progressive decrease in amplitude of wave V showed progressive hearing loss with 25% loss when amplitude fell by 50 and 100% loss when wave V was lost completely. However most of the patients did not have a clinically manifest hearing loss. Conclusions: A per-operative increase in the latency of wave V greater than 0.9 ms and a fall of amplitude of wave V of more than 50% indicates a risk to hearing.
“Don’t Be Frightened Dear … This Is Hollywood”: British Filmmakers in Early American Cinema
Ian Scott
European Journal of American Studies , 2010, DOI: 10.4000/ejas.8751
Abstract: British visitors to Hollywood from the late 1920s onward have captured the attention of writers as importing a particular view of their home country in a succession of ”British-Hollywood” movies. This article argues, however, that there was an initial wave of such trans-national pioneers – writer-directors Charles Brabin, Colin Campbell, Reginald Barker and Frank Lloyd – who not only did not demonstrate such “Britishness” in their work but instead made a crucial contribution to the development of classical Hollywood filmmaking. At times, they also offered a more nuanced view of social and historical complexities of the American past than many US-born directors.
Disentangling a group of lensed submm galaxies at z~2.9
Todd P. MacKenzie,Douglas Scott,Ian Smail,Edward L. Chapin,Scott C. Chapman,A. Conley,Asantha Cooray,James S. Dunlop,D. Farrah,M. Fich,Andy G. Gibb,R. J. Ivison,Tim Jenness,Jean-Paul Kneib,Gaelen Marsden,Johan Richard,E. I. Robson,Ivan Valtchanov,Julie L. Wardlow
Physics , 2013, DOI: 10.1093/mnras/stu1623
Abstract: MS$\,$0451.6$-$0305 is a rich galaxy cluster whose strong lensing is particularly prominent at submm wavelengths. We combine new SCUBA-2 data with imaging from Herschel SPIRE and PACS and HST in order to try to understand the nature of the sources being lensed. In the region of the "giant submm arc," we uncover seven multiply imaged galaxies (up from the previously known three), of which six are found to be at a redshift of $z\sim2.9$, and possibly constitute an interacting system. Using a novel forward-modelling approach, we are able to simultaneously deblend and fit SEDs to the individual galaxies that contribute to the giant submm arc, constraining their dust temperatures, far infrared luminosities and star formation rates. The submm arc first identified by SCUBA can now be seen to be composed of at least five distinct sources, four of these within the galaxy group at $z\sim2.9$. The total unlensed luminosity for this galaxy group is $(3.1\pm0.3) \times 10^{12}\,\mathrm{L}_\odot$, which gives an unlensed star formation rate of $(450\pm50)$ M$_\odot$ yr$^{-1}$. From the properties of this system, we see no evidence of evolution towards lower temperatures in the dust temperature versus far-infrared luminosity relation for high redshift galaxies.
Proliferative Regeneration of Zebrafish Lateral Line Hair Cells after Different Ototoxic Insults
Scott M. Mackenzie, David W. Raible
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0047257
Abstract: Sensory hair cells in the zebrafish lateral line regenerate rapidly and completely after damage. Previous studies have used a variety of ototoxins to kill lateral line hair cells to study different phenomena including mechanisms of hair cell death and regeneration. We sought to directly compare these ototoxins to determine if they differentially affected the rate and amount of hair cell replacement. In addition, previous studies have found evidence of proliferative hair cell regeneration in zebrafish, but both proliferation and non-mitotic direct transdifferentiation have been observed during hair cell regeneration in the sensory epithelia of birds and amphibians. We sought to test whether a similar combination of regenerative mechanisms exist in the fish. We analyzed the time course of regeneration after treatment with different ototoxic compounds and also labeled dividing hair cell progenitors. Certain treatments, including cisplatin and higher concentrations of dissolved copper, significantly delayed regeneration by one or more days. However, cisplatin did not block all regeneration as observed previously in the chick basilar papilla. The particular ototoxin did not appear to affect the mechanism of regeneration, as we observed evidence of recent proliferation in the majority of new hair cells in all cases. Inhibiting proliferation with flubendazole blocked the production of new hair cells and prevented the accumulation of additional precursors, indicating that proliferation has a dominant role during regeneration of lateral line hair cells.
