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Search Results: 1 - 10 of 201141 matches for " Christopher G. Lowe "
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Evidence of Maternal Offloading of Organic Contaminants in White Sharks (Carcharodon carcharias)
Christopher G. Mull, Kady Lyons, Mary E. Blasius, Chuck Winkler, John B. O’Sullivan, Christopher G. Lowe
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062886
Abstract: Organic contaminants were measured in young of the year (YOY) white sharks (Carcharodon carcharias) incidentally caught in southern California between 2005 and 2012 (n = 20) and were found to be unexpectedly high considering the young age and dietary preferences of young white sharks, suggesting these levels may be due to exposure in utero. To assess the potential contributions of dietary exposure to the observed levels, a five-parameter bioaccumulation model was used to estimate the total loads a newborn shark would potentially accumulate in one year from consuming contaminated prey from southern California. Maximum simulated dietary accumulation of DDTs and PCBs were 25.1 and 4.73 μg/g wet weight (ww) liver, respectively. Observed ΣDDT and ΣPCB concentrations (95±91 μg/g and 16±10 μg/g ww, respectively) in a majority of YOY sharks were substantially higher than the model predictions suggesting an additional source of contaminant exposure beyond foraging. Maternal offloading of organic contaminants during reproduction has been noted in other apex predators, but this is the first evidence of transfer in a matrotrophic shark. While there are signs of white shark population recovery in the eastern Pacific, the long-term physiological and population level consequences of biomagnification and maternal offloading of environmental contaminants in white sharks is unclear.
Local Naive Bayes Nearest Neighbor for Image Classification
Sancho McCann,David G. Lowe
Computer Science , 2011,
Abstract: We present Local Naive Bayes Nearest Neighbor, an improvement to the NBNN image classification algorithm that increases classification accuracy and improves its ability to scale to large numbers of object classes. The key observation is that only the classes represented in the local neighborhood of a descriptor contribute significantly and reliably to their posterior probability estimates. Instead of maintaining a separate search structure for each class, we merge all of the reference data together into one search structure, allowing quick identification of a descriptor's local neighborhood. We show an increase in classification accuracy when we ignore adjustments to the more distant classes and show that the run time grows with the log of the number of classes rather than linearly in the number of classes as did the original. This gives a 100 times speed-up over the original method on the Caltech 256 dataset. We also provide the first head-to-head comparison of NBNN against spatial pyramid methods using a common set of input features. We show that local NBNN outperforms all previous NBNN based methods and the original spatial pyramid model. However, we find that local NBNN, while competitive with, does not beat state-of-the-art spatial pyramid methods that use local soft assignment and max-pooling.
Piperidinols That Show Anti-Tubercular Activity as Inhibitors of Arylamine N-Acetyltransferase: An Essential Enzyme for Mycobacterial Survival Inside Macrophages
Areej Abuhammad, Elizabeth Fullam, Edward D. Lowe, David Staunton, Akane Kawamura, Isaac M. Westwood, Sanjib Bhakta, Alun Christopher Garner, David L. Wilson, Peter T. Seden, Stephen G. Davies, Angela J. Russell, Elspeth F. Garman, Edith Sim
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0052790
Abstract: Latent M. tuberculosis infection presents one of the major obstacles in the global eradication of tuberculosis (TB). Cholesterol plays a critical role in the persistence of M. tuberculosis within the macrophage during latent infection. Catabolism of cholesterol contributes to the pool of propionyl-CoA, a precursor that is incorporated into cell-wall lipids. Arylamine N-acetyltransferase (NAT) is encoded within a gene cluster that is involved in the cholesterol sterol-ring degradation and is essential for intracellular survival. The ability of the NAT from M. tuberculosis (TBNAT) to utilise propionyl-CoA links it to the cholesterol-catabolism pathway. Deleting the nat gene or inhibiting the NAT enzyme prevents intracellular survival and results in depletion of cell-wall lipids. TBNAT has been investigated as a potential target for TB therapies. From a previous high-throughput screen, 3-benzoyl-4-phenyl-1-methylpiperidinol was identified as a selective inhibitor of prokaryotic NAT that exhibited antimycobacterial activity. The compound resulted in time-dependent irreversible inhibition of the NAT activity when tested against NAT from M. marinum (MMNAT). To further evaluate the antimycobacterial activity and the NAT inhibition of this compound, four piperidinol analogues were tested. All five compounds exert potent antimycobacterial activity against M. tuberculosis with MIC values of 2.3–16.9 μM. Treatment of the MMNAT enzyme with this set of inhibitors resulted in an irreversible time-dependent inhibition of NAT activity. Here we investigate the mechanism of NAT inhibition by studying protein-ligand interactions using mass spectrometry in combination with enzyme analysis and structure determination. We propose a covalent mechanism of NAT inhibition that involves the formation of a reactive intermediate and selective cysteine residue modification. These piperidinols present a unique class of antimycobacterial compounds that have a novel mode of action different from known anti-tubercular drugs.
A Re-Evaluation of the Size of the White Shark (Carcharodon carcharias) Population off California, USA
George H. Burgess, Barry D. Bruce, Gregor M. Cailliet, Kenneth J. Goldman, R. Dean Grubbs, Christopher G. Lowe, M. Aaron MacNeil, Henry F. Mollet, Kevin C. Weng, John B. O'Sullivan
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098078
Abstract: White sharks are highly migratory and segregate by sex, age and size. Unlike marine mammals, they neither surface to breathe nor frequent haul-out sites, hindering generation of abundance data required to estimate population size. A recent tag-recapture study used photographic identifications of white sharks at two aggregation sites to estimate abundance in “central California” at 219 mature and sub-adult individuals. They concluded this represented approximately one-half of the total abundance of mature and sub-adult sharks in the entire eastern North Pacific Ocean (ENP). This low estimate generated great concern within the conservation community, prompting petitions for governmental endangered species designations. We critically examine that study and find violations of model assumptions that, when considered in total, lead to population underestimates. We also use a Bayesian mixture model to demonstrate that the inclusion of transient sharks, characteristic of white shark aggregation sites, would substantially increase abundance estimates for the adults and sub-adults in the surveyed sub-population. Using a dataset obtained from the same sampling locations and widely accepted demographic methodology, our analysis indicates a minimum all-life stages population size of >2000 individuals in the California subpopulation is required to account for the number and size range of individual sharks observed at the two sampled sites. Even accounting for methodological and conceptual biases, an extrapolation of these data to estimate the white shark population size throughout the ENP is inappropriate. The true ENP white shark population size is likely several-fold greater as both our study and the original published estimate exclude non-aggregating sharks and those that independently aggregate at other important ENP sites. Accurately estimating the central California and ENP white shark population size requires methodologies that account for biases introduced by sampling a limited number of sites and that account for all life history stages across the species' range of habitats.
The Association between Commonality in Liquidity and Corporate Disclosure Practices in Taiwan  [PDF]
Alpha Lowe
Modern Economy (ME) , 2014, DOI: 10.4236/me.2014.54030

With a sample of stocks listed on the Taiwan stock exchange (TWSE), this paper examines whether a firm’s disclosure practices influence its institutional ownership and inclusion of ETFs and, hence, its commonality in liquidity. Using the grade of Taiwan SFI’s Information Disclosure and Transparency Rankings System (IDtrs) as a proxy for corporate disclosure practices, my findings robustly indicate that TWSE-listed stocks with good (bad) corporate disclosure practices exhibit high (low) commonality in liquidity. I further show that this positive disclosure-commonality relation can be partly attributed to institutional investing and index trading. Overall, consistent with a demandside explanation of commonality in liquidity, I conclude that stocks with good (bad) disclosure practices would have a high (low) likelihood of institutionalization and indexation, which should imply a high (low) commonality in their liquidity.

A Device that can Produce Net Impulse Using Rotating Masses  [PDF]
Christopher G. Provatidis
Engineering (ENG) , 2010, DOI: 10.4236/eng.2010.28083
Abstract: This paper describes a device capable of producing net impulse, through two synchronized masses, which move along a figure-eight-shaped orbit. In addition to the detailed description of the mechanical components of this device, particular attention is paid to the theoretical treatment of the innovative principle on which the device is based. In more details, the mechanical system consists of two independent but simultaneous rotations, the former being related to the formation of the figure-eight-shaped path and the latter to an additional spinning. Based on the parametric equations of motion of the lumped masses, and considering semi-static tensile deformation of the connecting rods carrying them, it was found that the resultant impulse towards the direction of the spin vector includes a non-vanishing term that is linearly proportional to the time. In addition, reduced but encouraging experimental results are reported. These findings sustain the capability of the proposed mechanism to achieve propulsion.