Evidence of uneven selective pressure on different subsets of the conserved human genome; implications for the significance of intronic and intergenic DNA
Scott Davidson, Andrew Starkey, Alasdair MacKenzie
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-614
Abstract: We demonstrate that SNP density across the genome is significantly reduced in conserved human sequences. Unexpectedly, we further demonstrate that, despite being conserved to the same degree, SNP density differs significantly between conserved subsets. Thus, both the conserved exonic and intronic genomes contain a significantly reduced density of SNPs compared to the conserved intergenic component. Furthermore the intronic and exonic subsets contain almost identical densities of SNPs indicating that they have been constrained to the same degree.Our findings suggest the presence of a selective linkage between the exonic and intronic subsets and ascribes increased significance to the role of introns in human health. In addition, the identification of increased plasticity within the conserved intergenic subset suggests an important role for this subset in the adaptation and diversification of the human population.Although it is widely accepted that genome changes have driven evolution, there is still a lack of consensus as to what aspect of genome function are most affected to bring about phenotypic change. Many conjecture that changes within exonic coding regions are most important [1,2] whilst others suggest changes within regulatory regions as the driving force of adaptive and evolutionary change [3]. While the majority of changes produce no phenotypic effects a small number produce the characteristics that define individuals and populations of humans [4]. These functional polymorphisms are subject to selection by influences such as environment (climate, food availability, predation or disease) and sexual selection [5]. However, functional polymorphisms also contain a sub group of polymorphisms that reduce fitness and may increase disease susceptibility [6].One method to address the question of where the majority of functional polymorphisms lie within the human genome is to examine the densities of polymorphisms within the different functional components of the cons
SEDeblend: A new method for deblending spectral energy distributions in confused imaging
Todd MacKenzie,Douglas Scott,Mark Swinbank
Physics , 2015,
Abstract: For high-redshift submillimetre or millimetre sources detected with single dish telescopes, interferometric follow-up has shown that many are multiple submm galaxies blended together. Confusion-limited Herschel observations of such targets are also available, and these sample the peak of their spectral energy distribution in the far-infrared. Many methods for analysing these data have been adopted, but most follow the traditional approach of extracting fluxes before model spectral energy distributions are fit, which has the potential to erase important information on degeneracies among fitting parameters and glosses over the intricacies of confusion noise. Here, we adapt the forward-modelling method that we originally developed to disentangle a high-redshift strongly-lensed galaxy group, in order to tackle this problem in a more statistically rigorous way, by combining source deblending and SED fitting into the same procedure. We call this method "SEDeblend." As an application, we derive constraints on far-infrared luminosities and dust temperatures for sources within the ALMA follow-up of the LABOCA Extended Chandra Deep Field South Submillimetre Survey. We find an average dust temperature for an 870 micron-selected sample of (33.9+-2.4) K for the full survey. When selection effects of the sample are considered, we find no evidence that the average dust temperature evolves with redshift.
‘Either you bring the water to L.A. or you bring L.A. to the water’
Ian S. Scott
European Journal of American Studies , 2007, DOI: 10.4000/ejas.1203
Abstract: Probably the most famous phrase in Chinatown, Roman Polanski’s 1974 homage to detective noir, is virtually the last line spoken in the movie. The ensemble of characters is standing by the car that Evelyn Mulwray (Faye Dunaway) has attempted to escape in with her daughter, Katherine (Belinda Palmer). Detectives have fired shots from up the street in their attempt to prevent Evelyn from fleeing the scene and the result is that the long slow single horn sounding some yards away signals Evelyn’s ...
Application of a Groundwater Classification System and GIS Mapping System for the Lower Ruby Valley Watershed, Southwest Montana  [PDF]
Scott M. Payne, Ian A. Magruder, William W. Woessner
Journal of Water Resource and Protection (JWARP) , 2013, DOI: 10.4236/jwarp.2013.58079
Abstract:

Classification of groundwater conditions at the watershed scale synthesizes landscape hydrology, provides a mapped summary of groundwater resources, and supports water management decisions. The application of a recently developed watershed-scale groundwater classification methodology is applied and evaluated in the 100,000 hectare lower Ruby Valley watershed of southwestern Montana. The geologic setting, groundwater flow direction, aquifer productivity, water quality, anthropogenic impact to water levels, depth to groundwater, and the degree of connection between groundwater and surface water are key components of the classification scheme. This work describes the hydrogeology of the lower Ruby Valley watershed and illustrates how the classification system is applied to assemble, analyze, and summarize groundwater data. The classification process provides information in summary tables and maps of seamless digital overlays prepared using geographical information system (GIS) software. Groundwater conditions in the watershed are classified as low production bedrock aquifers in the mountainous uplands that recharge the moderate productivity basin-fill sediments. Groundwater levels approach the surface near the Ruby River resulting in sufficient groundwater discharge to maintain stream flow during dry, late summer conditions. The resulting classification data sets provide watershed managers with a standardized organizational tool that represents groundwater conditions at the watershed scale.

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