Deciphering the role of Epstein-Barr virus in the pathogenesis of T and NK cell lymphoproliferations
Christopher P Fox, Claire Shannon-Lowe, Martin Rowe
Herpesviridae , 2011, DOI: 10.1186/2042-4280-2-8
Abstract: Primary infection with EBV usually occurs via salivary transmission. It is unclear whether the initial infection occurs in epithelial cells or in B cells in mucosal tissues, but it is infection of B cells that enables life-long persistence of the virus as a largely asymptomatic infection [1]. EBV enters resting B cells via the CD21 receptor and MHC-II co-receptor surface molecules [2-4]. In vitro, infection of B cells results in expression of a limited subset of genes which cooperate to induce cell proliferation and transformation into lymphoblastoid cell lines; these genes include six nuclear antigens (EBNA1, EBNA2, EBNA3A, EBNA3B, EBNA3C and EBNA-LP) and three membrane proteins (LMP1, LMP2A and LMP2B) which are expressed together with abundant non-coding RNAs (EBER1 and EBER2) and several micro-RNAs [5]. In vivo, EBV-infected B cells may undergo limited expansion induced by the transformation-associated viral genes, but thereafter the infected B cells revert to a latent state in the circulating memory B cell pool to evade virus-specific immune T cell responses [1,6]. Normal plasmacytoid differentiation of virus-carrying B cells in lymphoid tissues may lead to reactivation of virus into lytic replication [7], which involves expression of around 80 viral genes and the production of new infectious virions [8]. Released virions may in turn infect epithelial cells in the oropharynx [9-12], facilitating further virus production in differentiating epithelium and release into the oropharynx [13] for horizontal transmission to new hosts.From this understanding of the normal life cycle of EBV, it is possible to envisage how genetic accidents might give rise to EBV-associated malignancies of B cell or epithelial cell origin [1]. What this classical model of the EBV life-cycle does not explain is how EBV-associated diseases of T or NK cells might arise. Indeed, as mature T and NK cells do not express CD21 it is unclear how these cells become infected in the first place. Howev
Interactions of juvenile Lumbricus terrestris with adults and their burrow systems in a two-dimensional microcosm
Grigoropoulou, Niki;Butt, Kevin R.;Lowe, Christopher N.;
Pesquisa Agropecuária Brasileira , 2009, DOI: 10.1590/S0100-204X2009000800025
Abstract: the objective of this work was to evaluate interactions of lumbricus terrestris juveniles with adults and with inherited burrow systems. an experiment was set up using a two dimensional evans' boxes microcosm. adult l. terrestris were added to 16 boxes (one individual per box) and kept in darkness at 17oc along with eight unoccupied boxes for two months. the adult l. terrestris were removed from eight randomly selected boxes, and l. terrestris juveniles were added (one juvenile per box), composing three treatments with eight replicates: 1, with an adult in an inherited burrow (abj); 2, alone in an inherited burrow (bj); and 3, alone in a previously uninhabited box (j). the proportion of juveniles occupying adult burrows observed was significantly different in treatments abj (48%) and bj (75%). the mean mass of juveniles at experimental termination differed significantly among treatments and was greater in treatment j (4.04±0.39 g) in comparison to the bj (3.09±0.93 g) and abj treatments (2.13±0.64 g). results suggest a negative influence of both the presence of an adult and its burrow system on juvenile growth. intraspecific competition partially explained this, but further investigation is required to examine how an inherited environment (i.e. burrow) could negatively affect the growth of juveniles.
A Rediscovered Ancient History of Motivational Interviewing and its Measurement
Christopher W. Dunn,Sarah Peregrine Lord,Jessica Lowe,Jutta Joesch
Motivational Interviewing : Training, Research, Implementation, Practice , 2012, DOI: 10.5195/mitrip.2012.20
Abstract: We wrote this piece for coding teams around the world, hoping to raise some measurement issues, to inspire, and to entertain (perhaps not in that order). This one’s for you, coders and for you, trainers of coders, you who work so hard to measure Motivational Interviewing using the standardized coding systems such as the MISC, MITI, and SCOPE.
Use of small-scale liquefaction features to assess paleoseismicity: an example from the Saline River fault zone, Southeast Arkansas, USA
Randel T. Cox,Christopher Lowe,Yanjun Hao,Shannon A. Mahan
Frontiers in Earth Science , 2014, DOI: 10.3389/feart.2014.00031
Abstract: Large-scale liquefaction features (e.g., sand blows, lateral-spread fissure vents) that can be recognized on remote-sensing imagery and photography have been of great utility in developing chronologies of paleo-earthquakes. In areas where large-scale features are obscured on imagery by forest cover and Holocene exposure is lacking, small-scale liquefaction features (e.g., convoluted bedding, clastic intrusions, foundered and suspended blocks, water-escape structures) offer an alternative data source that can be investigated in meter-scale excavations. In order to assess the geographic extent of Holocene sand blow fields in southeast Arkansas that were previously mapped on river terraces and flood plains using aerial photography, we investigated the distribution of small-scale liquefaction features in alluvium along streams within a forested region between the sand blow fields. Our results suggest that the fields are not continuous and do not reflect a single large liquefaction field related to paleo-earthquakes >M 6.5. Features at one of our sites suggests the Desha County sand blow field may be larger than presently mapped, and that the distance from the center of the field to the farthest liquefaction may be ~30 km. The empirical relationship of magnitude and distance to farthest liquefaction suggests a field of this size could have been produced by a M 6.3 earthquake. We also found Holocene liquefaction features that we interpret as resulting from ground shaking near previously documented Pleistocene and Holocene surface ruptures of the Saline River fault zone. Liquefaction during a paleo-earthquake (~M 5.5) may have coincided with movement on that fault zone ~AD 1700.
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